What are the recommended bolus and maintenance infusion doses of lidocaine and procainamide for ventricular tachycardia?

Lidocaine and Procainamide Dosing for Ventricular Tachycardia

For ventricular tachycardia, lidocaine should be administered as an initial IV bolus of 1 mg/kg (not exceeding 100 mg), followed by a maintenance infusion of 20-50 μg/kg/min (1.4-3.5 mg/min in a 70 kg patient); procainamide should be given as an IV bolus of 1-2 mg/kg over 5 minutes to a cumulative dose of approximately 1,000 mg, followed by a maintenance infusion of 20-80 μg/kg/min. 1

Lidocaine Dosing Protocol

Initial Bolus:

• 1 mg/kg IV (maximum 100 mg) 1
• Additional boluses of 0.5 mg/kg can be given every 8-10 minutes if needed
• Total cumulative bolus dose should not exceed 4 mg/kg 1

Maintenance Infusion:

• 20-50 μg/kg/min (1.4-3.5 mg/min for a 70 kg patient) 1
• Higher maintenance doses (up to 40-50 μg/kg/min) may be required in patients needing multiple initial boluses 1

Special Considerations:

• In cardiac arrest: Use bolus therapy only (100 mg), repeatable every 2-3 minutes as needed 1
• Reduce infusion rates in:
  • Elderly patients (>70 years)
  • Patients with heart failure or cardiogenic shock (half-life extends to >20 hours)
  • Patients with hepatic dysfunction (lidocaine is eliminated by the liver) 1, 2

Procainamide Dosing Protocol

Initial Bolus:

• 1-2 mg/kg IV over 5-minute intervals 1
• Continue until arrhythmia suppressed or maximum cumulative dose of 1,000 mg reached 1

Maintenance Infusion:

• 20-80 μg/kg/min IV 1

Comparative Efficacy

Procainamide is superior to lidocaine for terminating sustained monomorphic ventricular tachycardia. Studies show procainamide terminates 12 of 15 VT cases (80%) compared to only 3 of 14 cases (21%) with lidocaine 3. Additionally, procainamide successfully terminated 8 of 11 VTs that were unresponsive to lidocaine 3.

Monitoring Guidelines

• During lidocaine infusion:

  • First 15 minutes: Continuous ECG monitoring with blood pressure checks every 5 minutes
  • First hour: Observations every 15 minutes
  • After first hour: Hourly observations minimum 2
  • Check blood levels at 4 hours, 24 hours, and daily thereafter if infusion continues 2

• Target therapeutic range for lidocaine: 2-4 mg/L (or < 5 μg/ml) 2

Warning Signs of Toxicity

• Early signs: Perioral tingling, tinnitus, light-headedness, and restlessness
• Late signs: ECG changes, bradycardia, sinus arrest, and hypotension 2
• CNS symptoms: Nausea, drowsiness, confusion, slurred speech, muscle twitching 1

Key Clinical Pitfalls

1. Lidocaine half-life increases after 24-48 hours, requiring dose reduction by 1 mg/min preferably at 12 hours but at least by 24 hours 1

2. A second bolus of lidocaine (0.5 mg/kg) may be needed 30-120 minutes after initiation due to transient subtherapeutic plasma concentrations 1

3. Increasing maintenance infusion without an additional bolus results in very slow increase in plasma concentration (>6 hours to reach new plateau) 1

4. Procainamide has more significant QRS-widening effects than lidocaine, especially at faster heart rates 4

5. Lidocaine's effectiveness may be delayed in patients with chronic ventricular arrhythmias compared to those with acute-onset arrhythmias 5