THE COMBINATION OF INCREASED FIBRINOLYTIC ACTIVITY AND REDUCED PLATELET NUMBER AND FUNCTION CONTRIBUTES TO POSTOPERATIVE BLEEDING IN CARDIOPULMONARY BYPASS PATIENTS

Abstract

Both increased fibrinolysis and reduced platelet number and function have been reported postoperatively in cardiopulmonary (CP) bypass patients, but correlations with postoperative bleeding often have not been found. We simultaneously evaluated platelet and fibrinolytic parameters to assess their individual and combined contributions to postoperative blood loss. Plasminogen (pig) concentration, alpha-2-antiplasmin (AP) concentration, free protease activity (fPA), platelet count, and platelet aggregability were measured in nine patients undergoing cardiopulmonary bypass surgery. Hematocrit was also measured in order to determine the degree of blood dilution during CP bypass. Chest tube drainage was used as the measure of postoperative blood loss. Pig and AP concentrations decreased With hemodilution during bypass. fPA did not decrease with dilution but remained at pre-bypass levels. Platelet count decreased during bypass but aggregability to ADP and arachidonic acid (AA) did not change 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). Early chest tube drainage (1st 4 hrs postoperatively) correlated positively (p[0.05) with the combination of increase in free protease activity and decrease in platelet count. Total chest tube drainage correlated positively (p[ 0.05) with the combination of increase in free protease activity and decrease in platelet aggregability to ADP. None of the measured parameters individually showed significant correlation with chest tube drainage. In this patient sampling, however, the combination of changes in fibrinolytic activity and changes in platelet function did correlate significantly with chest tube drainage. These data indicate that the increased fibrinolytic activity and the decreased platelet number and function have a synergistic effect on postoperative blood loss in CP bypass patients.