Relative Bradycardia With Hypertension in Traumatic Brain Injury: A Marker for Mortality?

Abstract

Traumatic brain injury (TBI) is a leading cause of death in patients under 45 years of age. Hypertension has been shown to be associated with increased mortality in patients with moderate to severe traumatic brain injury (TBI). Furthermore, it is known that relative bradycardia is associated with increased mortality in hypotensive patients. We conducted a study to evaluate the relationship of initial heart rate (HR) with outcome in hypertensive TBI patients. This was a retrospective study of adult patients with moderate to severe blunt TBI (GCS <13) that presented to a Level I trauma center (2001-2011). Patients with hypertension, defined as an initial emergency department systolic blood pressure (SBP) ≥140 mmHg, were included in the analysis. The primary outcome was in-hospital mortality. Logistic regression analysis was used to control for age, injury severity, midline shift >5mm, pupil reflexes, hyperosmolar therapy, and blood transfusion. Secondary outcomes, including Glasgow Outcome Scale scores, were also analyzed. Of 490 patients with moderate to severe TBI, 53 patients were excluded. Of the remaining 437 patients, 223 (51%) presented with hypertension. Total in-hospital mortality was 31% in this group and the initial HR was significantly lower in the group that died (86±26 vs. 96±23; p=0.009). Bradycardia (HR≤60) upon presentation, which was identified in 21 (9%) patients, was associated with increased mortality (71% in HR≤60 vs. 27% in HR>60; p<0.001). Logistic regression identified bradycardia as an independent predictor of mortality (odds ratio 4.82; 95% confidence interval 1.36-17.10; p=0.015). Further subgroup analysis of relative bradycardia failed to identify HR between 60 and 90 as a predictor of mortality (p=0.113), although HR≤60 remained significant (p=0.006). The combination of initial hypertension and bradycardia in moderate to severe blunt TBI patients is associated with increased mortality.