Hemostasis during cardiopulmonary bypass

Cardiopulmonary bypass (CPB) extensively activates the hemostatic system. When blood comes into contact with nonendothelial surfaces, it activates platelets and factor XII triggering the coagulation intrinsic pathway. At the same time, cardiac surgery itself is responsible for mechanical tissue damage, tissue factor exposure, and activation of the extrinsic pathway. Laminar flow induces proinflammatory cytokines release. Hemodilution, together with hypothermia, significantly reduces concentration of fibrinogen and coagulation factors. Longer CPB runs decrease postoperative platelets count and function. Moreover, medications affecting the coagulation system are commonly used by patients undergoing cardiac surgery. Thus careful anticoagulation management during CPB is required to avoid life-threatening thromboembolic and bleeding complications. Unfractionated heparin (UFH) is the gold-standard anticoagulant used with extracorporeal circulation and it is monitored with the point-of-care activated clotting time test. Careful attention should be paid in case of antithrombin deficiency due to increased risk of heparin resistance. Furthermore, inadequate heparin reversal with protamine may lead to postoperative heparin rebound. In the event of specific clinical conditions such as active heparin-induced thrombocytopenia, heparin allergy, and protamine allergy, alternatives to UFH must be considered.