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During a physical examination, an infant appears blue. Cyanosis is a physical sign indicating a bluish/purplish discoloration of the skin and/or mucous membranes. There are many different types of cyanosis, and it is important to differentiate physiologic versus pathologic cyanosis. This chapter will focus mainly on central cyanosis because it is a potentially serious condition that requires an immediate evaluation. The differential diagnosis of central cyanosis includes disorders involving an increase in deoxygenated hemoglobin (respiratory, cardiovascular, neurologic, or other) or hematologic disorders involving abnormal hemoglobin (methemoglobinemia/sulfhemoglobinemia). Early diagnosis and treatment for any cyanotic infant is essential.


  1. What type of cyanosis does the infant have? Some types of cyanosis are not considered pathologic and require no workup; others such as central cyanosis can be associated with a life-threatening disease. Differentiate the type of cyanosis to help guide the workup and treatment.

    1. Central cyanosis: bluish skin, including the tongue, mucosal membranes, and lips. This is caused by lack of oxygen in the blood (low PaO2 and low SaO2). While this can occur immediately after birth, persistent central cyanosis is never normal and needs to be evaluated to rule out major cardiac, lung, central nervous system (CNS), metabolic, or hematologic diseases.

    2. Peripheral cyanosis: bluish skin with pink lips, mucous membranes, and tongue. Associated with normal PaO2 and normal (or falsely low if sensor wrapped around a cold blue finger or toe) arterial oxygen saturation. It is caused by decreased/sluggish local circulation leading to an increase in deoxygenated blood on the venous side. This is a consequence of increased oxygen extraction by the tissues and may be a physiologic response. Peripheral cyanosis can be a normal finding; can be associated with causes of central cyanosis; or can be caused by vasomotor instability, venous obstruction (venous thrombosis), polycythemia, low cardiac output (cardiomyopathies, hypocalcemia), shock, sepsis, hypothermia, hypoadrenalism, hypoglycemia, vasoconstriction secondary to cold exposure, and elevated venous pressure. Peripheral cyanosis is common in Down syndrome (vasomotor instability).

    3. Acrocyanosis (bluish hands and feet only). There is normal oxygen saturation in the blood. A type of peripheral cyanosis, it is cyanosis of the extremities and around the mouth and may be considered a normal finding immediately after birth, within the first 1 to 2 days, or with cold stress. Spasm of smaller arterioles is the cause. In a normothermic older infant, consider hypovolemia as the main cause.

    4. Perioral/cirumoral cyanosis (bluish color around the lips and philtrum [nose to upper lip]). There is normal oxygen saturation in the blood. It is common after birth and is due to the close proximity of the blood vessels to the skin. Infants have a prominent superficial perioral venous plexus that can engorge with feeding, and this is not a sign of peripheral or central cyanosis and usually resolves after 48 hours.

    5. Traumatic cyanosis. There is normal oxygen saturation in the blood. This is cyanosis of the ...

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