Analgesic and motor effects of a high-volume intercoccygeal epidural injection of 0.125% or 0.0625% bupivacaine in adult cows.

The objectives of this study were to determine the analgesic and motor effects of a high-volume intercoccygeal epidural injection of bupivacaine at 2 concentrations in cows. A prospective, randomized, blinded, crossover trial was conducted on 6 adult cows. An indwelling epidural catheter was placed in the first intercoccygeal space and advanced 10 cm cranially. All the cows received 3 treatments with a washout period of 48 h: saline (control), 0.125% bupivacaine (high dose), or 0.0625% bupivacaine (low dose), at a final volume of 0.15 mL per kilogram of body weight, infused manually into the epidural space over a period of 15 min. The anal and tail tone and motor deficits of the pelvic limbs were evaluated in 5 of the cows with use of a numerical rating scale and a visual analogue scale (VAS). Sensory block was assessed in 4 of the cows by the response to needle pricks in different regions with the use of a VAS. Measurements were obtained before and at different time points after injection, up to 360 min. Analysis of variance for repeated measures and post-hoc Tukey's and Dunnett's tests were used. Differences were considered significant when the P-value was ≤ 0.05. One cow became recumbent 6 h after injection. Anal and tail tones were significantly decreased and motor deficits of the pelvic limbs were significantly increased after bupivacaine treatment compared with control treatment. The overall mean VASpain scores ± standard deviation were 66 ± 8 after control treatment, 52 ± 5 after low-dose bupivacaine treatment, and 43 ± 5 after high-dose bupivacaine treatment. The pain scores were significantly lower in caudal regions up to the saphenous nerve after high-dose bupivacaine treatment compared with control treatment and significantly lower in the anus, vulva, and tail after low-dose bupivacaine treatment compared with control treatment. Thus, analgesia with moderate motor deficits of the pelvic limbs may be obtained with 0.125% bupivacaine administered epidurally.