Some aspects of the clinical use of thermodilution in measuring cardiac output. With particular reference to the Swan-Ganz thermodilution catheters.

Accuracy of the thermodilution method in measuring cardiac output was tested in a model and against Fick in ten patients. Reproducibility was determined from 573 thermodilution curves. The influence of catheter position, catheter irrigation, post-injection aspiration, and the substitution of rectal temperature for central blood temperature was also studied. The thermodilution method showed very good correlation to direct measurements in the model (corr. coeff. 1.00) and the Fick method in patients (corr. coeff. 0.97). Mean standard deviation for cardiac outputs calculated from individual thermodilution curves was 5%. Post-injection aspiration and variation in catheter tip location did not influence the results. Catheter irrigation during recordings and the use of rectal temperature for TB resulted in underestimation of cardiac output.