Results suggested that both PPV and PVI may be useful for identification of dogs that respond to VR with increases in SI and CI (ie, dogs in the preload-dependent limb of the Frank-Starling curve).

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 (À0.11 to 1.35), 16%, and 19% for TI 5 ; and 0.33 (À0.25 to 0.91), 9%, and 16% for TI 10 . Mean bias (LOA), PB, and PE were 0.22 (À0.63 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°(À10°to 14°) and À1°(À9°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.

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