AN EVALUATION OF THE INFLUENCE OF MEDETOMIDINE HYDROCHLORIDE AND ATIPAMEZOLE HYDROCHLORIDE ON THE ARRHYTHMOGENIC DOSE OF EPINEPHRINE IN DOGS DURING HALOTHANE ANESTHESIA

Alterations in the arrhythmogenic dose of epinephrine (ADE) were deter mined following administration of medetomidine hydrochloride (750 mu g /M(2)) and a saline placebo, or medetomidine hydrochloride (750 mu g/M (2)), followed by specific medetomidine reversal agent, atipamezole hy drochloride (50 mu g/kg) 20 min later, in halothane-anesthetized dogs (n = 6), ADE determinations were made prior to the administration of e ither treatment, 20 min and 4 h following medetomidine/saline or medet omidine/atipamezole administration, Epinephrine was infused for 3 min at increasing dose rates (2.5 and 5.0 mu g/kg/min) until the arrhythmi a criterion (4 or more intermittent or continuous premature ventricula r contractions) was reached, The interinfusion interval was 20 min, Th ere were no significant differences in the amount of epinephrine requi red to reach the arrhythmia criterion following the administration of either treatment, In addition, the ADE at each determination was not d ifferent between treatment groups. In this study, the administration o f medetomidine to halothane-anesthetized dogs did not alter their arrh ythmogenic response to infused epinephrine.