Evaluation of preoperative intraperitoneal injection of bupivacaine for intraoperative antinociception in cats undergoing ovariohysterectomy: A randomized clinical trial

Objective: To determine if preoperative intraperitoneal bupivacaine can minimize intra- and postoperative nociception/pain in cats undergoing ovariohysterectomy. Study design: Prospective, randomized, investigator-blinded, placebo-controlled clinical trial. Animals: Forty-seven, intact female cats. Methods: Cats were anesthetized using a standard protocol and randomized to receive ultrasound-guided intraperitoneal 0.9 % saline (US-S) or 0.25 % bupivacaine (US-IPLA) before ovariohysterectomy. On recovery, US-S cats received 2 mg/kg robenacoxib subcutaneously and US-IPLA cats received equivalent volume of 0.9 % saline subcutaneously. Intraoperative outcome variables included heart rate (HR), respiratory rate (fR), systolic arterial pressure (SAP), and vaporizer setting associated with relevant surgical events characterized by manipulation of each ovarian pedicle (OP1, OP2) and the uterine body (UB). The postoperative outcome variable was need for rescue analgesia, determined using the Glasgow Composite Measure Pain Scale during 6 h after tracheal extubation. Intraoperative data were analyzed using two-way ANOVA and Šidák's multiple comparisons test. The probability of postoperative rescue analgesia was analyzed using the Gehan–Breslow–Wilcoxon test. Significance was p < 0.05. Results: Compared to baseline, all surgical events caused significant increases in HR and SAP in both groups, fR increased in US-IPLA but not in US-S, vaporizer settings remained unchanged during OP1, OP2 and UB in group US-IPLA, and were significantly higher only during OP1 in group US-S. There were no significant between-group differences in intraoperative variables and postoperative need for rescue analgesia. Conclusions and clinical relevance: Preoperative intraperitoneal bupivacaine had minimal effects on intraoperative indicators of nociception. The need for rescue analgesia was not significantly different between groups.