Evaluation of analgesia induced by epidural administration of medetomidine to cows.

OBJECTIVE

To evaluate analgesic effects after epidural administration of medetomidine to cows, compared with effects of lidocaine hydrochloride and 0.9% NaCl solution.

ANIMALS

6 adult beef cows.

PROCEDURE

3 treatments were administered to each cow, with a 1-week interval between subsequent treatments. Treatments consisted of 5 ml of physiologic saline (0.9% NaCl) solution; 0.2 mg of lidocaine/kg of body weight, not to exceed 100 mg (5 ml); and 15 micrograms of medetomidine/kg, diluted with 0.9% NaCl solution to provide a volume of 5 ml. Epidural injections were given in the first or second coccygeal space. Heart rate, respiratory rate, and arterial blood pressure values were recorded before injection, 5 and 10 minutes after injection, and at 10-minute intervals thereafter. Onset and duration of analgesia, sedation, and ataxia were recorded. A repeated-measures ANOVA was used to detect differences between treatments.

RESULTS

Epidural administration of 0.9% NaCl solution did not induce analgesia. Lidocaine induced analgesia within 5 to 20 minutes, which lasted 10 to 115 minutes (mean +/- SD, 43.3 +/- 37.2 minutes). Heart rate decreased during lidocaine-induced analgesia. Heart and respiratory rates decreased, but blood pressure remained unchanged, after medetomidine administration. Medetomidine induced analgesia within 5 to 10 minutes, which lasted 412 +/- 156 minutes. Mild to moderate sedation and moderate ataxia were observed. Two cows became recumbent, but were easily coaxed to stand. Medetomidine-induced salivation and increased frequency of urination were observed in all cows.

CONCLUSIONS AND CLINICAL RELEVANCE

Epidural administration of medetomidine induced prolonged analgesia that was suitable for perineal surgery, postoperative analgesia, and relief of continuous straining.