Mortality outcomes in trauma patients undergoing prehospital red blood cell transfusion: a systematic literature review

The value of prehospital red blood cell (RBC) transfusion for trauma patients is controversial. The purposes of this literature review were to determine the mortality rate of trauma patients with hemodynamic instability and the benefit of prehospital RBC transfusion. A 30-year systematic literature review was performed in 2016. Eligible studies were combined for meta-analysis when tests for heterogeneity were insignificant. The synthesized mortality was 35.6% for systolic blood pressure ≤ 90 mmHg; 51.1% for ≤ 80 mmHg; and 63.9% for ≤ 70 mmHg. For patients with either hypotension or emergency trauma center transfused RBCs, the synthesized Injury Severity Score (ISS) was 27.0 and mortality was 36.2%; the ISS and mortality correlation was r = 0.766 (P = 0.0096). For civilian patients receiving prehospital RBC transfusions, the synthesized ISS was 27.5 and mortality was 39.5%. One civilian study suggested a decrement in mortality with prehospital RBC transfusion; however, patient recruitment was only one per center per year and mortality was < 10% despite an ISS of 37. The same study created a matched control subset and indicated that mortality decreased using multivariate analysis; however, neither the assessed factors nor raw mortality was presented. Civilian studies with patients undergoing prehospital RBC transfusion and a matched control subset showed that the synthesized mortality was similar for those transfused (37.5%) and not transfused (38.7%; P = 0.8933). A study of civilian helicopter patients demonstrated a similar 30-day mortality for those with and without prehospital blood product availability (22% versus 21%; P = 0.626). Mortality in a study of matched military patients was better for those receiving prehospital blood or plasma (8%) than the controls (20%; P = 0.013). However, transfused patients had a shorter prehospital time, more advanced airway procedures, and higher hospital RBC transfusion (P < 0.05). A subset with an ISS > 16 showed similar mortality with and without prehospital RBC availability (27.6% versus 32.0%; P = 0.343). Trauma patient mortality increases with the magnitude of hemodynamic instability and anatomic injury. Some literature evidence indicates no survival advantage with prehospital RBC availability. However, other data suggesting a potential benefit is confounded or likely to be biased.