Postoperative Analgesic Effect of Bilateral Quadratus Lumborum Block (QLB) for Canine Laparoscopic Ovariectomy: Comparison of Two Concentrations of Ropivacaine

The aim of this study was to evaluate the effect of the transverse quadratus lumborum block (QLB(LQL-T)) on time to the first postoperative rescue analgesia in dogs submitted to laparoscopic ovariectomy. A total of twenty-three female dogs were included. Dogs were randomly assigned to receive a bilateral QLB(LQL-T), performed either with 0.3 mL kg(-1) ropivacaine 0.5% [group QLB(0.5%) (n = 8)] or with ropivacaine 0.33% [group QLB(0.33%) (n = 8)] or a fentanyl-based protocol [group No-QLB (n = 7)]. Dogs were premedicated intravenously (IV) with fentanyl 5 mcg kg(-1), general anesthesia was induced IV with propofol and maintained with sevoflurane. Invasive mean arterial pressure (MAP) values were recorded five minutes before and five minutes after performing the QLB(LQL-T). The short-form of the Glasgow composite measure pain scale was used every hour after extubation, and methadone 0.2 mg kg(-1) was administered IV when pain score was >= 5/24. Kolmogorov-Smirnov test, ANOVA test combined with Tukey post hoc test, Student's T-test and Chi-square test were used to analyze data; p < 0.05. Time from QLB(LQL-T) to the first rescue analgesia was significantly longer in QLB(0.5%) than in group QLB(0.33%) and No-QLB. MAP pre- and post-block decreased significantly only in group QLB(0.33%).