Download Cyanosis

Physical Diagnosis
Cyanosis
Definition
Cyanosis refers to a bluish(带蓝色的；
带青色的)color of the skin and mucous
membranes resulting from an increased
quantity of reduced hemoglobin(亚铁血
红蛋白；还原血红蛋白), or of
hemoglobin derivatives, in the small blood
vessels of those areas. It is usually most
marked in the lips, nail beds(甲床), ears,
and malar(颧骨的；颊的)eminences(隆
起).
Definition of cyanosis
A bluish color of skin and mucous
membranes, especially in lips, nail beds, and malar
eminences, caused by increased amount
of reduced hemoglobin(Hb) or abnormal
Hb derivatives in small blood vessels.
Mechanism of Cyanosis
Cyanosis, especially if developed
recently, is more commonly
detected by a family member than
the patient. The florid(鲜红色的
；气色好的) skin characteristic
of polycythemia vera(真性红细胞
增多症) must be distinguished
from the true cyanosis discussed
here.
A cherry(樱桃)-colored flush(潮
红), rather than cyanosis, is caused
by COHb(Carboxyhemoglobin
碳氧血红蛋白).
The degree of cyanosis is
modified by the color of the
cutaneous(皮肤的) pigment and
the thickness of the skin, as well
as by the state of the cutaneous
capillaries.
The accurate clinical detection of
the presence and degree of
cyanosis is difficult, as proved by
oximetric(血氧定量法的)studies.
In some instances, central cyanosis can be
detected reliably when the SaO2 has fallen
to 85%; in others, particularly in darkskinned persons, it may not be detected
until it has declined to 75%. In the latter
case, examination of the mucous
membranes in the oral cavity and the
conjunctivae(结膜)rather than
examination of the skin is more helpful in
the detection of cyanosis.
The increase in the quantity of
reduced hemoglobin in the
mucocutaneous(皮肤粘膜的) vessels
that produces cyanosis may be
brought about either by an increase in
the quantity of venous blood as the
result of dilatation of the venules(小
静脉) and venous ends of the
capillaries or by a reduction in the
SaO2 in the capillary blood.
In general, cyanosis becomes
apparent when the mean capillary
concentration of reduced
hemoglobin exceeds 50 g/L
(5g/dL). It is the absolute rather
than the relative quantity of
reduced hemoglobin that is
important in producing cyanosis.
Thus, in a patient with severe anemia, the
relative amount of reduced hemoglobin in
the venous blood may be very large when
considered in relation to the total amount
of hemoglobin in the blood. However,
since the concentration of the latter is
markedly reduced, the absolute quantity
of reduced hemoglobin may still be small,
and therefore patients with severe anemia
and even marked arterial desaturation(稀释
)do not display cyanosis.
Conversely, the higher the total
hemoglobin content, the greater is
the tendency toward cyanosis;
thus, patients with marked
polycythemia(红细胞增多症)tend
to be cyanotic at higher levels of
SaO2 than patients with normal
hematocrit(红细胞压积) values.
Likewise, local passive congestion,
which causes an increase in the
total amount of reduced
hemoglobin in the vessels in a
given area, may cause cyanosis.
Cyanosis also is observed when
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.
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
18
16
14
12
10
8
6
4
2
0
20
15
Total Hb
R-Hb
5
Normal
5
Polycythemia
5
5
Anemia
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)

