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Coma

Coma

:For other meanings of the word "coma", especially in astronomy, see coma (disambiguation) In medicine, a coma (from the Greek koma, meaning deep sleep) is a profound state of unconsciousness. A comatose patient cannot be awakened, fails to respond properly or at all to stimuli such as pain or light, does not have sleep-wake cycles, and does not take voluntary actions (BAIUSA). Coma may result from a variety of conditions, including intoxication, metabolic abnormalities, central nervous system diseases, and hypoxia.

Causes

An impairment that affects a large part of the brain, called diffuse pathology, is the most common cause of coma, accounting for about 60% of the cases. To maintain consciousness, the brain requires the correct temperature, pressure, pH, oxygenation, and nutrients; denying the brain any of these necessities will lead to coma. A variety of common causes of coma can be classified as diffuse pathologies. For example, head trauma associated with an increased intracranial pressure can lead to coma by compressing delicate brain tissue, as can subarachnoid hemorrhage. Various toxins can also lead to coma, including poisons, alcohol, barbiturates, opiate narcotics, sedatives, amphetamines, cocaine and aspirin. Metabolic abnormalities that lead to either elevated or reduced glucose levels in the blood, liver or kidney failure, hypoxia (poor oxygenation), and electrolyte imbalances can also produce unconsciousness. Seizure disorders and central nervous system infections, such as meningitis and encephalitis and are further examples. Coma can also be caused by focal lesions, those that affect only a small part of the brain and may be either supratentorial or infratentorial. Focal supratentorial injuries account for 30% of coma cases, and can be caused by problems with blood vessels or by expansive lesions such as neoplasia or hydrocephalus. Focal infratentorial lesions account for the remaining 10% of comas, and can be of vascular nature, expansive or demyelinating lesions. Medical professionals may intentionally induce a coma with drugs to reduce swelling of the brain after injury.

Contrasts to Other Conditions

Some conditions share characteristics with coma and must be ruled out in a differential diagnosis before coma is conclusively diagnosed. These include locked-In syndrome, akinetic mutism and catatonic stupor. The difference between coma and stupor is that a patient with coma cannot give a suitable response to either noxious or verbal stimuli, whereas a patient in a stupor can give a crude response, such as screaming, to an unpleasant stimulus. Some psychiatric diseases appear similar to coma. Some forms of Schizophrenia, Catatonia, and extremely severe major depression are responsibile for behaviour that appears comatose. Coma is also to be distinguished from the persistent vegetative state which may follow it. This is a condition in which the individual has lost cognitive neurological function and awareness of the environment but does have noncognitive function and a preserved sleep-wake cycle. Spontaneous movements may occur and the eyes may open in response to external stimuli, but the patient does not speak or obey commands. Patients in a vegetative state may appear somewhat normal and may occasionally grimace, cry, or laugh. Likewise, coma is not the same as brain death, which is the irreversible cessation of all brain activity. One can be in a coma but still exhibit spontaneous respiration; one who is brain-dead, by definition, cannot. Coma is different from sleep; sleep is always reversible.

Outcome

There are several levels of coma, through which patients may or may not progress. As coma deepens, responsiveness of the brain lessens, normal reflexes are lost, and the patient no longer responds to pain. The chances of recovery depend on the severity of the underlying cause. 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. The outcome for coma and vegetative state depends on the cause, location, severity and extent of neurological damage: outcomes range from recovery to death. People may emerge from a coma with a combination of physical, intellectual and psychological difficulties that need special attention. Recovery usually occurs gradually, with patients acquiring more and more ability to respond. Some patients never progress beyond very basic responses, but many recover full awareness. Gaining consciousness again is not instant: in the first days, patients are only awake for a few minutes, and duration of time awake gradually increases. Coma generally lasts a few days to a few weeks, and rarely lasts more than 2 to 4 weeks. After this time, some patients gradually come out of the coma, some progress to a vegetative state, and others die. Many patients who have gone into a vegetative state go on to regain a degree of awareness. Others may remain in a vegetative state for years or even decades. Predicted chances of recovery are variable due to different techniques used to measure the extent of neurological damage. All the predictions are 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 for recovery, with the chances for recovery after 3 months of brain damage induced coma being low (less than 10%), and full recovery being very low. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15118882&query_hl=5] [http://www.braininjury.com/coma.html] 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.

Controversy

There have been controversies and legal cases over whether to keep comatose patients alive for long periods using life support equipment. Two such cases are those of Karen Ann Quinlan and Terri Schiavo.

Diagnosis and Treatment

The Glasgow Coma Scale is used to quantify the severity of a coma. There are three components to the score: Eye opening response, Verbal response, and Motor response. In Germany, music therapy is used to quicken the awakening traject. In Belgium a project is set up to train dogs' and cats's "sixth sense" to warn patients and medical staff that a coma patient has awakened.

External links

- Some of the information in this section is from the public domain resource provided by the [http://www.ninds.nih.gov/health_and_medical/disorders/coma_doc.htm National Institute of Neurological Diseases and Stroke].

Reference

# Brain Injury Association of America (BIAUSA). [http://www.biausa.org/Pages/types_of_brain_injury.html#diffuse Types of Brain Injury]. This article contains text from the NINDS public domain pages on TBI at http://www.ninds.nih.gov/health_and_medical/disorders/tbi_doc.htm and http://www.ninds.nih.gov/health_and_medical/pubs/tbi.htm Category:Neurology Category:Intensive care medicine Category:Emergency medicine

Astronomy

:This article is about the science branch. For information about the magazine, see Astronomy (magazine). Astronomy (magazine) as they circled the Moon in 1969. Located near the center of the far side of Earth's Moon, its diameter is about 58 miles (93 km).]] Astronomy (Greek: αστρονομία = άστρον + νόμος, astronomia = astron + nomos, literally, "law of the stars") is the science of celestial objects and phenomena that originate outside the Earth's atmosphere, such as stars, planets, comets, galaxies, and the cosmic background radiation. It is concerned with the formation and development of the universe, the evolution and physical and chemical properties of celestial objects and the calculation of their motions. Astronomical observations are not only relevant for astronomy as such, but provide essential information for the verification of fundamental theories in physics, such as general relativity theory. Complementary to observational astronomy, theoretical astrophysics seeks to explain astronomical phenomena. Astronomy is one of the oldest sciences, with a scientific methodology existing at the time of Ancient Greece and advanced observation techniques possibly much earlier (see archaeoastronomy). Historically, amateurs have contributed to many important astronomical discoveries, and astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and observation of transient phenomena. Astronomy is not to be confused with astrology, which assumes that people's destiny and human affairs in general are correlated to the apparent positions of astronomical objects in the sky -- although the two fields share a common origin, they are quite different; astronomers embrace the scientific method, while astrologers do not. In other words, there is no proof that the stars predict our future, but there is proof that our planet is 93 million miles from the sun.

Divisions

In ancient Greece and other early civilizations, astronomy consisted largely of astrometry, measuring positions of stars and planets in the sky. Later, the work of Kepler and Newton, whose work led to the development of celestial mechanics, mathematically predicting the motions of celestial bodies interacting under gravity, and solar system objects in particular. Much of the effort in these two areas, once done largely by hand, is highly automated nowadays, to the extent that they are rarely considered as independent disciplines anymore. Motions and positions of objects are now more easily determined, and modern astronomy is more concerned with observing and understanding the actual physical nature of celestial objects. Since the twentieth century, the field of professional astronomy has split into observational astronomy and theoretical astrophysics. Although most astronomers incorporate elements of both into their research, because of the different skills involved, most professional astronomers tend to specialize in one or the other. Observational astronomy is concerned mostly with acquiring data, which involves building and maintaining instruments and processing the results; this branch is at times referred to as "astrometry" or simply as "astronomy". Theoretical astrophysics is concerned mainly with ascertaining the observational implications of different models, and involves working with computer or analytic models. The fields of study can also be categorized in other ways. Categorization by the region of space under study (for example, Galactic astronomy, Planetary Sciences); by subject, such as star formation or cosmology; or by the method used for obtaining information.

