Anatomy 5 - Anatomy of Anaesthesia for Labour Flashcards
Which type of nerves supply structures in the pelvis?
Sympathetic
Parasympathetic
Visceral afferent
(body cavity)
Which type of nerve supply structures in the perineum?
Somatic motor
Somatic sensory
What type of nerves cause uterine cramping/ contraction?
Sympathetic/ parasympathetic (under hormonal influence)
What type of nerves cause pelvic floor muscle contraction?
Somatic motor
What type of nerves cause pain from the annexe (ovaries + fallopian tubes)?
Visceral afferents
What type of nerves cause pain from the uterus?
Visceral afferents
What type of nerves cause pain from the vagina?
Visceral afferents (pelvic part) Somatic sensory (perineum)
What type of nerves cause pain from the perineum?
Somatic sensory
How do visceral afferent nerves from the superior aspect of pelvic organs (those touching the peritoneum) enter the spinal cord?
Run alongside the sympathetic fibres entering the spinal cord between levels T11-L2
Where is pain from superior aspect of pelvic organs (those touching the peritoneum) felt by the patient?
Suprapubic
How do visceral afferent nerves from the inferior aspect of pelvic organs (those not touching the peritoneum) enter the spinal cord?
Run alongside parasympathetic fibres entering the spinal cord at levels S2, 3, 4
Where is pain from inferior aspect of pelvic organs (those not touching the peritoneum) felt by the patient?
Perineum (S2, 3, 4 dermatome)
How do visceral afferent nerves from structures passing from pelvis to perineum located in the pelvis enter the spinal cord?
Run alongside the parasympathetic nerves and enter at levels S2, 3, 4
How do somatic sensory nerves from structures crossing from pelvis to perineum in the perineum pass into the spinal cord?
Via pudendal nerve to spinal cord S2, S3, S4
What are the 3 main types of anaesthesia used in pregnancy?
Spinal anaesthetic
Epidural anaesthetic
Pudendal nerve block
What type of structures does a spinal block via lumbar puncture anaesthetise?
Intraperitoneal viscera
Subperitoneal viscera
Somatic structures
What type of structures does a caudal epidural block anaesthetise?
Subperitoneal viscera
Somatic structures
What type of structures does a pudendal nerve block anaesthetise?
Somatic structures
At what vertebral level does the spinal cord become caudal equina?
L2 vertebra
At what spinal cord level does the subarachnoid space end?
S2
Between what spinal level is anaesthetic injected?
L3-L4 (L5) region
What structures does a needle pass through when giving a spinal anaesthetic? (7)
Supraspinous ligament interspinous ligament ligamentum flavum epidural space (fat and veins) dura mater arachnoid mater finally reaches subarachnoid space (contains CSF)
What structures does a needle pass through when giving an epidural anaesthetic? (4)
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Epidural space (fat and veins)
Which spinal nerves contain sympathetic fibres?
All (including named nerves e.g. femoral, sciatic, obturator, pudendal)
What happens when giving a spinal anaesthetic due to the blockade of sympathetic ton e to all arterioles in the lower limb?
Vasodilation (skin looks flushed, warm lower limbs)
Reduced sweating
-> hypotension
Nerve roots of pudendal nerve?
S2, S3, S4
Nerve modalities of pudendal nerve?
Somatic motor
Somatic sensory
Effect of pudendal nerve block?
Anaesthetises the majority of the perineum
3 circumstances when pudendal nerve block may be used?
Episiotomy incision
Forceps use
Perineal stitching post delivery
How does the pudendal nerve exit the pelvis?
Greater sciatic foramen
Where does the pudendal nerve pass in relation to the sacrospinous ligament?
Posterior
How does the pudendal nerve re-enter the pelvis/ perineum?
Via the lesser sciatic foramen
What 4 structures pass within the pudendal canal?
Pudendal nerve
Internal pudendal artery and vein
Nerve to obtruator itnernus
What is the pudendal canal a passageway through?
Obturator fascia
What is used as a landmark of where to administer a pudendal nerve block?
Ischial spine
