Labour analgesia (epidural, cse)

Physiology and pain pathways relevant to labour

• First stage pain
  • Visceral afferents from uterus/cervix travel with sympathetic fibres to spinal segments T10–L1
  • Pain worsens with cervical dilatation and uterine contractions; anxiety and catecholamines amplify pain
• Second stage pain
  • Somatic pain from distension/trauma to vagina, pelvic floor, perineum via pudendal nerve (S2–4)
• Maternal physiological effects of neuraxial analgesia
  • Sympathetic block → vasodilation, reduced SVR, hypotension (more likely with higher/rapid block e.g. CSE spinal component)
  • Reduced catecholamines may improve uteroplacental perfusion; hypotension can reduce uteroplacental blood flow

Indications

• Maternal request (no need to wait for a specific cervical dilatation if labour established and safe)
• High-risk maternal disease: severe pre-eclampsia, cardiac disease (avoid tachycardia/afterload swings), respiratory disease, obesity/anticipated difficult airway (reduce GA risk)
• Anticipated operative delivery (twin, malpresentation, VBAC, prolonged labour) where extension to surgical anaesthesia may be helpful

Contra-indications

• Patient refusal / lack of consent
• Raised intracranial pressure (due to space-occupying lesion)
• Infection
  • At insertion site
  • Systemic sepsis / untreated bacteraemia
• Coagulopathy / anticoagulation
  • Platelets <75 ×10⁹/L (context dependent)
  • INR >1.5 or significantly deranged clotting
  • Recent anticoagulants (e.g. LMWH <12 hours for prophylactic dose)
• Allergy to local anaesthetics
• Uncorrected hypovolaemia

Complications

• Failure / inadequate block (patchy or unilateral analgesia; may require replacement)
• Dural puncture (~1%) → post-dural puncture headache (may require blood patch)
• Hypotension (usually mild; treatable)
• Prolonged second stage of labour and increased likelihood of instrumental delivery
• Pruritus (opioid-related)
• Neurological injury (rare)
  • Temporary nerve symptoms ~1 in 2,000
  • Permanent harm ~1 in 24,000
• Infection (very rare)
  • Epidural abscess
  • Meningitis (~1 in 100,000)
• Epidural haematoma (~1 in 170,000)Local anaesthetic systemic toxicity (~1 in 100,000)

Technique

• Typical insertion level L3–4 or L4–5; loss-of-resistance to saline commonly used
• Catheter 4–6 cm in epidural space; aspirate; careful incremental dosing with monitoring
• Test dose: practice varies; aim is to detect intrathecal/intravascular placement (be cautious in labour: tachycardia is non-specific)

Test dose

• After negative aspiration, administer 10 mL of the PCEA solution (e.g. 0.1% levobupivacaine with fentanyl 2 micrograms/mL) as a test dose.
• Reassess after ~5 minutes for features of intrathecal or intravascular placement:
  • Rapid motor block
  • Dense or unexpectedly high sensory block
  • Hypotension / sympathetic block (e.g. warm, vasodilated legs)
  • Paraesthesia or other concerning symptoms → If present, suspect intrathecal catheter and manage accordingly.
• If no concerning features, give a further 10ml of the epidural solution incrementally.
• Formal assessment at ~20 minutes:
  • Effective analgesia (maternal report)
  • Reduced Entonox requirement
  • Evidence of bilateral sensory block (e.g. cold/ethyl chloride)
  • Block height appropriate for labour
  • No excessive motor block
• Always consider: “Is this epidural likely to be adequate for surgical top-up (e.g. LSCS)?”

