Epidural analgesia

Surgical approach (where epidurals are commonly used)

• Not an operation itself; used to provide intra- and/or postoperative analgesia for major surgery.
• Typical procedures benefiting from thoracic/lumbar epidurals:
  • Open abdominal surgery (colorectal, laparotomy, pancreatic, upper GI).
  • Thoracotomy / major thoracic surgery (thoracic epidural or paravertebral alternatives).
  • Major vascular (open AAA) and some major urology/gynae.
• Surgical factors affecting epidural performance:
  • Incision site and dermatomes required (e.g., upper midline vs lower midline).
  • Laparoscopic vs open (often less benefit in laparoscopy; consider alternatives).
  • Enhanced recovery pathways: early mobilisation, anticoagulation schedules, fluid strategy.

Anaesthetic management (typical scenarios)

• Type of anaesthesia:
  • Commonly combined with GA for major surgery (epidural for analgesia + sympathectomy).
  • Can be sole technique for labour analgesia and some lower limb/lower abdominal procedures (less common as sole for major surgery).
• Airway device:
  • If combined with GA: usually ETT for major abdominal/thoracic surgery; SGA for minor procedures where appropriate.
• Duration:
  • Insertion: typically 10–30 min (longer if difficult anatomy).
  • Analgesia duration: hours–days via infusion/PCEA; catheter commonly 2–5 days depending on indication and anticoagulation plan.
• How painful:
  • High benefit in very painful surgery (thoracotomy, open laparotomy) where dynamic pain impairs ventilation/mobilisation.
  • Moderate benefit in lower abdominal/pelvic surgery; less benefit in minimally invasive surgery where multimodal + regional alternatives may suffice.
• Key intraoperative considerations when epidural running:
  • Hypotension from sympathectomy: anticipate vasopressors (phenylephrine/metaraminol/noradrenaline) and judicious fluids.
  • Reduced volatile/opioid requirements; avoid excessive GA depth when epidural bolused.
  • Temperature management and urine output monitoring (urinary retention common).

Aims and benefits

• Provide segmental analgesia by blocking spinal nerve roots in the epidural space; can include sympathetic block.
• Benefits (procedure-dependent): improved analgesia (especially dynamic pain), reduced systemic opioid requirements, improved respiratory mechanics (thoracic/upper abdominal), facilitation of early mobilisation and physiotherapy.
• Potential outcome benefits: reduced pulmonary complications after thoracotomy/upper abdominal surgery; haemodynamic effects may be beneficial or harmful depending on context.

Anatomy and physiology

• Epidural space boundaries: ligamentum flavum posteriorly; dura mater anteriorly; pedicles/vertebral canal laterally. Contents: fat, lymphatics, epidural veins (Batson plexus), spinal nerve roots.
• Depth to epidural space varies (often 4–6 cm in adults; can be >8 cm). Midline approach traverses: skin → subcut tissue → supraspinous ligament → interspinous ligament → ligamentum flavum → epidural space.
• Spread determinants: volume, concentration, site (thoracic vs lumbar), age, pregnancy (engorged veins/less CSF), height (weak predictor), catheter position, injection speed.
• Physiology: sympathetic block (T1–L2) causes vasodilation, reduced SVR, venous pooling; high block may reduce cardiac accelerator fibres (T1–T4) causing bradycardia.

Indications

• Labour analgesia (lumbar epidural).
• Major abdominal surgery (thoracic epidural often preferred for upper abdominal).
• Thoracic surgery (thoracic epidural; alternative: paravertebral/erector spinae plane).
• Rib fractures (thoracic epidural in selected patients; consider anticoagulation/trauma constraints).
• Chronic pain interventions (steroid/local anaesthetic injections) and epidural blood patch (separate indication).

