Arterial Blood Gas Measurement

Arterial blood gas (ABG) is the "gold standard" for evaluating a cyanotic patient. The test involves obtaining an arterial blood sample. For maximal diagnostic value, the ABG should be evaluated while the animal is receiving supplemental 100 percent oxygen. The response to supplemental oxygen can be used to help rule in or rule out certain causes of cyanosis. For example, if there is peripheral cyanosis due to obstruction of blood flow to one or two limbs, giving supplemental oxygen does not raise the amount of oxygen in the arterial blood, and does not resolve the cyanosis.

However, if the cyanosis is due to disease of the lungs (edema, infection), hypoventilation, or ventilation/perfusion mismatch, giving supplemental oxygen will raise the amount of oxygen in the arterial blood, and the cyanosis should resolve. Giving supplemental oxygen to animals who are cyanotic because of an abnormal form of hemoglobin (such as methemoglobin) will not be helpful, because methemoglobin cannot bind oxygen, regardless of how enriched the oxygen supply is.

Pulse Oximetry

Pulse oximetry is readily available to most practitioners nowadays. It is a noninvasive way to get an idea of the amount of oxygen in the bloodstream. A probe is applied to a fold of skin in the axillary (armpit) or inguinal (groin) area, or the lip or tongue in an anesthetized animal. The major advantage of pulse oximetry is that you get a continuous reading, allowing sequential monitoring in response to supplemental oxygen.

Further Diagnostic Tests

Depending on the cause of the cyanosis, further diagnostic tests may be warranted. For example, if cardiac abnormalities are the cause of the cyanosis, cardiac ultrasound, electrocardiography, or angiocardiography may be necessary. If respiratory diseases are the cause of the cyanosis, various diagnostic tests such as thoracocentesis (removal of fluid or air from the chest cavity), a transtracheal wash, complete blood count, chemistry panel, urinalysis, chest X-rays, thoracic ultrasound, and fecal analysis may be warranted.

Therapy In-depth

One or more of the diagnostic tests described above may be recommended by your veterinarian. In the meantime, treatment of the symptoms might be needed, especially if the problem is severe. The following nonspecific symptomatic treatments may be applicable to some pets with cyanosis. These treatments may reduce the severity of symptoms or provide relief for your pet. However, nonspecific therapy is not a substitute for definite treatment of the underlying disease responsible for your pet's condition.

Therapy of cyanosis is dependent on understanding the cause of the condition.

Peripheral cyanosis. Peripheral cyanosis is usually not life threatening. Therapy is directed more toward the underlying disease. For example, a cat with a blood clot that has cut off circulation to a leg, causing cyanosis to the foot pads, acquires this condition secondary to severe heart disease. The main concern in this instance is getting the heart disease under control. The cyanosis is of much less significance.

Central cyanosis is treated as an emergency until the cause of the cyanosis can be determined.

Emergency Measures

Provide supplemental oxygen. In cases of central cyanosis, a reduced supply of oxygen is to be assumed until it can be disproved and supplemental oxygen is to be provided until the actual cause can be ascertained. Obvious mechanical obstructions to airflow (such as a foreign body in the mouth or throat) are removed and a patent airway is established. Then, oxygen is administered immediately either by face mask, a nasal oxygen tube, an oxygen cage, or endotracheal intubation.

If congenital heart disease is the cause of cyanosis, the treatment may involve surgery to correct the defect.

If respiratory disease is the cause, the treatment is:

Thoracocentesis to remove pus, blood, lymphatic fluid (chyle), or air that may be impeding the ability of the lungs to expand

Antibiotics to treat infection

Nebulization (use of a vaporizer) to moisten and loosen tenacious secretions down in the lungs and, possibly, to deliver antibiotics or other drugs down into the lungs

If excessive amounts of methemoglobin is the cause of the cyanosis, treatment involves:

Elimination of the cause of the formation of the methemoglobin

Acetylcysteine (Mucomyst®) can be given to cats who have received a toxic dose of Tylenol®.