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Cyanosis is the change of body tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the
red blood cells Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek language, Greek ''erythros'' for "red" and ''k ...
of the capillary bed. Body tissues that show cyanosis are usually in locations where the skin is thinner, including the mucous membranes, lips, nail beds, and ear lobes. Some medications containing amiodarone or silver, Mongolian spots, large birth marks, and the consumption of food products with blue or purple dyes can also result in the bluish skin tissue discoloration and may be mistaken for cyanosis. Cyanosis is further classified into central cyanosis vs. peripheral cyanosis.


Pathophysiology

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


Central cyanosis

Central cyanosis is caused by a decrease in arterial oxygen saturation (SaO2) and begins to show once the concentration of
deoxyhemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...
in the blood reaches a concentration of ≥ 5.0 g/dL (≥ 3.1 mmol/L or oxygen saturation of ≤ 85 %). Causes of central cyanosis are discussed
below Below may refer to: *Earth *Ground (disambiguation) *Soil *Floor *Bottom (disambiguation) Bottom may refer to: Anatomy and sex * Bottom (BDSM), the partner in a BDSM who takes the passive, receiving, or obedient role, to that of the top or ...
.


Peripheral cyanosis

Peripheral cyanosis happens when there is increased concentration of deoxyhemoglobin on the 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. On the other hand, patients with increased amounts of red blood cells (e.g. polycythemia vera) can appear cyanotic even with lower concentrations of deoxyhemoglobin.


Causes


Central cyanosis

Central cyanosis is often due to a circulatory or ventilatory problem that leads to poor blood
oxygenation Oxygenation may refer to: * Oxygenation (environmental), a measurement of dissolved oxygen concentration in soil or water * Oxygen saturation (medicine), the process by which concentrations of oxygen increase within a tissue * Water oxygenation, t ...
in the lungs. It develops when arterial oxygen saturation drops below 85% or 75%. Acute cyanosis can be a result of asphyxiation or choking and is one of the definite signs that ventilation is being blocked. Central cyanosis may be due to the following causes: # Central nervous system (impairing normal ventilation): #* Intracranial hemorrhage #*
Drug overdose A drug overdose (overdose or OD) is the ingestion or application of a drug or other substance in quantities much greater than are recommended.
(e.g.
heroin Heroin, also known as diacetylmorphine and diamorphine among other names, is a potent opioid mainly used as a recreational drug for its euphoric effects. Medical grade diamorphine is used as a pure hydrochloride salt. Various white and brow ...
) #* Generalized tonic–clonic seizure (GTCS) # Respiratory system: #* Pneumonia #* Bronchiolitis #* Bronchospasm (e.g. asthma) #* Pulmonary hypertension #* Pulmonary embolism #* Hypoventilation #* Chronic obstructive pulmonary disease, or COPD (
emphysema Emphysema, or pulmonary emphysema, is a lower respiratory tract disease, characterised by air-filled spaces ( pneumatoses) in the lungs, that can vary in size and may be very large. The spaces are caused by the breakdown of the walls of the alve ...
) #
Cardiovascular system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
: #* Congenital heart disease (e.g. Tetralogy of Fallot, right to left shunts in heart or great vessels) #*
Heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...
#* Valvular heart disease #* Myocardial infarction # Hemoglobinopathies: #*
Methemoglobinemia Methemoglobinemia, or methaemoglobinaemia, is a condition of elevated methemoglobin in the blood. Symptoms may include headache, dizziness, shortness of breath, nausea, poor muscle coordination, and blue-colored skin (cyanosis). Complications m ...
#*
Sulfhemoglobinemia Sulfhemoglobinemia is 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 ...
#* Polycythemia #* Congenital cyanosis (HbM Boston) arises from a mutation in the α-codon which results in a change of primary sequence, H → Y. Tyrosine stabilises the Fe(III) form (
oxyhaemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...
) creating a permanent T-state of Hb. # Others: #* High altitude, cyanosis may develop in ascents to altitudes >2400 m. #* Hypothermia #* Frostbite #*
Obstructive sleep apnea Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and is characterized by recurrent episodes of complete or partial obstruction of the upper airway leading to reduced or absent breathing during sleep. These episod ...


