Cyanosis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Zand, M.D.[2]
Overview
Cyanosis is the condition that there is inadequate oxygen delivery to peripheral tissue. Oxygen in the blood is carried in two physiologic states. Approximately 2% is dissolved in plasma and the other 98% bound to hemoglobin. In central cyanosis there is increased level of deoxyhemoglobin around 3-5 g/dl. In peripheral cyanosis there is increased oxygen extraction by the peripheral tissues. .Several factors can affect the appearance of cyanosis includes skin pigmentation,Hemoglobin (Hb) levels, oxygen affinity to the hemoglobin (Hb). Cyanosis was first described by deSenac who was physician of King Louis XV in 1749. He described as admixture of arterial and venous blood due to abnormal connection between two sides of the heart. In 1761, Morgagini showed association of cyanosis with pulmonary stenosis due to stasis of blood. Cyanosis was described by Sandifort, an European, in 1777 as a "blue boy" with tetralogy of Fallot. In 1892, Vaquez described the first case of polycythemia, as a cause of cyanosis. In 1919, Christen Lundsgaard quantified the amount of blood required to be deoxygenated to give the bluish discoloration of cyanosis. Blalock and Taussid performed the first anastomosis of subclavian to pulmonary artery on November 9, 1944 to lessen the cyanosis in tetralogy of Fallot. United States' Olympian and gold medalist Shaun White was born with tetralogy of Fallot and had cyanosis because of that. Cyanosis may be classified into two groups including central cyanosis and peripheral cyanosis. Right to left shunt in congenital heart disease causes central cyanosis. Secondary erythrocytosis (increased red blood cell mass due to hypoxia) and polycythemia (neoplastic proliferation of red blood cell) are different conditions and need different evaluation. Two mechanisms involved in the development of cyanosis, Systemic arterial oxygen desaturation and increased oxygen absorption by tissues. Cyanosis is evident when arterial oxygen desaturation falls below 85% or the concentration of deoxygenated hemoglobin (Hb) exceeds 5 gm/dl. Common causes in the development of cyanosis include congenital heart diseases with right to left shunt, presence of abnormal hemoglobin, carbon monoxide poisoning, respiratory disorders associated with impaired gas exchange, impaired gas diffusion via the alveoli, embolism, pulmonary arteriovenous malformations, cold exposure, and raynaud's phenomenon.
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