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
Reduced cardiac output.
Peripheral vasoconstriction.
Slow speed of circulation in the extremities.
What is the mechanism of Central cyanosis?
In central cyanosis either due to imperfect oxygenation blood in the lung or admixture of venous and arterial blood, heart failure, shock, polycythemia and high altitude.
It is evident when O2 saturation falls below 80 to 85%.