array:24 [ "pii" => "S2013251419301002" "issn" => "20132514" "doi" => "10.1016/S2013-2514(19)30100-2" "estado" => "S300" "fechaPublicacion" => "2017-01-01" "aid" => "37001" "copyright" => "Sociedad Española de Nefrología" "copyrightAnyo" => "2017" "documento" => "article" "crossmark" => 0 "licencia" => "http://creativecommons.org/licenses/by-nc-nd/4.0/" "subdocumento" => "fla" "cita" => "Nefrologia (English Version). 2017;37 Supl 1:1-191" "abierto" => array:3 [ "ES" => true "ES2" => true "LATM" => true ] "gratuito" => true "lecturas" => array:2 [ "total" => 3435 "formatos" => array:3 [ "EPUB" => 83 "HTML" => 2399 "PDF" => 953 ] ] "Traduccion" => array:1 [ "es" => array:20 [ "pii" => "S0211699517302175" "issn" => "02116995" "doi" => "10.1016/j.nefro.2017.11.004" "estado" => "S300" "fechaPublicacion" => "2017-11-01" "aid" => "441" "copyright" => "Sociedad Española de Nefrología" "documento" => "article" "crossmark" => 0 "licencia" => "http://creativecommons.org/licenses/by-nc-nd/4.0/" "subdocumento" => "fla" "cita" => "Nefrologia. 2017;37 Supl 1:1-191" "abierto" => array:3 [ "ES" => true "ES2" => true "LATM" => true ] "gratuito" => true "lecturas" => array:2 [ "total" => 48239 "formatos" => array:3 [ "EPUB" => 414 "HTML" => 38537 "PDF" => 9288 ] ] "es" => array:12 [ "idiomaDefecto" => true "titulo" => "Guía Clínica Española del Acceso Vascular para Hemodiálisis" "tienePdf" => "es" "tieneTextoCompleto" => "es" "tieneResumen" => array:2 [ 0 => "es" 1 => "en" ] "paginas" => array:1 [ 0 => array:2 [ "paginaInicial" => "1" "paginaFinal" => "191" ] ] "titulosAlternativos" => array:1 [ "en" => array:1 [ "titulo" => "Spanish Clinical Guidelines on Vascular Access for Haemodialysis" ] ] "contieneResumen" => array:2 [ "es" => true "en" => true ] "contieneTextoCompleto" => array:1 [ "es" => true ] "contienePdf" => array:1 [ "es" => true ] "resumenGrafico" => array:2 [ "original" => 0 "multimedia" => array:7 [ "identificador" => "fig0035" "etiqueta" => "Figura 7" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ …4] ] "descripcion" => array:1 [ "es" => "<p id="spar0055" class="elsevierStyleSimplePara elsevierViewall">Conducta a seguir ante la disfunción del catéter venoso tunelizado (CVT). CVC: catéter venoso central; HD: hemodíálisis; rt-PA: activador tisular del plasminógeno recombinante.</p>" ] ] ] "autores" => array:1 [ 0 => array:2 [ "autoresLista" => "José Ibeas, Ramon Roca-Tey, Joaquín Vallespín, Teresa Moreno, Guillermo Moñux, Anna Martí-Monrós, José Luis del Pozo, Enrique Gruss, Manel Ramírez de Arellano, Néstor Fontseré, María Dolores Arenas, José Luis Merino, José García-Revillo, Pilar Caro, Cristina López-Espada, Antonio Giménez-Gaibar, Milagros Fernández-Lucas, Pablo Valdés, Fidel Fernández-Quesada, Natalia de la Fuente, David Hernán, Patricia Arribas, María Dolores Sánchez de la Nieta, María Teresa Martínez, Ángel Barba" "autores" => array:26 [ 0 => array:2 [ …2] 1 => array:2 [ …2] 2 => array:2 [ …2] 3 => array:2 [ …2] 4 => array:2 [ …2] 5 => array:2 [ …2] 6 => array:2 [ …2] 7 => array:2 [ …2] 8 => array:2 [ …2] 9 => array:2 [ …2] 10 => array:2 [ …2] 11 => array:2 [ …2] 12 => array:2 [ …2] 13 => array:2 [ …2] 14 => array:2 [ …2] 15 => array:2 [ …2] 16 => array:2 [ …2] 17 => array:2 [ …2] 18 => array:2 [ …2] 19 => array:2 [ …2] 20 => array:2 [ …2] 21 => array:2 [ …2] 22 => array:2 [ …2] 23 => array:2 [ …2] 24 => array:2 [ …2] 25 => array:1 [ …1] ] ] ] ] "idiomaDefecto" => "es" "Traduccion" => array:1 [ "en" => array:9 [ "pii" => "S2013251419301002" "doi" => "10.1016/S2013-2514(19)30100-2" "estado" => "S300" "subdocumento" => "" "abierto" => array:3 [ "ES" => true "ES2" => true "LATM" => true ] "gratuito" => true "lecturas" => array:1 [ "total" => 0 ] "idiomaDefecto" => "en" "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S2013251419301002?idApp=UINPBA000064" ] ] "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S0211699517302175?idApp=UINPBA000064" "url" => "/02116995/00000037000000S1/v9_201804270419/S0211699517302175/v9_201804270419/es/main.assets" ] ] "itemSiguiente" => array:19 [ "pii" => "S2013251419301014" "issn" => "20132514" "doi" => "10.1016/S2013-2514(19)30101-4" "estado" => "S300" "fechaPublicacion" => "2017-01-01" "aid" => "37002" "copyright" => "Sociedad Española de Nefrología" "documento" => "simple-article" "crossmark" => 0 "licencia" => "http://creativecommons.org/licenses/by-nc-nd/4.0/" "subdocumento" => "edb" "cita" => "Nefrologia (English Version). 2017;37 Supl 1:i" "abierto" => array:3 [ "ES" => true "ES2" => true "LATM" => true ] "gratuito" => true "lecturas" => array:2 [ "total" => 195 "formatos" => array:3 [ "EPUB" => 60 "HTML" => 52 "PDF" => 83 ] ] "es" => array:6 [ "idiomaDefecto" => true "titulo" => "Credit Page" "tienePdf" => "es" "tieneTextoCompleto" => 0 "paginas" => array:1 [ 0 => array:1 [ "paginaInicial" => "i" ] ] "contienePdf" => array:1 [ "es" => true ] ] "idiomaDefecto" => "es" "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S2013251419301014?idApp=UINPBA000064" "url" => "/20132514/00000037000000S1/v4_201909280701/S2013251419301014/v4_201909280701/es/main.assets" ] "en" => array:16 [ "idiomaDefecto" => true "titulo" => "Spanish Clinical Guidelines on Vascular Access for Haemodialysis" "tieneTextoCompleto" => true "paginas" => array:1 [ 0 => array:2 [ "paginaInicial" => "1" "paginaFinal" => "191" ] ] "autores" => array:1 [ 0 => array:4 [ "autoresLista" => "José Ibeas, Ramon Roca-Tey, Joaquín Vallespín, Teresa Moreno, Guillermo Moñux, Anna Martí-Monrós, José Luis del Pozo, Enrique Gruss, Manel Ramírez de Arellano, Néstor Fontseré, María Dolores Arenas, José Luis Merino, José García-Revillo, Pilar Caro, Cristina López-Espada, Antonio Giménez-Gaibar, Milagros Fernández-Lucas, Pablo Valdés, Fidel Fernández-Quesada, Natalia de la Fuente, David Hernán, Patricia Arribas, María Dolores Sánchez de la Nieta, María Teresa Martínez, Ángel Barba" "autores" => array:26 [ 0 => array:4 [ "nombre" => "José" "apellidos" => "Ibeas" "email" => array:1 [ 0 => "jibeas@telefonica.net" ] "referencia" => array:2 [ 0 => array:2 [ …2] 1 => array:2 [ …2] ] ] 1 => array:3 [ "nombre" => "Ramon" "apellidos" => "Roca-Tey" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 2 => array:3 [ "nombre" => "Joaquín" "apellidos" => "Vallespín" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 3 => array:3 [ "nombre" => "Teresa" "apellidos" => "Moreno" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 4 => array:3 [ "nombre" => "Guillermo" "apellidos" => "Moñux" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 5 => array:3 [ "nombre" => "Anna" "apellidos" => "Martí-Monrós" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 6 => array:3 [ "nombre" => "José Luis" "apellidos" => "del Pozo" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 7 => array:3 [ "nombre" => "Enrique" "apellidos" => "Gruss" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 8 => array:3 [ "nombre" => "Manel Ramírez" "apellidos" => "de Arellano" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 9 => array:3 [ "nombre" => "Néstor" "apellidos" => "Fontseré" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 10 => array:3 [ "nombre" => "María Dolores" "apellidos" => "Arenas" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 11 => array:3 [ "nombre" => "José Luis" "apellidos" => "Merino" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 12 => array:3 [ "nombre" => "José" "apellidos" => "García-Revillo" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 13 => array:3 [ "nombre" => "Pilar" "apellidos" => "Caro" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 14 => array:3 [ "nombre" => "Cristina" "apellidos" => "López-Espada" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 15 => array:3 [ "nombre" => "Antonio" "apellidos" => "Giménez-Gaibar" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 16 => array:3 [ "nombre" => "Milagros" "apellidos" => "Fernández-Lucas" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 17 => array:3 [ "nombre" => "Pablo" "apellidos" => "Valdés" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 18 => array:3 [ "nombre" => "Fidel" "apellidos" => "Fernández-Quesada" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 19 => array:3 [ "nombre" => "Natalia" "apellidos" => "de la Fuente" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 20 => array:3 [ "nombre" => "David" "apellidos" => "Hernán" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 21 => array:3 [ "nombre" => "Patricia" "apellidos" => "Arribas" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 22 => array:3 [ "nombre" => "María Dolores Sánchez" "apellidos" => "de la Nieta" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 23 => array:3 [ "nombre" => "María Teresa" "apellidos" => "Martínez" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 24 => array:3 [ "nombre" => "Ángel" "apellidos" => "Barba" "referencia" => array:1 [ 0 => array:2 [ …2] ] ] 25 => array:1 [ "colaborador" => "on behalf of the Spanish Multidisciplinary Group on Vascular Access (GEMAV)" ] ] "afiliaciones" => array:22 [ 0 => array:3 [ "entidad" => "Servicio de Nefrología, Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Barcelona, Spain" "etiqueta" => "a" "identificador" => "aff1" ] 1 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital de Mollet, Fundació Sanitària Mollet, Mollet del Vallès, Barcelona, Spain" "etiqueta" => "b" "identificador" => "aff2" ] 2 => array:3 [ "entidad" => "Servicio de Cirugía Vascular, Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Barcelona, Spain" "etiqueta" => "c" "identificador" => "aff3" ] 3 => array:3 [ "entidad" => "Servicio de Radiología, Hospital Juan Ramón Jiménez, Huelva, Spain" "etiqueta" => "d" "identificador" => "aff4" ] 4 => array:3 [ "entidad" => "Servicio de Cirugía Vascular, Hospital Clínico, Madrid, Spain" "etiqueta" => "e" "identificador" => "aff5" ] 5 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital General de Valencia, Valencia, Spain" "etiqueta" => "f" "identificador" => "aff6" ] 6 => array:3 [ "entidad" => "Servicio de Microbiología Clínica y Enfermedades Infecciosas, Clínica Universidad de Navarra, Pamplona, Spain" "etiqueta" => "g" "identificador" => "aff7" ] 7 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital Universitario Fundación Alcorcón, Alcorcón, Madrid, Spain" "etiqueta" => "h" "identificador" => "aff8" ] 8 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital de Terrassa, Consorci Sanitari de Terrassa, Terrassa, Barcelona, Spain" "etiqueta" => "i" "identificador" => "aff9" ] 9 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain" "etiqueta" => "j" "identificador" => "aff10" ] 10 => array:3 [ "entidad" => "Servicio de Nefrología, Vithas Hospital Internacional Perpetuo, Alicante, Spain" "etiqueta" => "k" "identificador" => "aff11" ] 11 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital Universitario del Henares, Madrid, Spain" "etiqueta" => "l" "identificador" => "aff12" ] 12 => array:3 [ "entidad" => "Servicio de Radiología, Hospital Universitario Reina Sofía, Córdoba, Spain" "etiqueta" => "m" "identificador" => "aff13" ] 13 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital Ruber Juan Bravo, Madrid, Spain" "etiqueta" => "n" "identificador" => "aff14" ] 14 => array:3 [ "entidad" => "Servicio de Cirugía Vascular, Complejo Hospitalario Universitario de Granada, Granada, Spain" "etiqueta" => "ñ" "identificador" => "aff15" ] 15 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital Universitario Ramón y Cajal, Universidad de Alcalá, Madrid, Spain" "etiqueta" => "o" "identificador" => "aff16" ] 16 => array:3 [ "entidad" => "Servicio de Radiología, Hospital de Marbella, Málaga, Spain" "etiqueta" => "p" "identificador" => "aff17" ] 17 => array:3 [ "entidad" => "Servicio de Cirugía Vascular, Hospital Galdakao-Usansolo, Bizkaia, Spain" "etiqueta" => "q" "identificador" => "aff18" ] 18 => array:3 [ "entidad" => "Fundación Renal Íñigo Álvarez de Toledo, Madrid, Spain" "etiqueta" => "r" "identificador" => "aff19" ] 19 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital Universitario Infanta Leonor, Madrid, Spain" "etiqueta" => "s" "identificador" => "aff20" ] 20 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital General Universitario de Ciudad Real, Ciudad Real, Spain" "etiqueta" => "t" "identificador" => "aff21" ] 21 => array:3 [ "entidad" => "Servicio de Nefrología, Hospital General Universitario Gregorio Marañón, Madrid, Spain" "etiqueta" => "u" "identificador" => "aff22" ] ] "correspondencia" => array:1 [ 0 => array:3 [ "identificador" => "cor1" "etiqueta" => "*" "correspondencia" => "<span class="elsevierStyleItalic">Corresponding author</span>. Email address: jibeas@telefonica.net (J. Ibeas)." ] ] ] ] "resumenGrafico" => array:2 [ "original" => 0 "multimedia" => array:8 [ "identificador" => "f4" "etiqueta" => "Figure 4" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr4.jpeg" "Alto" => 1980 "Ancho" => 2591 "Tamanyo" => 149143 ] ] "detalles" => array:1 [ 0 => array:3 [ "identificador" => "at0020" "detalle" => "Figure " "rol" => "short" ] ] "descripcion" => array:1 [ "en" => "<p id="sp0020" class="elsevierStyleSimplePara elsevierViewall">Specificity of Doppler ultrasound versus fistulography to confirm significant stenosis in arteriovenous fistula in patients with clinical suspicion of stenosis obtained in a meta-analysis of 4 studies: 94.7 (95% confidence interval, 91.8-96.6).</p>" ] ] ] "textoCompleto" => "<span class="elsevierStyleSections"><span id="s0005" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0025">PREAMBLE</span><p id="p0845" class="elsevierStylePara elsevierViewall">Vascular access (VA) used to perform haemodialysis (HD) is fundamental in the case of patients with kidney disease and, currently, its influence on morbidity and mortality is no longer questioned. Therefore, due to the great significance it holds for these patients, a Guide on vascular access is needed for use in decision-making during routine clinical practice. This guide should not only collect all the available evidence, but also convey it to professionals in a way which allows daily clinical application.</p><p id="p0850" class="elsevierStylePara elsevierViewall">The first edition of the Sociedad Española de Nefrología (Spanish Society of Nephrology) Vascular Access Guide was published in 2005 with the collaboration of the other societies involved in the current guide. This Guide has been a reference point for professionals working in HD since then. It has become a key document to be consulted in dialysis units and has had a considerable impact on the literature. The current edition aims to renew this Guide, updating all the subjects included in it and adding new concepts that have been raised since its publication.</p><p id="p0855" class="elsevierStylePara elsevierViewall">The format of the current Guide maintains a similar structure, and thus has the same Sections. It is worth mentioning that the topic of “Quality indicators” has now grown to become a section in its own right (Section 7) with 29 indicators, rather than an appendix with only 5 indicators as it was in the previous version. With regard to content, a mixed approach has been preserved, that is to say, on the one hand, recommendations have been derived from the analysis of the current scientific evidence and, on the other, the teaching bent of the previous edition has not been discarded.</p></span><span id="s0010" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0030">COMPOSITION OF THE GROUP DEVELOPING THE GUIDE</span><p id="p0860" class="elsevierStylePara elsevierViewall">After a meeting in Madrid on 29 June, 2012 representatives of the Sociedad Española de Nefrología (Spanish Society of Nephrology [S.E.N.]), Sociedad Española de Angiología y Cirugía Vascular (Society of Angiology and Vascular Surgery [SEACV]), Sociedad Española de Radiología Vascular e Intervencionista-Sociedad Española de Radiología Médica (Spanish Society of Vascular and Interventional Radiology-Spanish Society of Medical Radiology [SERVEI-SERAM]), Sociedad Española de Enfermería Nefrológica (Spanish Society of Nephrology Nursing [SEDEN]) and in an subsequent meeting of the Grupo de Estudio de la Infección Relacionada con la Asistencia Sanitaria/Grupo de Estudio de la Infeccion Hospitalaria-Sociedad Española de Enfermedades Infecciosas y Microbiologia Clinica (Study Group of Healthcare-related Infection/Study Group of Hospital Infection-Spanish Society of Infectious Diseases and Clinical Microbiology [GEIRAS/GEIH-SEIMC]) took the decision to update the Spanish Clinical Guideline on Vascular Access for Haemodialysis. The multidisciplinary working group was composed of members of the 5 scientific societies involved and the members were chosen for both clinical and research experience in the area of vascular access. During the meeting of the 6 October, 2014, the group took the name Grupo Español Multidisciplinar del Acceso Vascular (Spanish Multidisciplinary Group on Vascular Access [GEMAV]), the name by which the group was to be known thereafter. It was also decided to use the methodological support of the Centro Cochrane Iberoamericano (Iberoamerican Cochrane Center) to systematically review the literature pertaining to the Guide’s clinical questions prioritised by GEMAV. All authors have been involved in the edition of the Guide in a strictly professional way, and have no type of conflict of interest. Some of the authors also carry out some representative tasks for their respective scientific societies. Below are the names of the coordinators of the Guideline, the editors, the members of GEMAV (in representation of the five societies), the external reviewers and the representatives of kidney patient associations.</p><p id="sect0035" class="elsevierStylePara elsevierViewall">Coordinators of the Guide</p><p id="p0865" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0160"><li class="elsevierStyleListItem" id="listi0730"><span class="elsevierStyleLabel">•</span><p id="p0870" class="elsevierStylePara elsevierViewall">Jose Ibeas. Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Barcelona</p></li><li class="elsevierStyleListItem" id="listi0735"><span class="elsevierStyleLabel">•</span><p id="p0875" class="elsevierStylePara elsevierViewall">Ramón Roca-Tey. Hospital de Mollet, Fundació Sanitària Mollet, Mollet del Vallès, Barcelona</p></li></ul></p><p id="sect0040" class="elsevierStylePara elsevierViewall">Editors</p><p id="p0880" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0165"><li class="elsevierStyleListItem" id="listi0740"><span class="elsevierStyleLabel">•</span><p id="p0885" class="elsevierStylePara elsevierViewall">Jose Ibeas. Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Barcelona</p></li><li class="elsevierStyleListItem" id="listi0745"><span class="elsevierStyleLabel">•</span><p id="p0890" class="elsevierStylePara elsevierViewall">Ramón Roca-Tey. Hospital de Mollet, Fundació Sanitària Mollet, Mollet del Vallès, Barcelona</p></li><li class="elsevierStyleListItem" id="listi0750"><span class="elsevierStyleLabel">•</span><p id="p0895" class="elsevierStylePara elsevierViewall">Joaquin Vallespín Aguado. Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Barcelona</p></li><li class="elsevierStyleListItem" id="listi0755"><span class="elsevierStyleLabel">•</span><p id="p0900" class="elsevierStylePara elsevierViewall">Carlos Quereda Rodríguez-Navarro. Editor of the journal <span class="elsevierStyleItalic">Nefrología</span> for Clinical Practice Guidelines</p></li></ul></p><p id="sect0045" class="elsevierStylePara elsevierViewall">On behalf of the five societies</p><p id="sect0050" class="elsevierStylePara elsevierViewall">S.E.N.</p><p id="p0905" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0170"><li class="elsevierStyleListItem" id="listi0760"><span class="elsevierStyleLabel">•</span><p id="p0910" class="elsevierStylePara elsevierViewall">Dolores Arenas. Vithas Hospital Internacional Perpetuo, Alicante.</p></li><li class="elsevierStyleListItem" id="listi0765"><span class="elsevierStyleLabel">•</span><p id="p0915" class="elsevierStylePara elsevierViewall">Pilar Caro. Hospital Ruber Juan Bravo, Madrid</p></li><li class="elsevierStyleListItem" id="listi0770"><span class="elsevierStyleLabel">•</span><p id="p0920" class="elsevierStylePara elsevierViewall">Milagros Fernández Lucas. Hospital Universitario Ramón y Cajal, Universidad de Alcalá, Madrid</p></li><li class="elsevierStyleListItem" id="listi0775"><span class="elsevierStyleLabel">•</span><p id="p0925" class="elsevierStylePara elsevierViewall">Néstor Fontseré. Hospital Clínic, Universitat de Barcelona, Barcelona</p></li><li class="elsevierStyleListItem" id="listi0780"><span class="elsevierStyleLabel">•</span><p id="p0930" class="elsevierStylePara elsevierViewall">Enrique Gruss. Hospital Universitario Fundación Alcorcón, Alcorcón, Madrid</p></li><li class="elsevierStyleListItem" id="listi0785"><span class="elsevierStyleLabel">•</span><p id="p0935" class="elsevierStylePara elsevierViewall">José Ibeas. Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Barcelona Secretary of Vascular Access Working Group of the Spanish Society of Nephrology</p></li><li class="elsevierStyleListItem" id="listi0790"><span class="elsevierStyleLabel">•</span><p id="p0940" class="elsevierStylePara elsevierViewall">José Luis Merino. Hospital Universitario del Henares, Coslada, Madrid</p></li><li class="elsevierStyleListItem" id="listi0795"><span class="elsevierStyleLabel">•</span><p id="p0945" class="elsevierStylePara elsevierViewall">Manel Ramírez de Arellano. Hospital de Terrassa, Consorci Sanitari de Terrassa, Barcelona</p></li><li class="elsevierStyleListItem" id="listi0800"><span class="elsevierStyleLabel">•</span><p id="p0950" class="elsevierStylePara elsevierViewall">Ramon Roca-Tey. Hospital de Mollet, Fundació Sanitària Mollet, Mollet del Vallès, Barcelona Official Representative of the Spanish Society of Nephrology. Coordinator of the Vascular Access Working Group of the Spanish Society of Nephrology and of the Spanish Multidisciplinary Group on Vascular Access (GEMAV)</p></li><li class="elsevierStyleListItem" id="listi0805"><span class="elsevierStyleLabel">•</span><p id="p0955" class="elsevierStylePara elsevierViewall">María Dolores Sánchez de la Nieta, Hospital General Universitario de Ciudad Real, Ciudad Real</p></li></ul></p><p id="sect0055" class="elsevierStylePara elsevierViewall">SEACV</p><p id="p0960" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0175"><li class="elsevierStyleListItem" id="listi0810"><span class="elsevierStyleLabel">•</span><p id="p0965" class="elsevierStylePara elsevierViewall">Angel Barba. Hospital Galdakao-Usansolo, Bizkaia</p></li><li class="elsevierStyleListItem" id="listi0815"><span class="elsevierStyleLabel">•</span><p id="p0970" class="elsevierStylePara elsevierViewall">Natalia de la Fuente. Hospital Galdakao-Usansolo, Bizkaia</p></li><li class="elsevierStyleListItem" id="listi0820"><span class="elsevierStyleLabel">•</span><p id="p0975" class="elsevierStylePara elsevierViewall">Fidel Fernández. Complejo Hospitalario Universitario de Granada, Granada</p></li><li class="elsevierStyleListItem" id="listi0825"><span class="elsevierStyleLabel">•</span><p id="p0980" class="elsevierStylePara elsevierViewall">Antonio Giménez. Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Barcelona</p></li><li class="elsevierStyleListItem" id="listi0830"><span class="elsevierStyleLabel">•</span><p id="p0985" class="elsevierStylePara elsevierViewall">Cristina López. Complejo Hospitalario Universitario de Granada, Granada</p></li><li class="elsevierStyleListItem" id="listi0835"><span class="elsevierStyleLabel">•</span><p id="p0990" class="elsevierStylePara elsevierViewall">Guillermo Moñux. Hospital Clínico Universitario San Carlos, Madrid Official Representative of the Sociedad Española de Angiología y Cirugía Vascular (SEACV), Coordinator of the Chapter of Vascular Access of the Sociedad Española de Angiología y Cirugía Vascular</p></li><li class="elsevierStyleListItem" id="listi0840"><span class="elsevierStyleLabel">•</span><p id="p0995" class="elsevierStylePara elsevierViewall">Joaquin Vallespín. Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Barcelona Secretary of the Chapter of Vascular Access of the Sociedad Española de Angiología y Cirugía Vascular</p></li></ul></p><p id="sect0060" class="elsevierStylePara elsevierViewall">SERVEI</p><p id="p1000" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0180"><li class="elsevierStyleListItem" id="listi0845"><span class="elsevierStyleLabel">•</span><p id="p1005" class="elsevierStylePara elsevierViewall">José García-Revillo García. Hospital Universitario Reina Sofía, Córdoba</p></li><li class="elsevierStyleListItem" id="listi0850"><span class="elsevierStyleLabel">•</span><p id="p1010" class="elsevierStylePara elsevierViewall">Teresa Moreno. Hospital Juan Ramón Jiménez, Complejo Hospitalario Universitario de Huelva, Huelva Official Representative of the Sociedad Española de Radiología Vascular e Intervencionista (SERVEI), Chapter of the Sociedad Española de Radiología Médica (SERAM)</p></li><li class="elsevierStyleListItem" id="listi0855"><span class="elsevierStyleLabel">•</span><p id="p1015" class="elsevierStylePara elsevierViewall">Pablo Valdés Solís. Hospital de Marbella, Málaga</p></li></ul></p><p id="sect0065" class="elsevierStylePara elsevierViewall">SEIMC</p><p id="p1020" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0185"><li class="elsevierStyleListItem" id="listi0860"><span class="elsevierStyleLabel">•</span><p id="p1025" class="elsevierStylePara elsevierViewall">José Luis del Pozo. Clínica Universidad de Navarra, Pamplona Official Representative of the Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica (Grupo de Estudio de la Infeccion Relacionada con la Asistencia Sanitaria/Grupo de Estudio de la Infección Hospitalaria [GEIRAS/GEIH])</p></li></ul></p><p id="sect0070" class="elsevierStylePara elsevierViewall">SEDEN</p><p id="p1030" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0190"><li class="elsevierStyleListItem" id="listi0865"><span class="elsevierStyleLabel">•</span><p id="p1035" class="elsevierStylePara elsevierViewall">Patricia Arribas. Hospital Infanta Leonor, Madrid</p></li><li class="elsevierStyleListItem" id="listi0870"><span class="elsevierStyleLabel">•</span><p id="p1040" class="elsevierStylePara elsevierViewall">David Hernán. Fundación Renal Íñigo Álvarez de Toledo, Madrid</p></li><li class="elsevierStyleListItem" id="listi0875"><span class="elsevierStyleLabel">•</span><p id="p1045" class="elsevierStylePara elsevierViewall">Anna Martí. Consorcio Hospital General Universitario, Valencia Official Representative of the Sociedad Española de Enfermería Nefrológica (SEDEN)</p></li><li class="elsevierStyleListItem" id="listi0880"><span class="elsevierStyleLabel">•</span><p id="p1050" class="elsevierStylePara elsevierViewall">María Teresa Martínez. Hospital General Universitario Gregorio Marañón, Madrid</p></li></ul></p><p id="sect0075" class="elsevierStylePara elsevierViewall">External reviewers</p><p id="sect0080" class="elsevierStylePara elsevierViewall">S.E.N.</p><p id="p1055" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0195"><li class="elsevierStyleListItem" id="listi0885"><span class="elsevierStyleLabel">•</span><p id="p1060" class="elsevierStylePara elsevierViewall">Fernando Álvarez Ude. Hospital de Segovia, Segovia</p></li><li class="elsevierStyleListItem" id="listi0890"><span class="elsevierStyleLabel">•</span><p id="p1065" class="elsevierStylePara elsevierViewall">Jose Antonio Herrero. Hospital Clínico Universitario San Carlos, Madrid</p></li><li class="elsevierStyleListItem" id="listi0895"><span class="elsevierStyleLabel">•</span><p id="p1070" class="elsevierStylePara elsevierViewall">Fernando García López. Centro Nacional de Epidemiología. Instituto de Salud Carlos III</p></li></ul></p><p id="sect0085" class="elsevierStylePara elsevierViewall">SEACV</p><p id="p1075" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0200"><li class="elsevierStyleListItem" id="listi0900"><span class="elsevierStyleLabel">•</span><p id="p1080" class="elsevierStylePara elsevierViewall">Sergi Bellmunt. Hospital Vall d’Hebron, Barcelona</p></li><li class="elsevierStyleListItem" id="listi0905"><span class="elsevierStyleLabel">•</span><p id="p1085" class="elsevierStylePara elsevierViewall">Melina Vega. Hospital Galdakao-Usansolo, Bizkaia</p></li></ul></p><p id="sect0090" class="elsevierStylePara elsevierViewall">SERVEI</p><p id="p1090" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0205"><li class="elsevierStyleListItem" id="listi0910"><span class="elsevierStyleLabel">•</span><p id="p1095" class="elsevierStylePara elsevierViewall">Jose Luis del Cura. Hospital de Basurto, Vizcaya.</p></li><li class="elsevierStyleListItem" id="listi0915"><span class="elsevierStyleLabel">•</span><p id="p1100" class="elsevierStylePara elsevierViewall">Antonio Segarra. Hospital Vall d’Hebron, Barcelona</p></li></ul></p><p id="sect0095" class="elsevierStylePara elsevierViewall">SEIMC</p><p id="p1105" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0210"><li class="elsevierStyleListItem" id="listi0920"><span class="elsevierStyleLabel">•</span><p id="p1110" class="elsevierStylePara elsevierViewall">Jesús Fortún Abete. Hospital Universitario Ramón y Cajal, Madrid</p></li></ul></p><p id="sect0100" class="elsevierStylePara elsevierViewall">SEDEN</p><p id="p1115" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0215"><li class="elsevierStyleListItem" id="listi0925"><span class="elsevierStyleLabel">•</span><p id="p1120" class="elsevierStylePara elsevierViewall">Isabel Crehuet. Hospital Universitario Río Hortega, Valladolid</p></li><li class="elsevierStyleListItem" id="listi0930"><span class="elsevierStyleLabel">•</span><p id="p1125" class="elsevierStylePara elsevierViewall">Fernando González. Hospital General Universitario Gregorio Marañón, Madrid</p></li></ul></p><p id="sect0105" class="elsevierStylePara elsevierViewall">Kidney patient associations</p><p id="sect0110" class="elsevierStylePara elsevierViewall">ADER</p><p id="p1130" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0220"><li class="elsevierStyleListItem" id="listi0935"><span class="elsevierStyleLabel">•</span><p id="p1135" class="elsevierStylePara elsevierViewall">Antonio Tombas. President</p></li></ul></p><p id="sect0115" class="elsevierStylePara elsevierViewall">ALCER</p><p id="p1140" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0225"><li class="elsevierStyleListItem" id="listi0940"><span class="elsevierStyleLabel">•</span><p id="p1145" class="elsevierStylePara elsevierViewall">Daniel Gallego Zurro. Council member</p></li></ul></p></span><span id="s0100" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0120">PURPOSE AND SCOPE OF THE GUIDE</span><p id="sect0125" class="elsevierStylePara elsevierViewall">Rationale of the Guide edition</p><p id="p1150" class="elsevierStylePara elsevierViewall">The aim of this Guide is to provide orientation in the comprehensive handling of vascular access for patients undergoing haemodialysis. It has been developed in order to provide information and assistance when making decisions in clinical practice. This Guide has been developed as a joint project of the five Scientific Societies referred to above, represented by experienced specialists in this field. The five Societies agreed on the need to update the first edition of the Vascular Access Guide, which was edited by the Spanish Society of Nephrology (S.E.N.) with the collaboration of the other four Societies and published in 2005.</p><p id="sect0130" class="elsevierStylePara elsevierViewall">Who is the Guide aimed at</p><p id="p1155" class="elsevierStylePara elsevierViewall">The Guide provides decision-making support for any professional involved in vascular access for haemodialysis. This includes nephrologists, vascular surgeons, interventional radiologists, infectious disease specialists and nephrological nursing. In addition, due to the Guide’s teaching bent, it is also directed at professionals undergoing training in these fields. It has therefore been considered of great interest to synthesise the necessary information for the user to build up the knowledge essential to understand the different aspects included in the Guide. Thus, sections are included with the additional explanations considered appropriate. And finally, it aims to provide a tool for healthcare managers responsible for administration and for health policy. To this end, the indicators section aims not only to provide professionals with the tools necessary to help improve the quality of care, but it also aims to support those responsible for resource management to be able to optimise resources as well as healthcare quality.</p><p id="sect0135" class="elsevierStylePara elsevierViewall">Scope of the Guide</p><p id="p1160" class="elsevierStylePara elsevierViewall">The Guide deals with patients with advanced chronic disease either in pre-dialysis or on dialysis who need a VA or treatment of its complications, as well as knowledge related to maintenance and care. The Guide does not include the paediatric population as it understands this group as patients who require a specific approach.</p></span><span id="s0120" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0140">METHODOLOGY FOR THE DEVELOPMENT OF THE GUIDE</span><p id="sect0145" class="elsevierStylePara elsevierViewall">Establishment of the Guide development group</p><p id="p1165" class="elsevierStylePara elsevierViewall">The board of the five participating societies, S.E.N., SEACV, SERVEI, SEDEN and SEIMC, approved the selection of the respective experts who were to represent these societies. The coordinators of the Guide consensually selected those responsible for each section, who coordinated the group of experts in these sections, who in turn were members of all the Societies involved. The group consisted of experts in vascular access creation, in the treatment of complications, both surgically and endovascularly, in catheter placement and the treatment of associated complications, in prevention and treatment of infections, in the preparation, monitoring, care and maintenance of the vascular access, in quality indicators and with knowledge of methodology of systematic reviews and evidence-based medicine. The Ibero-American Cochrane Center was asked to provide methodological support to develop the systematic review of the evidence in relation to clinical questions prioritised by GEMAV, and in some other stages in the development of the Guide.</p><p id="sect0150" class="elsevierStylePara elsevierViewall">Selection of clinical questions</p><p id="p1170" class="elsevierStylePara elsevierViewall">Firstly, the most relevant clinical questions in routine clinical practice were prioritised, and secondly, recommendations were formulated by applying a systematic and rigorous methodology. For this update, GEMAV selected the most relevant questions from the original guide regarding clinical practice and new questions were added if deemed necessary for the new Guide.</p><p id="p1175" class="elsevierStylePara elsevierViewall">Considering the scope of this Guide, specific clinical questions were identified and a systematic review performed:<ul class="elsevierStyleList" id="list0230"><li class="elsevierStyleListItem" id="listi0945"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">I.</span></span><p id="p1180" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Does the preservation of the venous network prevent complications/facilitate the creation of the arteriovenous fistula?</span></p></li><li class="elsevierStyleListItem" id="listi0950"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">II.</span></span><p id="p1185" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">In patients with chronic kidney disease, what are the demographic, clinical and analytical parameters in order to determine when the arteriovenous fistula (either native or prosthetic) should be created?</span></p></li><li class="elsevierStyleListItem" id="listi0955"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">III.</span></span><p id="p1190" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">What criteria are required for arteriovenous fistula planning (based on different types of fistula)?</span></p></li><li class="elsevierStyleListItem" id="listi0960"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">IV.</span></span><p id="p1195" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">What risk factors have been shown to influence the development of limb ischaemia after arteriovenous fistula creation?</span></p></li><li class="elsevierStyleListItem" id="listi0965"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">V.</span></span><p id="p1200" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Can an order of preference be recommended when performing the arteriovenous fistula?</span></p></li><li class="elsevierStyleListItem" id="listi0970"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">VI.</span></span><p id="p1205" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Are exercises useful for developing arteriovenous fistulae?</span></p></li><li class="elsevierStyleListItem" id="listi0975"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">VII.</span></span><p id="p1210" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">What is the minimum maturation time required for a native or prosthetic arteriovenous fistula to be mature enough for needling?</span></p></li><li class="elsevierStyleListItem" id="listi0980"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">VIII.</span></span><p id="p1215" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">What is the needling technique of choice for the different types of arteriovenous fistula: the three classical ones and self-cannulation?</span></p></li><li class="elsevierStyleListItem" id="listi0985"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">IXa.</span></span><p id="p1220" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">In which situations is it necessary to indicate antithrombotic prophylaxis after creating/repairing the arteriovenous fistula?</span></p></li><li class="elsevierStyleListItem" id="listi0990"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">IXb.</span></span><p id="p1225" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Does the use of antiplatelet agents prior to arteriovenous fistula creation have an impact on patency and reduce the risk of thrombosis?</span></p></li><li class="elsevierStyleListItem" id="listi0995"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">X.</span></span><p id="p1230" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">How reliable is Doppler ultrasound in determining blood flow in the arteriovenous fistula in comparison to dilution screening methods?</span></p></li><li class="elsevierStyleListItem" id="listi1000"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XI.</span></span><p id="p1235" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Can regulated Doppler ultrasound performed by an experienced examiner replace angiography as the gold standard to confirm significant arteriovenous fistula stenosis?</span></p></li><li class="elsevierStyleListItem" id="listi1005"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XII.</span></span><p id="p1240" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Which non-invasive monitoring or surveillance screening method for haemodialysis arteriovenous fistula presents predictive power of stenosis and thrombosis and increased patency of the prosthetic arteriovenous fistula in the prevalent patient and what is the frequency?</span></p></li><li class="elsevierStyleListItem" id="listi1010"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XIII.</span></span><p id="p1245" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Which non-invasive monitoring or surveillance screening method for haemodialysis arteriovenous fistula presents predictive power of stenosis and thrombosis and increased patency of the native arteriovenous fistula in the prevalent patient and what is the frequency?</span></p></li><li class="elsevierStyleListItem" id="listi1015"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XIV.</span></span><p id="p1250" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">What are the demographic, clinical and haemodynamic factors and variables with predictive power of thrombosis in an arteriovenous fistula that presents stenosis?</span></p></li><li class="elsevierStyleListItem" id="listi1020"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XV.</span></span><p id="p1255" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Is there a treatment with better outcomes (percutaneous transluminal angioplasty versus surgery) in juxta-anastomotic stenosis, assessed in terms of patency and/or thrombosis and cost/benefit?</span></p></li><li class="elsevierStyleListItem" id="listi1025"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XVI.</span></span><p id="p1260" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Are there any criteria that indicate in which cases, when and how to treat central vein stenosis, assessed in terms of usable arteriovenous fistula patency and/or thrombosis?</span></p></li><li class="elsevierStyleListItem" id="listi1030"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XVII.</span></span><p id="p1265" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">In native arteriovenous fistula thrombosis, what would be the initial indication (percutaneous transluminal angioplasty versus surgery) assessed in terms of patency of the native arteriovenous fistula and/or thrombosis? Does it depend on location?</span></p></li><li class="elsevierStyleListItem" id="listi1035"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XVIII.</span></span><p id="p1270" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">In prosthetic arteriovenous fistula thrombosis, what would be the initial indication (percutaneous transluminal angioplasty versus surgery versus fibrinolysis) assessed in terms of patency of the arteriovenous fistula and/or thrombosis? Does it depend on location?</span></p></li><li class="elsevierStyleListItem" id="listi1040"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XIX.</span></span><p id="p1275" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">In the presence of stenosis in the native arteriovenous fistula, is there a significant difference between elective intervention and performing treatment after thrombosis?</span></p></li><li class="elsevierStyleListItem" id="listi1045"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XX.</span></span><p id="p1280" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Is there a treatment with better outcomes (percutaneous transluminal angioplasty versus surgery or prosthesis interposition) in non-matured arteriovenous fistula management, evaluated on arteriovenous fistula, which enables it to be used in dialysis, patency and/or thrombosis?</span></p></li><li class="elsevierStyleListItem" id="listi1050"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXI.</span></span><p id="p1285" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">What is the approach to native or prosthetic arteriovenous fistula diagnosed with steal syndrome?</span></p></li><li class="elsevierStyleListItem" id="listi1055"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXII.</span></span><p id="p1290" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">In native and prosthetic arteriovenous fistula pseudoaneurysm, when is surgery versus percutaneous versus conservative management indicated, assessed in terms of severe bleeding complications or death?</span></p></li><li class="elsevierStyleListItem" id="listi1060"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXIII.</span></span><p id="p1295" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">In the high-flow arteriovenous fistula, what therapeutic approach should be taken and what are the criteria (risk factors)?</span></p></li><li class="elsevierStyleListItem" id="listi1065"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXIV.</span></span><p id="p1300" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">In patients who cannot undergo native arteriovenous fistula creation, is the central venous catheter the vascular access of choice versus prosthetic arteriovenous fistula?</span></p></li><li class="elsevierStyleListItem" id="listi1070"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXV.</span></span><p id="p1305" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Are there differences in the indication to use non-tunnelled catheters versus tunnelled catheters?</span></p></li><li class="elsevierStyleListItem" id="listi1075"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXVI.</span></span><p id="p1310" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">What is the best material and design for a tunnelled central venous catheter?</span></p></li><li class="elsevierStyleListItem" id="listi1080"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXVII.</span></span><p id="p1315" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Should ultrasound be used as a reference standard for the placement of central venous catheters?</span></p></li><li class="elsevierStyleListItem" id="listi1085"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXVIII.</span></span><p id="p1320" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">What is the best treatment for the persistent dysfunction of the tunnelled central venous catheter (stripping, fibrin sheath angioplasty, fibrinolytics or catheter replacement)?</span></p></li><li class="elsevierStyleListItem" id="listi1090"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXIX.</span></span><p id="p1325" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">What influence do the different types of central venous catheter lumen lock have on its dysfunction and infection?</span></p></li><li class="elsevierStyleListItem" id="listi1095"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXX.</span></span><p id="p1330" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Is the use of antibiotic prophylaxis justified to lock a tunnelled central venous catheter for haemodialysis?</span></p></li><li class="elsevierStyleListItem" id="listi1100"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXXI.</span></span><p id="p1335" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Does catheter-related bacteraemia secondary to infection with</span> Staphylococcus aureus, Pseudomonas <span class="elsevierStyleItalic">sp. and</span> Candida <span class="elsevierStyleItalic">spp. force catheter withdrawal and therefore contraindicate antibiotic lock treatment to attempt to preserve the catheter?</span></p></li><li class="elsevierStyleListItem" id="listi1105"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXXII.</span></span><p id="p1340" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Should empirical antibiotic treatment to cover gram-positive bacteraemia in haemodialysis patients who are tunnelled central venous catheter carriers initially be started with cefazolin (vancomycin if MRSA level > 15%) or daptomycin, associated with the treatment for gram-negatives, when the catheter is preserved?</span></p></li><li class="elsevierStyleListItem" id="listi1110"><span class="elsevierStyleLabel"><span class="elsevierStyleBold">XXXIII.</span></span><p id="p1345" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Does the detection and eradication of</span> Staphylococcus aureus <span class="elsevierStyleItalic">in nasal carriers reduce episodes of catheter-related bacteraemia? Is it cost-effective?</span></p></li></ul></p><p id="p1350" class="elsevierStylePara elsevierViewall">The previous recommendations of the former Guideline which have not been substantially updated can be consulted in each section of the Guide and which, therefore, GEMAV has made their own.</p><p id="p1355" class="elsevierStylePara elsevierViewall">Finally, GEMAV identified a series of questions with less impact on clinical practice, but for which the members of GEMAV themselves produced an update based on a narrative review of the literature. These sections can generate recommendations approved by consensus in GEMAV.</p><p id="sect0155" class="elsevierStylePara elsevierViewall">Development of clinical questions</p><p id="p1360" class="elsevierStylePara elsevierViewall">These questions have a structured format in order to identify the type of patient, the intervention or diagnostic test to be assessed, the comparisons, where necessary, and the outcomes of interest (PICO format). As detailed in the methodology section, recommendations for these clinical questions have been elaborated in accordance with the GRADE system guidelines.</p><p id="p1365" class="elsevierStylePara elsevierViewall">The working group collaborated in the development of these questions and formatted them to allow the systematic search of the evidence following the routine established by the PICO methodology. That is to say, the initial specification of the type of patient (P), the type of intervention (I), the comparator (C) and the outcome (O) for the questions related to interventions and diagnostic tests. For each question, the group agreed on some systematic review criteria including specific characteristics depending on the design of the sought-after studies.</p><p id="sect0160" class="elsevierStylePara elsevierViewall">Classification of the relative importance of the outcomes</p><p id="p1370" class="elsevierStylePara elsevierViewall">For each intervention question, the group compiled a list of possible outcomes, reflecting both the benefits and harm, and alternative strategies. These outcomes were categorised as critical, important or less important in relation to the decision-making process. For example, outcomes associated with important health variables such as mortality in the patient or thrombosis in vascular access were considered critical, and outcomes such as blood flow were pondered less important.</p><p id="sect0165" class="elsevierStylePara elsevierViewall">Identification of the clinical questions, recommendations from the previous version of the Guide and narrative updates of the literature</p><p id="p1375" class="elsevierStylePara elsevierViewall">Throughout the document, recommendations relating to clinical questions and updates are marked with the label “new”. Likewise, recommendations corresponding to clinical questions, which were elaborated on the basis of a systematic and rigorous process of formulating recommendations, are identified with the symbol (•). The contents expressed in the rest of the recommendations come from the previous version of the Guide.</p><p id="sect0170" class="elsevierStylePara elsevierViewall">Structure of the sections of the Guide</p><p id="p1380" class="elsevierStylePara elsevierViewall">The contents of the guide have been structured in areas of knowledge set out below. In order to coordinate the work in each of them, one or two area coordinators were selected along with some experts, depending on the volume and characteristics of the matter to be analysed. The areas studied, along with the respective coordinators and experts, are listed below.</p><p id="p1385" class="elsevierStylePara elsevierViewall">The current professional activity of the authors of this Guide and a brief summary of their trajectory, which accredits them as experts, are shown in <span class="elsevierStyleBold">Annex 1.</span><ul class="elsevierStyleList" id="list0235"><li class="elsevierStyleListItem" id="listi1115"><span class="elsevierStyleLabel">1.</span><p id="p1390" class="elsevierStylePara elsevierViewall">PROCEDURES PRIOR TO VASCULAR ACCESS CREATION Joaquín Vallespín, Fidel Fernández (coordinators), José Ibeas, Teresa Moreno.</p></li><li class="elsevierStyleListItem" id="listi1120"><span class="elsevierStyleLabel">2.</span><p id="p1395" class="elsevierStylePara elsevierViewall">ARTERIOVENOUS FISTULA CREATION Guillermo Moñux (coordinator), Joaquín Vallespín, Natalia de la Fuente, Fidel Fernández, Dolores Arenas.</p></li><li class="elsevierStyleListItem" id="listi1125"><span class="elsevierStyleLabel">3.</span><p id="p1400" class="elsevierStylePara elsevierViewall">ARTERIOVENOUS FISTULA CARE Néstor Fontseré (coordinator), Pilar Caro, Anna Martí, Ramon Roca-Tey, José Ibeas, José Luis del Pozo, Patricia Arribas, María Teresa Martínez.</p></li><li class="elsevierStyleListItem" id="listi1130"><span class="elsevierStyleLabel">4.</span><p id="p1405" class="elsevierStylePara elsevierViewall">MONITORING AND SURVEILLANCE OF ARTERIOVENOUS FISTULA Ramon Roca-Tey (coordinator), José Ibeas, Teresa Moreno, Enrique Gruss, José Luis Merino, Joaquín Vallespín, David Hernán, Patricia Arribas.</p></li><li class="elsevierStyleListItem" id="listi1135"><span class="elsevierStyleLabel">5.</span><p id="p1410" class="elsevierStylePara elsevierViewall">COMPLICATIONS OF ARTERIOVENOUS FISTULA José Ibeas, Joaquín Vallespín (coordinators), Teresa Moreno, José García-Revillo, Milagros Fernández Lucas, José Luis del Pozo, Antonio Giménez, Fidel Fernández, María Teresa Martínez, Ángel Barba.</p></li><li class="elsevierStyleListItem" id="listi1140"><span class="elsevierStyleLabel">6.</span><p id="p1415" class="elsevierStylePara elsevierViewall">CENTRAL VENOUS CATHETERS Manel Ramírez de Arellano, Teresa Moreno (coordinators), José Ibeas, María Dolores Sánchez de la Nieta, José Luis del Pozo, Anna Martí, Ramon Roca-Tey, Patricia Arribas.</p></li><li class="elsevierStyleListItem" id="listi1145"><span class="elsevierStyleLabel">7.</span><p id="p1420" class="elsevierStylePara elsevierViewall">QUALITY INDICATORS Dolores Arenas (coordinator), Enrique Gruss, Ramon Roca-Tey, Cristina López, Pablo Valdés.</p></li></ul></p><p id="p1425" class="elsevierStylePara elsevierViewall">The contents of the sections and their importance have been justified in a “preamble”. Subsequently, the “clinical aspects” develop the clinical contents of each section and bring together the recommendations, in the following sections:<ul class="elsevierStyleList" id="list0240"><li class="elsevierStyleListItem" id="listi1150"><span class="elsevierStyleLabel">•</span><p id="p1430" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Recommendations:</span> each section begins with the compilation of the recommendations, accompanied by a correlative numbering to facilitate identification. As mentioned, the new recommendations are identified with the label “new” and those corresponding to the clinical questions with the symbol (•).</p></li><li class="elsevierStyleListItem" id="listi1155"><span class="elsevierStyleLabel">•</span><p id="p1435" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Rationale:</span> discussion on the relevance and rationale of each clinical section.</p></li><li class="elsevierStyleListItem" id="listi1160"><span class="elsevierStyleLabel">•</span><p id="p1440" class="elsevierStylePara elsevierViewall">The <span class="elsevierStyleItalic">clinical questions</span> are identified in a correlative manner with Roman numerals (I, II, III, etc.). For these questions a formal review process of the scientific literature was followed and recommendations were formulated following the GRADE methodology, as detailed below. The section shows a summary of the results collected in the literature review assessed for each clinical question, with an electronic link to the original versions of the reviews. Then in a section called ‘From evidence to recommendation’, a rationale is laid out for the aspects assessed when formulating recommendations and grading their strength, and how agreement was reached among members of GEMAV, which in some situations was achieved through a formal process of voting. Finally, each clinical question is closed with recommendations derived from the assessment of the literature and the rationale process described.</p></li><li class="elsevierStyleListItem" id="listi1165"><span class="elsevierStyleLabel">•</span><p id="p1445" class="elsevierStylePara elsevierViewall">In the case of the <span class="elsevierStyleItalic">updates</span>, a section has been developed where the clinical content of every aspect of interest is described, followed by a table with the recommendations derived from consensus within GEMAV.</p></li></ul></p><p id="sect0175" class="elsevierStylePara elsevierViewall">Methodology to elaborate recommendations of the clinical questions</p><p id="p1450" class="elsevierStylePara elsevierViewall">As described in the previous section, the update of this Guide was initiated with a process of prioritisation in which the following were identified: <span class="elsevierStyleItalic">a)</span> sections of the original version that would be assumed as its own; <span class="elsevierStyleItalic">b)</span> aspects which GEMAV would update from a narrative review of the literature, and <span class="elsevierStyleItalic">c)</span> clinical questions that would follow a systematic and rigorous process of analysis of the scientific literature. For the development of the different phases, standardised methodological guidelines have been followed, taking as reference the Methodological Manual for elaborating National Health System Guides for Clinical Practice.<a class="elsevierStyleCrossRef" href="#bib1"><span class="elsevierStyleSup">1</span></a></p><p id="p1455" class="elsevierStylePara elsevierViewall">At an initial working meeting two methodologists introduced the clinical members of GEMAV to the theoretical principles used to formulate answerable questions.<a class="elsevierStyleCrossRef" href="#bib2"><span class="elsevierStyleSup">2</span></a> The scope of the contents addressed in the initial version of the Guide was then assessed and these contents were transformed into clinical questions, adding those aspects that GEMAV members considered appropriate. During the meeting and in a subsequent electronic exchange of comments using the Google Drive platform, the most relevant clinical questions that needed to be developed were systematically prioritised, and outcomes of interest for each question were identified.</p><p id="p1460" class="elsevierStylePara elsevierViewall">The clinical questions identify the type of patient, the intervention or diagnostic test to be assessed, the comparisons when necessary and the outcomes of interest (PICO format). Outcomes of interest were defined in order to assess the benefit and unwanted effects of the different procedures and were categorised according to their importance in decision-making.<a class="elsevierStyleCrossRef" href="#bib2"><span class="elsevierStyleSup">2</span></a></p><p id="p1465" class="elsevierStylePara elsevierViewall">Thereafter, exhaustive searches on the clinical questions were made, terminology related to the scope of each question defined, and controlled and natural language identified to recover adequate results from relevant studies in the bibliographic databases. In the case of updates, one methodologist with expertise in the design of exhaustive literature searches designed a search strategy on MEDLINE (accessed through PubMed) and gave the search results to the GEMAV members responsible for each of the sections.</p><p id="p1470" class="elsevierStylePara elsevierViewall">For the prioritised clinical questions an initial search of other Guides, literature reviews and clinical trials was designed to identify those questions with fewer studies to support them and require more exhaustive searches. Subsequently a search strategy on MEDLINE (accessed through PubMed) and The Cochrane Library was designed for each clinical question. In the event that the mentioned study designs were not identified, observational studies were assessed, and if no studies were identified, searches were refined based on networks of citations from relevant studies in ISI Web of Science (Thomson Reuters). The bibliographic search algorithms used in this work can be consulted in the following <a href="https://static.elsevier.es/nefroguiaaveng/00_E_electronico_Algoritmos_INGL.pdf">electronic link</a>. No relevant limits were applied to these algorithms, which were implemented between October 2013 and October 2014. From then up to the date of the edition, the Guide coordinators have carried out a sentinel search task to identify studies that could have a major impact on the recommendations, identifying the last relevant study in April 2016 (clinical question VI).</p><p id="p1475" class="elsevierStylePara elsevierViewall">A structured summary of the results of the most relevant studies was carried out within the scope of each clinical question. For each outcome of interest the quality of evidence was classified according to the standardised criteria defined in the GRADE system. This allows for the establishment of the confidence of the estimators of the effect available in the scientific literature to support the recommendations.<a class="elsevierStyleCrossRef" href="#bib3"><span class="elsevierStyleSup">3</span></a> The quality of evidence can be classified as high, moderate, low and very low. The following factors, which may modify the confidence in the outcomes available in the scientific literature, were considered: risk of bias, consistency between the results of the available studies, the availability of direct evidence, and the precision of the estimators of the effect.<a class="elsevierStyleCrossRef" href="#bib3"><span class="elsevierStyleSup">3</span></a> In the case of observational studies, the following were also taken into account: magnitude of the effect, dose – response relationship, and the potential impact on the results of confounding factors. Each clinical question is accompanied by a summary of findings obtained from the literature review, synthesised at the end of each question in a section called “Summary of evidence”. The summary of findings is accompanied in each case by the classification of the quality of evidence. This process is also contained in summary tables of the results, available for each clinical question in the electronic appendices.</p><p id="p1480" class="elsevierStylePara elsevierViewall">Based on the outcomes of the literature reviews, recommendations were formulated for each clinical question. These may be in favour of or against a particular intervention, and are graded as strong or weak. The strength of recommendations accompanying the questions is reflected by how they are expressed. Hence, strong recommendations are formulated using the expression “we recommend...” or “we recommend not...”, and weak recommendations, or ones where there is more uncertainty, use the expression ‘we suggest...” or “we suggest not...”.</p><p id="p1485" class="elsevierStylePara elsevierViewall">To grade the strength of recommendations, a number of aspects is evaluated. These determine the confidence with which the implementation of the recommendations results in more desirable than unwanted effects for patients.<a class="elsevierStyleCrossRef" href="#bib4"><span class="elsevierStyleSup">4</span></a> The strength of the recommendations is based on a balance between the benefits and risks of interventions, the costs, the quality of evidence, and the values and preferences of patients. Grading the strength of recommendations depends on the more or less favourable and relevant balance among these factors. The recommendations derived from the clinical questions are accompanied by a section called “From evidence to recommendation” in which GEMAV justifies the reasons for supporting a recommendation in a particular way. In exceptional circumstances, where there was insufficient agreement on the clinical questions and the rationale behind the strength of a specific recommendation, a method of consensus by voting was used.<a class="elsevierStyleCrossRef" href="#bib5"><span class="elsevierStyleSup">5</span></a></p><p id="p1490" class="elsevierStylePara elsevierViewall">The recommendations arising from the update sections did not follow a structured process like that previously described. The recommendations corresponding to these sections were formulated by consensus within GEMAV. The contents of the Guide should be updated within a maximum of five years, or sooner if new scientific literature provides relevant data for the current recommendations. In the upgrading process the guidelines of the corresponding methodological handbook will be followed.<a class="elsevierStyleCrossRef" href="#bib1"><span class="elsevierStyleSup">1</span></a></p><p id="sect0180" class="elsevierStylePara elsevierViewall">Perspective for users of this Guide. External review</p><p id="p1495" class="elsevierStylePara elsevierViewall">A draft of the Guide underwent external review by 1 to 3 experts selected by each of the scientific societies. A draft was also submitted to the 2 main renal patient societies in the country, ALCER and ADER. Finally, the final text was posted on the websites of the societies for evaluation by members. All comments and suggestions were answered. Both reviewers’ comments and responses are available via the following <a href="https://static.elsevier.es/nefroguiaaveng/00_E_electronico_Revision.pdf">electronic link</a>.</p></span><span id="s0165" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0185">CONFLICTS OF INTEREST</span><p id="p1500" class="elsevierStylePara elsevierViewall">The expert members of each group were independently proposed by each of the societies without receiving any financial compensation.</p><p id="p1505" class="elsevierStylePara elsevierViewall">All experts from GEMAV signed a form declaring any external relationships of a personal, professional, teaching or work-related nature that could have generated conflicts of interest in relation to the contents of this Guide. A summary of these can be found in <span class="elsevierStyleBold">Annex 2</span>.</p><p id="p1510" class="elsevierStylePara elsevierViewall">All professional societies participated directly in the financing of this Guide. The Spanish Society of Nephrology (S.E.N.), through the Foundation for Assistance to Research and Training in Nephrology (SENEFRO Foundation), received partial and unconditional assistance for the final edition of this Guide from AMGEN, BARD, BAXTER, COVIDIEN, FRESENIUS, HOSPAL, IZASA, MEDCOMP, NOVARTIS and RUBIO. The Spanish Society of Vascular and Interventional Radiology (SERVEI), in addition to its direct financing, also received financial support from BARD. The Spanish Nursing Society of Nephrology (SEDEN) received unconditional assistance from the non-profit Foundation Íñigo Álvarez de Toledo (FRIAT). The other professional societies: Spanish Society of Vascular Surgery (SEACV) and Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) participated directly in the financing of this work.</p></span><span id="s0170" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0190">DEVELOPMENT OF THE GUIDELINE SECTIONS</span><span id="s0175" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">1</span><span class="elsevierStyleSectionTitle" id="sect0195">P<span class="elsevierStyleSmallCaps">rocedures prior to vascular access creation</span></span><p id="p1515" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">CONTENTS</span><ul class="elsevierStyleList" id="list0245"><li class="elsevierStyleListItem" id="listi1170"><span class="elsevierStyleLabel">1.1.</span><p id="p1520" class="elsevierStylePara elsevierViewall">Clinical history</p></li><li class="elsevierStyleListItem" id="listi1175"><span class="elsevierStyleLabel">1.2.</span><p id="p1525" class="elsevierStylePara elsevierViewall">When to create the arteriovenous fistula</p></li><li class="elsevierStyleListItem" id="listi1180"><span class="elsevierStyleLabel">1.3.</span><p id="p1530" class="elsevierStylePara elsevierViewall">Pre-operative assessment</p></li></ul></p><p id="sect0200" class="elsevierStylePara elsevierViewall">Preamble</p><p id="p1535" class="elsevierStylePara elsevierViewall">Nephrology departments must have a clinical care programme for patients with advanced chronic kidney disease (ACKD). This programme should include the provision of detailed information about integrated renal replacement therapy (RRT) systems for patients and family members, and offer the appropriate treatment based on the patient’s clinical characteristics. RRT mode must be finally agreed upon in accordance with the preferences and specific circumstances of each patient.<a class="elsevierStyleCrossRef" href="#bib6"><span class="elsevierStyleSup">6</span></a></p><p id="p1540" class="elsevierStylePara elsevierViewall">The morbidity and mortality of patients on haemodialysis (HD), both before and during RRT, is directly related to vascular access (VA) type. The risk of infectious complications at the start of HD is multiplied by four with central venous catheter (CVC) as compared with native arteriovenous fistula (nAVF) and prosthetic arteriovenous fistula (pAVF). Infections increase sevenfold if CVC is the prevalent VA. Likewise, there is a significant increase in the risk of mortality associated with the use of CVC, especially in the first year of HD.<a class="elsevierStyleCrossRef" href="#bib7"><span class="elsevierStyleSup">7</span></a></p><p id="p1545" class="elsevierStylePara elsevierViewall">Handling the HD patient’s VA is a multidisciplinary task which involves different specialities: nephrology, vascular surgery, interventional radiology, nursing and infectious diseases. The goal is to maintain the highest incidence and prevalence of nAVF.<a class="elsevierStyleCrossRef" href="#bib8"><span class="elsevierStyleSup">8</span></a> But coordination is as important as the work of this multidisciplinary team: it has been shown that efficient management of the team can decrease the prevalence of CVC.<a class="elsevierStyleCrossRef" href="#bib9"><span class="elsevierStyleSup">9</span></a></p><p id="p1550" class="elsevierStylePara elsevierViewall">This first phase, prior to VA creation, is of particular importance, as the patient’s prognosis and illness are, to a great extent, determined by management and the measures undertaken. It is when patients must be informed of the types of RRT available so the most appropriate choice for their circumstances can be made, and strategies to preserve the venous network of upper limbs must be implemented. Likewise, the factors involved in the choice of the ideal access must be determined using oriented medical records and correct pre-operative assessment, and the risk of developing access-associated complications must also be assessed. Finally, the optimal timing for VA creation has to be decided so the need for CVC placement to start HD is minimised, and performing premature interventions should also be avoided.</p><span id="s0185" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">1.1</span><span class="elsevierStyleSectionTitle" id="sect0255a">Clinical history</span><p id="pa0210" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p1555" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0005"></elsevierMultimedia></p><p id="sect0215" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p1575" class="elsevierStylePara elsevierViewall">There are numerous circumstances associated with ACKD patient comorbidity that can influence the correct development of the VA, which requires prior awareness of all factors involved. During the review of the medical record, all the pathological antecedents that may increase the risk of AVF failure in some way or predispose to the appearance of morbidity related to its creation must be considered.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a></p><p id="p1580" class="elsevierStylePara elsevierViewall">Regarding the antecedents related to the risk of VA failure, firstly, there are the comorbidities associated with a bad prognosis of the VA in general (<a class="elsevierStyleCrossRef" href="#t1">Table 1</a>): advanced age, diabetes mellitus, peripheral arterial disease, smoking or obesity; and secondly, it is important to consider factors that will determine the optimal location of the arteriovenous fistula (<a class="elsevierStyleCrossRef" href="#t2">Table 2</a>): previous history of CVC or pacemaker (PM), previous VA, trauma or previous surgery in the arm, shoulder girdle or chest, and previous venous cannulations.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a></p><elsevierMultimedia ident="t1"></elsevierMultimedia><elsevierMultimedia ident="t2"></elsevierMultimedia><p id="p1585" class="elsevierStylePara elsevierViewall">Likewise, a particular underlying pathology, which may be aggravated by the presence of the new AVF, such as heart failure, or prosthetic valves, which may be infected if CVC is used, must be taken into consideration. Moreover, it is important to bear in mind the dominance of the upper limbs to minimise the impact on daily activity, as well as factors like anticoagulant therapy.</p><p id="p1590" class="elsevierStylePara elsevierViewall">Finally, other factors which may affect the election of a given type of AVF should be considered (<a class="elsevierStyleCrossRef" href="#t3">Table 3</a>). These include life expectancy associated with the patient’s comorbidity, which may advise a more conservative approach by using a CVC, or patients eligible for transplant from a living donor, where a CVC may also be highly recommended.</p><elsevierMultimedia ident="t3"></elsevierMultimedia><p id="p1595" class="elsevierStylePara elsevierViewall">The high prevalence of ischaemic heart disease in HD patients in our setting<a class="elsevierStyleCrossRef" href="#bib11"><span class="elsevierStyleSup">11</span></a> means bearing in mind that both the entire systemic situation and vascular tree of patients undergoing HD is significantly worse than the general population’s. Therefore, strategies must be established to choose the best territory in which to create the VA, taking into consideration the future of the VA and, of course, the patient.</p><p id="p1600" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question I Does the preservation of the venous network prevent complications/facilitate the creation of the arteriovenous fistula?</span></p><p id="p1605" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question I in <a href="https://static.elsevier.es/nefroguiaaveng/1_PCI_Preservacion_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0005"></elsevierMultimedia></p><p id="pa0220" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p1610" class="elsevierStylePara elsevierViewall">In order to create an AVF, a suitable vascular bed must be available, both arterial and venous, and the anatomical and functional integrity of both beds is required. Given its deeper location, the arterial bed mainly depends on the patient’s comorbidity and is less exposed to external forms of aggression than the venous bed. As the superficial venous bed may deteriorate and this may have repercussions on the success of the future AVF, the need for measures of protection has to be addressed. The absence of these measures explains why many patients do not have a mature nAVF when they need it to start HD.</p><p id="p1615" class="elsevierStylePara elsevierViewall">The superficial veins of the upper limbs are the most common venous access point in the hospital setting, given the ease of access and safety of the technique. In patients with multiple hospital admissions, this is precisely what causes the venous network to become impaired, as repeated and multiple cannulations produce trauma and the administration of medication provokes an inflammatory response at the vein level (chemical phlebitis).</p><p id="p1620" class="elsevierStylePara elsevierViewall">Despite this, there is no available evidence in the form of observational studies or randomised controlled clinical trials which answers the question of whether the preservation of the venous network prevents complications or facilitates the creation of the VA. Thus, the recommendations made by both clinical practice guidelines (CPG) and the literature are based on the opinions of different groups of experts.<a class="elsevierStyleCrossRef" href="#bib12"><span class="elsevierStyleSup">12</span></a></p><p id="p1625" class="elsevierStylePara elsevierViewall">Most of the CPG in use today,<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,13-15</span></a> and the literature,<a class="elsevierStyleCrossRef" href="#bib16"><span class="elsevierStyleSup">16</span></a> recommend an aggressive policy aimed at preserving the venous network in HD candidates, through a series of measures prepared to this end (<a class="elsevierStyleCrossRef" href="#t4">Table 4</a>) and summarised in 2 directives:</p><elsevierMultimedia ident="t4"></elsevierMultimedia><p id="p1630" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0255"><li class="elsevierStyleListItem" id="listi1190"><span class="elsevierStyleLabel">1.</span><p id="p1635" class="elsevierStylePara elsevierViewall">Patient education related to the importance and the measures required to preserve veins in the upper limb.</p></li><li class="elsevierStyleListItem" id="listi1195"><span class="elsevierStyleLabel">2.</span><p id="p1640" class="elsevierStylePara elsevierViewall">Information and commitment on the importance of vein preservation among healthcare professionals.</p></li></ul></p><p id="pa0225" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p1645" class="elsevierStylePara elsevierViewall">There is no quality scientific evidence to back up an evidence-based recommendation. Therefore, based on good clinical practice criteria, after voting on the recommendation, GEMAV unanimously agreed to formulate a strong recommendation in favour of a strict preservation strategy to preserve the vascular bed, given the clear relationship between its preservation and the viability of the future VA.</p><p id="p1650" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0010"></elsevierMultimedia></p><p id="pa0235" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Informing the patient about vascular access: when and how should it begin?</span></p><p id="p1660" class="elsevierStylePara elsevierViewall">Information on HD should include details relating to the VA, the need for its creation, its importance, care and complications. This information must be reinforced in subsequent ACKD check-ups and should be continued when the VA has been created and during the HD programme.<a class="elsevierStyleCrossRef" href="#bib17"><span class="elsevierStyleSup">17</span></a> If a patient has to start HD urgently, he must be informed that a VA is required when this situation is detected. This information will be completed in accordance with their evolution and needs.</p><p id="pa0240" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Time to start giving information about renal replacement therapy</span></p><p id="p1665" class="elsevierStylePara elsevierViewall">The optimal time to start RRT requires adequate planning. There is an increased risk of mortality associated with inadequate nephrological care in pre-dialysis and to the use of a CVC as the first VA.<a class="elsevierStyleCrossRef" href="#bib18"><span class="elsevierStyleSup">18</span></a> A lack of organisation at this stage causes greater incidence of starting HD through a CVC with its associated morbidity. If the patient is referred to the nephrologist with enough time, he will receive adequate treatment and preparation from the pre-dialysis phase, as well as information on different RRT techniques: HD, peritoneal dialysis (PD) and kidney transplant (KT). In the Sociedad Española de Nefrología (Spanish Society of Nephrology) agreement document for managing ACKD, the preparation of patients for RRT is based on estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73 m<span class="elsevierStyleSup">2</span>, if applicable. At this time, in addition to the information about different RRT techniques, the patient should receive VA-related information.<a class="elsevierStyleCrossRef" href="#bib19"><span class="elsevierStyleSup">19</span></a> This appropriate referral implies a lower incidence of complications, especially infections and cardiovascular complications.</p><p id="p1670" class="elsevierStylePara elsevierViewall">RRT should be considered when GFR is < 15 mL/min/1.73 m<span class="elsevierStyleSup">2</span> and, in general, dialysis is initiated with an eGFR between 8 and 10 mL/min/1.73 m<span class="elsevierStyleSup">2</span>, the limit being around 6 mL/min/1.73 m<span class="elsevierStyleSup">2</span>.<a class="elsevierStyleCrossRef" href="#bib19"><span class="elsevierStyleSup">19</span></a> Expectation of entry into HD is related to the time when detailed information about VA preparation has to be given to the patient. However, the nephrologist’s ability to predict the dialysis commencement is not totally precise and there is a tendency to underestimate the patient’s renal function, which means that HD may begin later than the time estimated.<a class="elsevierStyleCrossRef" href="#bib20"><span class="elsevierStyleSup">20</span></a> This delay is more common in elderly patients, primarily over 85. A number of unnecessary surgical procedures has been shown in this patient group, as they may die before starting dialysis.<a class="elsevierStyleCrossRef" href="#bib21"><span class="elsevierStyleSup">21</span></a> Thus, eGFR on its own may not be sufficient to decide on timing for VA creation.</p><p id="p1675" class="elsevierStylePara elsevierViewall">Informing the patient about ACKD and the various RRT options needs to be coordinated with VA creation. The very creation of the VA may determine the decision to choose HD to the detriment of other techniques, like PD or even conservative management. A systematic review of the timing of the decision-making process of patients and caregivers on RRT<a class="elsevierStyleCrossRef" href="#bib22"><span class="elsevierStyleSup">22</span></a> shows that, from the patient’s perspective, waiting until the final phase of ACKD may not be appropriate. This has important implications, as an unwanted surgical procedure may be performed or the patients perceive that a decision has been taken for them regarding RRT, without their participation. Once the AVF has been created, the patient tends to reject another type of RRT, due to the preference for maintaining the <span class="elsevierStyleItalic">status quo</span>, so this type of treatment is not changed. Therefore, information related to VA creation should be given after the patient has been informed of the various options for RRT and has specifically chosen HD.<a class="elsevierStyleCrossRef" href="#bib22"><span class="elsevierStyleSup">22</span></a></p><p id="pa0245" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Content and manner of providing the information</span></p><p id="p1680" class="elsevierStylePara elsevierViewall">At the time of providing information to the patient about the VA, it should be borne in mind that from their perspective, in addition to renal disease and RRT options, the VA is among the main concerns.<a class="elsevierStyleCrossRef" href="#bib23"><span class="elsevierStyleSup">23</span></a> For the patient who needs one, living with an AVF is an important issue as they depend on it and have to provide the necessary care to maintain the access viable. This may generate the feeling of vulnerability, dependence, distrust and it may even become a stigma. Therefore, informing the patient about the need for a VA may generate a pronounced emotional response that should be taken into account.<a class="elsevierStyleCrossRef" href="#bib24"><span class="elsevierStyleSup">24</span></a> Indeed, one of the largest barriers to the creation of the AVF is the actual patient’s refusal.<a class="elsevierStyleCrossRef" href="#bib25"><span class="elsevierStyleSup">25</span></a></p><p id="p1685" class="elsevierStylePara elsevierViewall">Because of all of this, the nephrologist must show particular sensitivity when informing the patient. There are studies which highlight that rejection of AVF creation may be explained by a previous negative experience and the information they receive from other patients and carers may not be well expressed. In addition, it is possible that the information has not been adequately assimilated as it is given at the same time as all the other details relating to entry into HD. Likewise, it is worth pointing out that patients are not usually aware that the use of CVC for HD carries a risk of mortality with it.<a class="elsevierStyleCrossRef" href="#bib26"><span class="elsevierStyleSup">26</span></a> Programmes aimed at helping patients decide which RRT technique to choose mean that patients opting for HD have a significantly higher likelihood of beginning treatment with an AVF.<a class="elsevierStyleCrossRef" href="#bib27"><span class="elsevierStyleSup">27</span></a> This is accomplished by motivating both patient and family from the creation phase to subsequent care. Moreover, the participation of other patients in the orientation of new patients can be of benefit. It has been shown that more patients with AVF recommend this VA than those who use a tunnelled CVC.<a class="elsevierStyleCrossRef" href="#bib28"><span class="elsevierStyleSup">28</span></a></p><p id="p1690" class="elsevierStylePara elsevierViewall">Finally, when providing the patient with all the necessary information on VA, as well as the different forms of RRT, the nephrologist should give information about the different types of definitive VA and their characteristics (nAVF, pAVF and tunnelled CVC). The advantages and drawbacks of each one should be explained, highlighting the fact that the tunnelled CVC is not an acceptable alternative to AVF, if the latter is possible, given its high association with morbidity and mortality (section 6). The risks of tunnelled CVC should be systematically explained, making it clear that CVC is only indicated as a temporary measure pending AVF creation or when it is impossible to create one.</p><p id="pa0250" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Ethical-legal considerations</span></p><p id="p1695" class="elsevierStylePara elsevierViewall">Some literature reviews propose that there may be legal implications, in addition to ethical issues, if severe complications of tunnelled CVC arise in a patient who may be eligible for an AVF. In this context, in the same way as the patient signs a consent form before the surgical procedure, some groups suggest that this should be done before inserting the tunnelled CVC, and all the risks agreed to.<a class="elsevierStyleCrossRef" href="#bib29"><span class="elsevierStyleSup">29</span></a></p></span><span id="s0235" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">1.2</span><span class="elsevierStyleSectionTitle" id="sect0255">When to create the arteriovenous fistula</span><p id="pa0260" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p1700" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0015"></elsevierMultimedia></p><p id="p1730" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question II In patients with chronic kidney disease, what are the demographic, clinical and analytical parameters in order to determine when the arteriovenous fistula (either native or prosthetic) should be created?