Decreased consciousness is reduced alertness or awareness.

A persistent coma is called vegetative state.

Many conditions can cause decreased consciousness, including:

• Alcohol intoxication
• Drug intoxication (particularly opiates, narcotics, sedatives, and anti-anxiety or seizure medications)
• Arrhythmia
• Brain disorders
• Central nervous system diseases
• Lack of oxygen (hypoxia)
• Abnormal blood sugars (diabetic coma)
• Electrolyte or mineral imbalance
• Exposure to heavy metals or hydrocarbons
• Extreme fatigue or sleep deprivation
• Ketoacidosis
• Head trauma
• Heart failure
• Hypoglycemia (low blood sugar)
• Increased carbon dioxide levels (hypercarbia) often seen in emphysema
• Infection
• Low blood pressure (hypotension)
• Metabolic disorders
• Thyroid or adrenal gland disorders
• Seizures such as those related to epilepsy
• Shock
• Stroke

A decrease in consciousness almost always require a doctor's attention, except perhaps when due to alcohol intoxication, simple fainting, or a previously recognized seizure disorder.

See the article on seizures for tips on how to care for a person who is having a seizure.

Persons with epilepsy or other seizure disorder should carry a Medic-Alert bracelet or pendant describing their condition. Such individuals should avoid situations that have previously triggered a seizure.

See medical help if someone has unexplained, decreased consciousness. Call your local emergency number (such as 911) if normal consciousness does not return quickly.

Most often, a person with decreased consciousness will be evaluated in an emergency room setting.

The doctor will perform a physical examination. The exam will include a detailed look at the cardiovascular, respiratory, and nervous systems.

The health care team will ask questions about the person's medical history and symptoms, including

• Time pattern
  • When did the decreased consciousness occur?
  • How long did it last?
  • Has it ever happened before? If so, how many times?
  • Did the person behave the same way on previous episodes?
• Medical history
  • Does the person have known epilepsy or seizure disorder?
  • Does the person have diabetes?
  • Has the person been sleeping well?
  • Has there been a recent head injury?
• Other
  • What medications does the person take?
  • Does the person habitually use alcohol or drugs?
  • What other symptoms are present?

Tests that may be done include:

• Complete blood count or blood differential
• Electrolyte panel
• CT scan or MRI of the head
• ECG (electrocardiogram)
• EEG (electroencephalogram)
• Chest x-ray
• Urinalysis
• Toxicology panel

Treatment depends on the underlying cause of the decreased consciousness. How well a person does depends on the cause of the condition. The longer the person has a decreased or altered level of consciousness, the worse the outcome.

Blok BK, Newman TM. Syncope. In: Tintinalli JE, Kelen GD, Stapczynski JS, Ma OJ, Cline DM, eds. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw-Hill; 2004:chap 52.

Huff JS. Altered mental status and coma. In: Tintinalli JE, Kelen GD, Stapczynski JS, Ma OJ, Cline DM, eds. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw-Hill; 2004:chap 259.

Kirsch TD. Head injury. In: Tintinalli JE, Kelen GD, Stapczynski JS, Ma OJ, Cline DM, eds. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw-Hill; 2004:chap 255.