Defining Hypotension in Patients with Severe Traumatic Brain Injury.

Background: Hypotension, a risk factor for increased mortality following traumatic brain injury (TBI), is traditionally defined as systolic blood pressure (SBP) <90 mm Hg. We aimed to redefine hypotension and determine its optimal threshold in patients with TBI.

Methods: We identified patients with severe TBI (Glasgow Coma Scale score ≤8 on admission) between 2004 and 2015 using data from the Japan Trauma Data Bank. Our endpoint was in-hospital mortality. Mixed effects logistic regression models were used to investigate the association between SBP on admission and in-hospital mortality, with hospitals considered as a random effects variable. We also conducted analyses stratified by age (≤60 years and >60 years) to determine age-specific optimal levels of SBP.

Results: A total of 12,537 patients (5665 patients ≤60 years old and 6872 patients >60 years old) were eligible for the analyses. Overall, SBP of 110 mm Hg was the optimal threshold for hypotension, and adjusted odds ratio and C-statistic for mortality at SBP <110 mm Hg on admission were 1.58 (95% confidence interval, 1.42-1.76, P < 0.001) and 0.78 (95% confidence interval, 0.77-0.79), respectively. Stratified analyses showed that optimal thresholds for hypotension in patients ≤60 years old and >60 years old were 100 mm Hg and 120 mm Hg.

Conclusions: The threshold for hypotension in patients with severe TBI should be redefined and modified by age, and patients ≤60 years old should be considered hypotensive at SBP <100 mm Hg, whereas in older patients, SBP <120 mm Hg should be diagnosed as hypotension.