Contraindications (absolute/relative)

• Patient refusal or inability to cooperate.
• Infection at insertion site; untreated systemic sepsis (relative—risk/benefit).
• Coagulopathy/anticoagulation not compatible with neuraxial techniques (follow ASRA/ESAIC and local policy).
  • Key principle: avoid insertion/removal during therapeutic anticoagulation; ensure appropriate timing for LMWH/DOACs/warfarin/UFH and platelet function inhibitors.
• Raised intracranial pressure due to mass lesion (risk of herniation with dural puncture).
• Severe uncorrected hypovolaemia/shock (risk profound hypotension).
• Fixed cardiac output states (e.g., severe aortic stenosis) and severe pulmonary hypertension: relative—specialist decision, invasive monitoring, vasopressor plan.
• Spinal pathology (previous surgery, severe scoliosis, spinal stenosis): relative; higher failure/complication risk.

Preparation and consent (key points)

• Explain benefits, alternatives (PCA opioids, regional blocks), and common/serious risks.
• Baseline assessment: vitals, neurological status (document), back exam, infection risk, anticoagulant/antiplatelet history, allergies.
• Monitoring and resuscitation readiness: IV access, standard monitors; vasopressors available; intralipid available for LAST.
• Asepsis: full sterile technique (hat/mask, sterile gown/gloves, chlorhexidine in alcohol allowing full drying time).

Technique (practical FRCA outline)

• Position: sitting or lateral; optimise flexion while maintaining comfort and oxygenation.
• Identify level: surface anatomy (Tuffier’s line ~L4/5), ultrasound can help (depth, midline, interspace).
• Local infiltration; insert Tuohy needle midline or paramedian; advance to ligamentum flavum; use loss-of-resistance (saline preferred by many to reduce patchy block/pneumocephalus risk).
• Thread catheter typically 3–6 cm into epidural space (too little: dislodgement; too much: unilateral/vascular placement).
• Aspirate (limited sensitivity); secure catheter; label clearly; document insertion details (level, depth, complications).
• Test dose: local policy; aims to detect intrathecal or intravascular placement.
  • Common approach: lidocaine 1.5% with adrenaline 1:200,000 (e.g., 3 mL) looking for tachycardia (intravascular) or rapid dense motor block (intrathecal).
  • Limitations: beta-blockade, labour pain, hypovolaemia, GA, and uteroplacental physiology may blunt signs; aspiration may be falsely negative.

Drugs and regimens

• Local anaesthetics: bupivacaine, levobupivacaine, ropivacaine (less motor block with ropivacaine at equipotent doses).
• Opioid adjuncts: fentanyl/diamorphine (lipophilic vs hydrophilic properties influence onset/duration/rostral spread).
• Typical postoperative infusion (adult, non-obstetric): low concentration LA + opioid (e.g., bupivacaine/levobupivacaine 0.1–0.125% + fentanyl 2 mcg/mL) at 6–12 mL/h; consider PCEA boluses.
• Labour: dilute LA + opioid (e.g., bupivacaine/levobupivacaine 0.0625–0.1% + fentanyl 2 mcg/mL) with PCEA; aim minimal motor block.
• Top-ups for surgical anaesthesia (if used): higher concentration LA (e.g., lidocaine 2% with adrenaline; bupivacaine 0.5%) titrated carefully; consider bicarbonate to speed onset (local practice).
• Dose safety: calculate maximum safe local anaesthetic dose; consider reduced thresholds in pregnancy, frailty, hepatic dysfunction; treat LAST promptly.

Assessment of block

• Sensory: cold/ice (A-delta), pinprick; map dermatomes; note that analgesia may not equal surgical anaesthesia.
• Motor: Bromage score (lumbar epidurals); thoracic epidurals may spare lower limb motor function.
• Sympathetic: hypotension, warm peripheries; beware high block signs (nausea, dyspnoea, bradycardia).

