Efficacy of A Collagen Hemostat Versus A Carrier-bound Fibrin Sealant

Aim: A fast activation time of hemostatic agents with blood must be sufficient to effectively stop bleeding within surgical procedures. However, there are no functional in vitro tests of hemostatic agents which mimick such a clinical application. Method: The efficacy of two common hemostatic agents was examined with heparinised human whole blood (0.7 IU/ml) and a contact time of only three minutes between blood and hemostatic agents. Traditional biochemical assays were compared with a new rheometric method for measuring clot formation. Results: Blood without previous material contact (negative control) induced a basal thrombin-antithrombin (TAT, 240 ± 85 μg/l) or ß-thromboglobulin (TG, 1000 ± 216 U/ml) complex formation. Stainless steel (positive control) or a thrombin coated equine collagen fleece failed to increase TAT or ß-TG. However, a bovine collagen fleece significantly increased formation of TAT (1426 ± 378 μg/l) or ß-TG (3829 ± 857 U/ml). In rheometric measurements of the negative control the clotting time (CT) was 17 ± 4 min and the clot strength (CS) was 71 ± 45Pa. In the positive control CT (stainless steel) was 9 ± 3 min and CS was 298 ± 68Pa. The equine collagen fleece caused no detectable stimulation of CT and CS whereas the bovine collagen fleece (CT 13 ± 3 min, CS 186 ± 86Pa) was almost as effective as stainless steel. Conclusion: Traditional biochemical parameters fail to indicate thrombogenicity under the tested conditions but oscillatory shear rheometry is a sensitive tool to analyse blood coagulation in vitro. Furthermore, mimicking the clinical relevant application times, the rheometric method detects functional differences of hemostatic agents. Since these differences correlate with in vivo data, the rheometric method is a valuable tool during the development of hemostatic agents.