NEFROLOGÍA. Vol. XXV. Número 2. 2005 Epidemiological study on hemodialysis treatment in Huesca and Teruel A. Gascón, R. Virto, R. Pernaute, L. M. Lou, and F. J. García On behalf of the 5 Hemodialysis Units in Huesca and Teruel SUMMARY A cross sectional study was performed in order to evaluate the treatment conditions and medical outcomes among 131 prevalent hemodialysis patients (57% males; mean age 66 ± 12 years) in Huesca and Teruel. Data were collected at 5 hemodialysis units in Huesca and Teruel. Diabetes mellitus, at 30 percent, was the most common cause of renal insufficiency. The mean (± SD) urea-reduction ratio (URR) was 66.0 ± 8.8%. We observed that 56.5% of the population reached an URR higher than 65%. The duration of dialysis session was 220 ± 24 minutes, with a rate of blood flow 297 ± 47 ml/min. 36% of patients used high-flux membranes. The patterns of vascular access were: 69% arteriovenous fistula, 5% synthetyc graft and 26% catheter. Eighty nine percent of patients were treated with erythropoietin. The mean dose of erythropoietin was 109 ± 62 UI/Kg weight/week. Thirty nine percent of patients had haemoglobin below 11.0 g/dl (mean 11.2 ± 1.4 g/dl). Ferritin levels were below 100 ng/ml in 24% of the patients and 25% showed a transferrin saturation index below 20%. Fifty percent of patients were receiving vitamin D. Serum calcium 9.3 ± 0.8 mg/dl; phosphorous 5.5 ± 1.5 mg/dl; calcium-phosphorous product 51.5 ± 14.3 mg/dl; PTHi 433 ± 459 pg/ml; and aluminium 26.8 ± 14.5 mcg/l were the mean of main biochemical markers of mineral metabolism. Sixty eight percent of patients had phosphorous levels below 6.0 mg/dl. Thirty seven percent of patients had aluminium levels lower than 20 mcg/l. The mean serum albumin was 3.4 ± 0.4 g/dl. Forty five percent of patients had albumin below 3.5 g/dl. Key words: Hemodialysis. Urea-reduction ratio. Haemoglobin. Erythropoietin. Phosphorous. Albumin. Medical outcomes. ESTUDIO EPIDEMIOLÓGICO SOBRE EL TRATAMIENTO CON HEMODIÁLISIS EN HUESCA Y TERUEL RESUMEN Nos planteamos evaluar el manejo de los pacientes en hemodiálisis (HD) en Huesca y Teruel. Presentamos resultados de 131 pacientes en HD prevalentes en Correspondence: Dr. Antonio Gascón Mariño Avda. América, 30 Edificio San Francisco, pta. 13 44002 Teruel E-mail: agasconm@salud.aragob.es 163 A GASCÓN y cols. el año 2001. La diabetes mellitus con un 30% fue la causa más frecuente de insuficiencia renal. La media de la dosis de diálisis aplicada, utilizando el porcentaje de reducción de urea (PRU), fue 66,0 ± 8,8%. El 56,5% de la población alcanzó un PRU superior a 65%. La duración media de la sesión de HD fue de 220 ± 24 minutos, y el flujo sanguíneo de 29,7 ± 47 ml/min. En un 36% de pacientes se emplearon membranas de alta permeabilidad. Los patrones de acceso vascular fueron: 69% fístulas arteriovenosas, 5% injerto sintético y 26% catéteres. El 88,5% de la población estaba en tratamiento con eritropoyetina. La dosis media utilizada fue de 109 ± 62 UI/kg de peso/semana. El 39% de los pacientes presentaba hemoglobina inferior a 11,0 g/dl (media 11,2 ± 1,4 g/dl). Un 24% de los enfermos tenía niveles de ferritina inferiores a 100 ng/ml y un 25% mostraba índice de saturación de la transferrina inferior al 20%. Un 50% de pacientes recibía vitamina D en alguna de sus formas. La media de los principales marcadores del metabolismo mineral fue: calcio sérico 9,3 ± 0,8 mg/dl; fósforo 5,5 ± 1,5 mg/dl; producto calcio-fósforo 51,5 ± 14,3 mg/dl; PTHi 433 ± 459 pg/ml; y aluminio 26,8 ± 14,5 mcg/l. Un 68% de pacientes tenía niveles de fósforo inferior a 6,0 mg/dl y el 37% niveles de aluminio inferior a 20 mcg/l. La albúmina sérica media fue 3,4 ± 0,4 g/dl. Un 41% de pacientes presentaba albúmina inferior a 3,5 g/dl. Palabras clave: Hemodiálisis. Porcentaje de reducción de urea. Hemoglobina. Eritropoyetina. Fósforo. Albúmina. Epidemiología. INTRODUCTION By the end of 2002, the last Report on Dialysis and Transplantation from the Spanish Society of Nephrology (SEN) and Autonomic Registries of the Year 2000 was published1. In