A two-year-old child with congestive heart failure has been receiving digoxin for one week. The nurse needs to recognize that an early sign of digitalis toxicity is:
A. Bradypnea
B. Failure to thrive
C. Tachycardia
D. Vomiting
Correct Answer: D. Vomiting
The earliest sign of digitalis toxicity is vomiting, although one episode does not warrant discontinuing the medication. Digitalis is a plant-derived cardiac glycoside commonly used in the treatment of chronic heart failure (CHF), atrial fibrillation, and reentrant supraventricular tachycardia. Digoxin is the only available preparation of digitalis in the United States.
Option A: Bradypnea (slow breathing) is not associated with digitalis toxicity. Bradycardia is associated with digitalis toxicity. The respiratory rate is sometimes increased. Basal crepitations are associated with CHF. Although GI symptoms are common, the abdominal examination is usually nonspecific. An enlarged liver secondary to CHF (ie, hepatic congestion) may be palpated. Hepatojugular reflux is present. Pedal edema is noted if the patient has renal failure or decompensated CHF.
Option B: Although children with congestive heart failure often have a related condition of failure to thrive, it is not directly related to digitalis administration. It is more related to chronic hypoxia. The therapeutic daily dose of digoxin ranges from 5-15 mcg/kg. The absorption of digoxin tablets is 70-80%; its bioavailability is 95%. The kidney excretes 60-80% of the digoxin dose unchanged.
Option C: Tachycardia is not a sign of digitalis toxicity. Bradycardia is a sign of digitalis toxicity. Digoxin and other cardiac glycosides cause direct vasoconstriction in the arterial and venous system in vascular smooth muscle. Bidirectional ventricular tachycardia is particularly characteristic of severe digitalis toxicity and results from alterations in intraventricular conduction, junctional tachycardia with aberrant intraventricular conduction, or, on rare occasions, alternating ventricular pacemakers.