Anatomy for Anaesthesia during Labour

Question 1

What are the nerve fibre types above the levator ani?

Answer 1

Pelvis

Body cavity - Sympathetic, Parasympathetic and Visceral Afferent

Question 2

What are the nerve fibre types below the levator ani?

Answer 2

Perineum

Body wall - Somatic motor and Somatic sensory

Question 3

What type of nerve is associated with pelvic floor muscle contraction eg when sneezing?

Answer 3

Somatic motor

Question 4

What nerve type is associated with pain from the adnexae, uterus and pelvic part of the vagina?

Answer 4

Visceral afferents

Question 5

What nerve type is associated with uterine cramping and contraction?

Answer 5

Hormonal - sympathetic/parasympathetic

Question 6

What nerve type is associated with pain from the perineal part of the vagina and pain in the perineum?

Answer 6

Somatic sensory

Question 7

In the SUPERIOR aspect of pelvic organs - those TOUCHING the peritoneum how do nerves reach the CNS?
Where does the patient perceive this pain?

Answer 7

VISCERAL afferents run alongside SYMPATHETIC fibres and entre spinal cord between levels T11-L2
SUPRAPUBIC pain

Question 8

In the INFERIOR aspect of pelvic organs - those NOT TOUCHING the peritoneum - how do the nerves reach the peritoneum?
Where does the patient perceive this pain?

Answer 8

VISCERAL afferents run alongside PARASYMPATHETIC fibres to spinal cord levels S2, S3 and S4
Pain in S2, S3 and S4 dermatome - perineum

Question 9

Below the levator ani describe the nerves, pain perception and spinal cord level

Answer 9

Somatic sensory
Pudendal nerve
S2, S3 and S4
Localised pain within perineum

Question 10

Which are the two important spinal cord levels in the female reproductive system (and have a think about why!)

Answer 10

T11-L2

S2-S4

Question 11

What is the major nerve supplying for pain sensation below the levator ani?
What does it innervate and what spinal levels does it go to?

Answer 11

pudendal nerve back to S2-S4: from those organs/structures within the perineum = inferior vagina, perineal muscles, glands, skin.

Question 12

In the peritoneum but ABOVE the levator ani - describe sensation, what innervated and spinal level

Answer 12

visceral afferents back to S2-S4: from pelvic organs inferior to peritoneum – cervix and superior vagina

Question 13

Where does the spinal cord become cauda equina?

Answer 13

L2

Question 14

Where does subarachnoid space end?

Answer 14

S2

Question 15

For a SPINAL anaesthetic where is the anaesthetic injected and at what level of the spine

Answer 15

Subarachnoid space

L3-L5

Question 16

What does a spinal anaesthetise?

Answer 16

Cauda Equina

Question 17

Name the structures that the needle passes in a spinal?

Answer 17

Needle passes through: - supraspinous ligament

• interspinous ligament
• ligamentum flavum
• epidural space (fat and veins)
• dura mater
• arachnoid mater
• finally reaches subarachnoid space (contains CSF)

Question 18

What spinal level and to where is the epidural anaesthetic delivered?

Answer 18

L3/L4

Epidural space

Question 19

What does the needle pass through for an epidural?

Answer 19

Needle passes through:

• supraspinous ligament
• interspinous ligament
• ligamentum flavum
• epidural space (fat and veins)

Question 20

Where do sympathetic nerves exit the spinal cord?

Answer 20

With T1-L2 spinal nerves

Question 21

Sympathetic fibres are in ALL spinal nerves and their named nerves.. With this in mind what do you expect to see in spinal anaesthesia?

Answer 21

Blockade of sympathetic tone to all arterioles in lower limb
   =   Vasodilation
- skin of lower limbs   looks flushed
- warm lower limbs
- reduced sweating

Question 22

If spinal anaesthetic is working what happens to the patient’s BP and why?

Answer 22

HYPOTENSION

Due to vasodilation

Question 23

What branch of sacral plexus is pudendal nerve?

Answer 23

S2, S3 and S4

Question 24

Describe when a pudendal nerve block would be useful (3)

Answer 24

Anaesthetise majority of perineum

Useful for
episiotomy incision
forceps use
perineal stitching post delivery

Question 25

Describe the course of the pudendal nerve in the pelvis and perineum

Answer 25

1. Exits pelvis via GREATER SCIATIC FORAMEN
2. Passes POSTERIOR to SACROSPINOUS ligament
3. Re-enters pelvis/perineum via LESSER SCIATIC FORAMEN
4. Travels in pudendal canal
5. Branches to supply structures of perineum

Question 26

Describe how the pudendal nerve travels in the pudendal canal

Answer 26

passageway within obturator fascia

with internal pudendal artery and vein (and nerve to obturator internus)

Question 27

What landmark is useful for administering a pudendal nerve block and why?

Answer 27

Ischial spine - pudendal nerve crosses lateral aspect of sacrospinous ligament

Question 28

What is an episiotomy?

Answer 28

Incision made in the perineum during childbirth

Question 29

Describe the episiotomy and anatomical relevance

Answer 29

Incision made posterolateal into the relatively safe fal filled ischioanal fossa
Median incision not usually used as if further tearing could involve anal sphincter