6. Cyanosis

Question 1

How can you classify cyanosis?

Answer 1

Cyanosis can be classified as central or peripheral.

> Central cyanosis:

• Most visible in the tongue and lips

• Commonest causes are 
cardio-respiratory problems, which may
be acute (e.g. obstructed airway) 
or chronic (e.g. some types of congenital 
heart disease).

> Peripheral cyanosis:

• Visible in the fingers and nail beds
• Caused by reduced peripheral perfusion
• May be seen in combination with central cyanosis.

Question 2

What are the causes of congenital

cyanotic heart disease?

Answer 2

Cyanosis occurs in patients with
congenital heart lesions that
result in a right to left shunt of blood:

> Tetralogy of Fallot

> Pulmonary stenosis or atresia with septal defect

> Truncus arteriosus

> Total anomalous pulmonary venous drainage

> Transposition of the great arteries.

Question 3

What are the common causes of peripheral cyanosis?

Answer 3

> All of the causes of central cyanosis

> Cold-induced peripheral vasoconstriction

> Raynaud’s phenomenon

> Low cardiac output states (e.g. cardiac failure).

In terms of relevance to anaesthesia,
the most important cause of cyanosis
is hypoxia, due to airway or
ventilatory compromise until proven otherwise.