Cyanosis

Definition

Cyanosis is a physical state characterized by bluish discoloration of the skin and mucus membranes.

Description

Cyanosis is a physical sign, rather than a diagnosis. The abnormal coloring of a cyanotic patient is due to a low oxygen content of the circulating red blood cells. Typically the abnormal bluish coloring is most noticeable in the nailbeds, lips, ears, and cheeks.

Causes and symptoms

One of the many important functions of blood is to pick up oxygen from the air sacs of the lungs and deliver it to sites around the body in need of oxygen. To carry oxygen, red blood cells (RBCs) contain a pigment called hemoglobin. When hemoglobin is carrying its full capacity of oxygen, it will cause the RBC to appear bright red. After the oxygen has been delivered, the RBC has a darker, bluish cast. If the darker-colored RBCs predominate, this gives the skin and mucus membranes the characteristic blue appearance of cyanosis.

Cyanosis can occur frequently in newborn babies and can result from a number of causes, which complicates diagnosis. Cyanosis may occur in association with neonatal airway obstruction, neonatal sepsis, cyanotic congenital heart disease, or as a result of abnormal forms of hemoglobin.

There are two basic types of cyanosis: central and peripheral. Central cyanosis means that the arterial blood simply does not contain normal levels of oxygen (hypoxemia). This can happen because of lung disease, heart defects, and certain problems with the hemoglobin. Peripheral cyanosis means that venous blood (or blood that has unloaded its oxygen) is contributing to skin color more than arterial (or oxygen-rich) blood. A patient may have normal oxygen levels in arterial blood, but still have the bluish color of cyanosis expressed in some part(s) of his body. With peripheral cyanosis the underlying condition may be exposure to the cold, decreased output from the heart, or local disruptions in the flow of arterial or venous blood.

Patients may or may not have symptoms with cyanosis, depending on its cause. With central cyanosis patients are often short of breath, dizzy, or even unconscious. With a peripheral cause of cyanosis, patients may have complaints localized to the affected parts of the body.

Diagnosis

Cyanosis is a subjective observation, so there is no test to confirm it. A patient's skin pigmentation and the presence or absence of anemia can make cyanosis more or less obvious. But there are objective tests to verify the presence or absence of hypoxemia (or low oxygen content of the blood). A non-invasive pulse oximeter can be used by a nurse or respiratory therapist to give a fairly accurate approximation of arterial oxygenation, and arterial blood gases can be drawn by a physician or respiratory therapist if detailed information is needed. If the arterial oxygen level is low, the cyanosis is central; if the oxygen level is normal, the cyanosis is peripheral in nature. If the affected body parts regain normal color with massage and warming, the cause was peripheral. Occasionally cyanosis has both central and peripheral elements.

Treatment

Treatment of cyanosis is based on identifying and treating its cause, and restoring normal flow of oxygenated blood.

Prognosis

Prognosis is dependent on the disease process underlying the cyanosis. If the underlying condition (such as heart or lung disease) can be properly treated, the skin will return to its normal coloring. Cyanosis in newborns can be more serious, particularly if it occurs in conjunction with abnormal forms of hemoglobin, which can be life-threatening.

Health care team roles

Health care team members should be alert to cyanosis as a warning sign, particularly as a new development in a given patient. Prompt recognition and treatment could be very important to clinical outcome.

KEY TERMS

Hemoglobin— A colored substance (pigment) in the red blood cell that carries oxygen to tissues and gives blood its red color.

Pulse oximeter— A painless device which uses a beam of light directed through the patient's finger, toe or earlobe to assess oxygen saturation of the blood.

Resources

BOOKS

Braunwald, Eugene, et al. Harrison's Principles of Internal Medicine. McGraw-Hill, 2001.

Carolson, Karen J., Stephanie A. Eisenstat, and Terra Ziporyn. The Harvard Guide to Women's Health. Harvard University Press, 1996.

PERIODICALS

Da-Silva, Shonola S., Imran S. Sajan, and Joseph P. Underwood III. "Congenital Methemoglobinemia: A Rare Cause of Cyanosis in the Newborn—A Case Report." Pediatrics (August 2003):403-405.

Kyriacou, Demetiros N., et al. "Clinical Predictors of Bioterrorism-related Inhalational Anthrax." The Lancet (July 31, 2004):449.

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.

Causes and symptoms

The blue color of the skin and mucous membranes is caused by a lack of oxygen in the blood. Low blood oxygen may be caused by poor blood circulation, or heart or breathing problems. It can also be caused by being in a low-oxygen environment or by carbon monoxide poisoning. More rarely, cyanosis can be present at birth as a sign of congenital heart disease, in which some of the blood is not pumped to the lungs where oxygen would make the blood a bright red color. Instead, the blood goes to the rest of the body and remains unoxygenated. Cyanosis also may be caused by poisoning from chemicals, drugs, or contaminated food and water.

Other signs of low blood oxygen may accompany cyanosis, including feeling lightheaded or fainting.

Treatment

Treatment of the underlying disease can restore proper color to the skin.

KEY TERMS

Hemoglobin— A colored substance (pigment) in the blood that carries oxygen to tissues and gives blood its red color.

Respiratory distress syndrome— Also known as hyaline membrane disease, this is a condition of premature infants in which the lungs are imperfectly expanded due to a lack of a substance on the lungs that reduces tension.

Prognosis

If the underlying condition (such as heart or lung disease) can be properly treated, the skin will return to its normal shade.

Resources

BOOKS

Carolson, Karen J., Stephanie A. Eisenstat, and Terra Ziporyn. The Harvard Guide to Women's Health. Cambridge, MA: Harvard University Press, 1996.

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

cy·a·no·sis / ˌsīəˈnōsəs/ • n. Med. a bluish discoloration of the skin resulting from poor circulation or inadequate oxygenation of the blood.DERIVATIVES: cy·a·not·ic / ˌsīəˈnätik/ adj.

cyanosis (sy-ă-noh-sis) n. a bluish discoloration of the skin and mucous membranes resulting from an inadequate amount of oxygen in arterial blood (central c.), due to reduced oxygenation of blood in the pulmonary circulation, or in venous blood (peripheral c.), due to excessive extraction of oxygen in the tissues. Cyanosis is associated with heart failure, lung diseases, the breathing of oxygen-deficient atmospheres, and asphyxia. Cyanosis is also seen in blue babies, because of congenital heart defects.
—cyanotic adj.