Evaluation of midazolam-ketamine with dexmedetomidine and fentanyl for injectable anaesthesia in dogs

A prospective randomized blinded study was conducted on 12 clinically healthy adult dogs of both sexes (mean weight of 18.34 +/- 0.78 kg) divided into three groups (n = 4). The animals received 0.4 mg/kg midazolam and 10 mu g/kg dexmedetomidine (group A), 0.4 mg/kg midazolam and 20 mu g/kg dexmedetomidine (group B) and 0.4 mg/kg midazolam + 20 mu g/kg dexmedetomidine + 4 mu g/kg fentanyl (group C) intramuscularly, using separate syringes. Ten minutes later Ketamine was administered intravenously in all the groups. A significantly (P<0.05) shorter weak time (onset of sedation) and down time (onset of recumbency) were recorded in animals in group C as compared to the animals of groups A and B. Muscle relaxation was excellent in group C. The pedal reflex was abolished up to 30 mm in groups A and B and up to 60 mm in group C. Intubation was only possible in groups B and C. The anaesthetic induction dose of ketamine was minimal in group C. Standing recovery time was shortest in the animals of group C. Respiratory rate (RR) decreased significantly (P<0.05) throughout the observation period, but rectal temperature (RT) decreased significantly (P<0.05) towards the end of the observation period in all the groups. Heart rate decreased significantly (P<0.05) in the animals of group B. Mean arterial pressure (MAP) was maintained within the physiological range in all the groups. It was concluded that dexmedetomidine (10 mu g/kg)-midazolam-ketamine can produce anaesthesia for about 20 mm in dogs. Increasing the dose of dexmedetomidine did not enhance the duration of anaesthesia, but the further addition of fentanyl not only reduced the induction dose of ketamine but also increased the duration of anaesthesia up to 50 mm. Dexmedetomidine-midazolam-fentanyl-ketamine can be used for prolonged duration of injectable anaesthesia in dogs.