What is cyanosis and how to detect it?

What is cyanosis ?

"Cyanosis  is defined as bluish discolouration of the skin and mucous membrane due to presence of increased amount of reduced haemoglobin in the capillary blood(5 g/dl)." Elevated levels of reduced hemoglobin  will  make the blood dark and gives bluish hue to skin and mucous membrane.

What are the types of cyanosis.

Cyanosis  is mainly of two types : Central and peripheral cyanosis.
In peripheral cyanosis the Tongue remains unaffected.

What are the sites you should examine for peripheral cyanosis.

Sites to be looked for (in good natural light)

• Tip of the nose.
• Ear lobules.
• Outer aspect of lips, chin and cheek.
• Tip of fingers and toes.
• Nail-bed of fingers and toes.
• Palms and soles.

What is the mechanism of peripheral cyanosis?

In peripheral cyanosis, the saturation of arterial blood is normal. But the oxygen saturation at the venous end of capillary is reduced. Excessive extraction of oxygen from the peripheral blood  is the central  mechanisms that play in peripheral cyanosis. Following are the conditions  associated with peripheral cyanosis

1. Reduced cardiac output.
2. Peripheral vasoconstriction.
3. Slow speed of circulation in the extremities.

What are the causes of peripheral cyanosis?

1. Exposure to cold air or cold water is possibly the most common cause of peripheral cyanosis.
2. Congestive cardiac failure
3. Frost bite.
4. Peripheral circulatory failure.
5. Venous obstruction  can produces local cyanosis (eg, SVC syndrome).
6. Hyperviscosity syndrome.
7. Peripheral vascular disease such as atherosclerosis and  Buerger's disease.
8. Cryoglobulinemia.
9. Raynaud's phenomenon  cyanosis is only seen in fingers.