Arrhythmic doses of epinephrine and dopamine during halothane, enflurane, methoxyflurane, and fluroxene anesthesia in goats.

The cardiac arrhythmicity of epinephrine and dopamine was compared in awake goats and during approximate equivalent levels of halothane, enflurane, methoxyflurane, and fluroxene anesthesia. The arrhythmic threshold dose for epinephrine and dopamine was significantly (p less than 0.05) reduced during halothane anesthesia when compared to values determined in awake animals. Enflurane anesthesia had no significant affect on the arrhythmic threshold dose for either catecholamine. However, methoxyflurane and fluroxene anesthesia significantly (p less than 0.05) elevated the arrhythmic threshold dose for dopamine. Epinephrine produced greater elevations in mean arterial pressure than dopamine with all anesthetics except enflurane, and dopamine produced significantly (p less than 0.05) higher heart rates in the awake animals and those anesthetized with halothane and enflurane. The authors conclude that, in terms of arrhythmic potential, there is no advantage in the use of dopamine rather than epinephrine for the reversal of halothane-induced myocardial depression during halothane or enflurane anesthesia.