A 3-month-old infant has irritability, facial edema, a 1-day history of diarrhea with adequate oral intake, and seizure activity. During assessment, the parents state that they have recently been diluting formula to save money. Which is the most likely cause for the infant's symptoms?

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Water intoxication (water overload) resulting in hyponatremia may occur in infants when formula is diluted to "stretch" the feeding to save money. Hyponatremia may also result from ingestion of plain water (eg, caregiver attempting to rehydrate an infant who has been ill). Infants have immature renal systems with a low glomerular filtration rate, which decreases their ability to excrete excess water and makes them susceptible to water intoxication. Symptoms of hyponatremia include irritability, lethargy, and, in severe cases, hypothermia and seizure activity. Breast milk and/or formula are the only sources of hydration an infant needs for the first 6 months of life. Formula should be prepared per the manufacturer's instructions. (Option A) Hypernatremia may be caused by dehydration (eg, decreased oral intake, vomiting, diarrhea) and presents with similar neurological symptoms (eg, restlessness, seizures). The infant's history indicates adequate oral intake and signs of fluid overload (eg, facial edema), not dehydration. (Option B) Hypoglycemia may present with irritability and seizures, but facial edema and recent history of over-diluting the formula should alert the nurse that water intoxication with hyponatremia is the most likely cause. (Option C) Hypokalemia secondary to diarrhea may present with irritability, muscle weakness, and cardiac arrhythmias. Educational objective: Infants are susceptible to hyponatremia secondary to water intoxication, which can present with neurological symptoms (eg, lethargy, irritability, seizures). Breast milk and/or formula provide sufficient hydration for the first 6 months of life. Formula should not be diluted to save money.

A 3-Month-Old Infant Has Irritability, Facial Edema, a 1-Day History