What is the recommended dose of lignocaine (lidocaine) for a hemodynamically stable patient with ventricular tachycardia (VT)?

Lidocaine Dosing for Hemodynamically Stable Ventricular Tachycardia

For hemodynamically stable monomorphic VT, administer an initial IV bolus of 1.0 to 1.5 mg/kg (not exceeding 100 mg), followed by supplemental boluses of 0.5 to 0.75 mg/kg every 5-10 minutes as needed, up to a maximum total loading dose of 3 mg/kg, then maintain with an infusion of 2-4 mg/min (30-50 mcg/kg/min). 1

Initial Bolus Dosing

• Give 1.0 to 1.5 mg/kg IV bolus as the first dose, with a maximum single bolus of 100 mg 1, 2
• If the initial bolus fails to terminate VT, administer additional boluses of 0.5 to 0.75 mg/kg every 5-10 minutes 1, 2
• Do not exceed a total loading dose of 3-4 mg/kg across all boluses 1, 2

The older 1990 ACC/AHA guideline recommended starting with 1 mg/kg (not exceeding 100 mg) with 0.5 mg/kg boluses every 8-10 minutes 1, but the more recent 1996 guideline increased the initial dose range to 1.0-1.5 mg/kg with slightly more frequent redosing 1.

Maintenance Infusion

• After successful conversion, start a continuous infusion at 2-4 mg/min (equivalent to 30-50 mcg/kg/min in a 70 kg patient) 1, 2
• Patients requiring multiple boluses for conversion typically need higher maintenance rates (up to 40-50 mcg/kg/min) 1, 2
• Reduce the infusion rate by 1 mg/min after 12-24 hours because lidocaine's half-life increases significantly over time 1, 2

Critical Dose Adjustments

You must substantially reduce doses in patients with heart failure, cardiogenic shock, or hepatic dysfunction—this is not optional. 1, 2

• In heart failure, lidocaine's half-life extends from 1-2 hours to >20 hours, requiring major dose reduction 1, 2
• In cardiogenic shock, the half-life can exceed 20 hours, necessitating even more aggressive dose reduction 1
• Elderly patients also require lower infusion rates to avoid toxicity 1

Important Clinical Context: When NOT to Use Lidocaine First-Line

Lidocaine is NOT the optimal first-line agent for stable monomorphic VT in most settings. The evidence clearly shows:

• Procainamide is superior to lidocaine for terminating stable monomorphic VT, with significantly higher conversion rates 1, 3, 4, 5
• Lidocaine converts only approximately 20% of stable monomorphic VT 3, 4
• In a head-to-head trial, ajmaline terminated VT in 19 of 30 patients versus lidocaine's 4 of 31 patients (P<0.001) 5

Lidocaine remains appropriate as first-line therapy specifically when:

• VT occurs in the setting of acute myocardial infarction or active ischemia 1, 2, 6
• Procainamide is contraindicated (severe heart failure, renal dysfunction, or QT prolongation) 3

Alternative Agents When Lidocaine Fails

If lidocaine does not terminate VT:

• Amiodarone 150 mg IV over 10 minutes is indicated for refractory VT, followed by 1 mg/min infusion for 6 hours, then 0.5 mg/min 1
• Procainamide 20-30 mg/min loading infusion (up to 12-17 mg/kg) is more effective than lidocaine for initial treatment 1
• Do not stack multiple antiarrhythmic drugs—if one fails, proceed to electrical cardioversion rather than adding another agent 7

Monitoring for Toxicity

Watch for these signs of lidocaine toxicity in order of severity:

• Early CNS symptoms: perioral numbness, nausea, drowsiness, dizziness 2, 6
• Progressive CNS toxicity: confusion, slurred speech, muscle twitching 2
• Severe toxicity: seizures, respiratory depression, cardiovascular collapse 2
• Cardiovascular effects: bradycardia, sinus arrest, hypotension, decreased myocardial contractility 2, 6

Common Pitfalls to Avoid

• Never use standard doses in heart failure or shock without major reduction—this is the most critical error leading to toxicity 1, 2
• Do not rely on lidocaine as first-line for stable VT outside the acute MI setting—procainamide or amiodarone are more effective 1, 3, 4
• Do not forget the second bolus at 30-120 minutes—plasma levels can drop to subtherapeutic ranges even with continuous infusion 1
• Do not continue infusion beyond 24-48 hours without dose reduction—accumulation is inevitable 1, 2

Hemodynamically Unstable VT

If the patient becomes unstable at any point (systolic BP <90 mmHg, altered mental status, chest pain, pulmonary edema):

• Immediate synchronized cardioversion is the primary intervention, not pharmacologic therapy 1, 6
• Start with 100J for monomorphic VT, escalating to 200J then 360J as needed 1, 6
• Provide sedation if the patient is conscious 1, 6