Atropine Dosing for Symptomatic Bradycardia
The initial recommended dose of atropine for an adult with symptomatic bradycardia is 0.5 to 1 mg IV, which can be repeated every 3 to 5 minutes as needed, up to a maximum total dose of 3 mg. 1, 2, 3
Initial Dosing Algorithm
Administer atropine 0.5-1 mg IV push as first-line therapy for symptomatic bradycardia with hemodynamic compromise (hypotension, altered mental status, chest pain, acute heart failure, or shock). 1, 2
Repeat the 0.5-1 mg dose every 3-5 minutes if bradycardia and symptoms persist, titrating to clinical response rather than aggressively targeting high heart rates. 1, 2
Do not exceed a maximum total dose of 3 mg (representing complete vagal blockade), as higher doses increase risk of central anticholinergic syndrome including confusion, agitation, and hallucinations. 1, 2
Critical Dosing Warnings
Never administer doses less than 0.5 mg, as this can cause paradoxical bradycardia through central vagal stimulation, potentially worsening the patient's condition. 1, 2, 3
In patients with coronary artery disease, limit the total dose to 0.03-0.04 mg/kg (approximately 2-3 mg for a 70 kg patient), as excessive tachycardia may worsen ischemia or increase infarct size. 1, 3
Target a heart rate of approximately 60 bpm rather than aggressive rate increases, particularly in acute MI patients where excessive tachycardia increases myocardial oxygen demand. 2
When Atropine Will NOT Work
Atropine is likely ineffective in type II second-degree AV block or third-degree AV block with wide QRS complex, as the block occurs at the infranodal level (His-Purkinje system) where vagal tone has minimal influence. 1, 4, 5
In heart transplant patients without autonomic reinnervation, atropine may cause paradoxical high-degree AV block or sinus arrest in up to 20% of cases—use epinephrine instead. 1, 2
Atropine is most effective for sinus bradycardia, AV nodal block, and sinus arrest where vagal tone is the primary mechanism. 1
Second-Line Therapies When Atropine Fails
Initiate dopamine 5-10 mcg/kg/min IV infusion if bradycardia persists after maximum atropine dosing, titrating every 2-5 minutes based on heart rate and blood pressure response. 1
Consider epinephrine 2-10 mcg/min IV infusion as an alternative chronotropic agent, particularly in severe hypotension or when both chronotropic and inotropic support are needed. 1
Apply transcutaneous pacing immediately for unstable patients who do not respond to atropine, as this is a Class IIa recommendation and should not be delayed. 1
Common Pitfalls to Avoid
Do not delay transcutaneous pacing while giving additional atropine doses in hemodynamically unstable patients—pacing should be initiated early if the first 1-2 doses of atropine are ineffective. 1
Avoid atropine in acute coronary ischemia when possible, as the resulting tachycardia can extend infarct size; if necessary, use minimal effective doses. 1, 2
Be prepared for paradoxical worsening in patients with infranodal heart block, where atropine may increase sinus rate without improving AV conduction, potentially causing ventricular standstill. 4, 5