CONTINUING EDUCATION Coagulation and Platelet Function During Cardiopulmonary Bypass Surgery

Bachmann and coworkers in Chicago have performed a careful study of coagulation parameters after cardiopulmonary bypass surgery .1 In 512 patients, they found a 4% incidence of postoperative bleeding. More than half of these cases were due to surgically correctable causes. About 2% of the population were considered to be bleeding because of an acquired coagulation disorder. One half of these cases, or approximately I% of the total population, had an acquired defect in the enzymatic coagulation system, and the remaining 1% had an acquired platelet defect. Twenty-nine patients, or 6% of the total population, were identified by having markedly abnormal coagulation tests. Only four of these bled. Two patients had pre-existing severe congestive heart failure with liver dysfunction. The liver dysfunction was thought to contribute significantly to the postoperative coagulation disorder and bleeding problem. One patient was thought to suffer from heparin rebound, and one patient was thought to have Disseminated Intravascular Coagulation. In general, it was thought that most abnormal coagulation tests were due to heparin rebound. Of interest was the frequent mild-to-moderate abnormality of the prothrombin time, which was not due to specific factor deficiencies. It was speculated that the prolonged prothrombin time was due to an unidentified inhibitor in the prothrombin system, which did not affect the partial thromboplastin time.