Cyanosis

Template:Short description Template:Redirect Template:Infobox medical condition (new) Cyanosis is the change of tissue color to a bluish-purple hue, as a result of decrease in the amount of oxygen bound to the hemoglobin in the red blood cells of the capillary bed.<ref name=":0">Template:Citation</ref> Cyanosis is apparent usually in the body tissues covered with thin skin, including the mucous membranes, lips, nail beds, and ear lobes.<ref name=":0"/> Some medications may cause discoloration such as medications containing amiodarone or silver. Furthermore, mongolian spots, large birthmarks, 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.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Appropriate physical examination and history taking is a crucial part to diagnose cyanosis. Management of cyanosis involves treating the main cause, as cyanosis is not a disease, but rather a symptom.<ref name=":0" />

Cyanosis is further classified into central cyanosis and peripheral cyanosis.

Pathophysiology

File:Cynosis Illustration.jpg

Presentation of cyanosis varies depending on the color of the skin

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

Central cyanosis

Central cyanosis occurs due to decrease in arterial oxygen saturation (SaO2), and begins to show once the concentration of deoxyhemoglobin in the blood reaches a concentration of ≥ 5.0 g/dL (≥ 3.1 mmol/L or oxygen saturation of ≤ 85%).<ref>Template:Cite book</ref> This indicates a cardiopulmonary condition.<ref name=":0"/>

Causes of central cyanosis are discussed below.

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. While patients with increased amounts of red blood cells (e.g., polycythemia vera) can appear cyanotic even with lower concentrations of deoxyhemoglobin.<ref name=":1" /><ref name=":2">Template:Cite journal</ref>

File:Cyanotic neonate.jpg

A baby with a heart condition. Note purple nailbeds.

Causes

Central cyanosis

Central cyanosis is often due to a circulatory or ventilatory problem that leads to poor blood oxygenation in the lungs. It develops when arterial oxygen saturation drops below 85% or 75%.<ref name=":1" />

Acute cyanosis can be a result of asphyxiation or choking and is one of the definite signs that ventilation is being blocked.

File:Child with measles modified by cyanosis Wellcome L0061496.jpg

Child with congenital heart disease with central cyanosis that is worsened by measles. Note the bluish-purple discoloration of the fingernails, lips, eyelids, and nose, along with prominent nail clubbing.

Central cyanosis may be due to the following causes:

1. Central nervous system (impairing normal ventilation):<ref name=":1" />
   • Intracranial hemorrhage
   • Drug overdose (e.g., heroin)
   • Generalized tonic–clonic seizure (GTCS)
2. Respiratory system:<ref name=":0"/><ref name=":1" />
   • Pneumonia
   • Bronchiolitis
   • Bronchospasm (e.g., asthma)
   • Pulmonary hypertension
   • Pulmonary embolism
   • Hypoventilation
   • Chronic obstructive pulmonary disease, or COPD (emphysema)<ref name=":1" />
3. Cardiovascular system:<ref name=":0"/><ref name=":1" />
   • Congenital heart disease (e.g., Tetralogy of Fallot, right to left shunts in heart or great vessels)
   • Heart failure
   • Valvular heart disease
   • Myocardial infarction
4. Hemoglobinopathies:<ref name=":1" />
   • MethemoglobinemiaTemplate:Efn
   • SulfhemoglobinemiaTemplate:Efn
   • Polycythemia
   • Congenital cyanosis (HbM Boston) arises from a mutation in the α-codon which results in a change of primary sequence, H → Y. Tyrosine stabilizes the Fe(III) form (oxyhaemoglobin) creating a permanent T-state of Hb.

     File:Peripheral Cyanosis due to Ischemia.jpg

     Peripheral cyanosis in an individual with peripheral vascular disease.

5. Others:
   • High altitude, cyanosis may develop in ascents to altitudes >2400 m.<ref name=":0"/><ref name=":1" />
   • Hypothermia<ref name=":1" />
   • Frostbite<ref>Template:Cite book</ref>
   • Obstructive sleep apnea<ref name=":1" />

Peripheral cyanosis

Peripheral cyanosis is the blue tint in fingers or extremities, due to an inadequate or obstructed circulation.<ref name=":1">Template:Cite web</ref> 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.<ref name=":1" /> Small blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood.<ref name=":1" />

File:Blausen 0707 PatentDuctusArteriosus.png

Initial direction of blood flow in patients with patent ductus arteriosus. Once the pressure of the pulmonary arteries increases more than the aorta due to right heart hypertrophy, the direction of blood flow reverses, sending deoxygenated blood through the patent duct directly into the descending aorta while sparing the brachiocephalic trunk, left common carotid, and left subclavian artery, therefore causing the differential cyanosis.

Peripheral cyanosis may be due to the following causes:<ref name=":1" />

• All common causes of central cyanosis
• Reduced cardiac output (e.g., heart failure or hypovolemia)
• 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

File:Local hypxia.jpg

This illustration depicts a self-induced local (tissue) hypoxia on the right hand (right side of the picture) versus a normal left hand (left side of the picture). The cyanosis was achieved by inflating and tightening the blood pressure cuff on the right arm.

Differential cyanosis is the bluish coloration of the lower but not the upper extremity and the head.<ref name=":1" /> This is seen in patients with a patent ductus arteriosus.<ref name=":1" /> Patients with a large ductus develop progressive pulmonary vascular disease, and pressure overload of the right ventricle occurs.<ref name=":5">Template:Citation</ref> As soon as pulmonary pressure exceeds aortic pressure, shunt reversal (right-to-left shunt) occurs.<ref name=":5"/> 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, and left subclavian arteries.

Evaluation

A detailed history and physical examination (particularly focusing on the cardiopulmonary system) can guide further management and help determine the medical tests to be performed.<ref name=":0"/> 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.<ref name=":4">Template:Cite journal</ref> Of note, mucous membranes remain pink in peripheral cyanosis as compared to central cyanosis where the mucous membranes are cyanotic.<ref name=":4"/>

File:CongenitalHeartCase-133.jpg

An example of cyanosis in an individual with darker skin pigmentation. Note the pale purple (instead of the typical bluish-purple hue) nail beds. This patient also had prominent digital clubbing due to a congenital heart disease with right-to-left shunting (this patient had Tetralogy of Fallot).

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.<ref name=":0"/> As mentioned above, patients with severe anemia may appear normal despite higher than normal concentrations of deoxyhemoglobin.<ref name=":1" /><ref name=":2"/> Signs of severe anemia may include pale mucosa (lips, eyelids, and gums), fatigue, lightheadedness, and irregular heartbeats.

File:Cyanoza .jpg

An example of cyanosis in an elderly individual with darker skin pigmentation. Note the dark purple hue of the lips.

Management

Cyanosis is a symptom, not 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.<ref>Template:Citation</ref><ref>Template:Cite journal</ref>

If the methemoglobin levels are positive for methemoglobinemia, first-line treatment is to administer methylene blue.<ref name=":0"/>

History

The name cyanosis literally means the blue disease or the blue condition. It is derived from the color cyan, which comes from cyanós (κυανός), the Greek word for blue.<ref>Template:Cite book</ref>

It is postulated by Dr. Christen Lundsgaard that cyanosis was first described in 1749 by Jean-Baptiste de Sénac, a French physician who served King Louis XV.<ref name=":3">Template:Cite journal</ref> 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.<ref name=":3"/>

See also

• Acrocyanosis
• Blue baby syndrome
• Raynaud's phenomenon
• Blue Fugates