Cyanosis Health Article

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.

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 itself. 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, or 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 under- lying the cyanosis. If the underlying condition (such as heart or lung disease) can be properly treated, the skin will return to its normal coloring.

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.

BOOKS

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

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

Erika J. Norris