Pudendal Nerve Block
In pediatrics, pudendal nerve blocks are performed to complement
an ilioinguinal and iliohypogastric nerve block when a scrotal incision is planned
(e.g., surgery of undescended testis, testicle fixation). The pudendal nerve is
a terminal branch of the sacral plexus that runs along the lateral wall of the ischiorectal
fossa within a sheath derived from the obturator fascia (i.e., Alcock's canal).
It gives off the inferior hemorrhoidal nerve, the perineal nerve, and the dorsal
nerve of the penis (or clitoris). It can
easily be blocked at the level of the ischial tuberosity. The patient is placed
in the supine position, with his knee flexed and the plantar aspects of his feet
conjoined (as for girls' bladder catheterization). The landmark is the skin projection
of the ipsilateral ischial tuberosity in the frontal plane.[267]
A short and short-beveled needle is inserted in the same frontal plane in the direction
of the ischial tuberosity, aiming at passing just medial to it until a give is felt
as the obturator fascia is pierced ( Fig.
45-20
). An injection of 0.1 mL/kg up to 5 mL of a plain solution of local
anesthetic is administered. The pudendal artery, which is close to the nerve, is
a terminal artery, and the administration of epinephrine must be avoided. If contact
is made with the medial aspect of the ischial tuberosity, the needle should be slightly
withdrawn before injection of the local anesthetic. Because this nerve is a mixed
nerve, electrolocation can be used; this has no advantages in terms of efficacy,
and the cost of an insulated needle is comparatively high.
