Systemic Vascular Resistance Calculator

Enter pressures, flow, and body size for fast resistance results. Check derived vascular tone clearly. Download useful reports for review, teaching, and documentation today.

Calculator Inputs

Formula Used

SVR = ((MAP - CVP) / CO) × 80

MAP is mean arterial pressure in mmHg.

CVP is central venous pressure in mmHg.

CO is cardiac output in L/min.

The factor 80 converts mmHg min/L to dyn s/cm5.

MAP = DBP + (SBP - DBP) / 3

Wood units = (MAP - CVP) / CO

SVRI = SVR × BSA

CI = CO / BSA

Stroke volume = CO × 1000 / heart rate

How to Use This Calculator

  1. Enter MAP directly, or enter systolic and diastolic pressure.
  2. Enter central venous pressure and select the matching unit.
  3. Enter cardiac output, or use cardiac index with BSA.
  4. Enter BSA directly, or add height and weight.
  5. Add heart rate when stroke volume is needed.
  6. Press Calculate to show the result above the form.
  7. Use CSV or PDF buttons to save the result.

Example Data Table

MAP CVP CO BSA SVR Interpretation
93 mmHg 5 mmHg 5.5 L/min 1.90 m2 1280 dyn s/cm5 High range
86.67 mmHg 6 mmHg 6 L/min 1.85 m2 1075.56 dyn s/cm5 Usual range
51.67 mmHg 4 mmHg 8 L/min 1.70 m2 476.67 dyn s/cm5 Low range

Understanding Systemic Vascular Resistance

Systemic vascular resistance describes the opposition to blood flow in the systemic circulation. It works like resistance in an electrical circuit. Pressure difference acts like voltage. Cardiac output acts like current. When pressure rises or flow falls, resistance increases. Clinicians use this value to review vascular tone, shock patterns, fluid status, and medication response.

Why This Calculator Helps

Manual SVR calculation is simple, but unit mistakes are common. Mean arterial pressure, central venous pressure, and cardiac output must use compatible units. This calculator converts common pressure and flow entries, derives MAP from systolic and diastolic pressure, and can estimate cardiac output from cardiac index and body surface area. It also reports Wood units, pressure gradient, and indexed resistance when body surface area is available.

Electrical Flow Analogy

The electrical category fits the basic model well. Ohm law says resistance equals voltage divided by current. Hemodynamics uses the same structure. The driving pressure is MAP minus CVP. The flow is cardiac output. A conversion factor of eighty changes mmHg minute per liter into dyn second per cubic centimeter. This makes the result comparable with common hemodynamic references.

Reading The Result

A usual adult SVR reference band is about 800 to 1200 dyn s/cm5. Lower values may reflect vasodilation, sepsis, anesthesia, or distributive shock. Higher values may appear with vasoconstriction, hypovolemia, heart failure, or cold stress. These ranges are guides only. Patient context, measurement method, and trend direction matter more than one isolated number.

Good Data Practices

Use measured MAP when available. Use arterial line data for critical decisions. Enter CVP in the same time period as cardiac output. Avoid mixing old pressure values with new output values. Record units and patient position. Repeat the calculation after interventions, then compare the trend. Exported CSV and PDF files help keep consistent notes.

Limitations

SVR is a model, not a full circulation map. It does not show regional perfusion, oxygen delivery, contractility, or microvascular behavior. Thermodilution, echocardiography, and pulse contour methods can vary. Always interpret values with qualified clinical guidance. Combine it with blood pressure trends, urine output, lactate, symptoms, and professional review when accuracy is important. The calculator supports learning and documentation. It does not diagnose or choose treatment.

FAQs

What is systemic vascular resistance?

Systemic vascular resistance is the calculated opposition to blood flow through systemic blood vessels. It compares pressure difference with cardiac output.

What is the main SVR formula?

The common formula is SVR equals MAP minus CVP, divided by cardiac output, then multiplied by 80.

Why is 80 used in the formula?

The factor 80 converts mmHg min/L into dyn s/cm5. This is the common reporting unit for SVR.

Can MAP be calculated from blood pressure?

Yes. The calculator can estimate MAP as diastolic pressure plus one third of pulse pressure.

What is a usual adult SVR range?

A common adult reference range is about 800 to 1200 dyn s/cm5. Local references may vary.

What does high SVR mean?

High SVR may suggest increased vascular tone. Causes vary, so clinical context and trends are important.

What does low SVR mean?

Low SVR may suggest vasodilation or reduced vascular tone. It must be checked with other patient data.

Is this calculator a medical decision tool?

No. It supports education and documentation. It does not replace professional clinical judgment or direct patient assessment.

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