By subject or problem addressed

theoretical astrophysics. Photographed by Mars Global Surveyor, the long dark streak is formed by a moving swirling column of Martian atmosphere (with similarities to a terrestrial tornado). The dust devil itself (the black spot) is climbing the crater wall. The streaks on the right are sand dunes on the crater floor.]]
- Astrometry: the study of the position of objects in the sky and their changes of position. Defines the system of coordinates used and the kinematics of objects in our galaxy.
- Astrophysics: the study of physics of the universe, including the physical properties (luminosity, density, temperature, chemical composition) of astronomical objects.
- Cosmology: the study of the origin of the universe and its evolution. The study of cosmology is theoretical astrophysics at its largest scale.
- Galaxy formation and evolution: the study of the formation of the galaxies, and their evolution.
- Galactic astronomy: the study of the structure and components of our galaxy and of other galaxies.
- Extragalactic astronomy: the study of objects (mainly galaxies) outside our galaxy.
- Stellar astronomy: the study of the stars.
- Stellar evolution: the study of the evolution of stars from their formation to their end as a stellar remnant.
- Star formation: the study of the condition and processes that led to the formation of stars in the interior of gas clouds, and the process of formation itself.
- Planetary Sciences: the study of the planets of the Solar System.
- Astrobiology: the study of the advent and evolution of biological systems in the Universe. Other disciplines that may be considered part of astronomy:
- Archaeoastronomy
- Astrochemistry
- Astrosociobiology
- Astrophilosophy See the list of astronomical topics for a more exhaustive list of astronomy-related pages.

Ways of obtaining information

list of astronomical topics :Main article: Observational astronomy. In astronomy, information is mainly received from the detection and analysis of light and other forms of electromagnetic radiation. Other cosmic rays are also observed, and several experiments are designed to detect gravitational waves in the near future. A traditional division of astronomy is given by the region of the electromagnetic spectrum observed:
- Optical astronomy is the part of astronomy that uses optical components (mirrors, lenses, CCD detectors and photographic films) to observe light from near infrared to near ultraviolet wavelengths. Visible light astronomy (using wavelengths that can be detected with the eyes, about 400 - 700 nm) falls in the middle of this range. The most common tool is the telescope, with electronic imagers and spectrographs.
- Infrared astronomy deals with the detection and analysis of infrared radiation (wavelengths longer than red light). The most common tool is the telescope but using a detector which is sensitive to the infrared. Space telescopes are also used to avoid atmospheric thermal emission, atmospheric opacity, and the effects of astronomical seeing at infrared and other wavelengths.
- Radio astronomy detects radiation of millimetre to dekametre wavelength. The receivers are similar to those used in radio broadcast transmission but much more sensitive. See also Radio telescopes.
- High-energy astronomy includes X-ray astronomy, gamma-ray astronomy, and extreme UV (ultraviolet) astronomy, as well as studies of neutrinos and cosmic rays. Optical and radio astronomy can be performed with ground-based observatories, because the atmosphere is transparent at the wavelengths being detected. Infrared light is heavily absorbed by water vapor, so infrared observatories have to be located in high, dry places or in space. The atmosphere is opaque at the wavelengths of X-ray astronomy, gamma-ray astronomy, UV astronomy and (except for a few wavelength "windows") Far infrared astronomy, so observations must be carried out mostly from balloons or space observatories. Powerful gamma rays can, however be detected by the large air showers they produce, and the study of cosmic rays can also be regarded as a branch of astronomy.

History of astronomy

cosmic ray :Main article: History of astronomy. In early times, astronomy only comprised the observation and predictions of the motions of the naked-eye objects. Aristotle said that the Earth was the center of the Universe and everything rotated around it in orbits that were perfect circles. Aristotle had to be right because people thought that Earth had to be in the center with everything rotating around it because the wind would not scatter leaves, and birds would only fly in one direction. For a long time, people thought that Aristotle was right, but it is probable that Aristotle accidentally did more to hinder our knowledge than help it. The Rigveda refers to the 27 constellations associated with the motions of the sun and also the 12 zodiacal divisions of the sky. The ancient Greeks made important contributions to astronomy, among them the definition of the magnitude system. The Bible contains a number of statements on the position of the earth in the universe and the nature of the stars and planets, most of which are poetic rather than literal; see Biblical cosmology. In 500 AD, Aryabhata presented a mathematical system that described the earth as spinning on its axis and considered the motions of the planets with respect to the sun. Observational astronomy was mostly stagnant in medieval Europe, but flourished in the Iranian world and other parts of Islamic realm. The late 9th century Persian astronomer al-Farghani wrote extensively on the motion of celestial bodies. His work was translated into Latin in the 12th century. In the late 10th century, a huge observatory was built near Tehran, Persia (now Iran), by the Persian astronomer al-Khujandi, who observed a series of meridian transits of the Sun, which allowed him to calculate the obliquity of the ecliptic. Also in Persia, Omar Khayyám performed a reformation of the calendar that was more accurate than the Julian and came close to the Gregorian. Abraham Zacuto was responsible in the 15th century for the adaptations of astronomical theory for the practical needs of Portuguese caravel expeditions. During the Renaissance, Copernicus proposed a heliocentric model of the Solar System. His work was defended, expanded upon, and corrected by Galileo Galilei and Johannes Kepler. Galileo added the innovation of using telescopes to enhance his observations. Kepler was the first to devise a system that described correctly the details of the motion of the planets with the Sun at the center. However, Kepler did not succeed in formulating a theory behind the laws he wrote down. It was left to Newton's invention of celestial dynamics and his law of gravitation to finally explain the motions of the planets. Newton also developed the reflecting telescope. Stars were found to be faraway objects. With the advent of spectroscopy it was proved that they were similar to our own sun, but with a wide range of temperatures, masses, and sizes. The existence of our galaxy, the Milky Way, as a separate group of stars was only proven in the 20th century, along with the existence of "external" galaxies, and soon after, the expansion of the universe, seen in the recession of most galaxies from us. Modern astronomy has also discovered many exotic objects such as quasars, pulsars, blazars and radio galaxies, and has used these observations to develop physical theories which describe some of these objects in terms of equally exotic objects such as black holes and neutron stars. Physical cosmology made huge advances during the 20th century, with the model of the Big Bang heavily supported by the evidence provided by astronomy and physics, such as the cosmic microwave background radiation, Hubble's Law, and cosmological abundances of elements.

