Anatomy of Anaethesia for Labour

Question 1

What are the 3 anaesthetics that can be used during labour?

Answer 1

spinal anaesthetic
epidural anaesthetic
pudendal nerve block

Question 2

In pain from the female reproductive system, what are the important spinal cord levels?

Answer 2

sympathetic outflow - T11-L2

pudendal nerve - S2-S4

Question 3

Where is anaesthetic injected in spinal and epidural anaesthetic?

Answer 3

L3-L4 (L5) region (measured using iliac crests)

Question 4

What is anaesthetised in spinal and epidural anaesthetics?

Answer 4

the cauda equina

Question 5

What does the needle pass through in spinal anaesthetic?

Answer 5

supraspinous ligament 
interspinous ligament 
ligamentum flavus 
epidural space 
dura mater 
arachnoid mater 
reaches subarachnoid space

Question 6

Where does the needle pass through in epidural anaesthetic?

Answer 6

supraspinous ligament
interspinous ligament
ligamentum flavus
reaches epidural space

Question 7

What are all signs that spinal anaesthetic is working and why?

Answer 7

skin of lower limbs looks flushed
warm lower limbs
reduced sweating

as there is blockade to sympathetic tone to all arterioles in lower limb (vasodilation)

Question 8

What makes up the pudendal nerve?

Answer 8

S2,3,4 - branch of sacral plexus

Question 9

What does a pudendal nerve block do?

Answer 9

anaesthetise majority of perineum

Question 10

What is a pudendal nerve block useful for?

Answer 10

episiotomy incision
forceps use
perineal stitching post delivery

Question 11

What type of fibres does the pudendal nerve have?

Answer 11

somatic motor and somatic sensory

Question 12

Describe the course of the pudendal nerve?

Answer 12

exits pelvis via greater sciatic foramen
passes posterior to sacrospinous ligament
enters perineum via lesser sciatic foramen
travels in pudendal canal
branches to supply structures of perineum

Question 13

What can be used as a landmark to administer pudendal nerve block?

Answer 13

ischial spine

Question 14

What can happen to the pudendal nerve during labour?

Answer 14

Can be stretched with resulting stretch of nerve fibres

Question 15

What can result in weakened pelvic floor and faecal incontinence?

Answer 15

Fibres within levator ani or external anal sphincter can be torn during delivery

Question 16

How can the tear extending into the rectum be avoided?

Answer 16

mediolateral episiotomy - controls direction

Question 17

What structures does the pudendal nerve supply?

Answer 17

levator ani 
external anal sphincter 
external urethral sphincter 
bulbospongiosus 
ischiocavernosis 

sensation to skin around anus and perineum