It is a consequence of a high concentration of deoxygenated hemoglobin (greater than 5 g/dL or 50 g/L) in the arterial blood, usually with a oxygen saturation of less than 90%. However, the more common causes arise from disorders with the respiratory or cardiovascular systems. There are a number of causes of cyanosis including metal toxicity, drugs and metabolic conditions like diabetic ketoacidosis. Pseudocyanosis is a bluish tinge of the skin and mucous membranes that ocurs with the exposure to certain metals and drugs and is not an indication of low oxygen saturation. In other conditions like sulfhemoglobinemia, sulfur binds to hemoglobin and prevents oxygen from bindng to it. ![]() With conditions like methemoglobinemia, oxygen cannot bind to the methemoglobin (oxidized form of hemoglobin) in red blood cells and due to a higher than normal concentration of methemoglobin, the oxygen saturation concentration of arterial blood is significantly reduced. There are certain blood disorders that will also contribute to cyanosis although respiratory and cardiovascular functioning is intact. Cyanosis associated with hypoxia will lead to other symptoms like breathlessness, dizziness, and swelling. The respiratory and cardiovascular components may sometimes co-exist. What does cyanosis mean?Ĭyanosis is an indication of one of two disturbances – lung oxygenation is compromised or blood circulation is inadequate. Cyanosis can be central where the bluish discoloration of the skin is evident on the face, particularly the mouth and tongue, or it may be peripheral where it is only evident in the arms and legs, particularly the fingertips and toes, and even the ears. Oxygen saturation is the measure of oxygen transported in the blood stream expressed as a percentage relative to the maximum oxygen-carrying capacity. This is hypoxemia which is the decrease in partial pressure of oxygen in the blood, or simply, insufficient blood oxygenation with an oxygen saturation (SaO2) of less than 90%. Cyanosis is evident when the blood in the arteries contain more than 5 grams of deoxygenated hemoglobin per 100 milliliters of blood (> 5g/dL or > 50g/L). However, under certain conditions, the blood may not be oxygenated fast enough and the deoxygenated hemoglobin builds up. This is usually not evident since the circulating red blood cells are quickly oxygenated again as it travels through the blood vessels of the lung. Hemoglobin molecules that do no contain oxygen (deoxygenated hemoglobin) has a dark red to purple color. The higher the blood oxygen saturation, the redder the color of blood. ![]() It gives the blood its characteristic red color. The red blood cells carry oxygen through the blood stream by binding it to the molecule hemoglobin. It occurs when there is an inadequacy in lung oxygenation or blood circulation. Cyanosis is a sign of low oxygen levels in the blood (hypoxemia). It may also be seen on the mucous membranes, especially of the mouth, tongue and eyes. Cyanosis is the medical term for a blue to purple discoloration of the skin which arises from deoxygenated hemoglobin in the blood stream.
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