Central Cyanosis

CLINICAL DIAGNOSTIC MANUAL

Central cyanosis is a condition characterised by a bluish discolouration of the skin and mucous membranes, resulting from inadequate oxygenation of arterial blood. Unlike peripheral cyanosis, which primarily affects the extremities, central cyanosis is observed in central areas of the body, such as the lips, tongue, and oral mucosa. This type of cyanosis indicates significant hypoxaemia and can be a sign of serious conditions affecting gas exchange in the lungs or blood circulation.

Pathology	Suspected Diagnosis	Confirmatory Diagnosis
Right-to-left cardiac shunt	Persistent cyanosis, dyspnoea, cardiac murmur.	Echocardiogram, cardiac catheterisation.
Right-to-left pulmonary shunt	Refractory hypoxaemia, dyspnoea, cyanosis.	Pulmonary function tests, chest X-ray, pulmonary CT scan.
Haemoglobin abnormalities (e.g., methaemoglobinaemia, sulphaemoglobinaemia)	Cyanosis with normal PaO2 levels, history of exposure to certain drugs or chemicals.	Blood levels of methaemoglobin and sulphaemoglobin, specific blood tests.