What is the appropriate use of lignocaine (lidocaine) in a patient with ventricular tachycardia?

Lignocaine (Lidocaine) Use in Ventricular Tachycardia

For hemodynamically stable ventricular tachycardia, lignocaine is administered as an initial bolus of 50 mg IV over 2 minutes, repeated every 5 minutes to a total dose of 200 mg, followed by a maintenance infusion of 2 mg/min. 1

Hemodynamic Assessment First

Before administering lignocaine, assess whether the patient is hemodynamically stable or unstable by checking for:

• Systolic blood pressure ≤90 mmHg 2
• Chest pain suggesting ongoing ischemia 2
• Acute heart failure with pulmonary edema 2
• Altered mental status indicating inadequate cerebral perfusion 2
• Signs of shock (cool extremities, decreased urine output) 2

If any of these adverse signs are present, immediate synchronized DC cardioversion (100J, 200J, 360J) takes priority over drug therapy. 3, 1, 2

Lignocaine Dosing Regimens

For Stable VT with Pulse

• Initial dose: 50 mg IV over 2 minutes 1
• Repeat: Every 5 minutes to a total dose of 200 mg 1
• Maintenance: 2 mg/min continuous infusion 1

Alternative Dosing (ACC/AHA Protocol)

• Loading bolus: 1.0-1.5 mg/kg IV (maximum 100 mg) 3, 1
• Additional boluses: 0.5-0.75 mg/kg every 8-10 minutes if needed 3
• Maximum total loading: 3-4 mg/kg 3
• Maintenance infusion: 2-4 mg/min (20-50 µg/kg/min) 3, 1

For Cardiac Arrest/Pulseless VT

• Initial bolus: 100 mg IV 1
• Repeat: After 5-10 minutes if needed 1
• Maintenance: 2-4 mg/min infusion 1

Current Position in Treatment Algorithm

Lignocaine is now considered a second-line agent for stable VT, with amiodarone and beta-blockers preferred as first-line therapy, particularly in patients with structural heart disease. 2 The European Society of Cardiology recommends amiodarone (150 mg IV over 10 minutes, then 1.0 mg/min infusion) combined with IV beta-blockers as the preferred initial treatment for hemodynamically stable VT. 2

However, lignocaine remains the drug of choice specifically in the acute MI setting when VT occurs 3, and is particularly useful when VT is thought to be ischemia-related. 1, 2 Research confirms that lignocaine exhibits well-investigated anti-arrhythmic effects by increasing the ventricular fibrillatory threshold and interrupting re-entrant tachycardias, especially in ischemic tissue. 4

Dose Adjustments Required

Reduce the maintenance infusion rate in the following situations:

• Elderly patients (≥70 years): Reduce dose due to decreased clearance 3, 5
• Heart failure or cardiogenic shock: Decrease dose as volume of distribution and clearance are reduced 3, 6
• Hepatic disease: Use with caution and reduce dose, as lignocaine is metabolized by the liver 6
• Low body weight (<50 kg) or high body weight (≥90 kg): Adjust infusion rate 5
• After 24-48 hours: Reduce infusion rate as the half-life increases over time 1

Patients requiring more than one bolus dose may need higher maintenance doses (up to 40-50 µg/kg/min). 3, 1

Critical Toxicity Monitoring

Monitor continuously for early signs of central nervous system toxicity:

• Nausea, drowsiness, perioral numbness 1
• Dizziness, confusion, slurred speech 1
• Muscle twitching, seizures (severe toxicity) 1, 7
• Respiratory depression (severe toxicity) 1

Lignocaine depresses myocardial contractility, requiring careful monitoring especially in hemodynamically compromised patients. 1 If toxicity occurs, immediately discontinue lignocaine and treat seizures with benzodiazepines. 7

Important Contraindications and Cautions

Do not use lignocaine as first-line therapy in the following situations:

• Polymorphic VT storm: IV beta-blockers are the single most effective therapy 8, 2
• Torsades de pointes: Magnesium 8 mmol (2 grams) IV bolus is indicated 3, 2
• Severe shock: Lignocaine is generally not well tolerated 3
• Heart block: Use with caution 6

Practical Administration Details

• Always follow IV lignocaine with a 20 mL saline bolus to aid delivery to central circulation 1
• Correct electrolyte abnormalities (potassium >4.0 mEq/L, magnesium >2.0 mg/dL) before and during therapy 2
• Have resuscitative equipment, oxygen, and cardioversion capability immediately available 6
• Monitor cardiovascular and respiratory vital signs continuously after each injection 6

When Lignocaine Fails

If VT persists or recurs despite lignocaine:

• Amiodarone is indicated for VT refractory to lignocaine: 5 mg/kg (300 mg) over 15 minutes for life-threatening situations, or over one hour for stable patients 1
• Procainamide is an alternative: 20-30 mg/min up to 10-17 mg/kg loading dose 1, 2
• Bretylium for refractory VT: 5 mg/kg diluted with 100 mL dextrose, with possible further dose of 10 mg/kg 3, 1

Evidence Quality Note

While older ACC/AHA guidelines from 1990-1996 positioned lignocaine as the drug of choice for VT in acute MI 3, more recent evidence shows that sotalol is significantly more effective than lignocaine for acute termination of sustained VT (69% vs 18% success rate) 9, and amiodarone may be superior, especially in patients with recurrent sustained VT requiring cardioversion. 3 Despite lignocaine's ability to reduce primary VF, mortality is not reduced, as VF deaths are offset by deaths from asystole and electromechanical dissociation. 3