Vascular resistance during cardiopulmonary bypass. Its effect on cardiac performance in the immediate post-bypass period.

A clinical study was undertaken to measure changes in systemic vascular resistance during cardiopulmonary bypass in 56 adults. Forty-five patients showed a rise in systemic vascular resistance and 77% required no inotropic support in the immediate post-bypass period. Eleven of the 33 patients undergoing valve replacement surgery showed only a small increase or an actual decrease in systemic vascular resistance and required inotropic support. These results were statistically significant. Factors affecting cardiac performance are discussed.