Aragon, with a population of 1,168,268 inhabitants, the prevalence of patients on hemodialysis (HD) at December 31st of 2000 was 318 per million population. Population of Teruel and Huesca regions in the year 2001 was 205,955 and 136,233 inhabitants, respectively. Both provinces are characterized by a low population density (13.17 inhabitants/km2) and a high proportion of population older than 65 years (24% in Huesca and 27% in Teruel). When reviewing the literature on HD patients in Spain, there are no published studies that describe the management characteristics of HD patients in certain geographical areas. The aim of this cross-sectional study was to know the characteristics and management of all HD patients in the provinces of Huesca and Teruel. Therefore, diverse issues such as cause of renal failure, doses of prescribed dialysis, vascular accesses used, anemia management, iron metabolism, renal osteodistrophy, calcium-phosphorus metabolism, and nutrition were analyzed. The analysis of these results will allow us to increase our understanding about the real situation of our HD patients and try to improve several issues of their treatment. 164 MATERIAL AND METHODS The data collection system was based on a questionnaire sent to all 5 HD units in Huesca and Teruel (Table I). That questionnaire was sent in November of 2000 and data collection ended up in May of 2001. In the questionnaire patient information was asked about: date of birth, gender, cause of renal disease, date of HD initiation, percentage of urea reduction (PUR), minutes of each HD session, membranes used, types of vascular access, and blood flow used (mL/min). Data on anemia management were also requested, such as hemoglobin (Hb) levels (g/dL), dose of recombinant human erythropoietin (rHuEPO) (IU/Kg of body weight/week), erythropoietin response index (ERI) [calculated as the ratio between rHuEPO dose (IU/Kg of body weight/week) and mean Hb (g/dL)], and ferritin blood levels (ng/mL), and transferrin saturation index (FSI) (%). With regards to renal osteodistrophy and management of calcium-phosp- Table I. HD units in Huesca and Teruel Hospital of Barbastro San Jorge Hospital of Huesca Hospital of Jaca Hospital of Alcañiz Obispo Polanco Hospital of Teruel HEMODIALYSIS IN HUESCA AND TERUEL horus metabolism, information was requested on whether patients were treated or not with vitamin D, and on calcium (mg/dL), phosphorus (mg/dL), intact parathyroid hormone (PTHi) (pg/mL) and aluminum (µg/mL) serum levels. Nutritional status was assessed by creatinine (mg/dL), albumin (g/dL), transferrin (mg/dL) serum levels, and absolute lymphocyte count per µL. Statistical analysis For data statistical analysis, an essentially descriptive approach has been followed. Results are expressed in percentages and as mean ± standard deviation. Besides descriptive statistics, for non-paired quantitative variables a univariate analysis by Student's t test was done. A p value < 0.05 was considered statistically significant. Statistical analyses have been performed with Stat View software (Abacus Concept Inc. Berkeley, CA). RESULTS All units answered the questionnaire, obtaining data for 100% of the HD population in Huesca and Teruel. Sample characteristics Table II. Renal failure causes Diabetic nephropathy Tubulointerstitial nephropathy Chronic glomerulonephritis Hypertensive nephropathy Polycystic renal disease Systemic Unknown Others 30% 19% 16% 13% 6% 2% 13% 2% greater or equal to 65%; and group B: lower than 65%-- it was observed that patients in group A had significant increases in the amount of minutes per session and blood flow as compared to patients in group B (Table III). Likewise, in patients dialyzed with high permeability membranes a significant increase in PUR and in amount of minutes per session could be detected as compared to patients not dialyzed with these membranes (Table IV). On the other hand, female patients (n = 57) presented a mean PUR of 68.6 ± 8.6% as compared to 63.9 ± 8.6% in male patients (n = 74) (p = 0.0023). In the same way, patients