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 administration of exogenous adrenergic agents given at physiologically relevant doses. Using 25-kg nonseptic dogs, we calculated Do2 and directly measured Vo2 in six groups (saline control, colloid fluid challenge, dopamine, dobutamine, norepinephrine, and epinephrine). The dogs were anesthetized with isoflurane, paralyzed, and maintained at a minimum baseline temperature of 37 degrees C. Measurements were taken at six time points: baseline, after each of four successively larger doses of drug, and after a recovery period. Our results demonstrated no significant changes in Vo2 in either the saline control or colloid challenge groups over the 6-hour experiment despite marked increases in cardiac 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 conclude that adrenergic agents cause a significant increase in whole body Vo2 at moderate doses in normal dogs.