Zyanose

Zyanose, known in English as cyanosis, is a bluish discoloration of the skin, lips, and mucous membranes that results from an increased amount of deoxygenated hemoglobin in the blood or from markedly reduced arterial oxygen saturation. It is typically detectable when deoxygenated hemoglobin exceeds about 5 g/dL or arterial oxygen saturation falls below around 85%.

Cyanosis is generally categorized as central or peripheral. Central cyanosis reflects systemic hypoxemia and can occur with cardiopulmonary disorders, significant lung disease, or conditions that reduce oxygen delivery. Peripheral cyanosis arises from slowed blood flow or increased vasoconstriction in the extremities and may occur with cold exposure, anxiety, or vascular problems, sometimes in the absence of major hypoxemia.

Common causes of central cyanosis include congenital heart defects with right-to-left shunts, severe lung disease (such as chronic obstructive pulmonary disease or pneumonia), acute respiratory failure, and certain hemoglobinopathies or methemoglobinemias. Peripheral cyanosis can accompany heart failure, shock, or exposure to cold, and may be seen in normal individuals when circulation is reduced in the extremities.

Diagnosis involves clinical assessment and objective measurements. Pulse oximetry and arterial blood gas analysis assess oxygenation, while co-oximetry can identify abnormal hemoglobin species such as methemoglobin or sulfhemoglobin. The evaluation seeks to identify underlying cardiopulmonary or hematologic conditions.

Management targets the underlying cause and may include supplemental oxygen, stabilization of airway and breathing, and specific therapies for methemoglobinemia or other hemoglobin abnormalities. Prognosis depends on the etiology and the effectiveness of treating the primary condition.