Assessment of thrombin generation measured before and after cardiopulmonary bypass surgery and its association with post-operative bleeding.J Thromb Haemost 2011; 9: 282-92.Summary. Background: Bleeding after cardiopulmonary bypass (CPB) is a major cause of morbidity and mortality and consumes large amounts of blood. Identifying patients at increased risk of bleeding secondary to hemostatic impairment may improve clinical outcomes by allowing early intervention. Methods: This present study recruited 77 patients undergoing CPB and measured coagulation screens, coagulation factors, TEG Ò , Rotem Ò and thrombin generation (TG) before surgery and 30 min after heparin reversal. The tests were analyzed to investigate whether they identified patients at increased risk of excess bleeding (defined as > 1000 mL) in the first 24 h postoperatively. Results: Patients who bled > 1000 mL had a lower: platelet count (P < 0.02), factors (F)IX, X and XI (P < 0.005), endogenous thrombin potential (ETP) and an initial rate of TG (P < 0.02) and higher activated partial thromboplastin time (aPTT) (P < 0.001) than patients who bled < 1000 mL. Receiver operating characteristic (ROC) analysis was significant for post-operative TG and aPTT (P < 0.001). Furthermore, reduced pre-operative TG was associated with increased postoperative bleeding (P < 0.02). Pre-and postoperative TG were correlated (q = 0.7, P < 0.001). TEG Ò , Rotem Ò and prothrombin time (PT) at either time point were not associated with increased bleeding. Conclusion: These data suggest that pre-operative defects in the propagation phase of hemostasis are exacerbated during CPB, contributing to bleeding post-CPB. TG taken both pre-and postoperatively could potentially be used to identify patients at an increased risk of bleeding post-CPB.

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The incidence of POCD reported varies depending on which battery of neurocognitive tasks is chosen and also which statistical tests are utilised. Although a wide range is demonstrated it would perhaps be better to have a smaller range defining POCD. Further work including exploration of the sensitivity and specificity of particular tests is required in order to ascertain how one should define POCD. Following on from this the role of blood markers may be explored. Routine coagulation tests are poorly predictive of bleeding because they are activated in non-physiological ways and do not measure the rate of clot formation (CF), an important aspect of in vivo haemostasis [1]. Tests that are activated by physiological concentrations of tissue factor (TF) and measure the rate of CF may better predict bleeding and be useful to guide blood products usage. MethodsTwenty-six patients undergoing cardiac bypass and at high risk of bleeding were recruited. Whole blood samples pre-and postbypass were assayed using standard and novel tests of CF. The novel tests were thromboelastometry (ROTEM) using a physiological concentration of TF with contact activation inhibited and clot flexibility data mathematically manipluated to calculate the maximum velocity (Vmax) and time to Vmax (TVmax) of CF. Normal values were established on 30 healthy volunteers (HV). Data were analysed with Wilcoxon* and Mann-Whitney U-tests**.Results (see Table 1) DiscussionThese data demonstrate that, after cardiac bypass, the maxium rate of clot formation is reduced and delayed. Further studies are underway to establish whether the measurement of the rate of clot fomration is more useful than standard assays in predicting postoperative bleeding endpoints. Results shown are median and inter-quartile ranges in HVs, pre-and post-bypass. No significant difference was shown between HVs and prebypass. p1, HV vs post-bypass; p2, pre-vs post-bypass.