Background: Recombinant hirudin (lepirudin) is a potent direct thrombin inhibitor, which has been approved for the treatment of heparin-induced thrombocytopenia type II (HIT). Because the drug is mainly eliminated by the kidneys, a single loading dose of hirudin may induce therapeutic anticoagulation for up to one week in patients with renal insufficiency. Thus, the use of hirudin in critically ill patients with renal failure could markedly increase their bleeding risk. In this study, hirudin was used in critically ill patients with suspected HIT while on continuous venovenous hemodialysis (CVVHD).
Methods: Hirudin anticoagulation was performed in seven critically ill patients with suspected HIT. Four patients were initially anuric. Three patients had residual renal function. In all 64 CVVHD treatments (mean duration 12 hr), a polysulfone high-flux hemodialyzer (0.75 m2) with a dialysate flow rate of 1.5 liter/hr and an ultrafiltration rate of up to 200 ml/hr was used. Hirudin was given either as continuous intravenous infusion or as repetitive intravenous boli. Monitoring of anticoagulation was performed by measurements of the systemic activated partial thromboplastin time (aPTT).
Results: Hirudin dosage had to be individualized according to the risk of bleeding or clotting. During CVVHD, a continuous intravenous infusion (0.006 to 0.025 mg/kg body wt/hr, N = 2) or repetitive intravenous boli (0.007 to 0.04 mg/kg, N = 5) were given. Two patients required blood transfusions prior to and during hirudin treatment. In five patients without a high bleeding risk, the hirudin dose was adjusted to achieve the target aPTT (1.5 to 2.0 x baseline) in order to prevent thrombotic complications or frequent clotting in the extracorporal circuit. Hirudin dose requirements depended on residual renal function and extracorporal clearance.
Conclusions: We conclude from these first clinical data that anticoagulation with hirudin in critically ill patients on continuous hemodialysis can be performed without excessive bleeding risk by combining close clinical and laboratory monitoring. The hirudin dose has to be reduced because of renal failure, and may require adjustment for residual or recovering renal function and extracorporal elimination.