Paramedic National Registry Practice

What can occur if more than 0.04 mg/kg of Atropine is administered?

1. Tachycardia

2. Respiratory depression

3. Reflex bradycardia

4. Hypertension

The correct answer is: Reflex bradycardia

Administering more than 0.04 mg/kg of Atropine can lead to reflex bradycardia due to the body's compensatory mechanisms in response to the drug's effects. Atropine is an anticholinergic medication that blocks the action of acetylcholine, primarily affecting the heart by increasing heart rate. However, if the dose is excessive, it can overstimulate the cardiac vagus nerve, resulting in reflex bradycardia. This compensatory response can occur when the heart rate exceeds normal limits and the body attempts to correct itself by slowing down the heart rate, hence the occurrence of bradycardia rather than tachycardia, which would be expected with a normal or lower dose. For context, while atropine is often used to increase heart rate and counteract bradycardia, excessive doses interfere with the normal balance of the autonomic nervous system, leading to unintended outcomes. It's also important to consider that although tachycardia is associated with appropriate dosing of atropine, it is not a direct result of overdose. Reflex bradycardia is particularly notable in cases where the body's homeostatic mechanisms are pushed to respond to elevated heart rates induced by higher-than-recommended doses.