Impact of Helicopter Emergency Medical Service in Traumatized Patients: Which Patient Benefits Most?

INTRODUCTION: The Helicopter Emergency Medical Service (HEMS) was established for the prehospital trauma care of patients. Improved rescue times and increased coverage areas are discussed as specific advantages of HEMS. We recently found evidence that HEMS exerts beneficial effects on outcomes for severely injured patients. However, it still remains unknown which group of trauma patients might benefit most from HEMS rescue. Consequently, the unique aim of this study was to reveal which patients might benefit most from HEMS rescue. METHODS: Trauma patients (ISS ≥9) primarily treated by HEMS or ground emergency medical services (GEMS) between 2002 and 2012 were analysed using the TraumaRegister DGU. A multivariate regression analysis was used to reveal the survival benefit between different trauma populations. RESULTS: The study included 52 281 trauma patients. Of these, 68.8% (35 974) were rescued by GEMS and 31.2% (16 307) by HEMS. HEMS patients were more severely injured compared to GEMS patients (ISS: HEMS 24.8±13.5 vs. GEMS 21.7±18.0) and more frequently suffered traumatic shock (SBP sys <90mmHg: HEMS 18.3% vs. GEMS 14.8%). However, logistic regression analysis revealed that HEMS rescues resulted in an overall survival benefit compared to GEMS (OR 0.81, 95% CI [0.75-0.87], p<0.001, Nagelkerke's R squared 0.526, area under the ROC curve 0.922, 95% CI [0.919-0.925]). Analysis of specific subgroups demonstrated that patients aged older than 55 years (OR 0.62, 95% CI [0.50-0.77]) had the highest survival benefit after HEMS treatment. Furthermore, HEMS rescue had the most significant impact after 'low falls' (OR 0.68, 95% CI [0.55-0.84]) and in the case of minor severity injuries (ISS 9-15) (OR 0.66, 95% CI [0.49-0.88]). CONCLUSIONS: In general, trauma patients benefit from HEMS rescue with in-hospital survival as the main outcome parameter. Focusing on special subgroups, middle aged and older patients, low-energy trauma, and minor severity injuries had the highest survival benefit when rescued by HEMS. Further studies are required to determine the potential reasons of this benefit.