Influence of heparin, heparin plus aprotinin and hirudin on contact activation in a cardiopulmonary bypass model

In the present study the authors used an in vitro cardiopulmonary bypass model to compare activation of the FXII-plasma kallikrein systems, coagulation pathway and blood cell changes, with heparin (3 U/ml), heparin plus aprotinin (3 U/ml and 250 KIU/ml) and recombinant hirudin (6 μg/ml). After 90 minutes circulation the results showed that with heparin plus aprotinin and with hirudin the activation of these cascade reactions was markedly lower. In particular kallikrein-like activities and PMN-Elastase-α₁-PI levels were significantly lower in the latter two groups. The least activation was detected with hirudin. The authors´ results confirm that the contact systems of blood are activated during CPB with heparin as anticoagulant that aprotinin reduces this activation and that recombinant hirudin would be preferred to heparin as an anticoagulant in cardiac surgery