Index of Suspicion

Case 1 Presentation

A 3,772 g boy is born at 38 weeks’ gestation by spontaneous vaginal delivery after an uneventful labor. He is pink and active, with normal vital signs and no remarkable findings on physical examination. His weight is at the 95th percentile for gestational age. At 4 hours of life, he becomes jittery, and a chemical stick test reveals a blood glucose concentration of 26 mg/dL (1.44 mmol/L).

Twenty minutes after being fed formula, the blood glucose level is 20 mg/dL (1.11 mmol/L). The infant remains jittery and receives 4 mL/kg of 10% dextrose in water (D10W), followed by a glucose infusion at a rate of 5 mg/kg per minute. Serial chemical stick glucose values range between 20 and 32 mg/dL (1.11 and 1.78 mmol/L). The infusion is increased incrementally to a rate of 10 mg/kg per minute. During this time, the baby becomes tachypneic and develops mild subcostal retractions. His heart rate and blood pressure remain normal.

Laboratory testing reveals mild hyponatremia (sodium, 129 mEq/L[ 129 mmol/L]), a finding believed to be due to fluid overload with D10W. Sodium chloride (3 mEq/kg per day) is added to the fluids, and furosemide is administered. One specific laboratory test points toward the underlying diagnosis.

Case 2 Presentation

A 3-year-old girl is brought to the emergency department because of vomiting and rapid breathing. Over the past 2 hours she has had six episodes of nonbilious, nonprojectile vomiting. No family members have been ill, and her parents report no fever, diarrhea, or abdominal pain.

On physical examination, the child appears lethargic. Her temperature is 100.3°F (38.4°C), pulse is 156 beats/min, respiratory rate is 60 breaths/min, and blood pressure is 122/66 mm Hg. Her pupils are 4 mm in diameter and respond to light. There are no signs of head injury, her neck is supple, and the tympanic …