Pass Machine - Regional/Neuraxial

Question 1

Most important determinant for variable neuraxial block height between patients, assuming dose is the same

Answer 1

CSF volume (and things that decrease it such as obstructing lesions, etc)

Question 2

What is the primary structure that prevents epidural meds to cross into the CSF

Answer 2

Arachnoid mater (more of a barrier than the dura mater)

Question 3

Proximal and distal edges of the epidural space

Answer 3

Foramen magnum -> sacral hiatus

Question 4

Borders of the epidural space

Answer 4

Anterior: posterior longitudinal ligaments
Posterior: ligamentum flavum
Lateral: pedicles, foramina

Question 5

Contents of the epidural space (5)

Answer 5

• Nerve roots passing through
• Fat
• Areolar tissue
• Vessels (ex. Batson venous plexus)
• Lymphatics

Question 6

What is the shape and continuity of the epidural space?

Answer 6

Very patchy, very thin when up against the spinous process or lamina, and thicker when in between these structures

Question 7

What Rexed lamina of the spinal cord gray matter are most likely to be blocked (i.e. contribute to pain) by local anesthetics?

Which one also contributes to pain and is blocked by opioids but not as much by local anesthetics?

Answer 7

1 and 5: A-delta fibers

4: C fibers

Question 8

Proximal/distal end points for the…

• Spinal cord
• Dura mater/epidural space
• Subarachnoid space

Answer 8

SC: foramen magnum -> L1 (L3 in peds)
DM/ES: down to S2
SAS: down to S2