The Anatomy of Anaesthesia for labour

Question 1

Above the levator ani muscle = _____
Below the levator ani muscle= _________

Answer 1

Above the levator ani muscle = pelvic
Below the levator ani muscle= perineum

Question 2

Which nerve fibre types are found in the perineum?

Answer 2

Body wall

Somatic motor and somatic sensory

Question 3

How do fibres responsible for uterine ‘cramping’ (e.g. menstruation) get from CNS to organs?

Answer 3

Hormonal (sympathetic/parasympathetic)

Question 4

How do fibres responsible for uterine contraction (e.g. during labour) get from CNS to organs?

Answer 4

Hormonal (sympathetic/parasynpathtic)

Question 5

How do fibres responsible for pelvic floor muscle contraction (e.g. during sneezing) get from CNS to organs?

Answer 5

Somatic motor

Question 6

How do fibres carrying pain from adnexae (ovaries and fallopian tubes) get to the CNS?

Answer 6

Visceral afferents

Question 7

How do fibres carrying pain from uterus get to the CNS?

Answer 7

Visceral afferents

Question 8

How do fibres carrying pain from vagina get to the CNS?

Answer 8

Visceral afferents (pelvic part)/somatic sensory (perineum)

Question 9

How do fibres carrying pain from perineum get to the CNS?

Answer 9

Somatic sensory

Question 10

• Superior aspect of pelvic organs / touching the peritoneum
  
  • Visceral afferents
  • Run alongside _________ ______
  • Enter spinal cord between levels _____
  • Pain is perceived by patient as ________

Answer 10

• Superior aspect of pelvic organs / touching the peritoneum
  
  • Visceral afferents
  • Run alongside sympathetic fibres
  • Enter spinal cord between levels T11-L2
  • Pain is perceived by patient as suprapubic

Question 11

• Inferior aspect of pelvic organs / not touching peritoneum
  
  • Visceral afferents
  • Run alongside ______________ _____
  • Enter spinal cord at levels __, __, __
  • Pain perceived in __, __, __ ________ (________)

Answer 11

• Inferior aspect of pelvic organs / not touching peritoneum
  
  • Visceral afferents
  • Run alongside parasympathetic fibres
  • Enter spinal cord at levels S2, S3, S4
  • Pain perceived in S2, S3, S4 dermatome (perineum)

Question 12

How do structures crossing from the pelvis to the perineum e.g. urethra, vagina: above the levator ani sense pain?

Answer 12

Via visceral afferents

Parasympathetic

Spinal cord levels S2, S3, S4

Question 13

How do structures below the levator ani sense pain?

Answer 13

Somatic sensory

Pudendal nerve

Spinal cord levels S2, S3, S4

Localised pain within perineum

Question 14

Describe the autonomic sympathetic nerves of the pelvis?

Answer 14

Sacral sympathetic trunks

T11-L2

Superior hypogastric plexus

Question 15

Describe the autonomic parasympathetic nerves of the pelvis?

Answer 15

Sacral outflow (S2, 3, 4)

Pelvic splanchnic nerves

Emerge from spinal roots

Mixes with sympathetics in inferior hypogastric plexus

Question 16

Which pelvic organs touch the peritoneum?

Answer 16

Uterine tubes, uterus, ovaries

Question 17

Which organs are inferior to peritoneum?

Answer 17

Cervix and superior vagina

Question 18

Which organs are within the perineum

Answer 18

Inferior vagina, perineal muscles, glands, skin

Question 19

What are the various types of anesthesia used in labour?

Answer 19

Spinal anaesthetic

Epidural anesthetic

Pudendal nerve block

Question 20

At what level does spinal cord become cauda equina?

Answer 20

L2 vertebra

Question 21

What level does subarachnoid space end at?

Answer 21

S2

Question 22

Where is spinal and epidural anaesthetic injected into?

Answer 22

L3-L4 (L5) region

Question 23

What does the needle pass though in epidural anesthetic?

Answer 23

Supraspinous ligament

Interspinous ligament

ligamentum flavum

Epidural space (Fat and veins)

Question 24

What does needle pass through in spinal anaesthetic?

Answer 24

Supraspinous ligament

Interspinous ligament

Ligamentum flavum

Epidural space (Fat and veins)

Dura mater

Arachnoid mater

Finally reaches subarachnoid space (contains CSF)

Question 25

Sympathetic outflow originates from **\_\_\_\_\_\_\_** centres in the **\_\_\_\_\_** Sympathetic nerves exit spinal cord with\_\_**-\_\_** **\_\_\_\_\_** nerves Travel to **\_\_\_\_\_\_\_\_\_** chains running the length of the **\_\_\_\_\_\_\_\_** **\_\_\_\_\_\_**

Answer 25

Sympathetic outflow originates from **autonomic** centres in the **brain** Sympathetic nerves exit spinal cord with **T1-L2** **spinal** nerves Travel to **sympathetic** chains running the length of the **vertebral** **column**

Question 26

After sympathetic chains sympathetic outflow passes into .....

Answer 26

Spinal nerves (anterior and posterior rami/named nerves)

Question 27

How does sympathetic outflow happen below level L2?

Answer 27

Sympathetic ganglia recieve fibres from L2 level via the sympathetic chain and distrubite tham via connections with lumbar, sacral and coccygeal spinal nerves

Question 28

All spinal nerves and their named nerves contain ______ \_\_\_\_\_\_; including femoral, sciatic, obturator, pudendal

Answer 28

All spinal nerves and their named nerves contain sympathetic fibres; including femoral, sciatic, obturator, pudendal

Question 29

What does blockade of sympathetic tone cause due to spinal anaesthetic?

Answer 29

Block of sympathetic tone to all arterioles in lower limb; Vasodilatation - skin looks flushed - warm limbs - reduced sweating

Question 30

What does the pudendal nerve supply?

Answer 30

Nerve of the perineum Somatic motor and somatic sensory to structures of the perineum

Question 31

What does pudendal nerve block cause?

Answer 31

Anaesthesia of majority of perineum

Question 32

The pudendal nerve; Exits pelvis via **\_\_\_\_\_\_ ____ \_\_\_\_\_\_** Passes posterior to **\_\_\_\_\_\_\_\_\_** **\_\_\_\_\_\_\_** Re-enters pelvis/perineum via **\_\_\_\_\_\_** **\_\_\_\_\_** **\_\_\_\_\_\_\_**

Answer 32

The pudendal nerve; Exits pelvis via **greater sciatic foramen** Passes posterior to **sacrospinous** **ligament** Re-enters pelvis/perineum via **lesser** **sciatic** **foramen**

Question 33

What does the pudendal nerve travel within and with?

Answer 33

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

Question 34

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

Answer 34

Ischial spine

Question 35

When can pudendal nerve block be used during labour?

Answer 35

* forceps delivery * painful vaginal delivery * episiotomy incision

Question 36

How is pudendal nerve anaesthetised in perineal suturing after delivery?

Answer 36

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

Question 37

What can be stretched and torn during labour?

Answer 37

* pudendal nerve * fibres within the levator ani * external anal sphincter

Question 38

How is episiotomy performed?

Answer 38

Posterolateral (mediolateral incision) - made into the relatively 'safe' fat filled ischianal fossa and avoids the incision extending into the rectum