Key Facts

Epidural anaesthesia/analgesia is one of the most versatile regional techniques, providing segmental blockade that can be titrated and maintained via a catheter. It is widely used in obstetrics, major surgery, and chronic pain management.

Epidemiology

Approximately 400,000 epidurals are performed annually in the UK. Labour epidural rates vary by unit (20-50%). Approximately 1% of epidurals result in accidental dural puncture (ADP). NAP3 estimated permanent harm from epidural anaesthesia at approximately 1 in 25,000.

Aetiology

The epidural space contains fat, lymphatics, and the internal vertebral venous plexus. LA injected into this space diffuses across the dura to block spinal nerve roots segmentally. The catheter allows continuous infusion or patient-controlled boluses.

Pathophysiology

Mechanism of action:

• LA diffuses through dural cuffs around nerve roots in the epidural space
• Also acts directly on spinal cord via transmeningeal diffusion
• Opioids act on spinal cord dorsal horn receptors (lipophilic: fentanyl — segmental; hydrophilic: morphine/diamorphine — more rostral spread)

Block characteristics:

• Onset slower than spinal (15-30 min)
• Incremental dosing allows titration of block height
• Less dense motor block than spinal (especially with dilute solutions)
• Sympathetic blockade causes vasodilation and hypotension (less than spinal)

Labour Epidural

• Effective pain relief within 15-30 minutes
• Low-dose technique maintains mobility (mobile epidural)
• PCEA with background infusion is standard practice

Surgical Epidural

• Higher concentration LA (bupivacaine 0.5%) for denser block
• Used for thoracic, abdominal, and lower limb surgery
• Thoracic epidural: T6-T10 for upper abdominal surgery; reduces respiratory complications

Post-Operative Epidural

• Continued infusion for 48-72 hours post-major surgery
• Superior analgesia to IV opioids for thoracotomy, major abdominal surgery
• Reduces respiratory complications, ileus, and opioid side effects

Complications

• Inadequate/patchy block (10-15%)
• Hypotension, nausea
• Pruritus (opioid-related)
• Urinary retention
• Accidental dural puncture → PDPH
• Epidural haematoma, abscess (rare)

Red Flags

• Sudden onset dense bilateral motor block — suspect intrathecal migration of catheter
• Unilateral block — catheter may be lateral; consider repositioning
• Severe back pain + fever + progressive weakness — epidural abscess (emergency MRI)
• High block with respiratory compromise — manage as for total spinal

Bedside

• Pre-procedure: Coagulation status, consent, IV access, monitoring
• Loss of resistance: Air or saline technique to identify epidural space
• Test dose: Lidocaine 2% 3mL with adrenaline 1:200,000 — detect intrathecal or intravascular placement
• Assessment: Bilateral cold sensation, motor power (Bromage scale)

Bloods

• Coagulation screen: Before insertion and removal in anticoagulated patients
• Platelet count: >75 × 10⁹/L required
• FBC: Baseline, especially if epidural for major surgery

Imaging

• Urgent MRI: If epidural haematoma or abscess suspected

Special Tests

• Hourly assessment: Sensory level, motor block, pain score, observations
• Daily catheter site inspection: Signs of infection (redness, swelling, discharge)
• PDPH assessment: Postural component, cranial nerve involvement (VI nerve palsy, hearing loss)

Non-pharmacological

• Positioning: Sitting or lateral for insertion; wedge/left tilt for obstetric procedures
• Aseptic technique: Full aseptic precautions including hat, mask, gown, gloves, drape
• Catheter care: Secure with adhesive dressing; daily inspection
• Nursing protocols: Hourly observations, motor block assessment, catheter site checks

Pharmacological

• Labour epidural: Bupivacaine 0.1% + fentanyl 2mcg/mL — PCEA 10mL bolus with 20min lockout ± background infusion 5-10mL/hr
• Surgical epidural: Bupivacaine 0.5% or levobupivacaine 0.5% — incremental 5mL boluses to desired level
• Post-operative infusion: Bupivacaine 0.1-0.125% + fentanyl 2mcg/mL at 5-15mL/hr
• Hypotension: Phenylephrine 50-100mcg IV or ephedrine 6-12mg IV; IV fluid co-loading
• PDPH: Paracetamol, caffeine 300mg PO TDS; epidural blood patch (15-20mL) if persistent

Surgical/Interventional

• Epidural blood patch: 15-20mL autologous blood injected into epidural space — success rate >85%
• Surgical decompression: For epidural haematoma or abscess with neurological deficit

Referral Criteria

• Failed epidural with inadequate analgesia — senior anaesthetic review
• Accidental dural puncture — anaesthetic follow-up for PDPH monitoring
• Neurological deficit post-epidural — emergency investigation and neurosurgical referral

• Labour epidural satisfaction: >85% rate effective pain relief
• Failure rate: 10-15% require re-siting or supplementation
• PDPH after ADP: Occurs in 50-80%; most resolve with conservative measures within 1-2 weeks; blood patch effective in >85%
• Permanent neurological injury: ~1 in 25,000 (NAP3) — includes epidural haematoma and abscess
• Post-operative epidural: Reduces respiratory complications by 30-50% after major abdominal/thoracic surgery (meta-analyses)

Epidural vs Spinal Anaesthesia

Labour Epidural and Obstetric Outcomes