A study of the effects of extracorporeal circulation on the immunologic system of humans.

Objectives: The objectives of this study were to quantify the immunosuppressive effects of cardiopulmonary bypass (CPB) and to identify mechanisms responsible for the postoperative immunosuppression of patients undergoing cardiac surgery.

Design: A prospective study from 20 consecutive patients.

Setting: The same team operated on all patients in a major teaching hospital, and the immunologic tests were performed in the hospital's hematology laboratory.