ACLS Drugs – Atropine
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Article at a Glance
- Atropine is an anticholinergic/parasympathetic blocker that speeds up the heart rate.
- Atropine is indicated for symptomatic sinus bradycardia.
- The dose of atropine is 0.5 mg IV/IO every 3–5 minutes to a total dose of 3 mg.
- The provider should be prepared for transcutaneous pacing if atropine does not raise the heart rate.
Atropine is an anticholinergic, also known as a parasympathetic blocker. Let’s review the sympathetic and parasympathetic nervous systems to better understand how atropine functions. Atropine is an anticholinergic, also known as a parasympathetic blocker.Atropine’s Mechanism of Action
Review of the Sympathetic and Parasympathetic Systems
The sympathetic nervous system is your “fight or flight” response. It speeds everything up. If the body were a car, the sympathetic nervous system would be the gas pedal. Conversely, the parasympathetic nervous system is the brake pedal, as it slows everything down. It’s the “rest and digest” system. Inside the body, both systems work simultaneously.
Related Video – What is the Parasympathetic System?
If you want to speed up the car and increase the heart rate, you have a couple of options. One, you could simply press harder on the gas. In the case of Advanced Cardiovascular Life Support (ACLS), a hard press constitutes administering a sympathomimetic drug. Sympathomimetic drugs stimulate the sympathetic nervous system. Epinephrine is a great example. It directly stimulates the sympathetic nervous system.
Read: ACLS Drugs – Aspirin
Or you could take your foot off the brake a bit, which is what atropine does. Atropine is a parasympathetic blocker. By blocking the parasympathetic system, or “taking your foot off the brake”, you’re allowing the sympathetic system to dominate. Remember, the sympathetic nervous system actually increases the heart rate.
Atropine affects the parasympathetic system through its effects on the SA and AV node.
Atropine impacts two areas of the heart: the sinoatrial (SA) node and the atrioventricular (AV) node. Atropine increases output from the SA node, which increases firing. Atropine also increases conduction through the AV node.
Related Video – Conduction System of the Heart Part 1: Basics of Conduction
Related Video – Conduction System of the Heart Part 2: Back-Up Pacemakers
Related Video – Conduction System of the Heart Part 3: Relating to an ECG
Atropine Indications and Dosing
Atropine is the first-line drug for symptomatic sinus bradycardia. The dosing of atropine for bradycardia is 1.0 mg administered IV/IO every 3–5 minutes for a total dose of 3 mg, or 0.04 milligrams per kilogram of body weight.
Related Video – Atropine – Arrhythmia
Atropine may also be used to treat organophosphate poisonings. You must administer quite a bit of atropine to reverse the toxin’s effects. The dosing is usually 4–6 mg IV as a bolus.
Special Considerations
If you’re using atropine to raise the heart rate and it’s ineffective, you must transcutaneously pace the patient.
Related Video – Transcutaneous Pacing
We must also ask why the patient is bradycardic. For example, a myocardial infarction may be present. In most people, the SA node receives its blood and oxygen supply from the right coronary artery. The right coronary artery also supplies the heart’s inferior wall. Therefore, it is not uncommon for bradycardia to be associated with an inferior wall myocardial infarction.
The right coronary artery supplies the SA node and inferior wall of the heart.
Summary
Atropine is an anticholinergic, otherwise known as a parasympathetic blocker. It blocks the parasympathetic nervous system, allowing the sympathetic to dominate, thus raising the heart rate. It increases output from the SA node and conduction through the AV node.
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ACLS Certification Association (ACA) uses only high-quality medical resources and peer-reviewed studies to support the facts within our articles. Explore our editorial process to learn how our content reflects clinical accuracy and the latest best practices in medicine. As an ACA Authorized Training Center, all content is reviewed for medical accuracy by the ACA Medical Review Board.
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