Background: Heart rate and systolic blood pressure are unreliable in geriatric trauma patients. Shock index (SI) (heart rate/systolic blood pressure) is a simple marker of worse outcomes after injury. The aim of this study was to assess the utility of SI in predicting outcomes. We hypothesized that SI predicts mortality in geriatric trauma patients.
Methods: We performed a 4-year (2007-2010) retrospective analysis using the National Trauma Data Bank. Patients 65 years or older were included. Transferred patients, patients dead on arrival, missing vitals on presentation, and patients with burns and traumatic brain injury were excluded. A cutoff value of SI greater than or equal to 1 (sensitivity, 81%; specificity, 79%) was used to define hemodynamic instability. The primary outcome measure was mortality. Secondary outcome measures were need for blood transfusion, need for exploratory laparotomy, and development of in-hospital complications. Multiple logistic regressions were performed.
Results: A total of 485,595 geriatric patients were reviewed, of whom 217,190 were included. The mean (SD) age was 77.7 (7.1) years, 60% were males, median Glasgow Coma Scale (GCS) score was 14 (range, 3-15), median Injury Severity Score (ISS) was 9 (range, 4-18), and mean (SD) SI was 0.58 (0.18). Three percent (n = 6,585) had an SI greater than or equal to 1. Patients with SI greater than or equal to 1 were more likely to require blood product requirement (p = 0.001), require an exploratory laparotomy (p = 0.01), and have in-hospital complications (p = 0.02). The overall mortality rate was 4.1% (n = 8,952). SI greater than or equal to 1 was the strongest predictor for mortality (odds ratio, 3.1; 95% confidence interval, 2.6-3.3; p = 0.001) in geriatric trauma patients. Systolic blood pressure (p = 0.09) and heart rate (p = 0.2) were not predictive of mortality.
Conclusion: SI is an accurate and specific predictor of morbidity and mortality in geriatric trauma patients. SI is superior to heart rate and systolic blood pressure for predicting mortality in geriatric trauma patients. Geriatric trauma patients with SI greater than or equal to 1 should be transferred to a Level 1 trauma center.
Level of evidence: Prognostic/epidemiologic study, level III.