Effects of fentanyl on coronary blood flow distribution and myocardial oxygen consumption in the dog.

Little data exist on the effects of fentanyl on coronary blood flow (CBF), myocardial oxygen balance, and the regional distribution of blood flow. These studies were designed to determine whether fentanyl had any intrinsic effects on myocardial oxygen consumption (MVO2) and blood flow distribution. In anesthetized dogs, fentanyl was administered in a dose of 50 micrograms/kg and various measurements were made at 5 and 20 minutes. After hemodynamic recovery from the fentanyl, the animals were treated with atropine to block the known vagomimetic effect of fentanyl and challenged with acetylcholine (3.5 micrograms/kg); then fentanyl (50 micrograms/kg) was again administered and measurements made at 5 and 20 minutes. In the untreated dogs at 5 minutes post-fentanyl, heart rate (HR) decreased 30% and at 20 minutes decreased 29%. Treatment with atropine essentially eliminated HR changes at both time periods. Mean arterial pressure (MAP) fell by 20% and 22% at 5 minutes and 20 minutes, respectively, in the untreated group, but when atropine was administered, MAP was observed to be intermediate between baseline and the untreated animals. Left ventricular MVO2 at 5 minutes in the untreated group was modestly but not significantly reduced. However, at 20 minutes post-fentanyl, MVO2 decreased significantly. MVO2 was essentially unchanged after atropine. Regional CBF (measured by radiolabelled microspheres) was unchanged at 5 minutes, but all layers exhibited significant reductions at 20 minutes. In the atropine group, only the LV epicardial area appeared to show decreases in flow.(ABSTRACT TRUNCATED AT 250 WORDS)