older than 65 years (n = 91) presented a PUR of 67.1 ± 9.4% as compared to a PUR of 63.5 ± 6.7% in patients younger than 65 (n = 49) (p = 0.0321). Vascular accesses Total number of studied patients was 131, 57% of whom were males. Mean age was 66 ± 12 years, with a range of 19 to 90 years. Sixty-nine percent were older than 65 years and 30% were older than 75 years. Mean age at the beginning of HD was 64 ± 12 years. Mean time on HD was 26 ± 33 months. Diabetic nephropathy was the main cause for renal failure in 30% of the cases. Distribution of renal failure etiology is summarized in Table II. Dialysis dose Mean PUR was 66.0 ± 8.8%, being less than 65% in 43.5% of cases and less than 70% in 35% of cases. The percentage of patients that did not reach a 65% PUR was reduced to 35% in the 92 patients that were on HD for more than 6 months. The average HD session duration (in minutes) was 220 ± 24 and mean blood flow was 297 ± 47 mL/min. Thirtysix percent of patients received HD with high permeability cellulose membranes. When comparing patients according to the PUR obtained --group A: With regards to vascular accesses, at the time of the study, 69% were dialyzed through an autologous arterial-venous fistula and 5% did so through a graft. Ten percent used a permanent catheter and 16% had a provisional one. Forty-one percent of patients that had started on HD within 6 months were using provisional catheters. This number decreased to 5% in patients that were on HD for longer than 6 months. Table III. Comparison of minutes per HD session and blood flow (mL/min) according to PUR obtained Minutes per session PUR < 65% (n = 57) PUR > 65% (n = 74) 214 ± 25 224 ± 24 p < 0.0304 Blood flow 279 ± 50 311 ± 40 p < 0.0001 165 A GASCÓN y cols. Table IV. Comparison of PUR, minutes per HD session and blood flow (mL/min) between patients dialyzed with high permeability membranes (group A) and patients dialyzed with low permeability membranes (group B) PUR Group A (n = 47) Group B (n = 84) 69.3 ± 6.4 64.1 ± 9.5 p < 0.0011 Minutes per session 232 ± 23 213 ± 23 p < 0.0001 Blood flow 306 ± 49 293 ± 45 p < 0.1203 Anemia management and iron balance With regards to anemia management, it was observed that mean Hb in the prevalent HD population was 11.2 ± 1.4 g/dL. Eighty-five percent was on treatment with subcutaneous rHuEPO with a mean dose of 109 ± 62 IU/kg of body weight/week. Mean Hb in these patients was 11.2 ± 1.4 g/dL, 32% of patients having an Hb lower than 11 g/dL. When categorizing population according to time on dialysis, patients that were on dialysis for less than 6 months had a mean Hb of 10.5 ± 1.3 g/dL (n = 39) as compared to a mean Hb of 11.5 ± 1.4 g/dL in patients that were on dialysis for more than 6 months (n = 92) (p < 0.0002). The percentage of patients with an Hb level lower than 11.0 g/dL was reduced to 26% in those that were on dialysis for more than 6 months. Mean ERI in the studied population was 10.1 ± 6.3, not showing significant differences between men and women, 9.9 ± 5.7 vs 10.2 ± 6.8. Mean serum ferritin and mean TSI were 284 ± 255 mg/mL and 27 ± 11%, respectively. Twenty-four percent of patients had ferritin levels lower than 100 ng/mL, 59% between 100-500 mg/mL, and 17% greater than 500 ng/mL. With regards to TSI, 25% of patients presented values lower than 20%, 41% between 20-30%, and 34% greater than 30%. Patients with TSI above 30% had higher Hb levels that the remaining patients, observing a graded distribution, so that Hb levels increased together with TSI increase. Patients with a TSI < 20% had a mean Hb of 10.7 ± 1.4 g/dL, in those with TSI 20-30% Hb increased to 11.3 ± 1.5 g/dL, an in those that reached a TSI > 30% mean Hb was 11.7 ± 1.5 g/dL. Renal osteodistrophy and calcium-phosphorus metabolism The analysis of the situation of the main markers of bone metabolism showed that mean va166 lues of PTHi, calcium blood levels, phosphorus blood levels, calcium-phosphorus product, and albumin blood levels were 433 ± 459 pg/mL, 9.3 ± 0.8 mg/dL, 5.5 ± 1.5 mg/dL, 51.5 ± 14.3 mg/dL, and 26.8 ± 14.5 