Anatomy of anaesthesia

Question 1

Difference between visceral and somatic pain

Answer 1

Visceral tends to be more generalised, achey dull pain; somatic tends to be localised, sharp stabbing pain

Question 2

Pain sensation from the pelvic organs a) superiorly and b) inferiorly

Answer 2

a) visceral afferents entering at T11-L2. Percieved as suprapubic pain
b) visceral afferents entering at S2-S4. Percieved in the perineum

Question 3

How does pain sensation differ above and below levator ani (i.e. from pelvis to perineum)

Answer 3

Pelvis- visceral afferents entering S2-S4, causing generalised perineal pain

Perineum- somatic sensory (pudendal) nerve, entering at S2-S4 and causing localised perineal pain

Question 4

What are the two most important levels of the spinal cord with relation to obstetric anesthesia?

Answer 4

T11-L2

S2-S4

Question 5

Which structures does the needle for spinal anaesthetic pass through?

Answer 5

Supraspinous ligament
Infraspinous ligament
Ligamentum flavum
Epidural  space
Dura mater 
Arachnoid mater

Question 6

Where does the spinal cord become the cauda equina?

Answer 6

L2

Question 7

What is a useful landmark for identifying the location for a spinal/epidural?

Answer 7

Most superior point on the iliac crests is just below the inferior aspect of the L4 spinous process

Question 8

Why does spinal/epidural anesthesia cause hypotension, flushed skin and reduced sweating?

Answer 8

Anesthetizes the sympathetic fibres, causing vasodilation of lower limb arterioles

Question 9

Where does the pudendal nerve arise from?

Answer 9

Sacral plexus from spinal nerves S2-S4

Question 10

What is the relationship of the pudendal nerve to the sacrospinous ligament?

Answer 10

Crosses its lateral aspect

Question 11

What is a useful landmark for the pudendal nerve?

Answer 11

The ischial spines, palpable on vaginal examination

Question 12

What are the indications for pudendal nerve block?

Answer 12

Painful vaginal delivery; repairing perineal tears; prior to episiotomy

Question 13

Describe the relationship of the pudendal nerve to the sciatic foraminae

Answer 13

Exits pelvis via the greater sciatic foramen, and re-enters via lesser

Question 14

What forms the lesser sciatic foramen?

Answer 14

The sacrotuberous and sacrospinous ligaments

Question 15

What is the preferred incision for episiostomy and why?

Answer 15

Mediolateral incision. This extends into the ischio-anal fossa, and avoids the possibility of involving the anal sphincter