Evaluation of opioid consumption using the quadratus lumborum block or intraperitoneal instillation with bupivacaine in dogs undergoing ovariohysterectomy in a teaching institution.

OBJECTIVE

To compare postoperative opioid consumption between ultrasound-guided quadratus lumborum block (QLB) with bupivacaine and intraperitoneal bupivacaine instillation.

STUDY

DESIGN

Prospective, randomized, single-blinded, cross-sectional, clinical study.

ANIMALS: A total of 74 owned female dogs undergoing elective ovariohysterectomy.

METHODS

Dogs were premedicated with dexmedetomidine (5 μg kg-1) and methadone (0.3 mg kg-1) intramuscularly. Anesthesia was induced with intravenous propofol and maintained with isoflurane in oxygen. Carprofen (4 mg kg-1) was given subcutaneously after orotracheal intubation. Dogs underwent either a QLB with 0.3 mL kg-1 (1.5 mg kg-1) per side of 0.5% bupivacaine (group QLB) or intraoperative intraperitoneal instillation (group IP) of 0.5% bupivacaine (3 mg kg-1) as part of a multimodal analgesic protocol. Ovariohysterectomies were performed by undergraduate students under instructor supervision. Postoperative pain was assessed at 1, 2, 3, 4, 6, and 8 hours after extubation, using the short form of the Glasgow Composite Measure Pain Scale, and methadone (0.2 mg kg-1) was given as rescue analgesia if the pain score was ≥ 6/24. Opioid consumption was quantified by the number of rescue boluses required, using Poisson regression models.

RESULTS

Methadone boluses were given at least once to 9/37 dogs (24%) in group QLB and 15/37 dogs (41%) in group IP. Dogs in group QLB were given 0-2 (range) methadone boluses, whereas those in group IP were given 0-3 boluses, with a total of 11 and 21 boluses, respectively. Methadone consumption was significantly reduced in group QLB versus group IP with a rate ratio of 0.42 (95% confidence interval = 0.19-0.92, p = 0.023).

CONCLUSIONS

As part of a multimodal analgesic protocol, the QLB reduced postoperative opioid consumption compared with intraperitoneal instillation of bupivacaine in dogs undergoing ovariohysterectomy performed by veterinary students.

CLINICAL RELEVANCE: The QLB can be an alternative to the IP instillation of bupivacaine in dogs undergoing OVH, particularly in teaching settings where surgical procedures may be longer and more stimulating.