clinical anatomy of anaesthesia for labour

Question 1

what are reproductive system motor functions?

Answer 1

-Uterine ‘cramping’ (menstruation)
-Uterine contraction (labour)
-Pelvic floor muscle contraction (during sneezing)

Question 2

What are the reproductive system sensory (pain) functions?

Answer 2

• Pain from the adnexae (ovaries and fallopian tube)
• Pain from the uterus
• Pain from the vagina
• Pain from the perineum

Question 3

what muscle splits the pelvis and perineum?

Answer 3

levator ani muscle
above= pelvis
below= perineum

Question 4

what type of nerve fibres are found in the pelvis?

Answer 4

This is the body cavity and so there will be:
-sympathetic
-parasympathetic
-visceral afferent (sensory info e.g. distention of organs)

Question 5

what type of nerve fibres are found in the perineum?

Answer 5

this is a body wall and so there will be:
-somatic motor
-somatic sensory

Question 6

what nerves supply motor innervation to uterine cramping and what controls it?

Answer 6

-sympathetic/ parasympathetic nerve fibres driven by hormonal control

uterus is in the body cavity and so there will be:
-sympathetic (motor)
-parasympathetic (motor)
-visceral afferent (sensory info e.g. distention of organs)

Question 7

what nerves supply motor innervation to uterine contraction and what controls it?

Answer 7

-sympathetic/ parasympathetic nerve fibres driven by hormonal control

uterus is in the body cavity and so there will be:
-sympathetic (motor)
-parasympathetic (motor)
-visceral afferent (sensory info e.g. distention of organs)

Question 8

what nerves supply motor innervation to pelvic floor muscle contraction?

Answer 8

somatic motor

perineum is a body wall and so there will be:
-somatic motor
-somatic sensory

Question 9

what nerves supply the sensory innervation for pain in the adnexae (ovaries + fallopian tubes)

Answer 9

Visceral afferents

adnexae in the body cavity and so there will be:
-sympathetic (motor)
-parasympathetic (motor)
-visceral afferent (sensory info e.g. distention of organs)

Question 10

what nerves supply the sensory innervation for pain in the uterus?

Answer 10

Visceral afferents

uterus is in the body cavity and so there will be:
-sympathetic (motor)
-parasympathetic (motor)
-visceral afferent (sensory info e.g. distention of organs)

Question 11

what nerves supply the sensory innervation for pain in the vagina?

Answer 11

Pelvic part- visceral afferent
Perineum part- somatic sensory

Question 12

what nerves supply the sensory innervation for pain in the perineum?

Answer 12

perineum is a body wall and so there will be:
-somatic motor
-somatic sensory

Question 13

what nerve supplies somatic sensation to the perineum

Answer 13

pudendal nerve (S2-S4)

Question 14

where is pain perceived from superior aspect or pelvic organs/ parts touching the peritoneum?

Answer 14

Perceived as suprapubic pain from the patient

Question 15

why is pain from the superior aspect of pelvic organs (parts touching the peritoneum) perceived as suprapubic pain in patients?

Answer 15

-This pain comes from visceral afferents
-Visceral afferents touching the peritoneum run alongside sympathetic fibres (along side not in!)
-The visceral afferents enter the spinal cord beside the sympathetic fibres between levels T11- L2 causing pain to be perceived as suprapubic

Question 16

why is pain from the inferior aspect of pelvic organs (parts NOT touching the peritoneum) perceived as perineum pain in patients?

Answer 16

-This pain comes from visceral afferents
-Visceral afferents NOT touching the peritoneum run alongside parasympathetic fibres (along side not in!)
-The visceral afferents enter the spinal cord beside the sympathetic fibres between levels S2, S3, S4 causing pain to be perceived from the perineum (S2, S3, S4 level)

Question 17

Where is pain from structures in the pelvis (above levator ani) felt and why?

Answer 17

Just like pain from structures not touching the peritoneum
-This pain comes from visceral afferents as it is part of the body cavity
-Visceral afferents run alongside parasympathetic fibres (along side not in!)
-The visceral afferents enter the spinal cord beside the sympathetic fibres between levels S2, S3, S4 causing pain to be perceived from the perineum (S2, S3, S4 level)

Question 18

where is pain felt from structures in the perineum (below levator ani) felt and why?

Answer 18

• the pain comes from somatic sensory nerves as it is part of the body wall
  -in the perineum this is the pudendal nerve
  -perineum enters the spinal cord at levels S2, S3 and S4 meaning that the pain is felt localised (sharp and stabbing) in the perineum

Question 19

Autonomic nerves of the pelvis:
-where do the sympathetics originate from and travel to?

