A randomized controlled pilot study of adherence to transfusion strategies in cardiac surgery

It is important to determine the optimal hemoglobin (Hb) concentration for red blood cell (RBC) transfusion for patients undergoing cardiac surgery because increased mortality has been associated with the severity of anemia and exposure to RBCs. Because a definitive trial will require thousands of patients, and because there is variability in transfusion practices, a pilot study was undertaken to determine adherence to proposed strategies.

A single-center parallel randomized controlled pilot trial was conducted in high-risk cardiac patients to assess adherence to two transfusion strategies. Fifty patients were randomly assigned either to a "restrictive" transfusion strategy (RBCs if their Hb concentration was 70 g/L or less intraoperatively during cardiopulmonary bypass [CPB] and 75 g/L or less postoperatively) or a "liberal" transfusion strategy (RBCs if their Hb concentration was 95 g/L or less during CPB and less than 100 g/L postoperatively).

The percentage of adherence overall was 84% in the restrictive arm and 41% in the liberal arm. Twenty-two (88%) patients were transfused 99 units of RBCs in the liberal group compared to 13 patients who were transfused 50 units in the restrictive group (p<0.01). There were no significant differences in individual adverse outcomes; however, more adverse events occurred in the restrictive group (38 vs. 15, p<0.01).

Adherence to the evaluated interventions is vital to all randomized controlled trials as it has the potential to affect outcomes. Further pilot studies are required to optimize enrollment and transfusion adherence before a definitive study is conducted.