Transpulmonary cardiac output with room temperature saline is accurate and tracks directional changes in anesthetized dogs.

Objective: To assess the performance of transpulmonary thermodilution (TPTD) using room-temperature saline (CORT) and waveform-derived continuous CO (CCO) compared with TPTD using iced saline (COICED) as the indicator for measurements of CO in isoflurane-anesthetized dogs.

Methods: 8 Beagles aged 1 to 2 years (7.4 to 11.2 kg) were enrolled in this experimental study from March 21 to 31, 2023. Dogs were anesthetized with 0.01 mg/kg acepromazine, 5 to 6 mg/kg propofol, and isoflurane and were mechanically ventilated. Dogs were instrumented with a central venous catheter and a femoral arterial catheter equipped with a thermistor. The COICED, CORT, and pulse wave-derived CCO values were obtained at baseline, during infusions of phenylephrine and norepinephrine, and during blood withdrawal and replacement. Data were analyzed with a mixed effect model, Bland-Altman plots, and concordance. Percent error was calculated. P < .05 was used for significance.

Results: Data were collected from 8 dogs. Significant effects of time and the interaction of time and method were found. Bland-Altman plots showed negligible bias with limits of agreement between -0.35 and 0.25 L/min for CORT versus COICED and -1.23 and 1.15 L/min for CCO versus COICED. Percent errors were 17.7% and 66.6%, respectively. In the 4-quadrant plots, the concordance rate was 95% and 68% for measurements obtained with CORT and for CCO, respectively.

Conclusions: Transpulmonary thermodilution using room temperature saline was accurate and able to track changes in CO. Continuous CO had a large percent error and low tracking ability.

Clinical relevance: Transpulmonary thermodilution using room temperature saline is reliable for monitoring CO and obviates the need for iced preparations in clinical scenarios.