Summary
Laparoscopic ventral hernia repair is an operation associated with significant postoperative pain, and regional anaesthetic techniques are of potential benefit. The erector spinae plane (ESP) block performed at the level of the T5 transverse process has recently been described for thoracic surgery, and we hypothesised that performing the ESP block at a lower vertebral level would provide effective abdominal analgesia. We performed pre-operative bilateral ESP blocks with 20–30 ml ropivacaine 0.5% at the level of the T7 transverse process in four patients undergoing laparoscopic ventral hernia repair. Median (range) 24-h opioid consumption was 18.7 mg (0.0–43.0 mg) oral morphine. The highest and lowest median (range) pain scores in the first 24 h were 3.5 (3.0–5.0) and 2.5 (0.0–3.0) on an 11-point numerical rating scale. We also performed the block in a fresh cadaver and assessed the extent of injectate spread using computerised tomography. There was radiographic evidence of spread extending cranially to the upper thoracic levels and caudally as far as the L2–L3 transverse processes. We conclude that the ESP block is a promising regional anaesthetic technique for laparoscopic ventral hernia repair and other abdominal surgery when performed at the level of the T7 transverse process. Its advantages are the ability to block both supra-umbilical and infra-umbilical dermatomes with a single-level injection and its relative simplicity.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/anae.13814

The analgesic efficacy of pre-operative bilateral erector spinae plane (ESP) blocks in patients having ventral hernia repair.

Current descriptions of thoracic paravertebral block techniques require the needle tip to be anterior to the superior costotransverse ligament. We hypothesised that an injection point midway between the posterior border of the transverse process and the pleura would result in spread to the paravertebral space. We completed bilateral injections of 5 ml methylene blue 0.2% midway between the posterior border of the transverse process and the pleura at T2, T4, T6, T8 and T10 in three unembalmed cadavers. The presence of methylene blue dye at the nerve root in the paravertebral space, the corresponding intercostal nerve and sympathetic chain at the level of injection, and at additional levels, was examined. We identified the superior costotransverse ligament, pleural displacement and spread to the erector spinae plane. We describe two case reports using this technique in patients. Our cadaver results and clinical cases demonstrate that, with the exception of cadaver 1, an injection point midway between the posterior border of the transverse process and pleura consistently achieved spread of dye at least to the paravertebral space at the level of injection, and frequently to adjacent levels. This may be a plausible explanation for the landmark technique's inability to reliably achieve a multilevel block. We describe a new ultrasound-guided technique for a single level paravertebral block.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/anae.14004

The mid-point transverse process to pleura (MTP) block: a new end-point for thoracic paravertebral block.

Resumen Introduccion El bloqueo del plano del musculo erector (ESP) es una tecnica novedosa para el tratamiento del dolor agudo y cronico Su lugar y mecanismo de accion todavia no han sido explicados Objetivos Determinar el mecanismo de accion del anestesico local en el bloqueo ESP a traves de la inyeccion del azul de metileno, describiendo su distribucion desde la cara anterior del torax Hallar o determinar un paso o canal por el cual el anestesico atraviesa las estructuras musculares y oseas de posterior a anterior Materiales y metodos Se utilizaron 4 columnas de cadaveres frescos criopreservados Se realizaron 9 bloqueos ESP ecoguiados en diferentes regiones de los especimenes con 20 ml de azul de metileno al 0,01% por bloqueo Se observo la distribucion del colorante desde la cara anterior de torax, midiendo la cantidad de espacios intercostales tenidos, antes y despues de la extraccion de la pleura parietal, y se registraron las estructuras en que se constato tintura Resultados En todos los bloqueos ESP se encontro colorante en el espacio paravertebral, los espacios intercostales y en algunos casos en la cadena prevertebral Los bloqueos tuvieron un promedio de 4,6 espacios intercostales tenidos, con un maximo de 7 y un minimo de 3 La intensidad del colorante fue mayor del lado de la inyeccion, dorsal a la columna, que el hallado en la parte ventral por debajo de la pleura No se logro constatar un mecanismo claro por el que el colorante difundiera hacia el la zona anterior Conclusiones Por los datos recogidos en este trabajo se puede deducir que el bloqueo ESP tiene un mecanismo de accion anestesico similar a los bloqueos paravertebrales El sitio por el cual el anestesico atravesaria desde el plano posterior de la columna a la region anterior del torax no fue aclarado y deberia ser investigado en futuros trabajos

Bloqueo del plano del músculo erector espinal: estudio anatómico-cadavérico para determinar su mecanismo de acción

