Cyanosis

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Central cyanosis
)
Cyanosis
low oxygen saturations
SpecialtyPulmonology, cardiology
TypesCentral, peripheral

Cyanosis is the change of body

symptom.[1]

Cyanosis is further classified into central cyanosis and peripheral cyanosis.

Pathophysiology

The mechanism behind cyanosis is different depending on whether it is central or peripheral.

Central cyanosis

Central cyanosis occurs due to decrease in

arterial oxygen saturation (SaO2), and begins to show once the concentration of deoxyhemoglobin in the blood reaches a concentration of ≥ 5.0 g/dL (≥ 3.1 mmol/L or oxygen saturation of ≤ 85%).[4] This indicates a cardiopulmonary condition.[5]

Causes of central cyanosis are discussed below.

Peripheral cyanosis

Peripheral cyanosis happens when there is increased concentration of

venous side of the peripheral circulation. In other words, cyanosis is dependent on the concentration of deoxyhemoglobin. Patients with severe anemia may appear normal despite higher-than-normal concentrations of deoxyhemoglobin. While patients with increased amounts of red blood cells (e.g., polycythemia vera) can appear cyanotic even with lower concentrations of deoxyhemoglobin.[6][7]

A baby with a heart condition. Note purple nailbeds.

Causes

Central cyanosis

Central cyanosis is often due to a circulatory or ventilatory problem that leads to poor blood

oxygenation in the lungs. It develops when arterial oxygen saturation drops below 85% or 75%.[6]

Acute cyanosis can be a result of

asphyxiation or choking and is one of the definite signs
that ventilation is being blocked.

Child with congenital heart disease with central cyanosis that is worsened by measles. Note the bluish-purple discoloration of the fingernails, lips, eyelids, and nose, along with prominent nail clubbing.

Central cyanosis may be due to the following causes:

  1. Central nervous system (impairing normal ventilation):[6]
  2. Respiratory system:[1][6]
  3. Cardiovascular system:[1][6]
  4. Hemoglobinopathies:[6]
  5. Others:
  1. ^ Note this causes "spurious" cyanosis, in that, since methemoglobin appears blue, the patient can appear cyanosed even in the presence of a normal arterial oxygen level.
  2. ^ Note a rare condition in which there is excess sulfhemoglobin (SulfHb) in the blood. The pigment is a greenish derivative of hemoglobin which cannot be converted back to normal, functional hemoglobin. It causes cyanosis even at low blood levels.

Peripheral cyanosis

Peripheral cyanosis is the blue tint in fingers or extremities, due to an inadequate or obstructed circulation.[6] The blood reaching the extremities is not oxygen-rich and when viewed through the skin a combination of factors can lead to the appearance of a blue color. All factors contributing to central cyanosis can also cause peripheral symptoms to appear, but peripheral cyanosis can be observed in the absence of heart or lung failures.[6] Small blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood.[6]

brachiocephalic trunk, left common carotid, and left subclavian artery
, therefore causing the differential cyanosis.

Peripheral cyanosis may be due to the following causes:[6]

Differential cyanosis

brachiocephalic trunk, left common carotid, and left subclavian arteries
.

Evaluation

A detailed history and

cardiopulmonary system) can guide further management and help determine the medical tests to be performed.[1] Tests that can be performed include pulse oximetry, arterial blood gas, complete blood count, methemoglobin level, electrocardiogram, echocardiogram, X-Ray, CT scan, cardiac catheterization, and hemoglobin electrophoresis
.

In

distal extremities, circumoral, and periorbital areas.[10] Of note, mucous membranes remain pink in peripheral cyanosis as compared to central cyanosis where the mucous membranes are cyanotic.[10]

An example of cyanosis in an individual with darker skin pigmentation. Note the pale purple (instead of the typical bluish-purple hue) nail beds. This patient also had prominent digital clubbing due to a congenital heart disease with right-to-left shunting (this patient had Tetralogy of Fallot).

It is important to note that

irregular heartbeats
.

An example of cyanosis in an elderly individual with darker skin pigmentation. Note the dark purple hue of the lips.

Management

Cyanosis is a

symptom not a disease
itself, so management should be focused on treating the underlying cause.

If it is an emergency, management should always begin with securing the

supplemental oxygen (in the form of nasal canula or continuous positive airway pressure depending on severity) should be given immediately.[11][12]

If the methemoglobin levels are positive for methemoglobinemia, first-line treatment is to administer methylene blue.[1]

History

The name cyanosis literally means the blue disease or the blue condition. It is derived from the color cyan, which comes from cyanós (κυανός), the Greek word for blue.[13]

It is postulated by Dr. Christen Lundsgaard that cyanosis was first described in 1749 by

venous blood circulation. But it was not until 1919, when Dr. Lundsgaard was able to derive the concentration of deoxyhemoglobin (8 volumes per cent) that could cause cyanosis.[14]

See also

References

External links