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Quadratus Lumborum Block
Anatomy
The ultrasound guided quadratus lumborum block has recently evolved as a solution for postoperative analgesia for major abdominal surgery. The ultrasound guided QL block provides both somatic and visceral analgesia therefore in many cases seems superior to the lateral TAP block which provides only somatic analgesia. The QL block may provide analgesia ranging from the T7-L1 dermatomes. Four approaches to the ultrasound guided QL approach have been described in recent literature. These are the QL1 or lateral approach, QL2 or posterior approach, QL3 or anterior approach and QL4 the intramuscular approach. The most common and in our opinion the easiest approach to learn is the QL1 approach thus this tutorial will concentrate on explaining only the QL1 approach.
The goal of performing a QL1 block is to deposit local anesthetic deep to the aponeurosis of the transverse abdominis muscle but superficial to the
transversalis fascia. This location is lateral to quadratus lumborum muscle. The local anesthetic injected in this fascial plane communicates (spreads) with the thoracolumbar fascial plane and eventually the paravertebral space by dissecting the space around the QL muscle. The thoracolumbar fascia itself contains a network of sympathetic fibers in addition to mechanoreceptors.
Block Procedure
The ultrasound guided QL1 block may be performed with the patient in the supine position. It should be noted that medial retraction of the abdomen may facilitate this approach in the obese patient. A linear transducer is placed on the midaxillary line between the iliac crest and costal margins. The external oblique, internal oblique and transverse abdominis muscles should be easily identified. The transducer is then moved posterior until the aponeurosis of the transverse abdominis muscle is identified. The block needle is inserted in plane anterior to the transducer. The target for deposition of local anesthetic is deep to the TAM aponeurosis (thoracolumbar fascia) lateral to the QL muscle. Similar to most fascial plane blocks the QL block is a volume block thus 20-30ml of local anesthetic is used. The concentration of local anesthetic used may be adjusted taking into consideration the patients weight and whether performing a unilateral vs. bilateral injection to avoid a toxic dose.
Ultrasound images of QL block. Deposition of local anesthetic just superficial to transversalis fascia but deep to the TAM aponeurosis is highlighted blue. QLM= Quadratus Lumborum Muscle, EOM= External Oblique Muscle, IOM=Internal Oblique Muscle, TAM=Transverse Abdominis Muscle, LA=Local Anesthetic.
Approach to QL block. Probe is moved posterior until TAM aponeurosis and transversals fascia is visualized by ultrasound. Needle insertion is in plane approximately 1cm from the probe.
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