What is the preferred medication between amiodarone and lidocaine (antiarrhythmic agents) for treating refractory ventricular fibrillation (v fib)?

Amiodarone vs Lidocaine in Refractory Ventricular Fibrillation

Amiodarone is the preferred medication over lidocaine for treating refractory ventricular fibrillation, as it has demonstrated superior rates of hospital admission compared to lidocaine in patients with shock-resistant VF. 1, 2

Evidence-Based Recommendation Algorithm

First-Line Therapy

1. Amiodarone should be administered for VF/pulseless VT that is unresponsive to:

   • CPR
   • Defibrillation (multiple shocks)
   • Vasopressor therapy

   Dosing: Initial dose of 300 mg IV/IO, followed by one dose of 150 mg IV/IO if needed 1

Second-Line Therapy

1. Lidocaine should only be considered if:

   • Amiodarone is not available
   • Contraindications to amiodarone exist

   Dosing: Initial dose of 1 to 1.5 mg/kg IV, with additional doses of 0.5 to 0.75 mg/kg IV push at 5-10 minute intervals to a maximum dose of 3 mg/kg 1

Strength of Evidence

The recommendation for amiodarone as first-line therapy is supported by several key studies:

1. Randomized controlled trials have shown that amiodarone improves hospital admission rates compared to placebo or lidocaine in patients with refractory VF/pulseless VT 1, 2

2. The ALIVE trial demonstrated that amiodarone (5 mg/kg) improved survival to hospital admission compared to lidocaine (1.5 mg/kg) in patients with shock-resistant VF 1, 2

3. The FDA-approved indication for IV amiodarone specifically includes initiation of treatment for frequently recurring VF and hemodynamically unstable VT in patients refractory to other therapy 3

Clinical Considerations

Timing of Administration

• Administer antiarrhythmic drugs after defibrillation attempts have failed
• Earlier administration may improve outcomes, as suggested by the ROC-ALPS subgroup analysis of witnessed arrests 1

Formulation Considerations

• Two formulations of IV amiodarone exist in the US:
  • Polysorbate-containing formulation (may cause hypotension)
  • Captisol-based formulation (fewer hemodynamic side effects) 1
• Consider pre-treatment with a vasopressor if using the polysorbate formulation to prevent hypotension 1

Special Situations

• For torsades de pointes (polymorphic VT with prolonged QT), magnesium sulfate (1-2g IV/IO) should be considered instead of amiodarone or lidocaine 1
• In patients with preserved left ventricular function, lidocaine may still be effective, particularly when combined with amiodarone in truly refractory cases 4

Common Pitfalls and Caveats

1. Do not delay defibrillation or CPR to administer antiarrhythmic medications. Quality CPR and timely defibrillation remain the cornerstone of VF management 1

2. Monitor for adverse effects:

   • Amiodarone: hypotension, bradycardia
   • Lidocaine: CNS toxicity, myocardial depression

3. Long-term survival impact: While amiodarone improves rates of ROSC and survival to hospital admission, neither amiodarone nor lidocaine has definitively demonstrated improved long-term survival or neurological outcomes 1

4. Combination therapy: In truly refractory cases, some evidence suggests that combination therapy with both amiodarone and lidocaine may be beneficial, particularly in patients with preserved left ventricular function 4

5. Persistence pays off: Continue resuscitation efforts including repeated defibrillation attempts as long as VF persists, as demonstrated by case reports of successful resuscitation after numerous shocks 5