Cyanosis is a sign of low oxygen levels in the blood (hypoxemia). As defined under what is cyanosis, it is a consequence of a high concentration of deoxygenated hemoglobin (greater than 5 g/dL or 50 g/L) in the arterial blood, usually with a oxygen saturation of less than 90%. Cyanosis occurs when there is an inadequacy in lung oxygenation or blood circulation. If the air intake and gas exchange between the lung and blood stream is compromised, cyanosis will gradually develop as the oxygen is taken up by the body’s cells but not replenished fast enough.
Signs and Symptoms with Cyanosis
Cyanosis is not a disease but rather a sign of deoxygenated hemoglobin in the blood. It is evident as a blue to purple discoloration of the skin and mucous membranes. With central cyanosis, this discoloration is seen on the mucous membranes lining the mouth, tongue and eyes. With peripheral cyanosis, the bluish discoloration may be seen on the hands, feet and ears and is more pronounced in cold weather.
Cyanosis may be accompanied by other signs and symptoms like :
- Breathlessness with rapid or deep breathing as the body signals the brain of low oxygen availability and the respiratory symptom responds by increasing respiration in an attempt to raise oxygen intake. In mild cases, this may only occur with exertion.
- Dizziness as the oxygen-sensitive brain tissue responds to the low oxygen availability. This may eventually progress to fainting.
- Swelling, especially peripheral edema (swelling of the legs), as the changes associated with concomitant hypercapnia (excess carbon dioxide) disrupts kidney functioning.
Other signs and symptoms that may be reported with cyanosis includes :
- Gasping / air hunger
- Tingling or numbness of the affected areas
- Rapid heart rate with or without elevated blood pressure
- Easily fatigued
- Signs of hypercapnia (excess carbon dioxide in the blood) and respiratory acidosis
- Clubbing of the fingers and toes (hypertrophic osteoarthropathy) may occur with long-standing hypoxemia
Causes of Cyanosis
There are a number of causes of cyanosis including metal toxicity, drugs and metabolic conditions like diabetic ketoacidosis. However, the more common causes arise from disorders with the respiratory or cardiovascular systems.
Conditions that affect the flow of air through the airways and gas exchange in the air sacs of the lung include :
- Upper airway obstruction (pharynx, larynx, trachea)
- Chronic obstructive pulmonary disease – emphysema or chronic bronchitis
- Asthma – acute attack
- Acute lung injury
- Acute respiratory distress
- Pulmonary edema
- Chronic interstitial lung disease
- Idiopathic pulmonary fibrosis
- Pulmonary alveolar proteinosis
- Spontaneous pneumothorax
- Lung cancer
Cyanosis in cardiac conditions may be due to various mechanisms that disrupt the blood flow through the pulmonary blood vessels thereby impairing gas exchange. Slowing of the circulation in the periphery of the body may also contribute to peripheral cyanosis.
- Acute myocardial infarction (heart attack)
- Congestive heart failure
- Congenital heart disease
- Tetralogy of Fallot
- Truncus arteriosus
- Tricuspid artresia
- Total anomalous pulmonary venous connection
- Atrial septal defect
- Ventricular septal defect
- Coarctation of the aorta
- Raynaud phenomenon
- Pulmonary embolus
Article reviewed by Dr. Greg. Last updated on March 11, 2011