Systolic Blood Pressure Lower Than the Heart Rate Indicates a Poor Outcome in Patients with Severe Isolated Traumatic Brain Injury: A Cross-sectional Study

Background: A systolic blood pressure (SBP) lower than the heart rate (HR) could indicate a poor condition in trauma patients. In such scenarios, the reversed shock index (RSI) is < 1, as calculated by the SBP divided by the HR. This study aimed to clarify whether RSI could be used to identify high-risk adult patients with isolated traumatic brain injury (TBI).

Methods: This retrospective study reviewed 1216 hospitalized adult patients with isolated TBI at a Level I trauma center between January 1, 2009 and December 31, 2015. The patients were grouped and analyzed according to RSI (<1 or ≥ 1). Subgroups of patients with severe TBI (Glasgow Coma Scale [GCS] ≤ 8) or non-severe TBI (GCS > 8) were also compared. The primary outcome was in-hospital mortality. The odds ratios (ORs) of categorical variables were calculated by chi-square tests with 95% confidence intervals (CIs). Mann-Whitney U-tests were used to analyze non-normally distributed continuous data.

Results: Among patients with isolated TBI, those with an RSI <1 had higher mortality (44.7% vs. 7.1%, OR: 10.5, 95% CI: 5.36-20.75; P < 0.001) than those with an RSI ≥1. An RSI <1 indicated a higher risk of mortality (OR: 5.1, 95% CI: 2.08-12.49; P < 0.001) in patients with severe isolated TBI but not in patients with non-severe isolated TBI (OR: 3.6, 95% CI: 0.45-28.71; P = 0.267).

Conclusion: Patients with isolated TBI may be at risk for shock. In trauma patients with severe isolated TBI, an SBP lower than the HR indicates a poor outcome.