2014-11-27T01:29:04Z

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==Overview==
'''Anesthesia''' or '''anaesthesia''' (from [[Greek language|Greek]] ''αν-'' ''an-'' “without” + ''αἲσθησις'' ''aisthesis'' “sensation”) has traditionally meant the condition of having the feeling of [[Pain and nociception|pain]] and other [[sensation]]s blocked. This allows patients to undergo [[surgery]] and other procedures without the distress and pain they would otherwise experience. The word was coined by [[Oliver Wendell Holmes, Sr.]] in 1846. Another definition is a "reversible lack of awareness", whether this is a total lack of awareness (e.g. a general anaesthestic) or a lack of awareness of a part of a the body such as a spinal anaesthetic or another nerve block would cause.

Today, the term '''general anesthesia''' in its most general form can include:
* [[Analgesic|Analgesia]]: blocking the [[consciousness|conscious]] sensation of pain;
* Hypnosis: produces [[unconsciousness]] without analgesia;
* [[Amnesia]]: preventing [[memory]] formation;
* [[Neuromuscular-blocking drugs|Relaxation]]: preventing unwanted movement or muscle tone;
* [[Obtundation]] of reflexes, preventing exaggerated autonomic reflexes.

Patients undergoing surgery usually undergo preoperative evaluation. It includes gathering history of previous anesthetics, and any other medical problems, physical examination, ordering required blood work and consultations prior to surgery.

There are several forms of anesthesia. The following forms refer to states achieved by anesthetics working on the brain:
*General anesthesia: "Drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation." Patients undergoing general anesthesia often cannot maintain their own airway and breathe on their own. While usually administered with inhalational agents, general anesthesia can be achieved with [[Intravenous therapy|intravenous]] agents, such as [[propofol]].<ref name="asadepth">{{Citation
| contribution = Continuum Of Depth Of Sedation Definition Of General Anesthesia And Levels Of Sedation/Analgesia
| title = American Society of Anesthesiologists
| publisher = ASA
| date = [[2004-10-27]]
| year = 2004
| contribution-url = http://www.asahq.org/publicationsAndServices/standards/20.pdf }}</ref>
*Deep [[sedation]]/analgesia: "Drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated or painful stimulation." Patients may sometimes be unable to maintain their airway and breathe on their own.<ref name="asadepth" />
*Moderate sedation/analgesia or conscious sedation: "Drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation." In this state, patients can breathe on their own and need no help maintaining an airway.<ref name="asadepth" />
* Minimal sedation or anxiolysis: "Drug-induced state during which patients respond normally to verbal commands." Though concentration, memory, and coordination may be impaired, patients need no help breathing or maintaining an airway.<ref name="asadepth" />

The level of anesthesia achieved ranges on a continuum of depth of consciousness from minimal sedation to general anesthesia. The depth of consciousness of a patient may change from one minute to the next.

The following refer to states achieved by anesthetics working outside of the brain:
*Regional anesthesia: Loss of pain sensation, with varying degrees of muscle relaxation, in certain regions of the body. Administered with local anesthesia to peripheral nerve bundles, such as the brachial plexus in the neck. Examples include the interscalene block for shoulder surgery, axillary block for wrist surgery, and [[femoral nerve]] block for leg surgery. While traditionally administered as a single injection, newer techniques involve placement of indwelling [[catheters]] for continuous or intermittent administration of local anesthetics.
**[[Spinal anesthesia]]: also known as subarachnoid block. Refers to a Regional block resulting from a small volume of local anesthetics being injected into the [[spinal canal]]. The spinal canal is covered by the [[dura mater]], through which the spinal needle enters. The spinal canal contains [[cerebrospinal fluid]] and the [[spinal cord]]. The sub arachnoid block is usually injected between the 4th and 5th [[lumbar]] [[vertebra]]e, because the spinal cord usually stops at the 1st lumbar vertebra, while the canal continues to the [[sacrum|sacral]] vertebrae. It results in a loss of pain sensation and muscle strength, usually up to the level of the chest (nipple line or 4th thoracic [[dermatomic area|dermatome]]).
**[[Epidural|Epidural anesthesia]]: Regional block resulting from an injection of a large volume of local anesthetic into the [[epidural space]]. The epidural space is a [[potential space]] that lies underneath the [[ligamenta flava]], and outside the dura mater (outside layer of the spinal canal). This is basically an injection around the spinal canal.
* [[Local anesthesia]] is similar to regional anesthesia, but exerts its effect on a smaller area of the body.

==History==
===Herbal derivatives===
The first [[herbalism|herbal]] anesthesia was administered in prehistory. [[Opium]] poppy capsules were collected in 4200 BC, and opium poppies were farmed in Sumeria and succeeding empires. The use of opium-like preparations in anaesthesia is recorded in the Ebers Papyrus of 1500 BC. By 1100 BC poppies were scored for opium collection in Cyprus by methods similar to those used in the present day, and simple apparatus for smoking of opium were found in a Minoan temple. Opium was not introduced to India and China until 330 BC and 600–1200 AD, but these nations pioneered the use of cannabis incense and [[aconitum]]. In the second century, according to the Book of Later Han, the physician Hua Tuo performed abdominal surgery using an anesthetic substance called ''mafeisan'' (麻沸散 "cannabis boil powder") dissolved in wine. Throughout Europe, Asia, and the Americas a variety of Solanum species containing potent [[tropane]] alkaloids were used, such as mandrake, [[henbane]], [[Datura metel]], and [[Datura inoxia]]. Classic Greek and Roman medical texts by Hippocrates, Theophrastus, Aulus Cornelius Celsus, Pedanius Dioscorides, and Pliny the Elder discussed the use of opium and Solanum species, and treatment with the combined alkaloids proved a mainstay of anaesthesia until the nineteenth century. In the Americas [[coca]] was also an important anaesthetic used in [[Trepanation|trephining]] operations. Incan shamans chewed [[coca]] leaves and performed operations on the skull while spitting into the wounds they had inflicted to anaesthetize the site. [[ethanol|Alcohol]] was also used, its [[vasodilation|vasodilatory]] properties being unknown. Ancient herbal anaesthetics have variously been called soporifics, [[anodyne]]s, and [[narcotic]]s, depending on whether the emphasis is on producing unconsciousness or relieving pain.

In Central Asia, in the 10th century work of Shahnameh, the author, Ferdowsi, describes a [[caesarean section]] performed on Rudaba when giving birth, in which a special wine agent was prepared as an anesthetic<ref>''Medicine throughout Antiquity''. Benjamin Lee Gordon. 1949. p.306</ref> by a Zoroastrian priest, and used to produce unconsciousness for the operation. Although largely mythical in content, the passage does at least illustrate knowledge of anesthesia in ancient Persia.

The use of herbal anaesthesia had a crucial drawback compared to modern practice — as lamented by Fallopus, "When soporifics are weak they are useless, and when strong, they kill." To overcome this, production was typically standardized as much as feasible, with production occurring from specific famous locations (such as opium from the fields of Thebes in ancient Egypt). Anaesthetics were sometimes administered in the spongia somnifera, a sponge into which a large quantity of drug was allowed to dry, from which a saturated solution could be trickled into the nose of the patient. At least in more recent centuries, trade was often highly standardized, with the drying and packing of [[opium]] in standard chests, for example. In the 19th century, varying [[aconitum]] alkaloids from a variety of species were standardized by testing with guinea pigs. Despite these refinements, the discovery of [[morphine]], a purified alkaloid that soon afterward could be injected by [[Hypodermic needle|hypodermic]] for a consistent dosage, was enthusiastically received and led to the foundation of the modern pharmaceutical industry.

Another factor affecting ancient anaesthesia is that drugs used systemically in modern times were often administered locally, reducing the risk to the patient. [[Opium]] used directly in a wound acts on peripheral [[opioid receptor]]s to serve as an analgesic, and a medicine containing willow leaves ([[salicylate]], the predecessor of [[aspirin]]) would then be applied directly to the source of inflammation.

In 1804, the Japanese surgeon Hanaoka Seishū performed general [[anaesthesia]] for the operation of a breast cancer ([[mastectomy]]), by combining Chinese herbal medicine know-how and Western [[surgery]] techniques learned through "Rangaku", or "Dutch studies". His patient was a 60-year-old woman called Kan Aiya.<ref>[http://www.general-anaesthesia.com/ Utopian surgery: Early arguments against anaesthesiain surgery, dentistry and childbirth]</ref> He used a compound he called Tsusensan, based on the plants Datura metel, Aconitum and others.

===Non-pharmacological methods===
[[Hypnosurgery|Hypnotism]] and [[acupuncture]] have a long history of use as anesthetic techniques. In China, Taoist medical practitioners developed anesthesia by means of [[acupuncture]]. Chilling tissue (e.g. with ice) can temporarily cause nerve fibers ([[axon]]s) to stop conducting sensation, while [[hyperventilation]] can cause brief alteration in conscious perception of stimuli including pain (see [[Lamaze]]).

In modern anesthetic practice, these techniques are seldom employed.

===Early gases and vapours===
The works of Greek authors such as [[Dioscorides]] were well-known in the Islamic Empire, and physicians such as al-Razi, [[Avicenna]], and Abu al-Qasim wrote medical textbooks of great importance in the development of medicine in Europe and the Middle East. Muslim [[anesthesiologist]]s were the first to utilize oral as well as [[Inhalational anaesthetic|inhalant anesthetics]]. In Islamic Spain, Abu al-Qasim (Abulcasis) and Ibn Zuhr (Avenzoar), among other Muslim surgeons, performed hundreds of [[Surgery|surgeries]] under inhalant anesthesia with the use of [[narcotic]]-soaked sponges which were placed over the face. Abulcasis and Ibn Sina (Avicenna) wrote about anasthesia in their influential medical encyclopedias, the ''al-Tasrif'' and ''[[The Canon of Medicine]]''.<ref>Dr. Kasem Ajram (1992). ''Miracle of Islamic Science'', Appendix B. Knowledge House Publishers. ISBN 0911119434.</ref><ref>[[Sigrid Hunke]] (1969), ''Allah Sonne Uber Abendland, Unser Arabische Erbe'', Second Edition, p. 279-280: {{quote|"The science of medicine has gained a great and extremely important discovery and that is the use of general anaesthetics for surgical operations, and how unique, efficient, and merciful for those who tried it the Muslim anaesthetic was. It was quite different from the drinks the Indians, Romans and Greeks were forcing their patients to have for relief of pain. There had been some allegations to credit this discovery to an Italian or to an Alexandrian, but the truth is and history proves that, the art of using the anaesthetic sponge is a pure Muslim technique, which was not known before. The sponge used to be dipped and left in a mixture prepared from cannabis, opium, hyoscyamus and a plant called Zoan."}} ([[cf.]] Prof. Dr. M. Taha Jasser, [http://www.islamset.com/hip/i_medcin/taha_jasser.html Anaesthesia in Islamic medicine and its influence on Western civilization], Conference
on Islamic Medicine)</ref>

[[Image:Southworth & Hawes - First etherized operation (re-enactment).jpg|thumb|right|300px|Contemporary re-enactment of Morton's October 16, 1846, ether operation; daguerrotype by Southworth & Hawes.]]

