Dose-dependent effects of intraoperative low volume red blood cell transfusions on postoperative outcomes in cardiac surgery patients

Objective: To determine the incremental risk associated with each intraoperative red blood cell transfusion in cardiac surgery patients.

Design: Retrospective analysis on prospectively collected data.

Setting: Single tertiary care hospital.

Participants: Seven hundred forty-five patients undergoing on-pump cardiac surgery between January 2010 and June 2012 who received between 1 and 3 units of red blood cell transfusion intraoperatively.

Interventions: All patients received between 1 and 3 units of red blood cell transfusions. All transfusions were with leukoreduced blood that had been stored for < 14 days.

Measurements and main results: Postoperative complications and length of intubation were associated with the number of red blood cell units transfused. Transfusion of each additional unit of red blood cells was associated with incrementally worse outcomes. Median length of intubation was 11 hours, 12 hours, and 13 hours in patients receiving 1, 2, and 3 units of red blood cell transfusions, respectively (p < 0.005). Similarly, each additional unit of red blood cell transfusion was associated with increasing postoperative septicemia (0% v 0.35% v 2.29%, p < 0.006) and postoperative pneumonia (0% v 0.70% v 2.29%, p < 0.013).

Conclusions: There is a step-wise increase in length of postoperative intubation with each red blood cell transfusion in patients undergoing cardiac surgery. Each additional unit of intraoperative RBC transfusion also may increase postoperative infectious complications. Thus, even single-unit reductions in red blood cell transfusions may have significant impact on outcomes.