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: Randomized, 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 L_QLB, n = 7) or latero-ventral approach (group LV_QLB, 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 of the 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 U test compared scores between the groups at each time point; p < 0.05.

Results: Significantly fewer dogs required intraoperative rescue fentanyl in group L_QLB than in group LV_QLB. 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 owing to the confounding effects of methadone, dexmedetomidine and meloxicam.