Single-syringe ketamine-propofol for induction of anaesthesia in rabbits

To evaluate and compare three intravenous (IV) doses of a ketamine-propofol admixture (ketofol) for induction of anaesthesia in unpremedicated rabbits.

Prospective, randomized 'blinded' trial.

Twenty-one healthy female New Zealand rabbits weighing 2.7 ± 0.1 kg.

Animals were allocated randomly into three groups of seven animals and received 1 (KP1), 3 (KP3) or 5 (KP5) mg kg(-1) of both ketamine and propofol in a 1:1 mg kg(-1) ratio admixture. Cardiorespiratory parameters and arterial blood gases were measured at baseline, 2 and 5 minutes after drug administration. The time to loss of the righting reflex (LORR) and the duration of action and apnoea were recorded. The quality of induction and intubation were scored. Data were compared using a two-way anova or a t-test for unpaired data, as relevant.

The time to LORR was the shortest (11 ± 5 seconds) and the duration of action the longest (374 ± 26 seconds) in group KP5. Group KP1 did not lose the righting reflex; instead mild to moderate sedation was observed in this group. The quality of induction in group KP5 was smooth, but ranged from smooth to fair in group KP3. Intubation was not possible in the KP1 group, and 10 animals in the other two groups showed some resistance to intubation. At 2 and 5 minutes, the pulse rate was significantly higher in all three groups compared with baseline, but no statistical differences were seen in arterial blood pressures. Hypoxaemia and dose-dependent respiratory depression were observed in all groups, with periods of apnoea in the KP5 group.

The IV ketamine-propofol admixture had a dose-dependent effect. Haemodynamic function was well maintained in all groups but hypoxemia was observed at the highest doses and oxygen administration is recommended. Addition of premedication or topical lidocaine is advisable to make intubation easier.