Comparison of Transpulmonary Thermodilution and Calibrated Pulse Contour Analysis with Pulmonary Artery Thermodilution Cardiac Output Measurements in Anesthetized Dogs

BACKGROUND: Transpulmonary thermodilution (TPTD(CO)) and calibrated pulse contour analysis (PCA(CO)) are alternatives to pulmonary artery thermodilution cardiac output (PATD(CO)) measurement. HYPOTHESIS: Ten mL of ice‐cold thermal indicator (TI (10)) would improve the agreement and trending ability between TPTD(CO) and PATD(CO) compared to 5 mL of indicator (TI (5)) (Phase‐1). The agreement and TA between PCA(CO) and PATD(CO) would be poor during changes in systemic vascular resistance (SVR) (Phase‐2). ANIMALS: Eight clinically normal dogs (20.8–31.5 kg). METHODS: Prospective, experimental study. Simultaneous TPTD(CO) and PATD(CO) (averaged from 3 repetitions) using TI (5) and TI (10) were obtained during isoflurane anesthesia combined or not with remifentanil or dobutamine (Phase‐1). Triplicate PCA(CO) and PATD(CO) measurements were recorded during phenylephrine‐induced vasoconstriction and nitroprusside‐induced vasodilation (Phase‐2). RESULTS: Mean bias (limits of agreement: LOA) (L/min), percentage bias (PB), and percentage error (PE) were 0.62 (−0.11 to 1.35), 16%, and 19% for TI (5); and 0.33 (−0.25 to 0.91), 9%, and 16% for TI (10). Mean bias (LOA), PB, and PE were 0.22 (−0.63 to 1.07), 6%, and 23% during phenylephrine; and 2.12 (0.70–3.55), 43%, and 29% during nitroprusside. Mean angular bias (radial LOA) values were 2° (−10° to 14°) and −1° (−9° to 6°) for TI (5) and TI (10), respectively (Phase‐1), and 38° (5°–71°) (Phase‐2). CONCLUSIONS AND CLINICAL IMPORTANCE: Although TI (10) slightly improves the agreement and trending ability between TPTD(CO) and PATD(CO) in comparison to TI (5), both volumes can be used for TPTD(CO) in replacement of PATD(CO). Vasodilation worsens the agreement between PCA(CO) and PATD(CO). Because of PCA(CO)'s poor agreement and trending ability with PATD(CO) during SVR changes, this method has limited clinical application.