title: Extremes of shock index predicts death in trauma patients.
abstract: BACKGROUND
  We noted a bimodal relationship between mortality and shock index (SI), the ratio of heart rate to systolic blood pressure.
  
  
  OBJECTIVE
  To determine if extremes of SI can predict mortality in trauma patients.
  
  
  METHODS
  Retrospective evaluation of adult trauma patients at a tertiary care center from 2000 to 2012 in the United States.
  
  
  METHODS
  We examined the SI in trauma patients and determined the adjusted mortality for patients with and without head injuries.
  
  
  METHODS
  Descriptive statistics and multivariable logistic regression.
  
  
  RESULTS
  SI values demonstrated a U-shaped relationship with mortality. Compared with patients with a SI between 0.5 and 0.7, patients with a SI of <0.3 had an odds ratio for death of 2.2 (95% confidence interval [CI] 21.2-4.1) after adjustment for age, Glasgow Coma score, and injury severity score while patients with SI >1.3 had an odds ratio of death of 3.1. (95% CI 1.6-5.9). Elevated SI is associated with increased mortality in patients with isolated torso injuries, and is associated with death at both low and high values in patients with head injury.
  
  
  CONCLUSIONS
  Our data indicate a bimodal relationship between SI and mortality in head injured patients that persists after correction for various co-factors. The distribution of mortality is different between head injured patients and patients without head injuries. Elevated SI predicts death in all trauma patients, but low SI values only predict death in head injured patients.
authors: Department of Surgery, Division of Acute Care Surgery, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors: Stephen R
authors: SR
authors: Odom
authors: Division of Pulmonary, Critical Care, and Sleep Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors: Michael D
authors: MD
authors: Howell
authors: Department of Surgery, Division of Acute Care Surgery, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors: Alok
authors: A
authors: Gupta
authors: Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors: George
authors: G
authors: Silva
authors: Department of Surgery, Division of Acute Care Surgery, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors: Charles H
authors: CH
authors: Cook
authors: Department of Anesthesia, Critical Care, and Pain Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors: Daniel
authors: D
authors: Talmor
keywords: Mortality in trauma; shock; shock index