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in medicine, a bluish violet discoloration of the skin and mucous membranes that occurs with human diseases accompanied by circulatory and respiratory disorders.
a bluish discoloration of the skin and mucous membranes. The condition ranges in coloration from gray-blue to black-blue (“cast iron”). Cyanosis is due to an increase in the concentration (more than 5 g percent) of reduced hemoglobin, which has a bluish coloration, in capillary blood. Intense cyanosis of the extremities is called acrocyanosis. A distinction is made between central cyanosis, which results from a disturbance of oxygen saturation of blood in the lungs, and peripheral cyanosis, which results from a slowing of the blood flow and from extensive oxygen extraction into the surrounding tissues. Central cyanosis is observed mainly in pulmonary diseases, congenital heart diseases, and poisonings by carbon dioxide and aniline derivatives. Peripheral cyanosis is seen in heart diseases caused by circulatory disturbances and conditions such as thrombophlebitis and Raynaud’s disease in which a local slowing of blood flow occurs. False cyanosis is caused by a change in the color of the skin itself.