Loss of Consciousness (Syncope and Coma) in Cats

Unconscious cats are responsive only to strong, unpleasant stimuli such as a toe pinch, but not to sounds or touch
Unconsciousness with no response to even powerful stimuli is called coma
Cats can experience sudden loss of consciousness, like fainting; this is called syncope
Syncope is usually a brief event with rapid and complete recovery
There are many potential causes of syncope and coma, ranging from low blood sugar to poisoning
Diagnostics include physical examination, bloodwork, diagnostic imaging, and thorough examination of heart and lung function
Treatment varies extensively depending on the underlying cause of loss of consciousness
Prognosis also depends on the underlying cause; syncope is associated with better outcomes than coma

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A closer look: Loss of Consciousness (Syncope and Coma) in Cats

There are dozens of causes for a cat to lose consciousness, and all of them are potentially serious and life-threatening. Syncope is most often associated with cardiovascular disease, while coma can be caused by a number of underlying diseases and is very grave. In general, syncope cannot be prevented unless the precipitating event can be avoided.

Possible causes

A wide range of conditions can lead to loss of consciousness.

Examples include

Congestive heart failure

Heart Disease (Hypertrophic Cardiomyopathy) in Cats Enlarged Heart (Dilated Cardiomyopathy) in Cats

Severe respiratory disease

Low blood sugar

Severe anemia

Rat Bait Poisoning (Rodenticide Toxicosis) in Cats

Head injury

Hemorrhagic gastroenteritis syndrome

Drowning/near drowning

Hypothyroidism in Cats

Nervous system dysfunction

Narcolepsy and Cataplexy in Cats

Pressure on the neck or collar can cause syncope in some animals, such as those with hypersensitive carotid sinus syndrome.

Risk factors

Unconsciousness varies in the degree to which the animal is unresponsive to its environment, as well as in duration of episode. Syncope is usually short-lived with complete and rapid recovery, while coma is persistent until the underlying cause can be treated.

Any cat with an untreated or poorly managed life threatening illness may lose consciousness if disease is advanced.

Testing and diagnosis

In addition to medical history and physical exam, diagnostics for coma or syncope include:

Reflex tests
Exercise test (pre- and post-exercise heart examination)
Blood pressure measurement
Blood tests, including a blood glucose, biochemical tests, and complete blood count
Additional blood tests, such as those evaluating hormone function
Electrocardiogram (EKG)
Chest x-rays, especially when indicated from history and physical examination
Pulse oximetry to measure oxygen levels, if there is evidence of lung disease
Heartworm test in appropriate areas
Ultrasound examination of the heart (echocardiogram)
Advanced imaging (CT scan or MRI)
Spinal tap

Some diagnostics may require referral to a specialist.

Treatment varies widely depending on the underlying cause of syncope or coma. Once a basic cause of syncope or coma is identified, supportive care measures to stabilize cats while further diagnostics occur include:

Intravenous (IV) fluids may be indicated, unless the patient has congestive heart failure
Administration of glucose for hypoglycemia
Arrhythmias may be treated with drugs or, in some cases, a pacemaker
Blood transfusion in cases of anemia

Similar symptoms

During syncope, the forelimbs may briefly become rigid and the head may be pulled back, causing confusion with a seizure disorder (such as epilepsy). In syncope, any movement is brief, whereas seizure disorders usually involve a lot of movement.

Loss of consciousness may be mistaken for very deep sleeping, especially in old or deaf cats. It also may be mistaken for collapse: cats that collapse still respond to stimuli.