CYANOSIS
DR.Bilal Natiq Nuaman
C.A.B.M. ,F.I.B.M.S. ,D.I.M. ,M.B.Ch.B.
2015-2016
• Cyanosis is a blue or purple discoloration of
the skin and mucous membranes caused by :
increased concentration of reduced
hemoglobin in the capillary bed. (i.e.,
deoxygenated hemoglobin exceeding about
5 g/dL
) or
increased concentration of hemoglobin
derivatives (e.g.,
methemoglobin
) in the
superficial blood vessels.
• It is usually most marked in the lips, nail beds,
and malar eminences.
• It can be difficult to detect, particularly in black
and Asian patients.
Approximately 5 g/dL of deoxygenated hemoglobin in the
capillaries generates the dark blue color appreciated
clinically as cyanosis. For this reason, patients who are
anemic may be hypoxemic without showing any cyanosis.
Conversely, the higher the total hemoglobin content, the
greater the tendency toward cyanosis.
• Methemoglobin results from the presence of iron in the
ferric (oxidized) form instead of the usual ferrous form.
This results in a decreased availability of oxygen to the
tissues.
• When 15-20% of hemoglobin is methemoglobin ,
Cyanosis will result , though patients may be relatively
asymptomatic
Types of cyanosis
•
1-central
• This is seen at the lips and tongue .
It corresponds to an arterial oxygen saturation (SpO) of
<90% and usually indicates underlying cardiac or
pulmonary disease.
• Cardiac causes include pulmonary edema
and congenital heart disease.
Congenital defects associated with central cyanosis
include those in
which desaturated venous blood bypasses the lungs by
('reversed') shunting through septal defects or a
patent ductus arteriosus (e.g. Eisenmenger's syndrome,
Fallot's tetralogy).right-to-left shunt
•
2-peripheral
Peripheral cyanosis may result when cutaneous
vasoconstriction slows the blood flow and increases
oxygen extraction in the limbs (
acrocyanosis
).
Not affect tongue
It is physiological during cold exposure.
• It occurs in heart failure, when reduced cardiac output
produces reflex cutaneous vasoconstriction,
vascular disease and venous obstruction, e.g. deep vein
thrombosis. .
• Cardiogenic shock with
pulmonary edema, there
may be a mixture of both
central and peripheral
cyanosis.
APPROACH TO THE PATIENT:
1. It is important to ascertain the time of onset of cyanosis.
Cyanosis present since birth or infancy is usually due to
congenital heart disease.
2. Central and peripheral cyanosis must be differentiated.
Evidence of disorders of the respiratory or cardiovascular
systems is helpful.
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 should
be ascertained. The combination of cyanosis and clubbing
Is frequent in patients with congenital heart disease and
right-to-left shunting and is seen occasionally in patients 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. Pao2 and Sao should be determined,
and, in patients with cyanosis in whom the mechanism is
obscure,spectroscopic examination of the blood should be
performed to look for abnormal types of
hemoglobin(methemoglobin).
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