important because the infant who is discharged from the nursery with undetected CHD, is at increased risk for mortality and morbidity In the ED, history should focus on age at presentation, feeding patterns, weight gain, breathing patterns, and color changes When the patient presents in shock, cardiac and noncardiac diagnoses must be considered Cardiac lesions that present with shock include those dependent on the DA for systemic blood flow (LV obstructive lesions) or severe ductal dependent right ventricular outflow tract obstruction (RVOTO) In addition, identifying a genetic syndrome may shed light on likely cardiac diagnoses ( Table 86.4 ) Management/Diagnostic Testing of an Infant in Shock, Suspected Ductal Dependent Lesion While immediate attention to airway, breathing, circulation, and high-quality CPR are first steps in the management of a patient in shock, initiation of prostaglandin (PGE1 ) to re-establish ductal patency is a lifesaving therapy The dose of PGE1 is 0.05 to 0.1 µg/kg/min via intravenous (IV) or intraosseous (IO) line Side effects of PGE1 include hypotension, apnea, fever, and rash Titrate PGE1 until femoral pulses are palpable or oxygen saturations improve Effect should be seen within 30 minutes Endotracheal intubation and mechanical ventilation decrease the work of breathing by reducing cardiac demands and guard against apnea caused by PGE1 Epinephrine and other drugs for resuscitation should be prepared for administration during endotracheal intubation, since there is a high likelihood of cardiac arrest during this procedure Once the airway is secured, aim to maintain oxygen saturations at approximately 75% Over ventilation and hyperoxygenation may cause systemic blood pressure to drop significantly since oxygen is a potent pulmonary vasodilator Pulmonary vasodilation drops the PVR, thereby increasing shunting of systemic blood flow into the lungs, and thus causing systemic hypotension If the blood pressure falls, check for over ventilation or oxygen saturations above 75% to 85% If possible, lower saturations to control PBF and restore systemic BP Chest x-ray (CXR) is useful to assess heart size and pulmonary circulation or pulmonary vascular markings It also reveals the cardiac silhouette, thoracic and abdominal situs, and aortic arch sidedness Cardiac rhythm should be monitored EM physicians trained in emergency ultrasound may assess cardiac function Electrocardiogram (EKG) with rhythm strip is the gold standard for arrhythmia diagnosis, and may also offer clues in structural heart disease Refer to Table 86.2 for typical presenting signs and symptoms, CXR, and EKG findings on initial