A coma, sometimes also called persistent vegetative state, is a profound or deep state of unconsciousness lasting more than 6 hours. Persistent vegetative state is not brain-death. An individual in a state of coma is alive but unable to move or respond to his or her environment. A person in a coma cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions.
Coma may occur as a complication of an underlying illness, or as a result of injuries, such as head trauma. Conditions that may result in a coma include:
- Intoxication – such as illicit drug abuse, overdose or misuse of over the counter medications, prescribed medication, or controlled substances
- Metabolic abnormalities
- Central nervous system diseases
- Acute neurologic injuries such as strokes or herniations
- Traumatic injuries such as head trauma caused by falls or vehicle collisions
It may also be deliberately induced by pharmaceutical agents in order to preserve higher brain functions following a brain trauma, or to save the patient from extreme pain during healing of injuries or diseases.
Individuals in such a state have lost their thinking abilities and awareness of their surroundings, but retain non-cognitive function and normal sleep patterns. Even though those in a persistent vegetative state lose their higher brain functions, other key functions such as breathing and circulation remain relatively intact. Spontaneous movements may occur, and the eyes may open in response to external stimuli. Individuals may even occasionally grimace, cry, or laugh. Although individuals in a persistent vegetative state may appear somewhat normal, they do not speak and they are unable to respond to commands.
Once an individual is out of immediate danger, the medical care team focuses on preventing infections and maintaining a healthy physical state. This will often include preventing pneumonia and bedsores and providing balanced nutrition. Physical therapy may also be used to prevent contractures (permanent muscular contractions) and deformities of the bones, joints, and muscles that would limit recovery for those who emerge from coma.
The outcome for coma and persistent vegetative state depends on the cause, severity, and site of neurological damage. Individuals may emerge from coma with a combination of physical, intellectual, and psychological difficulties that need special attention. Recovery usually occurs gradually, with some acquiring more and more ability to respond. Some individuals never progress beyond very basic responses, but many recover full awareness.
Individuals recovering from coma require close medical supervision. A coma rarely lasts more than 2 to 4 weeks. Some patients may regain a degree of awareness after persistent vegetative state. Others may remain in that state for years or even decades. The most common cause of death for someone in a persistent vegetative state is infection, such as pneumonia.