Effects of a microdose of medetomidine on diazepam-ketamine induced anesthesia in dogs.

OBJECTIVE: To evaluate cardiorespiratory and anesthetic effects of a microdose of medetomidine hydrochloride on diazepam-ketamine (DK) hydrochloride induced anesthesia in dogs. DESIGN: Randomized crossover study. ANIMALS: 6 two-year-old healthy female dogs. PROCEDURE: A study was designed to compare quality of anesthetic induction, recovery, analgesia, muscle relaxation, duration of immobilization, and ease of endotracheal intubation between diazepam-ketamine-medetomidine (DKM) and diazepam-ketamine induced anesthesia in 6 dogs. Diazepam (0.25 mg/kg [0.114 mg/lb] of body weight, i.v.) and ketamine (5 mg/kg [2.27 mg/lb], i.v.) with or without a microdose of medetomidine (5 micrograms/kg, i.v.) were administered to dogs. A baseline ECG was obtained, and baseline measurements of arterial blood gas tensions, arterial pressures, heart and respiratory rates, and minute volume were taken before drug administration. All measurements were repeated again 5, 10, 20, and 30 minutes after drug administration. Endotracheal intubation was attempted 1 minute after drug administration and then again 5, 10, 20, and 30 minutes after drug administration. Analgesia was evaluated by tail clamp and needle prick testing. RESULTS: Medetomidine improved quality of anesthetic induction, ease of endotracheal intubation, and extended duration of analgesia and lateral recumbency in anesthetized dogs. The addition of medetomidine to DK increased blood pressure and decreased heart and respiratory rates and minute volume. Hypoxemia was observed in 1 dog after DKM induced anesthesia. CLINICAL IMPLICATIONS: Administration of a microdose of medetomidine provides a useful adjunct to DK induced anesthesia in dogs. Oxygen insufflation is recommended for a minimum of the first 5 minutes of DKM induced anesthesia.