Prehospital whole-blood transfusion in two countries: comparison of patient characteristics in Sweden and the Northeastern United States

BACKGROUND: Prehospital transfusion of whole blood (WB) is being adopted in civilian Emergency Medical Services (EMS) systems, but the characteristics of patients receiving WB may differ by region. We aimed to compare prehospital WB transfusion programs in Sweden and in the Northeastern United States, focusing on patient demographics and transfusion details. METHODS: We conducted a retrospective observational study of EMS-initiated WB transfusions in three regions in Sweden (2020-2024) and in multiple EMS programs in the Northeastern United States (2024). We compared patient age, sex (with female patients categorized as of childbearing potential (FCP) if ≤ 50 years), indication for transfusion (trauma vs. non-trauma), and prehospital WB transfusion practice (number of units initiated/completed and RhD type). RESULTS: A total of 196 patients received prehospital WB (85 in Sweden, 111 in U.S.). Sweden's WB recipients were younger (median age ~ 41 vs. 59 years) and more often trauma patients (90.6% vs. 72.1%) compared to the U.S. COHORT: The proportion of female patients was similar, but Sweden had a higher percentage of FCPs among WB recipients (24% vs. 8%). Swedish EMS were more likely to transfuse multiple units before hospital arrival. Practice differed in RhD type: 97% of U.S. patients received RhD-positive WB, whereas 91% of Swedish patients received RhD-negative WB. Consequently, all 9 FCPs in the U.S. group received at least one Rh-positive unit, compared to 1 of 18 FCPs in Sweden. CONCLUSION: Significant differences exist between Sweden and the Northeastern U.S. in prehospital WB transfusion demographics and practices. These findings highlight that one should not assume similar patient profiles or transfusion strategies across different countries' EMS WB programs.