Anatomy for Anaesthesia during Labour Flashcards
What are the nerve fibre types above the levator ani?
Pelvis
Body cavity - Sympathetic, Parasympathetic and Visceral Afferent
What are the nerve fibre types below the levator ani?
Perineum
Body wall - Somatic motor and Somatic sensory
What type of nerve is associated with pelvic floor muscle contraction eg when sneezing?
Somatic motor
What nerve type is associated with pain from the adnexae, uterus and pelvic part of the vagina?
Visceral afferents
What nerve type is associated with uterine cramping and contraction?
Hormonal - sympathetic/parasympathetic
What nerve type is associated with pain from the perineal part of the vagina and pain in the perineum?
Somatic sensory
In the SUPERIOR aspect of pelvic organs - those TOUCHING the peritoneum how do nerves reach the CNS?
Where does the patient perceive this pain?
VISCERAL afferents run alongside SYMPATHETIC fibres and entre spinal cord between levels T11-L2
SUPRAPUBIC pain
In the INFERIOR aspect of pelvic organs - those NOT TOUCHING the peritoneum - how do the nerves reach the peritoneum?
Where does the patient perceive this pain?
VISCERAL afferents run alongside PARASYMPATHETIC fibres to spinal cord levels S2, S3 and S4
Pain in S2, S3 and S4 dermatome - perineum
Below the levator ani describe the nerves, pain perception and spinal cord level
Somatic sensory
Pudendal nerve
S2, S3 and S4
Localised pain within perineum
Which are the two important spinal cord levels in the female reproductive system (and have a think about why!)
T11-L2
S2-S4
What is the major nerve supplying for pain sensation below the levator ani?
What does it innervate and what spinal levels does it go to?
pudendal nerve back to S2-S4: from those organs/structures within the perineum = inferior vagina, perineal muscles, glands, skin.
In the peritoneum but ABOVE the levator ani - describe sensation, what innervated and spinal level
visceral afferents back to S2-S4: from pelvic organs inferior to peritoneum – cervix and superior vagina
Where does the spinal cord become cauda equina?
L2
Where does subarachnoid space end?
S2
For a SPINAL anaesthetic where is the anaesthetic injected and at what level of the spine
Subarachnoid space
L3-L5
What does a spinal anaesthetise?
Cauda Equina
Name the structures that the needle passes in a spinal?
Needle passes through: - supraspinous ligament
- interspinous ligament
- ligamentum flavum
- epidural space (fat and veins)
- dura mater
- arachnoid mater
- finally reaches subarachnoid space (contains CSF)
What spinal level and to where is the epidural anaesthetic delivered?
L3/L4
Epidural space
What does the needle pass through for an epidural?
Needle passes through:
- supraspinous ligament
- interspinous ligament
- ligamentum flavum
- epidural space (fat and veins)
Where do sympathetic nerves exit the spinal cord?
With T1-L2 spinal nerves
Sympathetic fibres are in ALL spinal nerves and their named nerves.. With this in mind what do you expect to see in spinal anaesthesia?
Blockade of sympathetic tone to all arterioles in lower limb = Vasodilation - skin of lower limbs looks flushed - warm lower limbs - reduced sweating
If spinal anaesthetic is working what happens to the patient’s BP and why?
HYPOTENSION
Due to vasodilation
What branch of sacral plexus is pudendal nerve?
S2, S3 and S4
Describe when a pudendal nerve block would be useful (3)
Anaesthetise majority of perineum
Useful for
episiotomy incision
forceps use
perineal stitching post delivery
