Effects of transfusing older red blood cells on patient outcomes in critical illness: A retrospective cohort study.

Background and objectives: Randomized controlled trials have demonstrated morbidity and mortality in critically ill patients are unaffected by transfusing fresh (<7 days old) packed red blood cells (pRBCs); however, there is limited evidence regarding transfusion with pRBCs nearing expiry (35-42 days). The aim of this study was to investigate the effects of transfusing pRBCs close to the end of shelf life (≥35 days) on clinical outcomes in critically ill patients.

Materials and methods: A retrospective observational analysis of data obtained from centralized electronic medical records (2007-2013), sourced from all public and licensed private hospitals in Queensland, Australia, with intensive care units. Multivariate logistic and linear regressions were used to analyse association between transfusion with pRBCs nearing expiry, and in-hospital mortality, hospital length of stay (HLOS) and rate of discharge home. Comparisons are presented as odds ratios (ORs) with 95% confidence intervals (CIs).

Results: The study included 10,350 critically ill adult patients transfused ≥1 unit of non-irradiated pRBCs (64,594 pRBCs units transfused). Receiving at least 1-unit pRBCs ≥ 35 days old was associated with increased mortality (OR 1.21 [95% CI 1.06-1.38]; p = 0.005), decreased discharge to usual residence (OR 0.81 [95% CI 0.73-0.89]; p < 0.0001) and increased hospital LOS (estimate 2.55 [95% CI 1.60-3.49]; p < 0.0001). There was also association with increased sepsis (OR 1.27 [95% CI 1.13-1.42]; p < 0.0001) and delirium (OR 1.25 [95% CI 1.06-1.49]; p = 0.01).

Conclusion: Transfusion of ≥1-unit pRBCs ≥ 35 days old was associated with higher morbidity and mortality in critically ill patients.