coma

Definition

Coma, from the Greek word "koma," meaning deep sleep, is a state of extreme unresponsiveness, in which an individual exhibits no voluntary movement or behavior. Furthermore, in a deep coma, even painful stimuli (actions which, when performed on a healthy individual, result in reactions) are unable to affect any response, and normal reflexes may be lost.

Description

Coma lies on a spectrum with other alterations in consciousness. The level of consciousness required by, for example, someone reading this passage lies at one extreme end of the spectrum, while complete brain death lies at the other end of the spectrum. In between are such states as obtundation, drowsiness, and stupor. All of these are conditions which, unlike coma, still allow the individual to respond to stimuli, although such a response may be brief and require stimulus of greater than normal intensity.

In order to understand the loss of function suffered by a comatose individual, it is necessary to first understand the important characteristics of the conscious state. Consciousness is defined by two fundamental elements: awareness and arousal.

Awareness allows one to receive and process all the information communicated by the five senses, and thus relate to oneself and to the outside world. Awareness has both psychological and physiological components. The psychological component is governed by an individual's mind and mental processes. The physiological component refers to the functioning of an individual's brain, and therefore that brain's physical and chemical condition. Awareness is regulated by cortical areas within the cerebral hemispheres, the outermost layer of the brain that separates humans from other animals by allowing for greater intellectual functioning.

Arousal is regulated solely by physiological functioning and consists of more primitive responsiveness to the world, as demonstrated by predictable reflex (involuntary) responses to stimuli. Arousal is maintained by the reticular activating system (RAS). This is not an anatomical area of the brain, but rather a network of structures (including the brainstem, the medulla, and the thalamus) and nerve pathways, which function together to produce and maintain arousal.

— Rosalyn Carson-DeWitt, MD

A state of deep, often prolonged unconsciousness, usually the result of injury, disease, or poison, in which an individual is incapable of sensing or responding to external stimuli and internal needs.

[Greek kōma, deep sleep.]

1. Astronomy. The nebulous luminescent cloud containing the nucleus and constituting the major portion of the head of a comet.
2. Botany. A usually terminal tuft or cluster, especially a tuft of hairs on a seed, as on a willow or milkseed.
3. Physics. A diffuse, comet-shaped image of a point source of light or radiation caused by aberration in the optical system.

[Latin, hair, from Greek komē.]

All persons in coma are unconscious, but not all who are unconscious are in coma. Sleep is a state of unconsciousness from which a person can be roused. The vegetative state is unconsciousness with the eyes open, the person being awake but not aware. Coma is a state of unrousable, sleep-like (eyes closed) unconsciousness. Although asleep and unaware, only those in the deepest states of coma are unresponsive. Most patients in coma respond reflexly — the pupils react to light and the limbs move in response to a painful stimulus (such as pinching the skin or pressing the nailbed). A person in coma may move restlessly and make sounds, but utters no words.

Different levels of coma, and of impaired consciousness not severe enough to be called coma, are defined by the Glasgow Coma Scale or Score — often referred to internationally as the GCS. This grades three items of behaviour: eye opening, motor responses (limb movements on command or in response to a painful stimulus), and verbal activity. For each of these there is a score of 1 to 5 according to how good the response is, with higher numbers indicating the more normal responses. At a combined score of 15 the eyes open spontaneously, commands are obeyed, and the patient can say who he is and where he is and when it is. A patient is considered to be in coma if the eyes remain closed, there are no motor responses on command, and no recognizable words are uttered — if all three of these conditions are satisfied, as well as the total score being 8 or less. At the lowest score of 3 the eyes are closed, the limbs show no response even to pain, and no sounds at all are made.

