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Medical Encyclopedia:

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


 
 
Dictionary: co·ma1  (kō'mə) pronunciation
n., pl. -mas.

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.]


co·ma2 (kō'mə) pronunciation
n., pl. -mae (-mē).
  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.]

comal co'mal adj.
 
World of the Body: coma

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.

 
Antonyms: coma

n

Definition: deep unconsciousness
Antonyms: alertness, consciousness, wakefulness

 
Britannica Concise Encyclopedia: coma

Complete lack of consciousness, with loss of reaction to stimulus and of spontaneous nervous activity. It is usually associated with cerebral injury of metabolic or physical origin. Simple concussions cause short losses of consciousness. Coma from lack of oxygen may last several weeks and is often fatal. Coma caused by stroke can be sudden, while that caused by metabolic abnormalities (as in diabetes mellitus) or cerebral tumours comes on gradually. Treatment depends on the cause.

For more information on coma, visit Britannica.com.

 
Sports Science and Medicine: coma

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.

 
Columbia Encyclopedia: coma,
in medicine, deep state of unconsciousness from which a person cannot be aroused even by painful stimuli. The patient cannot speak and does not respond to command. Coma is the result of damage to the brain stem and cerebrum that may be caused by severe head or brain injury, cardiac arrest, stroke, diabetes, drug overdose, shock, or hemorrhage. It occurs just before death in many diseases. There are various depths of coma; the nature of the injury determines the level of supportive treatment necessary (see artificial life support). Survival and prognosis depend upon the cause, extent of damage, and duration of the coma.

The term persistent vegetative state was coined in 1972 to describe an unconscious state in which sleep and wake cycles remain and eyes may open, but there is no thinking, feeling, or awareness of one's surroundings (although one may react reflexive to certain stimulations). The brain stem is usually relatively intact but the cerebral cortex is severely impaired. It is this state that sometimes results from resuscitation and life support of people who otherwise would have died; partial emergence from such a state sometimes occurs with a year or two, but not after that.

 
Health Dictionary: coma
(koh-muh)

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.

 
Veterinary Dictionary: coma

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.

 
Cosmic Lexicon: Coma

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

 
Word Tutor: coma
pronunciation

IN BRIEF: A condition of unconsciousness.

pronunciation Sir Winston Churchill slipped into a coma before he died.

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

 
Wikipedia: coma


Name of Symptom/Sign:
Coma
Classifications and external resources
ICD-10 R40.2
ICD-9 780.01

In medicine, a coma (from the Greek κῶμα koma, meaning deep sleep) is a profound state of unconsciousness. A comatose patient cannot be awakened, fails to respond normally to pain or light, 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. It may also be deliberately induced by pharmaceutical agents in order to preserve higher brain function following another form of brain trauma.

Severity

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.

Contrary to popular belief, a patient in a coma does not always lie still and quiet. They may talk, walk, and perform other functions that may sometimes appear to be conscious acts but are not.[1]

Two scales of measurement often used in 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 15-point scale 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.

Outcome

Outcomes range from recovery to death. Comas generally last a few days to a few weeks, rarely more than 2 to 5 weeks. 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.

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 recovery is less than 15%, and 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 coma, Terry Wallis spontaneously began speaking and regained awareness of his surroundings. [5]

A brain-damaged man, trapped in a comalike state for six years, has recently been brought back to consciousness by doctors who planted electrodes deep inside his brain. The method, called deep-brain electrical 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. If the researchers are able to replicate the results more widely, they may offer a glimmer of hope for people with all kinds of brain injury. [6]

See also

References

Sources consulted
Endnotes
  1. ^ http://news.bbc.co.uk/2/hi/europe/6715313.stm
  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. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15118882&query_hl=5
  4. ^ http://www.braininjury.com/coma.html
  5. ^ http://www.smh.com.au/articles/2003/07/11/1057783356390.html
  6. ^ "Electrodes stir man from six-year coma-like state", Cosmos Magazine, 02 August2007. 

External links

Symptoms and signs (R00-R69, 780-789)
Circulatory and
respiratory systems		 Tachycardia - Bradycardia - Palpitation - Heart murmur - Epistaxis - Hemoptysis - Cough - abnormalities of breathing (Dyspnea, Orthopnoea, Stridor, Wheeze, Cheyne-Stokes respiration, Hyperventilation, Mouth breathing, Hiccup, Bradypnea, Hypoventilation) - Chest pain - Asphyxia - Pleurisy - Respiratory arrest - Sputum - Bruit/Carotid bruit - Rales
Digestive system and abdomen Abdominal pain - Acute abdomen - Nausea - Vomiting - Heartburn - Dysphagia - Flatulence - Burping - Fecal incontinence - Encopresis - Hepatomegaly - Splenomegaly - Hepatosplenomegaly - Jaundice - Ascites - Fecal occult blood - Halitosis
Skin and subcutaneous tissue disturbances of skin sensation (Hypoesthesia, Paresthesia, Hyperesthesia) - Rash - Cyanosis - Pallor - Flushing - Petechia - Desquamation - Induration - Diaphoresis
Nervous and
musculoskeletal systems		 abnormal involuntary movements (Tremor, Spasm, Fasciculation, Athetosis) - Gait abnormality - lack of coordination (Ataxia, Dysmetria, Dysdiadochokinesia, Hypotonia) - Tetany - Meningism - Hyperreflexia
Urinary system Dysuria - Vesical tenesmus - Urinary incontinence - Urinary retention - Oliguria - Polyuria - Nocturia
Cognition, perception,
emotional state and behaviour		 Anxiety - Somnolence - Coma - Amnesia (Anterograde amnesia, Retrograde amnesia) - Dizziness/Vertigo - smell and taste (Anosmia, Ageusia, Parosmia, Parageusia)
Speech and voice speech disturbances (Dysphasia, Aphasia, Dysarthria) - symbolic dysfunctions (Dyslexia, Alexia, Agnosia, Apraxia, Acalculia, Agraphia) - voice disturbances (Dysphonia, Aphonia)
General symptoms and signs Fever (Hyperpyrexia) - Headache - Chronic pain - Malaise - Fatigue - Fainting (Vasovagal syncope) - Febrile seizure - Shock (Cardiogenic shock) - Lymphadenopathy - Edema (Peripheral edema, Anasarca) - Hyperhidrosis (Sleep hyperhidrosis) - Delayed milestone - Failure to thrive - food and fluid intake (Anorexia, Polydipsia, Polyphagia) - Cachexia - Xerostomia - Clubbing

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

 
Translations: Translations for: Coma

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

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Medical Encyclopedia. © 2006 through a partnership of Answers Corporation. All rights reserved.  Read more
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Sports Science and Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/  Read more
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