Ultrasound‐guided transmuscular quadratus lumborum block catheter technique: a reply

Abstract

We would like to thank Andersen et al. 1 for their critical appraisal of our recent article 2. We agree that the ultrasound picture used as Fig. 2 may be misinterpreted and is difficult to align with the drawing beside it. Referring to an excellent anatomical depiction of the different modalities of quadratus lumborum (QL) block on the New York School of Regional Anaesthesia (NYSORA) website 3, we maintain that our target is similar to what they describe as transmuscular quadratus lumborum (TQL) block, although our approach is slightly posterolateral; with the aim to reach the fascia covering the anterior aspect of QL muscle next to the psoas muscle. This target area between the psoas muscle and QL block is comparable to the one Børglum et al. originally described 4. We have included a more detailed ultrasound image (Fig. 1) with an example of the needle trajectory we used in our series. The anatomical differences with regard to the QL block and psoas muscle depictions may also relate to the different lumbar levels and the quite pronounced individual anatomical variability we have observed. We appreciate the highly informative step-by-step description provided by Andersen et al., particularly in relation to the observation of respiratory movements in order to distinguish the renal fat compartments from the relevant muscles, which is very accurate. The comment that we did not find an overall significant difference between the two treatment modalities can be explained by the fact that we used a proven active control group (pre-peritoneal catheter technique) 5 in contrast to the saline control sham groups in the studies Andersen et al. refer to 6, 7. Our findings suggest that both techniques are equally effective in providing postoperative analgesia following abdominal surgery, with the pre-peritoneal catheter technique being a more cost effective and viable alternative. We believe that we have extended the application of TQL block by a continuous catheter technique and achieving sensory dermatomal coverage from T4 to L1. We argue that our technique is valid and once again admit that a better illustration in our published article would have resulted in less ambiguity in the interpretation of the needle trajectory. Therefore, we do not agree with the statement by Andersen et al. that our study should not be included in any possible future reviews regarding the TQL block.