Coma is associated with loss of function in the arousal centre in the brain stem which is responsible both for eye opening and for activating the cerebral cortex, which has to be functioning for a person to be aware of self and surroundings. Some causes of coma temporarily affect the arousal mechanisms alone. These include normal doses of anaesthetic agents, overdoses of sedative drugs or alcohol, and a generalized epileptic seizure. Toxic body chemicals can also cause coma, due to disease in other organs, as a complication of diabetes, or of failure of kidney or liver function. More often coma is a feature of major structural insults in various parts of the brain, such as those resulting from severe head injury, brain haemorrhage, infection, tumour, or oxygen lack (either in part of the brain from a blocked blood vessel (stroke), or in the brain as a whole due to stoppage of the heart or the breathing). In all these conditions the development of coma is a sign that the condition is very serious and that there is much less likelihood of recovery than if coma had not occurred.

The person in coma is at immediate risk of obstruction of the airway, as the normal coughing reflex is depressed. Obstruction may come from the tongue falling back or from inhalation of vomited stomach contents. This complication, which can be fatal, is less likely to occur if as a first-aid measure the person is turned over with the face down — the so-called coma position. Paramedics or doctors will later deal more effectively with this threat by passing a tube through the nose or mouth into the trachea (endotracheal intubation), and artificial ventilation may be set up. Since a person in coma is unable to take food and fluids normally, if coma lasts more than 24 hours artificial feeding will be necessary to ensure survival. This may be by a tube in the stomach (passed through the mouth or nose), or by a infusion into a vein.

Recovery from coma depends on the cause. Chemically-caused coma with no other brain damage or complications can be followed by complete recovery. When there has been a major structural insult the rapidity of recovery and the degree of residual disability will depend on how much permanent brain damage has been caused. How long the coma lasts is often a good indication of how severe this damage is, but a good recovery is still possible when coma has lasted 2 or 3 weeks. On the other hand, severe brain damage can occur without the patient ever being in coma, for example after a severe stroke. In survivors of even the most severe brain damage, however, coma seldom lasts more than 3-4 weeks; the eyes then open and the patient passes into another state of reduced responsiveness such as the vegetative state. Press reports of patients in ‘coma’ for months or years are therefore misleading.

— Bryan Jennett

Bibliography

• Teasdale, G. and Jennett, B. (1976). Assessment of coma and impaired consciousness. A practical scale. Lancet, 1, 1031

See also brain death; consciousness; vegetative state.

Definition: deep unconsciousness
Antonyms: alertness, consciousness, wakefulness

For more information on coma, visit Britannica.com.

Condition of depressed consciousness in which, unlike sleep, oxygen use is below resting levels and the comatose person is totally unresponsive to sensory stimuli for an extended period of time. A coma can be induced by hypothermia. hyperthermia, and direct trauma. See also Glasgow Coma scale.

An abnormal state of deep unconsciousness. A coma may occur as the result of trauma to the head, disease (such as meningitis, stroke, or diabetes mellitus), or poisoning.

A state of unconsciousness from which the patient cannot be aroused, even by powerful stimuli.

• alpha c. — coma in which there are electroencephalographic findings of dominant alpha-wave activity.
• diabetic c. — the coma of severe diabetic acidosis. See also diabetes mellitus.
• hepatic c. — results from reversible biochemical abnormalities of the cerebrum, caused by elevated blood levels of toxic substances such as ammonia, amino acids, short-chain fatty acids and beta hydroxylated biogenic amines that accumulate in severe liver disease. See also hepatic encephalopathy.
• irreversible c. — coma in which for a period of 24 hours there is complete nonreceptivity and nonresponsivity even to the most intensely painful stimuli, no spontaneous movement or breathing, absence of elicitable reflexes, and a flat electroencephalogram. Called also brain death.
• myxedema c. — the mental stupor caused by severe hypothyroidism; seen most often in Doberman pinchers, it is associated with hypoventilation, hypothermia, hypotension and bradycardia. Death may occur.

A large cloud of dust and gas which escapes from the nucleus of an active comet.

