Anatomy of anaesthesia for labour

Question 1

What is the motor function of the reproductive system in women?

Answer 1

Uterine cramping (menstruation) 
Uterine contraction (labour) 
Pelvic floor muscle contraction (sneezing)

Question 2

What is the sensory function of the female reproductive system?

Answer 2

Pain from adnexae (ovaries and fallopian tubes)
Pain from uterus
Pain from vagina
Pain from perineum

Question 3

Why is it important to know if the pain is from pelvis or perineum?

Answer 3

Fundamental to deciding which nerve fibre types are carrying out which function
Pelvis: body cavity, sympathetic, parasymp or visceral afference
Perineum; body wall, somatic motor and sensory

Question 4

What separates the pelvis from perineum?

Answer 4

Levator ani

Question 5

Which nerve fibres mediate uterine cramping?

Answer 5

Hormonal; sympathetic and parasymp

Question 6

Which nerve fibres mediate uterine contraction?

Answer 6

Hormonal; symp and parasymp

Question 7

Which nerve fibres mediate pelvic floor muscle contraction?

Answer 7

Somatic motor

Question 8

Which nerve fibres mediate pain from adnexae?

Answer 8

Visceral afferents

Question 9

Which nerve fibres mediate pain from uterus?

Answer 9

Visceral afferents

Question 10

Which nerve fibres mediate pain from vagina?

Answer 10

Visceral afferents (pelvic) 
Somatic sensory (perineum)

Question 11

Which nerve fibres mediate pain from perineum?

Answer 11

Somatic sensory

Question 12

How is pain sensed from the superior aspect of pelvic organs/ touching peritoneum?

Answer 12

Visceral afferents
Run alongside symp fibres
Enter spinal cord between levels T11-L2
Pain is perceived by patient as suprapubic

Question 13

How is pain sensed from the inferior aspect of pelvic organs/ not touching peritoneum?

Answer 13

Visceral afferents
Run alongside parasymp fibres
Enter spinal cord at levels S2,3,4
Pain perceived in S2,3,4 dermatome (perineum)

Question 14

How is pain sensed from the urethra/ vagina in the pelvis (above levator ani)?

Answer 14

Visceral afferents
Parasymp
Spinal cord levels S2,3,4

Question 15

How is pain sensed from the urethra/ vagina in the perineum below the levator ani?

Answer 15

Somatic sensory
Pudendal nerve
Spinal cord levels S2,3,4
Localised pain within perineum

Question 16

What spinal cord levels will the symps that supply the pelvis arise from?

Answer 16

Sacral sympathetic trunks
T11-L2
Superior hypogastric plexus

Question 17

What spinal cord levels will the parasymps that supply the pelvis arise from?

Answer 17

Sacral outflow (S2,3,4)
Pelvic splanchinic nerves
Emerge from spinal roots
Mixes with sympathetic in inferior hypogastric plexus

Question 18

In the female reproductive system; where will visceral afferents travel to?

Answer 18

Back to T11-L2 from pelvic organs which touch the peritoneum (uterine tubes, uterus, ovaries)

Question 19

In the female reproductive system; where will the pudendal nerve travel to?

Answer 19

Back to S2,3,4

Organs within the perineum; inferior vagina, perineal muscles, glands, skin

Question 20

What are the 2 important spinal cord levels in terms of pain from female repro system?

Answer 20

T11-L2

S2-4

Question 21

Pain sensation from perienum?

Answer 21

Body wall
Somatic sensation
Pudendal nerve
S2,3,4

Question 22

Pain sensation from pelvis

Answer 22

Body cavity
Autonomics/ visceral afferents
Then distinguish if touching peritoneum or not

Question 23

Pain sensation from pelvic structures touching peritoneum

Answer 23

Superior
Follows sympathetics
T11-L2

Question 24

Pain sensation from pelvic structures not touching peritoneum?

Answer 24

More inferior
Follows parasymps
S2,3,4

Question 25

What are the 3 modes for anaesthesia in labour?