Timelines in astronomy

cosmological abundances of elements
- Artificial satellites and space probes
- Astronomical maps, catalogs, and surveys
- Big Bang
- Black hole physics
- Cosmic microwave background astronomy
- Cosmology
- Galaxies, clusters of galaxies, and large scale structure
- Interstellar medium and intergalactic medium
- Natural satellites
- Other background radiation fields
- Solar astronomy
- Solar system astronomy
- Stellar astronomy
- Telescopes, observatories, and observing technology
- White dwarfs, neutron stars, and supernovae

External Links

- [http://www.space.com/ Space.com]
- [http://www.Astronomy.com/ Astronomy.com]
- [http://www.AbsoluteAstronomy.com/ AbsoluteAstronomy.com]
- [http://www.badastronomy.com/ Bad Astronomy]
- [http://www.nasa.gov/ Nasa]
- [http://www.run4space.com Run4Space Forum]
- [http://antwrp.gsfc.nasa.gov/apod/astropix.html/ Astronomy Picture of the Day] ko:천문학 ms:Astronomi ja:天文学 simple:Astronomy th:ดาราศาสตร์

Coma (disambiguation)

Coma have more than one meaning:
- In medicine, a coma refers to a particular state of unconsciousness.
- In astronomy, a coma is part of the tail of a comet, produced by vapor boiled off the comet as it nears the sun. It is named for "hair".
- In astronomy, sometimes "Coma" is shorthand for the constellation Coma Berenices.
- In optics, a coma is an optical aberration in an astronomical telescope which causes a V-shaped flare to the image of a star. [http://www.opticalmechanics.com/about_coma.htm About coma in an Newtonian telescope].
- In computer science, COMA is the abbreviation of Cache Only Memory Architecture.
- Coma is a 1977 novel by Robin Cook.
- Coma is a 1978 film based upon the previous book starring Geneviève Bujold and Michael Douglas.
- "Coma" is a song by Guns N' Roses, appearing on the album Use Your Illusion I.
- Coma is a Polish band.

Greek language

Greek (Greek Ελληνικά, IPA – "Hellenic") is an Indo-European language with a documented history of 3,500 years. Today, it is spoken by 15 million people in Greece, Cyprus, the former Yugoslavia, particularly The Former Yugoslav Republic of Macedonia, Bulgaria, Albania and Turkey. There are also many Greek emigrant communities around the world, such as those in Melbourne, Australia which is the third-largest Greek-populated city in the world, after Athens and Thessaloniki. Greek has been written in the Greek alphabet, the first true alphabet, since the 9th century B.C. and before that, in Linear B and the Cypriot syllabaries. Greek literature has a long and rich tradition.

History

This article does not cover the reconstructed history of Greek prior to the use of writing. For more information, see main article on Proto-Greek language. Greek has been spoken in the Balkan Peninsula since the 2nd millennium BC. The earliest evidence of this is found in the Linear B tablets dating from 1500 BC. The later Greek alphabet (q.v.) is unrelated to Linear B, and was derived from the Phoenician alphabet (abjad); with minor modifications, it is still used today. Greek is conventionally divided into the following periods:
- Mycenean Greek: the language of the Mycenean civilisation. It is recorded in the Linear B script on tablets dating from the 16th century BC onwards.
- Classical Greek (also known as Ancient Greek): In its various dialects was the language of the Archaic and Classical periods of Greek civilisation. It was widely known throughout the Roman empire. Classical Greek fell into disuse in western Europe in the Middle Ages, but remained known in the Byzantine world, and was reintroduced to the rest of Europe with the Fall of Constantinople and Greek migration to Italy.
- Hellenistic Greek (also known as Koine Greek): The fusion of various ancient Greek dialects with Attic (the dialect of Athens) resulted in the creation of the first common Greek dialect, which gradually turned into one of the world's first international languages. Koine Greek can be initially traced within the armies and conquered territories of Alexander the Great, but after the Hellenistic colonisation of the known world, it was spoken from Egypt to the fringes of India. After the Roman conquest of Greece, an unofficial diglossy of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. Through Koine Greek it is also traced the origin of Christianity, as the Apostles used it to preach in Greece and the Greek-speaking world. It is also known as the Alexandrian dialect, Post-Classical Greek or even New Testament Greek (after its most famous work of literature).
- Medieval Greek: The continuation of Hellenistic Greek during medieval Greek history as the official and vernacular (if not the literary nor the ecclesiastic) language of the Byzantine Empire, and continued to be used until, and after the fall of that Empire in the 15th century. Also known as Byzantine Greek.
- Modern Greek: Stemming independently from Koine Greek, Modern Greek usages can be traced in the late Byzantine period (as early as 11th century). Two main forms of the language have been in use since the end of the medieval Greek period: Dhimotikí (Δημοτική), the Demotic (vernacular) language, and Katharévousa (Καθαρεύουσα), an imitation of classical Greek, which was used for literary, juridic, and scientific purposes during the 19th and early 20th centuries. Demotic Greek is now the official language of the modern Greek state, and the most widely spoken by Greeks today. It has been claimed that an "educated" speaker of the modern language can understand an ancient text, but this is surely as much a function of education as of the similarity of the languages. Still, Koinē , the version of Greek used to write the New Testament and the Septuagint, is relatively easy to understand for modern speakers. Greek words have been widely borrowed into the European languages: astronomy, democracy, philosophy, thespian, etc. Moreover, Greek words and word elements continue to be productive as a basis for coinages: anthropology, photography, isomer, biomechanics etc. and form, with Latin words, the foundation of international scientific and technical vocabulary. See English words of Greek origin, and List of Greek words with English derivatives.

Classification

Greek is an independent branch of the Indo-European language family. The ancient languages which were probably most closely related to it, Ancient Macedonian language (which may be regarded as a dialect of Greek) and Phrygian, are not well enough documented to permit detailed comparison. Among living languages, Armenian seems to be the most closely related to it.

Geographic distribution

Modern Greek is spoken by about 15 million people mainly in Greece and Cyprus. There are also Greek-speaking populations in Georgia, Ukraine, Egypt, Turkey, Albania, Former Yugoslav Republic of Macedonia and Southern Italy. The language is spoken also in many other countries where Greeks have settled, including Armenia, Australia, Austria, Belgium, Bulgaria, Canada, Denmark, France, Germany, Netherlands, Sweden, United Kingdom, and the United States.

Official status

Greek is the official language of Greece where it is spoken by about 99.5% of the population. It is also, alongside Turkish, the official language of Cyprus. Due to the membership of Greece and Cyprus, Greek is one of the 20 official languages of the European Union.

Phonology

This section generally describes the post-Classic phonology of the Greek language. :All phonetic transcriptions in this section use the International Phonetic Alphabet

Vowel sounds

Greek has 5 vowel sounds, all phonemic:

Unconsciousness

Unconsciousness, more appropriately referred to as loss of consciousness or lack of consciousness, is a dramatic alteration of mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is an illustration of unconsciousness. Fainting due to a drop in blood pressure and a decrese of the oxygen supply to the brain is an illustration of a temporary loss of consciousness. Loss of consciousness must not be confused with altered states of consciousness, such as delirium (when the person is confused and only partially responsive to the environment), normal sleep, hypnosis, and other altered states in which the person responds to stimuli. Loss of consciousness must not be confused with the notion of the psychoanalytic unconscious or cognitive processes (e.g., implicit cognition) that take place outside of awareness. Loss of consciousness may occur as the result of traumatic brain injury, brain hypoxia (e.g., due to a brain infarction or cardiac arrest), severe poisoning with drugs that depress the activity of the central nervous system (e.g., alcohol and other hypnotic or sedative drugs), and other causes.

Law and medicine

In jurisprudence, unconsciousness may entitle the criminal defendant to the defense of automatism, an excusing condition which allows a defendant to argue that they should not be held criminally liable for what would otherwise have been actions or omissions which broke the law. Courts rarely consider "falling asleep" (especially while driving or during surgery) to be an acceptable defense because natural sleep rarely overcomes an ordinary person without warning; however incidents related to epileptic seizures, neurological dysfunctions and sleepwalking may be considered acceptable excusing conditions because the loss of control may not be foreseeable. On the other hand, someone who is less conscious cannot give informed consent to anything. This is relevant in the case of sexual behavior (not allowed with such a person), and also in the case of a patient, with regard to starting or stopping a treatment, and euthanasia.

Intoxication

Drunkenness, in its most common usage, is the state of being intoxicated with alcohol (i.e. ethanol) to a sufficient degree to impair mental and motor functioning. A person who is habitually intoxicated in this manner is labeled an alcoholic, often referred to as a "drunk" (a shortened form of the more traditional term "drunkard") or colloquially as a "lush" or "jakey".

