A very worrying if a new acute sign suggests severe hypoxia and needs urgent assessment. In some, this may be a chronic problem in those with certain cardiac and lung disease
- Central Cyanosis is defined as greater than 3.5-5.0 g/dl of reduced (deoxygenated)haemoglobin. Cyan means blue in Greek.
- Cyanosis is seen more commonly in those who are polycythaemic as they have 15 g/dl oxygenated and can easily tolerate 5 g/dl of reduced Hb.
- Look for the blue colour of the buccal mucosa and tongue
- Look for the blue colour of the peripheries
- This is when the lips and tongue are blue as well as fingers and toes
- It suggests severe hypoxia and needs urgent measurement of saturations and ABG
- It is a medical emergency and suggests O2 saturation of 85%
Causes of Central Cyanosis
- Respiratory failure due to Severe asthma (very worrying), COPD, ARDS, Lung fibrosis, Pulmonary embolism, Pneumonia, High altitude, Fistulas, or other cause
- Cardiac disease: Pulmonary oedema, Large ASD/VSD, Congenital cyanotic heart disease (Tetralogy of Fallot, Transposition of vessels, Total anomalous venous drainage, tricuspid atresia, truncus arteriosus (The 5 Ts)
- Hypoventilation: drugs, sedation, paralysis of respiratory muscles
- The lips and tongue are pink and normal looking but fingers and toes are blue.
Causes of Peripheral Cyanosis
- Peripheral vascular disease
- Raynauds Phenomenom
- Low cardiac output
- Cold exposure
- Localised arterial or venous obstruction
Investigations of Central Cyanosis
- FBC, U&E, CRP, D Dimers
- CXR, CTPA, Echocardiogram
- ABC. Oxygen. Treat cause
- Oxygen does not help if a significant cardiac shunt bypasses the lungs