clinical anatomy of anaesthesia for labour Flashcards
what are reproductive system motor functions?
-Uterine ‘cramping’ (menstruation)
-Uterine contraction (labour)
-Pelvic floor muscle contraction (during sneezing)
What are the reproductive system sensory (pain) functions?
- Pain from the adnexae (ovaries and fallopian tube)
- Pain from the uterus
- Pain from the vagina
- Pain from the perineum
what muscle splits the pelvis and perineum?
levator ani muscle
above= pelvis
below= perineum
what type of nerve fibres are found in the pelvis?
This is the body cavity and so there will be:
-sympathetic
-parasympathetic
-visceral afferent (sensory info e.g. distention of organs)
what type of nerve fibres are found in the perineum?
this is a body wall and so there will be:
-somatic motor
-somatic sensory
what nerves supply motor innervation to uterine cramping and what controls it?
-sympathetic/ parasympathetic nerve fibres driven by hormonal control
uterus is in the body cavity and so there will be:
-sympathetic (motor)
-parasympathetic (motor)
-visceral afferent (sensory info e.g. distention of organs)
what nerves supply motor innervation to uterine contraction and what controls it?
-sympathetic/ parasympathetic nerve fibres driven by hormonal control
uterus is in the body cavity and so there will be:
-sympathetic (motor)
-parasympathetic (motor)
-visceral afferent (sensory info e.g. distention of organs)
what nerves supply motor innervation to pelvic floor muscle contraction?
somatic motor
perineum is a body wall and so there will be:
-somatic motor
-somatic sensory
what nerves supply the sensory innervation for pain in the adnexae (ovaries + fallopian tubes)
Visceral afferents
adnexae in the body cavity and so there will be:
-sympathetic (motor)
-parasympathetic (motor)
-visceral afferent (sensory info e.g. distention of organs)
what nerves supply the sensory innervation for pain in the uterus?
Visceral afferents
uterus is in the body cavity and so there will be:
-sympathetic (motor)
-parasympathetic (motor)
-visceral afferent (sensory info e.g. distention of organs)
what nerves supply the sensory innervation for pain in the vagina?
Pelvic part- visceral afferent
Perineum part- somatic sensory
what nerves supply the sensory innervation for pain in the perineum?
perineum is a body wall and so there will be:
-somatic motor
-somatic sensory
what nerve supplies somatic sensation to the perineum
pudendal nerve (S2-S4)
where is pain perceived from superior aspect or pelvic organs/ parts touching the peritoneum?
Perceived as suprapubic pain from the patient
why is pain from the superior aspect of pelvic organs (parts touching the peritoneum) perceived as suprapubic pain in patients?
-This pain comes from visceral afferents
-Visceral afferents touching the peritoneum run alongside sympathetic fibres (along side not in!)
-The visceral afferents enter the spinal cord beside the sympathetic fibres between levels T11- L2 causing pain to be perceived as suprapubic
why is pain from the inferior aspect of pelvic organs (parts NOT touching the peritoneum) perceived as perineum pain in patients?
-This pain comes from visceral afferents
-Visceral afferents NOT touching the peritoneum run alongside parasympathetic fibres (along side not in!)
-The visceral afferents enter the spinal cord beside the sympathetic fibres between levels S2, S3, S4 causing pain to be perceived from the perineum (S2, S3, S4 level)
Where is pain from structures in the pelvis (above levator ani) felt and why?
Just like pain from structures not touching the peritoneum
-This pain comes from visceral afferents as it is part of the body cavity
-Visceral afferents run alongside parasympathetic fibres (along side not in!)
-The visceral afferents enter the spinal cord beside the sympathetic fibres between levels S2, S3, S4 causing pain to be perceived from the perineum (S2, S3, S4 level)
where is pain felt from structures in the perineum (below levator ani) felt and why?
- the pain comes from somatic sensory nerves as it is part of the body wall
-in the perineum this is the pudendal nerve
-perineum enters the spinal cord at levels S2, S3 and S4 meaning that the pain is felt localised (sharp and stabbing) in the perineum
Autonomic nerves of the pelvis:
-where do the sympathetics originate from and travel to?