Cultural attitudes

Many societies have cultural stereotypes associated with drunkenness; some consider the ability to drink vast quantities of alcohol worthy of respect. Arguably, such an attitude can be regarded as pathological, as it may lead to alcoholism. In many public places for alcoholic consumption such as bars, the act of not drinking alcohol and refusing offers of alcoholic drinks may appear to be "spoiling the atmosphere" and be met with social disapproval. However, an intoxicated person is often considered unable to control his/her urges or acknowledging limits of drinking and is thus treated with disrespect, related to annoying, or intrusive behavior. The symptoms of drunkenness are generally reported to be positive, at least initially. As the effects diminish, the associated hangover starts, mostly a result of dehydration and exhaustion. The ancient Greeks believed that putting a piece of amethyst in the glass or in one's mouth while drinking prevented drunkenness, and indeed the name of the gem alludes to this belief (Ancient Greek: "a-methyst" meaning "not intoxicated"). Many religions discourage or prohibit alcohol consumption. The Qur'an, or book of Islam, declares that God prohibits the consumption of alcohol by humankind, because of harmful effects for the body, harmful effects for the consumer's life and family, social problems, and distraction from mindfulness of God. The Catechism of the Roman Catholic Church states in paragraph 2290: "The virtue of temperance disposes us to avoid every kind of excess: the abuse of food, alcohol, tobacco, or medicine. Those incur grave guilt who, by drunkenness or a love of speed, endanger their own and others' safety on the road, at sea, or in the air." The Church does not prohibit the use of alcohol if it is done in moderation. Buddhists abstain from alcohol to avoid unintentionally harming others. The intoxication of the mind also is at odds with the teaching of mindfulness.

Hypoxia (medical)

Hypoxia is a pathological condition in which the body as a whole (generalized hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. Hypoxia is often associated with high altitudes, where it is called altitude sickness. Hypoxia can also occur while diving underwater, especially with closed-circuit rebreather systems that control the amount of oxygen in the air breathed in. Symptoms of generalized hypoxia depend on its severity and speed of onset. They include headaches, fatigue, shortness of breath, nausea, unsteadiness, and sometimes even seizures and coma. Severe hypoxia induces a blue discoloration of the skin (deoxygenated blood cells lose their bright red color in favor of a dark blue/red color).

Categories of hypoxia

- Cerebral hypoxia in which the brain is deprived of oxygen despite normal blood flow.
- Hypoxic hypoxia when there's an inadequate supply of oxygen (as caused by high altitudes).
- Anemic hypoxia in which arterial oxygen pressure is normal, but total oxygen content of the blood is reduced.
- Hypemic Hypoxia when there's an inability of the blood to carry oxygen.
- Ischemic or stagnant hypoxia in which blood flow to the tissues is too low.
- Histotoxic hypoxia in which quantity of oxygen reaching the cells is normal, but the cells are unable to effectively use the oxygen.

Intracranial pressure

Intracranial pressure, or ICP, is the pressure of the brain, Cerebrospinal fluid (CSF), and the brain's blood supply within the intracranial space. Intracranial pressure can be measured in centimetres of water (cmH₂O) or millimeters of mercury (mmHg). ICP is normally 0 to 15 mmHg in adults, up to 10 mmHg in children, and up to 5 mmHg in infants (Shepherd, 2004, Tolias and Sgouros, 2003). Since the skull is a rigid compartment of a fixed size, swelling of the brain can lead to increases in ICP, with potentially deadly results.

Increased ICP

One of the most damaging aspects of brain trauma and other conditions, directly correlated with poor outcome, is an elevated intracranial pressure (Orlando Regional Healthcare, 2004). ICP cannot go past 40 mmHg in an adult without causing severe harm (Dawodu, 2004). Even intracranial pressures between 25 and 30 mm Hg are usually fatal if prolonged, except in children, who can tolerate higher pressures for longer times (Tolias and Sgouros, 2003). Most commonly due in head injury to intracranial hematoma or cerebral edema, an increase in pressure can crush brain tissue, shift brain structures, contribute to hydrocephalus, cause the brain to herniate, and restrict blood supply to the brain, leading to an ischemic cascade (Graham and Gennareli, 2000).

Results of increased ICP

One of the main dangers of increased ICP is that it can cause ischemia by decreasing cerebral perfusion pressure (CPP), the amount of blood able to reach the brain. As pressure in the brain increases, it becomes more and more difficult to squeeze blood into the intracranial space. The body’s response to a decrease in CPP is to raise blood pressure and dilate blood vessels in the brain. This results in increased cerebral blood volume, which increases ICP, lowering CPP further and causing a vicious cycle. Increased blood pressure can also make intracranial hemorrhages bleed faster, also increasing ICP. Highly increased ICP can result in midline shift, a dangerous condition in which the brain moves toward one side as the result of massive swelling in a cerebral hemisphere. Midline shift can compress the ventricles and lead to buildup of CSF (Downie, 2001). Prognosis is much worse in patients with midline shift than in those without it (National Guideline Clearinghouse, 2005). Another dire consequence of increased ICP is brain herniation, in which the brain is squeezed past structures within the skull, severely compressing it.

Monro-Kellie model of ICP

According to the Monro-Kellie model of intracranial pressure, the brain, CSF, and cerebral blood make up three compartments within the skull, which remains a fixed size (Gruen, 2002). The extent to which each compartment takes up space within the skull is the amount of pressure it exerts; if a compartment increases in size, the intracranial pressure increases accordingly (Gruen, 2002). Thus if the brain swells, intracranial pressure goes up, unless the volume of CSF or blood can be reduced by the same amount (Gruen, 2002). Thus in head injury, CSF is commonly displaced and blood flow is reduced to reduce the intracranial volume. Unfortunately, reduction in cerebral perfusion pressure can lead to ischemia and damage to or death of brain cells, which in turn can cause the brain to swell more. The need to reduce blood volume and pressure and the need for adequate blood supply are opposing factors that make management of increased intracranial pressure especially difficult.

Causes of increased ICP

Causes of increased intracranial pressure include:
- Traumatic brain injury
- Pseudotumor cerebri
- Arnold-Chiari malformation
- A brain tumor or other mass lesion
- Severe hypertension
- Lyme disease
- Hydrocephalus One major reason for increased ICP in brain injury is dilatation of cerebral blood vessels due to a loss of autoregulation (Su and Huh, 2005). Another is cerebral edema. Another contributor to increased ICP is the reduced ability of veins to remove blood from the intracranial space, leading to its buildup. This can occur when the head is turned to the side or when medical instruments such as spinal stabilization collars are too tight, restricting flow from the jugular veins (Tolias and Sgouros, 2003). It can also occur in a condition called venous sinus thrombosis, in which a clot becomes lodged in a cerebral vein and prevents blood from exiting the skull (Shepherd, 2004). The treatment is thrombolysis to dissolve the clot, but this procedure is risky in head injury patients because it could cause other intracranial bleeds (Shepherd, 2004).

Signs and symptoms of increased ICP

The body's compensatory response to an increase in ICP leads to a set of symptoms by which the condition can be recognized in a patient. In addition to other symptoms that suggest a rise in ICP including headache, visual disturbances, nausea, vomiting, and altered level of consciousness, a cluster of symptoms called Cushing's triad indicate the body’s response to a rise in ICP. Cushing's triad involves an increased systolic blood pressure, an increasing difference between systolic and diastolic blood pressures, a decrease in pulse rate, and an abnormal respiratory pattern (Sanders et al). Irregular respirations occur when injury to parts of the brain interfere with the respiratory drive. Cheyne-Stokes respiration, in which breathing is rapid for a period and then absent for a period, occurs because of injury to the cerebral hemispheres or diencephalon (Stock and Singer, 2004). Hyperventilation occurs when the brain stem or tegmentum is damaged (Stock and Singer, 2004). In children, a slow heart rate is especially suggestive of high ICP. In infants, the fontanels, or soft spots on the head where the skull bones have not yet fused, bulge when ICP gets too high. Papilledema, while being a classic sign of elevated intracranial pressure, takes several hours to develop and is often not present in an acute setting. However, these symptoms may be vague or absent. The most reliable sign of increased intracranial pressure is decreased level of consciousness.

