Is increased mortality associated with post-operative infections after leukocytes containing red blood cell transfusions in cardiac surgery? An extended analysis

In two randomized trials in cardiac surgery we observed that leukoreduced allogeneic red blood cell (RBC) transfusions (LR) compared with standard buffy-coat-depleted RBC transfusions (BCD) resulted in lower rates of post-operative infections and mortality. To unravel whether this comprises two independent side effects or could be related complications of allogeneic leukocytes, we performed a re-analysis on the patients of these two trials. For all analyses, homogeneity tests were shown not to be significant. Data on characteristics of post-operative infections, nature of microorganisms, number of transfusions and causes of death in both studies were subjected to an integrated analysis. In both studies combined, 1085 patients had been assigned to prestorage leukoreduced RBCs (LR, n= 542) or standard buffy-coat-depleted RBCs (BCD, n= 543). Post-operative infections were significantly higher in the BCD group [BCD: 34.2% vs. LR: 24.0%, common odds ratios (COR): 1.65, 95% confidence interval (CI): 1.27-2.15], whereas the species of cultured microorganisms and the type of the infections were similar in both randomization arms. Mortality with infections was significantly higher in patients receiving BCD compared with LR (BCD: 5.5% vs. LR: 2.2%, COR: 2.59, 95% CI: 1.31-5.14), whereas mortality without infections was similar in both arms (BCD: 3.9% vs. LR: 3.1%, COR: 1.24, 95% CI: 0.65-2.38). The only cause of death that differed significantly between BCD and LR was the combination of multiple organ dysfunction syndrome with infections. This re-analysis shows that transfusion of leukocytes containing RBCs during cardiac surgery may be associated with more infections with fatal outcome. This should be confirmed in a larger extended analysis or a prospective study