Comparative Evaluation of the Sedative and Analgesic Effects of Caudal Epidural Administration of Lidocaine Alone or in Combination With Xylazine, Detomidine, Medetomidine, and Dexmedetomidine in Mediterranean Miniature Donkeys.

This study examines the sedative and analgesic effects of epidural injections of lidocaine, both alone or in combination with different α-adrenergic drugs, in miniature donkeys. The results show that lidocaine combined with α-adrenergics had stronger sedative effects, but similar onset times and duration, compared to lidocaine alone. No significant effects on heart and respiratory rates, or rectal temperatures, were observed.

Research Design

• The study involved ten healthy Mediterranean miniature donkeys, both male and female. The subjects were about five years old, 100 kilograms, and 0.8 meters tall.
• The trial was experimental, randomized, and blind, following a Latin square crossover design. This means each donkey received every treatment in a randomized order, with significant washout period between each treatment.
• Five treatment groups were tested – with each donkey receiving lidocaine on its own, or in combination with either xylazine, detomidine, medetomidine, or dexmedetomidine.

Measurement and Results

• Sedation levels were measured using a scale from 0 to 3, with larger scores indicating deeper levels of sedation.
• The level of analgesia (inability to feel pain) was assessed using a pinprick test.
• The results showed that the combination of lidocaine with any of the α-adrenergic agonists resulted in higher sedative effects compared to lidocaine alone, particularly 45-75 minutes after administration.
• There were no significant differences among the groups in terms of the onset of analgesia (time it took for the treatment to take effect), onset of ataxia (lack of muscle control), or the number of animals that experienced complete perineal analgesia (absence of sensation in the lower body) or ataxia.
• Duration of analgesia and ataxia were longer when lidocaine was combined with an α-adrenergic.
• No significant differences were observed in either heart rate, respiratory rate, or rectal temperature among the treatment groups or across different time points within the groups.

Study Implications

• This research suggests that combining α-adrenergics with lidocaine in epidural injections produces more effective sedation in miniature donkeys than lidocaine alone, without any significant impact on heart and respiratory rates or rectal temperatures.
• The study recommends these combined treatments when superior analgesia is needed for this species.