Tutor's tip: A "coma" is an unconscious condition caused by accident or disease, a "comma" is a mark of punctuation that looks like (,) and indicates a pause in a sentence, while "karma" is the Hindu belief that actions determine a person's destiny in his or her next

For other uses, see Coma (disambiguation).

Coma

ICD-10	R40.2
ICD-9	780.01

In medicine, a coma, or comatose, (from the Greek κῶμα koma, meaning deep sleep) is a profound state of unconsciousness. A comatose person cannot be awakened, fails to respond normally to pain, light or sound, does not have sleep-wake cycles, and does not take voluntary actions.

Coma may result from a variety of conditions, including intoxication, metabolic abnormalities, central nervous system diseases, acute neurologic injuries such as stroke, and hypoxia. A coma may also result from head trauma caused by mechanisms such as falls or car accidents. It may also be deliberately induced by pharmaceutical agents in order to preserve higher brain function following another form of brain trauma, or to save the patient from extreme pain during healing of injuries or diseases. The underlying cause of coma is bilateral damage to the Reticular formation of the midbrain, which is important in regulating sleep.^[1]

If the cause of coma is not clear, various investigations (blood tests, medical imaging) may be performed to establish the cause and identify reversible causes. Coma usually necessitates admission to a hospital and often the intensive care unit.

Contents 1 Signs and symptoms 2 Diagnosis 3 Classification 4 Prognosis 5 Comas in films and novels 6 See also 7 References

Signs and symptoms

This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2008)

Main article: Level of consciousness

The severity and mode of onset of coma depends on the underlying cause. For instance, deepening hypoglycemia (low blood sugar) or hypercapnia (increased carbon dioxide levels in the blood) initially cause mild agitation and confusion, then progress to obtundation, stupor and finally complete unconsciousness. In contrast, coma resulting from a severe traumatic brain injury or subarachnoid hemorrhage can be instantaneous. The mode of onset may therefore be indicative of the underlying cause.

In the initial assessment of coma, it is common to gauge the level of consciousness by spontaneously exhibited actions, response to vocal stimuli ("Can you hear me?"), and painful stimuli; this is known as the AVPU (alert, vocal stimuli, painful stimuli, unconscious) scale. More elaborate scales, such as the Glasgow coma scale (see below), quantify individual reactions such as eye opening, movement and verbal response on a scale.

In those with deep unconsciousness, there is a risk of asphyxiation as the control over the muscles in the face and throat is diminished. As a result, those presenting to a hospital with coma are typically assessed for this risk ("airway management"). If the risk of asphyxiation is deemed to be high, doctors may use various devices (such as an oropharyngeal airway, nasopharyngeal airway or endotracheal tube) to safeguard the airway.

Diagnosis

Please help improve this article by expanding it. Further information might be found on the talk page. (September 2008)

Once a person in a coma is stable, investigations are performed to assess the underlying cause. These may be simple; a computed tomography scan of the brain, for example, is performed to identify specific causes of the coma, such as hemorrhage.

A diagnosis will direct the appropriate therapy, However it does not reduce the need for generic supportive care, such as that offered on intensive care. Sometimes, the diagnosis allows the withdrawal of care, if the cause of coma is untreatable and the brain damage is irreversible.

Classification

This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (September 2008)

The severity of coma impairment is categorized into several levels. Patients may or may not progress through these levels. In the first level, the brain responsiveness lessens, normal reflexes are lost, the patient no longer responds to pain and cannot hear.

Two scales of measurement often used in Traumatic Brain Injury (TBI) diagnosis to determine the level of coma are the Glasgow Coma Scale (GCS) and the Ranchos Los Amigos Scale (RLAS). The GCS is a simple 3 to 15-point scale (3 being the worst and 15 being that of a normal person) used by medical professionals to assess severity of neurologic trauma, and establish a prognosis. The RLAS is a more complex scale that has eight separate levels, and is often used in the first few weeks or months of coma while the patient is under closer observation, and when shifts between levels are more frequent.

