Indication
Inguinal, groin and lower abdominal incisions
Inguinal hernia repair, gastrointestinal stoma formation, iliac crest bone harvest, laparoscopic procedures, orchidopexy, abdominal wall procedures
In contrast to posterior TAP blocks, the lateral QL provides visceral coverage
A lateral QL block can be performed bilaterally.
Contraindications
Complications
Anatomy
The innervation of the anterior abdominal wall is complex and includes thoracoabdominal, lateral cutaneous, subcostal, iliohypogastric and ilioinguinal nerves. The thoracoabdominal nerves are derived from T7-11 and run in the plane between the internal obliques and the transversalis muscles. The lumbar plexus T12/L1-4 runs between the psoas muscle and the quadratus lumborum muscle. Lumbar plexus nerve fibres that will make up the iliohypogastric and ilioinguinal nerves (mostly T12-L1), traverse along the ventral surface of the quadratus lumborum before travelling through the flat abdominal muscles.
The quadratus lumborum muscle (QL) is a quadrangular posterior abdominal wall muscle that stretches between the posteromedial iliac crest, the medial border of the 12th rib and the transverse processes of the L1-L4/5 vertebra bodies. It assists in lateral flexion of the vertebral column and provides stabilisation of spine, pelvis (posture) and 12th rib (respiration). It lies dorsolateral to the psoas muscles and anterior to the erector spinae muscles.
The muscles of the posterior abdominal wall at this level (QL, psoas and erector spinae) are encompassed by different layers of the thoracolumbar fascia (TLF) which separates them from the paraspinal muscles. This fascia contains mechanoreceptors, nociceptors, and sympathetic nerve fibres.
A lateral QL block aims to deposit local anaesthesia along the ventrolateral border of the QL muscle with a horseshoe-like spread to allow the local anaesthetic to travel along the aponeuroses of the flat abdominal muscles (transversus abdominis, internal oblique and external oblique muscles), covering the nerves lying there, and for the local anaesthetic to travel towards the psoas muscle to cover iliohypogastric and ilioinguinal nerves and lumbar plexus.
A lateral QL block provides a broad dermatomal sensory blockade from T7-12 to L1-L2. The spread of local anaesthetic to the paravertebral space and to the sympathetic fibres in the TLF is believed to be responsible for coverage of visceral pain. This makes a lateral QL block superior to a posterior TAP block.
Patient Position
Supine (TIP: place a sandbag under ipsilateral hip for tilt to improve ultrasound probe access)
Alternatively position the patient in lateral decubitus with the block side up
Sonoanatomy
Ultrasound probe selection: linear high frequency probe for a patient < 20kg;
For a patient > 20kg curvilinear probe might be preferential.
Place the ultrasound probe in a transverse plane at the level of the umbilicus between the iliac crest and the costal margin. Identify the 3 layers of abdominal muscles starting from deep to superficial: transverse abdominis, internal oblique and external oblique muscles. If the abdominal muscles are not clear, scan from the midline to orientate yourself (see section on rectus sheath block).
Slide the ultrasound probe more laterally/posterior to identify where the transverse abdominis muscle transitions into the transversus aponeurosis. The muscle deeper and slightly more posterior to this tapered end of the transversus abdominis muscle is the quadratus lumborum, appearing as a triangular shaped, more hypoechoic muscle (darker). The target site for the local anaesthetic is the ventrolateral border of the QL muscle.
NOTE: Identifying the QL muscle or distinguishing it from perinephric fat tissue can pose a challenge. If unsure, find the tapered end of the transverse abdominus muscle, then increase the depth and slightly tilt your probe cephalad or caudad. identify the transverse spinal process and the vertebral body (= Hypoechoic thumbs-up sign) and the 3 muscles around it that form the shamrock sign.
- The erector spinae muscle lies posteriorly to the transverse process
- The psoas muscle lies anteriorly to the transverse process, on top of the vertebra body.
- The QL muscle lies on top of the psoas muscle, between the tip of the transverse process and the tapered end of the transverse abdominis muscle. (quadrangular/triangular structure, different echogenicity (darker) compared to the psoas muscle)
Identify the target area: ventrolateral border of the QL muscle
Tips and tricks
Needling
Use a 50-60mm block needle in most cases (longer needle might be required depending on the patient’s size).
Target depth: 1-5 cm
Insert the needle in plane in an anterior to posterior needle trajectory. Advance the needle tip towards the lateral border of the QL muscle and penetrate the transversus abdominis aponeurosis.
Ideally the local anaesthetic will spread both along the anterior border and lateral border of the QL muscle creating a horseshoe appearance.
Levobupivacaine 0.25% 0.3-0.5ml/kg each side (+/- clonidine 1mcg/kg for increased duration)
Neonatal QL Block