## **Core Concept**
Digitalis toxicity can manifest through various symptoms, both cardiac and noncardiac, primarily due to its effect on the **Na+/K+-ATPase pump**. This inhibition leads to increased intracellular calcium levels, affecting cardiac contractility and potentially causing arrhythmias. In infants, due to their smaller body size and developing physiology, the margin for error with digitalis dosing is narrow.

## **Why the Correct Answer is Right**
The correct answer, **.**, highlights the importance of gastrointestinal symptoms in digitalis toxicity. Nausea and vomiting are common noncardiac manifestations of digitalis toxicity. These symptoms occur due to the direct effect of digitalis on the **gastrointestinal tract** and the **central nervous system**. In infants, vomiting is a critical sign because it can quickly lead to dehydration and electrolyte imbalances, complicating the clinical picture.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While changes in vision, including blurred vision or disturbances in color perception (like xanthopsia), can occur in digitalis toxicity, they are not the most important noncardiac manifestation, especially in infants who may not be able to report these symptoms.
- **Option B:** Altered mental status, including confusion, disorientation, or even seizures, can be a manifestation of digitalis toxicity. However, in infants, these signs might be harder to detect early on or might not be as immediately apparent as gastrointestinal symptoms.
- **Option C:** This option might seem plausible but isn't directly relevant to the most immediate concern in digitalis toxicity.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that digitalis toxicity can present with a wide range of symptoms, and in pediatric patients, vigilance for noncardiac symptoms like vomiting is crucial. Early recognition of toxicity is vital because it can progress rapidly to life-threatening arrhythmias. A useful clinical correlation is that **digitalis toxicity should be considered in any patient with nausea, vomiting, or cardiac arrhythmias who is taking digitalis**.

## **Correct Answer:** . Vomiting