In the West, the development of effective anesthetics in the 19th century was, with Listerian techniques, one of the keys to successful surgery. Henry Hill Hickman experimented with [[carbon dioxide]] in the 1820s. The anesthetic qualities of [[nitrous oxide]] (isolated in 1773 by Joseph Priestley) were discovered by the British chemist Humphry Davy about 1799 when he was an assistant to Thomas Beddoes, and reported in a paper in 1800. But initially the medical uses of this so-called "laughing gas" were limited — its main role was in entertainment. It was used on 30 September 1846 for painless tooth extraction upon patient Eben Frost by American [[dentist]] William Thomas Green Morton. Horace Wells of Connecticut, a traveling dentist, had demonstrated it the previous year 1845, at Massachusetts General Hospital. Wells made a mistake, in choosing a particularly sturdy male volunteer, and the patient suffered considerable pain. This lost the colorful Wells any support. Later the patient told Wells he screamed in shock and not in pain. A subsequently drunk Wells died in jail, by cutting his femoral artery, after allegedly assaulting a prostitute with sulfuric acid.

Another dentist,William E. Clarke, performed an extraction in January 1842 using a different chemical, [[diethyl ether]] (discovered by Valerius Cordus in 1540). In March 1842 in Danielsville, Georgia, Dr. Crawford Long was the first to use anaesthesia during an operation, giving it to a boy (John Venables) before excising a cyst from his neck; however, he did not publicize this information until later.

On October 16, 1846, another dentist, William Thomas Green Morton, invited to the Massachusetts General Hospital, performed the first public demonstration of diethyl ether (then called sulfuric ether) as an anesthetic agent, for a patient (Edward Gilbert Abbott) undergoing an excision of a vascular tumor from his neck. In a letter to Morton shortly thereafter, Oliver Wendell Holmes, Sr. proposed naming the procedure ''anæsthesia''.
[[Image:CrawfordLong.jpg|left|thumb|180px|Anesthesia pioneer Crawford W. Long]]
Despite Morton's efforts to keep "his" compound a secret, which he named "Letheon" and for which he received a US patent, the news of the discovery and the nature of the compound spread very quickly to Europe in late 1846. Here, respected surgeons—including Liston, Dieffenbach, Pirogoff, and Syme—undertook numerous operations with [[ether]].
An American-born physician, Boott — who had traveled to London — encouraged a leading dentist, Mr James Robinson, to perform a dental procedure on a Miss Lonsdale. This was the first case of an operator-anesthetist. On the same day, 19 December 1846 in Dumfries Royal Infirmary, Scotland, a Dr. Scott used ether for a surgical procedure. The first use of anesthesia in the Southern Hemisphere took place in Launceston, Tasmania, that same year. Ether has a number of drawbacks, such as its tendency to induce [[vomiting]] and its flammability. In England it was quickly replaced with [[chloroform]].

Discovered in 1831, the use of chloroform in anesthesia is usually linked to James Young Simpson, who, in a wide-ranging study of organic compounds, found chloroform's efficacy on 4 November 1847. Its use spread quickly and gained royal approval in 1853 when John Snow gave it to Queen Victoria during the birth of Prince Leopold. Unfortunately, chloroform is not as safe an agent as ether, especially when administered by an untrained practitioner (medical students, nurses, and occasionally members of the public were often pressed into giving anesthetics at this time). This led to many deaths from the use of chloroform that (with hindsight) might have been preventable. The first fatality directly attributed to chloroform anesthesia (Hannah Greener) was recorded on 28 January 1848.

John Snow of London published articles from May 1848 onwards 'On Narcotism by the Inhalation of Vapours' in the London Medical Gazette. Snow also involved himself in the production of equipment needed for inhalational anesthesia.

The surgical amphitheatre at Massachusetts General Hospital, or "ether dome" still exists today, although it is used for lectures and not surgery. The public can visit the amphitheater on weekdays when it is not in use.

===Early local anesthetics===
The first effective local anesthetic was [[cocaine]]. Isolated in 1859, it was first used by Karl Koller, at the suggestion of Sigmund Freud, in ophthalmic surgery in 1884. Before that doctors had used a salt and ice mix for the numbing effects of cold, which could only have limited application. Similar numbing was also induced by a spray of ether or ethyl chloride. A number of cocaine derivatives and safer replacements were soon produced, including [[procaine]] (1905), Eucaine (1900), Stovaine (1904), and [[lidocaine]] (1943).

[[Opioid]]s were first used by Racoviceanu-Piteşti, who reported his work in 1901.

==Anesthesia providers==

Physicians specialising in peri-operative care, development of an anesthetic plan, and the administration of anesthetics are known in the United States as anesthesiologists and in the UK and Canada as anaesthetists or anaesthesiologists. All anaesthetics in the UK, Australia, New Zealand and Japan are administered by physicians. Nurse anesthetists also administer anesthesia in 109 nations.<ref>{{cite web | title = Nurse anestheisa worldwide: practice, education and regulation | url = http://ifna-int.org/ifna/e107_files/downloads/Practice.pdf| format = PDF | publisher = International Federation of Nurse Anesthetists | accessdate = 2007-02-08}}</ref> In the US, 35% of anesthetics are provided by physicians in solo practice, about 55% are provided by ACTs with anesthesiologists medically directing Anesthesiologist Assistants, CRNAs, and about 10% are provided by CRNAs in solo practice. <ref>{{cite web | date = [[2007-02-01]] | title = Is Physician Anesthesia Cost-Effective? | url = http://www.anesthesia-analgesia.org/cgi/content/full/98/3/750#R7-138848 | format = html | publisher = Anesth Analg | accessdate = 2007-02-15}}</ref> <ref>{{cite web | date = [[2007-02-01]] | title = When do anesthesiologists delegate? | url = http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&list_uids=2725080&dopt=Abstract | format = html | publisher = Med Care | accessdate = 2007-02-15}}</ref> <ref>{{cite web | title = Nurse anestheisa worldwide: practice, education and regulation | url = http://ifna-int.org/ifna/e107_files/downloads/Practice.pdf| format = PDF | publisher = International Federation of Nurse Anesthetists | accessdate = 2007-02-08}}</ref>
- <ref>{{cite web | date = [[2007-02-25]] | title =Surgical mortality and type of anesthesia provider | url = http://www.aana.com/news.aspx?ucNavMenu_TSMenuTargetID=171&ucNavMenu_TSMenuTargetType=4&ucNavMenu_TSMenuID=6&id=1606&terms=medical+direction+percent&searchtype=1&fragment=True | format = html | publisher = AANA | accessdate = 2007-02-25}}</ref>
- <ref>{{cite web | date = [[2007-02-25]] | title = Anesthesia Providers, Patient Outcomes, and Cost | url = http://nursing.fiu.edu/anesthesiology/COURSES/Semester%203/NGR%206760%20ANE%20Prof%20Aspects/PROF%20Readings/Abenstein.pdf | format = pdf | publisher = Anesth Analg | accessdate = 2007-02-25}}</ref>

===Physician anesthesiologists/anaesthetists/anaesthesiologists===

In the US, medical doctors who specialize in anesthesiology are called anesthesiologists. Such physicians in the UK and Canada are called anaesthetists or anaesthesiologists.

In the U.S., a physician specializing in anesthesiology completes 4 years of college, 4 years of medical school, 1 year of internship, and 3 years of residency. According to the American Society of Anesthesiologists, anesthesiologists provide or participate in more than 90 percent of the 40 million anesthetics delivered annually.<ref>{{cite web | title = ASA Fast Facts: Anesthesiologists Provide Or Participate In 90 Percent Of All Annual Anesthetics | url = http://www.asahq.org/PressRoom/homepage.html | format = html | publisher = ASA | accessdate = 2007-03-22}}</ref>

In the UK this training lasts a minimum of seven years after the awarding of a medical degree and two years of basic residency, and takes place under the supervision of the [[Royal College of Anaesthetists]]. In Australia and New Zealand, it lasts five years after the awarding of a medical degree and two years of basic residency, under the supervision of the Australian and New Zealand College of Anaesthetists. Other countries have similar systems, including Ireland (the Faculty of Anaesthetists of the Royal College of Surgeons in Ireland), Canada and South Africa (the College of Anaesthetists of South Africa).

In the UK, completion of the examinations set by the Royal College of Anaesthetists leads to award of the Diploma of Fellowship of the Royal College of Anaesthetists (FRCA). In the US, completion of the written and oral Board examinations by a [[physician]] [[anesthesiologist]] allows one to be called "Board Certified" or a "Diplomate" of the American Board of Anesthesiology.

Other specialties within medicine are closely affiliated to anaesthetics. These include [[intensive care medicine]] and [[Pain management|pain medicine]]. Specialists in these disciplines have usually done some training in anaesthetics. The role of the anaesthetist is changing. It is no longer limited to the operation itself. Many anaesthetists consider themselves to be peri-operative physicians, and will involve themselves in optimizing the patient's health before surgery (colloquially called "work-up"), performing the anaesthetic, following up the patient in the [[post anesthesia care unit]] and post-operative wards, and ensuring optimal [[analgesia]] throughout.

It is important to note that the term ''anesthetist'' in the United States usually refers to registered nurses who have completed specialized education and training in nurse anesthesia to become certified registered nurse anesthetists (CRNAs). As noted above, the term ''anaesthetist'' in the UK and Cananda refers to medical doctors who specialize in anesthesiology.

===Nurse Anesthetists===
In the United States, advance practice nurses specializing in the provision of anesthesia care are known as Certified Registered Nurse Anesthetists (CRNAs). CRNAs provide 27 million hands-on anesthetics each year, roughly two thirds of the US total and are the sole providers of anesthesia in more than 70 percent of rural area hospitals. According to the American Association of Nurse Anesthetists, the 36,000 CRNAs in the US administer approximately 27 million anesthetics each year.[[http://aana.com/aboutaana.aspx?ucNavMenu_TSMenuTargetID=127&ucNavMenu_TSMenuTargetType=4&ucNavMenu_TSMenuID=6&id=38]] CRNAs are the sole providers of anesthesia in more than 70 percent of rural area hospitals. Thirty-four percent of nurse anesthetists practice in communities of less than 50,000. CRNAs start school with a bachelors degree and at least 1 year of acute care nursing experience[[http://aana.com/BecomingCRNA.aspx?ucNavMenu_TSMenuTargetID=18&ucNavMenu_TSMenuTargetType=4&ucNavMenu_TSMenuID=6&id=1018]], and gain a masters degree in nurse anesthesia before passing the mandatory Certification Exam. The average CRNA student has 5-7 years of nursing experience before entering a 27-36 month masters level anesthesia program.<ref>{{cite web | date = [[2006-02-01]] | title = Television conferencing: Is it as effective as "in person" lectures for nurse anesthesia education? | url = http://www.aana.com/uploadedFiles/Resources/Publications/AANA_Journal_-_Public/2006/February_2006/p19-21.pdf | format = PDF | publisher = AANA Journal | accessdate = 2007-02-05}}</ref>

CRNAs may work with podiatrists, dentists, anesthesiologists, surgeons, obstetricians and other professionals requiring their services. CRNAs administer anesthesia in all types of surgical cases, and are able to apply all the accepted anesthetic techniques -- general, regional, local, or sedation. Nurse Anesthetists are licensed to practice anesthesia independently, as well as in Anesthesia Care Teams.<ref>{{cite web | title = Anethesiology Care Team | url = http://www.durhamregional.org/healthlibrary/behind_the_scenes/20060518173014802 | format = html | publisher = durhamregional.org | accessdate = 2007-02-11}}</ref> CRNAs may also practice in parallel with their physician colleagues in certain institutions, both types of provider caring for their own patients independently and consulting whenever collaboration is appropriate to patient outcome. CRNAs may also practice in parallel with their physician colleagues in certain institutions, both types of provider caring for their own patients independently and consulting whenever collaboration is appropriate to patient outcome.

