Introduction: Object of this study was to evaluate the effect of the Helicopter Emergency Medical Services (HEMS) on trauma patient mortality and the effect of prehospital time on the association between HEMS and mortality.
Materials and methods: Trauma patients admitted to a level 1 trauma centre and treated on-scene by the HEMS and Emergency Medical Services (EMS) between 2003 and 2008 were included (n = 186). A control group treated by EMS only (n = 186) was created by matching on ISS, age and severe traumatic brain injury (TBI). Mortality was compared by calculating odds ratios (OR) and numbers needed to treat (NNT), with adjustment for prehospital coded Revised Trauma Score. The effect of prehospital time mortality was tested by a logistic regression. Analyses were made for patients with and without TBI.
Results: The OR of early trauma fatality for the HEMS/EMS versus EMS-only groups was 0.8 for patients both with TBI (95% CI 0.4-1.7; NNT: 22) and without TBI (95% CI 0.2-3.3; NNT: 273). The risk of in-hospital mortality was non-significantly higher for patients with TBI in the HEMS/EMS group (OR = 1.3; 95% CI 0.6-2.7; NNT: -15) compared to the EMS-only group and non-significantly lower for patients without TBI (OR = 0.9; 95% CI 0.3-2.5; NNT: 129). After adjustment for prehospital time, the risk of early trauma fatality for patients with TBI treated by the HEMS decreased (OR = 0.6; 95% CI 0.3-1.6). The risk of in-hospital mortality for these patients decreased from 1.3 to 0.8 (95% CI 0.4-2.0). The effect of the HEMS on patients without TBI did not change after adjustment for prehospital time.
Discussion: HEMS treatment is associated with a non-significantly higher risk of in-hospital mortality for patients with TBI and a non-significantly lower risk for patients without TBI. This increased risk of mortality in TBI patients is attributable to the increased prehospital time. These results indicate that HEMS does not have a positive impact on survival.
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