When is enough enough? Odds of survival by unit transfused

Balanced transfusion is lifesaving for hemorrhagic shock. The American Red Cross critical blood shortage in 2022 threatened the immediate availability of blood. To eliminate waste, we reviewed the utility of transfusions per unit to define expected mortality at various levels of balanced transfusion.

A retrospective study of 296 patients receiving massive transfusion on presentation at a level 1 trauma center was performed from January 2018 to December 2021. Units of packed red blood cells (PRBCs), fresh frozen plasma (FFP), and platelets received in the first 4 hours were recorded. Patients were excluded if they died in the emergency department, died on arrival, received <2 U PRBCs or FFP, or received PRBC/FFP >2:1. Primary outcomes were mortality and odds of survival to discharge. Subgroups were defined as transfused if receiving 2 to 9 U PRBCs, massive transfusion for 10 to 19 U PRBCs, and ultramassive transfusion for ≥20 U PRBCs.

A total of 207 patients were included (median age, 32 years; median Injury Severity Score, 25; 67% with penetrating mechanism). Mortality was 29% (61 of 207 patients). Odds of survival is equal to odds of mortality at 11 U PRBCs (odds ratio [OR], 0.95; 95% confidence interval [CI], 0.50-1.79). Beyond 16 U PRBCs, odds of mortality exceed survival (OR, 0.36; 95% CI, 0.16-0.82). Survival approaches zero >36 U PRBCs (OR, 0.09; 95% CI, 0.00-0.56). Subgroup mortality rates increased with unit transfused (16% transfused vs. 36% massive transfusion, p = 0.003; 36% massive transfusion vs. 67% ultramassive transfusion, p = 0.006).

Mortality increases with each unit balanced transfusion. Surgeons should view efforts heroic beyond 16 U PRBCs/4 hours and near futile beyond 36 U PRBCs/4 hours. While extreme outliers can survive, consider cessation of resuscitation beyond 36 U PRBCs. This is especially true if hemostasis has not been achieved or blood supplies are limited.

Prognostic and Epidemiologic; Level IV.