Modified Shock Index (MSI)
MSI = Heart Rate / Mean Arterial Pressure. More sensitive than standard shock index for detecting haemodynamic instability in trauma, sepsis, and haemorrhage.
Score interpretation
MSI ≤0.7 — haemodynamically stable.
→ Routine monitoring. Reassess with clinical change.
MSI 0.71–1.2 — early haemodynamic compromise. Standard SI may still be normal.
→ Closer monitoring. IV access and fluid challenge if indicated. Identify source of instability.
MSI >1.2 — severe haemodynamic compromise.
→ Immediate resuscitation. Haemorrhage control, vasopressors, blood products as indicated. Urgent senior review.
Interpretation bands for the Modified Shock Index. Apply clinical judgement and local guidance.
References
- Torabi M et al. Modified shock index and mortality in older emergency department patients: a multi-site validation study. J Emerg Med. 2016;51(1):1-8.
- Rousseaux et al. Modified shock index versus shock index in the evaluation of the haemodynamically injured adult patient. Eur J Emerg Med. 2015.
Related
Curated clinical cross-links plus same-class fallbacks.
- Hydrocortisone (ICU — Stress Dosing) · Corticosteroid (ICU/Septic Shock)
- Tranexamic Acid (ICU/Trauma/Surgical) · Antifibrinolytic
- Noradrenaline (Cardiogenic Shock / Vasopressor) · Vasopressor / Cardiogenic Shock
- Vasopressin / Terlipressin · Vasopressin Analogue — Vasodilatory Shock / Variceal Bleeding
- Hydrocortisone (Oral Replacement) · Glucocorticoid Replacement
- Morphine (Oral) · Strong Opioid Analgesic — Step 3 WHO Ladder
- Acute Heart Failure · ESC 2021 Heart Failure Guidelines; NICE NG106
- NSTEMI / Unstable Angina · ESC 2020 NSTEMI Guidelines; NICE NG185
- New-Onset Atrial Fibrillation · ESC 2020 AF Guidelines; NICE NG196
- Hypertensive Emergency · ESC/ESH 2018 Hypertension Guidelines; NICE NG136
- Bradycardia Management · Resuscitation Council UK ABCDE; ESC 2021 Pacing Guidelines
- Ventricular Tachycardia / Fibrillation · Resuscitation Council UK ACLS; ESC 2022 Ventricular Arrhythmia Guidelines
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.