µg/L, respectively. Thirty-two percent of patients presented phosphorus levels greater than 6.0 mg/dL and only in 19% phosphorus was overtly elevated (> 6.5 mg/dL). With regards to calcium serum levels, in 35% of the population they were lower than 9.0 mg/dL. By contrast, calcium was found greater than 11.0 mg/dL in 4% of patients. Patients with calcium lower than 9.0 mg/dL were more anemic and had a greater ERI than the remaining patients (Table V). Of the total population, 16% of patients had PTHi within the ideal range (150-250 pg/mL) and 84% showed inadequate values. Of them, 27% had PTHi levels lower than 120 pg/mL and 57% greater than 250 pg/mL. When analyzing this 57% of patients with elevated PTHi (n = 70), it was observed that 44% of them (n = 31) showed moderately increased values (PTHi between 250-500 pg/mL), 32% (n = 22) highly increased values (between 500-750 mg/dL), and in 24% (n = 17) levels were above the later values (> 750 pg/mL). With regards to treatment with vitamin D, 50% of patients were on treatment with any of its formulations. There were no differences in the calcium-phosphorus product between patients that received vitamin D as compared to those that did not (52.3 ± 13.4 vs 50.1 ± 14.9 mg/dL). It should be noted that 44% of patients with an elevated PTHi (>250 pg/mL) and 56% of patients with calcium blood levels lower than 9.0 mg/dL did not receive vitamin D, and that 33% of patients with a low PTHi ( < 120 pg/mL) were receiving vitamin D inadequately. With regards to aluminum, 37% of patients had aluminum levels lower than 20 µg/L, 47% between 20-40 µg/L, and 16% greater than 40 µg/L. Table V. Comparison between clinical-biological parameters (mean ± SD) of patients with different calcium serum levels (Ca) (mg/dL) Ca > 9 (n = 85) Age (years) PUR (%) Ca-P product (mg/dL) PTHi (pg/mL) Aluminum (g/L) Hb (g/dL) ERI 67.2 66.0 66.9 397 26.9 11.6 9.1 ± ± ± ± ± ± ± 8.5 11.0 11.5 485 14.9 1.4 5.7 Ca < 9 (n = 46) 63.9 66.0 44.2 504 26.6 10.6 11.8 ± ± ± ± ± ± ± 9.1 11.0 10.7 399 13.9 1.7 7.1 p 0.0472 0.9872 0.0001 0.2226 0.909 0.0003 0.0267 HEMODIALYSIS IN HUESCA AND TERUEL Nutritional parameters With regards to nutritional parameters, mean values of lymphocytes, and serum creatinine, albumin, and transferrin were of 1,32 ± 475/µL, 8.5 ± 2.5 mg/mL, 3.4 ± 0.4 g/dL, and 185 ± 35 mg/dL, respectively. Forty-eight percent of patients had a serum albumin between 3.5-3.9 g/dL, 45% lower than 3.5 g/dL, and only 7% reached a 4.0 g/dL value. Patients with albumin lower than 3.5 g/dL (n = 61) were older and their Hb, transferrin and calcium blood levels ware significantly decreased, although creatinine and lymphocytes were normal as compared to the remaining patients (Table IV). DISCUSSION The present cross-sectional study compiles data from 131 patients that represent 100% of the HD population of Huesca and Teruel in the year 2001, a figure that allows us to consider these data representative of our situation, although it should be taken into account that a in cross-sectional study performed on a such limited number of patients the rates could be biased by the situation at the time of the cross-section. The population is characterized for having an advanced age. This situation is general in all the Autonomous Communities, as it is observed in the SEN Dialysis Report referred to the year 20011. In Spain, the proportion of patients on HD older than 65 years has been increasing from 2% in 1977 to 39% in 19922, and it keeps on growing1. In Huesca and Teruel, because of their demographic characteristics, the percentage of patients older than 65 years is important. In fact, mean age of our patients is greater than those recently described in several studies on HD patients in Spain3-5. In the epidemiological study on anemia management in Spain5, almost 30% of patients were older than 65 years, in our population this group represents 69%. With regards to renal failure causes, the distribution is different from that on the SEN Dialysis Report of 20011, with a greater percentage of diabetic nephropathy (30%), and