===Anesthesiology assistants===

In the US, anesthesiologist assistants (AAs) are physician assistants who have undertaken specialized education and training to provide anesthesia care. AAs typically hold a masters degree and practice under physician supervision in sixteen states through licensing, certification or physician delegation.<ref>{{cite web |title = Five facts about AAs| url = http://www.anesthetist.org/content/view/14/38/ | format = HTML | publisher = American Academy of Anesthesiologist Assistants | accessdate = 2007-02-08}}</ref>

In the UK, a similar group of assistants are currently being evaluated. In Scotland they are named Physician's Assistant - Anaesthesia and in the rest of the UK, they are called anaesthesia practitioners. Their background can be nursing, operating department professional or another profession allied to medicine or a science graduate. Training takes 27 months and to date, the first five have graduated in England.

Anesthesiology Assistants should be distinguished from Anesthesia Technicians.

===Anesthesia technicians===
Anesthesia technicians are specially trained biomedical technicians who assist anesthesiologists, nurse anesthetists, and anesthesiology assistants with monitoring equipment, supplies, and patient care procedures in the operating room.

In New Zealand, anaesthetic technicians complete a course of study recognized by the New Zealand Association of Anaesthetic Technicians and Nurses.

In the United Kingdom, personnel known as ODPs ([[operating department practitioner]]s) or anaesthetic nurses provide support to the physician anaesthetist (anaesthesiologist).

===Veterinary Anesthetists/anesthesiologists===
{{main|Veterinary anesthesia}}
Veterinary anesthetists utilize much the same equipment and drugs as those who provide anesthesia to human patients. In the case of animals, the anesthesia must be tailored to fit the species ranging from large land animals like horses or elephants to birds to aquatic animals like fish. For each species there are ideal, or at least less problematic, methods of safely inducing anesthesia. For wild animals, anesthetic drugs must often be delivered from a distance by means of remote projector systems ("dart guns") before the animal can even be approached. Large domestic animals, like cattle, can often be anesthetized for standing surgery using only local anesthetics and sedative drugs. While most clinical veterinarians and veterinary technicians routinely function as anesthetists in the course of their professional duties, veterinary anesthesiologists in the U.S. are veterinarians who have completed a two-year residency in anesthesia and have qualified for certification by the American College of Veterinary Anesthesiologists.

==Anesthetic agents==
===Local anesthetics===
{{main|Local anesthetic}}
* [[procaine]]
* [[Tetracaine|amethocaine]]
* [[cocaine]]
* [[lidocaine]]
* [[prilocaine]]
* [[Bupivacaine|bupivicaine]]
* [[levobupivacaine]]
* [[ropivacaine]]
* [[Cinchocaine|dibucaine]]

Local anesthetics are agents which prevent transmission of nerve impulses without causing unconsciousness. They act by binding to fast [[sodium channels]] from within (in an open state). Local anesthetics can be either [[ester]] or [[amide]] based.

Ester local anesthetics (e.g., procaine, amethocaine, cocaine) are generally unstable in solution and fast-acting, and allergic reactions are common.

Amide local anesthetics (e.g., lidocaine, prilocaine, bupivicaine, levobupivacaine, ropivacaine and dibucaine) are generally heat-stable, with a long shelf life (around 2 years). They have a slower onset and longer half-life than ester anaesthetics, and are usually [[racemic]] mixtures, with the exception of levobupivacaine (which is S(-) -bupivacaine) and ropivacaine (S(-)-ropivacaine). These agents are generally used within regional and epidural or spinal techniques, due to their longer duration of action, which provides adequate analgesia for surgery, labor, and symptomatic relief.

Only preservative-free local anesthetic agents may be injected [[intrathecal]]ly.

====Adverse effects of local anaesthesia====
Adverse effects of local anesthesia are generally referred to as [[Local Anesthetic Toxicity]].

Effects may be localized or systemic.

Examples of systemic effects of local anesthesia:

Local anesthetic drugs are toxic to the heart (where they cause [[arrhythmia]]) and brain (where they may cause unconsciousness and [[seizures]]). Arrhythmias may be resistant to [[defibrillation]] and other standard treatments, and may lead to loss of heart function and death.

The first evidence of local anesthetic toxicity involves the nervous system, including agitation, confusion, dizziness, blurred vision, tinnitus, a metallic taste in the mouth, and nausea that can quickly progress to seizures and cardiovascular collapse.

Toxicity can occur with any local anesthetic as an individual reaction by that patient. Possible toxicity can be tested with pre-operative procedures to avoid toxic reactions during surgery.

An example of localized effect of local anesthesia:

Direct infiltration of local anesthetic into [[skeletal muscle]] will cause temporary paralysis of the muscle.

===Current inhaled general anesthetic agents===
{{main|General anaesthesia}}
*[[Nitrous oxide]]
*[[Halothane]]
*[[Enflurane]]
*[[Isoflurane]]
*[[Sevoflurane]]
*[[Desflurane]]
*[[Xenon]] (rarely used)

Volatile agents are specially formulated organic liquids that evaporate readily into vapors, and are given by inhalation for induction and/or maintenance of general anesthesia. Nitrous oxide and xenon are gases at room temperature rather than liquids, so they are not considered volatile agents. The ideal anesthetic vapor or gas should be non-flammable, non-explosive, lipid-soluble, and should possess low blood gas solubility, have no end organ (heart, liver, kidney) toxicity or side-effects, should not be metabolized, and should be non-irritant when inhaled by patients.

No anesthetic agent currently in use meets all these requirements. The agents in widespread current use are [[isoflurane]], [[desflurane]], [[sevoflurane]], and [[nitrous oxide]]. [[Nitrous oxide]] is a common adjuvant gas, making it one of the most long-lived drugs still in current use. Because of its low potency, it cannot produce anesthesia on its own but is frequently combined with other agents. Halothane, an agent introduced in the 1950s, has been almost completely replaced in modern anesthesia practice by newer agents because of its shortcomings.<ref name="town">{{cite book | last = Townsend | first = Courtney | title = Sabiston Textbook of Surgery | publisher = Saunders | location = Philadelphia | pages = Chapter 17 – Anesthesiology Principles, Pain Management, and Conscious Sedation | year = 2004 | isbn = 0721653685 }}</ref> Partly because of its side effects, enflurane never gained widespread popularity. <ref name="town"/>

In theory, any inhaled anesthetic agent can be used for induction of general anesthesia. However, most of the halogenated anesthetics are irritating to the airway, perhaps leading to coughing, laryngospasm and overall difficult inductions. For this reason, the most frequently used agent for inhalational induction is sevoflurane. All of the volatile agents can be used alone or in combination with other medications to maintain anesthesia (nitrous oxide is not potent enough to be used as a sole agent).

As of 2007, research into the use of [[xenon]] as an anesthetic is underway, but the gas is very expensive to produce and requires special equipment for delivery, as well as special monitoring and scavenging of waste gas.

Volatile agents are frequently compared in terms of potency, which is inversely proportional to the [[minimum alveolar concentration]]. Potency is directly related to lipid solubility. This is known as the [[Minimum alveolar concentration|Meyer-Overton hypothesis]]. However, certain pharmacokinetic properties of volatile agents have become another point of comparison. Most important of those properties is known as the blood:gas partition coefficient. This concept refers to the relative solubilty of a given agent in blood. Those agents with a lower blood solubility (i.e., a lower blood–gas partition coefficient; e.g., desflurane) give the anesthesia provider greater rapidity in titrating the depth of anesthesia, and permit a more rapid emergence from the anesthetic state upon discontinuing their administration. In fact, newer volatile agents (e.g., sevoflurane, desflurane) have been popular not due to their potency (minimum alveolar concentration), but due to their versatility for a faster emergence from anesthesia, thanks to their lower blood–gas partition coefficient.

===Current intravenous anesthetic agents (non-opioid)===
While there are many drugs that can be used intravenously to produce anesthesia or sedation, the most common are:
*[[Barbiturates]]
**[[Thiopental]]
**[[Methohexital]]
*[[Benzodiazepines]]
**[[Midazolam]]
**[[Lorazepam]]
**[[Diazepam]]
*[[Propofol]]
*[[Etomidate]]
*[[Ketamine]]

The two barbiturates mentioned above, thiopental and methohexital, are ultra-short-acting, and are used to induce and maintain anesthesia.<ref name="miller">{{cite book | last = Miller | first = Ronald | title = Miller's Anesthesia | publisher = Elsevier/Churchill Livingstone | location = New York | year = 2005 | isbn = 0443066566 }}</ref> However, though they produce unconsciousness, they provide no [[analgesia]] (pain relief) and must be used with other agents.<ref name="miller"/> Benzodiazepines can be used for sedation before or after surgery and can be used to induce and maintain general anesthesia.<ref name="miller"/> When benzodiazepines are used to induce general anesthesia, midazolam is preferred.<ref name="miller"/> Benzodiazepines are also used for sedation during procedures that do not require general anesthesia.<ref name="miller"/> Like barbiturates, benzodiazepines have no pain-relieving properties.<ref name="miller"/> Propofol is one of the most commonly used intravenous drugs employed to induce and maintain general anesthesia.<ref name="miller"/> It can also be used for sedation during procedures or in the ICU.<ref name="miller"/> Like the other agents mentioned above, it renders patients unconscious without producing pain relief.<ref name="miller"/> Because of its favorable physiological effects, "etomidate has been primarily used in sick patients".<ref name="miller"/> Ketamine is infrequently used in anesthesia practice because of the unpleasant experiences which sometimes occur upon emergence from anesthesia, which include "vivid dreaming, extracorporeal experiences, and illusions."<ref>Garfield JM, Garfield FB, Stone JG, et al: A comparison of psychologic responses to ketamine and thiopental-nitrous oxide-halothane anesthesia. Anesthesiology 1972; 36:329-338.</ref> However, like etomidate it is frequently used in emergency settings and with sick patients because it produces fewer adverse physiological effects.<ref name="miller"/> Unlike the intravenous anesthetic drugs previously mentioned, ketamine produces profound pain relief, even in doses lower than those which induce general anesthesia.<ref name="miller"/> Also unlike the other anesthetic agents in this section, "patients who receive ketamine alone appear to be in a cataleptic state, unlike other states of anesthesia that resemble normal sleep. Ketamine-anesthetized patients have profound analgesia but keep their eyes open and maintain many reflexes."<ref name="miller"/>