</span></p><p id="p1735" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical QUESTION II in <a href="https://static.elsevier.es/nefroguiaaveng/2_PCII_Determinantes_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0010"></elsevierMultimedia></p><p id="pa0265" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p1740" class="elsevierStylePara elsevierViewall">For the patient with ACKD it is very important to have a functional AVF when starting HD to avoid the use of CVC and its associated comorbidity. This requires careful planning of its creation.</p><p id="p1745" class="elsevierStylePara elsevierViewall">There are no clinical trials, only observational studies designed to determine when a definitive VA should be created. Recommendations in clinical guidelines are based on this type of studies and experts’ opinions and the proximity of HD is established according to levels in the decline in renal function. They highlight the importance of using these parameters adjusted for age, gender and body surface area. There are 6 CPG that assess the appropriate timing for VA creation in the literature review.<a class="elsevierStyleCrossRefs" href="#bib6"><span class="elsevierStyleSup">6,10,13-15,30</span></a></p><p id="pa0270" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Clinical practice guidelines recommendations</span></p><p id="p1750" class="elsevierStylePara elsevierViewall">The previous edition of this guide, as well as the Japanese and Canadian guidelines, consider that the VA should be created when eGFR is less than 20 mL/min/1.73 m<span class="elsevierStyleSup">2</span>. KDOQI (Kidney Disease Outcomes Quality Initiative), European and British guidelines recommend VA planning when eGFR falls below 30 mL/min/1.73 m<span class="elsevierStyleSup">2</span>. The recommended minimum time elapsed between the creation of VA and the beginning of dialysis varies. The Spanish guidelines recommend 4 to 6 months; KDOQI and European guidelines, between 2 and 3 months; British guidelines, between 3 months to one year and Japanese guidelines, between 2 and 4 weeks. They all recommend assessing the earliest possible VA creation when ACKD evolves rapidly, there is VA failure and in patients with a CVC. They all agree that as the pAVF takes around 3 weeks to mature, it has to be created at least 3 weeks before initiation of HD. Finally, CVC does not require specific preparation, except that needed for the placement procedure itself, as it is for immediate use.</p><p id="pa0275" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Available evidence</span></p><p id="p1755" class="elsevierStylePara elsevierViewall">The latest review of clinical guidelines still fails to bring to light clinical trials, only observational studies. These publications emphasise the need for early referral to the nephrologist to guarantee adequate information on the various aspects of RRT and the possibility of starting HD with an AVF. Different observational studies made in recent years present data on how influential and important the time taken to refer the patient to the nephrologist and surgeon is regarding the appropriate moment to construct the VA.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,13-15,30</span></a></p><p id="p1760" class="elsevierStylePara elsevierViewall">These observational studies show there is a direct relationship between the length of time in the care of a nephrologist and the significantly higher number of AVF created prior to the initiation of HD. This time period ranges from 4<a class="elsevierStyleCrossRefs" href="#bib31"><span class="elsevierStyleSup">31,32</span></a> to 12 months<a class="elsevierStyleCrossRefs" href="#bib33"><span class="elsevierStyleSup">33,34</span></a>, passing through 6 months.<a class="elsevierStyleCrossRefs" href="#bib35"><span class="elsevierStyleSup">35,36</span></a></p><p id="p1765" class="elsevierStylePara elsevierViewall">However, there have been changes in the latest recommendations for starting RRT. In recent years these criteria have evolved from higher levels of eGFR, > 15 mL/min, to much lower values approaching 5 mL/min. After the publication of clinical trials showing not only the lack of benefit, but even a higher morbidity with the early initiation of dialysis,<a class="elsevierStyleCrossRefs" href="#bib37"><span class="elsevierStyleSup">37-39</span></a> the KDIGO guidelines<a class="elsevierStyleCrossRef" href="#bib40"><span class="elsevierStyleSup">40</span></a> (Kidney Disease Improving Global Outcomes) suggest that HD should be started when clinical symptoms of terminal CRF (chronic renal failure) are visible, seen with eGFR ranges between 5 and 10 mL/min/1.73 m<span class="elsevierStyleSup">2</span>. In the agreement document for managing ACKD produced by the Sociedad Española de Nefrología (Spanish Society of Nephrology), RRT is considered when GFR is < 15 mL/min/1.73 m<span class="elsevierStyleSup">2</span>, although an earlier start may be considered if there are symptoms of uraemia, hyperhydration, hypertension difficult to control, or a worsening nutritional status. In general, dialysis is initiated when GFR is between 8 and 10 mL/min/1.73 m<span class="elsevierStyleSup">2</span> and would be mandatory if eGFR was < 6 mL/min/1.73 m<span class="elsevierStyleSup">2</span>, even in the absence of uraemic symptoms.<a class="elsevierStyleCrossRef" href="#bib19"><span class="elsevierStyleSup">19</span></a> However, in patients at risk, an early start for HD should be considered on a case-by-case basis.</p><p id="pa0280" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p1770" class="elsevierStylePara elsevierViewall">In the absence of clinical trials or observational studies addressing criteria related to timing for VA creation and clinical trials addressed to HD commencement, GEMAV put this recommendation to the vote. It was thought appropriate to consider 2 options. For the first option<span class="elsevierStyleItalic">—when eGFR drops below 15 mL/min and/or estimation of entry at 6 months—there were 15 votes, and for the second option < 20 mL/min and/or estimation of entry at 6 months there were 2 in favour and 3 abstentions. Therefore, considering that three quarters were clearly in favour of one of the options, the working group decided to formulate as a strong recommendation</span> that the creation of the definitive VA should be requested when eGFR ≤ 15 mL/min, or with an estimation of entry into dialysis lower than 6 months.</p><p id="p1775" class="elsevierStylePara elsevierViewall">Patients with rapid CKD progression, with a non-matured AVF or a non-tunnelled CVC should be given priority.</p><p id="p1780" class="elsevierStylePara elsevierViewall">As pAVF take between 3 to 6 weeks to mature (except in those with immediate needling), we suggest this be the time period required for creation prior to the planned HD commencement (section 3).</p><p id="p1785" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0020"></elsevierMultimedia></p></span><span id="s0270" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">1.3</span><span class="elsevierStyleSectionTitle" id="sect0290">Pre-operative assessment</span><p id="s0295" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p1810" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0025"></elsevierMultimedia></p><p id="sect0300" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p1840" class="elsevierStylePara elsevierViewall">An important factor to consider in choosing the ideal VA location is the influence that this location will have on subsequent accesses. The surgeon must plan a long-term strategy for possible future access locations. Despite the absence of randomised clinical trials (RCTs) on the order to be followed in access creation, there is general consensus among different groups<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,23,24</span></a> that access location should be as distal as possible, thereby allowing the creation of further VA in the same limb in the future. The VA should preferably be created in the non-dominant limb to maintain patient’s comfort. Furthermore, the creation of nAVF with preference to pAVF is recommended, although individual conditions may suggest a different approach.</p><p id="p1845" class="elsevierStylePara elsevierViewall">Patient assessment must include a detailed clinical history to identify risk factors for early failure and lack of maturation of the nAVF. It is also necessary to perform a physical examination to detect limitations in joints, motor or sensory deficits, thickness of the skin and subcutaneous fat, limb oedema, presence of collateral circulation in the arm or shoulder, scars or indurated veins.</p><p id="p1850" class="elsevierStylePara elsevierViewall">Physical examination must include pulse palpation to assess presence and quality, including the Allen test, measurement of blood pressure in both upper limbs and the examination of the venous system by palpation with and without tourniquet<a class="elsevierStyleCrossRef" href="#bib41"><span class="elsevierStyleSup">41</span></a> (<a class="elsevierStyleCrossRef" href="#t5">Table 5</a>).</p><elsevierMultimedia ident="t5"></elsevierMultimedia><p id="p1855" class="elsevierStylePara elsevierViewall">Complementary examinations should be performed as a necessary and indispensable aid to define what strategy to follow when deciding which order to choose for VA creation.</p><p id="p1860" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question III What criteria are required for arteriovenous fistula planning (based on different types of fistula)?</span></p><p id="p1865" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question III in <a href="https://static.elsevier.es/nefroguiaaveng/3_PCIII_Criterios_previos_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0015"></elsevierMultimedia></p><p id="s0305" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="s0310" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">1.3.1 The role of Doppler ultrasound in arteriovenous fistula planning</span></p><p id="p1870" class="elsevierStylePara elsevierViewall">Since its incorporation into daily clinical practice, different publications have attempted to determine the usefulness of Doppler ultrasound (DU) in the pre-operative assessment of VA candidates.</p><p id="p1875" class="elsevierStylePara elsevierViewall">According to a review by Ferring et al.,<a class="elsevierStyleCrossRef" href="#bib42"><span class="elsevierStyleSup">42</span></a> in order to assess a suitable place for AVF surgery, physical examination must initially be performed in all patients, reserving pre-operative (DU) for certain cases: patients with poor physical exam (obese, no pulses, multiple previous surgeries on the limb), patients with possible arterial disease (elderly, diabetes, cardiovascular diseases) or in patients with possible venous disease (previous cannulation).</p><p id="p1880" class="elsevierStylePara elsevierViewall">Later, Wong et al.<a class="elsevierStyleCrossRef" href="#bib43"><span class="elsevierStyleSup">43</span></a> published a systematic review of the literature, based on the three RCTs published to date on the systematic use of pre-operative ultrasound mapping.<a class="elsevierStyleCrossRefs" href="#bib44"><span class="elsevierStyleSup">44-46</span></a> Two of the articles showed the systematic use of pre-operative DU was significantly beneficial, while in the third no benefit in terms of effective access use was shown to carry out HD. The authors conclude that the review suggests positive results in patients who underwent ultrasound mapping prior to VA creation, which may improve long-term patency rates.</p><p id="p1885" class="elsevierStylePara elsevierViewall">Besides the reviews assessed while preparing the recommendations in this section, other more recently published systematic reviews have shown non-uniform results. Although a meta-analysis of five clinical trials suggests that the routine preoperative use of DU is beneficial<a class="elsevierStyleCrossRef" href="#bib47"><span class="elsevierStyleSup">47</span></a> in line with the publication by Wong et al.,<a class="elsevierStyleCrossRef" href="#bib43"><span class="elsevierStyleSup">43</span></a> a systematic Cochrane review<a class="elsevierStyleCrossRef" href="#bib48"><span class="elsevierStyleSup">48</span></a> emphasises that using preoperative imaging does not improve AVF outcome and that new studies with a better design are needed to confirm the result.</p><p id="s0315" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">1.3.2 Vessel diameter as a criterion for arteriovenous fistula planning</span></p><p id="p1890" class="elsevierStylePara elsevierViewall">Several studies have tried to determine the ultrasound parameters that may predict AVF outcome.<a class="elsevierStyleCrossRefs" href="#bib16"><span class="elsevierStyleSup">16,42,49-51</span></a> Some degree of correlation has been found between the following ultrasound parameters and AVF function: diameter of the artery, presence of arteriosclerosis (measurement of intima/media thickness), flow characteristics at artery level (resistance index after reactive hyperaemia, peak systolic velocity), vein diameter and venous compliance.<a class="elsevierStyleCrossRef" href="#bib52"><span class="elsevierStyleSup">52</span></a></p><p id="p1895" class="elsevierStylePara elsevierViewall">Among these, the parameter most widely documented and in which a higher level of evidence has been found as predictor of AVF function is the inner diameter of artery and vein measured by DU.<a class="elsevierStyleCrossRefs" href="#bib53"><span class="elsevierStyleSup">53-59</span></a></p><p id="p1900" class="elsevierStylePara elsevierViewall">Several articles have published series trying to document the minimum diameter of the artery and the vein associated with good AVF prognosis (<a class="elsevierStyleCrossRef" href="#t6">Tables 6</a> and <a class="elsevierStyleCrossRef" href="#t7">7</a>).<a class="elsevierStyleCrossRefs" href="#bib49"><span class="elsevierStyleSup">49,53-58,60-63</span></a></p><elsevierMultimedia ident="t6"></elsevierMultimedia><elsevierMultimedia ident="t7"></elsevierMultimedia><p id="s0320" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">1.3.3 Patient comorbidity as a criterion for arteriovenous fistula planning</span></p><p id="p1905" class="elsevierStylePara elsevierViewall">There is considerable evidence of the influence of underlying pathology, comorbidities and the patient’s own parameters on the prognosis of the VA to be created.<a class="elsevierStyleCrossRefs" href="#bib42"><span class="elsevierStyleSup">42,49,59</span></a></p><p id="s0325" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Advanced age</span></p><p id="p1910" class="elsevierStylePara elsevierViewall">The available evidence suggests VA prognosis is considerably worse in older patients.<a class="elsevierStyleCrossRef" href="#bib64"><span class="elsevierStyleSup">64</span></a> The authors suggest that distal AVF should be avoided in the elderly.</p><p id="s0330" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Female gender</span></p><p id="p1915" class="elsevierStylePara elsevierViewall">Contrary to general opinion and to some authors,<a class="elsevierStyleCrossRef" href="#bib65"><span class="elsevierStyleSup">65</span></a> the best available evidence does not demonstrate that female gender is a risk factor for AVF prognosis<a class="elsevierStyleCrossRef" href="#bib66"><span class="elsevierStyleSup">66</span></a>; this is attributed to the small diameter of vessels found in female patients.</p><p id="s0335" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Diabetes</span></p><p id="p1920" class="elsevierStylePara elsevierViewall">Different prospective series show the negative effect of diabetes on AVF prognosis, having less impact in proximal AVF.<a class="elsevierStyleCrossRefs" href="#bib67"><span class="elsevierStyleSup">67,68</span></a></p><p id="s0340" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Hypotension</span></p><p id="p1925" class="elsevierStylePara elsevierViewall">Evidence from prospective series suggests a negative effect of sustained hypotension in the prognosis of AVF due to an increased risk of access thrombosis.<a class="elsevierStyleCrossRefs" href="#bib69"><span class="elsevierStyleSup">69,70</span></a></p><p id="s0345" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Smoking</span></p><p id="p1930" class="elsevierStylePara elsevierViewall">Smoking has been associated with a worse AVF prognosis in published prospective studies.<a class="elsevierStyleCrossRefs" href="#bib71"><span class="elsevierStyleSup">71-73</span></a></p><p id="s0350" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Obesity</span></p><p id="p1935" class="elsevierStylePara elsevierViewall">While a worse prognosis in obese patients with Body Mass Index (BMI) > 30 has not been proved, the evidence available suggests that obesity with a BMI > 35 is a risk factor in AVF prognosis.<a class="elsevierStyleCrossRef" href="#bib74"><span class="elsevierStyleSup">74</span></a></p><p id="s0355" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Other factors</span></p><p id="p1940" class="elsevierStylePara elsevierViewall">Several studies have tried to determine the influence of other factors in access prognosis. These factors are considered to have a minor impact, either due to the lack of clinical evidence (use of systemic heparin during surgery, type of anastomosis, suture technique), or because despite the importance they have shown in limited studies, there is a need for further studies to demonstrate their usefulness in clinical practice (intra-operative heparin dose, use of transdermal nitrates, range of distribution of red blood cells).<a class="elsevierStyleCrossRefs" href="#bib42"><span class="elsevierStyleSup">42,49,59,75-77</span></a></p><p id="s0360" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">1.3.4 Models/rules to predict arteriovenous fistula failure</span></p><p id="p1945" class="elsevierStylePara elsevierViewall">Using data from 422 patients, Lok et al.<a class="elsevierStyleCrossRef" href="#bib78"><span class="elsevierStyleSup">78</span></a> developed a rule for predicting the risk of AVF failure. They found that poor prognosis factors include age ≥ 65 years, peripheral vascular disease and coronary heart disease, while being Caucasian was a good prognostic factor. These data were used to elaborate a classification of risk of AVF failure.</p><p id="p1950" class="elsevierStylePara elsevierViewall">Despite the acceptable predictive capability shown in this study, there have been no subsequent studies to confirm its clinical usefulness; in fact, it has been questioned by other studies.<a class="elsevierStyleCrossRef" href="#bib79"><span class="elsevierStyleSup">79</span></a></p><p id="s0365" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">1.3.5 Determining factors for the success of a prosthetic arteriovenous fistula</span></p><p id="p1955" class="elsevierStylePara elsevierViewall">Rosas et al.<a class="elsevierStyleCrossRef" href="#bib80"><span class="elsevierStyleSup">80</span></a> found some factors of poor prognosis: presence of vascular claudication, number of previously implanted grafts, dialysis dependence at the time of surgery and the use of vascular clamps during the procedure. On the other hand, the use of the brachial artery and the axillary vein, acute-angle anastomosis and grafts of a specific brand (Gore-Tex<span class="elsevierStyleSup">®</span>) were factors suggesting favourable prognosis.</p><p id="s0370" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p1960" class="elsevierStylePara elsevierViewall">The introduction of portable DU in the pre-operative examination of AVF candidates has undoubtedly helped professionals to decide when to create an AVF.</p><p id="p1965" class="elsevierStylePara elsevierViewall">DU has proved to be an essential tool in those units where it is available because it provides a reliable image plus haemodynamic information on the vessels in the pre-operative evaluation.</p><p id="p1970" class="elsevierStylePara elsevierViewall">The progressive increase in the age of patients candidates to arteriovenous fistula creation, with the resulting increase in associated comorbidities, as well as the high prevalence of obesity, often make it difficult to carry out a complete physical examination in these patients, so essential information required to create the AVF is missing (<a class="elsevierStyleCrossRef" href="#t5">Table 5</a>). In these cases, both clinical practice and the available evidence unanimously recommend the use of DU as the imaging test of choice, before requesting other radiological examinations (phlebography, magnetic resonance imaging).<a class="elsevierStyleCrossRefs" href="#bib16"><span class="elsevierStyleSup">16,42,81,82</span></a></p><p id="p1975" class="elsevierStylePara elsevierViewall">However, there is no unanimity in the available literature regarding DU use in patients with a favourable physical examination. There are studies documenting that routine pre-operative ultrasound increases VA patency.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,44,46,47,49,65,83</span></a> However, in most of these reports the benefit does not reach the level of significance needed to make a recommendation about the generalised use of DU.<a class="elsevierStyleCrossRefs" href="#bib42"><span class="elsevierStyleSup">42,43,45</span></a> Thus, in fact, these authors do not recommend the routine use of DU because it has no proven benefits, both because of the delay other tests may cause and because of the possibility of ruling out AVF creation in vessels with borderline diameter. In contrast, the reasons given in favour of its routine use include the reduction in the number of unnecessary surgical interventions due to low vessel size, no creation of AVF with poor venous drainage, the detection of subclinical arterial disease and the better use of the available vascular bed.</p><p id="p1980" class="elsevierStylePara elsevierViewall">This last point, together with the trend described in the literature, was the main argument which led GEMAV to unanimously decide to recommend the systematic use of DU in the pre-operative examination of all candidates for AVF. It allows physicians to non-invasively obtain a map of a patient’s entire venous capital during the pre-operative evaluation, thus allowing them to decide on the location of the VA bearing in mind the real options for future accesses.</p><p id="p1985" class="elsevierStylePara elsevierViewall">During this examination, the diameter and quality of the arterial wall, as well as the anatomy and patency of the limb’s superficial and deep venous system, must be assessed by creating a map of the aforementioned venous capital of the patient.<a class="elsevierStyleCrossRefs" href="#bib16"><span class="elsevierStyleSup">16,42,52,81,82,84</span></a></p><p id="p1990" class="elsevierStylePara elsevierViewall">Current evidence does not allow for a recommendation regarding the minimum diameter of vessels to be used for the AVF; the decision whether the vein or artery should be considered apt for AVF creation must be taken in accordance with diameter – basically, the bigger the diameter, the better the prognosis – and with the available VA alternatives. In any case, in accordance with published articles, arteries < 1.5 mm and veins < 1.6 mm in diameter, following placement of a proximal tourniquet, are considered of dubious feasibility.</p><p id="p1995" class="elsevierStylePara elsevierViewall">Finally, although the prognostic factors in each case should be taken into consideration, it is suggested that the VA location not be decided by taking into account any isolated clinical or socio-demographic factor, or any specific multivariate risk prediction model. It is recommended that the decision be based on a global assessment of each patient’s medical history, physical vascular examination, pre-operative DU and on their individual preferences.</p><p id="p2000" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0030"></elsevierMultimedia></p><p id="p2015" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question IV What risk factors have been shown to influence the development of limb ischaemia after arteriovenous fistula creation?</span></p><p id="p2020" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question IV in <a href="https://static.elsevier.es/nefroguiaaveng/4_PCIV_Riesgo_isquemia_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0020"></elsevierMultimedia></p><p id="s0380" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p2025" class="elsevierStylePara elsevierViewall">AVF creation in an upper limb determines significant changes in the limb’s haemodynamics. The direct communication created between the arterial and venous system, which avoids passing through the capillary bed, causes a <span class="elsevierStyleItalic">shunt</span> with a large flow rate that may compromise the vascularisation of the arterial bed distal to the access. In many cases of ischaemia, the situation is aggravated by the presence of previous arterial disease in the proximal or distal territories.</p><p id="p2030" class="elsevierStylePara elsevierViewall">This can lead to the development of distal hypoperfusion ischaemic syndrome in the limb, known as “fistula steal”. This is an uncommon complication after the access creation, with an incidence ranging between 1% and 20%,<a class="elsevierStyleCrossRefs" href="#bib85"><span class="elsevierStyleSup">85-87b</span></a> but it may have serious consequences and could lead to important tissue loss and amputation.</p><p id="p2035" class="elsevierStylePara elsevierViewall">That is why various authors have tried to identify epidemiological and clinical factors which may be associated with the development of this syndrome so that patients at risk of ischaemia following VA creation can be detected.</p><p id="s0385" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Type of arteriovenous fistula</span></p><p id="p2040" class="elsevierStylePara elsevierViewall">The main prognostic factor, accepted by all authors, is the type of VA.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,85-89</span></a> Accesses with increased risk of ischaemia are nAVF created in the brachial artery (brachiocephalic, brachiobasilic and brachioperforating); 10-25% of patients with these VA present clinically relevant ischaemia. This percentage drops to 4.3-6% in pAVF, while nAVF created in the forearm and wrist are those with the lowest risk of ischaemia (1-1.8%).<a class="elsevierStyleCrossRef" href="#bib87"><span class="elsevierStyleSup">87</span></a> These authors associate this difference with the greater flow present in proximal AVF and the presence of collateral circulation through the ulnar artery, which decreases the severity of ischaemia in AVF in the wrist and forearm.</p><p id="s0390" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Peripheral arterial disease</span></p><p id="p2045" class="elsevierStylePara elsevierViewall">The great prevalence of cardiovascular risk factors in the HD population implies a high incidence of patients with symptomatic peripheral arterial disease. Although this disease usually affects the upper limbs less than other territories, the presence of haemodynamically significant lesions has been reported in up to 62-100% of patients with distal hypoperfusion syndrome.<a class="elsevierStyleCrossRef" href="#bib86"><span class="elsevierStyleSup">86</span></a> The prior existence of these lesions, both in the proximal artery and distal trunk territories, is an important predisposing factor to the onset of ischaemic symptoms in the limb upon creation of the VA.<a class="elsevierStyleCrossRefs" href="#bib86"><span class="elsevierStyleSup">86-88,90</span></a></p><p id="s0395" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Diabetes mellitus</span></p><p id="p2050" class="elsevierStylePara elsevierViewall">The presence of DM is, for all authors, one of the main risk factors for developing ischaemia.<a class="elsevierStyleCrossRefs" href="#bib86"><span class="elsevierStyleSup">86-88,90,91</span></a> Observational studies show that the presence of diabetes is a predictor for developing ischaemia.<a class="elsevierStyleCrossRefs" href="#bib85"><span class="elsevierStyleSup">85,92</span></a> The effect on the distal arterial bed determines the lack of vasodilation capacity in that territory and the appearance of distal tissue hypoperfusion.</p><p id="s0400" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Advanced age</span></p><p id="p2055" class="elsevierStylePara elsevierViewall">Advanced age, which is considered to be > 60 years, is widely accepted as a predisposing factor in the onset of ischaemia, due to a mechanism similar to the one in diabetic patients.<a class="elsevierStyleCrossRefs" href="#bib87"><span class="elsevierStyleSup">87,88,90,91</span></a></p><p id="s0405" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Female gender</span></p><p id="p2060" class="elsevierStylePara elsevierViewall">Female gender is unanimously considered in the literature to be an isolated risk factor for presenting ischaemia.<a class="elsevierStyleCrossRefs" href="#bib85"><span class="elsevierStyleSup">85,87,88,90,91</span></a> The authors do not deter mine the mechanisms involved, although hormonal and vessel size factors are suggested.</p><p id="s0410" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Other factors</span></p><p id="p2065" class="elsevierStylePara elsevierViewall">Different publications describe the influence of other factors on the development of ischaemia, such as time on dialysis,<a class="elsevierStyleCrossRef" href="#bib73"><span class="elsevierStyleSup">73</span></a> end-to-side anastomoses,<a class="elsevierStyleCrossRef" href="#bib85"><span class="elsevierStyleSup">85</span></a> previous VA in the same limb<a class="elsevierStyleCrossRefs" href="#bib87"><span class="elsevierStyleSup">87,88,90</span></a> and racial factors.<a class="elsevierStyleCrossRef" href="#bib92"><span class="elsevierStyleSup">92</span></a> However, the potential influence they have in these cases is not unanimously accepted.</p><p id="p2070" class="elsevierStylePara elsevierViewall">Regarding the drainage vein used in elbow nAVF, a direct comparison between brachiocephalic and brachiobasilic nAVF has not shown a difference in terms of incidence of ischaemia.<a class="elsevierStyleCrossRef" href="#bib85"><span class="elsevierStyleSup">85</span></a></p><p id="p2075" class="elsevierStylePara elsevierViewall">Finally, despite the evident relationship between the blood flow in the AVF and the development of ischaemia, no direct relationship has been shown, probably due to the intervention of other factors in the physiopathology of the disease. Nevertheless, some authors recommend anastomosis creation < 7 mm to limit excessive flow rate to the VA.<a class="elsevierStyleCrossRef" href="#bib87"><span class="elsevierStyleSup">87</span></a></p><p id="s0415" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p2080" class="elsevierStylePara elsevierViewall">There are no systematic reviews or clinical trials on this subject. The level of evidence is limited to published observational articles and to experts’ opinion stated in the various clinical guidelines.</p><p id="p2085" class="elsevierStylePara elsevierViewall">While there are well defined ischaemia risk factors, whose influence is unanimously taken into consideration (type of access, peripheral arterial disease, diabetes mellitus, advanced age and female gender), there are other factors whose role has not been well defined.</p><p id="p2090" class="elsevierStylePara elsevierViewall">Furthermore, there are no published recommendations regarding the strategy to follow in daily clinical practice in the presence of these risk factors, which are highly prevalent in HD patients.</p><p id="p2095" class="elsevierStylePara elsevierViewall">There is, however, widespread agreement among authors regarding the need for close post-operative monitoring of those patients considered high risk (diabetics, aged > 60, presence of peripheral arterial disease, female), so distal ischaemia can be detected and treated as soon as possible to avoid serious consequences. Authors also agree on the need to prioritise the creation of distal accesses in these patients over an access on the brachial artery.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,85-88,92</span></a></p><p id="p2100" class="elsevierStylePara elsevierViewall">For all these reasons, although there are no systematic reviews or clinical trials on the subject, based on the published studies, the opinion of experts and good clinical practice, GEMAV suggests that firstly, surgical techniques aimed at minimising the risk of ischaemia be promoted; and secondly, that there must be close clinical monitoring of patients considered high risk after VA creation, in order to prevent the appearance of irreversible complications.</p><p id="p2105" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0035"></elsevierMultimedia></p></span></span><span id="se0405" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">2</span><span class="elsevierStyleSectionTitle" id="sect0425">A<span class="elsevierStyleSmallCaps">rteriovenous fistula creation</span></span><p id="p2115" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">CONTENTS</span><ul class="elsevierStyleList" id="list0275"><li class="elsevierStyleListItem" id="listi1235"><span class="elsevierStyleLabel">2.1.</span><p id="p2120" class="elsevierStylePara elsevierViewall">Types of arteriovenous fistula</p></li><li class="elsevierStyleListItem" id="listi1240"><span class="elsevierStyleLabel">2.2.</span><p id="p2125" class="elsevierStylePara elsevierViewall">Native arteriovenous fistula</p></li><li class="elsevierStyleListItem" id="listi1245"><span class="elsevierStyleLabel">2.3.</span><p id="p2130" class="elsevierStylePara elsevierViewall">Prosthetic arteriovenous fistula</p></li><li class="elsevierStyleListItem" id="listi1250"><span class="elsevierStyleLabel">2.4.</span><p id="p2135" class="elsevierStylePara elsevierViewall">Fall-back techniques</p></li><li class="elsevierStyleListItem" id="listi1255"><span class="elsevierStyleLabel">2.5.</span><p id="p2140" class="elsevierStylePara elsevierViewall">Sequence for vascular access creation</p></li><li class="elsevierStyleListItem" id="listi1260"><span class="elsevierStyleLabel">2.6.</span><p id="p2145" class="elsevierStylePara elsevierViewall">Antibiotic prophylaxis for arteriovenous fistula creation</p></li></ul></p><p id="sect0430" class="elsevierStylePara elsevierViewall">Preamble</p><p id="p2150" class="elsevierStylePara elsevierViewall">The mission of the multidisciplinary team treating a patient in a haemodialysis (HD) programme must be to create an arteriovenous fistula (AVF), preferably native, which has a high patency and as few complications as possible. To this end the strategies needed to ensure that the patient with advanced chronic kidney disease (ACKD) starts dialysis with a mature AVF must be set up. In addition, subsequent AVF, if required, should be done in a timely manner and all the professionals involved and the patient must take an active role.</p><span id="se0415" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">2.1</span><span class="elsevierStyleSectionTitle" id="sect0435">Types of arteriovenous fistula</span><p id="s0440" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p2155" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0040"></elsevierMultimedia></p><p id="sect0445" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p2180" class="elsevierStylePara elsevierViewall">Prioritising nAVF over pAVF is a basic recommendation in numerous clinical guidelines and among experts, given the low rate of complications and excellent long-term patency it presents once the nAVF has matured.</p><p id="s0450" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Arteriovenous fistula patency</span></p><p id="p2185" class="elsevierStylePara elsevierViewall">Primary patency rates for nAVF at 6 and 18 months is 72% and 51%, while secondary patency is 86% and 77% respectively. In pAVF, however, primary patency at 6 and 18 months is 58% and 33% and secondary is 76% and 55%, respectively.<a class="elsevierStyleCrossRef" href="#bib93"><span class="elsevierStyleSup">93</span></a> The main disadvantage of nAVF versus pAVF lies in the high risk of primary failure, due to the high rate of immediate thrombosis (5-30% for radiocephalic nAVF) and in maturation failure (28-53%), compared to only 0-13% primary failure for pAVF in the forearm and 0-3% for pAVF in the arm.<a class="elsevierStyleCrossRef" href="#bib8"><span class="elsevierStyleSup">8</span></a></p><p id="p2190" class="elsevierStylePara elsevierViewall">In addition, there has been a demographic change in incident patients starting renal replacement therapy (RRT) in recent years. This means that there has been a progressive trend towards a decrease in patency rates reported in the literature.<a class="elsevierStyleCrossRef" href="#bib94"><span class="elsevierStyleSup">94</span></a> Thus, the analysis of results from 46 articles between 2000 and 2012 provided by Al-Jaishi et al.<a class="elsevierStyleCrossRef" href="#bib94"><span class="elsevierStyleSup">94</span></a> estimate a primary failure rate for nAVF of 23%—significantly higher in distal nAVF (28%) than in proximal (20%). They found a primary patency (including primary failures) of 60% after 1 year and 51% after 2 years, with a significant difference depending on the location of the nAVF (distal or proximal) after 1 year, but not after 2 years. These same authors found a secondary patency rate of 71% after 1 year and 64% after 2 years, with no difference in the location of the nAVF.<a class="elsevierStyleCrossRef" href="#bib94"><span class="elsevierStyleSup">94</span></a> It has also been reported that the routine use of a preoperative ultrasound study may reduce immediate nAVF failures.<a class="elsevierStyleCrossRef" href="#bib46"><span class="elsevierStyleSup">46</span></a></p><p id="s0455" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rate of complications</span></p><p id="p2195" class="elsevierStylePara elsevierViewall">nAVF are associated with a decreased morbidity and mortality compared to pAVF and catheters (CVC).<a class="elsevierStyleCrossRef" href="#bib95"><span class="elsevierStyleSup">95</span></a> According to Ravani et al.,<a class="elsevierStyleCrossRef" href="#bib96"><span class="elsevierStyleSup">96</span></a> the use of pAVF and CVC versus nAVF is associated with an increased mortality of 18% and 53%, respectively. In addition, nAVF have a lower rate of infections than pAVF, which is lower than CVC.<a class="elsevierStyleCrossRefs" href="#bib96"><span class="elsevierStyleSup">96,97</span></a></p><p id="p2200" class="elsevierStylePara elsevierViewall">As a result of all this, when compared with nAVF, the risk of hospitalisation increases by 26% with pAVF and by 68% with CVC.<a class="elsevierStyleCrossRef" href="#bib96"><span class="elsevierStyleSup">96</span></a></p><p id="p2205" class="elsevierStylePara elsevierViewall">Another advantage of nAVF is that they have a lower rate of re-intervention than pAVF, which implies a lower maintenance cost.<a class="elsevierStyleCrossRef" href="#bib98"><span class="elsevierStyleSup">98</span></a></p><p id="p2210" class="elsevierStylePara elsevierViewall">Thus, in any patient who requires RRT using HD, the ideal VA must be created, one which allows appropriate dialysis, has greater patency and a lower rate of complications. The VA that brings all of these characteristics together is nAVF<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,99-102</span></a> and, therefore, this must be the first VA to be considered. When nAVF cannot be constructed because there is no venous capital or venous capital is damaged, pAVF should be used<a class="elsevierStyleCrossRefs" href="#bib99"><span class="elsevierStyleSup">99-101</span></a>, while CVC placement must only be considered when neither of the above are possible or when HD treatment must be initiated without a mature VA.<a class="elsevierStyleCrossRefs" href="#bib103"><span class="elsevierStyleSup">103,104</span></a></p><p id="p2215" class="elsevierStylePara elsevierViewall">Permanent VA should be indicated on a case-by-case basis, depending on vascular examination, the patient’s previous VA, as well as other factors such as age, comorbidity and the urgency for VA use.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,82,99-101,105-108</span></a></p></span><span id="s0445" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">2.2</span><span class="elsevierStyleSectionTitle" id="sect0460">Native arteriovenous fistula</span><p id="p2220" class="elsevierStylePara elsevierViewall">In the case of nAVF, the most distal location possible should be chosen as first option when planning VA creation, in order to preserve the maximum peripheral venous network for future VA. All things being equal, the non-dominant limb should be prioritised to help facilitate patient comfort both during HD sessions and in their daily activities.<a class="elsevierStyleCrossRef" href="#bib109"><span class="elsevierStyleSup">109</span></a></p><p id="s0465" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">2.2.1 Native arteriovenous fistula in wrist and forearm</span></p><p id="s0470" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Radiocephalic native arteriovenous fistula at the wrist (Brescia-Cimino arteriovenous fistula)</span></p><p id="p2225" class="elsevierStylePara elsevierViewall">The radiocephalic AVF at the wrist, described by Brescia-Cimino in 1966, is still the VA reference for HD.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,110,111</span></a> It preserves proximal venous capital for future VA, has a low rate of complications, especially VA-induced ischaemia and infections, and those that mature correctly have an excellent patency rate.<a class="elsevierStyleCrossRefs" href="#bib99"><span class="elsevierStyleSup">99-101,109</span></a> The main limitation of this technique is the relatively high immediate failure rate, which ranges between 10% and 30%, but reaches almost 50% in some groups, especially in diabetic, elderly and female gender.<a class="elsevierStyleCrossRefs" href="#bib100"><span class="elsevierStyleSup">100,112,113</span></a> A further disadvantage of the radiocephalic AVF is its high incidence of maturation failure, so that approximately 30% of these AVF have not matured enough for use at 3 months.<a class="elsevierStyleCrossRefs" href="#bib100"><span class="elsevierStyleSup">100,102,105</span></a> Primary patency at 6 months ranges from 65% to 81%; this is lower than the 79-89% found in pAVF, although they equal out after the first year, with fewer complications.<a class="elsevierStyleCrossRefs" href="#bib100"><span class="elsevierStyleSup">100,101</span></a></p><p id="s0475" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Arteriovenous fistula in the anatomical snuffbox</span></p><p id="p2230" class="elsevierStylePara elsevierViewall">The anatomical snuffbox AVF, using the posterior branch of the radial artery located between the tendons of extensor pollicis brevis and extensor pollicis longus as a donor, is used less frequently due to its greater surgical complexity. Despite this, results in units where it is normally performed are good<a class="elsevierStyleCrossRef" href="#bib114"><span class="elsevierStyleSup">114</span></a>: 11% immediate thrombosis, 80% maturation at 6 weeks and cumulative patency at one and five years of 65% and 45%, respectively. In this case, its greatest benefit is that it does not exclude the possibility of performing a radiocephalic nAVF in the same limb if the access fails. Both sites allow proximal reconstructions in the forearm when either juxta-anastomotic stenosis or thrombosis appears.</p><p id="s0480" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Radiocephalic arteriovenous fistula in forearm</span></p><p id="p2235" class="elsevierStylePara elsevierViewall">This technique differs from the previous one in that it is performed in a more proximal area; it is indicated as surgical treatment in AVF juxta-anastomotic stenosis in the wrist, and in cases of non-viability of the cephalic vein in the wrist, usually due to early bifurcations.</p><p id="s0485" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Radiobasilic transposition</span></p><p id="p2240" class="elsevierStylePara elsevierViewall">When the cephalic vein in the forearm is not adequate for a radiocephalic AVF, a possible option before using more proximal veins is radiobasilic transposition.<a class="elsevierStyleCrossRefs" href="#bib115"><span class="elsevierStyleSup">115,116</span></a> The basilic vein must be transposed from the wrist proximally towards the antecubital fossa and subcutaneously tunnelled as far as the radial artery to create anastomosis. The antebrachial basilic vein is usually free of previous vein cannulations. However, its lower consistency makes it more vulnerable to possible lesions during the transposition process, with a greater tendency to torsion, so its use in clinical practice is limited by the vein’s development and by the experience of the surgical team.</p><p id="s0490" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Other venous transpositions</span></p><p id="p2245" class="elsevierStylePara elsevierViewall">When the radial artery is not suitable for radiocephalic AVF, other possible venous transpositions in the forearm include the cephalic or basilic vein, placed in the shape of a loop in the palmar face of the forearm, towards the proximal radial artery in the antecubital fossa.<a class="elsevierStyleCrossRef" href="#bib117"><span class="elsevierStyleSup">117</span></a> This is how different ulnar-basilic transposition options in the forearm, as well as brachiobasilic in the shape of a loop, and different configurations using the great saphenous vein have been reported.<a class="elsevierStyleCrossRef" href="#bib111"><span class="elsevierStyleSup">111</span></a> Its use is limited in practice to specific anatomical situations in certain patients.</p><p id="s0495" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">2.2.2 Native arteriovenous fistula in the antecubital fossa (elbow)</span></p><p id="p2250" class="elsevierStylePara elsevierViewall">According to the <span class="elsevierStyleItalic">Kidney Disease Outcomes Quality Initiative (KDOQI)</span> guidelines<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> radiocephalic and brachiocephalic AVF are the first and second options for creating a VA, respectively.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> The antecubital fossa contains larger vessels, which usually provide higher flow and have lower rates of primary failure and alterations in maturation, while their main drawback is the shorter needling segment available and the fact that they limit subsequent use of a more distal access.</p><p id="s0500" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Brachio-cephalic arteriovenous fistula</span></p><p id="p2255" class="elsevierStylePara elsevierViewall">The brachiocephalic AVF is the vascular access of choice for this location.<a class="elsevierStyleCrossRefs" href="#bib6"><span class="elsevierStyleSup">6,10,109</span></a> It has the advantage over radiocephalic AVF of achieving higher flow and the cephalic vein in the arm is usually more accessible for needling and aesthetically more discrete than in the forearm. However, it may cause greater oedema in the limb and it has an increased risk of causing VA-induced distal ischaemia.</p><p id="s0505" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Brachioperforating arteriovenous fistula (Gracz arteriovenous fistula)</span></p><p id="p2260" class="elsevierStylePara elsevierViewall">A widely used variant of the previous technique consists of creating the AVF between the brachial artery and the perforating vein in the antecubital fossa (brachioperforating AVF), using the technique described by Gracz<a class="elsevierStyleCrossRef" href="#bib118"><span class="elsevierStyleSup">118</span></a> and subsequently modified by Konner et al.<a class="elsevierStyleCrossRefs" href="#bib67"><span class="elsevierStyleSup">67,119</span></a> in order to obtain arterialisation of both the cephalic and the basilic vein.<a class="elsevierStyleCrossRef" href="#bib120"><span class="elsevierStyleSup">120</span></a></p><p id="s0510" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Arteriovenous fistula using the proximal radial artery</span></p><p id="p2265" class="elsevierStylePara elsevierViewall">As an alternative to the brachial artery, the proximal radial artery in the antecubital fossa can be used as a donor.<a class="elsevierStyleCrossRefs" href="#bib113"><span class="elsevierStyleSup">113,119,121-123</span></a> This technique has certain functional advantages. The risk of VA-related distal ischaemia is lower when the donor artery is the radial, compared to procedures performed with the brachial artery. As this anastomosis is constructed on the radial artery, its smaller size favours the appropriate resistance of the new VA and minimises the risk of distal ischaemia. Likewise, as a lower flow in the AVF is obtained, it limits the cardiological impact in patients at risk. Moreover, venous confluence in this location allows the possibility of setting up a two-way flow in the venous drain.</p><p id="p2270" class="elsevierStylePara elsevierViewall">In cases where few veins are available for needling, technical variations have been proposed to promote two-way flow in the veins distal to the AVF, mainly in the elbow, in order to increase the segment available for cannulation,<a class="elsevierStyleCrossRef" href="#bib124"><span class="elsevierStyleSup">124</span></a> by retrograde valvotomy of the drainage veins.<a class="elsevierStyleCrossRef" href="#bib125"><span class="elsevierStyleSup">125</span></a></p><p id="p2275" class="elsevierStylePara elsevierViewall">The antecubital fossa presents multiple anastomoses between veins that may allow the intervention to be performed. Although short case studies are described in the literature, there is not enough documented evidence to determine its usefulness in practice and to assess the clinical significance of venous hypertension arising from this technique. As a result, its use is limited to cases with short needling trajectory in which this is anatomically feasible.<a class="elsevierStyleCrossRef" href="#bib111"><span class="elsevierStyleSup">111</span></a></p><p id="s0515" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Brachiobasilic arteriovenous fistula</span></p><p id="p2280" class="elsevierStylePara elsevierViewall">Those patients who cannot have a radiocephalic or brachiocephalic AVF created may opt for a brachiobasilic AVF with venous superficialisation or transposition as an alternative to vascular prosthetic implants.<a class="elsevierStyleCrossRef" href="#bib126"><span class="elsevierStyleSup">126</span></a></p><p id="p2285" class="elsevierStylePara elsevierViewall">The depth of the basilic vein protects it against repeated venipunctures so it tends to be preserved in HD candidates; however, this greater depth may cause difficulty when needling, requiring superficialisation. In addition, the trajectory of the basilic vein is adjacent to the neurovascular bundle in the limb, which leaves these structures vulnerable to potential cannulation lesions during dialysis. Therefore, as well as being superficialised, it can be transposed to an anterior and lateral location in the arm to move away from these structures and to improve patient comfort during dialysis.</p><p id="p2290" class="elsevierStylePara elsevierViewall">Given that two surgical procedures are usually required, in clinical practice they can either be carried out in the same intervention, or in two procedures separated in time.</p><p id="p2295" class="elsevierStylePara elsevierViewall">When the surgery is performed, the basilic vein is dissected and transposed; thus the new trajectory is created and finally the arteriovenous anastomosis constructed. The advantage of performing the two procedures in one session is that it shortens the time required before being able to cannulate the VA; the disadvantage is that it increases the likelihood of mechanical complications during surgery, as the mobilisation and/or transposition of the vein has to be performed with a vein without the necessary prior arterialisation.</p><p id="p2300" class="elsevierStylePara elsevierViewall">When performed in two procedures, the anastomosis is firstly constructed between the basilic vein and the brachial artery, and from day 30-90, after using a Doppler ultrasound to check the correct maturation of the AVF and the absence of stenosis, the second procedure is performed and the vein is superficialised and/or transposed.<a class="elsevierStyleCrossRef" href="#bib127"><span class="elsevierStyleSup">127</span></a></p><p id="p2305" class="elsevierStylePara elsevierViewall">Three superficialisation techniques are described in order to allow cannulation in this type of access<a class="elsevierStyleCrossRef" href="#bib128"><span class="elsevierStyleSup">128</span></a>: <span class="elsevierStyleItalic">a)</span> anterior transposition in the arm, by creating a new subcutaneous tunnel; <span class="elsevierStyleItalic">b)</span> anterior transposition in the arm, by creating a lateral flap of skin and subcutaneous tissue, and c) simple superficialisation without transposition.</p><p id="s0520" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Brachiobrachial fistula</span></p><p id="p2310" class="elsevierStylePara elsevierViewall">When there are no available superficial veins, a suggested alternative is to create an arteriovenous fistula between the brachial artery and the brachial vein.<a class="elsevierStyleCrossRefs" href="#bib129"><span class="elsevierStyleSup">129-131</span></a></p><p id="p2315" class="elsevierStylePara elsevierViewall">The brachial vein lies next to the artery and can be single or double. As this vein corresponds to the deep venous system, it is well preserved from prior needling. As a result, despite being a complex operation, if the vein develops well, it may be technically feasible.</p><p id="p2320" class="elsevierStylePara elsevierViewall">The surgical procedure is the same as brachiobasilic AVF: the anastomosis is created in the antecubital fossa, mobilising the brachial vein with collaterals ligation, and performing superficialisation and/or transposition.<a class="elsevierStyleCrossRef" href="#bib129"><span class="elsevierStyleSup">129</span></a></p><p id="p2325" class="elsevierStylePara elsevierViewall">Once the VA has matured, the results in terms of patency and complications are similar to those of the brachiobasilic AVF. However, the severe limitation of this technique is the high rate of primary failure, which may reach 53%, and its low primary patency after one year (35-40%),<a class="elsevierStyleCrossRefs" href="#bib129"><span class="elsevierStyleSup">129,131</span></a> probably related to the increased technical complexity of mobilising and transposing the brachial vein. Therefore, given the lack of broader studies, this technique is not usually considered as a valid alternative option to using synthetic prostheses in the arm.<a class="elsevierStyleCrossRef" href="#bib128"><span class="elsevierStyleSup">128</span></a></p><p id="s0525" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Other venous transpositions</span></p><p id="p2330" class="elsevierStylePara elsevierViewall">As in the forearm, there are also various possibilities for venous transpositions; their use is limited to certain clinical situations with particular anatomical layouts.<a class="elsevierStyleCrossRef" href="#bib111"><span class="elsevierStyleSup">111</span></a></p></span><span id="se0520" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">2.3</span><span class="elsevierStyleSectionTitle" id="sect0530">Prosthetic arteriovenous fistula</span><p id="s0535" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p2335" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0045"></elsevierMultimedia></p><p id="sect0540" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="s0545" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">2.3.1 Rationale for prosthetic arteriovenous fistulae</span></p><p id="p2345" class="elsevierStylePara elsevierViewall">The use of prosthetic material to create VA for HD has been shown to be a viable and effective solution to achieve a permanent VA.<a class="elsevierStyleCrossRefs" href="#bib93"><span class="elsevierStyleSup">93,99,132,133</span></a></p><p id="p2350" class="elsevierStylePara elsevierViewall">However, the high economic cost involved and the associated morbidity and deterioration in the patient’s quality of life, due to the need for procedures to maintain VA usefulness, mean that it is not considered a first choice technique when planning the VA, a role reserved for nAVF.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,93,98,109,132-135</span></a></p><p id="p2355" class="elsevierStylePara elsevierViewall">As it is technically less complex to perform, this may help surgeons who have little expertise in creating VA lean towards this procedure from the onset.<a class="elsevierStyleCrossRef" href="#bib99"><span class="elsevierStyleSup">99</span></a></p><p id="p2360" class="elsevierStylePara elsevierViewall">Despite not being the first-choice VA, nowadays this access plays a highly relevant role because an ever increasing number of patients require HD for very long periods of their lives, consequently putting the vascular bed at risk, and there is also a progressive increase in the average age of the patients on a HD programme. In addition, pAVF offer some theoretical advantages, such as a shorter maturation time and greater ease of needling in certain cases, as in the case of obese patients. They may also make it easier to create a secondary native VA, by helping to dilate previously unsuitable veins in the arms to create an AVF.<a class="elsevierStyleCrossRef" href="#bib132"><span class="elsevierStyleSup">132</span></a></p><p id="s0550" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">2.3.2 Prosthetic arteriovenous fistula planning and creation</span></p><p id="p2365" class="elsevierStylePara elsevierViewall">Arteries or veins with a diameter suitable for pAVF placement should first be identified (not less than 4 mm).<a class="elsevierStyleCrossRefs" href="#bib63"><span class="elsevierStyleSup">63,116,133</span></a> In most cases, with an already exhausted distal venous bed, arterial anastomosis should be as distal as possible; venous anastomosis should also be as distal as possible, whenever correct drainage towards central venous trunks can be ensured.</p><p id="p2370" class="elsevierStylePara elsevierViewall">It should be noted that the use of antecubital fossa veins for anastomosis involves the integrity of that territory and its respective drainage veins. Therefore, in these cases, the priority indication would be nAVF creation using these veins. For this reason, there are authors<a class="elsevierStyleCrossRef" href="#bib136"><span class="elsevierStyleSup">136</span></a> who recommend avoiding prosthetic loops in the forearm, since they consider that in these cases a native AVF can be created.</p><p id="s0555" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Expanded polytetrafluoroethylene</span></p><p id="p2375" class="elsevierStylePara elsevierViewall">The material recommended for the prosthesis is ePTFE, given that it offers better rates of infection and integration than Dacron.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> Apart from this standard material, there are other prostheses which may be used in special circumstances.<a class="elsevierStyleCrossRefs" href="#bib137"><span class="elsevierStyleSup">137,138</span></a></p><p id="s0560" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Immediate puncture prosthesis</span></p><p id="p2380" class="elsevierStylePara elsevierViewall">Immediate needling prostheses are bilayer ePTFE prostheses reinforced with a third elastomer layer between the two, which means it does not need to be integrated in the tissues for needling. It provides similar results to conventional prostheses with the advantage of allowing cannulation after 24 hours, if necessary.<a class="elsevierStyleCrossRef" href="#bib139"><span class="elsevierStyleSup">139</span></a></p><p id="s0565" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Biosynthetic prostheses</span></p><p id="p2385" class="elsevierStylePara elsevierViewall">Good results have also been published in relation to bioengineered prostheses. This is a prosthesis manufactured from a polyester matrix in which collagen from sheep is cultivated. It has a potential benefit in terms of presenting a lower incidence of infections when it is not possible to create an nAVF.<a class="elsevierStyleCrossRef" href="#bib140"><span class="elsevierStyleSup">140</span></a> The main evidence regarding the use of this type of prosthesis is that published by Morosetti et al., comparing the prosthetic access with the brachiobasilic AVF access in patients without other alternatives; although results with autologous access were more favourable, patency results and complication rates were similar to those of other studies with ePTFE.<a class="elsevierStyleCrossRef" href="#bib135"><span class="elsevierStyleSup">135</span></a></p><p id="s0570" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Surgical technique</span></p><p id="p2390" class="elsevierStylePara elsevierViewall">The prosthesis can be implanted in a straight line or in the shape of a loop, the latter being the preferred layout in the forearm.<a class="elsevierStyleCrossRef" href="#bib141"><span class="elsevierStyleSup">141</span></a> These layouts are determined by the characteristics of the patient.</p><p id="p2395" class="elsevierStylePara elsevierViewall">The order of preference for arterial anastomosis location is the brachial artery in antecubital fossa, brachial artery in arm, brachial artery close to axilla and axillary artery. However, because a pAVF is usually created after several failed nAVF, the location will depend on the well preserved vascular bed. Venous anastomosis can be performed on the veins in the antecubital fossa or above the elbow, as well as in the cephalic, basilic, axillary, subclavian and jugular vein.</p><p id="p2400" class="elsevierStylePara elsevierViewall">Arterial anastomosis of the prosthesis should preferably be end to side. There are no studies showing differences depending on the anastomosis type between the vein and the prosthesis. The prosthesis should be between 20 and 40 cm in length to ensure a large needling segment. Prosthesis diameter must range between 6 and 8 mm. According to some authors,<a class="elsevierStyleCrossRef" href="#bib142"><span class="elsevierStyleSup">142</span></a> bigger diameters are associated with better long-term outcomes in this type of VA.</p></span><span id="se0570" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">2.4</span><span class="elsevierStyleSectionTitle" id="sect0575">Fall-back techniques</span><p id="p2405" class="elsevierStylePara elsevierViewall">Patients who have exhausted all their venous capital for VA in the upper limbs, including nAVF and pAVF, are a small, but growing, percentage of patients on HD.</p><p id="p2410" class="elsevierStylePara elsevierViewall">In view of the greater morbidity and mortality discussed when performing HD through CVC, surgical techniques known as “fall-back” techniques have been described. These allow permanent access when there are no viable veins in the upper limbs. These techniques make it possible to avoid the use of CVC despite the higher level of complications, the greater operative morbidity and lower patency than conventional VA.<a class="elsevierStyleCrossRefs" href="#bib93"><span class="elsevierStyleSup">93,97,122,132,133,143</span></a></p><p id="s0580" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">2.4.1 Vascular access at lower limbs</span></p><p id="p2415" class="elsevierStylePara elsevierViewall">There is widespread evidence regarding VA creation in the lower limbs, using a vascular prosthesis (proximal in the thigh or mid-thigh section) or else using nAVF (AVF in femoral vein with transposition). pAVF creation in the lower limb is the most widely used of all the fall-back techniques described, since it offers acceptable patency rates and is the least complex surgical technique.<a class="elsevierStyleCrossRefs" href="#bib111"><span class="elsevierStyleSup">111,122,132,133</span></a></p><p id="s0585" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">2.4.2 Prosthesis-tunnelled catheter device</span></p><p id="p2420" class="elsevierStylePara elsevierViewall">The hybrid prosthesis-tunnelled catheter device <span class="elsevierStyleItalic">Haemodialysis Reliable Outflow</span> (HeRO-device) is indicated in cases where there is a central venous obstruction which prevents the creation of any other VA in the upper limb. It consists of a VA that is created in a mixed way. On the one hand, it is a tunnelled catheter which is inserted through the internal jugular vein to the atrium; on the other, it is connected to an ePTFE prosthesis that is anastomosed at the level of the brachial artery. This means that the needling area is the prosthesis which is subcutaneously tunnelled and distal drainage is carried out directly in the atrium. The objective is to go through the stenosis and central vein occlusions which would prevent AVF creation.</p><p id="p2425" class="elsevierStylePara elsevierViewall">The advantage of using this in clinical practice is that it is a VA that can be implanted in patients without adequate central venous drainage, in which all nAVF and pAVF options have been depleted, without compromising future accesses; main disadvantages include the technical complexity of the operation and its high cost.</p><p id="s0590" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">2.4.3 “Exotic” vascular access</span></p><p id="p2430" class="elsevierStylePara elsevierViewall">“Exotic” VA are those considered when there are extensive occlusions of venous trunks, both in upper and lower limbs. They have two great advantages: firstly they allow a new VA to be created in a theoretically exhausted territory; secondly, they can sometimes be used to salvage VA which have failed due to occlusion in the drainage veins and where endovascular therapy has not been effective.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a>4,145</p><p id="p2435" class="elsevierStylePara elsevierViewall">Given the exhaustion of the venous bed in these patients, these accesses are created using ePTFE prosthetic grafts, in the form of artery bypass between the donor artery and recipient vein.</p><p id="p2440" class="elsevierStylePara elsevierViewall">Unfortunately, despite the initial advantage of providing access when the venous bed is depleted, there is a higher incidence of complications than in nAVF, because they are made of heterologous material. This is particularly serious in infection, because it involves central vessels which are difficult for the surgeon to access.</p><p id="p2445" class="elsevierStylePara elsevierViewall">Furthermore, they are complex surgical procedures which are not exempt from morbidity and mortality and are performed on patients with significant associated comorbidities, who frequently have a history of multiple failed VA.</p><p id="p2450" class="elsevierStylePara elsevierViewall">Therefore, as a general rule, the benefit/risk of the surgical intervention should be assessed on a case-by-case basis, the intervention required and the existing access options.</p><p id="s0595" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Prosthetic accesses in the anterior chest wall</span></p><p id="p2455" class="elsevierStylePara elsevierViewall">These VA are created either as a <span class="elsevierStyleItalic">loop</span>, placing a prosthesis between the vein and axillary artery on the same side, or in a straight line, placing the prosthesis between the vein and contralateral axillary artery. These VA can be considered for patients with an exhausted venous bed but with central vein patency; they especially benefit those patients at high risk of ischaemia in the limb. Results report patency rates similar to more conventional pAVF in the arm.<a class="elsevierStyleCrossRefs" href="#bib146"><span class="elsevierStyleSup">146,147</span></a></p><p id="s0600" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Bypass to central veins</span></p><p id="p2460" class="elsevierStylePara elsevierViewall">In the case of distal axillary vein thrombosis, the technique consists of creating a bypass between the brachial artery and proximal axillary vein, while in cases of extensive axillosubclavian thrombosis with internal jugular vein and brachiocephalic trunk patency, the technique of choice is to perform a bypass between the brachial artery and internal jugular vein.<a class="elsevierStyleCrossRef" href="#bib144"><span class="elsevierStyleSup">144</span></a></p><p id="s0605" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Bypass to leg veins</span></p><p id="p2465" class="elsevierStylePara elsevierViewall">If the two brachiocephalic venous trunks or the superior vena cava are occluded, the surgical alternative is to perform a bypass between the axillary artery and iliac vein<a class="elsevierStyleCrossRefs" href="#bib144"><span class="elsevierStyleSup">144,148</span></a> or else to the popliteal vein.<a class="elsevierStyleCrossRefs" href="#bib145"><span class="elsevierStyleSup">145,149</span></a></p><p id="s0610" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Other derivative techniques</span></p><p id="p2470" class="elsevierStylePara elsevierViewall">Other alternative derivative techniques have been described, such as bypassing to the right atrium,<a class="elsevierStyleCrossRef" href="#bib150"><span class="elsevierStyleSup">150</span></a> femorofemoral crossover bypass,<a class="elsevierStyleCrossRef" href="#bib145"><span class="elsevierStyleSup">145</span></a> axillo-renal bypass,<a class="elsevierStyleCrossRef" href="#bib151"><span class="elsevierStyleSup">151</span></a> or axillo-inferior vena cava bypass.<a class="elsevierStyleCrossRef" href="#bib144"><span class="elsevierStyleSup">144</span></a> In all cases, these are techniques which are considered extraordinary, and evidence is restricted to a few documented cases.</p><p id="s0615" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Types of vascular access</span></p><p id="p2475" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0280"><li class="elsevierStyleListItem" id="listi1265"><span class="elsevierStyleLabel">•</span><p id="p2480" class="elsevierStylePara elsevierViewall">nAFV at wrist and in forearm.<ul class="elsevierStyleList" id="list0285"><li class="elsevierStyleListItem" id="listi1270"><span class="elsevierStyleLabel">–</span><p id="p2485" class="elsevierStylePara elsevierViewall">Radiocephalic AVF in the wrist (Brescia-Cimino AVF).</p></li><li class="elsevierStyleListItem" id="listi1275"><span class="elsevierStyleLabel">–</span><p id="p2490" class="elsevierStylePara elsevierViewall">AVF in the anatomical snuffbox.</p></li><li class="elsevierStyleListItem" id="listi1280"><span class="elsevierStyleLabel">–</span><p id="p2495" class="elsevierStylePara elsevierViewall">Radiocephalic AVF in forearm.</p></li><li class="elsevierStyleListItem" id="listi1285"><span class="elsevierStyleLabel">–</span><p id="p2500" class="elsevierStylePara elsevierViewall">Radiobasilic transposition.</p></li><li class="elsevierStyleListItem" id="listi1290"><span class="elsevierStyleLabel">–</span><p id="p2505" class="elsevierStylePara elsevierViewall">Other venous transpositions.</p></li></ul></p></li><li class="elsevierStyleListItem" id="listi1295"><span class="elsevierStyleLabel">•</span><p id="p2510" class="elsevierStylePara elsevierViewall">nAVF in antecubital fossa (elbow) and arm.<ul class="elsevierStyleList" id="list0290"><li class="elsevierStyleListItem" id="listi1300"><span class="elsevierStyleLabel">–</span><p id="p2515" class="elsevierStylePara elsevierViewall">Brachiocephalic AVF.</p></li><li class="elsevierStyleListItem" id="listi1305"><span class="elsevierStyleLabel">–</span><p id="p2520" class="elsevierStylePara elsevierViewall">Brachioperforating AVF (Gracz AVF).</p></li><li class="elsevierStyleListItem" id="listi1310"><span class="elsevierStyleLabel">–</span><p id="p2525" class="elsevierStylePara elsevierViewall">AVF using the proximal radial artery.</p></li><li class="elsevierStyleListItem" id="listi1315"><span class="elsevierStyleLabel">–</span><p id="p2530" class="elsevierStylePara elsevierViewall">Brachiobasilic AVF.</p></li><li class="elsevierStyleListItem" id="listi1320"><span class="elsevierStyleLabel">–</span><p id="p2535" class="elsevierStylePara elsevierViewall">Brachiobrachial AVF.</p></li><li class="elsevierStyleListItem" id="listi1325"><span class="elsevierStyleLabel">–</span><p id="p2540" class="elsevierStylePara elsevierViewall">Other venous transpositions.</p></li></ul></p></li><li class="elsevierStyleListItem" id="listi1330"><span class="elsevierStyleLabel">•</span><p id="p2545" class="elsevierStylePara elsevierViewall">pAVF in upper limbs.<ul class="elsevierStyleList" id="list0295"><li class="elsevierStyleListItem" id="listi1335"><span class="elsevierStyleLabel">–</span><p id="p2550" class="elsevierStylePara elsevierViewall">Radioantecubital Straight graft.</p></li><li class="elsevierStyleListItem" id="listi1340"><span class="elsevierStyleLabel">–</span><p id="p2555" class="elsevierStylePara elsevierViewall">Brachio/radioantecubital loop.</p></li><li class="elsevierStyleListItem" id="listi1345"><span class="elsevierStyleLabel">–</span><p id="p2560" class="elsevierStylePara elsevierViewall">Brachiobrachial/axillary straight graft.</p></li><li class="elsevierStyleListItem" id="listi1350"><span class="elsevierStyleLabel">–</span><p id="p2565" class="elsevierStylePara elsevierViewall">Brachiobrachial/axillary loop.</p></li></ul></p></li><li class="elsevierStyleListItem" id="listi1355"><span class="elsevierStyleLabel">•</span><p id="p2570" class="elsevierStylePara elsevierViewall">Fall-back techniques.<ul class="elsevierStyleList" id="list0300"><li class="elsevierStyleListItem" id="listi1360"><span class="elsevierStyleLabel">–</span><p id="p2575" class="elsevierStylePara elsevierViewall">VA in lower limbs.</p></li><li class="elsevierStyleListItem" id="listi1365"><span class="elsevierStyleLabel">–</span><p id="p2580" class="elsevierStylePara elsevierViewall">Proximal femorofemoral (groin) graft.</p></li><li class="elsevierStyleListItem" id="listi1370"><span class="elsevierStyleLabel">–</span><p id="p2585" class="elsevierStylePara elsevierViewall">Femorofemoral graft in the middle third of the thigh.</p></li><li class="elsevierStyleListItem" id="listi1375"><span class="elsevierStyleLabel">–</span><p id="p2590" class="elsevierStylePara elsevierViewall">Transposition of femoral vein.</p></li><li class="elsevierStyleListItem" id="listi1380"><span class="elsevierStyleLabel">–</span><p id="p2595" class="elsevierStylePara elsevierViewall">Prosthesis tunnelled catheter device (HeRO).</p></li><li class="elsevierStyleListItem" id="listi1385"><span class="elsevierStyleLabel">–</span><p id="p2600" class="elsevierStylePara elsevierViewall">“Exotic” vascular access.</p></li></ul></p></li><li class="elsevierStyleListItem" id="listi1390"><span class="elsevierStyleLabel">•</span><p id="p2605" class="elsevierStylePara elsevierViewall">Central venous catheter.</p></li></ul></p></span><span id="s0620" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">2.5</span><span class="elsevierStyleSectionTitle" id="sect0620">Sequence for vascular access creation</span><p id="s0625" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p2610" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0050"></elsevierMultimedia></p><p id="p2660" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question V Can an order of preference be recommended when performing the arteriovenous fistula?</span></p><p id="p2665" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question V in <a href="https://static.elsevier.es/nefroguiaaveng/5_PCV_Orden_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0025"></elsevierMultimedia></p><p id="s0630" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="s0635" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Preferred arteriovenous fistula location</span></p><p id="p2670" class="elsevierStylePara elsevierViewall">Experts and guidelines both indicate that the procedure should be started by placing an AVF as distally as possible to preserve the option of future, more proximal accesses if necessary.<a class="elsevierStyleCrossRefs" href="#bib6"><span class="elsevierStyleSup">6,10,109,111</span></a> However, no study has been found comparing the results of different AVF locations for HD in patients where any of these options would initially seem viable.</p><p id="p2675" class="elsevierStylePara elsevierViewall">According to published clinical guidelines,<a class="elsevierStyleCrossRefs" href="#bib6"><span class="elsevierStyleSup">6,10,111</span></a> arteriovenous radiocephalic and brachiocephalic nAVF are the first and second choice for VA, respectively. If these options are not possible, they recommend the creation of an autologous brachiobasilic nAVF in the upper arm or a radioantecubital pAVF in the forearm.</p><p id="s0640" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Using the non-dominant limb</span></p><p id="p2680" class="elsevierStylePara elsevierViewall">Although the first VA is generally recommended in the non-dominant upper limb, no studies have been found which explicitly compare the option of prioritising the dominant or the contralateral hand.</p><p id="p2685" class="elsevierStylePara elsevierViewall">In this respect, Koksoy et al.<a class="elsevierStyleCrossRef" href="#bib152"><span class="elsevierStyleSup">152</span></a> document, in an RCT on efficacy and safety in brachiocephalic and brachiobasilic nAVF, that the <span class="elsevierStyleItalic">use of the dominant arm</span> may increase the risk of fistula failure. However, this trend could not be confirmed in any other study conducted to date.</p><p id="s0645" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal versus proximal location</span></p><p id="p2690" class="elsevierStylePara elsevierViewall">Moreover, no studies have been found specifically comparing whether it is more effective or safer to prioritise the most distal locations possible, alternating between non-dominant limb and dominant, or, on the other hand, to continue using the same limb until all other surgical options have been exhausted. Given the lack of solid evidence clearly favouring either of the options, it seems reasonable to leave the decision on a future AVF proximally in the same limb or distally in the contralateral limb to the patient, with professional advice.</p><p id="p2695" class="elsevierStylePara elsevierViewall">Reinhold et al.<a class="elsevierStyleCrossRef" href="#bib8"><span class="elsevierStyleSup">8</span></a> point out that the first VA should be placed as distally as possible. The main disadvantages of a distal radiocephalic nAVF in the anatomical snuffbox or wrist are the relatively high rates of occlusion and non-maturation, which are affected by patient risk factors such as age, diabetes mellitus and cardiovascular disease.</p><p id="p2700" class="elsevierStylePara elsevierViewall">A previous review with meta-analysis<a class="elsevierStyleCrossRef" href="#bib66"><span class="elsevierStyleSup">66</span></a> based on 38 observational studies estimated a primary failure rate of 15.3%, and primary and secondary patency rates of 62.5% and 66.0%, respectively, for radiocephalic fistula in the wrist.</p><p id="s0650" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Options prior to placing a prosthetic arteriovenous fistula: role of the brachiobasilic native arteriovenous fistula</span></p><p id="p2705" class="elsevierStylePara elsevierViewall">As an option prior to pAVF use, a brachiobasilic nAVF with superficialisation or venous transposition in the arm is indicated.</p><p id="s0655" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Brachiobasilic arteriovenous fistula. Results</span></p><p id="p2710" class="elsevierStylePara elsevierViewall">The systematic review of Dukkipati et al.<a class="elsevierStyleCrossRef" href="#bib128"><span class="elsevierStyleSup">128</span></a> analyses the results of brachiobasilic nAVF, based on several observational studies and an RCT.<a class="elsevierStyleCrossRef" href="#bib134"><span class="elsevierStyleSup">134</span></a> This review finds acceptable rates for primary failure (15% to 20%), and primary patency after one year (72%) and 2 years (62%).</p><p id="s0660" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Brachiobasilic arteriovenous fistula versus prosthetic arteriovenous fistula</span></p><p id="p2715" class="elsevierStylePara elsevierViewall">2 RCTs and 2 retrospective studies compare results between the two procedures.<a class="elsevierStyleCrossRefs" href="#bib134"><span class="elsevierStyleSup">134,135,153,154</span></a> All of them report similar results, with significantly better primary patency rates and primary assisted patency rates in the group of brachiobasilic AVF patients. However, when secondary patency results are analysed, these differences disappear, although the number of surgical interventions required to maintain this secondary patency is markedly greater in the case of pAVF.<a class="elsevierStyleCrossRef" href="#bib134"><span class="elsevierStyleSup">134</span></a></p><p id="p2720" class="elsevierStylePara elsevierViewall">Complications are more frequent in pAVF,<a class="elsevierStyleCrossRefs" href="#bib134"><span class="elsevierStyleSup">134,135,153</span></a> especially those with infection; however, maturation time is higher in brachiobasilic AVF.<a class="elsevierStyleCrossRef" href="#bib154"><span class="elsevierStyleSup">154</span></a></p><p id="s0665" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Brachiobasilic versus brachiocephalic arteriovenous fistula</span></p><p id="p2725" class="elsevierStylePara elsevierViewall">The RCT conducted by Koksoy et al.<a class="elsevierStyleCrossRef" href="#bib152"><span class="elsevierStyleSup">152</span></a> comparing the efficacy and safety of brachiocephalic AVF versus brachiobasilic AVF found no differences in relation to mortality, wound complications, immediate thrombosis, post-operative bleeding, AVF maturation and time to AVF maturation, and there were no significant differences regarding patency rates. Other authors<a class="elsevierStyleCrossRefs" href="#bib155"><span class="elsevierStyleSup">155,156</span></a> reported similar results. In the aforementioned studies, brachiobasilic AVF also show a tendency to present better VA maturation rates, albeit with no statistically significant differences. This may be due to the better preservation of the basilic vein than the cephalic vein in most patients.</p><p id="p2730" class="elsevierStylePara elsevierViewall">All these results make the brachiobasilic fistula a safe technique with good results when considering permanent VA.</p><p id="s0670" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Brachiobasilic arteriovenous fistula versus brachiocephalic arteriovenous fistula versus prosthetic arteriovenous fistula</span></p><p id="p2735" class="elsevierStylePara elsevierViewall">There are also several published studies which analyse the results by comparing the three main types of AVF in the arm.<a class="elsevierStyleCrossRefs" href="#bib156"><span class="elsevierStyleSup">156-159</span></a> All of them concur in describing better statistically significant patency in autologous VA, even though they present a greater primary failure rate.</p><p id="p2740" class="elsevierStylePara elsevierViewall">Likewise, they also find a higher rate of complications and number of interventions needed to maintain patency in pAVF, but no significant differences between both types of nAVF.</p><p id="p2745" class="elsevierStylePara elsevierViewall">There is no consensus between the different groups on the suitability of transposing the basilic vein during the same surgical procedure or after dilatation and arterialisation. Nor do they agree on which the technique of choice should be (transposition with subcutaneous tunnel, transposition with flap or simple superficialisation).<a class="elsevierStyleCrossRef" href="#bib128"><span class="elsevierStyleSup">128</span></a></p><p id="s0675" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">One-stage procedure versus two-stage surgeries</span></p><p id="p2750" class="elsevierStylePara elsevierViewall">In El Mallah’s RCT,<a class="elsevierStyleCrossRef" href="#bib160"><span class="elsevierStyleSup">160</span></a> which offers the best evidence to date, significantly better primary patency is described after two-stage surgery (50% versus 80%), although the number of patients is not high (n = 39). Similar results are subsequently described by Ozcan et al.,<a class="elsevierStyleCrossRef" href="#bib161"><span class="elsevierStyleSup">161</span></a> who found a higher rate of maturation and lower number of complications when surgery is performed in two stages. Finally, the case series published by Pflederer et al.<a class="elsevierStyleCrossRef" href="#bib158"><span class="elsevierStyleSup">158</span></a> highlighted that most complications in two-stage surgery occurred in the interval between both stages, so the authors recommend this technique to minimise surgical aggression.</p><p id="s0680" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Superficialisation versus transposition</span></p><p id="p2755" class="elsevierStylePara elsevierViewall">There is agreement among authors that transposition through a subcutaneous tunnel is associated with a lower rate of complications,<a class="elsevierStyleCrossRefs" href="#bib117"><span class="elsevierStyleSup">117,162</span></a> but not a better maturation rate. Finally, Hossny<a class="elsevierStyleCrossRef" href="#bib117"><span class="elsevierStyleSup">117</span></a> describes a greater level of satisfaction among nursing staff responsible for needling in the cases where transposition is performed by creating a subcutaneous tunnel.</p><p id="s0685" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Prosthetic arteriovenous fistula in an upper limb</span></p><p id="s0690" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Results of prosthetic arteriovenous fistula</span></p><p id="p2760" class="elsevierStylePara elsevierViewall">The primary patency of prostheses is between 20% and 50% at 24 months and, through successive surgical interventions, can reach a level of assisted patency of between 45% and 70% at 2 years.