Loss of indicator in the thermodilution technique

Abstract

The use of a second thermistor for detecting the injectate temperature in the extravascular segment of a standard right heart thermodilution catheter is described. Experiments with chilled (0 degrees C) indicator show that the temperature of the injectate as it enters the catheter is always greater than zero and that it depends on time and the gradient between indicator and surroundings; that serial injections made 30 to 60 seconds apart are successively cooler and do not plateau until the third injection. These variables amount to an overestimation in the cardiac output of 3 to 12%.