Anatomy of Anaesthesia in Labour Flashcards
Define the distinction between the pelvis and the perineum
above levator ani = pelvis
below= perineum
How do visceral afferents from superior pelvic organs/those touching the peritoneum enter the spinal cord
run alongside SYMPATHETIC NERVE fibres
enter at T11-L2
where is pain felt from the superior pelvic organs
as suprapubic
How do visceral afferents from the inferior pelvic organs enter the spinal cord
run alongside PARASYMPATHETICS
enter spinal cord at S2, 3, 4
how is pain from the inferior pelvic organs felt
in a dermatomal distribution S2, 3, 4
How does pain from structures below the levator ani i.e. in the perineum enter the spinal cord
Somatic sensory - via the pudendal nerve
levels S2, 3, 4
how is pian below the levator ani felt as
localised to the area within the perineum
At what level does the spinal cord become the cauda equina
L2
When does the subarachnoid space end
S2
At what level of the spinal cord is anaesthesia usually injected into
L3-L4
Name all the ligaments that the needle passes through in either a spinal or epidural
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
What is the difference between a spinal and epidural
Spinal - into subarachnoid space
Epidural - epidural space
Where do sympathetic nerves exit the spinal cord
T1-L2
What effect does the anaesthetic have on the arterioles
Affects sympathetic fibres - which supply all arterioles
results in vasodilation
What can happen in a spinal/epidural due to vasodilation
skin of lower limbs looks flushed
warm lower limbs
reduced sweating
HYPOTENSION
What does the pudendal nerce supply
the perineum
what is the routes of the pudendal nerve
branch of sacral plexus S2, 3, 4
When is a pudendal nerve block used
Episiotomy
Forceps use
Perineal stitching post delivery
Describe the course of the pudendal nerve
exits pelvis via greater sciatic foramen
Passes posterior to sacrospinous ligament
Re-enters pelvis/perineum via the lesser sciatic foramen
Travels in pudendal canal
To supply the perineum
where is the pudendal canal
a passageway within the obturator fascia (also contains internal pudendal artery and vein and nerve to obturator internus)
How is the location to inject anaestetic for a pudendal nerve block determined
The ischal spine is palpated transvaginally and used as a landmark
The pudendal nerve crosses the lateral aspect of the sacrospinous ligamnent
Why is an episiotomy done
a posteriolaterl incision into the ischioanal fossa - prevents tearing into the anal spincter and anus/rectum.