===Current intravenous opioid analgesic agents===
While opioids can produce unconsciousness, they do so unreliably and with significant side effects.<ref>Philbin DM, Rosow CE, Schneider RC, et al: Fentanyl and sufentanil anesthesia revisited: how much is enough?. Anesthesiology 1990; 73:5-11.</ref><ref>Streisand JB, Bailey PL, LeMaire L, Ashburn MA, Tarver SD, Varvel J, Stanley TH: Fentanyl-induced rigidity and unconsciousness in human volunteers. Incidence, duration, and plasma concentrations. Anesthesiology 1993; 78:629-634.</ref> So, while they are rarely used to induce anesthesia, they are frequently used along with other agents such as intravenous non-opioid anesthetics or inhalational anesthetics.<ref name="miller"/> Furthermore, they are used to relieve pain of patients before, during, or after surgery. The following opioids have short onset and duration of action and are frequently used during general anesthesia:
*[[Fentanyl]]
*[[Alfentanil]]
*[[Sufentanil]]
*[[Remifentanil]]

The following agents have longer onset and duration of action and are frequently used for post-operative pain relief:
*[[Buprenorphine]]
*[[Butorphanol]]
*[[Heroin|Diamorphine]], (diacetyl morphine, also known as [[heroin]], not available in U.S.)
*[[Hydromorphone]]
*[[Levorphanol]]
*[[Meperidine]], also called '''pethidine''' in the UK, New Zealand, Australia and other countries
*[[Methadone]]
*[[Morphine]]
*[[Nalbuphine]]
*[[Oxycodone]], (not available intravenously in U.S.)
*[[Oxymorphone]]
*[[Pentazocine]]

===Current muscle relaxants===
Muscle relaxants do not render patients unconscious or relieve pain. Instead, they are sometimes used after a patient is rendered unconscious (induction of anesthesia) to facilitate [[intubation]] or surgery by paralyzing skeletal muscle.

*Depolarizing muscle relaxants
**[[Succinylcholine]] (also known as '''suxamethonium''' in the UK, New Zealand, Australia and other countries)
*Non-depolarizing muscle relaxants
**Short acting
***[[Mivacurium]]
***[[Rapacuronium]]
**Intermediate acting
***[[Atracurium]]
***[[Cisatracurium]]
***[[Vecuronium]]
***[[Rocuronium]]
**Long acting
***[[Pancuronium]]
***Metocurine
***d-[[Tubocurarine]]
***[[Gallamine]]
***[[Alcuronium]]
***[[Doxacurium]]
***[[Pipecuronium bromide|Pipecuronium]]

====Adverse effects of muscle relaxants====
Succinylcholine may cause [[hyperkalemia]] if given to burn patients, or paralyzed (quadraplegic, paraplegic) patients. The mechanism is reported to be through upregulation of [[Acetylcholine receptor|acetylcholine receptors]] in those patient populations. Succinylcholine may also trigger [[malignant hyperthermia]] in susceptible patients.

Another potentially disturbing complication can be '[[anesthesia awareness]]'. In this situation, patients paralyzed with muscle relaxants may awaken during their anesthesia, due to decrease in the levels of drugs providing sedation and/or pain relief. If this fact is missed by the anaesthesia provider, the patient may be aware of his surroundings, but be incapable of moving or communicating that fact. Neurological monitors are becoming increasingly available which may help decrease the incidence of awareness. Most of these monitors use proprietary algorithms monitoring brain activity via evoked potentials. Despite the widespread marketing of these devices many case reports exist in which awareness under anesthesia has occurred despite apparently adequate anesthesia as measured by the neurologic monitor.

===Current intravenous reversal agents===
*[[Naloxone]], reverses the effects of opioids
*[[Flumazenil]], reverses the effects of benzodiazepines
*[[Neostigmine]], reverses the effects of non-depolarizing muscle relaxants
* Suggamadex, more effectively reverses [[rocuronium]] and [[norcuronium]]

==Anesthetic equipment==
{{main|Anaesthetic equipment}}
In modern anesthesia, a wide variety of medical equipment is desirable depending on the necessity for portable field use, surgical operations or intensive care support. Anesthesia practitioners must possess a comprehensive and intricate knowledge of the production and use of various '''medical gases''', anaesthetic agents and '''vapours''', medical '''[[breathing circuits]]''' and the variety of [[anaesthetic machine]]s (including vaporizers, ventilators and pressure gauges) and their corresponding safety features, hazards and limitations of each piece of equipment, for the safe, clinical competence and practical application for day to day practice.

==Anesthetic monitoring==
Patients being treated under general anesthetics must be monitored continuously to ensure the patient's safety. For minor surgery, this generally includes monitoring of [[heart rate]] (via [[ECG]] or [[pulse oximetry]]), [[oxygen saturation]] (via [[pulse oximetry]]), non-invasive [[blood pressure]], inspired and expired gases (for [[oxygen]], [[carbon dioxide]], [[nitrous oxide]], and volatile agents). For moderate to major surgery, monitoring may also include [[body temperature|temperature]], urine output, invasive blood measurements ([[arterial blood pressure]], [[central venous pressure]]), pulmonary artery pressure and pulmonary artery occlusion pressure, cerebral activity (via [[EEG]] analysis), neuromuscular function (via [[peripheral nerve]] stimulation monitoring), and [[cardiac output]]. In addition, the operating room's environment must be monitored for temperature and humidity and for buildup of exhaled [[Inhalational anaesthetic|inhalational anesthetics]] which might impair the health of operating room personnel.

==Anesthesia record==
The anesthesia record is the medical and legal documentation of events during an anesthetic.<ref>Stoelting RK, Miller RD: Basics of Anesthesia, 3rd edition, 1994.</ref> It reflects a detailed and continuous account of drugs, fluids, and blood products administered and procedures undertaken, and also includes the observation of cardiovascular responses, estimated blood loss, urinary body fluids and data from physiologic monitors (Anesthetic monitoring, see above) during the course of an anesthetic. The anesthesia record may be written manually on paper; however, the paper record is increasingly replaced by an electronic record as part of an Anesthesia Information Management System (AIMS).

==Anesthesia Information Management System (AIMS)==
An AIMS refers to any information system that is used as an automated electronic anesthesia record keeper (i.e., connection to patient physiologic monitors and/or the [[Anaesthetic machine]]) and which also may allow the collection and analysis of anesthesia-related perioperative patient [[data]].

==See also==
* [[ASA score]]
* [[EEG measures during anesthesia]]
* [[Patient safety]]
* [[Perioperative mortality]]
* [[Anaesthetic Technician]]
* [[Anaesthesia awareness]]
* [[Allergic reactions during anaesthesia]]

==References==

==External links==
* [http://www.nda.ox.ac.uk/wfsa/ World Anaesthesia Online] International resource of anaesthetic articles
* [http://www.iars.com/default/default.asp International Anesthesia Research Society]
* [http://ifna-int.org/ifna/page.php International Federation of Nurse Anesthetists]

{{General anesthetics}}
{{Local anesthetics}}
{{Ancient anaesthesia-footer}}
{{Major Drug Groups}}

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[[Category:Surgery]]

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Anesthesia

2014-11-27T01:28:20Z

AKAZamkz12: /* Overview */

__NOTOC__
{{SI}}
{{CMG}}

==Overview==
'''Anesthesia''' or '''anaesthesia''' (from [[Greek language|Greek]] ''αν-'' ''an-'' “without” + ''αἲσθησις'' ''aisthesis'' “sensation”) has traditionally meant the condition of having the feeling of [[Pain and nociception|pain]] and other [[sensation]]s blocked. This allows patients to undergo [[surgery]] and other procedures without the distress and pain they would otherwise experience. The word was coined by [[Oliver Wendell Holmes, Sr.]] in 1846. Another definition is a "reversible lack of awareness", whether this is a total lack of awareness (e.g. a general anaesthestic) or a lack of awareness of a part of a the body such as a spinal anaesthetic or another nerve block would cause.

Today, the term '''general anesthesia''' in its most general form can include:
* [[Analgesic|Analgesia]]: blocking the [[consciousness|conscious]] sensation of pain;
* Hypnosis: produces [[unconsciousness]] without analgesia;
* [[Amnesia]]: preventing [[memory]] formation;
* [[Neuromuscular-blocking drugs|Relaxation]]: preventing unwanted movement or muscle tone;
* [[Obtundation]] of reflexes, preventing exaggerated autonomic reflexes.

Patients undergoing surgery usually undergo preoperative evaluation. It includes gathering history of previous anesthetics, and any other medical problems, physical examination, ordering required blood work and consultations prior to surgery.

There are several forms of anesthesia. The following forms refer to states achieved by anesthetics working on the brain:
*General anesthesia: "Drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation." Patients undergoing general anesthesia often cannot maintain their own airway and breathe on their own. While usually administered with inhalational agents, general anesthesia can be achieved with [[Intravenous therapy|intravenous]] agents, such as [[propofol]].<ref name="asadepth">{{Citation
| contribution = Continuum Of Depth Of Sedation Definition Of General Anesthesia And Levels Of Sedation/Analgesia
| title = American Society of Anesthesiologists
| publisher = ASA
| date = [[2004-10-27]]
| year = 2004
| contribution-url = http://www.asahq.org/publicationsAndServices/standards/20.pdf }}</ref>
*Deep [[sedation]]/analgesia: "Drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated or painful stimulation." Patients may sometimes be unable to maintain their airway and breathe on their own.<ref name="asadepth" />
*Moderate sedation/analgesia or conscious sedation: "Drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation." In this state, patients can breathe on their own and need no help maintaining an airway.<ref name="asadepth" />
* Minimal sedation or anxiolysis: "Drug-induced state during which patients respond normally to verbal commands." Though concentration, memory, and coordination may be impaired, patients need no help breathing or maintaining an airway.<ref name="asadepth" />

The level of anesthesia achieved ranges on a continuum of depth of consciousness from minimal sedation to general anesthesia. The depth of consciousness of a patient may change from one minute to the next.

