Effect of Injectate Temperature and Thermistor Position on Reproducibility of Thermodilution Cardiac Output Determinations

¹ From the Department of Internal Medicine (Cardiology), Yale University School of Medicine and West Haven Veterans Affairs Medical Center, West Haven, Conn.

Study objective: The purpose of this study was to evaluate the effect of thermistor position with varying injectate temperatures on the reproducibility of thermodilution cardiac output determination. The key hypothesis to be tested was that the positioning of the proximal thermistor at the right atrial port would improve the reproducibility of thermodilution cardiac output determination, independent of injectate temperature.

Design: Prospective randomized trial.

Setting: The study was performed in the cardiac catherization laboratory of the West Haven Veterans Affairs Medical Center.

Participants: Twenty consecutive patients undergoing right and left heart catherizations were enrolled in the study.

Interventions: Each patient underwent triplicate determination of thermodilution cardiac output measurements under four experimental conditions: (1) ambient or room temperature injectate using an external thermistor in the injectate reservoir; (2) iced injectate using an external thermistor; (3) room temperature injectate using an internal right atrium (RA) thermistor; and (4) iced injectate using an RA thermistor. Reproducibility was assessed by the coefficient of variation (CV) and standard error of the mean percent (SEM%), of the triplicate measurements.

Measurements and results: Using an internal RA thermistor improved the reproducibility of cardiac output determinations independent of injectate temperature. Using room temperature injectate, the CV was 12.8 percent using an external thermistor and 7.9 percent using an internal RA thermistor (p<0.05). Using iced injectate, the CV was 10.2 percent using an external thermistor and 5.5 percent using an internal RA thermistor (p<0.05).

Conclusions: Reproducibility of thermodilution cardiac output determinations is improved when injectate temperature is measured internally, at the RA, as opposed to externally in the reservoir. This has clinical implications for determining significant changes in serial cardiac output determinations.

Key Words: coefficient of variation • reproducibility • thermodilution cardiac output

Submitted on November 12, 1993
Accepted on February 28, 1994

This article has been cited by other articles:

				K. G. Lehmann and M. S. Platt Improved accuracy and precision of thermodilution cardiac output measurement using a dual thermistor catheter system J. Am. Coll. Cardiol., March 1, 1999; 33(3): 883 - 891. [Abstract] [Full Text] [PDF]