thermodilution (measurement of cardiac output)

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The most convenient method for estimating the cardiac output requires the measurement of blood cooling following the injection of cold saline. Measurements are performed on the right side of the heart using a Swan-Ganz catheter.

It is assumed that there is no intra-cardiac shunt, so that the output of the right side of the heart is identical to the output of the left side of the heart.

The principles of the method are:

  • a known volume of cold saline of known temperature is injected into the right atrium
  • a thermister in the pulmonary artery measures the resulting cooling of the blood
  • the cooling profile permits the estimation of cardiac output

Last reviewed 01/2018

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