In vivo Evaluation of Different Anesthetic Effects in a Rabbit Model

Abstract

Background: Injectable anaesthetics are widely used in rabbits in routine veterinary practice. However, selecting an anaesthetic combination that provides rapid induction, adequate surgical anaesthesia, smooth recovery, and minimal physiological disturbances remains an important clinical consideration in Bangladesh. Objective: This study aimed to compare the efficacy and effects of atropine–xylazine–ketamine (AXK), xylazine–ketamine (XK), and atropine–ketamine (AK) combinations in New Zealand White rabbits. Methods: Eighteen clinically healthy New Zealand White rabbits (9 male and 9 female) were randomly assigned to three anaesthetic treatment groups (n = 6 per group): AK (atropine 0.04 mg/kg + ketamine 30 mg/kg), AXK (atropine 0.04 mg/kg + xylazine 3 mg/kg + ketamine 30 mg/kg), and XK (xylazine 3 mg/kg + ketamine 30 mg/kg). Drugs were administered intramuscularly, with ketamine injected 5 minutes after premedication. Heart rate, respiratory rate, and rectal temperature were recorded at baseline (0 min) and at 15-minute intervals thereafter, up to 75 minutes post-administration. Physiological reflexes were evaluated over time, followed by assessment of serum biochemical parameters and histopathological changes in major organs. Data were analysed using two-way ANOVA followed by Tukey's post hoc test (p < 0.05). Results: The results showed that the AXK group produced the shortest induction time (5.58 ± 0.24 min), significantly longer loss of ear pinch (37.42 ± 0.66 min) and pedal withdrawal reflexes (35.17 ± 0.70 min), and an intermediate recovery period (51.00 ± 0.58 min). On the other hand, the XK group required the longest recovery time (67.50 ± 0.43 min) despite a longer induction time (8.00 ± 0.29 min). The AK group showed the longest induction period (12.00 ± 0.29 min) with only brief anaesthetic depth, as reflected by the shortest duration of reflex loss (approximately 5 min). Importantly, the physiological variables differed significantly among the three groups throughout the observation period, with XK showing a progressive decline in heart rate, whereas AXK and AK exhibited transient increases before stabilisation (p < 0.05). Respiratory rate and rectal temperature also varied significantly over time (p < 0.05). Serum biochemical values remained largely within normal reference ranges, except for inorganic phosphate, which exceeded the published reference interval. Histopathological examination of the brain, liver, tongue, spleen, testes, and ovaries revealed normal tissue architecture without detectable anaesthetic-induced lesions. Conclusion: The AXK combination provided the most balanced anaesthetic profile by producing rapid induction, prolonged surgical anaesthesia, acceptable recovery, and no apparent adverse histopathological effects. The findings suggest that the AXK protocol may be the most suitable injectable anaesthetic regimen among those evaluated for short surgical procedures in New Zealand White rabbits. Future studies incorporating larger sample sizes, multiple dosing regimens, extended monitoring, and controlled environmental conditions would strengthen the translational relevance of these findings to clinical veterinary practice.