Answer 19

-sympathetic fibres originate and come out at T11- L2
-they then travel down the sacral sympathetic trunks and form the superior hypogastric plexus
-sympathetic fibres come out of the superior hypogastric plexus and supply the pelvis/ perineum with visceral motor innervation

Question 20

Autonomic nerves of the pelvis:
-where do the parasympathetics originate from and travel to?

Answer 20

-Parasympathetics originate from S2, S3, S4 spinal cord level (sacral outflow)
-they then travel in the pelvic splanchnic nerves
-these contribute to the inferior hypogastric plexus and mix with the sympathetic autonomic nerves to give rise to the mixed autonomic nerves of the pelvis

Question 21

what female reproductive structures in the body cavity touch the peritoneum?

Answer 21

Uterine tubes
Uterus
Ovaries

Question 22

what nerves supply sensory innervation to uterine tubes, uterus and ovaries, where is the pain felt and why?

Answer 22

Visceral afferents supply uterine tubes, uterus and ovaries as they are in the body cavity (above levator ani)

• touching the peritoneum so visceral afferents run alongside sympathetic fibres (along side not in!)
  -The visceral afferents enter the spinal cord beside the sympathetic fibres between levels T11- L2 causing pain to be perceived as suprapubic

Question 23

what nerves supply sensory innervation to superior part of vagina and cervix where is the pain felt and why?

Answer 23

Visceral afferents supply superior part of vagina and cervix as they are in the body cavity (above levator ani)

-NOT touching the peritoneum so visceral afferents run alongside parasympathetic fibres (along side not in!)
-The visceral afferents enter the spinal cord beside the sympathetic fibres between levels S2, S3, S4 causing pain to be perceived from the perineum (S2, S3, S4 level)

Question 24

where does the spinal cord end and become the cauda equina?

Answer 24

L2 vertebra

Question 25

where does the subarachnoid space end?

Answer 25

S2 level

Question 26

where is anaesthetic injected for a spinal/ epidural anesthetic?

Answer 26

L3-L4 intervertebral space

sometimes the L4-L5

Question 27

when administering an epidural, what structures must the needle pass through?

Answer 27

-supraspinous ligament
-interspinous ligament
-ligamentum flavum (will feel pop)
-epidural space

Question 28

what is the epidural space filled with

Answer 28

fat and veins

Question 29

when administering a spinal anaesthetic, what structures must the needle pass through?

Answer 29

-supraspinatous ligament
-interspinous ligament
-ligamentum flavum (will feel pop)
-epidural space
-dura mater
-arachnoid mater
-reaches subarachnoid space (containing CSF)

Question 30

when spinal anaesthetic is delivered are motor or sensory fibres blocked?

Answer 30

Both motor (including sympathetic) and sensory fibres are blocked

Question 31

what spinal nerves contain sympathetic fibres?

Answer 31

all spinal nerves contain sympathetic fibres

Question 32

what arterials do sympathetic fibres supply?

Answer 32

all arterioles

Question 33

what affect do sympathetic fibres have on arterioles

Answer 33

cause vasoconstriction

Question 34

what affect does spinal anaesthesia have on arterioles in the lower limb, why and what is overall affect?

Answer 34

-at this level is causes blackade of sympathetic tone to all arterioles of lower limb causing vasodilation

-this leads to warmth and reduced sweating in lower limb

-can also cause hypotension (monitor patient closely!)

Question 35

where do sympathetic nerves exit the spinal cord?

Answer 35

between T1- L2 with the spinal nerves

Question 36

what plexus is the pudendal nerve a branch of?

Answer 36

S2, S3, S4

Question 37

How does the pudendal nerve exit the pelvis and enter perineum?

Answer 37

-exits the pelvis via the greater sciatic foramen
-travels posterior to the sacrospinous ligament
-reenters at the pelvis/ perineum via the lesser sciatic foramen
-travels in pudendal canal

Question 38

how is a pudendal nerve block administered?

Answer 38

The pudendal nerve passes the posterior of the sacrospinous ligament

-the ischael spine can be felt as a bony landmark and the nerve block is delivered either through the skin or more commonly internal and aim slightly medial to this

Question 39

when would a pudendal nerve block be administered in/ after labour?

Answer 39

-forceps delivery
-painful vaginal delivery
-episiotomy incision
-perineal suturing post delivery

Question 40

what inciscion can be done to try and prevent anal tearing during labour?

Answer 40

episiotomy
-posterolateral incision

sometimes mediolateral but this is more often avoided