Prognosis

Outcomes range from recovery to death. Comas generally last a few days to a few weeks. They rarely last more than 2 to 5 weeks but some have lasted as long as several years. After this time, some patients gradually come out of the coma, some progress to a vegetative state, and others die. Some patients who have entered a vegetative state go on to regain a degree of awareness. Others remain in a vegetative state for years or even decades (the longest recorded period being 37 years).^[2]

The outcome for coma and vegetative state depends on the cause, location, severity and extent of neurological damage. A deeper coma alone does not necessarily mean a slimmer chance of recovery, because some people in deep coma recover well while others in a so-called milder coma sometimes fail to improve.

People may emerge from a coma with a combination of physical, intellectual and psychological difficulties that need special attention. Recovery usually occurs gradually—patients acquire more and more ability to respond. Some patients never progress beyond very basic responses, but many recover full awareness. Regaining consciousness is not instant: in the first days, patients are only awake for a few minutes, and duration of time awake gradually increases. This is unlike the situation in many movies where people who awake from comas are instantly able to continue their normal lives. In reality, the coma patient awakes sometimes in a profound state of confusion, not knowing how they got there and sometimes sufferering from dysphasia, the inability to articulate any speech, and with many other disabilities.

Predicted chances of recovery are variable owing to different techniques used to measure the extent of neurological damage. All the predictions are based on statistical rates with some level of chance for recovery present: a person with a low chance of recovery may still awaken. Time is the best general predictor of a chance of recovery: after 4 months of coma caused by brain damage, the chance of partial recovery is less than 15%, and the chance of full recovery is very low.^[3][4]

The most common cause of death for a person in a vegetative state is secondary infection such as pneumonia which can occur in patients who lie still for extended periods.

Occasionally people come out of coma after long periods of time. After 19 years in a minimally conscious state, Terry Wallis spontaneously began speaking and regained awareness of his surroundings.^[5] Similarly, Polish railroad worker Jan Grzebski woke up from a 19-year coma in 2007.

A brain-damaged man, trapped in a coma-like state for six years, was brought back to consciousness in 2003 by doctors who planted electrodes deep inside his brain. The method, called deep brain stimulation (DBS) successfully roused communication, complex movement and eating ability in the 38-year-old American man who suffered a traumatic brain injury. His injuries left him in a minimally conscious state (MCS), a condition akin to a coma but characterized by occasional, but brief, evidence of environmental and self-awareness that coma patients lack.^[6]

Comas in films and novels

Research by Dr. Elias Reinhardt on the depiction of comas in movies was published in Neurology in May 2006. Dr. Reinhardt studied 30 films (made between 1970 and 2004) that portrayed actors in prolonged comas, and he concluded that only two films accurately depicted the state of a coma victim and the agony of waiting for a patient to awaken: Reversal of Fortune (1990) and The Dreamlife of Angels (1998). The remaining 28 were criticised for portraying miraculous awakenings with no lasting side effects, unrealistic depictions of treatments and equipment required, and comatose patients remaining muscular and tanned.

In the 2005 novel The Coma by Alex Garland, a man assaulted in the London Underground tries to put his life back into order from his comatose state. Extraordinary Means, a 1987 novel by Donna Levin, is a literary fantasy in which a comatose woman is able to overhear her family dispute over whether to end life support. Coma, published in 1977 by Robin Cook, is a medical thriller in which a med student unravels a plot to purposely induce comas in patients in order to harvest their organs.

