What is a common cause of tachycardia in febrile children?

• A. Fever and infection with dehydration contributing.
• B. Hypoxia due to airway obstruction.
• C. Pain or agitation not related to fever.
• D. Cardiac arrhythmia due to congenital heart disease.

Answer: (A)

When a child has a fever, the body's metabolism speeds up, raising the demand for oxygen and nutrients. This metabolic push tends to raise heart rate. Fever also often comes with reduced fluid intake and sweating, which can lead to dehydration. Dehydration decreases circulating blood volume, so the heart beats faster to maintain blood pressure and tissue perfusion. Together, fever-driven metabolic demand and dehydration are a common, expected reason for tachycardia in febrile children (often about 10 bpm for each degree Celsius of fever). Other causes like hypoxia from airway obstruction, pain or agitation, or congenital heart–related arrhythmias can raise heart rate, but they are not as consistently tied to the febrile state as the combination of fever and dehydration.