BLOCK AT A GLANCE
Comprises a group of interfascial plane injections of local anesthetic at different locations around the quadratus lumborum muscle.
Indications: Analgesia for the anterolateral abdominal wall and parietal peritoneum
Goal: Local anesthetic spread either lateral (QL1), posterior (QL2), or anterior (QL3) to the quadratus lumborum muscle to block the anterior rami of spinal nerves T10-L1 (and, eventually, the paravertebral sympathetic chain)
Local anesthetic volume: 15 to 30 mL
The ultrasound-guided quadratus lumborum (QL) block was developed from the transversus abdominis plane (TAP) block to achieve a more consistent and extended block of the anterior rami of spinal nerves supplying the abdominal wall. The various QL block techniques (i.e., QL1, QL2, QL3) aim to improve the analgesia after surgeries involving the abdominal wall. Several technique variations have been devised to enhance the spread of local anesthetic (LA) to reach the thoracic paravertebral space, and eventually the sympathetic chain. Other variations aim to extend the block to the lumbar plexus and provide analgesia to the lower extremity. New modifications continue to be implemented: the transverse oblique paramedian (TOP) and the supra-iliac anterior QL3, for instance, are thought to result in a more cranial and caudal spread of the LA, respectively. However, the available evidence so far is insufficient to draw conclusions.
Mechanisms of action of QL block variants are mainly related to the anatomical injection site but inconsistent. As an example, the spread of the LA with an anterior QL block (QL3) may reach the paravertebral space, lumbar nerve roots, and sympathetic chain, and result in weakness of the lower extremities, as has been reported. For safety and efficacy of QL blocks, adequate ultrasound (US) images are crucial, yet often challenging to obtain. Without adequate images, the QL blocks are associated with variable success rates and risks of iatrogenic injury to the kidney, liver, and/or spleen.
Similar to many interfascial plane blocks, the duration, extent, and quality of the analgesia between the different QL blocks vary. The block characteristics depend on the injection site, anatomical characteristics of the fascial planes, the volume of the LA injected, and whether the injectate reaches the intended target nerves.
The QL muscle originates from the posterior part of the iliac crest and the iliolumbar ligament and inserts on the 12th rib and the transverse processes of vertebrae L1-L4. The QL muscle is located between the psoas muscle (anterior) and the erector spinae muscles (posterior). Both the QL and psoas muscles pass posterior to the medial and lateral arcuate ligaments of the diaphragm to insert in the transverse processes (Figure 40-1). To understand the potential mechanisms of action of the QL block, it is essential to understand the anatomy of the fasciae that surround the muscles at this level.
Anatomy of the quadratus lumborum.