The Shock Index (SI) is the ratio of the heart rate to systolic blood pressure. The index is a sensitive indicator of left ventricular dysfunction and can become elevated following a reduction in left ventricular stroke work. It can be used in the Emergency Department and Intensive Care Unit to identify patients needing a higher level of care despite vital signs that may not appear strikingly abnormal.

shock index =

= (heart rate in beats per minute) / (systolic blood pressure in mm Hg)



• normal: 0.5 to 0.7

• An elevated shock index (> 0.9) was found helpful by Rady et al (1994) to identify patients in the Emergency Department requiring admission and/or intensive care despite apparently stable vital signs.

• Persistent elevation of the SI has been associated with poor outcome in critically ill patients.

• An elevated SI may be an early warning sign for impending shock even when vital signs appear normal.

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