Treatment of increased ICP

One of the most important treatments for high ICP is to ensure adequate airway, breathing, and oxygenation, since inadequate oxygen levels or excess carbon dioxide cause cerebral blood vessels to dilate and ICP to rise (Su and Huh, 2005). Inadequate oxygen also forces brain cells to produce energy using anaerobic metabolism, which produces lactic acid and lowers pH, which dilates blood vessels (Orlando Regional Healthcare, 2004). On the other hand, blood vessels constrict when carbon dioxide levels are below normal, so hyperventilating a patient with a respirator or bag valve mask can temporarily reduce ICP but limits blood flow to the brain in a time when the brain may already be ischemic. Artificially ventilating a patient at a fast rate used to be a standard part of head trauma treatment because of its ability to rapidly lower ICP, but the chance of developing ischemia was recognized as too much of a risk (Shepherd, 2004). Furthermore, the brain adjusts to the new level of carbon dioxide after 48 to 72 hours of hyperventilation, which could cause the vessels to rapidly dilate if carbon dioxide levels were returned to normal too quickly (Shepherd, 2004). Now hyperventilation is used when signs of brain herniation are apparent because the damage herniation can cause may make it worthwhile to constrict blood vessels. Another way to lower ICP is to raise the head of the bed, allowing for venous drainage. A side effect of this is that it could lower pressure of blood to the head, resulting in inadequate blood supply to the brain. In the hospital, blood pressure can be artificially raised in order to increase CPP, increase perfusion, oxygenate tissues, remove wastes and thereby lessen swelling (Shepherd, 2004). Since hypertension is the body's way of forcing blood into the brain, medical professionals do not normally interfere with it when it is found in a head injured patient (Stock and Singer, 2004). When it is necessary to decrease cerebral blood flow, MAP can be lowered using common antihypertensive agents such as calcium channel blockers (Orlando Regional Healthcare, 2004). Struggling can increase metabolic demands and oxygen consumption, as well as increasing blood pressure (Bechtel, 2004; Su and Huh, 2005). Thus children may be paralyzed with drugs if other methods for reducing ICP fail. Paralysis allows the cerebral veins to drain more easily, but can mask signs of seizures, and the drugs can have other harmful effects (Su and Huh, 2005). Pain is also treated to reduce agitation and metabolic needs of the brain, but some pain medications may cause low blood pressure and other side effects (Orlando Regional Healthcare, 2004). Intracranial pressure can be measured by means of a lumbar puncture or continuously with intracranial transducers (only used in neurosurgical intensive care). A catheter can be surgically inserted into one of the brain's lateral ventricles. The same catheter can also be used to drain CSF to reduce pressure (Orlando Regional Healthcare, 2004). Craniotomies are holes drilled in the skull to remove intracranial hematomas or relieve pressure from parts of the brain (Orlando Regional Healthcare, 2004). A drastic treatment for increased ICP is decompressive craniectomy, in which a part of the skull is removed and the dura mater is expanded to allow the brain to swell without crushing it or causing herniation (Shepherd, 2004).

Low ICP

It is also possible for the intracranial pressure to drop below normal levels, though increased intracranial pressure is a far more common (and far more serious) sign. The symptoms for both conditions are often the same, leading many medical experts to believe that it is the change in pressure rather than the pressure itself causing the above symptoms.

References

# Bechtel K. 2004. "Pediatric Controversies: Diagnosis and Management of Traumatic Brain Injuries." Trauma Report. Supplement to Emergency Medicine Reports, Pediatric Emergency Medicine Reports, ED Management, and Emergency Medicine Alert. Volume 5, Number 3. Thomsom American Health Consultants. # Dawodu S. 2004. [http://www.emedicine.com/pmr/topic212.htm "Traumatic Brain Injury: Definition, Epidemiology, Pathophysiology"] Emedicine.com. # Downie A. 2001. [http://www.radiology.co.uk/srs-x/tutors/cttrauma/tutor.htm "Tutorial: CT in Head Trauma"] # Gruen P. 2002. [http://uscneurosurgery.com/infonet/glossary/m/monro%20kellie%20model.htm "Monro-Kellie Model" Neurosurgery Infonet. USC Neurosurgery]. # [http://www.guideline.gov/summary/summary.aspx?ss=14&doc_id=3122&string= National Guideline Clearinghouse]. 2005. Firstgov. # Orlando Regional Healthcare, Education and Development. 2004. [http://www.orhs.org/classes/nursing/TBI_04.pdf "Overview of Adult Traumatic Brain Injuries."] # Sanders MJ and McKenna K. 2001. Mosby’s Paramedic Textbook, 2nd revised Ed. Chapter 22, "Head and Facial Trauma." Mosby. # Shepherd S. 2004. [http://www.emedicine.com/med/topic2820.htm "Head Trauma."] Emedicine.com. # Stock A and Singer L. 2004. [http://www.emedicine.com/ped/topic929.htm "Head Trauma."] Emedicine.com. # Su F and Huh J. 2005. [http://www.chop.edu/ "Neurointensive Care for Traumatic Brain Injury in Children."] Emedicine.com # Tolias C and Sgouros S. 2003. [http://www.emedicine.com/med/topic3216.htm "Initial Evaluation and Management of CNS Injury."] Emedicine.com. Category:Sign (medicine) Category:Neurotrauma

Subarachnoid hemorrhage

A subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space surrounding the brain, i.e., the area between the arachnoid and the pia mater. It may arise due to trauma or spontaneously, and is a medical emergency which can lead to death or severe disability even if recognized and treated in an early stage.

Symptoms and causes

SAH can result from head trauma, the most common cause, or may occur spontaneously. Spontaneous SAH most commonly follows the rupture of a cerebral aneurysm or cerebral arteriovenous malformation, but can also be due to angioma, thrombosis, hematoma, or brain tumor.

Traumatic

SAH in a trauma patient is often detected when a patient who has been involved in an accident becomes less responsive or develops hemiplegia (one-sided weakness) or changed pupillary reflexes, and Glasgow Coma Score calculations deteriorate. Headache is not necessarily present.

Spontaneous

In spontaneous SAH, the cardinal symptom is sudden severe headache, described by patients as "like being hit over the head with a heavy object" and "the worst headache of my life". In contrast to other types of headaches which have slower onsets, the headache of SAH is sometimes called a "thunderclap headache". Neurological symptoms (like slurred speech, paralysis, and visual symptoms) and meningism are not necessarily present, but nausea, vomiting and loss of consciousness are often seen. Aneurysm related SAH has a 50% pre-hosptial mortality, highlighting the significant nature of the hemorrhage.

Diagnosis

The diagnosis is made by the clinical history, physical examination, and CT scanning. The scan may reveal blood in the sub-arachnoid space, cerebral ventricles or brain parenchyma, depending on the size and location of the bleed. In traumatic SAH (tSAH), the scan may also identify any additional intracranial injuries. Lumbar puncture may be needed for diagnosis in small subarachnoid bleeds that may not be detected on CT scans; the presence of xanthochromia -- a yellow tinge to the cerebrospinal fluid consequent to breakdown of blood -- is indicative of SAH, whereas gross blood may merely indicate a traumatic lumbar puncture. Cerebral angiography can isolate the source of bleeding prior to surgical treatment.

