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Coma is a term that is used to describe a state of unconsciousness from which a person cannot be aroused.

What is going on in the body?

A person in a coma is unable to respond to the environment. He or she cannot be awakened by any means. A coma may or may not be reversible with treatment.


What are the causes and risks of the condition?

There are many possible causes of a coma, including:
  • stroke, also called brain attack. This is brain damage that usually occurs due to a lack of oxygen because the blood supply to a part of the brain was interrupted.
  • diabetes that is out of control
  • severe liver disease or kidney disease
  • seizures, jerking movements or other unusual symptoms caused by abnormal electrical activity in the brain
  • abnormally low body temperature, also called hypothermia
  • severe salt imbalances, such as abnormally low or high sodium levels in the blood
  • medication, drug, or toxin exposure. This may include alcohol, barbiturate, or narcotic overdose, or carbon monoxide poisoning.
  • bleeding into or around the brain. This may occur with a subdural hematoma, epidural hematoma, subarachnoid hemorrhage, or severe head injury.
  • infections, such as the brain infections called meningitis and encephalitis
  • low blood sugar levels, called hypoglycemia
  • low oxygen levels in the blood. This can occur with severe lung or heart disease. For example, severe asthma, emphysema, irregular heartbeats, or arrhythmias, and a blood clot in the lung, called a pulmonary embolus, can all cause coma from low oxygen levels.
  • brain tumors
Other causes are also possible. Sometimes, the cause cannot be found.


What can be done to prevent the condition?

Prevention is related to the cause. For example, avoiding drug use can prevent cases due to overdose. Proper treatment of diabetes can prevent many cases due to this cause. Wearing a helmet when riding a motorcycle or bike can prevent head injuries leading to coma. Following sports safety guidelines for children, adolescents, and adults can avoid unnecessary injuries. Many cases cannot be prevented.


How is the condition diagnosed?

When a person is unconscious and does not respond to painful stimulation, it is generally considered a medical emergency. Diagnosis begins with a history and physical exam. Information obtained from friends, family members, or witnesses may be life saving. For example, knowing that a person was recently using large amounts of heroin may allow quick treatment that can reverse the coma.
In many cases, further tests are needed to help figure out the cause of a coma. For example, blood tests can detect salt imbalances, low blood sugar, and other conditions. Urine tests may help detect drugs in someone's system or diagnose kidney disease. X-ray tests, such as a cranial CT scan of the brain, may detect a stroke, brain tumor, or bleeding into or around the brain. Other tests may be needed in certain cases.

Long Term Effects

What are the long-term effects of the condition?

Most people in a coma are at a high risk of death. A person may stay in a coma for weeks, months, or even years. Those who come out of the coma may be permanently disabled. In some cases, such as heroin overdose or out of control diabetes, treatment cures the coma and the person may have no long-term effects.

Other Risks

What are the risks to others?

A coma is not contagious. If an infection is the cause of coma, the infection may sometimes be contagious.


What are the treatments for the condition?

Basic vital functions, such as breathing, circulation, and blood pressure, are monitored closely and maintained with medications and a ventilator if necessary. Supplemental oxygen and intravenous fluids are usually needed as well.
Further treatment is directed at the cause, if known. When the cause is not known, certain treatments may be given right away in the hope that they may work. For example, glucose, a form of sugar, may be given through an IV in case the coma is due to low blood sugar. Naloxone, a drug that can reverse a heroin overdose, may be given in case this is the cause.
Once the initial tests are back, the cause can often be discovered and more specific treatment can be given. For example, those with a subdural hematoma may need surgery. Those with an infection may need antibiotics.

Side Effects

What are the side effects of the treatments?

Each medication has its own list of possible side effects. For example, antibiotics may cause allergic reactions or stomach upset. Surgery can be complicated by bleeding, infection, or a reaction to the anesthetic. Ventilators may sometimes cause lung damage or an infection.

After Treatment

What happens after treatment for the condition?

A person who recovers completely may soon return to normal activities. Others may not survive even with the best treatment. A person who does survive may be left with permanent disabilities that require skilled nursing care for life. Further treatment may be ongoing for the condition that caused the coma, such as diabetes.


How is the condition monitored?

A person with coma is often monitored closely in the intensive care unit. Specific monitoring often depends on the cause. For example, those with salt imbalances may need repeated blood tests until the salt imbalance is corrected.


Harrison's Principles of Internal Medicine, 1998, Fauci et al.

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