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)
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.
