Question Is prehospital blood product transfusion among military combat casualties associated with improved acute and 30-day survival? Findings In this retrospective cohort study of 502 US military combat casualties undergoing medical evacuation, prehospital transfusion was associated with improved survival at 24 hours (adjusted hazard ratio for mortality, 0.26) and at 30 days (adjusted hazard ratio for mortality, 0.39). Meaning Prehospital transfusion of blood products in a military combat setting was associated with greater likelihood of survival. Importance Prehospital blood product transfusion in trauma care remains controversial due to poor-quality evidence and cost. Sequential expansion of blood transfusion capability after 2012 to deployed military medical evacuation (MEDEVAC) units enabled a concurrent cohort study to focus on the timing as well as the location of the initial transfusion. Objective To examine the association of prehospital transfusion and time to initial transfusion with injury survival. Design, Setting, and Participants Retrospective cohort study of US military combat casualties in Afghanistan between April 1, 2012, and August 7, 2015. Eligible patients were rescued alive by MEDEVAC from point of injury with either (1) a traumatic limb amputation at or above the knee or elbow or (2) shock defined as a systolic blood pressure of less than 90 mm Hg or a heart rate greater than 120 beats per minute. Exposures Initiation of prehospital transfusion and time from MEDEVAC rescue to first transfusion, regardless of location (ie, prior to or during hospitalization). Transfusion recipients were compared with nonrecipients (unexposed) for whom transfusion was delayed or not given. Main Outcomes and Measures Mortality at 24 hours and 30 days after MEDEVAC rescue were coprimary outcomes. To balance injury severity, nonrecipients of prehospital transfusion were frequency matched to recipients by mechanism of injury, prehospital shock, severity of limb amputation, head injury, and torso hemorrhage. Cox regression was stratified by matched groups and also adjusted for age, injury year, transport team, tourniquet use, and time to MEDEVAC rescue. Results Of 502 patients (median age, 25 years [interquartile range, 22 to 29 years]; 98% male), 3 of 55 prehospital transfusion recipients (5%) and 85 of 447 nonrecipients (19%) died within 24 hours of MEDEVAC rescue (between-group difference, −14% [95% CI, −21% to −6%]; P = .01). By day 30, 6 recipients (11%) and 102 nonrecipients (23%) died (between-group difference, −12% [95% CI, −21% to −2%]; P = .04). For the 386 patients without missing covariate data among the 400 patients within the matched groups, the adjusted hazard ratio for mortality associated with prehospital transfusion was 0.26 (95% CI, 0.08 to 0.84, P = .02) over 24 hours (3 deaths among 54 recipients vs 67 deaths among 332 matched nonrecipients) and 0.39 (95% CI, 0.16 to 0.92, P = .03) over 30 days (6 vs 76 deaths, respectively). Time to initial transfusion, regardless of location (prehospital or during hospitalization), was associated with reduced 24-hour mortality only up to 15 minutes after MEDEVAC rescue (median, 36 minutes after injury; adjusted hazard ratio, 0.17 [95% CI, 0.04 to 0.73], P = .02; there were 2 deaths among 62 recipients vs 68 deaths among 324 delayed transfusion recipients or nonrecipients). Conclusions and Relevance Among medically evacuated US military combat causalities in Afghanistan, blood product transfusion prehospital or within minutes of injury was associated with greater 24-hour and 30-day survival than delayed transfusion or no transfusion. The findings support prehospital transfusion in this setting. This cohort study examines associations between prehospital blood product transfusion and injury survival among US military combat casualties in Afghanistan.
