Description of ultrasound-guided quadratus lumborum block technique and evaluation of injectate spread in canine cadavers.

Objective: To describe a quadratus lumborum (QL) block technique in canine cadavers and the spread of injectate.
Study Design: Prospective, randomized, descriptive, experimental anatomic study.
Animals: A group of 12 adult canine cadavers.
Methods: Gross and ultrasound anatomy of the sublumbar musculature and the relationship with the spinal nerves was studied in two cadavers. Bilateral ultrasound-guided injections were performed in eight cadavers in the fascial plane between the QL and psoas muscle using a dye-lidocaine solution [low volume (LV) 0.15 mL kg ^-1 or high volume (HV) 0.3 mL kg ^-1 ]. The ultrasound transducer was positioned caudal and parallel to the proximal aspect of the last rib, and an insulated needle was introduced in-plane using a ventrolateral to dorsomedial approach. Dissections were performed to determine the number of spinal nerves successfully stained (>1 cm) and the presence of injectate in the epidural space or abdominal cavity. Additionally, two cadavers were transversally cryosectioned after QL injection.
Results: Ventral branches of the last thoracic and first three lumbar spinal nerves ran between the bundles of the QL muscle and between the QL and psoas muscles. The target fascial plane was ultrasonographically identified and filled with the dye solution following all injections. Ventral branches of the thirteenth thoracic and first, second and third lumbar nerves were stained by 0.0%, 71.4%, 100%, 100%, and 25%, 100%, 100%, 100% using LV and HV, respectively. Multisegmental spread stained the lumbar sympathetic trunk on 0 (0-3) and 3 (0-4) vertebral levels with LV and HV, respectively. No abdominal or epidural spread was identified.
Conclusion and Clinical Relevance: Although no significant differences were found, HV resulted in a higher percentage of stain on spinal nerves and sympathetic trunk than LV. Further studies are warranted to determine if the QL block provides somatic and visceral abdominal analgesia in dogs.
(Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)