Standard coagulation assays during cardiopulmonary bypass predict post-bypass levels in cardiac surgery

Cardiac surgery with cardiopulmonary bypass (CPB) requires precise hemostasis management to limit postoperative bleeding. Fibrinogen, platelet count, and pro-coagulant factors guide transfusion decisions, yet Clauss fibrinogen measurement during CPB is debated, and prothrombin time (PT) cannot be measured accurately due to interference from high-dose heparin. This study investigated whether intraoperative measurements of fibrinogen, prothrombin (FII), factor V (FV), and platelet obtained during CPB could reliably predict post-CPB values.

We conducted a single-center, prospective observational study involving 73 adult patients undergoing cardiac surgery with CPB. Blood samples were collected before aortic unclamping and five minutes after completion of protamine administration. Fibrinogen (Clauss method), FII, and FV activities were measured using HemosIL reagents on an ACL TOP analyzer.

Using appropriate reagents, fibrinogen, FII, and FV were reliably measured during CPB, despite high-dose heparin. Strong correlations were observed between intra-CPB and post-CPB values for fibrinogen (r = 0.81), FII (r = 0.78), and FV (r = 0.73), supporting their reliability in anticipating post-bypass coagulation status. ROC curve analyses demonstrated good predictive performance for transfusion-relevant thresholds, with AUCs of 0.93 for platelet count <100 G/L, 0.86 for fibrinogen <1.5 g/L, and 0.84 for FII < 50% activity.

This study showed that fibrinogen and factor II (a surrogate for PT) levels remain consistent between the CPB period and after protamine administration in adult cardiac surgery patients, confirming the reliability of their intraoperative assessment.