Adverse Prehospital Events and Outcomes After Traumatic Brain Injury

Importance: While national guidelines recommend avoidance of hypoxia, hypotension, and hypocarbia in the prehospital care of traumatic brain injury (TBI), limited data validate the association of these adverse physiologic events with TBI outcomes. Objective: To validate the associations of prehospital hypoxia, hypotension, and hypocarbia with TBI outcomes in a US national trauma network. Design, Setting, and Participants: This cohort study examined data from 8 level I trauma centers and their affiliated ground and air emergency medical services (EMS) agencies in the Linking Investigations in Trauma and Emergency Services (LITES) Network from January 1, 2017, to June 30, 2021. Adult patients (aged ≥18 years) with confirmed TBI (head Abbreviated Injury Score [AIS] of 1-6) and Injury Severity Score (ISS) of at least 9 were included. Interfacility transfers and patients who underwent prehospital cardiopulmonary resuscitation were excluded. Data were analyzed between April 20, 2022, and November 27, 2023. Exposures: Adverse prehospital TBI events, including hypoxia, hypotension, or hypocarbia. Main Outcomes and Measures: The primary outcomes were death in the emergency department (ED), hospital death, and unfavorable discharge disposition. Log-binomial regression models were used to estimate the association between adverse TBI events and outcomes, adjusting for sex, race and ethnicity, age, study site, transport mode, initial Glasgow Coma Scale, ISS, head AIS score, injury mechanism, and multiple trauma. Results: The analytic cohort included 14994 patients (median [IQR] age, 47 [31-64] years; 71% male; median [IQR] head AIS, 3 [2-4]). Patients with adverse TBI events included 12% (1577 of 13604) with hypoxia, 10% (1426 of 14842) with hypotension, and 61% (650 of 1068) with hypocarbia among those with advanced airway management. Patient outcomes included 2% (259 of 14939) who died in the ED, 12% (1764 of 14623) who died in the hospital, and 25% (3705 of 14623) with an unfavorable discharge disposition. Hypoxia (adjusted relative risk [ARR], 2.24; 95% CI, 1.69-2.97), hypotension (ARR, 2.05; 95% CI, 1.54-2.72), and hypocarbia (ARR, 7.99; 95% CI, 2.47-25.85) were associated with increased risks of ED death. Each adverse TBI event exposure was also associated with higher risks of hospital death and unfavorable discharge disposition. Conclusions and Relevance: In this multicenter cohort study, prehospital hypoxia, hypotension, and hypocarbia were associated with poorer TBI outcomes. These results underscore the importance of optimal oxygenation, ventilation, and perfusion in prehospital TBI care.