A 3-week-old baby girl with an unknown birth history presents to the emergency department with 3 days of poor feeding and recurrent cyanotic episodes. On exam, she is agitated, tachypneic, tachycardic with central cyanosis and a harsh systolic crescendo decrescendo murmur along the left mid-to-upper sternal border. An arterial oxygen saturation is 78% and a chest X-ray shows a boot-shaped heart. What is the best initial step in management?
-Administer morphine 0.2 mg/kg IM
-Administer propanolol 0.01 mg/kg IV
-Console the child in a knee-chest position
-Start positive pressure ventilation