The erector spinae plane block (ESPB) is an ultrasound-assisted fascial block used to manage perioperative pain in dogs undergoing hemilaminectomy. This study set out to evaluate how a bilateral ESPB compares with a fentanyl constant rate infusion (CRI) for analgesia in this setting. This retrospective cohort review examined anaesthesia records from client-owned dogs that underwent hemilaminectomy between June 2019 and August 2020 and received a bilateral ESPB (group ESPB). Their outcomes were contrasted with those from 39 dogs operated between September 2014 and June 2017 who received fentanyl via CRI (2 μg/kg bolus, then 5 μg/kg/hour) as their main intraoperative analgesic (group CRI). The analysis focused on how many dogs needed rescue fentanyl doses during surgery, the cumulative amount administered, postoperative methadone usage, and adverse anaesthetic events within 24 hours. Univariate statistics were applied. Group ESPB included 93 dogs. The block was performed with a median (range) levobupivacaine volume of 1 (0.5–1.7) mL/kg per side at 0.125% (0.12–0.25). Rescue fentanyl was required in 54.8% of dogs in group ESPB and 56.4% in group CRI (p > 0.99). Dogs in the CRI cohort received a greater total number of rescue boluses (p = 0.006), particularly during lumbar procedures. From the moment of skin incision through vertebral lamina drilling, rescue boluses were administered more often in group CRI (p = 0.001), whereas from the end of drilling until surgery completion, the ESPB cohort received more additions (p = 0.0002). In the first 6 postoperative hours (p = 0.0035) and the 6–12 hour period (p = 0.0005), methadone use was more frequent in group CRI. Hypothermia occurred more often in the ESPB cohort (p = 0.04). One dog not included in the dataset experienced sinus arrest following a caudal thoracic ESPB. Within the limits of this dataset, bilateral ESPB corresponded with fewer fentanyl rescue boluses during hemilaminectomy, most notably from skin incision through lamina drilling. Although opioid requirements were reduced in the ESPB group during the first 12 postoperative hours, variations in postoperative care limited conclusions regarding longer-term analgesic effects.
