Rotational thrombelastometry for the bedside monitoring of recombinant hirudin

Background: Recombinant hirudin is used as an alternative anticoagulant, particularly in patients with heparin-induced thrombocytopenia type II. However, bedside monitoring for hirudin is not available. The present study aims to evaluate rotational thrombelastometry regarding its suitability to detect the effects of recombinant hirudin on whole blood coagulation. Hirudin was added to whole blood samples from healthy donors (n = 5) and thrombelastometry variables resulting from activation of samples with tissue factor, ellagic acid, and ecarin were determined. Methods: Hirudin (0.1-10 μg/ml) was added to citrated blood. Thereafter, rotational thrombelastometry was performed by initiating coagulation via recalcification and addition of tissue factor, ellagic acid, and ecarin, respectively, using the commercially available assays. Results: In the absence of hirudin, clotting times (CT) induced by ellagic acid, tissue factor, and ecarin, respectively, were 141.7 ± 18.0, 54.0 ± 7.6, and 64.5 ± 4.1 s. Increasing concentrations of hirudin led to dose-dependent prolongation of the clotting time with the three activators. All assays were capable to detect hirudin concentrations in the range of 0.5-5 μg/ml. At a final hirudin concentration of 1 μg/ml, clotting time increased to 268.0 ± 25.1, 84.0 ± 9.3, and 107.5 ± 9.9s, respectively, with the above-mentioned activators. The other thrombelastographic variables, including clot formation time, angle α, and maximum clot firmness, were not altered by hirudin at concentrations up to 5 μg/ml. Conclusions: Our study demonstrates the suitability of rotational thrombelastometry to detect anticoagulant effects of recombinant hirudin.