Approach to cyanosis

Question 1

Definition of cyanosis

Answer 1

Blue discoloration of tongue, lips and exremities

- central implies hypoxaemia

Question 2

Causes of cyanosis

Answer 2

• respiratory disease
• shock
• metabolic derangement (hypoglycemia, hypothermia)
• congenital heart disease
• methaemoglobinaemia
• persistent foetal circulation

Question 3

Describe the hyperoxia test

Answer 3

• administer oxygen at highest concentration possible
• take a blood gas from Right radial artery
• pO2 <150mmHg = cardiac
• pO2 >250mmHg = respiratory

Question 4

Tests to investigate cyanosis

Answer 4

• CXRAY
• ABG and hyperoxia test
• sepsis screen and blood glucose
• ECG and ECHO

Question 5

Causes of methaemoglobinaemia

Answer 5

• drugs
• diarrhoea
• congenital causes

Question 6

Describe methaemoglobinaemia

Answer 6

• haemoglobin is in the oxidized form and can’t transport oxygen efficiently

Question 7

How to treat methaemoglobinaemia

Answer 7

With methylene blue (NADH methaemoglobin reductase cofactor)

Question 8

Examples of RV outflow tract obstruction

Answer 8

• TOF

- tetralogy with pulmonary valve atresia

Question 9

Describe Eisenmengers

Answer 9

• longstanding L-R shunt will eventually develop pulmonary hypertension
• shunt reverses and hypoxic blood is pumped to circulation

Question 10

Who is at risk of Eisenmengers?

Answer 10

Down syndrome plus AVSD

Question 11

What is a tetralogy spell?

Answer 11

• occurs between 6m and 2 years
• increasing cyanosis, syncope and floppiness
• exact mechanism is debated (infundibular spasm and hyperventilation)

Question 12

How to treat tet spell acutely

Answer 12

• keep child calm/ sedate
• give morphine
• oxygen and knee to chest position
• drip (10ml/kg)
• sodium bicarb
• IV esmolol (cardioselective beta blocker)