Increased long-term mortality with plasma transfusion after coronary artery bypass surgery

Patients undergoing cardiac surgery often require transfusions of red blood cells, plasma and platelets. These components differ widely in both indications for use and composition. However, from a statistical point of view there is a significant colinearity between the components. This study explores the relation between the transfusion of different blood components and long-term mortality.

A retrospective single-centre study was performed including 5,261 coronary artery bypass grafting patients, excluding patients receiving more than eight units of red blood cells, those suffering early death (7 days) and emergency cases. Patients were followed up for a period of up to 7.5 years. A broad spectrum of potential risk factors was analysed using Cox proportional hazards survival regression. Non-significant risk factors were removed by step-wise elimination, and transfusion of red blood cells, plasma and platelets was forced to remain in the model.

The transfusion of red blood cells was not associated with decreased long-term mortality (HR = 1.007, p = 0.775), whereas the transfusion of plasma was associated with decreased long-term survival (HR = 1.060, p < 0.001), and the transfusion of platelets was associated with increased long-term survival (HR = 0.817, p = 0.011). The risk associated with transfusion of plasma was mainly attributed to patients receiving large amounts of plasma. All hazard ratios are per unit of blood product transfused.

No association was found between the transfusion of red blood cells and mortality during the study period. However, transfusion of plasma was associated with increased mortality while transfusion of platelets was associated with decreased mortality during the study period.