Ketamine-propofol for total intravenous anaesthesia in rabbits: a comparison of premedication with acepromazine-medetomidine, acepromazine-midazolam or acepromazine-morphine.

ABSTRACT

OBJECTIVE: To describe ketamine-propofol total intravenous anaesthesia (TIVA) following premedication with acepromazine and either medetomidine, midazolam or morphine in rabbits. STUDY DESIGN: Randomized, crossover experimental study. ANIMALS A total of six healthy female New Zealand White rabbits (2.2 ± 0.3 kg). METHODS: Rabbits were anaesthetized on four occasions, each separated by 7 days an intramuscular injection of saline alone (treatment Saline) or acepromazine (0.5 mg kg-1) in combination with medetomidine (0.1 mg kg-1), midazolam (1 mg kg-1) or morphine (1 mg kg-1), treatments AME, AMI or AMO, respectively, in random order. Anaesthesia was induced and maintained with a mixture containing ketamine (5 mg mL-1) and propofol (5 mg mL-1) (ketofol). Each trachea was intubated and the rabbit administered oxygen during spontaneous ventilation. Ketofol infusion rate was initially 0.4 mg kg-1 minute-1 (0.2 mg kg-1 minute-1 of each drug) and was adjusted to maintain adequate anaesthetic depth based on clinical assessment. Ketofol dose and physiological variables were recorded every 5 minutes. Quality of sedation, intubation and recovery times were recorded. RESULTS: Ketofol induction doses decreased significantly in treatments AME (7.9 ± 2.3) and AMI (8.9 ± 4.0) compared with treatment Saline (16.8 ± 3.2 mg kg-1) (p < 0.05). The total ketofol dose to maintain anaesthesia was significantly lower in treatments AME, AMI and AMO (0.6 ± 0.1, 0.6 ± 0.2 and 0.6 ± 0.1 mg kg-1 minute-1, respectively) than in treatment Saline (1.2 ± 0.2 mg kg-1 minute-1) (p < 0.05). Cardiovascular variables remained at clinically acceptable values, but all treatments caused some degree of hypoventilation. CONCLUSIONS AND CLINICAL RELEVANCE Premedication with AME, AMI and AMO, at the doses studied, significantly decreased the maintenance dose of ketofol infusion in rabbits. Ketofol was determined to be a clinically acceptable combination for TIVA in premedicated rabbits.