Anatomy of Anaesthesia of Labour

Question 1

motor function in reproductive system?

Answer 1

uterine cramping (mentsruation)
uterine contraction (during labour)
pelvic floor muscle contraction (during sneezing etc)

Question 2

sensory function in reproductive system?

Answer 2

pain from the adnexe (ovaries + fallopian tubes)
pain from uterus
pain from vagina
pain from perineum

Question 3

which type of nerve fibres supply structure in pelvis?

Answer 3

sympathetic
parasympathetic
visceral afferent

Question 4

what type of nerve fibres supply structure in perineum

Answer 4

somatic motor

somatic sensory

Question 5

control of uterine cramping?

Answer 5

hormonal

sympathetic/parasympathetic

Question 6

what controls uterine contraction?

Answer 6

hormonal (sympathetic/parasympathetic)

Question 7

what controls pelvic floor muscle contraction?

Answer 7

somatic motor

Question 8

what controls pain from adnexe, uterus and vagina?

Answer 8

visceral afferents
(part of vagina in perineum = somatic sensory)

Question 9

what controls pain from the perineum?

Answer 9

somatic sensory

Question 10

pain sensation in superior aspect of pelvic organs (organs touching peritoneum)?

Answer 10

visceral afferents run alongside sympathetic fibres and enter the spinal cord between T11-L2
pain is percieved by patient as suprapubic

Question 11

pain sensation in inferior aspect of pelvic organs (not touching peritoneum)?

Answer 11

visceral afferents run alongside parasympathetic fibres and enter the spinal cord at levels S2, S3, S4
pain percieved in S2, S3, S4 dermatome (peritoneum)

Question 12

pain sensation in structures which pass from pelvis to perineum when above levator ani (in pelvis)?

Answer 12

visceral afferents
parasympathetic
enters spinal cord levels S2, S3, S4

Question 13

pain sensation in structures which pass from pelvis to perineum when below levator ani (in perineium)?

Answer 13

somatic sensory
pudendal nerve
enters spinal cord levels S2, S3, S4
localised pain within perineum

Question 14

sympathetic autonomic nerves in pelvis?

Answer 14

sacral sympathetic trunks T11-L2

superior hypogastric plexus

Question 15

parasympathetic autonomic nerves of pelvis?

Answer 15

sacral outflow(S2, S3, S4)
pelvic splanchnic nerves emerge from spinal roots and mix with sympathetics in inferior hypogastric plexus

Question 16

2 important spinal cord levels in pain sensation in females?

Answer 16

T11-L2
- sympathetic visceral afferents from pelvic organs which touch the peritoneum (uterine tubes, uterus, ovaries) returns back to T11-L2

S2-S4

• parasympathetic visceral afferents from pelvic organs inferior to peritoneum (cervix and superior vagina) return back to S2-S4
• pudendal nerve from organs/structures within the perineum (inferior vagina, perineal muscles, glands and skin) return back to S2-S4

Question 17

perineum pain sensation summary?

Answer 17

perineum > body wall > somatic sensation via pudendal nerve (S2, S3, S4)

Question 18

pelvis pain sensation summary?

Answer 18

body cavity
autonomics/visceral afferent
- touching peritoneum (more superior) = follows sympathetics back to T11-L2
- not touching peritoneum (more inferior) = follows parasympathetics back to S2, S3, S4

Question 19

3 types of anaesthetic used in childbirth?

Answer 19

spinal anaesthetic
epidural anaesthetic
pudendal nerve block

Question 20

two important spinal levels in female reproductive pain?

Answer 20

T11-L2

S2-S4

Question 21

what level is spinal/epidural anaesthetic injected and why?

Answer 21

L3-L4

as spinal cord ends at L2 and becomes cauda equina and subarachnoid space ends at S2

Question 22

what does needle pass through in epidural anaesthetic?

Answer 22

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

Question 23

what does needle pass through in spinal anaesthetic?

Answer 23

skin
fat
supraspinous ligament
interspinous ligament
ligamentum flavum
epidural space (fat and veins)
dura mater
arachnoid mater
finally reaches subarachnoid space (containing CSF)

Question 24

sympathetic nerves exit the spinal cord between which levels?

Answer 24

T1 - L2
travel to sympathetic chains running length of vertebral column and pass into all spinal nerves (anterior and posterior rami/named nerves)

Question 25

what happens to sympathetic outflow below L2?

Answer 25

sympathetic ganglia receive fibres from L2 level via the sympathetic chain and distribute them via connections with lumbar, sacral and coccygeal spinal nerves

Question 26

all spinal nerves and their named nerves contain which types of fibres?

Answer 26

sympathetic fibres (including femoral, sciatic, obturator, pudendal)

Question 27

what is the main risk of spinal anaesthesia and how does this occur?

Answer 27

hypotension sympathetic fibres supply all arterioles (sympathetic tone), therefore spinal anaesthetic causes blockade of sympathetic tone to all arterioles in lower limb (vasodilation)

Question 28

signs of vasodilation in lower limb?

Answer 28

skin of lower limb looks flushed warm lower limbs reduced sweating

Question 29

pudendal nerve has a role in which systems?

Answer 29

GI renal motor control of external anal and external urethral sphincters nerve of the perineum (somatic motor and somatic sensory to structures of perineum)

Question 30

pudendal nerve origin?

Answer 30

S2, S3, S4

Question 31

describe the course of the pudendal nerve?

Answer 31

originates at S2, S3, S4 exits pelvis via greater sciatic foramen passes posterior to sacrospinous ligament re-enters the pelvis/perineum via lesser sciatic foramen then travels in pudendal canal within obturator fascia with internal pudendal artery and vein (and nerve to obturator internus) then branches to supply structures of the perineum

Question 32

which landmarks is the pudendal nerve associated with?

Answer 32

``` crosses the lateral aspect of the sacrospinous ligament ischial spine (can be used as a landmark to administer block) ```

Question 33

when is pudendal nerve used in anaesthesia?

Answer 33

forceps delivery painful vaginal delivery episotomy incision perineal suturing post delivery (injected along site of tear/episotomy to anaesthetise branches of pudendal)

Question 34

what damage could occur during labour?

Answer 34

branches of pudendal nerve can be stretched fibres within the levator ani (puborectalis) or external anal sphincter muscle could be torn and as a result the muscle is weakened - 1st/2nd/3rd degree - can cause weakened pelvic floor and faecal incontinence

Question 35

what is an episiotomy?

Answer 35

posterolateral/mediolateral incision made into safe fat filled ischioanal fossa to avoid tearing right into the rectum