Effects of intratesticular injection of bupivacaine and epidural administration of morphine in dogs undergoing castration

Objective -To determine the intraoperative and postoperative analgesic efficacy of intratesticular or epidural injection of analgesics for dogs undergoing castration. Design-Randomized controlled trial. Animals-51 healthy male dogs. Procedures-Dogs were assigned to a control group that received analgesics systemically (hydromorphone [0.1 mg/kg {0.045 mg/lb}, IM] and carprofen [4.4 mg/kg {2.0 mg/lb}, SC]; n = 17), an epidural treatment group that received analgesics systemically and morphine (0.1 mg/kg) epidurally (17), or an intratesticular treatment group that received analgesics systemically and bupivacaine (0.5 mg/kg [0.23 mg/lb]/testis) intratesticularly (17). Dogs were anesthetized and castrated by veterinary students. Responses to surgical stimulation were monitored intraoperatively, and treatments were administered as required. Pain scores were assigned via a modified Glasgow composite pain scale after surgery. Serum cortisol concentrations were determined at various times. Rescue analgesia included fentanyl (intraoperatively) and hydromorphone (postoperatively). Results -Compared with control dogs, dogs in the intratesticular bupivacaine and epidural morphine treatment groups received significantly fewer doses of fentanyl intraoperatively (11, 1, and 5 doses, respectively) and hydromorphone postoperatively (14, 7, and 3 doses, respectively) and had significantly lower postoperative pain scores (mean ± SEM score at first assessment time, 71 ± 0.5, 4.8 ± 0.2, and 4.5 ± 0.4, respectively). At 15 minutes after removal of the testes, serum cortisol concentrations were significantly higher than they were immediately prior to surgery for all groups and values for the intratesticular bupivacaine treatment group were significantly lower versus the other 2 groups. Conclusions and Clinical Relevance – Intratesticular or epidural injection of analgesics improved perioperative analgesia for dogs undergoing castration. The study is from the College of Veterinary Medicine, Washington State University, Pullman, Washington, USA.

Perez TE, Grubb TL, Greene SA, et al. J Am Vet Med Assoc  2013; 242(5): 631-642.

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