In thermodilution cardiac output measurement, which parameter primarily determines the cardiac output?

In thermodilution cardiac output measurement, which parameter primarily determines the cardiac output?

• A. Temperature change of the injected bolus
• B. Heart rate
• C. Blood pressure
• D. Oxygen saturation

Answer: (A)

Thermodilution relies on the indicator-dilution principle: a known amount of cold saline is injected and a downstream temperature sensor records the resulting temperature change as the bolus passes. Cardiac output is calculated from the area under the temperature‑time curve (the thermodilution curve), and the magnitude of the injected bolus’s temperature change enters the calculation directly. In other words, how much cooling the bolus produces (the temperature change of the injected bolus) largely sets the signal that is used to compute CO. Heart rate, blood pressure, and oxygen saturation influence overall hemodynamics but do not themselves determine the thermodilution signal or the calculated CO.

Thermodilution relies on the indicator-dilution principle: a known amount of cold saline is injected and a downstream temperature sensor records the resulting temperature change as the bolus passes. Cardiac output is calculated from the area under the temperature‑time curve (the thermodilution curve), and the magnitude of the injected bolus’s temperature change enters the calculation directly. In other words, how much cooling the bolus produces (the temperature change of the injected bolus) largely sets the signal that is used to compute CO. Heart rate, blood pressure, and oxygen saturation influence overall hemodynamics but do not themselves determine the thermodilution signal or the calculated CO.