See also

• Persistent vegetative state (vegetative coma), deep coma without detectable awareness
• Brain death (irreversible coma), irreversible end of all brain activity
• Process Oriented Coma Work, for an approach to working with residual consciousness in comatose patients
• Level of consciousness

References

This article includes a list of references or external links, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations where appropriate. (January 2009)

1. ^ Sundsten, John W.; Nolte, John (2001). The human brain: an introduction to its functional anatomy. St. Louis: Mosby. ISBN 0-323-01320-1. 
2. ^ According to the Guinness Book of Records, the longest period spent in coma was by Elaine Esposito. She did not wake up after being anaesthetized for an appendectomy on August 6, 1941, at age 6. She died on November 25, 1978 at age 43 years 357 days, having been in a coma for 37 years 111 days.
3. ^ Formisano R, Carlesimo GA, Sabbadini M, et al. (May 2004). "Clinical predictors and neuopleropsychological outcome in severe traumatic brain injury patients". Acta Neurochir (Wien) 146 (5): 457–62. doi:10.1007/s00701-004-0225-4. PMID 15118882. 
4. ^ brain injury .com | Coma traumatic brain injury - Brain Injury Coma
5. ^ Mother stunned by coma victim's unexpected words - smh.com.au
6. ^ "Electrodes stir man from six-year coma-like state". Cosmos Magazine. 2 August2007. http://www.cosmosmagazine.com/node/1513. 

v • d • e Symptoms and signs: cognition, perception, emotional state and behaviour (R40-R46, 780.0-780.5,781.1) Cognition Alteration of consciousness Confusion (Delirium) · Somnolence · Obtundation · Stupor · Unconsciousness (Syncope, Coma, Persistent vegetative state) Fainting/Syncope Carotid sinus syncope • Heat syncope • Vasovagal episode Other Amnesia (Anterograde amnesia, Retrograde amnesia) · Dizziness (Vertigo, Presyncope/Lightheadedness, Disequilibrium) · Convulsion Emotional state Anxiety · Irritability · Hostility · Suicidal ideation Behavior Verbosity Perception/ sensation disorder Olfaction : Anosmia · Hyposmia · Dysosmia · Parosmia · Hyperosmia Taste: Ageusia · Hypogeusia · Dysgeusia  · Parageusia · Hypergeusia Hallucination: Auditory hallucination psychology navs: mental processes, disorders, symptoms/signs, speech/voice, psychotherapy olfaction navs: anatomy, symptoms/signs taste navs: anatomy, symptoms/signs

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
1.
n. - koma, dyb bevidstløshed

2.
n. - støvsky omkring komet, frøuld

Nederlands (Dutch)
coma, zaadpluis

Français (French)
1.
n. - coma

2.
n. - (Astron) enveloppe nébuleuse, (Opt) défaut de la lentille, (Bot) touffe, comète (d'une image)

Deutsch (German)
1.
n. - Koma, (andauernde tiefe Bewußtlosigkeit)

2.
n. - (Astr) Koma

Ελληνική (Greek)
n. - (παθολ.) (βαθύ) κώμα, κωματώδης κατάσταση, (αστρον.) ουρά, κόμη ή χαίτη (κομήτη)

Italiano (Italian)
coma

Português (Portuguese)
n. - coma (f) (Med.)

Русский (Russian)
кома

Español (Spanish)
1.
n. - coma

2.
n. - cabellera de un cometa

Svenska (Swedish)
n. - koma, koma (astron.), koma (optik.), tofs (bot.), trädkrona (bot.), bladrosett (bot.)

中文（简体）(Chinese (Simplified))
1. 昏迷

2. 慧星的头

中文（繁體）(Chinese (Traditional))
1.
n. - 昏迷

2.
n. - 慧星的頭

한국어 (Korean)
1.
n. - 혜성이 핵 둘레의 대기, 씨에 난 솜털

2.
n. - 혼수 상태

日本語 (Japanese)
n. - 昏睡

العربيه (Arabic)
‏(الاسم) غيبوبه‏

עברית (Hebrew)
n. - ‮תרדמת, חוסר-הכרה או תרדמה ממושכים‬
n. - ‮ענן גז ואבק סביב ראש שביט, ציצת שערות משייות בקצה זרעים מסוימים‬

If you are unable to view some languages clearly, click here.

To select your translation preferences click here.