Correlation of perioperative platelet function and coagulation tests with bleeding after cardiopulmonary bypass surgery.

The authors evaluated the correlation of post-cardiopulmonary bypass surgery bleeding, measured as 24-hour chest tube output/kilogram body weight, with platelet function tests using glass bead adhesion and Thrombelastograph Platelet Mapping (Haemoscope Corporation, Niles, Ill); coagulation tests; patient characteristics; surgery parameters; and visual assessment of surgical field bleeding before closure as not bleeding (code 1), oozing (code 2), and excessive bleeding (code 3). All platelet function and coagulation tests indicated significant dysfunction 15 minutes after protamine neutralization of heparin. With the exception of glass bead adherence, these assays indicated poor recovery of function 1 hour postoperatively. By multiple regression, the most significant predictors of postoperative bleeding were a low body mass index (BMI) (P < 0.0001), lowest core body temperature (P = 0.0006), and cross clamp time (P < 0.0001). Low core temperature was significantly (P < 0.0001) correlated with cross clamp time, which the authors believe is the most likely cause of coagulation and platelet dysfunction. None of the platelet function tests significantly correlated with bleeding. Looking at the highest quartile of chest tube output patients (n = 19) versus the upper and lower 50th percentile of coagulation and platelet function, bleeding could be explained for 11 patients by BMI plus surgery parameters along with coagulation and/or platelet dysfunction. In three cases without negative surgery parameters, coagulation dysfunction was observed. The remaining five cases did not give a clear indication of which parameters were primarily responsible for the bleeding.