How is thermodilution cardiac output calculated?

The Stewart-Hamilton equation: CO = V_i × (T_b − T_i) × K / ∫ΔT_b(t)dt, where V_i is injectate volume (typically 10 mL), T_b is blood temperature, T_i is injectate temperature, K is a computation constant accounting for specific heat and density of injectate and blood, and the denominator is the area under the temperature-time curve. Three consecutive measurements within 10% of each other are averaged for accuracy.

What conditions cause inaccurate thermodilution cardiac output measurements?

Inaccurate readings occur with: tricuspid regurgitation (prolongs indicator dilution, overestimates CO); intracardiac shunts (unpredictable effects); severe hypothermia (baseline temperature fluctuations create signal noise); rapid fluid infusion during measurement (alters baseline temperature); and injection timing inconsistency. In these situations, the Fick method or transpulmonary thermodilution (PiCCO) may provide more reliable estimates.

Cardiac Output (Thermodilution)

Calculate cardiac output using the thermodilution method from pulmonary artery catheter data (injectate temperature, blood temperature change, and injectate volume) via the Stewart-Hamilton equation.

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Cardiac Output (Thermodilution)

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Frequently Asked Questions

How is thermodilution cardiac output calculated?

What conditions cause inaccurate thermodilution cardiac output measurements?