Human whole blood was anticoagulated with different concentrations of heparin (0.75, 1, 2 or 3 IU/ml) and circulated in the Chandler-loop model for up to 240 min at 37 掳C. Next to ACT, ECC-mediated changes in free active thrombin, prothrombin fragment 1 + 2 (F1 + 2) and thrombin-antithrombin-III (TAT) levels were measured before and during circulation. Platelet activation and cell count parameters were further investigated.
Our study shows that detection of ECC-mediated changes in free thrombin is possible in blood anticoagulated with 0.75 or 1 IU/ml heparin, whereas no thrombin was detectable at higher heparin concentrations. Thrombin generation during 240 min of ECC is comparable to F 1 + 2 and TAT plasma levels during ECC.
Thrombin is the key enzyme in the coagulation cascade and hence represents a promising marker for monitoring the coagulation status of patients. Although detection of free thrombin was not feasible at high heparin concentrations, the employed test represents an additional test to current laboratory methods investigating blood coagulation at low heparin concentrations.