Cyanosis in Dogs and Cats
What is cyanosis?
Cyanosis is a bluish to red-purple tinge of the tissues, seen best in the gums and skin, and typically accompanying respiratory distress (i.e., difficulty breathing). When cyanosis is seen in dogs and cats, it’s an indicator of a severe lack of oxygen in the blood (called hypoxemia). It typically means that hemoglobin in the red blood cells doesn’t have enough oxygen or isn’t able to carry oxygen at all.
Cyanosis can be classified as central or peripheral.
- Peripheral cyanosis occurs when there’s a localized increase in deoxygenated hemoglobin.
- Central cyanosis is usually due to problems with the lungs or due to abnormal hemoglobin (as seen with Tylenol or acetaminophen poisoning).
Why is cyanosis difficult to diagnose?
There are several factors that may hinder you and your veterinarian from being able to detect physical signs of cyanosis. For example, the red blood cell (RBC) count can affect signs of cyanosis—a pet with severe anemia and a low number of RBCs may never show signs of cyanosis. The lower the hemoglobin concentration in a pet, the more the oxygen levels must fall before cyanosis can be clinically detected. Also, patients with shock, carbon monoxide poisoning, or those with abnormal hemoglobin may not show cyanosis well during a physical exam.
Keep in mind that just because your pet’s gums are pink, it doesn't necessarily mean that his oxygen levels are normal. Signs of cyanosis aren’t always seen until end-stage or severe hypoxemia.
Causes of cyanosis include:
- Congestive heart failure
- Pulmonary thromboembolism
- Trauma (e.g., lung bruises or lung tears)
- Infections within the chest cavity (e.g., pyothorax)
- Abnormal fluid within the chest cavity (e.g., chylothorax or hemothorax)
- Abnormal tissue or foreign material within the chest cavity or lungs (e.g., cancer, fungal infections, or foreign bodies)
- Heart abnormalities or defects (e.g., ventricular septal defect or Tetralogy of Fallot)
- Airway problems (e.g., tracheal collapse or laryngeal paralysis)
- Certain poisonings (e.g., Tylenol/acetaminophen, phenazopyridine)
- Changes to hemoglobin (e.g., methemoglobin, etc.)
- Brachycephalic airway problems
[Note, this list is not all-inclusive!]
How is cyanosis diagnosed?
To find out what’s causing the cyanosis, diagnostic tests may include blood work, chest x-rays, measurements of oxygen levels (e.g., pulse oximetry, arterial blood gases, etc.), electrocardiogram, an ultrasound of the heart (i.e., echocardiogram), a chest tap, and more.
How is cyanosis treated?
Treatment for cyanosis typically includes immediate oxygen therapy along with certain types
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Justine has more than 18 years of experience in the veterinary industry and is a board-certified emergency critical care veterinary specialist and toxicologist as well as the CEO and founder of Vetgirl. She is also a founding member of IDEXX’s Pet Health Network team.