<a class="elsevierStyleCrossRefs" href="#bib163"><span class="elsevierStyleSup">163-167</span></a></p><p id="p2765" class="elsevierStylePara elsevierViewall">The best available evidence comes from Huber’s systematic review with meta-analysis,<a class="elsevierStyleCrossRef" href="#bib93"><span class="elsevierStyleSup">93</span></a> which found thirt y-four studies, mostly case studies and some non-randomised controlled studies, comparing outcomes in nAVF and pAVF in the upper limb. Primary patency rates for nAVF were 72% at 6 months and 51% at 18 months, and for pAVF 58% and 33%, respectively. Secondary patency rates for nAVF were 86% and 77%, and for pAVF, 76% and 55%, respectively. It must be noted that there is significantly much greater patency in nAVF across all categories analysed (arm/forearm and primary/secondary patency).</p><p id="p2770" class="elsevierStylePara elsevierViewall">To improve this patency, technical improvements, such as the inclusion of bioactive surface with heparin, have been introduced in the prostheses. So far, it has not been possible to demonstrate improvements in patency or in the need for fewer re-interventions.<a class="elsevierStyleCrossRefs" href="#bib168"><span class="elsevierStyleSup">168,169</span></a></p><p id="s0695" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Prosthetic arteriovenous fistula indication</span></p><p id="p2775" class="elsevierStylePara elsevierViewall">There is overall consensus among authors that nAVF are superior to pAVF,<a class="elsevierStyleCrossRef" href="#bib93"><span class="elsevierStyleSup">93</span></a> and this is reflected in the various clinical practice guidelines published.<a class="elsevierStyleCrossRefs" href="#bib6"><span class="elsevierStyleSup">6,10,111</span></a> Thus, there is currently no controversy regarding pAVF indication in cases where venous capital in the patient has been exhausted and no other nAVF can be created.<a class="elsevierStyleCrossRefs" href="#bib93"><span class="elsevierStyleSup">93,132,136</span></a></p><p id="p2780" class="elsevierStylePara elsevierViewall">However, there is debate among authors related to the possible use of pAVF as the first choice in patients where the venous bed has not been exhausted.<a class="elsevierStyleCrossRefs" href="#bib132"><span class="elsevierStyleSup">132,136,170</span></a></p><p id="p2785" class="elsevierStylePara elsevierViewall">In recent years there has been a progressive increase in the average age of patients starting RRT with HD, and underlying pathology, which has meant there is a growing percentage of nAVF with impaired maturation and of nAVF which do not become functional.<a class="elsevierStyleCrossRef" href="#bib78"><span class="elsevierStyleSup">78</span></a> In some studies these have reached 60%.<a class="elsevierStyleCrossRef" href="#bib171"><span class="elsevierStyleSup">171</span></a> Inevitably, this results in a growing dependence on CVC in these patients, thus increasing the risk of sepsis and related complications.<a class="elsevierStyleCrossRef" href="#bib132"><span class="elsevierStyleSup">132</span></a></p><p id="p2790" class="elsevierStylePara elsevierViewall">This has made several authors re-assess the suitability of prioritising nAVF in all cases over pAVF.<a class="elsevierStyleCrossRefs" href="#bib78"><span class="elsevierStyleSup">78,132,136,170</span></a> They have also proposed assessing clinical situations in which a pAVF may be indicated as the technique of first choice, where the potential benefits of pAVF (shorter maturation time, lower rate of primary failure) would outweigh the advantages of nAVF (higher patency, lower rate of complications).</p><p id="p2795" class="elsevierStylePara elsevierViewall">According to Sgroi et al.,<a class="elsevierStyleCrossRef" href="#bib136"><span class="elsevierStyleSup">136</span></a> clinical situations in which a pAVF would be the VA of first choice would be the absence of anatomically appropriate veins in the forearm or arm, a patient with end-stage kidney disease with limited life expectancy, the urgent need to start HD and patients with clinical risk factors for nAVF failure.</p><p id="p2800" class="elsevierStylePara elsevierViewall">Urbanes<a class="elsevierStyleCrossRef" href="#bib132"><span class="elsevierStyleSup">132</span></a> recommends deciding on a case-by-case basis approach, and considering pAVF in cases of limited life expectancy, absence of suitable vessels in forearm and previous failed nAVF. He also considers the possibility of constructing “bridge” pAVF in patients with an urgent need for HD to avoid CVC placement.</p><p id="p2805" class="elsevierStylePara elsevierViewall">Other authors<a class="elsevierStyleCrossRefs" href="#bib170"><span class="elsevierStyleSup">170,172</span></a> propose an algorithm that decides between nAVF and pAVF based on the calculation of the likelihood of primary failure on the basis of three basic parameters: if HD has commenced, life expectancy of above or below 2 years, and a history of previous failed VA.</p><p id="s0700" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Fall-back techniques</span></p><p id="p2810" class="elsevierStylePara elsevierViewall">As mentioned previously, once “conventional” VA have been exhausted, other fall-back VA may be performed. There is limited evidence available on the results of these techniques, so their role remains uncertain in VA choice in clinical practice.</p><p id="s0705" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Vascular access in the lower limb</span></p><p id="p2815" class="elsevierStylePara elsevierViewall">The main recorded evidence comes from the systematic review carried out by Antoniou et al.<a class="elsevierStyleCrossRef" href="#bib173"><span class="elsevierStyleSup">173</span></a> in 2009. Patency and complications of the following types of AVF were assessed: pAVF in the upper thigh (inguinal region), pAVF in mid-thigh and nAVF with femoral vein transposition. These studies obtained acceptable results in terms of patency of these techniques, with a primary patency at 12 months of 48%, 43% and 83%; and a secondary patency at 12 months of 69%, 67% and 93%, respectively. The patency study found greater patency in the nAVF with femoral vein compared to the pAVF, with statistically significant differences, while there were none between both types of pAVF. Infection-related complications are described with more frequency in pAVF while femoral vein nAVF present the highest rate of ischaemia in the limb.</p><p id="p2820" class="elsevierStylePara elsevierViewall">Other observational studies published compare the patency and complications of pAVF in the lower limbs with those created in the upper limbs. Miller et al.<a class="elsevierStyleCrossRef" href="#bib174"><span class="elsevierStyleSup">174</span></a> also show similar patency rates between both territories but with a higher incidence of primary failure and of infectious complications in lower limb VA. In turn, Harish and Allon<a class="elsevierStyleCrossRef" href="#bib175"><span class="elsevierStyleSup">175</span></a> report more serious infections arising from pAVF in these lower limbs.</p><p id="s0710" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Prosthesis-tunnelled catheter device</span></p><p id="p2825" class="elsevierStylePara elsevierViewall">The first study published<a class="elsevierStyleCrossRef" href="#bib176"><span class="elsevierStyleSup">176</span></a> described a reduced incidence of infection compared to tunnelled CVC, obtained via a review of the literature conducted by the same authors (0.7 VA-associated bacteraemias per 1000 days versus 2.3 VA-associated bacteraemias per 1000 days).</p><p id="p2830" class="elsevierStylePara elsevierViewall">Steerman et al.<a class="elsevierStyleCrossRef" href="#bib143"><span class="elsevierStyleSup">143</span></a> conducted a comparative study between this device and pAVF in the thigh, but found no differences in terms of secondary patency, infection and mortality rate. The main advantage of this device is therefore considered to lie in the use of the arm, which allows the thigh to be preserved for future accesses, and in possible use in patients with peripheral arterial disease.</p><p id="p2835" class="elsevierStylePara elsevierViewall">Currently, the best available evidence refers to a meta-analysis published by Al Shakarchi et al.<a class="elsevierStyleCrossRef" href="#bib177"><span class="elsevierStyleSup">177</span></a> in which various published case series are referenced. Likewise, in two studies the results of this device are compared versus pAVF in lower limbs.<a class="elsevierStyleCrossRefs" href="#bib143"><span class="elsevierStyleSup">143,178</span></a> Overall VA patency results described show a 1-year primary patency of 21.9% and a secondary patency of 59.4%, while in the comparison of pAVF there were no significant differences in patency. With regard to infection rate using the device, the authors report an incidence of 0.13 - 0.7 VA-associated bacteraemias per 1000 days, which is significantly better than the rates associated with CVC.<a class="elsevierStyleCrossRef" href="#bib177"><span class="elsevierStyleSup">177</span></a></p><p id="s0715" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">“Exotic” vascular access</span></p><p id="p2840" class="elsevierStylePara elsevierViewall">As mentioned previously, once “conventional” VA have been exhausted, fall-back VA may be constructed. These include pAVF in the anterior chest wall, central vein bypasses, lower limb vein bypasses, and other derivative techniques.</p><p id="p2845" class="elsevierStylePara elsevierViewall">In all cases, the available evidence refers to the publication of case series.<a class="elsevierStyleCrossRefs" href="#bib144"><span class="elsevierStyleSup">144-151</span></a> They all provide acceptable results considering that these are fall-back techniques, but there are no studies with a sufficient level of evidence showing what the first choice is in each case.</p><p id="s0720" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Assessment of the preferred vascular access in the elderly patient</span></p><p id="p2850" class="elsevierStylePara elsevierViewall">As mentioned previously, the VA of choice is nAVF, due mainly to much higher primary, primary assisted and secondary patency rates than pAVF and CVC.<a class="elsevierStyleCrossRef" href="#bib93"><span class="elsevierStyleSup">93</span></a> Likewise, they have a lower complication incidence than other accesses, especially in terms of infections and thrombosis. In contrast, the major drawback of nAVF lies in their low maturation rate and in the lengthy period required for them to mature, especially in cases where secondary procedures are needed to induce them.</p><p id="p2855" class="elsevierStylePara elsevierViewall">This high incidence of primary failure offered by nAVF, which in some studies reaches 60%,<a class="elsevierStyleCrossRef" href="#bib171"><span class="elsevierStyleSup">171</span></a> is considered its real Achilles’ heel. Moreover, it is even more pronounced in elderly patients, where there is an increased risk of primary failure (OR = 1.79) compared to non-elderly patients.<a class="elsevierStyleCrossRef" href="#bib64"><span class="elsevierStyleSup">64</span></a></p><p id="p2860" class="elsevierStylePara elsevierViewall">Added to this is the low survival of this type of patient, due to their age and the frequent presence of significant comorbidities, with a mortality rate > 50% at 2 years for patients older than 75 when starting HD.<a class="elsevierStyleCrossRef" href="#bib179"><span class="elsevierStyleSup">179</span></a> A mortality rate of 30% is described in octogenarians even before they started RRT.<a class="elsevierStyleCrossRef" href="#bib180"><span class="elsevierStyleSup">180</span></a></p><p id="p2865" class="elsevierStylePara elsevierViewall">In the light of these facts, it is the common opinion among several authors that the suitability of nAVF in the geriatric patient and/or with limited life expectancy should be reconsidered, as in these cases, attempting to start RRT through nAVF can lead to a greater dependency on CVC, with their associated complications.<a class="elsevierStyleCrossRefs" href="#bib64"><span class="elsevierStyleSup">64,128,132,136,170,180</span></a></p><p id="p2870" class="elsevierStylePara elsevierViewall">As a result, one of the major issues being debated today, due to the increased average age in the population in HD, is whether nAVF should be created in elderly patients, despite potential maturation issues, or pAVF, despite problems related to infection and medium-term patency. Direct placement of a tunnelled CVC is even considered in patients with limited life expectancy.</p><p id="p2875" class="elsevierStylePara elsevierViewall">When performing a systematic search, no randomised controlled studies have been found regarding this issue. The best available evidence currently consists of a meta-analysis,<a class="elsevierStyleCrossRef" href="#bib64"><span class="elsevierStyleSup">64</span></a> a retrospective study with a cohort of patients from the United States Renal Data System,<a class="elsevierStyleCrossRef" href="#bib181"><span class="elsevierStyleSup">181</span></a> as well as several literature reviews and expert opinions.<a class="elsevierStyleCrossRefs" href="#bib132"><span class="elsevierStyleSup">132,136,170</span></a></p><p id="p2880" class="elsevierStylePara elsevierViewall">In a retrospective study of a cohort of 82,202 patients aged 70 and older when starting HD and whose data were collected in the United States Renal Data System, DeSilva et al.<a class="elsevierStyleCrossRef" href="#bib181"><span class="elsevierStyleSup">181</span></a> analysed the global mortality and survival of these patients. They found a lower mortality rate and better survival in patients who started HD with nAVF. He also highlights that pAVF results are better than CVC. Only in the group of patients over 90, although the trend described is maintained, the differences between nAVF and pAVF did not reach statistical significance. This leads to the consideration that, in general terms, nAVF is also valid as the VA of first choice for most elderly patients, even for those with comorbidities.</p><p id="p2885" class="elsevierStylePara elsevierViewall">With regard to nAVF of choice in the elderly, the review with meta-analysis conducted by Lazarides et al.,<a class="elsevierStyleCrossRef" href="#bib64"><span class="elsevierStyleSup">64</span></a> based on retrospective cohort studies, finds a higher risk of failure for radiocephalic nAVF in elderly patients compared to younger patients. When comparing the results according to nAVF location, they notice a lower failure rate in brachiocephalic nAVF than in radiocephalic nAVF. They consider that the advantage of conserving proximal access sites for possible future accesses found in distal nAVF has minimal importance in patients with a short life expectancy. Therefore, the authors consider that brachiocephalic nAVF should be the first choice in elderly patients with short life expectancy or with a late start in HD. The main limitation of this study is the heterogeneous definition of old age, ranging between 50 and 70 years, depending on the study in question.</p><p id="p2890" class="elsevierStylePara elsevierViewall">Finally, articles based on the literature review and expert opinion concur in considering a patient’s life expectancy as a main parameter rather than specific age as a criterion for the VA of choice. In this respect, they recommend pAVF in cases of patients with a life expectancy of less than 2 years, since this is the average accumulated patency for pAVF for HD.<a class="elsevierStyleCrossRefs" href="#bib132"><span class="elsevierStyleSup">132,136,170</span></a></p><p id="s0725" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="s0730" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Preferred arteriovenous fistula location</span></p><p id="s0735" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Using the non-dominant limb</span></p><p id="p2895" class="elsevierStylePara elsevierViewall">Although there are no studies in this respect, it is widespread practice to create nAVF as the first VA in the non-dominant limb, based on the reasonable assumption that the patient will prefer to have the dominant hand free during the HD session, and also because an AVF in the non-dominant limb will interfere less in daily activities.</p><p id="s0740" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal versus proximal location</span></p><p id="p2900" class="elsevierStylePara elsevierViewall">As mentioned above, there are currently no studies that allow an unequivocal indication of which VA should be the first to be taken into consideration. Nevertheless, experts and guidelines unanimously agree on recommending the most distal AVF possible to preserve the option of future, more proximal VA if necessary.<a class="elsevierStyleCrossRefs" href="#bib6"><span class="elsevierStyleSup">6,10,109,111</span></a> This broadly accepted criterion, based on good clinical practice, has prevailed in the recommendation put forward. However, clinical situations may occur in which other considerations could take priority (elderly patient, patients with short life expectancy in HD).</p><p id="p2905" class="elsevierStylePara elsevierViewall">As a logical exception, in cases where the matured venous bed previously developed for a former, more distal AVF could be exploited to create a proximal AVF, the use of the aforementioned bed must be prioritised.</p><p id="s0745" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Vascular access of choice in the arm</span></p><p id="p2910" class="elsevierStylePara elsevierViewall">After all nAVF options have been used up in the forearm, the next access to consider is the AVF in the arm/antecubital fossa. There are three conventional options: brachiocephalic nAVF, brachiobasilic nAVF or pAVF.</p><p id="p2915" class="elsevierStylePara elsevierViewall">There is currently no discussion among authors on the suitability of nAVF (brachiocephalic AVF and brachiobasilic AVF) over pAVF, given their greater patency and their lower rate and severity of complications. However, there is currently a debate on specific cases in which pAVF may be a reasonable first indication. In accordance with the literature review and the majority opinion of the authors, GEMAV has decided to consider the recommendation to propose pAVF in cases of:<ul class="elsevierStyleList" id="list0315"><li class="elsevierStyleListItem" id="listi1435"><span class="elsevierStyleLabel">1.</span><p id="p2920" class="elsevierStylePara elsevierViewall">Patients without anatomically appropriate veins in the arm or forearm.</p></li><li class="elsevierStyleListItem" id="listi1440"><span class="elsevierStyleLabel">2.</span><p id="p2925" class="elsevierStylePara elsevierViewall">Patients requiring urgent HD (placement of immediate needling pAVF).</p></li></ul></p><p id="p2930" class="elsevierStylePara elsevierViewall">The first assumption is the main indication for pAVF, given the greater patency and the lower rate of complications versus CVC. For patients who require urgent HD without a mature nAVF, the indication of pAVF is restricted to those cases where the patient’s overall status does not allow for the consequences of potential CVC complications to be accepted. In this case, an immediate cannulation pAVF may be indicated, although the patient’s status should be carefully assessed, since pAVF placement without having used up the venous bed may lead to the early exhaustion of the limb’s veins.</p><p id="p2935" class="elsevierStylePara elsevierViewall">Where life expectancy is short (as described above) some experts are of the opinion that an elective pAVF may be suitable. The choice should also be made carefully, as the available evidence does not allow for a minimum value of life expectancy from which to indicate pAVF to be established. In other words, the appropriateness of such a choice must be considered on a case-by-case basis. In any case, pAVF should not be indicated to the detriment of nAVF when life expectancy is over 2 years, as this is the average secondary patency of pAVF.</p><p id="p2940" class="elsevierStylePara elsevierViewall">With regard to the convenience of prioritising brachiocephalic nAVF over brachiobasilic nAVF, the available evidence detects no significant differences in patency, so the decision to propose brachiocephalic AVF as first choice has been based on its lower surgical aggressiveness, greater comfort for the patient and the shorter maturation period required, especially when compared to those brachiobasilic AVF created with two-stage surgery.</p><p id="p2945" class="elsevierStylePara elsevierViewall">Finally, concerning second-choice access in the arm (after brachiocephalic AVF), published studies are clear that there are better rates of primary and primary assisted patency for brachiobasilic AVF, as well as a lower incidence and severity of infections. Thus, although some groups have not documented differences in secondary patency and it takes longer to mature, the evidence recommends prioritising the use of brachiobasilic AVF over pAVF.</p><p id="s0750" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Fall-back techniques</span></p><p id="p2950" class="elsevierStylePara elsevierViewall">After having exhausted access options in the forearm and arm, a fall-back VA can be considered as an alternative to tunnelled CVC. Except in the case of AVF in the thigh, the other techniques lack the casuistry to provide sufficient evidence to support their usefulness and safety in practice. Consequently, their use is recommended selectively, on a case-by-case basis.</p><p id="s0755" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Vascular access at the lower limbs</span></p><p id="p2955" class="elsevierStylePara elsevierViewall">As discussed, AVF use in the thigh is a valid alternative to CVC, supported by the available evidence, with patency results comparable to pAVF in the upper limb.</p><p id="p2960" class="elsevierStylePara elsevierViewall">From the three techniques described (transposition of femoral vein, prosthetic loop in groin and prosthetic loop mid-thigh), the transposition of the superficial femoral vein offers better patency at the expense of an increased risk of ischaemia and greater technical complexity, while the mid-thigh loop shows a non-significantly lower rate of infections in pAVF. In any case, as each technique has different advantages and disadvantages, no recommendation as to the technique of choice has generally been made; it is the patient’s clinical condition and individual preferences which advise their use.</p><p id="s0760" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Prosthesis-tunnelled catheter device</span></p><p id="p2965" class="elsevierStylePara elsevierViewall">As this is a relatively new technique, there are no RCTs supporting its usefulness and safety. Existing evidence reports lower rates of complications than CVC. For this reason, its indication should be assessed after all AVF options have been exhausted prior to the catheter placement.</p><p id="p2970" class="elsevierStylePara elsevierViewall">The only published meta-analysis to date describes rates of complications without significant differences compared to pAVF in the lower limbs, so it can be considered an alternative indication.</p><p id="p2975" class="elsevierStylePara elsevierViewall">However, as with other fall-back techniques, there is currently insufficient evidence to be able to indicate its general use.</p><p id="p2980" class="elsevierStylePara elsevierViewall">The order of sequence for creating VA in function of the location and type of VA is summarised in <a class="elsevierStyleCrossRef" href="#f1">Figure 1</a>.</p><elsevierMultimedia ident="f1"></elsevierMultimedia><p id="s0765" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Preferred vascular access in elderly patients</span></p><p id="p2985" class="elsevierStylePara elsevierViewall">As mentioned in the evidence synthesis development, there is a debate on the VA of first choice in elderly patients. As a result, the high primary failure rate of autologous fistulae in wrist and the older patient’s limited life expectancy, the advisability of prioritising the use of pAVF over nAVF, and of nAVF in arm over nAVF in wrist, are being discussed.</p><p id="p2990" class="elsevierStylePara elsevierViewall">A priori, pAVF is considered as a good option in these patients, since it has a low primary failure rate and drastically shortens the complex process of maturation. The disadvantage to be found in their worse patency rates and higher incidence of complications would be minimised because these are patients with low or very low life expectancy; for this reason, it has been included in the proposals put forward by several authors. Despite this, the studies which validate them have a small number of patients, and studies with a large number of elderly patients continue to confirm the benefits of nAVF across all age groups compared with pAVF and CVC, even in cases with significant comorbidities, with the possible exception of nonagenarian patients. For this reason, GEMAV believes it is important to put forward carefully thought-out indications for this group of patients, while highlighting that the main aim is still the need to achieve HD through nAVF, even in the advanced age group.</p><p id="p2995" class="elsevierStylePara elsevierViewall">Available evidence on the possibility of considering VA in the arm from the outset confirms the worse prognosis for nAVF in the forearm compared to the general population. However, it is difficult and subjective to assess whether this justifies a general recommendation in this regard. In contrast, GEMAV suggests a careful assessment of the elderly patient, including ultrasound mapping, before deciding on the type of nAVF to be created. We consider there is insufficient evidence to be able to recommend constructing nAVF in the arm as a first option in all cases for this group, although in the same way we advise not creating AVF of dubious feasibility where possible, given the greater importance that morbidity/mortality associated with primary VA failure has in this group of patients. As already mentioned, ultrasound mapping is considered to be the most useful tool in this regard.</p><p id="p3000" class="elsevierStylePara elsevierViewall">Finally, GEMAV considers that no time limit can be established to be able to classify patients as elderly. This is due, on the one hand, to the great heterogeneity of inclusion criteria in the main studies, which range from 50 to 90 years of age, and on the other, to the subordination of age criterion to life expectancy. The latter is the factor that will be most important when indicating VA.</p><p id="p3005" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0055"></elsevierMultimedia></p></span><span id="s0775" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">2.6</span><span class="elsevierStyleSectionTitle" id="sect0775">Antibiotic prophylaxis for arteriovenous fistula creation</span><p id="s0780" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p3050" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0060"></elsevierMultimedia></p><p id="sect0785" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p3060" class="elsevierStylePara elsevierViewall">Infection is one of the most significant complications associated with VA and in many cases leads to VA loss. Added to this, as these are superficial structures, infection of the surgical wound can lead to infection of the whole AVF relatively easily.</p><p id="p3065" class="elsevierStylePara elsevierViewall">However, nAVF have a very low rate of peri-operative infection, so there is no evidence to justify systematic preoperative prophylaxis in these patients.</p><p id="p3070" class="elsevierStylePara elsevierViewall">In contrast, a higher incidence and greater severity of infections is reported in pAVF, which in many cases necessitate their withdrawal in a patient who has very limited options for creating further VA. The micro-organisms that most often colonise or infect the pAVF are usually part of the cutaneous microbiota (staphylococci, streptococcus and corinebacterias), the most common being <span class="elsevierStyleItalic">Staphylococcus aureus</span>. For this reason, numerous studies advocate the pre-operative administration of prophylactic antibiotics, the most commonly accepted being a single dose of vancomycin.<a class="elsevierStyleCrossRefs" href="#bib133"><span class="elsevierStyleSup">133,182</span></a></p></span></span><span id="s0790" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">3</span><span class="elsevierStyleSectionTitle" id="sect0790">A<span class="elsevierStyleSmallCaps">rteriovenous fistula care</span></span><p id="p3075" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">CONTENTS</span><ul class="elsevierStyleList" id="list0325"><li class="elsevierStyleListItem" id="listi1455"><span class="elsevierStyleLabel">3.1.</span><p id="p3080" class="elsevierStylePara elsevierViewall">Care in the immediate post-operative period</p></li><li class="elsevierStyleListItem" id="listi1460"><span class="elsevierStyleLabel">3.2.</span><p id="p3085" class="elsevierStylePara elsevierViewall">Care in the maturation period</p></li><li class="elsevierStyleListItem" id="listi1465"><span class="elsevierStyleLabel">3.3.</span><p id="p3090" class="elsevierStylePara elsevierViewall">Use of the arteriovenous fistula</p></li><li class="elsevierStyleListItem" id="listi1470"><span class="elsevierStyleLabel">3.4.</span><p id="p3095" class="elsevierStylePara elsevierViewall">Arteriovenous fistula care by the patient in the interdialytic period</p></li><li class="elsevierStyleListItem" id="listi1475"><span class="elsevierStyleLabel">3.5.</span><p id="p3100" class="elsevierStylePara elsevierViewall">Antiplatelet treatment in arteriovenous fistula</p></li></ul></p><p id="sect0795" class="elsevierStylePara elsevierViewall">Preamble</p><p id="p3105" class="elsevierStylePara elsevierViewall">Arteriovenous fistula (AVF) care, both for native (nAVF) and prosthetic (pAVF), includes all the actions undertaken by the multidisciplinary team and the patients themselves, whose main aim is to achieve optimal development and appropr iately maintain a funct ioning arteriovenous access (VA). Care must begin in the immediate post-operative period, and continue during the maturation period and the whole time the AVF is used.</p><span id="s0800" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">3.1</span><span class="elsevierStyleSectionTitle" id="sect0800">Care in the immediate post-operative period</span><p id="s0805" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p3110" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0065"></elsevierMultimedia></p><p id="s0810" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Care in the immediate post-operative period. Prevention and early diagnosis of complications</span></p><p id="p3120" class="elsevierStylePara elsevierViewall">Strict monitoring of the patient with a newly-created AVF must allow for any possible complication that may arise to be prevented and diagnosed in the early stages and be treated appropriately. The main complications associated with VA creation include haemorrhage, seroma, infection, distal ischaemia, neuropathy and thrombosis.</p><p id="p3125" class="elsevierStylePara elsevierViewall">In the operating theatre, once the AVF has been performed, before concluding the surgical procedure, the surgeon must check the presence of peripheral pulse and AVF function by palpating the thrill.<a class="elsevierStyleCrossRef" href="#bib183"><span class="elsevierStyleSup">183</span></a></p><p id="p3130" class="elsevierStylePara elsevierViewall">A functioning AVF has a palpable thrill and an audible bruit on auscultation at the level of the anastomosis. If there is any doubt about functioning, a Doppler ultrasound (DU) can be performed<a class="elsevierStyleCrossRef" href="#bib183"><span class="elsevierStyleSup">183</span></a> to demonstrate its permeability. To this end, some authors have proposed intra-operative flowmetry.<a class="elsevierStyleCrossRef" href="#bib184"><span class="elsevierStyleSup">184</span></a> The absence of bruit at the end of the procedure in conjunction with end-diastolic velocity values under 24.5 cm/s, obtained by intraoperative DU, represent an effective predictive test for AVF thrombosis, which is better than the absence of thrill.<a class="elsevierStyleCrossRef" href="#bib185"><span class="elsevierStyleSup">185</span></a></p><p id="p3135" class="elsevierStylePara elsevierViewall">It is important that the surgeon includes a clear diagram of the newly-created AVF in the patient’s medical record. The more information the nursing staff have about the AVF, the greater the likelihood of successful cannulation and improved VA patency.<a class="elsevierStyleCrossRef" href="#bib184"><span class="elsevierStyleSup">184</span></a></p><p id="p3140" class="elsevierStylePara elsevierViewall">Most AVF can be created in major outpatient surgery without the need for hospital admission. During the time that the patient remains in the health centre, the AVF must be observed carefully in case any of the three major complications, i.e. bleeding, ischaemia and thrombosis, appear.</p><p id="s0815" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Care in the immediate post-operative period</span></p><p id="p3145" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0330"><li class="elsevierStyleListItem" id="listi1480"><span class="elsevierStyleLabel">1.</span><p id="p3150" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Monitor vital signs</span>. Blood pressure (BP), heart rate, and body temperature should be checked. BP must never be taken in the arm with the AVF.<a class="elsevierStyleCrossRefs" href="#bib183"><span class="elsevierStyleSup">183,186</span></a> The patient’s haemodynamic stability must always be maintained, minimising the risk of AFV thrombosis.<a class="elsevierStyleCrossRefs" href="#bib183"><span class="elsevierStyleSup">183,186</span></a>.</p></li><li class="elsevierStyleListItem" id="listi1485"><span class="elsevierStyleLabel">2.</span><p id="p3155" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Physical examination of the AVF</span> (see section “Monitoring and surveillance of arteriovenous fistula”). The existence of bruit and thrill in the AVF should be checked in order to detect early failure and thrombosis. There are various pre-operative factors related to lower patency immediately after nAVF creation, associated with age over 65, female gender, diabetes, coronary disease and the patient’s peripheral vascular disease history, which are discussed in section 1 of this guide.<a class="elsevierStyleCrossRefs" href="#bib58"><span class="elsevierStyleSup">58,185,187,188</span></a></p><p id="p3160" class="elsevierStylePara elsevierViewall">In the case of pAVF, Monroy-Cuadros et al. observed lower patency in patients with the aforementioned clinical history and an access flow (Q<span class="elsevierStyleInf">A</span>) < 650 mL/min when starting needling.<a class="elsevierStyleCrossRef" href="#bib189"><span class="elsevierStyleSup">189</span></a> Q<span class="elsevierStyleInf">A</span> values < 500 mL/min in the nAVF represent an independent risk factor associated with lower primary patency.<a class="elsevierStyleCrossRef" href="#bib71"><span class="elsevierStyleSup">71</span></a></p></li><li class="elsevierStyleListItem" id="listi1490"><span class="elsevierStyleLabel">3.</span><p id="p3165" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Monitor the dressing</span> for signs of bleeding. No compression dressings should be placed on the arm with the AVF.</p></li><li class="elsevierStyleListItem" id="listi1495"><span class="elsevierStyleLabel">4.</span><p id="p3170" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">The limb with the arteriovenous fistula should be raised</span>, resting on a pillow to promote venous return and prevent oedema.<a class="elsevierStyleCrossRefs" href="#bib183"><span class="elsevierStyleSup">183,186</span></a></p></li><li class="elsevierStyleListItem" id="listi1500"><span class="elsevierStyleLabel">5.</span><p id="p3175" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Examine the limb where the AVF has been created and check the patient’s blood flow</span>. Distal pulses of the AVF limb must be palpated and the capillary refill checked. Distal areas of the limb should be observed to rule out signs of ischaemia, such as the occurrence of pain, coldness, pallor and motor and sensory changes in the affected hand.</p><p id="p3180" class="elsevierStylePara elsevierViewall">The <span class="elsevierStyleItalic">distal hypoperfusion syndrome (steal syndrome)</span> associated with AVF during the post-operative period is an uncommon but important complication. It is caused by a sudden drop in distal perfusion pressure, due to the occurrence of a preferred flow or diversion of arterial blood flow through the VA, causing symptomatic ischaemia in the affected limb. It occurs more frequently in arm nAVF with an incidence of between 1% and 20%, which is higher than in forearm or radiocephalic AVF<a class="elsevierStyleCrossRefs" href="#bib85"><span class="elsevierStyleSup">85,87,87a,87b</span></a> (see section “Complications of arteriovenous fistula”). Although less common, it may also be caused by an obstruction of the artery proximal to the anastomosis due to a technical failure.</p><p id="p3185" class="elsevierStylePara elsevierViewall">If a distal pulse to the AVF is observed, a differential diagnosis should be made with <span class="elsevierStyleItalic">ischaemic monomelic neuropathy</span> (IMN). This is a neurological pathology that affects the three nerves in the forearm: the radial, ulnar and median nerve, without other signs that suggest arterial ischaemia. The main risk factors for steal syndrome and IMN are common (diabetes, female gender and brachial artery flow). In any case, the ischaemic hand of an AVF, whether due to arterial steal syndrome or the existence of IMN, may necessitate a revascularisation procedure or the complete ligation of the AVF.<a class="elsevierStyleCrossRef" href="#bib190"><span class="elsevierStyleSup">190</span></a></p></li><li class="elsevierStyleListItem" id="listi1505"><span class="elsevierStyleLabel">6.</span><p id="p3190" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Post-operative bleeding and/or haematoma should be checked</span> (see section 5) <span class="elsevierStyleItalic">and whether an immediate surgical review is required assessed</span>. Although bleeding complications are uncommon, we should not forget that this is a surgical procedure which involves a vascular anastomosis and, therefore, it is important to check there is no haematoma in the surgical area which might necessitate an urgent review of the VA before discharge.<a class="elsevierStyleCrossRef" href="#bib191"><span class="elsevierStyleSup">191</span></a></p></li></ul></p><p id="s0820" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Initial care during the outpatient follow-up</span></p><p id="p3195" class="elsevierStylePara elsevierViewall">The first outpatient check-up should be carried about 7 days after the procedure. Depending on the status of the wound, the suture may be substituted by adhesive strips for some more days, or half of the stitches removed alternately. Antihypertensive medication should be reviewed and adjusted in order to avoid hypotensive episodes and minimise the risk of thrombosis of the AVF.<a class="elsevierStyleCrossRef" href="#bib191"><span class="elsevierStyleSup">191</span></a></p><p id="p3200" class="elsevierStylePara elsevierViewall">This check-up should assess AVF patency and rule out the presence of complications. Skin and subcutaneous tissue should be examined to rule out any signs of infection, which can occur in between 1% and 5% of cases.<a class="elsevierStyleCrossRef" href="#bib192"><span class="elsevierStyleSup">192</span></a> If swelling, erythema, cellulitis or skin induration is observed, DU can help us to diagnose the specific existing pathology. Treatment of complications is discussed in section 5.</p><p id="p3205" class="elsevierStylePara elsevierViewall">In the case of oedema in the AVF arm, venous hypertension should be ruled out. This complication occurs in 3% of patients and is usually associated with a central venous stenosis secondary to a previous CVC placement.<a class="elsevierStyleCrossRef" href="#bib190"><span class="elsevierStyleSup">190</span></a></p><p id="p3210" class="elsevierStylePara elsevierViewall">Moreover, in pre-dialysis patients with ACKD, episodes of decompensated heart failure are not uncommon following nAVF creation. Up to 17% of cases of heart failure in patients with stage 4-5 CKD have been reported after AVF surgery related to an increase in cardiac output.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,193</span></a> It should be suspected when the AVF flow is > 2 L/min or ≥ 30% of the cardiac output.<a class="elsevierStyleCrossRefs" href="#bib190"><span class="elsevierStyleSup">190,194</span></a> This is described in detail in section 5.</p><p id="p3215" class="elsevierStylePara elsevierViewall">Medical and nursing staff are responsible for informing the patient about the characteristics of the AVF, its importance for their future haemodialysis (HD) treatment and the self-care that they should give their newly-created AVF (see self-care plan in point 3.4 of this section).<a class="elsevierStyleCrossRef" href="#bib191"><span class="elsevierStyleSup">191</span></a></p></span><span id="s0825" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">3.2</span><span class="elsevierStyleSectionTitle" id="sect0825">Care in the maturation period</span><p id="sect0830" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p3220" class="elsevierStylePara elsevierViewall">Inadequate nAVF maturation may increase the incidence of complications associated with needling (haematoma, thrombosis) and reduce patency. In addition, when needling begins, a non-matured nAVF may require CVC placement in the incident patient in order to start the HD programme or CVC withdrawal should be delayed in the prevalent patient. Therefore, it is important to establish strategies that encourage the maturation process so that the nAVF can be cannulated at the right time.</p><p id="s0835" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p3225" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0070"></elsevierMultimedia></p><p id="p3250" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question VI Are exercises useful for developing arteriovenous fistulae?</span></p><p id="p3255" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question VI in <a href="https://static.elsevier.es/nefroguiaaveng/6_PCVI_Ejercicios_dilatacion_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0030"></elsevierMultimedia></p><p id="s0840" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p3260" class="elsevierStylePara elsevierViewall">The study by Leaf et al.<a class="elsevierStyleCrossRef" href="#bib195"><span class="elsevierStyleSup">195</span></a> showed that the performance of a simple programme of exercises can cause a significant increase in cephalic vein diameter prior to the creation of the VA (n = 5). The diameter of the cephalic vein in the exercised arm increased significantly compared with the control arm when measured, both without (0.048 ± 0.016 versus 0.024 ± 0.023 cm<span class="elsevierStyleSup">2</span>) and with a tourniquet (0.056 ± 0.022 versus 0.028 ± 0.027 cm<span class="elsevierStyleSup">2</span>).</p><p id="p3265" class="elsevierStylePara elsevierViewall">Order et al.<a class="elsevierStyleCrossRef" href="#bib196"><span class="elsevierStyleSup">196</span></a> analysed the impact of physical exercise in 20 patients prior to surgery. The mean change seen in the diameter of the nAVF was 0.051 cm or 9.3% (p < 0.0001).</p><p id="p3270" class="elsevierStylePara elsevierViewall">The study by Uy et al.<a class="elsevierStyleCrossRef" href="#bib197"><span class="elsevierStyleSup">197</span></a> included 15 patients with small cephalic vein diameter (< 2.5 mm). After four weeks of exercise, the average diameter of the vein increased significantly, both proximally (1.66 to 2.13 mm) and distally (2.22 to 2.81 mm).</p><p id="p3275" class="elsevierStylePara elsevierViewall">The prospective randomised study by Salimi et al.<a class="elsevierStyleCrossRef" href="#bib198"><span class="elsevierStyleSup">198</span></a> analysed the influence of a regulated scheme of exercises on nAVF maturation in 50 patients in a HD programme (25 patients in control group). Checks were performed by DU at 24 h and 2 weeks after AVF creation. Significant increases in the diameter of the efferent vein, wall thickness, venous area and Q<span class="elsevierStyleInf">A</span> were observed in the study group after exercise. Although there were no significant differences with regard to criteria of ultrasound maturation, significantly higher maturation was observed by clinical criteria. Its beneficial effects include the increase in venous diameter, as well as the increase in muscle mass and the decrease in the amount of fat tissue.</p><p id="p3280" class="elsevierStylePara elsevierViewall">Fontseré et al.<a class="elsevierStyleCrossRef" href="#bib199"><span class="elsevierStyleSup">199</span></a> carried out a prospective randomised controlled study on the effect of a post-operative programme on nAVF maturation 1 month after creation in 69 patients with CKD in the pre-dialysis stage (65.2%) and in chronic HD programme. After 1 month, an assessment was made using criteria of adequate clinical maturation (specialist nursing staff) and ultrasound (Q<span class="elsevierStyleInf">A</span> > 500 mL/min, diameter > 5mm and depth < 6mm) in all patients. The rates of clinical and ultrasound maturation 1 month after nAVF construction were 88.4% and 78.3% respectively (Kappa coefficient = 0.539). The exercise group showed a non-significant trend towards better clinical and ultrasound maturation compared with the control group (94.7% versus 80.6%, p = 0.069; 81.6% versus 74.2%, p = 0.459). Logistic regression analysis identified nAVF location as a confounding factor so that, in distal nAVF, the exercise group showed significantly higher clinical maturation, but not in ultrasound (odds ratio [OR]: 5.861, 95% confidence interval [CI], 1.006-34.146, and OR: 2.403, 95% CI, 0.66-8.754, respectively).<a class="elsevierStyleCrossRef" href="#bib199"><span class="elsevierStyleSup">199</span></a></p><p id="s0845" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p3285" class="elsevierStylePara elsevierViewall">Although there are few studies on this subject, performing isometric exercises on the limb, before and/or after AVF construction, may promote the maturation process of the nAVF.</p><p id="p3290" class="elsevierStylePara elsevierViewall">GEMAV suggests advising patients with ACKD to do exercises before and after nAVF creation in order to promote muscle and vascular development, and, consequently, to accelerate the maturation process, increase nAVF patency and development, and reduce morbidity associated with lack of maturation.</p><p id="p3295" class="elsevierStylePara elsevierViewall">However, further clinical research is needed to analyse the advantages of doing exercises as a factor promoting the correct nAVF maturation process.</p><p id="p3300" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0075"></elsevierMultimedia></p><p id="p3310" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question VII What is the minimum maturation time required for a native or prosthetic arteriovenous fistula to be mature enough for needling?</span></p><p id="p3315" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question VII in <a href="https://static.elsevier.es/nefroguiaaveng/7_PCVII_Tiempo_minimo_INGL.pdf">electronic appendices</a>)</p><p id="sect0855" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p3320" class="elsevierStylePara elsevierViewall">The maturation period for the VA is the time needed from the creation of the AVF until the moment when the first HD session can be carried out with the minimum risk of complications arising from needling. Although timing to begin needling is a controversial issue, both in nAVF and pAVF, it is accepted that excessively early use of any AVF may lead to a significant reduction in patency in relation to associated complications. Therefore, it is very important to determine the ideal time to initiate AVF cannulation.</p><p id="p3325" class="elsevierStylePara elsevierViewall">The criteria for mature AVF are discussed in section 2. The lack of nAVF maturation has been associated with: <span class="elsevierStyleItalic">a)</span> insufficient arterial dilatation, present in patients with severe vascular disease and diabetes mellitus in the context of accelerated arteriosclerosis; <span class="elsevierStyleItalic">b)</span> deficiency in venous vasodilation secondary to the existence of collateral venous circulation; <span class="elsevierStyleItalic">c)</span> presence of a central stenosis, and <span class="elsevierStyleItalic">d)</span> development of accelerated neointimal hyperplasia secondary to juxta-anastomotic stenosis after the surgical procedure in areas of low tangential force.<a class="elsevierStyleCrossRefs" href="#bib58"><span class="elsevierStyleSup">58,187,188</span></a><elsevierMultimedia ident="ut0035"></elsevierMultimedia></p><p id="s0860" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p3330" class="elsevierStylePara elsevierViewall">There are only two observational studies that deal with this question.<a class="elsevierStyleCrossRefs" href="#bib200"><span class="elsevierStyleSup">200,201</span></a> The first, based on data provided by the DOPPS study (Dialysis Outcomes and Practice Patterns Study), showed that the first nAVF puncture was performed within 2 months of construction in 36% of North American patients, 79% of European patients and 98% of Japanese patients.<a class="elsevierStyleCrossRef" href="#bib200"><span class="elsevierStyleSup">200</span></a> In the study by Rayner et al.,<a class="elsevierStyleCrossRef" href="#bib201"><span class="elsevierStyleSup">201</span></a> nAVF cannulation within 2 weeks after creation was associated with a significant decrease in patency, with a relative risk of 2.27 (p = 0.02). DOPPS studies<a class="elsevierStyleCrossRefs" href="#bib200"><span class="elsevierStyleSup">200,201</span></a> suggest that, while nAVF cannulation is not recommended within 2 weeks of creation, first cannulation between 2 and 4 weeks afterwards may be considered following close clinical evaluation without it necessarily increasing the risk of nAVF failure.</p><p id="p3335" class="elsevierStylePara elsevierViewall">In the case of pAVF, according to the data provided by the DOPPS study,<a class="elsevierStyleCrossRef" href="#bib200"><span class="elsevierStyleSup">200</span></a> needling starts between 2 and 4 weeks in 62% of North American patients, 61% of European patients and 42% of Japanese patients. No significant reductions in pAVF patency were observed in this study when cannulation started before 2 weeks or after 4 weeks following surgical placement, taking the 2-3-week subgroup as reference. However, needling a polytetrafluoroethylene pAVF within 2 weeks of its construction is not recommended due to the high risk of haematoma. Except those immediate cannulation pAVF, the remaining pAVF may usually be cannulated 2-4 weeks after construction once the subcutaneous oedema has disappeared and the graft can be easily palpated along its entire length.</p><p id="s0865" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p3340" class="elsevierStylePara elsevierViewall">In the case of nAVF, we recommend that needling not be started within the first 2 weeks after creation. From this date onwards, risks must be studied on a case-by-case basis in order to decide the ideal moment to perform the first cannulation.</p><p id="p3345" class="elsevierStylePara elsevierViewall">For those patients with pAVF, we recommend that needling starts between two to four weeks after construction, except immediate cannulation pAVF. In this subgroup of patients, it is important to be familiar with the type of prosthetic material used.</p><p id="p3350" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0080"></elsevierMultimedia></p></span><span id="s0875" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">3.3</span><span class="elsevierStyleSectionTitle" id="sect0875">Use of the arteriovenous fistula</span><p id="s0880" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p3365" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0085"></elsevierMultimedia></p><p id="sect0885" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p3400" class="elsevierStylePara elsevierViewall">A direct relationship has been described between a premature start to needling in nAVF and shorter patency.<a class="elsevierStyleCrossRefs" href="#bib202"><span class="elsevierStyleSup">202,203</span></a> An AVF should only be cannulated when an optimal level of maturation has been reached. Therefore, nAVF must be monitored in all ACKD check-ups and, if insufficient development is observed, the nAVF must be examined using DU for diagnosis and the corrective treatment applied using percutaneous transluminal angioplasty (PTA) and/or surgery.</p><p id="s0890" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Basic examination to be performed prior to the first arteriovenous fistula cannulation</span></p><p id="p3405" class="elsevierStylePara elsevierViewall">Physical examination is the most commonly used method for nAVF monitoring in the ACKD outpatient check-up to detect a deficiency in maturation and to attempt to identify its cause at the earliest possible moment. Different studies have shown that where this is done exhaustively, there is an increased diagnostic capability and an extraordinary cost-benefit relationship in the detection of significant stenosis and collateral venous circulation.<a class="elsevierStyleCrossRefs" href="#bib204"><span class="elsevierStyleSup">204,205</span></a> The procedure for physical examinations is described in section 4.</p><p id="p3410" class="elsevierStylePara elsevierViewall">DU is an essential tool in ACKD outpatient clinics and should be used both to perform pre-operative vascular mapping and to identify the cause of any post-surgical maturation deficit observed in physical examination. In the presence of any nAVF with insufficient clinical maturation, which is highly unlikely to be ready to use in the first HD session, GEMAV considers it necessary to carry out a DU to diagnose the precise cause of the lack of maturation. The objective is to repair any non-matured nAVF using an endovascular and/or surgical procedure in the pre-dialysis stage so that it can be cannulated in the first HD session.</p><p id="s0895" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Asepsis during arteriovenous fistula cannulation. Use of local anaesthetics</span></p><p id="p3415" class="elsevierStylePara elsevierViewall">It must not be forgotten that AVF cannulation is an invasive procedure and, therefore, extreme care must be taken with asepsis measures. Before placing the sterile field and disinfecting the needling area, the arm or the needling area in the leg must be washed with soap and water, taking particular care where patients have used anaesthetic cream and if there are highly prominent aneurysms. Alcoholic chlorhexidine, alcohol 70% or povidone-iodine can be used to disinfect the area. The first takes effect after 30 seconds and lasts for up to 48 h. Alcohol has a shorter bacteriostatic effect and should be applied 1 min before needling. Povidone requires 2-3 min to fully develop its bacteriostatic capability. In an international survey conducted at 171 HD centres on 10,807 cannulations with two needles in patients mainly dialysed with nAVF (91%), an alcohol-based disinfectant was used for most cannulations (69.7%) and certain specific preferences were observed depending on the country: chlorhexidine in the United Kingdom, Ireland, Italy and South Africa, and povidone-iodine in Spain.<a class="elsevierStyleCrossRef" href="#bib206"><span class="elsevierStyleSup">206</span></a></p><p id="p3420" class="elsevierStylePara elsevierViewall">Some patients with hypersensitivity to pain on needling the AVF may benefit from topical local anaesthetics. The most commonly used are the combination of lidocaine with prilocaine (cream) and ethyl chloride (spray) which need to be applied at least 1 hour before and 20 seconds before needling, respectively. In the same study by Gauly et al., the use of local anaesthetics was uncommon (overall, in 8.5% of cases), except in the United Kingdom, Ireland and Spain, where 29.4%, 31.7% and 27.2%, respectively, of cannulations were performed with their prior application.<a class="elsevierStyleCrossRef" href="#bib206"><span class="elsevierStyleSup">206</span></a></p><p id="s0900" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Characteristics of the dialysis needles</span></p><p id="p3425" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Types of needles</span></p><p id="p3430" class="elsevierStylePara elsevierViewall">HD needles may have a sharp or a blunt tip. They have a silicone coating to facilitate insertion and reduce their resistance to Q<span class="elsevierStyleInf">A</span>.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> The bloodstream can be accessed through AVF via 2 needles with a different structure to carry out the HD session<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a>: <span class="elsevierStyleItalic">a)</span> conventional stainless steel needle; this type of needle is the most commonly used, and <span class="elsevierStyleItalic">b)</span> catheter-fistula; made up of a polyurethane cannula and an internal metal needle designed to cannulate nAVF. Upon withdrawal of the needle, the cannula remains inside the arterialised vein for the entire HD session.<a class="elsevierStyleCrossRefs" href="#bib208"><span class="elsevierStyleSup">208-210</span></a> This type of cannula can reduce pain both cannulating and removing the needle,<a class="elsevierStyleCrossRef" href="#bib209"><span class="elsevierStyleSup">209</span></a> besides decreasing the risk of extravasations and haematoma,<a class="elsevierStyleCrossRef" href="#bib208"><span class="elsevierStyleSup">208</span></a> especially in the case of nAVF in the elbow flexure in elderly patients.</p><p id="p3435" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Gauge and length of needles</span></p><p id="p3440" class="elsevierStylePara elsevierViewall">HD prescription should be adapted to the needle type used.<a class="elsevierStyleCrossRef" href="#bib211"><span class="elsevierStyleSup">211</span></a> As a general rule, the smallest gauge and shortest needle which allows an adequate blood flow (Q<span class="elsevierStyleInf">A</span>) must always be chosen to suit the specific needs of each individual patient.<a class="elsevierStyleCrossRef" href="#bib212"><span class="elsevierStyleSup">212</span></a></p><p id="p3445" class="elsevierStylePara elsevierViewall">With regard to needle gauge, these are available from 17 G up to 14 G, with the numbering being inverse to the gauge, i.e. a 17 G needle is the smallest and, on the other hand, a 14 G needle is the largest.<a class="elsevierStyleCrossRef" href="#bib213"><span class="elsevierStyleSup">213</span></a> After the first nAVF cannulations without complications, the choice of a higher-sized needle (lower number) depends on the diameter of the arterialised vein and the existing Q<span class="elsevierStyleInf">A</span>.<a class="elsevierStyleCrossRef" href="#bib213"><span class="elsevierStyleSup">213</span></a> In the study by Gauly et al., the needle gauge most commonly used was 15 G (61.3%), followed by 16 G in one-third of cases. 14 G and 17 G needles were used in less than 3% of cases.<a class="elsevierStyleCrossRef" href="#bib206"><span class="elsevierStyleSup">206</span></a></p><p id="p3450" class="elsevierStylePara elsevierViewall">Moreover, the needle length chosen should be the shortest possible to reach the centre of the AVF lumen and thus reduce the risk of perforating the posterior wall.<a class="elsevierStyleCrossRef" href="#bib213"><span class="elsevierStyleSup">213</span></a></p><p id="p3455" class="elsevierStylePara elsevierViewall">Only if we consider the relationship between a particular needle gauge, the maximum blood pump velocity and the duration of the HD session will we be able to adequately use nAVF without causing haematoma.<a class="elsevierStyleCrossRef" href="#bib211"><span class="elsevierStyleSup">211</span></a> Again, in the survey by Gauly et al., when larger needles were used (14 G) most patients were dialysed using a high pump flow (Q<span class="elsevierStyleInf">B</span>) (> 400 mL/min) and, on the other hand, when small needles were used (17 G) more than 80% of patients were dialysed with a Q<span class="elsevierStyleInf">B</span> ≤ 300 mL/min.<a class="elsevierStyleCrossRef" href="#bib206"><span class="elsevierStyleSup">206</span></a></p><p id="p3460" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Arterial needle backeye</span></p><p id="p3465" class="elsevierStylePara elsevierViewall">In the study by Gauly et al., the arterial needle with backeye was used in most cases (65%).<a class="elsevierStyleCrossRef" href="#bib206"><span class="elsevierStyleSup">206</span></a> An arterial needle with backeye should always be used to maximise the flow aspirated through it and to prevent the adhesion of the bevel to the vessel wall due to negative pressure, which could cause damage.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,212</span></a></p><p id="p3470" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">First cannulations of a new native arteriovenous fistula</span></p><p id="p3475" class="elsevierStylePara elsevierViewall">Use the needle with the smallest gauge available (usually, 17 G)<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a>. The selection of this “arterial” needle gauge ensures a sufficient blood flow to meet a demand for 200 mL/min from the blood flow pump of the HD machine and, simultaneously, minimises resulting haematoma if extravasation occurs during the HD session.<a class="elsevierStyleCrossRef" href="#bib213"><span class="elsevierStyleSup">213</span></a> Pre-pump arterial pressure monitoring (–250 mmHg or less) is recommended to ensure that the blood pump velocity does not exceed what the “arterial” needle can provide.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a></p><p id="s0905" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Arteriovenous fistula cannulation. Methodology</span></p><p id="p3480" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Arteriovenous fistula cannulation</span></p><p id="p3485" class="elsevierStylePara elsevierViewall">All professionals involved in a kidney patient’s care are aware of the existing difficulty in ensuring that the incident patient is dialysed through a mature nAVF from the very first HD session.<a class="elsevierStyleCrossRef" href="#bib214"><span class="elsevierStyleSup">214</span></a> Perhaps the main barrier lies in the maturation period but, undoubtedly, the final crucial hurdle that must be overcome for the nAVF to be usable for HD is its cannulation.<a class="elsevierStyleCrossRef" href="#bib214"><span class="elsevierStyleSup">214</span></a> Inadequate cannulation of the nAVF may require the placement of a CVC to carry out the first HD session and, therefore, all the previous work done in the pre-dialysis phase to achieve the best VA to start the HD programme will have been lost.</p><p id="p3490" class="elsevierStylePara elsevierViewall">There is a relationship between cannulation practices (technique used, needle gauge, direction of the arterial needle), patient factors (age, comorbidity) and centre factors (Q<span class="elsevierStyleInf">B</span>, duration of the session), all of which may influence one of the key issues in any HD programme in a prevalent patient: the AVF patency.<a class="elsevierStyleCrossRefs" href="#bib215"><span class="elsevierStyleSup">215,216</span></a> In this respect, Parisotto et al.,<a class="elsevierStyleCrossRef" href="#bib217"><span class="elsevierStyleSup">217</span></a> applying a Cox multivariate regression model on the results of an international survey on cannulation practices (n = 7058, majority nAVF), showed that AVF patency was significantly lower in the case of HD through pAVF, small-gauge needle (16 G), which may have been due to the endothelial damage caused by the increased velocity of the blood return, retrograde direction of the arterial needle and cannulation with the bevel down, Q<span class="elsevierStyleInf">B</span> < 300 mL/min, venous pressure < 100 mmHg (perhaps due to inflow stenosis) or progressively increasing pressure (perhaps due to outflow stenosis) and, finally, without compression of the arm at the time of cannulation or with compression using a tourniquet (versus compression of the arm by the patient). In addition, AVF patency was significantly greater if needling was performed using the rope ladder or the buttonhole technique compared to the area method.<a class="elsevierStyleCrossRef" href="#bib217"><span class="elsevierStyleSup">217</span></a></p><p id="p3495" class="elsevierStylePara elsevierViewall">Repeated venous cannulation itself may damage the AVF due to direct trauma of the needle and/or to increased endothelial damage by shear forces created during blood return.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,211,212,218</span></a> These factors may stimulate the development of intimal hyperplasia, which could decrease patency of the AVF and, probably, also the survival of the patient.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,211,212,218</span></a> In this respect, the Frequent Hemodialysis Network Trial Group has conducted two controlled randomised trials: <span class="elsevierStyleItalic">a)</span> diurnal trial, comparing patients in in-centre HD during the day (6 days a week) and patients in conventional HD (3 days per week) for 1 year, and <span class="elsevierStyleItalic">b)</span> nocturnal trial, comparing patients in nocturnal home HD (6 nights per week) and patients in conventional HD (3 days per week) for 1 year.<a class="elsevierStyleCrossRef" href="#bib218"><span class="elsevierStyleSup">218</span></a> In both diurnal and nocturnal trials, the HD regimen of 6 times per week significantly increased the risk of AVF complications compared to the HD regimen performed 3 times per week. The authors concluded that frequent HD increases the risk of VA complications, largely because of the need for more repair procedures in patients with AVF. In other words, the more frequent nAVF use itself causes VA dysfunction.<a class="elsevierStyleCrossRef" href="#bib218"><span class="elsevierStyleSup">218</span></a></p><p id="p3500" class="elsevierStylePara elsevierViewall">Cannulation practices are key factors in the process of AVF care and attention. An inadequate AVF cannulation technique could lead to short and long-term complications, such as infiltration-haematoma, infection, formation of aneurysms and pain at the cannulation site, resulting in situations of anxiety and fear in the patient, which often lead to a refusal to remove the CVC.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,211,212</span></a> These complications have a number of direct consequences, such as the need for additional needling, suboptimal or missed HD sessions, patient discomfort due to interruption of their regular treatment regimen and the need for longer sessions, the need to use CVC to bridge the gap between the creation and maturation of a new AVF, increase in hospital admissions and interventions, as well as higher HD treatment costs.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,211,212</span></a> These complications and their consequences can reduce VA patency and patient survival.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,211,212</span></a></p><p id="p3505" class="elsevierStylePara elsevierViewall">Lee et al. analysed the risk factors and consequences of extravasations caused by needling the nAVF comparing 47 patients with a sufficiently significant nAVF infiltration to prolong CVC dependence for HD with 643 patients in the control group without nAVF infiltration.<a class="elsevierStyleCrossRef" href="#bib208"><span class="elsevierStyleSup">208</span></a> These authors showed that nAVF infiltration caused by needles is more common in elderly patients (aged 65 years or above) and those with recent nAVF (less than 6 months).<a class="elsevierStyleCrossRef" href="#bib208"><span class="elsevierStyleSup">208</span></a> In addition, as a result of these infiltrations, numerous diagnostic studies and interventions on the nAVF were carried out. There was a notable percentage of thrombosis (26%) and CVC dependence for HD was prolonged for more than 3 months.<a class="elsevierStyleCrossRef" href="#bib208"><span class="elsevierStyleSup">208</span></a> Finally, the financial impact of CVC-related bacteraemia, linked to the increase in the days of CVC dependence secondary to major nAVF infiltration, was estimated at US $ 8 million per year.<a class="elsevierStyleCrossRef" href="#bib208"><span class="elsevierStyleSup">208</span></a></p><p id="p3510" class="elsevierStylePara elsevierViewall">Van Loon et al. published two prospective observational studies in 2009 (from the first cannulation until 6-months follow-up) on incident HD patients with nAVF and pAVF using the rope ladder technique.<a class="elsevierStyleCrossRefs" href="#bib219"><span class="elsevierStyleSup">219,220</span></a> In most patients miscannulations (defined as the need to use more than one needle for the arterial and venous connection) were recorded between 1 and 10 times, being always greater the percentage of miscannulations for nAVF than for pAVF<a class="elsevierStyleCrossRef" href="#bib219"><span class="elsevierStyleSup">219</span></a>. Although miscannulations were recorded on over 10 occasions for 37% of patients with nAVF and 19% of patients with pAVF, ultrasound-guided needling of the AVF was only used in 4% of patients.<a class="elsevierStyleCrossRef" href="#bib219"><span class="elsevierStyleSup">219</span></a> The percentage of patients with haematoma secondary to inadequate cannulation was always higher for nAVF than for pAVF, and it was higher for AVF in the arm than in the forearm.<a class="elsevierStyleCrossRef" href="#bib219"><span class="elsevierStyleSup">219</span></a> In the multiple regression model applied, complications associated with cannulation (need to use a CVC or carry out the HD session using single needle) were predictive of AVF thrombosis.<a class="elsevierStyleCrossRef" href="#bib219"><span class="elsevierStyleSup">219</span></a> In addition, these authors showed that these complications depend on the type of existing AVF so the percentage of AVF without complications was always significantly lower for pAVF than for nAVF.<a class="elsevierStyleCrossRef" href="#bib220"><span class="elsevierStyleSup">220</span></a></p><p id="p3515" class="elsevierStylePara elsevierViewall">The use of the portable DU has been recommended in all HD Units in Spain for several years.<a class="elsevierStyleCrossRef" href="#bib216"><span class="elsevierStyleSup">216</span></a> There is no doubt that ultrasound guided cannulation is a tool of invaluable assistance for successful cannulation in difficult nAVF and, therefore, it can reduce errors in needling.<a class="elsevierStyleCrossRefs" href="#bib221"><span class="elsevierStyleSup">221,222</span></a> In a national study covering 119 examinations using portable DU performed by the same nephrologist on 67 AVF, 31 previously unsuspected stenoses were identified in 44 cases where needling was difficult.<a class="elsevierStyleCrossRef" href="#bib223"><span class="elsevierStyleSup">223</span></a></p><p id="p3520" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Methodology of arteriovenous fistula cannulation</span><ul class="elsevierStyleList" id="list0345"><li class="elsevierStyleListItem" id="listi1540"><span class="elsevierStyleLabel">•</span><p id="p3525" class="elsevierStylePara elsevierViewall">The AVF must be used exclusively to carry out HD treatment.</p></li><li class="elsevierStyleListItem" id="listi1545"><span class="elsevierStyleLabel">•</span><p id="p3530" class="elsevierStylePara elsevierViewall">Cannulation of any AVF must be performed exclusively by specialised nursing staff in HD units who have demonstrated a high level of knowledge and specific skills.<a class="elsevierStyleCrossRef" href="#bib222"><span class="elsevierStyleSup">222</span></a></p></li><li class="elsevierStyleListItem" id="listi1550"><span class="elsevierStyleLabel">•</span><p id="p3535" class="elsevierStylePara elsevierViewall">The initial cannulation of all new AVF should be performed exclusively by experienced nursing staff members of the HD Unit.<a class="elsevierStyleCrossRefs" href="#bib212"><span class="elsevierStyleSup">212,213,222,224,225</span></a></p></li><li class="elsevierStyleListItem" id="listi1555"><span class="elsevierStyleLabel">•</span><p id="p3540" class="elsevierStylePara elsevierViewall">All needling incidents should be recorded for investigation and for appropriate corrective measures to be adopted in order to ensure that the patient will receive the best nephrological care possible.<a class="elsevierStyleCrossRefs" href="#bib213"><span class="elsevierStyleSup">213,225</span></a></p></li><li class="elsevierStyleListItem" id="listi1560"><span class="elsevierStyleLabel">•</span><p id="p3545" class="elsevierStylePara elsevierViewall">Multiple unsuccessful needling attempts made by the same cannulator represent unacceptable practice.<a class="elsevierStyleCrossRef" href="#bib213"><span class="elsevierStyleSup">213</span></a></p></li><li class="elsevierStyleListItem" id="listi1565"><span class="elsevierStyleLabel">•</span><p id="p3550" class="elsevierStylePara elsevierViewall">Prior to AVF cannulation, it is essential to know type, anatomy and the direction of Q<span class="elsevierStyleInf">A</span> in order to plan the location of the needling areas. For this purpose, it is extremely useful to have an AVF map in the patient’s medical record. All nursing staff needling an AVF for the first time should have prior knowledge of the map to correctly needle the area.</p></li><li class="elsevierStyleListItem" id="listi1570"><span class="elsevierStyleLabel">•</span><p id="p3555" class="elsevierStylePara elsevierViewall">Before starting each HD session, an exhaustive physical examination of the AVF is needed, as detailed in section 4.</p></li><li class="elsevierStyleListItem" id="listi1575"><span class="elsevierStyleLabel">•</span><p id="p3560" class="elsevierStylePara elsevierViewall">Needling should not be performed without first checking whether the AVF functions properly.<a class="elsevierStyleCrossRef" href="#bib225"><span class="elsevierStyleSup">225</span></a></p></li><li class="elsevierStyleListItem" id="listi1580"><span class="elsevierStyleLabel">•</span><p id="p3565" class="elsevierStylePara elsevierViewall">Needling must be avoided at all times in areas of redness or areas with signs of infection, in areas with haematoma, crusting or altered skin and in apical areas of aneurysms.</p></li><li class="elsevierStyleListItem" id="listi1585"><span class="elsevierStyleLabel">•</span><p id="p3570" class="elsevierStylePara elsevierViewall">In difficult or first cannulations, it is advisable to check for correct AVF cannulation using a syringe with physiological saline solution to avoid blood extravasations and the subsequent formation of a haematoma.</p></li><li class="elsevierStyleListItem" id="listi1590"><span class="elsevierStyleLabel">•</span><p id="p3575" class="elsevierStylePara elsevierViewall">Topography of the needles. The “venous” needle should always be inserted proximal to the “arterial” needle to avoid recirculation.</p></li><li class="elsevierStyleListItem" id="listi1595"><span class="elsevierStyleLabel">•</span><p id="p3580" class="elsevierStylePara elsevierViewall">Direction of the needles. The tip from the “venous” needle should always point in the same direction as Q<span class="elsevierStyleInf">A</span> (anterograde direction) to ensure optimal venous return.<a class="elsevierStyleCrossRef" href="#bib222"><span class="elsevierStyleSup">222</span></a> Whether the “arterial” needle tip should be oriented in the same direction (anterograde direction) or in the opposite direction to Q<span class="elsevierStyleInf">A</span> (retrograde direction) has been the subject of debate.<a class="elsevierStyleCrossRef" href="#bib213"><span class="elsevierStyleSup">213</span></a> In the Gauly et al. study, the “arterial” needle was placed in an anterograde direction in most cases (63%),<a class="elsevierStyleCrossRef" href="#bib206"><span class="elsevierStyleSup">206</span></a> but this situation does not necessarily increase the risk of recirculation as long as Q<span class="elsevierStyleInf">A</span> in the AVF is significantly higher than Q<span class="elsevierStyleInf">B</span>.<a class="elsevierStyleCrossRef" href="#bib222"><span class="elsevierStyleSup">222</span></a> According to recent data, anterograde direction of the “arterial” needle is associated with higher AVF patency<a class="elsevierStyleCrossRef" href="#bib217"><span class="elsevierStyleSup">217</span></a> as it leads to a lower turbulent Q<span class="elsevierStyleInf">A</span> and, probably, less intimal vascular damage.<a class="elsevierStyleCrossRef" href="#bib212"><span class="elsevierStyleSup">212</span></a></p></li><li class="elsevierStyleListItem" id="listi1600"><span class="elsevierStyleLabel">•</span><p id="p3585" class="elsevierStylePara elsevierViewall">Orientation of the needle bevel. In the Gauly et al. case series, the bevel pointed upwards in most cases (72.3%).<a class="elsevierStyleCrossRef" href="#bib206"><span class="elsevierStyleSup">206</span></a> Although the upward or downward orientation of the bevel has been associated with the degree of pain at the time of needling,<a class="elsevierStyleCrossRef" href="#bib226"><span class="elsevierStyleSup">226</span></a> it has recently been shown that the bevel-up orientation is associated with higher AVF patency.<a class="elsevierStyleCrossRef" href="#bib217"><span class="elsevierStyleSup">217</span></a></p></li><li class="elsevierStyleListItem" id="listi1605"><span class="elsevierStyleLabel">•</span><p id="p3590" class="elsevierStylePara elsevierViewall">Rotation of the needle (180º) at the time of cannulation. In the survey by Gauly et al., this manoeuvre was performed in around 50% of cases<a class="elsevierStyleCrossRef" href="#bib206"><span class="elsevierStyleSup">206</span></a> but nowadays it is discouraged since it enlarges the needle entry hole. It may also tear the body of the pAVF or damage the endothelium of the arterialised vein, and give rise to blood infiltrations in the lateral wall of the arterialised vein during the HD session.<a class="elsevierStyleCrossRefs" href="#bib212"><span class="elsevierStyleSup">212,213</span></a> In addition, performing this rotation is unnecessary if backeye needles are used.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,213</span></a></p></li></ul></p><p id="p3595" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Process of native arteriovenous fistula cannulation</span><ul class="elsevierStyleList" id="list0350"><li class="elsevierStyleListItem" id="listi1610"><span class="elsevierStyleLabel">•</span><p id="p3600" class="elsevierStylePara elsevierViewall">After preparing the skin, proximal compression (manual, tourniquet) should be performed to cause venous stasis, and to stretch the skin in the opposite direction from the cannulation in order to fix but not obliterate the arterialised vein. The vein should always be compressed even if it is very well developed and/or the buttonhole method is used.<a class="elsevierStyleCrossRefs" href="#bib213"><span class="elsevierStyleSup">213,217</span></a> In the study by Parisotto et al., compression by the patient at the time of nAVF cannulation had a favourable effect on its patency compared with no compression or the use of a tourniquet.<a class="elsevierStyleCrossRef" href="#bib217"><span class="elsevierStyleSup">217</span></a></p></li><li class="elsevierStyleListItem" id="listi1615"><span class="elsevierStyleLabel">•</span><p id="p3605" class="elsevierStylePara elsevierViewall">Using the rope ladder method, the insertion angle of the needles in the nAVF must be approximately 25°, although this may vary according to the depth of the arterialised vein. The needles should be located at a distance of at least 2.5 cm from the anastomosis and should maintain a distance of at least 2.5 cm between their tips.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,212</span></a> In an international survey covering more than 10,000 cannulations with two needles in patients undergoing dialysis, mostly by nAVF (91%), the average distance between the two needles was 7.0 ± 3.7 cm and very similar to the distance recorded in a national study (7.3 ± 3.1 cm).<a class="elsevierStyleCrossRefs" href="#bib206"><span class="elsevierStyleSup">206,227</span></a></p></li></ul></p><p id="p3610" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Prosthetic arteriovenous fistula cannulation process</span><ul class="elsevierStyleList" id="list0355"><li class="elsevierStyleListItem" id="listi1620"><span class="elsevierStyleLabel">•</span><p id="p3615" class="elsevierStylePara elsevierViewall">The angle of insertion of the needles in pAVF should be approximately 45°, although this may vary depending on their depth. The needles should be located at a distance of at least 5 cm from the anastomosis and should maintain a distance of at least 2.5 cm between tips.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,212</span></a> Rotation of needling sites for each HD session is particularly important in pAVF and consequently new needling sites should be selected between 0.5 cm and 1.25 cm from the previous sites to preserve the fullest integrity of the pAVF wall.<a class="elsevierStyleCrossRef" href="#bib212"><span class="elsevierStyleSup">212</span></a></p></li><li class="elsevierStyleListItem" id="listi1625"><span class="elsevierStyleLabel">•</span><p id="p3620" class="elsevierStylePara elsevierViewall">Once the pAVF is needled, the angle must decrease to avoid needling the posterior wall, and it is then cannulated, making sure the tip of the needle is located in the centre of the pAVF lumen.</p></li><li class="elsevierStyleListItem" id="listi1630"><span class="elsevierStyleLabel">•</span><p id="p3625" class="elsevierStylePara elsevierViewall">The area should not be proximally compressed when needling.</p></li></ul></p><p id="p3630" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Fixing the needles and haemodialysis blood lines</span><ul class="elsevierStyleList" id="list0360"><li class="elsevierStyleListItem" id="listi1635"><span class="elsevierStyleLabel">•</span><p id="p3635" class="elsevierStylePara elsevierViewall">Needles must be securely fixed on the skin of the limb to prevent accidental dislodgement and should remain visible for the entire treatment. The needle tip must be checked so that it does not damage the vessel wall.</p></li><li class="elsevierStyleListItem" id="listi1640"><span class="elsevierStyleLabel">•</span><p id="p3640" class="elsevierStylePara elsevierViewall">The lines can be fixed onto the VA limb. It is not recommended that they be attached to anything mobile (armchair, bed or pillow). The main aim is to prevent extravasations as the patient moves.</p></li><li class="elsevierStyleListItem" id="listi1645"><span class="elsevierStyleLabel">•</span><p id="p3645" class="elsevierStylePara elsevierViewall">Accidental needle dislodgement during HD session.<a class="elsevierStyleCrossRefs" href="#bib228"><span class="elsevierStyleSup">228-230</span></a> This is a serious complication that may have catastrophic results.<a class="elsevierStyleCrossRef" href="#bib228"><span class="elsevierStyleSup">228</span></a> The reasons why needles may accidentally be dislodged are the following: poor fixation of the needles to the skin, defective adhesive tape, traction on any of the circuit lines or sudden movement of the AVF-bearing arm.<a class="elsevierStyleCrossRef" href="#bib230"><span class="elsevierStyleSup">230</span></a> To prevent needle dislodgement, the needles and blood lines must be properly secured with enough space so as to avoid dangerous traction.<a class="elsevierStyleCrossRef" href="#bib230"><span class="elsevierStyleSup">230</span></a> The limb must always be kept in view and, if necessary, kept still. If one of the needles is dislodged, the bleeding exit site must be immediately compressed, the blood pump stopped if this has not happened automatically, and the corresponding line clamped.<a class="elsevierStyleCrossRef" href="#bib230"><span class="elsevierStyleSup">230</span></a> The volume of blood lost must always be estimated and the patient’s haemodynamic stability must be checked.</p></li></ul></p><p id="p3650" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question VIII What is the needling technique of choice for the different types of arteriovenous fistula: the 3 classical ones and self-cannulation?</span></p><p id="p3655" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question VIII in <a href="https://static.elsevier.es/nefroguiaaveng/8_PCVIII_Tecnica_puncion_INGL.pdf">electronic appendices</a>)</p><p id="sect0910" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p3660" class="elsevierStylePara elsevierViewall">Three different types of AVF cannulation techniques have been described.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,211-213,231</span></a></p><p id="s0915" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rope ladder or rotating needling technique (sharp needle tip)</span></p><p id="p3665" class="elsevierStylePara elsevierViewall">This is the needling method of choice for most patients. The needling sites are distributed regularly throughout the length of the arterialised vein for nAVF or pAVF body. In each HD session, two new sites are chosen for needle placement, thus allowing the skin to heal between HD sessions. With this technique, there is a moderate increase in diameter over the entire length of the arterialised vein with no or very little development of aneurysms (this avoids progressive weakening of the vein wall secondary to the blood return flow when this always occurs at the same point). The main problem is that it requires an arterialised vein which has a long enough trajectory to allow needling to rotate.