What is the recommended dose of atropine (anti-muscarinic agent) in cardiac arrest?

Atropine Dosing in Cardiac Arrest

The recommended dose of atropine for ventricular asystole in cardiac arrest is 1 mg intravenously, which may be repeated in 5 minutes if asystole persists, with a maximum total cumulative dose of 2.5 mg over 2.5 hours. 1

Dosing Guidelines for Atropine in Cardiac Arrest

• Atropine is indicated for ventricular asystole during cardiac arrest 1
• Initial dose: 1 mg IV bolus 1
• May repeat in 5 minutes if asystole persists (while continuing CPR) 1
• Maximum total dose: 2.5 mg over 2.5 hours 1
• Peak action occurs within 3 minutes of IV administration 1

Mechanism of Action

• Atropine is a parasympatholytic (anticholinergic) agent that reduces vagal tone 1
• It enhances sinus node discharge and facilitates atrioventricular (AV) conduction 1
• In cardiac arrest, it aims to counter any excess vagal tone that may be contributing to asystole 1

Important Considerations and Cautions

• Atropine doses <0.5 mg may paradoxically result in further slowing of heart rate due to central reflex stimulation of the vagus or peripheral parasympathomimetic effects 1
• Atropine will likely be ineffective in patients who have undergone cardiac transplantation because the transplanted heart lacks vagal innervation 1
• Atropine should be used cautiously in the presence of acute coronary ischemia or MI, as increased heart rate may worsen ischemia or increase infarction size 1
• Current evidence suggests that atropine has no long-term neurological benefit in adults with out-of-hospital cardiac arrest due to non-shockable rhythm 2

Efficacy in Different Types of Cardiac Arrest

• For asystole: Atropine (1 mg) combined with epinephrine has shown higher rates of return of spontaneous circulation compared to epinephrine alone, though without improvement in long-term neurological outcomes 2
• For pulseless electrical activity (PEA): Evidence suggests atropine provides no additional benefit and may potentially be associated with lower 30-day survival rates 2
• Recent research indicates that the addition of atropine (within 2 mg) following epinephrine may be an independent predictor of survival to hospital admission for non-shockable (especially asystole) out-of-hospital cardiac arrest 3

Route of Administration

• Intravenous administration is strongly preferred 4
• Endotracheal administration of atropine (even at currently recommended doses of twice the IV dose) has shown poor efficacy in cardiac arrest settings 4
• If IV access is unavailable, focus should be on establishing IO (intraosseous) access rather than using the endotracheal route 4

Pediatric Considerations

• In pediatric advanced life support, atropine dosing differs significantly from adult dosing 1
• Pediatric dose: 0.02 mg/kg IV/IO 1
• Minimum single dose: 0.1 mg 1
• Maximum single dose: 0.5 mg 1
• May repeat once 1

While atropine remains in cardiac arrest protocols for asystole, it's important to note that its routine use in cardiac arrest has been questioned in more recent guidelines, with emphasis placed on high-quality CPR, early defibrillation when indicated, and epinephrine administration as the cornerstones of resuscitation.