Patient Characteristics to Inform Military Medical Evacuation Decision-Making in Mild Isolated Head Injury

Introduction: Management of head trauma in austere military environments is challenging as current head injury scoring systems have limited triage utility in the absence of advanced imaging. Additionally, unlike the recent past, future conflicts will be characterized by limited opportunities for aeromedical evacuation. We hypothesize that safe hospital discharge within 48 h may be an effective surrogate endpoint to identify patients appropriate for averted or delayed evacuation in military settings. To analyze this, we assess mild head-injured patients for associations between clinical factors and serious head injury patterns or hospital discharge within 48 h. Materials and Methods: This is a secondary analysis of case data collected in a DoD-funded study, "EpiC," a prospective, multicenter cohort study of major trauma in the Western Cape, South Africa, with median time to definitive care of 12.5 h. Patients aged 18-50 years who presented from March 2021 to October 2023 with mild head injury, defined as lowest Glasgow Coma Scale (GCS) >= 14 in the first 24 h, were eligible. Exclusions include any nonminor injury outside the head (Abbreviated Injury Scale score >1). Serious head injury was defined as nonnasal bone facial fractures, skull fractures, or intracranial injury. Clinical characteristics were evaluated for association with serious head injury or hospital discharge before 48 h, calculated as odds ratios (ORs) with 95% confidence intervals. Results: We identified 2031 patients among whom: the mechanism of injury was blunt in 60%, penetrating in 30%, and both in 11%. A total of 87% of patients were discharged within 48 h. Among patients with blunt head injury, factors most strongly associated with <= 48-h discharge include GCS of 15 (89.3% of patients, OR 5.73, 95% CI 3.84-8.54) and negative or no ordered head imaging (89.3% of patients, OR 13.96, 95% CI 9.58-20.33). Combinations of factors including GCS of 14 and SBP >160 (1.6% of patients, OR 0.14, 95% CI 0.06-0.35) or SBP < 100 (2.2% of patients, OR 0.35, 95% CI 0.15-0.83) were less likely to be discharged by 48 h. Conclusions: In a military-relevant, austere, prolonged-care, civilian trauma setting, we identified factors associated with discharge after 48 h or an abnormal computed tomography head. We believe that further evaluation of individual and combinations of clinical factors may prove beneficial in imaging and transport decision-making in remote military settings.