Coma is defined as a state in which the patient appears to be asleep, shows no awareness of his or her surroundings, and cannot be aroused. Coma frequently is only a transient state, whereby patients recover, die, or progress to a permanent state of impairment. Often a medical emergency, immediate intervention may be required to preserve life and brain function.
- Coma is at the far end of a spectrum of acute impaired consciousness, which also includes the following:
- Lethargy or stupor: patient arousable but does not stay awake; impaired responses to commands
- Delirium: a confused, agitated or hypoactive patient with fragmented attention, concentration, and memory
- Coma may progress to
- Persistent vegetative state: chronic state of unconsciousness with no awareness or cognition, no voluntary responses, and no language abilities; preserved autonomic functions and sleep–wake cycles
- Brain death: lack of cortical and brainstem responses
Incidence varies by age, season (infection), and ethnicity (inborn errors of metabolism [IEM]).
Dysfunction of the reticular activating system in the brainstem or bilateral cerebral dysfunction causes impaired arousal and consciousness.
Coma etiology can be traumatic or nontraumatic. Infection is a common cause of nontraumatic coma.
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