Cyanosis in Cats

By Malcolm Weir, DVM, MSc, MPH; Robin Downing, DVM, DAAPM, DACVSMR, CVPP, CRPP

What is cyanosis?

Cyanosis is defined as a bluish discoloration of the skin and mucous membranes of the body (e.g., the gums), caused by inadequate oxygen levels. There are several different conditions involving the cardiovascular/circulatory system and/or the respiratory system that can lead to cyanosis. Treatment will depend upon the underlying reason for the low oxygen levels.

What are some causes of cyanosis involving the circulatory system?

Some cats are born with defects or abnormalities in the structure of their heart and surrounding blood vessels. The blood with low levels of oxygen may be shunted from the right side of the heart to the left, mixing with blood that has high levels of oxygen. This means the oxygen levels have been reduced before the blood is pumped out to the rest of the body. These structural abnormalities include patent ductus arteriosus (PDA), ventricular septal defect (VSD), atrial septal defect (ASD), tetralogy of Fallot, an abnormal return of blood from the lungs, and an abnormal opening of the heart valves.

Some cats may develop circulatory abnormalities that can lead to cyanosis. These acquired conditions include:

  • degeneration of the heart valves
  • deterioration of the heart muscle itself
  • accumulation of blood or fluid in the sac surrounding the heart (the pericardium)
  • blood clots in the lungs
  • high blood pressure in the lungs (pulmonary hypertension)
  • destruction of the red blood cells by the body’s own immune system (immune mediated hemolytic anemia or IMHA)
  • shock

What are some of the causes of cyanosis involving the respiratory system?

There are many different abnormalities in the respiratory system that can contribute to cyanosis, particularly since oxygen exchange is largely a function of the respiratory system. These conditions include:

  • paralysis of the larynx
  • pneumonia
  • asthma
  • lung parasites (worms or flukes)
  • bruising of the lungs from trauma
  • smoke inhalation
  • electrical shock

Are there any other major causes of cyanosis in cats?

Muscle damage like trauma to the diaphragm (the muscle between the chest and abdomen that facilitates breathing) or to the chest wall can interfere with breathing and cause cyanosis. The nervous system can also influence the development of cyanosis by interfering with breathing. Nervous system issues that may affect breathing include inflammation of the brain or brainstem, brain trauma, stroke, or a brain tumor. Other nervous system influences on breathing and potential cyanosis include paralysis or poisoning.

Can cyanosis be treated?

Treatment of cyanosis must include managing the underlying problem that led to cyanosis in the first place. The root cause of cyanosis in any cat may be life-threatening and may or may not be reversible. The presence of cyanosis reflects an emergency and demands immediate care to stabilize the cat in ways that improve oxygen levels in the blood and tissues.

"Treatment of cyanosis must include managing the underlying problem
that led to cyanosis in the first place."

Oxygen therapy, removing fluid from the chest to relieve pressure on the lungs that prevent them from inflating, or creating an opening in the windpipe to facilitate breathing may be needed. Prescribed medications will depend upon the underlying diagnosis, and there may be a need for modified activity or a special diet depending on the underlying cause of the cyanosis.

What kind out outlook can I expect for my cat with cyanosis?

For a cat who is hospitalized for cyanosis, assessments will happen frequently in order to fine-tune treatment. This provides your veterinary health care team with the opportunity to respond to any changes in your cat’s status in a timely fashion.

Once the cat is back at home, monitoring of gum color, breathing rate, and activity/mobility will be important. Homecare will be heavily dependent upon the underlying diagnosis that caused the cyanosis. It will be important to follow homecare instructions very carefully, and to seek veterinary care should any changes occur. If primary heart or lung disease is presence, the long-term outlook may be very guarded.

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