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Modified Shock Index (MSI)
Hemodynamic Index
Formula: MSI = Heart Rate / Mean Arterial Pressure (MAP)
Enter Vital Signs
Provide Heart Rate and Blood Pressure to evaluate global hemodynamic status.
Guidelines & Evidence
Verified
Last Review: 2026
When to Use
The Modified Shock Index (MSI) is a refinement of the traditional Shock Index (SI). By substituting Mean Arterial Pressure (MAP) for Systolic Blood Pressure (SBP), the MSI accounts for the contribution of diastolic pressure to global perfusion and systemic vascular resistance. It is specifically designed to identify "occult shock"—a state where a patient has significant hemorrhage but remains normotensive due to compensatory mechanisms.
Feature
Shock Index (SI)
Modified Shock Index (MSI)
Age-SI
Formula
HR / SBP
HR / MAP
Age × SI
Normal Range
0.5 – 0.7
0.7 – 1.3
< 50
Sensitivity
Moderate
Higher
Highest (Geriatric)
Complexity
Low
Moderate (requires MAP)
Low
Related Scores in Practice
In clinical practice, this assessment is frequently evaluated alongside other validated measures. Depending on the patient's presentation and specific diagnostic requirements, you may also need to utilize the Shock Index, Age Shock Index, Si Calculator, or the Mtp Score to formulate a comprehensive care plan.
