COMPARISON OF A CONSCIOUS VERSUS ANESTHETIZED CANINE MODEL IN RESPONSE TO MILRINONE, HYDRALAZINE AND NITROPRUSSIDE

The purpose of this study was to demonstrate, based on previous and ne w data, that the differences between a conscious and anesthetized cani ne model in the cardiovascular responses to cardiovasoactive agents we re beyond their difference in the sensitivity of the compensatory mech anism. In both conscious and anesthetized canine models, mean arterial pressure (MAP) was decreased by hydralazine (at 1-3 mg/kg and 0.3-3 m g/kg; by -265 +/- 4.5 and -18.8 +/- 11.7% [max. changes expressed as m ean +/- SEM], respectively). MAP was also decreased by nitroprusside ( both at 0.01-0.1 mg/kg, by -54.6 +/- 2.8 and -60.5 +/- 3.0%, respectiv ely) in the conscious and anesthetized models. However the differentia l MAP responses to hydralazine and nitroprusside between the two model s are inconsistent with a difference in the sensitivity of the two mod els. Hydralazine at 1 mg/kg decreased MAP greater in the conscious tha n anesthetized model, whereas nitroprusside decreased MAP similarly in the two models. In conclusion not all differential responses to hydra lazine and nitroprusside between conscious and anesthetized canine mod els can be explained by a difference in the sensitivity of their compe nsatory mechanisms.