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Definition: coma from The Penguin Dictionary of Science
1 (Phys.)


2 (Astron.)

A bright cloud of ions and dust surrounding the nucleus of a comet.

3 (Med.)

A deep state of unconsciousness in which a patient is unresponsive to stimuli such as sound, light and touch, and is unrousable. Coma may be induced by drugs, hypoglycaemia, hypoxia or trauma. The outcome ranges from death to full recovery, depending on the degree of pharmacological or traumatic damage, but many patients recovering from coma exhibit ongoing neurological symptoms.

Summary Article: Coma
From Encyclopedia of Global Health

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 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.

The majority of coma patients are young people who have been in accidents, but they are more likely to survive than people over 50.


Diagnoses of the severity of comas and the likelihood of recovery are based on interpretation of physical signs and brain activity. Since the majority of coma patients are young people who have been involved in traumatic accidents, there are great emotional, social, and financial stakes involved in charting treatment plans. A coma resulting from a severe head injury is diagnosed after a period of unconsciousness that lasts for at least six hours. One study found that in 96 percent of such patients, death took place within 48 hours.

Physicians are not able to predict outcomes for coma patients with accuracy, and they are often forced to take a wait-and-see attitude. As a general rule, the longer patients are in comas, the less likely they are to recover. If severe edema is present after a traumatic injury, physicians may place a patient in an artificial coma so that he or she will not wake up in order to give the body a chance to heal and the swelling to disappear. If this happens, the patient is allowed to awaken gradually. In cases where edema persists along with extensive brain damage, the prognosis for recovery is poor. Findings from several neurosurgical centers have revealed that around half of coma patients with head injuries recover. In one study of patients with nontraumatic coma, 16 percent made a full or partial recovery. However, 70 percent either died or remained in a vegetative state for at least a month after the onset of the coma.

The most significant factor in potential recovery is whether or not patients exhibit signs of brain stem function. If papillary response, oculocephalic responses, or both, are absent, the prognosis is poor. There is evidence that 96 percent of those who do not exhibit these responses die within six hours of the onset of a coma. In 91 percent of coma patients whose pupils were fixed after 24 hours, death followed. Only four percent achieved satisfactory recovery. Some studies support the findings that young people are more likely than people over the age of 50 to survive, regardless of the length of the coma. In the latter group, less than half were able to return to work if they had remained unconscious for more than a day. In all age groups, among patients who exhibited abnormalities in both eye signs and motor defects, the survival rate was only 7.8 percent.

In 2006, The Journal of Head Trauma Rehabilitation reported on a study designed to determine postinjury outcomes of 339 patients with traumatic head injuries. Brain injuries ranged from mild (230) to moderate (48) to severe (52). In addition to social factors such as age and prior-injury educational level, post-trauma prognoses were based on the Glasgow Coma Scale score, duration of post-traumatic amnesia, cerebral imaging results, and presence or lack of neurosurgical interventions. The Extended Glasgow Outcome Scale was used in determining outcome measures. The team conducting the study concluded that patients with the shortest period of post-traumatic amnesia were the least likely to develop moderate to severe disabilities. Patients with positive cerebral imaging, indicating epidural, subdural, subarachnoid, parenchymal, or intraparenchymal lesions, skull fracture, and unilateral or bilateral lesions, were the least likely to be discharged from professional supervision.

Some patients who recover from comas after experiencing traumatic brain injury have been diagnosed with depression. In an article published in The Journal of Head Trauma Rehabilitation in spring 2007, a team of scholars examined factors related to post-coma depression, including age, education, substance abuse, family support, and psychiatric history. Standard classifications were used to identify the extent of individual injuries. There was no statistically significant difference in the level of depression among those with mild, moderate, and severe brain injury. Some differences in levels were explained by pre-injury level of education, previous psychiatric history, and preconceived support levels. The strongest impact on both early and late surfacing depression was patients’ self-assessment at the time of discharge.


The first Humane Society was founded in Amsterdam in the Netherlands in the 17th century. Other countries followed suit, and the first North American society was founded in Philadelphia, Pennsylvania, in 1780. The focus at that time was in developing ways to revive drowning victims. Mechanical respirators later provided a major breakthrough in dealing with coma patients who were not able to breathe on their own, and brain resuscitation methods were instituted to promote survival of the neurons and prevent brain death. Major breakthroughs in respiratory resuscitation and intensive care occurred in the 1950s. During the following decade, cardiac resuscitation and emergency cardiac care paved the way for greater numbers of coma patients to survive, offering hopes of recovery to relatives and friends. Since the 1970s, improvements in critical care medicine have precipitated even greater progress in treating coma patients. Efforts at brain resuscitation in the 21st century involve basic and advanced life support, diagnostic and monitoring techniques, and brain activity measurements.

Because advanced medical technology allows patients in prolonged comas to live for years, the right-to-die issue has become a hot-button political topic throughout much of the world. Advocates of the right to die believe that life should not be prolonged when there is no hope of recovery, particularly in instances where patients have made prior acknowledgment that they would not choose to remain on life support. Hospice care has surfaced as a humane alternative, giving patients and their families a comforting environment in which patients are allowed to die with dignity. Opponents of the right to die argue that as long as a person is breathing and has a heart beat, even if it is by artificial means, all efforts should be directed toward prolonging life.