tubulointerstitial nephropathy emerges as the second cause (19%) (Table II). With regards to dialysis doses, we must point out that 43.5% of patients did not reach the goal of a PUR equal or greater than 65% as recommended by the American guidelines6. Besides, these patients were those having the lowest blood flows and the lowest duration of HD sessions (Table III). Therefore, as a first measure, minutes per HD session and blood flows through the vascular access must be increased in those patients that do not reach a 65% PUR. Anot- Table VI. Comparison between clinical-biological parameters (mean ± SD) of patients with different serum albumin levels (mg/dl) Albumin > 3.5 (n = 70) Age (years) Hb (g/dl) Serum calcium (mg/dl) Transferrin (mg/dl) 65 11.5 9.5 194 ± ± ± ± 13 1.4 0.8 29 Albúmina < 3.5 (n = 61) 68 10.8 9.1 171 ± ± ± ± 11 1.4 0.8 40 p 0.2377 0.0289 0.0088 0.0010 her effective option is the use of high permeability membranes. If we compare our data with those of the multicenter Spanish study of adequate dialysis7, we observe that mean PUR was lower than that presented by our patients (66.0 vs 62.4%). In that study7, blood flows and minutes per HD session were similar to the ones applied to our patients. More recently, in the HEMO study results8, the dialyzed population with a dialysis dose less stringent had a PUR of 66.3 ± 2.5%, similar to the one applied to our patients, although with a shorter duration of dialysis sessions (190 ± 23 minutes), greater blood flows (311 ± 51 mL/min), and a greater percentage of high permeability membranes usage (60%). One of the HEMO study conclusions8 has been that for patients with three HD sessions per week a benefit is not obtained with the use of high permeability membranes (except in those patients that have been on HD for more than 3.7 years), or with prescription of higher dialysis doses than those recommended in the American guidelines6, although a PUR of at least 65% must be obtained. Finally, we must highlight that patients older than 65 and women are the two groups of patients that receive higher dialysis doses in our population. With regards to vascular accesses, and comparing our results with those of the study on vascular accesses in Spain9, the percentage of patients with autologous arterial-venous fistula is lower (69.0 vs 81.0%), that for grafts is also lower (5.0 vs 9.0%), and that for catheters is higher (26.0 vs 10.0%). Similarly to the Spanish study9, it is still observed a high percentage of patients that receive dialysis through catheters among those on HD for less than 6 months (41 vs 44%). In our study, the percentage of patients that receive dialysis through provisional catheters is reduced to 5% in the group of patients that are on HD for more than one year. It is likely that advanced age in our patients made difficult to obtain functioning arterial-venous fistulae. In fact, in a recent study on vascular accesses for dialysis in elderly people, it was detected that the rate of long167 A GASCÓN y cols. term complications was greater in patients older than 65 years with autologous arterial-venous fistulae10. On the other hand, 30% of our patients were diabetics, in whom the vascular bed is more deteriorated and difficulty for obtaining functioning vascular accesses is increased. These difficulties may have conditioned that 10% of our patients were dialyzed through a permanent catheter with a dracon cuff. Another possibility that may explain the high percentage of patients with provisional catheters, among patients with less than 6 months on dialysis, could be the lack of consideration of this situation as a surgical emergency by the vascular surgery departments. With regards to anemia management in our HD patients, the goal of achieving that 85% of the population present Hb levels greater than 11.0 g/dL11 is not reached. If we compare our data with those of the EucliD study in Spain4 on anemia management, mean subcutaneous rHuEPO dose used (109.6 vs 111.9 IU/kg of body weight/week) and percentage of patients on rHuEPO treatment (88.5 vs 