Cyanosis - Causes and Symptoms

Definition

Cyanosis is the bluish-purple color of the skin or mucous membranes, due to an excessive concentration of non-oxygenated hemoglobin in the blood. This manifestation is more evident in thinner and vascularized skin areas (lips, ear lobes, nose, cheekbones and nail bed).

There are forms of central cyanosis (generalized, affecting the whole body) and peripheral forms (limited to a single district of the body, such as the limbs or fingers).

Central cyanosis is the result of a systemic oxygen desaturation, associated with a difficulty in respiratory and / or cardiovascular function. The localized form is connected, instead, to the slowing down of the peripheral blood circulation (blood stasis in the tissues).

In cyanosis, the skin can be warm (central form) or cold (peripheral form).

Central cyanosis

Central cyanosis is generalized and often due to a circulatory or pulmonary problem, which leads to poor blood oxygenation. It develops when the concentration of deoxygenated hemoglobin is equal to or greater than 5 g / 100 ml, ie when at least one third of the total amount of normal hemoglobin (13.5-17 g / dL in men, 12-16 g / dL in women ) is not oxygenated. However, central cyanosis is generally evident when oxygen saturation is ≤ 85%.

This manifestation can originate from pathologies that affect the respiratory system (including emphysema, chronic bronchitis, pulmonary fibrosis, extended pneumonia, atelectasis, pneumothorax, pulmonary embolism and pleural effusion). In other cases, it is due to cardiovascular disorders, such as: myocardial infarction, severe hypotension (shock), chronic pericarditis and valvulopathies.

In newborns, central cyanosis may occur in cases of respiratory distress syndrome and congenital heart defects (eg tetralogy of Fallot, cardiopathies with left-right shunt and septal defects).

The alteration of normal ventilation can also be attributed to extra-pulmonary causes, such as obesity, obstructive sleep apnea, costal fractures, muscular diseases, polycythemia, laryngospasm and conditions that affect the central nervous system (intracranial hemorrhage and epilepsy).

Other possible causes of central cyanosis include: abuse of some drugs, drug overdose (eg heroin), airway obstruction caused by a foreign body (suffocation), hypothermia (prolonged exposure to extreme cold) and reaching altitudes above 2400 m (decreases the partial pressure of oxygen in the atmosphere). Central cyanosis is observed with greater difficulty in patients suffering from anemia, while it is easily evident during poliglobulia, due to the high concentration of absolute hemoglobin in the blood.

Peripheral cyanosis

Peripheral cyanosis is district and can result from a difference in arteriovenous oxygenation, which can lead to an increase in the extraction of oxygen by peripheral tissues. This form can also occur in the absence of cardiac or pulmonary dysfunction. It can occur in the case of acrocyanosis (a form of persistent, painless and symmetrical cyanosis of the hands, feet or face, triggered by exposure to cold) and Raynaud's syndrome (vasoconstriction of the extremities, followed by cyanosis and redness). Other causes include: reduced cardiac output (pericarditis, valvular stenosis, heart failure etc.), venous obstruction (eg deep vein thrombosis and thrombophlebitis) and arterial (embolism or thrombosis).

Pseudocianosi

A cyanosis can also occur when abnormal hemoglobin compounds (eg methaemoglobin or sulfoemoglobin) are formed, such as during particular poisonings (ingestion of drugs, toxins or metals, such as silver or lead). In the latter case, however, one speaks more correctly about "pseudocyanosis".