Changes in the coagulation and fibrinolytic systems during and after cardiopulmonary bypass surgery.

Components of the coagulation and fibrinolytic systems were determined in patients undergoing open heart surgery with cardiopulmonary bypass. The variables studied included prothrombin, antithrombin-III, spontaneous plasmin activity, plasminogen and functional antiplasmin activity. The variables were measured using chromogenic peptide substrate assays. A marked, transitory, increase in spontaneous plasmin activity prior to cardiopulmonary bypass, but after heparin injection was found. A decrease in antiplasmin activity during bypass was observed, while actual plasminogen level, when correcting for hemodilution, was unchanged. Both prothrombin and antithrombin-III paralleled the decrease in hemoglobin concentration during bypass. These findings suggest that the injection of heparin induced a transient activation of the fibrinolytic system, whereas no detectable consumption of the measured coagulation variables was observed.