93.0%) were similar. ERI in our patients was also similar to that of patients treated with subcutaneous rHuEPO in the EucliD study4, although in our population we could not detect differences in the ERI in relation to gender. In the EucliD study4, 31% of patients did not reach a target Hb of 11.0 g/dL, and in our population this figure was 39%. In both studies it was observed that Hb level was lower in patients on HD for less than 6 months. With regards to management of iron metabolism, the percentage of patients with a ferritin level lower than 100 ng/mL was greater (24.0 vs 10.0%), although the percentage of cases with a TSI below 20% was similar to that described in the EucliD study4 (25.0 vs 26.5%). In our population, the group of patients with a TSI above 30% showed greater Hb levels than the group of patients with a TSI between 20-30%. This datum would endorse the convenience of assessing iron metabolism through TSI since it is the most sensible index to measure iron levels and availability, both in absolute terms and in the presence of iron functional deficit4. On the other hand, in the epidemiological study on anemia in Spain5, in the initial assessment it was detected that 35% of patients presented an Hb lower than 11.0 g/dL and that mean Hb was 11.3 g/dL, results that are similar to those found in our population. Lastly, if we compare our results with those described in the DOPPS study for Spanish and European patients3, we observe that ours are better in relation to mean Hb (11.2 vs 10.8 g/dL). In that study3, as well as in the ESAM study done in Europe12, 50% of the population was below the Hb target limit set up in the European guidelines11. 168 Management of bone metabolism and bone disease is another goal that we must achieve when treating HD patients13. Our patients showed different results than those showed in the Spanish multicenter study on renal osteodistrophy14 in relation to mean calcium (9.3 vs 9.7 mg/dL) and mean PTHi (433 vs 294 pg/mL). A greater percentage of our patients showed calcium levels below 9.0 mg/dL (35 vs 23%) and PTHi levels above 250 pg/mL (57 vs 37%) as compared to patients in the Spanish multicenter study14. By contrast, the percentage of patients with PTHi within the range of bone adynamia ( < 120 pg/mL) was lower (27 vs 41%). The association that we have observed between calcium below 9.0 mg/dL with greater anemia and greater ERI must be highlighted, an association that we have already described15. On the other hand, mean aluminum and phosphorus levels were similar in both studies14. However, when analyzing management of phosphorus blood levels, our results were better than those described in the Spanish multicenter study14, only 19% of patients showed serum phosphorus higher than 6.5 mg/dL. This fact is important since serum phosphorus levels higher than 6.5 mg/dL have been associated to a greater mortality with dialysis16. With regards to treatment with vitamin D, 50% of our patients were receiving it, a percentage greater than that described in the Spanish multicenter study, where it was 44%14. However, as observed in that study14, vitamin D is not always correctly used. Finally, analysis of parameters related to nutritional status shows a tendency to hypoalbuminemia in our patients. Although there is no single ideal parameter to measure the nutritional status of patients on HD, serum albumin is a valid and clinically useful indicator, besides of predicting a future risk of death17. In this sense, 45% of our patients presented serum albumin levels lower than 3.5 g/dL together with greater anemia than the remaining patients (Table IV). This association was also observed in hypoalbuminemic patients in the EucliD study4. The goal of maintaining patients with albumin levels equal of greater than 4.0 g/dL17 was achieved in only 7% of our population. Probably, one of the essential causes was the advanced age in our patients that favors a worse nutritional status and that is also manifested with a lower creatinine and transferrin serum levels. Patients on HD with