What is an early sign of digitalis toxicity in a child with congestive heart failure?

An early sign of digitalis toxicity, particularly in a child who is being treated for congestive heart failure, is vomiting. Digitalis medications, such as digoxin, are used to improve heart function but can have a narrow therapeutic range, meaning that toxicity can occur with relatively small increases in the drug level.

When digitalis toxicity occurs, one of the body's responses is gastrointestinal disturbance, which often manifests as vomiting. This symptom can be particularly noticeable in children, who may not be able to communicate other signs effectively. Catching this early sign is crucial because it can lead to more severe complications if the dosage is not adjusted or the drug is not discontinued.

The other options, although potentially relevant in cases of digitalis toxicity, are not typically the most immediate or prominent early signs. Tachycardia can occur in other situations and may not specifically indicate toxicity, whereas bradypnea and failure to thrive are more associated with chronic conditions and might not be specific indicators of digitalis levels. Therefore, recognizing vomiting as an early sign allows for timely intervention and management of the child's care.