Ultrasound-guided bilateral quadratus lumborum block in dogs undergoing abdominal surgery: A retrospective study

This retrospective cohort study evaluated the intraoperative analgesic efficacy and complications of bilateral quadratus lumborum block (QLB) in dogs undergoing abdominal laparotomy between January 2022 and April 2023. Dogs were assigned to either a QLB group, receiving loco-regional ropivacaine, or a systemic analgesic (SA) group, treated with fentanyl, lidocaine, or ketamine via boluses and/or continuous infusion. Data collected included demographics, American Society of Anaesthesiologists (ASA) physical status, surgery type, procedure duration, analgesic management, minimum alveolar concentration (MAC), incidence of hypotension (IH) and cardiovascular interventions (CVI). Statistical analyses used Wilcoxon, Mann-Whitney and Pearson's Chi-squared tests, with significance at p < 0.05. Forty-six dogs met inclusion criteria for the QLB group and 40 for the SA group, with no significant differences in demographics, anaesthesia, or surgery types between groups. Splenectomies and enterectomies were the most common procedures. In the QLB group, median ropivacaine dose was 2.50 mg kg^-1 (2.00 - 3.30) at 0.3% concentration (0.25 - 0.50), with a median volume of 0.40 mg kg^-1 per side. Intraoperative fentanyl use was significantly lower in the QLB group (0.00 µg kg-1 min-1) versus the SA group (0.07 µg kg-1 min-1, p < 0.001). MAC was 0.857 (0.652 - 0.998) and 0.935 (0.820 - 1.104) in QLB and SA respectively (p < 0.001). IH and CVI did not differ between groups. IH showed no correlation with ASA status, fentanyl, nor ropivacaine. However, in the SA group, IH correlated with a lower MAC (p = 0.003). This correlation was not found in QLB group (p = 0.817). In conclusion, the QLB technique reduced fentanyl consumption and MAC in dogs undergoing abdominal surgery.