Anatomical bases of prolonged ilio-inguinal-hypogastric regional anesthesia

Although anesthesia and post-operative analgesia are associated with specific morbidity, regional anesthesia is not systematically given during groin hernia surgery. The goals of this work were to determine the anatomical bases of safe ilio-inguinal (II)-hypogastric anesthesia that can be prolonged into the post-operative period and to validate this technique on anatomical preparations and in clinical situations. We studied the courses of the ilio-hypogastric (IH) and II nerves in 33 halves of 20 embalmed adult cadavers. The intermediate portion of the IH and II nerves, located between the transverse and the internal oblique muscles, were found to be suitable for a simultaneous block with a single injection. We assessed the feasibility of injecting a percutaneous infiltration into this space by injecting a dye before dissection. In 75% of cases, we observed percutaneous coloring of the nerves, confirming that this site was suitable. To guide the infiltration, the points where the nerves passed through the transverse and the internal oblique muscles were located from the iliac crest and anterior and superior iliac spine, respectively. The nerve trunks were grouped for over 5 cm in a cell-fat layer running between these two deep muscles. It was possible to position a micro-catheter in this anatomical space to allow repeated injections. The results of this anatomical study were used to modify the technique so that it could be used to provide regional anesthesia in five patients operated on for hernia. Post-operative pain was very effectively controlled in four cases with no complications.