Greater ischiatic notch plane versus parasacral block in dogs undergoing pelvic limb surgery: a retrospective noninferiority cohort study on perioperative opioid consumption.

Objective: To compare perioperative opioid consumption in dogs undergoing pelvic limb surgeries and receiving a lumbosacral plexus block by combining a lumbar [lateral pre-iliac (LPI)] block with a lumbosacral trunk [i.e. parasacral (PS group) or greater ischiatic notch plane (GIN group)] block. Study design Retrospective, descriptive, exploratory, noninferiority cohort study.

Methods: Medical records of 37 client-owned dogs were analyzed. Intraoperative (primary outcome) and postoperative (24 hours) opioid use, 24 hour cumulative pain scores and prevalence of complications were compared between the two groups. Opioid use was quantified in morphine equivalents (ME, mg kg ). The noninferiority limit for intraoperative opioid consumption was set at 0.05 ME kg hour. Demographic data, procedure duration, surgery type and perioperative dexmedetomidine and ketamine use were also collected. A t-test or Wilcoxon rank-sum test, a Fisher's exact test and multivariable linear regression were used. Significance was set at p < 0.05.

Results: The GIN and PS groups comprised 17 and 20 dogs, respectively. Total intraoperative ME consumption was 0.17 (0.11-0.21) and 0.22 (0.16-0.30) mg kg hour for the GIN and PS groups, respectively (p = 0.077). The noninferiority analysis adjusted by surgery type and body mass revealed that the mean difference between the groups (GIN - PS) was -0.039 (95% CI -0.11-0.03, p = 0.247) ME mg kg hour, indicating that the GIN group was not inferior to the PS group regarding intraoperative ME consumption. Dexmedetomidine and ketamine use, postoperative ME consumption and pain scores were similar between groups.

Conclusions And Clinical Relevance: This retrospective study and preliminary observations support the clinical use of the GIN plane block, demonstrating its noninferiority to the PS block when combined with the LPI block for multimodal perioperative analgesia in dogs undergoing pelvic limb surgeries.