Coma Summary
Coma is the inability to waken or react to the surrounding environment. The Glasgow Coma Scale is frequently used to measure the depth of coma. Causes of coma include trauma, bleeding, edema, lack of oxygen, poisoning, or hypoglycemia. Prognosis for a patient in a coma depends on the cause of the coma.
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What is a "coma"?

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Coma is a state of decreased consciousness whereby a patient cannot react with the surrounding environment. The patient cannot be easily wakened when outside physical or auditory stimulation are applied. Patients may have different levels of unconsciousness and unresponsiveness depending upon how much or how little of the brain is functioning. Patients in coma do not voluntarily interact with their environment.

The inability to waken differentiates coma from sleep.

Medically Reviewed by a Doctor on 11/15/2013

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