Peripheral cyanosis

Peripheral cyanosis is the blue tint in fingers or extremities, due to an inadequate or obstructed circulation. 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. Small blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood. Peripheral cyanosis may be due to the following causes: * All common causes of central cyanosis * Reduced cardiac output (e.g.
heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...
or
hypovolemia Hypovolemia, also known as volume depletion or volume contraction, is a state of abnormally low extracellular fluid in the body. This may be due to either a loss of both salt and water or a decrease in blood volume. Hypovolemia refers to the los ...
) * Cold exposure * Chronic obstructive pulmonary disease (COPD) *Arterial obstruction (e.g. peripheral vascular disease, Raynaud phenomenon) * Venous obstruction (e.g. deep vein thrombosis)


Differential cyanosis

Differential cyanosis is the bluish coloration of the lower but not the upper extremity and the head. This is seen in patients with a patent ductus arteriosus. Patients with a large ductus develop progressive pulmonary vascular disease, and pressure overload of the right ventricle occurs. As soon as pulmonary pressure exceeds aortic pressure, shunt reversal (right-to-left shunt) occurs. The upper extremity remains pink because deoxygenated blood flows through the patent duct and directly into the descending aorta while sparing the brachiocephalic trunk,
left common carotid In anatomy, the left and right common carotid arteries (carotids) (Entry "carotid"
in
left subclavian arteries.


Evaluation

A detailed history and physical examination (particularly focusing on the cardiopulmonary system) can guide further management and help determine the choice of testing to be performed. 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 newborns, peripheral cyanosis typically presents in the distal extremities, circumoral, and periorbital areas. Of note, mucous membranes remain pink in peripheral cyanosis as compared to central cyanosis where the mucous membranes are cyanotic. It is important to note that skin pigmentation and hemoglobin concentration can affect the evaluation of cyanosis. Cyanosis may be more difficult to detect on people with darker skin pigmentation. However, cyanosis can still be diagnosed with careful examination of the typical body areas such as nail beds, tongue, and mucous membranes where the skin is thinner and more vascular. As mentioned above, patients with severe anemia may appear normal despite higher than normal concentrations of deoxyhemoglobin. Signs of severe anemia may include pale mucosa (lips, eyelids, and gums), fatigue, lightheadedness, and irregular heartbeats.


Management

Cyanosis is a symptom rather than 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 airway, breathing, and circulation. In patients with significant respiratory distress, supplemental oxygen (in the form of nasal canula or continuous positive airway pressure depending on severity) should be given immediately. If the methemoglobin levels are positive for methemoglobinemia, first-line treatment is to administer methylene blue.


History

The name ''cyanosis'' literally means ''the blue disease'' or ''the blue condition''. It is derived from the color
cyan Cyan () is the color between green and blue on the visible spectrum of light. It is evoked by light with a predominant wavelength between 490 and 520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK color ...
, which comes from ''cyanós (κυανός)'', the Greek word for ''blue''. It is postulated by Dr. Christen Lundsgaard that cyanosis was first described in 1749 by
Jean-Baptiste de Sénac Jean-Baptiste de Sénac (1693–1770) was a French physician was born in the district of Lombez in Gascony, France. Early life and education Details of his early life are sketchy, however, it is generally thought that he studied medicine at the Un ...
, a French physician who served King Louis XV. De Sénac concluded from an autopsy that cyanosis was caused by a heart defect that led to the mixture of arterial and 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.


See also

* Acrocyanosis * Blue baby syndrome * Raynaud's phenomenon *
Blue Fugates The Fugates, a family living in the hills of Kentucky starting in the 19th century, were commonly known as the "Blue Fugates" or the "Blue People of Kentucky". They are known for being carriers of a genetic trait that led to the blood disorder ...


References


External links

{{Respiratory system symptoms and signs Medical signs Symptoms and signs: Skin and subcutaneous tissue