BACKGROUND: Hemostatic resuscitation strategy using blood components with a balanced ratio is adopted in the civilian trauma setting. However, there is usually limited availability of blood components in the austere setting. Warm fresh whole blood (WFWB) has been used for trauma patients with life-threatening hemorrhage necessitating massive transfusions in the Okinawa Islands, Japan. The purpose of this study was to evaluate the safety and feasibility of WFWB use in the austere civilian trauma setting.METHODS: We conducted a retrospective cohort study between January 1999 and June 2019, including trauma patients who received WFWB within 24 hours of admission. Immediately after WFWB was collected from blood donors, the sample was typed and screened for transmissible infectious diseases. Approximately half of the study population received irradiated WFWB to prevent graft versus host disease. We evaluated the incidence of transfusion-associated adverse events. Transfusion requirements and patient outcomes were compared between early and late WFWB use.RESULTS: A total of 28 patients from three civilian institutions were eligible. Of those, 93% sustained blunt trauma. The median Injury Severity Score was 37 (interquartile range, 32-49). All patients required operative hemostatic intervention, and half of the patients required both operative and endovascular hemostatic interventions. Patients received a median of 1,800 mL WFWB transfusions from seven volunteer blood donors. None of our subjects developed hemolytic reactions, transmissible infectious diseases, or graft versus host disease. Early WFWB use (within 4 hours of admission) was associated with a significant reduction in platelet transfusion requirement compared with the late WFWB group in univariate analysis (16 units vs. 47 units,p= 0.002).CONCLUSION: Warm fresh whole blood use is safe and feasible in an austere civilian trauma setting. Prospective studies with larger cohorts are necessary to determine whether early WFWB use will affect patient outcomes, transfusion requirement, and treatment cost. (Copyright (c) 2020 Wolters Kluwer Health, Inc. All rights reserved.)LEVEL OF EVIDENCE: Therapeutic, Level IV.