Anatomy of Anaesthesia for Labour Flashcards
List nerves associated with the perineum
BODY WALL
Somatic motor
Somatic sensory
List nerves associated with the pelvis
BODY CAVITY
Sympathetic
Parasympathetic
Visceral afferent
Which nerve structures transmit pain from the pelvis?
Visceral afferents - sympathetic or parasympathetic
Which nerve structures transmit pain from the perineum?
Pudenal nerve - somatic sensory
Where do visceral afferents enter the spinal cord for pelvic organs that TOUCH THE PERITONEUM? Where is pain perceived? List these organs
T11-L2 via sympathetic fibres
Suprapubic region
Uterine tubes, uterus, ovaries
Where do visceral afferents enter the spinal cord for pelvic organs that are not touching the peritoneum (ABOVE LEVATOR ANI)? Where is pain perceived? List these organs
S2-S4 via parasympathetic fibres
S2,3,4 dermatome
Cervix and superior vagina
Where does the pudenal nerve enter the spinal cord for structures in the perineum (BELOW LEVATOR ANI)? Where is pain perceived? List these organs
S2-S4 via somatic sensory fibres
Localised pain in perineum
Inferior vagina, perineal muscles, glands, skin
Structures above levator ani are supplied by which nerve fibres?
IN PELVIS
Visceral afferents
Structures below levator ani are supplied by which nerve fibres?
IN PERINEUM
Pudenal nerve
What type of anaesthesia targets intraperitoneal, subperitoneal and somatic structures?
Spinal anaesthetic
What type of anaesthesia targets subperitoneal and somatic structures?
Epidural anaesthetic
What type of anaesthesia targets somatic structures only?
Pudenal nerve block
Spinal cord becomes cauda equina at what vertebral level?
L2 vertebra
SAS ends at which vertebral level?
S2
Anaesthesia is injected into which vertebral region?
L3-L4 to anaesthetise cauda equina
What is the surface landmark for injecting anaesthesia?
L4 spinous process
Superior point on iliac crests
Describe the layers a needle passes through for spinal anaesthetic
Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space Dura matter Arachnoid matter SAS with CSF
Describe the layers a needle passes through for epidural anaesthetic
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Epidural space
What is the distinguishing feature of ligamentum flavum?
Yellow as it is elastic
Describe sympathetic outflow below L2 vertebra
Sympathetic ganglia receive fibres from L2 via sympathetic chain
Distribute to lumbar, sacral, coccygeal spinal nerves
All spinal nerves and named nerves contain sympathetic fibres. True/ False?
True
What do sympathetic fibres supply, creating sympathetic tone? Blockage of sympathetic tone causes…
All arterioles
Vasodilatation
List signs that spinal anaesthetic is working
Flushed lower limbs
Warm lower limbs
Reduced sweating
The pudenal nerve supplies all of the perineum. True/False?
False
Supplies most of it - also supplied by ilioinguinal nerve
Outline the route taken by the pudenal nerve to structures of the perineum
Exits pelvis via greater sciatic foramen –>
Passes posterior to sacrospinous ligament –>
Reenters pelvis/ perineum via lesser sciatic foramen –>
Travels in pudenal canal –>
Branches supply perineum
What is the pudenal canal?
Passage in obturator fascia containing internal pudenal artery and vein, pudenal nerve and nerve to obturator internus
Which bony landmark is used in the administration of pudenal nerve block?
Ischial spine
List instances in which a pudenal nerve block can be applied
Labour
Forceps delivery
Vaginal delivery
Epiostomy
During labour, branches of which nerve can be torn?
Pudenal nerve (supplying levator ani and external anal sphincter)
Which component of the levator ani is typically torn fist during labour?
Puborectalis
How is tearing in the perineum during childbirth described?
First degree
Second degree
Third degree
What is the clinical significance of damage to dtructures due to perineal tearing?
Weakened pelvic floor
Faecal incontinence
What is an ‘epiostomy’
A surgical cut made at the opening of the vagina during childbirth, to aid a difficult delivery and prevent rupture of tissues
List types of epiostomy incision
Posterolateral
Median
A posterolateral epiostomy incision is made into which anatomical structure?
Ischioanal fossae
A median incision is not used as often as it can damage which structure?
External anal sphincter if further tearing occurs posteriorly
The pudenal canal passes on the surface of which muscle?
Obturator internus
