Response of hypotensive dogs to dopamine hydrochloride and dobutamine hydrochloride during deep isoflurane anesthesia

Objective - To evaluate the dose-related cardiovascular and urine output (UrO) effects of dopamine hydrochloride and dobutamine hydrochloride, administered individually and in combination at various ratios, and identify individual doses that achieve target mean arterial blood pressure (MAP; 70 mm Hg) and cardiac index (CI; 150 mL/kg/min) in dogs during deep isoflurane anesthesia. Animals - 10 young clinically normal dogs. Procedures - Following isoflurane equilibration at a baseline MAP of 50 mm Hg on 3 occasions, dogs randomly received IV administration of dopamine (3, 7, 10, 15, and 20 mu g/kg/min), dobutamine (1, 2, 4, 6, and 8 mu g/kg/min), and dopamine-dobutamine combinations (3.5:1, 3.5:4, 7:2, 14:1, and 14:4 mu g/kg/min) in a crossover study. Selected cardiovascular and UrO effects were determined following 20-minute infusions at each dose. Results - Dopamine caused significant dose-dependent responses and achieved target MAP and Cl at 7 mu g/kg/min; dobutamine at 2 mu g/kg/min significantly affected only Cl values. At any dose, dopamine significantly affected UrO, whereas dobutamine did not. Target MAP and Cl values were achieved with a dopamine-dobutamine combination at 7:2 mu g/kg/min,a dopamine-related dose response for MAP and dopamine- and dobutamine-related dose responses for Cl were identified. Changes in UrO were associated with dopamine only. Conclusions and Clinical Relevance - In isoflurane-anesthetized dogs, a guideline dose for dopamine of 7 mu g/kg/min is suggested; dobutamine alone did not improve MAP Data regarding cardiovascular and UrO effects indicated that the combination of dopamine and dobutamine did not provide greater benefit than use of dopamine alone in dogs.