Mil Med. 2019 Jul 23;Epub ahead of print

# Influence of Time to Transport to a Higher Level Facility on the Clinical Outcomes of US Combat Casualties with TBI: A Multicenter 7-Year Study.

Maddry J, Arana A, Perez C, Medellin K, Paciocco J, Mora A, Holder W, Davis W, Herson P, Bebarta V

INTRODUCTION: Traumatic brain injury (TBI) is a leading cause of death and disability worldwide and is associated with mortality rates as high as 30%. Patients with TBI are at high risk for secondary injury and need to be transported to definitive care expeditiously. However, the physiologic effects of aeromedical evacuation are not well understood and may compound these risks. Combat TBI patients may benefit from delayed aeromedical evacuation. The goal of this study was to evaluate the impact of transport timing out of theater via Critical Care Air Transport Teams (CCATT) to a higher level facility on the clinical outcomes of combat casualties with TBI.

MATERIALS AND METHODS: We performed a retrospective review of patients with TBI who were evacuated out of theater by CCATT from January 2007 to May 2014. Data abstractors collected flight information, vital signs, procedures, in-flight assessments, and outcomes. Time to transport was defined as the time from injury to CCATT evacuation out of combat theater. We calculated descriptive statistics and constructed regression models to determine the association between time to transport and clinical outcomes. This study was approved by the U.S. Air Force 59th Medical Wing Institutional Review Board.

RESULTS: We analyzed the records of 438 patients evacuated out of theater via CCATT and categorized them into three groups: patients who were transported in one day or less (n = 165), two days (n = 163), and three or more days (n = 110). We used logistic regression models to compare outcomes among patients who were evacuated in two days or three or more days to those who were transported within one day while adjusting for demographics, injury severity, and injury type. Patients who were evacuated in two days or three or more days had 50% lower odds of being discharged on a ventilator and were twice as likely to return to duty or be discharged home than those who were evacuated within one day. Additionally, patients transported in three or more days were 70% less likely to be ventilated at discharge with a GCS of 8 or lower and had 30% lower odds of mortality than those transported within one day.

CONCLUSIONS: In patients with moderate to severe TBI, a delay in aeromedical evacuation out of the combat theater was associated with improved mortality rates and a higher likelihood of discharge to home and return to duty dispositions. This study is correlational in nature and focused on CCATT transports from Role III to Role IV facilities; as such, care must be taken in interpreting our findings and future studies are needed to establish a causal link between delayed evacuation and improved discharge disposition. Our study suggests that delaying aeromedical evacuation of TBI patients when feasible may confer benefit.