Cyanosis: Definition, Types, Causes, Symptoms, Diagnosis and Treatment

It is the condition in which the skin, nails, and mucosa take on a blue or purple hue due to the more significant amount of reduced hemoglobin in the capillary blood.

Red blood cells provide oxygen to the different tissues of the body and, in return, absorb carbon dioxide and other wastes that will be expelled from the body.

It usually begins on the lips, tongue, or nails and is most visible in the same areas. It is indicative of the decrease in oxygen in the bloodstream.

It can indicate underlying lung disease, but it can also involve a defect in the heart or a major blood vessel.

Cyanosis can be challenging to detect when oxygen levels drop by only a tiny amount, especially in dark-skinned people.

For dark-skinned people, it may be easier to detect cyanosis on the lips, gums, around the eyes, and other mucous membranes.

The medical term cyanosis “Cyan” originates from the Greek word kyanos, which means “dark blue.”


Their skin typically has a pink or red tint. When your body is getting enough oxygen through your lungs and into your bloodstream, this predominant red hue reflects oxygen-carrying blood, which is red.

Blood that does not have a lot of oxygen contains mainly residual carbon dioxide from the cells to be exhaled from the lungs as part of respiration.

This oxygen-poor blood is darker in color and more bluish-red than red.

It is usual for veins to reflect this bluish color as veins carry blood, with its residual carbon dioxide charge, to the heart and lungs to remove carbon dioxide.

But when parts of the body turn blue or purple due to cyanosis, the muscles, organs, and other tissues may not be receiving the oxygen they need to function correctly.


In an adult, on average, there is 15 gm% of hemoglobin, 95% of which is saturated with oxygen, and only 5%, that is, 0.75 g%, is reduced.

Therefore, in capillaries, an average of the two, that is, only 2 to 3 gm%, is reduced hemoglobin and the color of the skin and mucous membranes are pink.

When reduced hemoglobin exceeds five gm% in the capillaries, the blood appears dark, giving the tissues a bluish hue.

Types of cyanosis


Central cyanosis is seen in high circulation areas, such as the palate, tongue, inner sides of the lips, and the conjunctiva.

In central cyanosis, the causes are the following:

  • Congenital and cyanotic heart disease: tetrad of Fallot, Eisenmenger complex, etc.
  • Congestive heart failure
  • Chronic obstructive pulmonary diseases.
  • Pulmonary collapses and fibrosis.
  • It marked lung destruction due to any cause.
  • High altitude due to low oxygen partial pressure.

Peripheral cyanosis occurs due to the decrease in the speed of the blood, which allows a longer time of oxygen elimination by the tissues, so the cyanosis is visible at the tip of the nose, the earlobe, the fingertip, the nail bed, and the cheek.

In peripheral cyanosis the causes are the following:

  • Cold (local vasoconstriction).
  • Increased viscosity of the blood.
  • Shock.


In mixed cyanosis, there is arterial hypoxemia and slow circulation. In mixed cyanosis the causes are the following:

  • Acute left ventricular failure.
  • Mitral stenosis (left atrial regurgitation and peripheral vasoconstriction).

Cyanosis due to abnormal pigments

Normal hemoglobin has iron in the ferrous form.

In methemoglobinemia, iron is in the iron form.

Various substances such as ingestion of nitrate (well water), sulfonamide, or aniline dyes oxidize hemoglobin to methemoglobinemia, but this is immediately reduced back to hemoglobin by methemoglobin reductase I or diaphorase I.

Methemoglobinemia circulates in the blood if diaphorase deficiency is present and causes cyanosis.

Sulfhemoglobin is an abnormal sulfur-containing substance that is not usually present but is formed by the toxic action of drugs and chemicals such as sulfonamides, phenacetin, and acetanilide.

Sulfhemoglobin forms an irreversible change in the pigment of hemoglobin that cannot transport oxygen and causes cyanosis.

Differential cyanosis

  • Lower extremities only: patent ductus arteriosus with shunt reversal.
  • Only in upper limbs: patent ductus arteriosus with shunt inversion in a transposition of the great vessels.
  • Cyanosis of the left upper and lower limbs: patent ductus arteriosus with reversal of the shunt and preductal coarctation of the aorta.

Conditions where cyanosis does not occur

In severe anemia, where the hemoglobin is less than five gm%, even if all the hemoglobin is reduced in the capillaries, it will be less than the critical level of 5 gm%, and cyanosis will not occur.

In carbon monoxide poisoning, carboxyhemoglobin prevents the reduction of oxyhemoglobin, and the former has a cherry red color.

Therefore, cyanosis does not occur.

Causes of cyanosis

Usually, blood returns from the body and flows through the heart and lungs. Low oxygen blood (blue blood) returns from the body to the right side of the heart.

Oxygen-rich blood returns from the lungs to the left side of the heart. And later, it is pumped into the rest of the organism.

Some related issues can lead to cyanosis. These include:

  • Blood clots block the blood supply to the extremities.
  • Raynaud’s phenomenon.
  • Heart problems.
  • Congenital heart defects.
  • Heart failure.
  • Cardiac arrest.
  • Lung problems.
  • Pulmonary embolism.
  • Bronchiolitis.
  • Asthma.
  • Chronic obstructive pulmonary disease.
  • Severe pneumonia.
  • It is at extreme altitudes.
  • Hold your breath.
  • Suffocation.
  • Problems with the epiglottis.
  • Drug overdoses.
  • We are ingesting toxins.
  • Exposure to cold air or water (hypothermia).

