Anatomy 3 - Anaesthesia for Labour Flashcards
What nerve fibre types cause uterine cramping e.g. in menstruation?
Autonomic control - parasympathetic/ sympathetic causing hormone release
What nerve fibre types cause uterine contraction?
Autonomic control - parasympathetic/ sympathetic causing hormone release (oxytocin)
What nerve fibre types cause pelvic floor contraction e.g. which sneezing?
Somatic motor
What nerve fibre types sense pain from adnexae?
Visceral afferents (i.e. organ to spinal cord)
What nerve fibre types sense pain from uterus?
Visceral afferents
What nerve fibre types sense pain from vagina?
Pelvic part - visceral afferents
Perineum - somatic sensory
What nerve fibre types sense pain from perineum?
Somatic sensory
What nerve fibres are associated with structures in the pelvis (body cavity)?
Sympathetic
Parasympathetic
Visceral afferent
What nerve fibres are associated with structures in the perineum (body wall)?
Somatic motor
Somatic sensory
How does pain sensation travel from the superior aspect of pelvic organs/ touching the peritoneum to CNS?
Visceral afferents
What do the visceral afferent nerve fibres from from the superior aspect of pelvic organs/ touching the peritoneum run alongside?
Sympathetic fibres
Where do the visceral afferents from the superior aspect of pelvic organs/ touching the peritoneum enter the spinal cord?
Between T11 and L2
How is pain from between T11 and L2 perceived by patient?
Suprapubic pain
How does pain sensation travel from the inferior aspect of pelvic organs/ NOT touching the peritoneum to CNS?
Visceral afferents
What do the visceral afferent nerve fibres from the inferior aspect of pelvic organs/ NOT touching the peritoneum run alongside?
Parasympathetic fibres
Where do the visceral afferents from the inferior aspect of pelvic organs/NOT touching the peritoneum enter the spinal cord?
S2, S3, S4
Where is the S2, S3, S4 dermatome?
Perineum
How does pain sensation travel from the structures crossing pelvis to perineum below levator ani (i.e. in the perineum) to CNS?
Somatic sensory - pudendal nerve S2, S3, S4
Where do the somatic sensory nerve fibres from structures in the perineum enter the spinal cord?
S2, S3, S4
How does pain sensation travel from the structures crossing pelvis to perineum above levator ani (i.e. in the pelvis - urethra, vagina) to CNS?
Visceral afferents
What are the 2 important spinal cord levels with regards to pain from the female reproductive system?
T11 - L2
S2 - S4
Where is the ‘pelvic pain line’?
Peritoneum
Where does sympathetic outflow go from?
T1 - L2/L3
What are splanchnic nerves?
Paired visceral nerves
What do splanchnic nerves carry?
Fibres of the autonomic nervous system (visceral efferents) - all sympathetic except pelvic splanchinc which carry parasympathetic fibres
Sensory fibres from the organs (visceral afferents)
What are pelvic splanchnic nerves?
Splanchnic nerves that arise from sacral spinal nerves S2, S3, S4 to provide parasympathetic innervation to the hindgut
Where do the sympathetic nerves synapse?
Anterior to aorta - prevertebral ganglia
What do sympathetic nerves form at prevertebral ganglia?
Superior and inferior mesenteric ganglia
How do the sympathetic nerves reach the distal aspect of the fallopian tube?
‘Hitch a ride’ on periarticular plexis
What is the hypogastric nerve?
Transition between superior and inferior hypogastric plexuses
Where does the hypogastric nerve enter sympathetic chain?
T10 - L2
Where is the superior hypogastric plexus situated?
On vertebral bodies anterior to bifurcation of abdominal aorta
What does the superior hypogastric plexus contain?
Parasympathetic fibres which arise form pelvic splanchnic nerves S2 - S4
p - parasympathetic
p - pelvis
What does the inferior hypogastric plexus supply?
Viscera of pelvic cavity (visceral afferents)
What is the ilioinguinal nerve a branch of?
Lumbar plexus
What nerve root is ilioinguinal nerve?
L1
What modality is ilioinguinal nerve?
Motor
Sensory
What is the motor function of ilioinguinal nerve?
Internal oblique
Transverse abdominis
What is the sensory function of ilioinguinal nerve?
