Review Question - QID 109633

A 4-month-old girl is seen for ongoing lethargy and vomiting. She was born to a 31-year-old G2P2 mother with a history of hypertension. 3 days prior, she was noticed to have a runny nose, congestion, and cough, consistent with an upper respiratory infection. Because of her symptoms, she has had poor oral intake over the previous 3 days. Over the last 24 hours, she has had 7 episodes of non-bloody, non-bilious vomiting and 3 wet diapers. Laboratory results are shown below.

Serum:
Na+: 132 mEq/L
Cl-: 100 mEq/L
K+: 3.2 mEq/L
HCO3-: 27 mEq/L
BUN: 13 mg/dL
Glucose: 30 mg/dL
Lactate: 2 mmol/L
Urine ketones: < 20 mg/dL

Which of the following is the most likely diagnosis?