🫀 Modified Shock Index (MSI)
The Modified Shock Index (MSI) is the ratio of heart rate to mean arterial pressure, a simple early marker of circulatory instability that outperforms the conventional shock index in some cohorts.
Because MAP weights diastolic pressure, MSI captures both pump rate and perfusion pressure, making it more sensitive than HR/SBP for occult hypoperfusion. (original synthesis · not guideline verbatim)
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.
When to use
Enter heart rate and systolic/diastolic blood pressure; the tool computes MAP and MSI. A higher MSI signals greater hemodynamic compromise and worse outcomes.
How it works
MAP = (SBP + 2×DBP)/3. MSI = HR / MAP. Reference: < 0.7 low normal · 0.7–1.3 normal · > 1.3 suggests hypoperfusion / increased mortality risk.
Key points
- Because MAP weights diastolic pressure, MSI captures both pump rate and perfusion pressure, making it more sensitive than HR/SBP for occult hypoperfusion. (original synthesis · not guideline verbatim)
- MSI > 1.3 has been associated with higher mortality and ICU admission across trauma, sepsis, and obstetric-hemorrhage cohorts.
- It is confounded by beta-blockers, pacing, and pre-existing hypertension; treat it as a trend and trigger, not a standalone diagnosis.
References
- Liu YC, et al. Modified shock index and mortality rate of emergency patients. World J Emerg Med. 2012;3(2):114-117.
- Singh A, et al. Utility of the Shock Index and Modified Shock Index. J Emerg Trauma Shock. 2014;7(2):84-89.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Heart rate | 100 bpm |
|---|---|
| Systolic BP | 110 mmHg |
| Diastolic BP | 70 mmHg |
→Modified shock index1.2
- MAP：83 mmHg
- Normal range：≈ 0.7–1.3
Frequently asked questions
- What is Modified Shock Index (MSI)?
- The Modified Shock Index (MSI) is the ratio of heart rate to mean arterial pressure, a simple early marker of circulatory instability that outperforms the conventional shock index in some cohorts.
- How is Modified Shock Index (MSI) calculated? What is the core formula?
- MAP = (SBP + 2×DBP)/3. MSI = HR / MAP. Reference: < 0.7 low normal · 0.7–1.3 normal · > 1.3 suggests hypoperfusion / increased mortality risk.
- When is Modified Shock Index (MSI) used?
- Enter heart rate and systolic/diastolic blood pressure; the tool computes MAP and MSI. A higher MSI signals greater hemodynamic compromise and worse outcomes.
- What are the key clinical points for Modified Shock Index (MSI)?
- Because MAP weights diastolic pressure, MSI captures both pump rate and perfusion pressure, making it more sensitive than HR/SBP for occult hypoperfusion. (original synthesis · not guideline verbatim) MSI > 1.3 has been associated with higher mortality and ICU admission across trauma, sepsis, and obstetric-hemorrhage cohorts. It is confounded by beta-blockers, pacing, and pre-existing hypertension; treat it as a trend and trigger, not a standalone diagnosis.
- What are the limits and cautions when using Modified Shock Index (MSI)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is Modified Shock Index (MSI) calculated in practice? Can you show a worked example?
- Inputs: Heart rate 100 bpm, Systolic BP 110 mmHg, Diastolic BP 70 mmHg → Result: Modified shock index 1.2（MAP: 83 mmHg, Normal range: ≈ 0.7–1.3）