Epidural anaesthesia

Surgical approach (context: when epidural is used for surgery)

• Not an operation itself; used to facilitate or supplement surgery (e.g. lower limb, abdominal, thoracic) and for labour analgesia.
• Typical surgical timelines relevant to epidural planning:
  • Incision-to-close may be 1–6+ hours depending on procedure; epidural can provide intra-op anaesthesia/analgesia and extended post-op analgesia.
  • Positioning (lithotomy, lateral, prone) may limit access to epidural after induction—consider siting pre-op.
  • Major abdominal/thoracic surgery: significant fluid shifts, blood loss, and sympathetic stress response—epidural may attenuate response but increases hypotension risk.

Anaesthetic management (typical patterns)

• Type of anaesthesia:
  • Regional: epidural alone for suitable surgery (less common than spinal for short lower limb/perineal cases).
  • Combined: epidural + GA for major abdominal/thoracic surgery; epidural provides intra-op opioid-sparing and post-op analgesia.
  • Obstetrics: epidural for labour analgesia; can be topped up for operative delivery/CS (if time and functioning catheter).
• Airway device (if GA used):
  • ETT common for major surgery; SGA sometimes for shorter/lower risk cases.
• Duration:
  • Epidural catheter can provide hours–days of analgesia; intra-op use depends on procedure length and local protocols.
• How painful:
  • Major abdominal/thoracic surgery: very painful—epidural often gold-standard where appropriate.
  • Labour: dynamic pain; epidural provides superior analgesia vs systemic opioids.
• Core management points:
  • Consent: benefits, failure rate, hypotension, motor block, PDPH (rare), nerve injury (very rare), infection/epidural abscess, haematoma, LAST.
  • Monitoring: standard AAGBI; close BP monitoring after dosing/top-ups; consider arterial line for high thoracic/major surgery.
  • Haemodynamics: treat sympathectomy with vasopressors (phenylephrine/metaraminol/ephedrine) + fluids as appropriate; avoid overload in high-risk patients.
  • Analgesic regimen: local anaesthetic ± opioid; infusion or PCEA; regular paracetamol ± NSAID if appropriate; rescue opioids if needed.

Definition and aims

• Injection of local anaesthetic (± adjuncts) into the epidural space to produce segmental analgesia/anaesthesia via spinal nerve roots and (to a lesser extent) spinal cord effects.
• Aims: analgesia/anaesthesia, attenuation of stress response, improved respiratory mechanics (thoracic/upper abdominal), facilitation of early mobilisation and physiotherapy.

Relevant anatomy

• Epidural space boundaries:
  • Anterior: posterior longitudinal ligament.
  • Posterior: ligamentum flavum and vertebral laminae.
  • Lateral: pedicles and intervertebral foramina (communication with paravertebral space).
• Contents: fat, lymphatics, epidural venous plexus (engorged in pregnancy/raised IAP), spinal nerve roots, dura.
• Ligamentum flavum: thickest in lumbar region; may be discontinuous in midline at cervical/thoracic levels → false loss of resistance.
• Epidural depth: variable (often ~4–6 cm in non-obese adults, but wide range).

Physiology and block characteristics

• Differential block: sympathetic (B fibres) > sensory (Aδ, C) > motor (Aα).
• Onset slower than spinal; can be titrated and extended with catheter.
• Spread influenced by: dose/volume, concentration, site of injection, age, pregnancy, height (weak predictor), epidural pressure, catheter position, and anatomical variability.
• Haemodynamic effects: sympathectomy → vasodilation, ↓SVR, venous pooling, ↓preload; bradycardia if high block (T1–T4 cardioaccelerator fibres).
• Respiratory effects: minimal in healthy patients; high thoracic block can reduce intercostal function; concern is often hypotension and sedation rather than ventilatory failure.

Indications

• Obstetrics: labour analgesia; operative delivery/CS top-up if functioning and time allows.
• Perioperative analgesia: major abdominal, thoracic, vascular, urological, lower limb surgery (especially when opioid-sparing desired).
• Chronic pain: steroid injections, adhesiolysis, trial analgesia (specialist settings).

