Abstract
Cyanosis is a blue or purple discoloration of the skin or mucous membranes, which occurs when the level of deoxyhemoglobin in capillary blood is higher than 5 g/dL or when there is a high level of abnormal hemoglobin, such as methemoglobin. As the presence of cyanosis is dependent on various factors, it does not always indicate hypoxia. The recognition and appropriate management of multisystem disorders caused by long-standing cyanosis are needed in patients with cyanotic congenital heart disease or Eisenmenger’s syndrome.
