How are caudal lumbar epidural blocks administered for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Caudal lumbar epidural spinal blocks have become more popular as a method of inducing epidural anesthesia and for catheter entry to locate specific spinal pain generators and to provide meaningful relief. To perform caudal blockade using the technique described by Brown, the patient is placed in a lateral decubitus or prone position. The prone position is more amenable to accurate identification of midline anatomical targets in adults. A pillow placed beneath the lower abdomen produces slight flexion of the lumbar spine. Mild sedation improves patient comfort. Relaxation of the gluteal muscles is induced in the prone patient by a 20° hip adduction and the feet pointed inward by internal rotation of the hips. A 25-gauge or 22-gauge needle varying in length from 1.5-3.5 inches is recommended for adult patients, and some needles allow introduction of a catheter, if desired, which can be directed under fluoroscopy using a steering wire. See the images below.

Surface anatomy of caudal block and sacral hiatus Surface anatomy of caudal block and sacral hiatus localization.
Patient in the prone position for caudal block tec Patient in the prone position for caudal block technique.
Caudal block technique. See text for details. Caudal block technique. See text for details.

After the sacral hiatus is identified, the index and middle fingers of the palpating hand are placed on the sacral cornu and the caudal needle is inserted at an angle approximately 45° to the sacrum. As the needle is advanced, the operator can sense a reduction in resistance when the needle enters the caudal canal. The needle is advanced until bone is contacted on the dorsal aspect of the ventral plate of the sacrum. The needle is then withdrawn slightly and redirected at an angle more parallel to the skin surface. In male subjects this angle is usually about parallel to the tabletop, whereas in female patients a slightly steeper angle is often necessary. After the needle is redirected, it should be advanced approximately 1-1.5 cm into the caudal canal. Further needle advancement should be avoided to prevent unintentional intravascular cannulation or dural puncture. At this point in the procedure, a catheter can be threaded and directed by fluoroscopy to the desired spinal level and structures.

Caudal anesthesia and neural blockade are fraught with the same complications that can accompany lumbar epidural anesthesia; however, the incidence of subarachnoid puncture is much lower with the caudal technique. The dural sac ends approximately at the level of S2; therefore, unless the needle is inserted deeply within the caudal canal, subarachnoid puncture is unlikely. The most commonly encountered problem with caudal anesthesia is ineffective neural blockade.

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