Shock Index Calculator — Bedside Hemodynamic Assessment
The Shock Index (SI) is a simple bedside tool calculated as heart rate divided by systolic blood pressure. It is used for rapid assessment of hemodynamic stability in acute care settings, particularly useful in trauma, sepsis, and hemorrhage detection.
About
The Shock Index (SI) is a physiologically intuitive metric that captures the relationship between heart rate and systolic blood pressure. In healthy adults, the SI ranges from 0.5 to 0.7. As hemodynamic compromise develops — whether from hypovolemia, hemorrhage, sepsis, or cardiogenic shock — the heart rate rises and blood pressure falls, driving the SI upward. An SI >1.0 is traditionally considered abnormal and suggestive of shock, while SI >1.3 indicates severe shock with significantly increased mortality risk. The SI is particularly valuable in occult shock detection — patients may have a normal blood pressure but an elevated SI, indicating compensated shock. It has been validated in trauma, sepsis, myocardial infarction, and obstetric hemorrhage. The SI is also used for risk stratification and to guide early resuscitation interventions.
Formula
Shock Index = Heart Rate (bpm) / Systolic Blood Pressure (mmHg)
The Shock Index is calculated by dividing the heart rate (beats per minute) by the systolic blood pressure (mmHg). A normal SI is 0.5-0.7. Values between 0.7-1.0 are borderline and require close monitoring. An SI >1.0 is consistent with shock, and >1.3 indicates severe shock. The SI is a continuous variable and should be trended over time to assess response to resuscitation.
Score Interpretation
The Shock Index has emerged as a valuable triage and monitoring tool across multiple acute care settings. In trauma, SI >1.0 is associated with significant injury, need for blood transfusion, and increased mortality. In sepsis, an elevated SI predicts need for ICU admission and vasopressor support. In myocardial infarction, SI predicts cardiogenic shock development and in-hospital mortality. The SI is most valuable when trended — a decreasing SI indicates response to resuscitation, while a rising SI despite intervention suggests ongoing deterioration. The SI is not a substitute for comprehensive hemodynamic monitoring but provides a rapid, reproducible, and cost-free bedside assessment.
Normal — 0.5–0.699
SI 0.5-0.7. Normal hemodynamic status.
Management: No acute intervention needed based on SI alone.
Borderline — 0.7–0.999
SI 0.7-1.0. Borderline hemodynamic status. Requires increased vigilance.
Management: Monitor vitals closely. Assess volume status and signs of hypoperfusion.
Shock — 1–1.299
SI 1.0-1.29. Elevated. Indicates hemodynamic instability consistent with shock.
Management: Initiate shock management: IV fluids, assess source of shock, consider vasopressors.
Severe Shock — 1.3+
SI >1.3. Markedly elevated. Indicates severe hemodynamic compromise with high mortality risk.
Management: Immediate resuscitation. Aggressive fluids, vasopressors, blood products. Critical care consultation.
Reference Ranges
| Population | Normal Range | Notes |
|---|---|---|
| Healthy adults | 0.5 - 0.7 | SI varies with age, fitness, and medications (beta-blockers lower SI) |
Dr. Khaled Hassan
Dr. Khaled is a cardiology consultant with experience in acute cardiac care.
View medical review board & editorial policy →Example Calculation
A 30-year-old trauma patient arrives after a motor vehicle collision. HR 120 bpm, SBP 90 mmHg. SI = 120/90 = 1.33. This SI >1.3 indicates severe shock. The patient is found to have a splenic laceration and receives 4 units of PRBCs in the trauma bay before going to the OR for splenectomy.
Related Conditions
Related Medications
Common Mistakes
Relying solely on SI without other vital sign trends
SI is a screening tool and should be interpreted alongside blood pressure, heart rate, respiratory rate, mental status, urine output, and lactate levels for a complete clinical picture.
Frequently Asked Questions
Can the Shock Index be normal in shock?
Is Shock Index validated in pediatric patients?
References
- Birkhahn RH, Gaeta TJ, Terry D, et al. Shock index in diagnosing early acute hypovolemia. Am J Emerg Med. 2005;23(1):50-54. PubMed
- Cannon CM, Braxton CC, Kling-Smith M, et al. Utility of the shock index in predicting mortality in traumatically injured patients. J Trauma. 2009;67(6):1426-1430. PubMed
- Berger T, Green J, Horeczko T, et al. Shock index and early recognition of sepsis in the emergency department. Shock. 2013;40(1):1-7. PubMed