THE EFFECTS OF ADRENERGIC AGENTS ON OXYGEN DELIVERY AND OXYGEN-CONSUMPTION IN NORMAL DOGS

This study measured changes in whole body Do2 and Vo2 caused by the ad ministration of exogenous adrenergic agents given at physiologically r elevant doses. Using 25-kg nonseptic dogs, we calculated Do2 and direc tly measured Vo2 in six groups (saline control, colloid fluid challeng e, dopamine, dobutamine, nonrepinephrine, and epinephrine). The dogs w ere anesthetized with isoflurane, paralyzed, and maintained at a minim um baseline temperature of 37-degrees-C. Measurements were taken at si x time points: baseline, after each of four successively larger doses of drug, and after a recovery period. Our results demonstrated no sign ificant changes in Vo2 in either the saline control or colloid challen ge groups over the 6-hour experiment despite marked increases in cardi ac output and oxygen delivery during colloid challenge. At the maximum dose used, adrenergic agents increased Vo2 by the following: dopamine , 56%; dobutamine, 51%; norepinephrine, 43%; epinephrine, 61%. We conc lude that adrenergic agents cause a significant increase in whole body Vo2 at moderate doses in normal dogs.