Effects of pre-medication of acepromazine associated to methadone, morphine or meperidine in anesthetic induction dose of propofol and cardiopulmonary alteration in dogs

Abstract

Pre-anesthetic medications can induct anesthesia calmly, diminishing animals' stress, and decrease anesthetic dose, and consequently can attenuate or even prevent collateral effects.Propofol is an intravenous hypnotic with short action commonly used to induction and maintenance of anesthesia in dogs, because rapidly, calmly and safety unconsciousness promoted in healthy animals, besides minimal cumulative effect. However, this drug is not a good analgesic, so it is necessary to associate to other agents that promote analgesia.Morphine is a pure agonist-mu (OP3) considered standard opioid that promotes excellent analgesia. Meperidine has hypnoanalgesic effects similar to morphine, but analgesic potency and hypnotic activity is lower than morphine. Methadone is an agonist-mu (OP3) synthetic opioid that has additional affinity to N-metil-D-aspartate (NMDA) and a-2 adrenergics receptors. It has analgesic effect farmacologically similar to morphine. These drugs have been used as preanesthetic medication in addition to tranquilizers or sedatives to produce profound sedation, or during perioperative period.There are not many information available referring to the effects of methadone administration associated to acepromazine as pre-anesthetic medication or as adjunct of anesthesia with propofol, when compared to other opioids. Then, the purpose of the study is to compare the cardiopulmonary effects of acepromazine-methadone, acepromazine-morphine, or acepromazine-meperidine association, as preanesthetic medications in dogs induced to anesthesia with propofol, as well as to verify the influence of drugs on the induction dose of propofol.