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Dog Fainting: What Causes It and What Should You Do?

Posted August 26, 2014 in Dog Diseases & Conditions A-Z

Fainting, also called syncope, is a loss of consciousness that is typically due to a lack of normal blood flow to the brain. Fainting is uncommon in dogs and not always caused by a lack of blood flow; there are other similar medical causes that result in fainting for both humans and animals. That said, no matter how scared dogs or cats may get, they never faint from fright the way a human might (e.g., from panic attacks, hyperventilating, etc.).

Why would a dog faint?
Fainting in dogs is typically attributed to one of two main problems: neurologic (e.g., brain or spinal cord) or cardiac (e.g., heart arrhythmias, etc.).

Dog laying on the floorNeurologic problems may include:

  • Seizures
  • Abnormal brain activity

Cardiac problems may include:

  • Abnormal heart rhythms (such as sick sinus syndrome)
  • A-V block
  • Ventricular tachycardia
  • Ventricular fibrillation

What to do if your dog faints:

  • Put your hands over the heart and see if you can feel a heartbeat. Try to tell if the heart rate is very, very slow or extremely rapid. This will help your veterinarian determine if the cause of fainting is cardiac in origin.
  • Try to videotape the episode quickly. Often times, your veterinarian or veterinary specialist (e.g., neurologist, cardiologist) can determine the cause by physical appearance.
  • Seek immediate veterinary attention.

Once you get to your veterinarian or emergency veterinarian, the doctor will need to check the heart rate on an electrocardiogram (ECG) right away to look for the presence of abnormal arrhythmias, and perform blood work to make sure that there are no metabolic causes (e.g., liver, kidney, etc.) or blood sugar problems causing the episode.

If neurologic problems are detected, further evaluation by a neurologist is warranted. Unique tests such as an electroencephalogram (EEG) may need to be done to monitor the brain for any unusual seizure activity. Alternatively, an MRI or spinal tap may also be necessary. If cardiac abnormalities are detected, a referral to a cardiologist for an ultrasound of the heart (e.g., echocardiogram), x-rays of the heart, and a Holter monitor (to monitor the heart rhythm) may be necessary.

Collapsing is not fainting
Fainting in dogs needs to be differentiated from the more common problem of collapsing. With collapse, loss of consciousness typically doesn’t occur—in other words, your dog or cat may be weak and unable to get up, but he’s still conscious. There are numerous causes for collapse including:

  • Dehydration
  • Shock or
Related symptoms: 

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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.