Bilateral quadratus lumborum block for post-caesarean analgesia

Sir,

We read with a great interest the review article titled, ‘Post-caesarean analgesia: What is new?’ by Kerai et al.[1] The last decade has seen a revolution in the practice of regional anaesthesia due to the use of ultrasonography (USG). Several fascial plane blocks have been successfully described and used after confirming the local anaesthetic (LA) spread with dyes and imaging. Transversus abdominis plane (TAP) block and ilioinguinal-iliohypogastric block have been successfully used in patients undergoing caesarean section. However, an USG-guided fascial plane block that needs to be mentioned is the quadratus lumborum block (QLB).

Four variants of QLB have been described in literature. Anterior QLB involves injection of LA in the fascial plane between psoas major (PM) and quadratus lumborum (QL) muscle. A lateral QLB involves injection of LA between QL muscle and thoracolumbar fascia. This injection is done in supine position. Posterior QLB is performed by injecting LA between QL muscle and the aponeurosis formed by external and internal oblique muscles [Figure 1].[2] Transmuscular QLB involves identification of QL, PM, erector spinae muscle and transverse process of L4 vertebra. On USG, this appears like a Shamrock where the three muscles form the leaves and the transverse process forms the stem of clover. Therefore, this appearance is called a Shamrock sign. The injection is given with the patient in the lateral position between the fascial plane between QL and PM muscle by piercing the QL muscle. A high-volume QLB (around 30 mL LA) has been shown to cover dermatomal segments from T4 to L2 with LA reaching paravertebral spaces, thereby providing effective analgesia [Figure 2].[3] Blanco et al. randomised 55 parturients to receive USG-guided QLB using 0.125% bupivacaine 0.2 mL/kg versus normal saline at a similar dose of morphine consumption. Visual analogue scale score was significantly less in the first 24 h in the group who received QLB.[4] Later, Blanco et al. randomised 76 parturients and compared QLB with TAP block and compared morphine consumption post-operatively for 48 h. The authors found QLB to be superior to TAP block in terms of morphine consumption and demand for rescue analgesia.[5]

Figure 1.

Lateral, posterior and anterior approaches to quadratus lumborum block. 1 - quadratus lumborum muscle, 2 - psoas major muscle, 3 - erector spinae muscle, 4 - transverse process of L4 vertebra

Figure 2.

The Shamrock sign seen on ultrasound. The bellies of quadratus lumborum, psoas major and erector spinae which are circled form the three leaves of clover. The transverse process of L4 vertebra forms the stem of clover

Although the block is easy to perform with USG, the anterior, posterior and transmuscular variants of QLB involve turning a parturient on the lateral side twice for performing bilateral QLB which can be quite cumbersome for the operating room staff and also uncomfortable to the patient. This can be managed by becoming proficient in performing QLB in supine position with a wedge under ipsilateral buttock to facilitate the injection. The potential of bilateral QLB in parturients needs to be explored in future with well-designed studies.

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