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% .