Evaluation of targeted bupivacaine for reducing acute postoperative pain in cats undergoing routine ovariohysterectomy.

Objectives: This study sought to determine if bupivacaine targeted at specific, potentially painful sites could enhance postoperative analgesia in routine feline ovariohysterectomies. A secondary objective was to assess the utility of multiple acute pain scales for cats in a high-volume surgery setting.

Methods: Two hundred and twelve cats were included in a prospective, randomized, double-blinded, placebo-controlled clinical trial. Anesthesia included buprenorphine, ketamine, dexmedetomidine and isoflurane. A ventral midline ovariohysterectomy was performed and cats were administered bupivacaine (2 mg/kg), placebo control (0.9% saline) or sham control (observation only) intraoperatively at the ovarian suspensory ligaments and vessels, uterine body and incisional subcutaneous tissues. Two pain scales were used to assess cats postoperatively. Initially, a multidimensional composite pain scale (MCPS) and a 0-10 numeric pain rating scale (NRS) were used. Subsequently, the MCPS was replaced with a modified Colorado State University Feline Acute Pain Scale (mCSU). Pain scores for the test groups were compared using a one-way ANOVA and a Holm-Bonferroni post hoc analysis when a difference was found ( <0.05).

Results: Pain for the bupivacaine group was lower than the control groups at 1 h post-recovery and discharge, attaining significance with higher body weights. The values were 0.008 and 0.004 for 1 h post-recovery and discharge, respectively. Pain scores between evaluators for the MCPS and NRS correlated poorly with values for 1 h post-recovery and discharge of -0.08 and 0.22, respectively. Additionally, the MCPS proved difficult to use and time consuming, especially for feral and fractious patients, and was replaced with the mCSU.

Conclusions And Relevance: Targeted bupivacaine reduced early postoperative pain scores following routine feline ovariohysterectomies. The technique used was simple, requiring just over a minute to perform at minimal additional cost. The MCPS was not ideal for use in a high-volume spay setting.