The hyperoxia test is the gold standard for differentiating pulmonary disorders and hemoglobinopathies from cardiac disorders. The practitioner must first obtain an arterial blood gas from the right radial artery when the infant is breathing room air (FiO2 0.21) and then again after the infant is placed on 100% oxygen (FiO2 1) for 10-15 minutes.

If unable to obtain arterial blood gas, the physician can compare the pulse oximetry findings of the patient breathing room air vs. the patient breathing 100% oxygen. In infants with cyanotic congenital heart disease, the PaO2 will not be greater than 150 mm Hg (or the pulse oximetry will not significantly rise) with administration of 100% oxygen.

In comparison, patients with a respiratory disorder will have a PaO2 greater than 150 mm Hg after administration of 100% oxygen, indicating that the cyanosis is not the result of a significant shunt.

If after administering 100% oxygen the PaO2 increases to greater than 200 mm Hg but the pulse oximetry remains low, then the patient may have a hemoglobinopathy, such as methemoglobinemia.

In addition to these tests, when there are concerns about an infectious process, the workup should also include a blood culture, urinalysis, urine culture, and cerebrospinal fluid analysis. Hypoglycemia, hyperglycemia, metabolic acidosis, and jaundice all are metabolic findings that commonly accompany neonatal sepsis.

Suspected pulmonary or cardiac disease warrants a chest radiograph to evaluate cardiac silhouette, pulmonary markings, or presence of an infiltrate. With any suspicion for cardiac disease, the workup should also include an echocardiogram and pediatric cardiology consultation.

Treatment

Treatment of the cyanotic neonate depends on the underlying etiology of the cyanosis. All patients should be immediately placed on oxygen via a non-rebreather mask until the airway is secured. Place the patient on a cardiorespiratory monitor and monitor any changes in vital signs.