Dalley, 10th Edition

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94

Caudal Epidural Anesthesia

which the agent ascends is controlled by the amount injected and the position of the patient. Sensation is lost inferior to the epidural block. Anesthetic and analgesic agents can also be injected through the posterior sacral foramina into the sacral canal around the spinal nerve roots ( transsacral epi dural anesthesia ) (Fig. B2.7B). Epidural anesthesia during childbirth is discussed in Chapter 6, Pelvis and Perineum. Injury of Coccyx An abrupt fall onto the buttocks may cause a pain ful subperiosteal bruising or fracture of the coccyx, or a fracture–dislocation of the sacrococcygeal joint. Displacement is common, and surgical re moval of the fractured bone may be required to relieve pain. An especially dif cult childbirth occasionally injures the mother’s coccyx. A troublesome syndrome, coccygodynia (or coccydynia), often follows coccygeal trauma; pain relief is commonly dif cult.

In living persons, the sacral hiatus is closed by the membranous sacrococcygeal ligament (Fig. B2.7A), which is pierced by the lum terminale (a connec tive tissue strand extending from the tip of the spi nal cord to the coccyx) (Fig. B2.7C). Deep (superior) to the ligament, the epidural space of the sacral canal is lled with fatty connective tissue (Fig. B2.7B). In caudal epidural anesthesia or analgesia , anesthetic or analgesic agents are injected into the fat of the sacral canal that surrounds the proximal portions of the sacral nerves. This can be accom plished by several routes, including the sacral hiatus (Fig. B2.7B–D). Because the sacral hiatus is located be tween the sacral cornua and inferior to the S4 spinous pro cess or median sacral crest, these palpable bony landmarks are important for locating the hiatus (Fig. B2.7A). The agent spreads superiorly and extradurally, where it acts on the S2–Co1 spinal nerves of the cauda equina. The height to

Sacrococcygeal ligament

4th sacral spinous process

Sacral cornua

Sacral hiatus

Filum terminale internum

(A) Posterior view

Dural sac

Subarachnoid space

Pia mater (transparent, covering nerve roots of cauda equina) Arachnoid mater (purple) Dura mater (gray) of dural sac Cauda equina in CSF

Dura mater

Lumbar cistern of subarachnoid space

Filum terminale externum

Epidural space

S1 vertebral level

Epidural space

S2 vertebral level

Sacral foramina S1 spinal nerve S5 spinal nerve

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Transsacral (epidural) anesthesia (site options)

(C) Median section, caudal epidural anesthesia

Sacral canal

Sacral cornua

Filum terminale externum

Caudal epidural anesthesia

(B) Posterior view

(D) Posterior view, transsacral (epidural) anesthesia

FIGURE B2.7. Epidural anesthesia. A. Palpation of sacrococcygeal ligament. B and C. Sacrum cut to show needle position. D. Position of patient.