Cyanosis

Correct answer : a

Cyanosis refers to abnormal blue discoloration of the skin and mucous membranes. The term is derived from the Greek word kuaneos meaning dark blue.

Controversy about the definition of Cyanosis: Traditionally cyanosis is define as de oxygenated Hb >5gm%

Cyanosis is of 2 type:

1. Central cyanosis

2. Peripheral cyanosis

Central cyanosis  cause – 

1. Decreased arterial oxygen saturation

     a. Decreased atmospheric pressure, high altitude

     b. Impaired pulmonary function – (i) Alveolar hypoventilation (Chronic bronchitis) – Most common cause (ii) impaired O2 diffusion

     c. Anatomic Shunts

     d. Multiple small intrapulmonary shunts

2. Hemoglobin abnormalities

    a. Methemoglobinemia

    b. Sulfhemoglobinemia

    c. Carboxyhemoglobinemia

Peripheral cyanosis cause

It result from Vasoconstriction and diminished peripheral blood flow

e.g. 

1. Reduced cardiac output

2. cold exposure

3. Redistribution of blood flow from extremities

4. Arterial obstruction

5. venous obstruction