Comparison between two methods for cardiac output measurement in propofol-anesthetized dogs: thermodilution and Doppler

Objective To compare cardiac output (CO) measured by Doppler echocardiography and thermodilution techniques in spontaneously breathing dogs during continuous infusion of propofol. To do so, CO was obtained using the thermodilution method (COTD) and Doppler evaluation of pulmonary flow (CODP) and aortic flow (CODA). Study design Prospective cohort study. Animals Eight adult dogs weighing 8.3 +/- 2.0 kg. Methods Propofol was used for induction (7.5 +/- 1.9 mg kg-1 IV) followed by a continuous rate infusion at 0.7 mg kg-1 minute-1. The animals were positioned in left lateral recumbency on an echocardiography table that allowed for positioning of the transducer at the 3rd and 5th intercostal spaces of the left hemithorax for Doppler evaluation of pulmonary and aortic valves, respectively. CODP and CODA were calculated from pulmonary and aortic velocity spectra, respectively. A pulmonary artery catheter was inserted via the jugular vein and positioned inside the lumen of the pulmonary artery in order to evaluate COTD. The first measurement of COTD, CODP and CODA was performed 30 minutes after beginning continuous infusion (T0) and then at 15-minute intervals (T15, T30, T45 and T60). Numeric data were submitted to two-way anova for repeated measurements, Pearson's correlation coefficient and Bland & Altman analysis. Data are presented as mean +/- SD. Results At T0, COTD was lower than CODA. CODA was higher than COTD and CODP at T30, T45 and T60. The difference between the COTD and CODP, when all data were included, was -0.04 +/- 0.22 L minute-1 and Pearson's correlation coefficient (r) was 0.86. The difference between the COTD and CODA was -0.87 +/- 0.54 L minute-1 and r = 0.69. For COTD and CODP, the difference was -0.82 +/- 0.59 L minute-1 and r = 0.61. Conclusion Doppler evaluation of pulmonary flow was a clinically acceptable method for assessing the CO in propofol-anesthetized dogs.