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Clinical metrics in emergency medicine: the shock index and the probability of hospital admission and inpatient mortality
  1. Kamna S Balhara1,
  2. Yu-Hsiang Hsieh2,
  3. Bachar Hamade2,
  4. Ryan Circh3,
  5. Gabor D Kelen2,
  6. Jamil D Bayram2
  1. 1Department of Emergency Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
  2. 2Department of Emergency Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
  3. 3Department of Emergency Medicine, Baltimore Washington Medical Center, University of Maryland, Glen Burnie, Maryland, USA
  1. Correspondence to Dr Jamil D Bayram, Department of Emergency Medicine, Johns Hopkins University School of Medicine, 5801 Smith Ave. Davis Building, Suite 3220, Baltimore, MD 21209, USA; jbayram1{at}


Study objectives The shock index (SI), defined as the ratio of HR to systolic BP, has been studied as an alternative prognostic tool to traditional vital signs in specific disease states and subgroups of patients. However, literature regarding its utility in the general ED population is lacking. Our main objective was to determine the probability of admission and inpatient mortality based on the first measured SI at initial presentation in the general adult ED population in our tertiary care centre.

Methods A retrospective chart review of all adult patients (≥18 years old) presenting to the ED at our tertiary care centre over a 12-month period was conducted. Likelihood ratios (LRs) were calculated in order to determine the optimal SI cut-off for predicting hospital admission and inpatient mortality.

Results We reviewed 58 336 ED patient encounters occurring between 1 October 2012 and 30 September 2013. SI >1.2 was associated with a large increase in the likelihood of hospital admission, with a positive LR (+LR) of 11.69 (95% CI 9.50 to 14.39) and a moderate increase in the likelihood of inpatient mortality with a +LR of 5.82 (95% CI 4.31 to 7.85). SI >0.7 and >0.9, the traditional ‘normal’ cut-offs cited in the literature, were only associated with minimal to small increases in the likelihood of admission and inpatient mortality.

Conclusions In our single-centre study, the initial SI recorded in the ED shows promise as a clinical metric in the general adult ED population, increasing the probability of both hospital admission and inpatient mortality, specifically at a threshold of SI >1.2.

  • emergency department
  • acute care
  • clinical assessment

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  • Presented at the meeting for the Society of Academic Emergency Medicine, San Diego, 2015.

  • Contributors JDB conceived the study. KSB and JDB obtained Institutional Review Board approval. KSB and BH obtained and verified the data. JDB and KSB designed the study and Y-HH provided statistical analysis of the data. JDB, KSB, BH, and GDK interpreted the data analysis. KSB, BH, Y-HH, RC, GDK and JDB drafted various sections of the manuscript, and all authors contributed substantially to its revision. JDB takes responsibility for the paper as a whole.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.