Unconsciousness is when a person is unable to respond to people and activities. Often, this is called a coma or being in a comatose state.
Other changes in awareness can occur without becoming unconscious. Medically, these are called "altered mental status" or "changed mental status." They include sudden confusion, disorientation, or stupor.
Unconsciousness or any other sudden change in mental status must be treated as a medical emergency.
If someone is awake but less alert than usual, ask a few simple questions, such as:
Wrong answers or an inability to answer the question suggest a change in mental status.
Being asleep is not the same thing as being unconscious. A sleeping person will respond to loud noises or gentle shaking -- an unconscious person will not.
An unconscious person cannot cough or clear his or her throat. This can lead to death if the airway becomes blocked.
Brief unconsciousness (or fainting) is often caused by dehydration, low blood sugar, or temporary low blood pressure. However, it can also be caused by serious heart or nervous system problems. Your doctor will determine if you need tests.
Other causes of fainting include straining during a bowel movement, coughing very hard, or breathing very fast (hyperventilating).
The person will be unresponsive (does not respond to activity, touch, sound, or other stimulation).
The following symptoms may occur after a person has been unconscious:
Call 911 if the person is unconscious and:
Call 911 if the person regains consciousness but:
People with known medical conditions, such as diabetes, should always wear a medical alert tag or bracelet.
Loss of consciousness - first aid; Coma - first aid; Mental status change; Altered mental status
Cooke JL. Depressed consciousness and coma. In: Marx JA, Hockberger RS, Walls RM, et al., eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 14.
Biros MH, Heegaard WG. Head injury. In: Marx JA, Hockberger RS, Walls RM, et al., eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 38.
Kothari RU, Crocco TJ, Barsan WG. Stroke. In: Marx J, ed. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 6th ed. Philadelphia, Pa: Mosby Elsevier; 2006:chap 99.
Updated by: Jacob L. Heller, MD, MHA, Emergency Medicine, Virginia Mason Medical Center, Seattle, Washington, Clinic. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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