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

SIMPLE SUMMARY: The quadratus lumborum (QL) block is an ultrasound-guided regional anesthesia technique that aims to provide analgesia to the abdomen. Previous studies show that this technique may fail to provide analgesia in the cranial abdominal wall in dogs. The QL block is a difficult technique with the risk of damaging vital structures. The objective of this study is to assess a new latero-ventral approach to the QL (LVQL), which could be easier and safer to perform than the interfascial approach (IQL) widely reported. Another objective is to evaluate the distribution of high-volume injections (0.6 mL/kg) of dye/contrast achieved by both approaches. Six thawed dog cadavers were used to randomly perform the LVQL in one hemiabdomen and the IQL in the other. Distribution of the injectate throughout the ventral branches of the spinal nerves from T10 to L4 and the sympathetic trunk (CT and dissection) was assessed. The two approaches consistently stained L1-L3 ventral branches, which is compatible with obtaining somatic analgesia in the middle and caudal abdominal wall. The administration of high-volume injections did not result in a more cranial distribution of the injectate compared to previous studies. The sympathetic trunk was more consistently stained by the IQL, therefore, the LVQL may not promote visceral desensitization of the abdomen. 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.