A coma is a state of prolonged unconsciousness that results from changes in the structure of the brain. Most brain function shuts down and comatose patients may appear as if they are sleeping. Due to reduced brain function, patients with comas typically have no or minimal response to external stimuli. However, brain activity for the body’s basic functions, such as the respiratory, circulatory and digestive systems, is maintained. 

Comas may result from a physical injury, disease or toxin. Any severe head injury has the potential to physically change the structure of the brain. Diseases and toxins may alter the typical chemical processes of the brain and cause it to shut down. Medications may also be used to induce a coma to reduce brain swelling due to trauma or reduce the risk of severe complications during brain surgery.

Most comas last several days to a few weeks, though some may last many months. Following this period, patients may improve and gain more awareness of their environment. In contrast, some patients may instead enter a persistent vegetative state or become brain dead, which means that damage to the brain is irreversible and body functions can be maintained only with artificial means.

Treatment for comas focuses on the cause. For physical injuries, surgery may be necessary to repair the skull or remove foreign objects or injured nervous tissue. For comas caused by disease, medications may be administered. When drugs or toxins cause a coma, treatment may require a combination of medications, vitamins and modifying blood sugar to normalize brain function. Beyond supportive care, there is little that healthcare professionals can do to revive a comatose patient.

Preventing comas requires preventing their causes. Basic safety measures help reduce the occurrence of the many causes of head injuries that may lead to comas. These include using a seatbelt or helmet when appropriate and safely handling firearms. Patients with diabetes, seizure disorders and other conditions should follow their physician’s recommendations to reduce the chance of a coma occurring.

About coma

A coma is a state of prolonged unconsciousness. It may result from a brain injury, disease (e.g., brain tumor, diabetes) or toxin (e.g., illicit drugs). During a coma, the patient has only minimal brain function, does not respond to external stimuli, and may appear to be asleep. The name itself comes from the Greek word koma, which means deep sleep.

The length of a coma is unpredictable. While most last from a couple of days to a few weeks, some persist a few hours and others may extend over many months. After this time, patients often enter another level of consciousness. They may become fully conscious, though recovery is not always complete. Possible permanent disabilities include partial paralysis or changes in personality or mental ability.

Other patients never regain full consciousness. They may enter a vegetative state. Patients in a vegetative state may move in response to stimuli, but are unable to interact with the environment. When this condition lasts longer than one month, it is considered a persistent vegetative state (PVS). Other patients who lose cerebral and brainstem function may be classified as brain dead.

Comatose patients require supportive treatment to prevent possible complications that could lead to death. The risk of severe complications rises as the length of the coma increases. The complications that most often occur in conjunction with a coma include:

  • Pressure sores on skin
  • Bladder infection
  • Pneumonia
  • Organ failure

In some instances, comas may be medically induced. This is accomplished by physicians administering medications to reduce brain activity. A coma may be induced to reduce swelling of the brain associated with trauma. If the swelling were to continue without treatment, the brain tissue could be further injured because of increased pressure within the skull. Comas may also be induced prior to brain surgery or to stop prolonged seizures.

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