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Etiology and evaluation of cyanosis in children

Anne M Stack, MD
Section Editor
Stephen J Teach, MD, MPH
Deputy Editor
James F Wiley, II, MD, MPH


This topic will discuss the differential diagnosis and approach to the child with cyanosis.


Cyanosis, a bluish purple discoloration of the tissues due to an increased concentration of deoxygenated hemoglobin in the capillary bed, results from a variety of conditions, many of which are life-threatening [1]. It is most easily appreciated in the lips, nail beds, earlobes, mucous membranes, and locations where the skin is thin. It may be enhanced or obscured by lighting conditions and skin pigmentation. In children, life-threatening cyanosis most often results from respiratory disorders.


Two mechanisms result in cyanosis: systemic arterial oxygen desaturation and increased oxygen extraction by the tissues. Based upon these mechanisms, two types of cyanosis are described: central and peripheral. In addition, dermatologic conditions may result in blue skin color that mimics cyanosis in the absence of increased levels of deoxygenated blood in the capillary beds. (See 'Dermatologic conditions' below.)

Central cyanosis — Central cyanosis is evident when systemic arterial concentration of deoxygenated hemoglobin (Hb) in the blood exceeds 5 gm/dL (3.1 mmol/L) (oxygen saturation ≤85 percent) [2]. Of note, cyanosis cannot be detected by observation in patients with severe anemia (Hb <5 gm/dL [3.1 mmol/L]).

Peripheral cyanosis — Patients with peripheral cyanosis have a normal systemic arterial oxygen saturation. However, increased oxygen extraction results in a wide systemic arteriovenous oxygen difference and increased deoxygenated blood on the venous side of the capillary beds. The increased extraction of oxygen results from sluggish movement of blood through the capillary circulation. Causes include vasomotor instability, vasoconstriction caused by exposure to cold, venous obstruction, elevated venous pressure, polycythemia, and low cardiac output.


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Literature review current through: Sep 2016. | This topic last updated: Dec 16, 2015.
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