Answer 25

Spinal Epidural Pudendal nerve block

Question 26

Describe a spinal block

Answer 26

Anaesthetizes from waist down; intra and sub peritoneal plus somatic area

Question 27

Describe an epidural block

Answer 27

Anesthetizes subperitoneal plus somatic innervated by pudendal

Question 28

Describe a pudendal nerve block

Answer 28

Anaesthetizes areas innervated by pudendal nerve

Question 29

When does the spinal cord become cauda equina?

Answer 29

L2

Question 30

Where does the SA space end?

Answer 30

S2

Question 31

Where is anaesthetic injected in a spinal and epidural?

Answer 31

L3-4 (L5) region

Question 32

With which pelvic bony landmark is L4 in line with?

Answer 32

Superior point on iliac crests

Question 33

Through which structures will the needle for an epidural pass through?

Answer 33

Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space (fat and veins)

Question 34

Through which structures will the needle for a spinal pass through?

Answer 34

``` Supraspinous Interspinous Ligamentum flavum Epidural space Dura mater Arachnoid mater Subarachnoid space ```

Question 35

Where do symp nerves exit the spinal cord?

Answer 35

T1-L2

Question 36

What occurs with sympathetic outflow below L2?

Answer 36

Sympathetic ganglia recieve fibers from L2 via symp chain and then distrubute them via connections with lumbar, sacral and occygeal spinal nerves

Question 37

Do spinal nerves contain symp?

Answer 37

Yes; with their named nerve (femoral, sciatic, obturator, pudendal)

Question 38

Which part of the circulation is supplied by sympathetics?

Answer 38

Arterioles

Question 39

What will blockade of symp tone in arterioles in lower limb result in?

Answer 39

Vasodilation; skin of lower limbs looks flushed Warm lower limbs Reduced sweating

Question 40

What is a sign that spinal anaesthetic is working?

Answer 40

Vasodilation in lower limbs | Hypotension

Question 41

What is the nerve of the perineum?

Answer 41

Pudendal nerve; somatic motor and somatic sensory, parasymp (S2,3,4)

Question 42

Through which structure will the pudendal nerve exit the pelvis and then re-enter the pelvis?

Answer 42

Exit; greater sciatic foramen Posterior to sacrospinous ligament Re-enters via lesser sicatic foramen

Question 43

Through which canal does the pudendal nerve travel in?

Answer 43

Pudendal canal Passageway within the obturator fascia With internal pudendal artery and vein (and nerve to obturator internus)

Question 44

Which aspect of the sacrospinous ligament does the pudendal nerve cross?

Answer 44

Lateral

Question 45

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

Answer 45

Ischial spine (can be felt on internal examination at the 4 and 8 o'clock position)

Question 46

When is a pudendal nerve block utilised?

Answer 46

Forceps delivery Painful vaginal delivery Episiotomy incision

Question 47

What mechanism for nerve block is utilised for perineal suturing post delivery?

Answer 47

LA is injected along site of tear/ episiotomy to anaesthetise branches of pudendal

Question 48

How is the pudendal nerve damaged in labour?

Answer 48

Branches can be stretched with resultant stretch of nerve fibres Fibres within levator ani (puborectalis) or external anal sphincter muscle could be torn and as a result weakened

Question 49

What are the different types of perineal tears?

Answer 49

1st 2nd 3rd degree

Question 50

Where is a posterolateral episiotomy incision made?

Answer 50

"Safe" fat filled ischioanal fossa to avoid the incision extending into the rectum

Question 51

Where is a medial episiotomy incision made?

Answer 51

Not used as much as if further tearing occurs, it will involve the anal sphincter

Question 52

What is a 1st degree tear?

Answer 52

Fourchette and vaginal mucosa are damaged and underlying muscles are exposed but not torn

Question 53

What is a 2nd degree tear?

Answer 53

Posterior vaginal walls and perennial muscles but anal sphincter is intact

Question 54

What is a 3rd degree tear?

Answer 54

Extends to anal sphincter that is torn, but rectal mucosa is intact

Question 55

What is a 4th degree tear?

Answer 55

Anal canal is opened, and tear may spread to rectum