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Calculates Shock Index from heart rate and systolic blood pressure.
Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.
The shock index is the ratio of heart rate to systolic blood pressure (HR/SBP). Because heart rate often rises as stroke volume falls, the ratio can signal impaired systemic perfusion earlier than hypotension alone; a proportionally high heart rate relative to blood pressure suggests reduced hemodynamic reserve. It is used as an adjunctive, rapid bedside screen in settings such as trauma, hemorrhage, and sepsis. Reference values center on an approximate normal range of 0.5-0.7, but published thresholds vary by population and clinical setting, and normal values differ in children. The index is therefore best interpreted as a trend and as one component of a hemodynamic assessment rather than as a fixed diagnostic threshold. The index does not measure cardiac output, lactate, or tissue perfusion directly, and heart rate is influenced by factors unrelated to perfusion, including rate-control medications, beta-blockade, pacemakers, arrhythmias, pain, and autonomic dysfunction. A single normal value does not exclude compensated shock, and an abnormal value mandates clinical reassessment rather than automatic diagnosis. This calculator provides an educational decision-support estimate of the HR/SBP ratio. It does not diagnose shock or hypoperfusion; interpretation requires the full clinical picture, serial measurements, and appropriate laboratory and monitoring studies.
Specialty
Emergency MedicineCategory
EmergencyDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-08-06
Formula
Keywords
Normal Range
0.5–0.7
Relates heart rate to systolic blood pressure to flag patients whose heart rate is inappropriately high relative to blood pressure, indicating impaired hemodynamic reserve.
The shock index is the heart rate divided by the systolic blood pressure (SI = HR / SBP). Normal values are approximately 0.5-0.7; values of 0.9 or higher suggest hemodynamic compromise.
Heart rate in beats per minute, used as the numerator.
Systolic blood pressure in mmHg, used as the denominator.
A shock index of 0.5–0.7 is generally considered normal. Values above 0.7 are commonly regarded as elevated and warrant investigation; progressively higher values indicate increasing concern for impaired hemodynamic reserve, particularly in trauma, hemorrhage, and sepsis.
The shock index is a simple, inexpensive screening tool that can identify compensated shock before frank hypotension develops, because heart rate often rises before blood pressure falls.
A 45-year-old man after a motor vehicle accident has a heart rate of 120 bpm and a systolic blood pressure of 80 mmHg.
Inputs:
Expected Result: Shock Index = 120 / 80 = 1.5. This is well above the normal range (0.5–0.7) and indicates significant hemodynamic compromise requiring urgent evaluation.
A shock index above 0.7 is commonly regarded as elevated and warrants investigation, while 0.5 to 0.7 is generally normal. An abnormal value does not diagnose shock or hypoperfusion; it calls for clinical reassessment with serial measurements, blood pressure trends, lactate, urine output, and perfusion findings. Progressively higher values suggest worsening hemodynamic reserve, particularly in trauma, hemorrhage, and sepsis, but the result must always be read within the full clinical picture.
The calculator is intended as an adult bedside screen. Normal reference values differ in children and vary by age, so the adult range of 0.5 to 0.7 does not apply there. In children, use age-appropriate assessment and interpret vital signs alongside the clinical picture rather than relying on this ratio, which has not been validated as a fixed diagnostic threshold in that population.
No. A single value within 0.5 to 0.7 does not exclude compensated shock, because the ratio does not measure cardiac output, lactate, or tissue perfusion directly. Heart rate can also be modified by rate-control medications, pacemakers, arrhythmias, pain, and autonomic dysfunction, which can mask an abnormality. The index works best as a trend and as one component of a broader hemodynamic assessment.
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. The shock index is a screening adjunct and must be interpreted with full hemodynamic and clinical assessment.