Help in Labour - Epidural & Spinal (W/S 8) Flashcards
What is neuraxial blockade?
The administration of analgesics into the epidural or spinal space.
- Enables analgesics to be administered close to the spinal nerves and spinal cord where they can have a powerful analgesic effect.
What do we mean by “neuraxial” blocks?
Epidurals and spinals - the neural axis of the body
What are spinals and epidurals used for?
Pain relief:
- Labour
- During caesareans
- After caesareans
- After other types of surgery
What influences women’s expectations around pain in labour?
- Background
- Peer influences
- Culture
- Geography
- Availability
How do epidurals and spinals work?
- They work by blocking pain fibres.
By directly blocking the pain fibres epidurals can selectively block pain transmission
Selectively blocking pain fibres decreases side effects e.g. nausea/vomiting with
intravenous medications
Describe the main function of the vertebral column and the anatomy of the vertebrae.
The vertebral column protects the spinal cord and consists of vertebrae divided into 5 regions:
- Cervical -7
- Thoracic -12
- Lumbar -5
- Sacral -5 fused
- Caudal (Coccyx) -4 fused
What ligaments are found along the vertebral column?
Supraspinous
- Strong and fibrous
- Thickest in lumbar region
Interspinous
- Thin membranous
- Thickest in lumbar region
Ligamentum flavum
- Yellow ligament
- Comprises of elastic fibres
- Connects adjacent laminae of vertebrae
Longitudinal ligaments
- The anterior and posterior longitudinal ligaments bind the vertebral bodies together
What are meninges?
3 connective tissue layers that run continuously around the spinal cord and brain providing protection and containing cerebrospinal fluid (CSF)
What are the meninges layers?
(DAP)
Dura mater
- Outermost layer
- Tough fibrous membrane continuous with cerebral dura
- The epidural space lies between this and the ligamentum flavum
Arachnoid mater
- Middle layer
- Delicate, non-vascular, closely attached to the dura
Pia mater
- Delicate highly vascular membrane closely surrounding the spinal cord and brain
What are the spinal layers?
(SPADE)
Spinal cord Pia mater (Subarachnoid cavity) Arachnoid mater (Subdural cavity) Dura mater Epidural space (Ligamentum flavum)
A spinal purposely punctures what spinal layer?
Dura mater
What is the spinal cord protected by?
By the bony vertebrae, intervertebral ligaments
and CSF.
The spinal cord extends from where to where?
The spinal cord extends from the FORAMEN MAGNUM at the base of the skull to L1
From L1 is a bundle of nerve roots called what?
The cauda equina
What are the three types of nerves?
- Sensory
- Motor
- Autonomic (sympathetic)
Describe sensory nerves.
- Carry messages about touch (pain, temperature, touch and pressure)
- Large and small diameter
- Enter the spinal cord through posterior roots and can be followed into the dorsal horns of the grey matter
Describe motor nerves.
- Carry message to the muscles
- Large diameter
- Formed in anterior root nerves
Describe autonomic (sympathetic) nerves.
- Maintain venous and arterial tone
- Small diameter
- Regulates autonomic tone (cardiovascular, GIT, endocrine)
- Formed in anterior root nerves
How do we assess which nerves are affected by an epidural / spinal?
By testing dermatomes (and therefore efficacy of the epidural block)
What affect does local anesthetic have on nerve impluses from spinal nerves?
When local anaesthetic is used there is an interruption
of the conduction of the nerve impulses from these spinal nerves.
What are the reasons for checking dermatomes?
To check for:
- Unilateral block (only covering one side)
- High block (above T4)
- Low block (not covering incision/contractions)
- Adequate block but still experiencing pain
(requires larger opioid doses)
When should dermatomes be checked?
- Prior to giving a bolus containing local anaesthetic and 20 minutes following the bolus
- Prior to leaving the recovery room in theatre
- Prior to increasing an epidural infusion rate containing local anaesthetic and 20 minutes following the increase
- Poor pain control
- If you suspect the block may be high
- Three times in 24 hours (at the beginning of each shift)
- Only when local anaesthetic is used
How do you test dermatomes?
By applying an ice pack to the skin surface assesses sensory block.
- Apply the ice pack at a level you would expect to have normal sensation (e.g. face). The woman
should be able to describe as “cold”. - Assessment is then done bilaterally one side at a time. Commence on the outer thigh and slowly make
your way up at increments of approximately 3-4 cm. - The level below where the woman feels normal cold sensation is the upper level of the sensory block.
What ilevel of block is required for normal labour?
Need block from T10 (umbilicus) to S1
(Or to S5 for operative vaginal birth - sit woman up
for this top up so that LA moves into S5 area)
What level of block is required for a caesarean section?
Need block from T4 (nipple level) to S5 (sacral area)
