Relationship of fibrinolysis and platelet function to bleeding after cardiopulmonary bypass.

In order to study the effects of cardiopulmonary bypass (CPB) on fibrinolysis and platelet function and the possible relationship of these effects on post-operative blood loss, 127 patients undergoing CPB were examined. There was a significant reduction in the median levels of fibrinogen, plasminogen, alpha 2-antiplasmin, fibrinolytic potential and platelet aggregation during CPB (P < or = 0.001). Median levels of soluble fibrin, fibrinogen degradation products, D-dimer and PAI-1 were increased, while the level of t-PA activity remained constant. Post-CPB levels of fibrinogen and plasminogen correlated negatively with blood loss (P = 0.003 and P < 0.001, respectively) and interestingly, lower levels of alpha 2-antiplasmin and higher levels of t-PA activity before CPB were associated with greater blood loss after CPB (P < 0.001 and P = 0.004, respectively). Better pre-CPB platelet function correlated with lower levels of D-dimer before and after CPB. As expected, haemodilution had a significant effect on fibrinolytic and coagulation parameters post-CPB; the greater the haemodilution, the more the concentration of fibrinogen, plasminogen and alpha 2-antiplasmin fell post-CPB and the greater the blood loss. The increase in PAI-1 levels intra-CPB appeared to result in mean t-PA activity remaining unchanged 1 h post-CPB. Post-CPB increases in soluble fibrin were paralleled by increases in fibrinogen degradation products and D-dimer, suggesting that intra-operative contact activation is related to activation of the fibrinolytic system. The present findings indicate the greater the fibrinolytic activation, the greater the post-CPB blood loss.