UC Davis

OBJECTIVE: To characterize the correlation, agreement and concordance of cardiac output (CO) measured with transthoracic ultrasound and the correlation and concordance of aortic blood flow (ABF) minute distance (MD) measured by transesophageal Doppler with CO measured by pulmonary artery thermodilution (PATD) in cats. STUDY DESIGN: Experimental study. ANIMALS: A group of six healthy male neutered cats, aged 2-8 years and weighing 5.3 ± 0.3 kg. METHODS: Cats were anesthetized with isoflurane in oxygen. CO was measured by PATD (COPATD) and transthoracic echocardiography (COECHO). ABF MD was measured using an esophageal Doppler flow probe aligned with descending ABF. All measurements were made under three conditions: dexmedetomidine (20 μg kg-1) intravenously; atipamezole (200 μg kg-1) intramuscularly and atropine (20 μg kg-1) intravenously as needed to achieve a minimum heart rate of 140 beats minute-1; and dopamine (20 μg kg-1 minute-1) intravenously in that order. Correlation between COPATD and COECHO, and COPATD and Doppler MD was evaluated using repeated measures correlation. Agreement between COPATD and COECHO was evaluated using Bland-Altman method. Differences between consecutive pairs of CO measurements were calculated for concordance analysis. RESULTS: Correlation between COPATD and COECHO and between COPATD and MD was significant (p < 0.001), with correlation coefficients greater than 0.92. A bias of > 27% and upper limits of agreement of 66% were found between COPATD and COECHO. Concordance rate with COPATD was 76-80% for COECHO and 72% for MD. CONCLUSIONS AND CLINICAL RELEVANCE: Echocardiographic methods for the measurement of CO showed poor agreement and concordance with PATD. MD showed poor concordance with PATD. As such, these methods cannot be used as an alternative to PATD nor can they appropriately track changes in CO in anesthetized cats.