In an adult without severe hepatic or renal impairment, how long should a lidocaine infusion be administered for acute ventricular tachycardia?

Duration of Lidocaine Infusion for Ventricular Tachycardia

Lidocaine infusion should be reduced by 1 mg/min at 12 hours (or at minimum by 24 hours) and discontinued within 24-48 hours for acute ventricular tachycardia, as the drug's half-life increases significantly after this period, raising the risk of toxicity without additional clinical benefit. 1, 2

Critical Timing Considerations

Initial 12-24 Hour Period

• The half-life of lidocaine increases substantially after 24-48 hours of continuous infusion 1, 2
• Dose reduction of 1 mg/min should occur preferably at 12 hours but must occur by 24 hours to prevent drug accumulation 1, 2
• In patients with uncomplicated myocardial infarction, the half-life extends from 1-2 hours (normal) to >4 hours 1
• In heart failure or cardiogenic shock, the half-life can exceed 20 hours, necessitating even earlier dose reduction 1

Duration Beyond 24 Hours

• Prophylactic lidocaine beyond 24 hours is not recommended due to lack of mortality benefit and increased risk of adverse effects 3
• A randomized controlled trial demonstrated that extending lidocaine infusion from 8 hours to 48 hours resulted in significantly more congestive heart failure (9% vs 2%, p=0.03) without preventing ventricular fibrillation 4
• After 36 hours of infusion, drug clearance decreases significantly, requiring further dose reduction to avoid accumulation 5

Practical Management Algorithm

For Hemodynamically Stable VT

• Initial phase (0-12 hours): Standard maintenance infusion at 2-4 mg/min (30-50 µg/kg/min) after successful bolus therapy 1
• 12-24 hour mark: Reduce infusion rate by 1 mg/min 1, 2
• 24-48 hours: Plan discontinuation; consider transitioning to oral antiarrhythmic therapy if ongoing suppression needed 2

For VT in Acute MI Setting

• Lidocaine remains appropriate as first-line therapy when VT is thought related to acute ischemia 6
• Duration should still be limited to 24-48 hours with dose reduction at 12-24 hours 1, 2
• If arrhythmias persist beyond this timeframe, transition to alternative agents (amiodarone or procainamide) rather than prolonging lidocaine 6, 3

Method of Discontinuation

Abrupt vs Gradual Tapering

• Research comparing abrupt cessation versus 3-hour tapering found no difference in recurrence of ventricular arrhythmias (3/18 vs 2/11 patients) 5
• Either method is acceptable, though monitoring should continue for at least 12 hours after discontinuation 5
• Recurrence of arrhythmias occurred in both groups but was not related to the method of discontinuation 5

High-Risk Populations Requiring Earlier Discontinuation

Patients Requiring Dose Reduction and Shorter Duration

• Age >70 years: Significantly reduced clearance necessitates lower doses and earlier discontinuation 1, 2, 3
• Heart failure or cardiogenic shock: Half-life >20 hours requires aggressive dose reduction and discontinuation within 24 hours 1, 6
• Hepatic dysfunction: Lidocaine is eliminated almost exclusively by the liver; severe dysfunction mandates shorter infusion duration 1

Monitoring During Infusion

Plasma Concentration Monitoring

• Check for subtherapeutic levels at 30-120 minutes after initiation (may require additional 0.5 mg/kg bolus without increasing infusion rate) 1, 2
• Monitor serum levels with prolonged infusions (>24 hours) or high infusion rates 3
• Target therapeutic range is up to 5 µg/ml 1

Toxicity Surveillance

• CNS toxicity: Nausea, drowsiness, perioral numbness, dizziness, confusion, slurred speech, muscle twitching, tremor, respiratory depression, altered consciousness 1, 2, 6, 3
• Cardiovascular toxicity: Bradycardia, sinus arrest, hypotension 1, 2, 6, 3
• Increased risk of asystole with prolonged use 1

Common Pitfalls to Avoid

• Do not continue standard-dose infusions beyond 24 hours without dose reduction—this is the most common error leading to toxicity 1, 2
• Do not increase maintenance infusion rate without giving an additional bolus—this results in >6 hours to reach new therapeutic plateau 1, 2
• Do not use lidocaine for prolonged prophylaxis in uncomplicated MI beyond 24-48 hours—no mortality benefit and increased adverse effects 3, 4
• Do not rely on lidocaine as monotherapy if VT persists beyond 24-48 hours—procainamide and amiodarone are more effective for sustained monomorphic VT 6, 3, 7, 8

When to Transition to Alternative Therapy

• If VT recurs after 8-10 hours at steady infusion rate, give additional bolus and increase maintenance rate, but plan transition to alternative agent if this occurs repeatedly 1
• Procainamide is superior to lidocaine for terminating sustained monomorphic VT (75.7% vs 35.0% success rate) and should be considered if lidocaine fails 7, 8
• Amiodarone (150 mg over 10 minutes followed by 1.0 mg/min for 6 hours, then 0.5 mg/min maintenance) is indicated for VT refractory to lidocaine 1, 6