Contraindications

• Absolute:
  • Patient refusal or inability to consent.
  • Infection at site; untreated systemic sepsis (relative/individualised but generally avoid).
  • Uncorrected hypovolaemia/shock.
  • Coagulopathy/unsafe anticoagulation (follow ASRA/ESAIC/RA-UK guidance).
  • Raised intracranial pressure due to mass lesion (risk of herniation).
• Relative:
  • Fixed cardiac output states (severe AS, HOCM) – sympathectomy poorly tolerated.
  • Severe spinal deformity/previous surgery (technical difficulty, patchy block).
  • Neurological disease (e.g. MS, peripheral neuropathy): careful risk–benefit, documentation of baseline deficits.
  • Uncooperative patient, inability to position, raised BMI (technical).

Equipment and technique (loss of resistance)

• Preparation: IV access, resus drugs, intralipid available, monitoring, asepsis (chlorhexidine in alcohol allowed to dry), sterile gown/gloves/drape.
• Position: sitting or lateral; optimise flexion; identify midline; ultrasound may help (depth, midline, interspace).
• Approach: midline (through supraspinous/interspinous ligaments) or paramedian (useful in elderly/calcified ligaments).
• Loss of resistance (LOR): to saline (common in UK) or air; saline reduces risk of pneumocephalus/patchy block from air bubbles.
• Catheter: typically thread 3–6 cm into epidural space (too little → dislodgement; too much → unilateral/vascular/foraminal placement).
• Test dose: aims to detect intrathecal or intravascular placement; practice varies (e.g. lidocaine with adrenaline). Interpret in context (beta-blockers, pregnancy).
• Incremental dosing: fractionated boluses with frequent aspiration and haemodynamic monitoring.

Drugs and dosing (typical UK practice)

• Local anaesthetics:
  • Bupivacaine: labour 0.0625–0.125% (often with fentanyl); surgical anaesthesia 0.25–0.5% (caution toxicity).
  • Ropivacaine: similar use; less cardiotoxic than bupivacaine; often 0.1–0.2% for analgesia.
  • Lidocaine: faster onset; sometimes for top-ups (e.g. 2% with adrenaline ± bicarbonate) for urgent surgical anaesthesia.
• Opioid adjuncts:
  • Fentanyl (lipophilic): rapid onset, limited rostral spread; common in labour (e.g. 2 mcg/mL in infusion).
  • Diamorphine/morphine (hydrophilic): longer duration; more pruritus, nausea, urinary retention; risk of delayed respiratory depression (esp morphine).
• Other adjuncts (specialist/variable): clonidine (sedation/hypotension), adrenaline (marker + prolongation), bicarbonate (faster onset with lidocaine).
• Infusions/PCEA: low concentration LA + opioid reduces motor block and improves satisfaction; set local protocols (e.g. background infusion + demand bolus + lockout).

Assessment of block

• Sensory: cold (ice/ethyl chloride) or light touch; note that analgesia ≠ surgical anaesthesia (pinprick more relevant for surgery).
• Motor: Bromage score (lumbar); assess ability to straight leg raise; for thoracic epidurals motor assessment less informative.
• Sympathetic: warmth, vasodilation; BP changes; beware high block signs (hypotension, bradycardia, dyspnoea, arm tingling).

Failure and troubleshooting

• Common patterns: patchy block, unilateral block, sacral sparing, inadequate density for surgery, catheter migration/dislodgement.
• Immediate actions: check connections/pump, aspiration, assess sensory level, review dosing and timing, consider catheter depth/position.
• Unilateral block: withdraw catheter 1–2 cm; reposition patient to blocked side down; give incremental bolus; consider replacement if persistent.
• Sacral sparing: increase volume, use more concentrated LA, consider opioid adjunct; ensure adequate time; consider alternative technique if urgent.
• Suspected intrathecal migration: dense motor block, rapid high sensory level—stop dosing, manage as high spinal, urgent help.

