Effects of Cardiopulmonary Bypass on Hemostasis

摘要

The vast majority of cardiac surgical operations are performed with cardiopulmonary bypass (CPB). Blood contact with the extracorporeal circuit used during CPB elicits a wide spectrum of pathophysiological changes that affect a variety of organ systems. In a broad, sense the hematologic changes brought about by CPB are probably the most important of these pathophysiologic states because they result in the most pronounced clinical abnormality, increased postoperative bleeding, and because they affect several of the abnormal clinical manifestations of other organ systems (e.g., increased capillary permeability leading to respiratory abnormalities). It has long been recognized that CPB results in abnormal hemostasis that leads to increased postoperative bleeding. The exact nature of this hemostatic abnormality remains the subject of intense investigation, although platelet function abnormalities and hyperfibrinolysis have been shown to contribute to it significantly. The purpose of this chapter is to provide a description of our current knowledge of the hematologic changes observed in the course of CPB, to review our understanding of the nature of the hemostatic defect elicited by contact with the extracorporeal circuit, and to address clinical issues related to postoperative blood loss, the most important clinical outcome of these pathophysiologic states.