The single-shot caudal block is indicated for treating children ranging in age from infancy to approximately 8 years. Single-shot caudal blocks are usually placed at the end of the procedure to maximize the duration of postoperative analgesia; however, practice varies. If this block is placed at the beginning of the procedure, be aware that total anesthetic requirements will be decreased. Always discuss the planned block with the pediatric patient’s parents. The older child should also be made aware that his or her legs may be difficult to feel after the surgery or that he or she may have trouble walking for a few hours.

The single-shot caudal block is contraindicated for treating children with infection around the sacral hiatus, coagulopathy, increased intracranial pressure (ICP), uncorrected hypotension, or known anatomic abnormality and children whose parents refuse to consent.

In patients younger than 1 year of age, the caudal extent of the dura and spinal cord ends at S3-4. The caudal space can be accessed through the
sacral hiatus, which is flanked laterally by the prominent sacral cornu and covered by the sacral-coccygeal ligament.

The patient should be placed in lateral decubitus position (left lateral for the right-handed anesthesiologist and right lateral for the left-handed anesthesiologist), with hips and knees flexed to help spread the gluteal muscles away from the sacral hiatus. Using aseptic technique, a 22-gauge needle (or 22-gauge Teflon intravenous catheter) is placed approximately 45 degrees to the skin until a “pop” is felt, which indicates penetration of the sacrococcygeal ligament. The needle should be slightly withdrawn and the angle lowered before advancing a few more millimeters into the canal. Aspiration is necessary to check for blood or cerebrospinal fluid. An initial test dose of 0.1 mL/kg of local anesthetic with 1:200,000 epinephrine can be used to exclude intravascular placement (see below). Resistance to injection should be minimal. Any resistance strongly suggests that the needle tip is not in the epidural space.