What is a complication of administering IV atropine in doses less than 0.5 mg?

Administering IV atropine in doses less than 0.5 mg can lead to further slowing of the heart rate because lower doses may not effectively block the vagal effects on the heart. Atropine is an anticholinergic medication primarily used to increase the heart rate by inhibiting the action of the vagus nerve. However, when given in subtherapeutic doses, the vagal tone can overpower the effects of atropine, leading to bradycardia rather than the desired increase in heart rate. Therefore, doses below 0.5 mg may not provide sufficient blockade of parasympathetic activity, potentially resulting in a decrease in heart rate. This understanding underscores the importance of administering an appropriate dose to achieve the desired pharmacological effect and avoid complications during resuscitation efforts.