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Shock Index
Rapid haemodynamic instability assessment — Heart Rate ÷ Systolic BP
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Shock Index (HR/SBP)
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Modified SI (HR/MAP)
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Age × Shock Index
MAP: — mmHg | Pulse Pressure: — mmHg
Shock Index Classification
| SI | Category | Estimated Blood Loss | Action |
|---|---|---|---|
| 0.5–0.7 | Normal | None | Routine monitoring |
| 0.7–1.0 | Mild shock | ~10–20% | Closer observation; IV access |
| 1.0–1.4 | Moderate shock | ~20–40% | IV fluids; blood typing; urgent workup |
| >1.4 | Severe shock | >40% | Immediate resuscitation; blood products; activate MTP |
Shock Index (SI) = HR / SBP | Normal: 0.5–0.7
MAP = DBP + (SBP − DBP) / 3
Modified SI (mSI) = HR / MAP | Normal: 0.7–1.0
Age-Shock Index = Age × SI (elevated in elderly at lower SI thresholds)
MAP = DBP + (SBP − DBP) / 3
Modified SI (mSI) = HR / MAP | Normal: 0.7–1.0
Age-Shock Index = Age × SI (elevated in elderly at lower SI thresholds)
Clinical Use: SI >1.0 predicts need for massive transfusion in trauma. In pregnancy, normal SI is lower (~0.7–0.9). Age-adjusted SI helps identify occult shock in elderly patients who may maintain near-normal vital signs despite significant blood loss. Not validated for septic shock.
For clinical decision support only. Not a substitute for professional medical judgment.
