Elsevier

Surgery

Volume 159, Issue 3, March 2016, Pages 947-959
Surgery

Trauma/Critical Care
Helicopter transport improves survival following injury in the absence of a time-saving advantage

Meeting Presentation: Data from this paper were presented at the 10th annual Academic Surgical Congress in Las Vegas, Nevada, February 2015.
https://doi.org/10.1016/j.surg.2015.09.015Get rights and content

Background

Although survival benefits have been shown at the population level, it remains unclear what drives the outcome benefits for helicopter emergency medical services (HEMS) in trauma. Although speed is often cited as the vital factor of HEMS, we hypothesized a survival benefit would exist in the absence of a time savings over ground emergency medical services (GEMS). The objective was to examine the association of survival with HEMS compared with GEMS transport across similar prehospital transport times.

Methods

We used a retrospective cohort of scene HEMS and GEMS transports in the National Trauma Databank (2007–2012). Propensity score matching was used to match HEMS and GEMS subjects on the likelihood of HEMS transport. Subjects were stratified by prehospital transport times in 5-minute increments. Conditional logistic regression determined the association of HEMS with survival across prehospital transport times strata controlling for confounders. Transport distance was estimated from prehospital transport times and average HEMS/GEMS transport speeds.

Results

There were 155,691 HEMS/GEMS pairs matched. HEMS had a survival benefit over GEMS for prehospital transport times between 6 and 30 minutes. This benefit ranged from a 46% increase in odds of survival between 26 and 30 minutes (adjusted odds ratio [AOR], 1.46; 95% CI, 1.11–1.93; P < .01) to an 80% increase in odds of survival between 16 and 20 minutes (AOR, 1.80; 95% CI, 1.51–2.14; P < .01). This prehospital transport times window corresponds to estimated transport distance between 14.3 and 71.3 miles for HEMS and 3.3 and 16.6 miles for GEMS.

Conclusion

When stratified by prehospital transport times, HEMS had a survival benefit concentrated in a window between 6 and 30 minutes. Because there was no time-savings advantage for HEMS, these findings may reflect care delivered by HEMS providers.

Section snippets

Study population

Patients aged ≥16 years undergoing either HEMS or GEMS transport from the scene of injury in the National Trauma Databank (NTDB) between 2007 and 2012 were eligible for inclusion. The NTDB represents a national database containing >3 million injured patients from >900 hospitals in the United States.17 Subjects transferred from another hospital, who were dead on arrival, or had unknown United States geographic census region were excluded. Subjects with missing prehospital transport time were

Results

Of the 1,273,836 subjects available for matching, 155,691 pairs were matched giving a final study population of 311,382 subjects for analysis (Fig 1). After matching in each region, no variable included in the estimation of the propensity score remained unbalanced with an absolute value of the standardized difference of >0.2 (Table I), and standardized difference was reduced for each propensity score variable within each region (Fig 2). The propensity score model C-statistic ranged from 0.87 in

Discussion

The current results demonstrate HEMS transport has a significant survival benefit over GEMS transport for prehospital transport times between 6 and 30 minutes after propensity score matching and stratification by transport time. Thus, HEMS does demonstrate a survival benefit in the absence of a time savings over GEMS transport. This benefit peaked at a transport time between 16 and 20 minutes with a nearly 2-fold increase in the odds of in-hospital survival. Survival in very short transport

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    Funding/Support: No funding or support was directly received to perform the current study. Dr Brown receives support from an institutional T32 Ruth L. Kischstein National Research Service Award training grant (5T32GM008516-20) from the National Institutes of Health. Dr Sperry receives support from a career development award (K23GM093032) from the National Institute of General Medical Sciences.

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