Classification

The Hunt and Hess scale (1968) of subarachnoid hemorrhage severity is:
- Grade 1: Asymptomatic; or minimal headache and slight nuchal rigidity.
- Grade 2: Moderate to severe headache; nuchal rigidity; no neurologic deficit except cranial nerve palsy.
- Grade 3: Drowsy; minimal neurologic deficit.
- Grade 4: Stuporous; moderate to severe hemiparesis; possibly early decerebrate rigidity and vegetative disturbances.
- Grade 5: Deep coma; decerebrate rigidity; moribund.

Treatment

Neurosurgical intervention is necessary in severe or traumatic SAH, especially in the case of high or increasing Hunt-Hess scoring. This may be by craniotomy and external clipping of the bleeding vessel or aneurysm, or by interventional radiology (neuroradiology), which employs transfemoral angiography and inserting of metal coils to stem the bleeding (which is especially useful in aneurysmatic hemorrhage). In case of spontaneous rupture of aneurysm, there are few evidence-based guidelines on the timing of neurosurgical interventions, and this often depends on the clinical experience and guidelines of local interventional centers. There is, however, a risk of re-rupture of the aneurysm and most experts favor intervention as soon as the appropriate operating room and personnel resources can be mobilized. Medical treatment also involves absolute bedrest with the head slightly elevated to encourage venous flow away from the area of the hemorrhage. Apart from neurosurgery and nimodipine, the somewhat obsolete "Triple H" approach is used by some centers. This involves hypertensive hypervolemic hemodilution (keeping blood pressure and circulating volume high with relative anemia). This treatment is most useful in patients exhibiting symptoms of vasospasm, which may be verified by transcranial doppler or cerebral angiography. A patient who recovers without immediate intervention may receive follow-up angiography to identify aneurysms which may be amenable to coiling to prevent recurrent episodes of SAH.

Complications

Complications of SAH can be acute, subacute, or chronic.
- Acute:
- Coma and brainstem herniation due to increased intracranial pressure (ICP)
- Pulmonary edema ("neurogenic pulmonary edema") as a result of the suddenly increased ICP
- Cardiac arrhythmias and myocardial damage
- Hydrocephalus, which may also happen in the subacute time frame
- Subacute:
- Vasospasm, leading to ischemia of the brain (can be prevented partially with the calcium channel antagonist nimodipine)
- Hyponatremia (low sodium levels) - due to SIADH or cerebral salt wasting syndrome
- Chronic:
- Long-term immobility
- Pneumonia and pulmonary embolism (due to immobility)
- SAH recurrence (20% within two weeks if the aneurysm is not secured by clipping or coiling)
- Persistent neurologic deficits

External links

- [http://www.emedicine.com/NEURO/topic357.htm Emedicine] article on SAH
- [http://neuroland.com/cvd/sah.htm Neuroland] SAH page
- [http://www.rnceus.com/course_frame.asp?exam_id=21&directory=sah| Subarachnoid Hemorrhage: Caring for the Patient] Continuing Ed for Nurses

Reference

- Hunt WE, Hess RM. Surgical risk as related to time of intervention in the repair of intracranial aneurysms. J Neurosurg 1968;28:14-9. PMID 5635959. Category:Neurotrauma Category:Neurosurgery Category:Intensive care medicine ja:%E3%82%AF%E3%83%A2%E8%86%9C%E4%B8%8B%E5%87%BA%E8%A1%80

Alcohol

In general usage, alcohol (from Arabic al-ghawl الغول) refers almost always to ethanol, also known as grain alcohol, and often to any beverage that contains ethanol (see alcoholic beverage). This sense underlies the term alcoholism (addiction to alcohol). Other forms of alcohol are usually described with a clarifying adjective, as in isopropyl alcohol or by the suffix -ol, as in isopropanol. In chemistry, alcohol is a more general term, applied to any organic compound in which a hydroxyl group (-O H) is bound to a carbon atom, which in turn is bound to other hydrogen and/or carbon atoms. The general formula for a simple acyclic alcohol is C_nH_2n+1OH. As a drug, common alcohol (ethanol) is known to have a depressing effect that decreases the responses of the central nervous system.

Structure

central nervous system The functional group of an alcohol is a hydroxyl group bonded to an sp³ hybridized carbon. It can therefore be regarded as a derivative of water, with an alkyl group replacing one of the hydrogens. If an aryl group is present rather than an alkyl, the compound is generally called a phenol rather than an alcohol. The oxygen in an alcohol has a bond angle of around 109° (c.f. 104.5° in water), and two nonbonded electron pairs. The O-H bond in methanol (CH₃OH) is around 96 picometres long.

Primary, secondary, and tertiary alcohols

There are three major subsets of alcohols- 'primary' (1°), 'secondary' (2°) and 'tertiary' (3°), based upon the number of carbons the C-OH carbon (shown in red) is bonded to. Methanol is the simplest 'primary' alcohol. The simplest secondary alcohol is isopropanol (propan-2-ol), and a simple tertiary alcohol is tert-butanol (2-methylpropan-2-ol). butanol

Methanol & ethanol

The simplest and most commonly used alcohols are methanol and ethanol (common names methyl alcohol and ethyl alcohol, respectively), which have the structures shown above. Methanol was formerly obtained by the distillation of wood, and was called "wood alcohol". It is now a cheap commodity chemical produced by the high pressure reaction of carbon monoxide with hydrogen. In common usage, "alcohol" often refers simply to ethanol or "grain alcohol". Methylated spirits ("Meths"), also called "surgical spirits", is a form of ethanol rendered undrinkable by the addition of methanol. Aside from its major use in alcoholic beverages, ethanol is also used (though highly controlled) as an industrial solvent and raw material.

Uses

Alcohols are in wide use in industry and science as reagents, solvents, and fuels. Ethanol and methanol can be made to burn more cleanly than gasoline or diesel. Because of its low toxicity and ability to dissolve non-polar substances, ethanol is often used as a solvent in medical drugs, perfumes, and vegetable essences such as vanilla. In organic synthesis, alcohols frequently serve as versatile intermediates. Ethanol is also commonly used in beverages after fermentation to promote flavor or induce a euphoric intoxication commonly known as "drunkenness" or "being drunk". The use of ethanol for this purpose is illegal in some jurisdictions.

Sources

Many alcohols can be created by fermentation of fruits or grains with yeast, but only ethanol is commercially produced this way, chiefly for fuel and drink. Other alcohols are generally produced by synthetic routes from natural gas, petroleum, or coal feed stocks, for example via acid catalyzed hydration of alkenes. For more details see Chemistry of alcohols

Nomenclature

Systematic names

In the IUPAC system, the name of the alkane chain loses the terminal "e" and adds "ol", e.g. "methanol" and "ethanol". When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the "ol": propan-1-ol for CH₃CH₂CH₂OH, propan-2-ol for CH₃CH(OH)CH₃. Sometimes, the position number is written before the IUPAC name: 1-propanol and 2-propanol. If a higher priority group is present (such as an aldehyde, ketone or carboxylic acid), then it is necessary to use the prefix "hydroxy", for example: 1-hydroxy-2-propanol (CH₃COCH₂OH). Some examples of simple alcohols and how to name them: carboxylic acid Common names for alcohols usually take the name of the corresponding alkyl group and add the word "alcohol", e.g. methyl alcohol, ethyl alcohol or tert-butyl alcohol. Propyl alcohol may be n-propyl alcohol or isopropyl alcohol depending on whether the hydroxyl group is bonded to the 1st or 2nd carbon on the propane chain. Isopropyl alcohol is also occasionally called sec-propyl alcohol. As mentioned above alcohols are classified as primary (1°), secondary (2°) or tertiary (3°), and common names often indicate this in the alkyl group prefix. For example (CH₃)₃COH is a tertiary alcohol is commonly known as tert-butyl alcohol. This would be named 2-methylpropan-2-ol under IUPAC rules, indicating a propane chain with methyl and hydroxyl groups both attached to the middle (#2) carbon. An alcohol with two hydroxyl groups is commonly called a "glycol", e.g. HO-CH₂-CH₂-OH is ethylene glycol. The IUPAC name is ethane-1,2-diol, "diol" indicating two hydroxyl groups, and 1,2 indicating their bonding positions. Geminal glycols (with the two hydroxyls on the same carbon atom), such as ethane-1,1-diol, are generally unstable. For three or four groups, "triol" and "tetraol" are used.

