Coma

Originating from the Greek word for “deep sleep” (koma), a coma is a profound state of unconsciousness. Consciousness, on the other hand, is the state of awareness of the self and the environment in which individuals are responsive to stimuli. Scientists believe that the neurotransmission of chemical signals to the brain is essential to consciousness and responsiveness. Because the brain of a person in a coma is malfunctioning, responsiveness is absent. At the functional level, a coma is caused by a primary or secondary brain stem injury and by diffuse cortical causes that may be toxic, anoxic (characterized by a lack of oxygen), or metabolic. Swelling in the brain (edema) causes intracranial pressure, which may be limited to one part of the brain or may encompass the entire brain. Intracranial causes of coma tend to be neoplastic, inflammatory, hemorrhagic, infectious, and traumatic in nature. Extracranial causes may be toxic, anoxic, circulatory, or metabolic. Herniation occurs when areas of the brain shift from their proper positions.

Degrees of decreased responsiveness to stimuli may be separated into four distinct groups. In Grade I drowsiness, lethargic, somnolent, and uninterested individuals are easily aroused into consciousness. During Grade II stupor, patients immediately lapse into sleep if left undisturbed. The deep stupor of Grade III is marked by responses to strong, painful stimuli but motor responses and facial movements are inappropriate. Patients in all three categories are able to breathe on their own. Patients may not be able to breathe on their own in the deep coma of Grade IV. In this state, patients do not respond to any kind of stimuli, and reflexes are absent. Using a scale of 3 to 15, the Glasgow Coma or Responsiveness Scale ranks eye opening, verbal response, and motor responses to determine the extent of consciousness. Eye movement rankings range from spontaneous (4) to never (1). Best verbal responses are ranked from orientated (5) to none (1). Best motor responses are classified from obeys commands (6) to nil (1).

A coma may be a response to an illness such as diabetes, uremia, or stroke, or to chemical or biological agents, or it may result from severe head traumas. Brain measurements of persons in comas are vastly dissimilar to those taken in individuals who are sleeping. In most cases, a coma lasts no longer than a few weeks; and many individuals return to normal physical and mental activity after waking. Patients who have been in extended comas or who have neural or physical damage ranging from moderate to severe may need to undergo rehabilitation or remain in managed care. Patients often slip from a coma into a vegetative state from which they do not recover. In this state, the patient is able to breathe, either on his or her own or with a respirator; however, cognitive neural functions are absent even if the patient seems to be awake. In rare cases, patients have periods in which they arouse followed by relapses into a coma state.

How much individuals in comas understand about the world around them has been hotly debated. One study of 111 patients who had awakened from comas at a Hartford, Connecticut, hospital revealed that 27 percent had no recollection of anything that had happened while they were unconsciousness. Out-of-body [Page 431]experiences were reported by 23 percent. Fourteen percent stated that they had experienced distorted consciousness involving hallucinations, memory lapses, or personality changes. Nine percent reported that they had an inner awareness of outside events.

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