</p><p id="s0920" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Area technique or needling circumscribed to the same area (sharp needle tip)</span></p><p id="p3670" class="elsevierStylePara elsevierViewall">The main reasons for the use of this method are: short length of the arterialised vein, difficult trajectory for cannulation, nursing assessment that needling in another area will fail and patient refusal to be needled in another area. This technique involves repeated needling in a very restricted area of the arterialised vein, which causes damage to the venous wall and forms aneurysms in nAVF, as well as causing risk of pseudoaneurysms and thrombosis in pAVF. Therefore, this method is to be avoided whenever possible. However, the current situation in the “real world” is disappointing: according to an international survey mentioned above, the most commonly used technique (61%) was the area needling method.<a class="elsevierStyleCrossRef" href="#bib206"><span class="elsevierStyleSup">206</span></a></p><p id="s0925" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Buttonhole technique or constant needling at the same site (blunt needle tip)</span></p><p id="p3675" class="elsevierStylePara elsevierViewall">This method must be used exclusively in nAVF and never in pAVF. The same hole is used to needle vessels in all HD sessions (the same entry into the skin, same angle of entry and same depth of entry into the vein). Following the creation of a subcutaneous tunnel of fibrous scar tissue, access to blood circulation is obtained with a blunt needle tip which eliminates the risk of internal tearing and bleeding.</p><p id="p3680" class="elsevierStylePara elsevierViewall">The technique is based on repeatedly inserting a sharp needle tip into the same site and at the same angle of entry, preferably by a single cannulator, over six to ten HD sessions. This strategy allows a tunnel of fibrous scar tissue to be built up to the vein wall, which can then be cannulated with blunt-tipped needles. An arterial and a venous buttonhole are created. Once the tunnel is well formed, any trained member of the nursing staff or the patients themselves can needle the nAVF. In addition to the conventional sharp needle tip, the construction of the subcutaneous tunnel by other methods has been reported.<a class="elsevierStyleCrossRefs" href="#bib232"><span class="elsevierStyleSup">232,233</span></a></p><p id="p3685" class="elsevierStylePara elsevierViewall">It is very important to follow strict aseptic protocol. Before inserting the blunt-tipped needle into the subcutaneous tunnel, the two buttonhole sites must be carefully disinfected both before and after every HD session (double aseptic method), making sure that the scar crusts are completely removed from the previous session. The scab should never be removed with the same blunt needle which will subsequently be used for cannulation. Most blunt needles have a specially designed cap for removing the scab safely, without the need to use an additional needle and without damaging the walls of the hole.</p><p id="p3690" class="elsevierStylePara elsevierViewall">All highly motivated patients with sufficient capability, treated in an HD unit or else in home HD, are offered the option to self-needle using the rope ladder method and, in some selected cases, using the buttonhole method.<a class="elsevierStyleCrossRefs" href="#bib213"><span class="elsevierStyleSup">213,224</span></a><elsevierMultimedia ident="ut0040"></elsevierMultimedia></p><p id="s0930" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p3695" class="elsevierStylePara elsevierViewall">The initial enthusiasm generated by the buttonhole method, which was even reflected in some clinical guides,<a class="elsevierStyleCrossRef" href="#bib13"><span class="elsevierStyleSup">13</span></a> has been curbed by the evidence which subsequently appeared.<a class="elsevierStyleCrossRefs" href="#bib234"><span class="elsevierStyleSup">234,235</span></a> For example, regarding the degree of pain perceived by the patient using the buttonhole method, studies have been published which report less pain,<a class="elsevierStyleCrossRefs" href="#bib236"><span class="elsevierStyleSup">236-238</span></a> greater pain<a class="elsevierStyleCrossRefs" href="#bib239"><span class="elsevierStyleSup">239,240</span></a> and the same amount pain versus rope ladder technique.<a class="elsevierStyleCrossRefs" href="#bib241"><span class="elsevierStyleSup">241,242</span></a> In other words, there is equivocal evidence regarding the degree of pain using the buttonhole method, so taking all combined observational studies into account, buttonhole method is associated with a significant reduction in pain but this benefit disappears when analysing the randomised controlled trials.<a class="elsevierStyleCrossRef" href="#bib235"><span class="elsevierStyleSup">235</span></a> Therefore, with the currently available evidence, we cannot state that the pain produced by needling is significantly reduced using the buttonhole method, either in in-centre HD or in home HD with self-cannulation.<a class="elsevierStyleCrossRef" href="#bib235"><span class="elsevierStyleSup">235</span></a></p><p id="p3700" class="elsevierStylePara elsevierViewall">Van Loon et al. published a prospective observational study with a 9-month follow-up in 2010 comparing 145 prevalent patients on HD using rope ladder technique (n = 70) and buttonhole method (n = 75).<a class="elsevierStyleCrossRef" href="#bib240"><span class="elsevierStyleSup">240</span></a> Despite seeing a significantly greater number of miscannulations in the buttonhole group compared with the rope ladder group, the number of haematomas was significantly lower in the buttonhole group, probably because an unsuccessful cannulation with a blunt-tipped needle causes less tissue damage than a sharp-tipped needle.<a class="elsevierStyleCrossRef" href="#bib240"><span class="elsevierStyleSup">240</span></a> In addition, the buttonhole group required significantly fewer interventions on the nAVF at the expense of fewer PTA; no differences were noted in the number of thrombectomies and surgical procedures between both groups of patients.<a class="elsevierStyleCrossRef" href="#bib240"><span class="elsevierStyleSup">240</span></a> The formation of aneurysms was significantly lower in the buttonhole group but, on the other hand, this group of patients received antibiotic treatment for nAVF-related infection significantly more frequently.<a class="elsevierStyleCrossRef" href="#bib240"><span class="elsevierStyleSup">240</span></a> Finally, patients in the buttonhole group experienced significantly greater pain and fear compared to the rope ladder group, although the application of local anaesthetic cream was significantly more frequent in this latter group.<a class="elsevierStyleCrossRef" href="#bib240"><span class="elsevierStyleSup">240</span></a></p><p id="p3705" class="elsevierStylePara elsevierViewall">MacRae et al. carried out a randomised controlled trial in 2012 comparing 140 prevalent patients on HD using the standard (rope ladder, n = 70) and buttonhole needling (n = 70) methods. There was no difference in the perception of pain on needling between both groups of patients<a class="elsevierStyleCrossRef" href="#bib241"><span class="elsevierStyleSup">241</span></a>. In the same study, although haematoma was significantly higher in the standard group, the signs of local infection and episodes of bacteraemia were significantly higher for the buttonhole group; no differences were found in post-dialysis bleeding between both groups<a class="elsevierStyleCrossRef" href="#bib241"><span class="elsevierStyleSup">241</span></a>. Finally, the degree of difficulty in needling by the nursing staff was significantly higher in the buttonhole group (for both the <span class="elsevierStyleItalic">arterial</span> and the <span class="elsevierStyleItalic">venous</span> needle) compared with standard needling from 4 weeks, which coincided with the use of the blunt needle by multiple nurses.<a class="elsevierStyleCrossRef" href="#bib241"><span class="elsevierStyleSup">241</span></a></p><p id="p3710" class="elsevierStylePara elsevierViewall">Subsequently, in 2014 MacRae et al. published the follow-up results of these patients (17.2 months with standard and 19.2 months with buttonhole needling): no differences were found in nAVF patency between HD patients using standard (rope ladder, n = 69) and buttonhole technique (n = 70).<a class="elsevierStyleCrossRef" href="#bib243"><span class="elsevierStyleSup">243</span></a> However, the total number of infections, both local and <span class="elsevierStyleItalic">Staphylococcus aureus</span> bacteraemia, was significantly higher in the buttonhole group.<a class="elsevierStyleCrossRef" href="#bib243"><span class="elsevierStyleSup">243</span></a> They found no differences in thrombosis rates, fistulography, PTA and surgical procedure when comparing the two groups of patients.<a class="elsevierStyleCrossRef" href="#bib243"><span class="elsevierStyleSup">243</span></a> The conclusions of this RCT were that the lack of patency benefit in nAVF and the increased risk of infection should be taken into careful consideration when promoting buttonhole technique.<a class="elsevierStyleCrossRef" href="#bib243"><span class="elsevierStyleSup">243</span></a></p><p id="p3715" class="elsevierStylePara elsevierViewall">In 2013 Vaux et al. carried out a prospective randomised clinical trial comparing 140 prevalent patients on HD using the standard method (n = 70) and buttonhole technique (n = 70) with 1 year follow-up. They showed a significantly higher nAVF patency rate, significantly fewer procedures to maintain nAVF function (due to a lower number of PTA in stenosis) and no episodes of nAVF-related bacteraemia in the buttonhole group.<a class="elsevierStyleCrossRef" href="#bib233"><span class="elsevierStyleSup">233</span></a> The beneficial effects of the buttonhole method seen in this study may be explained by the different methodology used in constructing the subcutaneous tunnel, as a polycarbonate peg was used as a tutor inserted into the tunnel between HD sessions during the tunnel creation stage using a sharp-tipped needle.<a class="elsevierStyleCrossRefs" href="#bib233"><span class="elsevierStyleSup">233,241,244</span></a></p><p id="p3720" class="elsevierStylePara elsevierViewall">Muir et al. conducted a retrospective review of 90 consecutive patients in home HD comparing rope ladder (n = 30) and buttonhole needling (n = 60). No difference was found between the two groups with regard to definitive nAVF loss or the need for surgical intervention (any surgical revision or event requiring the definitive loss of the nAVF and/or the creation of a new nAVF).<a class="elsevierStyleCrossRef" href="#bib245"><span class="elsevierStyleSup">245</span></a> However, the total number of infections was significantly lower for rope ladder compared to buttonhole: 0.10 versus 0.39 events per 1000 days of nAVF use, respectively<a class="elsevierStyleCrossRef" href="#bib245"><span class="elsevierStyleSup">245</span></a>. In addition, these authors also conducted a systematic review of 15 studies (4 randomised controlled trials and 11 observational studies) and found that, compared to the rope ladder method, the risk of infection was approximately three times greater using the buttonhole method.<a class="elsevierStyleCrossRef" href="#bib245"><span class="elsevierStyleSup">245</span></a></p><p id="p3725" class="elsevierStylePara elsevierViewall">The rate of total recorded infections in the group of patients on dialysis using buttonhole in the study by Muir et al.<a class="elsevierStyleCrossRef" href="#bib245"><span class="elsevierStyleSup">245</span></a> was very similar to the rate of CVC-related bacteraemia (0.40 episodes of bacteraemia/per 1000 days CVC) recorded in HD units with optimal CVC management.<a class="elsevierStyleCrossRef" href="#bib246"><span class="elsevierStyleSup">246</span></a> Therefore, one of the main benefits of nAVF compared to CVC, i.e. its low infection rate, is thrown into serious doubt when using the buttonhole method.<a class="elsevierStyleCrossRef" href="#bib244"><span class="elsevierStyleSup">244</span></a></p><p id="p3730" class="elsevierStylePara elsevierViewall">This increased risk of local and systemic infection when using buttonhole has been confirmed in other studies and systematic reviews<a class="elsevierStyleCrossRefs" href="#bib234"><span class="elsevierStyleSup">234,235,239,247,248</span></a> and calls into question the use of this method in routine clinical practice.<a class="elsevierStyleCrossRef" href="#bib245"><span class="elsevierStyleSup">245</span></a> Favourable results have been reported in the prevention of bacteraemia caused by <span class="elsevierStyleItalic">Staphylococcus aureus</span> via the application of topical mupirocin in each buttonhole after performing haemostasis.<a class="elsevierStyleCrossRef" href="#bib249"><span class="elsevierStyleSup">249</span></a> However, the fundamental cornerstone for reducing infectious episodes using this technique is the continuing education of nursing staff and/or the patient through periodic step-by-step review of the asepsis protocol used.<a class="elsevierStyleCrossRef" href="#bib248"><span class="elsevierStyleSup">248</span></a></p><p id="p3735" class="elsevierStylePara elsevierViewall">In 2013, Grudzinski et al. carried out a systematic review of 23 full text articles and 4 abstracts on the buttonhole method: 3 were open-label trials and the rest were observational studies of different methodological design and quality.<a class="elsevierStyleCrossRef" href="#bib234"><span class="elsevierStyleSup">234</span></a> The main conclusions of these authors were as follows: <span class="elsevierStyleItalic">a)</span> there were no qualitative differences in the results obtained between home HD patients and those who were dialysed using this method in HD centres; <span class="elsevierStyleItalic">b)</span> studies which considered nAVF patency, hospital admission, quality of life, pain and the formation of aneurysms had serious methodological limitations with an impact on the analysis of the results considered; <span class="elsevierStyleItalic">c)</span> bacteraemia rates were generally higher when using buttonhole cannulation, and <span class="elsevierStyleItalic">d)</span> the buttonhole method may be associated with an increased risk of infection.<a class="elsevierStyleCrossRef" href="#bib234"><span class="elsevierStyleSup">234</span></a></p><p id="p3740" class="elsevierStylePara elsevierViewall">More recently, Wong et al. published another systematic review of 23 articles, 5 randomised trials and 18 observational studies on the buttonhole method, in which they highlighted the following main aspects<a class="elsevierStyleCrossRef" href="#bib235"><span class="elsevierStyleSup">235</span></a>: <span class="elsevierStyleItalic">a)</span> this method does not significantly reduce pain during cannulation and appears to be associated with an increased risk of local and systemic infections; <span class="elsevierStyleItalic">b)</span> considering nAVF patency, interventions in the nAVF, hospital admissions or nAVF-related mortality, haemostasis, and hospital admission or mortality for any other cause, there are no data that enable us to impose one needling technique over the other, and <span class="elsevierStyleItalic">c)</span> the buttonhole method is only beneficial in reducing the formation of haematomas and aneurysms. The final conclusion of these authors<a class="elsevierStyleCrossRef" href="#bib235"><span class="elsevierStyleSup">235</span></a> was that: <span class="elsevierStyleItalic">a)</span> the evidence does not support the preferred use of the buttonhole method over rope ladder, either in a conventional in-centre HD or in home HD, and <span class="elsevierStyleItalic">b)</span> the evidence does not exclude buttonhole cannulation as appropriate for some patients with nAVF which are difficult to cannulate.</p><p id="p3745" class="elsevierStylePara elsevierViewall">Although experience is limited, there is a surgical placement device<a class="elsevierStyleCrossRef" href="#bib250"><span class="elsevierStyleSup">250</span></a> which allows deep nAVF, at a depth of up to 15 mm, to be needled using the buttonhole method without the need for surgical superficialisation. This is a funnel-shaped titanium guide sutured over the vein. Its use is also indicated in nAVF which have a very limited space for needling and are difficult to cannulate. This device can only be used with the buttonhole technique.</p><p id="s0935" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p3750" class="elsevierStylePara elsevierViewall">According to the scientific evidence reviewed, there are no conclusive data to recommend one cannulation technique for all HD patients. However, rope ladder technique has been proven to offer fewer complications in both nAVF and pAVF. Buttonhole technique results in terms of reduction in the number of aneurysms, duration of AVF, local and systemic infections, pain on needling and post-dialysis bleeding time vary from one study to another. These data reinforce the idea that it is a “centre and cannulator-dependent” needling technique. However, the incidence of infections reported in controlled studies contraindicates its systematic use in the AVF, and hence GEMAV considers that the buttonhole method should be reserved exclusively for selected nAVF with great tortuosity and/or a short vein segment available for needling.</p><p id="p3755" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0090"></elsevierMultimedia></p><p id="s0945" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Single needle cannulation</span></p><p id="p3775" class="elsevierStylePara elsevierViewall">The single needle cannulation technique is occasionally used in routine clinical practice when nAVF cannulation with two needles is impossible. It is a transitory fall-back puncture technique in order to avoid CVC placement, when the arterialised vein only presents a very short segment for double needling, as there has been some kind of complication during cannulation and/or withdrawal of the needles (haematoma) in the preceding HD session, or to attempt to continue the development of an incomplete arterialised vein, especially in a brachial location. A Y-shaped dual-exit bevel 14G or 15G needle and a double pump system in the HD monitor are required. HD adequacy should be monitored strictly, increasing the surface of the dialyser and/or duration of the HD session if necessary.</p><p id="s0950" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Needle withdrawal</span></p><p id="p3780" class="elsevierStylePara elsevierViewall">The technique used to withdraw needles is just as important as cannulation as it must protect the AVF, avoid any additional injury (tears) and facilitate appropriate haemostasis.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> Each needle should be removed at approximately the same angle as it was inserted.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> No pressure should be placed on the exit site until the needle has been completely withdrawn in order not to damage the AVF.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a></p><p id="p3785" class="elsevierStylePara elsevierViewall">At the time of cannulation, 2 holes are created for each needle: one that goes through the skin (external) and another through the arterialised vein wall of the nAVF or of the pAVF body (internal).<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> Therefore, even though they are not on the same plane, both external and internal holes should be compressed after removing the needle to ensure that there is no bleeding.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> If the internal orifice is not adequately compressed, bleeding will occur in the subcutaneous tissue with subsequent haematoma development.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,251</span></a> As previously mentioned in AVF cannulation methodology,<a class="elsevierStyleCrossRef" href="#bib208"><span class="elsevierStyleSup">208</span></a> this haematoma may jeopardise the AVF as it may hinder subsequent cannulation, limit the options for future cannulations and cause thrombosis due to increased extrinsic pressure or the development of stenosis.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> Therefore, 2 fingers should always be used for haemostasis after removing the needle, one intended to compress the outer hole and the other the inner hole.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> During haemostasis, the pressure exerted must be constant, without interruption and intense enough to stop bleeding at the exit sites but without interrupting the Q<span class="elsevierStyleInf">A</span> in the AVF.<a class="elsevierStyleCrossRefs" href="#bib207"><span class="elsevierStyleSup">207,251</span></a> To minimise the risk of re-bleeding through the “arterial” needle hole once haemostasis has been achieved at this point (due to a sudden backward increase in pressure inside the AVF secondary to compression of the “venous” needle hole), it is preferable to first remove the “venous” needle, carry out the corresponding haemostasis at this level and then remove the “arterial” needle.<a class="elsevierStyleCrossRef" href="#bib251"><span class="elsevierStyleSup">251</span></a></p><p id="p3790" class="elsevierStylePara elsevierViewall">Manual compression must be maintained for at least 10 min before checking if there is still bleeding at the needling site.<a class="elsevierStyleCrossRef" href="#bib252"><span class="elsevierStyleSup">252</span></a> In general, the time of haemostasis is higher for pAVF than for nAVF.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> When there is no excessive anticoagulation, a prolonged haemostasis time (more than 20 min) may indicate increased pressure inside the AVF secondary to a stenosis as detailed in section 4.<a class="elsevierStyleCrossRefs" href="#bib251"><span class="elsevierStyleSup">251-253</span></a> If there are problems of bleeding and/or patients with a prolonged bleeding time, haemostatic dressings may be effective.<a class="elsevierStyleCrossRef" href="#bib251"><span class="elsevierStyleSup">251</span></a> A transparent micro-perforated dressing, which significantly reduces haemostasis time in both “arterial” and “venous” holes compared with conventional manual compression, has recently been introduced.<a class="elsevierStyleCrossRef" href="#bib254"><span class="elsevierStyleSup">254</span></a></p><p id="p3795" class="elsevierStylePara elsevierViewall">Haemostasis in the first needling sessions must always be carried out by an expert member of the nursing staff. Subsequently, if the patient characteristics and AVF allow it, the patient himself should be taught how to perform haemostasis with a non-sterile glove.<a class="elsevierStyleCrossRef" href="#bib251"><span class="elsevierStyleSup">251</span></a> If this is not possible, a staff member of the HD Unit must be responsible for haemostasis.<a class="elsevierStyleCrossRef" href="#bib251"><span class="elsevierStyleSup">251</span></a> Clamps should not be used to perform haemostasis on pAVF and their use is discouraged in nAVF.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> If their use is necessary, they should only be applied to a well-developed nAVF with an adequate Q<span class="elsevierStyleInf">A</span> and the continuing nAVF function should be continually checked while the clamp is placed.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a></p><p id="p3800" class="elsevierStylePara elsevierViewall">Adhesive dressings or bandages should be applied to needling sites but never before haemostasis has been fully achieved.<a class="elsevierStyleCrossRef" href="#bib252"><span class="elsevierStyleSup">252</span></a> The bandage should never cover the whole circumference of the limb.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> AVF patency should always be checked after applying the dressing.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a> The patient will be instructed to remove the dressing 24 h after application.<a class="elsevierStyleCrossRef" href="#bib207"><span class="elsevierStyleSup">207</span></a></p></span><span id="se0960" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">3.4</span><span class="elsevierStyleSectionTitle" id="sect0955">Arteriovenous fistula care by the patient in the interdialytic period</span><p id="s0960" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p3805" class="elsevierStylePara elsevierViewall">The self-care plan involves fully training the patient to take all the actions needed to help maintain a correctly functioning AVF, prolong its patency and acquire the necessary habits to allow them to detect, avoid and prevent AVF complications.</p><p id="s0965" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Training the patient to look after the arteriovenous fistula</span></p><p id="p3810" class="elsevierStylePara elsevierViewall">This section describes the AVF self-care plan from its creation and the steps to be taken in the interdialytic period.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,255</span></a></p><p id="s0970" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Monitoring arteriovenous fistula function</span></p><p id="p3815" class="elsevierStylePara elsevierViewall">Where possible, depending on their characteristics, patients must be taught to perform a daily physical AVF examination as detailed in <a class="elsevierStyleCrossRef" href="#f2">Figure 2</a> of section 4.</p><elsevierMultimedia ident="f2"></elsevierMultimedia><p id="s0975" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Detection of possible complications</span></p><p id="p3820" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0365"><li class="elsevierStyleListItem" id="listi1650"><span class="elsevierStyleLabel">•</span><p id="p3825" class="elsevierStylePara elsevierViewall">Signs and symptoms of infection such as redness patches/irritations, warmth, pain and suppuration.</p></li><li class="elsevierStyleListItem" id="listi1655"><span class="elsevierStyleLabel">•</span><p id="p3830" class="elsevierStylePara elsevierViewall">Signs and symptoms of ischaemia on the AVF-bearing arm such as coldness, pallor and pain.</p></li><li class="elsevierStyleListItem" id="listi1660"><span class="elsevierStyleLabel">•</span><p id="p3835" class="elsevierStylePara elsevierViewall">Signs and symptoms of thrombosis such as the appearance of hardening or pain, and absence of bruit and thrill.</p></li><li class="elsevierStyleListItem" id="listi1665"><span class="elsevierStyleLabel">•</span><p id="p3840" class="elsevierStylePara elsevierViewall">Signs and symptoms of decreased venous return such as the presence of oedema.</p></li></ul></p><p id="s0980" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Local care</span></p><p id="p3845" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0370"><li class="elsevierStyleListItem" id="listi1670"><span class="elsevierStyleLabel">•</span><p id="p3850" class="elsevierStylePara elsevierViewall">From the first 24-48 h after AVF creation, gentle movements should be made with the fingers and arm of the AVF to promote blood circulation, but no brusque movements should be made when doing the exercises as they are likely to lead to bleeding from the wound or hinder venous return. In elbow nAVF and in pAVF created in the flexure, the arm must not be flexed.</p></li><li class="elsevierStyleListItem" id="listi1675"><span class="elsevierStyleLabel">•</span><p id="p3855" class="elsevierStylePara elsevierViewall">The dressing should be kept clean and dry at all times and changed if dirty or wet.</p></li><li class="elsevierStyleListItem" id="listi1680"><span class="elsevierStyleLabel">•</span><p id="p3860" class="elsevierStylePara elsevierViewall">In these early stages, situations that may contaminate the surgical wound are to be avoided and, if necessary, adequate protective measures should be taken (work in the countryside, work with animals.).</p></li><li class="elsevierStyleListItem" id="listi1685"><span class="elsevierStyleLabel">•</span><p id="p3865" class="elsevierStylePara elsevierViewall">After the surgical stitches have been removed, the whole arm of the AVF should be thoroughly cleansed with warm water and soap on a daily basis. Skin should be kept hydrated to prevent the appearance of wounds.</p></li><li class="elsevierStyleListItem" id="listi1690"><span class="elsevierStyleLabel">•</span><p id="p3870" class="elsevierStylePara elsevierViewall">When the patient has started HD therapy, the dressing covering the needling sites must be removed the day after the HD session. If the dressing is stuck to the skin, it is advisable to wet it with saline solution to prevent any injury which might lead to bleeding or infection of the AVF. The scab covering the wound must never be lifted.</p></li><li class="elsevierStyleListItem" id="listi1695"><span class="elsevierStyleLabel">•</span><p id="p3875" class="elsevierStylePara elsevierViewall">If bleeding occurs through the needling hole in the skin, a gauze should be applied and compressed gently with the fingers as in the HD session. If bleeding does not stop in a reasonable amount of time, the patient should attend a healthcare facility for assessment. A circular compression bandage should never be used.</p></li></ul></p><p id="s0985" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Acquiring certain habits in order to preserve arteriovenous fistula function</span></p><p id="p3880" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0375"><li class="elsevierStyleListItem" id="listi1700"><span class="elsevierStyleLabel">•</span><p id="p3885" class="elsevierStylePara elsevierViewall">Blood pressure must not be taken or venipunctures be performed on the same arm as the AVF.</p></li><li class="elsevierStyleListItem" id="listi1705"><span class="elsevierStyleLabel">•</span><p id="p3890" class="elsevierStylePara elsevierViewall">The AVF must not be knocked or compressed. Tight clothing, watches, bracelets and occlusive bandages should not be worn and the patient should not sleep on the arm of the AVF.</p></li><li class="elsevierStyleListItem" id="listi1710"><span class="elsevierStyleLabel">•</span><p id="p3895" class="elsevierStylePara elsevierViewall">Weights must not be lifted or brusque movements made during exercise with this arm.</p></li><li class="elsevierStyleListItem" id="listi1715"><span class="elsevierStyleLabel">•</span><p id="p3900" class="elsevierStylePara elsevierViewall">Sudden changes of temperature must be avoided.</p></li></ul></p><p id="p3905" class="elsevierStylePara elsevierViewall">If complications are detected, the nearest medical centre of reference must be contacted.</p></span><span id="se0995" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">3.5</span><span class="elsevierStyleSectionTitle" id="sect0990">Antiplatelet treatment in arteriovenous fistula</span><p id="s0995" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p3910" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0095"></elsevierMultimedia></p><p id="sect1000" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p3930" class="elsevierStylePara elsevierViewall">AVF failure may be early or late. Early AVF failure is common, with an incidence of 9 to 53%.<a class="elsevierStyleCrossRefs" href="#bib94"><span class="elsevierStyleSup">94,256</span></a> Late failure is associated with acquired stenosis in the arterial and mainly venous territory. The physiopathology of the failure is not at all well-defined, but it has been associated with different triggers that initially cause a stenosis that can lead to thrombosis and VA loss.<a class="elsevierStyleCrossRef" href="#bib257"><span class="elsevierStyleSup">257</span></a> Thrombosis is therefore the common factor in both early and late failure.</p><p id="p3935" class="elsevierStylePara elsevierViewall">There are vascular diseases where the territory affected by a thrombosis has severe clinical repercussions, such as coronary or cerebral arteries.<a class="elsevierStyleCrossRef" href="#bib258"><span class="elsevierStyleSup">258</span></a> As antithrombotic medication may be beneficial in these diseases, for this reason it has been suggested that it could also reduce AVF thrombosis and, therefore, VA loss.</p><p id="p3940" class="elsevierStylePara elsevierViewall">The first time this type of drug was proposed for VA thrombosis prevention was with the Scribner cannula in 1967.<a class="elsevierStyleCrossRef" href="#bib259"><span class="elsevierStyleSup">259</span></a> This cannula connected vessels in the wrist (radial artery and cephalic vein or ulnar artery and basilic vein) or in the lower third of the leg (posterior tibial and internal saphenous), through a permanently installed external bridge made of synthetic material (external AVF), so that the artificial kidney might be connected as often as necessary. Since then the result of the use of antiplatelet agents to reduce AVF failure has not been conclusive. Salicylates have been linked to a decrease in early failure, but observational studies such as the DOPPS found no increase in the proportion of usable AVF for HD.<a class="elsevierStyleCrossRef" href="#bib260"><span class="elsevierStyleSup">260</span></a> A clinical trial comparing clopidogrel with placebo demonstrated a reduction in early thrombosis in incident AVF but the proportion of AVF useful for HD did not change.<a class="elsevierStyleCrossRef" href="#bib171"><span class="elsevierStyleSup">171</span></a> Moreover, another DOPPS review found a lower risk of AVF failure in patients taking acetylsalicylic acid for at least one year<a class="elsevierStyleCrossRef" href="#bib261"><span class="elsevierStyleSup">261</span></a> and a meta-analysis including studies with the short-term use of different antiplatelet drugs also demonstrated a reduction in thrombosis in nAVF and pAVF.<a class="elsevierStyleCrossRef" href="#bib262"><span class="elsevierStyleSup">262</span></a></p><p id="p3945" class="elsevierStylePara elsevierViewall">However, the follow-up period of these studies is limited, usually less than one year, and they fail to clearly show the benefit on patency without showing an increased risk of bleeding.</p><p id="p3950" class="elsevierStylePara elsevierViewall">The HD patient presents a higher risk of bleeding as a result of multiple factors, including platelet dysfunction, anaemia or heparin use during HD. Added to this is the uncertainty of the extra risk due to the use of antiplatelet agents or oral anticoagulants, knowing that bleeding risk scores developed for the general population have not been validated for patients on HD.</p><p id="p3955" class="elsevierStylePara elsevierViewall">This greater tendency towards haemorrhage has been observed in one of the DOPPS study reviews in patients with specific antiplatelet indications, such as rhythm disorders, in which the use of both antiplatelet agents and anticoagulants was associated with an elevated risk of mortality, both from cardiovascular and all-cause mortality.<a class="elsevierStyleCrossRef" href="#bib263"><span class="elsevierStyleSup">263</span></a> In a retrospective study that included a 5-year follow-up of 41,000 patients, there was also a higher association with a higher mortality with antiplatelet or anticoagulants in HD patients, although the confounding factor of the treatment indication could not be totally ruled out.<a class="elsevierStyleCrossRef" href="#bib264"><span class="elsevierStyleSup">264</span></a> When studies assessing the risk of bleeding are analysed using the results of antiplatelet therapy in AVF patency, these are limited and without conclusive results. Although appearing to show a decrease in the risk of thrombosis in nAVF and not in pAVF, a systematic review assessing the risk of bleeding in HD patients cannot find agreement on an indication in antiplatelet therapy in the presence of increased risk of bleeding in kidney patients.<a class="elsevierStyleCrossRef" href="#bib265"><span class="elsevierStyleSup">265</span></a></p><p id="p3960" class="elsevierStylePara elsevierViewall">It is therefore considered necessary to assess whether antithrombotic therapy can be indicated in the prevention of AVF dysfunction.</p><p id="p3965" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question IXa In which situations is it necessary to indicate antithrombotic prophylaxis after creating/repairing the arteriovenous fistula?</span></p><p id="p3970" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question IXa in <a href="https://static.elsevier.es/nefroguiaaveng/9a_PCIX_Profilaxis_antitrombotica_INGL.pdf">electronic appendices</a>)</p><p id="p3975" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question IXb Does the use of antiplatelet agents prior to arteriovenous fistula creation have an impact on patency and reduce the risk of thrombosis?</span></p><p id="p3980" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question IXb in <a href="https://static.elsevier.es/nefroguiaaveng/9b_PCIX_Profilaxis_antitrombotica_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0045"></elsevierMultimedia></p><p id="s1005" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="s1010" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">In which situations is it necessary to indicate antithrombotic prophylaxis after creating/repairing the arteriovenous fistula?</span></p><p id="p3985" class="elsevierStylePara elsevierViewall">The systematic review of Palmer et al.<a class="elsevierStyleCrossRef" href="#bib266"><span class="elsevierStyleSup">266</span></a> (arising from the Cochrane review of Palmer et al.<a class="elsevierStyleCrossRef" href="#bib267"><span class="elsevierStyleSup">267</span></a>) analyses the effect of antiplatelet therapy on the rate of thrombosis and patency of the VA in HD patients, including both nAVF and pAVF. In 12 trials (with 3118 participants), antiplatelet therapy started at the time of surgery; in 6 trials, 1-2 days before; in 2 trials, 7-10 days before; in 2 trials, 1-2 days after; in 1 trial 1 month after, and was not specified in another. The median of intervention was 3 months (interquartile range, 1.25-6). Ticlopidine, acetylsalicylic acid and clopidogrel were the most commonly used antiplatelet drugs.</p><p id="p3990" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Limitation:</span> risk of high or unclear bias in most trials and limited data for analysis of some effects, especially in pAVF and VA adequacy for HD.</p><p id="s1015" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Results</span></p><p id="p3995" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0385"><li class="elsevierStyleListItem" id="listi1730"><span class="elsevierStyleLabel">•</span><p id="p4000" class="elsevierStylePara elsevierViewall">AVF failure due to thrombosis or loss of patency. Antiplatelet therapy reduced the thrombosis or loss of patency in nAVF to half (6 trials, 188 events, 1242 participants; relative risk [RR]: 0.49; 95% CI, 0.30-0.81; I2 = 29%). In absolute terms, the treatment of 100 individuals with antiplatelet agents for 1-6 months (acetylsalicylic acid, ticlopidine or clopidogrel) would prevent failure of the fistula in between 6 and 21 individuals, assuming a baseline risk of 30% of one or more events.</p><p id="p4005" class="elsevierStylePara elsevierViewall">However, antiplatelet therapy had little or no effect on pAVF thrombosis or patency (3 trials, 374 events, 956 participants; RR: 0.94; 95% CI, 0.80-1.10).</p></li><li class="elsevierStyleListItem" id="listi1735"><span class="elsevierStyleLabel">•</span><p id="p4010" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">AVF failure due to thrombosis or early loss of patency</span>. VA failure was assessed in 5 trials (1105 participants) in the 8 weeks after surgery. In this subgroup, treatment with antiplatelet drugs significantly reduced early thrombosis or failure in AVF patency in 57% compared with placebo treatment or no treatment (177 events, RR: 0.43; 95% CI, 0.26-0.73; I2 = 25%). There were no data in the review on patients with pAVF.</p></li><li class="elsevierStyleListItem" id="listi1740"><span class="elsevierStyleLabel">•</span><p id="p4015" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Failure to achieve a suitable VA for HD</span>. The effect of antiplatelet therapy on the adequacy of VA for HD was investigated in 5 trials (1503 participants). The differences were not statistically significant, either in nAVF (2 trials, 470 events, 794 participants; RR: 0.57; 95% CI, 0.13-2.51) or in pAVF (1 trial, 12 events, 649 participants; RR: 0.51; 95% CI, 0.16-1.68).</p></li><li class="elsevierStyleListItem" id="listi1745"><span class="elsevierStyleLabel">•</span><p id="p4020" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Need for intervention to maintain AVF patency or maturation</span>. There were no statistically significant differences in the need for intervention to maintain patency or maturation of the AVF, in nAVF (1 study, 17 events, 866 participants; RR: 0.69; 95% CI, 0.26-1.83) or in pAVF (1 study, 196 events, 649 participants; RR: 0.89; 95% CI, 0.64-1.25).</p></li><li class="elsevierStyleListItem" id="listi1750"><span class="elsevierStyleLabel">•</span><p id="p4025" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Risk of bleeding</span>. Information is provided on bleeding events in 10 trials (3930 participants). There were no statistically significant differences in severe bleeding—retroperitoneal, intraocular, intra-articular, cerebral or gastrointestinal—(10 studies, 3930 participants; RR: 0.93; 95% CI, 0.58-1.49) or minor bleeding (4 studies, 237 participants; RR: 1.22; 95% CI, 0.51-2.91).</p></li><li class="elsevierStyleListItem" id="listi1755"><span class="elsevierStyleLabel">•</span><p id="p4030" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Abandonment of treatment</span>. There were no statistically significant differences in abandoning treatment compared with the control group (8 studies, 1973 participants; RR: 1.01; 95% CI, 0.84-1.20).</p></li><li class="elsevierStyleListItem" id="listi1760"><span class="elsevierStyleLabel">•</span><p id="p4035" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Antithrombotic prophylaxis after VA repair</span>. No studies have been found that analyse the effects of antithrombotic prophylaxis after VA repair.</p></li></ul></p><p id="s1020" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Does the use of antiplatelet agents prior to arteriovenous fistula creation have an impact on patency and reduce the risk of thrombosis?</span></p><p id="p4040" class="elsevierStylePara elsevierViewall">No studies were found on the use of antiplatelet agents prior to VA creation and the impact it has on patency and the risk of thrombosis in the publications by Palmer et al.,<a class="elsevierStyleCrossRefs" href="#bib266"><span class="elsevierStyleSup">266,267</span></a> so there is no comparison of antiplatelet use prior to or post VA creation, or prior and post versus only post VA creation. Since the studies found analyse peri-operative, i.e. both prior to and post, treatment in all cases, the evidence available is considered to be indirect.</p><p id="s1025" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Results</span></p><p id="p4045" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0390"><li class="elsevierStyleListItem" id="listi1765"><span class="elsevierStyleLabel">•</span><p id="p4050" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">AVF failure (due to thrombosis or loss of patency)</span>. Reviews provide information on 5 RCTs in which antithrombotic therapy begins before AVF creation and continues for up to four or six weeks after creation; however, there is a great deal of variability in the number of days the drug is received prior to the operation in each study. In one study, the drugs were given one day before and for 28 days after creation; in another, 2 days before and for one month afterwards; in another two, 7 days before and then for 28 days; in yet another, 7 to 10 days before and then for 6 weeks. This meta-analysis also includes another study in which drugs are administered on day 1 of the operation and continue for 6 weeks.</p><p id="p4055" class="elsevierStylePara elsevierViewall">Antiplatelet therapy reduced the risk of thrombosis or patency failure by almost 50% (6 trials, 218 events, 1365 participants; RR: 0.54; 95% CI, 0.39 to 0.74; I2 =10%).</p></li><li class="elsevierStyleListItem" id="listi1770"><span class="elsevierStyleLabel">•</span><p id="p4060" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Early thrombosis of the VA (within 8 weeks) in AVF</span>. Antiplatelet therapy reduced the risk of early VA thrombosis by close to half (6 trials, 218 events, 1365 participants; RR: 0.54; CI: 95%, 0.39 to 0.74; I2 = 10%).</p><p id="p4065" class="elsevierStylePara elsevierViewall">There were no significant differences between treatments relating to: all-cause mortality; cardiovascular-related mortality; fatal or non-fatal infarcts; fatal or non-fatal strokes; minor, major or fatal bleeding; loss of primary patency; need to perform any intervention to maintain patency and hospital admission.</p></li><li class="elsevierStyleListItem" id="listi1775"><span class="elsevierStyleLabel">•</span><p id="p4070" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">pAVF</span>. No differences were found between treatments for any outcome measure in patients who undergo VA creation using pAVF.</p></li><li class="elsevierStyleListItem" id="listi1780"><span class="elsevierStyleLabel">•</span><p id="p4075" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">pAVF failure (due to thrombosis or loss of patency)</span>. No significant differences were found between treatments (2 trials, 266 events, 756 participants; RR, 0.94; 95% CI, 0.79 to 1.11; I2 = 0%).</p></li></ul></p><p id="p4080" class="elsevierStylePara elsevierViewall">In a systematic Cochrane review on the use of medical treatment to improve nAVF and pAVF patency,<a class="elsevierStyleCrossRef" href="#bib268"><span class="elsevierStyleSup">268</span></a> the antiplatelet ticlopidine showed a significant reduction in the risk of failure of nAVF due to thrombosis compared with placebo, which in relative terms was 48% (3 clinical trials, 339 participants; OR: 0.45; 95% CI, 0.25 to 0.82). No significant differences were seen when comparing other treatments such as acetylsalicylic acid, clopidogrel or warfarin with placebo. According to the authors of the review, the quality of evidence was low due to the limited follow-up of the studies and the low availability of studies to test the efficacy of the treatment.</p><p id="s1030" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p4085" class="elsevierStylePara elsevierViewall">VA thrombosis is the consequence of both early and late failure leading to the loss of the vascular access. Based on other vascular territories, where antiplatelet therapy is effective in reducing risk of thrombosis, it has been proposed that this benefit might even be applied to improve AVF patency. However, patients on HD present a greater risk of multifactorial component bleeding, meaning the introduction of antiplatelet therapy could potentially increase this risk.</p><p id="p4090" class="elsevierStylePara elsevierViewall">The evidence review shows that in HD patients with nAVF antiplatelet therapy reduces the risk of thrombosis, and there are no differences in the effects on maturation and use of the nAVF for HD. It must be noted that bleeding risk analysis gives uncertain results. The authors point out that not every adverse effect was reported accurately, because the number of events identified in both groups was limited. In addition, episodes of serious haemorrhaging events were defined a priori and systematically described in only 2 out of 21 trials. Therefore, GEMAV interpreted that the use of antiplatelet therapy should be studied on a case-by-case basis, due to the potential side effects in this population.</p><p id="p4095" class="elsevierStylePara elsevierViewall">On the other hand, in HD patients with pAVF, antiplatelet treatment is not effective in preventing thrombosis or maintaining VA patency.</p><p id="p4100" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0100"></elsevierMultimedia></p></span></span><span id="s1045" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4</span><span class="elsevierStyleSectionTitle" id="sect1040">M<span class="elsevierStyleSmallCaps">onitoring and surveillance of arteriovenous fistula</span></span><p id="p4115" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">CONTENTS</span><ul class="elsevierStyleList" id="list0395"><li class="elsevierStyleListItem" id="listi1785"><span class="elsevierStyleLabel">4.1.</span><p id="p4120" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p></li><li class="elsevierStyleListItem" id="listi1790"><span class="elsevierStyleLabel">4.2.</span><p id="p4125" class="elsevierStylePara elsevierViewall">Clinical monitoring</p></li><li class="elsevierStyleListItem" id="listi1795"><span class="elsevierStyleLabel">4.3.</span><p id="p4130" class="elsevierStylePara elsevierViewall">Monitoring and surveillance of arteriovenous fistula pressure</p></li><li class="elsevierStyleListItem" id="listi1800"><span class="elsevierStyleLabel">4.4.</span><p id="p4135" class="elsevierStylePara elsevierViewall">Recirculation of arteriovenous fistula</p></li><li class="elsevierStyleListItem" id="listi1805"><span class="elsevierStyleLabel">4.5.</span><p id="p4140" class="elsevierStylePara elsevierViewall">Unexplained decrease in haemodialysis adequacy</p></li><li class="elsevierStyleListItem" id="listi1810"><span class="elsevierStyleLabel">4.6.</span><p id="p4145" class="elsevierStylePara elsevierViewall">Dilution screening methods for indirect determination of arteriovenous fistula flow</p></li><li class="elsevierStyleListItem" id="listi1815"><span class="elsevierStyleLabel">4.7.</span><p id="p4150" class="elsevierStylePara elsevierViewall">Imaging tests. Arteriovenous fistula surveillance using Doppler ultrasound</p></li><li class="elsevierStyleListItem" id="listi1820"><span class="elsevierStyleLabel">4.8.</span><p id="p4155" class="elsevierStylePara elsevierViewall">Predictive power of first- and second-generation methods for detecting stenosis and thrombosis of arteriovenous fistula</p></li><li class="elsevierStyleListItem" id="listi1825"><span class="elsevierStyleLabel">4.9.</span><p id="p4160" class="elsevierStylePara elsevierViewall">Predictive factors of thrombosis in arteriovenous fistula with stenosis</p></li></ul></p><p id="sect1045" class="elsevierStylePara elsevierViewall">Preamble</p><p id="p4165" class="elsevierStylePara elsevierViewall">The aim of monitoring and surveillance of the arteriovenous fistula (AVF) is early diagnosis of its pathology both in native (nAVF) and prosthetic (pAVF). The AVF follow-up should permit the prevention of thrombosis through early detection of significant stenosis and increase its patency.</p><span id="se1055" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4.1</span><span class="elsevierStyleSectionTitle" id="sect1050">Rationale</span><p id="s1055" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p4170" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0105"></elsevierMultimedia></p><p id="p4190" class="elsevierStylePara elsevierViewall">Several obstacles have to be overcome to obtain a valid AVF which can be used to start a chronic haemodialysis (HD) programme.<a class="elsevierStyleCrossRef" href="#bib214"><span class="elsevierStyleSup">214</span></a> The biggest of them is to achieve an adequate maturation, particularly in the case of nAVF, since the current percentage of maturation failures is about 40%.<a class="elsevierStyleCrossRef" href="#bib214"><span class="elsevierStyleSup">214</span></a> Once this difficult objective has been achieved, we must remain in a state of alertness and use all available means at our disposal to prevent thrombosis and to maintain AVF patency in the prevalent patient.</p><p id="p4195" class="elsevierStylePara elsevierViewall">Irreversible thrombosis of the AVF results in a series of negative consequences for the prevalent patient included on an HD programme<a class="elsevierStyleCrossRef" href="#bib269"><span class="elsevierStyleSup">269</span></a>: reduction in venous capital, need for central venous catheter (CVC) placement, lower HD efficacy, possible central vein stenosis or thrombosis, chronic inflammation in the case of pAVF, and construction of a new AVF. All of this increases the frequency of hospital admission, morbidity and mortality and healthcare spending for the chronic HD patient.<a class="elsevierStyleCrossRef" href="#bib270"><span class="elsevierStyleSup">270</span></a> Therefore, preventing thrombosis of the AVF is paramount for these patients.</p><p id="p4200" class="elsevierStylePara elsevierViewall">Regarding AVF thrombosis, it must be taken into account that:<ul class="elsevierStyleList" id="list0400"><li class="elsevierStyleListItem" id="listi1830"><span class="elsevierStyleLabel">•</span><p id="p4205" class="elsevierStylePara elsevierViewall">It is not always technically possible to restore AVF patency in all cases of thrombosis of the AVF, even in the hands of experienced specialists.<a class="elsevierStyleCrossRef" href="#bib271"><span class="elsevierStyleSup">271</span></a></p></li><li class="elsevierStyleListItem" id="listi1835"><span class="elsevierStyleLabel">•</span><p id="p4210" class="elsevierStylePara elsevierViewall">Secondary AVF patency is significantly lower after restoring AVF patency post-thrombosis when compared with elective repair of AVF stenosis before thrombosis (see section 5 “Complications of arteriovenous fistula”, recommendation 5.2.6).<a class="elsevierStyleCrossRefs" href="#bib272"><span class="elsevierStyleSup">272,273</span></a></p></li></ul></p><p id="p4215" class="elsevierStylePara elsevierViewall">Therefore, it is very important to note that thrombosis should preferably be prevented through early diagnosis and treatment of significant stenosis rather than be salvaged via interventional radiology or vascular surgery.</p><p id="p4220" class="elsevierStylePara elsevierViewall">The most common cause of thrombosis is severe stenosis of the AVF.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,253</span></a> Currently, in order to qualify a stenosis as significant, it is necessary to demonstrate a reduction in the vascular lumen greater than 50% using ultrasound and/or angiography together with the repeated alteration of one or several parameters obtained by monitoring and/or surveillance methods.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> The diagnosis of significant stenosis is an indication that corrective treatment by percutaneous transluminal angioplasty (PTA) and/or surgery should be performed electively or preventatively to avoid thrombosis.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a></p><p id="p4225" class="elsevierStylePara elsevierViewall">AVF follow-up programmes comprise two key aspects: <span class="elsevierStyleItalic">a)</span> the early diagnosis of significant stenosis using different screening methods or techniques, and <span class="elsevierStyleItalic">b)</span> its elective or preventive correction to prevent thrombosis and improve AVF patency.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a></p><p id="p4230" class="elsevierStylePara elsevierViewall">The philosophy of these programmes is based on the fact that, in the vast majority of cases, AVF stenosis develops over varying time intervals and, if diagnosed and corrected in time, sub-dialysis can be avoided and the rate of thrombosis reduced by between 40% and 75%.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,274</span></a> These follow-up programmes should be developed in every HD unit systematically, protocolised and with multidisciplinary participation involving nursing staff, nephrology, radiology and vascular surgery.<a class="elsevierStyleCrossRef" href="#bib253"><span class="elsevierStyleSup">253</span></a><a class="elsevierStyleCrossRef" href="#t8">Table 8</a> shows the AVF follow-up programme objectives for both nAVF and pAVF.<a class="elsevierStyleCrossRefs" href="#bib275"><span class="elsevierStyleSup">275-277</span></a></p><elsevierMultimedia ident="t8"></elsevierMultimedia><p id="p4235" class="elsevierStylePara elsevierViewall">According to DOPPS (Dialysis Outcomes and Practice Patterns Study I and II, 1996-2004) study data, the likelihood that a prevalent patient be dialysed through a CVC is directly related to the number of permanent AVF previously placed.<a class="elsevierStyleCrossRef" href="#bib32"><span class="elsevierStyleSup">32</span></a> It is likely that if AVF follow-up programmes had previously been introduced in these DOPPS centres, many cases of thrombosis could have been avoided; therefore, the prevalence of patients on HD with CVC would have been reduced.<a class="elsevierStyleCrossRef" href="#bib32"><span class="elsevierStyleSup">32</span></a> In this respect, an inverse relationship between the rate of preventive intervention and the rate of AVF thrombosis has been demonstrated in Spain for both nAVF and pAVF.<a class="elsevierStyleCrossRef" href="#bib278"><span class="elsevierStyleSup">278</span></a></p><p id="p4240" class="elsevierStylePara elsevierViewall">The screening methods or techniques for the early diagnosis of significant stenosis are classified in 2 major groups<a class="elsevierStyleCrossRef" href="#bib279"><span class="elsevierStyleSup">279</span></a> (<a class="elsevierStyleCrossRef" href="#t9">Table 9</a>):<ul class="elsevierStyleList" id="list0405"><li class="elsevierStyleListItem" id="listi1840"><span class="elsevierStyleLabel">1.</span><p id="p4245" class="elsevierStylePara elsevierViewall">First-generation methods.<ul class="elsevierStyleList" id="list0410"><li class="elsevierStyleListItem" id="listi1845"><span class="elsevierStyleLabel">•</span><p id="p4250" class="elsevierStylePara elsevierViewall">Clinical monitoring:<ul class="elsevierStyleList" id="list0415"><li class="elsevierStyleListItem" id="listi1850"><span class="elsevierStyleLabel">–</span><p id="p4255" class="elsevierStylePara elsevierViewall">Physical examination.</p></li><li class="elsevierStyleListItem" id="listi1855"><span class="elsevierStyleLabel">–</span><p id="p4260" class="elsevierStylePara elsevierViewall">Problems during the HD session.</p></li><li class="elsevierStyleListItem" id="listi1860"><span class="elsevierStyleLabel">–</span><p id="p4265" class="elsevierStylePara elsevierViewall">Blood pump (Q<span class="elsevierStyleInf">B</span>) stress test for nAVF.</p></li></ul></p></li><li class="elsevierStyleListItem" id="listi1865"><span class="elsevierStyleLabel">•</span><p id="p4270" class="elsevierStylePara elsevierViewall">Monitoring and surveillance of AVF pressure: dynamic venous pressure (DVP), intra-access pressure (IAP) in its normalised static version.</p></li><li class="elsevierStyleListItem" id="listi1870"><span class="elsevierStyleLabel">•</span><p id="p4275" class="elsevierStylePara elsevierViewall">Determining the percentage of recirculation.</p></li><li class="elsevierStyleListItem" id="listi1875"><span class="elsevierStyleLabel">•</span><p id="p4280" class="elsevierStylePara elsevierViewall">Unexplained decrease in HD adequacy: Kt/V index, urea reduction ratio (URR), Kt index.</p></li></ul></p></li><li class="elsevierStyleListItem" id="listi1880"><span class="elsevierStyleLabel">2.</span><p id="p4285" class="elsevierStylePara elsevierViewall">Second-generation methods. These allow the calculation of AVF blood flow (Q<span class="elsevierStyleInf">A</span>).<ul class="elsevierStyleList" id="list0420"><li class="elsevierStyleListItem" id="listi1885"><span class="elsevierStyleLabel">•</span><p id="p4290" class="elsevierStylePara elsevierViewall">Dilution screening methods.</p></li><li class="elsevierStyleListItem" id="listi1890"><span class="elsevierStyleLabel">•</span><p id="p4295" class="elsevierStylePara elsevierViewall">Doppler ultrasound (DU).</p></li></ul></p></li></ul></p><elsevierMultimedia ident="t9"></elsevierMultimedia><p id="p4300" class="elsevierStylePara elsevierViewall">In addition, these techniques can also be classified as “monitoring methods” and “surveillance methods” depending on whether special instrumentation is not or is required, respectively. All first-generation methods, except static venous pressure, fall within monitoring methods.<a class="elsevierStyleCrossRef" href="#bib274"><span class="elsevierStyleSup">274</span></a> Static venous pressure (see section 4.3.2.) and second-generation methods are considered to be surveillance methods. With regard to periodicity of determination, although these methods should be applied monthly,<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> it is acceptable to measure Q<span class="elsevierStyleInf">A</span> in the nAVF every 2-3 months.<a class="elsevierStyleCrossRefs" href="#bib14"><span class="elsevierStyleSup">14,15</span></a></p><p id="p4305" class="elsevierStylePara elsevierViewall">Regarding the different monitoring and surveillance techniques used, it is important to consider that:<ul class="elsevierStyleList" id="list0425"><li class="elsevierStyleListItem" id="listi1895"><span class="elsevierStyleLabel">•</span><p id="p4310" class="elsevierStylePara elsevierViewall">The prospective analysis of any monitoring or surveillance parameter used has greater predictive power to detect AVF dysfunction than any isolated values.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> In this respect, it is essential to have a record of each AVF in the HD unit to allow it to be assessed over time.</p></li><li class="elsevierStyleListItem" id="listi1900"><span class="elsevierStyleLabel">•</span><p id="p4315" class="elsevierStylePara elsevierViewall">They are not exclusive but complementary. The application of several monitoring or surveillance methods simultaneously increases the performance of the follow-up programme.<a class="elsevierStyleCrossRefs" href="#bib280"><span class="elsevierStyleSup">280,281</span></a> In addition, it has been demonstrated that the precision of each AVF monitoring and surveillance technique is related to stenosis location.<a class="elsevierStyleCrossRef" href="#bib282"><span class="elsevierStyleSup">282</span></a></p></li></ul></p><p id="p4320" class="elsevierStylePara elsevierViewall">Many of the screening methods described, both first- and second-generation, can be used to non-invasively assess the functional outcome of elective procedure performed on the AVF stenosis.<a class="elsevierStyleCrossRefs" href="#bib282"><span class="elsevierStyleSup">282-284</span></a> In this regard, Q<span class="elsevierStyleInf">A</span> measurement has also been used in situ immediately after performing PTA on the AVF stenosis to check the functional outcome of the elective treatment.<a class="elsevierStyleCrossRef" href="#bib285"><span class="elsevierStyleSup">285</span></a></p></span><span id="se1065" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4.2</span><span class="elsevierStyleSectionTitle" id="sect1060">Clinical monitoring</span><p id="p4325" class="elsevierStylePara elsevierViewall">Although clinical monitoring lost a certain amount of importance when dilution methods were introduced for non-invasive Q<span class="elsevierStyleInf">A</span> determination and DU use became more widespread, its central role in AVF monitoring is currently undisputed.<a class="elsevierStyleCrossRefs" href="#bib282"><span class="elsevierStyleSup">282,286,287</span></a> The AVF’s clinical monitoring takes into account two key aspects<a class="elsevierStyleCrossRefs" href="#bib253"><span class="elsevierStyleSup">253,270,282,286-293</span></a>: physical examination and problems during the HD session. The stress test for nAVF according to Q<span class="elsevierStyleInf">B</span> (Q<span class="elsevierStyleInf">B</span> stress test) has recently been described, and seems to be effective in diagnosing so-called inflow stenosis.<a class="elsevierStyleCrossRef" href="#bib294"><span class="elsevierStyleSup">294</span></a></p><p id="s1065" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">4.2.1 Physical examination</span></p><p id="p4330" class="elsevierStylePara elsevierViewall">This should be carried out regularly using inspection, palpation and auscultation<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,282,286,293</span></a> (<a class="elsevierStyleCrossRef" href="#t10">Table 10</a>). This is an easy method to learn and perform; it takes very little time, does not require any special instrumentation or additional staff and, therefore, is a low cost test. In addition to nursing staff and the nephrologist, it is advisable that this examination should be partially carried out by the patients themselves daily (<a class="elsevierStyleCrossRef" href="#f2">Figure 2</a>).<a class="elsevierStyleCrossRef" href="#bib295"><span class="elsevierStyleSup">295</span></a> The detection of changes in the characteristics of the pulse, bruit and thrill of the AVF, compared with prior checks, makes it possible to diagnose a stenosis and specify its location.<a class="elsevierStyleCrossRefs" href="#bib282"><span class="elsevierStyleSup">282,286,293</span></a> Unlike other AVF follow-up methods, physical examination also allows the identification of pathologies other than stenosis, such as aneurysms or infection.<a class="elsevierStyleCrossRef" href="#bib286"><span class="elsevierStyleSup">286</span></a></p><elsevierMultimedia ident="t10"></elsevierMultimedia><p id="p4335" class="elsevierStylePara elsevierViewall"><a class="elsevierStyleCrossRef" href="#t11">Table 11</a> summarises the findings obtained by physical examination for the differential diagnosis between inflow stenosis (located in the feeding artery, in the anastomosis itself or in the initial segment of the arterialised vein up to 5 cm post-anastomosis), outflow stenosis (located in the arterialised vein segment from the needling area to the right atrium) and nAVF thrombosis. Central venous stenosis is an outflow stenosis which is located in the venous segment from the cephalic vein arch at the level of the first rib to the right atrium. The nAVF without stenosis has a smooth or soft, easily compressible pulse, a predominant thrill over the anastomosis and a continuous bruit (systolic and diastolic) of low intensity (<a class="elsevierStyleCrossRef" href="#t11">Table 11</a>).</p><elsevierMultimedia ident="t11"></elsevierMultimedia><p id="p4340" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0430"><li class="elsevierStyleListItem" id="listi1905"><span class="elsevierStyleLabel">•</span><p id="p4345" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Inspection</span>. <a class="elsevierStyleCrossRef" href="#t10">Table 10</a> summarises the basic information to be taken into account during AVF examination. It is very important to observe the entire limb where the vascular access (VA) is located. In the case of AVF in the upper limbs, oedema and collateral circulation are signs that suggest total or partial central venous stenosis. The extension of an oedema can help us to locate the level of the central stenosis: if the oedema only involves the arm, this suggests that the stenosis is in the subclavian vein; if the oedema includes the chest, breast and/or ipsilateral face, stenosis is more likely in the brachiocephalic vein; bilateral oedema (chest, breasts, shoulders and face) suggests a superior vena cava stenosis.<a class="elsevierStyleCrossRef" href="#bib286"><span class="elsevierStyleSup">286</span></a> The distal areas of the limb must be assessed for signs of ischaemia (coldness, pallor and ischaemic digital ulcers) and signs of venous hypertension (hyperpigmentation and stasis digital ulcers).<a class="elsevierStyleCrossRefs" href="#bib286"><span class="elsevierStyleSup">286,296-298</span></a> The entire AVF segment must be inspected to detect the presence of haematomas, aneurysmal dilatations and signs of swelling.<a class="elsevierStyleCrossRefs" href="#bib299"><span class="elsevierStyleSup">299,300</span></a> Any arterialised vein which does not collapse, at least partially, after lifting the arm, probably has a proximal stenosis (<a class="elsevierStyleCrossRef" href="#t10">Tables 10</a> to <a class="elsevierStyleCrossRef" href="#t12">12</a>).<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,282,286,293</span></a></p><elsevierMultimedia ident="t12"></elsevierMultimedia></li><li class="elsevierStyleListItem" id="listi1910"><span class="elsevierStyleLabel">•</span><p id="p4350" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Palpation</span>.<a class="elsevierStyleCrossRefs" href="#bib282"><span class="elsevierStyleSup">282,286,293,301</span></a> Pulse is observed more correctly using the finger tips. Under normal conditions, the nAVF pulse is of low intensity, soft and easily compressible. Usually, an increased nAVF pulse is indicative of proximal stenosis (hyperpulsatile nAVF) and the amount that this increases is directly proportional to the existing degree of stenosis. In contrast, a pulse which is excessively weak (hypopulsatile nAVF, flat access), with little increase through transitory manual occlusion, suggests the presence of inflow stenosis (pulse augmentation test, <a class="elsevierStyleCrossRef" href="#t12">Table 12</a>).</p><p id="p4355" class="elsevierStylePara elsevierViewall">Thrill is a palpable nAVF vibration, which is more easily explored using the palm of the hand, and reflects the Q<span class="elsevierStyleInf">A</span> circulating along the arterialised vein.<a class="elsevierStyleCrossRefs" href="#bib282"><span class="elsevierStyleSup">282,286,293</span></a> The absence of thrill indicates a deficit of Q<span class="elsevierStyleInf">A</span>. This sign, together with the absence of pulse, is characteristic of AVF thrombosis. Two different types of thrill can be palpated:<ul class="elsevierStyleList" id="list0435"><li class="elsevierStyleListItem" id="listi1915"><span class="elsevierStyleLabel">–</span><p id="p4360" class="elsevierStylePara elsevierViewall">A diffuse basal thrill in a normal AVF. This is gentle, continuous (systolic and diastolic), palpable throughout the whole AVF segment but more intense at the level of the venous anastomosis.</p></li><li class="elsevierStyleListItem" id="listi1920"><span class="elsevierStyleLabel">–</span><p id="p4365" class="elsevierStylePara elsevierViewall">A locally increased thrill. This reflects the presence of turbulent flow located at a stenosis area in the arterialised vein. As the degree of stenosis progressively increases, with a concomitant increase in resistance to the Q<span class="elsevierStyleInf">A</span>, thrill shortens and loses its diastolic component. The whole trajectory of the arterialised vein should be examined to detect the presence of abnormal thrill. In the event of a stenosis in the subclavian vein or cephalic vein arch, thrill can be detected below the clavicle.<a class="elsevierStyleCrossRef" href="#bib286"><span class="elsevierStyleSup">286</span></a></p></li></ul></p></li><li class="elsevierStyleListItem" id="listi1925"><span class="elsevierStyleLabel">•</span><p id="p4370" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Auscultation</span>. The normal AVF bruit and the temporary changes that may occur in this bruit, as well as the occurrence of abnormal bruits,<a class="elsevierStyleCrossRefs" href="#bib282"><span class="elsevierStyleSup">282,286,293</span></a> must be assessed. This is the auditory manifestation of thrill. Two different types of bruit can be heard:<ul class="elsevierStyleList" id="list0440"><li class="elsevierStyleListItem" id="listi1930"><span class="elsevierStyleLabel">–</span><p id="p4375" class="elsevierStylePara elsevierViewall">A diffuse basal bruit in a normal AVF. This has a low tone, like a soft and continuous murmur (systolic and diastolic).</p></li><li class="elsevierStyleListItem" id="listi1935"><span class="elsevierStyleLabel">–</span><p id="p4380" class="elsevierStylePara elsevierViewall">An abnormal bruit associated with stenosis. The increased resistance caused by a progressive stenotic lesion will lead to the gradual loss of the diastolic component of the bruit and a simultaneous increase in its tone. The whole trajectory of the arterialised vein, including the area below the clavicle, should be examined to assess the presence of an abnormal bruit.<a class="elsevierStyleCrossRef" href="#bib286"><span class="elsevierStyleSup">286</span></a></p></li></ul></p></li></ul></p><p id="p4385" class="elsevierStylePara elsevierViewall">Juxta-anastomotic or peri-anastomotic nAVF stenosis, i.e. the stenosis located in an area of 2-3 cm immediately adjacent to the anastomosis, which can affect both the afferent artery and the efferent vein, behaves like an inflow stenosis and may be diagnosed easily by exploring the anastomosis and the most distal segment of the arterialised vein<a class="elsevierStyleCrossRef" href="#bib286"><span class="elsevierStyleSup">286</span></a>. At anastomosis level, thrill is only palpated during the systole and the pulse is greatly increased (defined as “water-hammer” according to English-speaking authors) but it suddenly disappears when the examiner’s finger moves proximally along the trajectory of the vein and finds the precise location of the stenosis; proximally to the stenosis, the pulse is very weak and may be difficult to detect. On occasions, the stenosis can be seen as a gap related with a sudden decrease in vein size.</p><p id="p4390" class="elsevierStylePara elsevierViewall">Several prospective observational studies have shown that physical examination diagnoses stenosis with a high degree of sensitivity and specificity, as well as precision, and therefore, it should have a prominent position among AVF screening methods.<a class="elsevierStyleCrossRefs" href="#bib204"><span class="elsevierStyleSup">204,286,287,301-308</span></a> The efficacy of physical examination carried out by qualified staff is equivalent to other more sophisticated screening methods<a class="elsevierStyleCrossRefs" href="#bib287"><span class="elsevierStyleSup">287,301,302</span></a>; the key lies in the examiner’s judgement.<a class="elsevierStyleCrossRef" href="#bib302"><span class="elsevierStyleSup">302</span></a> In this respect, in the study by Coentrão et al., conducted on 177 consecutive prevalent patients with nAVF dysfunction, diagnostic agreement of physical examination with fistulography for diagnosis of stenosis at all locations was always higher when a resident nephrology doctor with six months’ training performed the study compared with several general nephrologists without any specific training in nAVF examination (overall agreement 86% versus 49%, respectively).<a class="elsevierStyleCrossRef" href="#bib302"><span class="elsevierStyleSup">302</span></a></p><p id="s1070" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">4.2.2 Problems during the haemodialysis session</span></p><p id="p4395" class="elsevierStylePara elsevierViewall">These could be indirect signs of AVF stenosis if they appear persistently (three consecutive HD sessions), compared with the previous HD sessions<a class="elsevierStyleCrossRef" href="#bib253"><span class="elsevierStyleSup">253</span></a>:<ul class="elsevierStyleList" id="list0445"><li class="elsevierStyleListItem" id="listi1940"><span class="elsevierStyleLabel">•</span><p id="p4400" class="elsevierStylePara elsevierViewall">Difficulty in AVF needling and/or cannulation.</p></li><li class="elsevierStyleListItem" id="listi1945"><span class="elsevierStyleLabel">•</span><p id="p4405" class="elsevierStylePara elsevierViewall">Aspiration of clots during needling.</p></li><li class="elsevierStyleListItem" id="listi1950"><span class="elsevierStyleLabel">•</span><p id="p4410" class="elsevierStylePara elsevierViewall">Increase in negative pre-pump arterial pressure.</p></li><li class="elsevierStyleListItem" id="listi1955"><span class="elsevierStyleLabel">•</span><p id="p4415" class="elsevierStylePara elsevierViewall">Failure to reach prescribed Q<span class="elsevierStyleInf">B</span>.</p></li><li class="elsevierStyleListItem" id="listi1960"><span class="elsevierStyleLabel">•</span><p id="p4420" class="elsevierStylePara elsevierViewall">Increase in the return or venous pressure.</p></li><li class="elsevierStyleListItem" id="listi1965"><span class="elsevierStyleLabel">•</span><p id="p4425" class="elsevierStylePara elsevierViewall">Prolonged haemostasis time, without excessive anticoagulation.</p></li></ul></p><p id="s1075" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">4.2.3 Native arteriovenous fistula stress test according to the pump flow</span></p><p id="p4430" class="elsevierStylePara elsevierViewall">This test has proved effective in diagnosing inflow nAVF stenosis (positive predictive value of 76.3%) and is based on the decrease that occurs in Q<span class="elsevierStyleInf">A</span> when raising the upper limb from 0° to 90° for 30 s and Q<span class="elsevierStyleInf">B</span> of 400 mL/min.<a class="elsevierStyleCrossRef" href="#bib294"><span class="elsevierStyleSup">294</span></a> To carry it out, with the arm in this raised position, Q<span class="elsevierStyleInf">B</span> is reduced progressively to 300, 200 and 100 mL/min and the test is considered positive when the alarm on the HD machine is triggered because negative arterial pressure falls below -250 mmHg. The existence of a positive test with low Q<span class="elsevierStyleInf">B</span> values (100-200 mL/min) involves the presence of decreased Q<span class="elsevierStyleInf">A</span> and, therefore, high probability of relevant stenosis.</p></span><span id="se1090" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4.3</span><span class="elsevierStyleSectionTitle" id="sect1080">Monitoring and surveillance of arteriovenous fistula pressure</span><p id="p4435" class="elsevierStylePara elsevierViewall">The presence of significant AVF stenosis may cause a retrograde increase in pressure inside it and can be detected by monitoring and surveillance of AVF pressure.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,274,283,303,309-315</span></a><a class="elsevierStyleCrossRef" href="#t13">Table 13</a> provides details of how to determine AVF pressure.</p><elsevierMultimedia ident="t13"></elsevierMultimedia><p id="p4440" class="elsevierStylePara elsevierViewall">These methods are preferred for the follow-up of proximal nAVF and, especially, pAVF.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,283</span></a> Collateral veins of a radiocephalic nAVF can cause decompression and a decrease in the sensitivity of these techniques when used for detecting distal nAVF stenosis.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,283</span></a></p><p id="p4445" class="elsevierStylePara elsevierViewall">The pioneering work of Besarab et al.<a class="elsevierStyleCrossRef" href="#bib309"><span class="elsevierStyleSup">309</span></a> showed that the sensitivity to diagnose significant pAVF stenosis by determining normalised static pressure (see section 4.3.3.) was 91%. In the presence of the most common stenosis diagnosed in pAVF, i.e. the stenosis located in the anastomosis between the venous end of the graft and the efferent vein, there is a retrograde increase in pressure throughout the whole pAVF and the pressure level reached is directly related to the existing degree of stenosis.<a class="elsevierStyleCrossRef" href="#bib316"><span class="elsevierStyleSup">316</span></a></p><p id="s1085" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">4.3.1 Dynamic venous pressure</span></p><p id="p4450" class="elsevierStylePara elsevierViewall">DVP is the pressure needed to return the dialysed blood into the AVF through the venous needle recorded by the venous pressure transducer of the HD monitor. In fact, it is the sum of the pressure required to overcome resistance exerted by the venous needle and the pressure existing inside the AVF (<a class="elsevierStyleCrossRef" href="#t13">Table 13</a>).<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a></p><p id="p4455" class="elsevierStylePara elsevierViewall">There are contradictory results in the literature with regard to DVP efficacy in detecting AVF with significant stenosis and high risk of thrombosis.<a class="elsevierStyleCrossRefs" href="#bib311"><span class="elsevierStyleSup">311,312,317-321</span></a> In the classic Schwab et al.<a class="elsevierStyleCrossRef" href="#bib312"><span class="elsevierStyleSup">312</span></a> study, the incidence of thrombosis obtained when comparing AVF with electively corrected significant stenosis (previous DVP > 150 mmHg) and AVF with normal DVP with no suspected stenosis was similar (0.15 versus 0.13 episodes/patient/year). Smits et al.<a class="elsevierStyleCrossRef" href="#bib311"><span class="elsevierStyleSup">311</span></a> showed a significant reduction in the incidence of pAVF thrombosis by the application of a follow-up programme which included DVP measurements, static venous pressure and Q<span class="elsevierStyleInf">A</span>. However, this same Dutch group failed to previously demonstrate the efficacy of DVP in predicting pAVF thrombosis.<a class="elsevierStyleCrossRef" href="#bib322"><span class="elsevierStyleSup">322</span></a></p><p id="p4460" class="elsevierStylePara elsevierViewall">To sum up, the current available data suggesting the usefulness of DVP to diagnose stenosis and predict thrombosis are limited and inconclusive. It is not acceptable to use DVP as a screening method for AVF stenosis in a non-standardised way.</p><p id="s1090" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">4.3.2 Intra-access pressure or static pressure</span></p><p id="p4465" class="elsevierStylePara elsevierViewall">This is determined by the presence of Q<span class="elsevierStyleInf">B</span> = 0 mL/min (pump stopped). Unlike DVP, IAP is not influenced by the type of needle used, Q<span class="elsevierStyleInf">B</span> or blood viscosity.</p><p id="p4470" class="elsevierStylePara elsevierViewall">The simplified determination by Besarab et al. is used to calculate it. This takes into account the pressure obtained by the pressure transducer connected to the venous or arterial line of the HD monitor (mmHg) and the height between the venous or arterial needle (or the arm of the patient’s armchair) and the level of blood in the venous or arterial chamber (cm).<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,314</span></a></p><p id="p4475" class="elsevierStylePara elsevierViewall">In a national study, referring to 24 brachial pAVF, the VA with stenosis had a significantly higher IAP than the other AVF (48.7 ± 22.2 versus 27.6 ± 0.1 mmHg).<a class="elsevierStyleCrossRef" href="#bib283"><span class="elsevierStyleSup">283</span></a> It is considered that a DVP ≥ 150 mmHg with a Q<span class="elsevierStyleInf">B</span> = 200 mL/min (PV200) corresponds to an IAP > 60 mmHg.<a class="elsevierStyleCrossRef" href="#bib313"><span class="elsevierStyleSup">313</span></a> In the aforementioned study by Besarab et al., pAVF surveillance using static pressure achieved a 70% decrease in the incidence of thrombosis.<a class="elsevierStyleCrossRef" href="#bib309"><span class="elsevierStyleSup">309</span></a></p><p id="s1095" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">4.3.3 Equivalent or normalised static intra-access pressure</span></p><p id="p4480" class="elsevierStylePara elsevierViewall">As IAP relates to mean arterial pressure (MAP), the results are expressed in an equivalent or normalised form using the IAP/MAP ratio.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> In the absence of significant stenosis and because of existing collateral circulation, the IAP/MAP ratio will always be lower in nAVF than in pAVF. In another study by Besarab et al.,<a class="elsevierStyleCrossRef" href="#bib315"><span class="elsevierStyleSup">315</span></a> the IAP/MAP ratio in cases without stenosis was higher in pAVF (0.43 ± 0.02, n = 414) compared with nAVF (0.26 ± 0.01, n = 286), but without significant differences in relation to Q<span class="elsevierStyleInf">A</span>.</p><p id="p4485" class="elsevierStylePara elsevierViewall">Normalised intra-access pressure profiles have been described according to the situation of the stenosis in the pAVF at the level of the arterial anastomosis, body (between the 2 needles) or venous anastomosis. It is considered that, when faced with a stenosis located in the venous anastomosis of the pAVF, the IAP/MAP ratio at the level of the venous and arterial needles is > 0.5 and 0.75, respectively.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,315</span></a> In the aforementioned study by Caro et al.,<a class="elsevierStyleCrossRef" href="#bib283"><span class="elsevierStyleSup">283</span></a> there was a significant difference between the IAP/MAP ratio determined in pAVF with and without stenosis: 0.5 ± 0.2 and 0.3 ± 0.1, respectively.</p><p id="p4490" class="elsevierStylePara elsevierViewall">When there is a significant stenosis located in the venous anastomosis of a pAVF, there is an inverse relationship between normalised IAP and the Q<span class="elsevierStyleInf">A</span> of AVF.<a class="elsevierStyleCrossRefs" href="#bib315"><span class="elsevierStyleSup">315,323</span></a> In this functional situation of raised normalised IAP and low Q<span class="elsevierStyleInf">A</span>, the AVF comes fully within the area of high risk for thrombosis.<a class="elsevierStyleCrossRef" href="#bib274"><span class="elsevierStyleSup">274</span></a></p></span><span id="se1115" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4.4</span><span class="elsevierStyleSectionTitle" id="sect1100">Recirculation of arteriovenous fistula</span><p id="p4495" class="elsevierStylePara elsevierViewall">When significant stenosis is present, the Q<span class="elsevierStyleInf">A</span> of AVF decreases and the percentage of already dialysed blood re-entering the dialyser through the arterial needle increases. In the absence of technical errors, recirculation occurs as a consequence of a severe AVF stenosis when Q<span class="elsevierStyleInf">A</span> is close to or decreases below the planned Q<span class="elsevierStyleInf">B</span> (300-500 mL/min).<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,313,315</span></a></p><p id="p4500" class="elsevierStylePara elsevierViewall">Therefore, the measurement of recirculation is not the best method for early detection of stenosis.<a class="elsevierStyleCrossRefs" href="#bib279"><span class="elsevierStyleSup">279,324</span></a> Above all, it is not recommended that it be applied to monitoring pAVF.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,274</span></a> In this type of AVF, recirculation occurs late when there is severe stenosis and a very high risk of thrombosis.<a class="elsevierStyleCrossRef" href="#bib274"><span class="elsevierStyleSup">274</span></a> In addition, we must remember that the presence of a localised stenosis between the two AVF needles does not cause recirculation.<a class="elsevierStyleCrossRef" href="#bib324"><span class="elsevierStyleSup">324</span></a></p><p id="p4505" class="elsevierStylePara elsevierViewall">The recirculation percentage can be determined using the following two methods<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a>:<ul class="elsevierStyleList" id="list0450"><li class="elsevierStyleListItem" id="listi1970"><span class="elsevierStyleLabel">•</span><p id="p4510" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Determination of urea recirculation</span>.