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Emergency Protocol

Local Anaesthetic Systemic Toxicity (LAST)

Local Anaesthetic Systemic Toxicity (LAST) is a life-threatening complication of regional anaesthesia resulting from systemic absorption or inadvertent intravascular injection of local anaesthetic. Bupivacaine is the most cardiotoxic agent. LAST can present with central nervous system (CNS) and/or cardiovascular (CVS) manifestations. Early recognition and prompt treatment are critical.

Incidence0.03–0.1% of PNBs
Antidote20% Intralipid
Most CardiotoxicBupivacaine

20% Intralipid Protocol — LAST Treatment

1 — Bolus
1.5 mL/kg IV
Over ~1 minute. For 70 kg ≈ 105 mL
2 — Infusion
0.25 mL/kg/min
For 70 kg ≈ 17.5 mL/min (≈400 mL over 60 min)
3 — If Unstable
Repeat bolus ×3
At 5-minute intervals. Increase infusion to 0.5 mL/kg/min
Maximum Dose
12 mL/kg
In first 30 minutes. Continue until stable
Critical
20% Intralipid must be stocked wherever regional anaesthesia is performed. Check availability before every block. After using, complete a yellow-card report and replace immediately.
CNS

CNS Presentation

  • Prodromal: perioral tingling/numbness, metallic taste in mouth, tinnitus, visual disturbance
  • Anxiety, agitation, restlessness
  • Slurred speech, confusion, drowsiness
  • Muscle twitching, tremors
  • Generalised tonic-clonic seizures
  • Loss of consciousness
  • Respiratory arrest (CNS depression of respiratory centre)
  • NOTE: CNS symptoms typically precede CVS in mild-moderate LAST, but CVS may present first with bupivacaine (high lipid solubility — rapid cardiac binding)
CVS

Cardiovascular Presentation

  • Hypertension and tachycardia (early excitatory phase)
  • Hypotension
  • PR prolongation and wide complex QRS
  • Ventricular tachycardia / ventricular fibrillation
  • Bradycardia progressing to heart block
  • Asystole
  • Haemodynamic collapse
  • BUPIVACAINE: particularly prone to causing intractable VF — resistant to standard ALS
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Risk Factors

  • Large volumes/doses of LA (especially >3 mg/kg bupivacaine)
  • Highly vascular injection site (intercostal, paracervical, epidural, intercalene)
  • Inadvertent intravascular injection
  • Rapid injection rate
  • Extremes of age (neonates, elderly)
  • Low body weight / cachexia
  • Hepatic impairment (reduced LA metabolism)
  • Cardiac disease or conduction abnormalities
  • Mitochondrial disease
  • Metabolic acidosis (increases cardiotoxicity)
✓

Prevention

  • Calculate maximum safe dose BEFORE performing block (weight-based)
  • Use the lowest effective concentration and volume
  • Aspirate before injection and every 5 mL during injection
  • Inject incrementally — small aliquots with pauses
  • Use ultrasound guidance to confirm correct position
  • Test dose: Lignocaine with adrenaline (1:200,000) 3 mL — HR increase >20 bpm suggests intravascular injection
  • Avoid highly vascular sites or use lower doses
  • Use levobupivacaine or ropivacaine where possible (less cardiotoxic than bupivacaine)
  • Have resuscitation equipment and Intralipid available
  • Monitor patient for minimum 30 minutes post-block
ABCD

Immediate Management

Immediate
  • STOP injection of local anaesthetic IMMEDIATELY
  • Call for help — this is an emergency
  • Assess and secure airway — 100% oxygen by mask or intubate if unconscious/seizing
  • Position patient supine; establish IV access if not already done
Seizure Control
  • Benzodiazepines: Diazepam 5–10 mg IV or Midazolam 2–5 mg IV
  • Thiopentone 1–2 mg/kg IV if refractory
  • Propofol 1–2 mg/kg IV (NOTE: Propofol is also a cardiovascular depressant — use with caution)
  • Avoid lidocaine for seizure treatment in LAST
Cardiac Arrest
  • Cardiac arrest: start CPR to ACLS/ALS guidelines
  • AVOID: vasopressin (may impair outcome in LAST), calcium channel blockers, beta-blockers
  • AVOID: excessive adrenaline doses (small doses only: 1 mcg/kg IV increments)
  • Defibrillation for shockable rhythms as per ALS protocol
  • Prolonged CPR may be required — do not give up early
Advanced
  • ECMO/cardiopulmonary bypass if available and conventional resuscitation fails
  • Transfer to cardiac centre if ECMO considered
  • Bicarbonate (1 mmol/kg) for severe metabolic acidosis (worsens cardiotoxicity)
  • Atropine 0.5–1 mg IV for bradycardia
  • Prolonged resuscitation (>60 minutes) reported successful with Intralipid
20%

Intralipid — Full Protocol Detail

  • 20% INTRALIPID EMULSION — SPECIFIC ANTIDOTE for LAST
  • Bolus: 1.5 mL/kg (approximately 100 mL for 70 kg adult) IV over 1 minute
  • Infusion: 0.25 mL/kg/min (approximately 400 mL over 60 min for 70 kg)
  • If haemodynamic instability persists: repeat bolus up to 3 times (q5 minutes)
  • Increase infusion rate to 0.5 mL/kg/min
  • Maximum dose: 12 mL/kg within first 30 minutes
  • Continue infusion until haemodynamic stability achieved
  • Mechanism: "lipid sink" — sequesters lipid-soluble LA from tissues; also direct cardiac effects
  • Intralipid should be immediately available wherever regional anaesthesia is performed
  • Stock Intralipid at any resuscitation trolley in an area performing nerve blocks