Written by Clay Smith
Shock Index (SI) >1.3 was predictive of both hospital admission and inpatient mortality. This could act as an early warning to flag patients likely to need increased resources in the ED and a bed in the hospital.
Why does this matter?
A SI of 0.7 to 0.9 is often used as a cutoff to prognosticate in trauma patients. The higher the ratio, the sicker the patient. But what about all-comers to the ED? Does SI offer any prognostic information in a general ED population? They considered a positive likelihood ratio (+LR) > 5 to be clinically meaningful.
Sock Index = Socks into washer|dryer / Socks out of washer|dryer (ratio always >1)
This was a study utilizing a very large national database from 2005 to 2010 to determine if SI, defined as the ratio of HR to SBP, correlated with admission rate or inpatient mortality. They analyzed >500 million (yes…million) ED visits and found that a SI of >1.3 had a +LR of 6.64 for hospital admission and 5.67 for inpatient mortality. As a concrete example, a HR 118 and SBP 90 = SI >1.3. In the era of electronic health records, the computer could use this simple, readily available metric to flag such patients as higher acuity and as more likely to need greater resources while in the ED. This massive data collection can’t account for type of illness, medication use (i.e. beta blockers), care provided, etc. It only shows the association of this number with these outcomes. That said, SI is a readily available, objective metric that was a strong predictor. It is something we could easily incorporate with other acuity measures, like ESI, as we determine resource allocation in the ED and make disposition decisions.
Shock index as a predictor of hospital admission and inpatient mortality in a US national database of emergency departments. Emerg Med J. 2019 Mar 25. pii: emermed-2018-208002. doi: 10.1136/emermed-2018-208002. [Epub ahead of print]
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Reviewed by Thomas Davis