Etymology

The word "alcohol" almost certainly comes from the Arabic language (the "al-" prefix being the Arabic definite article); however, the precise origin is unclear. It was introduced into Europe, together with the art of distillation and the substance itself, around the 12th century by various European authors who translated and popularized the discoveries of Islamic alchemists. A popular theory, found in many dictionaries, is that it comes from الكحل = ALKHL = al-kuhul, originally the name of very finely powdered antimony sulfide Sb₂S₃ used as an antiseptic and eyeliner. The powder is prepared by sublimation of the natural mineral stibnite in a closed vessel. According to this theory, the meaning of alkuhul would have been first extended to distilled substances in general, and then narrowed to ethanol. This conjectured etymology has been circulating in England since 1672 at least (OED). However, this derivation is suspicious since the current Arabic name for alcohol, الكحول = ALKHWL = al???, does not derive from al-kuhul. The Qur'an in verse 37:47 uses the word الغول = ALGhWL = al-ghawl — properly meaning "spirit" ("spiritual being") or "demon" — with the sense "the thing that gives the wine its headiness". The word al-ghawl also originated the English word "ghoul", and the name of the star Algol. This derivation would, of course, be consistent with the use of "spirit" or "spirit of wine" as synonymous of "alcohol" in most Western languages. (Incidentally, the etymology "alcohol" = "the devil" was used in the 1930s by the U.S. Temperance Movement for propaganda purposes.) According to the second theory, the popular etymology and the spelling "alcohol" would not be due to generalization of the meaning of ALKHL, but rather to Western alchemists and authors confusing the two words ALKHL and ALGhWL, which have indeed been transliterated in many different and overlapping ways.

Physical and chemical properties

The hydroxyl group generally makes the alcohol molecule polar. Those groups can form hydrogen bonds to one another and to other compounds. Two opposing solubility trends in alcohols are: the tendency of the polar OH to promote solubility in water, and of the carbon chain to resist it. Thus, methanol, ethanol, and propanol are miscible in water because the hydroxyl group wins out over the short carbon chain. Butanol, with a four-carbon chain, is moderately soluble because of a balance between the two trends. Alcohols of five or more carbons (Pentanol and higher) are effectively insoluble because of the hydrocarbon chain's dominance. Because of hydrogen bonding, alcohols tend to have higher boiling points than comparable hydrocarbons and ethers. All simple alcohols are miscible in organic solvents. This hydrogen bonding means that alcohols can be used as protic solvents. The lone pairs of electrons on the oxygen of the hydroxyl group also makes alcohols nucleophiles. Alcohols, like water, can show either acidic or basic properties at the O-H group. With a pK_a of around 16-19 they are generally slightly weaker acids than water, but they are still able to react with strong bases such as sodium hydride or reactive metals such as sodium. The salts that result are called alkoxides, with the general formula RO^- M⁺. Meanwhile the oxygen atom has lone pairs of nonbonded electrons that render it weakly basic in the presence of strong acids such as sulfuric acid. For example, with methanol: sulfuric acid Alcohols can also undergo oxidation to give aldehydes, ketones or carboxylic acids, or they can be dehydrated to alkenes. They can react to form ester compounds, and they can (if activated first) undergo nucleophilic substitution reactions. For more details see the #Chemistry of alcohols section below.

Toxicity

Alcohols often have an odor described as 'biting' that 'hangs' in the nasal passages. Ethanol in the form of alcoholic beverages has been consumed by humans since pre-historic times, for a variety of hygienic, dietary, medicinal, religious, and recreational reasons. While infrequent consumption of ethanol in small quantities may be harmless or even beneficial, larger doses result in a state known as drunkenness or intoxication and, depending on the dose and regularity of use, can cause acute respiratory failure or death and with chronic use has medical repercussions. Other alcohols are substantially more poisonous than ethanol, partly because they take much longer to be metabolized, and often their metabolism produces even more toxic substances. Methanol, or wood alcohol, for instance, is oxidized by alcohol dehydrogenase enzymes in the liver to the poisonous formaldehyde, which can cause blindness or death. Interestingly, an effective treatment to prevent formaldehyde toxicity after methanol ingestion is to administer ethanol. This will bind to alcohol dehydrogenase, preventing methanol from binding and thus acting as a substrate. Any formaldehyde will be converted to formic acid and excreted before it causes damage.

Chemistry of alcohols

Preparation

Laboratory

There are three common methods:
- From alkyl halides: react with aqueous NaOH or KOH (mainly 1° alcohols). :R-Br + KOH → R-OH + KBr
- From aldehydes or ketones: reduction with sodium borohydride or lithium aluminium hydride. :R-CHO - [O] → R-OH
- From alkenes: an acid catalysed hydration reaction using concentrated sulfuric acid as a catalyst (gives usually 2° or 3° alcohols). :C₂H₄ + H₂SO₄ (l) → C₂H₅-HSO₄ :C₂H₅-HSO₄ + H₂O → C₂H₅OH + H₂SO₄ The formation of a secondary alcohol via the last two methods is shown: sulfuric acid

Industrial

- Fermentation: using glucose produced from sugar from the hydrolysis of starch, in the presence of yeast and temperature of <37°C to produce ethanol. :C₁₂H₂₂O₁₁ → C₆H₁₂O₆ + C₆H₁₂O₆ :Invertase → glucose + fructose :C₆H₁₂O₆ + H₂O → C₂H₅OH + CO₂ :Glucose → zymase + ethanol
- Direct hydration: using ethene or other alkenes from cracking of fractions of distilled crude oil. Uses a catalyst of phosphoric acid under high temperature and pressure.
- Methanol from water gas: It is manufactured from synthesis gas, where CO + 2 H₂ are combined to produce methanol using a Cu, ZnO and Al₂O₃ catalyst at 250°C and a pressure of 50-100 atm. :[CO + H₂] + H₂O (g) → CH₃OH

Reactions

See the physical and chemical properties section above for a general overview.

Deprotonation

Alcohols can behave as weak acids, undergoing deprotonation. The deprotonation reaction to produce an alkoxide salt is either performed with a strong base such as sodium hydride or n-butyllithium, or with sodium or potassium metal. : 2 R-OH + 2 NaH → 2 R-O^-Na⁺ + H₂↑ : 2 R-OH + 2Na → 2R-O⁻Na⁺ : e.g. 2 CH₃CH₂-OH + 2 Na → 2 CH₃-CH₂-O⁻Na⁺ Water is similar in pK_a to many alcohols, so with sodium hydroxide there is an equilibrium set up which usually lies to the left: : R-OH + NaOH <=> R-O^-Na⁺ + H₂O (equilibrium to the left)

Nucleophilic substitution

The OH group is not a good leaving group in nucleophilic substitution reactions, so neutral alcohols do not react in such reactions. However if the oxygen is first protonated to give R−OH₂⁺, the leaving group (water) is much more stable, and nucleophilic substitution can take place. For instance, tertiary alcohols react with hydrochloric acid to produce tertiary alkyl halides, where the hydroxyl group is replaced by a chlorine atom. If primary or secondary alcohols are to be reacted with hydrochloric acid, an activator such as zinc chloride is needed. Alternatively the conversion may be performed directly using thionyl chloride.^[1] thionyl chloride Alcohols may likewise be converted to alkyl bromides using hydrobromic acid or phosphorus tribromide, for example: : 3 R-OH + PBr₃ → 3 RBr + H₃PO₃ In the Barton-McCombie deoxygenation an alcohol is deoxygenated to an alkane with tributyltin hydride or a trimethylborane-water complex in a radical substitution reaction.

