Lignocaine Infusion Duration for Ventricular Tachycardia
For ventricular tachycardia, lignocaine (lidocaine) should be maintained as a continuous infusion at 2-4 mg/min after successful termination of VT, with the infusion rate reduced after 24-48 hours as the drug's half-life increases over time. 1, 2
Initial Loading and Maintenance Dosing
The standard approach involves:
Initial bolus: 1.0-1.5 mg/kg (typically 75-100 mg), with additional boluses of 0.5-0.75 mg/kg every 5-10 minutes as needed, up to a maximum total loading dose of 3 mg/kg 1
Maintenance infusion: 2-4 mg/min (30-50 µg/kg/min) following successful VT termination 1, 2
For stable VT specifically: 50 mg over 2 minutes, repeated every 5 minutes to a total of 200 mg if needed, then 2 mg/min maintenance 2
Duration Considerations and Dose Adjustments
The infusion rate should be reduced after 24-48 hours because lidocaine's half-life increases significantly over time. 2 This is a critical point often overlooked—continuing the same infusion rate beyond 48 hours substantially increases toxicity risk.
High-Risk Populations Requiring Lower Doses
Reduce the maintenance infusion rate in: 1, 2
- Older patients (age-related decreased clearance)
- Congestive heart failure (reduced hepatic blood flow)
- Hepatic dysfunction (impaired metabolism)
- Shock states (poor drug tolerance)
For these patients, consider starting at the lower end (2 mg/min) or even reducing to 1-2 mg/min. 1
Patients Requiring Higher Doses
Patients who require more than one bolus dose during loading may need higher maintenance infusions (up to 40-50 µg/kg/min or approximately 3-4 mg/min in a 70 kg patient). 2 This reflects higher drug clearance or more refractory arrhythmia.
Monitoring for Toxicity
Watch for central nervous system symptoms indicating toxicity: 2
- Early signs: Nausea, drowsiness, perioral numbness, dizziness, confusion, slurred speech
- Severe toxicity: Muscle twitching, seizures, respiratory depression
Lidocaine also depresses myocardial contractility, requiring careful hemodynamic monitoring especially in compromised patients. 2
Clinical Effectiveness Caveat
It's important to recognize that lidocaine has limited efficacy for VT termination—only 8-27% success rates in clinical studies—and is significantly inferior to alternatives like amiodarone (67-78% success) or procainamide. 3, 4, 5, 6 Despite being recommended as first-line therapy in guidelines, particularly for acute MI-related VT, its actual effectiveness is modest. 1, 2
For refractory or recurrent VT, consider switching to amiodarone (150 mg over 10 minutes, then 1.0 mg/min for 6 hours, then 0.5 mg/min maintenance) rather than continuing ineffective lidocaine therapy. 1, 2, 7
When to Discontinue
While the guidelines don't specify an exact maximum duration, the practical approach is:
- Continue the infusion as long as the patient remains at risk for recurrent VT
- Taper and discontinue once the underlying trigger (ischemia, electrolyte abnormalities) is corrected
- Transition to oral antiarrhythmic therapy or definitive treatment (revascularization, ICD) as appropriate 7