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Resumen Introduccion El bloqueo en el plano del erector espinal (erector spinae plane [ESP]) a nivel toracico se ha introducido como metodo analgesico postoperatorio. Sin embargo, a pesar de que su empleo a nivel lumbar ha sido publicada, su distribucion y su mecanismo de accion no han sido esclarecidos. Nos propusimos describir la tecnica de puncion del bloqueo ESP a nivel lumbar y evaluar la distribucion de 20 ml administrados a nivel de la transversa de L4 en un modelo cadaverico. Metodos Estudio observacional tras 12 bloqueos del ESP lumbar en L4, sobre un modelo de cadaver fresco (6 bilaterales). Se valoro la distribucion de 20 ml de solucion inyectada contrastada mediante tomografia computarizada en las 6 muestras. Fueron evaluados mediante estudio anatomico 4 de las muestras, 2 mediante diseccion por planos y otros 2 fueron congelados y seccionados con cortes axiales de 2-2,5 cm de grosor. Resultados La distribucion de la solucion inyectada se distribuyo en el interior de la musculatura erectora espinal craneo-caudal desde L2 a L5, con limite medial en la articulares interapofisarias y lateral en la fascia toracolumbar. El paso anterior a la transversa no se observo en el 33% de los casos, fue minimo y sin afectacion de los nervios espinales correspondientes en el 51%, siendo extenso en 2 muestras (16%) y con afectacion del nervio espinal correspondiente. Conclusiones El ESP lumbar a nivel de L4 tiene una accion constante sobre los ramos posteriores de los nervios espinales, siendo infrecuente su paso al espacio paravertebral y bloquear el nervio espinal.

Resumen Introduccion Conocer la relacion entre la aguja y el nervio durante el bloqueo de nervio periferico es de interes para evitar el dano neural; sin embargo, los signos de inyeccion intraneural no se hallan claramente establecidos. Nos propusimos determinar los cambios observados en el nervio periferico tras inyectar 1 ml de solucion en disposicion intraneural o perineural de la aguja. Material y metodos Se utilizaron 10 cadaveres frescos, a los cuales se les realizo bloqueo de nervio mediano ecoguiado en plano en 60 ocasiones (3 por brazo), realizando una puncion intraneural (n = 30) o perineural (n = 30) segun aleatorizacion previa. Tras el consenso de localizacion por 7 especialistas, se inyecto 1 ml de solucion y se evaluo el cambio en el area de seccion del nervio y el desplazamiento a lo largo del mismo. Resultados El area de seccion del nervio mediano se aumento en ambos grupos, sin embargo, el incremento fue significativamente mayor en el grupo intraneural (perineural 0,007 ± 0,013 vs. intraneural 0,032 ± 0,021 cm2, p Conclusiones En base a nuestro estudio experimental concluimos que la inyeccion de un pequeno volumen (1 ml) permite discriminar la disposicion de la aguja intraneural vs. perineural en un porcentaje elevado de casos. Por ello, sugerimos que esta «dosis test» debe de considerarse en los algoritmos de seguridad si queremos reducir la incidencia de inyeccion intraneural.

Thoracic erector spinae plane (ESP) block is now used for postoperative analgesia. However, although reports of lumbar ESP have been published, the anesthetic spread and mechanism of action of this technique remains unclear. We describe the lumbar ESP block technique and evaluate the spread of 20ml of solution administered at the level of the transverse process of L4 in a cadaver model.Observational study after 12 lumbar ESP blocks at L4 on a fresh cadaver model (6 bilaterally). The spread of 20ml of injected contrast solution was assessed by computed tomography in all 6 samples. Four of the samples were evaluated by anatomical study, 2 by plane dissection, and 2 others were frozen and cut into 2-2.5cm axial slices.The injected solution spread from L2 to L5 in a cranio-caudal direction in the erector spinae muscle, reaching the facet joints medially and the thoracolumbar fascia laterally. In 33% of cases the solution did not spread anterior to the transverse process; in 51%, spread was minimal and did not affect the corresponding spinal nerves, and in 2 samples (16%), spread was extensive and reached the corresponding spinal nerves.Lumbar ESP at L4 always acts on the posterior branches of the spinal nerves, but seldom spreads to the paravertebral space to block the spinal nerve.

To recognise the relationship between the needle tip and the median nerve during peripheral nerve block is of interest to avoid neural damage. However, signs of intraneural injection are not clearly established. The aim of this study was to define the changes observed in the peripheral nerve after the intraneural or perineural administration of 1ml of solution.Ultrasound guided median nerve blocks were performed in the forearm of 10 fresh cadavers on 60 occasions (3 per forearm). They were randomised into the intraneural (n=30) or perineural (n=30) location of the needle tip, after the consensus of location by 7 specialists. After 1ml of solution was injected an evaluation was made of the changes in the cross-sectional area of the nerve, as well as the displacement along the nerve.The cross-sectional area of the median nerve was increased in both groups, however, the increase was significantly higher in the intraneural group (perineural 0.007±0.013cm2 vs. intraneural 0.032±0.021cm2, P.0001). An increase of more than 27% of the area ensures an intraneural injection in the median nerve according to the ROC curve analysis. Both proximal and distal diffusion were observed more frequently in the intraneural group (proximal: 86% vs 14%, P.0001, Distal: 43% vs 4%, P.0001).Based on this experimental study, it is concluded that the injection of a small volume (1ml) allows to discriminate the disposition of the intraneural vs perineural needle in a high percentage of cases. Therefore, it is suggested that this "dose test" should be considered in the safety algorithms if it is required to reduce the incidence of intraneural injection.