Dehydration

Alcohols are themselves nucleophilic, so R−OH₂⁺ can react with ROH to produce ethers and water, although this reaction is rarely used except in the manufacture of diethyl ether. More useful is the E1 elimination reaction of alcohols to produce alkenes. The reaction generally obeys Zaitsev's Rule, which states that the most stable (usually the most substituted) alkene is formed. Tertiary alcohols eliminate easily at just above room temperature, but primary alcohols requre a higher temperature. This is a diagram of acid catalysed dehydration of ethanol to produce ethene: 550px

Esterification

To form an ester from an alcohol and a carboxylic acid the reaction, known as "Fischer esterification", is usually performed at reflux with a catalyst of concentrated sulfuric acid: : R-OH + R'-COOH

\Leftrightarrow

R'-COOR + H₂O In order to drive the equilibrium to the right and produce a good yield of ester, water is usually removed, either by an excess of H₂SO₄ or by using a Dean-Stark apparatus. Esters may also be prepared by reaction of the alcohol with an acid chloride in the presence of a base such as pyridine. Other types of ester are prepared similarly- for example p-toluenesulfonate (tosylate) esters are made by reaction of the alcohol with p-toluenesulfonyl chloride in pyridine.

Oxidation

Primary alcohols generally give aldehydes or carboxylic acids upon oxidation, while secondary alcohols give ketones. Traditionally strong oxidants such as the dichromate ion or potassium permanganate are used, under acidic conditions, for example: :3 CH₃-CH(-OH)-CH₃ + K₂Cr₂O₇ + 4 H₂SO₄ → 3 CH₃-C(=O)-CH₃ + Cr₂(SO₄)₃ + K₂SO₄ + 7 H₂O Frequently in aldehyde preparations these reagents cause a problem of over-oxidation to the carboxylic acid. To avoid this, other reagents such as PCC, Dess-Martin periodinane, IBX acid, TPAP or methods such as Swern oxidation are now preferred. Alcohols with a methyl group attached to the alcohol carbon can also undergo a haloform reaction (such as the iodoform reaction) in the presence of the halogen and a base such as sodium hydroxide. Tertiary alcohols resist oxidation, but can be oxidised by reagents such as 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.

External links

- [http://www.french-paradox.net/fpbksb1.html What Is Alcohol, Anyway?] Interesting information about alcohols.
- Category:Drugs Category:Antiseptics Category:Arabic words Category:functional groups ja:アルコール simple:Alcohol

Opiate

The term opiate refers to the alkaloids found in opium, an extract from the seed pods of the opium poppy (Papaver somniferum L.). It has also traditionally referred to natural and semi-synthetic derivatives of morphine. The term is often incorrectly used to refer to all drugs with opium-/morphine-like pharmacological action, which are more properly classified under the broader term opioid. The main opiates from opium are morphine, codeine and thebaine. Papaverine is also present, but has essentially no effect on the central nervous system, so is not an opioid. Papaverine is sometimes used as a vasodilator in cardiac patients. See opioid for a fuller discussion. Category:Opioids th:โอปิแอต

Sedative

A sedative is a drug that depresses the central nervous system (CNS), which causes calmness, relaxation, reduction of anxiety, sleepiness, slowed breathing, slurred speech, staggering gait, poor judgment, and slow, uncertain reflexes. Sedatives may be referred to as tranquilizers, depressants, anxiolytics, soporifics, sleeping pills, downers, or sedative-hypnotics. At high doses or when they are abused, many of these drugs can cause unconsciousness and death.

Types of sedative

- Barbiturates
- secobarbital (Seconal)
- pentobarbital (Nembutal)
- amobarbital (Amytal)
- Benzodiazepines
- diazepam (Valium)
- clonazepam (Klonopin)
- chlordiazepoxide (Librium)
- flunitrazepam (Rohypnol)
- lorazepam (Ativan)
- chlorazepate (Tranxene)
- Imidazopyridines
- zolpidem (Ambien)
- alpidem
- Pyrazolopyrimidines
- Zaleplon (Sonata)
- Antihistamines
- diphenhydramine (Benadryl)
- dimenhydrinate (Dramamine) (Sominex)
- doxylamine
- Herbal sedatives
- valerian plant
- Mandrake
- kava
- Uncategorized sedatives
- methaqualone (Sopor, Quaalude)
- ethchlorvynol (Placidyl)
- chloral hydrate (Noctec)
- meprobamate (Miltown)
- glutethimide (Doriden)
- methyprylon (Noludar)
- gamma-hydroxybutyrate (GHB)
- ethyl alcohol (Alcoholic beverage)
- diethyl ether (Ether)
- methyl trichloride (Chloroform)

Therapeutic use

Doctors and nurses often administer sedation to patients in order to dull the patient's anxiety related to painful or anxiety-provoking procedures. Athough sedatives do not relieve pain in themselves, they can be a useful adjunct to analgesics in preparing patients for surgery, and are commonly given to patients before they are anaesthetized, or before other highly uncomfortable and invasive procedures like cardiac catheterization or MRI. They increase tractability and compliance of children or troublesome or demanding patients. Patients in intensive care units are almost always sedated (unless they are unconscious from their condition anyway).

Sedative dependence

All sedatives can cause physical and psychological dependence when taken regularly over a period of time, even at therapeutic doses. When dependent users decrease or end use suddenly, they will exhibit withdrawal symptoms ranging from restlessness, insomnia and anxiety to convulsions and death. When users become psychologically dependent, they feel as if they need the drug to function although there is no biological dependence. In both types of dependence, finding and using the drug becomes the focus in life. Both physical and psychological dependence can be treated (see [http://www.mentalhealth.com/rx/p23-sb10.html Sedative Dependence]).

Abuse and overdoses

All sedatives can be abused, but barbiturates are responsible for most of the problems with sedative abuse due to their widespread "recreational" or non-medical use, as well as over-prescribing by medical doctors. People who have difficulty dealing with stress, anxiety or sleeplessness may overuse or become dependent on sedatives. Heroin users take them either to supplement their drug or to substitute for it. Stimulant users frequently take sedatives to calm excessive jitteriness. Others take sedatives recreationally to relax and forget their worries. Barbiturate overdose is a factor in nearly one-third of all reported drug-related deaths. These include suicides and accidental drug poisonings. Accidental deaths sometimes occur when a drowsy, confused user repeats doses. In the US, in 1998, a total of 70,982 sedative exposures were reported to US poison control centers, of which 2310 (3.2%) resulted in major toxicity and 89 (0.1%) resulted in death. About half of all the people admitted to emergency rooms in the US as a result of nonmedical use of sedatives have a legitimate prescription for the drug, but have taken an excessive dose or combined it with alcohol or other drugs. Others get sedatives from friends who have authentic prescriptions or by using fake prescriptions. See also Barbiturate#Other_non-therapeutical_use.

Sedatives and alcohol

Sedatives and alcohol are sometimes combined recreationally or carelessly. Since alcohol also is a strong CNS depressant that slows brain function and depresses respiration, the two substances reinforce each other and this combination can prove fatal.

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