1. Cyanosis Dr Kevin Zammit MD FRCEM Emergency Medicine Consultant
Lister Hospital, Stevenage

2. Cyanosis

3. Cyanosis

4. What is Cyanosis?

5. Cyanosis
Abnormal bluish discolouration of the skin and mucous membranes.
Increased amounts of bluish-coloured haemoglobin – deoxygenated haemoglobin.
Superficial vessels of the skin.
Best appreciated – lips, nose, cheeks, oral cavity (vessels abundant and overlying dermis is thin).
Central vs Peripheral – bedside decision – implies different aetiologies.

6. History
1761 – Morgagni described cyanosis first in relation to pulmonary stenosis.
1869 – Bernard described the qualitative difference in blood gases between blue venous blood and red arterial blood.
1919 – Lundsgaard quantified how much deoxygenated haemoglobin is needed to produce cyanosis.

7. The blue colour
Minimal amount of deoxygenated blood is reached (2.38g/dL in arterial blood).
Blue blood can be seen through the opaque dermis.
Cyanosis will remain if absolute amount of deoxygenated blood stays the same – oxyhaemoglobin concentration irrelevant.
Colour of skin depends on colour of blood flowing through dermal capillaries.
Blanches in response to pressure on skin.

8. The blue colour
Appearance of cyanosis depends on the absolute quantity of deoxyhaemoglobin NOT the relative amount.
If anaemic, a patient has less haemoglobin and will reach the minimal amount of deoxyhaemoglobin later than a polycythaemic patient!
Cyanosis appears later in anaemic patients than in polycythaemic patients.
Anaemic patient will be more hypoxic once cyanosis appears.

9. Cyanosis and Haemoglobin Concentration
Haemoglobin Concentration (g/dL)
CYANOSIS APPEARS
Oxygen Sats (%)
Arterial PO2 (KPa) 6 60
4.1 8 70
4.8 10 76
5.3 12 80
6.0 14 83
6.26 16 85
6.66 18 87
7.19 20 88
7.47

10. Central vs Peripheral CENTRAL Blood leaving heart coloured blue.
Lips, hands, feet.
Long standing – associated clubbing.
PERIPHERAL
Blood leaving heart is red but becomes blue by the time it reaches peripheries.
Hands and feet.
Increased extraction of oxygen by peripheral tissues.
Deoxygenated blood in capillaries increases.
Rubber band around finger.
Warming.

11. Pulse oximetry / ABGs
Central cyanosis – abnormal ABGs and pulse oximetry readings.
Peripheral cyanosis – normal ABGs (proximal sampling) BUT abnormal oximetry readings.

12. What causes Cyanosis?

13. Causes of cyanosis
ANY DISORDER CAUSING HYPOXAEMIA enough to achieve the minimum absolute amount of abnormal haemoglobin (>2.38 g/dL arterial deoxyhaemoglobin).
INTRACARDIAC RIGHT TO LEFT SHUNTS
PERIPHERAL – low cardiac output, arterial disease, Raynaud’s disease, venous disease.
ABNORMAL HAEMOGLOBINS

14. Methemoglobinaemia
The Fugates of Kentucky (“The Blue Fugates”)

15. Methemoglobinaemia Congenital or Acquired
Chocolate cyanosis (brownish hue)
ABGs will show normal PaO2.
Does not improve with oxygen therapy.
Severity of symptoms depends on quantity, rapidity of onset and presence of comorbidities.
Reversible with Methylene blue.

16. Sulfhemoglobinaemia

17. Causes Sulfhemoglobinaemia Phenacetin Industrial aniline compounds
Rare due to improved occupational health standards
Irreversible.
Methemoglobinaemia
Hereditary – NADH methemoglobin reductase
Benzocaine
Nitrates
Nitrites

18. Carboxyhaemoglobinaemia
Does not cause real cyanosis
Cherry red colour of the skin?

19. Flexman AM. Dark green blood in the operating theatre. Lancet
Flexman AM. Dark green blood in the operating theatre. Lancet Jun 9;369(9577)1972

20. Pseudocyanosis

21. Pseudocyanosis “Papa Smurf”
Drank and applied colloidal silver for a skin condition.

22. Pseudocyanosis

23. Pseudocyanosis Does not blanch with pressure.
Colour is not from abnormally coloured blood but from abnormal deposition of blue pigments in the skin.
Mucous membranes of mouth are pink.
Normal ABGs and normal pulse oximetry readings.
Causes include – silver therapy, gold therapy, amiodarone, minocycline, chloroquine.

25. Summary LATE SIGN – prevent it if possible. OXYGEN!
If no improvement with oxygen, think of differential diagnosis.