Shock Index

What Is Shock Index?

Shock Index (SI) is a simple bedside clinical calculation defined as Heart Rate divided by Systolic Blood Pressure ($SI = rac{HR}{SBP}$), with normal values ranging from 0.5 to 0.7.

Why Shock Index Matters on the Fireground

Compensated shock maintains a normal blood pressure through tachycardia and vasoconstriction. A Shock Index > 0.9 indicates occult shock and significant occult bleeding before frank hypotension occurs, guiding early trauma center activation.

Relevant NFPA Standards

• NREMT Standards: National Registry of Emergency Medical Technicians Practice Standards
• NFPA 455: Standard for Emergency Medical Services (EMS)

Field Procedures & Tactical Steps

1. Obtain accurate resting heart rate and manual systolic blood pressure.
2. Calculate Shock Index by dividing HR by SBP ($SI = rac{HR}{SBP}$).
3. Interpret result: Normal = 0.5-0.7; Elevated > 0.9 (occult shock); High > 1.0 (severe shock / high mortality).
4. Initiate aggressive shock resuscitation (oxygen, IV fluids, warm blankets, rapid transport) for SI > 0.9.
5. Recalculate SI every 5 minutes to assess patient response to fluid boluses.

Common Context & Application

Calculated during prehospital vital sign assessments on trauma, internal bleeding, sepsis, and postpartum hemorrhage calls.

Frequently Asked Questions about Shock Index