Rate of change of clot flexibility during cardiac bypass surgery

Abstract

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.