Use of ecarin clotting time in whole blood for monitoring recombinant hirudine treatment during cardiopulmonary bypass in patients with heparin-induced thrombocytopenia

Lepirudin (Refludan is a recombinant hirudin, approved for anticoagulation treatment of heparin-induced thrombocytopenia patients with thrombosis. We report here our method for laboratory monitoring with ecarin clotting time (ECT) of hirudin therapy as anticoagulation for cardiac surgery. Ecarin is extracted from the Echis carinatus snake venom and directly converts prothrombin to its intermediate, meizothrombin. This one binds in a stoechiometric way to hirudin to be proportioned in whole blood. The activation of coagulation starts up only when the totality of the hirudin is bound to the meizothrombin. To minimize the effect of dilution related to the CEC on the prothrombin and fibrinogen levels, thus lengthening the ECT, the specimen to be tested is diluted with normal whole blood. In 1997, when we have performed our first surgery with cardiopulmonary bypass, only one team (P?tzsch et al., 1997) had described the use of the ECT in whole blood. We describe in this work our assay to dose hirudin with ECT after dilution in whole blood. This assay was used during 8 CEC among 7 patients affected with HIT (n = 6) or potentially sensitized with heparin (n = 1). Experimental conditions and interpretation of the assay are reported here. This test is fast enough to provide useful information for adjusting the dose during cardiopulmonary bypass.