1. Cyanosis

2. Definition
Cyanosis refers to a bluish color of the skin and mucous membranes resulting from an increased quantity of reduced hemoglobin/deoxyhemoglobin (脱氧血红蛋白；还原血红蛋白), or abnormal hemoglobin derivatives, in the small blood vessels of those areas.

3. Mechanism of Cyanosis
Absolute increase of amount of reduced hemoglobin in blood, > 50g/L (capillary)
Nonfunctional hemoglobin such as methemoglobin(正铁血红蛋白，高铁血红蛋白)or sulfhemoglobin(硫化血红蛋白) is present in blood.

4. reduced hemoglobin in blood desaturation of oxygen
Arterial desaturation of oxygen:5%
Venous desaturation of oxygen:30%
Capillary desaturation of oxygen:average of both
SaO2:66% reduced Hb 50g/L

5. Mean capillary concentration of reduced hemoglobin exceeds 50 g/L
Mean capillary concentration of reduced hemoglobin exceeds 50 g/L. It is the absolute rather than the relative increase.

6. Caused by absolute increase of amount of reduced
Mechanisms of Cyanosis
Caused by absolute increase of amount of reduced
Hb in blood, usually > 5g/dl (capillary)
The higher the hemoglobin concentration,
The greater tendency toward cyanosis.
g/dl
Normal Polycythemia Anemia

7. severe anemia
the relative amount of reduced hemoglobin in the venous blood may be very large
the absolute quantity of reduced hemoglobin may still be small

8. polycythemia
patients with marked polycythemia tend to be cyanotic at higher levels of SaO2 than patients with normal hematocrit(红细胞压积) values.

9. Clinical Classification & Etiology
True Cyanosis (increased amount of reduced Hb)
— Central Type
— Peripheral Type
— Mixed Type
Cyanosis due to abnormal Hb derivatives
— Methemoglobinemia(高铁血红蛋白血症)
— Sulfhemoglobinemia(硫化血红蛋白血症)

10. Central cyanosis is caused by decreased SaO2(increased amount of reduced Hb)

11. Central cyanosis only occurs when the oxygen saturation of arterial blood is less than 85%.

12. Cause of decreased SaO2 Parenchymal lung disease(肺实质病变)
Right to left cardiac shunt - congenital cyanotic heart disease
Decreased PO2 of inspired air - high altitude
Hypoventilation(低通气)

13. Parenchymal lung disease
Airway obstruction,pneumonia,massive pulmonary embolism(肺栓塞), pulmonary edema(肺水肿) ,chronic airflow obstruction emphysema (肺气肿)
Seriously impaired pulmonary function, through perfusion of unventilated or poorly ventilated areas of the lung or alveolar(肺泡) hypoventilation,resulting in decresed alveolar PO2 and SaO2

14. the presence and severity of cyanosis
Shunting of systemic venous blood into the arterial circuit
Congenital cardiac lesion : tetralogy of Fallot (the combination of ventricular septal defect and pulmonary outflow tract obstruction ).
Pulmonary arteriovenous fistulae(肺动静脉瘘) :congenital or acquired, solitary or multiple, microscopic or massive.
the presence and severity of cyanosis
depend on the size of the shunt relative to the systemic flow as well as on the Hb-O2 saturation of the venous blood.

16. Central Cyanosis Impaired pulmonary function Right-to-left shunting
1. Airway obstruction
2. Pulmonary diseases
Right-to-left shunting
of blood
Tetralogy of Fallot

17. Decreased PO2 of inspired air
At 2500 m the FIO2 is about 120 mmHg, the alveolar PO2 is approximately 80 mmHg, and the SaO2 is nearly normal
At 3500 m the FIO2 and alveolar PO2 are about 85 and 50 mmHg, respectively, and the SaO2 is only about 75%.
Cyanosis is marked in a further ascent to 3500 m. The reason :the S shape of the Hb-O2 dissociation curve.