In 1968, the term death was first used in the United States to refer to the point at which the heart and lungs no longer functioned. The term brain dead was used to describe the state in which these functions were performed by artificial means on patients who could no longer function on their own. Controversy continues over the care and monitoring of patients experiencing prolonged unconsciousness. In the face of the controversy, most countries have responded in ways that reflect their own cultures. In Japan, for instance, the term brain dead has no legitimate scientific meaning. Because of this, Japanese physicians are banned from harvesting organs to be used in organ transplants. At the other end of the spectrum, the Dutch strongly support the right to die and consider it an individual decision.


In 1976, at the age of 22, Karen Ann Quinlan was determined to be legally brain dead after a drug overdose. A decision by her parents to subsequently remove her from a respirator was challenged in court. Nevertheless, the respirator was ultimately removed, and Quinlan lived for several years in a vegetative state. In 1983, at the age of 26, Nancy Beth Cruzan went into a coma after being involved in an automobile accident. She was kept alive via hydration and a feeding tube. Her parents’ decision to remove her from life support was also challenged. A number of witnesses testified in court that Cruzan had repeatedly stressed the fact that she would not wish to be kept alive through artificial means if there was no hope of recovery. In 1990, in Cruzan versus Director, Missouri Department of Health (497 U.S. 261), the United States Supreme Court acknowledged that competent individuals have a liberty interest that is derived from the Due Process Clause of the 14th Amendment that allows them to refuse medical treatment. However, patients who are in comas are not considered competent; unless compelling evidence of their disinclination to remain on life support exists, the state retains a compelling interest in sustaining life.

No other case of a coma patient who relapsed into a years-long vegetative state has received more attention around the world than the case of Terri Schiavo. The Florida resident had developed an eating disorder, dropping from 250 pounds as a teenager to 110 pounds within six years of her marriage to Michael Schiavo. On February 25, 1990, at the age of 26, Schiavo was alone in her apartment when she went into cardiac arrest. In the absence of immediate medical help, her brain was without oxygen for 10 to 12 minutes. Around half that period has been known to cause irreversible brain damage. Emergency personnel resuscitated her, and she was placed on a respirator.

Terri Schiavo emerged from the coma a month later, lapsing into a persistent vegetative state. Her husband Michael and her mother, Mary Schindler, served as her caregivers for the next three and one-half years. Experimental treatment in California was unsuccessful, and Schiavo was diagnosed with irreversible and extreme brain damage. Michael Schiavo won a malpractice lawsuit against Shiavo’s fertility doctor, claiming that he had been negligent in treating his wife. The jury awarded Michael $300,000 for loss of consortium, and $700,000 was placed in a court-managed trust to pay for Terri Schiavo’s care. In 2003, Michael Schiavo sought legal permission to remove his wife’s feeding tube. After her parents challenged the decision, a legal and moral uproar ensued that ultimately involved Florida governor Jeb Bush, his brother, President George W. Bush, and the United States Congress. The Supreme Court refused to enter the fray. Terri Schiavo died two weeks after her feeding tube was removed in 2005. Autopsy reports supported Michael Schiavo’s conviction that his wife could not have recovered.

  • Adolescent Health; Brain Injuries; Depression; Diabetes Type I (Juvenile Diabetes); Diabetes Type II; High Blood Pressure; Neuroscience; Organ Donation; Organ Transplantation; Rehabilitation; Stroke.

  • Arthur L. Caplan, et al., The Care of Terri Schiavo: Ethics at the End of Life (Prometheus Books, 2006).
  • Alexander Capron; Margaret Lock, eds., Deadly Disputes: Understanding Death in Europe, Japan, and North America (University of California Berkeley, 1995).
  • C. A. Carlsson, et al., “Factors Affecting the Clinical Course of Patients with Severe Head Injuries,” Neurosurgery (v.29, 1968).
  • Elaine de Guise, et al., “Prediction of Outcome at Discharge from Acute Care Following Traumatic Brain Injury,” The Journal of Head Trauma Rehabilitation (v.21/6, 2006).
  • Leslie B. Ivan; Derek A. Bruce, Coma: Physiopathology, Diagnosis, and Management (Charles C. Thomas, 1982).
  • Madelaine Lawrence, In a World of Their Own: Experiencing Unconsciousness (Praeger, 1997).
  • Barbara J. Logue, Last Rights: Death Control and the Elderly in America (Lexington Books, 1993).
  • James F. Malec, et al., “Self-Assessment of Impairment, Impaired Self-Awareness, and Depression after Traumatic Brain Injury,” The Journal of Head Trauma Rehabilitation (v.22/3, 2007).
  • Neurology Channel, “Coma,” (cited July 2007).
  • Fred Plum; Jerome B. Posner, The Diagnosis of Stupor and Coma (Davis, 1982).
  • Sue Woodman, Last Rights: The Struggle over the Right to Die (Plenum Trade, 1998).
  • Elizabeth R. Purdy, Ph.D.
    Independent Scholar
    Copyright © 2008 by SAGE Publications, Inc.

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