What are the indications for lidocaine infusion in patients with ventricular arrhythmias, such as ventricular tachycardia or ventricular fibrillation, and a history of cardiac disease, including myocardial infarction or heart failure?

Indications for Lidocaine Infusion

Lidocaine infusion is indicated for hemodynamically stable sustained ventricular tachycardia and for ventricular fibrillation during cardiac arrest, but prophylactic use in uncomplicated acute myocardial infarction is no longer recommended due to lack of mortality benefit and risk of toxicity. 1

Class I Indications (Definite Use)

Ventricular Tachycardia and Fibrillation

• Hemodynamically stable sustained ventricular tachycardia: Administer 1 mg/kg IV bolus (maximum 100 mg), followed by maintenance infusion of 20-50 μg/kg/min 2
• Ventricular fibrillation during cardiac arrest: Give 100 mg bolus initially, repeatable every 2-3 minutes as needed during resuscitation 1, 2
• Recurrent ventricular tachycardia or fibrillation: Use in conjunction with defibrillation and cardiopulmonary resuscitation 1

High-Risk Ventricular Premature Beats in Acute MI

Lidocaine is indicated when ventricular premature beats exhibit any of these features 1, 3:

• Frequent (>6 per minute)
• Closely coupled (R-on-T phenomenon)
• Multiform configuration
• Occurring in short bursts of three or more in succession

Class II Indications (Reasonable to Use)

• Suspected acute myocardial ischemia or infarction with high-risk ventricular premature beats as defined above 1

Class III Indications (NOT Recommended)

Prophylactic Use is Contraindicated

• Uncomplicated acute myocardial infarction without ventricular arrhythmias: Meta-analysis of 14 randomized trials showed lidocaine reduces ventricular fibrillation by 33% but provides no mortality benefit, while adverse effects may offset any benefits 1
• Routine prophylaxis in all MI patients: The risk of toxicity (particularly in elderly patients >70 years) outweighs potential benefits 1, 4

Comparative Effectiveness

Lidocaine is less effective than alternative agents for stable monomorphic VT 1:

• Inferior to sotalol (100% vs lower conversion rate) 1
• Inferior to procainamide (improved reversion rate over lidocaine 1.5 mg/kg) 1
• Inferior to amiodarone (20-40% conversion rate for amiodarone vs lower for lidocaine) 1

When lidocaine fails to control ventricular arrhythmias, procainamide (1-2 mg/kg IV bolus over 5-minute intervals to cumulative 1,000 mg) should be the next agent. 1

Critical Dosing Adjustments

Patients Requiring Reduced Doses 1, 2, 5

• Age >70 years: Significantly reduce infusion rates due to increased half-life
• Congestive heart failure: Half-life increases to >20 hours (vs 1-2 hours normally) 5
• Cardiogenic shock: Even longer half-life requires substantial dose reduction 5
• Hepatic dysfunction: Reduce maintenance infusion rates
• Severe renal dysfunction: Lower infusion rates needed
• Preexisting neurologic dysfunction: Use caution with reduced doses

Maintenance Infusion Adjustments

• Reduce dose by 1 mg/min at 12 hours, or at minimum by 24 hours 2
• Higher maintenance doses (40-50 μg/kg/min) may be required only if multiple boluses were needed initially 2

Monitoring for Toxicity

CNS Toxicity (Most Common) 1, 2

• Nausea, drowsiness, perioral numbness
• Dizziness, confusion, slurred speech
• Muscle twitching, tremor
• Respiratory depression, altered consciousness

Cardiovascular Toxicity 1, 2

• Bradycardia
• Sinus arrest
• Hypotension

Timing of Monitoring

• Check plasma concentrations at 30-120 minutes after initiation 2
• Measure serum levels with prolonged or high infusion rates 1

Common Pitfalls to Avoid

• Do not increase maintenance infusion without an additional bolus: This results in very slow increase in plasma concentration (>6 hours to reach new plateau) 2
• Do not use prophylactically beyond 24 hours unless specific therapeutic indications persist 1
• Do not use in patients >6 hours post-MI onset: These patients are less likely to develop ventricular fibrillation and do not benefit from prophylaxis 1
• Avoid in reperfusion arrhythmias: Lidocaine does not prevent reperfusion-related ventricular tachyarrhythmias following thrombolysis 6
• Calculate dose based on lean body weight, not total body weight 1

Historical Context

While lidocaine was the antiarrhythmic of choice for decades 7, current evidence and guidelines have shifted away from routine prophylactic use due to lack of mortality benefit and the availability of more effective alternatives like amiodarone for sustained VT 1. Its primary role now is limited to acute treatment of hemodynamically stable VT when electrical cardioversion is not immediately performed, and as an adjunct during cardiac arrest with VF/VT 1.