Retransfusion of pericardial blood does not trigger systemic coagulation during cardiopulmonary bypass

During cardiopulmonary bypass (CPB), systemic coagulation is believed to become activated by blood contact with the extracorporeal circuit and by retransfusion of pericardial blood. To which extent retransfusion activates systemic coagulation, however, is unknown. We investigated to which extent retransfusion of pericardial blood triggers systemic coagulation during CPB.

Thirteen patients undergoing elective coronary artery bypass grafting surgery were included. Pericardial blood was retransfused into nine patients and retained in four patients. Systemic samples were collected before, during and after CPB, and pericardial samples before retransfusion. Levels of prothrombin fragment F(1+2) (ELISA), microparticles (flow cytometry) and non-cell bound (soluble) tissue factor (sTF; ELISA) were determined.

Compared to systemic blood, pericardial blood contained elevated levels of F(1+2), microparticles and sTF. During CPB, systemic levels of F(1+2) increased from 0.28 (0.25-0.37; median, interquartile range) to 1.10 (0.49-1.55) nmol/l (p=0.001). This observed increase was similar to the estimated (calculated) increase (p=0.424), and differed significantly between retransfused and non-retransfused patients (1.12 nmol/l vs 0.02 nmol/l, p=0.001). Also, the observed systemic increases of platelet- and erythrocyte-derived microparticles and sTF were in line with predicted increases (p=0.868, p=0.778 and p=0.205, respectively). Before neutralization of heparin, microparticles and other coagulant phospholipids decreased from 464 microg/ml (287-701) to 163 microg/ml (121-389) in retransfused patients (p=0.001), indicating rapid clearance after retransfusion.

Retransfusion of pericardial blood does not activate systemic coagulation under heparinization. The observed increases in systemic levels of F(1+2), microparticles and sTF during CPB are explained by dilution of retransfused pericardial blood.