cyanosis

Definition

Cyanosis is a physical sign causing bluish discoloration of the skin and mucous membranes. Cyanosis is caused by a lack of oxygen in the blood. Cyanosis is associated with cold temperatures, heart failure, lung diseases, and smothering. It is seen in infants at birth as a result of heart defects, respiratory distress syndrome, or lung and breathing problems.

Description

Blood contains a red pigment (hemoglobin) in its red blood cells. Hemoglobin picks up oxygen from the lungs, then circulates it through arteries and releases it to cells through tiny capillaries. After giving up its oxygen, blood circulates back to the lungs through capillaries and veins. Hemoglobin, as well as blood, is bright red when it contains oxygen, but appears dark or "bluish" after it gives up oxygen.

The blue discoloration of cyanosis is seen most readily in the beds of the fingernails and toenails, and on the lips and tongue. It often appears transiently as a result of slowed blood flow through the skin due to the cold. As such, it is not a serious symptom. However, in other cases, cyanosis is a serious symptom of underlying disease.

— Carol A. Turkington

Cyanosis this, like any word with the prefix cyan, derives from the Greek for dark blue. It refers to a blue tinge seen on the surface of the whole or part of the body, due to lack of oxygen in the blood. The apparent colour of the skin depends on the state of oxygenation of the blood in the microscopic vessels below the surface. Blood in the arteries is normally bright red, the colour of red blood cells when the haemoglobin they contain is carrying its full quota of oxygen. In conditions of hypoxia due to altitude, lung disease, heart defects, or heart failure, the blood leaves the lungs without being fully oxygenated, and the arterial blood is less red. The degree of desaturation of haemoglobin at which such ‘central cyanosis’ is detectable varies between observers as well as between patients. Detection also depends on the superficial blood vessels being well-filled; if they are largely ‘shut down’ the skin is simply pale whatever the colour of the blood. Undoubtedly, however, if blueness is evident, there is significant hypoxia.

When arterial oxygen saturation is normal, the extent to which the blood becomes desaturated as it flows through the skin depends on the rate of blood flow. If blood flow is sluggish, a larger fraction of the oxygen is removed than if it is florid. Thus when cheeks are flushed, increased blood flow brings bright red blood near the surface; the oxygen supply is far in excess of need, with very little being removed. But when hands and feet are cold, the reflex constriction of blood vessels — to conserve heat as part of body temperature regulation — reduces the flow, so a higher proportion of the oxygen is removed to supply the skin tissue, and the blood becomes bluer before it moves on. Hence we can become ‘blue with cold’ — but only superficially. The arterial blood itself remains bright red, if everything else is normal. For similar reasons of diminished blood flow, cyanosis is seen locally in a part of the body — say a leg or a big toe — when the circulation in that part is compromised by arterial disease.

— Sheila Jennett

See also breathing; haemoglobin; hypoxia; lungs; oxygen.

A characteristic bluish tinge or color of the skin and mucous membranes associated with reduction in hemoglobin brought about by inadequate respiratory change (5 gm/100 ml are necessary for color to be perceptible).

Bluish discoloration of the skin and mucous membranes caused by lack of oxygen.

A bluish discoloration of the skin and mucous membranes due to excessive concentration of reduced hemoglobin in the blood. Used wrongly by clinicians describing skin lesions in pigs where there is severe congestion of cutaneous vessels and some leakage of blood into perivascular tissues.

• central c. — that due to arterial unsaturation, the aortic blood carrying reduced hemoglobin.
• enterogenous c. — a syndrome due to absorption of nitrites and sulfides from the intestine, principally marked by methemoglobinemia and/or sulfhemoglobinemia associated with cyanosis.
• peripheral c. — that due to an excessive amount of reduced hemoglobin in the venous blood as a result of extensive oxygen extraction at the capillary level.

Cyanosis

ICD-10	R23.0
ICD-9	782.5

Baby with a heart condition and purple nailbeds (click image to magnify)

Cyanosis is a blue coloration of the skin and mucous membranes due to the presence of > 5g/dl deoxygenated hemoglobin in blood vessels near the skin surface.

Although human blood is always a shade of red (except in rare cases of hemoglobin-related disease), the optical properties of skin distort the dark red color of deoxygenated blood to make it appear bluish^[1].

