blue baby

A 6-day-old male presents with increased work of breathing for last 4 hours and an episode of turning blue, which concerned the family. The baby is lethargic, afebrile, and cyanotic, with a weak cry to stimulation. There is a sunken fontanelle, perioral cyanosis with purple intra-oral mucosa, and blue tongue. He is tachypneic and has mild retractions, clear lung sounds, and dullness to percussion 4 cm past right costal margin. There is poor tone and mottled extremities. What should you consider?