Emergency and Critical Care

Shock Index (HR/SBP) Calculator

Q: Can the shock index be used alone?

No. The shock index is a screening and dynamic marker, not a diagnosis. It must be combined with clinical findings, lactate, capillary refill, and urine output monitoring.

Q: Is it suitable for children?

Not the standard shock index, since normal heart rate in children varies by age. A pediatric shock index or PALS shock criteria should be used instead.

HR / SBP ratio for rapid hemodynamic assessment

Primary source: Allgöwer M et al. (шоковый индекс); клиническое применение в неотложной практике

Aleksandr A. Aulov, MD, internal medicine Last clinical review: April 28, 2026

Online calculation

bpm

SBP

mm Hg

About this score

The shock index (Allgöwer M. and Buri C., 1967) is a simple calculation equal to the ratio of heart rate to systolic blood pressure (HR / SBP). The normal range is typically 0.5 to 0.7. An increase to ≥ 0.9 is associated with clinically significant hypovolemia and may precede a drop in blood pressure below 90 mm Hg.

It is used as an early marker of shock of any etiology: hemorrhagic (trauma, postpartum hemorrhage, GI bleeding), septic, cardiogenic, or hypovolemic. It is particularly useful in settings with limited monitoring capacity, such as the prehospital setting, the emergency department, and combat casualty care. A shock index ≥ 1.0 warrants rapid fluid resuscitation and a search for a bleeding source; ≥ 1.4 is a critical value.

An age-adjusted modification exists (age shock index = shock index × age), which is useful in elderly patients, in whom compensatory tachycardia may be blunted. In children, a modified pediatric shock index with age-specific norms is used.

When to use

Suspected occult bleeding in trauma, postpartum, or GI bleeding patients.
Early triage in shock of any etiology before laboratory results are available.
Assessing the response to fluid resuscitation: tracking the decline in shock index after a bolus.
Prehospital settings and environments with limited monitoring (EMS, disaster medicine).

Clinical example

Case

A 28-year-old woman, 30 minutes postpartum: HR 130/min, BP 95/60 mm Hg. Blood loss is visually estimated as "moderate."

Calculation

HR 130 / SBP 95 = 1.37.

Interpretation and management

The shock index is markedly elevated (normal 0.5–0.7), approaching the critical value of 1.4. Occult massive hemorrhage is likely. Immediate actions: two large-bore IV lines, crystalloid infusion 30 mL/kg, obstetric team activation, activation of the massive transfusion protocol if bleeding is confirmed, and identification of the source (uterine atony, lacerations).

Limitations and cautions

Beta-blockers and bradycardia (e.g., trained athletes) can mask an increase in the index despite blood loss.
In elderly patients, compensatory tachycardia is blunted; a normal shock index does not rule out shock.
Exertional tachycardia or anxiety can produce false-positive elevations.
In the third trimester of pregnancy, the physiologic shock index is higher due to increased heart rate; the alarm threshold shifts to 1.1.

Frequently asked questions

At what shock index value should concern begin?

≥ 0.9 warrants careful assessment, ≥ 1.0 warrants active intervention (fluid resuscitation, search for bleeding), and ≥ 1.4 is critical.

What is the age shock index?

Age shock index = shock index × age. It is used in elderly patients (> 55 years), in whom compensatory capacity is reduced. Normal is < 50, and concern arises at ≥ 50.

Can the shock index be used alone?

No. The shock index is a screening and dynamic marker, not a diagnosis. It must be combined with clinical findings, lactate, capillary refill, and urine output monitoring.

Is it suitable for children?

Not the standard shock index, since normal heart rate in children varies by age. A pediatric shock index or PALS shock criteria should be used instead.

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Aleksandr A. Aulov Physician, internal medicine, Sechenov School — independent medical education platform. Calculators are compiled from the original publications and current clinical guidelines. Interpretation thresholds follow the source study unless stated otherwise.

This calculator is intended for healthcare professionals. Do not use it for self-diagnosis or self-treatment. Management decisions are made by the treating clinician based on the full clinical picture of the individual patient.