Evaluation of High-Volume Injections Using a Modified Dorsal Quadratus Lumborum Block Approach in Canine Cadavers.

Abstract

Simple SummaryThe quadratus lumborum (QL) block is an ultrasound-guided locoregional anesthesia technique. Its objective is to promote both visceral and somatic analgesia for abdominal procedures. Previous spread studies carried out in canine cadavers demonstrated its viability in this species but failed in consistently reach the spinal nerves responsible for the cranial abdominal wall innervation. Therefore, we hypothesize that a modified QL block technique, based on the administration of a higher volume of solution (0.6 mL kg−1) in a dorso-medial position compared to the interfascial injection point between the QL and psoas minor muscles, could enhance its cranial spread, and promote a consistent distribution spread through the ventral branches of the spinal nerves and sympathetic trunk. For this purpose, a solution of dye/contrast was ultrasound-guide injected into six canine cadavers. The results were assessed through computed tomography and dissection, showing that the proposed technique is viable, safe, and stained the median and caudal abdominal nerves and the sympathetic trunk up to T13 consistently. However, our modified technique of QL block did not increase the cranial distribution of dye/contrast to the thoracic spinal nerves, and may not provide adequate somatic analgesia of the cranial abdominal wall.The quadratus lumborum (QL) block targets the fascial plane surrounding the QL muscle providing abdominal somatic and visceral analgesia. The extension of its analgesic effects is a subject of research, as it could not cover areas of the cranial abdomen in dogs. This study assesses in eight thawed canine cadavers, the distribution of high-volume injections (0.6 mL kg−1 of a mixture of methylene blue and iopromide) injected between the psoas minor muscle and the vertebral body of L1. Anatomical features of the area of interest were studied in two cadavers. In another six dogs, QL blocks were performed bilaterally under ultrasound-guidance. The distribution of contrast was evaluated by computed tomography (CT). Hypaxial abdominal muscles were dissected to visualize the dye spread (spinal nerves and sympathetic trunk) in 5 cadavers. The remaining cadaver was refrozen and cross-sectioned. CT studies showed a maximum distribution of contrast from T10 to L7. The methylene blue stained T13 (10%), L1 (100%), L2 (100%), L3 (100%), L4 (60%) and the sympathetic trunk T10 (10%), T11 (20%), T12 (30%), T13 (70%), L1 (80%), L2 (80%), L3 (60%) and L4 (30%). These findings may suggest that despite the high volume of injectate administered, this modified QL block could not produce somatic analgesia of the cranial abdomen, although it could provide visceral analgesia in dogs.