Download Physical Diagnosis

Cyanosis
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.
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.
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
Mean capillary concentration of
reduced hemoglobin exceeds 50 g/L.
It is the absolute rather than the
relative increase.
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
20
20
15
15
Total Hb
R-Hb
10
5
5
5
5
5
0
Normal
Polycythemia
Anemia
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
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.
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)
Central cyanosis is caused by
decreased SaO2(increased amount
of reduced Hb)
Central cyanosis only occurs when
the oxygen saturation of arterial
blood is less than 85%.
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)
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
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.
Central Cyanosis
Impaired pulmonary
function
1. Airway obstruction
2. Pulmonary diseases
Right-to-left shunting
of blood
Tetralogy of Fallot
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.
High O2
affinity Hgb
normal
Low O2
affinity Hgb
Peripheral cyanosis is due to poor
peripheral circulation and increased
oxygen consumption in peripheral
tissue.
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
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
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.
Possible causes of mixed cyanosis


all causes of central cyanosis may
lead to peripheral cyanosis
low cardiac output e.g. heart failure
Cyanosis due to abnormal Hb derivatives
Central cyanosis may be simulated by
methaemoglobulinaemia and
sulphaemoglobulinaemia.
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.
Sulfhemoglobinemia



Sulfhemoglobin >5g/L
Caused by some drugs or chemicals,
Spectroscope is helpful to diagnose
Clinical Classification
— Central Type
— Peripheral Type
— Mixed Type
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
Possible clinical features include
----peripheral cyanosis



Cool skin and mucous membrance
Site (lower extremities,fingers)
Diminish after massage
Note that the absolute
discriminating feature between
central and peripheral cyanosis
is obtained from testing the
oxygen saturation of arterial
blood.
Differentiation of central as
opposed to peripheral
Cyanosis
Central
Peripheral
Skin temp.
Massage or warming
Warm
Cool
No change
Cyanosis fades
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
Sulfhemoglobin


Long duration(several months)
Spectroscope-630nm
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)
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
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)
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

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