[Verified Answer]: A one week old female infant with trisomy…

A one week old female infant with trisomy 21 presents to the emergency department with persistent non-bilious vomiting and abdominal distention. Her parents report decreased wet diapers and no stools in over 24 hours. The baby is lethargic and slightly jaundiced. No masses are palpated on physical examination of the baby’s abdomen. Abdominal x-ray shows a classic “double-bubble” sign associated with duodenal obstruction. Heart and lung sounds are normal. Chest x-ray shows clear lung fields and a normal cardiac silhouette. Vitals signs include: HR 188, BP 75/40, RR 30, SpO2 100% while breathing room air Of the following, which is the most important additional laboratory study to obtain while caring for this baby? Amylase and lipase Coomb’s antibody assay Creatinine clearance TSH, T3 and T4