Skin on upper medial thigh
Skin over root of penis and anterior scrotum
Skin over mons pubis and labia majora
What nerve root is iliohypogastric nerve?
First major root of lumbar plexus - L1
Also T12
What modality is iliohypogastric nerve?
Motor
Sensory
What is the motor function of iliohypogastric nerve?
Internal oblique
Transverse abdominis
What is the sensory function of iliohypogastric nerve?
Posterolateral gluteal skin in pubic region
What sacral nerves is pudendal from?
S2, S3, S4
What modality is pudendal nerve?
Motor
Sensory
Does the pudendal nerve carry sympathetic and parasympathetic nerve fibres?
Sympathetic yes
Parasympathetic no
Name all the layers a needle passes through for a spinal anaesthetic (7)
Supraspinous ligament Interspinous space Ligamentum flavum Epidural space Dura mater Arachnoid mater Subarachnoid space (CSF)
At what vertebral level does the spinal cord become the cauda equina?
L2
At what vertebral level does the subarachnoid space end?
S2
At what vertebral level should spinal anaesthesia be injected?
L3 - L4 (L5)
What does a spinal anaesthetic anaesthetise?
Cauda equina (waist to toes)
What surgeries is spinal anaesthetic used for?
Prolapse repairs
Some hysterectomies
C-sections
What levels does the needle pass through in an epidural anaesthetic?
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Epidural space
At what vertebral level should epidural anaesthesia be injected?
L3 - L4
What is the aim of epidural?
Analgesia rather than complete lack of feeling
How can an epidural stop a patient feeling contractions?
Target specific nerves
Where does sympathetic outflow originate in the brain?
Autonomic centres
At what spinal nerve level does the sympathetic outflow exit?
T1 - L2
Once the sympathetic outflow exits the T1 - L2 spinal nerves, where does it travel?
To the sympathetic chains
That run the length of the vertebral column
Once the sympathetic outflow reaches the sympathetic chains, where does it pass into?
All spinal nerves - anterior and posterior rami and named nerves
How do sympathetic ganglia receive fibres below the L2 level?
From L2 level via sympathetic chain
Distributed via connections with lumbar, sacral and coccygeal spinal nerves
What is sympathetic tone?
Sympathetic fibres supply all arterioles
What effects does spinal anaesthetic have on sympathetic tone?
Blocks all sympathetic tone to all arterioles in lower limb
What vaso- effect does spinal anaesthetic have on sympathetic tone of aterioles?
Vasodilation
What are 3 signs that spinal anaesthetic is working? (i.e. signs of vasodilation)
Skin of lower limbs looks flushed
Warm lower limbs
Reduced sweating
Why does spinal anaesthetic cause reduced sweating?
No sympathetic input to glands
What is a risk/ complication of spinal anaesthesia?
Hypotension
What is the aim of a pudendal nerve block?
Anaesthetise majority of perineum
What surgeries/ procedures is a pudendal nerve block used for?
Episiotomy incision
Forceps use
Perineal stitching post-delivery
Painful delivery
What route is taken by pudendal nerve?
Exit pelvis via greater sciatic foramen
Passes posterior to sacrospinous ligament
Re-enters pelvis/ perineum via lesser sciatic foramen
Travels within Alcock’s canal
What is Alcock’s canal?
Passageway within obturator fascia
Pudendal nerve, internal pudendal artery and vein and nerve to obturator internus
What do branches of the pudendal nerve supply?
Perineum
What can be used as a landmark in a pudenal nerve block?
Ischial spine
What 2 incisions can be used for an episiotomy?
Medial
Mediolateral
Why is a medial incision episiotomy not used often?
Further tearing can occur that involves the anal sphinchter
Why is a mediolateral incision episiotomy used?
Incises into safe fat filled fossa
Avoids extension into rectum
What is a 1st degree perineal tear?
Through skin
What is a 2nd degree perineal tear?
Skin and mucosa
What is a 3rd degree perineal tear?
Severely through muscle
What is a 4th degree perineal tear?
Involves anal sphincter and rectal mucosa
Rare in UK
What can be the result of a perineal tear?
Weakened pelvic floor
Faecal incontinence
