Anatomy of Anaesthesia in Labour Flashcards Preview

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Flashcards in Anatomy of Anaesthesia in Labour Deck (30)
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1
Q

Pain from which structures of the female reproductive system is transmitted via sensory nerve fibres?

A
  • adnexae (ovaries + fallopian tubes)
  • uterus
  • vagina
  • perineum
2
Q

What motor functions does the female reproduction system have?

A
  • Uterine “cramping” (e.g. menstruation)
  • Uterine contraction (e.g. during labour)
  • Pelvic floor muscle contraction (e.g. during sneezing)
3
Q

How do we know what nerve fibres carry out which function in the reproductive tract?

A

If structure supplied is ABOVE levator ani muscle
=> PELVIS
=> sympathetic, parasympathetic and visceral afferent

If structure supplied is BELOW levator ani muscle
=> PERINEUM
=> somatic motor and somatic sensory

4
Q

What type of nerves carry out the uterine “cramping” and “contraction”?

A

hormonally driven

=> sympathetic/parasympathetic

5
Q

What type of nerves carry out pelvic floor muscle contraction?

A

somatic motor

6
Q

What sensory nerve fibres are responsible for pain in the adnexae, uterus and upper part of the vagina?

A

visceral afferents

7
Q

What sensory nerve fibres are responsible for pain from the lower part of the vagina and the perineum?

A

somatic sensory

8
Q

How do sensory nerve fibres get to the SUPERIOR aspect of pelvic organs / those touching the peritoneum, and where do these fibres enter/exit the spinal cord?

A
  • Visceral afferents
  • Run alongside sympathetic fibres
  • Enter spinal cord between levels T11-L2
  • Pain is perceived by patient as suprapubic
9
Q

How do sensory nerve fibres get to the INFERIOR aspect of pelvic organs / those NOT touching the peritoneum, and where do these fibres enter/exit the spinal cord?

A
  • Visceral afferents
  • Run alongside parasympathetic fibres
  • Enter spinal cord at levels S2, S3, S4
  • Pain perceived in S2, S3, S4 dermatome (perineum)
10
Q

What sensory nerve fibres are responsible for pain sensation in structures which cross between the pelvis and the perineum? (e.g. urethra, vagina)

A

ABOVE levator ani – in the pelvis

  • visceral afferents (parasympathetic - craniosacral)
  • S2, S3 and S4

BELOW levator ani – in the perineum

  • somatic sensory (pudendal nerve)
  • S2, S3 and S4
11
Q

What sympathetic autonomic nerves are found in the pelvis?

A
  • Sacral sympathetic trunks
  • T11-L2
  • Superior hypogastric plexus
12
Q

What parasympathetic autonomic nerves are found in the pelvis?

A
  • Sacral outflow (S2, 3, 4)
  • Pelvic splanchnic nerves
  • Mix with sympathetics in INFERIOR hypogastric plexus
13
Q

Pain in the female reproductive system localises to what 2 regions in the spinal cord?

A
  • T11-L2

- S2-S4

14
Q

If a structure in the female reproductive tract is described as being in the body cavity, how can the type of its sensory nerve fibre be identified?

A
  • If in body cavity => pelvis => autonomic nerves
  • if touching peritoneum = more Superior = follows Sympathetics back (T11-L2)
  • if NOT touching peritoneum = more Inferior = follows parasympathetics back (S2-4)
15
Q

What are the 3 main types of anaesthesia used in labour?

A

Spinal anaesthetic (into subarachnoid space)

Epidural anaesthetic (into epidural space)

Pudendal nerve block

16
Q

How is spinal anaesthesia given and what structures are affected by the numbing agent?

A
  • Given via lumbar puncture
  • Numb from waist down
  • Intraperitoneal, subperitoneal and somatic structures are numbed
17
Q

What structures are numbed by an epidural block?

A

Subperitoneal and somatic structures

18
Q

What structures are numbed by a pudendal nerve block?

A

Somatic structures innervated by pudendal nerve

19
Q

At what level does the spinal cord become the cauda equina?

A

L2

20
Q

At what spinal level is anaesthetic given in a spinal or epidural procedure?

A

Anaesthetic injected into L3-L4 (L5) region

21
Q

What layers does the needle pass through during an epidural anaesthetic?

A

Needle passes through:

  • supraspinous ligament
  • interspinous ligament
  • ligamentum flavum
  • epidural space (fat and veins)
22
Q

What layers must the needle pass trough during a spinal anaethetic?

A
  • supraspinous ligament
  • interspinous ligament
  • ligamentum flavum
  • epidural space (fat and veins)
    + dura mater
    + arachnoid mater
    + subarachnoid space (contains CSF)
23
Q

If the sympathetic nerves exit the spinal cord between levels T1-L2, how do sympathetics reach the organs below the level of L2?

A

Below L2 level

  • Nerve signals travel down sympathetic chain to ganglia lower down than L2
  • These gangla distribute nerve signals via connections with lumbar, sacral and coccygeal spinal nerves
24
Q

How can we tell if anaethesia is working?

A
  • All spinal nerves + named nerves contain sympathetics
  • Sympathetics supply all arterioles (sympathetic tone)

=> Blockade of sympathetic tone to all arterioles in lower limb = VASODILATION

=> skin looks flushed, warm lower limbs, reduced sweating, hypotension

25
Q

Describe the course of the pudendal nerve?

A
  • Exits pelvis via GREATER sciatic foramen
  • Passes posterior to sacrospinous ligament
  • Re-enters pelvis/perineum via LESSER sciatic foramen
  • Travels in pudendal canal through obturator fascia
    (with internal pudendal artery and vein)
26
Q

What bony prominence can be used as a landmark to administer pudendal nerve block during labour?

A

ischial spine (this is where the sacrospinous ligament attaches, which the pudendal nerve crosses over)

27
Q

What circumstances in labour may indicate the need for a pudendal nerve block?

A
  • Forceps delivery
  • Painful vaginal delivery
  • episiotomy incision
28
Q

How is a pudendal nerve block partially used during perineal suturing?

A
  • local anaesthetic is injected along site of tear/episiotomy
    => anaesthetise branches of pudendal (not FULL block)
29
Q

What can occur if branches of the pudendal nerve are stretched or torn during labour?

A

If fibres within the levator ani or external anal sphincter are torn
=> muscle weakened (1st, 2nd, 3rd degree)
=> can cause incontinence/ prolapse

30
Q

What direction is an incision made during an episiotomy and why is this the case?

A

– Posterolateral direction
=> into the relatively “safe” fat filled ischioanal fossa
=> avoids the incision extending into the rectum

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