LAUSR

In recent years, ultrasound-guided fascial plane blocks (FPBs) have become commonly used in the field of anesthesia and pain medicine, and the development and modification of new FPB techniques are happening rapidly. New FPB techniques developed based on innovative ideas may have some benefits, including superior efficacy and safety, which may ultimately change the standard of care. Such new approaches should be used with caution, however, because the differences in expected sensory block areas, as well as technical difficulties and complications, between new FPBs and conventional blocks have yet to be determined. The use of ultrasound has the potential to broadly expand the use of FPB in pain management. Ultrasound provides visualization that the injectate is administered to the proper fascial plane and enhances the accuracy of the FPB procedure, which had previously been performed using the tactile sensation of fascial plane entry. As a result, conventional FPBs such as the fascia iliaca compartment block and the transversus abdominis plane (TAP) block have become more reliable with ultrasound guidance. Moreover, the advanced understanding of the sonoanatomy of fascial planes and surrounding structures may have contributed to the development of truncal FPBs that can be safer and easier than the traditional epidural block. The concept of multimodal analgesia, the need for alternatives to epidural anesthesia, and the popularity of minimally invasive surgery have also accelerated the development of ultrasound-guided FPBs. Ultrasound-guided FPBs, unlike selective peripheral nerve blocks, do not require direct imaging of the target nerves, instead ensuring sufficient dermatomal coverage of sensory blockade by injection of much larger volumes of LA than is necessary for peripheral nerve blocks. In addition to the spread throughout the fascial plane to which the LA is administered, the spread of LA to adjacent tissues may also be a mechanism of analgesic action in some FPBs. The drawback with this approach is that it is nearly impossible to monitor the entire spread of LA and control it intentionally. Thus, the volume of LA injected may be larger than is necessary for adequate nerve blockade. The quadratus lumborum (QL) block is a relatively new FPB and was developed based on the concept of the original TAP block, which uses the triangle of Petit as the main anatomical landmark [1]. In the QL block, the LA is administered to the thoracolumbar fascia (TLF) that surrounds the QL muscle. The QL block mainly covers the subcostal, ilioinguinal, and iliohypogastric nerves, which are on the ventral aspect of the QL muscle. One clinical study found that the analgesic effects of the QL block are superior to those of the ultrasound-guided lateral TAP block in patients undergoing Cesarean Section [2]. Use of magnetic resonance imaging has demonstrated that contrast media administered to the TLF at the lumbar level can extend into the thoracic paravertebral space (PVS) [3], as has a cadaver study [4]. The spread of LA into the thoracic PVS is presumed to be the mechanism of the extensive sensory blockade provided by the QL block. Several approaches to the injection site in QL block have been reported: QLB1 (lateral approach), QLB2 (posterior approach), QLB3 (anterior approach), and the intramuscular approach. The spread of LA differs between the different techniques, leading to variation in the sensory block area. Previous clinical trials have assessed the analgesic effect of the QL blocks in various types of surgery [5–9]. In the anterior approach, the LA is administered to the fascial plane between the QL and psoas major muscles and can block the lumbar plexus [10]. In a study comparing the QLB2 and intramuscular approach, the spread of injectate into the thoracic PVS was less extensive in the intramuscular approach * Kunihisa Hotta [email protected]