Lidocaine Dilution for Ventricular Tachycardia
For hemodynamically stable monomorphic VT, administer lidocaine as an initial IV bolus of 1 to 1.5 mg/kg (typically 75-100 mg), followed by repeat boluses of 0.5 to 0.75 mg/kg every 5-10 minutes if needed, up to a maximum cumulative dose of 3 mg/kg, then maintain with a continuous infusion of 1 to 4 mg/min (30-50 mcg/kg/min). 1
Initial Bolus Dosing
The loading strategy requires no dilution for the bolus doses - lidocaine is given as direct IV push:
- First bolus: 1-1.5 mg/kg IV push (75-100 mg for average adult)
- Repeat boluses: 0.5-0.75 mg/kg (25-50 mg) every 5-10 minutes as needed
- Maximum total loading dose: 3 mg/kg 1, 2
For shock-refractory VT/VF (cardiac arrest), simplified dosing is easier: give 100 mg IV push, which may be repeated after 5-10 minutes 3, 4
Maintenance Infusion Preparation
After successful bolus therapy, prepare the maintenance infusion:
- Standard concentration: Mix to achieve 1-4 mg/min infusion rate
- Typical preparation: 1-2 grams lidocaine in 250-500 mL D5W (creates 2-4 mg/mL solution)
- Infusion rate: 1-4 mg/min (30-50 mcg/kg/min) 1
For patients with heart failure, start at the lower end: 1 mg/min achieves the highest probability of therapeutic levels (78.6%) while minimizing toxicity risk 5. This is critical because lidocaine clearance is significantly reduced in heart failure, with half-life extending from 1-2 hours to >20 hours in severe cases 6.
Important Clinical Considerations
Lidocaine is now a second-line agent for stable VT. The 2010 AHA guidelines clearly position amiodarone, procainamide, and sotalol ahead of lidocaine for hemodynamically stable monomorphic VT 1. The 2025 AHA guidelines further downgrade lidocaine, noting it is "less effective than amiodarone, procainamide, or sotalol" and "unclear if more efficacious than placebo" 7.
However, lidocaine remains useful in specific scenarios:
- Shock-refractory VT/VF during cardiac arrest (after defibrillation and epinephrine) 1, 4
- Polymorphic VT with normal QT interval when acute ischemia is present 4
- Electrical storm in combination with beta-blockers and amiodarone 4
Critical dosing adjustments:
- Heart failure: Reduce maintenance to 1 mg/min 5
- Cardiogenic shock: Further dose reduction required; half-life >20 hours 6
- Elderly/debilitated: Reduce all doses 8
Efficacy Reality Check
The evidence shows lidocaine has poor efficacy for stable VT: only 8% termination rate in one prospective study 9, though it performs better in acute ischemic settings versus chronic VT 10. Amiodarone demonstrates 78% immediate VT termination versus 27% with lidocaine 11, and lidocaine is associated with better outcomes than amiodarone specifically for in-hospital cardiac arrest 12.
Common pitfall: Do not use lidocaine for wide-complex tachycardia of uncertain etiology without considering amiodarone or procainamide first 7. The narrow therapeutic window (1.5-5.0 μg/L) and risk of CNS toxicity (slurred speech, altered consciousness, seizures) require vigilant monitoring 1.