-sympathetic fibres originate and come out at T11- L2
-they then travel down the sacral sympathetic trunks and form the superior hypogastric plexus
-sympathetic fibres come out of the superior hypogastric plexus and supply the pelvis/ perineum with visceral motor innervation
Autonomic nerves of the pelvis:
-where do the parasympathetics originate from and travel to?
-Parasympathetics originate from S2, S3, S4 spinal cord level (sacral outflow)
-they then travel in the pelvic splanchnic nerves
-these contribute to the inferior hypogastric plexus and mix with the sympathetic autonomic nerves to give rise to the mixed autonomic nerves of the pelvis
what female reproductive structures in the body cavity touch the peritoneum?
Uterine tubes
Uterus
Ovaries
what nerves supply sensory innervation to uterine tubes, uterus and ovaries, where is the pain felt and why?
Visceral afferents supply uterine tubes, uterus and ovaries as they are in the body cavity (above levator ani)
- touching the peritoneum so visceral afferents run alongside sympathetic fibres (along side not in!)
-The visceral afferents enter the spinal cord beside the sympathetic fibres between levels T11- L2 causing pain to be perceived as suprapubic
what nerves supply sensory innervation to superior part of vagina and cervix where is the pain felt and why?
Visceral afferents supply superior part of vagina and cervix as they are in the body cavity (above levator ani)
-NOT touching the peritoneum so visceral afferents run alongside parasympathetic fibres (along side not in!)
-The visceral afferents enter the spinal cord beside the sympathetic fibres between levels S2, S3, S4 causing pain to be perceived from the perineum (S2, S3, S4 level)
where does the spinal cord end and become the cauda equina?
L2 vertebra
where does the subarachnoid space end?
S2 level
where is anaesthetic injected for a spinal/ epidural anesthetic?
L3-L4 intervertebral space
sometimes the L4-L5
when administering an epidural, what structures must the needle pass through?
-supraspinous ligament
-interspinous ligament
-ligamentum flavum (will feel pop)
-epidural space
what is the epidural space filled with
fat and veins
when administering a spinal anaesthetic, what structures must the needle pass through?
-supraspinatous ligament
-interspinous ligament
-ligamentum flavum (will feel pop)
-epidural space
-dura mater
-arachnoid mater
-reaches subarachnoid space (containing CSF)
when spinal anaesthetic is delivered are motor or sensory fibres blocked?
Both motor (including sympathetic) and sensory fibres are blocked
what spinal nerves contain sympathetic fibres?
all spinal nerves contain sympathetic fibres
what arterials do sympathetic fibres supply?
all arterioles
what affect do sympathetic fibres have on arterioles
cause vasoconstriction
what affect does spinal anaesthesia have on arterioles in the lower limb, why and what is overall affect?
-at this level is causes blackade of sympathetic tone to all arterioles of lower limb causing vasodilation
-this leads to warmth and reduced sweating in lower limb
-can also cause hypotension (monitor patient closely!)
where do sympathetic nerves exit the spinal cord?
between T1- L2 with the spinal nerves
what plexus is the pudendal nerve a branch of?
S2, S3, S4
How does the pudendal nerve exit the pelvis and enter perineum?
-exits the pelvis via the greater sciatic foramen
-travels posterior to the sacrospinous ligament
-reenters at the pelvis/ perineum via the lesser sciatic foramen
-travels in pudendal canal
how is a pudendal nerve block administered?
The pudendal nerve passes the posterior of the sacrospinous ligament
-the ischael spine can be felt as a bony landmark and the nerve block is delivered either through the skin or more commonly internal and aim slightly medial to this
when would a pudendal nerve block be administered in/ after labour?
-forceps delivery
-painful vaginal delivery
-episiotomy incision
-perineal suturing post delivery
what inciscion can be done to try and prevent anal tearing during labour?
episiotomy
-posterolateral incision
sometimes mediolateral but this is more often avoided
