How many minutes matter: Association between time saved with air medical transport and survival in trauma patients.

Abstract

Background: Air medical transport (AMT) offers a survival advantage to trauma patients for several reasons, including time-savings over ground transport. Triage guidelines suggest AMT use when there are significant time-savings, but how much time needs to be saved to confer a benefit is unclear. Our objective was to define the time-savings threshold for which AMT has a survival benefit over ground transport.

Methods: Retrospective cohort of adult trauma patients transported ≤40 miles by ground or air in the Pennsylvania Trauma Outcomes Study 2000 to 2017. Geographic information system network analysis generated the counterfactual transport mode times, and we calculated a time-savings of AMT for each patient. We used restricted cubic splines to allow for non-linear effects of time-saved within multilevel logistic regression to identify a threshold of AMT time-savings associated with survival. Subgroups of patients meeting physiologic or anatomic criteria from the National Field Triage Guidelines (NFTG) and those with a positive Air Medical Prehospital Triage (AMPT) Score were analyzed.

Results: There were 280,271 patients included. The NFTG subgroup had survival advantage starting at 13 minutes of AMT time-saved (adjusted odds ratio, 1.14; 95% confidence interval, 1.01-1.30). The AMPT subgroup had survival advantage starting at 23 minutes with the greatest magnitude of improvement (adjusted odds ratio, 1.22; 95% confidence interval, 1.01-1.48). Among patients that did not meet either NFTG criteria or the AMPT score, no amount of time-saved by AMT was associated with survival (p > 0.05). Sensitivity analysis accounting for injury severity in scene time showed the survival benefit starting at 17 minutes of AMT time-saved for the NFTG subgroup and remained 23 minutes in the AMPT subgroup.

Conclusion: Among patients meeting physiologic or anatomic NFTG criteria, a ≥ 13- to 17-minute AMT time-savings threshold was associated with improved survival. There is heterogeneity among this threshold among different patient groups that may be due to other benefits of AMT, such as advanced capabilities. These findings can inform AMT triage guidelines.

Level of evidence: Therapeutic; Level IV.