Systemic Vascular Resistance Calculator

Systemic vascular resistance is the pressure drop across the circulation divided by the flow through it, scaled into dyne-second units by a factor of 80. Enter the arterial pressure, the central venous pressure and the cardiac output and this returns SVR in both dyn-s/cm^5 and Wood units, adding the indexed figure when you give a height and a weight. A second tab does the pulmonary version from the mean pulmonary artery pressure and the wedge, and a third turns a heart rate and a stroke volume into the cardiac output the other two need. The output is the divisor in every one of these, so whatever error it carries lands straight on the resistance.

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Height And Weight In
Only used for the body surface area, and only when both boxes are filled in.

Enter the arterial pressure, the filling pressure and the cardiac output measured at the same moment. Height and weight are optional and only add the indexed figure.

Leave blank to take (systolic + 2 x diastolic) / 3. Fill it in if you have a mean straight off an arterial line, which is the real integrated mean rather than the cuff estimate.
Right atrial pressure. 2 to 6 mmHg is the usual range; without a central line many bedside calculations simply assume 5.
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Height And Weight In
Only used for the body surface area, and only when both boxes are filled in.

The same arithmetic across the lung: the mean pulmonary artery pressure less the wedge, divided by the output.

Left atrial pressure stands in for it when a wedge is not available. 15 mmHg or less is the normal ceiling.
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Height And Weight In
Only used for the body surface area, and only when both boxes are filled in.

The resistance is only as trustworthy as the output underneath it. This is the stroke volume route, the one an echo gives you. The Fick principle, with its assumed oxygen consumption and its dissolved oxygen term, belongs on a page of its own and is not attempted here.

From an echo this is usually the left ventricular outflow tract area multiplied by the velocity time integral. Millilitres per beat is the only unit a stroke volume is ever reported in.
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