The heart problems that babies are often born with can change the way blood flows through the lungs and heart.

This causes non-oxygenated blood to be pumped into the body bypassing the lungs to pick up oxygen. As a result:

  • The blood that is pumped into the body has less oxygen.
  • There is less oxygen supplied to the body which can cause the skin to appear blue (cyanosis).

Many of these heart defects involve the heart valves.

Some defects that occur in the heart valve can cause cyanosis, such as:

  • The tricuspid or pulmonary valve may not have formed or may not have sufficient capacity to open.
  • The aortic valve cannot be extended far enough.
  • Coarctation or complete disruption of the aorta.
  • Ebstein’s anomaly.
  • Hypoplastic left heart syndrome.
  • Tetralogy of Fallot.
  • Total anomalous pulmonary venous return.
  • Transposition of the great arteries.
  • Arterial trunk.

Cyanotic heart disease can be caused by:

  • Exposure to chemicals.
  • Genetic and chromosomal syndromes include Down syndrome, trisomy 13, Turner syndrome, Marfan syndrome, and Noonan syndrome.
  • Infections such as rubella during pregnancy.
  • Medicines and illegal drugs are used during pregnancy.


Some heart defects cause significant problems right after birth.

The main symptom is a bluish color on the fingers, lips, and toes.

Some people have breathing problems (dyspnea), or their bodies are suddenly deprived of oxygen.

During these episodes, symptoms may also include:

  • The anxiety
  • Hyperventilation
  • A sudden increase in the bluish color of the skin.
  • Babies can become tired or sweat excessively when feeding.
  • I was having fainting (syncope) and chest pain.
  • Decreased appetite, leading to poor growth.
  • Greyish skin.
  • Swollen eyes or face
  • Tired all the time


Cyanosis refers to the blue color of the skin and mucous membranes due to excessive concentrations of reduced hemoglobin in the capillary blood.

The oxygen content of capillary blood is assumed to be midway between arterial and venous blood.

Areas with high blood flow and a slight oxygen difference (for example, the tongue and mucous membranes) will not turn cyanotic as quickly as those with low blood flow and a sizeable arteriovenous oxygen difference, such as the skin of hands and feet.

Therefore, a distinction is made between peripheral cyanosis (acrocyanosis), which is confined to the skin of the extremities, and central cyanosis, which includes the tongue and mucous membranes.

Circumoral cyanosis is not an expression of central cyanosis and is rarely pathologic.

The absolute concentration of reduced hemoglobin in the capillaries necessary to produce cyanosis is 4–6 g / dL of blood.

This level is generally present when the reduced hemoglobin concentration in arterial blood exceeds 3 g / 100 ml.

Clinical cyanosis will occur at different arterial oxygen saturation levels, depending on the amount of total hemoglobin.

Physiologically, five mechanisms can cause the desaturation of arterial hemoglobin in a patient who breathes air in a room at an average height:

  • Alveolar hypoventilation.
  • Deterioration of diffusion.
  • Right-to-left shunt mismatch of ventilation and perfusion.
  • Inadequate oxygen transport by hemoglobin.

The doctor with a stethoscope will be able to hear abnormal heart sounds, such as a heart murmur and crackles in the lungs.

Tests will vary depending on the cause but may include:

  • I passed a thin, flexible tube (catheter) into the right or left side of the heart, usually in the groin (cardiac catheterization).
  • Arterial blood gases.
  • Complete blood count: the level of hemoglobin increases with chronic cyanosis—the white blood cell count increases in pneumonia and pulmonary embolism.
  • Electrocardiogram to rule out heart abnormalities.
  • Chest X-ray to rule out pneumonia, pulmonary infarction, and heart failure.
  • Ventilation-perfusion scan or pulmonary angiography to rule out pulmonary embolism.
  • Echocardiography to look for heart defects.
  • Hemoglobin spectroscopy to detect methemoglobinemia and sulfhaemoglobinemia.
  • Digital subtraction angiography to rule out acute arterial occlusion.
  • Duplex Doppler or venography to find acute venous occlusion.

Cyanosis treatment

As with all common symptoms, cyanosis is treated according to its underlying cause.

Some of the treatments for cyanosis are as follows:

  • Oxygen therapy.
  • Warming of affected areas.
  • Surgery.
  • IV fluids.
  • Drug treatment.

As a symptom, cyanosis can indicate severe, life-threatening conditions and should be treated immediately.

Understanding cyanosis can help when taking first aid courses, primarily on respiratory or blood flow conditions.

Surgery is the most recommended treatment for congenital heart disease.

Prognosis and complications

Possible complications of cyanotic heart disease include:

  • Abnormal heart rhythms and sudden death.
  • Chronic high blood pressure in the blood vessels of the lung.
  • Heart failure.
  • Infections in the heart.

Management of cyanosis

Cyanosis is a sign, the manifestation of an underlying cause. So for the best management of cyanosis, the underlying cause must be treated.

Oxygen treatment for hypoxic patients is indicated.