The following refer to states achieved by anesthetics working outside of the brain:
*Regional anesthesia: Loss of pain sensation, with varying degrees of muscle relaxation, in certain regions of the body. Administered with local anesthesia to peripheral nerve bundles, such as the brachial plexus in the neck. Examples include the interscalene block for shoulder surgery, axillary block for wrist surgery, and [[femoral nerve]] block for leg surgery. While traditionally administered as a single injection, newer techniques involve placement of indwelling [[catheters]] for continuous or intermittent administration of local anesthetics.
**[[Spinal anesthesia]]: also known as subarachnoid block. Refers to a Regional block resulting from a small volume of local anesthetics being injected into the [[spinal canal]]. The spinal canal is covered by the [[dura mater]], through which the spinal needle enters. The spinal canal contains [[cerebrospinal fluid]] and the [[spinal cord]]. The sub arachnoid block is usually injected between the 4th and 5th [[lumbar]] [[vertebra]]e, because the spinal cord usually stops at the 1st lumbar vertebra, while the canal continues to the [[sacrum|sacral]] vertebrae. It results in a loss of pain sensation and muscle strength, usually up to the level of the chest (nipple line or 4th thoracic [[dermatomic area|dermatome]]).
**[[Epidural|Epidural anesthesia]]: Regional block resulting from an injection of a large volume of local anesthetic into the [[epidural space]]. The epidural space is a [[potential space]] that lies underneath the [[ligamenta flava]], and outside the dura mater (outside layer of the spinal canal). This is basically an injection around the spinal canal.
* [[Local anesthesia]] is similar to regional anesthesia, but exerts its effect on a smaller area of the body.

==History==
===Herbal derivatives===
The first [[herbalism|herbal]] anesthesia was administered in prehistory. [[Opium]] poppy capsules were collected in 4200 BC, and opium poppies were farmed in Sumeria and succeeding empires. The use of opium-like preparations in anaesthesia is recorded in the Ebers Papyrus of 1500 BC. By 1100 BC poppies were scored for opium collection in Cyprus by methods similar to those used in the present day, and simple apparatus for smoking of opium were found in a Minoan temple. Opium was not introduced to India and China until 330 BC and 600–1200 AD, but these nations pioneered the use of cannabis incense and [[aconitum]]. In the second century, according to the Book of Later Han, the physician Hua Tuo performed abdominal surgery using an anesthetic substance called ''mafeisan'' (麻沸散 "cannabis boil powder") dissolved in wine. Throughout Europe, Asia, and the Americas a variety of Solanum species containing potent [[tropane]] alkaloids were used, such as mandrake, [[henbane]], [[Datura metel]], and [[Datura inoxia]]. Classic Greek and Roman medical texts by Hippocrates, Theophrastus, Aulus Cornelius Celsus, Pedanius Dioscorides, and Pliny the Elder discussed the use of opium and Solanum species, and treatment with the combined alkaloids proved a mainstay of anaesthesia until the nineteenth century. In the Americas [[coca]] was also an important anaesthetic used in [[Trepanation|trephining]] operations. Incan shamans chewed [[coca]] leaves and performed operations on the skull while spitting into the wounds they had inflicted to anaesthetize the site. [[ethanol|Alcohol]] was also used, its [[vasodilation|vasodilatory]] properties being unknown. Ancient herbal anaesthetics have variously been called soporifics, [[anodyne]]s, and [[narcotic]]s, depending on whether the emphasis is on producing unconsciousness or relieving pain.

In Central Asia, in the 10th century work of Shahnameh, the author, Ferdowsi, describes a [[caesarean section]] performed on Rudaba when giving birth, in which a special wine agent was prepared as an anesthetic<ref>''Medicine throughout Antiquity''. Benjamin Lee Gordon. 1949. p.306</ref> by a Zoroastrian priest, and used to produce unconsciousness for the operation. Although largely mythical in content, the passage does at least illustrate knowledge of anesthesia in ancient Persia.

The use of herbal anaesthesia had a crucial drawback compared to modern practice — as lamented by Fallopus, "When soporifics are weak they are useless, and when strong, they kill." To overcome this, production was typically standardized as much as feasible, with production occurring from specific famous locations (such as opium from the fields of Thebes in ancient Egypt). Anaesthetics were sometimes administered in the spongia somnifera, a sponge into which a large quantity of drug was allowed to dry, from which a saturated solution could be trickled into the nose of the patient. At least in more recent centuries, trade was often highly standardized, with the drying and packing of [[opium]] in standard chests, for example. In the 19th century, varying [[aconitum]] alkaloids from a variety of species were standardized by testing with guinea pigs. Despite these refinements, the discovery of [[morphine]], a purified alkaloid that soon afterward could be injected by [[Hypodermic needle|hypodermic]] for a consistent dosage, was enthusiastically received and led to the foundation of the modern pharmaceutical industry.

Another factor affecting ancient anaesthesia is that drugs used systemically in modern times were often administered locally, reducing the risk to the patient. [[Opium]] used directly in a wound acts on peripheral [[opioid receptor]]s to serve as an analgesic, and a medicine containing willow leaves ([[salicylate]], the predecessor of [[aspirin]]) would then be applied directly to the source of inflammation.

In 1804, the Japanese surgeon Hanaoka Seishū performed general [[anaesthesia]] for the operation of a breast cancer ([[mastectomy]]), by combining Chinese herbal medicine know-how and Western [[surgery]] techniques learned through "Rangaku", or "Dutch studies". His patient was a 60-year-old woman called Kan Aiya.<ref>[http://www.general-anaesthesia.com/ Utopian surgery: Early arguments against anaesthesiain surgery, dentistry and childbirth]</ref> He used a compound he called Tsusensan, based on the plants Datura metel, Aconitum and others.

===Non-pharmacological methods===
[[Hypnosurgery|Hypnotism]] and [[acupuncture]] have a long history of use as anesthetic techniques. In China, Taoist medical practitioners developed anesthesia by means of [[acupuncture]]. Chilling tissue (e.g. with ice) can temporarily cause nerve fibers ([[axon]]s) to stop conducting sensation, while [[hyperventilation]] can cause brief alteration in conscious perception of stimuli including pain (see [[Lamaze]]).

In modern anesthetic practice, these techniques are seldom employed.

===Early gases and vapours===
The works of Greek authors such as [[Dioscorides]] were well-known in the Islamic Empire, and physicians such as al-Razi, [[Avicenna]], and Abu al-Qasim wrote medical textbooks of great importance in the development of medicine in Europe and the Middle East. Muslim [[anesthesiologist]]s were the first to utilize oral as well as [[Inhalational anaesthetic|inhalant anesthetics]]. In Islamic Spain, Abu al-Qasim (Abulcasis) and Ibn Zuhr (Avenzoar), among other Muslim surgeons, performed hundreds of [[Surgery|surgeries]] under inhalant anesthesia with the use of [[narcotic]]-soaked sponges which were placed over the face. Abulcasis and Ibn Sina (Avicenna) wrote about anasthesia in their influential medical encyclopedias, the ''al-Tasrif'' and ''[[The Canon of Medicine]]''.<ref>Dr. Kasem Ajram (1992). ''Miracle of Islamic Science'', Appendix B. Knowledge House Publishers. ISBN 0911119434.</ref><ref>[[Sigrid Hunke]] (1969), ''Allah Sonne Uber Abendland, Unser Arabische Erbe'', Second Edition, p. 279-280: {{quote|"The science of medicine has gained a great and extremely important discovery and that is the use of general anaesthetics for surgical operations, and how unique, efficient, and merciful for those who tried it the Muslim anaesthetic was. It was quite different from the drinks the Indians, Romans and Greeks were forcing their patients to have for relief of pain. There had been some allegations to credit this discovery to an Italian or to an Alexandrian, but the truth is and history proves that, the art of using the anaesthetic sponge is a pure Muslim technique, which was not known before. The sponge used to be dipped and left in a mixture prepared from cannabis, opium, hyoscyamus and a plant called Zoan."}} ([[cf.]] Prof. Dr. M. Taha Jasser, [http://www.islamset.com/hip/i_medcin/taha_jasser.html Anaesthesia in Islamic medicine and its influence on Western civilization], Conference
on Islamic Medicine)</ref>

[[Image:Southworth & Hawes - First etherized operation (re-enactment).jpg|thumb|right|300px|Contemporary re-enactment of Morton's October 16, 1846, ether operation; daguerrotype by Southworth & Hawes.]]

In the West, the development of effective anesthetics in the 19th century was, with Listerian techniques, one of the keys to successful surgery. Henry Hill Hickman experimented with [[carbon dioxide]] in the 1820s. The anesthetic qualities of [[nitrous oxide]] (isolated in 1773 by Joseph Priestley) were discovered by the British chemist Humphry Davy about 1799 when he was an assistant to Thomas Beddoes, and reported in a paper in 1800. But initially the medical uses of this so-called "laughing gas" were limited — its main role was in entertainment. It was used on 30 September 1846 for painless tooth extraction upon patient Eben Frost by American [[dentist]] William Thomas Green Morton. Horace Wells of Connecticut, a traveling dentist, had demonstrated it the previous year 1845, at Massachusetts General Hospital. Wells made a mistake, in choosing a particularly sturdy male volunteer, and the patient suffered considerable pain. This lost the colorful Wells any support. Later the patient told Wells he screamed in shock and not in pain. A subsequently drunk Wells died in jail, by cutting his femoral artery, after allegedly assaulting a prostitute with sulfuric acid.

Another dentist,William E. Clarke, performed an extraction in January 1842 using a different chemical, [[diethyl ether]] (discovered by Valerius Cordus in 1540). In March 1842 in Danielsville, Georgia, Dr. Crawford Long was the first to use anaesthesia during an operation, giving it to a boy (John Venables) before excising a cyst from his neck; however, he did not publicize this information until later.

On October 16, 1846, another dentist, William Thomas Green Morton, invited to the Massachusetts General Hospital, performed the first public demonstration of diethyl ether (then called sulfuric ether) as an anesthetic agent, for a patient (Edward Gilbert Abbott) undergoing an excision of a vascular tumor from his neck. In a letter to Morton shortly thereafter, Oliver Wendell Holmes, Sr. proposed naming the procedure ''anæsthesia''.
[[Image:CrawfordLong.jpg|left|thumb|180px|Anesthesia pioneer Crawford W. Long]]
Despite Morton's efforts to keep "his" compound a secret, which he named "Letheon" and for which he received a US patent, the news of the discovery and the nature of the compound spread very quickly to Europe in late 1846. Here, respected surgeons—including Liston, Dieffenbach, Pirogoff, and Syme—undertook numerous operations with [[ether]].
An American-born physician, Boott — who had traveled to London — encouraged a leading dentist, Mr James Robinson, to perform a dental procedure on a Miss Lonsdale. This was the first case of an operator-anesthetist. On the same day, 19 December 1846 in Dumfries Royal Infirmary, Scotland, a Dr. Scott used ether for a surgical procedure. The first use of anesthesia in the Southern Hemisphere took place in Launceston, Tasmania, that same year. Ether has a number of drawbacks, such as its tendency to induce [[vomiting]] and its flammability. In England it was quickly replaced with [[chloroform]].

Discovered in 1831, the use of chloroform in anesthesia is usually linked to James Young Simpson, who, in a wide-ranging study of organic compounds, found chloroform's efficacy on 4 November 1847. Its use spread quickly and gained royal approval in 1853 when John Snow gave it to Queen Victoria during the birth of Prince Leopold. Unfortunately, chloroform is not as safe an agent as ether, especially when administered by an untrained practitioner (medical students, nurses, and occasionally members of the public were often pressed into giving anesthetics at this time). This led to many deaths from the use of chloroform that (with hindsight) might have been preventable. The first fatality directly attributed to chloroform anesthesia (Hannah Greener) was recorded on 28 January 1848.

