Perioperative analgesic efficacy of lumbar erector spinae plane block in dogs undergoing hemilaminectomy: a randomized blinded clinical trial

Objective: To evaluate the perioperative analgesic effect of the unilateral lumbar erector spinae plane block (ESPB_L) in dogs undergoing hemilaminectomy.

Study design: Randomized, blinded clinical study.

Animals: A total of 30 client-owned dogs undergoing thoracolumbar or lumbar hemilaminectomy for intervertebral disc extrusion (IVDE).

Methods: Dogs were randomly assigned to receive a unilateral ESPB_L, performed either with 0.4 mL kg^-1 ropivacaine 0.5% [group ROPI (n = 15)] or with saline solution [CNT group (n = 15)]. Dogs were premedicated intravenously (IV) with acepromazine 5 μg kg^-1 and methadone 0.2 mg kg^-1, general anaesthesia was induced by administering IV midazolam 0.2 mg kg^-1 and propofol to effect and maintained with isoflurane. Fentanyl was administered as rescue analgesia. Bradycardia [heart rate (HR) < 60 beats minute^-1] with hypotension was treated with atropine IV. The Short-Form of the Glasgow Composite Pain Scale was used pre- and postoperatively at 1, 2, 4, 8, 12, 16, 20 and 24 hours after extubation, and methadone 0.2 mg kg^-1 was administered IV when pain score was ≥ 5/20. HR and end-tidal concentration of isoflurane (Fe'Iso) were compared between groups with anova combined with a Dunnet's post hoc test. Time to the first rescue methadone and total dose of fentanyl (FEN_tot, μg kg^-1 hour^-1) and methadone (MET_tot, mg kg^-1) in the first 24 postoperative hours were compared using unpaired Student's t test. Postoperative pain scores were compared with the Mann-Whitney test and atropine administration with a Fisher's exact test; p < 0.05.

Results: HR, Fe'Iso, FEN_tot, MET_tot and atropine administration were significantly lower in group ROPI compared to CNT. Postoperative analgesic effect was significantly longer, and pain scores were significantly lower in group ROPI for all time points.

Conclusions and clinical relevance: Unilateral ESPB_L with ropivacaine reduced perioperative opioid consumption and the occurrence of bradycardia in dogs undergoing hemilaminectomy.