Shock Index Calculator

bpm
mmHg
Health

Calculate the Shock Index (SI = HR / SBP) to rapidly assess hemodynamic instability.

Formula

Shock Index = HR (bpm) / SBP (mmHg). Normal: 0.5–0.7; concern > 1.0; critical > 1.4
  • SI > 1.0 associated with increased mortality in trauma, sepsis, PE, GI bleed.
  • Modified Shock Index (MSI): MSI = HR / MAP.
  • Age-adjusted SI for elderly patients (> 65): normal range shifted upward.

HR 120, SBP 90

Inputs
  • Heart Rate: 120 bpm
  • Systolic Blood Pressure: 90 mmHg

SI = 120/90 = 1.33. Mildly elevated — consider urgent evaluation.

Frequently asked questions

What does a shock index > 1.0 mean?
SI >1.0 suggests the heart is compensating for reduced blood pressure. It correlates with 1+ units of blood loss. SI >1.4 suggests >2 units blood loss and significant hemodynamic compromise.