1: Anatomy - Anaesthesia of labour Flashcards
Where is visceral pain felt when organs are affected in
a) the superior pelvis
b) the inferior pelvis?
a) Suprapubic region
b) S2,3,4 region (bullseye around the anus i.e the perineum)
What colour is the ligamentum flavum?
Why?
Yellow
Contains elastin
What are the main symptoms of raised intracranial pressure?
Headache
Visual changes
The uterine contractions of menstruation and childbirth are controlled by ___ which trigger which type of nerve?
hormones
autonomic nerves (sympathetic and parasympathetic, or ‘visceral motor’)
Which modality of nerve controls the pelvic floor muscles?
Somatic motor
Which sensory modality supplies organs
a) above the pelvic pain line
b) below the pelvic pain line
c) in the perineum?
a) Visceral afferent
b) Visceral afferent
c) Somatic sensory
Which organs are above the pelvic pain line?
Those which touch the parietal peritoneum
So the bladder, ovaries and uterine tubes, uterus, superior vagina
Which organs are below the pelvic pain line?
Those which are above the levator ani muscle but don’t touch the parietal peritoneum
Cervix, inferior vagina
Which named nerve supplies somatic sensory fibres to structures in the perineum?
Pudendal nerve (S2,3,4)
Which nerve roots supply sensory fibres to structures
a) above the pelvic pain line
b) below the pelvic pain line
c) in the perineum?
a) T11 - L2
b) S2-4
c) S2-4
Are organs below the pelvic pain line all supplied by the pudendal nerve?
No - VISCERAL AFFERENTS from S2,3,4 (I appreciate this is confusing)
Structures in the perineum are supplied with somatic sensory fibres by the pudendal nerve (S2,3,4)
How do
a) visceral afferents from above the pelvic pain line
b) visceral afferents from below the pelvic pain line
c) somatic sensory fibres from the perineum
plug into the spinal cord, and at which levels?
a) Travel with sympathetics back to T11-L2 within periarterial plexuses
b) Travel with parasympathetics back to S2-4 within pelvic splanchnic nerves
c) Travel back to S2-4 within the pudendal nerve
What are the two important sets of spinal cord levels for the female reproductive system?
T11 - L2 (visceral afferents ABOVE pelvic pain line)
S2 - S4 (visceral afferents BELOW pelvic pain line; perineum)
What are three kinds of anaesthesia which can be given to pregnant women?
Spinal anaesthesia
Epidural anaesthesia
Pudendal nerve block
Where are spinal and epidural anaesthetics injected?
L3/4 or L4/5
Just like a lumbar puncture
Remember L2 is the termination of the spinal cord
What is the difference between a spinal and epidural anaesthetic?
Spinal anaesthetic injected through all layers into SUBARACHNOID SPACE
Epidural anaesthetic injected into EPIDURAL SPACE - fewer layers breached
From superficial to deep, name the layers a needle passes through when giving spinal anaesthesia.
Skin
Fascia
Supraspinous lig.
Interspinous lig.
Ligamentum flavum
Epidural space
Dura
Arachnoid
Subarachnoid space!
From superficial to deep, name the layers a needle passes through when giving epidural anaesthesia.
Skin
Fascia
Supraspinous lig.
Infraspinous lig.
Ligamentum flavum
Epidural space!
At what levels can
a) spinal
b) epidural anaesthesia be given?
Both are L3/4 or L4/5
Same as a lumbar puncture
What are the risks involved in giving spinal anaesthesia?
Raised ICP - increased volume in subarachnoid space
Hypotension - widespread vasodilation due to anaesthetic’s effect on sympathetics
Also: nerve damage, haemorrhage, infection
What structures are numbed by a spinal anaesthetic?
Intraperitoneal structures and everything below the waist - above PPL, below PPL, perineum, lower limbs
What structures are numbed by an epidural anaesthetic?
Structures above and below PPL + perineum
Can an epidural anaesthetic cause
a) raised intracranial pressure
b) hypotension?
a) No - doesn’t penetrate subarachnoid space
b) Yes - same effect on sympathetic nerves
Why can spinal and epidural anaesthetics cause hypotension?
All spinal nerves contain sympathetics
Sympathetics control arteriolar vasoconstriction (sympathetic tone)
Sympathetics blocked - widespread vasodilation, hypotension
Which branch of the sacral plexus has roles in the GI, renal and female reproductive systems?
Pudendal nerve (S2,3,4)
Which nerve supplies somatic sensory fibres to the external anal and urethral sphincters?
Pudendal nerve
Which type of anaesthesia numbs the perineum only?
Pudendal nerve block
Which type of anaesthesia would be given to a woman undergoing an episiotomy?
Pudendal nerve block
Where does the pudendal nerve EXIT the pelvis?
Greater sciatic foramen
Where does the pudendal nerve RE-ENTER the pelvis?
Lesser sciatic foramen
Which pelvic structure does the pudendal nerve pass POSTERIOR to?
Sacrospinous ligament
Which passageway, found within the pelvis, does the pudendal nerve travel within?
Pudendal canal
Which fossa is the pudendal canal found in?
Ischioanal fossa
Which fascia is the pudendal canal found in?
Obturator fascia
What are the contents of the pudendal canal?
Pudendal nerve
Internal pudendal artery
Internal pudendal vein
Nerve to obturator internus
Which muscle is in close relation to the obturator canal?
Obturator internus
The pudendal canal is found in the ___ fossa, within the ___ fascia. It contains the ___ nerve and ___ ___ artery and vein. It is bounded by the muscle called ___ ___.
ischioanal fossa
obturator fascia
pudendal nerve
internal pudendal artery and vein
obturator internus
The pudendal nerve supplies which area with somatic sensory fibres?
Perineum
Which bony landmark is used in pudendal nerve block?
Why?
Ischial spine
Palpated with one hand in vagina and anaesthetic injected at fingertips
Pudendal nerve travels closely with sacrospinous ligament
What is pudendal nerve block used for?
Episiotomy
Repair of tears
Forceps delivery
What can happen to the pudendal nerve during childbirth?
Stretching > Nerve damage
Which specific muscles can be damaged during childbirth?
Puborectalis (part of levator ani group)
External anal sphincter
What is an episiotomy?
Incision made below posterior fourchette to prevent spontaneous tearing during childbirth
In which direction is an episiotomy usually made?
Inferolaterally
Median (vertical) episiotomy isn’t commonly done.
Why not?
Potential to damage PERINEAL BODY - mass acting as insertion for loads of pelvic floor muscles
AND
Further tearing in that direction will involve the external anal sphincter
What is the bony landmark for L4?
Posterior iliac crests