Cyanosis may be subdivided into
central and peripheral types. In the
central type, the SaO2 is reduced or
an abnormal hemoglobin derivative is
present, and the mucous membranes
and skin are both affected.
Peripheral cyanosis is due to a
slowing of blood flow and abnormally
great extraction of O2 from normally
saturated arterial blood. It results
from vasoconstriction and diminished
peripheral blood flow, such as occurs
in cold exposure, shock, congestive
failure, and peripheral vascular disease.
Often in these conditions the mucous
membranes of the oral cavity or those
beneath the tongue may be spared. 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.
Central Cyanosis
Impaired pulmonary
function
1. Airway obstruction
2. Pulmonary diseases
3. Pleural(胸膜的)diseases
Right-to-left shunting
of blood
Tetralogy of Fallot
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
Mixed Cyanosis
(Central + Peripheral)
Cardiogenic
Shock
Pulmonary
Edema
Central Cyanosis Decreased SaO2
results from a marked reduction in the
PaO2. This reduction may be brought
about by a decline in the FIO2(fraction of
inspired oxygen 吸人氧气分数)without
sufficient compensatory alveolar(肺泡的)
hyperventilation(通气过度,换气过度)to
maintain alveolar PO2.
Cyanosis does not occur to a
significant degree in an ascent to
an altitude of 2500 m (8000 ft) but
is marked in a further ascent to
5000 m (16,000 ft). The reason for
this difference becomes clear on
studying the S shape of the Hb-O2
dissociation curve.
At 2500 m (8000 ft) the FIO2 is
about 120 mmHg, the alveolar
PO2 is approximately 80 mmHg,
and the SaO2 is nearly normal.
However, at 5000 m (16,000 ft) the
FIO2 and alveolar PO2 are about
85 and 50 mmHg, respectively, and
the SaO2 is only about 75%. This
leaves 25% of the hemoglobin in
the arterial blood in the reduced
form, an amount likely to be
associated with cyanosis in the
absence of anemia.
Similarly, a mutant hemoglobin
with a low affinity for O2 (e.g., Hb
Kansas) causes lowered SaO2 and
resultant central cyanosis.
Seriously impaired pulmonary
function, through perfusion(灌注
) of unventilated or poorly
ventilated areas of the lung or
alveolar hypoventilation, is a
common cause of central cyanosis.
This condition may occur acutely,
as in extensive pneumonia or
pulmonary edema, or chronically
with chronic pulmonary diseases
(e.g., emphysema 肺气肿). In the
last situation, secondary
polycythemia(红血球增多症) is
generally present, and clubbing(杵
状指)of the fingers may occur.
However, in many types of
chronic pulmonary disease with
fibrosis and obliteration(闭塞)of
the capillary vascular bed, cyanosis
does not occur because there is
relatively little perfusion of
underventilated areas.
Another cause of reduced SaO2
is shunting of systemic
venous blood into the arterial
circuit. Certain forms of
congenital heart disease are
associated with cyanosis.
Since blood flows from a higherpressure to a lower-pressure
region, for a cardiac defect to
result in a right-to-left shunt, it
must ordinarily be combined with
an obstructive lesion distal to the
defect or with elevated pulmonary
vascular resistance.
The most common congenital
cardiac lesion associated with
cyanosis in the adult is the
combination of ventricular septal
defect and pulmonary outflow
tract obstruction (tetralogy of Fallot).
The more severe the obstruction, the
greater the degree of right-to-left
shunting and resultant cyanosis. In
patients with patent ductus arteriosus,
pulmonary hypertension, and right-toleft shunt, differential cyanosis results;
that is, cyanosis occurs in the lower
but not in the upper extremities.
Pulmonary arteriovenous
fistulae may be congenital or
acquired, solitary or multiple,
microscopic or massive. The
severity of cyanosis produced by
these fistulae depends on their size
and number.
They occur with some frequency in
hereditary hemorrhagic telangiectasia
(毛细管扩张). SaO2 reduction and
cyanosis may also occur in some
patients with cirrhosis, presumably as
a consequence of pulmonary
arteriovenous fistulas or portal veinpulmonary vein anastomose(吻合术).
In patients with cardiac or
pulmonary right-to-left shunts, 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.
With increased extraction of O2
from the blood by the exercising
muscles, the venous blood
returning to the right side of the
heart is more unsaturated than at
rest, and shunting of this blood or
its passage through lungs
incapable of normal oxygenation
intensifies the cyanosis.
Also, since the systemic vascular
resistance falls with exercise, the rightto-left shunt is augmented by exercise
in patients with congenital heart
disease and communications between
the two sides of the heart. Secondary
polycythemia occurs frequently in
patients with arterial O2 unsaturation
and contributes to the cyanosis.
Cyanosis can be caused by small amounts
of circulating methemoglobin and by even
smaller amounts of sulfhemoglobin.
Although they are uncommon causes of
cyanosis, these abnormal hemoglobin
pigments should be sought by
spectroscopy(分光镜检查)when cyanosis
is not readily explained by malfunction of
the circulatory or respiratory systems.
Generally, digital clubbing does
not occur with them. The
diagnosis of methemoglobinemia
can be suspected if the patient's
blood remains brown after being
mixed in a test tube and exposed
to air.
Cyanosis due to abnormal Hb derivatives


Methemoglobinemia
— Hereditary: very rare
— Acquired: >3g/dl in blood
- intake or exposure to some drugs or
chemicals, such as sulfa drugs, nitrite
salt. “ enterogenic cyanosis ”
Sulfhemoglobinemia
— Caused by some drugs or chemicals,
— Sulfhemoglobin > 0.5g/dl in blood
Approach to Patients with Cyanosis

