What is the management of a local anaesthetic (local anesthetic) overdose?

Management of Local Anaesthetic Overdose

Immediately administer 20% intravenous lipid emulsion (1.5 mL/kg bolus over 1 minute, followed by 0.25 mL/kg/min infusion) while providing aggressive airway support, oxygenation, and cardiovascular resuscitation—this is the definitive antidote for local anaesthetic systemic toxicity (LAST). 1, 2, 3

Immediate Recognition and Initial Actions

Stop all local anaesthetic administration immediately and call for help, alerting the nearest facility with cardiopulmonary bypass capability. 2, 4, 5

Early manifestations include:

• Central nervous system signs: agitation, confusion, metallic taste, perioral numbness, tinnitus, followed by seizures (often the first dramatic sign) 4, 6, 7
• Cardiovascular signs: hypertension and tachycardia initially, progressing to bradycardia, conduction delays, QRS prolongation, arrhythmias, hypotension, and ultimately cardiac arrest 2, 6, 7

Airway Management and Oxygenation (First Priority)

Secure the airway immediately and ventilate with 100% oxygen. 2, 4, 8, 6 Hypoxia and acidosis dramatically worsen local anaesthetic cardiotoxicity. 2, 5

• Prepare for immediate tracheal intubation if airway patency cannot be maintained or if prolonged ventilatory support is needed 8, 6
• Institute positive pressure ventilation capability by mask immediately 8

Lipid Emulsion Therapy (Primary Antidote)

Administer 20% lipid emulsion without delay—this is the cornerstone treatment and should not be delayed while awaiting definitive diagnosis. 1, 2, 3

Dosing Protocol:

• Initial bolus: 1.5 mL/kg lean body mass over approximately 1 minute 1, 2, 3
• Continuous infusion: 0.25 mL/kg per minute immediately after bolus 1, 2, 3
• Repeat boluses: May be given once or twice for persistent cardiovascular collapse 1, 2
• Duration: Continue infusion for 30-60 minutes 1, 2

The mechanism involves active shuttling of lipophilic local anaesthetic away from cardiac and neural tissue, increased cardiac contractility, and direct cardioprotective effects. 1, 3

Seizure Management

Administer benzodiazepines as first-line therapy for seizures. 4, 8, 6

• Midazolam 0.1-0.2 mg/kg IV or diazepam in small increments 4, 8
• Avoid propofol for seizure control in LAST, as it worsens cardiovascular depression 4, 6, 5
• Ultra-short acting barbiturates (thiopental, thiamylal) may be used only if benzodiazepines fail and circulation permits 8

Cardiovascular Support

For Bradycardia:

Administer atropine (Class IIa recommendation from American Heart Association). 2

For Wide-Complex Tachycardia/QRS Prolongation >120 ms:

Give sodium bicarbonate to overcome sodium channel blockade (Class IIa recommendation). 1, 2

For Hypotension:

• Administer 10-20 mL/kg balanced salt solution fluid bolus 2, 6
• Consider small-dose vasopressors if needed 2, 6

Cardiac Arrest Management (Critical Modifications)

Use reduced-dose epinephrine or avoid it initially—standard 1 mg doses impair lipid emulsion effectiveness and worsen outcomes. 1, 2, 3

• Two animal studies demonstrated lipid emulsion was superior to standard vasopressor therapy (including epinephrine) for return of spontaneous circulation 1, 3
• High-dose epinephrine (0.1 mg/kg) showed no additional benefit when combined with lipid emulsion 1, 3
• Avoid vasopressin entirely 4, 5
• Prioritize lipid emulsion as the primary antidote over standard vasopressor therapy 2, 3

Initiate standard high-quality CPR but prepare for prolonged resuscitation efforts, as LAST may require extended CPR. 2, 3

Refractory Cases

Consider ECMO (extracorporeal membrane oxygenation) for refractory shock or cardiac arrest (Class IIb recommendation). 1, 2, 3

• Contact the perfusion team early in the resuscitation 2, 5
• ECMO has shown improved outcomes in retrospective studies for drug toxicity-related cardiac arrest 1

Agent-Specific Considerations

Bupivacaine is the most frequently implicated agent in LAST-related cardiovascular collapse and requires particularly aggressive lipid emulsion therapy. 1, 2, 3 The American Heart Association specifically recommends lipid emulsion for patients with cardiac arrest due to bupivacaine toxicity. 1, 3

Other commonly implicated agents include lidocaine and ropivacaine. 1, 6

Monitoring During Treatment

• Assess block height every 5 minutes until no further extension is observed 1
• Monitor for signs of high block: increasing agitation, significant hypotension, bradycardia, upper limb weakness, dyspnoea, or difficulty speaking 1
• Document vital signs continuously, including oxygen saturation and heart rate 4, 3

Special Populations

Neonates and Infants:

• Reduce all amide local anaesthetic doses by 30% for infants younger than 6 months 4
• Use midazolam 0.1-0.2 mg/kg for seizures 4
• Administer isotonic fluid boluses of 10 mL/kg each for hypotension 4

High-Risk Patients:

Patients at extremes of age, with decreased liver function, or low cardiac output are particularly vulnerable to systemic toxicity. 6, 7

Critical Medications to Avoid

• Avoid propofol if cardiovascular instability is present 2, 4
• Avoid vasopressin entirely 4, 5
• Avoid calcium channel blockers and beta-blockers 4
• Limit epinephrine to small doses only if absolutely necessary 2, 3, 5

Prevention Strategies

• Calculate maximum allowable dose before any procedure 4, 6
• Aspirate frequently before each injection to avoid intravascular administration 4, 6
• Use small-dose, divided administration 6, 7
• Consider agents with lower toxicity (ropivacaine, levobupivacaine over bupivacaine) 6
• Use ultrasound guidance when available 7
• Have lipid emulsion protocol immediately available whenever long-acting local anaesthetics are administered 4, 6