Ultrasound-guided transmuscular quadratus lumborum block catheter technique.

Abstract

We read the article by Rao Kadam et al. with great interest 1. We congratulate the authors and find the prospect of using catheter placement to prolong analgesia following transmuscular quadratus lumborum (TQL) block very useful and we applaud the authors for conducting this randomised controlled trial that included more than 80 patients. However, we respectfully disagree with Rao Kadam et al. regarding their description of the TQL block and the catheter's actual anatomical placement. Rao Kadam et al. reference the original description of the TQL block published by Børglum et al. in 2013 2, but unfortunately fail to execute the procedure as originally described. Rao Kadam et al. describe their TQL block placement as “below the anterior thoracolumbar fascia near the perinephretic fascia”. This technique is corroborated by the ultrasound image in their Figure 2 1, where the authors indicate that they place the TQL block between the para- and peri-renal fat compartments. This, however, is certainly not the TQL block that was originally described by Børglum et al. This may explain why, in their study, Rao Kadam et al. did not find a significant difference between the two treatment modalities. A correct TQL block is placed in the fascial interspace and plane between the psoas major and the quadratus lumborum (QL) muscles and posterior to the transversalis fascia 2, 3. Only if the local anaesthetic is injected posterior to the transversalis fascia will the injectate spread cephalad to reach the diaphragm and spread further cephalad posterior to the arcuate ligaments and thereby reach the thoracic paravertebral space (and the thoracic spinal nerves) and the thoracic sympathetic trunk 3. We have recently published two randomised controlled trials using the correct TQL block placement and achieved significantly improved postoperative pain management 4, 5. We realise the sono-anatomy in the lumbar paravertebral area can be difficult to interpret correctly. For this purpose, we have attempted a step-by-step description of how to perform the TQL block: Firstly, we identify the anterior abdominal wall muscles; that is, external oblique and internal oblique muscles superficial to the transversus abdominis muscle. The aponeurosis of the transversus abdominis muscle will always blend with the posterior thoracolumbar fascia on the lateral (superficial) side of the QL muscle (Fig. 1). Secondly, we identify the ‘shamrock’ sign, where the stem of the shamrock is the transverse process, and the three leafs of the clover are the psoas major, the QL and the erector spinae muscles 5, 6. Thirdly, we visualise the respiratory movements of the para- and peri-renal fat compartments with dynamic ultrasound imaging. This is essential to distinguish between the QL muscle and the para-nephric fat. We acknowledge that it can be difficult to distinguish between the (often) hypo-echoic QL muscle and the (always) hypo-echoic para-renal fat in some patients. The key is to identify respiratory movements with dynamic ultrasound scanning before block execution. Para- and peri-renal fat compartments will move with respiration, whereas the QL and psoas major muscles will not. Note in the ultrasound image of Fig. 1, that Gerota's fascia (the renal fascia) separates the para- and peri-renal fat compartments. Placement of the TQL block should be in the fascial interspace between the QL and psoas major muscles posterior to the transversalis fascia, whereas it is not considered a TQL block if the placement of the local anaesthetic and the catheter is at the Gerota's fascia between the para- and peri-renal fat compartments. We believe the study by Rao Kadam et al. should not be included in any possible future reviews regarding the TQL block, nor TQL catheter placement, because the block execution does not represent the original description of a TQL block. Rather, the authors perform an injection of local anaesthetic between the two renal fat compartments, which may explain their findings.