What is the management of lignocaine (lidocaine) toxicity?

Management of Lignocaine (Lidocaine) Toxicity

The management of lignocaine toxicity requires immediate cessation of the drug, supportive care, and in severe cases, administration of 20% lipid emulsion therapy.

Recognition of Toxicity

Early recognition of lignocaine toxicity is crucial for effective management. Signs and symptoms progress in a predictable pattern:

Central Nervous System (CNS) Manifestations

• Early signs (appear first):

  • Circumoral numbness and facial tingling
  • Perioral numbness
  • Lightheadedness and dizziness
  • Tinnitus (ringing in ears)
  • Slurred speech
  • Numbness of lips or tongue 1

• Progressive signs:

  • Confusion
  • Drowsiness
  • Muscle twitching
  • Visual disturbances (blurred or double vision)
  • Tremor
  • Altered consciousness 1, 2

• Severe toxicity:

  • Seizures
  • Respiratory depression or arrest
  • Unconsciousness 2

Cardiovascular Manifestations (usually occur later)

• Bradycardia
• Hypotension
• Sinus arrest
• Cardiovascular collapse
• Cardiac arrest 1, 2

Immediate Management

1. Stop the administration of lignocaine immediately 1

2. Maintain airway, breathing, and circulation:

   • Ensure patent airway
   • Provide supplemental oxygen
   • Monitor vital signs continuously (ECG, pulse oximetry, blood pressure) 3

3. Seizure management:

   • Benzodiazepines (first-line treatment for seizures)
   • Protect the patient from injury during seizures 2

4. Cardiovascular support:

   • IV fluids for hypotension
   • Vasopressors if needed for persistent hypotension
   • Advanced cardiac life support (ACLS) protocols for cardiac arrest 2

5. Lipid emulsion therapy for severe toxicity:

   • 20% lipid emulsion should be readily available wherever IV lignocaine is used 1
   • Follow the Association of Anaesthetists' management guideline for lipid emulsion administration 1
   • Typical regimen: 1.5 mL/kg bolus of 20% lipid emulsion, followed by infusion of 0.25 mL/kg/min 3

Laboratory Assessment

• Obtain blood samples for lignocaine levels in both EDTA tubes and lithium heparin tubes 1
• Preserve the infusion pump with its settings and memory intact for investigation 1
• Monitor electrolytes, particularly in patients with cardiac manifestations
• Check for methemoglobinemia, especially in susceptible patients 2

Special Considerations

High-Risk Patients

Extra vigilance is required in:

• Patients >70 years of age
• Patients with congestive heart failure, cardiogenic shock, or hepatic dysfunction
• Patients with severe renal dysfunction
• Patients with preexisting neurologic dysfunction 1

Prevention of Toxicity

1. Calculate doses based on lean body weight 1
2. Do not use lignocaine in patients weighing <40 kg 1
3. Do not exceed 120 mg/h infusion rate 1
4. Avoid concurrent use with other local anesthetics 1, 3
5. Reduce infusion rates in patients with:
   • Cardiac failure (lignocaine half-life increases after 24-48h)
   • Hepatic dysfunction (primary route of metabolism)
   • Renal impairment 1, 4

Monitoring During Recovery

• Continue cardiac monitoring until symptoms resolve
• Monitor neurological status regularly
• For patients who received IV infusions, monitoring should continue for at least 24 hours after cessation due to the prolonged half-life in certain conditions 1

Specific Scenarios

Massive Overdose

In cases of massive overdose, more aggressive supportive care may be needed, with consideration for:

• Hemodialysis (though of limited value due to high protein binding)
• Prolonged lipid emulsion therapy
• Extended ICU monitoring 5

Pediatric Toxicity

• Children are more susceptible to toxicity due to lower body weight
• Careful dose calculation is essential (mg/kg basis)
• Symptoms may develop at lower doses compared to adults 6, 7

By following this systematic approach to management, the morbidity and mortality associated with lignocaine toxicity can be significantly reduced.