Retrolaminar block (RLB) and erector spinae plane block (ESPB) are alternative approaches to paravertebral block (PVB) and are advantageous in that they are easier and safer techniques compared with the traditional PVB. Many clinical reports of these blocks have described their efficacy for ipsilateral thoracic analgesia. The local anesthetic injection points of RLB and ESPB are the lamina and transverse process, respectively. Despite the similarity of the puncture sites, there have been no clinical studies comparing RLB and ESPB. In addition, the underlying mechanism of these blocks has not been clarified. Recent anatomical investigations indicated that the injectate was distributed in the paravertebral space and spread laterally into the intercostal spaces. The limited distribution into the paravertebral space indicated that compared to PVB, RLB and ESPB exert their effects via a different mechanism. In this review, we describe the features of and differences between RLB and ESPB based on current clinical and anatomical reports. We also propose the clinical indication and discuss the differences, clinical outcomes, and anatomical mechanisms of the techniques.

/pdf/comparison-of-clinical-efficacy-and-anatomical-investigation-2zf1ietc0w.pdf

Comparison of Clinical Efficacy and Anatomical Investigation between Retrolaminar Block and Erector Spinae Plane Block.

Introduction The erector spinae plane (ESP) block is a novel technique for the treatment of acute and chronic pain. Its mechanism and site of action has not yet been explained properly. Objectives In order to explain the mechanism of action of the ESP block, injections were performed with methylene blue to simulate the local anaesthetics and to determine its distribution from the anterior side of the thorax. To find an aperture or channel through which the local anaesthetic passes from posterior to anterior through the muscular and bone structures. Materials and methods Four spinal columns of fresh cryopreserved corpses were used. A total of 9 ultrasound-guided ESP blocks were performed in different regions of the specimens using 20 ml of 0.01% methylene blue per block. The distribution of the dye was observed from the anterior side of the thorax, measuring the amount of intercostal spaces stained, before and after the removal of the parietal pleura, and the structures in which the stain was found were recorded. Results In all blocks of the ESP, dye was found in the paravertebral space, intercostal spaces, and in some cases in the prevertebral chain. The blocks had a mean of 4.6 intercostal spaces stained, with a maximum of 7 and a minimum of 3. The intensity of the dye was greater on the side of the injection, dorsal to the column, than that found in the ventral part below of the pleura. It was not possible to verify a clear channel through which the dye diffuses towards the previous zone. Conclusions From the data collected in this study, it can be deduced that the blockade of the ESP has a mechanism of anaesthetic action similar to paravertebral blocks. The site from which the anaesthetic would cross from the posterior plane of the spine to the anterior region of the thorax was not clear, and should be investigated in future works.

Erector spinae plane block: A cadaver study to determine its mechanism of action

We read the article by Yoshida et al. on the effects of ropivacaine concentration on the spread of sensory block produced by continuous thoracic paravertebral block [1]. Both traditional landmark and ultrasound techniques for thoracic paravertebral block (PVB) assume that the needle tip needs to lie anterior to the superior costotransverse ligament (SCTL) for block success. However, we have achieved successful PVB with deliberate injection posterior to the SCTL, and frequently observe pleural displacement with the needle tip and local anesthetic injection clearly posterior to the SCTL. Surgical experience provides a rationale for this occurrence. The paravertebral area is exposed for many spinal surgical procedures. During procedures requiring the removal of ligaments involving the rib and/or transverse process, the ligaments in the immediate paravertebral area are often not visualised as distinct entities; rather, the proximal ligament complex involving the rib head and transverse process may appear as a single structure. Additionally, there can be variability in the density and the continuity of these ligaments such that they may not form a definitive tissue layer. Consequently, the fascial planes in the paravertebral region may not be truly compartmentalised, resulting in locally-injected anesthetic travelling through septations and fenestrations in the ligamentous tissues. Unpredictable spread of PVB in previous studies could be explained by injections posterior to the SCTL resulting in a single level, cloud-like spread, and injections anterior to the SCTL resulting in a multilevel spread. We use dynamic ultrasound with a parasagittal scan, in-plane needle insertion cephalad to the probe, and injection posterior to the SCTL. In an unembalmed cadaver, we noted that injections of 5 ml of methylene blue 1% posterior to the SCTL from T2 to T7 bilaterally (except injections anterior to SCTL on left T4+5) stained the sympathetic chain (T1–T7 on the left, and T4– T8 on the right), and the intercostal nerves T1–T7, and their nerve roots in the paravertebral spaces, bilaterally. Our ultrasound observations and cadaver investigation suggest that the paravertebral space is not a true anatomical compartment and that the SCTL is not a barrier to diffusion of injectate as previously thought. We believe that successful PVB can be achieved with the needle tip further distant from the pleura than currently described, with greater potential for patient safety. Further studies will be required to confirm our preliminary work.

Does paravertebral block require access to the paravertebral space

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Does paravertebral block require access to the paravertebral space