Complications (recognition and management)

• Hypotension/bradycardia: treat with left uterine displacement in pregnancy, fluids judiciously, vasopressors (phenylephrine/metaraminol; ephedrine if bradycardic), reduce/stop infusion, consider high block.
• Accidental dural puncture (wet tap): risk post-dural puncture headache (PDPH). Manage with hydration, simple analgesia, caffeine (limited), consider epidural blood patch if severe/persistent; document and follow-up.
• High/total spinal (from intrathecal dosing or unrecognised dural puncture): hypotension, bradycardia, respiratory insufficiency, LOC. Immediate airway support, intubation/ventilation, vasopressors, left uterine displacement, call for help.
• Intravascular injection and LAST: tinnitus, metallic taste, agitation, seizures, arrhythmias/cardiac arrest. Stop LA, call for help, airway/oxygen, treat seizures, start lipid emulsion per AAGBI/RA-UK guidance, manage arrhythmias (avoid large-dose adrenaline; avoid lidocaine).
• Epidural haematoma: severe back pain, motor weakness, sensory changes, sphincter dysfunction. Emergency MRI and neurosurgical decompression ideally within hours; stop infusion; check coagulation; treat as time-critical.
• Epidural abscess/meningitis: fever, back pain, neurological deficit. Urgent imaging, microbiology, antibiotics, neurosurgical input.
• Nerve injury: direct trauma, ischaemia, haematoma/abscess, neurotoxicity. Document, urgent assessment if progressive deficit; consider neurology/neurosurgery.
• Urinary retention: bladder scan/catheterisation; common with neuraxial opioids and sympathetic block.
• Pruritus, nausea, respiratory depression (opioid-related): treat with antiemetics, consider naloxone infusion for significant respiratory depression; monitor sedation/resp rate.
• Catheter issues: migration (intrathecal/intravascular), dislodgement, kinking, occlusion; unilateral/patchy block.

Troubleshooting a poorly working epidural (systematic approach)

• Assess patient and analgesia: pain score at rest and movement, dermatomal level, unilateral vs bilateral, sensory modality used, timing since last bolus.
• Check equipment: pump settings, line connections, filter, clamps, leakage at insertion site, catheter marking at skin (migration).
• Interventions (stepwise):
  • Optimise position (lateral with painful side down for unilateral block).
  • Give a test bolus/top-up (per protocol) and reassess; consider higher volume vs concentration depending on pattern (patchy vs inadequate density).
  • Withdraw catheter 1–2 cm if too far in (unilateral); never advance a withdrawn catheter back in (infection/track contamination risk).
  • If still inadequate: resite early rather than repeated ineffective boluses; provide alternative analgesia (PCA, blocks).
• Always consider serious causes if new severe pain or neuro deficit: haematoma/abscess; stop and escalate urgently.

Anticoagulation and epidurals (principles for FRCA answers)

• Risk to avoid: neuraxial bleeding causing epidural haematoma (time-critical neurological emergency).
• Principles: follow local neuraxial anticoagulation guideline; document timing of last dose and planned next dose; coordinate with surgeons/ward; avoid catheter removal at peak anticoagulant effect.
• Common high-level rules (always check policy):
  • LMWH prophylaxis: allow an appropriate interval before insertion and before removal; delay next dose after insertion/removal.
  • Therapeutic anticoagulation (LMWH/UFH/DOAC): usually incompatible with an indwelling epidural catheter unless strict timing and specialist oversight.
  • Warfarin: ensure INR acceptable before insertion/removal; avoid removal with elevated INR.
  • Antiplatelets: aspirin alone usually acceptable; P2Y12 inhibitors require cessation period; dual antiplatelet therapy is high risk.

Postoperative management and monitoring

• Regular observations: pain scores (rest/movement), sensory level, motor power, haemodynamics, sedation/respiratory rate, catheter site, infusion totals.
• Escalation triggers: increasing motor block, new weakness, severe back pain, fever, confusion, hypotension refractory to treatment, respiratory depression.
• Adjuncts: paracetamol ± NSAID (if appropriate), gabapentinoids rarely; avoid duplicating opioids excessively if epidural opioid running; prescribe rescue analgesia.
• Removal: check anticoagulation timing; inspect catheter tip; document intact removal; continue neuro checks after removal as per policy.