Comparative study between lateral versus latero-ventral quadratus lumborum block for perioperative analgesia in canine laparoscopic ovariectomy

Objective: To compare the perioperative analgesic effect of lateral versus latero-ventral quadratus lumborum block (QLB) in dogs undergoing laparoscopic ovariectomy. Study design: Randomised, blinded clinical study. Animals: A total of 15 client-owned female dogs undergoing laparoscopic ovariectomy. Methods: Animals were randomly assigned to receive a bilateral QLB, performed with 0.3 mL kg−1 ropivacaine 0.5%, either with lateral [group LQLB (n = 7)] or latero-ventral approach [group LVQLB 9 (n = 7)]. Dogs were premedicated intramuscularly with methadone 0.2 mg kg−1 and dexmedetomidine 3 μg kg-1. General anaesthesia was induced intravenously (IV) with propofol and maintained with isoflurane. Cardiovascular and respiratory variables were continuously monitored and recorded every 5 minutes during surgery. Fentanyl 3 μg kg-1 was administered IV if there was a 20% increase in heart rate and/or mean arterial pressure from previous values recorded 5 minutes before. Meloxicam 0.2 mg kg-1 was administered IV to all dogs during recovery. The Short-Form ofthe Glasgow Composite Pain Scale was used hourly for 8 hours post-QLB. Methadone 0.2 mg kg−1 was administered IV when pain score was ≥ 6/24. A Chi-square test compared the number of dogs requiring intraoperative rescue fentanyl. A Friedman test with a Dunn’s post hoc was used to evaluate the trend in postoperative pain scores within each group, and a Mann-Whitney test compared scores between the groups at each time point; p < 0.05. Results: Significantly fewer dogs required intraoperative rescue fentanyl in group LQLB, than in group LVQLB. No dog required postoperative rescue methadone and there were no significant differences in pain scores. Conclusions and clinical relevance: Bilateral QLB performed with lateral approach reduced the number of dogs requiring intraoperative rescue analgesia in comparison with the latero-ventral approach. No differences were detected postoperatively, possibly due to the confounding effects of methadone, dexmedetomidine, and meloxicam.