Anatomy of the Anaesthesia of Labour Flashcards
What type of nerve fibres will supply structures in the pelvic cavity?
Sympathetic or parasympathetic
Visceral afferents
What type of nerve fibres will supply structures in the perineum?
Somatic motor
Somatic sensory
How can we tell what is the pelvis and what is the perineum
Above levator ani= pelvis
Below= perineum
What type of nerve fibres will sense pain in the superior aspect of the pelvic organs ie the part touching the peritoneum
Visceral afferent
How do visceral afferents enter the spinal cord and at what level do they enter
travel alongside sympathetic nerve fibres
T11-L2
How is pain in the superior aspect of the pelvic organs perceived by the patient
Suprapubic
What type of nerve fibres sense pain in the inferior aspect of the pelvic organs
visceral afferents
How do nerve fibres sensing pain in the inferior aspect of the pelvic organs get to the spinal cord and at what level do they enter
alongside parasympathetics
enter at S2, 3 and 4
WHere is pain perceive from the inferor aspect of pelvic orgaisn
S2,3 and 4 dermatome
What type of nerve fibres innervate structures what pass throught the perineum eg vagina, urethra
ABOVE (pelvis)- visceral afferents, parasympathetic, spinal cord levels S2, 3, 4
BELOW (perineum)- somatic sensory, pudendal nerve, S2, 3, 4
At what point does the spinal cord become the cauda equina
L2 vertebrae
Where does the subarachnoid space end
S2
Where is anaesthesia injected to in a spinal and epidural anaestetic
L3-L5 region
Name the levels that the needle will pass through when giving a spinal anaesthetic
Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural Space Dura mater Arachnoid mater The it reaches the subarachnoid space
What is the difference between an epidural and a spinal anaesthetic
- Epidural injected into epidural space but spinal goes into subarachnoid space
- epidural can be used anywhere in spinal cord, spinal cannot
What is a caudal epidural
anaesthetic inject through sacral hiatus (instead of L3/4)
what is a 1st degree tear
skin
not usually stitched up
2nd degree
skin
peritoneal muscle
usually stitched up
3rd degree
skin
peritoneal muscle
anal sphincter
needs stitched up
4th degree
skin
peritoneal muscle
anal sphincter
rectum
Where do sympathetic nerves exit the spinal cord?
T1-L2
What signs in the lower limbs may indicate that spinal anaestetic is working and why
skin is flushed
warm
reduced sweating
blockade of sympathetic tone causes vasodilation
What type of nerve fibres is the pudendal nerv
somatic motor and somatic sensory to the perineum
What are the roots of the pudendal nerve
S2, 3, 4
When may a pudendal nerve block be used
episiotomy
forceps
perineal stitching post delivery
Describe the pathway of the pudendal nerve
- exits the pelvis via the greater sciatic foramen
- passes posterior to sacrospinous ligament
- re-enters pelvis/perineum via lesser sciatic foramen
- travels in pudendal canal
What is the pudendal canal
passageway withing the obturator fascia
with internal pudendal artery and vein (and nerve to obturator internus)
How does the clinician know where to inject the anaesthesia in pudendal nervw block
Pudendal nerve crosses the latera aspect of sacrospinal ligament
-ischial spine can be used as a landmark to administer blocj
What can result from damage to the pudendal nerve/levator ani or externa anal sphincter during labout
weak pelvic foor
faecal incontinence
What is a episiotomy
posterolateral (mediolateral incision) made into the ischioanal fossa to avoid incision or tearing into the rectum during labour
Median incisions used less often as tearing of these further will restul in damage to the anal sphincter
