Simultaneous intraoperative measurement of cardiac output by thermodilution and transtracheal Doppler

Intraoperative measurement of cardiac output with transtracheal Doppler (DOP) was compared with that measured by thermodilution (TD). Cardiac output was measured simultaneously with both methods in 17 adult patients. For 86 pairs of measurements, the average difference between the two techniques was -0.21.min-1. This bias had a standard deviation of 1.71.min-1. The average of the absolute value of the difference between measurements made with the two techniques was 1.31.min-1, with a standard deviation of 1.11.min-1. The limits of agreement were -3.6 to 3.11.min-1. Linear regression yielded the following equation: DOP = 0.62 TD + 1.54 l.min-1 (r = 0.63). To evaluate the ability of transtracheal DOP to trend changes in cardiac output, the changes in cardiac output at sequential time points were compared for the two techniques. The average difference in the changes in cardiac output measured by the two techniques was 0.01.min-1. This bias had a standard deviation of 1.71.min-1. In conclusion, the transtracheal DOP technique did not reproduce the measurement of cardiac output by TD intraoperatively. Transtracheal DOP did not accurately trend changes in the TD measurement. These findings were obtained from patients with cardiovascular disease, and the conclusions may depend in part on the patient population and the investigators' experience with the transtracheal DOP technique.