Effect of Red Blood Cell Storage Duration on Major Postoperative Complications in Cardiac Surgery: A Randomized Trial

Abstract Objectives Although observational studies suggest an association between transfusion of older red blood cell units (RBCs) and increased postoperative risk, randomized trials have not supported this. The objective of this randomized trial was to test the effect of RBC storage age on outcomes after cardiac surgery. Methods From 7/2007–5/2016, 3,835 adults undergoing CABG, valve procedures, or ascending aorta repair, alone or combined, were randomized to transfusion of RBCs stored ≤14 days (younger units) or ≥20 days (older units) intraoperatively and throughout postoperative hospitalization. By protocol, 2,448 patients were excluded because they were not transfused. Among the remaining 1,387 modified intent-to-treat patients, 701 were randomized to receive younger RBC units (median 11 days) and 686 to receive older units (median 25 days). The primary endpoint was composite morbidity and mortality, analyzed using a generalized estimating equation (GEE). The trial was discontinued midway for enrollment constraints. Results 5,470 RBC units were transfused, 2,783 in younger and 2,687 in older RBC storage groups. GEE average relative-effect odds ratio was 0.77 (95% CI 0.50–1.19; P=.083) for the composite morbidity and mortality endpoint. Observed in-hospital mortality was lower for younger versus older RBCs (n=15 [2.1%] vs n=23 [3.4%]), as was occurrence of other adverse events except for atrial fibrillation, although all CIs crossed 1.0. Conclusions This clinical trial, stopped at midpoint for enrollment constraints, supports neither efficacy nor futility of transfusing either younger or older RBC units. The effects of transfusing RBCs after even more prolonged (35–42 days) storage remains untested.