No association between storage time of transfused red blood cells and in-hospital mortality in massively transfused patients: Results from the Australian and New Zealand massive transfusion registry.

Background: Clinical trials comparing transfusion of fresher vs. older red blood cells (RBCs) have not focused on patients experiencing massive transfusion (MT). The clinical impact of storage lesions may be accentuated in this patient group. Method(s): 2007-2018 data from 25 participating hospitals in the Australian and New Zealand Massive Transfusion Registry were analysed to determine the association between in-hospital mortality and RBC storage time (ST) in MT cases (>=5 RBCs within 4 hours, any bleeding context). Logistic regression was used with in-hospital mortality as the outcome, number of transfused RBCs as a co-variate, and mean storage time quartiles of transfused RBCs as the predictor, along with an interaction term. Two sensitivity analyses were run using (1) maximum storage time of the transfused RBCs and (2) proportion of RBCs >=30 days old as predictors. Result(s): Mean storage times for the database's 7890 MT episodes were (by quartile) STmean-Q1 = 13.0 days; STmean-Q2 = 18.9 days; mean-Q3 = 23.5 days; STmean-Q4 = 30.6 days. Using the first quartile (freshest blood) as a control, the second quartile had a higher in-hospital mortality (OR = 1.30 [95% CI: 1.03 to 1.64; P = 0.02]). Difference in mortality for other quartiles compared to the first were not statistically significant, nor was the interaction term for mean storage time and number of RBCs. Sensitivity analyses showed no difference in mortality between quartiles based on maximum storage time or proportion of longer-stored (>=30 days) RBCs. Conclusion(s): No systematic correlation between in-hospital mortality and storage time of transfused RBCs was observed. The one statistically significant result (mortality of storage-timeQ2 vs. storage-timeQ1) was not detected in either sensitivity analysis. These results are consistent with those of large multi-centre trials on the subject1-4. We find no previous study addressing this research question in a large cohort of MT patients.