<a class="elsevierStyleCrossRef" href="#bib325"><span class="elsevierStyleSup">325</span></a> This is described in <a class="elsevierStyleCrossRef" href="#t14">Table 14</a>. The presence of a percentage of urea recirculation > 10% is a criterion for investigating a possible AVF stenosis by means of an imaging test.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a></p><elsevierMultimedia ident="t14"></elsevierMultimedia></li><li class="elsevierStyleListItem" id="listi1975"><span class="elsevierStyleLabel">•</span><p id="p4515" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Determination of recirculation using dilution screening techniques</span> (<a class="elsevierStyleCrossRef" href="#t15">Table 15</a>).<a class="elsevierStyleCrossRefs" href="#bib326"><span class="elsevierStyleSup">326-330</span></a> These methods present higher sensitivity and specificity than the urea recirculation method.<a class="elsevierStyleCrossRefs" href="#bib328"><span class="elsevierStyleSup">328,329</span></a> There are published studies using the ultrasound dilution method, the thermodilution method with BTM (blood temperature monitor) sensor and the glucose perfusion method.<a class="elsevierStyleCrossRefs" href="#bib327"><span class="elsevierStyleSup">327,328,330</span></a> In this respect, Wang et al.<a class="elsevierStyleCrossRef" href="#bib330"><span class="elsevierStyleSup">330</span></a> demonstrated that recirculation values higher than 15% obtained using the BTM sensor provided a high sensitivity (81.8%) and specificity (98.6%) in the detection of nAVF requiring elective intervention. The presence of AVF stenosis should be investigated in the case of a recirculation percentage greater than 5% and 15% using the ultrasound dilution and thermodilution methods, respectively.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,330</span></a></p><elsevierMultimedia ident="t15"></elsevierMultimedia></li></ul></p></span><span id="se1120" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4.5</span><span class="elsevierStyleSectionTitle" id="sect1105">Unexplained decrease in haemodialysis adequacy</span><p id="p4520" class="elsevierStylePara elsevierViewall">The decrease, for no apparent reason, in HD adequacy assessed by the Kt/V index or PUR may be an indirect sign of AVF dysfunction.<a class="elsevierStyleCrossRefs" href="#bib279"><span class="elsevierStyleSup">279,331</span></a> In one study, patients with significant nAVF stenosis (n = 50) presented a Kt/V index lower (1.15 ± 0.20) than the remaining patients (1.33 ± 0.16) (p < 0.0001).<a class="elsevierStyleCrossRef" href="#bib303"><span class="elsevierStyleSup">303</span></a> It is considered that HD efficacy is affected at a late stage during the natural development of AVF stenosis when a high percentage of recirculation becomes evident.<a class="elsevierStyleCrossRef" href="#bib279"><span class="elsevierStyleSup">279</span></a></p><p id="p4525" class="elsevierStylePara elsevierViewall">However, it has been published that the persisting decrease in the Kt index, determined online using the ionic dialysance method in each HD session, makes it possible to detect early recirculation caused by significant nAVF stenosis.<a class="elsevierStyleCrossRef" href="#bib332"><span class="elsevierStyleSup">332</span></a></p></span><span id="s1125" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4.6</span><span class="elsevierStyleSectionTitle" id="sect1110">Dilution screening methods for indirect determination of arteriovenous fistula flow</span><p id="s1115" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale for dilution methods</span></p><p id="p4530" class="elsevierStylePara elsevierViewall">The objective follow-up of AVF function should be carried out regularly by determining its Q<span class="elsevierStyleInf">A</span>.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a> In the presence of a significant stenosis, Q<span class="elsevierStyleInf">A</span> always decreases irrespective of the AVF type (nAVF or pAVF), its location (upper or lower limb) or the topography of the stenosis (feeding artery, anastomosis, arterialised vein, central vein) .<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,279,333,334</span></a> This is very important and is a notable advantage compared with first-generation methods. For example, in the presence of a significant nAVF stenosis in the arterialised vein, Q<span class="elsevierStyleInf">A</span> will decrease but, depending on the venous needle position in the arterialised vein, it is possible that the venous pressure (determined by DVP) does not increase.<a class="elsevierStyleCrossRef" href="#bib279"><span class="elsevierStyleSup">279</span></a></p><p id="p4535" class="elsevierStylePara elsevierViewall">The introduction of the ultrasound dilution method by Nicolai Krivitski in 1995 meant a qualitative change in the field of AVF study as, for the first time, it was possible to perform non-invasive Q<span class="elsevierStyleInf">A</span> estimation.<a class="elsevierStyleCrossRef" href="#bib335"><span class="elsevierStyleSup">335</span></a> Since then, several dilution techniques that allow the indirect determination of Q<span class="elsevierStyleInf">A</span> during HD and, therefore, the functional follow-up of the AVF have been described (<a class="elsevierStyleCrossRef" href="#t15">Tables 15</a> and <a class="elsevierStyleCrossRef" href="#t16">16</a>).<a class="elsevierStyleCrossRefs" href="#bib336"><span class="elsevierStyleSup">336-343</span></a></p><elsevierMultimedia ident="t16"></elsevierMultimedia><p id="p4540" class="elsevierStylePara elsevierViewall">Q<span class="elsevierStyleInf">A</span> is calculated by quantifying the difference in recirculation before and after the dilution of a particular indicator (haematocrit, temperature), with or without inversion of the HD blood lines. If both <span class="elsevierStyleItalic">arterial</span> and <span class="elsevierStyleItalic">venous</span> needles have been inserted into the same arterialised vein, artificial recirculation is created when reversing the blood lines, with the dilution of the indicator that enables us to calculate Q<span class="elsevierStyleInf">A</span> according to the formulae shown in <a class="elsevierStyleCrossRef" href="#t16">Table 16</a>.</p><p id="p4545" class="elsevierStylePara elsevierViewall">The dilution methods requiring the HD blood lines to be reversed are those most commonly used today. However, in some cases, they cannot be applied: when we insert the <span class="elsevierStyleItalic">venous</span> needle through which blood returns into a vein other than the AVF-bearing arterialised vein, AVF recirculation is zero and, therefore, Q<span class="elsevierStyleInf">A</span> calculation is impossible.<a class="elsevierStyleCrossRefs" href="#bib338"><span class="elsevierStyleSup">338,344</span></a></p><p id="p4550" class="elsevierStylePara elsevierViewall">Dilution techniques that calculate Q<span class="elsevierStyleInf">A</span> during HD should be performed within the first hour of the session to avoid haemodynamic changes secondary to ultrafiltration.<a class="elsevierStyleCrossRef" href="#bib270"><span class="elsevierStyleSup">270</span></a></p><p id="p4555" class="elsevierStylePara elsevierViewall">According to the European guidelines, there is no clear preference for any of these methods<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a> and most studies have shown similar results for Q<span class="elsevierStyleInf">A</span> after applying different dilution techniques.<a class="elsevierStyleCrossRefs" href="#bib345"><span class="elsevierStyleSup">345-348</span></a> Indeed, all of them have advantages and disadvantages when used. For example, the time required to determine Q<span class="elsevierStyleInf">A</span> using the Delta-H method is long (more than 20 min) but, in contrast, it is a completely examiner-independent method and Q<span class="elsevierStyleInf">A</span> value automatically displays on the Crit-Line monitor screen immediately after the completion of the examination.<a class="elsevierStyleCrossRefs" href="#bib270"><span class="elsevierStyleSup">270,348</span></a> Other methods, like thermodilution and temperature gradient, have an advantage over those previously mentioned, as the sensor (BTM) is already incorporated into the HD machine, but Q<span class="elsevierStyleInf">A</span> value is not obtained automatically and needs to be calculated subsequently<a class="elsevierStyleCrossRefs" href="#bib345"><span class="elsevierStyleSup">345,348</span></a>; both methods are only validated for high-flux HD with Q<span class="elsevierStyleInf">B</span> of 300 mL/min.<a class="elsevierStyleCrossRef" href="#bib349"><span class="elsevierStyleSup">349</span></a> The use of certain devices allows the instant inversion of the HD blood lines and, therefore, the time required to obtain Q<span class="elsevierStyleInf">A</span> value is significantly reduced.<a class="elsevierStyleCrossRef" href="#bib348"><span class="elsevierStyleSup">348</span></a></p><p id="s1120" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Interpreting the results</span></p><p id="p4560" class="elsevierStylePara elsevierViewall">When any functional AVF alteration is detected by any of these screening methods, an imaging test should be carried out in the event of suspected AVF stenosis. The functional criteria for this are as follows<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,15,350</span></a>:<ul class="elsevierStyleList" id="list0455"><li class="elsevierStyleListItem" id="listi1980"><span class="elsevierStyleLabel">•</span><p id="p4565" class="elsevierStylePara elsevierViewall">Absolute Q<span class="elsevierStyleInf">A</span> value. The threshold value or cut-off point of Q<span class="elsevierStyleInf">A</span> which indicates the need for an imaging test varies according to the ROC curves of sensitivity-specificity obtained in several studies: < 500, 650, 700 or 750 mL/min.<a class="elsevierStyleCrossRefs" href="#bib269"><span class="elsevierStyleSup">269,288,327,350,351</span></a> The KDOQI guide considers a Q<span class="elsevierStyleInf">A</span> < 600 mL/min for pAVF and < 400-500 mL/min for nAVF,<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> whereas the European Guide indicates elective intervention in the case of a Q<span class="elsevierStyleInf">A</span> < 600 mL/min in pAVF or < 300 mL/min in nAVF of the forearm.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a></p></li><li class="elsevierStyleListItem" id="listi1985"><span class="elsevierStyleLabel">•</span><p id="p4570" class="elsevierStylePara elsevierViewall">Temporary decrease in Q<span class="elsevierStyleInf">A</span> > 20-25%, regardless of whether nAVF or pAVF, in relation to the baseline Q<span class="elsevierStyleInf">A</span>.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,15,227,352,353</span></a></p></li></ul></p><p id="p4575" class="elsevierStylePara elsevierViewall">As mentioned previously, prospective analysis of Q<span class="elsevierStyleInf">A</span> evolution over time is of higher value for diagnosing AVF stenosis than isolated determinations.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> In a longitudinal study by Neyra et al.,<a class="elsevierStyleCrossRef" href="#bib353"><span class="elsevierStyleSup">353</span></a> involving 95 AVF, Q<span class="elsevierStyleInf">A</span> decrease over time was a powerful predictive variable of thrombosis, so that the relative risk (RR) of thrombosis increased when there was a drop in Q<span class="elsevierStyleInf">A</span> higher than 15% and was maximum (34.7%) when the decrease in Q<span class="elsevierStyleInf">A</span> was > 50%. Paulson et al.<a class="elsevierStyleCrossRef" href="#bib354"><span class="elsevierStyleSup">354</span></a> consider that a 20% to 25% decrease in Q<span class="elsevierStyleInf">A</span> percentages may be secondary only to haemodynamic changes and that only a decrease in Q<span class="elsevierStyleInf">A</span> greater than 33% should be considered significant.</p><p id="p4580" class="elsevierStylePara elsevierViewall">It has been demonstrated that Q<span class="elsevierStyleInf">A</span> is related to AVF type (for example, radiocephalic versus brachiocephalic nAVF) as well as various demographic and clinical factors of the patient<a class="elsevierStyleCrossRefs" href="#bib345"><span class="elsevierStyleSup">345,349,352,355,356</span></a>. An inverse relationship between Q<span class="elsevierStyleInf">A</span> of the AVF and patient age has been demonstrated<a class="elsevierStyleCrossRefs" href="#bib269"><span class="elsevierStyleSup">269,349</span></a> so that the application of a multiple linear regression model showed a reduction of 11.6 mL/min in baseline Q<span class="elsevierStyleInf">A</span> of the AVF for every year of the patient’s life, with the rest of the variables considered remaining constant.<a class="elsevierStyleCrossRef" href="#bib269"><span class="elsevierStyleSup">269</span></a> The functional AVF profile also depends on its location, as demonstrated in a case series by Treacy et al.,<a class="elsevierStyleCrossRef" href="#bib356"><span class="elsevierStyleSup">356</span></a> referring to 53 nAVF studied using the thermodilution method: the functional result obtained differed depending on the nAVF topography in the snuff box, distal forearm, proximal forearm, brachiocephalic and brachiobasilic, from the lowest to the highest Q<span class="elsevierStyleInf">A</span>.</p><p id="p4585" class="elsevierStylePara elsevierViewall">In some studies, better AVF function, that is to say, a higher Q<span class="elsevierStyleInf">A</span>, has been shown in patients with a history of some previous ipsilateral AVF.<a class="elsevierStyleCrossRefs" href="#bib345"><span class="elsevierStyleSup">345,357</span></a> The existence of previous venous arterialisation may explain this functional difference. In other words, a previous functional distal AVF in the same limb may determine the function of a secondary nAVF of proximal location. In this respect, in a study by Begin et al.,<a class="elsevierStyleCrossRef" href="#bib357"><span class="elsevierStyleSup">357</span></a> referring to 45 patients with nAVF, Q<span class="elsevierStyleInf">A</span> of patients with brachiocephalic nAVF, measured by the ultrasound dilution method, was higher in cases of a previously functioning radiocephalic nAVF in the same arm compared with the remaining patients (1800 ± 919 versus 1167 ± 528 mL/min).</p><p id="p4590" class="elsevierStylePara elsevierViewall">Functional AVF surveillance through Q<span class="elsevierStyleInf">A</span> determination has allowed a higher incidence of pathology to be shown in the feeding artery than that reported in historical studies and currently estimated at around 30% of all dysfunctional AVF cases.<a class="elsevierStyleCrossRefs" href="#bib333"><span class="elsevierStyleSup">333,358,359</span></a> In addition, through this AVF surveillance, the radial artery pathology in radiocephalic nAVF could be classified in 3 differentiated groups.<a class="elsevierStyleCrossRef" href="#bib333"><span class="elsevierStyleSup">333</span></a></p><p id="p4595" class="elsevierStylePara elsevierViewall">In addition to diagnosing AVF stenosis, AVF surveillance through periodic Q<span class="elsevierStyleInf">A</span> measurements allows the identification of hyperdynamic AVF with excessive Q<span class="elsevierStyleInf">A</span> which may cause heart failure.<a class="elsevierStyleCrossRefs" href="#bib360"><span class="elsevierStyleSup">360,361</span></a> There is increased risk of heart failure secondary to AVF when its Q<span class="elsevierStyleInf">A</span> is ≥ 2000 mL/min or 20% of cardiac output.<a class="elsevierStyleCrossRef" href="#bib194"><span class="elsevierStyleSup">194</span></a> In such cases, it is reasonable to perform strict cardiological follow-up by periodic echocardiograms. On the other hand, cardiac decompensation can also occur with a Q<span class="elsevierStyleInf">A</span>< 2000 mL/min in patients with a reduced myocardial reserve.<a class="elsevierStyleCrossRef" href="#bib360"><span class="elsevierStyleSup">360</span></a></p><p id="p4600" class="elsevierStylePara elsevierViewall">In some cases, the estimation of both Q<span class="elsevierStyleInf">A</span> of the AVF and the systolic pulmonary artery pressure jointly using non-invasive methods (Delta-H method and Doppler echocardiogram, respectively) has allowed a diagnosis to be made, surgical indication to be established (banding) and post-operative follow-up of the AVF with haemodynamic repercussions to be carried out.<a class="elsevierStyleCrossRef" href="#bib361"><span class="elsevierStyleSup">361</span></a></p></span><span id="se1140" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4.7</span><span class="elsevierStyleSectionTitle" id="sect1125">Imaging tests. Arteriovenous fistula surveillance using Doppler ultrasound</span><p id="s1130" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p4605" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0110"></elsevierMultimedia></p><p id="p4630" class="elsevierStylePara elsevierViewall">DU is an imaging technique that allows examination of both nAVF and pAVF using a linear sender and receiver ultrasound transducer applied on the different AVF planes (<a class="elsevierStyleCrossRef" href="#t17">Table 17</a>). Despite some drawbacks (operator-dependent technique, impossible to use in case of bandages and/or wounds and difficulties in assessment in the case of vascular calcification), the use of ultrasound image together with Doppler is growing as an AVF surveillance method since this is a second-generation non-invasive method which does not use ionising radiation or iodinated contrast media and which, in addition, is inexpensive and readily available.<a class="elsevierStyleCrossRef" href="#bib362"><span class="elsevierStyleSup">362</span></a> In <a class="elsevierStyleCrossRef" href="#t18">Table 18</a> other imaging methods for studying AVF are described.</p><elsevierMultimedia ident="t17"></elsevierMultimedia><elsevierMultimedia ident="t18"></elsevierMultimedia><p id="p4635" class="elsevierStylePara elsevierViewall">DU has the following benefits in AVF surveillance<a class="elsevierStyleCrossRefs" href="#bib52"><span class="elsevierStyleSup">52,363,364</span></a>:<ul class="elsevierStyleList" id="list0465"><li class="elsevierStyleListItem" id="listi2005"><span class="elsevierStyleLabel">•</span><p id="p4640" class="elsevierStylePara elsevierViewall">Method for quick diagnosis that can be used in situ in the HD room (portable ultrasound machine) when any change in the AVF is detected by a first-generation method or by a decrease in Q<span class="elsevierStyleInf">A</span> recorded by a dilution method.<a class="elsevierStyleCrossRef" href="#bib223"><span class="elsevierStyleSup">223</span></a> In a Spanish study referring to 119 portable DU examinations carried out by the nephrologist on 67 AVF, 31 stenoses were diagnosed in 44 cases of needling difficulty with no other warning signs for stenosis,<a class="elsevierStyleCrossRef" href="#bib223"><span class="elsevierStyleSup">223</span></a> demonstrating the usefulness of DU in the hands of a well-trained professional.</p></li><li class="elsevierStyleListItem" id="listi2010"><span class="elsevierStyleLabel">•</span><p id="p4645" class="elsevierStylePara elsevierViewall">Regulated surveillance method for periodic AVF assessment. DU allows direct visualisation of the AVF and, therefore, makes it possible to perform morphological surveillance.<a class="elsevierStyleCrossRefs" href="#bib365"><span class="elsevierStyleSup">365-368</span></a></p></li><li class="elsevierStyleListItem" id="listi2015"><span class="elsevierStyleLabel">•</span><p id="p4650" class="elsevierStylePara elsevierViewall">Haemodynamic information related to the AVF. DU allows direct Q<span class="elsevierStyleInf">A</span> determination and, therefore, functional AVF surveillance.<a class="elsevierStyleCrossRef" href="#bib369"><span class="elsevierStyleSup">369</span></a> Q<span class="elsevierStyleInf">A</span> (mL/min), preferably in the brachial artery, is calculated using the following formula<a class="elsevierStyleCrossRef" href="#bib367"><span class="elsevierStyleSup">367</span></a>:QA=Time-averaged mean velocity (m/s)× cross-sectional area (mm2)×60</p><p id="p4655" class="elsevierStylePara elsevierViewall">Various authors have found that Q<span class="elsevierStyleInf">A</span> determined by DU is significantly lower in AVF with stenosis compared with other AVF without stenosis.<a class="elsevierStyleCrossRefs" href="#bib303"><span class="elsevierStyleSup">303,369</span></a> A positive correlation has been shown between Q<span class="elsevierStyleInf">A</span> of the arterialised vein in nAVF determined by DU and diameter and parameters of the feeding artery (diameter and arterial blood flow).<a class="elsevierStyleCrossRef" href="#bib369"><span class="elsevierStyleSup">369</span></a> A significant correlation has also been found between Q<span class="elsevierStyleInf">A</span> obtained by DU and by various dilution methods.<a class="elsevierStyleCrossRefs" href="#bib369"><span class="elsevierStyleSup">369,370</span></a></p></li><li class="elsevierStyleListItem" id="listi2020"><span class="elsevierStyleLabel">•</span><p id="p4660" class="elsevierStylePara elsevierViewall">Imaging test of choice to confirm, locate and quantify AVF stenosis detected by screening methods prior to elective treatment.<a class="elsevierStyleCrossRefs" href="#bib303"><span class="elsevierStyleSup">303,371-373</span></a> In this respect, a linear correlation has been described between DU and fistulography to diagnose significant AVF stenosis.<a class="elsevierStyleCrossRefs" href="#bib373"><span class="elsevierStyleSup">373,374</span></a> In addition, it allows for the surveillance of stenoses which are considered non-significant.<a class="elsevierStyleCrossRef" href="#bib375"><span class="elsevierStyleSup">375</span></a> The ultrasound criteria described for the diagnosis of significant AVF stenosis are shown in <a class="elsevierStyleCrossRef" href="#t19">Table 19</a>.<a class="elsevierStyleCrossRefs" href="#bib52"><span class="elsevierStyleSup">52,84,376</span></a></p><elsevierMultimedia ident="t19"></elsevierMultimedia></li><li class="elsevierStyleListItem" id="listi2025"><span class="elsevierStyleLabel">•</span><p id="p4665" class="elsevierStylePara elsevierViewall">It allows the morphological and functional assessment of other AVF dysfunctions which are not related to stenosis or thrombosis, such as aneurysms and pseudoaneurysms, haematoma, abscesses, etc.</p></li></ul></p><p id="p4670" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question X How reliable is Doppler ultrasound in determining blood flow in the arteriovenous fistula in comparison to dilution screening methods?</span></p><p id="p4675" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question X in <a href="https://static.elsevier.es/nefroguiaaveng/10_PCX_Qa_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0050"></elsevierMultimedia></p><p id="s1135" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="s1140" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Doppler ultrasound versus ultrasound dilution</span></p><p id="p4680" class="elsevierStylePara elsevierViewall">The study by Weitzel et al.<a class="elsevierStyleCrossRef" href="#bib377"><span class="elsevierStyleSup">377</span></a> evaluated the comparability of Q<span class="elsevierStyleInf">A</span> measurements through DU with those taken by ultrasound dilution method in 24 patients with pAVF. In this study the reproducibility in 54 pairs of DU measurements was also assessed. Measurement variations by DU were 4% for pAVF with Q<span class="elsevierStyleInf">A</span> < 800 mL/min (n = 17), 6% for pAVF with Q<span class="elsevierStyleInf">A</span> flow between 801 and 1600 mL/min (n = 22), and 11% for pAVF with Q<span class="elsevierStyleInf">A</span> > 1600 mL/min (n = 15). The mean variation coefficient of measurement was 7% for DU compared with 5% for ultrasound dilution method. Correlation coefficients (r) between Q<span class="elsevierStyleInf">A</span> measurements by DU and by ultrasound dilution were 0.79 (n = 24, p < 0.0001), 0.84 for pAVF with Q<span class="elsevierStyleInf">A</span> < 2000 mL/min (n = 20, p < 0.0001), and 0.91 for pAVF with Q<span class="elsevierStyleInf">A</span> < 1600 mL/min (n = 18, p < 0.0001). They concluded that DU gives reproducible Q<span class="elsevierStyleInf">A</span> measurements which correlate with ultrasound dilution measurements.<a class="elsevierStyleCrossRef" href="#bib377"><span class="elsevierStyleSup">377</span></a></p><p id="p4685" class="elsevierStylePara elsevierViewall">The study by Schwarz et al.<a class="elsevierStyleCrossRef" href="#bib378"><span class="elsevierStyleSup">378</span></a> compared both techniques using fistulography as a reference. They assessed 59 HD patients with forearm nAVF using ultrasound dilution, DU and fistulography, in that order, and diagnosed nAVF stenosis in 41 patients, who were treated with PTA. The accuracy of both techniques, assessed by ROC curves, was similar: average areas under the curve were 0.79 (95% CI, 0.66 to 0.91) for ultrasound dilution and 0.80 (95% CI: 0.65 to 0.94) for DU. The correlation between Q<span class="elsevierStyleInf">A</span> values obtained by ultrasound dilution and by DU measurements was 0.37 (Spearman = 0.004). The optimal cut-off value calculated for stenosis prediction was 465 mL/min for ultrasound dilution and 390 mL/min for DU. Both ultrasound techniques were valid for predicting nAVF stenosis (p < 0.01). In 13 patients restenosis occurred in the first 6 months after PTA. Q<span class="elsevierStyleInf">A</span> obtained by ultrasound dilution after PTA was significantly lower in these 13 patients, compared with the other 21 patients. The authors concluded that Q<span class="elsevierStyleInf">A</span> surveillance of nAVF for HD using ultrasound techniques provides a reasonable prediction of stenosis and restenosis.<a class="elsevierStyleCrossRef" href="#bib378"><span class="elsevierStyleSup">378</span></a></p><p id="p4690" class="elsevierStylePara elsevierViewall">The study by Lopot et al.<a class="elsevierStyleCrossRef" href="#bib379"><span class="elsevierStyleSup">379</span></a> provided measurement comparative data for DU and dilution ultrasonography, which was used as the reference technique in 27 patients, and found a good correlation between both techniques (r = 0.8691).</p><p id="p4695" class="elsevierStylePara elsevierViewall">The study by Lin et al.<a class="elsevierStyleCrossRef" href="#bib380"><span class="elsevierStyleSup">380</span></a> compared the reproducibility and correlation of Q<span class="elsevierStyleInf">A</span> measurements using a variable Q<span class="elsevierStyleInf">B</span>based Doppler method combined with spectral analysis of Duplex Doppler images (VPFDUM), with the ultrasound dilution method, and conventional DU method, in 73 HD patients, 70 with nAVF and 3 with pAVF. The mean value of Q<span class="elsevierStyleInf">A</span> by VPFDUM (870.8 ± 412.0 mL/min) showed a high degree of similarity to that of measurements by ultrasound dilution (868.6 ± 417.9 mL/min) but was higher than measurements by conventional DU (685.1 ± 303.6 mL/min; p < 0.005). The mean coefficient of variation values was similar using VPFDUM (1.6%) and ultrasound dilution (1.4%) but lower than conventional DU (6.8 %, p < 0.01). The correlation coefficient and the intra-class correlation coefficient (ICC) of repeated Q<span class="elsevierStyleInf">A</span> measurements by VPFDUM (0.985 and 0.993, p < 0.001) were also similar to those by ultrasound dilution (0.992 and 0.995, p < 0.001), but slightly higher than those of conventional DU (0.917 and 0.948, p < 0.005).The reproducibility of the VPFDUM technique (r = 0.98, p < 0.0001) and the correlation between VPFDUM and ultrasound dilution (r = 0.99, p < 0.0001) for Q<span class="elsevierStyleInf">A</span> measurements were good. Unassisted AVF patency at 6 months was significantly lower in patients with a Q<span class="elsevierStyleInf">A</span> < 500 mL/min than in those with a Q<span class="elsevierStyleInf">A</span> > 500 mL/min (13.6 % versus 92.2 %, p < 0.0001). They concluded that the VPFDUM technique is a non-invasive, accurate and reliable procedure for measuring Q<span class="elsevierStyleInf">A</span> and has predictive power regarding AVF patency.<a class="elsevierStyleCrossRef" href="#bib380"><span class="elsevierStyleSup">380</span></a></p><p id="s1145" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Doppler ultrasound versus other dilution methods</span></p><p id="p4700" class="elsevierStylePara elsevierViewall">Roca-Tey et al.<a class="elsevierStyleCrossRef" href="#bib369"><span class="elsevierStyleSup">369</span></a> carried out a functional study comparing DU and Delta-H methods for Q<span class="elsevierStyleInf">A</span> determination in AVF (84.8% of nAVF) in 33 prevalent patients on chronic HD. In diagnostic concordance analysis, the ICC between Q<span class="elsevierStyleInf">A</span> values of the AVF obtained using both methods was 0.74 (p < 0.0001). The authors concluded that DU and Delta-H methods are super-imposable for Q<span class="elsevierStyleInf">A</span> determination of the AVF.<a class="elsevierStyleCrossRef" href="#bib369"><span class="elsevierStyleSup">369</span></a></p><p id="p4705" class="elsevierStylePara elsevierViewall">Fontseré et al.<a class="elsevierStyleCrossRef" href="#bib381"><span class="elsevierStyleSup">381</span></a> compared thermodilution and DU, which they used as the reference technique, to measure Q<span class="elsevierStyleInf">A</span> in a cross-sectional study conducted in 64 HD patients using nAVF (54) and pAVF (10). The mean Q<span class="elsevierStyleInf">A</span> obtained by DU was 1426 ± 753 mL/min for nAVF and 1186 ± 789 mL/min for pAVF. The values obtained by thermodilution were 1372 ± 770 for nAVF (bias: 54.6; ICC: 0.923) and 1176 ± 758 for pAVF (bias: 10.2; ICC: 0.992). In the subgroup of 28 patients with end-to-side radiocephalic nAVF, the Q<span class="elsevierStyleInf">A</span> obtained by DU was 1232 ± 767 mL/min.; in the radial artery, 942 (ICC: 0.805); radialulnar artery, 1103 (ICC: 0.973); cephalic vein, 788 (ICC: 0.772) and with thermodilution, 1026 (ICC: 0.971). They concluded that thermodilution is a useful indirect method for Q<span class="elsevierStyleInf">A</span> measurement. In the subgroup of patients with radiocephalic nAVF the sum of Q<span class="elsevierStyleInf">A</span> obtained in radial and ulnar arteries was more accurate. However, thermodilution also had an excellent correlation with the brachial artery.<a class="elsevierStyleCrossRef" href="#bib381"><span class="elsevierStyleSup">381</span></a></p><p id="p4710" class="elsevierStylePara elsevierViewall">Sacquépée et al.<a class="elsevierStyleCrossRef" href="#bib382"><span class="elsevierStyleSup">382</span></a> studied the correlation of Q<span class="elsevierStyleInf">A</span> values obtained using thermodilution and DU in 15 patients dialysed through nAVF (14) and pAVF (1). The Q<span class="elsevierStyleInf">A</span> mean was 1088 ± 576 mL/min measured by DU and 1094 ± 570 measured by thermodilution. The comparison of Q<span class="elsevierStyleInf">A</span> values obtained with both techniques showed a strong linear relationship.</p><p id="s1150" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p4715" class="elsevierStylePara elsevierViewall">Due to their high concordance for determining Q<span class="elsevierStyleInf">A</span> of AVF, dilution screening methods such as ultrasound dilution, Delta-H and thermodilution are equivalent to DU.<a class="elsevierStyleCrossRefs" href="#bib369"><span class="elsevierStyleSup">369,370,377-382</span></a></p><p id="p4720" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0115"></elsevierMultimedia></p><p id="p4730" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XI Can regulated Doppler ultrasound performed by an experienced examiner replace angiography as the gold standard to confirm significant arteriovenous fistula stenosis?</span></p><p id="p4735" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XI in <a href="https://static.elsevier.es/nefroguiaaveng/11_PCXI_Diagnostico_estenosis_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0055"></elsevierMultimedia></p><p id="s1160" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p4740" class="elsevierStylePara elsevierViewall">In order to formulate the recommendations in this guide, a meta-analysis was carried out (using the program MetaAnalyst, 11-11-2013) on four studies conducted in the last ten years. These studies provide complete data, thereby making it possible to calculate the sensitivity and specificity of regulated DU compared with fistulography to confirm diagnosis of significant AVF stenosis in patients with clinically suspected stenosis.<a class="elsevierStyleCrossRefs" href="#bib364"><span class="elsevierStyleSup">364,374,383,384</span></a> Using data from 755 patients, of which 319 were diagnosed with significant stenosis by fistulography (prevalence: 42.3%), the meta-analysis provided high overall values of sensitivity of 89.3% (95% CI, 84.7-92.6) and a specificity of 94.7% (95% CI, 91.8-96.6) for DU (<a class="elsevierStyleCrossRef" href="#f3">Figures 3</a> and <a class="elsevierStyleCrossRef" href="#f4">4</a>). These levels are high, but they are insufficient to consider DU as a substitute for fistulography as the “gold standard” for confirming diagnosis of significant AVF stenosis. No diagnostic test which leaves 10% of cases undetected can be considered as a “gold standard”.</p><elsevierMultimedia ident="f3"></elsevierMultimedia><elsevierMultimedia ident="f4"></elsevierMultimedia><p id="p4745" class="elsevierStylePara elsevierViewall">However, the answer to this clinical question leads us to ask other questions: Which test should patients initially be assessed with in cases of suspected AVF stenosis: DU or fistulography? Are DU findings enough to indicate elective intervention in patients with suspected stenosis, a suspicion arising from the use of other screening methods?</p><p id="p4750" class="elsevierStylePara elsevierViewall">Clinical decisions are not solely dependent on the sensitivity and specificity of DU to correctly diagnose significant stenosis, but they also depend heavily on real prevalence of significant stenosis among patients with suspected stenosis that arise after applying methods of AVF monitoring and/or surveillance. For fixed sensitivity and specificity, incorrect and accurate diagnoses will be heavily influenced by the prevalence of the pathology being studied. As can be seen in <a class="elsevierStyleCrossRef" href="#t20">Table 20</a>, the positive predictive value of DU, i.e. the percentage of patients who really present a significant stenosis among those diagnosed by DU, progressively increases as prevalence of significant stenosis rises among patients who are suspected of having one. Thus, when the prevalence of significant stenosis is 50%, the positive predictive value of DU is 94.4%, and this percentage increases as higher prevalence is reached.</p><elsevierMultimedia ident="t20"></elsevierMultimedia><p id="p4755" class="elsevierStylePara elsevierViewall">The option of using DU as an initial diagnostic test to assess possible significant stenosis would have a significant impact from the start: angiography would no longer be performed on all patients, as it is an invasive test, with potential side effects, and is more expensive for health services.</p><p id="p4760" class="elsevierStylePara elsevierViewall">There is no doubt that there are two patient groups which clearly benefit from using DU without fistulography, because the same conclusion would be reached as in fistulography, patients would be exposed to lower risks and it is economically cheaper. On the one hand, there would be true positives: patients with significant stenosis, for whom preventive intervention of the stenosis would be directly indicated. On the other, there would be true negatives: patients without any stenosis who would be kept on the routine follow-up programme.</p><p id="p4765" class="elsevierStylePara elsevierViewall">It is especially important to consider the <span class="elsevierStyleItalic">false-negative</span> cases, i.e. AVF with significant stenosis in which DU has been unable to establish the diagnosis. In these particular cases, the suspicion will persist despite the DU result and therefore, it seems reasonable to then carry out fistulography, which will end up providing the definitive diagnosis of the stenosis.</p><p id="p4770" class="elsevierStylePara elsevierViewall">Therefore, the use of DU as a first choice diagnostic imaging test for patients with suspected significant stenosis seems to be a sensible decision, both clinically and economically. Given that false-positive rates are low, those who showed positive on the DU could be treated electively, without the need to undergo fistulography for confirmation. In patients with persisting suspected significant stenosis in whom a previous DU was not conclusive, it is advisable to perform fistulography and preventive treatment if the stenosis is then confirmed.</p><p id="p4775" class="elsevierStylePara elsevierViewall">There are no controlled studies which have assessed the clinical consequences of testing patients with AVF dysfunctions that may make us suspect the possible presence of significant stenosis, by means of only DU or angiography.</p><p id="p4780" class="elsevierStylePara elsevierViewall">No relevant studies have been identified regarding patient preferences. It seems logical to think that if there were equal clinical performances, patients would prefer the non-invasive techniques which do not imply exposure to radiation.</p><p id="p4785" class="elsevierStylePara elsevierViewall">No relevant studies have been identified related to the use of resources and costs, either. DU is a less expensive technique than fistulography. The diagnostic approach of using DU at the beginning of the study and keeping fistulography for cases where stenosis is repeatedly suspected, but with a negative result in DU, is more cost-effective than performing fistulography on all patients with suspected stenosis.</p><p id="s1165" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p4790" class="elsevierStylePara elsevierViewall">Although it cannot replace fistulography as the “gold standard”, DU is a non-invasive imaging diagnostic method, does not harm the patient, and is highly sensitive and specific for the diagnosis of significant stenosis. Furthermore, it provides valuable additional functional information, its portable version can be used in situ in the HD room and, in addition, it offers a favourable cost-effectiveness profile. For all these reasons, GEMAV unanimously considers that the best diagnostic approach is to perform DU as the initial imaging examination if there is any suspicion of stenosis and keep fistulography for cases of negative outcome and persisting suspicion of stenosis.</p><p id="p4795" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0120"></elsevierMultimedia></p></span><span id="se1190" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4.8</span><span class="elsevierStyleSectionTitle" id="sect1175">Predictive power of first- and second-generation methods for detecting stenosis and thrombosis of arteriovenous fistula</span><p id="s1180" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p4810" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0125"></elsevierMultimedia></p><p id="p4835" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XII Which non-invasive monitoring or surveillance screening method for haemodialysis arteriovenous fistula presents predictive power of stenosis and thrombosis and increased patency of the prosthetic arteriovenous fistula in the prevalent patient and what is the frequency?</span></p><p id="p4840" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XII in <a href="https://static.elsevier.es/nefroguiaaveng/12_PCXII_Vigilancia_FAVp_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0060"></elsevierMultimedia></p><p id="s1185" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p4845" class="elsevierStylePara elsevierViewall">Two systematic reviews with meta-analysis have been found, both published in 2008, which address the clinical effects of pAVF monitoring and surveillance.<a class="elsevierStyleCrossRefs" href="#bib385"><span class="elsevierStyleSup">385,386</span></a> The review by Tonelli et al.<a class="elsevierStyleCrossRef" href="#bib385"><span class="elsevierStyleSup">385</span></a> includes only randomised clinical trials (RCTs), whereas the Casey et al review<a class="elsevierStyleCrossRef" href="#bib386"><span class="elsevierStyleSup">386</span></a> also includes non-randomised studies. Both studies found the same clinical trials and come to similar conclusions. For this Guide, the Tonelli et al. meta-analyses were used as they provide more complete data in the stratified analysis for patients with pAVF.<a class="elsevierStyleCrossRef" href="#bib385"><span class="elsevierStyleSup">385</span></a></p><p id="s1190" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Clinical benefit of screening compared with usual practice</span></p><p id="p4850" class="elsevierStylePara elsevierViewall">The systematic review with meta-analysis by Tonelli et al.<a class="elsevierStyleCrossRef" href="#bib385"><span class="elsevierStyleSup">385</span></a> included 6 clinical trials comparing active pAVF screening (using Q<span class="elsevierStyleInf">A</span> or DU measurements) versus usual follow-up by monitoring methods in 446 patients. In this study, there were no significant differences in the rate of pAVF thrombosis between active methods of surveillance and regular monitoring (RR 0.94, 95% CI, 0.77 to 1.16). Using data from 1 clinical trial and 126 patients, there were no statistically significant differences in the time to pAVF thrombosis between the two follow-up options (hazard ratio [HR]: 1.13; 95% CI, 0.71 to 1.80). Meta-analysis with data from 4 clinical trials and 381 patients did not show statistically significant differences in pAVF loss between the active methods of surveillance and those of usual monitoring (HR: 1.08; 95% CI, 0.83 to 1.40). Data from 2 clinical trials and 315 patients also showed no differences in the time to pAVF loss (HR: 0.51; 95% CI, 0.15 to 1.74; high statistical heterogeneity I<span class="elsevierStyleSup">2</span>: 85%).</p><p id="p4855" class="elsevierStylePara elsevierViewall">Some causes have been reported which may explain these disappointing results obtained by clinical trials in pAVF surveillance<a class="elsevierStyleCrossRefs" href="#bib316"><span class="elsevierStyleSup">316,354,387-394</span></a>:<ul class="elsevierStyleList" id="list0475"><li class="elsevierStyleListItem" id="listi2045"><span class="elsevierStyleLabel">•</span><p id="p4860" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Diameter of the artery and the vein involved in anastomosis</span>. This diameter controls the relationship between Q<span class="elsevierStyleInf">A</span> (or venous pressure) and the stenosis. In the event of a low artery/vein ratio, progression of the stenosis is so fast that regular surveillance is unable to detect a decrease in Q<span class="elsevierStyleInf">A</span> (or an increase in venous pressure) before thrombosis.</p></li><li class="elsevierStyleListItem" id="listi2050"><span class="elsevierStyleLabel">•</span><p id="p4865" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">MAP</span>. The significant decrease in blood pressure can play a central role in some cases of pAVF thrombosis without prior suspicion of stenosis.</p></li><li class="elsevierStyleListItem" id="listi2055"><span class="elsevierStyleLabel">•</span><p id="p4870" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Preventive intervention by PTA</span>. In a stable stenotic lesion or slow growth PTA can stimulate intimal hyperplasia, lead to rapidly developing restenosis and have a negative impact on pAVF patency.</p></li><li class="elsevierStyleListItem" id="listi2060"><span class="elsevierStyleLabel">•</span><p id="p4875" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Sample size</span>. An insufficient sample size in the published studies could explain the results obtained.</p></li></ul></p><p id="s1195" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p4880" class="elsevierStylePara elsevierViewall">There are no significant differences in the risk of thrombosis or in survival of the pAVF if surveillance methods are added to usual methods of monitoring. Therefore, according to the current concept of significant stenosis included in the KDOQI guide,<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> we cannot recommend pAVF surveillance using second-generation screening methods, whether they be dilution techniques to estimate the Q<span class="elsevierStyleInf">A</span> or DU. The application of these methods in pAVF is not predictive of thrombosis and will not help increase their patency compared with first-generation methods, based on current criteria for significant stenosis. It is recommended that pAVF monitoring be performed using first-generation screening methods.<a class="elsevierStyleCrossRef" href="#bib287"><span class="elsevierStyleSup">287</span></a></p><p id="p4885" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0130"></elsevierMultimedia></p><p id="p4900" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XIII Which non-invasive monitoring or surveillance screening method for haemodialysis arteriovenous fistula presents predictive power of stenosis and thrombosis and increased patency of the native arteriovenous fistula in the prevalent patient and what is the frequency?</span></p><p id="p4905" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XIII in <a href="https://static.elsevier.es/nefroguiaaveng/13_PCXIII_Vigilancia_FAVn_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0065"></elsevierMultimedia></p><p id="s1205" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="s1210" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">First-generation methods</span></p><p id="p4910" class="elsevierStylePara elsevierViewall">A prospective study by Asif et al.<a class="elsevierStyleCrossRef" href="#bib204"><span class="elsevierStyleSup">204</span></a> of 142 patients with nAVF analysed the accuracy of physical examination in detecting stenotic lesions in comparison with fistulography, which is considered the gold standard test. The sensitivity and specificity of physical examination was 92% and 86%, respectively, for outflow stenosis and 85% and 71% for inflow stenosis.</p><p id="p4915" class="elsevierStylePara elsevierViewall">A study by Campos et al.<a class="elsevierStyleCrossRef" href="#bib303"><span class="elsevierStyleSup">303</span></a> analysed the accuracy of physical examination and pressure measurement in detecting stenotic lesions in comparison with DU, which they used as the reference technique. Out of the 84 patients analysed, 50 of them, i.e. 59%, showed positive for stenosis by DU. Upon physical examination 56 patients showed positive, representing a sensitivity for the test of 96%, a specificity of 76%, a positive predictive value of 86% and a negative predictive value of 93%. Intra-access pressure measurement for 34 patients showed positive, i.e. 40%, representing a sensitivity for the test of 60%, a specificity of 88%, a positive predictive value of 88% and a negative predictive value of 60%.</p><p id="s1215" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Second-generation methods</span></p><p id="p4920" class="elsevierStylePara elsevierViewall">With respect to second-generation methods, several published meta-analyses should be highlighted.<a class="elsevierStyleCrossRefs" href="#bib385"><span class="elsevierStyleSup">385,386,395</span></a> On analysing data from four controlled clinical trials and 360 patients, Tonelli et al.<a class="elsevierStyleCrossRef" href="#bib385"><span class="elsevierStyleSup">385</span></a> describe that active screening by ultrasound causes a statistically significant decrease in the risk of nAVF thrombosis (RR: 0.47; 95% CI, 0.28-0.77). In addition, the time to reach nAVF thrombosis was significantly higher in the “surveillance” group compared to the “control” group (HR: 0.30; 95% CI, 0.16-0.56). Regarding AVF loss, when carrying out a meta-analysis with data from 2 RCTs and 141 patients, no statistically significant differences were found (RR: 0.65; 95% CI, 0.28 to 1.51), and, finally, with data from 1 RCT and 60 patients, slightly statistically significant differences were found with respect to time to access loss (HR: 0.38; 95% CI, 0.14 to 0.99).<a class="elsevierStyleCrossRef" href="#bib385"><span class="elsevierStyleSup">385</span></a></p><p id="p4925" class="elsevierStylePara elsevierViewall">Moreover, after analysing the functional criteria selected for the diagnosis of stenosis in various controlled and uncontrolled clinical trials as well as observational studies, Tessitore et al.<a class="elsevierStyleCrossRef" href="#bib395"><span class="elsevierStyleSup">395</span></a> concluded that nAVF surveillance through Q<span class="elsevierStyleInf">A</span> determination significantly reduces the risk of thrombosis. In this respect, a case-control study from Spain demonstrates a significantly lower incidence of AVF thrombosis (mostly nAVF) in patients dialysed in a hospital HD unit and under Q<span class="elsevierStyleInf">A</span> surveillance compared with patients dialysed at a satellite HD centre without Q<span class="elsevierStyleInf">A</span> measurements<a class="elsevierStyleCrossRef" href="#bib352"><span class="elsevierStyleSup">352</span></a>. Salman et al.<a class="elsevierStyleCrossRef" href="#bib396"><span class="elsevierStyleSup">396</span></a> analysed 4 RCTs (n = 395) to assess the benefit of nAVF surveillance using Q<span class="elsevierStyleInf">A</span> determination and the result was positive for the 3 trials in which the main aim was to reduce the rate of thrombosis.<a class="elsevierStyleCrossRef" href="#bib396"><span class="elsevierStyleSup">396</span></a> Muchayi et al.<a class="elsevierStyleCrossRef" href="#bib397"><span class="elsevierStyleSup">397</span></a> performed a meta-analysis on these same 4 studies and showed a non-significant reduction of 36% in thrombosis risk by nAVF surveillance.</p><p id="p4930" class="elsevierStylePara elsevierViewall">Concerning nAVF patency, the meta-analysis by Tessitore et al.,<a class="elsevierStyleCrossRef" href="#bib395"><span class="elsevierStyleSup">395</span></a> carried out on two controlled clinical trials, demonstrated a 50% reduction in risk of nAVF loss using screening with Q<span class="elsevierStyleInf">A</span> determination, but the difference was not statistically significant given that they are two single-centre studies (Verona, Italy) with a limited sample size and follow-up.<a class="elsevierStyleCrossRefs" href="#bib276"><span class="elsevierStyleSup">276,398</span></a> Recently, the preliminary results have been published from a controlled, multicentre clinical trial carried out in Spain (METTRO) on the effect of second-generation methods compared with conventional monitoring on the incidence of thrombosis and patency of nAVF. These results show a significantly lower rate of thrombosis and better primary assisted patency after 1 year of follow-up.<a class="elsevierStyleCrossRef" href="#bib399"><span class="elsevierStyleSup">399</span></a></p><p id="p4935" class="elsevierStylePara elsevierViewall">The implementation of second-generation screening techniques for nAVF surveillance makes it possible to reduce the incidence of thrombosis and, therefore, decrease the rate of CVC placement and its associated morbidity/mortality.<a class="elsevierStyleCrossRefs" href="#bib269"><span class="elsevierStyleSup">269,368,385</span></a></p><p id="s1220" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Use of resources and costs</span></p><p id="p4940" class="elsevierStylePara elsevierViewall">No specific cost-effectiveness studies were found when these interventions were analysed for the setting in which this Guide is to be applied. Neither are there studies on the budget impact that the generalisation of continued and regular use of active screening techniques by DU would suppose on nAVF patients in our setting.</p><p id="s1225" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p4945" class="elsevierStylePara elsevierViewall">The regular application of second-generation screening methods (both dilution techniques to estimate AVF flow or Q<span class="elsevierStyleInf">A</span> and DU) is recommended for nAVF surveillance as existing evidence indicates a beneficial effect with relation to the reduction in thrombosis incidence and CVC placement rate. There are no arguments against such methods in relation to the rate of nAVF thrombosis and patency.</p><p id="p4950" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0135"></elsevierMultimedia></p></span><span id="se1250" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">4.9</span><span class="elsevierStyleSectionTitle" id="sect1235">Predictive factors of thrombosis in arteriovenous fistula with stenosis</span><p id="s1240" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p4960" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0140"></elsevierMultimedia></p><p id="p4995" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XIV What are the demographic, clinical and haemodynamic factors and variables with predictive power of thrombosis in an arteriovenous fistula that presents stenosis?</span></p><p id="p5000" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XIV in <a href="https://static.elsevier.es/nefroguiaaveng/14_PCXIV_Valor_predictivo_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0070"></elsevierMultimedia></p><p id="s1245" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p5005" class="elsevierStylePara elsevierViewall">The application of various methods of AVF surveillance in routine clinical practice has shown cases of AFV thrombosis preceded by a Q<span class="elsevierStyleInf">A</span> value > 600 mL/min without apparent stenosis, as well as cases of stenosis > 50% which are stable over time and never actually become thrombosed.<a class="elsevierStyleCrossRefs" href="#bib400"><span class="elsevierStyleSup">400-403</span></a> Therefore, in the case of any vascular reduction > 50% in nAVF or pAVF, it is necessary to know its thrombosis risk. It is important to identify whether this stenosis involves a high risk of thrombosis, i.e. a high likelihood of progressing over time and leading to total vascular lumen occlusion of the AVF if an early elective intervention through PTA or surgery is not carried out. However, if we perform preventive treatment when there is a vascular lumen reduction > 50% of nAVF or pAVF with a low thrombosis risk, in addition to this being an unnecessary procedure with a noteworthy financial cost, we may cause an unwanted accelerated restenosis and AVF thrombosis which would not have occurred with therapeutic abstention.</p><p id="p5010" class="elsevierStylePara elsevierViewall">It is necessary to identify factors or variables (demographic, clinical, haemodynamic) which are predictive of thrombosis in any AVF with stenosis. The presence or absence of these will define the existing risk of thrombosis and, therefore, make it possible to distinguish if any vascular lumen reduction > 50% in nAVF or pAVF has a high or low risk of thrombosis.</p><p id="p5015" class="elsevierStylePara elsevierViewall">In this respect, Paulson et al.<a class="elsevierStyleCrossRef" href="#bib403"><span class="elsevierStyleSup">403</span></a> demonstrated in a prospective study in 2000, through ROC curve analysis, that the functional variable Q<span class="elsevierStyleInf">A</span> did not provide enough predictive value of pAVF thrombosis on its own for it to be used as an isolated criterion in decision-making. They thus concluded that the inclusion of other predictive variables in association with Q<span class="elsevierStyleInf">A</span> could provide the predictive value required.</p><p id="p5020" class="elsevierStylePara elsevierViewall">In 2005, Malik et al.<a class="elsevierStyleCrossRef" href="#bib367"><span class="elsevierStyleSup">367</span></a> published a randomised clinical trial in 192 patients with pAVF comparing pAVF patency (mean follow-up 392 ± 430 days) between two subgroups of patients who were categorised according to the different monitoring and surveillance strategy applied: group 1 (n = 97) using traditional screening (clinical monitoring, venous pressure, and Q<span class="elsevierStyleInf">A</span>) associated with DU surveillance every 3 months and group 2 (n = 95) only by traditional screening. Cumulative pAVF patency was significantly higher in group 1 compared to group 2, which the authors attributed to the early diagnosis of stenosis and, therefore, more common elective procedures on the pAVF stenosis.<a class="elsevierStyleCrossRef" href="#bib367"><span class="elsevierStyleSup">367</span></a> Unlike other clinical trials on pAVF with negative results,<a class="elsevierStyleCrossRef" href="#bib404"><span class="elsevierStyleSup">404</span></a> why was this positive result obtained in this study? The answer lies in the methodology, as DU indications for carrying out fistulography and/or a therapeutic procedure using PTA or surgery were as follows:<ul class="elsevierStyleList" id="list0485"><li class="elsevierStyleListItem" id="listi2090"><span class="elsevierStyleLabel">•</span><p id="p5025" class="elsevierStylePara elsevierViewall">Finding a significant stenosis, defined by the presence of a peak systolic velocity (PSV) ratio > 2 with or without decrease in Q<span class="elsevierStyleInf">A</span>.</p></li><li class="elsevierStyleListItem" id="listi2095"><span class="elsevierStyleLabel">•</span><p id="p5030" class="elsevierStylePara elsevierViewall">Finding a non-significant stenosis in appearance but associated with a decrease in Q<span class="elsevierStyleInf">A</span> > 25% over time.</p></li></ul></p><p id="p5035" class="elsevierStylePara elsevierViewall">In the case of uncertainty over significant or non-significant stenosis, the existence of a residual diameter of less than 2.0 mm was an additional indication for fistulography. Patients that only met one of the above-mentioned criteria were examined after 4-6 weeks by DU.<a class="elsevierStyleCrossRef" href="#bib367"><span class="elsevierStyleSup">367</span></a> In other words, in this study a series of additional ultrasound factors were introduced which allowed preventive action to be taken on significant stenoses with the risk of thrombosis and pAVF patency to be prolonged.</p><p id="p5040" class="elsevierStylePara elsevierViewall">In 2009 the same group published a retrospective study in which pAVF stenoses were classified by DU into 2 distinct groups<a class="elsevierStyleCrossRef" href="#bib375"><span class="elsevierStyleSup">375</span></a>:<ul class="elsevierStyleList" id="list0490"><li class="elsevierStyleListItem" id="listi2100"><span class="elsevierStyleLabel">•</span><p id="p5045" class="elsevierStylePara elsevierViewall">Significant pAVF stenosis or high risk of thrombosis defined by a combination of the following criteria: reduction > 50% in the vascular lumen + PSV ratio > 2 + at least 1 additional criterion (residual diameter < 2 mm or Q<span class="elsevierStyleInf">A</span> < 600 mL/min or decreased Q<span class="elsevierStyleInf">A</span> > 25%).</p></li><li class="elsevierStyleListItem" id="listi2105"><span class="elsevierStyleLabel">•</span><p id="p5050" class="elsevierStylePara elsevierViewall">Borderline pAVF stenosis or low thrombosis risk (n = 102): defined with the same criteria but without any additional criteria.</p></li></ul></p><p id="p5055" class="elsevierStylePara elsevierViewall">The first group of stenoses was treated electively by PTA and the second underwent a strategy of “wait and see” with repeated DU after 6 – 8 weeks. After 14 ± 6 weeks, the follow-up of the 102 borderline stenoses was as follows: 55 without stenosis progression, 38 with an increase in the degree of stenosis, 8 treated using PTA because of clinical indication and 1 single case of thrombosis<a class="elsevierStyleCrossRef" href="#bib375"><span class="elsevierStyleSup">375</span></a>; in other words, at the time of the next DU (14 ± 6 weeks), more than half of the borderline stenoses remained stable over time with a risk of thrombosis < 1%. The significant risk factors for progression of borderline stenosis to significant stenosis were a history of previous PTA and female gender. The authors concluded that delaying PTA in asymptomatic borderline stenosis is safe using this expectant management and stenoses remain stable, at least in the short term, but with a high risk of progression, especially if there is a history of previous PTA.<a class="elsevierStyleCrossRef" href="#bib37"><span class="elsevierStyleSup">37</span></a> In Spain, when a similar protocol for selecting AVF with a greater risk of thrombosis was implemented, a thrombosis rate < 0.05/patient/year was achieved.<a class="elsevierStyleCrossRef" href="#bib52"><span class="elsevierStyleSup">52</span></a></p><p id="p5060" class="elsevierStylePara elsevierViewall">To sum up, according to current data, AVF surveillance methods could be optimised for both nAVF and pAVF by redefining the concept of significant stenosis, which would include only those AVF with an increased risk of thrombosis and, therefore, really require elective intervention (<a class="elsevierStyleCrossRef" href="#f5">Figure 5</a>).<a class="elsevierStyleCrossRef" href="#bib405"><span class="elsevierStyleSup">405</span></a> In this way, in addition to the criteria of stenosis according to the current KDOQI Guide, the haemodynamic repercussion of the stenosis should be assessed and some additional criteria added, both morphological and functional, that have enough predictive power to discern whether nAVF or pAVF with stenosis has a high or low risk of thrombosis.<a class="elsevierStyleCrossRef" href="#bib394"><span class="elsevierStyleSup">394</span></a> These criteria are:</p><elsevierMultimedia ident="f5"></elsevierMultimedia><p id="p5065" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0495"><li class="elsevierStyleListItem" id="listi2110"><span class="elsevierStyleLabel">•</span><p id="p5070" class="elsevierStylePara elsevierViewall">Two main criteria: vascular lumen reduction percentage > 50% + PSV ratio > 2.</p></li><li class="elsevierStyleListItem" id="listi2115"><span class="elsevierStyleLabel">•</span><p id="p5075" class="elsevierStylePara elsevierViewall">At least one of the following additional criteria: morphological criterion (residual diameter < 2 mm) or functional criterion (Q<span class="elsevierStyleInf">A</span> [mL/min] < 500 [nAVF]-600 [pAVF] or ∇Q<span class="elsevierStyleInf">A</span> > 25% if Q<span class="elsevierStyleInf">A</span> < 1000 mL/min).</p></li></ul></p><p id="s1250" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p5080" class="elsevierStylePara elsevierViewall">Optimising AVF surveillance methods requires redefining significant stenosis. Some ultrasound variables, both morphological and functional, have been described that allow the risk of thrombosis of stenosis to be clarified and therefore, whether this stenosis really requires elective intervention. The new concept of significant stenosis would only include stenosis with high risk of thrombosis. As a result, some criteria were established to define it (<a class="elsevierStyleCrossRef" href="#f5">Figure 5</a>): some main criteria (reduction of vascular lumen > 50% + PVS ratio > 2) and some additional criterion should be added (residual diameter < 2 and/or Q<span class="elsevierStyleInf">A</span> < 500 mL/min in nAVF/< 600 mL/min in pAVF and/or reduction in Q<span class="elsevierStyleInf">A</span> > 25% if Q<span class="elsevierStyleInf">A</span> < 1000 mL/min). This redefinition of significant stenosis would result in a series of benefits over AVF, such as the decrease in unnecessary procedures that may endanger the AVF itself, the reduction in the thrombosis rate and the increase in patency (<a class="elsevierStyleCrossRef" href="#t21">Table 21</a>).</p><elsevierMultimedia ident="t21"></elsevierMultimedia><p id="p5085" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0145"></elsevierMultimedia></p></span></span><span id="se1275" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">5</span><span class="elsevierStyleSectionTitle" id="sect1260">C<span class="elsevierStyleSmallCaps">omplications of arteriovenous fistula</span></span><p id="p5115" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">CONTENTS</span><ul class="elsevierStyleList" id="list0500"><li class="elsevierStyleListItem" id="listi2120"><span class="elsevierStyleLabel">5.1.</span><p id="p5120" class="elsevierStylePara elsevierViewall">Treatment of stenosis</p></li><li class="elsevierStyleListItem" id="listi2125"><span class="elsevierStyleLabel">5.2.</span><p id="p5125" class="elsevierStylePara elsevierViewall">Treatment of thrombosis</p></li><li class="elsevierStyleListItem" id="listi2130"><span class="elsevierStyleLabel">5.3.</span><p id="p5130" class="elsevierStylePara elsevierViewall">Management of the non-matured fistula</p></li><li class="elsevierStyleListItem" id="listi2135"><span class="elsevierStyleLabel">5.4.</span><p id="p5135" class="elsevierStylePara elsevierViewall">Treatment of infection</p></li><li class="elsevierStyleListItem" id="listi2140"><span class="elsevierStyleLabel">5.5.</span><p id="p5140" class="elsevierStylePara elsevierViewall">Distal hypoperfusion syndrome (“steal syndrome”)</p></li><li class="elsevierStyleListItem" id="listi2145"><span class="elsevierStyleLabel">5.6.</span><p id="p5145" class="elsevierStylePara elsevierViewall">Aneurysms and pseudoaneurysms</p></li><li class="elsevierStyleListItem" id="listi2150"><span class="elsevierStyleLabel">5.7.</span><p id="p5150" class="elsevierStylePara elsevierViewall">High-flow syndrome</p></li></ul></p><p id="sect1265" class="elsevierStylePara elsevierViewall">Preamble</p><p id="p5155" class="elsevierStylePara elsevierViewall">The aim of treating arteriovenous fistula (AVF) complications is to address the different types of pathology that may affect AVF. These include, on the one hand, treatment of stenosis and thrombosis to achieve the greatest possible patency time and, on the other hand, complications not directly related with patency, such as infection, distal hypoperfusion, aneurysms or pseudoaneurysms and complications derived from high blood flow (Q<span class="elsevierStyleInf">A</span>).</p><span id="se1285" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">5.1</span><span class="elsevierStyleSectionTitle" id="sect1270">Treatment of stenosis</span><p id="s1275" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p5160" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0150"></elsevierMultimedia></p><p id="sect1280" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p5210" class="elsevierStylePara elsevierViewall">The aim of correcting stenosis requiring elective treatment is to ensure sufficient Q<span class="elsevierStyleInf">A</span>, proper haemodialysis (HD) adequacy, to prevent the occurrence of thrombosis and to increase AVF patency. Only significant stenosis should be treated electively as described in section 4.</p><p id="s1285" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Types of stenosis</span></p><p id="p5215" class="elsevierStylePara elsevierViewall">Anatomically and functionally, vascular stenosis with haemodynamic repercussion in the AVF function can be located in the segment prior to the arteriovenous anastomosis (arterial stenosis), in the anastomosis itself or in the outflow vein of the AVF (venous stenosis).<ul class="elsevierStyleList" id="list0515"><li class="elsevierStyleListItem" id="listi2180"><span class="elsevierStyleLabel">•</span><p id="p5220" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Arterial stenosis</span>. Vascular lesions located in the arterial tree that feeds the vascular access (VA). The haemodynamic alteration they cause is a decrease in AVF flow. It is mainly due to the presence of stenosing or occlusive lesions arising from the progression of an existing underlying atherosclerosis.</p></li><li class="elsevierStyleListItem" id="listi2185"><span class="elsevierStyleLabel">•</span><p id="p5225" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Stenosis in the arteriovenous anastomosis</span>. They are usually due to a technical problem during anastomosis creation. Clinically, they present as immediate or early thrombosis of the access or as alterations in maturation (non-mature fistula).</p></li><li class="elsevierStyleListItem" id="listi2190"><span class="elsevierStyleLabel">•</span><p id="p5230" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Venous stenosis</span>. It is the most common cause of access dysfunction. Depending on location along the venous pathway, aetiology, frequency and response to treatment vary. Therefore, it is usually classified into four groups:<ul class="elsevierStyleList" id="list0520"><li class="elsevierStyleListItem" id="listi2195"><span class="elsevierStyleLabel">–</span><p id="p5235" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Juxta-anastomotic or peri-anastomotic stenosis</span>. This is the one located in an area covering the zone immediately adjacent to the anastomosis and up to 5 cm post-anastomosis. It is of complex aetiopathogenesis, involving haemodynamic factors and alterations in the inflammatory response of the endothelium.</p></li><li class="elsevierStyleListItem" id="listi2200"><span class="elsevierStyleLabel">–</span><p id="p5240" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Stenosis of the cannulation segment</span>. Stenosis located in needling areas. It usually occurs in response to mechanical trauma caused by cannulation of the vessel.</p></li><li class="elsevierStyleListItem" id="listi2205"><span class="elsevierStyleLabel">–</span><p id="p5245" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Stenosis of the cephalic vein arch (CVA)</span>. Stenosis located in the cephalic vein segment immediately adjacent to its confluence in the axillary vein. Like stenosis located in the juxta-anastomotic region, it is usually due to haemodynamic factors, presenting a poor response to percutaneous treatment.</p></li><li class="elsevierStyleListItem" id="listi2210"><span class="elsevierStyleLabel">–</span><p id="p5250" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Central venous stenosis</span>. Stenosis located in the venous sector from the subclavian vein to its drainage in the right atrium, and covers the subclavian vein, brachiocephalic trunk and superior vena cava. It is usually associated with endothelial trauma caused by the presence of venous catheters inside the vessel.</p></li></ul></p></li></ul></p><p id="p5255" class="elsevierStylePara elsevierViewall">Another classification used in different publications prioritises a criterion of functionality in relation to the cannulation point, classifying them between <span class="elsevierStyleItalic">inflow</span> stenosis (arterial stenosis, arteriovenous anastomosis and the juxta-anastomotic venous segment) and <span class="elsevierStyleItalic">outflow</span> stenosis (venous stenosis of the cannulation segment, CVA, and central venous stenosis).<a class="elsevierStyleCrossRefs" href="#bib374"><span class="elsevierStyleSup">374,406</span></a></p><p id="p5260" class="elsevierStylePara elsevierViewall">As described, stenosis location is the main determining factor when considering therapeutic option. In this context, the success of the results should weigh up not only the efficacy of the treatment, but also any possible associated comorbidity and complications.</p><p id="p5265" class="elsevierStylePara elsevierViewall">There are several examples that can demonstrate this factor, as will be seen below. There is consensus that central vessel (arterial or venous) stenosis be given endovascular treatment as it is difficult to access these vessels in surgery and there is high morbidity and mortality.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,407</span></a> Venous stenosis of the needling segment has traditionally been treated by percutaneous transluminal angioplasty (PTA) because HD can be continued using the same VA and without the need for CVC placement. On the other hand, there has arisen more controversy in the treatment of juxta-anastomotic stenosis, which entails most AVF stenosis, in both native arteriovenous fistula (nAVF) and prosthetic arteriovenous fistula (pAVF), since they can be approached from both a surgical and an interventionist point of view, although the first usually offers better overall results than percutaneous treatment.</p><p id="s1290" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Types of treatment</span></p><p id="p5270" class="elsevierStylePara elsevierViewall">Stenosis can be treated either by an endovascular procedure consisting of PTA and/or endoprosthesis placement or by surgical review.</p><p id="p5275" class="elsevierStylePara elsevierViewall">In general terms, percutaneous treatment is the least invasive alternative, has lower morbidity and does not require CVC placement to continue HD. However, a significant disadvantage is that it presents a high rate of restenosis which determines the need to periodically perform additional interventional procedures to maintain access patency.</p><p id="p5280" class="elsevierStylePara elsevierViewall">On the other hand, surgical treatment usually has better primary patency in the medium and long term, although, in terms of drawbacks, it is more invasive and sometimes requires the use of venous capital and CVC placement for HD after the intervention. Thus, even though the technique provides better results overall, in daily clinical practice treatment must be decided on a case-by-case basis, precisely delimiting if the greater patency of the procedure justifies the possible consumption of venous segment and the possibility of CVC placement.</p><p id="s1295" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Percutaneous transluminal angioplasty</span></p><p id="p5285" class="elsevierStylePara elsevierViewall">PTA is a percutaneous technique of intravascular dilation using a balloon that allows the treatment of vascular stenosis. In addition to the use of the conventional balloon, the technical improvements that have arisen in recent years for the treatment of stenosis have allowed the development of high-pressure balloons, cutting balloons and drug-coated balloons.</p><p id="p5290" class="elsevierStylePara elsevierViewall">The advantages of PTA include the fact that it can be performed during diagnosis by fistulography, especially in the case of central venous stenosis, and preserves the vascular tree, unlike surgery. On the other hand, it has a higher recurrence rate versus surgery. The success of the procedure can be considered from the anatomical and functional perspective: anatomically, when residual stenosis is < 30% after balloon removal and, functionally, with the improvement of AVF haemodynamic parameters and the restoration of flow (Q<span class="elsevierStyleInf">A</span>).</p><p id="p5295" class="elsevierStylePara elsevierViewall">The only absolute contraindication for this procedure is the active AVF infection. Relative contraindications would include allergy to the contrast, a <span class="elsevierStyleItalic">shunt</span> from pulmonary to systemic circulation and severe pulmonary disease.</p><p id="s1300" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">High pressure balloons</span></p><p id="p5300" class="elsevierStylePara elsevierViewall">High pressure balloons are those that bear an inflation pressure higher than 25-30 atm. Their use is indicated in the treatment of symptomatic stenosis that has not responded to dilation with conventional <span class="elsevierStyleItalic">semi-compliance</span> balloons. The use of high pressure balloons does not initially provide better patency results when compared to conventional balloons.<a class="elsevierStyleCrossRef" href="#bib408"><span class="elsevierStyleSup">408</span></a> High cost, the need to use thicker introducers, emptying difficulty and lower compliance and flexibility make it advisable not to use them as first choice in the treatment of stenosis</p><p id="s1305" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Cutting balloon</span></p><p id="p5305" class="elsevierStylePara elsevierViewall">When small blades or atherotomes are incorporated into a conventional balloon, they are called <span class="elsevierStyleItalic">cutting balloons</span>. Its use is controversial and is not justified as initial treatment for stenosis. In a recent randomised study,<a class="elsevierStyleCrossRef" href="#bib409"><span class="elsevierStyleSup">409</span></a> no significant differences were found in the treatment of stenosis between cutting balloon and conventional balloon except for a greater primary assisted patency at 6 and 12 months, in favour of the cutting balloon, when treating juxta-anastomotic venous stenosis of pAVF (86% and 63% versus 56% and 37%). However, higher cost, management difficulties (they need finer guides) and the larger size of the introducer make them less indicated for the initial treatment of a dysfunctional access.</p><p id="p5310" class="elsevierStylePara elsevierViewall">Eighty-five per cent of stenosis responds satisfactorily to conventional balloon angioplasty.<a class="elsevierStyleCrossRef" href="#bib410"><span class="elsevierStyleSup">410</span></a> In the rest, which do not have an appropriate response, both high pressure and cutting balloons would be useful. Existing studies comparing both procedures find no significant difference in immediate outcomes<a class="elsevierStyleCrossRefs" href="#bib410"><span class="elsevierStyleSup">410-413</span></a> but there was an increase in the 6-month assisted patency of stenosis treated with cutting balloon versus high-pressure balloon (66.4% versus 39.9%).<a class="elsevierStyleCrossRefs" href="#bib410"><span class="elsevierStyleSup">410-413</span></a></p><p id="s1310" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Angioplasty with pharmacoactive balloon</span></p><p id="p5315" class="elsevierStylePara elsevierViewall">Drug coated balloons impregnated with paclitaxel have recently appeared as an alternative in the treatment of arterial stenosis. Application in nAVF stenosis is very low, though some randomised clinical trials (RCTs) with satisfactory results at 6 months<a class="elsevierStyleCrossRef" href="#bib414"><span class="elsevierStyleSup">414</span></a> and at 1 year follow-up<a class="elsevierStyleCrossRef" href="#bib415"><span class="elsevierStyleSup">415</span></a> have been reported.</p><p id="s1315" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Stents</span></p><p id="p5320" class="elsevierStylePara elsevierViewall">Indications for stent placement are limited given the lack of evidence regarding improvement of secondary VA patency after their use. This controversial use is relegated to the treatment of stenosis with recoil, vascular ruptures after PTA or in dissections that condition stenosis > 30%.</p><p id="p5325" class="elsevierStylePara elsevierViewall">It can be considered for use with refractory AVF following early recurrence (< 3 months) after several PTA and due to vascular recoil (elastic stenosis) following PTA.<a class="elsevierStyleCrossRef" href="#bib416"><span class="elsevierStyleSup">416</span></a> However, <span class="elsevierStyleItalic">stent</span> use is highly controversial in these two indications, given that on the one hand, a certain number of AVF maintain an adequate function even if there is residual post-PTA stenosis up to 50%, and on the other, there are early recurrences (< 3 months) in angioplasties with good immediate outcomes.<a class="elsevierStyleCrossRefs" href="#bib417"><span class="elsevierStyleSup">417,418</span></a></p><p id="p5330" class="elsevierStylePara elsevierViewall">Regarding stent use for vessel rupture treatment, it should be noted that this is the most frequent PTA complication. The initial treatment is tamponade with prolonged inflation at low pressure and external manual compression at the point of rupture. After three failed attempts, the placement of covered prostheses is considered indicated.<a class="elsevierStyleCrossRefs" href="#bib417"><span class="elsevierStyleSup">417,418</span></a></p><p id="s1320" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Vascular endoprosthesis</span></p><p id="p5335" class="elsevierStylePara elsevierViewall">Recently stent graft has been increasingly used in an attempt to improve outcomes. A controlled multicentre study found a patency of covered <span class="elsevierStyleItalic">stents</span> at 6 months that was significantly higher (51% versus 23%) than simple PTA in the treatment of venous anastomotic stenosis in pAVF.<a class="elsevierStyleCrossRef" href="#bib419"><span class="elsevierStyleSup">419</span></a> Use in other locations has been reported on several occasions,<a class="elsevierStyleCrossRefs" href="#bib420"><span class="elsevierStyleSup">420,421</span></a> with better outcomes than those obtained with PTA alone or with placement of uncovered metal stents.<a class="elsevierStyleCrossRefs" href="#bib422"><span class="elsevierStyleSup">422,423</span></a> In the most recent study of Schmelter et al.,<a class="elsevierStyleCrossRef" href="#bib424"><span class="elsevierStyleSup">424</span></a> conducted on 66 AVF (41 pAVF and 25 nAVF), found good initial results but with no increase in overall patency. They observed a high rate of restenosis and thrombosis, although not associated with the stent graft, which were responsible only for a minority of the new cases of dysfunction. The authors conclude that the placement of covered stents can be used to solve local problems but they do not improve the average patency of the VA because they are associated with lesions situated in other locations.</p><p id="p5340" class="elsevierStylePara elsevierViewall">Regarding endoprosthesis-related disadvantages, it is important to emphasise that there is great difficulty in creating new accesses in the treated vein segment and can be associated with a not insignificant percentage of complications.<a class="elsevierStyleCrossRefs" href="#bib420"><span class="elsevierStyleSup">420,425</span></a> Although <span class="elsevierStyleItalic">stent</span> placement may increase the interval between first dilatation and stenosis recurrence, once intra-<span class="elsevierStyleItalic">stent</span> neointimal hyperplasia stenosis is established, it is very difficult to treat. Recent studies must be added here, in which a high percentage of post<span class="elsevierStyleItalic">-stent</span> complications are observed (28.9%),<a class="elsevierStyleCrossRef" href="#bib426"><span class="elsevierStyleSup">426</span></a> as well as others describing migrations,<a class="elsevierStyleCrossRef" href="#bib427"><span class="elsevierStyleSup">427</span></a> fractures<a class="elsevierStyleCrossRef" href="#bib428"><span class="elsevierStyleSup">428</span></a> and infections.<a class="elsevierStyleCrossRefs" href="#bib429"><span class="elsevierStyleSup">429,430</span></a></p><p id="p5345" class="elsevierStylePara elsevierViewall">Ultimately, it can be concluded that further multicentre, randomised, prospective, multidisciplinary studies are required to adequately rate the advantages of the new versus traditional materials when performing PTA, the usefulness of <span class="elsevierStyleItalic">stents</span> and their benefit or disadvantages versus surgical treatment.</p><p id="s1325" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Surgical treatment</span></p><p id="p5350" class="elsevierStylePara elsevierViewall">There are multiple surgical techniques described for AVF stenosis correction. The major advantage of this type of treatment is that it tends to have better patency rates than endovascular, but has higher morbidity, depletes the venous segment, may require CVC placement and is technically more complex, especially in central vessels.</p><p id="s1330" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Arterial stenosis</span></p><p id="p5355" class="elsevierStylePara elsevierViewall">In the case of stenosis located in the arterial segment prior to the arteriovenous anastomosis, endovascular treatment through PTA presents low morbidity and acceptable results, which is why surgery is considered as a fall-back technique. Surgical revascularisation is performed through the interposition of a bypass of autologous material, presenting excellent patency in the medium and long term.</p><p id="s1335" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Anastomotic stenosis</span></p><p id="p5360" class="elsevierStylePara elsevierViewall">In the case of stenosis located in the arteriovenous anastomosis (related to the surgical procedure to create the access), surgical review of the anastomosis, as well as the correction of the underlying technical defect, are indicated.</p><p id="s1340" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Juxta-anastomotic stenosis</span></p><p id="p5365" class="elsevierStylePara elsevierViewall">In many cases, reanastomosis between the artery and the outflow vein in the area immediately proximal to the AVF is the surgical technique of choice. Likewise, the interposition of a bypass made of prosthetic material has been reported between the artery and the proximal sector of the outflow vein.</p><p id="s1345" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Stenosis of the cannulation segment</span></p><p id="p5370" class="elsevierStylePara elsevierViewall">In the event of stenosis of the venous cannulation segment, the surgical treatment of choice consists of interposing a bypass made of prosthetic material, which can be placed in the shape of a loop, to allow the newly implanted segment to be cannulated.</p><p id="s1350" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Stenosis of the cephalic arch</span></p><p id="p5375" class="elsevierStylePara elsevierViewall">As discussed below, the technique of choice consists of transposing the cephalic vein and its anastomosis with the proximal brachial or axillary vein. The surgical re-implantation of this cephalic arch has also been described.</p><p id="s1355" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Central venous stenosis</span></p><p id="p5380" class="elsevierStylePara elsevierViewall">As surgery in central veins is complex and aggressive, it is considered a fall-back technique. Interventions using extra-anatomical derivative techniques to allow drainage to central venous trunks have been reported.