CAUDAL ANESTHESIA-ANATOMY OF SACRUM IN ADULT & DIFFERENCES IN NEONATES & INFANTS.

Dr. Arjun chhetri

History

October 1941 (Robert Andrew Hingson) developed the technique of continuous caudal anesthesia.

The first use of continuous caudal anesthesia in a laboring woman was on January 6, 1942.

Introduction

Caudal epidural anesthesia is one of the most commonly used regional techniques in pediatric patients and for anorectal surgery in adults.

The caudal space is the sacral portion of the epidural space.

Involves needle or catheter penetration of the sacrococcygeal ligament covering the sacral hiatus that is created by the unfused S4 and S5 laminae

Anatomy

Embryology

The somites that give rise to the VC begin to develop from head to tail along the length of the notochord.

Anatomy of sacrum

Prior to the adoption of sacrum,

the bone was also called holy bone in English Posterior bone of the pelvic cavity,

formed of five sacral vertebrae fused together. Shape: triangular or wedge

with the base above and

its apex below.

It is slightly concave anteriorly.

CONTD…

The anterior upper border of the body of first sacral (S1) vertebra projects inwards. It is called sacral promontory

The lateral mass on each side is a fan-shaped,

called ala of sacrum. The superior articular process of

S1 vertebra carries articular facet

directed posteriorly.

CONTD…

The sacral foramina form together the sacral canal.

The lower opening of sacral canal is called sacral hiatus.

It is surrounded on either sides by sacral cornua, that are of great importance for identification of sacral hiatus on the body surface.

CONTD…

The anterior surface is smooth and concave It has four pair of anterior sacral foramina.

The posterior surface is irregular and convex. It has four pair of posterior sacral foramina.

CONTD…

The lateral surface shows articular surface, called auricular surface for articulation with the hip bone at sacro-iliac joint.

Sex differences

MALE SACRUM

FEMALE SACRUM

Length and width It is longer and narrower

It is shorter and wider

Curvature of bone It shows a gentle and uniform curvature

It descends nearly straight in its upper part, while the lower part turns forwards.

Auricular surface Longer Shorter

Upper surface Body is wider than the ala

Body is narrower or equal to ala.

Contents of the Sacral canal

Dural sac which ends at the border of the 2ND sacral vertebra on a line joining the posterior iliac spine.

The pia mater is continued as the filum terminale.

Sacral nerves and the coccygeal nerve Venous plexus formed by the lower end of the

internal vertebral plexus. Areolar and fatty tissue.

Contd…

Sacral hiatus:

1. One pair of sacral (5th ) nerves.

2. One pair of coccygeal nerves.

3. Filum terminale. It ends through blending with periosteum at the back of periosteum.

Contd…

Anterior sacral foramina: 1. Anterior rami of the 1st four sacral nerves

"exit". 2. Lateral sacral arteries "entrance".

- Posterior sacral foramina: 1. Posterior rami of the 1st four sacral nerves

"exit". 2. Lateral sacral arteries "exit".

Differences

At birth the dura mater ends at the level of the 3rd or 4th sacral vertebra and the cord (conus medullaris) at the L3 or L4 level.

Sacral hiatus is relatively wider in children.

Palpating sacral hiatus in children is easier.

Contd…

In infants –the sacral canal is filled with fluid fat and loose areolar connective tissue which allows easy spread of anesthethetic solutions up to age of 6 or 7 years, also this fluidity of epidural fat allows catheter insertion easier.

 Main Anatomic and Physiologic Factors in the Pediatric Period That Can Influence the Selection or Performance of a Regional Block Procedure

Pediatric Factors (Infants Mainly)

Resulting Danger Implications for Regional Anesthesia

Lower termination of spinal cord

Increased risk of direct trauma to the spinal cord

Avoid epidural approaches above L3 whenever possible.

Lower projection of dural sac

Increased risk of inadvertent penetration of the dura mater

Check for cerebrospinal fluid reflux, including during caudal approaches.Favor low approaches to the epidural space

Delayed myelinization of nerve fibers

Easier intraneural penetration of local anesthetics

Onset time is shortened, and diluted local anesthetic is as effective as more concentrated anesthetic in adults

Contd….

Pediatric Factors (Infants Mainly)

Resulting Danger Implications for Regional Anesthesia

Lack of fusion of sacral vertebrae

Persistence of sacral intervertebral spaces

Intervertebral sacral epidural approaches can be performed throughout childhood

Changing axis of coccyx and absence of growth of sacral hiatus

Sacral hiatus comparatively smaller with increasing age

Identification of sacral hiatus becomes more difficult above 6-8 years (increased failure rate of caudal anesthesia).

Increased fluidity of epidural fat

Increased diffusion of local anesthetic up to 6-7 years of age

Excellent blockade after caudal anesthesia can be achieved up to 6-7 years of age

T.Y

The atlas of Human body Millers anesthesia 7th edition