Effect of injectate temperature and thermistor position on reproducibility of thermodilution cardiac output determinations.
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.


METHODS
Prospective randomized trial.


METHODS
The study was performed in the cardiac catheterization laboratory of the West Haven Veterans Affairs Medical Center.


METHODS
Twenty consecutive patients undergoing right and left heart catheterizations were enrolled in the study.


METHODS
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.


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.
Williams
J E
JE
Department of Internal Medicine (Cardiology), Yale University School of Medicine.
Pfau
S E
SE
Deckelbaum
L I
LI
D000704:Analysis of Variance; D006328:Cardiac Catheterization; D002302:Cardiac Output; D003936:Diagnosis, Computer-Assisted / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D006801:Humans; D011446:Prospective Studies; D015203:Reproducibility of Results; D012666:Semiconductors; D013696:Temperature; D013815:Thermodilution / Q000295:instrumentation* / Q000379:methods / Q000706:statistics & numerical data