A 6-month-old infant with congenital heart failure is admitted to the pediatric unit. The infant is receiving digoxin 0.025 mg PO daily and furosemide 10 mg PO twice daily. During the morning assessment, the nurse notes the infant is lethargic, has vomiting, and the apical heart rate is 92 beats per minute. What is the nurse's priority action?

Digoxin toxicity in infants presents with bradycardia (HR 92 bpm is below normal 110-160 bpm), lethargy, and vomiting. The priority is to hold digoxin and notify the provider to prevent life-threatening arrhythmias. Other options (administering digoxin, increasing monitoring, feeding) do not address the acute toxicity.

Clinical Presentation Analysis

The infant is exhibiting classic signs of digoxin toxicity. The triad of lethargy, vomiting, and bradycardia in a pediatric patient receiving digoxin and a loop diuretic like furosemide should immediately raise concern for drug toxicity. The apical heart rate of 92 beats per minute is below the standard hold parameter for an infant (typically less than 90-100 bpm), making this a critical safety stop point.

Pathophysiology and Risk Factors

The concurrent use of furosemide, a potent loop diuretic, significantly elevates the risk for digoxin toxicity. Furosemide promotes the renal excretion of potassium, leading to hypokalemia. When serum potassium levels are low, digoxin binds more readily to the sodium-potassium ATPase pump on myocardial cells, enhancing its therapeutic and toxic effects at the same serum drug concentration. This pharmacodynamic interaction means that a standard, previously tolerated dose of digoxin can become toxic in the setting of electrolyte disturbances, a phenomenon supported by evidence that electrolyte disturbances are common predisposing factors for toxicity ^[1].

Additionally, infants with congenital heart disease possess unique physiological profiles that increase their vulnerability to drug-related side effects, making meticulous monitoring for toxicity a cornerstone of safe pharmacotherapy in this population ^[3].

Clinical Decision Making

The nurse's priority action is to hold the scheduled dose and notify the healthcare provider. In the presence of clinical signs of toxicity (vomiting, lethargy) and a heart rate below the hold parameter, administering the next dose would be dangerous and could precipitate a more severe bradyarrhythmia, such as the second-degree atrioventricular block noted in pediatric cases of ongoing toxicity ^[1]. Pediatric antiarrhythmic medications carry a narrow therapeutic index, and emergency clinicians must be skilled in the detection and management of toxicity, which begins with immediate discontinuation of the offending agent upon recognition of adverse effects ^[2].

Increasing the frequency of vital sign monitoring is an appropriate intervention after the provider has been notified and the dose has been held, but it does not address the immediate threat of administering a toxic dose. Encouraging more frequent feeding is not a priority and may be contraindicated in a vomiting infant with lethargy, as it increases the risk of aspiration. The recognition and immediate withholding of the drug is the critical nursing action that prevents progression to more severe cardiotoxicity [1,2].