Thrombin generation during cardiac bypass surgery

Current concepts of haemostasis suggest that the amount of thrombin produced and the rate at which this occurs is the critical step in clot formation. Thrombin generation (TG) is measured by calibrated automated thrombography (CAT) activated by physiological concentrations of tissue factor in platelet rich (PRP) and poor (PPP) plasma [1]. CAT may therefore be useful in predicting bleeding and be a better guide to blood product use. CAT establishes values for rate of TG, lag time to commence TG, peak thrombin level and endogenous thrombin potential (ETP), a measure of total thrombin produced. The aim of this study was to compare CAT in healthy volunteers and patients undergoing cardiac bypass surgery. Blood was taken from 26 patients at high risk of bleeding before and after cardiac bypass. TG was measured in PRP and PPP by CAT. Normal values were established from 30 healthy volunteers (HV). Wilcoxon* and Mann–Whitney U-tests** were used to analyse data. The data show that all parameters of TG are reduced after cardiac surgery in both PRP and PPP. It is possible that these assays may better predict bleeding than current standard assays and they may have a role in patient management. Ongoing studies will establish whether parameters of TG taken following cardiac bypass predict postoperative bleeding.