Ultrasound-guided Pudendal Nerve Block in Children: A Descriptive Study of Feasibility

Children under general anesthesia were positioned supine, flexed legs and balls of the feet joined. A 12 MegaHertz (MHz) (38 mm) ultrasound probe was positioned on a horizontal axis passing through the ischial tuberosity, previously palpated.The probe was then moved medially on the axis, until the rectum appeared. Pudendal artery was identified if possible, using colour Doppler. The needle (22 Ga, 50 mm) was then introduced at the middle of the superior edge of the probe, in an out-of-plane approach. Tip of the needle was identified by direct vision, through displacement of adjacent anatomical structures or with saline injection. Nerve stimulation was started after placement of the tip of needle in the ischiorectal fossa, before local anaesthetic injection. After a negative aspiration test, a mix of Ropivacaine 2 % and clonidine 0.2µg/kg was injected in the ischiorectal fossa under ultrasound guidance.