Original Research
The Impact of Aeromedical Response to Patients With Moderate to Severe Traumatic Brain Injury

https://doi.org/10.1016/j.annemergmed.2005.01.024Get rights and content

Study objective

Aeromedical crews offer an advanced level of practice and rapid transport to definitive care; however, their efficacy remains unproven. Previous studies have used relatively small sample sizes or have been unable to adequately control for the effect of other potentially influential variables. Here we explore the impact of aeromedical response in patients with moderate to severe traumatic brain injury.

Methods

This was a retrospective analysis using our county trauma registry. All patients with head Abbreviated Injury Score of 3 or greater were included; interfacility transfers were excluded. The impact of aeromedical response was determined using logistic regression, adjusting for age, sex, mechanism, preadmission Glasgow Coma Scale score, head Abbreviated Injury Score, Injury Severity Score, and the presence of preadmission hypotension. Propensity scores were used to account for variability in selection of patients to undergo air versus ground transport. Patients with moderate and severe traumatic brain injury, as defined by head Abbreviated Injury Score and Glasgow Coma Scale score, were compared. Finally, aeromedical patients undergoing field intubation were compared with ground patients undergoing emergency department (ED) intubation.

Results

A total of 10,314 patients meeting all inclusion and exclusion criteria and with complete data sets were identified and included 3,017 transported by aeromedical crews. Overall mortality was 25% in the air- and ground-transported cohorts, but outcomes were significantly better for the aeromedical patients when adjusted for age, sex, mechanism of injury, hypotension, Glasgow Coma Scale score, head Abbreviated Injury Score, and Injury Severity Score (adjusted odds ratio [OR] 1.90; 95% confidence interval [CI] 1.60 to 2.25; P<.0001). Good outcomes (discharge to home, jail, psychiatric facility, rehabilitation, or leaving against medical advice) were also higher in aeromedical patients (adjusted OR 1.36; 95% CI 1.18 to 1.58; P<.0001). The primary benefit appeared to be in more severely injured patients, as reflected by head Abbreviated Injury Score and Glasgow Coma Scale score. Improved survival was also observed for air-transported patients intubated in the field versus ground-transported patients given emergency intubation in the ED (adjusted OR 1.42; 95% CI 1.13 to 1.78; P<.001).

Conclusion

Here we analyze a large database of patients with moderate to severe traumatic brain injury. Aeromedical response appears to result in improved outcomes after adjustment for multiple influential factors in patients with moderate to severe traumatic brain injury. In addition, out-of-hospital intubation among air-transported patients resulted in better outcomes than ED intubation among ground-transported patients. Patients with more severe injuries appeared to derive the greatest benefit from aeromedical transport.

Introduction

Multiple factors have been demonstrated to affect outcome in traumatic brain injury, including those influenced by care received in the out-of-hospital environment.1, 2, 3, 4 Foremost among these factors include the avoidance of secondary insults, such as hypoxia and hypotension, and the identification of potential traumatic brain injury and subsequent triage to a facility capable of definitive care,5, 6, 7, 8, 9, 10 which has led to the development of emergency medical services (EMS) systems that provide a rapid response to major trauma victims and can offer a variety of therapeutic interventions, such as endotracheal intubation and intravenous fluids, as well as rapid transport to a designated receiving facility.11, 12

Helicopters are used in many systems to respond to major trauma victims, with 3 theoretical therapeutic advantages: (1) rapid transport to a designated receiving facility when ground transport is unavailable or would lead to inordinate delays, (2) response by advanced practitioners with an expanded scope of practice to optimize early care, and (3) response by crews with greater experience managing critically injured patients. Establishing the efficacy of aeromedical response to major trauma victims has been challenging, however, because controlled trials are difficult and may not be ethical in systems with established aeromedical presence, which has resulted in descriptive, pseudoexperimental (eg, revised trauma score and injury severity score [TRISS]), or cohort analyses that have generally supported the use of aeromedical resources but may have been influenced by selection bias.13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52 Several large, registry-based analyses have been performed that attempt to control for various factors that influence outcome in major trauma victims; however, results have been inconsistent, and a complete set of data available for regression modeling has not been available.33, 38, 46

Here we perform an analysis using a large database of head-injured patients from the same EMS system, including multiple factors that affect outcome in traumatic brain injury. The following specific issues were addressed: (1) the impact of air medical response in moderate to severe traumatic brain injury, (2) identification of patients who benefit most from aeromedical transport, and (3) the relative efficacy of field intubation in patients transported by air versus emergency department (ED) intubation in patients transported by ground.

Section snippets

Study Design

This was a retrospective analysis using data from the San Diego County Trauma Registry. Waiver of informed consent was granted by our investigational review board. Approval for this project was obtained from each of the 5 adult trauma centers.

San Diego County has a population of about 3 million in an area of more than 4,000 square miles. A minimum of 2 paramedics respond to all adult major trauma victims, who are transported to 1 of 5 designated trauma centers, all of which are Level I or II

Results

A total of 13,625 patients were identified with a head Abbreviated Injury Score of 3 or greater; the overall mortality in this group was 23%. A total of 3,313 patients were excluded from this analysis, which included 1,398 patients who underwent interfacility transport by helicopter (mortality 14%) and 1,913 patients with incomplete data (mortality 18%).

The remaining 10,314 patients were included in this analysis, with an overall mortality of 25%. Demographic and clinical variables for all

Limitations

There are several limitations to the analysis that must be considered when these data are interpreted. Although our registry is subject to several layers of quality-assurance oversight, it is ultimately limited by the ability of out-of-hospital providers to accurately collect and communicate these data. In addition, we selected patients for inclusion based on head Abbreviated Injury Score score, which is calculated after admission based on radiographic, operative, and autopsy findings that are

Discussion

Defining the optimal role of helicopters in an EMS or trauma system is difficult for a variety of reasons. Performing a randomized, controlled trial to define the efficacy of aeromedical response would be logistically challenging, prohibitively expensive, and ethically suspect in a system with established aeromedical presence. Thus, it is not surprising that so many previous studies have relied on suboptimal methodologies or had limited generalizability outside of their local EMS system.13, 14,

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    Supervising editor: William G. Barsan, MD

    Author contributions: DD, JS, CB, GV, MS, and DH conceived the study design. Data collection was completed by DD, MS, FK, ABE, TV, and DH. Data analysis was done by DD, JP, JS, CB, GV and AS. All authors contributed substantially to manuscript preparation. DD takes responsibility for the paper as a whole.

    Funding and support: The authors report this study did not receive any outside funding or support.

    Presented at Air Medical Transport Conference, 2004, Cincinnati, OH.

    Reprints not available from these authors.

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