Is lidocaine (anti-arrhythmic medication) the right choice for pharmacological treatment of a patient presenting with tachycardia (rapid heart rate) and a pulse?

Pharmacological Treatment for Tachycardia with Pulse: Is Lidocaine the Right Choice?

Lidocaine is NOT the first-line pharmacological choice for most tachycardias with pulse—the correct drug depends entirely on whether you're treating stable ventricular tachycardia (where amiodarone is preferred) or supraventricular tachycardia (where adenosine is first-line), and lidocaine serves only as a second-line alternative for VT, particularly when ischemia-related. 1

Critical First Step: Hemodynamic Assessment

Before any pharmacological intervention, you must determine hemodynamic stability by assessing for adverse signs 1:

• Hypotension (systolic BP ≤90 mmHg) 1
• Chest pain suggesting ongoing ischemia 1
• Acute heart failure (pulmonary edema, dyspnea) 1
• Altered mental status indicating inadequate cerebral perfusion 1
• Signs of shock (decreased urine output, cool extremities) 1

If ANY of these adverse signs are present, skip pharmacological therapy entirely and proceed immediately to synchronized DC cardioversion (100J, 200J, 360J) with sedation if the patient is conscious. 1, 2 Do not delay cardioversion to establish IV access or administer medications. 1

For Hemodynamically STABLE Ventricular Tachycardia

First-Line: Amiodarone (NOT Lidocaine)

The European Society of Cardiology and American College of Cardiology recommend amiodarone as the preferred antiarrhythmic for hemodynamically stable VT, particularly in patients with structural heart disease or heart failure. 1

• Dosing: 150 mg IV over 10 minutes, followed by maintenance infusion of 1.0 mg/min for 6 hours, then 0.5 mg/min 1, 3
• Combine with IV beta-blockers for optimal efficacy 1
• Amiodarone's antiarrhythmic effect may take up to 30 minutes, so it's not ideal for rapidly deteriorating patients 4

Alternative First-Line: Procainamide

Procainamide demonstrates the greatest efficacy among medical options for stable monomorphic VT, with a loading infusion of 20-30 mg/min up to a maximum 10-17 mg/kg. 1 However, reduce infusion rates in patients with renal dysfunction. 3

Second-Line: Lidocaine (Limited Role)

Lidocaine is relegated to second-line status and is particularly useful when VT is thought to be ischemia-related. 1

• Initial bolus: 1.0-1.5 mg/kg IV (maximum 100 mg) 1
• Supplemental boluses: 0.5-0.75 mg/kg every 5-10 minutes to maximum 3 mg/kg total loading dose 3
• Maintenance infusion: 2-4 mg/min 1, 2
• Older guideline dosing (British Journal of Sports Medicine): 50 mg over 2 minutes, repeated every 5 minutes to total 200 mg, then 2 mg/min infusion 4, 2

Important caveat: A 1989 study found lidocaine was effective in only 19% (6 of 31 episodes) of sustained wide QRS complex tachycardia, questioning its traditional role as first-choice therapy. 5 This low efficacy supports current guidelines downgrading lidocaine to second-line status.

Critical Monitoring for Lidocaine Toxicity

Watch for CNS symptoms 2:

• Early: nausea, drowsiness, perioral numbness, dizziness, confusion, slurred speech
• Severe: muscle twitching, seizures, respiratory depression

Reduce lidocaine doses in older patients, heart failure, hepatic dysfunction, or after 24-48 hours (half-life increases over time). 2, 3

For Supraventricular Tachycardia (SVT)

Lidocaine has NO role in SVT treatment. 6 The algorithm is completely different:

Stable SVT Algorithm

1. First attempt: Vagal maneuvers (Valsalva maneuver or unilateral carotid pressure if no carotid bruit) 4, 2

2. First-line drug: Adenosine (drug of choice for AV nodal re-entrant tachyarrhythmias) 4, 2

   • 3 mg rapid IV bolus with saline flush
   • If no effect after 1-2 minutes: 6 mg
   • Maximum: 12 mg 4
   • Must be given in monitored environment (can cause transient complete heart block) 4, 2
   • Contraindicated in asthmatics (risk of bronchospasm) 4, 2

3. Alternative: Verapamil for definite SVT 4, 2

   • 5-10 mg IV over 60 seconds
   • Absolutely contraindicated if patient has taken beta-blockers (risk of profound bradycardia/hypotension) 4, 2
   • Never use in Wolff-Parkinson-White syndrome (may precipitate VT/VF) 2

Drugs to AVOID in Wide-Complex Tachycardia/VT

These are critical contraindications that can be lethal 1:

• Calcium channel blockers (verapamil, diltiazem): Can precipitate ventricular fibrillation or profound hypotension, especially with myocardial dysfunction 1, 2
• Adenosine: Should not be used for unstable or irregular/polymorphic wide-complex tachycardias (may cause degeneration to VF) 1
• Class IC antiarrhythmics (flecainide, propafenone): Avoid in prior MI or structural heart disease 1, 3

Special Situations

Torsades de Pointes (Polymorphic VT with Long QT)

Magnesium 8 mmol (2 grams) IV bolus immediately, especially if hypomagnesemia suspected. 1, 3 IV beta-blockers are the single most effective therapy for polymorphic VT storm and should be combined with amiodarone. 1, 3

VT Storm (Recurrent/Incessant VT)

First-line: IV beta-blockers combined with amiodarone (150 mg over 10 minutes, then infusion). 3 Lidocaine may be considered for recurrent VT/VF not responding to beta-blockers or amiodarone. 3

Practical Administration Pearls

• Always follow IV drugs with 20 mL saline bolus to aid delivery to central circulation 4, 2
• Correct electrolytes BEFORE and DURING therapy: potassium >4.0 mEq/L, magnesium >2.0 mg/dL 1
• Keep cardioversion equipment immediately available when administering any antiarrhythmic 1
• Monitor continuously for hypotension, bradycardia, and AV block during antiarrhythmic administration 1

Bottom Line Algorithm

For tachycardia with pulse:

1. Assess hemodynamic stability → If unstable (hypotension, chest pain, heart failure, altered mental status, shock) → Immediate synchronized cardioversion 1

2. If stable, determine rhythm type:

   • Wide-complex (likely VT) → Amiodarone first-line, procainamide alternative, lidocaine second-line (especially if ischemia-related) 1
   • Narrow-complex (likely SVT) → Vagal maneuvers, then adenosine (lidocaine has no role) 4, 2

Lidocaine's historical prominence as "first-choice" for VT is outdated—modern evidence and guidelines clearly favor amiodarone for stable VT, relegating lidocaine to a supportive role primarily in ischemia-related ventricular arrhythmias. 1, 5, 7