The elementary principle behind cyanosis is that deoxygenated hemoglobin is more prone to the optical bluish discoloration, and also produces vasoconstriction that makes it more evident. The scattering of color that produces the blue hue of veins and cyanosis is similar to the process that makes the sky appear blue: some colors are refracted and absorbed more than others. During cyanosis, tissues are uncharacteristically low on oxygen, and therefore tissues that would normally be filled with bright oxygenated blood are instead filled with darker, deoxygenated blood. Darker blood is much more prone to the blue-shifting optical effects^[2], and thus oxygen deficiency - hypoxia - leads to blue discoloration of the lips and other mucous membranes.

The name is derived from the color cyan, which comes from kyanous, the Greek word for blue.

Contents 1 Types 1.1 Central cyanosis 1.1.1 Common causes 1.2 Peripheral cyanosis 1.2.1 Common causes 1.2.2 Genetic causes 2 References 3 See also 4 External links

Types

Cyanosis can occur in the fingers, including underneath the fingernails, as well as other extremities (called peripheral cyanosis), or in the lips and tongue (central cyanosis).

Central cyanosis

Central cyanosis is often due to a circulatory or ventilatory problem that leads to poor blood oxygenation in the lungs or greater oxygen extraction due to slowing down of blood circulation in the skin's blood vessels.

Acute cyanosis can be a result of asphyxiation or choking, and is one of the surest signs that respiration is being blocked.

Common causes

• Abnormal hemoglobin levels^{[citation needed]}
• Bronchospasm
• Congenital heart disease
• Heart failure
• Heart valve disease
• High altitude
• Hypothermia
• Hypoventilation
• Lung disease
• Myocardial infarction
• Polycythaemia
• Pulmonary embolism
• COPD (emphysema and chronic bronchitis)
• Asthma
• Methemoglobinemia
• Tetralogy of Fallot
• Right to left shunts in heart or great vessels

Peripheral cyanosis

Peripheral cyanosis is the blue tint in fingers or extremities, due to inadequate 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, however peripheral cyanosis can be observed without there being heart or lung failures. Small blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood.

Common causes

• All common causes of central cyanosis
• Arterial obstruction
• Cold exposure (due to vasoconstriction)
• Raynaud's phenomenon (vasoconstriction)
• Reduced cardiac output (e.g. heart failure, hypovolaemia)
• Vasoconstriction
• Venous obstruction (e.g. deep vein thrombosis)

Genetic causes

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) creating a permanent T-state of Hb.

References

1. ^ Kienle, Alwin; Lothar Lilge, I. Alex Vitkin, Michael S. Patterson, Brian C. Wilson, Raimund Hibst, and Rudolf Steiner (March 1, 1996). "Why do veins appear blue? A new look at an old question" (PDF). Applied Optics 35 (7): 1151–60. doi:10.1364/AO.35.001151. http://www.imt.liu.se/edu/courses/TBMT36/pdf/blue.pdf. 
2. ^ 1

See also

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

External links

• Cyanosis definition, types, causes, and general details
• eMedicine

v • d • e Symptoms and signs: skin and subcutaneous tissue (R20-R23, 782) Disturbances of skin sensation/ somatosensory disorder Hypoesthesia · Paresthesia (Formication) · Hyperesthesia Hypoalgesia · Hyperalgesia Circulation Cyanosis · Pallor · Flushing · Petechia Edema Peripheral edema · Anasarca Other Rash · Desquamation · Induration · Diaphoresis integument, SF, LCT navs: anat/physio, noncongen/congen/neoplasia, symptoms+signs/eponymous, proc skin appendage navs: anat, noncongen/congen/neoplasia, symptoms+signs/eponymous, proc

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Dansk (Danish)
n. - cyanose, blåsyge

Nederlands (Dutch)
blauwzucht

Français (French)
n. - cyanose

Deutsch (German)
n. - (Med.) Cyanose (bläuliche Verfärbung der Haut)

Ελληνική (Greek)
n. - (παθολ.) κυάνωση

Italiano (Italian)
cianosi

Português (Portuguese)
n. - cianose (m) (Med.)

Русский (Russian)
цианоз

Español (Spanish)
n. - cianosis

Svenska (Swedish)
n. - cyanos

中文（简体）(Chinese (Simplified))
苍白病, 黄萎病

中文（繁體）(Chinese (Traditional))
n. - 蒼白病, 黃萎病

한국어 (Korean)
n. - 청색증, 치아노오제

日本語 (Japanese)
n. - 紫藍症, チアノーゼ

العربيه (Arabic)
‏(الاسم) تزرق لون الجلد بسبب نقص الأوكسجين‏

עברית (Hebrew)
n. - ‮כיחלון, צבע עור כחול‬

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