Local anaesthetic can lead to toxicity due to blockade of sodium channels.

The maximum safe dose of lidocaine is 3mg/kg.

In a 70kg patient, this would be 210mg. Lidocaine 1% has 50mg in 5ml (10mg/ml)so the maximum volume of lidocaine in a 70kg patient would be 21 ml.

Symptoms and signs

• Altered mental status - Decreased consciousness
• Restlessness/agitation
• Numbness or tingling around the mouth
• Tinnitus
• Shivering
• Vertigo/dizziness
• Subtle tremors of the face and extremities
• Respiratory depression
• Apnoea
• Seizures
• Cardiovascular signs:
  • Sinus bradycardia
  • Tachycardia
  • Hypertension
  • Hypotension
  • Ventricular arrhythmias
  • Asystole

Management

• Stop administration of local anaesthetic!
• ABCDE approach including ECG monitoring