Monitoring of Haemostasis and Anticoagulation in Cardiopulmonary Bypass Patients

Patients undergoing cardiac surgery with cardiopulmonary bypass are at risk of increased blood loss and transfusion requirements. Contact of blood with the surgical wound and the artificial surfaces of the extra-corporeal circuit results in a coagulopathy. Haemodilution during cardiopulmonary bypass also aggravates the reduction of haemostatic factors even further. On the other hand, systemic anticoagulation using high dose unfractionated heparin challenges the adequate anticoagulant monitoring. The most frequently used test to monitor systemic anticoagulation is the whole blood activated clotting time. This has, however, proven not be a reliable test. Other haemostatic assays have their own advantages and disadvantages, but tools to monitor anticoagulation and haemostasis adequately during and after cardiopulmonary bypass are to date lacking and/or show only a weak association with clinical bleeding. Viscoelastic whole blood techniques (TEG/ROTEM) have emerged as alternatives to the routine coagulation tests, and could be more suitable for providing information about the different phases of the blood clotting. Platelet function tests give more information about the presence of platelet dysfunction one, which is a major cause of bleeding after cardiac surgery. Likewise, thrombin generation tests reflect much, if not all, of the overall function of the blood clotting system. Further research of the applicability and added values of the viscoelastic whole blood tests and the thrombin generation tests in the cardiac surgical patient undergoing cardiopulmonary bypass is warranted. Simplicity in performing the test, preferably point-of-care, and rapid availability of the results, should thereby be the primary focus for targeted haemostatic interventions.