Differentiation of central as opposed to peripheral
Cyanosis
Skin temp.
Massage(按摩)or warming
Central
Warm
No change
Peripheral
Cool
Cyanosis fades
Peripheral Cyanosis
Probably the most common
cause of peripheral cyanosis is
the normal vasoconstriction
resulting from exposure to cold
air or water.
When cardiac output is low, as in
severe congestive heart failure or
shock, cutaneous vasoconstriction
occurs as a compensatory mechanism
so that blood is diverted from the skin
to more vital areas such as the central
nervous system and heart, and intense
cyanosis associated with cool
extremities may result.
Even though the arterial blood
is normally saturated, the
reduced volume flow through
the skin and the reduced PO2 at
the venous end of the capillary
result in cyanosis.
Arterial obstruction to an extremity, as
with an embolus, or arteriolar(小动脉的)
constriction, as in cold-induced vasospasm
血管痉挛 (Raynaud’s phenomenon),
generally results in pallor(苍白) and
coldness, but there may be associated with
cyanosis. Venous obstruction, as in
thrombophlebitis(血栓性静脉炎), dilates
the subpapillary venous plexuses(丛) and
thereby intensifies cyanosis.
Approach to the Patient
Certain features are important in
arriving at the cause of cyanosis:
1. The history, particularly the onset
(cyanosis present since birth is usually
due to congenital heart disease), and
possible exposure to drugs or
chemicals that may produce abnormal
types of hemoglobin.
2. Clinical differentiation of central as
opposed to peripheral cyanosis.
Objective evidence by physical or
radiographic examination of disorders
of the respiratory or cardiovascular
systems. Massage or gentle warming
of a cyanotic extremity will increase
peripheral blood flow and abolish
peripheral but not central cyanosis.
3. The presence or absence of
clubbing of the digits.
Clubbing without cyanosis is
frequent in patients with infective
endocarditis and ulcerative colitis;
it may occasionally occur in
healthy persons, and in some
instances it may be occupational,
e.g., in jackhammer(手提钻)
operators.
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 or pulmonary
arteriovenous fistulae.
In contrast, peripheral cyanosis or
acutely developing central cyanosis
is not associated with clubbed
digits.
4. Determination of PaO2 tension
and SaO2 and spectroscopic and
other examinations of the blood
for abnormal types of hemoglobin
(critical in the differential
diagnosis of cyanosis).

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

Determination of arterial oxygen saturation
CLUBBING
The selective bullous(大疱的,大
泡的) enlargement of the distal
segments of the fingers and toes
due to proliferation of connective
tissue, particularly on the dorsal
surface, is termed clubbing; there
is increased sponginess(海棉质)
of the soft tissue at the base of
the nail.
Clubbing may be hereditary, idiopathic, or
acquired and associated with a variety of
disorders, including cyanotic congenital
heart disease, infective endocarditis, and a
variety of pulmonary conditions (among
them primary and metastatic lung cancer,
bronchiectasis(支气管扩张), lung abscess,
cystic fibrosis(囊肿性纤维化), and
mesothelioma间皮瘤), as well as with
some gastrointestinal diseases (including
regional enteritis, chronic ulcerative colitis,
and hepatic cirrhosis).
Bleeding in Skin & Mucous Membranes
Introduction of BSMM
BSMM is caused by the abnormalities of hemostasis(
止血) and /or coagulation mechanisms, and
characterized by local or extensive mucocutaneous
hemorrhage spontaneously or following slight
trauma.
According to its extent, there are
several types of BSMM. Pinpoint
hemorrhage, equal or less than
2mm in diameter is called
petechiae; 3 -5mm hemorrhagic
lesion called purpura; more than
5mm, ecchymosis; local elevation
and fluctuation, hematoma.
Small pinpoint hemorrhages into
the dermis due to the leakage of
red cells through capillaries are
called petechiae and are
characteristic of platelet disorders
¾ in particular, severe
thrombocytopenia (血小板减少
症).
Larger subcutaneous collections
of blood due to leakage of blood
from small arterioles and venules
are called ecchymoses (common
bruises) or, if somewhat deeper
and palpable, hematomas.
They are also common in patients
with platelet defects and result
from minor trauma. Dilated
capillaries, or telangiectasia, may
cause bleeding without any
hemostatic defect.
In addition, the loss of connective
tissue support for capillaries and small
veins that accompanies aging increases
the fragility of superficial vessels, such
as those on the dorsum(背部) of the
hand, leading to extravasation(外渗)
of blood into subcutaneous
tissue¾senile(老年的) purpura.
Type and Clinical Manifestation
Petechia(出血点;瘀点): pinpoint
hemorrhage
 Purpura(紫癜): > 5mm in diameter
 Ecchymosis(瘀斑): common bruise, >10mm
 Hematoma(血肿): local elevation and
fluctuation
bleeding in skin, mucous membrane, joint
cavity and viscera.

