Geospatial assessment of helicopter emergency medical service overtriage

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

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.

Advanced and alternative research methods for the acute care surgeon scientist

Clinical research has evolved significantly over the last few decades to include many advanced and alternative study designs to answer unique questions. Recognizing a potential knowledge gap, the AAST Associate Member Council and Educational Development Committee created a research course at the 2022 Annual Meeting in Chicago to introduce junior researchers to these methodologies. This manuscript presents a summary of this AAST Annual Meeting session, and reviews topics including hierarchical modeling, geospatial analysis, patient-centered outcomes research, mixed methods designs, and negotiating complex issues in multicenter trials.

Impact of patient, system, and environmental factors on utilization of air medical transport after trauma

BACKGROUND

Air medical transport (AMT) improves outcomes for severely injured patients. The decision to fly patients is complex and must consider multiple factors. Our objective was to evaluate the interaction between geography, patient and environmental factors, and emergency medical services (EMS) system resources on AMT after trauma. We hypothesize that significant geographic variation in AMT utilization will be associated with varying levels of patient, environmental, and EMS resources.

METHODS

Patients transported by EMS in the Pennsylvania state trauma registry 2000 to 2017 were included. We used our previously developed Air Medical Prehospital Triage (AMPT; ≥2 points triage to AMT) score and Geographic Emergency Medical Services Index (GEMSI; higher indicates more system resources) as measures for patient factors and EMS resources, respectively. A mixed-effects logistic regression model determined the association of AMT utilization with patient, system, and environmental variables.

RESULTS

There were 195,354 patients included. Fifty-five percent of variation in AMT utilization was attributed to geographic differences. Triage to AMT by the AMPT score was associated with nearly twice the odds of AMT utilization (adjusted odds ratio, 1.894; 95% confidence interval, 1.765-2.032; p < 0.001). Each 1-point increase in GEMSI was associated with a 6.1% reduction in odds of AMT (0.939; 0.922-0.957; p < 0.001). Younger age, rural location, and more severe injuries were also associated with increased odds of AMT ( p < 0.05). When categorized by GEMSI level, the AMPT score and patient factors were more important for predicting AMT utilization in the middle tercile (moderate EMS resources) compared with the lower (low EMS resources) and higher tercile (high EMS resources). Weather, season, time-of-day, and traffic were all associated with AMT utilization ( p < 0.05).

CONCLUSION

Patient, system, and environmental factors are associated with AMT utilization, which varies geographically and by EMS/trauma system resource availability. A more comprehensive approach to AMT triage could reduce variation and allow more tailored efforts toward optimizing resource allocation and outcomes.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level III.

Direct Trauma Center Access by Helicopter Emergency Medical Services is Associated With Improved Survival After Severe Injury

OBJECTIVE

Evaluate the association of survival with helicopter transport directly to a trauma center compared with ground transport to a non-trauma center (NTC) and subsequent transfer.

SUMMARY BACKGROUND DATA

Helicopter transport improves survival after injury. One potential mechanism is direct transport to a trauma center when the patient would otherwise be transported to an NTC for subsequent transfer.

METHODS

Scene patients 16 years and above with positive physiological or anatomic triage criteria within PTOS 2000-2017 were included. Patients transported directly to level I/II trauma centers by helicopter were compared with patients initially transported to an NTC by ground with a subsequent helicopter transfer to a level I/II trauma center. Propensity score matching was used to evaluate the association between direct helicopter transport and survival. Individual triage criteria were evaluated to identify patients most likely to benefit from direct helicopter transport.

RESULTS

In all, 36,830 patients were included. Direct helicopter transport was associated with a nearly 2-fold increase in odds of survival compared with NTC ground transport and subsequent transfer by helicopter (aOR 2.78; 95% CI 2.24-3.44, P <0.01). Triage criteria identifying patients with a survival benefit from direct helicopter transport included GCS≤13 (1.71; 1.22-2.41, P <0.01), hypotension (2.56; 1.39-4.71, P <0.01), abnormal respiratory rate (2.30; 1.36-3.89, P <0.01), paralysis (8.01; 2.03-31.69, P <0.01), hemothorax/pneumothorax (2.34; 1.36-4.05, P <0.01), and multisystem trauma (2.29; 1.08-4.84, P =0.03).

CONCLUSIONS

Direct trauma center access is a mechanism driving the survival benefit of helicopter transport. First responders should consider helicopter transport for patients meeting these criteria who would otherwise be transported to an NTC.