Epidural drug regimens and maintenance

• Modern low-dose epidural aims
  • Good analgesia with minimal motor block to aid mobilisation and pushing; reduce instrumental delivery risk compared with dense blocks
• Maintenance methods
  • PCEA: patient-controlled epidural analgesia (bolus + lockout; reduces clinician workload; improves satisfaction)
  • PIEB: programmed intermittent epidural bolus (often superior spread vs continuous infusion; may reduce LA consumption and breakthrough pain)
  • Continuous infusion: acceptable but may have higher LA use and more motor block vs PIEB in some studies

Combined spinal–epidural (CSE)

• Rationale
  • Rapid onset from intrathecal component + flexibility/maintenance via epidural catheter
  • Useful in severe pain, advanced labour, obesity (confirm neuraxial space), or when rapid reliable analgesia desired
• Technique (needle-through-needle common)
  • Identify epidural space; pass spinal needle to puncture dura; give intrathecal drug; then thread epidural catheter
  • Intrathecal drugs (examples): opioid (fentanyl 10–25 micrograms) ± very low-dose LA (bupivacaine 1.25–2.5 mg) depending on local practice
• Advantages vs epidural
  • Faster onset and often better sacral spread; may reduce unilateral/patchy block early on
• Disadvantages/risks
  • More hypotension and pruritus (intrathecal opioid); risk of high/total spinal if dosing errors
  • Fetal heart rate changes can occur soon after initiation (multifactorial; possibly rapid pain relief → catecholamine shift → uterine hypertonus)
  • Epidural catheter function not immediately tested by analgesia (spinal may mask a poorly functioning epidural)

Complications and management (epidural/CSE and remifentanil)

• Hypotension
  • Treat promptly: left uterine displacement, IV fluids (judicious), vasopressor (phenylephrine or ephedrine per scenario), assess block height, fetal status
  • Phenylephrine often preferred for spinal-related hypotension in obstetrics; ephedrine may be used if bradycardic/low CO state (local practice)
• High/total spinal (especially with CSE or accidental intrathecal dosing of epidural)
  • Features: rapid hypotension, bradycardia, dyspnoea, arm numbness, loss of consciousness; fetal compromise
  • Management: call for help, left uterine displacement, airway support/ventilation, vasopressors, treat bradycardia, prepare for GA and urgent delivery if needed
• Accidental dural puncture (ADP) and post-dural puncture headache (PDPH)
  • Recognise: CSF aspiration, sudden loss of resistance; counsel and document; consider intrathecal catheter (local policy) or resite epidural
  • PDPH: postural headache ± neck stiffness, photophobia, tinnitus; treat with hydration/analgesia/caffeine; epidural blood patch for significant symptoms
• Inadequate/patchy/unilateral block (common FRCA scenario)
  • Check: catheter position/marking, aspiration, connections/pump, sensory level, maternal position, labour progress
  • Interventions: optimise position, give top-up bolus, withdraw catheter 1–2 cm if too deep, replace catheter if persistent failure
  • Be cautious with repeated large boluses: risk of high block if catheter migrates intrathecally
• Local anaesthetic systemic toxicity (LAST)
  • Rare with low-dose labour solutions but possible with intravascular placement or large top-ups
  • Management: stop LA, call for help, airway/ventilation, seizure control, lipid emulsion therapy, ALS modifications
• Infection and epidural haematoma
  • Epidural abscess/meningitis: back pain, fever, neurological deficits—urgent MRI and neurosurgical input
  • Epidural haematoma: severe back pain, motor weakness/sensory loss, bladder/bowel dysfunction—time-critical MRI and decompression
• Remifentanil complications
  • Maternal: sedation, desaturation, apnoea, aspiration risk, chest wall rigidity (rare), nausea
  • Fetal/neonatal: potential respiratory depression at delivery; ensure neonatal team aware if used close to birth

Conversion/extension for operative delivery (instrumental delivery / Caesarean section)

• Instrumental delivery in theatre
  • Aim for dense perineal block (S2–4) and adequate analgesia for traction/repair; consider epidural top-up with stronger LA (e.g. Ropivacaine) per local policy
  • If inadequate neuraxial block: options include pudendal block + local infiltration, spinal, or GA depending on urgency and airway risk
• Epidural top-up for Caesarean section
  • Assess existing block quality and catheter function before dosing; give incremental doses with monitoring; aim for T4 sensory level
  • Common agents: Ropivacaine (although lots of different options)
  • If top-up fails or time-critical: spinal (if safe) or GA; anticipate difficult airway and aspiration risk