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Complications of Regional Anaesthesia

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1. Local Anaesthetic Systemic Toxicity (LAST)

Mechanism

CNS Manifestations (dose-dependent — Lidocaine model)

Cardiovascular Toxicity

• Dose-dependent slowing of cardiac conduction → prolonged PR interval, widened QRS
• Bupivacaine binds Na⁺ channels during systole and dissociates very slowly in diastole, leading to cumulative channel blockade at physiological heart rates — explaining its propensity for ventricular dysrhythmias and refractory cardiac arrest
• Vasodilation, myocardial depression, and pulmonary artery hypertension also occur
• Ropivacaine and levobupivacaine are ~30–40% less cardiotoxic than bupivacaine in animal models

Prevention

• Strict adherence to maximum dose limits
• Ultrasound guidance to visualise needle tip and local anaesthetic spread
• Aspiration before injection
• Incremental fractionated injection (test dose)
• Avoid large-volume fascial plane blocks without epinephrine (e.g., TAP blocks: max 0.25% bupivacaine ≤20–25 mL per side + epinephrine 1:200,000)

Treatment

1. Stop injection immediately; call for help
2. Maintain airway, oxygenation, ventilation
3. Treat seizures: benzodiazepines (midazolam 1–5 mg IV) or propofol
4. Intralipid (lipid emulsion 20%) — cornerstone of LAST treatment:
   • Bolus: 1.5 mL/kg over 1 minute
   • Infusion: 0.25 mL/kg/min for ≥10 minutes after haemodynamic stability
5. ACLS as needed; avoid vasopressin, calcium channel blockers, β-blockers
6. Amiodarone for ventricular dysrhythmias
7. Consider cardiopulmonary bypass for refractory cases

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2. Post-Dural Puncture Headache (PDPH)

Pathophysiology

Clinical Features

• Postural headache: worsens upright, relieved by lying supine (orthostatic pattern is pathognomonic)
• May be accompanied by neck stiffness, photophobia, tinnitus/muffled hearing (cochlear aqueduct connects middle ear to CSF)
• Diplopia (CN VI palsy) in severe cases → indicates urgent epidural blood patch

Incidence

• Related to needle gauge and tip design: >70% with 16G cutting needle → <1% with 25G pencil-point (Whitacre/Sprotte) needles
• Unintentional dural puncture during epidural placement: 1–1.5%; headache follows in 30–60% of these
• Higher risk: young females, parturients, previous PDPH, multiple attempts

Differential Diagnosis (important)

• Meningitis (fever, nuchal rigidity — urgent)
• Postpartum preeclampsia (hypertension)
• Cerebral venous thrombosis, subdural haematoma, stroke
• Tension/migraine/caffeine withdrawal headache

Treatment

1. Conservative: bed rest, oral hydration, NSAIDs, paracetamol, opioids, caffeine (500 mg IV / 300 mg oral — short-term benefit via vasoconstriction)
2. Epidural Blood Patch (EBP): definitive treatment for severe/incapacitating PDPH
   • 20 mL autologous blood injected into lumbar epidural space
   • ~83–92% respond to first patch; 8–17% require a second
   • Indicated immediately if cranial nerve signs present

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3. Epidural/Spinal Haematoma

Risk Factors

• Coagulopathy or anticoagulant therapy (most important)
• Platelet count <70,000/mm³ (risk substantially increased)
• Traumatic needle/catheter insertion
• Highly vascular epidural space

Incidence

• Extremely rare in healthy patients: ~1 in 251,463 obstetric epidurals (SCORE project)

Clinical Features

• Severe back pain (often new-onset or "different" pain)
• Persistent or progressive motor blockade beyond expected duration
• Bladder/bowel dysfunction

Management

• Urgent MRI if suspected
• Neurosurgical decompression within 6–8 hours to prevent permanent neurological deficit
• Follow ASRA guidelines for anticoagulant timing around neuraxial procedures

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4. Neurological Injury

Direct Spinal Cord Injury

• Rare when procedures performed below the conus medullaris (L1–L2)
• Spinal cord syrinx formation reported when injection occurs at an unintentionally high level — pain on injection is a warning sign: stop injecting immediately
• Incidence: ~0.6/100,000 (epidural), ~3/100,000 (spinal)

Transient Neurological Symptoms (TNS)

• Back pain radiating to buttocks/legs without sensory/motor deficit, resolving within days
• Most associated with hyperbaric lidocaine (incidence up to 12%)
• Also reported with tetracaine (2%), bupivacaine (1%), mepivacaine, prilocaine
• Greatest in lithotomy position and day-case surgery

Peripheral Neuropathy

• Postpartum femoral and lateral femoral cutaneous neuropathies: ~0.92% incidence
• Associated with nulliparity and prolonged second stage — not epidural use
• Usually resolves with time; neurology follow-up advised

Anterior Spinal Artery Syndrome

• Rare ischaemic injury to anterior spinal cord following profound hypotension
• Presents with motor paralysis + loss of pain/temperature sensation but preserved proprioception

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5. Total Spinal Block

Causes

• Unintentional intrathecal injection of an epidural dose
• Spinal catheter after dural puncture
• Spinal anaesthesia following failed epidural (epidural drug already in place)

Risk Factors

Features

• Rapidly ascending sensorimotor block
• Dyspnoea → respiratory failure
• Inability to phonate, dysphagia
• Profound hypotension → brainstem hypoperfusion → loss of consciousness

Treatment (supportive)

1. Airway: rapid sequence intubation
2. Circulation: IV fluids, vasopressors (ephedrine/phenylephrine), left lateral tilt (obstetric patient)
3. Leg elevation

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6. Infectious Complications

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7. Haemodynamic Complications

Hypotension

• Most common complication of spinal/epidural anaesthesia
• Due to sympathetic blockade → arterial and venous vasodilation → reduced preload and afterload
• Higher blocks (>T4) block cardiac accelerator fibres → bradycardia

Bradycardia and Cardiac Arrest

• Occurs with high sympathetic block (T1–T4 blockade)
• Atropine, ephedrine, epinephrine as appropriate
• Rare but documented cases of cardiac arrest during spinal anaesthesia

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8. Complications Specific to Peripheral Nerve Blocks

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9. Allergic / Hypersensitivity Reactions

• Allergy to preservatives (methylparaben, metabisulphite) is more common than allergy to the local anaesthetic itself
• Anaphylaxis managed with epinephrine, antihistamines, steroids, fluid resuscitation

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Summary Table

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