RESUMO
OBJECTIVE: To determine the quality and duration of anesthesia and the cardiopulmonary effects of a morphine, medetomidine, ketamine (MMK) combination administered intramuscularly (IM) to dogs. STUDY DESIGN: Descriptive injectable anesthetic protocol evaluation. ANIMALS: Eight intact adult Beagle dogs: five males, three females. METHODS: The electrocardiogram, heart rate, direct arterial blood pressure, and core body temperature were monitored in eight chronically instrumented dogs. Each dog received 0.2 mg kg(-1) morphine sulfate, 20 microg kg(-1) medetomidine hydrochloride, and 5 mg kg(-1) ketamine hydrochloride IM. Anesthetic and analgesic effects (clamping the tail and metatarsus) were categorized, and the times to lateral recumbency, orotracheal intubation, extubation, and sternal recumbency were recorded. Respiratory, cardiovascular, temperature, and acid-base variables were recorded 5 minutes before, and 3, 10, 20, 30, 45, 50, and 60 minutes after MMK. Atipamezole, 100 microg kg(-1) IM, was administered 60 minutes after MMK administration and data recorded 10 minutes later. RESULTS: The onset of anesthesia was uneventful and rapid. Time to lateral recumbency was 7.1 +/- 4.1 minutes. The tracheas of four dogs were orally intubated in 5.1 +/- 0.8 minutes. After MMK administration most dogs were unresponsive to noxious stimulation from 20 to 60 minutes and heart rate, cardiac index and venous blood pH were significantly decreased from baseline values. Arterial blood pressure increased initially and then returned to baseline values. Times to extubation (four dogs) and return to sternal recumbency after atipamezole administration were 2.8 +/- 1.8 and 4.3 +/- 4.4 minutes, respectively. CONCLUSION: The IM administration of MMK produced anesthesia and analgesia in Beagle dogs. Hemodynamic data were within accepted normal values. Atipamezole administration produced rapid return to consciousness in all dogs. CLINICAL RELEVANCE: Morphine/medetomidine/ketamine may be used for minor medical and surgical procedures requiring short-term anesthesia and analgesia but it is not recommended for medical procedures that are painful.