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 determined following administration of medetomidine hydrochloride (750 micrograms/M2) and a saline placebo, or medetomidine hydrochloride (750 micrograms/M2), followed by specific medetomidine reversal agent, atipamezole hydrochloride (50 micrograms/kg) 20 min later, in halothane-anesthetized dogs (n = 6). ADE determinations were made prior to the administration of either treatment, 20 min and 4 h following medetomidine/saline or medetomidine/atipamezole administration. Epinephrine was infused for 3 min at increasing dose rates (2.5 and 5.0 micrograms/kg/min) until the arrhythmia criterion (4 or more intermittent or continuous premature ventricular contractions) was reached. The interinfusion interval was 20 min. There were no significant differences in the amount of epinephrine required to reach the arrhythmia criterion following the administration of either treatment. In addition, the ADE at each determination was not different between treatment groups. In this study, the administration of medetomidine to halothane-anesthetized dogs did not alter their arrhythmogenic response to infused epinephrine.
Pettifer
G R
GR
Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Ontario.
Dyson
D H
DH
McDonell
W N
WN
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000769:Anesthesia, Inhalation / Q000662:veterinary*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000503:physiopathology / Q000662:veterinary*; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000187:drug effects; D004283:Dog Diseases / Q000139:chemically induced* / Q000503:physiopathology*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004837:Epinephrine / Q000009:adverse effects* / Q000494:pharmacology; D005260:Female; D006221:Halothane; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D020926:Medetomidine; D013997:Time Factors
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D007093:Imidazoles; C050701:atipamezole; D020926:Medetomidine; D006221:Halothane; D004837:Epinephrine