To the editor: Heparin-induced  thrombocytopenia (HIT) is a hypercoagulability  state  resulting from production of antibodies against a heparin-platelet factor  4  complex  that  occurs  in  0.2%-1% of patients receiving heparin.(1) The condition should be considered when a greater than 40% decrease from baseline is detected in platelet count between 4 and 10 days since the start of heparinization.(1,2) Mortality  from  thrombosis is high (30%), and urgent action consisting of heparin discontinuation and administration of an antithrombotic, lepidurin  in  our  setting,  is  therefore required.(3)



A 72-year-old male patient who experienced an acute myocardial infarction during coronary bypass surgery is reported here. The patient required insertion  of  an  aortic  counterpulsation balloon and administration of unfractionated  heparin  (UFH).  Three  days later,  fever,  hypotension,  and  renal failure  requiring  hemodialysis  occurred. Four days later, circuit thrombosis, not prevented by prostacyclin addition,  was  detected.  Platelet  count

decreased  to 42,000(mL from a baseline value of 210,000/mL. On  the  following  day,  the  patient  showed  cyanosis  in  the  fingers  of  both  feet (Figure  1),  impossibility  of  hemodialysis persisted, and a right femoral

thrombosis  was  detected  by  echo Doppler. HIT was suspected and confirmed  by  platelet  aggregation  tests and  ELISA.  Heparin  was  discontinued,  and  a  lepidurin  bolus  of 0.1 mg/kg was  administered. Activated  partial  thromboplastin  time (APTT)  increased  from  36¿ to  72¿, and  hemodialysis  was  normally  performed. APTT was monitored every 2 hours  to maintain  it between 2  and 3 times  the  control  value  (33¿). A new lepidurin administration (0.05 mg/kg) was not  required until 16 hours  later. When renal function improved, a continuous  lepidurin  infusion  (0.005 mg/kg/h)  was  started.  Platelet  function  recovery was noted  at 48 h  (fig. 2). Seven days  later  the  patient  was stabilized  and  treatment  was  started with  acenocoumarol.  Six  days  later, international  normalized  ratio  (INR) was  2.8,  and  lepidurin was  therefore discontinued.



Lepidurin  is  the  therapeutic  option for patients with HIT in our setting. Lepidurin  is  an  antithrombotic  drug  that

inactivates thrombin directly,  so  that  it also  has  a  bleeding  risk(3) and  requires monitoring. Recent studies suggest that the doses recommended by the supplier are too high.(3,4) This recommendation is relevant in renal failure patients because lepidurin excretion depends exclusively on the glomerular filtration rate.



The  reported  case  alerts  about  two significant  issues  in  clinical  practice. The  first  issue  is  that  HIT should  be considered  as  a  potential  cause  of  thrombosis of the hemodialysis circuit in patients  treated  with  heparin.  Moreover,  in  patients  with  renal  impairment lepidurin  should  be  started  at  low doses,  and  drug  levels  should  be  frequently monitored.