Depression of host-defence mechanisms following cardiac surgery.

The purpose of the present study was to determine the effects of open-heart surgery on host-defence mechanisms, by studying serial changes in serum immunoglobulins, circulating lymphocyte function in patients undergoing open-heart surgery. Serum proteins and immunoglobulins were significantly depressed immediately after operation and these depressions were correlated to the degree of the durations of cardiopulmonary bypass and associated hypothermia. White cell counts in peripheral blood increased significantly after operation. In contrast, total circulating lymphocytes were depressed postoperatively. The depression of circulating lymphocytes was mainly due to a marked decrease in the number of T-cells. Mitogen responses of lymphocytes stimulated by phytohemagglutinin were also depressed postoperatively. The quantitative and qualitative depression of cell-mediated immunity following open-heart surgery was observed. However, these depressions returned to preoperative levels in one week and had no clinical significance.