</p><p id="p5385" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XV Is there a treatment with better outcomes (percutaneous transluminal angioplasty versus surgery) in juxta-anastomotic stenosis, assessed in terms of patency and/or thrombosis and cost/benefit?</span></p><p id="p5390" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XV in <a href="https://static.elsevier.es/nefroguiaaveng/15_PCXV_Estenosis_yuxtaanastomotica_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0075"></elsevierMultimedia></p><p id="s1360" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="s1365" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Native arteriovenous fistula</span></p><p id="p5395" class="elsevierStylePara elsevierViewall">No clinical trials comparing PTA versus surgery for the treatment of stenosing AVF in patients with nAVF have been identified. Two publications comparing series of patients treated with surgery and patients treated with PTA have been identified.</p><p id="p5400" class="elsevierStylePara elsevierViewall">In the study of Napoli et al.,<a class="elsevierStyleCrossRef" href="#bib432"><span class="elsevierStyleSup">432</span></a> conducted on 66 PTA and 68 surgical procedures with juxta-anastomotic stenosis of the AVF, the efficacy of the interventions was evaluated by measuring the brachial artery flow. The comparative analysis between the two options showed a significantly better primary patency for surgery, but with no difference in primary assisted patency, although PTA showed a greater tendency to restenosis.</p><p id="p5405" class="elsevierStylePara elsevierViewall">Tessitore et al.<a class="elsevierStyleCrossRef" href="#bib431"><span class="elsevierStyleSup">431</span></a> conducted a retrospective analysis of clinical data of 64 patients with juxta-anastomotic stenosis of the fistula in the distal part of the forearm, of which 43 were treated with PTA and 21 with surgery. The restenosis rate was 0.168 and 0.519 events per year of fistula follow-up for surgery and PTA, respectively (p = 0.009), with an adjusted relative risk 2.77 times higher for PTA than for surgery. The cost profile was similar for both procedures. Both procedures show similar primary assisted patency and costs.</p><p id="p5410" class="elsevierStylePara elsevierViewall">The other studies evaluate the two techniques individually. Thus, in an article from 2012<a class="elsevierStyleCrossRef" href="#bib435"><span class="elsevierStyleSup">435</span></a> evaluating the medium-and long-term results of surgery in juxta-anastomotic stenosis in 96 radiocephalic nAVF, the authors found very high results for immediate patency, without the need for CVC. Primary patency was higher than that recommended in international guidelines (89% versus 50%) with a low rate of maintenance procedures (0.035 procedures/patient/year). These patency data are superior to those shown in the study by Mortamais et al.,<a class="elsevierStyleCrossRef" href="#bib436"><span class="elsevierStyleSup">436</span></a> where the results of angioplasty are evaluated in 147 procedures performed on 75 radiocephalic nAVF. They obtained a primary patency at 1 and 3 years of 46.6% and 25.5%, respectively, with assisted patency in the same periods of 81.3% and 63.2%. They associate worse outcomes and early relapse of stenosis to the presence of post-PTA residual stenosis > 50%. They consider that in these cases evaluation and surgical repair would be indicated.</p><p id="p5415" class="elsevierStylePara elsevierViewall">Although neither study conducted a comparative analysis with the other repair technique, their results support the use of surgery as an initial technique in the treatment of juxta-anastomotic stenosis, provided that there is a surgical team which has 24-hour availability and repair can be executed without the use of CVC.</p><p id="p5420" class="elsevierStylePara elsevierViewall">Recently, a meta-analysis including the clinical series discussed in this section has shown results similar to those of the original studies. The combined results from the case study data showed significantly better primary patency of the AVF in patients treated with surgery at 12 (odds ratio [OR]: 0.42) and 18 months (OR: 0.33), an effect that seems to become moderate at 24 months of follow-up (OR: 0.53).<a class="elsevierStyleCrossRef" href="#bib433"><span class="elsevierStyleSup">433</span></a></p><p id="s1370" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Prosthetic arteriovenous fistula</span></p><p id="p5425" class="elsevierStylePara elsevierViewall">Only one RCT has been identified in the literature comparing surgery and PTA in patients with pAVF and juxta-anastomotic stenosis.<a class="elsevierStyleCrossRef" href="#bib434"><span class="elsevierStyleSup">434</span></a> This is the RCT of Brooks et al.,<a class="elsevierStyleCrossRef" href="#bib434"><span class="elsevierStyleSup">434</span></a> which included 43 patients with venous stenosis at the pAVF access in the forearm, 19 of which were treated with surgery and 24 with PTA. Those treated with surgery obtained greater median long-term patency (12 months) versus PTA (4 months) (p < 0.01). It is not mentioned whether CVC was needed to perform any of the procedures.</p><p id="p5430" class="elsevierStylePara elsevierViewall">No more recent studies comparing both procedures have been found, although there are several studies in the literature that support PTA use in the treatment of these lesions<a class="elsevierStyleCrossRef" href="#bib437"><span class="elsevierStyleSup">437</span></a> versus surgery<a class="elsevierStyleCrossRef" href="#bib167"><span class="elsevierStyleSup">167</span></a> as it allows proximal venous capital to be preserved, is more widely accepted by the patient and it is difficult to treat proximal anastomoses located on brachial and axillary veins surgically.<a class="elsevierStyleCrossRef" href="#bib8"><span class="elsevierStyleSup">8</span></a> Surgery is reserved for failed PTA treatment and prior to <span class="elsevierStyleItalic">stent</span> placement as well as in cases of recurrence.<a class="elsevierStyleCrossRefs" href="#bib167"><span class="elsevierStyleSup">167,438</span></a></p><p id="p5435" class="elsevierStylePara elsevierViewall">Stent use with stenosis recurrence has not improved patency<a class="elsevierStyleCrossRef" href="#bib439"><span class="elsevierStyleSup">439</span></a> in the same way as other technical improvements such as high pressure<a class="elsevierStyleCrossRef" href="#bib408"><span class="elsevierStyleSup">408</span></a> or cutting<a class="elsevierStyleCrossRef" href="#bib440"><span class="elsevierStyleSup">440</span></a> balloons, among others, have. Recently, however, a multicentre controlled study found significantly greater patency in the treatment of anastomotic venous stenosis at 6 months using covered stents versus simple PTA (51% versus 23%).<a class="elsevierStyleCrossRef" href="#bib419"><span class="elsevierStyleSup">419</span></a> The study is limited as long-term follow-up was not performed. In a more recent article<a class="elsevierStyleCrossRef" href="#bib424"><span class="elsevierStyleSup">424</span></a> where a retrospective study was conducted on 41 patients with complex pAVF stenosis (defined as rigid and resistant stenosis, stenosis with recoil or intra-stent stenosis) treated with vascular endoprosthesis (stent graft), good results in primary patency, but elevated restenosis and thrombosis rates, are obtained. Restenosis, however, is not located in the stent graft in place and is only responsible for a few cases of new dysfunctions. The authors conclude that the placement of stent grafts can be used to solve local problems but they do not improve the average patency of the access because it is associated with lesions in other locations.</p><p id="p5440" class="elsevierStylePara elsevierViewall">The use of stents is controversial, though there seems to be agreement on the use of stent graft versus uncovered stents. Several articles in the literature have found an improvement in the primary patency rates of these devices versus PTA and uncovered stents.<a class="elsevierStyleCrossRefs" href="#bib420"><span class="elsevierStyleSup">420,421,441,442</span></a> The increase in primary patency, according to some authors, seems to be related to a lower presence or absence of neointimal hyperplasia inside the stent graft.<a class="elsevierStyleCrossRefs" href="#bib442"><span class="elsevierStyleSup">442,443</span></a></p><p id="s1375" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p5445" class="elsevierStylePara elsevierViewall">In the case of nAVF, and although observational studies report no differences between both techniques, as there are no randomised cost-benefit studies, and despite the advantages and drawbacks of using both (PTA does not deplete the bed, but requires procedures to be repeated, and surgery depletes the vessel, but may still allow cannulation and has better primary patency), studies coincide that there is better patency with surgery, though assisted patency is similar. Surgery, therefore, can be considered the initial indication if it is technically possible, as it requires fewer procedures to maintain patency. However, if surgery requires catheter placement, the endovascular technique should be considered as the first option.</p><p id="p5450" class="elsevierStylePara elsevierViewall">This recommendation was submitted to a vote by GEMAV. The wording of the recommendation was unanimously accepted. However, the number of members of the working group who felt that the recommendation should be strong (one third) was not sufficient to award it this category. The remaining members felt that it was weak, or abstained in the vote.</p><p id="p5455" class="elsevierStylePara elsevierViewall">In pAVF, endovascular therapy is more advantageous as it is less invasive than surgery; it does not deplete the venous bed and does not exclude surgical procedure. Thus, despite its higher cost and lower primary patency rate, it can be considered an equally valid therapeutic option to surgery. However, until the publication of comparative studies with surgery, a degree of evidence cannot be established in favour of either technique.</p><p id="p5460" class="elsevierStylePara elsevierViewall">The use of covered stents (stent graft) to treat early recurrence of venous stenosis in prosthetic fistulae seems to provide an improvement in medium-term survival but more studies and longer-term assessment are needed to recommend use.</p><p id="p5465" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0155"></elsevierMultimedia></p><p id="sect1385" class="elsevierStylePara elsevierViewall">Treatment of non-perianastomotic stenosis</p><p id="p5480" class="elsevierStylePara elsevierViewall">Non-perianastomotic venous stenosis, i.e. those located proximally to the juxta-anastomotic area, also referred to as the middle segment or needling area, are usually caused by mechanical trauma during AVF cannulation, and can be associated with the aneurysmal degeneration of the vein,<a class="elsevierStyleCrossRef" href="#bib444"><span class="elsevierStyleSup">444</span></a> with risk of skin necrosis, and with bleeding after HD sessions.<a class="elsevierStyleCrossRef" href="#bib445"><span class="elsevierStyleSup">445</span></a> They might not be associated with alterations during HD or to pump flow (Q<span class="elsevierStyleInf">B</span>) problems and, as a result, they may remain undetected if there is no careful clinical assessment or follow-up.</p><p id="p5485" class="elsevierStylePara elsevierViewall">Treatment options include surgical repair by performing a prosthetic bypass or percutaneous repair using PTA. Although there are studies in the literature comparing both techniques, there are no randomised studies and they are unable to establish a better treatment option. Despite showing that the results of surgery are better in terms of patency,<a class="elsevierStyleCrossRef" href="#bib446"><span class="elsevierStyleSup">446</span></a> most support the initial use of percutaneous AVF treatment since they treat dysfunctional AVF less aggressively.</p><p id="p5490" class="elsevierStylePara elsevierViewall">Although endovascular treatment is not a permanent solution, it is effective in increasing patency; it is a relatively non-invasive, repeatable technique that rarely requires CVC placement and preserves vascular bed integrity without compromising subsequent surgical procedures.</p><p id="p5495" class="elsevierStylePara elsevierViewall">Surgical treatment of stenosis in this location includes creating a bypass excluding the stenotic segment; likewise, its placement in the shape of a loop may be considered, thereby lengthening the cannulation area. Surgery in the access cannulation area may cause the need for temporary HD through CVC, which is the main limitation of the technique. In contrast, when stenosis is associated with aneurysmal dilatation with cutaneous disorders, surgery can treat both during the same intervention.</p><p id="p5500" class="elsevierStylePara elsevierViewall">In studies in the literature, results of surgery versus endovascular treatment are better in terms of the primary patency rate,<a class="elsevierStyleCrossRef" href="#bib446"><span class="elsevierStyleSup">446</span></a> but similar in assisted patency. These same studies support the initial use of percutaneous treatment because it is relatively non-invasive, can be performed in an outpatient’s clinic, avoids CVC and preserves the vascular bed, allowing new surgical procedures. However, PTA and surgery should be considered complementary and uncompetitive techniques.</p><p id="p5505" class="elsevierStylePara elsevierViewall">There is no evidence to support the use of stents in the treatment of stenosis and it is recommended they not be used except in early and repeated recurrences after PTA of middle segments of nAVF and in vein ruptures that do not respond to balloon compressions.</p><p id="p5510" class="elsevierStylePara elsevierViewall">It is advisable to keep in mind that heart failure or distal ischaemia after PTA should be prevented in patients at risk, especially if the flow is high.<a class="elsevierStyleCrossRefs" href="#bib194"><span class="elsevierStyleSup">194,447</span></a> In these cases it is important not to over-dilate the stenosis, mainly in the first PTA and in those located in the arm, to avoid an excessive increase in Q<span class="elsevierStyleInf">A</span>. In patients at risk, such as diabetics or the elderly, caution should be exercised, and it is advisable to avoid using balloons with a diameter > 7 mm. If there is recurrence and there are no signs of ischaemia, the stenosis may be over-dilated 1 mm more.<a class="elsevierStyleCrossRef" href="#bib425"><span class="elsevierStyleSup">425</span></a> For this reason, it is imperative to know the Q<span class="elsevierStyleInf">A</span> of the AVF to indicate therapy.</p><p id="p5515" class="elsevierStylePara elsevierViewall">If post-HD haemostasis problems are important, stenosis dilation is indicated by under-dilating and assessing risk-benefits. In this respect, a double dilation technique associated with surgical reduction of Q<span class="elsevierStyleInf">A</span> has been proposed.<a class="elsevierStyleCrossRef" href="#bib448"><span class="elsevierStyleSup">448</span></a></p><p id="p5520" class="elsevierStylePara elsevierViewall">To sum up, both surgical and endovascular treatment have proven to be safe techniques in stenosis of the needling segment, with good rates of technical and clinical success. However, although there is a better rate of primary patency with surgery, and although assisted patency is similar, the majority opinion of experts, as well as of GEMAV, suggests that percutaneous treatment should be introduced at the outset because it is less aggressive as a technique. In AVF that require an additional surgical procedure, such as in aneurysmal AVF, which have a large mural thrombus or are associated with trophic lesions, surgery is suggested as the first repair technique. Despite the possibility of using endovascular techniques with endoprosthesis placement, there is no experience that can endorse this indication at the present time.</p><p id="sect1390" class="elsevierStylePara elsevierViewall">Treatment of cephalic arch stenosis</p><p id="p5525" class="elsevierStylePara elsevierViewall">The cephalic vein is part of the superficial venous system of the upper limb, and follows an anterolateral subcutaneous trajectory along the arm; proximal to the arm it continues in a superficial position in the deltopectoral groove until it flows into the deep venous system in the axillary vein just before the clavicle. This confluence occurs in the anatomical region known as the cephalic vein arch (CVA), which is the segment in which this vein changes direction through the clavipectoral fascia. It then moves from a superficial position to a deeper level, eventually flowing into the axillary vein, which is the venous drainage trunk of the upper limb.<a class="elsevierStyleCrossRefs" href="#bib449"><span class="elsevierStyleSup">449,450</span></a></p><p id="p5530" class="elsevierStylePara elsevierViewall">As it is an anatomical transition segment between the superficial and deep venous systems, its access stenosis presents a series of particular characteristics that force it to be considered separately from stenosis that occurs in the trajectory of the cephalic vein in the arm.</p><p id="p5535" class="elsevierStylePara elsevierViewall">First, it is one of the most common causes of nAVF dysfunction,<a class="elsevierStyleCrossRefs" href="#bib451"><span class="elsevierStyleSup">451-453</span></a> and this dysfunction usually presents with significant haemodynamic changes<a class="elsevierStyleCrossRef" href="#bib334"><span class="elsevierStyleSup">334</span></a> and a marked association with arm nAVF (39%) versus nAVF in the forearm (2%).<a class="elsevierStyleCrossRefs" href="#bib451"><span class="elsevierStyleSup">451,452</span></a></p><p id="p5540" class="elsevierStylePara elsevierViewall">Likewise, in comparison to stenosis in other locations, these are lesions with a significantly poorer response to treatment using PTA, with greater resistance to dilation (4.8% versus 1.3%), higher rate of vascular rupture (14.9% versus 8.3%) and shorter free interval between angioplasties (10.6 versus 18.3 months).<a class="elsevierStyleCrossRefs" href="#bib449"><span class="elsevierStyleSup">449,451</span></a> Finally, a higher rate of thrombosis has been found in patients with stenosis in CVA.<a class="elsevierStyleCrossRefs" href="#bib334"><span class="elsevierStyleSup">334,454</span></a></p><p id="p5545" class="elsevierStylePara elsevierViewall">Several possible pathophysiological mechanisms for the development of this type of stenosis have been put forward, such as lack of adaptation to the high-flow situation, presence of valves in the cephalic-axillary confluent, alterations due to the angle of the confluent, absence of elasticity at the level of the clavipectoral fascia or intrinsic alterations in the venous wall due to uraemia.<a class="elsevierStyleCrossRefs" href="#bib449"><span class="elsevierStyleSup">449,454-456</span></a> The sequence of mechanisms that leads to the development of stenosis has not been identified to date, leading some authors to consider the possibility that all the indicated agents could be involved in a variable way.<a class="elsevierStyleCrossRef" href="#bib453"><span class="elsevierStyleSup">453</span></a></p><p id="s1395" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Therapeutic options of cephalic arch stenosis</span></p><p id="p5550" class="elsevierStylePara elsevierViewall">As mentioned, the management of this type of stenosis involves greater complexity, given its poor response to treatment and the higher rate of recurrence and complications.</p><p id="p5555" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Percutaneous transluminal angioplasty</span></p><p id="p5560" class="elsevierStylePara elsevierViewall">It is the most widely used therapeutic technique, in many cases due to the unavailability of other technical options in practice. The study by Rajan et al.<a class="elsevierStyleCrossRef" href="#bib452"><span class="elsevierStyleSup">452</span></a> reports a technical success rate of 76%, having required the use of high pressure balloons (> 15 atm) in 58% of cases, with 6% ruptures of the target vessel. Primary patency at 6 months was 42% and 23% at 12 months, with primary assisted patency of 83% and 75% at 6 and 12 months, respectively, requiring an average of 1.6 procedures per year to achieve this, results similar to those later published by Vesely and Siegel.<a class="elsevierStyleCrossRef" href="#bib440"><span class="elsevierStyleSup">440</span></a> Dukkipati et al.,<a class="elsevierStyleCrossRef" href="#bib457"><span class="elsevierStyleSup">457</span></a> in a study on the results of PTA in the CVA, describe an average of 91.5 days between PTA to maintain VA patency.</p><p id="p5565" class="elsevierStylePara elsevierViewall">Thus, results of PTA on CVA stenosis demonstrate a markedly lower effectiveness than in other venous territories, with a higher rate of complications and with lower primary patency than the standards recommended by some clinical practice guidelines.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a> However, it is a minimally invasive and widely available treatment mode, justifying its extensive use in clinical practice. Despite this, new treatment options have been proposed in different studies which have been published.</p><p id="p5570" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Percutaneous transluminal angioplasty with stent placement</span></p><p id="p5575" class="elsevierStylePara elsevierViewall">In order to improve the clinical success and patency of the procedure, placement of an intravascular stent has been proposed.<a class="elsevierStyleCrossRefs" href="#bib449"><span class="elsevierStyleSup">449,453</span></a> As already mentioned, it is a technique commonly used in clinical practice for the treatment of PTA complications, in cases of vessel rupture, and also for recurrent stenosis, as it is a safe and minimally invasive procedure. On the other hand, it is a technically complex procedure, since it requires placement adjacent to the cephalic-axillary venous confluent, which means there is a risk of compromising axillary vein permeability with stent deployment or with posterior migrations of the stent, thereby limiting the creation of new accesses in the limb.<a class="elsevierStyleCrossRef" href="#bib453"><span class="elsevierStyleSup">453</span></a> In addition, in the case of peripheral veins, stent placement has not been shown to increase VA patency.<a class="elsevierStyleCrossRef" href="#bib458"><span class="elsevierStyleSup">458</span></a></p><p id="p5580" class="elsevierStylePara elsevierViewall">Currently available evidence on stent placement in the CVA comes from two published studies, in comparison to simple PTA<a class="elsevierStyleCrossRef" href="#bib457"><span class="elsevierStyleSup">457</span></a>and stent versus the deployment of endoprosthesis,<a class="elsevierStyleCrossRef" href="#bib442"><span class="elsevierStyleSup">442</span></a> with 39% primary patency of the procedure at 6 months. The study of Dukkipati et al.,<a class="elsevierStyleCrossRef" href="#bib457"><span class="elsevierStyleSup">457</span></a> which compares simple PTA versus PTA with stent placement, found an association between stent deployment and an increase in patency, reducing the number of PTA needed after the procedure to maintain it.</p><p id="p5585" class="elsevierStylePara elsevierViewall">Despite providing a modest improvement in primary and primary assisted patency for simple angioplasty, the overall results of stent deployment in the CVA hardly justify the cost/benefit of its use in a systematic way, except in cases of technical complication during PTA.<a class="elsevierStyleCrossRef" href="#bib4"><span class="elsevierStyleSup">4</span></a>42</p><p id="p5590" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Cutting balloon</span></p><p id="p5595" class="elsevierStylePara elsevierViewall">As this is a stenosis with poor response to simple PTA, the possibility of treatment using PTA with cutting balloon has also been proposed.</p><p id="p5600" class="elsevierStylePara elsevierViewall">Despite the theoretical benefit that this technique might offer, evidence from a prospective randomised study of 340 patients (including stenosis at various sites)<a class="elsevierStyleCrossRef" href="#bib440"><span class="elsevierStyleSup">440</span></a> found no benefit in relation to the primary patency of the procedure, and a higher complication rate (5.2%) was observed versus PTA with conventional balloon. Subsequently, another study<a class="elsevierStyleCrossRef" href="#bib459"><span class="elsevierStyleSup">459</span></a> also failed to find better patency of cutting balloon versus simple PTA.</p><p id="p5605" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Endoprosthesis</span></p><p id="p5610" class="elsevierStylePara elsevierViewall">Placement of a vascular endoprosthesis—stent covered with prosthetic material (polytetrafluoroethylene [ePTFE])—may prevent the development of endothelial hyperplasia present in the recurrence of CVA stenosis. It is, however, a technique with a high medical cost.<a class="elsevierStyleCrossRef" href="#bib449"><span class="elsevierStyleSup">449</span></a></p><p id="p5615" class="elsevierStylePara elsevierViewall">The RCT conducted by Shemesh et al.,<a class="elsevierStyleCrossRef" href="#bib442"><span class="elsevierStyleSup">442</span></a> comparing stent and endoprosthesis placement, describes a technical success rate of 100%, with 82% primary patency at 6 months, significantly greater compared to that reported in uncovered stents. Similar results have been reported by Shawyer et al.,<a class="elsevierStyleCrossRef" href="#bib460"><span class="elsevierStyleSup">460</span></a> who found primary patency at 6 and 12 months of 82% and 73%, respectively, and a secondary one of 91% at 6 months.</p><p id="p5620" class="elsevierStylePara elsevierViewall">Despite the improvement found with this technique, given the high financial cost of the procedure, new studies are needed to confirm the results in order to recommend its widespread use in clinical practice.</p><p id="p5625" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Surgical transposition</span></p><p id="p5630" class="elsevierStylePara elsevierViewall">Given the suboptimal results obtained by PTA in this type of stenosis, the surgical transposition of the cephalic vein into the brachial or basilic vein has been proposed by different authors.<a class="elsevierStyleCrossRefs" href="#bib449"><span class="elsevierStyleSup">449,453</span></a> The described technique consists of disconnecting the cephalic vein arch with ligation of the proximal vein and reanastomosis in the basilic or brachial vein in the axillary cavity, by subcutaneous tunnelling, so that drainage to the deep venous system occurs at this level. This surgery is of a moderate technical complexity, and can be performed with locoregional anaesthesia.</p><p id="p5635" class="elsevierStylePara elsevierViewall">The evidence currently available is from several published case studies,<a class="elsevierStyleCrossRefs" href="#bib461"><span class="elsevierStyleSup">461-463</span></a> and there are no direct comparisons with other types of treatment. The results show primary procedure patency of 70-79% at 6 months and 60-79% at 12 months, with a complication rate of 8%.<a class="elsevierStyleCrossRefs" href="#bib453"><span class="elsevierStyleSup">453-463</span></a></p><p id="p5640" class="elsevierStylePara elsevierViewall">Likewise, significantly better patency has been reported in PTA procedures performed after surgery, so there are authors<a class="elsevierStyleCrossRef" href="#bib462"><span class="elsevierStyleSup">462</span></a> who recommend their use in combination.</p><p id="p5645" class="elsevierStylePara elsevierViewall">Thus, the surgical transposition of the CVA is a safe therapeutic option that offers superior patency results to PTA with or without stent placement, presenting the disadvantage of being an invasive technique of intermediate complexity. Large-scale studies that can confirm its usefulness in clinical practice are therefore necessary.</p><p id="p5650" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Other techniques</span></p><p id="p5655" class="elsevierStylePara elsevierViewall">Given the association between turbulent flow and development of endothelial hyperplasia, the indication of flow reduction techniques has been put forward to reduce this turbulence. In the retrospective study of Miller<a class="elsevierStyleCrossRef" href="#bib456"><span class="elsevierStyleSup">456</span></a> on a group of patients with intervention (<span class="elsevierStyleItalic">minimally invasive limited ligation endoluminal-assisted revision</span> [MILLER]) to reduce the flow for other reasons (distal hypoperfusion syndrome (DHS) or high flow), there is a significant improvement in PTA patency after reducing access flow. However, there are no further studies on the role that flow reduction may play in the treatment of these lesions.</p><p id="p5660" class="elsevierStylePara elsevierViewall">Finally, the possibility of performing a surgical procedure through surgical angioplasty with patch through a direct approach of the CVA has also been proposed.<a class="elsevierStyleCrossRef" href="#bib464"><span class="elsevierStyleSup">464</span></a> While it is a technically relatively complex technique, further studies are necessary to determine its role in clinical practice.</p><p id="s1400" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Cephalic arch stenosis: therapeutic management</span></p><p id="p5665" class="elsevierStylePara elsevierViewall">Only a relatively small number of studies supporting the use of the different treatment methods in a clinical setting are available for CVA stenosis, despite their significant prevalence. Consequently, the available evidence is based, in most cases, on a small number of published cases that do not compare different techniques. Therefore, the recommendations made are essentially based on the opinion of GEMAV members, taken on the basis of currently available studies and criteria for good clinical practice (<a class="elsevierStyleCrossRef" href="#t22">Table 22</a>).</p><elsevierMultimedia ident="t22"></elsevierMultimedia><p id="p5670" class="elsevierStylePara elsevierViewall">PTA has been the treatment of choice in cases of CVA stenosis, as it is a safe technique, with low complexity and acceptable results in other venous sectors.<a class="elsevierStyleCrossRef" href="#bib453"><span class="elsevierStyleSup">453</span></a> It is, in addition, a widely available procedure in practice that, in many cases, has no feasible therapeutic alternatives. We realise that both expert opinion and studies confirm the suboptimal result, with poor patency and higher rate of complications than in other locations.<a class="elsevierStyleCrossRefs" href="#bib452"><span class="elsevierStyleSup">452,462</span></a> Despite this, PTA is still considered as a first-line technique for treating these lesions, given its good cost/benefit ratio, its minimally aggressive nature and the acceptable rates of both assisted patency and number of procedures required to maintain it.</p><p id="p5675" class="elsevierStylePara elsevierViewall">In contrast, the use of stents has not shown a parallel increase in the effectiveness of the technique<a class="elsevierStyleCrossRef" href="#bib442"><span class="elsevierStyleSup">442</span></a>; therefore, its use is not justified in a generalised and systematic way given its greater cost. Their placement would be reserved for cases of technical failure in simple PTA (vessel rupture or persistent stenosis).</p><p id="p5680" class="elsevierStylePara elsevierViewall">Along the same lines, incorporating the cutting balloon device, one study has not shown better patency than simple PTA,<a class="elsevierStyleCrossRef" href="#bib459"><span class="elsevierStyleSup">459</span></a> and the results of the largest study to date (340 patients in all sites along the whole AVF segment)<a class="elsevierStyleCrossRef" href="#bib440"><span class="elsevierStyleSup">440</span></a> do not show an improvement in results and even have a higher rate of complications, so its widespread use raises doubts regarding the cost of the procedure and its safety.</p><p id="p5685" class="elsevierStylePara elsevierViewall">The results of studies on endoprosthesis placement have actually shown better results versus simple PTA.<a class="elsevierStyleCrossRefs" href="#bib442"><span class="elsevierStyleSup">442,460</span></a> Although this is a recently introduced technique with little available evidence to support it and it is a procedure with far higher costs than the rest, its routine use is determined by evidence that may arise from new studies.</p><p id="p5690" class="elsevierStylePara elsevierViewall">With regard to surgical techniques, although there is relatively limited evidence, transposition of the cephalic vein has also proved to be a useful treatment as it both increases primary patency and decreases the need for angioplasty after surgery.<a class="elsevierStyleCrossRefs" href="#bib461"><span class="elsevierStyleSup">461-462</span></a> Therefore, it can also be considered a first-line treatment in the treatment of CVA stenosis.</p><p id="p5695" class="elsevierStylePara elsevierViewall">Finally, it was considered that the very limited evidence on flow reduction techniques and surgical angioplasty do not allow us to make any recommendation regarding use, as future studies must be conducted in order to determine their usefulness in clinical practice.</p><p id="p5700" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XVI Are there any criteria that indicate in which cases, when and how to treat central vein stenosis, assessed in terms of usable arteriovenous fistula patency and/or thrombosis?</span></p><p id="p5705" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XVI in <a href="https://static.elsevier.es/nefroguiaaveng/16_PCXVI_Estenosis_central_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0080"></elsevierMultimedia></p><p id="sect1405" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p5710" class="elsevierStylePara elsevierViewall">Central veins are considered to be the subclavian vein, the brachiocephalic vein (also called the innominate vein) and the superior vena cava. The subclavian vein is a continuation of the axillary vein and starts on the lateral edge of the first rib. Due to their intra-thoracic location, i.e. protected by rib arcs, clavicle and sternum, central veins are less accessible to surgery than the peripheral veins of the arm, and are also larger, support more flow and are more elastic.<a class="elsevierStyleCrossRefs" href="#bib465"><span class="elsevierStyleSup">465,466</span></a></p><p id="p5715" class="elsevierStylePara elsevierViewall">Stenosis or occlusion in the central veins of an upper limb in which VA has been created may lead to venous hypertension that is symptomatic, secondary to progressive oedema of the arm that may become refractory, VA dysfunction, trophic disorders of the limb and increase in collateral circulation in the neck and thorax. This may appear in 15-20% of patients on HD, often with previous history of handling and cannulation of the central, subclavian or jugular vein.<a class="elsevierStyleCrossRefs" href="#bib427"><span class="elsevierStyleSup">427,428</span></a> Regardless of CVC location, the greater the number and duration of the CVC, the greater the risk of developing stenosis. A higher prevalence of stenosis is also described in CVC placed on the left side because of the longer and more tortuous trajectory of the central veins on this side.<a class="elsevierStyleCrossRef" href="#bib466"><span class="elsevierStyleSup">466</span></a> In patients with defibrillators or pacemakers requiring AVF, this should be created in the arm opposite the location of the cardiac device. In the HD patient, central stenosis usually remains asymptomatic until an AVF is made in the ipsilateral limb, at which point, the stenosis becomes symptomatic as Q<span class="elsevierStyleInf">A</span> increases.<a class="elsevierStyleCrossRef" href="#bib466"><span class="elsevierStyleSup">466</span></a></p><p id="p5720" class="elsevierStylePara elsevierViewall">The main cause of central venous stenosis in patients on HD is the development of intimal hyperplasia secondary to chronic trauma caused by a CVC, plus high flow and secondary turbulence in patients with AVF in the arm.<a class="elsevierStyleCrossRef" href="#bib467"><span class="elsevierStyleSup">467</span></a> Ninety percent of patients with stenosis have had a central venous catheter.<a class="elsevierStyleCrossRef" href="#bib468"><span class="elsevierStyleSup">468</span></a> Forty percent of CVC in the subclavian vein and 10% of CVC implanted in the jugular vein cause central vein stenosis.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a></p><p id="p5725" class="elsevierStylePara elsevierViewall">When central venous stenosis is suspected, the imaging test of choice is fistulography or venography. If the patient already has an AVF, the study can be performed by direct vein needling of the AVF (<span class="elsevierStyleItalic">outflow</span> segment). As it is impossible to directly view central vessels with US, this imaging test is relegated to a secondary place, although it must be performed before fistulography to rule out stenosis in any other segment of the access that is accessible to ultrasound waves. Fistulography also allows the VA to be treated during the procedure, if indicated.</p><p id="p5730" class="elsevierStylePara elsevierViewall">Other diagnostic means for the study of central veins are Computed Tomography angiography (CT angiography) and Magnetic Resonance angiography (MR angiography). CT angiography has an advantage over MR angiography in that it provides better image resolution, but both techniques have disadvantages (see section “Monitoring and surveillance of arteriovenous fistula”), as they have a high cost and will not prevent fistulography if there is central stenosis. In cases of iodinated contrast allergies, MR angiography may be indicated, although there is a risk of nephrogenic systemic fibrosis.</p><p id="s1410" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p5735" class="elsevierStylePara elsevierViewall">The literature unanimously agrees that only symptomatic cases should be treated.<a class="elsevierStyleCrossRefs" href="#bib14"><span class="elsevierStyleSup">14,15,466,469</span></a> In the review of Levit et al.<a class="elsevierStyleCrossRef" href="#bib469"><span class="elsevierStyleSup">469</span></a> of asymptomatic patients in HD with central stenosis > 50%, in 28% of them angioplasty was not performed and none developed symptoms later. However, in 8% of patients treated the stenosis worsened and became symptomatic which, according to the author, would be the result of endothelial damage produced by the balloon. Chang et al.<a class="elsevierStyleCrossRef" href="#bib470"><span class="elsevierStyleSup">470</span></a> described similar findings.</p><p id="p5740" class="elsevierStylePara elsevierViewall">The treatment of choice in central vein stenosis is dilation with balloon catheter.<a class="elsevierStyleCrossRefs" href="#bib14"><span class="elsevierStyleSup">14,15,466</span></a> PTA in central veins has a high technical success rate ranging from 70% to 90% depending on the studies.<a class="elsevierStyleCrossRef" href="#bib466"><span class="elsevierStyleSup">466</span></a> Buriankova et al.<a class="elsevierStyleCrossRef" href="#bib471"><span class="elsevierStyleSup">471</span></a> obtained a 96% success rate in stenosis and only 50% in occlusions. Results of patency after PTA vary (according to authors) between primary patency of 12% to 50% at one year and secondary patency of 13% to 100%,<a class="elsevierStyleCrossRef" href="#bib466"><span class="elsevierStyleSup">466</span></a> although these results can be improved with the systematic and increasingly widespread use of larger diameter and high pressure balloons.<a class="elsevierStyleCrossRefs" href="#bib466"><span class="elsevierStyleSup">466,471</span></a> The most serious complication following central venous PTA is vein rupture, which, although exceptional, should be immediately identified and initially treated by low pressure balloon compression for 6 min, three consecutive times. If it is not possible to stop the bleeding, the other option is to implant a covered stent.<a class="elsevierStyleCrossRef" href="#bib465"><span class="elsevierStyleSup">465</span></a></p><p id="p5745" class="elsevierStylePara elsevierViewall">The different guidelines and recent bibliographic reviews recommend stent implantation in dilation-resistant elastic stenosis and in recurrence under three months following the last PTA.<a class="elsevierStyleCrossRefs" href="#bib14"><span class="elsevierStyleSup">14,15,466</span></a> When a stent is placed, it is very important not to occlude areas of venous confluence such as the internal jugular ostium and the contralateral brachiocephalic trunk, to prevent problems during the placement of future VA.</p><p id="p5750" class="elsevierStylePara elsevierViewall">Outcomes of stents, the same as with PTA, vary according to the authors, with primary patency rates at one year which fluctuate between 14.3% and 100% and secondary patency between 33% and 91%.<a class="elsevierStyleCrossRef" href="#bib466"><span class="elsevierStyleSup">466</span></a> In some comparative studies between PTA and <span class="elsevierStyleItalic">stent</span> implants, there appears to be no significant differences in primary and secondary patency.<a class="elsevierStyleCrossRefs" href="#bib472"><span class="elsevierStyleSup">472,473</span></a> In the future, the development of new specific stents for veins which have adequate diameters and high radial strength may make these outcomes improve. Covered <span class="elsevierStyleItalic">stents</span> may be another option, and show promising initial results, although there are no prospective and randomised studies.<a class="elsevierStyleCrossRef" href="#bib467"><span class="elsevierStyleSup">467</span></a></p><p id="p5755" class="elsevierStylePara elsevierViewall">Theoretically, covered stents cause less intimal hyperplasia than uncovered ones. As a factor against, as they are covered, they can more easily occlude venous confluence areas that prevent CVC placement in the future. With regard to complications, the most common ones are shortening, fracture and migration of the stent.<a class="elsevierStyleCrossRef" href="#bib467"><span class="elsevierStyleSup">467</span></a> Shortening and migration are less common since nitinol stents are used; due to their thermal memory, these best adapt to tortuous venous areas.<a class="elsevierStyleCrossRef" href="#bib418"><span class="elsevierStyleSup">418</span></a></p><p id="s1415" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p5760" class="elsevierStylePara elsevierViewall">If central venous stenosis is clinically suspected during VA follow-up in HD patients, fistulography is required to confirm the diagnosis. Fistulography is the diagnostic method that locates the lesion and prepares the therapeutic approach.</p><p id="p5765" class="elsevierStylePara elsevierViewall">In central stenosis processes where collateral circulation has developed to compensate the stenosis and there is no clinical significance, treatment would not be necessary given there is no positive risk-benefit balance. Therefore, it is only recommended to treat the stenosis with clinical repercussions.</p><p id="p5770" class="elsevierStylePara elsevierViewall">Should stenosis require treatment, the approach of choice would be endovascular treatment by means of balloon PTA, reserving stent placement for cases of stenosis that present resistance to dilation or frequent or early recurrence of the stenosis, within 3 months. While placing the stent, occluding areas of venous confluence should be avoided to prevent problems with future VA.</p><p id="p5775" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0160"></elsevierMultimedia></p></span><span id="se1445" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">5.2</span><span class="elsevierStyleSectionTitle" id="sect1425">Treatment of thrombosis</span><p id="sect1430" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p5800" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0165"></elsevierMultimedia></p><p id="sect1435" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p5840" class="elsevierStylePara elsevierViewall">Thrombosis is suspected when physical examination fails to detect murmur or thrill through AVF auscultation and palpation, and must be confirmed with an image test.</p><p id="p5845" class="elsevierStylePara elsevierViewall">Thrombosis is the main AVF complication. The main predisposing factor is the presence of venous stenosis and accounts for 80% to 90% of thromboses.<a class="elsevierStyleCrossRefs" href="#bib291"><span class="elsevierStyleSup">291,474</span></a> Most stenosis are usually located in the proximal segment of arteriovenous anastomoses in the nAVF and in the venous anastomosis of pAVF.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a> Any thrombosed VA should be evaluated urgently, and access patency restored when indicated, within the first 24-48 h after the event. Whether the salvage procedure performed is endovascular or surgical, once the thrombus has been removed, fistulography should be performed to locate the stenosis and, in the same procedure, resolve the underlying cause to prevent episodes of rethrombosis.<a class="elsevierStyleCrossRefs" href="#bib475"><span class="elsevierStyleSup">475,476</span></a> Other causes of thrombosis are arterial stenosis and non-anatomical factors such as excessive VA compression after HD, hypotension, elevated levels of haematocrit, hypovolaemia and states of hypercoagulability.<a class="elsevierStyleCrossRefs" href="#bib477"><span class="elsevierStyleSup">477-480</span></a></p><p id="p5850" class="elsevierStylePara elsevierViewall">Due to the importance of VA for the patient’s clinical evolution, the morbidity associated with CVC and the anatomical limitation for multiple VA creation, the salvage of every potentially recoverable AVF should be attempted. The only absolute contraindication is the active infection of the VA. Relative contraindications include allergy to iodinated contrast, unstable or life-threatening clinical situation; biochemical or hydroelectrolytic alterations requiring treatment with urgent dialysis such as pulmonary oedema, hyperkalaemia or severe metabolic acidosis; right-to-left heart shunt; severe pulmonary disease and aneurysmal AVF with thrombosis of a great length of the VA.</p><p id="p5855" class="elsevierStylePara elsevierViewall">Thrombosis of the VA for HD should be regarded as a therapeutic emergency requiring immediate solution. Strategies must be established to take this into account so that in each centre, all the professionals involved participate in a multidisciplinary approach to the problem. Urgent restoration of VA patency allows, in the first place, temporary CVC placement to be avoided, with the morbidity that this implies. However, prior to any therapeutic procedure, a clinical assessment of the patient and an analytical study should be performed to rule out situations of potential risk or severity (pulmonary oedema and severe hyperkalaemia). If the patient requires urgent HD, a CVC should be placed, and the thrombectomy procedure delayed. This delay should be less than 48 h after thrombosis occurred.<a class="elsevierStyleCrossRefs" href="#bib14"><span class="elsevierStyleSup">14,481</span></a> The thrombi become progressively fixed to the vein wall or the ePTFE prosthesis making thrombectomy more difficult the later the unblocking procedure is attempted.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a> However, the “time” factor is not necessarily restricted, given that thrombosed accesses have been salvaged even after several weeks following thrombosis.<a class="elsevierStyleCrossRef" href="#bib271"><span class="elsevierStyleSup">271</span></a></p><p id="s1440" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Endovascular thrombectomy</span></p><p id="p5860" class="elsevierStylePara elsevierViewall">The main objective of the endovascular technique is to re-cannulate the thrombus, using hydrophilic guides, preferably with an angled tip, as they are less traumatic and avoid venous dissection. Thrombus aspiration is performed with manual thromboaspiration systems with negative pressure<a class="elsevierStyleCrossRefs" href="#bib271"><span class="elsevierStyleSup">271,482</span></a> with a thick catheter of 7 to 9 Fr or thromboaspiration by suction. To avoid any procedure-related complications, it is advisable to administer sodium heparin. At the end of the procedure there is no standardised indication for pharmacological treatment, although some authors recommend low molecular weight heparin on alternate days to HD to prevent AVF rethrombosis,<a class="elsevierStyleCrossRef" href="#bib271"><span class="elsevierStyleSup">271</span></a> and other anti-aggregants with acetylsalicylic acid or clopidogrel during 72 h post-thrombectomy.<a class="elsevierStyleCrossRef" href="#bib475"><span class="elsevierStyleSup">475</span></a></p><p id="p5865" class="elsevierStylePara elsevierViewall">Wen et al.<a class="elsevierStyleCrossRef" href="#bib475"><span class="elsevierStyleSup">475</span></a> review their results using the AngioJet thrombus aspiration system in 109 patients with nAVF thrombosis. They obtain a technical success score of 76% (80% before three days and 63% after three days) with primary patency rates of 67%, 57% and 39% at 30, 90 and 180 days, respectively. These results are similar to those obtained with other thromboaspiration devices (Arrow-Trerotola, Hydrolyser and thrombectomy with balloon) and pharmacological thrombolysis.<a class="elsevierStyleCrossRefs" href="#bib475"><span class="elsevierStyleSup">475,483</span></a> These same authors considered nAVF revascularisation more difficult than in pAVF, since, in their experience, native veins are more susceptible to lesion or breakdown, and have a more complex anatomy with occasional onset of multiple stenosis and/or aneurysmal formations. In conjunction with these data, several authors recommend the use of manual thromboaspiration with catheter in nAVF as the catheters are more flexible, are pre-shaped, are smaller in size than other thrombectomy devices, and are therefore less damaging to the vascular endothelium.<a class="elsevierStyleCrossRefs" href="#bib271"><span class="elsevierStyleSup">271,484</span></a></p><p id="p5870" class="elsevierStylePara elsevierViewall">The complications described during the procedure are pulmonary thromboembolism, arterial embolism, rupture or dissection of the vein and haematoma at the needling site, which can become anaemic.<a class="elsevierStyleCrossRefs" href="#bib271"><span class="elsevierStyleSup">271,475</span></a> The use of stents in cases of thrombosis is poorly documented but could be useful in aneurysmal dilatations with residual thrombi after thromboaspiration.<a class="elsevierStyleCrossRef" href="#bib271"><span class="elsevierStyleSup">271</span></a></p><p id="s1445" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Surgical thrombectomy</span></p><p id="p5875" class="elsevierStylePara elsevierViewall">Traditionally, nAVF thrombosis has been treated surgically,<a class="elsevierStyleCrossRefs" href="#bib485"><span class="elsevierStyleSup">485,486</span></a> and it is still performed in many HD units<a class="elsevierStyleCrossRef" href="#bib487"><span class="elsevierStyleSup">487</span></a> through embolectomy catheter, early surgical review of the access and its afferent and efferent vessels. Intra-operative radiological evaluation is also used to treat the underlying lesions found with good results and at a low cost. Treatment includes repair with the reconstruction or creation of a new anastomosis a few centimetres more proximal, or bypass of the stenotic area by interposing an ePTFE segment. If the thrombosis is located in the area adjacent to the anastomosis of radiocephalic and brachiocephalic AVF, the vein may be preserved and the creation of a new anastomosis is recommended, even if several days have elapsed.<a class="elsevierStyleCrossRefs" href="#bib291"><span class="elsevierStyleSup">291,485</span></a> In addition to the surgical technique normally used to perform a proximal reanastomosis, there are authors who have proposed the interposition of an ePTFE segment, in order to avoid depleting the venous pathway inherent to surgery. The results published by these authors show similar patency rates to proximal reanastomosis, although as a drawback, they introduce prosthetic material in the VA.<a class="elsevierStyleCrossRefs" href="#bib273"><span class="elsevierStyleSup">273,488</span></a></p><p id="p5880" class="elsevierStylePara elsevierViewall">New surgical techniques that have been proposed via manual thrombus extraction followed by PTA of stenotic lesions show good results (technical success in 87% of procedures). The authors consider that this is a simpler and cheaper procedure than percutaneous thrombectomy or thrombolysis, and also allows acute and chronic thrombus to be eliminated as well as that in aneurysmal segments.<a class="elsevierStyleCrossRef" href="#bib489"><span class="elsevierStyleSup">489</span></a></p><p id="p5885" class="elsevierStylePara elsevierViewall">Finally, one of the indications for review and surgical treatment is in early nAVF thrombosis (first hours or days), which is mainly related to technical problems.</p><p id="s1450" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Pharmacomechanical fibrinolysis</span></p><p id="p5890" class="elsevierStylePara elsevierViewall">Percutaneous pharmacomechanical fibrinolysis is a minimally invasive method that uses thrombolytic drugs and a PTA balloon for the treatment of thrombosis. The commonly used thrombolytic drugs are urokinase and the recombinant tissue plasminogen activator (rt-PA). The procedure combines releasing fibrinolytics locally, which can be performed in several ways, and PTA of the thrombus. The fibrinolytic drug is released after breaking through the thrombus and the stenotic area responsible for the thrombosis with the hydrophilic guidewire; <span class="elsevierStyleItalic">pulse-spray</span> is the most commonly used system.<a class="elsevierStyleCrossRef" href="#bib490"><span class="elsevierStyleSup">490</span></a> After patency is partially restored, a thrombectomy and PTA of the thrombus,<a class="elsevierStyleCrossRefs" href="#bib491"><span class="elsevierStyleSup">491,492</span></a> using balloon catheter, and the treatment of lesion(s) responsible for the occlusion are also carried out, in the same procedure.</p><p id="p5895" class="elsevierStylePara elsevierViewall">The literature contains four RCTs<a class="elsevierStyleCrossRefs" href="#bib493"><span class="elsevierStyleSup">493-496</span></a> and a retrospective study<a class="elsevierStyleCrossRef" href="#bib497"><span class="elsevierStyleSup">497</span></a> comparing fibrinolysis with urokinase and percutaneous mechanical thromboplasty. No statistically significant differences were observed between either technique in relation to technical success, patency and complications<a class="elsevierStyleCrossRefs" href="#bib493"><span class="elsevierStyleSup">493-495,497</span></a> with the exception of a study conducted by Vogel,<a class="elsevierStyleCrossRef" href="#bib496"><span class="elsevierStyleSup">496</span></a> where the authors found a higher percentage of bleeding complications, primarily at the needling site, with the use of fibrinolytics. The impossibility of lysing the entire thrombus should be added to this drawback.</p><p id="p5900" class="elsevierStylePara elsevierViewall">On the other hand, although most studies found the longer procedures to be a disadvantage of fibrinolysis, in the study conducted by Vashchenko in 2010, where 563 procedures were studied comparing fibrinolysis of thrombosed access by the technique of “urokinase injection and wait” versus mechanical thrombectomy with mechanical device,<a class="elsevierStyleCrossRef" href="#bib497"><span class="elsevierStyleSup">497</span></a> they found the lower cost of fibrinolysis to be an advantage, given the high price of mechanical thrombectomy devices. There is no study comparing the financial cost of VA fibrinolysis to thrombectomy with catheter.</p><p id="p5905" class="elsevierStylePara elsevierViewall">In the review conducted by Bush et al. in 2004,<a class="elsevierStyleCrossRef" href="#bib498"><span class="elsevierStyleSup">498</span></a> comparing different techniques of both endovascular and surgical revascularisation, including fibrinolysis, they also found no differences between the different methods used.</p><p id="p5910" class="elsevierStylePara elsevierViewall">Even with its drawbacks, fibrinolysis is a therapeutic tool that may be useful in certain cases when mechanical or aspiration thrombectomy is not sufficient for the complete removal of thrombi.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a> Its greatest usefulness is in combination with mechanical thrombectomy, allowing the use of lower dose of fibrinolytic drugs and reducing the systemic complications derived from its use.</p><p id="s1455" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">5.2.1 Treatment of native arteriovenous fistula thrombosis</span></p><p id="p5915" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XVII In native arteriovenous fistula thrombosis, what would be the initial indication (percutaneous transluminal angioplasty versus surgery) assessed in terms of patency of the native arteriovenous fistula and/or thrombosis? Does it depend on location?</span></p><p id="p5920" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XVII in <a href="https://static.elsevier.es/nefroguiaaveng/17_PCXVII_Trombosis_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0085"></elsevierMultimedia></p><p id="s1460" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p5925" class="elsevierStylePara elsevierViewall">So far there have been no RCTs comparing the results obtained with surgical treatment and endovascular therapy. There are, however, recent retrospective studies. Ito et al.<a class="elsevierStyleCrossRef" href="#bib476"><span class="elsevierStyleSup">476</span></a> compare both techniques in a sample of 587 patients of which 25% had nAVF. In this subgroup, a patency of 33.7% at 2 years with endovascular treatment stands out compared to 37.5% with surgical thrombectomy and 59.8% if surgery is performed with an additional graft or a new VA (p = 0.0005).</p><p id="p5930" class="elsevierStylePara elsevierViewall">In the review of Tordoir<a class="elsevierStyleCrossRef" href="#bib499"><span class="elsevierStyleSup">499</span></a> in which there are only observational studies to describe the behaviour of both techniques in the nAVF, surgery maintains better results in primary patency at 1 year (74% versus 40%) and secondary patency (87% versus 72%), with the results being similar in technical success (90% versus 89%).</p><p id="p5935" class="elsevierStylePara elsevierViewall">In forearm nAVF, there is a slight advantage of surgical treatment over PTA when comparing long-term primary and secondary patency. The study does not establish a separation between stenosis in different locations, so the best results in the forearm may be related to the treatment of the juxta-anastomotic stenosis.</p><p id="p5940" class="elsevierStylePara elsevierViewall">Similar findings regarding outcomes by location have been found in two studies analysing endovascular treatment in the arm and forearm<a class="elsevierStyleCrossRefs" href="#bib500"><span class="elsevierStyleSup">500,501</span></a> and in one study with patients treated with surgery.<a class="elsevierStyleCrossRef" href="#bib502"><span class="elsevierStyleSup">502</span></a> All of them report a greater primary patency for AVF located in the forearm.</p><p id="s1465" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p5945" class="elsevierStylePara elsevierViewall">The results obtained from retrospective studies, and in the absence of RCTs, indicate a moderately better primary patency of surgery versus endovascular treatment. When results are analysed in the thrombosed fistulae secondary to juxta-anastomotic stenosis, better long-term primary and secondary patency rates are found, which allows surgical treatment to be recommended at this location, given the better results in the treatment of this stenosis. This decision should be associated with the priority of avoiding CVC placement, so if surgery does not guarantee it, endovascular procedure can be contemplated.</p><p id="p5950" class="elsevierStylePara elsevierViewall">In the treatment of thromboses not associated with juxta-anastomotic stenosis, both endovascular and surgical treatment has a high clinical success rate, with no evidence currently available to recommend a specific therapeutic alternative. Therefore, the technique of choice should be decided in accordance with the patient’s clinical context, and the avoidance of CVC placement made a priority whenever possible.</p><p id="p5955" class="elsevierStylePara elsevierViewall">In any case, existing evidence on the treatment of thrombosis of nAVF is difficult to interpret since not only are there no studies that directly compare the procedures, but these studies present considerable technical heterogeneity, both in the endovascular and surgical approach. It cannot be ruled out that the use of different devices in different circumstances may play a role in this variability. Therefore, the limited available evidence also allows a partial therapeutic orientation with these recommendations being based on the interpretation of GEMAV.</p><p id="p5960" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0170"></elsevierMultimedia></p><p id="s1475" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">5.2.2 Treatment of prosthetic arteriovenous fistula thrombosis</span></p><p id="p5975a" class="elsevierStylePara elsevierViewall">Treatment of prosthetic arteriovenous fistula thrombosis</p><p id="sect1480" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p5975" class="elsevierStylePara elsevierViewall">Despite having a higher rate of complications than nAVF, pAVF is a good solution for patients with an exhausted venous vascular bed and in elderly patients, with thrombosis being the main complication. In these cases, thrombosis is located mostly in the venous anastomosis.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a> and is secondary to intimal hyperplasia derived from haemodynamic mechanisms due to lack of adjustment between the vein and the ePTFE prosthesis.<a class="elsevierStyleCrossRefs" href="#bib503"><span class="elsevierStyleSup">503,504</span></a></p><p id="p5980" class="elsevierStylePara elsevierViewall">As in nAVF, urgent assessment with subsequent thrombectomy in recoverable pAVF is indicated, if possible, in the first 24-48 h after the event, in order to avoid CVC placement and associated morbidity. The same strategies mentioned in the previous section are established (section 5.2.1). Imaging studies (DU or fistulography) should be performed after restoring patency to locate stenosis, and in the same procedure to perform treatment of the lesions conditioning episodes of rethrombosis.<a class="elsevierStyleCrossRefs" href="#bib475"><span class="elsevierStyleSup">475,476</span></a></p><p id="p5985" class="elsevierStylePara elsevierViewall">Stenosis and thromboses can be treated endovascularly or surgically. Numerous studies have evaluated both methods, concluding that a combination of both can be highly beneficial. At the end of the 1990s, thrombosed prosthetic accesses were primarily treated surgically followed by angiographic assessment to identify the cause of thrombosis and the presence of residual thrombus. The development of new endovascular devices and the lower invasiveness of this type of procedure have resulted in a predominance of the latter. In any case, the aim of both types of treatment in the detection and treatment of underlying stenosis is always to ensure their ongoing long-term patency.</p><p id="p5990" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XVIII In prosthetic arteriovenous fistula thrombosis, what would be the initial indication (percutaneous transluminal angioplasty versus surgery versus fibrinolysis) assessed in terms of patency of the arteriovenous fistula and/or thrombosis? Does it depend on location?</span></p><p id="p5995" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XVIII in <a href="https://static.elsevier.es/nefroguiaaveng/18_PCXVIII_Trombosis_injerto_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0090"></elsevierMultimedia></p><p id="s1485" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p6000" class="elsevierStylePara elsevierViewall">Traditionally, surgical thrombectomy has been used in pAVF thrombosis, followed by repair with bypass by interposing a graft or associating reanastomosis in a proximal segment of vein without stenosis. Percutaneous treatment of VA thrombosis is a therapeutic option that is less invasive than surgery<a class="elsevierStyleCrossRef" href="#bib475"><span class="elsevierStyleSup">475</span></a> and allows the preservation of proximal venous territory. As a disadvantage, there is a need for a greater number of procedures to maintain pAVF patency.<a class="elsevierStyleCrossRefs" href="#bib451"><span class="elsevierStyleSup">451,474</span></a></p><p id="p6005" class="elsevierStylePara elsevierViewall">A meta-analysis by Green et al.<a class="elsevierStyleCrossRef" href="#bib474"><span class="elsevierStyleSup">474</span></a> concluded in 2002 that surgery was superior, both in terms of technical failures and in primary patency. However, in a recent meta-analysis performed by Kuhan et al.,<a class="elsevierStyleCrossRef" href="#bib505"><span class="elsevierStyleSup">505</span></a> analysing 6 RCTs comparing endovascular therapy and surgery in thrombosis of pAVF, the results were comparable between both techniques. Technical success rates were, on average, 74.5% with endovascular treatment versus 80.3% with surgery (p = 0.13); primary patency at 30 days was 64.6% for endovascular therapy and 66.8% for surgery (p = 0.46); at one year, 14.2% with the endovascular approach versus 23.9% with surgery (p = 0.06). Primary assisted patency at one year was analysed in a single study, with 20.5% with endovascular treatment versus 43.9% with surgery (p = 0.03); however, secondary patency at one year, also analysed in a single study, was 86% for endovascular treatment versus 62.5% for surgical (p = 0.14).</p><p id="p6010" class="elsevierStylePara elsevierViewall">Unlike the meta-analysis conducted by Green et al.,<a class="elsevierStyleCrossRef" href="#bib474"><span class="elsevierStyleSup">474</span></a> in which results were clearly favourable for surgery, the study of Kuhan et al.<a class="elsevierStyleCrossRef" href="#bib505"><span class="elsevierStyleSup">505</span></a> placed endovascular therapy on a par with surgical, with the former being less aggressive. Endovascular techniques, using mechanical and aspiration thrombectomy devices, and the incorporation of new angioplasty balloons with more technical features, have levelled the balance between surgery and endovascular treatment, the latter having the advantage of being less invasive. The comparison of percutaneous mechanical techniques with pharmacological fibrinolysis in three RCTs<a class="elsevierStyleCrossRefs" href="#bib493"><span class="elsevierStyleSup">493-495</span></a> shows no significant differences in patency results.</p><p id="p6015" class="elsevierStylePara elsevierViewall">In this respect, however, despite its invasiveness, urgent surgery avoiding CVC placement with subsequent assessment and endovascular treatment has recently been reported with very good results.<a class="elsevierStyleCrossRef" href="#bib167"><span class="elsevierStyleSup">167</span></a> The authors obtained a patency rate of 67% at three years and a thrombosis rate of 0.45 events per patient per year.</p><p id="p6020" class="elsevierStylePara elsevierViewall">Finally, the use of uncovered metallic prostheses is highly controversial, and results similar to those described for the treatment of non-thrombosis-related VA stenosis have been reported (section 5.1). With regard to the use of covered metallic prostheses (<span class="elsevierStyleItalic">stent graft</span>), in the study by Nassar et al.<a class="elsevierStyleCrossRef" href="#bib505a"><span class="elsevierStyleSup">505a</span></a> where the results of 66 patients with thrombosed pAVF are analysed, the authors find poorer outcomes than those observed in other studies referring to treatment of venous stenosis without thrombosis,<a class="elsevierStyleCrossRefs" href="#bib419"><span class="elsevierStyleSup">419-421</span></a> with poor primary patency (47% and 21% at 3 and 12 months), similar to that observed following thrombectomy without stenosis treatment.<a class="elsevierStyleCrossRef" href="#bib498"><span class="elsevierStyleSup">498</span></a> The thromboses were not associated with the development of an intra-stent stenosis, and so the authors concluded that there must be other factors that determine VA thrombosis different to stenosis in the venous anastomosis, and do not recommend its use in case of thrombosed pAVF.</p><p id="s1490" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p6025" class="elsevierStylePara elsevierViewall">The reviewed studies and clinical trials show no significant differences in patency results between surgery and endovascular treatment, being lower in all cases than those obtained in nAVF. Surgical treatment has better rates of technical success, primary and assisted primary patency (although not significantly), while on the other hand, percutaneous treatment is less aggressive and avoids CVC placement.</p><p id="p6030" class="elsevierStylePara elsevierViewall">Therefore, the approach to thrombosed pAVF can be therapeutically oriented indistinctly, either using the endovascular or surgical approach. The choice of technique should take the patient’s clinical context into consideration, and CVC placement be avoided where possible.</p><p id="p6035" class="elsevierStylePara elsevierViewall">Thrombosis due to stenosis in the axillary vein territory warrants separate consideration, as the technical complexity of exposing a proximal venous segment in surgery makes percutaneous treatment the treatment of first choice.</p><p id="p6040" class="elsevierStylePara elsevierViewall">Finally, similar to nAVF, the heterogeneity, both of the studies and the technical conditions, means that the opinion of GEMAV has contributed to the interpretation of the evidence.</p><p id="p6045" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0175"></elsevierMultimedia></p><p id="s1500" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">5.2.3 Elective treatment of arteriovenous fistula stenosis versus post-thrombosis</span></p><p id="p1370f" class="elsevierStylePara elsevierViewall">Elective treatment of arteriovenous fistula stenosis versus post-thrombosis</p><p id="sect1505" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p6055" class="elsevierStylePara elsevierViewall">As mentioned, thrombosis is the main AVF complication and the main cause of its definitive loss. The main predisposing factor is the presence of venous stenosis which accounts for 80 to 90% of thromboses.<a class="elsevierStyleCrossRefs" href="#bib291"><span class="elsevierStyleSup">291,474</span></a> Most stenosis is usually located in the segment proximal to arteriovenous anastomoses in nAVF and in the venous anastomosis in pAVF.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a></p><p id="p6060" class="elsevierStylePara elsevierViewall">Irreversible AVF thrombosis will have a series of negative consequences on the prevalent HD patient,<a class="elsevierStyleCrossRef" href="#bib269"><span class="elsevierStyleSup">269</span></a> increasing morbidity and mortality, frequency of hospital admissions and healthcare costs.<a class="elsevierStyleCrossRef" href="#bib270"><span class="elsevierStyleSup">270</span></a> In relation to the access thrombosis, it should be noted:<ul class="elsevierStyleList" id="list0530"><li class="elsevierStyleListItem" id="listi2235"><span class="elsevierStyleLabel">•</span><p id="p6065" class="elsevierStylePara elsevierViewall">It is not always possible to restore all thrombosed AVF.<a class="elsevierStyleCrossRef" href="#bib271"><span class="elsevierStyleSup">271</span></a></p></li><li class="elsevierStyleListItem" id="listi2240"><span class="elsevierStyleLabel">•</span><p id="p6070" class="elsevierStylePara elsevierViewall">Several studies indicate that the secondary AVF patency after post-thrombotic restoration is lower than elective AVF stenosis repair prior to thrombosis.<a class="elsevierStyleCrossRefs" href="#bib272"><span class="elsevierStyleSup">272,273</span></a></p></li></ul></p><p id="p6075" class="elsevierStylePara elsevierViewall">These data suggest that it is appropriate to perform elective stenosis treatment prior to AVF thrombosis and this means it is important to conduct surveillance and monitoring of both nAVF and pAVF.</p><p id="p6080" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XIX In the presence of stenosis in the native arteriovenous fistula, is there a significant difference between elective intervention or performing treatment after thrombosis?</span></p><p id="p6085" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XIX in <a href="https://static.elsevier.es/nefroguiaaveng/19_PCXIX_Cirugia_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0095"></elsevierMultimedia></p><p id="s1510" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p6090" class="elsevierStylePara elsevierViewall">Two retrospective studies compared results of elective surgery of nAVF with stenosis but without occlusion versus thrombosed AVF surgery.<a class="elsevierStyleCrossRefs" href="#bib273"><span class="elsevierStyleSup">273,506</span></a></p><p id="p6095" class="elsevierStylePara elsevierViewall">The retrospective study of Lipari et al.<a class="elsevierStyleCrossRef" href="#bib273"><span class="elsevierStyleSup">273</span></a> provided results of 64 patients with forearm AVF stenosis, treated 32 with elective surgery and 32 after thrombosis. It did not find differences in the <span class="elsevierStyleItalic">restenosis rate of access</span>: 0.189 per AVF year, the same for both types of surgery, but there were differences in <span class="elsevierStyleItalic">VA loss:</span> rate of 0.016 per AVF year for the elective surgery group and 0.148 for surgery after thrombosis (p = 0.048). <span class="elsevierStyleItalic">Technical success</span> was 100% for elective surgery and 84% for surgery after thrombosis.</p><p id="p6100" class="elsevierStylePara elsevierViewall">The retrospective study of Cohen et al.<a class="elsevierStyleCrossRef" href="#bib506"><span class="elsevierStyleSup">506</span></a> reports on 43 patients with AVF in arm who had received 48 interventions in stenosed AVF and 15 in already thrombosed AVF. They did not find significant differences in terms of patency of the access at 12 months:<ul class="elsevierStyleList" id="list0535"><li class="elsevierStyleListItem" id="listi2245"><span class="elsevierStyleLabel">•</span><p id="p6105" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Primary patency of the access at 12 months:</span> 56% for AVF with stenosis and 64% for already thrombosed AVF (p = 0.22).</p></li><li class="elsevierStyleListItem" id="listi2250"><span class="elsevierStyleLabel">•</span><p id="p6110" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Secondary patency of the access at 12 months:</span> 64% for AVF with stenosis and 63% for already thrombosed AVF (p = 0.75).</p></li></ul></p><p id="p6115" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Technical success</span> of the surgery was 95% overall (60 of 63; two failures in thrombolysis and one in the primary surgery for the stenosis).</p><p id="p6120" class="elsevierStylePara elsevierViewall">In one prospective study elective surgery to correct the AVF stenosis versus waiting and operating when thrombosis of the AVF develops<a class="elsevierStyleCrossRef" href="#bib272"><span class="elsevierStyleSup">272</span></a> are compared. Researchers describe a greater patency in AVF salvaged following dysfunction than following thrombosis, both as a whole and when analysed in a disaggregated way by type (native or prosthetic). In this prospective study with a 5-year follow-up, 317 AVF were evaluated (73% nAVF and the rest pAVF [ePTFE]), on 282 patients. 88 thromboses occurred, corresponding to a rate of thrombosis/access/year of 0.06 for nAVF and 0.38 in pAVF. In total, 66.6% of AVF salvage repairs were elective, with emergency surgery in 76% of thromboses. The added patency of all incident AVF repaired after dysfunction was 1062 ± 97 days versus 707 ± 132 in those repaired for thrombosis (p < 0.02). The increased risk for AVF loss in those repaired post-thrombosis versus dysfunction was 4.2 (p < 0.01).</p><p id="s1515" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p6125" class="elsevierStylePara elsevierViewall">Despite the lack of randomised studies and their scarcity and methodological limitation, studies analysing the evolution of elective versus post-thrombotic treatment show a preference for elective therapy in their results, with both lower AVF loss and better patency.</p><p id="p6130" class="elsevierStylePara elsevierViewall">At the same time, the outlook of a patient with a thrombosed access must be taken into account regarding elective procedure. The greater likelihood of there being less controllable factors, such as patient clinical situation, extent of the thrombosis or CVC requirement, means that the guarantees of success may be compromised.</p><p id="p6135" class="elsevierStylePara elsevierViewall">Therefore, GEMAV recommends performing an elective or preventive intervention of the stenosis rather than post-thrombosis salvage, following the criteria presented in section 4, associated with the high risk of thrombosis.</p><p id="p6140" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0180"></elsevierMultimedia></p><p id="s1525" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">5.2.4 Thrombosis: salvage versus new vascular access</span></p><p id="p1370g" class="elsevierStylePara elsevierViewall">Thrombosis: salvage versus new vascular access</p><p id="sect1530" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p6150" class="elsevierStylePara elsevierViewall">AVF thrombosis results in a substantial number of hospital admissions, the use of CVC and, consequentially, an increase in healthcare expenditure. In addition to this, CVC-associated morbidity and mortality and anatomical limitation for multiple accesses must be considered, which is why clinical guidelines currently in force consider AVF thrombosis to be a medical emergency.<a class="elsevierStyleCrossRef" href="#bib6"><span class="elsevierStyleSup">6</span></a></p><p id="p6155" class="elsevierStylePara elsevierViewall">When an AVF is thrombosed, the possible options are:<ul class="elsevierStyleList" id="list0540"><li class="elsevierStyleListItem" id="listi2255"><span class="elsevierStyleLabel">•</span><p id="p6160" class="elsevierStylePara elsevierViewall">Place a CVC to dialyse the patient and then refer him/her for a new AVF;</p></li><li class="elsevierStyleListItem" id="listi2260"><span class="elsevierStyleLabel">•</span><p id="p6165" class="elsevierStylePara elsevierViewall">Attempt to urgently salvage the AVF for later use, to avoid hospital admission and CVC placement.</p></li></ul></p><p id="p6170" class="elsevierStylePara elsevierViewall">Both procedures imply healthcare costs and expenditure, and cost analysis studies should be conducted on these procedures.</p><p id="p6175" class="elsevierStylePara elsevierViewall">With regard to pAVF treatment, there appears to be an agreement in the literature on a major advantage of urgent thrombectomy, either surgical or endovascular, versus a new VA.<a class="elsevierStyleCrossRefs" href="#bib272"><span class="elsevierStyleSup">272,507</span></a> That is not the case in native accesses. While nAVF are considered superior to pAVF as VA, they are not problem-free. Over the last decade, thrombosed nAVF have been managed surgically or endovascularly. Despite this, attempts to salvage them have not been widely established. Although the percutaneous management of a thrombosed nAVF is highly successful, repeated interventions are usually required to sustain long-term patency.<a class="elsevierStyleCrossRef" href="#bib507"><span class="elsevierStyleSup">507</span></a> Data published in relation to the healthcare expenditure involved in the surveillance and elective treatment of stenosis to prevent thrombosis of VA are controversial<a class="elsevierStyleCrossRefs" href="#bib281"><span class="elsevierStyleSup">281,508</span></a> with few cost-effectiveness studies.</p><p id="p6180" class="elsevierStylePara elsevierViewall">However, there are several studies on the significant healthcare costs caused by VA in prevalent patients undergoing HD.<a class="elsevierStyleCrossRef" href="#bib509"><span class="elsevierStyleSup">509</span></a> The study of Manns et al.<a class="elsevierStyleCrossRef" href="#bib510"><span class="elsevierStyleSup">510</span></a> shows the high cost of HD incident patients with primary failure in their AVF due, in part, to the increase in the number of diagnostic procedures: image and interventional procedures. For health systems which strictly control financial expenditure, this is extremely relevant.</p><p id="p6185" class="elsevierStylePara elsevierViewall">After conducting a financial analysis of expenditure on AVF maintenance, Bittl et al.<a class="elsevierStyleCrossRef" href="#bib508"><span class="elsevierStyleSup">508</span></a> conclude that this is higher than the cost of creating a greater number of nAVF in the prevalent population (with lower percentage of thrombosis and dysfunctions). The article does not refer to what would happen with a prevalent population with a very high percentage of nAVF.</p><p id="p6190" class="elsevierStylePara elsevierViewall">On the other hand, in the study by Coentrao,<a class="elsevierStyleCrossRef" href="#bib511"><span class="elsevierStyleSup">511</span></a> a retrospective analysis of healthcare costs and expenses was conducted comparing the treatment of thrombosed nAVF and the subsequent follow-up with the creation of a new AVF. They observed that percutaneous thrombectomy and treatment of stenosis versus creation of a new VA and waiting for its maturation is associated with a reduction in costs. The group where this procedure was conducted is associated with a higher number of hospital admissions and problems with AVF management (4 times greater), with shorter patency of the new AVF and the consequent comorbidity associated with the CVC.</p><p id="p6195" class="elsevierStylePara elsevierViewall">Finally, in a very recent study where urgent surgical treatment of 268 AVF thrombosis episodes versus scheduled surgery was tested retrospectively and over a period of 11 years,<a class="elsevierStyleCrossRef" href="#bib487"><span class="elsevierStyleSup">487</span></a> the authors obtain a financial saving of €5397 in favour of urgent AVF repair versus creation of a new access. This benefit is derived from the greater hospital expenses associated with creating a new AVF (CVC complications), and the need to perform interventions to achieve maturation. Extrapolation of savings to the entire Spanish population with 23,000 patients undergoing HD would be €9,930,480/year. The study does not analyse, however, the differences between nAVF and pAVF; nor does it include endovascular therapy of the thrombosed AVF.</p><p id="p6200" class="elsevierStylePara elsevierViewall">Therefore, although no prospective studies or clinical trials comparing both of these procedures have been found, the data obtained from the literature seem to suggest that the creation of a new VA results in higher expenditure and morbidity associated with CVC placement than by urgent restoration of the thrombosed AVF.</p></span><span id="se1555" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">5.3</span><span class="elsevierStyleSectionTitle" id="sect1535">Management of the non-matured fistula</span><p id="sect1540" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p6205" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0185"></elsevierMultimedia></p><p id="sect1545" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p6245" class="elsevierStylePara elsevierViewall">It is estimated that between 28% and 53% of AVF do not mature enough for use in HD.<a class="elsevierStyleCrossRef" href="#bib512"><span class="elsevierStyleSup">512</span></a> In general, Q<span class="elsevierStyleInf">A</span> of 500 mL/min and a diameter of at least 4 mm are required for nAVF to be suitable for dialysis. In successful fistulae, these parameters are met in 4 to 6 weeks. In other cases, from 4–6 months must be waited to conclude that the AVF has failed. In the interval, if HD is needed, a tunnelled CVC is inserted exposing the patient to the morbidity and mortality associated with the use of this VA.</p><p id="p6250" class="elsevierStylePara elsevierViewall">This problem could hypothetically be resolved through the early detection of cases of lack of maturation and treated using surgical or endovascular methods to induce VA maturation.</p><p id="p6255" class="elsevierStylePara elsevierViewall">Two factors, separately or combined, tend to cause most cases of lack of nAVF maturation: venous stenosis and the presence of a significant accessory vein (a venous branch that leaves the primary venous channel which forms the AVF). Both problems can be suspected during clinical check-ups and, after being confirmed with DU, therapeutic intervention could be considered.</p><p id="p6260" class="elsevierStylePara elsevierViewall">The increase in Q<span class="elsevierStyleInf">A</span> and the diameter of the outflow vein occur soon after nAVF creation.<a class="elsevierStyleCrossRefs" href="#bib513"><span class="elsevierStyleSup">513-515</span></a> These studies have shown that fistulae that are definitively going to mature do so in the first 2-4 weeks. Thus, good medical practice would advise VA assessment after 4-6 weeks from creation.