The Association of Lowest Prehospital Blood Pressure with Mortality in Severe Traumatic Brain Injury from a Nationwide Emergency Medical Services Database.

Objectives: Clinical management of traumatic brain injury (TBI) focuses on preventing secondary injury from cerebral edema and ongoing anoxic injury. Consensus guidelines recommend maintaining systolic blood pressure (SBP) ≥ 110 mmHg. A recent prehospital study suggested lowest adjusted mortality from 130 mmHg to 180 mmHg, suggesting the ideal pressure may be higher. This study aims to explore and externally validate the association between lowest out-of-hospital SBP and mortality in a nationwide database.

Methods: Retrospective observational study of nationwide data from the ESO© (Austin, TX) prehospital electronic health record. Inclusion criteria were an ICD-10 code for TBI, age >10 years, admission to the hospital, abbreviated injury severity head/neck sub-score ≥ 3. Data were split into 70% training and 30% test sets. Unadjusted and adjusted generalized additive models with splines for the continuous variables of SBP and age were created to assess the relationship between lowest SBP and mortality. Adjusted model covariates included age, sex, injury severity score, mechanism, polytrauma, trauma center transport (level 1, 2, or 3), hypoxia and airway management. To evaluate the independent association of lowest SBP with mortality, the adjusted marginal means for predicted probability of death at any fixed value of SBP were estimated and an optimized SBP range was identified. Age and injury severity were evaluated as possibly relevant interaction terms with SBP.

Results: From 2018 to 2022, 44,360 encounters with ICD-10 codes for TBI were screened and 9,449 met final inclusion criteria, with 2,005 meeting the primary outcome (21.2%). Both unadjusted and adjusted analysis identified lowest prehospital SBP as a significant predictor (p < 0.001). Based on adjusted marginal means, the optimized SBP for mortality was 132 mmHg (range 110-158 mmHg). The interaction between SBP and age was significant with a higher optimized SBP of 133 mmHg (range 125-145 mmHg) for patients aged 65 and older.

Conclusions: Out-of-hospital SBP is a significant predictor of mortality in subjects with severe TBI. These results suggest an optimized SBP range 110-158 mmHg, consistent with current consensus guidelines of SBP > 110 mmHg but may suggest benefit for higher SBP targets in older patients.