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Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine
Published in: Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine 1/2016

Open Access 01-12-2016 | Original research

Outcomes after helicopter versus ground emergency medical services for major trauma--propensity score and instrumental variable analyses: a retrospective nationwide cohort study

Authors: Asuka Tsuchiya, Yusuke Tsutsumi, Hideo Yasunaga

Published in: Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine | Issue 1/2016

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Abstract

Background

Because of a lack of randomized controlled trials and the methodological weakness of currently available observational studies, the benefits of helicopter emergency medical services (HEMS) over ground emergency medical services (GEMS) for major trauma patients remain uncertain. The aim of this retrospective nationwide cohort study was to compare the mortality of adults with serious traumatic injuries who were transported by HEMS and GEMS, and to analyze the effects of HEMS in various subpopulations.

Methods

Using the Japan Trauma Data Bank, we evaluated all adult patients who had an injury severity score ≥ 16 transported by HEMS or GEMS during the daytime between 2004 and 2014. We compared in-hospital mortality between patients transported by HEMS and GEMS using propensity score matching, inverse probability of treatment weighting and instrumental variable analyses to adjust for measured and unmeasured confounding factors.

Results

Eligible patients (n = 21,286) from 192 hospitals included 4128 transported by HEMS and 17,158 transported by GEMS. In the propensity score-matched model, there was a significant difference in the in-hospital mortality between HEMS and GEMS groups (22.2 vs. 24.5%, risk difference −2.3% [95% confidence interval, −4.2 to −0.5]; number needed to treat, 43 [95% confidence interval, 24 to 220]). The inverse probability of treatment weighting (20.8% vs. 23.9%; risk difference, −3.9% [95% confidence interval, −5.7 to −2.1]; number needed to treat, 26 [95% confidence interval, 17 to 48]) and instrumental variable analyses showed similar results (risk difference, −6.5% [95% confidence interval, −9.2 to −3.8]; number needed to treat, 15 [95% confidence interval, 11 to 27]). HEMS transport was significantly associated with lower in-hospital mortality after falls, compression injuries, severe chest injuries, extremity (including pelvic) injuries, and traumatic arrest on arrival to the emergency department.

Conclusions

HEMS was associated with a significantly lower mortality than GEMS in adult patients with major traumatic injuries after adjusting for measured and unmeasured confounders.
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Metadata
Title
Outcomes after helicopter versus ground emergency medical services for major trauma--propensity score and instrumental variable analyses: a retrospective nationwide cohort study
Authors
Asuka Tsuchiya
Yusuke Tsutsumi
Hideo Yasunaga
Publication date
01-12-2016
Publisher
BioMed Central
DOI
https://doi.org/10.1186/s13049-016-0335-z

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