Comparison of Dorsal Quadratus Lumborum and Rectus Sheath Blocks for Canine Ovariectomy: A Randomised Clinical Trial

This study aimed to compare the analgesic properties of the dorsal quadratus lumborum block (QLB) and the rectus sheath block (RSB) as part of a multimodal analgesic protocol in female dogs undergoing ovariectomy. A total of 57 dogs were included in the study. They were randomly divided into three groups: QLB, RSB or control. All the animals were premedicated with dexmedetomidine 0.125 mg m−2 and methadone 0.1 mg kg−1, induced with propofol and maintained with isoflurane. The blocks were performed using 0.4 mL kg−1 per hemiabdomen of bupivacaine 0.25%. In the intraoperative period, when the heart rate, mean arterial pressure or respiratory rate increased ≥ 20% from baseline, fentanyl 0.002 mg kg−1 was administered as rescue analgesia. During the early postoperative period, pain was assessed using the short form of the Glasgow Composite Pain Scale (GCPS-SF). Methadone 0.2 mg kg−1 was administered if GCPS-SF scores were ≥6/24 as rescue analgesia. No differences were found in fentanyl doses between groups (p = 0.4406). However, a clinically significant reduction of postoperative methadone rescue doses was found in the QLB group compared to the control group (26,32% absolute risk difference, with a 95% confidence interval of 6.64% to 49.10%), but not between QLB-RSB or RSB-control groups. In conclusion, dorsal QLB reduced early postoperative rescue analgesia requirements when included in a multimodal analgesic protocol in female dogs undergoing ovariectomy.