<a class="elsevierStyleCrossRefs" href="#bib512"><span class="elsevierStyleSup">512,516</span></a> The recommendation for early monitoring is based on the fact that most nAVF with delay or no maturation have stenotic lesions in the AVF circuit, which, because vascular stenoses are usually progressive, will lead to thrombosis and VA loss over time.</p><p id="p6265" class="elsevierStylePara elsevierViewall">In most cases, potential patients with non-matured nAVF can be detected through careful physical examination, as indicated in section 4, which can provide orientation on the cause of the dysfunction (<a class="elsevierStyleCrossRef" href="#t23">Table 23</a>).</p><elsevierMultimedia ident="t23"></elsevierMultimedia><p id="p6270" class="elsevierStylePara elsevierViewall">After the presumptive diagnosis, a DU scan will confirm the immature fistula diagnosis (diameter < 0.4 cm and Q<span class="elsevierStyleInf">A</span> < 500 mL/m), and will also allow the cause of the absence of maturation to be detected in most cases. In situations where the DU does not do this, an imaging test (fistulography) may be indicated.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,512,566,517</span></a></p><p id="p6275" class="elsevierStylePara elsevierViewall">Different studies have shown the usefulness of early therapy in cases with impaired AVF maturation,<a class="elsevierStyleCrossRefs" href="#bib512"><span class="elsevierStyleSup">512,516,518,519</span></a> thereby producing the likelihood of an increase in maturation by 47% in these patients.<a class="elsevierStyleCrossRef" href="#bib520"><span class="elsevierStyleSup">520</span></a> Likewise, the procedures performed (surgical and endovascular) have been shown to be safe, with a low rate of complications.<a class="elsevierStyleCrossRef" href="#bib521"><span class="elsevierStyleSup">521</span></a></p><p id="p6280" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XX Is there a treatment with better outcomes (percutaneous transluminal angioplasty versus surgery or prosthesis interposition) in non-matured arteriovenous fistula management, evaluated on arteriovenous fistula, which enables it to be used in dialysis, patency and/or thrombosis?</span></p><p id="p6285" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XX in <a href="https://static.elsevier.es/nefroguiaaveng/20_PCXX_FAV_no_madura_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0100"></elsevierMultimedia></p><p id="s1550" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="s1555" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Treatment of non-matured fistula</span></p><p id="p6290" class="elsevierStylePara elsevierViewall"><ul class="elsevierStyleList" id="list0550"><li class="elsevierStyleListItem" id="listi2290"><span class="elsevierStyleLabel">•</span><p id="p6295" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Juxta-anastomotic stenosis</span>. The most common cause of maturation failure is the presence of stenosis in the segment of the vein that, in most cases is located in the juxta-anastomotic region. Therapeutic alternatives are surgical treatment (proximal reanastomosis) and PTA.</p><p id="p6300" class="elsevierStylePara elsevierViewall">In general, the same considerations as those for the treatment of juxta-anastomotic stenosis of mature AVF can be applied. Thus, several reviews<a class="elsevierStyleCrossRefs" href="#bib517"><span class="elsevierStyleSup">517,519,521-523</span></a> that include different clinical case series, which have analysed the effectiveness and safety of percutaneous angioplasty to treat non-maturing AVF, show good rates of immediate results. However, cumulative patency of the AVF that has undergone one or more interventions to induce maturation has been shown to be significantly lower than of those not requiring such techniques.<a class="elsevierStyleCrossRef" href="#bib524"><span class="elsevierStyleSup">524</span></a> In the only study comparing one technique with the other (reanastomosis versus PTA), results have shown that cumulative patency of the fistula at one year was significantly higher among patients treated by surgery (83%) than in those treated with PTA (40%).<a class="elsevierStyleCrossRef" href="#bib525"><span class="elsevierStyleSup">525</span></a></p></li><li class="elsevierStyleListItem" id="listi2295"><span class="elsevierStyleLabel">•</span><p id="p6305" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Accessory veins</span>. The influence of dilated accessory veins in the non-matured fistula has not been fully elucidated.<a class="elsevierStyleCrossRef" href="#bib516"><span class="elsevierStyleSup">516</span></a> Though it is a common finding in these patients (46%), its development has been interpreted by some authors more as a result of proximal stenosis than as a cause of AVF non-maturation.<a class="elsevierStyleCrossRefs" href="#bib517"><span class="elsevierStyleSup">517,526</span></a></p><p id="p6310" class="elsevierStylePara elsevierViewall">Some authors have found good outcomes in isolated disconnection,<a class="elsevierStyleCrossRef" href="#bib527"><span class="elsevierStyleSup">527</span></a> although in most studies this was indicated as a complementary treatment of venous stenosis,<a class="elsevierStyleCrossRefs" href="#bib512"><span class="elsevierStyleSup">512,516,517</span></a> with the best results being described in cases where the accessory veins were disconnected,<a class="elsevierStyleCrossRef" href="#bib526"><span class="elsevierStyleSup">526</span></a> suggesting they have a certain influence on the lack of AVF maturation.</p><p id="p6315" class="elsevierStylePara elsevierViewall">There are three techniques described in the literature: percutaneous ligation, surgical disconnection or endovascular embolisation using <span class="elsevierStyleItalic">coils</span>. Different publications have shown they are safe and have good results, in isolation or in combination with the treatment of co-existing stenosis, although there are no studies that compare them with each other.<a class="elsevierStyleCrossRefs" href="#bib516"><span class="elsevierStyleSup">516,519,527,528</span></a></p></li><li class="elsevierStyleListItem" id="listi2300"><span class="elsevierStyleLabel">•</span><p id="p6320" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Proximal stenosis</span>. There are no published case series on isolated cases of proximal stenosis; the main articles and reviews are with joint data from proximal and juxta-anastomotic stenosis, which are all treated endovascularly.</p><p id="p6325" class="elsevierStylePara elsevierViewall">Results describe a high rate of immediate success and safety of the procedure, as well as a high rate of restenosis.<a class="elsevierStyleCrossRefs" href="#bib517"><span class="elsevierStyleSup">517,519,521,522</span></a> There are no published case series on surgical treatment of this type of lesion.</p></li><li class="elsevierStyleListItem" id="listi2305"><span class="elsevierStyleLabel">•</span><p id="p6330" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Arterial stenosis</span>. The evidence on the isolated treatment of lesions in the afferent artery in nAVF with impaired maturation comes from a single study by interventional radiology.<a class="elsevierStyleCrossRef" href="#bib526"><span class="elsevierStyleSup">526</span></a> The authors describe a high rate of immediate success as well as access maturation, although there was a high incidence of arterial ruptures during the procedure (18%), 7% limb ischaemia after the procedure and an undetermined number during follow-up.</p><p id="p6335" class="elsevierStylePara elsevierViewall">No studies were found on surgical or conservative treatment in cases of arterial lesions proximal to the nAVF.</p></li></ul></p><p id="p6340" class="elsevierStylePara elsevierViewall">Medium- and long-term results of interventions to promote access maturation have been evaluated in different studies.<a class="elsevierStyleCrossRefs" href="#bib519"><span class="elsevierStyleSup">519,524,525,529</span></a></p><p id="p6345" class="elsevierStylePara elsevierViewall">Lee et al.<a class="elsevierStyleCrossRef" href="#bib524"><span class="elsevierStyleSup">524</span></a> found a significant decrease in cumulative access patency in AVF that required interventions of any type to induce maturation. The tendency to restenosis of these procedures seems to be due, according to most authors, to the mechanical aggression of the angioplasty balloon on the vascular endothelium and the subsequent intimal hyperplasia that it entails.<a class="elsevierStyleCrossRefs" href="#bib512"><span class="elsevierStyleSup">512,530</span></a></p><p id="p6350" class="elsevierStylePara elsevierViewall">A subsequent work<a class="elsevierStyleCrossRef" href="#bib525"><span class="elsevierStyleSup">525</span></a> identifies the group of lower cumulative patency in those patients treated by angioplasty, whereas no significant differences are found between the surgery group and the group of AVF that did not require any procedure for their maturation.<a class="elsevierStyleCrossRef" href="#bib525"><span class="elsevierStyleSup">525</span></a> Similar results were described by Long et al.<a class="elsevierStyleCrossRef" href="#bib529"><span class="elsevierStyleSup">529</span></a></p><p id="s1560" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p6355" class="elsevierStylePara elsevierViewall">Most of the haemodynamic and morphological changes produced after VA creation take place during the first 2-4 weeks; after that, there is no progression or even a progressive decrease in access flow in cases of immature fistula; this is the reason why early clinical control (4-6 weeks) is recommended to detect cases with alterations in AVF maturation and to use DU on non-matured AVF to confirm the clinical diagnosis and search for associated lesions.</p><p id="p6360" class="elsevierStylePara elsevierViewall">Early treatment of the underlying lesions may increase the likelihood of access maturation by 47%, so it is recommended to act in cases where there is an indication. If we take into consideration the poor prognosis of immature nAVF (diagnosed as such within 4-6 weeks after its creation), on the one hand, and on the other, the worse prognosis for accesses subjected to percutaneous treatment to induce maturation (early restenosis), it could be considered that the best therapeutic option in juxta-anastomotic stenosis is surgery (proximal reanastomosis), since it will allow the access to be salvaged without determining a poorer prognosis in relation to the AVF that have not presented maturation problems. In these cases, percutaneous angioplasty is a safe option with a high rate of success in AVF maturation, although the higher incidence of associated restenosis makes its use advisable in cases where its surgical correction is not indicated.</p><p id="p6365" class="elsevierStylePara elsevierViewall">Some authors defend the choice to perform PTA systematically and at an early stage in all fistulae to induce maturation, but this systematic use is not recommended due to the high incidence of restenosis and the poor access patency associated to these interventions, although more studies are needed to define indications in clinical practice. Therefore, at present maturation inducement techniques can only be recommended in the diagnosed cases of AVF non-maturation.</p><p id="p6370" class="elsevierStylePara elsevierViewall">In cases of immature nAVF associated with significant collaterals, the three therapeutic options described in the literature (percutaneous ligation, surgical disconnection or endovascular embolisation using coils) have proved to be reliable techniques with low morbidity and high rate of immediate success. Therefore, the technique of choice should be indicated by the procedure associated with the surgery, as in the case where venous stenoses coexist. In cases of veins developed with no other lesions, the choice of treatment mode depends on the characteristics of the accessory vein (depth, surgical accessibility, proximity to needling areas, etc.), although the greater technical complexity and higher healthcare cost of percutaneous techniques is recognised.<a class="elsevierStyleCrossRef" href="#bib529"><span class="elsevierStyleSup">529</span></a> As a result, as there are no significant differences regarding success and complications, surgical or percutaneous ligation should be the first choice for treatment.</p><p id="p6375" class="elsevierStylePara elsevierViewall">At present, the limited available evidence on the treatment of lesions located in the outflow vein and in the afferent artery refers to series of PTA-treated nAVF.</p><p id="p6380" class="elsevierStylePara elsevierViewall">Proximal vein stenosis in non-matured nAVF may be treated endovascularly, as it is a safe and effective procedure, although it should be associated with a follow-up protocol due to tendency to restenosis.</p><p id="p6385" class="elsevierStylePara elsevierViewall">Evidence for endovascular treatment of arterial stenosis comes from the case series published by Turmel-Rodrigues et al.,<a class="elsevierStyleCrossRef" href="#bib531"><span class="elsevierStyleSup">531</span></a> which show a high success rate using the procedure, but associated with arterial rupture and an undefined percentage of ischaemia of the limb. As PTA is performed on the artery responsible for the vascularisation of the limb, PTA as well as possible restenosis and arterial thrombosis could adversely affect the natural course of the obliterating disease in these patients and cause ischaemia of the limb, a risk that is not resolved once the AVF is disconnected. Good clinical practice recommends the indication of these techniques only in those patients in which there is a proven compensatory trajectory in the vascularisation of the limb (PTA in radial arteries with proven patency of the ulnar artery and palmar arch).</p><p id="p6390" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0190"></elsevierMultimedia></p></span><span id="se1590" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">5.4</span><span class="elsevierStyleSectionTitle" id="sect1570">Treatment of infection</span><p id="sect1575" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p6420" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0195"></elsevierMultimedia></p><p id="sect1580" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p6445" class="elsevierStylePara elsevierViewall">AVF infection is usually due to inadequate application of asepsis measures for VA management. Therefore, the whole protocol of action should be reconsidered and training should be provided for health staff on hygienic preventive measures of VA infection. Knowledge of activities related to hand hygiene and skin disinfection must be reinforced before accessing AVF.</p><p id="p6450" class="elsevierStylePara elsevierViewall">Infection can present as an area with pain, heat and redness or as a small abscess or scar in the needling area. If any sign or symptom denoting the presence of infection appears, the infection control protocol must be started.</p><p id="p6455" class="elsevierStylePara elsevierViewall">If the AVF can still be used, a series of precautions must be taken. The infection site should be isolated to prevent contamination of the skin where the cannulation is to be made and to keep needling as far as possible from the area. The infected area should not be managed or cleansing performed during the HD session.</p><p id="s1585" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Microbiology of arteriovenous fistula infections</span></p><p id="p6460" class="elsevierStylePara elsevierViewall">Staphylococci are unanimously considered the most frequent cause of infection associated with VA in the literature. A close relationship between personal hygiene and <span class="elsevierStyleItalic">S. aureus</span> nasal and/or cutaneous colonisation has been described, as well as a higher incidence of VA infections in patients with nasal <span class="elsevierStyleItalic">S. aureus</span>.<a class="elsevierStyleCrossRefs" href="#bib97"><span class="elsevierStyleSup">97,532</span></a></p><p id="p6465" class="elsevierStylePara elsevierViewall">The second most frequent group is gram-negative bacilli, being especially frequent in infections of pAVF in lower limbs. Consequently, empirical antibiotic coverage in cases of infection should be active against gram-positives and gram-negatives. It is important to know the local susceptibility data of the microorganisms in order to define the appropriate empirical treatment in each centre. Once the responsible microorganism is isolated, antibiotic treatment will be adapted to it.</p><p id="s1590" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Infection in the native arteriovenous fistula</span></p><p id="p6470" class="elsevierStylePara elsevierViewall">nAVF-related infections are relatively infrequent, and they are the VA type with the lowest incidence of this complication. Clinical presentation corresponds to skin and soft tissue infections: pain, local erythema, plus drainage of purulent material and appearance of fluctuating masses on the vein trajectory.<a class="elsevierStyleCrossRefs" href="#bib14"><span class="elsevierStyleSup">14,533</span></a></p><p id="p6475" class="elsevierStylePara elsevierViewall">Diagnosis is essentially clinical and analytical, and its extent is defined by physical examination.</p><p id="p6480" class="elsevierStylePara elsevierViewall">These infections usually respond adequately to antibiotic treatment, which should be initiated intravenously when there is fever and/or bacteraemia. The treatment will be maintained for 6 weeks adjusted for microorganism susceptibility.</p><p id="p6485" class="elsevierStylePara elsevierViewall">They are most frequently located in the venous pathway, due to previous cannulations, so cannulation in the affected area should also be suspended.</p><p id="p6490" class="elsevierStylePara elsevierViewall">With adequate medical treatment, the vast majority of cases present a good clinical response, which usually allows the AVF to be completely preserved.</p><p id="p6495" class="elsevierStylePara elsevierViewall">In cases where the physical findings suggest the presence of fluid collections, these should be drained through needling or surgery after ultrasound confirmation.</p><p id="p6500" class="elsevierStylePara elsevierViewall">The infection may, on rare occasions, be located in the arteriovenous anastomosis, in which case AVF disconnection is indicated, due to the high risk of bleeding in artery-vein anastomosis.</p><p id="p6505" class="elsevierStylePara elsevierViewall">In cases of infected thrombus and/or septic embolisms, AVF disconnection is also be indicated.</p><p id="s1595" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Infection in the prosthetic arteriovenous fistula</span></p><p id="p6510" class="elsevierStylePara elsevierViewall">pAVF infection is 2 to 3 times more frequent than in nAVF, and it is also more frequent in lower limb pAVF. Known risk factors include lack of hygiene, diabetes mellitus, hypoalbuminemia, advanced age, cannulation difficulties, formation of periprosthetic haematomas, prolonged post-dialysis bleeding and lack of sterility at the needling site.<a class="elsevierStyleCrossRef" href="#bib97"><span class="elsevierStyleSup">97</span></a> Clinical symptoms may include local pain, graft exposure, appearance of a fistulous tract with drainage of purulent material or a fluctuating mass on the prosthetic tract, localised erythema or a combination of the above, with or without the onset of fever or septicemia.<a class="elsevierStyleCrossRef" href="#bib14"><span class="elsevierStyleSup">14</span></a></p><p id="p6515" class="elsevierStylePara elsevierViewall">The diagnosis is primarily clinical and should be complemented with a DU of the VA to rule out or determine the extension of possible periprosthetic collections. In diagnostic doubt or subacute or chronic infections, a leukocyte scintigraphy should be indicated to detect the presence and extent of infection.<a class="elsevierStyleCrossRef" href="#bib533"><span class="elsevierStyleSup">533</span></a></p><p id="p6520" class="elsevierStylePara elsevierViewall">VA patency is not a necessary condition for prosthetic infection, so it can also occur in old non-functioning pAVF, and this possibility should be ruled out in the presence of any fever or sepsis in these patients.</p><p id="p6525" class="elsevierStylePara elsevierViewall">Antibiotic treatment should start empirically until the causative microorganism has been identified, making sure the most frequently involved microorganisms are covered (<span class="elsevierStyleItalic">S. aureus</span>, coagulase-negative staphylococci and gram-negative bacteria).</p><p id="p6530" class="elsevierStylePara elsevierViewall">In disorder management priority should first be placed on complete resolution of the infection process but at the same time an attempt should also be made, where possible, to preserve the VA. This is why an imaging test of pAVF should be done in order to determine the presence and extent of fluid collections and thus to limit the infection area.<a class="elsevierStyleCrossRef" href="#bib533"><span class="elsevierStyleSup">533</span></a></p><p id="p6535" class="elsevierStylePara elsevierViewall">The only definitive treatment for the infected prosthetic area is surgical excision.<a class="elsevierStyleCrossRefs" href="#bib97"><span class="elsevierStyleSup">97,534</span></a> Based on this, several surgical possibilities have been described in the literature:<ul class="elsevierStyleList" id="list0555"><li class="elsevierStyleListItem" id="listi2310"><span class="elsevierStyleLabel">•</span><p id="p6540" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Total prosthesis excision</span>. It is the classic surgical treatment technique in prosthetic infection. The graft is completely excised with closure of the arteriotomy using a patch of autologous material. It involves CVC placement for HD. Indicated in cases of extensive prosthesis involvement. The anatomical area is not usable in future AVF.</p></li><li class="elsevierStyleListItem" id="listi2315"><span class="elsevierStyleLabel">•</span><p id="p6545" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Subtotal prosthesis excision</span>. Similar technique to the previous one. The prosthesis is excised preserving the proximal and distal segments, which are ligated. It is performed to avoid dissecting the tissues proximal to the anastomosis and associated morbidity. It is indicated in cases of widespread infection, but perianastomotic territory is preserved. It involves CVC placement for HD.<a class="elsevierStyleCrossRef" href="#bib533"><span class="elsevierStyleSup">533</span></a></p></li><li class="elsevierStyleListItem" id="listi2320"><span class="elsevierStyleLabel">•</span><p id="p6550" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Partial prosthesis excision</span>. Indicated in cases of segmental pAVF involvement. The infected segments are re-sectioned preserving those uninfected, and replaced by another prosthetic segment located in a new trajectory through the tissues. CVC placement can be avoided. It is considered the technique of choice in those cases where technically feasible.<a class="elsevierStyleCrossRefs" href="#bib533"><span class="elsevierStyleSup">533,535-537</span></a></p></li><li class="elsevierStyleListItem" id="listi2325"><span class="elsevierStyleLabel">•</span><p id="p6555" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Excision and replacement with cryopreserved vein graft</span>. The infected pAVF is totally excised and exchanged for a cryopreserved vein graft prosthesis from a deceased donor. The technique is reported by some authors with good initial outcomes,<a class="elsevierStyleCrossRef" href="#bib538"><span class="elsevierStyleSup">538</span></a> but other published studies have found high rates of serious complications such as infection, dilatation and rupture of the pAVF, so they advise against use.<a class="elsevierStyleCrossRef" href="#bib539"><span class="elsevierStyleSup">539</span></a></p></li><li class="elsevierStyleListItem" id="listi2330"><span class="elsevierStyleLabel">•</span><p id="p6560" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Prosthesis excision with brachial artery ligation</span>. Indicated in cases of patients with compromised general condition, this technique offers the advantage of eliminating much of the surgical morbidity secondary to arterial repair; by making the ligation distally at the deep brachial artery exit site, patients have a good tolerance to ischaemia.<a class="elsevierStyleCrossRef" href="#bib540"><span class="elsevierStyleSup">540</span></a> It is considered a fall-back technique.</p></li></ul></p><p id="p6565" class="elsevierStylePara elsevierViewall">The technique of choice should be discussed on a case-by-case basis, taking into account the patient’s general condition, how widespread the infection is and what VA alternatives are available. In general, the removal of all infected material will be mandatory in all cases, and an effort made to maintain VA patency through a new trajectory and a new prosthesis. The use of cryopreserved grafts cannot be recommended.</p><p id="p6570" class="elsevierStylePara elsevierViewall">Alternatively, the use of prostheses with high resistance to infection (biosynthetic collagen prosthesis on Dacron matrix) has been proposed. Although these have presented good results in the first published studies,<a class="elsevierStyleCrossRefs" href="#bib541"><span class="elsevierStyleSup">541,542</span></a> there is still a shortage of broader studies that may determine their role in the treatment of prosthetic infection.</p></span><span id="se1620" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">5.5</span><span class="elsevierStyleSectionTitle" id="sect1600">Distal hypoperfusion syndrome (“steal syndrome”)</span><p id="sect1605" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p6575" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0200"></elsevierMultimedia></p><p id="sect1610" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p6615" class="elsevierStylePara elsevierViewall">One of the potentially more serious, but fortunately infrequent, complications is the development of ischaemia in the distal territory of the limb following AVF creation. The incidence of the disease varies from 1% to 20% of all AVF in the upper limbs<a class="elsevierStyleCrossRefs" href="#bib85"><span class="elsevierStyleSup">85,87-87b</span></a>; it is more common in nAVF in the arm (10-25%), with its incidence being lower in pAVF (4-6%), and is not very common in nAVF located in the forearm (1-2%).<a class="elsevierStyleCrossRef" href="#bib87"><span class="elsevierStyleSup">87</span></a></p><p id="s1615" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Pathophysiology</span><a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88,543</span></a></p><p id="p6620" class="elsevierStylePara elsevierViewall">After AVF creation, the presence of a communication between the arterial and venous circuits causes a flow shunt towards the latter, with much lower peripheral resistance, to the detriment of the distal vascular bed of the limb. This effectively produces a phenomenon whereby much of the flow from the brachial artery is ‘stolen’ and shunted to the venous sector of the AVF. This is the reason why limb ischaemia is known as “AVF steal syndrome”.</p><p id="p6625" class="elsevierStylePara elsevierViewall">This short circuit between arterial and venous circulation causes a physiological response in the body in the form of compensatory mechanisms to maintain tissue perfusion in the distal territory of the limb, which is why the vast majority of patients present no ischaemia in this territory. Ischaemia only presents clinically in cases where, due to previous patient conditions, compensation mechanisms are altered.</p><p id="p6630" class="elsevierStylePara elsevierViewall">These mechanisms consist primarily of an increase in size and hypertrophy in the access afferent artery, which allows the increase in arterial flow necessary for the correct development of the AVF. Secondly, circulation develops through collaterals, especially at the expense of the deep brachial artery in arm fistulae and ulnar artery and palmar arch in forearm fistulae. Finally, in response to ischaemia, generalised vasodilation occurs in the vascular bed distal to the AVF, which causes a decrease in the resistances in this territory and an increase in perfusion.</p><p id="p6635" class="elsevierStylePara elsevierViewall">Thus, in addition to haemodynamic “steal” phenomenon, other factors commonly predispose the appearance of DHS: presence of stenosis or occlusion in the proximal arterial territory or an inability of the distal vascular bed to adapt to the new haemodynamic situation created. That is why most authors, as well as the clinical guidelines, prefer the use of the term “distal hypoperfusion syndrome” to “fistula steal” to refer to this disorder.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,14,87,87b,88,543</span></a></p><p id="s1620" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Risk factors</span></p><p id="p6640" class="elsevierStylePara elsevierViewall">Diabetes mellitus, use of the brachial artery, peripheral arteriopathy, advanced age, smoking, female gender, previous failed VA in the same limb and a history of DHS in the contralateral limb are considered risk factors for developing ischaemia.<a class="elsevierStyleCrossRefs" href="#bib88"><span class="elsevierStyleSup">88,92,54</span></a>4,545</p><p id="p6645" class="elsevierStylePara elsevierViewall">In contrast, authors do not agree on anastomosis diameter as an isolated risk factor,<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a> since although there appears to be a direct relationship between the diameter of the anastomosis and the flow in small-sized AVF, that relationship disappears from a given diameter (75% of the donor artery).<a class="elsevierStyleCrossRef" href="#bib544"><span class="elsevierStyleSup">544</span></a></p><p id="s1625" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Clinical presentation</span><a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,545</span></a></p><p id="p6650" class="elsevierStylePara elsevierViewall">Symptomatology can present acutely (after the intervention), subacutely (in the first days), or chronically (one month after creation). The acute form, while less common, tends to occur in pAVF while the chronic version is usually progressive over time and is related to nAVF at brachial artery level.<a class="elsevierStyleCrossRef" href="#bib546"><span class="elsevierStyleSup">546</span></a></p><p id="p6655" class="elsevierStylePara elsevierViewall">Clinical presentation is superposable to that developed in other territories with ischaemia, pain, paraesthesia, paralysis, loss of distal pulse, coldness and pallor.<a class="elsevierStyleCrossRef" href="#bib545"><span class="elsevierStyleSup">545</span></a> In more severe cases, it can lead to necrosis and irreversible tissue loss.</p><p id="p6660" class="elsevierStylePara elsevierViewall">In clinical practice, severity of the disease is determined by the analogous classification proposed by Fontaine et al.<a class="elsevierStyleCrossRef" href="#bib547"><span class="elsevierStyleSup">547</span></a> for chronic ischaemia of the lower limbs<a class="elsevierStyleCrossRefs" href="#bib87"><span class="elsevierStyleSup">87,87b,548,549</span></a> (<a class="elsevierStyleCrossRef" href="#t24">Table 24</a>).</p><elsevierMultimedia ident="t24"></elsevierMultimedia><p id="s1630" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Diagnosis</span></p><p id="p6665" class="elsevierStylePara elsevierViewall">The disorder is diagnosed on the basis of anamnesis (history of previous VA) and on the presence of the previously mentioned symptomatology.</p><p id="p6670" class="elsevierStylePara elsevierViewall">Although DHS diagnosis is essentially clinical, it can be confirmed by means of vascular laboratory testing. Of all the tests proposed, the one that has proved most useful in practice is the Digital Pressure Index (DPI), which consists of measuring the ratio between the digital pressure of one limb and the contralateral brachial artery<a class="elsevierStyleCrossRef" href="#bib550"><span class="elsevierStyleSup">550</span></a>. Other useful tests in practice are the calculation of the systolic pressure index between the two limbs, photoplethysmography and oxygen saturation.<a class="elsevierStyleCrossRefs" href="#bib87"><span class="elsevierStyleSup">87,87b,551</span></a></p><p id="s1635" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Differential diagnosis. Ischaemic monomelic neuropathy</span></p><p id="p6675" class="elsevierStylePara elsevierViewall">The symptoms, together with access creation history, do not usually pose any diagnostic doubts, and differential diagnosis is proposed with few illnesses: carpal tunnel syndrome, nerve injury associated with surgery and destructive cases of arthropathy, in which a detailed anamnesis and physical examination plus electromyogram usually allow the diagnosis.<a class="elsevierStyleCrossRefs" href="#bib87"><span class="elsevierStyleSup">87,87b</span></a></p><p id="p6680" class="elsevierStylePara elsevierViewall">Of particular importance is the differential diagnosis of the entity known as ischaemic monomelic neuropathy (IMN). IMN appears acutely after VA creation surgery, and is an exclusive pathology of diabetic patients and of brachial artery accesses.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="p6685" class="elsevierStylePara elsevierViewall">This disorder is considered to be related to a selective ischaemia of the nervous tissue in the antecubital fossa and has a global effect on the three main nervous trunks of the forearm (radial, ulnar and median nerves). It presents clinically immediately after surgery as refractory pain and motor deficit, coinciding with a physical examination showing no signs of ischaemia and laboratory tests that rule out significant ischaemia. In diagnostic uncertainty, electromyography will typically show the joint involvement of the three nerves mentioned.<a class="elsevierStyleCrossRef" href="#bib552"><span class="elsevierStyleSup">552</span></a></p><p id="p6690" class="elsevierStylePara elsevierViewall">The main risk of the condition lies in the irreversible sensory and motor deficit it can cause; therefore, in these cases, immediate ligation of the AVF is indicated to minimise such sequelae.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,552</span></a></p><p id="s1640" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Prevention of distal hypoperfusion syndrome</span></p><p id="p6695" class="elsevierStylePara elsevierViewall">Once ischaemia has developed, despite proper medical and surgical management, there is a high risk of access loss. For this reason, the ideal approach to adopt should be to detect cases that have a high risk of ischaemia in order to create an AVF with a low risk of DHS.</p><p id="p6700" class="elsevierStylePara elsevierViewall">Firstly, this condition may present depending on the number of ischaemia risk factors in the patient,<a class="elsevierStyleCrossRefs" href="#bib88"><span class="elsevierStyleSup">88,546</span></a> so some authors consider the presence of two or more of these factors to identify patients at high risk of DHS.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="p6705" class="elsevierStylePara elsevierViewall">Correct pre-operative assessment should also identify this group of patients. This assessment should include systolic blood pressure determination in both limbs, palpation of peripheral pulses and Allen test. The presence of pressure differences > 20 mmHg between the two limbs, the lack of peripheral pulses or a pathological Allen test are signs indicating a high risk of presenting ischaemia after VA creation.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="p6710" class="elsevierStylePara elsevierViewall">Finally, alterations in pre-operative haemodynamic tests are also suggestive of a high risk of ischaemia, especially alterations in the DPI and the reactive hyperaemia test.<a class="elsevierStyleCrossRefs" href="#bib60"><span class="elsevierStyleSup">60,87b,553,554</span></a></p><p id="p6715" class="elsevierStylePara elsevierViewall">Although authors agree it is important to detect patients at risk of developing ischaemia after the VA is created, there is little published literature on the approach to be followed in these cases. Thus, in a given patient, it is not possible to determine if DHS will present.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88</span></a> Also, the progressive increase in age of the patient in HD leads to the presence of multiple risk factors for ischaemia in the majority of AVF candidates.<a class="elsevierStyleCrossRef" href="#bib555"><span class="elsevierStyleSup">555</span></a></p><p id="p6720" class="elsevierStylePara elsevierViewall">In spite of this, the clinical importance of DHS means that it is necessary to adopt all the measures aimed at minimising the possible presentation of ischaemia in the limb after identifying the patient at risk<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88,113</span></a> (see section 1).</p><p id="p6725" class="elsevierStylePara elsevierViewall">Thus, for a patient with a high risk of ischaemia, the authors recommend the use of the proximal radial artery (PRA) for AVF in the forearm, given the lower incidence of DHS in this procedure.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,113</span></a> The use of the PRA for the AVF in the antecubital fossa has been shown to be a safe technique with no additional morbidity, presenting a lower risk of ischaemia,<a class="elsevierStyleCrossRefs" href="#bib113"><span class="elsevierStyleSup">113,119</span></a> with less technical complexity than the other techniques described. Thus, it is considered to be the technique of choice for the prevention of DHS in those cases where technically feasible.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="s1645" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Treatment objective</span></p><p id="p6730" class="elsevierStylePara elsevierViewall">There is general agreement in stating that the goal of therapy should be twofold: to relieve ischaemia and to preserve the access. The different surgical techniques used in treatment are reviewed.</p><p id="p6735" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XXI What is the approach to native or prosthetic arteriovenous fistula diagnosed with steal syndrome?</span></p><p id="p6740" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XXI in <a href="https://static.elsevier.es/nefroguiaaveng/21_PCXXI_Sindrome_robo_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0105"></elsevierMultimedia></p><p id="s1650" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p6745" class="elsevierStylePara elsevierViewall">As mentioned, DHS is a potentially serious complication after VA creation. This makes the early detection of symptomatology and the need to act in an appropriate way to prevent irreversible lesions important. Also, given the growing evidence available on surgical techniques that have haemodynamic repercussions and preserve the access, today the aim of treatment should be considered twofold: to improve ischaemia and preserve the VA.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88,543,545,549</span></a></p><p id="p6750" class="elsevierStylePara elsevierViewall">Symptom management must be appropriate for the clinical stage and severity of the symptoms. In mild cases (stage I and IIa), therefore, in which the intensity of symptomatology does not incapacitate the patient nor represent a risk for limb viability, medical treatment (pentoxifylline, naftidrofuryl, cilostazol, etc.), physical measures (protection and warmth of the limb) and clinical follow-up should be indicated and initiated. In situations where symptoms are incapacitating or involve the risk of tissue loss (stages IIb-IVa), a surgical intervention should be indicated to resolve ischaemia. Finally, in cases of irreversible widespread necrosis (stage IVb) or when it presents acutely, VA closure should be prioritised as treatment of choice<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88,545,549</span></a> (<a class="elsevierStyleCrossRef" href="#t25">Table 25</a>).</p><elsevierMultimedia ident="t25"></elsevierMultimedia><p id="p6755" class="elsevierStylePara elsevierViewall">Once the disorder has been identified, when the clinical stage indicates surgery, DU should be performed routinely on the VA and an angiographic study of the limb vascularisation conducted.</p><p id="p6760" class="elsevierStylePara elsevierViewall">Angiography should be performed in all cases in which surgical treatment is considered, and the proximal arterial trunks from the thoracic portion must be examined, since up to 50% of patients with DHS may have significant lesions associated with VA inflow.<a class="elsevierStyleCrossRefs" href="#bib543"><span class="elsevierStyleSup">543,556</span></a></p><p id="p6765" class="elsevierStylePara elsevierViewall">Likewise, the access must be studied using DU, since it will provide essential information on Q<span class="elsevierStyleInf">A</span> in the AVF, which is necessary in order to indicate the procedure to be performed.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="p6770" class="elsevierStylePara elsevierViewall">After studying each case individually, surgical correction is indicated, and several techniques have been described in the literature.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,545</span></a></p><p id="s1655" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Closure of the access</span></p><p id="p6775" class="elsevierStylePara elsevierViewall">This is the surgical disconnection of the created AVF in order to reverse the haemodynamic situation and make the ischaemic symptoms disappear. Since it does not fulfil the objective of preserving the access, it is a fall-back technique, indicated only where other techniques fail, in cases of high surgical risk, in acute ischaemia, IMN or where there are lesions with important associated tissue loss<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,549,552</span></a> (<a class="elsevierStyleCrossRef" href="#t26">Table 26</a>).</p><elsevierMultimedia ident="t26"></elsevierMultimedia><p id="s1660" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Endovascular treatment. Percutaneous transluminal angioplasty</span></p><p id="p6780" class="elsevierStylePara elsevierViewall">In significant stenosis of the arterial inflow associated with DHS, treatment using PTA should be indicated with or without stent placement, which can be performed during diagnosis. It is a safe technique with a high rate of immediate clinical success, resolves symptomatology, and is indicated in cases of arterial lesions in the feeding artery.<a class="elsevierStyleCrossRefs" href="#bib359"><span class="elsevierStyleSup">359,556</span></a></p><p id="s1665" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Banding</span></p><p id="p6785" class="elsevierStylePara elsevierViewall">The banding technique consists of restricting the flow in the AVF by limiting the diameter in the anastomosis or in the segment of the juxta-anastomotic vein. There are a number of techniques described, which can be performed by a ligature of non-reabsorbable material, by surgical plication in the outflow vein, interposing a segment of prosthetic material (ePTFE, Dacron), or by placing an external band of the aforesaid prosthetic material.<a class="elsevierStyleCrossRefs" href="#bib545"><span class="elsevierStyleSup">545,549</span></a> The aim of banding is to restrict Q<span class="elsevierStyleInf">A</span> through the access, improving perfusion of the distal territory. Therefore, it is indicated exclusively in AVF with high Q<span class="elsevierStyleInf">A</span>, and is especially recommended in cases of AVF with very high output that require significant Q<span class="elsevierStyleInf">A</span> reduction.<a class="elsevierStyleCrossRef" href="#bib88"><span class="elsevierStyleSup">88</span></a></p><p id="p6790" class="elsevierStylePara elsevierViewall">The main limitation of this technique lies in its capability to determine the degree of flow restriction that must be made to improve ischaemia symptomatology without compromising access viability. Therefore, several methods of intra-operative monitoring have been proposed to serve as a guide during surgical intervention: photoplethysmography monitoring, Q<span class="elsevierStyleInf">A</span> control in the AVF, clinical control—radial pulse recovery—, determination of the Doppler curve in the radial artery, monitoring by pulse oximetry and improvement of the patient’s symptomatology.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,545</span></a> Likewise, results are controversial in the medium and long term, and high Q<span class="elsevierStyleInf">A</span> recurrence rates of 52% per year have been described.<a class="elsevierStyleCrossRef" href="#bib557"><span class="elsevierStyleSup">557</span></a></p><p id="p6795" class="elsevierStylePara elsevierViewall">Banding is the first DHS treatment technique described, so it is extensively documented in the literature; the best available evidence comes from the review published by Scheltinga et al.,<a class="elsevierStyleCrossRef" href="#bib558"><span class="elsevierStyleSup">558</span></a> based on 39 clinical case series corresponding to a total of 226 cases. This author finds significant differences between the 16 case series in which there was no intra-operative monitoring or only radial pulse control, with a clinical success rate (recovery of ischaemic symptoms) of 60%, and of access patency of 53%, in comparison to the case series in which some of the monitoring methods described were used. Among these, there was a clinical success rate of 89% and a rate of VA patency of 97%, after an average follow-up of 17 months.</p><p id="p6800" class="elsevierStylePara elsevierViewall">With reference to Q<span class="elsevierStyleInf">A</span>, which should be highlighted as the main objective of banding, flow differs slightly according to the authors, with a value of 400-600mL/min in nAVF and 700-800 mL/min for pAVF being widely recommended, and there is an increased risk of thrombosis in pAVF with flows < 700 mL/min.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,545,559</span></a></p><p id="s1670" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal revascularisation and interval ligation</span></p><p id="p6805" class="elsevierStylePara elsevierViewall">First described by Schanzer et al. in 1988<a class="elsevierStyleCrossRef" href="#bib560"><span class="elsevierStyleSup">560</span></a>, the acronym DRIL (distal revascularisation and interval ligation) refers to the surgical procedure consisting of 2 combined techniques:<ul class="elsevierStyleList" id="list0565"><li class="elsevierStyleListItem" id="listi2365"><span class="elsevierStyleLabel">•</span><p id="p6810" class="elsevierStylePara elsevierViewall">Distal Revascularisation (DR): interposition of a bypass from the proximal to the distal artery to the VA, in order to ensure the perfusion of the distal territory.</p></li><li class="elsevierStyleListItem" id="listi2370"><span class="elsevierStyleLabel">•</span><p id="p6815" class="elsevierStylePara elsevierViewall">Interval Ligation (IL): Ligation of the distal artery to the VA anastomosis, in order to prevent the phenomenon of haemodynamic steal (retrograde flow in the artery distal to the AVF).</p></li></ul></p><p id="p6820" class="elsevierStylePara elsevierViewall">Thus, the overall effect sought is to prevent steal phenomenon in the access while favouring the distal perfusion of the limb by means of a bypass of lesser peripheral resistance than the original arterial circuit.</p><p id="p6825" class="elsevierStylePara elsevierViewall">Since this technique was described, it has been used by a large number of groups, and good results have been described in the treatment of DHS.<a class="elsevierStyleCrossRef" href="#bib561"><span class="elsevierStyleSup">561</span></a></p><p id="p6830" class="elsevierStylePara elsevierViewall">Reviews of the case series published<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,561</span></a> offer a clinical success rate of 78% to 90% (disappearance of clinical symptoms of ischaemia), maintaining a VA patency of 73% to 100%.<a class="elsevierStyleCrossRef" href="#bib549"><span class="elsevierStyleSup">549</span></a></p><p id="p6835" class="elsevierStylePara elsevierViewall">The main disadvantage of this technique is, firstly, an axial artery has to be ligated, which means that, despite the excellent rates of patency published,<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a> in case of occlusion, a more severe case of ischaemia than the previous one can be caused. Secondly, some studies find that the degree of clinical improvement is Q<span class="elsevierStyleInf">A</span>-dependent and is less effective as the Q<span class="elsevierStyleInf">A</span> increases in the VA.<a class="elsevierStyleCrossRef" href="#bib562"><span class="elsevierStyleSup">562</span></a> For this reason, it is mainly indicated in the treatment of DHS in AVF with normal or decreased Q<span class="elsevierStyleInf">A</span>.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="p6840" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Technical variants</span></p><p id="p6845" class="elsevierStylePara elsevierViewall">To minimise the risk of ligation in the axial artery, several authors have proposed performing the procedure without ligating the interval, i.e., performing only DR.<a class="elsevierStyleCrossRef" href="#bib563"><span class="elsevierStyleSup">563</span></a> At the same time, in order to increase distal perfusion and the effectiveness of the technique, it has been proposed that proximal anastomosis of the bypass be performed in the most proximal arterial sector, increasing the separation between the anastomosis and the AVF.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,562</span></a></p><p id="p6850" class="elsevierStylePara elsevierViewall">These technical variations are based on the findings of theoretical and experimental models<a class="elsevierStyleCrossRefs" href="#bib562"><span class="elsevierStyleSup">562,564</span></a>; however, confirmation of their clinical usefulness is necessary in studies with sufficient evidence in order to recommend their systematic use.</p><p id="s1675" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Proximalisation of arterial inflow</span></p><p id="p6855" class="elsevierStylePara elsevierViewall">In this technique, proximalisation of the arterial inflow (PAI), first described by Zanow et al.,<a class="elsevierStyleCrossRef" href="#bib565"><span class="elsevierStyleSup">565</span></a> the AVF in the anastomosis is ligated and this AVF is vascularised by a bypass of prosthetic material between the axillary or proximal brachial artery and the AVF outflow vein. It is applied to accesses located in the arm, improving ischaemia by a combination of several haemodynamic mechanisms: firstly, when a proximal vessel is used as feeding artery, the pressure drop in the distal bed caused by the access decreases; secondly, retrograde flow in the distal artery to the AVF (haemodynamic steal) is minimised or completely suppressed; and thirdly, when a small prosthetic graft (4-5 mm) is implanted, a flow limiting effect is achieved, as described in banding.<a class="elsevierStyleCrossRefs" href="#bib562"><span class="elsevierStyleSup">562,566</span></a></p><p id="p6860" class="elsevierStylePara elsevierViewall">As this is a relatively new technique, there is limited evidence regarding clinical outcomes.<a class="elsevierStyleCrossRef" href="#bib566"><span class="elsevierStyleSup">566</span></a> There are only two studies published in the literature with a total of 70 cases, with clinical success (disappearance of symptoms of ischaemia) being described in 84% to 90% of cases, with a primary patency 62-87% at two years.<a class="elsevierStyleCrossRefs" href="#bib565"><span class="elsevierStyleSup">565,567</span></a></p><p id="p6865" class="elsevierStylePara elsevierViewall">PAI has several advantages. As it is a technique that causes an increase in access flow, it can be performed in the AVF with a decreased flow and DHS. It also has an advantage over DRIL as it does not require ligation of an axial artery, which means it does not cause ischaemia in cases of occlusion of the procedure. However, as a drawback, it transforms nAVF into pAVF with the increase in associated infectious complications and thrombosis. There is also limited evidence currently available on its outcomes.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,545,562,566</span></a></p><p id="s1680" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Revision using distal inflow</span></p><p id="p6870" class="elsevierStylePara elsevierViewall">A technique initially described by Andrade et al.<a class="elsevierStyleCrossRef" href="#bib568"><span class="elsevierStyleSup">568</span></a>and by Minion et al.<a class="elsevierStyleCrossRef" href="#bib569"><span class="elsevierStyleSup">569</span></a> (revision using distal inflow [RUDI]). This consists of disconnecting the VA anastomosis and transposing it distally using a retrograde bypass—prosthetic or autologous—from a distal arterial trunk (radial or ulnar arteries) to the AVF outflow vein.</p><p id="p6875" class="elsevierStylePara elsevierViewall">When a smaller artery is used for the inflow of the VA, AVF flow is reduced, so it is indicated in DHS associated with a high-flow AVF.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,557</span></a></p><p id="p6880" class="elsevierStylePara elsevierViewall">As it is a relatively recent technique, the available evidence is based on case series; in the review published by Vaes et al.,<a class="elsevierStyleCrossRef" href="#bib570"><span class="elsevierStyleSup">570</span></a> only 51 cases have been identified to date, and symptomatology was improved in all cases, with a thrombosis rate of the access of 20%. These authors also describe a reduction in the flow of 60% in the access, together with the potential advantage versus banding of being a more durable technique over time, because flow shows no tendency to progressively increase in the AVF after surgery, unlike banding.<a class="elsevierStyleCrossRef" href="#bib570"><span class="elsevierStyleSup">570</span></a></p><p id="s1685" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal radial artery ligation</span></p><p id="p6885" class="elsevierStylePara elsevierViewall">When DHS is caused by an AVF at the wrist, it is frequently associated with hypertrophy of the palmar arch with inverted flow at the level of the radial artery distal to VA anastomosis.<a class="elsevierStyleCrossRef" href="#bib571"><span class="elsevierStyleSup">571</span></a> In these cases, after verifying palmar arch patency as well as retrograde flow in the distal radial artery by angiography and DU, disconnection of the radial artery distal to the AVF can resolve ischaemia (distal radial arterial ligation [DRAL]).<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88,549</span></a></p><p id="p6890" class="elsevierStylePara elsevierViewall">This disconnection may be performed through endovascular intervention, by inserting coils or through minimally invasive surgery.</p><p id="p6895" class="elsevierStylePara elsevierViewall">This technique is limited to rare cases of DHS associated with radiocephalic AVF, and is considered to be a technical variant of DRIL, in which distal vascularisation depends on the ulnar artery together with the palmar arch. For this reason, there is scarce evidence in the literature.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a> Miller et al.<a class="elsevierStyleCrossRef" href="#bib571"><span class="elsevierStyleSup">571</span></a> describe a case series (15 patients) in which it is shown to be a safe technique that achieves clinical improvement in a large number of these patients.</p><p id="s1690" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Endovascular banding</span></p><p id="p6900" class="elsevierStylePara elsevierViewall">A technique described by Beathard et al.<a class="elsevierStyleCrossRef" href="#bib518"><span class="elsevierStyleSup">518</span></a> and Goel et al.,<a class="elsevierStyleCrossRef" href="#bib572"><span class="elsevierStyleSup">572</span></a> which consists of performing minimally invasive banding (minimally invasive limited ligation endoluminal-assisted revision [MILLER]): an angioplasty balloon is percutaneously inserted in the VA anastomosis (balloon of 3 to 5 mm in diameter), then inflated in order to later perform <span class="elsevierStyleItalic">banding</span> through a skin incision, maintaining the balloon inflated in the vessel.<a class="elsevierStyleCrossRef" href="#bib573"><span class="elsevierStyleSup">573</span></a></p><p id="p6905" class="elsevierStylePara elsevierViewall">Technically and haemodynamically, it is a variant of the previously described banding technique, but it is less aggressive surgically and is more precise in determining the diameter of the residual lumen. Its main drawback is that morphological parameters (residual diameter of the vessel) rather than haemodynamic (Q<span class="elsevierStyleInf">A</span> in the AVF) are used for monitoring.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="p6910" class="elsevierStylePara elsevierViewall">The available evidence refers to two published case series,<a class="elsevierStyleCrossRefs" href="#bib572"><span class="elsevierStyleSup">572,573</span></a> with an immediate clinical success rate of 89% and primary patency of 75% at 6 months, and a secondary patency of the access of 77% at 36 months.<a class="elsevierStyleCrossRef" href="#bib573"><span class="elsevierStyleSup">573</span></a></p><p id="s1695" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Proximal radial artery ligation</span></p><p id="p6915" class="elsevierStylePara elsevierViewall">Bourquelot et al.<a class="elsevierStyleCrossRef" href="#bib574"><span class="elsevierStyleSup">574</span></a> describes this technique, consisting of the ligation of the PRA (proximal radial artery ligation [PRAL]) adjacent to the anastomosis, as a method of limiting Q<span class="elsevierStyleInf">A</span> rate in radiocephalic AVF with high flow. This procedure significantly reduces flow in the access and maintains vascularisation of the hand and of the AVF through the ulnar artery via the palmar arch and collaterals of the interosseous artery.</p><p id="p6920" class="elsevierStylePara elsevierViewall">Initially proposed as a treatment for cases of high-flow radiocephalic AVF, the author describes the resolution of any associated ischaemic condition.<a class="elsevierStyleCrossRef" href="#bib574"><span class="elsevierStyleSup">574</span></a> There is no further evidence published on this technique.</p><p id="s1700" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Therapeutic management of distal hypoperfusion syndrome</span></p><p id="p6925" class="elsevierStylePara elsevierViewall">Given the abundance of treatment techniques described for DHS, most of them of a reconstructive nature (maintaining VA patency), several authors have published proposals on the therapeutic decision of choice in ischaemia treatment, depending on the characteristics presented by each technique.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88,543,545,549,556,566</span></a></p><p id="p6930" class="elsevierStylePara elsevierViewall">As mentioned earlier, the degree of severity of the symptoms should be established in DHS diagnosis, with stages I-IIa being susceptible to medical management and follow-up; in contrast, stages IIb-IV should be diagnosed and surgical correction proposed.</p><p id="p6935" class="elsevierStylePara elsevierViewall">The authors unanimously indicate access reconstruction in preference to its disconnection, except in the cases mentioned above<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88,549,566</span></a> (<a class="elsevierStyleCrossRef" href="#t26">Table 26</a>).</p><p id="p6940" class="elsevierStylePara elsevierViewall">Thus, in stages IIb-IV a diagnostic study must be carried out in order to propose the best therapeutic option. This study must necessarily include an angiographic assessment of limb vascularisation and a DU study of the VA.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,545</span></a></p><p id="p6945" class="elsevierStylePara elsevierViewall">Arteriography is necessary to rule out the presence of stenosis or occlusion in any sector of the vascular tree, and must include the assessment of both the proximal (brachycephalic trunk, subclavian, axillary and brachial artery) and distal arteries. The AVF must be compressed to allow evaluation of the distal trunks and the patency and development of the palmar arch.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,543,556</span></a> Likewise, the precise topography of the vascular tree is considered necessary to propose any type of reconstructive VA surgery.<a class="elsevierStyleCrossRef" href="#bib545"><span class="elsevierStyleSup">545</span></a></p><p id="p6950" class="elsevierStylePara elsevierViewall">DU examination, as well as haemodynamic assessment of the access (inversion of flow in the distal artery, presence of accelerations, calculation of resistive indices, diameter of the anastomosis), should include the calculation of Q<span class="elsevierStyleInf">A</span> in the VA, which is essential information required to propose the appropriate treatment in each case.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88</span></a></p><p id="s1705" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Arterial pathology</span></p><p id="p6955" class="elsevierStylePara elsevierViewall">If the presence of significant arterial lesions is diagnosed in the segment proximal to the AVF, the authors agree to recommend percutaneous treatment, usually during the same diagnostic procedure.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,543,545,556</span></a> The resolution of the ischaemic condition has been described in most patients treated with this type of lesion.<a class="elsevierStyleCrossRefs" href="#bib556"><span class="elsevierStyleSup">556,575</span></a></p><p id="s1710" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal hypoperfusion syndrome in the high-flow vascular access</span></p><p id="p6960" class="elsevierStylePara elsevierViewall">DHS associated with a VA with high Q<span class="elsevierStyleInf">A</span> (> 800 mL/m for nAVF and > 1000 mL/m for pAVF) indicates the prevailing presence of haemodynamic steal phenomenon, due to the short circuit created when connecting the high pressure and high resistance arterial system to the venous system, of low peripheral resistance. In these cases, the logical proposal is one which reduces AVF flow, an option proposed by most authors.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,543,549,558,559</span></a></p><p id="p6965" class="elsevierStylePara elsevierViewall">Thus, the techniques posited for the treatment of DHS in these patients are banding with flow monitoring, endovascular banding (MILLER) and revascularisation using distal inflow (RUDI). The three have proven to be safe techniques with a high percentage of technical and clinical success,<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,545</span></a> although no publications determine differences in effectiveness between them. Consequently, recommendations of the different authors are primarily based on personal experience. However, it has been suggested that the reduction of Q<span class="elsevierStyleInf">A</span> in the VA of banding with monitoring is more effective in the cases of AVF with very high output, thanks to the intra-operative monitoring of the technique, which is why it is especially recommended in these cases.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="s1715" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal hypoperfusion syndrome in low flow vascular access</span></p><p id="p6970" class="elsevierStylePara elsevierViewall">The pathophysiology of cases of ischaemia associated with medium and low Q<span class="elsevierStyleInf">A</span> accesses (< 800 mL/min in nAVF and < 1000 mL/m in pAVF) is not considered to have direct relation to the existing vascular short circuit, but depends primarily on a failure in the physiological compensatory processes that maintain distal tissue perfusion in this type of patients.<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,88</span></a> For this reason, the main objective in these cases is not to effectively reduce the access flow, but improve perfusion pressure in the distal vascular bed.</p><p id="p6975" class="elsevierStylePara elsevierViewall">The techniques used to do this are PAI and distal revascularisation with interval ligation (DRIL) or without ligation of the arterial interval (DR).</p><p id="p6980" class="elsevierStylePara elsevierViewall">In this case, there are also no published studies in the literature comparing the effectiveness of these techniques, so the available evidence is based on case series and expert opinion.</p><p id="p6985" class="elsevierStylePara elsevierViewall">The most widespread technique, DRIL, was shown to be a safe technique with good outcomes,<a class="elsevierStyleCrossRefs" href="#bib87"><span class="elsevierStyleSup">87,561</span></a> besides being the technique that provides a greater increase in the perfusion pressure in the distal territory in experimental models.<a class="elsevierStyleCrossRef" href="#bib564"><span class="elsevierStyleSup">564</span></a> Its main drawback is the need for autologous material for revascularisation and, secondly, disconnection on an axial artery. As a result, some authors have suggested not ligating the interval if the bypass anastomosis is proximalised.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="p6990" class="elsevierStylePara elsevierViewall">PAI is also a safe technique with good outcomes, and is recommended by several authors<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,565</span></a> as it does not require ligation of the artery. It has, however, the disadvantage of introducing prosthetic material in nAVF.</p><p id="p6995" class="elsevierStylePara elsevierViewall">In spite of the above, the current level of evidence for these techniques makes it necessary to conduct further studies to help define their suitability in clinical practice.</p><p id="s1720" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal hypoperfusion syndrome in the distal accesses</span></p><p id="p7000" class="elsevierStylePara elsevierViewall">The presentation of DHS in distal accesses (forearm and wrist) is uncommon<a class="elsevierStyleCrossRefs" href="#bib87b"><span class="elsevierStyleSup">87b,545</span></a> because, in the first place, the smaller diameter of the radial artery predisposes development of high Q<span class="elsevierStyleInf">A</span> in the VA to a lesser extent; secondly, the ulnar and interosseous arteries have excellent collaterality that compensates steal phenomenon in these patients. Due to its low incidence, special emphasis must be placed on differential diagnosis, in order to rule out the presence of other conditions, especially neurological (carpal tunnel syndrome, post-surgical neuropathy). Likewise, the degree of impact of ischaemia is usually mild in most cases, so treatment is only required in a few cases.<a class="elsevierStyleCrossRef" href="#bib545"><span class="elsevierStyleSup">545</span></a></p><p id="p7005" class="elsevierStylePara elsevierViewall">Two techniques are essentially described for treatment: DRAL and PRAL. In both, available evidence in the literature is limited. The best available evidence in the case of DRAL is the study of 15 cases published by Miller et al.,<a class="elsevierStyleCrossRef" href="#bib571"><span class="elsevierStyleSup">571</span></a> which describes a clinical success rate at 9 months of 87%, without any loss of the access in any case. In PRAL, the best evidence comes from Bourquelot et al.,<a class="elsevierStyleCrossRef" href="#bib574"><span class="elsevierStyleSup">574</span></a> consisting of a case series where the technique is only used in 2 cases due to DHS symptomatology; it is mainly indicated by the existence of high-flow syndrome.</p><p id="s1725" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p7010" class="elsevierStylePara elsevierViewall">DHS is a condition with multifactorial aetiology and complex haemodynamics, triggered by AVF creation in the limb, with a consequent short circuit between the arterial and venous systems. Although inverted flow is detected in the distal artery in most patients with AVF, only in some cases does a clinically relevant ischaemia develop.</p><p id="s1730" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Therapeutic management of distal hypoperfusion syndrome</span></p><p id="p7015" class="elsevierStylePara elsevierViewall">When DHS develops, there is no difference between authors in relation to recommending surgical/interventional treatment in cases of severe ischaemia, with invalidating symptomatology or that jeopardises tissue viability, an opinion based on good clinical practice. Likewise, the indication of conservative treatment and evolutionary control in cases with mild non-disabling symptoms is also widely accepted, since in most patients with mild clinical symptoms after access creation, the condition progressively improves, with a tendency to spontaneous resolution.<a class="elsevierStyleCrossRef" href="#bib87b"><span class="elsevierStyleSup">87b</span></a></p><p id="p7020" class="elsevierStylePara elsevierViewall">The indication of technique of choice in each case must be determined by severity of the condition, Q<span class="elsevierStyleInf">A</span> of the access, anatomical characteristics and location of the VA. Several of these techniques are documented as safe techniques with low morbidity, which is why good clinical practice currently recommends the priority reconstruction of access prior to ligature, a technique restricted to the cases shown (<a class="elsevierStyleCrossRef" href="#f6">Figure 6</a>).</p><elsevierMultimedia ident="f6"></elsevierMultimedia><p id="p7025" class="elsevierStylePara elsevierViewall">The evidence surrounding surgical techniques available for reconstructing the access, as mentioned, is based on case series and expert opinion, but there are no studies comparing the different techniques with each other.</p><p id="s1735" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Arterial pathology</span></p><p id="p7030" class="elsevierStylePara elsevierViewall">Based on experience from case series, most authors first recommend angiographic assessment of the arterial tree and percutaneous management of the significant stenosis present. It has been decided to adopt this recommendation given the clinical evidence showing improvement in ischaemic symptoms after PTA of the significant stenosis, its minimal invasiveness, high technical success rate and lack of evidence on surgery in the treatment of this condition.</p><p id="s1740" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal hypoperfusion syndrome in the high-flow arteriovenous fistula</span></p><p id="p7035" class="elsevierStylePara elsevierViewall">In high-Q<span class="elsevierStyleInf">A</span> AVF, most authors recommend the implementation of a technique that prioritises reducing AVF flow. Thus, the techniques of choice are banding with flow monitoring, MILLER and RUDI. Surgical banding (with Q<span class="elsevierStyleInf">A</span> monitoring) is the most broadly documented, but at present there are no studies comparing techniques, so a recommendation cannot be made on the technique of choice based on the available evidence.</p><p id="p7040" class="elsevierStylePara elsevierViewall">When performing banding, GEMAV considers that the available evidence advises against its use in isolation (without Q<span class="elsevierStyleInf">A</span> monitoring), because it has low VA patency versus other techniques. Thus we recommend this intervention always be associated with intra-operative Q<span class="elsevierStyleInf">A</span> monitoring of VA.</p><p id="s1745" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal hypoperfusion syndrome in the low flow arteriovenous fistula</span></p><p id="p7045" class="elsevierStylePara elsevierViewall">When DHS is present in a VA with normal or low flow, treatment must aim to increase distal perfusion pressure. Among the techniques described (DRIL, PAI and DR), DRIL is the technique with the highest degree of evidence, where it has proved to be a safe technique with a high index of clinical success and VA patency. PAI results are similar to DRIL although there are few published case series, while DR has to date been poorly represented in the literature. As there is no evidence from studies comparing results between these procedures, the GEMAV considers that although there is sufficient evidence to justify the use of both techniques (DRIL and PAI), a firm recommendation on the technique of choice in these cases cannot be made at present, and further studies are needed.</p><p id="s1750" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Distal hypoperfusion syndrome in distal accesses</span></p><p id="p7050" class="elsevierStylePara elsevierViewall">As previously mentioned, DHS very rarely develops in these cases and in most cases only presents with light intensity. Consequently, available evidence does not allow any recommendation on the technique of choice to be proposed to treat the condition. Having said this, DRAL is the most widely documented technique in the scarce bibliography, and shows good outcomes in terms of safety, clinical success and VA patency.</p><p id="p7055" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0205"></elsevierMultimedia></p></span><span id="se1785" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">5.6</span><span class="elsevierStyleSectionTitle" id="sect1760">Aneurysms and pseudoaneurysms</span><p id="sect1765" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p7090" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0210"></elsevierMultimedia></p><p id="sect1770" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p7130" class="elsevierStylePara elsevierViewall">The formation of aneurysmal dilatations and pseudoaneurysms is a potentially serious complication that can develop in any AVF. True aneurysms are defined as dilatations or ectasias in vessels in the fistula territory that maintain the entire structure of the venous or arterial wall. In contrast, pseudoaneurysms or false aneurysms are known to be expandable dilatations caused by persistent bleeding through a loss of wall continuity in the nAVF and pAVF, which can be located at the needling site or in anastomosis.</p><p id="s1775" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">5.6.1 True aneurysms</span></p><p id="p7135" class="elsevierStylePara elsevierViewall">The dilatation of a vessel above its normal size is known as true aneurysm. Depending on morphology, these may be saccular (eccentric dilatation) or fusiform (concentric dilatation), the latter being almost exclusively related to the VA, and may develop both in the arterial territory of the feeding artery and in the drainage vein.</p><p id="s1780" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Definition and incidence</span></p><p id="p7140" class="elsevierStylePara elsevierViewall">Following AVF creation, normal physiological response comprises an increase in size, both of the artery and the venous pathway. The increase in the venous system may frequently lack uniformity, but have alternating segments of variable diameter. It is therefore difficult to define the term.</p><p id="p7145" class="elsevierStylePara elsevierViewall">There are definitions based on the absolute value of the vessel diameter (> 20-30 mm),<a class="elsevierStyleCrossRefs" href="#bib576"><span class="elsevierStyleSup">576,577</span></a> on the increase in size versus the preceding segment (increments of 2-3 times the previous diameter),<a class="elsevierStyleCrossRefs" href="#bib576"><span class="elsevierStyleSup">576,578</span></a> on the sum of longitudinal and transverse diameters of the dilatation,<a class="elsevierStyleCrossRef" href="#bib579"><span class="elsevierStyleSup">579</span></a> and even on vessel volume.<a class="elsevierStyleCrossRef" href="#bib580"><span class="elsevierStyleSup">580</span></a> Finally, other authors recommend a wide acceptance of the term, defining it as an “abnormal” dilatation of the vessel.<a class="elsevierStyleCrossRef" href="#bib581"><span class="elsevierStyleSup">581</span></a></p><p id="p7150" class="elsevierStylePara elsevierViewall">Given the different criteria used in its definition, incidence varies between 5% and 60%, depending on the studies published.<a class="elsevierStyleCrossRef" href="#bib581"><span class="elsevierStyleSup">581</span></a></p><p id="s1785" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Venous aneurysms</span></p><p id="p7155" class="elsevierStylePara elsevierViewall">As discussed above, following AVF creation, dilation of the drainage veins is a physiological and necessary response for the VA to function correctly.</p><p id="p7160" class="elsevierStylePara elsevierViewall">There are, however, certain circumstances that can cause anomalous and excessive dilatation of the vein. It can occur, firstly, due to a weakness in the vessel wall, as in patients with renal polycystic disease and in Alport’s syndrome, or because of an increase in endoluminal vessel pressure, as occurs when stenosis develops in a proximal venous segment and in AVF with long-term evolution.<a class="elsevierStyleCrossRefs" href="#bib579"><span class="elsevierStyleSup">579,581,582</span></a></p><p id="p7165" class="elsevierStylePara elsevierViewall">Repeated cannulation of the same vein segment may also cause a weakness in the wall that predisposes to ectasia, a phenomenon known as <span class="elsevierStyleItalic">unipuncturitis</span> (1-site-itis), and is usually detected in clinical practice.<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a></p><p id="p7170" class="elsevierStylePara elsevierViewall">A possible protective effect of diabetes mellitus on the formation of aneurysms has been reported in several published studies, probably in relation to the arterial system’s lower capacity to cause high flow, which occurs in these patients.<a class="elsevierStyleCrossRef" href="#bib579"><span class="elsevierStyleSup">579</span></a> In contrast, the mechanisms by which the use of the <span class="elsevierStyleItalic">buttonhole technique</span> appears to prevent the occurrence of aneurysms is unknown.<a class="elsevierStyleCrossRefs" href="#bib240"><span class="elsevierStyleSup">240,581</span></a></p><p id="p7175" class="elsevierStylePara elsevierViewall">The diagnosis is essentially clinical, and scanning with DU is useful to determine the diameter and presence of endoluminal thrombus.</p><p id="p7180" class="elsevierStylePara elsevierViewall">The presence of one or several venous dilatations in the cannulation trajectory does not usually require any intervention, given the benign and stationary nature of the process, which is usually stable for a long time.<a class="elsevierStyleCrossRef" href="#bib581"><span class="elsevierStyleSup">581</span></a></p><p id="p7185" class="elsevierStylePara elsevierViewall">Treatment is indicated when cutaneous changes can be seen, such as signs of cutaneous atrophy, erosions, appearance of inflammation or presence of eschars, which are signs that predict the risk of bleeding. AVF bleeding is the main complication of venous aneurysms; bleeding can be massive, putting the patient’s life at risk in the short term. Other indications of treatment include aneurysm thrombosis, venous hypertension, high flow, and cosmetic reasons.<a class="elsevierStyleCrossRefs" href="#bib576"><span class="elsevierStyleSup">576,583</span></a></p><p id="p7190" class="elsevierStylePara elsevierViewall">Bleeding due to VA breakage is a life-threatening emergency, so emergency surgery is indicated. The priority must be to control the bleeding, and, if possible, to preserve the VA.<a class="elsevierStyleCrossRef" href="#bib581"><span class="elsevierStyleSup">581</span></a> On remaining occasions, the main purpose of surgical correction should be to preserve the correct VA function, except in cases where the access is not in use, in which case ligation is indicated.<a class="elsevierStyleCrossRef" href="#bib576"><span class="elsevierStyleSup">576</span></a></p><p id="p7195" class="elsevierStylePara elsevierViewall">A wide variety of surgical techniques has been described for the treatment of venous aneurysms.<a class="elsevierStyleCrossRef" href="#bib581"><span class="elsevierStyleSup">581</span></a> All of them are described in published case series, and there are currently no studies comparing them to each other. The technique of choice, therefore, is determined by the patient’s individual characteristics and by the anatomy of each VA.</p><p id="p7200" class="elsevierStylePara elsevierViewall">These techniques include exclusion of the aneurysm (with or without excision of the aneurysm) with autologous or prosthetic graft interposition,<a class="elsevierStyleCrossRefs" href="#bib576"><span class="elsevierStyleSup">576,584</span></a> excision with direct end-to-side anastomosis,<a class="elsevierStyleCrossRef" href="#bib585"><span class="elsevierStyleSup">585</span></a> partial resection of the aneurysm<a class="elsevierStyleCrossRefs" href="#bib584"><span class="elsevierStyleSup">584,586,587</span></a> as well as different types of aneurysmorrhaphy.<a class="elsevierStyleCrossRefs" href="#bib585"><span class="elsevierStyleSup">585,588-590</span></a></p><p id="p7205" class="elsevierStylePara elsevierViewall">The percutaneous treatment of venous aneurysm consists of the placement of a covered stent (endoprosthesis) in the involved segment.<a class="elsevierStyleCrossRefs" href="#bib581"><span class="elsevierStyleSup">581,591</span></a> It offers the possibility of treating associated stenoses in the same act, without the need for CVC placement. In contrast, its drawbacks include possible difficulty in needling the stent-bearing segment and it is also often necessary to associate a partial aneurysm excision procedure or an aneurismorrhaphy to allow vessel cannulation. Despite the good results reported in published case series,<a class="elsevierStyleCrossRef" href="#bib592"><span class="elsevierStyleSup">592</span></a> at present the degree of evidence on the use of these devices does not allow recommending their systematic use, and further studies are needed to determine the indications of this technique.</p><p id="s1790" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Arterial aneurysms</span></p><p id="p7210" class="elsevierStylePara elsevierViewall">Aneurysmal degeneration in the afferent AVF artery is a rare complication after the access is created, with an estimated incidence of approximately 4.5% of all accesses. Its preferred site is in the distal segment of the brachial artery.<a class="elsevierStyleCrossRef" href="#bib593"><span class="elsevierStyleSup">593</span></a></p><p id="p7215" class="elsevierStylePara elsevierViewall">Its appearance is triggered by high Q<span class="elsevierStyleInf">A</span> in the AVF, which is also directly related to the time taken for the access to develop. Finally, several studies have reported a higher frequency in patients with renal transplantation, related to the possible effect of immunosuppressive drugs on the vessel wall. The progressive dilation of the artery has also been observed in these patients, even after the ligature of the access.<a class="elsevierStyleCrossRefs" href="#bib577"><span class="elsevierStyleSup">577,594</span></a></p><p id="p7220" class="elsevierStylePara elsevierViewall">It may present clinically as an asymptomatic pulsatile tumour in a third of cases, whereas, on other occasions, symptomatology may comprise symptoms derived from the compression of the median nerve, in the form of neuropathic pain and/or paraesthesia, compression pain from other neighbouring structures, oedema or ischaemia symptoms associated with distal embolisation. Contrary to what happens in other locations, rupture of an aneurysm is a rare complication.<a class="elsevierStyleCrossRefs" href="#bib577"><span class="elsevierStyleSup">577,593,594</span></a></p><p id="p7225" class="elsevierStylePara elsevierViewall">Diagnosis of suspicion is based on physical examination, while a DU confirms the diagnosis, offering information on the diameter, length and presence of intraluminal thrombus.</p><p id="p7230" class="elsevierStylePara elsevierViewall">Surgery is indicated by the presence of associated complications and in large aneurysms (> 30 mm) in cases that are technically feasible.<a class="elsevierStyleCrossRef" href="#bib577"><span class="elsevierStyleSup">577</span></a></p><p id="p7235" class="elsevierStylePara elsevierViewall">As it is rare and in many cases is asymptomatic, the evidence in the literature regarding treatment is scarce, restricted to case series with a limited number of patients.</p><p id="p7240" class="elsevierStylePara elsevierViewall">The surgical technique of choice, according to most authors, is the resection of the aneurysm maintaining arterial continuity through direct suture between the proximal and distal artery segments to the ectasia, thus avoiding the interposition of autologous or prosthetic material. If this option is technically not feasible, the use of autologous material (internal saphenous vein or veins of the affected limb) is recommended to revascularise the arterial tree, while the possibility of using prosthetic material (ePTFE) is usually reserved as a last option due to risk of infection and lower patency. The published results of the explained techniques are excellent in terms of patency and clinical success, and symptomatology has been resolved in all cases described.<a class="elsevierStyleCrossRefs" href="#bib577"><span class="elsevierStyleSup">577,593-595</span></a></p><p id="s1795" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">5.6.2 Pseudoaneurysms or false aneurysms</span></p><p id="p7245" class="elsevierStylePara elsevierViewall">The denomination of pseudoaneurysm refers to the presence of a haematoma which communicates with the lumen of the vessel. It differs from true aneurysm in that the wall of the dilatation is not composed of the usual layers that can be found in the vessel; it is a wall of fibrous tissue and organised haematoma created around a cavity with flow present.<a class="elsevierStyleCrossRef" href="#bib596"><span class="elsevierStyleSup">596</span></a> This is why they are also commonly called false aneurysms or pulsatile haematomas, which are synonymous terms.