Cardiac Output
Choose your preferred method: stroke volume × heart rate or the Fick principle. Enter the relevant values to obtain cardiac output in liters per minute along with clinical interpretation.
How to Use This Calculator
Select the calculation method
Choose stroke volume × heart rate for echocardiographic or thermodilution data, or the Fick method for oxygen consumption data.
Enter measured values
Ensure consistent units (mL, bpm, mL/dL). Use mixed venous samples for true Fick measurements when available.
Interpret in clinical context
Cardiac output should be assessed alongside blood pressure, systemic vascular resistance, and signs of perfusion.
Formula
Stroke volume method: CO = (Stroke volume × Heart rate) ÷ 1000
Fick principle: CO = VO₂ ÷ (CaO₂ − CvO₂)
VO₂ is oxygen consumption (mL/min). CaO₂ and CvO₂ are arterial and venous oxygen contents (mL/dL).
Full Description
Cardiac output reflects the volume of blood pumped by the heart each minute. It is crucial for evaluating hemodynamic status in critical care, heart failure management, shock states, and exercise physiology. The stroke volume method is widely used with echocardiographic LVOT measurements or thermodilution via pulmonary artery catheter.
The Fick principle is considered a gold standard when direct VO₂ measurement and mixed venous blood gases are available. Alterations in cardiac output must be interpreted alongside systemic vascular resistance, filling pressures, lactate, and clinical findings to guide therapy.
Frequently Asked Questions
How accurate is thermodilution compared to Fick?
Thermodilution correlates well with Fick in stable patients but may be less accurate in low-output states, severe tricuspid regurgitation, or intracardiac shunts. Fick with measured VO₂ remains reference standard.
Can I use estimated VO₂?
Estimated VO₂ (e.g., 125 mL/min/m² × BSA) provides an approximation when direct measurement is unavailable. However, conditions like sepsis or fever can make estimates inaccurate.
What stroke volume should I use?
Stroke volume may be measured via echocardiographic LVOT area × LVOT VTI, pulse contour devices, or thermodilution bolus curves. Ensure the stroke volume corresponds to the same hemodynamic state as the heart rate used.
How do shunts affect cardiac output measurements?
Left-to-right shunts can increase pulmonary blood flow relative to systemic flow, altering thermodilution and Fick results. Use oximetry step-up calculations to quantify shunt fractions when suspected.