Retransfusion of cardiotomy suction blood impairs haemostasis: ex vivo and in vivo studies.

Objectives: Cardiotomy suction blood in volumes corresponding to 10-20% of the systemic blood volume is retransfused during cardiopulmonary bypass. We hypothesized that retransfusion of unwashed cardiotomy suction blood influences coagulation and platelet function.

Design: Systemic blood samples collected during cardiopulmonary bypass were supplemented ex vivo with autologous wound blood (5, 10 and 20%, respectively). Clot formation and platelet function were assessed with thromboelastometry and platelet aggregometry. In an in vivo pilot study 30 patients were randomized into a retransfusion and a no-retransfusion group. Clot formation, platelet aggregability and thrombin generation capacity were compared between the groups.

Results: Cardiotomy suction blood had markedly impaired clot stability and reduced levels of fibrinogen and platelets compared with systemic blood. Ex vivo addition of 10% and 20% suction blood to systemic blood impaired platelet aggregability and clot stability. Retransfusion of small amounts of wound blood in vivo (mean volume 280 ml, corresponding to 5% of the blood volume) did not significantly influence haemostasis.

Conclusions: The ex vivo results suggest that addition of unwashed cardiotomy suction blood in clinically relevant volumes impairs systemic haemostasis. Retransfusion of smaller volumes in vivo has no or limited impact. Avoiding retransfusion of larger amounts of unwashed cardiotomy suction may improve postoperative haemostasis.