Petechiae
Purpura
Ecchymosis
(Bruise)
Hematoma
Etiology & Pathogenesis


Defects on the capillary wall
Abnormalities of blood platelets
— Quantitative platelets defects
— Qualitative platelets defects

Disturbance of coagulation
— Deficiency of coagulation factors
— Increase of anti-coagulation substances
There are a lot of factors
participating in the process
of the hemostasis and
coagulation. Defects in one
of following factors may
lead to BSMM.
First, extravascular factor:
Lack of tissue support to the vessel
due to tissue degeneration and
atrophy may facilitate BSMM. It is a
rare cause of BSMM, and is
responsible for senile purpura and
purpura in Cushing syndrome.
In this situation both bleeding time
and coagulation time are normal.
Second, the vascular factor
The constriction of a small vessel plays a role
in hemostasis and the pliability of a vessel
keeps it intact. If a small vessel becomes fragile
and fails to constrict after its damage, BSMM
may occur. For example, in allergic purpura,
Non-thrombocytopenic purpura due to
infection or vitamine C deficiency and
hereditary telangiectasis, vascular factor is the
contributory cause of BSMM.
In this situation, BT and CT are normal, but
capillary fragility test is positive.
Defects on Capillary Wall
Fragile, or failure to constriction after
damage



Allergic purpura;
Hereditary telangioectasia;
Non- thrombocytopenic purpura
— Severe infection
— Vitamin C deficiency
— Uremia(尿毒症)
The Third factor is the platelet defects.
Blood platelets play an important role in
hemostasis. Platelet defects can be divided
into two types, the quantitative type and
qualitative type. In the former one, the
blood platelet count (or BPC) is lower
than normal, that is, thrombocytopenia(血
小板减少症). In the latter one, BPC is
normal, but its function is abnormal, as in
thrombasthenia(血小板无力).
In platelet defects, BPC is
often lower, occasionally it is
normal. Bleeding time is
prolonged and clot retraction is
poor.
Abnormalities of Blood Platelets

Quantitative platelets defects
— BPC is low, as thrombocytopenia with
various causes
Qualitative platelets defects
— Platelets dysfunction, as thrombasthenia(血
小板无力)

The final cause is the
deficiency of coagulation
factors.
The mechanism of
coagulation is complex.There
are at least twelve coagulation
factors that participate in
coagulation.This process can be
roughly divided into three
stages.
The First stage is applied to
the formation of activated
thrombokinase. In the second
stage, thrombokinase converts
prothrombin into thrombin. In
the final stage, thrombin in turn
converts fibrinogen into fibrin.
Any failure in this process may
result in coagulopathy凝血病.
Most of the coagulation
disorders are congenital,such as
hemophilia. In classic
hemophilia, there is the
deficiency of coagulation factor
.
A few of coagulation disorders
are acquired, such as liver
diseases, as we know most of
coagulation factors are made by
liver. In this situation,
coagulation time is prolonged.
Disturbance of Coagulation
I. Formation of activated thrombokinase
II. Prothrombin
Thrombin
III.
Fibrinogen
Fibrin
 Deficiency of coagulation factors
— Congenital : Hemophilia
— Acquired : Severe liver disease
 Increase of anti-coagulation substances
— During anti-coagulation therapy
Approach to patients with BSMM
is a complex problem, here we
only discuss a few key points.
In history-taking, we should ask
whether bleeding is spontaneous
or following trauma, ask about
past history of bleeding tendency,
such as bleeding after tooth
extraction, and ask whether there
is liver disease.
In physical examination,
bleeding should be traced over
whole body, sometimes including
urine and stool. In addition, the
jaundice and the size of liver and
spleen should be noted. Capillary
fragility test is helpful if some
vascular factor is suspected.
Laboratory routine tests,
including blood routine, blood
platelet count, bleeding time, and
coagulation time, should be done.
If necessary, bone marrow study
and coagulation factors
determination should be added.
Approach to Patients with BSMM

History
— Bleeding whether spontaneously or after trauma
— Past history of bleeding tendency
— Liver disease

Physical Examination
— Jaundice,
— Size of liver and spleen,
— Joints

Laboratory Tests
— Blood routine, blood platelet count, bleeding time,
— Coagulation time, bone marrow study
— Coagulation factors determination