• Keyvan Karkouti, Stuart A McCluskey, Summer Syed, Chris Pazaratz, Humara Poonawala, and Mark A Crowther.
• Department of Anesthesia, Toronto General Hospital, 200 Elizabeth St., EN3-402, Toronto, ON, Canada M5G 2C4. keyvan.karkouti@uhn.on.c
• Anesth. Analg. 2010 Jun 1;110(6):1533-40.

IntroductionCoagulopathy leading to excessive blood loss is a serious complication of cardiac surgery. In this prospective cohort study, we measured patients' coagulation status before and after cardiopulmonary bypass (CPB) and examined their relationships with postoperative blood loss.MethodsPatients undergoing complex cardiac surgery with CPB who did not have preexisting coagulopathy were eligible. Detailed clinical and coagulation data were prospectively collected on all patients. Coagulation testing was performed before and after CPB, and included measures of thrombin generation, clotting factor consumption and dilution, clot stabilization, and fibrinolysis. The associations of variables with post-CPB blood loss (estimated loss from CPB to intensive care unit admission and 24-hour chest tube drainage) were assessed with the Spearman rank correlation test and multivariable linear regression.ResultsThe median blood loss among the 101 study patients was 952 mL (interquartile range, 601-1553 mL). Variables independently associated with increasing blood loss were as follows: previous sternotomies (P = 0.01), lower pre-CPB prothrombin fragment F1 + 2 levels (measure of thrombin generation; P = 0.001), lower post-CPB platelet counts (P = 0.01), larger percent decrease in fibrinogen levels (P = 0.05), and higher post-CPB soluble fibrin monomer levels (measure of thrombin activity and clot stabilization; P < 0.0001) (model R(2) = 0.43).ConclusionsIn complex cardiac surgery, blood loss is directly influenced by reduced pre-CPB thrombin generation rate, increased post-CPB consumption and dilution of clotting factors, as well as inadequate post-CPB clot stabilization. This information can aid in identifying patients at high risk for excessive blood loss and testing new interventions aimed at reducing the burden of this complication. The validity and generalizability of these findings need to be assessed by other studies.

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