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Abstract
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Background and Aims Posterior quadratus lumborum block (QL2), has been implemented as a part of multimodal analgesia in postoperative pain relief after abdominal surgery. However, cadaveric studies did not demonstrate an effective dye spread to the thoracic paravertebral space, the target are for mechanism of action. We aimed to determine, the spread of injectate in QL 2 blocks
Methods In 2 cadavers donated through body donation programme for science studies, QL2 injections were performed, with 30ml of 0.1% methylene blue dye. On the 2nd day, cross-sections were executed in one cadaver and open dissections was performed in the other. The cross-sections and the open dissections were examined in detail for the diffusion of the dye by anatomist and co-anaesthesiologist not involved in injection
Results The cross-sections revealed spread of the dye in following planes: Posterior surface of QL, Lateral to QL, Lateral in transverses abdominis plane (TAP plane). Open dissections depicted dye spread in soaking the ilio-inguinal, ilio-hypogastric and the sub-costal nerves. Exploring the lumbar plexus did not reveal staining of nerves. However, the visceral and parietal peritoneum was stained
Depicts spread in TAP plane; ATLF-anterior thoracolumbar fascia; MTLF-middle thoracolumbar fascia; QLM-quadratus lumborum; TAM-transverses abdominis muscle; IO-internal oblique; EO-external oblique Figure 1b: illustrates spread in peritoneal layers
Conclusions The mechanism of action of QL2 is probably through the lateral diffusion in the TAP plane and a caudal spread in the visceral plane.