Page 117 - Problem-Based Feline Medicine

8. The cyanotic cat

Grainne Muire McCarthy

KEY SIGNS
Bluish discoloration of the skin and/or mucous membranes.

MECHANISM?
● Cyanosis is bluish discoloration of the skin and/or mucous membranes due to reduced oxygen
saturation of hemoglobin in the blood causing hypoxia. Hypoxia producing cyanosis results either
from central (cardiac or respiratory) or peripheral causes.

WHERE?
● Central hypoxia results from cardiac or respiratory disease, including disease of the upper
or lower respiratory tract, pleural cavity, thoracic wall or diaphragm.
● Peripheral hypoxia may be generalized and associated with generalized vasoconstriction, or is
localized and the result of arterial or venous obstruction.
● Occasionally abnormal hemoglobin with decreased oxygen carrying capacity is the cause of
the cyanosis.

WHAT?
● The commonest causes of cyanosis are central causes and include bronchial and pulmonary
disease, pleural effusions, cardiac disease, mediastinal neoplasia, diaphragmatic hernia and poi-
soning with acetaminophen.
Peripheral cyanosis is usually the result of arterial thromboembolism.

QUICK REFERENCE SUMMARY
Diseases causing a cyanotic cat
CENTRAL HYPOXIA

WHERE? – CARDIAC HYPOXIA
ANOMALY
● Congential heart anomaly (p 113)
Tetralogy of Fallot, reversed shunting (R–L), patent ductus arteriosus, tricuspid valve atresia,
Eisenmenger’s syndrome, endocardial cushion defect, and transposition of the great arteries can all
cause cyanosis. Cats with congenital cyanotic heart conditions are usually stunted and cyanotic, and
frequently present with a history of lethargy and syncope. Abnormal heart sounds may be audible.

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