Cyanosis: Types, Causes, and Clinical Significance Explained

Cyanosis: Types, Causes, and Clinical Significance Explained

Question. Write a Short Note On Cyanosis.
Or
Write a Short Answer On Cyanosis.
Or
Enumerate the Causes of Cyanosis.

Answer. Cyanosis is a bluish discoloration of the skin and mucus membrane due to reduced hemoglobin (more than 5 mg%) in blood.

Type of Cyanosis: Generally, there are four types of cyanosis

1. Central cyanosis
2. Peripheral cyanosis
3. Cyanosis due to abnormal pigments
4. Mixed cyanosis.
5. Central Cyanosis
   • It occurs because of poor oxygenation of blood in the lungs due to interference of the exchange of gases, i.e. oxygen and carbon dioxide, in respiratory failure or pulmonary edema.
   • Central cyanosis is also visible in some congenital heart diseases where deoxygenated blood from the right side mixes with the oxygenated blood from the left side.
     This brings down the oxygen saturation of the blood.
   • Central cyanosis is visible under the surface of the tongue and mucous membrane of the oral cavity and palate.
6. Peripheral Cyanosis
   • It occurs because of the removal of oxygen from the blood when circulation is slow due to congestive cardiac failure or due to shock, causing vasoconstriction.
   • This can also occur in healthy people when extremities are very cold.
   • It is visible in the lip, nail, tip of the nose, and lobule of the ear.
7. Cyanosis Due To Abnormal Pigments
   • Normal hemoglobin has iron in ferrous form.
     In methemoglobinemia, iron is in the ferric form designated as methemoglobin.
     Several substances, like nitrite ingestion, sulfonamide, or aniline dyes, oxidize hemoglobin to methemoglobin, but this is immediately reduced back to hemoglobin by methemoglobin reductase I or diaphorase.
     If there is a deficiency of diaphorase I, methemoglobin circulates in the blood, causing cyanosis.
   • Sulfhemoglobin is an abnormal sulfur-containing substance, which is not normally present, but is formed by the toxic action of drugs and chemicals like sulphonamides, phenacetin, and acetanilide.
     Sulfhemoglobin forms an irreversible change in the hemoglobin pigment that cannot carry oxygen and causes cyanosis.
8. Mixed Cyanosis
   • • Due to a combination of both factors, e.g,. cor pulmonale due to pulmonary emphysema.

Four Types of Causes of Cyanosis

1. Central cyanosis

1. Pulmonary causes
   • Lobar pneumonia
   • High altitudes
   • Pneumothorax
   • Multiple small pulmonary thromboembolism
   • Chronic obstructive pulmonary disease
   • Respiratory failure
   • Severe acute asthma
2. Cardiovascular Causes
   • Cyanotic heart disease
   • Acute pulmonary edema
   • Cor pulmonale
   • Arteriovenous fistula
3. Abnormal hepatopulmonary syndrome

2. Peripheral Cyanosis

• Congestive heart failure
• Exposure to cold
• Due to arterial obstruction
• Due to venous obstruction

3. Cyanosis Due to Abnormal Pigments

1. Methemoglobin formation due to ingestion of sulphonamide and aniline dye
2. Sulfhemoglobin formation due to sulphonamide, phenacetin

4. Mixed Cyanosis

• Acute left ventricular failure
• Mitral stenosis