Hemodynamics

SVR Index (SVRI) Calculator

Systemic vascular resistance scaled to body size, for judging vasodilation or vasoconstriction in patients of different sizes.

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

Turn on JavaScript to use this calculator, or open it in the web app.

Formula

((MAP - CVP) / CI) * 80

Reference: Normal 1970–2390

How it is used

• Normal SVRI is 1970–2390 dyn·s/cm⁵·m².
• SVRI = SVR × BSA (the same as using cardiac index in place of output), so the units carry ·m², not ÷m².
• Low SVRI: vasodilatory (distributive) shock. High SVRI: compensatory vasoconstriction in cardiogenic or hypovolemic shock.

Same formula as the app. Open it in the web app.

Related one-pagers

• Hemodynamic NormalsSVRI · 1970–2390 · dyn·s/cm⁵·m²
• Shock Types at a GlanceLost volume lowers venous return and stroke volume; baroreceptors raise heart rate and SVR. Vasoconstriction holds diastolic pressure while systolic falls, so pulse pressure narrows before SBP drops, and young adults can lose 30% of blood volume first. Tachycardia, cool skin and a shock index (HR ÷ SBP) above 0.9–1.0 are the early signs. Non-hemorrhagic losses (GI, burns, DKA, diuresis) get balanced crystalloid (SMART 2018) and treatment of the cause.
• Vasopressors and InotropesJudge an inotrope by cardiac index, ScvO₂, lactate and urine output; keep K⁺ about 4 and Mg²⁺ about 2, and expect to add a vasopressor as SVR falls.

Related calculators

• Cardiac Index (CI)
• Cardiac Output (Fick Principle)
• Cardiac Output (HR × SV)
• Cerebral Perfusion Pressure (CPP)
• Coronary Perfusion Pressure
• Ejection Fraction (EF)
• Mean Arterial Pressure (MAP)
• Oxygen Delivery (DO₂)

For education and exam preparation only. Follow your institution’s protocols. For education and exam preparation only. Verify results independently and follow your institution’s protocols. Not a substitute for clinical judgment.