What is the first line medication for cardiac arrest?

First Line Medication for Cardiac Arrest

Epinephrine (1 mg IV/IO every 3-5 minutes) is the first-line medication for cardiac arrest regardless of the presenting rhythm. 1

Mechanism and Rationale

Epinephrine works primarily through its α-adrenergic receptor-stimulating (vasoconstrictor) properties, which:

• Increases coronary perfusion pressure (CPP)
• Increases cerebral perfusion pressure during CPR
• Improves chances of return of spontaneous circulation (ROSC)

Timing of Administration

The timing of epinephrine administration depends on the initial cardiac rhythm:

For Non-shockable Rhythms (PEA/Asystole):

• Administer epinephrine as soon as possible
• All observational studies show an association between earlier epinephrine administration and ROSC 1

For Shockable Rhythms (VF/pVT):

• Prioritize CPR and defibrillation initially
• Give epinephrine if initial attempts with CPR and defibrillation are unsuccessful
• Typically administered after the third shock 1

Dosing and Administration

• Standard dose: 1 mg IV/IO every 3-5 minutes during cardiac arrest 1
• Operationally, administering epinephrine every second cycle of CPR after the initial dose is reasonable 1
• If IV/IO access is delayed or cannot be established, epinephrine may be given endotracheally at a higher dose of 2-2.5 mg 1
• For pediatric patients: 0.01 mg/kg (0.1 mL/kg of 1:10,000) IV/IO or 0.1 mg/kg (0.1 mL/kg of 1:1000) via endotracheal tube 1

Evidence Quality and Outcomes

While epinephrine improves ROSC rates, the evidence for long-term benefits is mixed:

• Multiple studies show improved rates of ROSC with epinephrine 1, 2
• Some studies question whether epinephrine provides overall benefit for long-term survival or neurological outcomes 3
• Higher doses of epinephrine (beyond the standard 1 mg) have not shown improvement in survival to discharge or longer-term outcomes 1, 4, 5

Second-Line Medications

After epinephrine, other medications may be considered based on the specific cardiac arrest scenario:

For Refractory VF/pVT:

• Amiodarone (300 mg IV/IO initial dose, followed by 150 mg if needed) 1
• Lidocaine (1-1.5 mg/kg IV/IO initial dose, followed by 0.5-0.75 mg/kg if needed) 1, 6
• Current guidelines consider amiodarone and lidocaine as equivalent first-line antiarrhythmic agents for shock-refractory VF/pVT 6

Alternative Vasopressors:

• Vasopressin (40 units IV/IO) may replace either the first or second dose of epinephrine 1
• However, no alternative vasopressors have proven survival benefit compared with epinephrine alone 1, 7

Special Circumstances

For cardiac arrest due to specific causes, additional medications may be indicated:

Anaphylaxis-Induced Cardiac Arrest:

• Standard BLS and ACLS, including early epinephrine, is the recommended approach 1

Hyperkalemia-Induced Cardiac Arrest:

• Calcium and sodium bicarbonate may be considered in addition to standard ACLS protocols 1

Common Pitfalls to Avoid

1. Delayed administration: Early epinephrine administration is associated with better outcomes, especially in non-shockable rhythms
2. Excessive dosing: Higher doses of epinephrine have not shown improved outcomes and may be harmful
3. Route confusion: Endotracheal administration requires higher doses (2-2.5 mg) than IV/IO administration (1 mg)
4. Neglecting high-quality CPR: Medications are secondary to high-quality CPR and early defibrillation for shockable rhythms

Remember that CPR and defibrillation (for shockable rhythms) remain the only therapies consistently associated with improved survival in cardiac arrest, while medications primarily show benefits in short-term outcomes such as ROSC.