A nurse is caring for a 2 month old infant who has had projectile vomiting for several days and is admitted to the pediatric unit. The infant's mucous membranes are dry and his anterior fontanel is depressed. Diagnostic results from his ultrasound shows that the infant has pyloric stenosis, Which of the following priority actions should the nurse take?

Rationale: A. Plan to administer a plain water enema and maintain contact precautions is incorrect because pyloric stenosis is not an infectious condition and does not require contact precautions. Enemas, especially plain water enemas, are contraindicated in infants due to the risk of causing severe electrolyte imbalance and water intoxication. This intervention does not address the underlying problem of vomiting and dehydration. B. Monitor the infant for dehydration and electrolyte imbalance is correct because infants with pyloric stenosis experience projectile, non-bilious vomiting, which leads to significant loss of fluids and gastric electrolytes. This commonly causes metabolic alkalosis, hyponatremia, and hypokalemia. The infant in the scenario already shows signs of dehydration, including dry mucous membranes and a depressed anterior fontanel, making fluid and electrolyte monitoring the top priority. Restoring hydration and correcting electrolyte disturbances are essential before any surgical intervention (pyloromyotomy). C. Measure the infant's head circumference and weigh the infant is incorrect because although weight monitoring is part of routine assessment, head circumference measurement is not a priority in the context of acute dehydration from pyloric stenosis. The immediate concern is stabilizing fluid and electrolyte status. D. Offer the infant small, frequent feedings of thickened liquids is incorrect because infants with pyloric stenosis are typically NPO until after surgical correction. Continuing oral feedings would worsen vomiting and further dehydrate the infant. Feeding modifications are not an appropriate intervention at this stage.