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. Different causes of cyanosis may include pulmonary, cardiovascular, hematological, neurological, and vascular diseases. Central cyanosis in the first hours or days of life in the neonate may happen and implies life-threatening conditions such as congenital cardiac abnormalities , airway obstruction , central nervous system problem, hemoglobinopathy. Peripheral cyanosis may happen in neonate called acrocyanosis. If the underlying causes of cyanosis determine and treat the prognosis is generally good. Peripheral cyanosis improves with oxygen therapy. Conversely, central cyanosis does not respond to oxygen therapy because of the underlying intrapulmonary or intracardiac shunt which is responsible for mixing the nonoxygenated venous blood and oxygenated arterial blood. All causes of central cyanosis may cause peripheral cyanosis. cyanosis is a symptom of disease process careful physical examination for associated symptoms include tachypnea, tachycardia, abnormal heart sounds or murmurs, wheezing, crackles, fever, clubbing, edema of extremities will be necessary to identify underlying disease process.In every neonate presented with cyanosis and shock, congenital heart disease dependent on patency ductus arteriosus should be considered. The physiologic constriction of ductus arteriosus after birth in a neonate whose pulmonary blood flow or aortic blood flow is dependent on PDA leads to shock and collapse in the neonate. Infusion of prostaglan in such a neonate is life-saving and keeps patency ductus arteriosus. Treatment of underlying causes of peripheral cyanosis such as tamponade or cardiogenic shock due to low cardiac output state and peripheral vasoconstriction is considered.Cardiac defect causing central cyanosis include Transposition of the great arteries, Tetralogy of fallot, Tricuspid atresia, Truncus arteriosus,Total anomalous pulmonary venous connection, Ebstein anomaly, critical Pulmonary stenosis or atresia, functional single ventricle. The palliative surgical shunt maybe done in such lesions to increase pulmonary blood flow even in the presence of cyanosis. Complete repair procedure leads to relief of cyanosis and shunt and also has long term complications
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