John Snow of London published articles from May 1848 onwards 'On Narcotism by the Inhalation of Vapours' in the London Medical Gazette. Snow also involved himself in the production of equipment needed for inhalational anesthesia.

The surgical amphitheatre at Massachusetts General Hospital, or "ether dome" still exists today, although it is used for lectures and not surgery. The public can visit the amphitheater on weekdays when it is not in use.

===Early local anesthetics===
The first effective local anesthetic was [[cocaine]]. Isolated in 1859, it was first used by Karl Koller, at the suggestion of Sigmund Freud, in ophthalmic surgery in 1884. Before that doctors had used a salt and ice mix for the numbing effects of cold, which could only have limited application. Similar numbing was also induced by a spray of ether or ethyl chloride. A number of cocaine derivatives and safer replacements were soon produced, including [[procaine]] (1905), Eucaine (1900), Stovaine (1904), and [[lidocaine]] (1943).

[[Opioid]]s were first used by Racoviceanu-Piteşti, who reported his work in 1901.

==Anesthesia providers==

Physicians specialising in peri-operative care, development of an anesthetic plan, and the administration of anesthetics are known in the United States as anesthesiologists and in the UK and Canada as anaesthetists or anaesthesiologists. All anaesthetics in the UK, Australia, New Zealand and Japan are administered by physicians. Nurse anesthetists also administer anesthesia in 109 nations.<ref>{{cite web | title = Nurse anestheisa worldwide: practice, education and regulation | url = http://ifna-int.org/ifna/e107_files/downloads/Practice.pdf| format = PDF | publisher = International Federation of Nurse Anesthetists | accessdate = 2007-02-08}}</ref> In the US, 35% of anesthetics are provided by physicians in solo practice, about 55% are provided by ACTs with anesthesiologists medically directing Anesthesiologist Assistants, CRNAs, and about 10% are provided by CRNAs in solo practice. <ref>{{cite web | date = [[2007-02-01]] | title = Is Physician Anesthesia Cost-Effective? | url = http://www.anesthesia-analgesia.org/cgi/content/full/98/3/750#R7-138848 | format = html | publisher = Anesth Analg | accessdate = 2007-02-15}}</ref> <ref>{{cite web | date = [[2007-02-01]] | title = When do anesthesiologists delegate? | url = http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&list_uids=2725080&dopt=Abstract | format = html | publisher = Med Care | accessdate = 2007-02-15}}</ref> <ref>{{cite web | title = Nurse anestheisa worldwide: practice, education and regulation | url = http://ifna-int.org/ifna/e107_files/downloads/Practice.pdf| format = PDF | publisher = International Federation of Nurse Anesthetists | accessdate = 2007-02-08}}</ref>
- <ref>{{cite web | date = [[2007-02-25]] | title =Surgical mortality and type of anesthesia provider | url = http://www.aana.com/news.aspx?ucNavMenu_TSMenuTargetID=171&ucNavMenu_TSMenuTargetType=4&ucNavMenu_TSMenuID=6&id=1606&terms=medical+direction+percent&searchtype=1&fragment=True | format = html | publisher = AANA | accessdate = 2007-02-25}}</ref>
- <ref>{{cite web | date = [[2007-02-25]] | title = Anesthesia Providers, Patient Outcomes, and Cost | url = http://nursing.fiu.edu/anesthesiology/COURSES/Semester%203/NGR%206760%20ANE%20Prof%20Aspects/PROF%20Readings/Abenstein.pdf | format = pdf | publisher = Anesth Analg | accessdate = 2007-02-25}}</ref>

===Physician anesthesiologists/anaesthetists/anaesthesiologists===

In the US, medical doctors who specialize in anesthesiology are called anesthesiologists. Such physicians in the UK and Canada are called anaesthetists or anaesthesiologists.

In the U.S., a physician specializing in anesthesiology completes 4 years of college, 4 years of medical school, 1 year of internship, and 3 years of residency. According to the American Society of Anesthesiologists, anesthesiologists provide or participate in more than 90 percent of the 40 million anesthetics delivered annually.<ref>{{cite web | title = ASA Fast Facts: Anesthesiologists Provide Or Participate In 90 Percent Of All Annual Anesthetics | url = http://www.asahq.org/PressRoom/homepage.html | format = html | publisher = ASA | accessdate = 2007-03-22}}</ref>

In the UK this training lasts a minimum of seven years after the awarding of a medical degree and two years of basic residency, and takes place under the supervision of the [[Royal College of Anaesthetists]]. In Australia and New Zealand, it lasts five years after the awarding of a medical degree and two years of basic residency, under the supervision of the Australian and New Zealand College of Anaesthetists. Other countries have similar systems, including Ireland (the Faculty of Anaesthetists of the Royal College of Surgeons in Ireland), Canada and South Africa (the College of Anaesthetists of South Africa).

In the UK, completion of the examinations set by the Royal College of Anaesthetists leads to award of the Diploma of Fellowship of the Royal College of Anaesthetists (FRCA). In the US, completion of the written and oral Board examinations by a [[physician]] [[anesthesiologist]] allows one to be called "Board Certified" or a "Diplomate" of the American Board of Anesthesiology.

Other specialties within medicine are closely affiliated to anaesthetics. These include [[intensive care medicine]] and [[Pain management|pain medicine]]. Specialists in these disciplines have usually done some training in anaesthetics. The role of the anaesthetist is changing. It is no longer limited to the operation itself. Many anaesthetists consider themselves to be peri-operative physicians, and will involve themselves in optimizing the patient's health before surgery (colloquially called "work-up"), performing the anaesthetic, following up the patient in the [[post anesthesia care unit]] and post-operative wards, and ensuring optimal [[analgesia]] throughout.

It is important to note that the term ''anesthetist'' in the United States usually refers to registered nurses who have completed specialized education and training in nurse anesthesia to become certified registered nurse anesthetists (CRNAs). As noted above, the term ''anaesthetist'' in the UK and Cananda refers to medical doctors who specialize in anesthesiology.

===Nurse Anesthetists===
In the United States, advance practice nurses specializing in the provision of anesthesia care are known as Certified Registered Nurse Anesthetists (CRNAs). CRNAs provide 27 million hands-on anesthetics each year, roughly two thirds of the US total and are the sole providers of anesthesia in more than 70 percent of rural area hospitals. According to the American Association of Nurse Anesthetists, the 36,000 CRNAs in the US administer approximately 27 million anesthetics each year.[[http://aana.com/aboutaana.aspx?ucNavMenu_TSMenuTargetID=127&ucNavMenu_TSMenuTargetType=4&ucNavMenu_TSMenuID=6&id=38]] CRNAs are the sole providers of anesthesia in more than 70 percent of rural area hospitals. Thirty-four percent of nurse anesthetists practice in communities of less than 50,000. CRNAs start school with a bachelors degree and at least 1 year of acute care nursing experience[[http://aana.com/BecomingCRNA.aspx?ucNavMenu_TSMenuTargetID=18&ucNavMenu_TSMenuTargetType=4&ucNavMenu_TSMenuID=6&id=1018]], and gain a masters degree in nurse anesthesia before passing the mandatory Certification Exam. The average CRNA student has 5-7 years of nursing experience before entering a 27-36 month masters level anesthesia program.<ref>{{cite web | date = [[2006-02-01]] | title = Television conferencing: Is it as effective as "in person" lectures for nurse anesthesia education? | url = http://www.aana.com/uploadedFiles/Resources/Publications/AANA_Journal_-_Public/2006/February_2006/p19-21.pdf | format = PDF | publisher = AANA Journal | accessdate = 2007-02-05}}</ref>

CRNAs may work with podiatrists, dentists, anesthesiologists, surgeons, obstetricians and other professionals requiring their services. CRNAs administer anesthesia in all types of surgical cases, and are able to apply all the accepted anesthetic techniques -- general, regional, local, or sedation. Nurse Anesthetists are licensed to practice anesthesia independently, as well as in Anesthesia Care Teams.<ref>{{cite web | title = Anethesiology Care Team | url = http://www.durhamregional.org/healthlibrary/behind_the_scenes/20060518173014802 | format = html | publisher = durhamregional.org | accessdate = 2007-02-11}}</ref> CRNAs may also practice in parallel with their physician colleagues in certain institutions, both types of provider caring for their own patients independently and consulting whenever collaboration is appropriate to patient outcome. CRNAs may also practice in parallel with their physician colleagues in certain institutions, both types of provider caring for their own patients independently and consulting whenever collaboration is appropriate to patient outcome.

===Anesthesiology assistants===

In the US, anesthesiologist assistants (AAs) are physician assistants who have undertaken specialized education and training to provide anesthesia care. AAs typically hold a masters degree and practice under physician supervision in sixteen states through licensing, certification or physician delegation.<ref>{{cite web |title = Five facts about AAs| url = http://www.anesthetist.org/content/view/14/38/ | format = HTML | publisher = American Academy of Anesthesiologist Assistants | accessdate = 2007-02-08}}</ref>

In the UK, a similar group of assistants are currently being evaluated. In Scotland they are named Physician's Assistant - Anaesthesia and in the rest of the UK, they are called anaesthesia practitioners. Their background can be nursing, operating department professional or another profession allied to medicine or a science graduate. Training takes 27 months and to date, the first five have graduated in England.

Anesthesiology Assistants should be distinguished from Anesthesia Technicians.

===Anesthesia technicians===
Anesthesia technicians are specially trained biomedical technicians who assist anesthesiologists, nurse anesthetists, and anesthesiology assistants with monitoring equipment, supplies, and patient care procedures in the operating room.

In New Zealand, anaesthetic technicians complete a course of study recognized by the New Zealand Association of Anaesthetic Technicians and Nurses.

In the United Kingdom, personnel known as ODPs ([[operating department practitioner]]s) or anaesthetic nurses provide support to the physician anaesthetist (anaesthesiologist).

===Veterinary Anesthetists/anesthesiologists===
{{main|Veterinary anesthesia}}
Veterinary anesthetists utilize much the same equipment and drugs as those who provide anesthesia to human patients. In the case of animals, the anesthesia must be tailored to fit the species ranging from large land animals like horses or elephants to birds to aquatic animals like fish. For each species there are ideal, or at least less problematic, methods of safely inducing anesthesia. For wild animals, anesthetic drugs must often be delivered from a distance by means of remote projector systems ("dart guns") before the animal can even be approached. Large domestic animals, like cattle, can often be anesthetized for standing surgery using only local anesthetics and sedative drugs. While most clinical veterinarians and veterinary technicians routinely function as anesthetists in the course of their professional duties, veterinary anesthesiologists in the U.S. are veterinarians who have completed a two-year residency in anesthesia and have qualified for certification by the American College of Veterinary Anesthesiologists.

