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Atropine dose in acute myocardial infarction in man
Insights
Atropine effectively increases heart rate in acute myocardial infarction (MI) patients with bradycardia. A dose of 0.008 mg/kg is recommended as a safe initial intravenous therapy for MI.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Acute myocardial infarction (MI) can lead to bradycardia, a slow heart rate, which may require intervention.
- Atropine is a potential treatment for symptomatic bradycardia in the context of MI.
Observation:
- This study evaluated the heart rate response to intravenous atropine in 18 patients with acute MI.
- Atropine was administered for bradycardia (less than 60 bpm) with hypotension or ventricular premature beats, or extreme bradycardia (less than 40 bpm).
Findings:
- The degree of heart rate increase (cardioacceleration) varied with atropine dosage and administration route.
- Lower intravenous doses (0.0053-0.0088 mg/kg) increased heart rate by 20-72 bpm, not exceeding 120 bpm.
- Higher doses (0.120-0.148 mg/kg) resulted in greater heart rate increases (51-92 bpm), sometimes exceeding 120 bpm.
- One case of paradoxical heart rate slowing was observed with intramuscular atropine administration.
Implications:
- Intravenous atropine can safely and effectively manage bradycardia in acute MI.
- An initial intravenous dose of 0.008 mg/kg is suggested as a safe and suitable starting point for atropine therapy in acute MI.
- Understanding dose-response relationships is crucial for optimizing atropine treatment in MI patients.
Abstract:
Heart rate response to intravenous atropine therapy in acute myocardial infarction (MI) was assessed from detailed studies performed on 18 of 492 consecutively admitted coronary care unit patients. Atropine was given for extreme bradycardia (less than 40/min) or bradycardia (less than 60/min) coincident with hypotension or ventricular premature beats. 14 patients had posterior and 4 anterior infarction. Degree of cardioacceleration evoked by atropine depended upon drug dose and route of administration. Atropine, 0.0053-0.0088 mg/kg, given within 15 sec increased heart rate by 20-72/min but never beyond a peak rate of 120. Larger atropine doses, 0.120-0.148 mg/kg, increased heart rate by 51-92/min and, in four to five instances to a peak rate exceeding 120/min. Intramuscular atropine was associated with paradoxical slowing of heart rate in one case. Multiple neural, hormonal, and circulatory factors can modify heart rate response to fixed amounts of intravenous atropine but 0.008 mg/kg represents a safe and suitable initial drug dose for use in acute MI.