Geospatial assessment of helicopter emergency medical service overtriage

Background: Despite evidence of benefit after injury, helicopter emergency medical services (HEMS) overtriage remains high. Scene and transfer overtriage are distinct processes. Our objectives were to identify geographic variation in overtriage and patient-level predictors, and determine if overtriage impacts population-level outcomes.

Methods: Patients 16 years or older undergoing scene or interfacility HEMS in the Pennsylvania Trauma Outcomes Study were included. Overtriage was defined as discharge within 24 hours of arrival. Patients were mapped to zip code, and rates of overtriage were calculated. Hot spot analysis identified regions of high and low overtriage. Mixed-effects logistic regression determined patient predictors of overtriage. High and low overtriage regions were compared for population-level injury fatality rates. Analyses were performed for scene and transfer patients separately.

Results: A total of 85,572 patients were included (37.4% transfers). Overtriage was 5.5% among scene and 11.8% among transfer HEMS (p < 0.01). Hot spot analysis demonstrated geographic variation in high and low overtriage for scene and transfer patients. For scene patients, overtriage was associated with distance (odds ratio [OR], 1.03; 95% confidence interval [CI], 1.01-1.06 per 10 miles; p = 0.04), neck injury (OR, 1.27; 95% CI, 1.01-1.60; p = 0.04), and single-system injury (OR, 1.37; 95% CI, 1.15-1.64; p < 0.01). For transfer patients, overtriage was associated with rurality (OR, 1.64; 95% CI, 1.22-2.21; p < 0.01), facial injury (OR, 1.22; 95% CI, 1.03-1.44; p = 0.02), and single-system injury (OR, 1.35; 95% CI, 1.18-2.19; p < 0.01). For scene patients, high overtriage was associated with higher injury fatality rate (coefficient, 1.72; 95% CI, 1.68-1.76; p < 0.01); low overtriage was associated with lower injury fatality rate (coefficient, -0.73; 95% CI, -0.78 to -0.68; p < 0.01). For transfer patients, high overtriage was not associated with injury fatality rate (p = 0.53); low overtriage was associated with lower injury fatality rate (coefficient, -2.87; 95% CI, -4.59 to -1.16; p < 0.01).

Conclusion: Geographic overtriage rates vary significantly for scene and transfer HEMS, and are associated with population-level outcomes. These findings can help guide targeted performance improvement initiatives to reduce HEMS overtriage.

Level of evidence: Therapeutic, level IV.