Complications and management

• Hypotension/bradycardia:
  • Left uterine displacement in pregnancy; IV fluids judiciously; vasopressors (phenylephrine/metaraminol; ephedrine if bradycardic).
  • Treat high block early; consider atropine for significant bradycardia; escalate promptly.
• Accidental dural puncture (ADP) and PDPH:
  • Recognise: CSF flow via Tuohy/needle; increased risk PDPH (especially obstetrics).
  • Immediate options: resite epidural at different level; consider intrathecal catheter (local policy) to reduce PDPH and provide analgesia.
  • PDPH management: hydration/analgesia/caffeine (limited evidence), consider sphenopalatine ganglion block; epidural blood patch for significant headache (typically after conservative measures; urgent if severe/functional impairment).
• Local anaesthetic systemic toxicity (LAST):
  • Presentation: tinnitus, metallic taste, agitation, seizures; cardiovascular collapse/arrhythmias (bupivacaine worst).
  • Management: stop LA, call for help, airway/oxygen/ventilation, treat seizures (benzodiazepine), lipid emulsion therapy per AAGBI/RA-UK, manage arrhythmias (avoid large doses of adrenaline; avoid lidocaine).
• High/total spinal (from intrathecal dosing):
  • Features: rapid hypotension, bradycardia, dyspnoea, upper limb numbness, loss of consciousness/apnoea.
  • Management: airway support/intubation, 100% O2, vasopressors/inotropes, left uterine displacement if pregnant, treat bradycardia; ICU support until block recedes.
• Epidural haematoma:
  • Risk increased with anticoagulation/coagulopathy and traumatic insertion.
  • Presentation: severe back pain, motor weakness, sensory changes, sphincter dysfunction—may be delayed.
  • Action: emergency MRI and neurosurgical decompression; time-critical (aim decompression within hours of symptom onset).
• Infection (epidural abscess/meningitis):
  • Presentation: fever, back pain, neurological deficit; may have raised inflammatory markers.
  • Action: urgent imaging, microbiology, IV antibiotics, neurosurgical input.
• Neurological injury:
  • Rare; causes include direct trauma, ischaemia, haematoma, abscess, neurotoxicity, positioning/pressure palsies.
  • Prevention: avoid injection against pain/paraesthesia; stop and reposition; document baseline neurology; careful anticoagulation management.
• Other: urinary retention, pruritus (opioids), nausea/vomiting, motor block and falls risk, catheter migration, hypotension-related nausea.

Epidural in obstetrics (key FRCA points)

• Benefits: superior labour analgesia, reduced maternal catecholamines, can facilitate instrumental delivery/operative anaesthesia if catheter works.
• Common regimens: low-dose LA + opioid (e.g. bupivacaine/ropivacaine with fentanyl) via PCEA ± background infusion; aim minimal motor block.
• Physiology: epidural venous engorgement and reduced CSF volume in pregnancy → increased spread and increased intravascular placement risk.
• Fetal considerations: avoid maternal hypotension; treat promptly to maintain uteroplacental perfusion.
• Labour epidural and CS: top-up requires higher concentration/volume; assess block density carefully; have low threshold to convert to GA if inadequate and urgent.

Anticoagulation and epidural safety (principles)

• Always follow current local policy and national guidance (RA-UK/ASRA/ESAIC) for timing of insertion and catheter removal relative to anticoagulants.
• Key principle: neuraxial procedures and catheter removal carry bleeding risk; the highest risk period is around insertion/removal and when anticoagulation is restarted.
• If neurological symptoms occur in an anticoagulated patient with an epidural: treat as epidural haematoma until proven otherwise (urgent MRI/neurosurgery).

Postoperative epidural management

• Prescription: specify solution, rate, bolus, lockout, max dose; include rescue analgesia and antiemetics.
• Monitoring: regular pain scores at rest/movement, sensory level, motor block, BP, sedation/resp rate (if opioid), catheter site checks, urine output/retention.
• Hypotension: consider block height, sepsis/bleeding, dehydration; reduce infusion/bolus, treat with vasopressors/fluids, escalate if persistent.
• Mobilisation: assess motor power; falls precautions; physiotherapy coordination.
• Removal: coordinate with anticoagulation timing; ensure neurological observations continue after removal; document tip intact and site condition.