Analgesic efficacy of an ultrasound-guided transversus abdominis plane block with bupivacaine in cats: a randomised, prospective, masked, placebo-controlled clinical trial.

Abstract

OBJECTIVES: This randomised, prospective, masked clinical trial evaluated the postoperative analgesic efficacy of an ultrasound-guided transversus abdominis plane block (TAPB) with bupivacaine in cats undergoing ovariohysterectomy. METHODS: Thirty-two healthy adult female cats undergoing elective ovariohysterectomy were randomised to undergo TAPB with bupivacaine (treatment group [TG], n&#x2009;=&#x2009;16) vs placebo (control group [CG], n&#x2009;=&#x2009;16) in addition to preoperative analgesia with buprenorphine (0.02&#x2009;mg/kg IM). All patients received a general anaesthetic and, before surgical incision, a bilateral two-point (subcostal and lateral-longitudinal) TAPB was performed using 1&#x2009;ml/kg bupivacaine 0.25% (0.25&#x2009;ml/kg/point) or saline. Each cat was assessed by a blinded investigator before premedication (0&#x2009;h) and at 1, 2, 3, 4, 8, 10 and 24&#x2009;h postoperatively using the UNESP-Botucatu Feline Pain Scale - short form. Buprenorphine (0.02&#x2009;mg/kg IV) and meloxicam (0.2&#x2009;mg/kg SC) were administered when pain scores were &#x2a7e;4/12. Ten hours postoperatively, meloxicam was administered to cats that did not receive rescue analgesia. Statistical analysis included Student's-tests, Wilcoxon tests and &#x3c7;tests, and a linear mixed model with Bonferroni corrections (<0.05). RESULTS: Of the 32 cats enrolled, three in the CG were excluded from the analysis. The prevalence of rescue analgesia was significantly higher in the CG (n&#x2009;=&#x2009;13/13) than in the TG (n&#x2009;=&#x2009;3/16;<0.001). Only one cat in the CG required rescue analgesia twice. Pain scores were significantly higher in the CG compared with the TG at 2, 4 and 8&#x2009;h postoperatively. Mean&#x2009;&#xb1;&#x2009;SD pain scores were significantly higher in the CG, but not in the TG, at 2 (2.1&#x2009;&#xb1;&#x2009;1.9), 3 (1.9&#x2009;&#xb1;&#x2009;1.6), 4 (3.0&#x2009;&#xb1;&#x2009;1.4) and 8&#x2009;h postoperatively (4.7&#x2009;&#xb1;&#x2009;0.6) than at 0&#x2009;h (0.1&#x2009;&#xb1;&#x2009;0.3). CONCLUSIONS AND RELEVANCE: A bilateral ultrasound-guided two-point TAPB with bupivacaine in combination with systemic buprenorphine provided superior postoperative analgesia than buprenorphine alone in cats undergoing ovariohysterectomy.