Decreased platelet number and function and increased fibrinolysis contribute to postoperative bleeding in cardiopulmonary bypass patients.

We simultaneously evaluated platelet and fibrinolytic parameters to assess their individual and combined contributions to postoperative blood loss in cardiopulmonary (CP) bypass patients. Platelet count, platelet aggregability, hematocrit, plasminogen (PLG) concentration, alpha 2-antiplasmin (AP) concentration, free protease activity (fPA), and antithrombin-III (AT-III) were measured in nine patients undergoing surgery using cardiopulmonary bypass. Chest tube drainage was used as the measure of postoperative blood loss. Hematocrit, platelet count, PLG, AP, and AT-III all decreased during CP bypass, with PLG and AT-III decreasing much more than dilution. During CP bypass, platelet aggregability to ADP did not change significantly from pre-bypass, but aggregability to arachidonic acid (AA) decreased significantly. Following protamine administration there was a large increase (83%) in fPA, the platelet count showed a further drop (from 61% to 50% of pre-bypass levels), and platelet aggregability decreased significantly (from 95% to 34% of pre-bypass levels for ADP, and from 55% to 11.9% for AA). Chest tube drainage during the first four postoperative hours correlated positively (p less than 0.05) with the combination of increase in free protease activity and decrease in platelet count. The total chest tube drainage correlated significantly with the combination of decrease in platelet count and the decrease in platelet aggregability. These combinations of changes correlated significantly with postoperative blood loss whereas the individual changes did not.(ABSTRACT TRUNCATED AT 250 WORDS)