18. High O2 affinity Hgb
normal
Low O2 affinity Hgb

19. Peripheral cyanosis is due to poor peripheral circulation and increased oxygen consumption in peripheral tissue.

20. Peripheral Cyanosis
Caused by increased oxygen consumption in peripheral tissue.
Vasoconstriction
Low cardiac output
Exposure to cold air or water
Slowing of blood flow
Right heart failure

21. Peripheral cyanosis Congestive peripheral cyanosis
right-side heart failure, constrictive pericarditis, local venous diseases.
slowing of blood flow
abnormally great extraction of O2 from normally saturated arterial blood.
Ischmic peripheral cyanosis.
Ischemic peripheral cyanosis is often seen in severe shock.
Arterial obstruction or constriction.
vasoconstriction and diminished peripheral blood flow

22. Mixed Cyanosis
Clinical differentiation between central and peripheral cyanosis may not always be simple, and in conditions such as cardiogenic shock (心源性休克)with pulmonary edema(肺水肿)there may be a mixture of both types.

23. Possible causes of mixed cyanosis
all causes of central cyanosis may lead to peripheral cyanosis
low cardiac output e.g. heart failure

24. Cyanosis due to abnormal Hb derivatives
Central cyanosis may be simulated by methaemoglobulinaemia and sulphaemoglobulinaemia.

25. Spectroscope is helpful to diagnose methemoglobinemia.
Hereditary: very rare
Acquired: >30g/L in blood
- intake or exposure to some drugs or
chemicals, such as sulfa drugs, nitrite
salt. “ enterogenic cyanosis ”
Spectroscope is helpful to diagnose methemoglobinemia.

26. Sulfhemoglobinemia Sulfhemoglobin >5g/L
Caused by some drugs or chemicals,
Spectroscope is helpful to diagnose

27. Clinical Classification
— Central Type
— Peripheral Type
— Mixed Type

28. Possible clinical features include ----central cyanosis
the warm mucous membranes are blue, for example the tongue, the inside of the lips
central cyanosis increases immediately on exercise which is not the case for peripheral cyanosis
there is polycythaemia with an abnormally high haemoglobin and haematocrit
clubbing is often seen in patients with central cyanosis

29. Possible clinical features include ----peripheral cyanosis
Cool skin and mucous membrance
Site (lower extremities,fingers)
Diminish after massage

30. Note that the absolute discriminating feature between central and peripheral cyanosis is obtained from testing the oxygen saturation of arterial blood.

31. Differentiation of central as opposed to peripheral
Cyanosis Skin temp. Massage or warming
Central Warm No change
Peripheral Cool Cyanosis fades

32. Possible clinical features include ----abnormal hemoglobin
Acquired Methemoglobinemia
Acutely develop after intaking drugs or chemicals (often severe)
Not relieved after oxygen therapy
Blood remains brown after being mixed and exposed to air
Fades after infusion of methylene blue(亚甲兰）or administration of large dosage of vitamin C

33. Sulfhemoglobin
Long duration(several months)
Spectroscope-630nm

34. Certain features are important in arriving at the cause of cyanosis
History (age, gender, family disease history)
Clinical differentiation of central as opposed to peripheral cyanosis
The presence or absence of clubbing of the digits
Determination of PaO2 tension and SaO2
Spectroscopic and other examinations of the blood for abnormal types of hemoglobin (critical in the differential diagnosis of cyanosis)

35. History
particularly the onset (cyanosis present since birth is usually due to congenital heart disease)
possible exposure to drugs or chemicals that may produce abnormal types of hemoglobin

36. Lab tests Determination of arterial oxygen saturation
oximetric(血氧定量法的)studies
physical or radiographic examination ,
echocardiography(超声心动图), right heart catherixation and angiocardiography(心血管造影术)
Spectroscope(分光镜检查)

37. Clubbing
The combination of cyanosis and clubbing is frequent in patients with congenital heart disease and right-to-left shunting and is seen occasionally in persons with pulmonary disease such as lung abscess(脓肿) or pulmonary arteriovenous fistulae.
In contrast, peripheral cyanosis or acutely developing central cyanosis is not associated with clubbed digits

38. Cyanosis + Dyspnea(呼吸困难)
Disorders of respiratory or cardiovascular system
Cyanosis with mild or no dyspnea
Methemoglobinemia
Sulfhemoglobinemia: Spectroscopy helpful
Cyanosis + clubbing
Severe, long duration