What is the preferred medication between lidocaine and amiodarone (Antiarrhythmic medication) in Advanced Cardiovascular Life Support (ACLS) for treating ventricular fibrillation or pulseless ventricular tachycardia?

Lidocaine vs Amiodarone in ACLS for Ventricular Fibrillation or Pulseless Ventricular Tachycardia

Either amiodarone or lidocaine may be considered for ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT) that is unresponsive to defibrillation, with no clear superiority of one agent over the other in terms of survival to hospital discharge. 1

Current Recommendations

The 2018 American Heart Association (AHA) guidelines update on Advanced Cardiovascular Life Support (ACLS) specifically addresses the use of antiarrhythmic medications in cardiac arrest:

• Both amiodarone and lidocaine are included in the ACLS algorithm for shock-refractory VF/pVT 1
• Both medications receive a Class IIb recommendation (may be considered) with Level of Evidence B-R 1
• These drugs may be particularly useful for patients with witnessed arrest, where time to drug administration is shorter 1

Dosing Recommendations

Amiodarone:

• Initial dose: 300 mg IV/IO 1, 2
• Second dose: 150 mg IV/IO if required 1, 2
• Maximum dose: 2100 mg in 24 hours 2
• After ROSC: Maintenance infusion of 1 mg/minute for 6 hours, followed by 0.5 mg/minute for 18 hours 2

Lidocaine:

• Initial dose: 1.0 to 1.5 mg/kg IV/IO 1
• Second dose: 0.5 to 0.75 mg/kg IV/IO if required 1
• Maximum total dose: 3 mg/kg 2

Evidence Comparison

Efficacy:

• ROC-ALPS trial (2016): Neither amiodarone nor lidocaine showed statistically significant improvement in overall survival to hospital discharge compared to placebo 3
• However, in patients with bystander-witnessed arrest, both drugs showed approximately 5% absolute improvement in survival compared to placebo 1, 3
• No statistically significant difference in survival was found between amiodarone and lidocaine 3

Short-term Outcomes:

• ALIVE trial (2002): Amiodarone showed higher rates of survival to hospital admission (22.8%) compared to lidocaine (12.0%) 4
• ROC-ALPS trial: Lidocaine showed higher ROSC rates compared to placebo, while amiodarone did not 1
• Both drugs improved survival to hospital admission compared to placebo 1

Formulation Considerations:

• Amiodarone is available in two formulations in the US:
  • Polysorbate-based: Available in concentrated form for rapid administration during cardiac arrest 1
  • Captisol-based: Available only as premixed infusion, making it impractical for rapid administration during cardiac arrest 1

Clinical Decision Algorithm

1. For shock-refractory VF/pVT (after at least one shock):

   • Continue high-quality CPR
   • Administer vasopressor (epinephrine)
   • Consider antiarrhythmic therapy with either amiodarone or lidocaine

2. Selection factors to consider:

   • Availability of medications
   • Formulation of amiodarone available (polysorbate-based preferred during arrest)
   • Patient factors:
     • For witnessed arrest: Either drug may be beneficial 1, 3
     • For unwitnessed arrest: Limited evidence of benefit for either drug 3

3. If first antiarrhythmic fails:

   • Consider switching to the alternative agent
   • Continue high-quality CPR and defibrillation attempts

Important Caveats

• Neither drug has been shown to improve long-term survival or neurological outcomes in the overall cardiac arrest population 1
• The benefit appears greatest in witnessed arrests, likely due to shorter time to drug administration 1, 3
• Amiodarone may require temporary cardiac pacing more frequently than lidocaine 3
• Polysorbate-based amiodarone may cause hypotension due to the solvent 1

Special Considerations

• For torsades de pointes (polymorphic VT with long QT interval), magnesium sulfate may be considered instead of amiodarone or lidocaine 1
• Routine use of magnesium for cardiac arrest is not recommended 1

In summary, the current evidence supports using either amiodarone or lidocaine for shock-refractory VF/pVT in ACLS, with the choice potentially guided by medication availability, formulation considerations, and patient factors such as whether the arrest was witnessed.