introduction and mechanism

1. EPIDURAL ANESTHESIA
-SANDEEP REDDY
MODERATOR : Dr KEERTHI TEJA

2. INTRODUCTION
•Anesthesia obtained by blocking spinal nerves in the
epidural space as the nerves emerge from the dura and
then pass into the intervertebral foramina.
•Neuraxial technique with wide range of applications.
•Can be performed at the cervical, thoracic, lumbar and
caudal levels.
•Can be single shot or intermittent boluses or continuous
infusion.

3. ANATOMY

5. Other contents of epidural
space:
1. Fatty connective tissue
2. Lymphatics
3. Venous plexus (Batson’s)
4. Septa and connective
tissue bands

6. PHYSIOLOGY
Possible sites of anesthetic action include
•Paravertebral nerve roots
•Intradural spinal roots
•Dorsal and ventral spinal roots
•Dorsal root ganglia
•The spinal cord
•Brain (by diffusion)

7. •Initial blockade- probably at the spinal roots within dural sleeves
Dural cuffs/ sleeves
Proliferation of arachnoid villi and granulations
Reduce thickness of dura
Rapid diffusion of local anesthetics from epidural space
Through dura and into csf surrounding the nerve roots
Anesthesia to that particular dermatome

8. •Large volumes of Local Anesthetics are required as
epidural anesthesia is diffusion dependent.
•Spinal Anesthesia : DISTAL to the level of block
•Epidural : DIFFERENTIAL block depending on volume and
site of injection
ADVANTAGES:
•Better control of level and sympathetic blockade
•Cases of unpredicatable duration
•Post operative analgesia
•Chronic pain control
•Obstetric analgesia and anesthesia

9. FACTORS AFFECTING THE LEVEL OF
EPIDURAL BLOCK
1. Injection site
2. Dose, volume and concentration
3. Position
4. Age
5. Height and weight (?)
6. Pregnancy (?)
7. Speed of injection (?)

10. 1). Injection site:
•Segmental block that spreads both caudally and
cranially.
•Most important determinant of block.
•Should be in the middle of range of dermatomes that
need to be anesthetized and closest to main nerve roots.
•Caudal Blocks : Restricted to sacral and low lumbar;
thoracic levels can be reached only if large volumes
(30cc) are given.

11. •Lumbar Blocks : 10cc includes all sacral dermatomes;
20cc produce much better quality sacral blocks and
extend cranially to mid thoracic levels.
•Thoracic Blocks : Produce symmetrical segmental band
of anesthesia with minimal lumbar spread; Decrease
volume by 30-50% to prevent cranial spread; Ideally
suited for procedures of chest and upper abdomen and
post thoracotomy pain.