In cats undergoing midline ovariohysterectomy, is the use of local anaesthesia with bupivacaine associated with a reduction in postoperative pain score?

PICO question: In cats undergoing midline ovariohysterectomy, is the use of local anaesthesia with bupivacaine via intraperitoneal or subcutaneous injections, in comparison with the use of a control substance or other analgesic measure, associated with a reduction in postoperative pain score? Clinical bottom line: Category of research: Treatment. Number and type of study designs reviewed: Three studies were critically appraised in this Knowledge Summary. They included two prospective, blinded, randomised, controlled clinical trials and one prospective randomised, blinded clinical trial. Strength of evidence: Weak. Outcomes reported: Bupivacaine does not eliminate postoperative pain in cats undergoing ovariohysterectomies; minimal evidence was found to suggest that it was better at reducing postoperative pain scores in comparison to other analgesics. However, bupivacaine may provide analgesic benefits to cats when administered via intraperitoneal or subcutaneous injections as local anaesthesia and in combination with other analgesic agents. The need for postoperative rescue analgesia was minimised when bupivacaine was administered prior to or during the ovariohysterectomy. Conclusion: When compared to a control, pain scores for the participating cats were lower after administration of bupivacaine, however, statistical significance was only reached in one of the studies. Additionally, other medications were found to lower the post operative pain score to a greater effect. However, bupivacaine administration is cheap and simple to perform, so it's use as part of a multimodal analgesic protocol is supported. Confounding factors within the studies may have altered the perceived effectiveness of the analgesic properties of bupivacaine though, so further investigation involving larger cohorts with standardised controls would be prudent.