==Anesthetic agents==
===Local anesthetics===
{{main|Local anesthetic}}
* [[procaine]]
* [[Tetracaine|amethocaine]]
* [[cocaine]]
* [[lidocaine]]
* [[prilocaine]]
* [[Bupivacaine|bupivicaine]]
* [[levobupivacaine]]
* [[ropivacaine]]
* [[Cinchocaine|dibucaine]]

Local anesthetics are agents which prevent transmission of nerve impulses without causing unconsciousness. They act by binding to fast [[sodium channels]] from within (in an open state). Local anesthetics can be either [[ester]] or [[amide]] based.

Ester local anesthetics (e.g., procaine, amethocaine, cocaine) are generally unstable in solution and fast-acting, and allergic reactions are common.

Amide local anesthetics (e.g., lidocaine, prilocaine, bupivicaine, levobupivacaine, ropivacaine and dibucaine) are generally heat-stable, with a long shelf life (around 2 years). They have a slower onset and longer half-life than ester anaesthetics, and are usually [[racemic]] mixtures, with the exception of levobupivacaine (which is S(-) -bupivacaine) and ropivacaine (S(-)-ropivacaine). These agents are generally used within regional and epidural or spinal techniques, due to their longer duration of action, which provides adequate analgesia for surgery, labor, and symptomatic relief.

Only preservative-free local anesthetic agents may be injected [[intrathecal]]ly.

====Adverse effects of local anaesthesia====
Adverse effects of local anesthesia are generally referred to as [[Local Anesthetic Toxicity]].

Effects may be localized or systemic.

Examples of systemic effects of local anesthesia:

Local anesthetic drugs are toxic to the heart (where they cause [[arrhythmia]]) and brain (where they may cause unconsciousness and [[seizures]]). Arrhythmias may be resistant to [[defibrillation]] and other standard treatments, and may lead to loss of heart function and death.

The first evidence of local anesthetic toxicity involves the nervous system, including agitation, confusion, dizziness, blurred vision, tinnitus, a metallic taste in the mouth, and nausea that can quickly progress to seizures and cardiovascular collapse.

Toxicity can occur with any local anesthetic as an individual reaction by that patient. Possible toxicity can be tested with pre-operative procedures to avoid toxic reactions during surgery.

An example of localized effect of local anesthesia:

Direct infiltration of local anesthetic into [[skeletal muscle]] will cause temporary paralysis of the muscle.

===Current inhaled general anesthetic agents===
{{main|General anaesthesia}}
*[[Nitrous oxide]]
*[[Halothane]]
*[[Enflurane]]
*[[Isoflurane]]
*[[Sevoflurane]]
*[[Desflurane]]
*[[Xenon]] (rarely used)

Volatile agents are specially formulated organic liquids that evaporate readily into vapors, and are given by inhalation for induction and/or maintenance of general anesthesia. Nitrous oxide and xenon are gases at room temperature rather than liquids, so they are not considered volatile agents. The ideal anesthetic vapor or gas should be non-flammable, non-explosive, lipid-soluble, and should possess low blood gas solubility, have no end organ (heart, liver, kidney) toxicity or side-effects, should not be metabolized, and should be non-irritant when inhaled by patients.

No anesthetic agent currently in use meets all these requirements. The agents in widespread current use are [[isoflurane]], [[desflurane]], [[sevoflurane]], and [[nitrous oxide]]. [[Nitrous oxide]] is a common adjuvant gas, making it one of the most long-lived drugs still in current use. Because of its low potency, it cannot produce anesthesia on its own but is frequently combined with other agents. Halothane, an agent introduced in the 1950s, has been almost completely replaced in modern anesthesia practice by newer agents because of its shortcomings.<ref name="town">{{cite book | last = Townsend | first = Courtney | title = Sabiston Textbook of Surgery | publisher = Saunders | location = Philadelphia | pages = Chapter 17 – Anesthesiology Principles, Pain Management, and Conscious Sedation | year = 2004 | isbn = 0721653685 }}</ref> Partly because of its side effects, enflurane never gained widespread popularity. <ref name="town"/>

In theory, any inhaled anesthetic agent can be used for induction of general anesthesia. However, most of the halogenated anesthetics are irritating to the airway, perhaps leading to coughing, laryngospasm and overall difficult inductions. For this reason, the most frequently used agent for inhalational induction is sevoflurane. All of the volatile agents can be used alone or in combination with other medications to maintain anesthesia (nitrous oxide is not potent enough to be used as a sole agent).

As of 2007, research into the use of [[xenon]] as an anesthetic is underway, but the gas is very expensive to produce and requires special equipment for delivery, as well as special monitoring and scavenging of waste gas.

Volatile agents are frequently compared in terms of potency, which is inversely proportional to the [[minimum alveolar concentration]]. Potency is directly related to lipid solubility. This is known as the [[Minimum alveolar concentration|Meyer-Overton hypothesis]]. However, certain pharmacokinetic properties of volatile agents have become another point of comparison. Most important of those properties is known as the blood:gas partition coefficient. This concept refers to the relative solubilty of a given agent in blood. Those agents with a lower blood solubility (i.e., a lower blood–gas partition coefficient; e.g., desflurane) give the anesthesia provider greater rapidity in titrating the depth of anesthesia, and permit a more rapid emergence from the anesthetic state upon discontinuing their administration. In fact, newer volatile agents (e.g., sevoflurane, desflurane) have been popular not due to their potency (minimum alveolar concentration), but due to their versatility for a faster emergence from anesthesia, thanks to their lower blood–gas partition coefficient.

===Current intravenous anesthetic agents (non-opioid)===
While there are many drugs that can be used intravenously to produce anesthesia or sedation, the most common are:
*[[Barbiturates]]
**[[Thiopental]]
**[[Methohexital]]
*[[Benzodiazepines]]
**[[Midazolam]]
**[[Lorazepam]]
**[[Diazepam]]
*[[Propofol]]
*[[Etomidate]]
*[[Ketamine]]

The two barbiturates mentioned above, thiopental and methohexital, are ultra-short-acting, and are used to induce and maintain anesthesia.<ref name="miller">{{cite book | last = Miller | first = Ronald | title = Miller's Anesthesia | publisher = Elsevier/Churchill Livingstone | location = New York | year = 2005 | isbn = 0443066566 }}</ref> However, though they produce unconsciousness, they provide no [[analgesia]] (pain relief) and must be used with other agents.<ref name="miller"/> Benzodiazepines can be used for sedation before or after surgery and can be used to induce and maintain general anesthesia.<ref name="miller"/> When benzodiazepines are used to induce general anesthesia, midazolam is preferred.<ref name="miller"/> Benzodiazepines are also used for sedation during procedures that do not require general anesthesia.<ref name="miller"/> Like barbiturates, benzodiazepines have no pain-relieving properties.<ref name="miller"/> Propofol is one of the most commonly used intravenous drugs employed to induce and maintain general anesthesia.<ref name="miller"/> It can also be used for sedation during procedures or in the ICU.<ref name="miller"/> Like the other agents mentioned above, it renders patients unconscious without producing pain relief.<ref name="miller"/> Because of its favorable physiological effects, "etomidate has been primarily used in sick patients".<ref name="miller"/> Ketamine is infrequently used in anesthesia practice because of the unpleasant experiences which sometimes occur upon emergence from anesthesia, which include "vivid dreaming, extracorporeal experiences, and illusions."<ref>Garfield JM, Garfield FB, Stone JG, et al: A comparison of psychologic responses to ketamine and thiopental-nitrous oxide-halothane anesthesia. Anesthesiology 1972; 36:329-338.</ref> However, like etomidate it is frequently used in emergency settings and with sick patients because it produces fewer adverse physiological effects.<ref name="miller"/> Unlike the intravenous anesthetic drugs previously mentioned, ketamine produces profound pain relief, even in doses lower than those which induce general anesthesia.<ref name="miller"/> Also unlike the other anesthetic agents in this section, "patients who receive ketamine alone appear to be in a cataleptic state, unlike other states of anesthesia that resemble normal sleep. Ketamine-anesthetized patients have profound analgesia but keep their eyes open and maintain many reflexes."<ref name="miller"/>

===Current intravenous opioid analgesic agents===
While opioids can produce unconsciousness, they do so unreliably and with significant side effects.<ref>Philbin DM, Rosow CE, Schneider RC, et al: Fentanyl and sufentanil anesthesia revisited: how much is enough?. Anesthesiology 1990; 73:5-11.</ref><ref>Streisand JB, Bailey PL, LeMaire L, Ashburn MA, Tarver SD, Varvel J, Stanley TH: Fentanyl-induced rigidity and unconsciousness in human volunteers. Incidence, duration, and plasma concentrations. Anesthesiology 1993; 78:629-634.</ref> So, while they are rarely used to induce anesthesia, they are frequently used along with other agents such as intravenous non-opioid anesthetics or inhalational anesthetics.<ref name="miller"/> Furthermore, they are used to relieve pain of patients before, during, or after surgery. The following opioids have short onset and duration of action and are frequently used during general anesthesia:
*[[Fentanyl]]
*[[Alfentanil]]
*[[Sufentanil]]
*[[Remifentanil]]

The following agents have longer onset and duration of action and are frequently used for post-operative pain relief:
*[[Buprenorphine]]
*[[Butorphanol]]
*[[Heroin|Diamorphine]], (diacetyl morphine, also known as [[heroin]], not available in U.S.)
*[[Hydromorphone]]
*[[Levorphanol]]
*[[Meperidine]], also called '''pethidine''' in the UK, New Zealand, Australia and other countries
*[[Methadone]]
*[[Morphine]]
*[[Nalbuphine]]
*[[Oxycodone]], (not available intravenously in U.S.)
*[[Oxymorphone]]
*[[Pentazocine]]

===Current muscle relaxants===
Muscle relaxants do not render patients unconscious or relieve pain. Instead, they are sometimes used after a patient is rendered unconscious (induction of anesthesia) to facilitate [[intubation]] or surgery by paralyzing skeletal muscle.

*Depolarizing muscle relaxants
**[[Succinylcholine]] (also known as '''suxamethonium''' in the UK, New Zealand, Australia and other countries)
*Non-depolarizing muscle relaxants
**Short acting
***[[Mivacurium]]
***[[Rapacuronium]]
**Intermediate acting
***[[Atracurium]]
***[[Cisatracurium]]
***[[Vecuronium]]
***[[Rocuronium]]
**Long acting
***[[Pancuronium]]
***Metocurine
***d-[[Tubocurarine]]
***[[Gallamine]]
***[[Alcuronium]]
***[[Doxacurium]]
***[[Pipecuronium bromide|Pipecuronium]]

====Adverse effects of muscle relaxants====
Succinylcholine may cause [[hyperkalemia]] if given to burn patients, or paralyzed (quadraplegic, paraplegic) patients. The mechanism is reported to be through upregulation of [[Acetylcholine receptor|acetylcholine receptors]] in those patient populations. Succinylcholine may also trigger [[malignant hyperthermia]] in susceptible patients.