</p><p id="p7250" class="elsevierStylePara elsevierViewall">In the genesis of the false aneurysm, there is always a loss of integrity in the vessel wall or in the anastomosis, which leads to a leakage of flow to the adjacent tissue, a leak contained by the presence of the haematoma and the fibrous tissue mentioned, thereby determining the possibility of a rapid and expansive growth.<a class="elsevierStyleCrossRef" href="#bib583"><span class="elsevierStyleSup">583</span></a></p><p id="p7255" class="elsevierStylePara elsevierViewall">They are usually caused by traumatic needling in the venous pathway or to repeated needling in the same area in pAVF. When it presents in arteriovenous anastomosis, following VA creation, it is usually caused by a lack of sealing in the anastomosis, whereas late presentation is usually due to active infection in the VA.<a class="elsevierStyleCrossRef" href="#bib581"><span class="elsevierStyleSup">581</span></a></p><p id="p7260" class="elsevierStylePara elsevierViewall">Diagnosis of suspicion is clinical (presence of a rapidly growing pulsatile tumour with presence of haematoma/ecchymosis in the adjacent skin), while DU exploration confirms the diagnosis, and also allows the size of the pseudoaneurysm to be measured.</p><p id="p7265" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XXII In native and prosthetic arteriovenous fistula pseudoaneurysm, when is surgery versus percutaneous versus conservative management indicated, assessed in terms of severe bleeding complications or death?</span></p><p id="p7270" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XXII in <a href="https://static.elsevier.es/nefroguiaaveng/22_PCXXII_Pseudoaneurisma_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0110"></elsevierMultimedia></p><p id="s1800" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p7275" class="elsevierStylePara elsevierViewall">False aneurysms or pseudoaneurysms make up 2%-10% of pAVF. They may or may not be infectious, and can be located in an anastomosis or in repeated cannulation sites and where prosthetic material has deteriorated.</p><p id="p7280" class="elsevierStylePara elsevierViewall">No study was found comparing different treatment approaches to pseudoaneurysm in nAVF and pAVF (surgery versus percutaneous versus conservative management). The available studies are of very low quality, as they are only based on case series that analyse the effect of a single mode of treatment, without a comparison group.</p><p id="p7285" class="elsevierStylePara elsevierViewall">Likewise, the results obtained according to AVF type (nAVF or pAVF) and the location of the pseudoaneurysm (needling or anastomotic area) are not disaggregated in most published series.</p><p id="s1805" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Treatment of post-cannulation pseudoaneurysm in the native arteriovenous fistula</span></p><p id="p7290" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Conservative management: external manual compression guided by ultrasound</span></p><p id="p7295" class="elsevierStylePara elsevierViewall">Ultrasound-guided compression is routinely used in the treatment of post-cannulation arterial pseudoaneurysms, and its usefulness has been widely reported in the published literature.<a class="elsevierStyleCrossRef" href="#bib597"><span class="elsevierStyleSup">597</span></a></p><p id="p7300" class="elsevierStylePara elsevierViewall">Although the technique is widely used to treat pseudoaneurysms in autologous VA, there is very little evidence currently available, with reference to the publication of case series.<a class="elsevierStyleCrossRefs" href="#bib597"><span class="elsevierStyleSup">597,598</span></a> In these series, it is described as a safe and effective non-invasive technique that should be tried before resorting to surgical or endovascular treatment, with successful outcomes in 64% to 90% of patients.</p><p id="p7305" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Surgery</span></p><p id="p7310" class="elsevierStylePara elsevierViewall">The surgical technique of choice should be decided on a case-by-case basis, although in most pseudoaneurysms requiring surgery, it consists of manual drainage of the haematoma and direct suture of the leakage point, and may be performed with or without placement of a proximal tourniquet (surgery with ischaemia tourniquet).<a class="elsevierStyleCrossRef" href="#bib599"><span class="elsevierStyleSup">599</span></a></p><p id="p7315" class="elsevierStylePara elsevierViewall">There are no case series published with data from post-cannulation pseudoaneurysms in nAVF treated exclusively with surgery; all of them bring together cases of post-cannulation pseudoaneurysms, anastomotic and pAVF, in addition to reporting various surgical techniques.<a class="elsevierStyleCrossRefs" href="#bib585"><span class="elsevierStyleSup">585,599-601</span></a> Thus, the study of Zheng et al.<a class="elsevierStyleCrossRef" href="#bib600"><span class="elsevierStyleSup">600</span></a> describes surgery results in 20 pseudoaneurysms in AVF, with technical success in all cases and primary patency of 95%, leading the authors to consider surgery as the best option to repair pseudoaneurysms in fistulae. Georgiadis et al.<a class="elsevierStyleCrossRef" href="#bib601"><span class="elsevierStyleSup">601</span></a> evaluate surgery in 28 pseudoaneurysms in nAVF and pAVF, with primary patency of 75% at 6 months. In the study of Belli et al.,<a class="elsevierStyleCrossRef" href="#bib585"><span class="elsevierStyleSup">585</span></a> the results of the different processes are also not disaggregated. However, throughout the literature, regarding the outcomes of post-cannulation pseudoaneurysm, surgery offers a technical success rate of 100%.</p><p id="p7320" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Percutaneous treatment</span></p><p id="p7325" class="elsevierStylePara elsevierViewall">As in the other treatment modes, there is scant evidence of percutaneous ultrasound-guided treatment with thrombin injection for pseudoaneurysms in nAVF, which mostly refers to the treatment of pseudoaneurysms in other locations. With a technical success of 80%, Ghersin et al.<a class="elsevierStyleCrossRef" href="#bib602"><span class="elsevierStyleSup">602</span></a> recommend this treatment mode in anatomically favourable cases, based on minimal invasiveness and good technical outcome.</p><p id="p7330" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Endovascular treatment</span></p><p id="p7335" class="elsevierStylePara elsevierViewall">The endovascular treatment described consists of the placement of a stent or endoprosthesis at the point of leakage to seal it.<a class="elsevierStyleCrossRef" href="#bib603"><span class="elsevierStyleSup">603</span></a> As with the other therapeutic options, there is little evidence currently published, in series dealing with a very limited number of cases, with only 17 cases reported.<a class="elsevierStyleCrossRefs" href="#bib603"><span class="elsevierStyleSup">603-605</span></a></p><p id="p7340" class="elsevierStylePara elsevierViewall">These studies describe a technical success of 90-100%, with a primary patency of 70% to 90% at 6 months, without the availability of disaggregated statistics of the infection rate.<a class="elsevierStyleCrossRefs" href="#bib603"><span class="elsevierStyleSup">603-605</span></a></p><p id="s1810" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Treatment of post-cannulation pseudoaneurysm in the prosthetic arteriovenous fistula</span></p><p id="p7345" class="elsevierStylePara elsevierViewall">Repeated cannulation of a vascular prosthesis causes persistent structural damage in the wall of the ePTFE structure. This damage accumulates in space and time (accumulation of cannulations in the same segment, in prostheses with prolonged periods of use) and can lead to loss of structural integrity in the prosthetic wall.<a class="elsevierStyleCrossRef" href="#bib606"><span class="elsevierStyleSup">606</span></a></p><p id="p7350" class="elsevierStylePara elsevierViewall">It is for this reason that in clinical practice, pseudoaneurysms associated with repeated cannulation of a vascular prosthesis, and with or without infection of this prosthesis, can appear; these are subject to the same complication possibilities as nAVF (expansive growth, compression by neighbouring structures, spontaneous rupture).<a class="elsevierStyleCrossRef" href="#bib10"><span class="elsevierStyleSup">10</span></a></p><p id="p7355" class="elsevierStylePara elsevierViewall">Sometimes the diagnosis is a chance finding, as is the case of small pseudoaneurysms that can remain stable over time. In this case, conservative management can be carried out by ultrasound controls, avoiding the cannulation of the affected area in all circumstances.<a class="elsevierStyleCrossRef" href="#bib585"><span class="elsevierStyleSup">585</span></a></p><p id="p7360" class="elsevierStylePara elsevierViewall">In contrast, when the pseudoaneurysm presents a risk of developing potential complications, both clinical guidelines and expert opinion recommend its treatment. <a class="elsevierStyleCrossRef" href="#t27">Table 27</a> shows the main indications for treatment of prosthetic pseudoaneurysms.<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,585,607</span></a></p><elsevierMultimedia ident="t27"></elsevierMultimedia><p id="p7365" class="elsevierStylePara elsevierViewall">Because of the underlying disruption in the prosthesis wall, treatment must correct it. Both surgical and endovascular treatments have been described.</p><p id="p7370" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Surgical treatment</span></p><p id="p7375" class="elsevierStylePara elsevierViewall">The technique consists of excluding the affected segment, maintaining continuity of the circuit by performing a prosthetic bypass between the sectors proximal and distal to the lesion, through a new subcutaneous bed independent of the previous one.<a class="elsevierStyleCrossRef" href="#bib585"><span class="elsevierStyleSup">585</span></a></p><p id="p7380" class="elsevierStylePara elsevierViewall">Despite being the first standardised technique in the treatment of prosthetic pseudoaneurysm, the existing literature is scarce, and its evidence is limited to case series.<a class="elsevierStyleCrossRefs" href="#bib585"><span class="elsevierStyleSup">585,601</span></a> Georgiadis et al.<a class="elsevierStyleCrossRef" href="#bib601"><span class="elsevierStyleSup">601</span></a> describes primary patency of 78% at 6 months in the absence of significant technical complications.</p><p id="p7385" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Endovascular treatment</span></p><p id="p7390" class="elsevierStylePara elsevierViewall">The endovascular treatment of choice consists of the percutaneous deployment of a vascular endoprosthesis in order to seal the pathological prosthetic segment. Some authors recommend proceeding later with the drainage of the pseudoaneurysm thrombus by percutaneous puncture or surgical approach.<a class="elsevierStyleCrossRefs" href="#bib605"><span class="elsevierStyleSup">605,608</span></a> Contraindications are associated trophic skin lesions and the presence or suspicion of infection.<a class="elsevierStyleCrossRef" href="#bib607"><span class="elsevierStyleSup">607</span></a></p><p id="p7395" class="elsevierStylePara elsevierViewall">Characteristically, it is advantageous as it does not require surgical approach, and maintains the prosthesis functional and intact from the moment the procedure is performed, while the main drawback lies in the relatively high rate of associated infections (up to 42%).<a class="elsevierStyleCrossRef" href="#bib609"><span class="elsevierStyleSup">609</span></a></p><p id="p7400" class="elsevierStylePara elsevierViewall">Different studies support its clinical usefulness,<a class="elsevierStyleCrossRefs" href="#bib603"><span class="elsevierStyleSup">603-605,608-612</span></a> with a technical success rate of 85-100%, primary patency of 20-36% at 6 months, and secondary patency of 54-76%, slightly lower than those of surgical treatment.<a class="elsevierStyleCrossRef" href="#bib607"><span class="elsevierStyleSup">607</span></a> Prosthetic infection rate related to the procedure ranges from 23% to 42%. This high incidence is believed to be due, in most cases, to the presence of a prior subclinical infection associated with pseudoaneurysm.<a class="elsevierStyleCrossRefs" href="#bib607"><span class="elsevierStyleSup">607,609</span></a></p><p id="s1815" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Treatment of anastomotic pseudoaneurysm</span></p><p id="p7405" class="elsevierStylePara elsevierViewall">The presence of a pseudoaneurysm in the arteriovenous anastomosis of the AVF is due to the lack of sealing of the suture line. It can occur in two types of circumstances, depending on when it develops. Firstly, anastomotic pseudoaneurysm that appears after the intervention (hours or days after the access is created) is related to surgical technique, whereas after the post-operative period a leak in the anastomosis usually means the presence of a highly aggressive infection with colonisation of the suture line.<a class="elsevierStyleCrossRef" href="#bib581"><span class="elsevierStyleSup">581</span></a></p><p id="p7410" class="elsevierStylePara elsevierViewall">Repair of the pseudoaneurysm is indicated in both cases and must be done through surgical intervention. Placement of an endoprosthesis is contraindicated because of the high risk of infection.<a class="elsevierStyleCrossRef" href="#bib581"><span class="elsevierStyleSup">581</span></a> If it occurs in the post-operative period, surgery must be indicated with haemostasis of the leakage point, whereas if it occurs in relation to VA infection, the infected material must be removed and the AVF reconstructed if technically feasible,<a class="elsevierStyleCrossRef" href="#bib607"><span class="elsevierStyleSup">607</span></a> in accordance with the recommendations made in the section on VA infection treatment.</p><p id="p7415" class="elsevierStylePara elsevierViewall">In the case series published by Shojaiefard et al.<a class="elsevierStyleCrossRef" href="#bib599"><span class="elsevierStyleSup">599</span></a> on 8 patients with surgically treated anastomotic pseudoaneurysms, a technical success of 88% is reported with primary patency of 88% at 15 months. In the absence of complications, the procedure is considered viable, safe and cost-effective.</p><p id="s1820" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p7420" class="elsevierStylePara elsevierViewall">As discussed, the currently available evidence on the different therapeutic modes in false aneurysms is based on published case series of the different techniques, albeit without comparative studies. This makes it difficult to establish a criterion based exclusively on this evidence regarding which treatment option to recommend in each case. Recommendations have therefore unanimously been adopted on the basis of good practice by the members of GEMAV. Since these techniques have a good clinical success rate, the most important factor in determining their use has been the degree of procedural invasiveness, and the use of less aggressive techniques is firstly suggested.</p><p id="s1825" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Treatment of post-cannulation pseudoaneurysm in the native arteriovenous fistula</span></p><p id="p7425" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Manual external compression guided by ultrasound</span></p><p id="p7430" class="elsevierStylePara elsevierViewall">This technique, widely used in clinical practice, is the least complex option and can be applied immediately, while the diagnosis is being made by DU. Despite being one of the most widespread therapeutic options, the available evidence on its use is paradoxically scarce. However, for all of the above reasons, and in particular because it is the simplest and least invasive technique, it has been decided to suggest its use in the first instance, where technically feasible.</p><p id="p7435" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Percutaneous treatment</span></p><p id="p7440" class="elsevierStylePara elsevierViewall">The ultrasound-guided injection of thrombin in the pseudoaneurysm cavity is also a minimally invasive technique widely used in practice. Despite the limited published evidence on its use, it has been shown to be a safe technique with a high technical success rate, and has therefore been included as a second therapeutic option after manual compression.</p><p id="p7445" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Surgical treatment</span></p><p id="p7450" class="elsevierStylePara elsevierViewall">As it is the first type of treatment described, there is a greater number of published case series in the literature than in the previous cases. It is safe and has good outcomes in terms of technical success and patency of the procedure. Its main drawback is that it is a technique with a higher degree of invasiveness, so its indication is suggested when previous procedures are not technically feasible or after their failure.</p><p id="p7455" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Endovascular treatment</span></p><p id="p7460" class="elsevierStylePara elsevierViewall">Placement of intravascular stents and/or endoprostheses is another method that has proved useful in the treatment of AVF pseudoaneurysms. It is a minimally invasive technique and has good technical success rates; its disadvantage lies in the greater complexity in contrast to thrombin injection, lower patency in comparison to surgical treatment, as well as in the possibility of infection of the implanted prosthetic material. Finally, the greatest limitation for the placement of an endoprosthesis in AVF is due to the need for a favourable anatomy to achieve correct deployment, which restricts its use in clinical practice. As a result, its systematic use cannot be recommended for treatment in these cases.</p><p id="s1830" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Treatment of post-cannulation pseudoaneurysm in the prosthetic arteriovenous fistula</span></p><p id="p7465" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Surgical treatment</span></p><p id="p7470" class="elsevierStylePara elsevierViewall">Surgical treatment, despite the scarce existing literature, has traditionally been the only therapeutic option available, offering a high clinical success rate, without affecting the prognosis of the pAVF in terms of patency, with a low complication rate. Also, by excluding the affected segment and creating a new subcutaneous tunnel, it is possible to effectively resolve cases in which there is an undetected component of infection, so it remains the technique of choice in these cases. When the prosthetic segment that remains in situ is insufficient to allow correct cannulation, an immediate cannulation prosthesis should be put in place in order to avoid CVC placement.</p><p id="p7475" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Endovascular treatment</span></p><p id="p7480" class="elsevierStylePara elsevierViewall">The deployment of an endoprosthesis to seal the structural defect of the wall is a more recently introduced technique, despite which there are several published case series. This is a minimally invasive procedure, with a high rate of technical success and acceptable patency. In addition, the structural characteristics of the prostheses allow effective deployment in most cases.</p><p id="p7485" class="elsevierStylePara elsevierViewall">The presence of an active infection contraindicates use and makes it obligatory to assess risk/benefit placement on other occasions where infection has not been ruled out.</p><p id="s1835" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Treatment of anastomotic pseudoaneurysm</span></p><p id="p7490" class="elsevierStylePara elsevierViewall">Currently, the only viable therapeutic option in anastomotic pseudoaneurysms is surgery. Since this is a process that indicates active infection, it is recommended the intervention be proposed accordingly, as previously recommended in the section corresponding to the treatment of AVF infections.</p><p id="p7495" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0215"></elsevierMultimedia></p><p id="s1845" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Cannulation in the apical area of venous aneurysms</span></p><p id="p7525" class="elsevierStylePara elsevierViewall">The skin in areas above aneurysms is more prone to losing elasticity properties, healing power and barrier effect against infections. Therefore, it is more advisable to cannulate in areas of non-damaged skin and, if cannulation is needed in the aneurysm, it should be performed at its base. This avoids complications such as bleeding risk, both when cannulating and in haemostasis, poor healing with risk of scarring or necrosis, and infections.</p></span><span id="se1880" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect1850">5.7 High-flow syndrome</span><p id="sect1855" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p7530" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0220"></elsevierMultimedia></p><p id="sect1860" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p7550" class="elsevierStylePara elsevierViewall">Heart failure is the most common cardiovascular disease associated with CKD<a class="elsevierStyleCrossRef" href="#bib613"><span class="elsevierStyleSup">613</span></a> and is present in one third of patients undergoing HD,<a class="elsevierStyleCrossRef" href="#bib614"><span class="elsevierStyleSup">614</span></a> which involves a high risk of cardiovascular mortality for these patients.<a class="elsevierStyleCrossRef" href="#bib615"><span class="elsevierStyleSup">615</span></a> At the same time, up to 75% of patients with advanced chronic kidney disease have left ventricular hypertrophy at the beginning of dialysis, which is also a predictive variable of mortality.<a class="elsevierStyleCrossRef" href="#bib616"><span class="elsevierStyleSup">616</span></a> Heart failure in the HD patient differs from that of the non-uraemic patient due to several factors; among these, there stand out volume overload and Q<span class="elsevierStyleInf">A</span> of the VA, which could contribute to the development of heart failure.</p><p id="s1865" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Cardiovascular consequences of the arteriovenous fistula</span></p><p id="p7555" class="elsevierStylePara elsevierViewall">Several mechanisms have been proposed that could lead to the generation of cardiac pathology following AVF creation. Once created, there is a persistent reduction in blood pressure, arterial stiffness and peripheral resistance, which increases sympathetic nervous activity. This, in turn, increases cardiac frequency and contractility in order to maintain blood pressure, with the consequent increase in the ejection fraction and therefore cardiac output (CO), which can be increased by 10-25%.<a class="elsevierStyleCrossRefs" href="#bib617"><span class="elsevierStyleSup">617-620</span></a> Within days or weeks, blood volume and left ventricular end-diastolic volume and pressures increase. A greater increase in the CO can develop in about 3 months, with an increase in the mass and left ventricular size, as well as in the atrial size.<a class="elsevierStyleCrossRef" href="#bib621"><span class="elsevierStyleSup">621</span></a> A systolic and diastolic dysfunction, ventricular dilatation and reduction of the ejection fraction with an increase in pulmonary flow and subsequent pulmonary hypertension may progressively appear.<a class="elsevierStyleCrossRefs" href="#bib194"><span class="elsevierStyleSup">194,622</span></a> In fact, the incidence of pulmonary hypertension of up to 40% in the patient on HD with AVF has been described,<a class="elsevierStyleCrossRef" href="#bib623"><span class="elsevierStyleSup">623</span></a> in the context of high Q<span class="elsevierStyleInf">A</span>. However, it has been suggested that there may be an underlying dysfunction in pulmonary vascularisation in a uraemic environment which would cause AVF to precipitate the decompensation of the pulmonary circuit by causing a decrease in vasodilation.<a class="elsevierStyleCrossRef" href="#bib624"><span class="elsevierStyleSup">624</span></a></p><p id="p7560" class="elsevierStylePara elsevierViewall">This whole process would begin with cardiac remodelling at the expense of an eccentric left ventricular hypertrophy, in relation to volume overload, with a relatively normal wall thickening unlike concentric hypertrophy due to pressure overload.<a class="elsevierStyleCrossRef" href="#bib625"><span class="elsevierStyleSup">625</span></a> Hypertrophy and dilatation of the left ventricle, as adaptive phenomena in response to increased pressure and volume loading, usually occur in athletes, pregnant women, and in the growth period from childhood to adulthood. Volume overload produces an increase in systolic afterload which is associated with radial wall stress in the systolic phase, resulting in the addition of sarcomeres to the myocardial fibres predominantly with a serial pattern rather than in parallel. This myofibrillar elongation contributes to the enlargement of ventricular lumen and to eccentric rather than concentric hypertrophy.<a class="elsevierStyleCrossRefs" href="#bib626"><span class="elsevierStyleSup">626,627</span></a> But although ventricular dilatation may initially be adaptive, according to the Frank-Starling mechanism, progressive increase in ventricular volume, concomitant myocardial fibrosis, and relative myocardial ischaemia (even in the absence of coronary disease) may eventually result in an affectation of systolic contractility and to lead, in time, to cardiac failure.<a class="elsevierStyleCrossRef" href="#bib628"><span class="elsevierStyleSup">628</span></a> This ventricular remodelling has been associated with poor long-term prognosis in chronic renal failure.<a class="elsevierStyleCrossRef" href="#bib629"><span class="elsevierStyleSup">629</span></a></p><p id="p7565" class="elsevierStylePara elsevierViewall">The risk is potentially higher during the nAVF maturation period due to the haemodynamic changes that occur secondary to the large increase in Q<span class="elsevierStyleInf">A</span> caused by the nAVF,<a class="elsevierStyleCrossRef" href="#bib193"><span class="elsevierStyleSup">193</span></a> as well as during the first 120 days after starting HD, since the mortality rate is maximum within this period.<a class="elsevierStyleCrossRef" href="#bib630"><span class="elsevierStyleSup">630</span></a></p><p id="s1870" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Arteriovenous fistula flow and cardiac output</span></p><p id="p7570" class="elsevierStylePara elsevierViewall">High cardiac output in adults has been defined when it is > 8 L/min or a cardiac index > 3.9 L/min/m<span class="elsevierStyleSup">2</span>.<a class="elsevierStyleCrossRef" href="#bib631"><span class="elsevierStyleSup">631</span></a> The increase in CO is proportional to Q<span class="elsevierStyleInf">A</span>, which is usually between 1 and 2 L/min, in order to maintain adequate peripheral perfusion. If myocardial contractility is impaired, excess volume caused by Q<span class="elsevierStyleInf">A</span> in combination with inadequate peripheral compensatory vasoconstriction to maintain systemic blood pressure may lead to the onset of heart failure.<a class="elsevierStyleCrossRef" href="#bib632"><span class="elsevierStyleSup">632</span></a> Cases of patients with high symptomatic CO with Q<span class="elsevierStyleInf">A</span> 3-4 L/min and CO 7-10 L/min have been reported<a class="elsevierStyleCrossRefs" href="#bib360"><span class="elsevierStyleSup">360,633</span></a> where this relationship is evident. However, there are no clear criteria for defining a high-flow AVF, since the description of heart failure associated with chronic renal failure in high CO is limited and confined to case series.<a class="elsevierStyleCrossRefs" href="#bib360"><span class="elsevierStyleSup">360,634</span></a></p><p id="p7575" class="elsevierStylePara elsevierViewall">In a prospective study with 96 patients to describe the relationship between Q<span class="elsevierStyleInf">A</span> and CO, Basile et al.<a class="elsevierStyleCrossRef" href="#bib194"><span class="elsevierStyleSup">194</span></a> observed greater cardiac failure in the proximal AVF, describing a third-order polynomial regression as the best model to explain this relation, in which high-output heart failure could occur from values > 2 L/min. All 10 subjects who developed heart failure had Q<span class="elsevierStyleInf">A</span> of 2.3± 0.3 L/min, while in all other patients it was 1.0 ± 0.4 L/min. Other authors suggest that the Q<span class="elsevierStyleInf">A</span>/CO ratio may provide an estimate of the contribution of VA to CO, and if it is > 0.3, it may increase the risk of developing high output heart failure,<a class="elsevierStyleCrossRef" href="#bib635"><span class="elsevierStyleSup">635</span></a> or more specifically, if it is > 40%.<a class="elsevierStyleCrossRef" href="#bib636"><span class="elsevierStyleSup">636</span></a> Although it has not been confirmed with prospective studies and despite the scarce sample, it is suggested that it can be reasonably assumed from 2.0 L/min there is a predictive power of high CO heart failure, as well as a Q<span class="elsevierStyleInf">A</span>/CO ratio > 0.3. This could be a decompensatory factor for pre-existing cardiac failure and even lower flows could also decompensate for heart failure in patients with poor cardiac reserve.<a class="elsevierStyleCrossRefs" href="#bib637"><span class="elsevierStyleSup">637-639</span></a></p><p id="p7580" class="elsevierStylePara elsevierViewall">But this relationship of Q<span class="elsevierStyleInf">A</span> and CO is not demonstrated linearly from the clinical point of view. Wijnen et al.,<a class="elsevierStyleCrossRef" href="#bib640"><span class="elsevierStyleSup">640</span></a> like Basile et al.,<a class="elsevierStyleCrossRef" href="#bib194"><span class="elsevierStyleSup">194</span></a> noted that in patients without heart failure, CO is significantly higher among proximal AVF compared to distal AVF. However, only a small percentage of these proximal AVF are in a risk area for the development of high-output heart failure. At the same time, there are studies that demonstrate a low frequency of heart failure due to high Q<span class="elsevierStyleInf">A</span> in AVF (3.7%).<a class="elsevierStyleCrossRef" href="#bib641"><span class="elsevierStyleSup">641</span></a> Thus, the cause of evolution from left ventricular hypertrophy due to overload at heart failure is not clear. Therefore, some authors suggest, on the one hand, the participation of underlying heart disease<a class="elsevierStyleCrossRef" href="#bib625"><span class="elsevierStyleSup">625</span></a> and, on the other, possible participation of a high end-diastolic volume in the left ventricle.<a class="elsevierStyleCrossRef" href="#bib628"><span class="elsevierStyleSup">628</span></a> Indeed, it has been observed that Q<span class="elsevierStyleInf">A</span> > 2 L/min presents this greater tendency to a greater left ventricular end-diastolic volume<a class="elsevierStyleCrossRef" href="#bib642"><span class="elsevierStyleSup">642</span></a> and that flows < 2.2 L have no impact on CO.<a class="elsevierStyleCrossRef" href="#bib194"><span class="elsevierStyleSup">194</span></a> The causes of this behaviour are not known, but it can be hypothesised on the existence of some type of myocardial reserve that can allow the adaptation capable of supporting increases in Q<span class="elsevierStyleInf">A</span> in the long term without precipitating the occurrence of heart failure.<a class="elsevierStyleCrossRef" href="#bib637"><span class="elsevierStyleSup">637</span></a> For this reason, the aim would be to identify the patient with underlying heart disease with a higher risk of suffering the repercussions of a high flow on cardiac function in order to intervene.<a class="elsevierStyleCrossRefs" href="#bib639"><span class="elsevierStyleSup">639,643</span></a></p><p id="p7585" class="elsevierStylePara elsevierViewall">In this respect, although the relationship between AVF Q<span class="elsevierStyleInf">A</span> and CO is proven<a class="elsevierStyleCrossRef" href="#bib635"><span class="elsevierStyleSup">635</span></a> and there are studies that show AVF creation as the most determining factor for developing heart failure,<a class="elsevierStyleCrossRef" href="#bib193"><span class="elsevierStyleSup">193</span></a> no increase in mortality has been shown from the epidemiological point of view in relation to flow.<a class="elsevierStyleCrossRef" href="#bib644"><span class="elsevierStyleSup">644</span></a> There are even studies in which higher Q<span class="elsevierStyleInf">A</span> has been associated with less heart damage,<a class="elsevierStyleCrossRef" href="#bib645"><span class="elsevierStyleSup">645</span></a> and a reduction in peripheral resistance and blood pressure, with a parallel increase in ejection fraction which may be potentially beneficial.<a class="elsevierStyleCrossRef" href="#bib620"><span class="elsevierStyleSup">620</span></a> In this context, in an observational study of 4854 patients,<a class="elsevierStyleCrossRef" href="#bib646"><span class="elsevierStyleSup">646</span></a> the long-term association of the AVF with lower cardiovascular mortality of any type was demonstrated when compared to CVC use (p < 0.004), regardless of the comorbidity of both groups. This confirms the controversy surrounding the extent to which cardiac function is altered after AVF creation, given the presence of multiple confounding factors in these patients. In other words, whether the AVF contributes to the onset of heart failure, but from a limit, or it is an underlying heart disease that is decompensated by the AVF.<a class="elsevierStyleCrossRef" href="#bib647"><span class="elsevierStyleSup">647</span></a></p><p id="s1875" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Ligation of the arteriovenous fistula in the kidney transplant patient</span></p><p id="p7590" class="elsevierStylePara elsevierViewall">There is evidence to support the fact that there is a regression in the cardiac indexes after ligation or reduction in AVF Q<span class="elsevierStyleInf">A</span>. This has been demonstrated in transplanted patients who have undergone AVF ligation and have presented a regression in dilatation and in left ventricular mass<a class="elsevierStyleCrossRefs" href="#bib648"><span class="elsevierStyleSup">648,649</span></a> or a significant improvement in the ejection fraction.<a class="elsevierStyleCrossRef" href="#bib650"><span class="elsevierStyleSup">650</span></a> In addition, when comparing the effects of nAVF and pAVF, there are no differences in the increase in left ventricular measurements, suggesting that flow, rather than VA type, influences the development of high Q<span class="elsevierStyleInf">A</span>.<a class="elsevierStyleCrossRef" href="#bib651"><span class="elsevierStyleSup">651</span></a> These favourable results, however, have not been confirmed with clinical trials, so AVF ligation cannot be recommended in a standardised way in the asymptomatic transplanted patient.</p><p id="s1880" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Strategies to manage heart failure in relation to high flow of the arteriovenous fistula</span></p><p id="p7595" class="elsevierStylePara elsevierViewall">Management of symptomatic heart failure should be directed primarily to treat excess volume and symptoms medically, such as correction of anaemia and other treatable factors. In the absence of success, an attempt should be made to correct the cause of the high output. In this case, it would be necessary to reduce AVF flow, trying to preserve the VA. The same surgical techniques as those used to treat DHS in high-flow AVF reviewed in the previous section would apply. They would mainly include, on the one hand, banding or variants such as MILLER and, on the other, a new distal anastomosis (RUDI).<a class="elsevierStyleCrossRefs" href="#bib559"><span class="elsevierStyleSup">559,572,573,650,652-655</span></a> The aim, as in DHS, is to preserve AVF use and reduce heart failure, but bearing in mind, in the last instance, that AVF ligation should be performed when this reduction cannot be achieved.</p><p id="s1885" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Choosing arteriovenous type of in patients with cardiac pathology</span></p><p id="p7600" class="elsevierStylePara elsevierViewall">When planning AVF creation, it must be remembered that proximal AVF presents a higher Q<span class="elsevierStyleInf">A</span>. Thus, the risk must be weighed up in patients with underlying heart failure as they are more likely to present a worsening cardiac function with this type of access than in those who have a distal VA.<a class="elsevierStyleCrossRef" href="#bib640"><span class="elsevierStyleSup">640</span></a> This forces the choice of the most appropriate VA for each patient with heart failure, and should assess the risk of heart failure decompensation after AVF creation. In this respect, it has been suggested that patients with heart failure classified according to the New York Heart Association (NYHA) as class I-II could start HD through a distal nAVF (wrist or anatomical snuffbox)<a class="elsevierStyleCrossRefs" href="#bib646"><span class="elsevierStyleSup">646,656</span></a>; in patients with class III, the decision on the creation of a distal nAVF versus a tunnelled CVC placement or the transition to another dialysis technique, namely peritoneal, would have to be decided on a case-by-case basis according to the degree of cardiac affectation; and, finally, patients with heart failure and significant reduction in systolic function or class IV would be subject to CVC placement to initiate HD treatment or the choice of another dialysis technique.<a class="elsevierStyleCrossRefs" href="#bib646"><span class="elsevierStyleSup">646,656</span></a></p><p id="p7605" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XXIII In the high-flow arteriovenous fistula, what therapeutic approach should be taken and what are the criteria (risk factors)?</span></p><p id="p7610" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XXIII in <a href="https://static.elsevier.es/nefroguiaaveng/23_PCXXIII_alto_flujo_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0115"></elsevierMultimedia></p><p id="s1890" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="s1895" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Intervention criteria in the high-flow arteriovenous fistula</span></p><p id="p7615" class="elsevierStylePara elsevierViewall">Ideal HD AVF should work with a Q<span class="elsevierStyleInf">A</span> needed to prevent thrombosis while providing maximum efficiency for HD.<a class="elsevierStyleCrossRef" href="#bib657"><span class="elsevierStyleSup">657</span></a> Flows in the range of 600 to 1500 mL/min have been considered as optimum, with high-flow fistulae being classified as having flows between 1500 and 4000 mL/min.<a class="elsevierStyleCrossRef" href="#bib657"><span class="elsevierStyleSup">657</span></a></p><p id="p7620" class="elsevierStylePara elsevierViewall">Other authors<a class="elsevierStyleCrossRef" href="#bib658"><span class="elsevierStyleSup">658</span></a> consider that a flow between 400-600 mL/min in an arteriovenous fistula is generally sufficient to maintain effective HD. On the other hand, it is pointed out that although there is no consensus definition about when a flow can be considered high, a cut-off of 2000 mL/min is normally used since, as seen, some studies have found that heart failure is more frequent in HD patients with a Q<span class="elsevierStyleInf">A</span> of the VA above this threshold.</p><p id="p7625" class="elsevierStylePara elsevierViewall">The existence of a hyperfunctioning fistula with high Q<span class="elsevierStyleInf">A</span> has been associated with several potential problems: cardiac overload, cardiopulmonary recirculation, rapid access growth with formation of aneurysms, or recurrent venous stenosis resulting in VA failure.<a class="elsevierStyleCrossRef" href="#bib657"><span class="elsevierStyleSup">657</span></a> As already mentioned in previous sections, it may also cause distal hypoperfusion syndrome, as well as venous hypertension in the absence of central venous stenosis. After diagnosis of any of these situations, intervention should be performed to solve or mitigate the problem, while at the same time try to preserve VA.</p><p id="p7630" class="elsevierStylePara elsevierViewall">High Q<span class="elsevierStyleInf">A</span> is often detected by chance in a routine measurement<a class="elsevierStyleCrossRef" href="#bib658"><span class="elsevierStyleSup">658</span></a> that, if confirmed on repeated occasions, raises the question of whether to proceed to a flow reduction intervention. However, the decision to treat is controversial due to a lack of absolute criteria for starting it.</p><p id="p7635" class="elsevierStylePara elsevierViewall">No studies have been found comparing the clinical evolution of patients with high Q<span class="elsevierStyleInf">A</span> fistula, depending on whether they have been treated to reduce Q<span class="elsevierStyleInf">A</span> or not. The evidence available comes from expert opinions and case series, thus are of low quality.</p><p id="p7640" class="elsevierStylePara elsevierViewall">Recent reviews consider that the therapeutic approach should depend on each patient’s history and clinical condition.<a class="elsevierStyleCrossRefs" href="#bib657"><span class="elsevierStyleSup">657,658</span></a> For example, it makes sense for a patient with high Q<span class="elsevierStyleInf">A</span> in the AVF and with compromised cardiac function to undergo an intervention to reduce Q<span class="elsevierStyleInf">A</span> in the AVF, given that if this patient doesn’t, she/he may sooner or later develop an additional cardiac event. But it also seems a sensible decision not to intervene if a high Q<span class="elsevierStyleInf">A</span> is detected in an AVF in a young patient with normal cardiac function who is on the waiting list for a kidney transplant.</p><p id="p7645" class="elsevierStylePara elsevierViewall">It must not be forgotten that, in addition to cases related to distal hypoperfusion syndrome or cardiological repercussions of AVF, intervention may be required in patients who present aneurysms or with exaggerated AVF development, in cases of central venous stenosis, or when the difference between inflow and outflow causes inflammation in the arm and AVF dysfunction.<a class="elsevierStyleCrossRefs" href="#bib657"><span class="elsevierStyleSup">657,658</span></a></p><p id="s1900" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Treatment options</span></p><p id="p7650" class="elsevierStylePara elsevierViewall">As already comprehensively reviewed in the section of DHS, the main techniques that have been developed to reduce high Q<span class="elsevierStyleInf">A</span> in AVF are banding or one of its variants and RUDI.</p><p id="p7655" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Banding</span></p><p id="p7660" class="elsevierStylePara elsevierViewall">In the study published by Miller et al.,<a class="elsevierStyleCrossRef" href="#bib573"><span class="elsevierStyleSup">573</span></a> already discussed, with 183 patients treated with banding, in addition to the complete remission of symptoms in 109 of the 114 patients who had DHS, they also managed to achieve remission in 69 patients with high flow with diseases such as congestive heart failure, aneurysms and high venous pressure. The primary patency of the intervention at six months was 75% and 85%, respectively, for DHS and high flow. The secondary patency of the access at 24 months was 90% and 89% and thrombosis rates were 0.21, 0.10 and 0.92 per year with the access for nAVF of arm, forearm and pAVF, respectively.</p><p id="p7665" class="elsevierStylePara elsevierViewall">Moreover, two case series analyse the Miller banding technique in patients with central venous stenosis. Jennings et al.<a class="elsevierStyleCrossRef" href="#bib659"><span class="elsevierStyleSup">659</span></a> used banding in 22 patients with high flow and central venous occlusion with clinical repercussion in terms of inflammation of the limb. Inflammation disappeared immediately in 20 patients and showed sufficient improvement in the other two. The mean flow dropped from 1640 mL/min to 820 mL/min after the intervention (p < 0.01). Two of the AVF failed, one at 8 months and the other at 13 months.</p><p id="p7670" class="elsevierStylePara elsevierViewall">Miller et al.<a class="elsevierStyleCrossRef" href="#bib456"><span class="elsevierStyleSup">456</span></a> also analysed the effect of banding in 33 patients with stenosis of the brachiocephalic trunk followed up for a mean of 14.5 months. The reduction of the flow was from 2226 mL/min to 1225 mL/min, with a mean of 42%. Patency at 3, 6 and 12 months was 91%, 76% and 57%, respectively. The rate of interventions on the brachiocephalic trunk dropped from 3.34 to 0.9 per year of access.</p><p id="p7675" class="elsevierStylePara elsevierViewall">Schneider et al.<a class="elsevierStyleCrossRef" href="#bib660"><span class="elsevierStyleSup">660</span></a> describe a different mode of banding, T-banding, which aims to avoid possible movements of the graft, by a prosthesis that surrounds the vein in the post-anastomotic and the anastomotic zone. In a case series of 22 patients, 20 of them with heart failure, 6 of these patients also had DHS and two only DHS, a mean flow reduction of 44% (range 27-71%) was achieved, from a mean flow of 1956 mL/min to 983 mL/min one month following surgery. 72% of the patients showed complete improvement in symptoms and four, who presented partial improvement, required another intervention to achieve complete improvement. The procedure was successful in 95% (19/20) of patients with heart failure and in 83% of those with DHS (5/6). The access continued to be used in all patients, with primary patency of 90% and secondary patency of 100% at 1 month and 3 months.</p><p id="p7680" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Revascularisation using distal outflow</span></p><p id="p7685" class="elsevierStylePara elsevierViewall">Like the banding technique, RUDI can also be used for AVF with high flow, as mentioned above. Chemla describes a case series of 17 patients with symptoms of heart failure (15 nAVF and 2 pAVF)<a class="elsevierStyleCrossRef" href="#bib641"><span class="elsevierStyleSup">641</span></a> with Q<span class="elsevierStyleInf">A</span> > 1600 mL/min, on which the technique is performed, achieving a reduction in the flow from 3135 ± 692 to 1025 ± 551 mL/min (p = 0.0001). The decrease in CO was from 8 ± 3.1 to 5.6 ± 1.7 L/min (p = 0.001) achieving a resolution of symptoms. 7 stenosis or thrombosis were developed, of which 3 were submitted to surgical review.</p><p id="p7690" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Proximal radial artery ligation</span></p><p id="p7695" class="elsevierStylePara elsevierViewall">In a prospective study, Bourquelot et al.<a class="elsevierStyleCrossRef" href="#bib574"><span class="elsevierStyleSup">574</span></a> included 37 patients (8 children and 29 adults) who underwent PRAL to treat high flow in radiocephalic fistulae: 2 for ischaemia, 14 with aneurysmal degeneration of the vein, 7 for heart failure and 14 for the prevention of cardiac overload. The pre-operative Q<span class="elsevierStyleInf">A</span> in children of 1316 mL/min and 1736 mL/min in adults decreased by 50% and 53%, respectively. Primary patency rates at 1 and 2 years were 88% and 74%, and secondary patency, 88% and 78%, respectively.</p><p id="p7700" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Transposition of the radial artery</span></p><p id="p7705" class="elsevierStylePara elsevierViewall">Another study by Bourquelot et al.,<a class="elsevierStyleCrossRef" href="#bib448"><span class="elsevierStyleSup">448</span></a> in 47 patients with an AVF created on the brachial artery, transposed the distal radial artery to the elbow area, where it is anastomosed to the AVF, previously disconnected from the brachial artery in order to achieve a reduction in flow. Indications for treatment were hand ischaemia (4), heart failure (13), concern about future cardiac dysfunction (23) and chronic venous hypertension resulting in aneurysmal degeneration of the vein (7). Technical success was achieved in 91%. The mean reduction of flow was 66%, from an initial mean flow of 1681 mL/min. Clinical success in symptomatic patients was 75%. The fistula, however, had to be ligated in three cases of heart failure due to insufficient clinical improvement. Primary patency rates at 1 and 3 years were 61% and 40%, and secondary patency at 1 and 3 years were 89% and 70%.</p><p id="p7710" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Ultrasound-guided flow reduction surgery</span></p><p id="p7715" class="elsevierStylePara elsevierViewall">Tellioglu et al.<a class="elsevierStyleCrossRef" href="#bib661"><span class="elsevierStyleSup">661</span></a> analysed the role of Q<span class="elsevierStyleInf">A</span> reduction surgery by monitoring the flow by DU in 30 patients with high-flow AVF, 25 nAVF and 5 pAVF. The indications for the operation were heart failure (n = 18) or DHS (n = 12). The preoperative measurements of nAVF, pAVF and the diameter of the anastomosis were: 2663 mL/min (1856-3440 mL/min); 2751 mL/min (2140-3584 mL/min) and 7.3 mm (6.1-8.5 mm), respectively. The flow was reduced to 615 mL/min (552 - 810 mL/min) for nAVF and 805 mL/min (745-980 mL/min) for pAVF. The mean diameter of anastomosis was reduced to 4 mm (3.5-4.3 mm). There were no re-interventions. After a median of 1 year of follow-up, patency rates were 100% for nAVF and 80% for pAVF. Cardiac output rate decreased from 8.5 L/min to 6.1 L/min (p < 0.01).</p><p id="s1905" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p7720" class="elsevierStylePara elsevierViewall">VA impact is proportional to Q<span class="elsevierStyleInf">A</span>, while the development of heart failure symptomatology and high CO depends on both Q<span class="elsevierStyleInf">A</span> and adequate cardiac compensation capacity.</p><p id="p7725" class="elsevierStylePara elsevierViewall">In the event of heart failure, it should be suspected that the AVF is at least partly responsible when the patient’s heart symptoms worsen after the AVF creation, especially in VA with high Q<span class="elsevierStyleInf">A</span>, usually associated with proximal AVF. High values of Q<span class="elsevierStyleInf">A</span> should be considered when they are > 2 L/min and a Q<span class="elsevierStyleInf">A</span>/CO ratio > 0.3. In the asymptomatic patient, the risk of developing high-output cardiac failure may increase in the presence of these values, which is why these patients should be closely monitored.</p><p id="p7730" class="elsevierStylePara elsevierViewall">Likewise, anaemia, dry weight, and additional factors that may cause similar symptoms in this type of patient should also be monitored. Therefore, in the first place, the therapeutic approach should be based on medical management and treatment of volume excess in order to aim for surgical reduction of Q<span class="elsevierStyleInf">A</span> at a later stage and, in case of refractoriness, to AVF ligature.</p><p id="p7735" class="elsevierStylePara elsevierViewall">Although there is a limited number of case series, the main techniques that have demonstrated acceptable success in the reduction of flow, clinical improvement and VA patency are those based on banding or its variants and on RUDI.</p><p id="p7740" class="elsevierStylePara elsevierViewall">The patient’s underlying cardiovascular status should be taken into consideration before AVF is created. In NYHA class III patients, distal AVF should preferably be indicated on a case-by-case basis if peritoneal dialysis cannot be done, and CVC placement can be assessed; and in NYHA class IV, patients would need CVC and another dialysis technique.</p><p id="p7745" class="elsevierStylePara elsevierViewall">Although routine post-transplant ligation has shown good outcomes in the regression of cardiac affectation rates, it is not standardised. Thus, despite its favourable outcomes, clinical trials are needed before performing routine ligation in the stable transplanted patient.</p><p id="p7750" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0225"></elsevierMultimedia></p></span></span><span id="se1945" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleLabel">6</span><span class="elsevierStyleSectionTitle" id="sect1915"><span class="elsevierStyleSmallCaps">Central venous catheters</span></span><p id="p7765" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">CONTENTS</span><ul class="elsevierStyleList" id="list0580"><li class="elsevierStyleListItem" id="listi2410"><span class="elsevierStyleLabel">6.1.</span><p id="p7770" class="elsevierStylePara elsevierViewall">Indications</p></li><li class="elsevierStyleListItem" id="listi2415"><span class="elsevierStyleLabel">6.2.</span><p id="p7775" class="elsevierStylePara elsevierViewall">Catheter selection</p></li><li class="elsevierStyleListItem" id="listi2420"><span class="elsevierStyleLabel">6.3.</span><p id="p7780" class="elsevierStylePara elsevierViewall">Catheter insertion</p></li><li class="elsevierStyleListItem" id="listi2425"><span class="elsevierStyleLabel">6.4.</span><p id="p7785" class="elsevierStylePara elsevierViewall">Catheterisation control</p></li><li class="elsevierStyleListItem" id="listi2430"><span class="elsevierStyleLabel">6.5.</span><p id="p7790" class="elsevierStylePara elsevierViewall">Catheter handling</p></li><li class="elsevierStyleListItem" id="listi2435"><span class="elsevierStyleLabel">6.6.</span><p id="p7795" class="elsevierStylePara elsevierViewall">Catheter follow-up</p></li><li class="elsevierStyleListItem" id="listi2440"><span class="elsevierStyleLabel">6.7.</span><p id="p7800" class="elsevierStylePara elsevierViewall">Catheter-related complications</p></li><li class="elsevierStyleListItem" id="listi2445"><span class="elsevierStyleLabel">6.8.</span><p id="p7805" class="elsevierStylePara elsevierViewall">Catheter dysfunction</p></li><li class="elsevierStyleListItem" id="listi2450"><span class="elsevierStyleLabel">6.9.</span><p id="p7810" class="elsevierStylePara elsevierViewall">Catheter-related infections</p></li></ul></p><p id="sect1920" class="elsevierStylePara elsevierViewall">Preamble</p><p id="p7815" class="elsevierStylePara elsevierViewall">The use of central venous catheters (CVC) has risen progressively in patients undergoing haemodialysis (HD). However, the indications for their use should be limited because of increased complications, both thrombotic and infectious.</p><p id="p7820" class="elsevierStylePara elsevierViewall">Despite morbidity and mortality, CVC continue to be an essential vascular access (VA) for all Nephrology Departments. On the one hand, they allow immediate use after insertion, which makes it possible to perform HD in emergency situations when patients present serious clinical conditions, such as severe hyperkalaemia or acute pulmonary oedema. On the other hand, they provide definitive access in patients whose vascular bed is exhausted.</p><span id="se1955" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect1925">6.1. Indications</span><p id="s1930" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p7825" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0230"></elsevierMultimedia></p><p id="sect1935" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p7850" class="elsevierStylePara elsevierViewall">The use of CVC is an alternative to arteriovenous fistula (AVF) and, although the use of CVC is inadequate, there is no doubt that they play an important role in managing patients requiring HD. The first reason for this is that they can be used in theoretically any patient; secondly, they are placed easily and are available for use immediately after insertion. Two types of CVC are used in routine clinical practice: <span class="elsevierStyleItalic">a)</span> non-tunnelled central venous catheter (NTCVC), used primarily in acute situations, and <span class="elsevierStyleItalic">b)</span> tunnelled central venous catheter (TCVC), commonly used for long-term or permanent VA. NTCVC afford the following advantages: they are easy and rapid to place, can be inserted at the patient bedside using sterile Seldinger technique, do not require tunnelling, and there is minimal trauma. Although they provide a lower flow, they quickly access the vascular bed and do not require an image, which makes them very useful in emergency situations. TCVC were developed in 1987 as an alternative to NTCVC.<a class="elsevierStyleCrossRefs" href="#bib662"><span class="elsevierStyleSup">662,663</span></a> They are more complex to place and require imaging techniques to ensure tip location and absence of kinking. However, they present a lower rate of complications and reach higher flows, so they are the preferred choice for prolonged periods of time.</p><p id="p7855" class="elsevierStylePara elsevierViewall">However, despite their considerable advantages, CVC are also associated with a high cost in morbidity. For this reason, it is important to set clear indications of use and be familiar with related complications and treatment. They must be used only in those patients who cannot carry a native AVF (nAVF) or a prosthetic AVF (pAVF), either because AVF cannot be created (absence of arteries with an adequate flow or venous bed occlusion) or is pending maturation; and with contraindication for peritoneal dialysis; in the case of acute renal failure, or in special circumstances: reversible renal function deterioration requiring temporary HD, life expectancy of less than 6 months, cardiovascular condition that would contraindicate VA creation or the patient’s express wishes.</p><p id="p7860" class="elsevierStylePara elsevierViewall">According to various published clinical guidelines,<a class="elsevierStyleCrossRefs" href="#bib10"><span class="elsevierStyleSup">10,14</span></a> CVC should, in most cases, be considered after nAVF and pAVF when selecting the appropriate VA to start a chronic HD programme. In addition, some guidelines distinguish between TCVC and NTCVC as “third option” and “choice of necessity”, respectively.<a class="elsevierStyleCrossRef" href="#bib13"><span class="elsevierStyleSup">13</span></a> If this order of priority is followed, the situation is not optimal in most developed countries.<a class="elsevierStyleCrossRefs" href="#bib32"><span class="elsevierStyleSup">32,664-667</span></a> The multinational European study conducted by Noordzij et al.,<a class="elsevierStyleCrossRef" href="#bib666"><span class="elsevierStyleSup">666</span></a> from the data of the European Renal Association-European Dialysis and Transplant Association (ERA-EDTA) Registry on 13,044 patients in HD, showed that CVC use to start a HD programme significantly increased from 58% in 2005 to 68% in 2009. In Spain, recent data from the Registre de Malalts Renals de Catalunya Registry (RMRC-Catalan Registry of Kidney Patients), referring to almost 10,000 incident patients in HD, have shown that approximately 50% of patients with advanced chronic kidney disease (ACKD) started HD each year in Catalonia through a CVC during 2000-2011.<a class="elsevierStyleCrossRef" href="#bib667"><span class="elsevierStyleSup">667</span></a> The various factors involved in the excessive number of CVC, both in incident and in prevalent HD patients, have been previously analysed<a class="elsevierStyleCrossRef" href="#bib665"><span class="elsevierStyleSup">665</span></a> and some of these could be neutralised by improving organisation.<a class="elsevierStyleCrossRefs" href="#bib278"><span class="elsevierStyleSup">278,667</span></a> For example, the current rate of CVC may be reduced by introducing the figure of vascular access coordinator and/or prioritising the surgical waiting list.<a class="elsevierStyleCrossRefs" href="#bib668"><span class="elsevierStyleSup">668,669</span></a></p><p id="p7865" class="elsevierStylePara elsevierViewall">Why should TCVC not be considered as the first choice for VA for most patients? The answer is very clear: because of its greater associated comorbidity.<a class="elsevierStyleCrossRefs" href="#bib95"><span class="elsevierStyleSup">95,630,670,671</span></a> By applying a multivariate competitive risk model, it has recently been demonstrated that the risk of all-cause mortality in comparison with nAVF over the years is 55% and 43% higher for patients who start HD through TCVC and NTCVC, respectively.<a class="elsevierStyleCrossRef" href="#bib630"><span class="elsevierStyleSup">630</span></a> During the period of maximum mortality among these patients (the first 120 days), the risk of all-cause, as well as cardiac and infectious, mortality is significantly higher for both TCVC and NTCVC versus nAVF.<a class="elsevierStyleCrossRef" href="#bib630"><span class="elsevierStyleSup">630</span></a></p><p id="p7870" class="elsevierStylePara elsevierViewall">In recent years, there has been a change in the type of CVC used to start the chronic HD programme. In this respect, from 2002 onwards, TCVC use in the first HD session has increased gradually in Catalonia while NTCVC has decreased.<a class="elsevierStyleCrossRef" href="#bib667"><span class="elsevierStyleSup">667</span></a> Similarly, the proportion of incident patients in HD in Australia with a TCVC increased from 39% in 2008 to 42% in 2011 and, in contrast, the percentage of patients who started HD through NTCVC decreased from 22% in 2008 to 12% in 2011.<a class="elsevierStyleCrossRef" href="#bib672"><span class="elsevierStyleSup">672</span></a> This change in the type of CVC used can be attributed, on the one hand, to the generalisation of the tunnelling CVC procedure and, on the other hand, to the demonstration of a significantly increased risk of infection in NTCVC versus TCVC a few days after use, due to a lack of tunnel and anchorage (<span class="elsevierStyleItalic">cuff</span>) to the subcutaneous tissue.<a class="elsevierStyleCrossRefs" href="#bib667"><span class="elsevierStyleSup">667,673</span></a></p><p id="p7875" class="elsevierStylePara elsevierViewall">Moreover, CVC has specific indications for use as initial VA. Patients requiring TCVC use are those with total arterial/venous exhaustion or where AVF creation is absolutely impossible, with severe peripheral arterial disease, chronic arterial hypotension because of its association with recurrent AVF thrombosis (mainly pAVF), life expectancy of less than 6 months and severe cardiomyopathy with depressed left ventricular function.<a class="elsevierStyleCrossRefs" href="#bib390"><span class="elsevierStyleSup">390,674,675</span></a> In the latter case, after several weeks of HD through TCVC, cardiac function should be reassessed to identify those patients whose heart condition has improved and can benefit from AVF construction.<a class="elsevierStyleCrossRef" href="#bib675"><span class="elsevierStyleSup">675</span></a> In addition, TCVC has also been used as a “bridge” VA to allow time for the nAVF to mature. Occasionally, due to the existing haste, TCVC placement has been unavoidable and HD has been performed when the incident patient had previously chosen peritoneal dialysis technique or was awaiting a living donor transplant.</p><p id="p7880" class="elsevierStylePara elsevierViewall">NTCVC should always be placed transitorily in patients with ACKD,<a class="elsevierStyleCrossRef" href="#bib676"><span class="elsevierStyleSup">676</span></a> only when HD is required without delay in incident patients without AVF or with maturing AVF, or in prevalent patients presenting AVF thrombosis which cannot undergo immediate salvage.</p><p id="p7885" class="elsevierStylePara elsevierViewall">It is important to understand and make clear that CVC is inferior to AVF and is not a substitute. Early nAVF creation is the best way to prevent complications caused by CVC.</p><p id="p7890" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XXIV In patients who cannot undergo native arteriovenous fistula creation, is the central venous catheter the vascular access of choice versus prosthetic arteriovenous fistula?</span></p><p id="p7895" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XXIV in <a href="https://static.elsevier.es/nefroguiaaveng/24_PCXXIV_CVC_o_protesico_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0120"></elsevierMultimedia></p><p id="s1940" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p7900" class="elsevierStylePara elsevierViewall">The systematic review of Ravani et al.<a class="elsevierStyleCrossRef" href="#bib96"><span class="elsevierStyleSup">96</span></a> shows the evidence on the outcome of different types of VA published up to 2012; however, there are no clinical trials directly comparing the different types.</p><p id="p7905" class="elsevierStylePara elsevierViewall">This review discusses a meta-analysis of observational studies showing that CVC-bearing patients have poorer outcomes than those with pAVF in terms of:<ul class="elsevierStyleList" id="list0590"><li class="elsevierStyleListItem" id="listi2460"><span class="elsevierStyleLabel">•</span><p id="p7910" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">All-cause mortality:</span> 15 cohorts from 13 studies, 394,992 patients (relative risk [RR]: 1.38; 95% confidence interval [CI], 1.25-1.52).</p></li><li class="elsevierStyleListItem" id="listi2465"><span class="elsevierStyleLabel">•</span><p id="p7915" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Fatal infection:</span> 11 cohorts from 10 studies, 235,176 patients (RR: 1.49; 95% CI, 1.15-1.93).</p></li><li class="elsevierStyleListItem" id="listi2470"><span class="elsevierStyleLabel">•</span><p id="p7920" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Non-fatal infection:</span> 17 cohorts from 17 studies, 13,121 patients (RR: 2.78; 95% CI, 1.80-4.29).</p></li><li class="elsevierStyleListItem" id="listi2475"><span class="elsevierStyleLabel">•</span><p id="p7925" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Severe cardiovascular event:</span> 8 cohorts from 7 studies, 234,819 patients (RR: 1.26; 95% CI, 1.11-1.43).</p></li><li class="elsevierStyleListItem" id="listi2480"><span class="elsevierStyleLabel">•</span><p id="p7930" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Hospitalisation:</span> 4 cohorts from 4 studies, 56,734 patients (RR: 1.51; 95% CI, 1.30-1.75).</p></li></ul></p><p id="p7935" class="elsevierStylePara elsevierViewall">Some authors highlight that sometimes the VA is not chosen on the basis of clinical criteria but on the experience of professionals and the availability of expert vascular surgeons and/or radiological teams, thereby increasing the number of CVC in incident and prevalent patients.<a class="elsevierStyleCrossRef" href="#bib677"><span class="elsevierStyleSup">677</span></a></p><p id="p7940" class="elsevierStylePara elsevierViewall">Randomised studies comparing clinical outcomes and costs between pAVF and CVC are needed.<a class="elsevierStyleCrossRef" href="#bib678"><span class="elsevierStyleSup">678</span></a></p><p id="s1945" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Use of resources and costs</span></p><p id="p7945" class="elsevierStylePara elsevierViewall">James et al.<a class="elsevierStyleCrossRef" href="#bib678"><span class="elsevierStyleSup">678</span></a> found that average costs of placing and maintaining VA in HD incident patients in Canada were $13,543 for pAVF and $10,638 for CVC. VA maintenance costs in prevalent patients were $5866 and $3842, respectively.</p><p id="s1950" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p7950" class="elsevierStylePara elsevierViewall">Though there are no clinical trials comparing results of CVC and pAVF use, both the work of Ravani et al. and the literature reviewed indicate that CVC should be used as the last VA choice for patients with CKD due to poorer outcomes in all the morbidity/mortality-associated variables. For this reason, when it is impossible to create nAVF, GEMAV recommends constructing pAVF to avoid TCVC placement.</p><p id="p7955" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0235"></elsevierMultimedia></p></span><span id="se1990" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect1960">6.2. Selection of catheter</span><p id="sect1965" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Recommendations</span></p><p id="p7965" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0240"></elsevierMultimedia></p><p id="sect1970" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Rationale</span></p><p id="p7985" class="elsevierStylePara elsevierViewall">The function of CVC for HD is to access the bloodstream so as to provide enough continuous blood flow to appropriately dialyse the patient. In recent decades, there have been new developments in designs in CVC making placement and subcutaneous tunnelling easier, obtaining higher blood flows and improving adaptation for use in longer periods.</p><p id="p7990" class="elsevierStylePara elsevierViewall">Currently, CVC for HD are usually classified as NTCVC, indicated for use under 2 weeks, and TCVC, with the same indications for prolonged periods. The reason for this division is based on the greater number of infectious and non-infectious complications found in NTCVC.<a class="elsevierStyleCrossRefs" href="#bib673"><span class="elsevierStyleSup">673,679-681</span></a> NTCVC is reserved for patients who require HD with anticipated use of under two weeks, after which the incidence of infections increases.<a class="elsevierStyleCrossRef" href="#bib673"><span class="elsevierStyleSup">673</span></a> It is suggested that TCVC should preferably be used versus NTCVC in cases of acute renal failure, as there is greater efficacy for HD, fewer complications and a lower number of replacements,<a class="elsevierStyleCrossRef" href="#bib682"><span class="elsevierStyleSup">682</span></a> and NTCVC should be reserved for patients with suspected sepsis.</p><p id="p7995" class="elsevierStylePara elsevierViewall">In recent years, it has also been suggested that different placement and care strategies for NTCVC may reduce the number of complications.<a class="elsevierStyleCrossRef" href="#bib683"><span class="elsevierStyleSup">683</span></a></p><p id="p8000" class="elsevierStylePara elsevierViewall">NTCVC are usually made of materials such as polyvinyl, polyethylene or polyurethane. These materials have a relatively hard consistency at room temperature, so can be easily tunnelled in the subcutaneous tissue, and make it easier to insert with the help of a metal guide without requiring a sheath introducer. At the same time, they soften and become more flexible at body temperature, thereby minimising the risk of damage to the vessel wall.<a class="elsevierStyleCrossRef" href="#bib684"><span class="elsevierStyleSup">684</span></a> A smaller number are composed of silicone, a material which makes them less stiff but more difficult to place. NTCVC length usually ranges from 15 to 25 cm, with a double-lumen design and conical tip (proximal lumen of the arterial branch, located 2 to 3 cm from the distal lumen of the venous branch to decrease recirculation)<a class="elsevierStyleCrossRef" href="#bib685"><span class="elsevierStyleSup">685</span></a> and can optimally deliver blood flows > 300 mL/min with venous pressures < 200 mmHg. It can be straight or pre-curved in shape to reduce the risk of kinking at the exit site in the skin; catheter extensions are straight or curved depending on the vein to be cannulated (curved for jugular and subclavian and straight for femoral). As an advantage, these CVC can be placed while the patient is in the hospital bed and be used immediately.</p><p id="p8005" class="elsevierStylePara elsevierViewall">TCVC are usually made of silicone or thermoplastic polyurethane and its derivatives, such as Bio-Flex or carbothane (copolymer), which has become more widespread in use. Length depends on the vein being cannulated and catheter type. They usually have a Dacron or polyester cuff in the extravascular section, which aims to cause fibrosis to prevent the passage of infectious agents and act as anchorage in the subcutaneous tissue. These CVC are softer and more flexible and minimise damage to the intima of the veins, biocompatible, non-thrombogenic and resistant to chemical changes, which increases longevity and decreases the number of complications. The new polyurethane copolymers provide flexibility, maintaining the strength of the walls, which allows for greater internal lumen and greater flow than silicone CVC without needing to increase their calibre.<a class="elsevierStyleCrossRef" href="#bib686"><span class="elsevierStyleSup">686</span></a></p><p id="p8010" class="elsevierStylePara elsevierViewall">It is important to understand what material is used to manufacture the CVC, as certain antibiotics or antiseptic solutions currently in use are incompatible with this material. Alcohol, polyethylene glycol, which mupirocin cream contains, and povidone iodine interfere with polyurethane and can rupture the CVC, while copolymers like carbothane are resistant to alcohol and iodine. Povidone iodine also interferes with silicone, causing degradation and rupture.<a class="elsevierStyleCrossRefs" href="#bib682"><span class="elsevierStyleSup">682,687</span></a></p><p id="p8015" class="elsevierStylePara elsevierViewall">Some CVC are coated with anticoagulant, antiseptic or antibiotic products, which aims to minimise risks of thrombosis and infection. Experiences have been reported which show the effectiveness of this strategy, but only in NTCVC used in critical patients and for limited periods of time. There is no evidence to support its routine use in populations of HD with long-term TCVC.<a class="elsevierStyleCrossRef" href="#bib688"><span class="elsevierStyleSup">688</span></a></p><p id="p8020" class="elsevierStylePara elsevierViewall">CVC length for HD depends on the vein to be cannulated and the patient’s clinical condition. NTCVC to be placed in the right internal jugular or subclavian vein usually measure between 15 and 20 cm, and 20 to 24 cm in left internal jugular or subclavian vein. Shorter lengths could cause risk of injury when the CVC lies against the superior vena cava walls. If used in the femoral vein, the CVC should be long enough, between 20 and 24 cm, to avoid significant recirculation and place the tip in the inferior vena cava.<a class="elsevierStyleCrossRef" href="#bib687"><span class="elsevierStyleSup">687</span></a></p><p id="p8025" class="elsevierStylePara elsevierViewall">TCVC are usually longer in length, ranging from 20-50 cm depending on the vein to be cannulated, due to the subcutaneous portion. Length must be appropriate to place the tip in the right atrium (RA), in TCVC inserted through the superior central veins (it has also been suggested that the tip be placed in this location in silicone NTCVC)<a class="elsevierStyleCrossRef" href="#bib689"><span class="elsevierStyleSup">689</span></a> and in those inserted through the femoral vein, at least inside the inferior vena cava.<a class="elsevierStyleCrossRef" href="#bib685"><span class="elsevierStyleSup">685</span></a></p><p id="p8030" class="elsevierStylePara elsevierViewall">CVC can be designed with double lumen (with both lumens symmetrical in a double D or double O or with circular arterial lumen and the venous lumen in a crescent shape); double-lumen but divided distally; two separate single catheters; double with a common anchor; and implantable devices with subcutaneous reservoirs.<a class="elsevierStyleCrossRef" href="#bib690"><span class="elsevierStyleSup">690</span></a> The advantage of circular section lumens is that they do not collapse on kinking or when pressures are highly negative. As a disadvantage, the internal calibre is usually lower for the same external calibre. A double D lumen configuration would allow the best flows with less resistance by contact surface area.<a class="elsevierStyleCrossRef" href="#bib682"><span class="elsevierStyleSup">682</span></a></p><p id="p8035" class="elsevierStylePara elsevierViewall">Currently, different pre-curved CVC with different lengths are available on the market, allowing adaptation to the patient size. Improvement in and ease of placement, with a reduction in intervention time, are advantages to take into consideration, as is the decrease in the amount of kinking and improvement in function.</p><p id="p8040" class="elsevierStylePara elsevierViewall">Other design characteristics are related to CVC tip. They may have a double O (shotgun tip), coaxial, separate tips (split tip), step tip or spiral Z-tip, all with and without side holes.<a class="elsevierStyleCrossRefs" href="#bib686"><span class="elsevierStyleSup">686,690-692</span></a></p><p id="p8045" class="elsevierStylePara elsevierViewall">Extensions and hubs should be designed and made of highly resistant material to prevent erosion or rupture caused by the clamps. Depending on CVC type, there are connection accessories, both for insertion and replacement in case of damage.</p><p id="p8050" class="elsevierStylePara elsevierViewall">Although there are multiple comparative studies between different types of catheters that assess the material and design of the tip, they have not succeeded in proving significant differences among them to suggest the use of one model over another.<a class="elsevierStyleCrossRefs" href="#bib685"><span class="elsevierStyleSup">685,691,693-696</span></a></p><p id="p8055" class="elsevierStylePara elsevierViewall">Patients with a central venous obstruction that prevents the creation of a VA in the upper limb may benefit from a hybrid prosthesis-tunnelled catheter device (<span class="elsevierStyleItalic">haemodialysis reliable outflow -HeRO- device</span>). This is a VA created in a mixed way. On the one hand, it is a permanent catheter that is implanted through a central venous obstruction or stenosis, connected to a polytetrafluoroethylene (PTFE) prosthesis anastomosed at the level of the brachial artery. The cannulation area is the prosthesis which is tunnelled subcutaneously and drains distally, directly into the atrium (see section 2.4.2).</p><p id="p8060" class="elsevierStylePara elsevierViewall">Observational studies have shown lower rates of infection than TCVC, with primary and secondary patencies similar to those observed in pAVF, but as it is a relatively recent technique there are no randomised clinical trials (RCTs) to endorse its usefulness and safety. From this, it can be deduced that its use is limited to a very small number of patients who are unable to undergo nAVF or pAVF creation in upper limbs and with recoverable central stenosis and/or occlusions, and preserves the venous vascular bed of the lower limbs.<a class="elsevierStyleCrossRefs" href="#bib143"><span class="elsevierStyleSup">143,177,697-700</span></a></p><p id="p8065" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XXV Are there differences in the indication to use non-tunnelled catheters versus tunnelled catheters?</span></p><p id="p8070" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XXV in <a href="https://static.elsevier.es/nefroguiaaveng/25_PCXXV_Cateteres_temporales_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0125"></elsevierMultimedia></p><p id="s1975" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p8075" class="elsevierStylePara elsevierViewall">The observational study of Weijmer et al.<a class="elsevierStyleCrossRef" href="#bib673"><span class="elsevierStyleSup">673</span></a> analysed the results of 272 CVC (37 TCVC and 235 NTCVC) in 149 patients, and with a duration of use of 11,612 catheter days.</p><p id="p8080" class="elsevierStylePara elsevierViewall">Patients with NTCVC presented acute renal failure (40% versus 8% of TCVC, p < 0.001) and hospital admission rates were higher (54% versus 14%, p < 0.001) as a differential characteristic. Results of the comparison were:<ul class="elsevierStyleList" id="list0600"><li class="elsevierStyleListItem" id="listi2495"><span class="elsevierStyleLabel">•</span><p id="p8085" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">CVC withdrawal for any complication:</span> 45.5% (107/235) of NTCVC were withdrawn versus 28.7% (11/37) TCVC (p < 0.001, log-rank analysis). The rates were 1.80 per 1000 catheter days for TCVC and 19.48 for NTCVC (RR: 10.83; 95% CI, 5.82-20.15; p < 0.0000001).</p></li><li class="elsevierStyleListItem" id="listi2500"><span class="elsevierStyleLabel">•</span><p id="p8090" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">TCVC survival:</span> Actuarial survival analysis was better for both TCVC (95% at 14 days, 95% at 21 days and 95% at 28 days) than for femoral NTCVC (42% at 14 days, 37% at 21 days and 32% at 28 days, p < 0.001 for all periods) and for jugular NTCVC (75% at 14 days, 69% at 21 days and 58% at 28 days; p < 0.05 for all periods).</p></li><li class="elsevierStyleListItem" id="listi2505"><span class="elsevierStyleLabel">•</span><p id="p8095" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Infection:</span><ul class="elsevierStyleList" id="list0605"><li class="elsevierStyleListItem" id="listi2510"><span class="elsevierStyleLabel">–</span><p id="p8100" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Bacteraemia</span>. Rates per 1000 catheter days: 1.6 for TCVC and 4.6 for NTCVC (RR: 2.67; 95% CI, 1.28-5.59; p = 0.006).</p></li><li class="elsevierStyleListItem" id="listi2515"><span class="elsevierStyleLabel">–</span><p id="p8105" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Infections in catheter exit site</span>. Rates per 1000 catheter days: 1.3 for TCVC and 8.2 for NTCVC (RR: 6.26; 95% CI, 3.04-14.22; p < 0.000001).</p></li><li class="elsevierStyleListItem" id="listi2520"><span class="elsevierStyleLabel">–</span><p id="p8110" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Survival of infection-free catheter</span>. It was better for TCVC (91% at 14 days, 89% at 21 days and 89% at 28 days; p < 0.05 for all periods) than for jugular NTCVC.</p></li></ul></p></li></ul></p><p id="p8115" class="elsevierStylePara elsevierViewall">After adjusting for different patient clinical characteristics, the most important risk factor for catheter withdrawal (RR: 9.69; p < 0.001) and for infection (RR: 3.76; p < 0.001) was indwelling NTCVC.</p><p id="p8120" class="elsevierStylePara elsevierViewall">They conclude that, in accordance with these results, TCVC should be used whenever the need for CVC for HD is foreseen for more than 14 days.</p><p id="p8125" class="elsevierStylePara elsevierViewall">The review of Frankel<a class="elsevierStyleCrossRef" href="#bib679"><span class="elsevierStyleSup">679</span></a> on NTCVC has an impact on the indications in which immediate access to the bloodstream is required:<ul class="elsevierStyleList" id="list0610"><li class="elsevierStyleListItem" id="listi2525"><span class="elsevierStyleLabel">•</span><p id="p8130" class="elsevierStylePara elsevierViewall">Patients with reversible deterioration of renal function requiring temporary HD.</p></li><li class="elsevierStyleListItem" id="listi2530"><span class="elsevierStyleLabel">•</span><p id="p8135" class="elsevierStylePara elsevierViewall">Patients whose end-stage renal failure has not been previously diagnosed and require urgent HD or are waiting for creation or maturation of a permanent vascular access.</p></li><li class="elsevierStyleListItem" id="listi2535"><span class="elsevierStyleLabel">•</span><p id="p8140" class="elsevierStylePara elsevierViewall">Patients in transition when access has failed, whether AVF or peritoneal dialysis.</p></li></ul></p><p id="p8145" class="elsevierStylePara elsevierViewall">Frankel points out that the use of TCVC has a significantly lower rate of infection than NTCVC (8.42 cases versus 11.98 cases per 100 catheter months, respectively) and should be the preferred means of providing temporary VA for periods of more than 2 weeks.</p><p id="p8150" class="elsevierStylePara elsevierViewall">The study of Kukavica et al.<a class="elsevierStyleCrossRef" href="#bib680"><span class="elsevierStyleSup">680</span></a> compared 16 patients treated with a TCVC with 15 patients treated with NTCVC (36-month follow-up) and found the need to replace 24 NTCVC due to thrombosis versus only 2 in patients with TCVC. He also observed that the mean flow rate in patients with TCVC was significantly higher (296 mL/min) compared to NTCVC (226 mL/min) (p < 0.001).</p><p id="s1980" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">From evidence to recommendation</span></p><p id="p8155" class="elsevierStylePara elsevierViewall">Although there are no randomised studies directly comparing the results of both types of catheters, observational analyses show higher complication rates with NTCVC versus TCVC. Despite weak evidence, GEMAV has decided to recommend the use of NTCVC for periods of time no longer than 2 weeks and TCVC for longer periods.</p><p id="p8160" class="elsevierStylePara elsevierViewall"><elsevierMultimedia ident="tb0245"></elsevierMultimedia></p><p id="p8170" class="elsevierStylePara elsevierViewall">→ <span class="elsevierStyleBold">Clinical question XXVI What is the best material and design for a tunnelled central venous catheter?</span></p><p id="p8175" class="elsevierStylePara elsevierViewall">(See fact sheet for Clinical question XXVI in <a href="https://static.elsevier.es/nefroguiaaveng/26_PCXXVI_Materiales_INGL.pdf">electronic appendices</a>)<elsevierMultimedia ident="ut0130"></elsevierMultimedia></p><p id="s1990" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleBold">Evidence synthesis development</span></p><p id="p8180" class="elsevierStylePara elsevierViewall">The RCT of Hwang et al.<a class="elsevierStyleCrossRef" href="#bib701"><span class="elsevierStyleSup">701</span></a> compared CVC with a “Z” spiral tip design (Palindrome = 47) versus a CVC with step design (<span class="elsevierStyleItalic">step-tip</span> = 50) in 97 patients with 2-month follow-up. Results showed:<ul class="elsevierStyleList" id="list0615"><li class="elsevierStyleListItem" id="listi2540"><span class="elsevierStyleLabel">•</span><p id="p8185" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">CVC dysfunction-free survival rate</span> was significantly higher for Palindrome CVC than for <span class="elsevierStyleItalic">step-tip</span> CVC (78.9% versus 54.4% at 2 months; p = 0.008).</p></li><li class="elsevierStyleListItem" id="listi2545"><span class="elsevierStyleLabel">•</span><p id="p8190" class="elsevierStylePara elsevierViewall"><span class="elsevierStyleItalic">Overall CVC survival rate</span> was also higher for Palindrome CVC than for <span class="