creatinine levels lower than 10 mg/dL should be evaluated for a possible situation of proteinic hyponutrition or muscle wasting17. Contrary to our results, Spanish patients in the DOPPS study3 did present a mean albumin of 4.0 g/dL. However, if we compare our data with those of patients in the HEMO study8, conclusions are not so unfavorable since mean albumin levels were si- HEMODIALYSIS IN HUESCA AND TERUEL milar (3.4 vs 3.6 g/dL) in patients with a lower mean age (66.0 vs 57.6 years) and a greater mean serum creatinine (8.5 vs 10.3 mg/dL). In conclusion, population on HD in Huesca and Teruel has an advanced age and presents, in general, an acceptable management. However, there are some issues that must be improved such as reducing the number of patients dialyzed through provisional catheters, and increasing the percentage of patients that reach a PUR of 65% and a Hb of 11.0 g/dL. Further studies will be needed that will allow us to check whether we are advancing in the achievement of the goals of dialysis quality for our patients. REFERENCES 1. Informe de Diálisis y Trasplante de la Sociedad Española de Nefrología y Registros Autonómicos año 2000. Nefrología 22: 310-317, 2002. 2. Gómez Campderá FJ, Barrio V: Evolución demográfica y de los métodos de tratamiento de la insuficiencia renal terminal en el anciano en España en los años 1977 a 1992. Nefrología 26, 6: 499-503, 1996. 3. Cruz JM, Piera L, Bragg-Gresham JL, Feldman H, Port FK: Resultados del estudio internacional de hemodiálisis DOPPS en Europa y España. Nefrología 23: 437-443, 2003. 4. Avilés B, Coronel F, Pérez García R, Marcelli D, Orlandini G, Ayala JA, Rentero R: Control de la anemia en hemodiálisis. Base de datos EuCliD (European Clical Database) en España. Nefrología 22: 555-563, 2002. 5. Perez García R: Estudio epidemiológico sobre el tratamiento de la anemia en España. Nefrología 23: 300-311, 2003. 6. Eknoyan G, Levin N: NKF-K/DOQI clinical practice guidelines: up-date 2000. Am J Kidney Dis 37: (Supl. 1): S5-S6, 2001. 7. Grupo Cooperativo Español de Diálisis Adecuada: Influencia del modelo cinético de la urea en la prescripción de diálisis: un estudio comparativo de 2.703 pacientes. Nefrología 14: 78-86, 1994. 8. Eknoyan G, Beck GJ, Cheung AK, Daugirdas JT, Greene T. Kusek JW, Allon M, Bailey J, Delmez JA, Depner TA, Dwyer JT, Levey AS, Levin NW, Milford E, Ornt DB, Rocco MV, Schulman G, Schwab SJ, Teehan BP, Toto R: Effect of dialysis dose and membrane flux in maintenance hemodialysis. N Engl J Med 347: 2010-19, 2002. 9. Rodríguez Hernández JA, López Pedret J, Piera L: El acceso vascular en España: análisis de su distribución, morbilidad y sistemas de monitorización. Nefrología 21: 45-51, 2001. 10. Ridao N, Polo JR, Pérez-García R, Sánchez M, Réngel MA, Gómez-Campderá FJ: Accesos vasculares para diálisis en el anciano. Nefrología 28(Supl. 4): 22-26, 1998. 11. European Best Practice Guidelines for the management of anaemia in patients with chronic renal failure. Nephrol Dial Transplant 14(Supl. 5): S11-13, 1999. 12. European Survey on Anaemia Management (ESAM). Nephrol Dial Transplant 15(Supl. 1): S33-42, 2000. 13. K/DOQI clinical practice guidelines for bone metabolism and disease in chronic kidney disease. Am J Kidney Dis 42(Supl. 3): 2003. 14. Díaz Corte C, Rodríguez A, Naves ML, Fernández Martín JL, Cannata JB: Marcadores metabólicos óseos y uso de vitamina D en diálisis. Encuesta multicéntrica (II). Nefrología 20: 244-253, 2000. 15. Gascón A, Moragrega B, Moreno R, Virto R, Pernaute R, Castillón E, Pérez J, Lou LM, Aladrén MJ, Gómez R, Vives PJ, Álvarez R, García FJ, Castilla J, Gutiérrez Colón JA. Pacientes en hemodiálisis con pobre respuesta a la eritropoyetina: ¿influye el control del calcio y fósforo? DyT 24: 85-90, 2003. 16. Block G, Hulbert-Shearon T, Levin N, Port F: Association of serum phosphorous and calcium × phosphorous product with mortality risk in chronic hemodialysis patients: a national study. Am J Kidney Dis 31: 607-617, 1998. 17. K/DOQI nutrition in chronic renal failure. Am J Kidney Dis 35(Supl. 2): S20-24, 2000. 169