Improved Survival for Rural Trauma Patients Transported by Helicopter to a Verified Trauma Center: A Propensity Score Analysis

Abstract

Objectives

Recent studies using advanced statistical methods to control for confounders have demonstrated an association between helicopter transport (HT) vs. ground ambulance transport (GT) in terms of improved survival for adult trauma patients. The aim of this study was to apply a methodologically vigorous approach to determine if HT is associated with a survival benefit for when trauma patients are transported to a verified trauma center in a rural setting.

Methods

The ascertainment of trauma patients age ≥15 years (n=469 cases) by HT and (n=580 cases) by GT between 1999 and 2012 was restricted to the scene of injury in a rural area of 10 to 35 miles from the trauma center. The propensity score (PS) was determined using data including demographics, prehospital physiology, intubation, total prehospital time and injury severity. The propensity score matching was performed with different calipers to select a higher percentage of matches of HT compared to GT patients. The outcome of interest was survival to discharge from hospital. Identical logistic regression analysis was done taking into account for each matched design to select an appropriate effect estimate and confidence interval (CI) controlling for initial vital signs in emergency department, the need for urgent surgery, intensive care unit admission and mechanical ventilation.

Results

Unadjusted mortality for HT compared to GT was 7.7% and 5.3% respectively (p > 0.05). The adjusted rates were 4.0% for HT and 7.6% for GT (p < 0.05). In a PS well-matched dataset, HT was associated with a 2.69-fold increase in odds of survival compared to GT patients [adjusted OR (AOR) = 2.69; 95% C.I. = 1.21 to 5.97].

Conclusions

In a rural setting, we demonstrated improved survival associated with HT compared to GT for scene transportation of adult trauma patients to a verified level II trauma center using an advanced methodologic approach, which included adjustment for transport distance. The implication of survival benefit to rural population is discussed. We recommend larger studies with multiple trauma systems need to be repeated using similar study methodology to substantiate our findings.

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