Quadratus Lumborum Block

The quadratus lumborum block (QLB) is a plane block described by Blanco et al. in 2007. It is performed under ultrasound guidance at the posterior wall of the abdomen, just upstream the TAP space. It takes advantages of the arrangement of muscular, fascio-aponeurotic (thoraco-lumbar fascia) and nerve structures, while local anaesthetic is injected near the quadratus lumborum muscle. It allows somatic abdominal analgesia and also probably visceral analgesia whose mechanism is not clearly elucidated. Because of its analgesic efficacy, its wide metameric extension from T7 to L1 and its duration, QLB is often considered superior to TAP block and could be an alternative to neuraxial techniques. Four approaches have been described according to the site of injection in relation to the quadratus lumborum muscle: a lateral approach (QLB1), a posterior approach (QLB2), an anterior/transmuscular approach (QLB3) and an intramuscular approach (QLB4). To date, it is still difficult to choose an approach rather than another. The puncture is not difficult and very few complications have been described in the literature. However, the ultrasound scanning can be challenging and requires good knowledge in sonoanatomy. The close proximity of the retroperitoneal space and the renal compartment deserves special attention. Diffusion to the lower roots of the lumbar plexus is possible, resulting in quadriceps weakness. Over the past few years, the literature has gradually grown, making it possible to assess the analgesic efficacy of QLB in many postoperative situations and to clarify its potential indications: caesarean section, renal surgery, abdominal surgery, paediatric surgery, hip surgery... Nevertheless, many questions surrounding the QLB remain unsolved and require further investigations.