FRCA Notes

Epidural Analgesia for Labour

The curriculum asks us to describe "epidural or CSE analgesia in labour and... the indications, contraindications and complications"

Resources

  • Epidural analgesia remains the gold-standard for labour analgesia

Indications

Specific obstetric benefits

  • Higher patient satisfaction
  • Increased safety vs. GA if top-up used
  • Improved post-operative analgesia

Generic perioperative physiological benefits

Respiratory Cardiovascular Gastrointestinal Metabolic Haematological
↑ FVC at 24hrs ↓ incidence of post-operative MI Earlier return of GI motility ↓ catecholamines ↓ incidence of VTE
↑ FRC / reduced atelectasis ↓ incidence of post-operative HF Earlier return of enteral feeding ↓ cortisol Improved surgical graft function
↓ risk of pneumonia (39%) ↑ splanchnic blood flow Better glycaemic control ↓ blood loss
↓ opioid-induced respiratory depression



Absolute Relative
Patient refusal Unstable hypovolaemia or cardiovascular disease
Allergy to constituent drugs Anatomical abnormalities of the spine e.g. spina bifida
Coagulopathy:
INR>1.4
Platelets <50 x 109/L
Use of anticoagulants		 Platelets <80 x 109/L
Sepsis Raised WCC and/or CRP
Raised ICP
Lack of trained staff
Lack of suitable equipment


  • The data for this section largely comes from NAP3
  • Fortunately for the parturient, obstetric epidurals have a lower incidence of complicaitons than epidurals inserted in other settings

Inadequate analgesia (1 in 10)

  • Failure rate may be as high as 33% in obese patients
  • Re-site rate increases linearly with BMI

  • The dose required for an epidural to work is dependent on several factors
  • Approximately 1-2ml of LA is required per segment to be blocked

  • The incidence of inadequate analgesia can be reduced by:
    • LOR to saline rather than air reduces patchy block
    • Senior anaesthetist inserting

  • Trouble-shooting:
    • Ensure appropriate connections and functioning of equipment
    • Low block may necessitate further boluses of LA ± increased infusion rate
    • Unilateral block may require altered positioning ± withdrawal of catheter 1cm
    • Patchy block may require boluses of LA / fentanyl

Dural puncture and PDPH (1 in 100)

  • Higher prevalence in obese patients: 4 in 100
  • ncidence reduced by:
    • LOR to saline rather than air
    • Ultrasound guidance
    • Senior anaesthetist
  • See separate page on PDPH

Intrathecal injection and high/total spinal

  • Intrathecal injection produces a rapidly ascending block with characteristics of a spinal anaesthetic
  • See separate page on managing high neuraxial block

Neurological sequelae

  • Temporary nerve damage: 1 in 1,000
  • Permanent nerve damage: 1 in 15,000

Opioid-related side-effects

  • Itching (10%)
  • Nausea and vomiting
  • Shivering
  • Urinary retention and need for IDC
  • Delayed respiratory depression

Hypotension

  • A common occurrence
  • If block level is above T4, reduce the rate of infusion
  • Look for and treat other causes of hypotension

Infection

  • Epidurals cause an increase in body temperature/hyperthermia (BJA, 2021)
  • Epidural abscess: 2 in 100,000
  • Meningitis: 1.5 in 10,000
  • Most common organism is Staph. aureus

Obstetric-specific

  • Do not increase risk of LSCS
  • Do not increase duration of the 1st stage of labour

  • Prolonged 2nd stage
  • Increased need for assisted delivery
  • Not associated with neurodevelopmental disorders (BJA, 2021)

Haematological

  • Bruising is common
  • Epidural haematoma is rare: 1 in 168,000
    • However, if no improvement in motor block 4hrs post-cessation of epidural need to request urgent MRI
  • Ensure appropriate timing with respect to anti-platelet and anti-coagulant medication

  • Epidural opioids cross the dura, binding to opioid receptors in:
    • The spinal cord white matter
    • Substantia gelatinosa of the dorsal horns
  • They also spread cephalad and act on the brainstem
  • They're systemically absorbed via epidural veins and thus act systemically too

Choice of opioid

  • Fentanyl is the opioid of choice owing to:
    • Rapid onset of action
    • Short duration of action
    • Reduced cephalad spread, reducing the risk of respiratory depression

  • The Bromage score is a simple, eponymously named score from 1965
  • Modifications to the score (e.g. by Breen in 1993) add more categories, which I've never found particularly useful
Grade Criteria Degree of block
1 Free movement of legs and feet None
2 Just able to flex knees, free movement of feet Partial
3 Unable to flex knees, free movement of feet Near-complete
4 Unable to move knees or feet Complete