What is the dose of atropine (Anti-Cholinergic) in the treatment of tachyarrhythmias, specifically in relation to Advanced Cardiovascular Life Support (ACLS) protocols?

Atropine Dosing for Bradyarrhythmias in ACLS

For treatment of bradyarrhythmias, the recommended dose of atropine is 0.5 mg IV every 3-5 minutes to a maximum total dose of 3 mg. 1

Dosing Protocol for Symptomatic Bradycardia

Initial Dose

• 0.5 mg IV bolus 1
• Administer intravenously over 1-2 minutes
• Monitor heart rate, blood pressure, and symptoms

Subsequent Dosing

• May repeat 0.5 mg IV every 3-5 minutes as needed 1
• Maximum cumulative dose: 3 mg total 1
• Target heart rate: approximately 60 bpm 1

Important Considerations

• Doses less than 0.5 mg may paradoxically cause worsening bradycardia 1, 2
• For cardiac arrest with asystole: 1 mg IV, repeated every 3-5 minutes if asystole persists 3
• Maximum total dose should not exceed 2.5 mg over 2.5 hours in most situations 1

Special Populations and Precautions

Patients with Coronary Artery Disease

• Limit total dose to 0.03-0.04 mg/kg (approximately 2-3 mg maximum) 3
• Higher doses may cause excessive tachycardia that increases myocardial oxygen demand 3

Contraindications and Cautions

• Use with caution in acute myocardial infarction due to potential for increased heart rate and worsening ischemia 1
• May be ineffective or harmful in:
  • Type II second-degree AV block 1
  • Third-degree AV block with wide-complex escape rhythm 1
  • Infranodal blocks (His-Purkinje level) 2
  • Post-cardiac transplant patients 1

When to Move to Alternative Therapies

If atropine is ineffective (no response after 3 mg total or 0.04 mg/kg):

1. Consider transcutaneous pacing 1
2. Consider IV infusion of beta-adrenergic agonists 1:
   • Dopamine (2-10 μg/kg/min)
   • Epinephrine (2-10 μg/min)

Effectiveness by Clinical Scenario

• Most effective for sinus bradycardia within 6 hours of acute MI onset 1
• Effective for bradycardia associated with:
  • Vagal stimulation
  • AV block at nodal level (Type I second-degree or third-degree with narrow complex) 1
  • Hypotension after nitroglycerin administration 1

Common Pitfalls to Avoid

1. Underdosing: Doses less than 0.5 mg may cause paradoxical bradycardia 1
2. Overdosing: Doses exceeding 2.5 mg over 2.5 hours increase risk of adverse effects 1, 4
3. Inappropriate use: Atropine is unlikely to be effective for:
   • Asymptomatic sinus bradycardia (heart rate >40 bpm) 1
   • Infranodal AV blocks 2
   • Cardiac transplant patients 1
4. Delayed escalation: If no response after 2 doses, prepare for transcutaneous pacing 1

Remember that atropine is a temporizing measure for symptomatic bradycardia. If the patient remains unstable despite atropine, prepare for transcutaneous pacing and consider expert consultation for transvenous pacing.