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Fainting in Dogs

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Syncope in Dogs


Syncope is the clinical term for what is otherwise often described as fainting. This is a medical condition that is characterized as a temporary loss of consciousness and spontaneous recovery.


The most common cause of syncope is a temporary interruption in the brain blood supply leading to impairment in oxygen and nutrient delivery to brain. Another important cause of syncope in dogs is heart disease leading to interruption in the blood supply to the brain. Syncope is more commonly seen in older dogs, especially Cocker spaniels, miniature schnauzers, pugs, dachshunds, boxers, and German shepherds.




  • Heart diseases
  • Heart tumor
  • Emotional stress
  • Excitement
  • Low concentration of glucose, calcium, sodium in blood
  • Diseases leading to thickening of blood
  • Use of certain drugs


Situational syncope may be associated with:

  • Cough
  • Defecation
  • Urination
  • Swallowing
  • After pulling on the dog’s collar




Although syncope often only causes temporary loss of consciousness, diagnosing the underlying cause is important for the affected patient, since the underlying condition may be of a chronic and progressive nature, or may even be life-threatening.


Your veterinarian will take your dog's health history and will carry out a detailed physical examination. Routine laboratory tests include complete blood count, biochemistry profile, and urinalysis.


The results of these tests are often within normal ranges, but if hypoglycemia is the cause of syncope, the biochemistry profile will indicate lower than normal levels of glucose in the blood. In these patients, insulin concentration is also measured. Further testing may be required in patients with low sodium or potassium levels in blood. As heart disease remains one of the important causes of syncope, an electrocardiogram (ECG) and echocardiography will be conducted to determine whether there is an underlying heart disease.


Your veterinarian will also ask you to calculate your dog's heart rate during syncopic episodes at home and may recommend 24-hour ECG monitoring if your dog has been determined to have an underlying heart problems. A computed tomography (CT) scan of the head, and an analysis of cerebrospinal fluid (the fluid that bathes the brain and spinal cord) will be conducted if brain disease is suspected.




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