Neonatal cyanosis may be a signal of serious underlying pathology, and these patients require prompt and comprehensive evaluation when they present to the emergency department. This article will review the differential diagnosis, evaluation, and management of these infants in the ED setting.

Definition

Cyanosis is categorized as either central or peripheral. Peripheral cyanosis, also known as acrocyanosis, is a bluish discoloration of hands and feet caused by peripheral vasoconstriction. It is a common benign condition in the newborn.
By contrast, central cyanosis, a bluish discoloration of mucous membranes, lips, skin, and nailbeds, should be considered pathological until proven otherwise. It takes 3-5 g/dL of desaturated hemoglobin to manifest clinically as cyanosis, so it is important to keep in mind that an anemic patient may not look cyanotic despite a low pulse oximetry reading. Put another way, equal amounts of desaturated hemoglobin (producing comparable degrees of overt cyanosis) correspond to lesser oxygen saturation in the anemic patient. For example, a patient with a hemoglobin level of 18 and 3 g/dL of desaturated hemoglobin would have an oxygen saturation of 83%, whereas a patient with a hemoglobin level of 9 who has 3 g/dL of desaturated hemoglobin would have an oxygen saturation of 67%.

Epidemiology

When a cyanotic neonate presents to the emergency department, the differential diagnosis must include congenital heart disease (CHD), respiratory disorders, hematologic disorders, and infectious processes.

Cyanotic Congenital Heart Disease

Congenital heart disease that presents with cyanosis is associated with lesions causing blood to shunt from the pulmonary to the systemic circulation. The most common etiologies of cyanotic CHD are listed in Table 1.

In order to understand the pathophysiology and presentation of neonatal congenital heart disease, it is essential to recall the transitional circulatory changes of the newborn. In utero, the placenta oxygenates fetal blood. The deoxygenated fetal blood bypasses the lungs due to high pulmonary vascular resistance (PVR) and travels via the umbilical artery to the placenta, where it is oxygenated and returns to the fetus via the umbilical vein.