• Mean running time of two consecutive haemodialysis circuits [ Time Frame: seven days starting at time of HIT suspicion ] [ Designated as safety issue: No ]
  

• Incidence of bleeding, transfusion requirements, thromboembolic events, anaphylactic reactions, and SUSARs, length of hospital stay, mortality, time till target aPTT [ Time Frame: seven days starting at time of HIT suspicion ] [ Designated as safety issue: Yes ]
  

Critically ill patients are at increased risk to develop deep vein thrombosis due to immobilisation and/or the underlying disease. Usually, heparin is used for anticoagulation in these patients. However, a serious complication of heparin therapy is heparin-induced thrombocytopenia type II (HIT). HIT is an immune-mediated syndrome caused by antibodies directed against the heparin-PF4-complex, which bind to platelets via the Fc part, thereby activating platelets causing aggregation and hypercoagulability. Thus, with HIT the risk of thrombosis and organ damage paradoxically even increases during heparin administration. HIT is associated with significant morbidity and mortality if unrecognized. Therefore, patients, who develop thrombocytopenia and/or thrombosis during heparin therapy are suspicious for HIT and have to receive alternative anticoagulants2.

The direct thrombin inhibitor lepirudin (Refludan®) is equally effective as heparin in prevention of deep vein thrombosis and lung embolism3. The elimination half life of lepirudin averages 60 min, but in renal failure it may increase up to 48 hours. Critically ill patients often develop acute renal failure requiring continuous renal replacement therapy. Thus, if lepirudin is used in these patients, intensive dose adjustment is necessary to avoid accumulation and severe bleeding. In contrast, effective anticoagulation is needed to prevent clot formation within the extracorporeal circuit, as clotting substantially increases the patients´ risks and costs of therapy.

Argatroban (Argatra®), another direct thrombin inhibitor, has recently been shown to be safe and effective in prevention of deep vein thrombosis in patients with HIT. Interestingly, argatroban is eliminated by hepatic metabolism. Therefore, no initial dose adjustment is necessary in patients with renal failure. Preliminary reports document the feasibility of argatroban for anticoagulation during haemodialysis. Observational data in patients undergoing continuous haemodialysis suggest that life time of filters during argatroban anticoagulation is not limited due to clot formation. Thus, argatroban would be safer and more effective than lepirudin in critically ill patients requiring continuous renal replacement therapy.

Therefore, we propose a prospective randomized double-blinded trial to test the hypotheses that argatroban significantly increases efficacy and safety of renal replacement therapy measured as life time of haemodialysis filters as compared to lepirudin