Anaatomy of Anaesthesia for Labour Flashcards
What motor functions are involved in the female reproductive system?
- uterine cramping (menstruation)
- uterine contraction (labour)
- pelvic floor muscle contraction (during sneezing)
Sensory pains from the reproductive system?
- pain from the adnexae, uterus, vagina, perineum
What separates the pelvis from the perineum?
- Levator Ani Muscle
Structures in the pelvis?
- body cavity (organs: uterus, bladder, rectum)
- sympathetic, parasympathetic and visceral afferent
Structures in the perineum?
- body WALL
- somatic MOTOR and sensory
What motor function in the reproductive system is controlled hormonally?
- uterine cramping and contraction
What are the sources of visceral afferent pains?
-pain from the adnexae, uterus, vagina (pelvic part)
What parts of the reproductive system are under somatic sensory ?
- perineum part of the vagina
- pain from the perineum
How different is the sensory nerve supply between the superior aspect of the pelvic organs and the inferior aspect?
- pelvic organs in contact with peritoneum: VISCERAL afferents (run alongside sympathetic fibres)
- inferior aspect of pelvic organs: also VISCERAL afferent (runs along PARASYMPATH.)
Where does the sensory supply enter at the spinal cord in the superior aspect of the pelvic organs vs the inferior?
- superior: T11-T12
- Inferior: S2-S4
Where is the pain perceived to be with regards to whether it’s the superior or inferior aspect of the pelvic organs?
- Pain of the superior aspect: SUPRAPUBIC area
- pain from the inferior aspect: S2-S4 dermatome (perineum)
Distinct nerve supply for structures that cross over from the pelvis to the perineum.
- above the L.ani: visceral afferents/parasympa/S2-S4
- Below the L.ani: somatic sensory / PUDENDAL nerve/ S2-S4 —–pain localized to perineum
Where do the sympathetics arise from in spinal cord?
- sacral sympathetic trunks
- T11-L2
- Superior Hypogastric Plexus
Where do the parasympathetics arise from?
- sacral outflow (S2-s4)
- pelvic splanchnic nerves ; from spinal roots
- —-mixes with sympathetics in the inferior hypogastric plexus
What pelvic organs touch the peritoneum?
Spinal cord levels?
- uterine tubes
- uterus- ovaries
- —T11 -L2
INferior aspect, pelvic organs?
- cervix
- superior vagina
Structures within the perineum somative nerve supply and to which spinal level?
- Pudendal nerve back to S2-S4
- —–inferior vagina, perineal muscles, glands and skin
Where is the spinal anaesthetic given at and when?
- spinal block via Lumbar Puncture (anesthetisizes from waist down - intra+subperitoneal + somatic areas)
When is the caudal epidural nerve block given?
- anesthetisize areas innervated by the pudendal nerve + subperitoneal areas
Pudendal nerve block is specifically to block
—pudendal nerve supply to the majority of the PERINEUM
Site for injection of the spinal and epidural anaesthetic?
- L3-L4 (L5)
TRANSVERSE line from the superior points of the iliac crests
When does the spinal cord become the cauda equina?
- L2
When does the subarachnoid space end?
S2
What does the epidural anaesthetic pass through?
- supraspinous Ligament
- interspinous ligament
- ligamentum flavum
- epidural space
What does the spinal anaesthetic pass through?
- supra->infra-spinous ligament
- ligamentum flavum
- epidural space
- DURA mater
- arachnoid mater
- subarachnoid space
Where does the sympathetic outflow originate from? And where do they exit from and travel to next?
- the autonomic centres IN the brain
- —-sympathetic nerve sEXIT the spinal cord with T1-L2 spinal nerves> travels to the sympathetic chains
Where does the sympathetic supply originate from below L2?
- from L2 level via the sympathetic chain
- —distributes them via the Lumbar, Sacral and coccygeal spinal nerves
Where are sympathetic nerves found?
- in ALL spinal nerves and their named nerves (femoral, sciatic, obturator, pudendal)
What does the sympathetic fibres supply ? Blockade of these sympathetic fibres?
- -supplies all arterioles
- blockade of sympathetic tone > vasodilation of the lower limb arterioles
What are signs of the spinal anaesthetic working ?
- skin of lower limbs looks FLUSHED
- WARM lower limbs
- reduced sweating
What is the risk of spinal anaesthesia?
- HYPOTENSION
What is the role of the pudendal nerve across the systems?
- GI system
- Renal System
- role in MOTOR control of external anal and external urethral sphincters
What is the course of the pudendal nerve ?
- Exists pelvis via Greater Sciatic Foramen > passes POSTERIOR to sacrospinous ligament> RE-ENTERS pelvis via lesser sciatic foramen …
And what is the course of the pudendal nerve once it has re-entered the pelvis?
- travels in pudendal canal with the INTERNAL pudendal ARTERY and VEIN (and Nerve to obturator internus)….then branches out to supply perineal structures
What makes up the pudendal canal ?
- the passageway within the obturator fascia
How is the pudendal nerve block administered?
- via vaginal insertion; the ischial spine is palpated and used as a landmark to administer nerve block
When is the pudendal nerve block performed?
- during labour
(forceps delivery/painful vaginal delivery) - episiotomy incision
- Perineal suturing POST delivery (LA is injected along site of tear/episiotomy) to anesthetise branches.
Can the pudendal nerve be damaged during labour? How?
- brs. of the the nerve can be STRETCHED with resultant stretch of the nerve fibres
- —fibres within the levator ani/ext. anal sphincter m. could be torn and as a result = muscle weakness
Risk of multiple pregnancies?
- weakened pelvic floor
- fecal incontinence
What may occur with a perineal tear extending posteriorly?
—-may involve the external anal sphincter
Where is the episiotomy conducted?
- made into the fat filled ischioanal fossa
- –avoids the extension of the incision into the rectum
