Time matters in 1: 1 resuscitations: concurrent administration of blood: plasma and risk of death.

Background: The practice of 1:1 transfusion, administering packed red blood cells (PRBCs) with fresh frozen plasma (FFP), has been associated with improved survival. However, the reported ratios are the result of mathematical averages over 24 hours and do not necessarily represent concurrent administration. Using critical administration thresholds (CAT+) of more than 3 U of PRBC per hour to identify hemorrhaging patients, this study evaluates the effect of concurrent administration of PRBC/FFP on patient survival.
Methods: CAT+ patients identified retrospectively were eligible for analysis. The exact time of administration of each unit of PRBC and FFP was calculated. Each PRBC was matched to a corresponding unit of FFP given within 5 minutes before or after. Ideal 1:1 ratios were calculated for each hour during the first day of admission. Hourly ratio groups were created (25%, 50%, 75% of transfusion opportunities) and evaluated as time-varying covariates. Cox proportional hazard ratio (HR) was used to determine risk of mortality, and Student's t test or Wilcoxon signed-rank test was used to compare groups.
Results: A total of 169 patients were initially identified (70% with New Injury Severity Score [NISS] > 10), 77 of whom were CAT+. There were no clinical differences between the groups in this study. In terms of mortality, patients who reached the 1:1 ratio 25% of the transfusion opportunities had an HR of 8.806 (95% confidence interval [CI], 1.845-42.034). Patients meeting the 1:1 ratio 50% of the opportunities had an HR of 5.062 (95% CI, 1.115-22.982) while those meeting 75% of the opportunities had an HR of 1.888 (95% CI, 0.198-18.035).
Conclusion: CAT+ patients represent the trauma subset at highest risk of mortality and may benefit from a focused blood-based resuscitation. Patients who were able to meet the 1:1 ratio more often had a noticeable decrease in risk of death compared with those who achieved less than 1:1 transfusions. Administering FFP concurrently with PRBC is associated with a decrease in mortality in CAT+ patients.
Level of Evidence: Prognostic study, level III; therapeutic study, level IV.