Cyanosis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
Historical Perspective
Classification
Pathophysiology
Cyanosis is a bluish or purplish discoloration of skin and mucous membranes. 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) is below 5 gm/dl. Several factors can affect the appearance of cyanosis includes skin pigmentation, Hemoglobin (Hb) levels, oxygen affinity to the hemoglobin (Hb).
Causes
Cyanosis is commonly caused by respiratory disorders that inhibits oxygen from reaching the alveoli or interrupts its movement across the alveolar interface. It is also seen in a wide variety of cardiac and vascular disorders by mixing oxygenated blood with deoxygenated blood (eg, vascular shunts or intracardiac shunts), structural or vascular alteration in pulmonary blood flow, peripheral vascular diseases, and cardiac decompensation with pulmonary edema or shock.
Differentiating Cyanosis from Other Diseases
Epidemiology and Demographics
Risk Factors
Common risk factors in the development of cyanosis include congenital heart diseases with right to left shunting, 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.
Screening
Natural History, Complications, and Prognosis
Diagnosis
Diagnostic Study of Choice
History and Symptoms
The hallmark of cyanosis is blue discoration of skin and mucous membranes. Obtaining the history is most important aspect because of its association with wide variety of disorders (cardiac, pulmonary, vascular, neurologic and neuromuscular disorders). History taking also provide clues to specific cause, precipitating factors and associated comorbid conditions.
Physical Examination
Patients with cyanosis show bluish discolration of skin and mucous membranes. Common locations to look for cyanosis include tongue, buccal mucosa, lips, hands and feet.