Comparison of the Analgesic Effect of Clonidine and Lidocaine When Administered Epidurally in Cattle

Abstract

This study was conducted to compare clonidine and saline to lidocaine for epidural analgesia in cows. Four adult mixed-breed beef cattle weighing 1241±268 lb (564 ± 122 kg) were used. Each cow was randomly assigned to receive each of the three treatments, with a 1-week interval between each treatment. Treatments included epidural administration of 1) 5 ml of physiological saline (0.9% NaCl) solution, 2) 0.2 mg of lidocaine/kg of body weight, not to exceed 100 mg (5 ml), and 3) 5 pg of clonidine/kg, diluted with 0.9% NaCl to provide a volume of 5 ml. The site of epidural injection was the first or second caudal intervertebral space. Heart rate, respiratory rate and arterial blood pressure were recorded before injection; at 5, 10, 20 and 30 minutes after injection; and at 15-minute intervals thereafter. Onset and duration of analgesia, sedation and ataxia were recorded. Analgesia was evaluated by the response to an electrical stimulus and to a needle prick. Repeated-measures ANOVA was used to detect differences between treatments.
Lidocaine-induced analgesia occurred within 10 ± 7 minutes and lasted 56.3 ± 40.1 minutes. Analgesia induced with clonidine occurred within 34 ± 11 minutes and lasted at least 6 hours when tested with electrical stimulus, and 11.6 hrs (699 ± 178 minutes) when tested with needle prick. Epidurally administered 0.9% NaCl solution did not induce analgesia. Heart rate decreased significantly at 45 minutes and 30 minutes following epidural administration of lidocaine and clonidine, respectively. Slight to mild sedation and ataxia were observed in three cows, and one cow showed moderate sedation and ataxia following epidural administration of clonidine. Increased salivation and frequency of urination were observed in each cow treated with clonidine.