Why are epinephrine and amiodarone administered during a cardiac (cardiopulmonary) arrest?

Role of Epinephrine and Amiodarone in Cardiac Arrest

Epinephrine and amiodarone are administered during cardiac arrest because epinephrine increases coronary perfusion pressure through vasoconstriction while amiodarone helps terminate refractory ventricular fibrillation or pulseless ventricular tachycardia, though neither has definitively demonstrated improved long-term survival. 1

Epinephrine Administration

Epinephrine is the primary vasopressor used during cardiac arrest with the following characteristics:

• Mechanism: Acts through alpha-1-adrenergic effects to cause vasoconstriction, which increases coronary perfusion pressure and cerebral perfusion during CPR 2
• Dosing: 1 mg IV/IO every 3-5 minutes during cardiac arrest 1
• Timing: Should be administered early in the resuscitation algorithm
• Evidence: Improves return of spontaneous circulation (ROSC) and short-term survival, but has not been shown to improve survival to discharge or neurological outcomes 1

Important considerations:

• If IV/IO access is delayed, epinephrine can be administered endotracheally at 2-2.5 mg 1
• Higher doses may be considered for specific situations like beta-blocker or calcium channel blocker overdose 1
• Do not delay CPR or defibrillation to administer epinephrine 3

Amiodarone Administration

Amiodarone is the preferred antiarrhythmic for shock-refractory ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT):

• Mechanism: Class III antiarrhythmic that affects sodium, potassium, and calcium channels with alpha and beta-adrenergic blocking properties 4
• Indications: For VF or pulseless VT unresponsive to CPR, defibrillation, and vasopressor therapy 1, 3
• Dosing: Initial dose of 300 mg IV/IO, followed by one dose of 150 mg IV/IO if needed 1, 3
• Evidence: Improves rates of ROSC and survival to hospital admission compared to placebo or lidocaine, but has not been shown to improve long-term survival 1, 5

Important considerations:

• Two formulations exist in the US: polysorbate-containing and captisol-based, with the latter having fewer hemodynamic side effects 3
• Amiodarone alone can cause hypotension; consider administering after epinephrine to prevent this effect 6
• Amiodarone should be administered after defibrillation attempts have failed 3

Sequence and Timing

The American Heart Association guidelines recommend the following approach:

1. Begin high-quality CPR and apply defibrillator as soon as possible
2. Administer epinephrine early (1 mg every 3-5 minutes)
3. For shock-refractory VF/pVT (after at least 2-3 shocks):
   • Continue CPR and epinephrine
   • Administer amiodarone 300 mg IV/IO
   • Consider an additional 150 mg dose if VF/pVT persists

Evidence Quality and Limitations

• Despite widespread use, no vasopressor has shown improved survival to hospital discharge in placebo-controlled studies 1
• The ROC-ALPS trial showed that in witnessed cardiac arrests, amiodarone and lidocaine improved survival by about 5% compared to placebo, suggesting timing of administration may be important 1
• Most drug evaluations were conducted before advances in post-cardiac arrest care, including therapeutic hypothermia 1
• The quality of CPR significantly impacts drug effectiveness but is rarely controlled for in studies 1

Clinical Pitfalls to Avoid

• Do not delay defibrillation or CPR to administer medications
• Do not administer amiodarone without prior or concurrent epinephrine due to potential hypotension 6
• Do not expect medications alone to improve long-term outcomes; high-quality CPR and early defibrillation remain the cornerstone of resuscitation
• For torsades de pointes, consider magnesium sulfate instead of amiodarone 3

While these medications are standard in cardiac arrest algorithms, the focus should remain on high-quality CPR, early defibrillation for shockable rhythms, and addressing reversible causes of cardiac arrest.