An Ultrasound-Guided Latero-Ventral Approach to Perform the Quadratus Lumborum Block in Dog Cadavers

Abstract

The QL block is a high-level locoregional anesthesia technique, which aims to provide analgesia to the abdomen. Several approaches of the QL block have been studied to find out which one allows a greater distribution of the injectate. The aim of this study is to compare the traditional interfascial QL block (IQL) with a new latero-ventral approach (LVQL). We hypothesize that this new approach could be safer and easier to perform, since the injectate is administered more superficially and further away from vital structures. Our second objective is to assess whether a higher volume of injectate (0.6 mL/kg) could reach the ventral branches of the last thoracic nerves, leading to a blockade of the cranial abdomen. Six thawed canine cadavers (12 hemiabdomens) were used for this purpose. Both approaches were performed in all cadavers. A combination of methylene blue/iopromide was administered to each hemiabdomen, randomly assigned to the LVQL or IQL. No differences were found regarding the ease of perform the LVQL with respect to IQL. The results show that both techniques reached the ventral branches from L1 to L3, although only the IQL consistently stained the sympathetic trunk (5/6 IQL vs. 1/6 LVQL). The use of a higher volume did not enhance a more cranial distribution of the injectate.

Keywords: TAP block; abdominal analgesia; fascial block; latero-ventral approach; locoregional anesthesia; quadratus lumborum block.

Figure 1

(A) Schematic illustration of the anatomy at the level of the first lumbar vertebra in a dog placed in left lateral recumbency. (B) Sites of injection of the different approaches described for a QL block in dogs [2,3,4,6]. Adapted from Marchina-Gonçalves et al. [6]. Main anatomical structures L1, first lumbar vertebra; EO, external oblique muscle; IO, internal oblique muscle; TA, transverse abdominal muscle; ES, erector spinae muscles; QL, quadratus lumborum muscle; PM, psoas minor muscle; RK, right kidney; LVQL, latero-ventral quadratus lumborum block; L, lateral; M, medial; D, dorsal; V, ventral.

Figure 2

Ultrasound image of the anatomical structures identified to guide the LVQL (yellow needle) and IQL (red needle) approaches. EO external oblique muscle; ESP erector spinae muscles; IO internal oblique muscle; IP interfascial plane; PM psoas minor muscle; QL quadratus luborum muscle; TA transverse abdominal muscle; TAP transverse abdominal muscle aponeurosis; TP transverse process of L1; VB vertebral body of L1; D, dorsal; L, lateral; M, medial; V, ventral.

Figure 3

Staining of the ventral branches of the spinal nerves and the sympathetic trunk evaluated by computed tomography and anatomical dissection after the administration of 0.6 mL kg⁻¹ of a mixture of methylene blue and iopromide by the LVQL and IQL approaches. LVQL, latero-ventral quadratus lumborum block; IQL, interfascial quadratus lumborum block.

Figure 4

Computed tomographic image of the contrast media spread after the administration of 0.6 mL kg⁻¹ of a mixture of methylene blue and iopromide by the IQL and LVQL approaches. Transverse image at L1 level with soft tissue window setting. IQL, interfascial quadratus lumborum block; LVQL, latero-ventral quadratus lumborum block; D, dorsal; L, left; R, right; V, ventral.

Figure 5

(A) Distribution of the dye through QL and PM muscles, and the ventral branches of the spinal nerves in the LVQL and IQL approaches. (B) Same dissection image after removing the psoas minor muscle (PM). IQL, interfascial quadratus lumborum block; LVQL, latero-ventral quadratus lumborum block; PM, psoas minor muscle; QL, quadratus lumborum muscle; T13, L1, L2, L3 and L4, ventral branches of T13, L1, L2, L3 and L4 spinal nerves; Cd, caudal; Cr, cranial; L, left; R, right.

Figure 6

Distribution of the dye through the sympathetic truck after removing the PM and the aorta. IQL, interfascial quadratus lumborum block; LVQL, latero-ventral quadratus lumborum block; PM, psoas minor muscle; GF, genitofemoral nerve; LST, left sympathetic trunk; RST, right sympathetic trunk; T13, L1, L2, L3 and L4, ventral branches of T13, L1, L2, L3 and L4 spinal nerves; Cd, caudal; Cr, cranial; L, left; R, right.