What are the indications for atropine?

Indications for Atropine

Atropine is indicated for temporary blockade of severe or life-threatening muscarinic effects, including symptomatic bradycardia with hemodynamic compromise, ventricular asystole, organophosphate/nerve agent poisoning, and as an antisialagogue. 1

Primary Cardiovascular Indications

Symptomatic Bradycardia (Class I)

• Sinus bradycardia with hemodynamic compromise (heart rate <50 bpm with hypotension, low cardiac output, peripheral hypoperfusion, or frequent premature ventricular contractions) 2
• Bradycardia and hypotension following nitroglycerin administration 2
• Most effective when used within 6 hours of acute MI onset, particularly with inferior MI or right coronary artery involvement 2

Atrioventricular Block (Class I)

• Symptomatic Type I (Mobitz I) second-degree AV block at the AV nodal level, especially with acute inferior MI 2
• Third-degree AV block at the AV node level with narrow-complex escape rhythm 2
• Atropine is contraindicated (Class III) for Type II second-degree AV block or infranodal block with wide QRS complexes, as it may paradoxically worsen the block 2

Cardiac Arrest

• Ventricular asystole: 1 mg IV, repeated every 3-5 minutes if asystole persists during CPR 2, 1
• Bradyasystolic cardiac arrest 1

Toxicological Indications

Organophosphate/Nerve Agent Poisoning (Class I)

• Initial dose: 2-3 mg IV, repeated every 20-30 minutes until muscarinic symptoms resolve 1
• Atropine is the preferred antidote for cholinergic crisis from nerve agents or organophosphate insecticides 3, 4
• High-concentration formulations (2 mg/mL) facilitate intramuscular administration in mass casualty scenarios 3

Muscarinic Mushroom Poisoning

• Same dosing as organophosphate poisoning: 2-3 mg IV initially, repeated as needed 1

Adjunctive Indications (Class I)

Antisialagogue Effects

• Nausea and vomiting associated with morphine administration in acute MI 2
• Initial dose: 0.5-1 mg IV 1

Critical Dosing Considerations

Standard Dosing

• Bradycardia: 0.5 mg IV every 5 minutes, maximum total dose 2 mg (complete vagal blockade) 2
• Never use doses <0.5 mg IV, as this causes paradoxical bradycardia and worsened AV conduction through central vagal stimulation 2, 5
• Peak effect occurs within 3 minutes of IV administration 2

Special Population: Coronary Artery Disease

• Limit total dose to 0.03-0.04 mg/kg in patients with CAD to minimize risk of ischemia from tachycardia 1
• The sinus tachycardia induced by atropine increases myocardial oxygen demand and can extend infarct size 5

Contraindications and Cautions (Class III)

Do NOT Use Atropine For:

• Asymptomatic sinus bradycardia >40 bpm without hypoperfusion or ventricular ectopy 2
• Type II second-degree AV block or infranodal third-degree block (wide QRS), as atropine may increase sinus rate while worsening the block 2
• Routine prophylaxis during critical care intubation without specific indications 6

Important Safety Warnings

• Doses <0.5 mg or non-IV routes produce paradoxical bradycardia 2, 5
• Cumulative doses >2.5 mg over 2.5 hours increase risk of ventricular tachycardia/fibrillation, CNS toxicity (hallucinations, fever), and sustained sinus tachycardia 2, 7
• Monitor carefully for increased ischemia from tachycardia, particularly in acute MI 5, 7
• Rare allergic reactions can occur; alternatives include glycopyrrolate (peripheral effects) or scopolamine (central and peripheral effects) 4

Clinical Pitfalls to Avoid

• Never give atropine for wide-complex bradycardia or high-grade AV block with bundle branch block, as this represents infranodal disease requiring pacing, not atropine 2
• Always confirm asystole in two ECG leads before treating, as fine ventricular fibrillation may appear as asystole 2
• If bradycardia doesn't respond promptly to atropine, proceed immediately to transcutaneous or transvenous pacing rather than continuing to escalate atropine doses 2