What is the recommended lignocaine (lidocaine) bolus and infusion dose for ventricular tachycardia (VTach)?

Lignocaine (Lidocaine) Dosing for Ventricular Tachycardia

For ventricular tachycardia (VT), lignocaine (lidocaine) should be administered as a 1-3 mg/kg IV bolus (not exceeding 100 mg), followed by a maintenance infusion of 2-4 mg/min if cardioversion is successful. 1

Initial Assessment and Management

• First determine if the patient has a pulse and assess hemodynamic stability 1, 2
• For pulseless VT, follow the ventricular fibrillation protocol with immediate defibrillation as the primary intervention 1
• For VT with pulse but hemodynamic instability (systolic BP ≤90 mmHg, chest pain, heart failure, or heart rate ≥150 beats/min), perform immediate synchronized DC cardioversion (100J, 200J, 360J) with sedation if the patient is conscious 1, 2

Lignocaine (Lidocaine) Dosing for VT

For Cardiac Arrest/Pulseless VT:

• Initial bolus: 100 mg IV 1
• May repeat after 5-10 minutes if needed 1
• If successful, maintain with infusion at 2-4 mg/min 1

For Stable VT with Pulse:

• Initial dose: 50 mg IV over 2 minutes 1
• Repeat every 5 minutes to a total dose of 200 mg 1
• Start maintenance infusion at 2 mg/min 1

Alternative Dosing Regimen:

• Loading dose: 1 mg/kg IV (not exceeding 100 mg) 1
• Additional boluses of 0.5 mg/kg every 8-10 minutes if necessary, to a total of 4 mg/kg 1
• Maintenance infusion: 20-50 μg/kg/min (1.4-3.5 mg/min in a 70 kg patient) 1

Important Considerations

• Always follow IV drug administration with a 20 ml saline bolus to aid delivery to the central circulation 1, 2
• Patients who require more than one bolus dose may need higher maintenance doses (up to 40-50 μg/kg/min) 1
• Reduce the infusion rate after 24-48 hours as the half-life of lidocaine increases over time 1
• Decrease the dose in patients with:
  • Myocardial infarction (half-life >4 hours) 1
  • Cardiac failure (half-life >20 hours) 1
  • Cardiogenic shock (even longer half-life) 1
  • Older age or hepatic dysfunction 3

Monitoring and Toxicity

• Monitor for signs of toxicity including 1:
  • Central nervous system symptoms: nausea, drowsiness, perioral numbness, dizziness, confusion, slurred speech
  • More severe: muscle twitching, seizures, respiratory depression
  • Cardiovascular effects: bradycardia, sinus arrest, hypotension
• Lidocaine depresses myocardial contractility, requiring careful monitoring especially in hemodynamically compromised patients 1, 2

Alternative Antiarrhythmic Options

• If lignocaine fails, consider amiodarone: 5 mg/kg (300 mg) over one hour for stable patients, or over 15 minutes in life-threatening situations 1, 3
• Recent evidence suggests amiodarone may be more effective than lidocaine for shock-resistant VT, with a 78% immediate termination rate compared to 27% with lidocaine 4
• Procainamide has also shown superior efficacy to lidocaine in terminating spontaneous monomorphic VT (80% vs 19% success rate) 5

Special Situations

• For torsades de pointes, consider magnesium (8 mmol bolus followed by 2.5 mmol/h infusion) 1, 3
• Lidocaine is more effective for acute-onset ventricular arrhythmias compared to chronic arrhythmias 6
• For refractory VT, consider bretylium (5 mg/kg diluted with 100 ml dextrose, with possible further dose of 10 mg/kg) 1