Helicopter EMS for scene response to head-injured patients: systematic review & meta-analysis

Helicopter EMS (HEMS) is an important component of prehospital trauma scene response care worldwide, including for traumatic brain injury (TBI), a major cause of mortality in injured patients. Our objective was to perform a meta-analysis (MA) of trauma HEMS scene responses to patients with severe head injury to determine whether air medical response is associated with improved survival. A broad and systematic search of the literature was conducted from the years 1970–2024. We included studies with the outcome of mortality in HEMS vs. the control of ground EMS (GEMS) in trauma scene transports (adult or pediatric) with severe TBI as defined by Glasgow Coma Score (GCS) < 9 or Head Abbreviated Injury Score (AISHead) ≥ 3. A random effects restricted maximum likelihood MA was conducted, with post-analysis evaluation for bias. Of 21 HEMS outcomes studies evaluating TBI, 15 were eligible for MA, and effect estimates were HEMS-favorable in 13 and statistically significant in 9. The null hypothesis of no HEMS association with TBI survival was rejected (p < .01) for both the GCS < 9 and the AISHead3+ groups. Heterogeneity measures supported generation of a pooled effect estimate for the GCS < 9 group: HEMS survival OR 1.37 (95% CI 1.23–1.53, I2 0%) but not for the AISHead3+ group (for which HEMS had statistically significant association with improved survival in six of eight studies, but to different degrees with resulting I2 of 93%). There were no signs of small-study (publication) or other substantial bias, with overall evaluation of moderate to low risk of bias. The available evidence suggests a survival benefit associated with HEMS scene response for patients with severe head injuries as defined by GCS < 9. For this group, at the median mortality from all studies (24%), HEMS scene response to TBI saves one life for every 19 transports (95% CI for number needed to treat, 15–28).