Another potentially disturbing complication can be '[[anesthesia awareness]]'. In this situation, patients paralyzed with muscle relaxants may awaken during their anesthesia, due to decrease in the levels of drugs providing sedation and/or pain relief. If this fact is missed by the anaesthesia provider, the patient may be aware of his surroundings, but be incapable of moving or communicating that fact. Neurological monitors are becoming increasingly available which may help decrease the incidence of awareness. Most of these monitors use proprietary algorithms monitoring brain activity via evoked potentials. Despite the widespread marketing of these devices many case reports exist in which awareness under anesthesia has occurred despite apparently adequate anesthesia as measured by the neurologic monitor.

===Current intravenous reversal agents===
*[[Naloxone]], reverses the effects of opioids
*[[Flumazenil]], reverses the effects of benzodiazepines
*[[Neostigmine]], reverses the effects of non-depolarizing muscle relaxants
* Suggamadex, more effectively reverses [[rocuronium]] and [[norcuronium]]

==Anesthetic equipment==
{{main|Anaesthetic equipment}}
In modern anesthesia, a wide variety of medical equipment is desirable depending on the necessity for portable field use, surgical operations or intensive care support. Anesthesia practitioners must possess a comprehensive and intricate knowledge of the production and use of various '''medical gases''', anaesthetic agents and '''vapours''', medical '''[[breathing circuits]]''' and the variety of [[anaesthetic machine]]s (including vaporizers, ventilators and pressure gauges) and their corresponding safety features, hazards and limitations of each piece of equipment, for the safe, clinical competence and practical application for day to day practice.

==Anesthetic monitoring==
Patients being treated under general anesthetics must be monitored continuously to ensure the patient's safety. For minor surgery, this generally includes monitoring of [[heart rate]] (via [[ECG]] or [[pulse oximetry]]), [[oxygen saturation]] (via [[pulse oximetry]]), non-invasive [[blood pressure]], inspired and expired gases (for [[oxygen]], [[carbon dioxide]], [[nitrous oxide]], and volatile agents). For moderate to major surgery, monitoring may also include [[body temperature|temperature]], urine output, invasive blood measurements ([[arterial blood pressure]], [[central venous pressure]]), pulmonary artery pressure and pulmonary artery occlusion pressure, cerebral activity (via [[EEG]] analysis), neuromuscular function (via [[peripheral nerve]] stimulation monitoring), and [[cardiac output]]. In addition, the operating room's environment must be monitored for temperature and humidity and for buildup of exhaled [[Inhalational anaesthetic|inhalational anesthetics]] which might impair the health of operating room personnel.

==Anesthesia record==
The anesthesia record is the medical and legal documentation of events during an anesthetic.<ref>Stoelting RK, Miller RD: Basics of Anesthesia, 3rd edition, 1994.</ref> It reflects a detailed and continuous account of drugs, fluids, and blood products administered and procedures undertaken, and also includes the observation of cardiovascular responses, estimated blood loss, urinary body fluids and data from physiologic monitors (Anesthetic monitoring, see above) during the course of an anesthetic. The anesthesia record may be written manually on paper; however, the paper record is increasingly replaced by an electronic record as part of an Anesthesia Information Management System (AIMS).

==Anesthesia Information Management System (AIMS)==
An AIMS refers to any information system that is used as an automated electronic anesthesia record keeper (i.e., connection to patient physiologic monitors and/or the [[Anaesthetic machine]]) and which also may allow the collection and analysis of anesthesia-related perioperative patient [[data]].

==See also==
* [[ASA score]]
* [[EEG measures during anesthesia]]
* [[Patient safety]]
* [[Perioperative mortality]]
* [[Anaesthetic Technician]]
* [[Anaesthesia awareness]]
* [[Allergic reactions during anaesthesia]]

==References==
22. {Apfelbaum JL, Caplan RA, Connis RT, Epstein BS, Nickinovich DG, Warner MA. An Updated Report by the American Society of Anesthesiologists Committee on Standards and Practice Parameters. Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures. Anesthesiology 2011:114 (3): 495-511.

23. Cote CJ: Preoperative preparation and premedication. Br J Anaesth 83:16-28.

24. Hackel A, Gregory, GA. Committee on Pediatric Anesthesiology. Providing Anesthesia for Pediatric Patients. American Society of Anesthesiolgists. 2005: 69 (3): https://www.asahq.org/For-Members/Publications-and-Research/Newsletter-Articles/2005/March2005/providing-anesthesia-for-pediatric-patients.aspx

25. Miller BR, Friesen RH. Oral atropine premedication in infants attenuates cardiovascular depression during halothane anesthesia. Anesth. Analg 1988: 67:180-185{reflist|2}}

==External links==
* [http://www.nda.ox.ac.uk/wfsa/ World Anaesthesia Online] International resource of anaesthetic articles
* [http://www.iars.com/default/default.asp International Anesthesia Research Society]
* [http://ifna-int.org/ifna/page.php International Federation of Nurse Anesthetists]

{{General anesthetics}}
{{Local anesthetics}}
{{Ancient anaesthesia-footer}}
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{{SI}}
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==Overview==
'''Anesthesia''' or '''anaesthesia''' (from [[Greek language|Greek]] ''αν-'' ''an-'' “without” + ''αἲσθησις'' ''aisthesis'' “sensation”) has traditionally meant the condition of having the feeling of [[Pain and nociception|pain]] and other [[sensation]]s blocked. This allows patients to undergo [[surgery]] and other procedures without the distress and pain they would otherwise experience. The word was coined by [[Oliver Wendell Holmes, Sr.]] in 1846. Another definition is a "reversible lack of awareness", whether this is a total lack of awareness (e.g. a general anaesthestic) or a lack of awareness of a part of a the body such as a spinal anaesthetic or another nerve block would cause.

Today, the term '''general anesthesia''' in its most general form can include:
* [[Analgesic|Analgesia]]: blocking the [[consciousness|conscious]] sensation of pain;
* Hypnosis: produces [[unconsciousness]] without analgesia;
* [[Amnesia]]: preventing [[memory]] formation;
* [[Neuromuscular-blocking drugs|Relaxation]]: preventing unwanted movement or muscle tone;
* [[Obtundation]] of reflexes, preventing exaggerated autonomic reflexes.

Patients undergoing surgery usually undergo preoperative evaluation. It includes gathering history of previous anesthetics, and any other medical problems, physical examination, ordering required blood work and consultations prior to surgery.

There are several forms of anesthesia. The following forms refer to states achieved by anesthetics working on the brain:
*General anesthesia: "Drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation." Patients undergoing general anesthesia often cannot maintain their own airway and breathe on their own. While usually administered with inhalational agents, general anesthesia can be achieved with [[Intravenous therapy|intravenous]] agents, such as [[propofol]].<ref name="asadepth">{{Citation
| contribution = Continuum Of Depth Of Sedation Definition Of General Anesthesia And Levels Of Sedation/Analgesia
| title = American Society of Anesthesiologists
| publisher = ASA
| date = [[2004-10-27]]
| year = 2004
| contribution-url = http://www.asahq.org/publicationsAndServices/standards/20.pdf }}</ref>
*Deep [[sedation]]/analgesia: "Drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated or painful stimulation." Patients may sometimes be unable to maintain their airway and breathe on their own.<ref name="asadepth" />
*Moderate sedation/analgesia or conscious sedation: "Drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation." In this state, patients can breathe on their own and need no help maintaining an airway.<ref name="asadepth" />
* Minimal sedation or anxiolysis: "Drug-induced state during which patients respond normally to verbal commands." Though concentration, memory, and coordination may be impaired, patients need no help breathing or maintaining an airway.<ref name="asadepth" />

The level of anesthesia achieved ranges on a continuum of depth of consciousness from minimal sedation to general anesthesia. The depth of consciousness of a patient may change from one minute to the next.

The following refer to states achieved by anesthetics working outside of the brain:
*Regional anesthesia: Loss of pain sensation, with varying degrees of muscle relaxation, in certain regions of the body. Administered with local anesthesia to peripheral nerve bundles, such as the brachial plexus in the neck. Examples include the interscalene block for shoulder surgery, axillary block for wrist surgery, and [[femoral nerve]] block for leg surgery. While traditionally administered as a single injection, newer techniques involve placement of indwelling [[catheters]] for continuous or intermittent administration of local anesthetics.
**[[Spinal anesthesia]]: also known as subarachnoid block. Refers to a Regional block resulting from a small volume of local anesthetics being injected into the [[spinal canal]]. The spinal canal is covered by the [[dura mater]], through which the spinal needle enters. The spinal canal contains [[cerebrospinal fluid]] and the [[spinal cord]]. The sub arachnoid block is usually injected between the 4th and 5th [[lumbar]] [[vertebra]]e, because the spinal cord usually stops at the 1st lumbar vertebra, while the canal continues to the [[sacrum|sacral]] vertebrae. It results in a loss of pain sensation and muscle strength, usually up to the level of the chest (nipple line or 4th thoracic [[dermatomic area|dermatome]]).
**[[Epidural|Epidural anesthesia]]: Regional block resulting from an injection of a large volume of local anesthetic into the [[epidural space]]. The epidural space is a [[potential space]] that lies underneath the [[ligamenta flava]], and outside the dura mater (outside layer of the spinal canal). This is basically an injection around the spinal canal.
* [[Local anesthesia]] is similar to regional anesthesia, but exerts its effect on a smaller area of the body.

Pediatric Anaesthesia:

Anatomic and physiologic differences among neonates, children and adults require differences in the administration of anesthesia compared to adults.

Preoperative Preparation:

The anesthesiologist first assesses the medical condition of the child and psychological status of the child and family while considering the surgical procedure. The anesthesia induction plan is made and explained to the family in order to alleviate fears the child and family may have. Chart review, physical examination is performed. Any medications to be used and equipment monitoring should be explained to patient. Informed consent should be obtained. Care should be taken to alleviate the anxiety of a child and parents, as anxiety felt by the parents my be transferred to the child. For the extremely anxious child that cannot be consoled by these methods heavy premedication is often used. Premedication combination is often [[midazolam]],[[ketamine]], and atropine [[atropine]].

Fasting: Infants and children have a higher metabolic rate and a larger body surface area:weight than adults. As such they become dehydrated more easily than adults. Studies have found not difference in gastric residual volume and pH in children permitted unlimited clear liquids 2 to 3 hours prior to anesthesia induction [[anesthesia induction]].

Current guidelines American Association of Anesthesiologists:

Ingested Material Minimum Fasting Period

Clear liquids 2 h

Breast milk 4 h

Infant formula 6 h

Nonhuman milk 6 h

Light meal 6 h

Premedication: Premedication is not often necessary for children 6 months and younger. Premedication is often used in the extremely fearful child or 10-12 month olds as this is the peak time a child has severe separation anxiety from parents. Oral[[midazolam]] is most commonly used .25-.33 mg/Kg in the US. Premedications may be administered orally, intravenously, intramuscularly, nasally, rectally and sublingually.

Except for atropine, anticholinergics are not commonly used in infants and children as they often do not reduce laryngeal reflexes during anesthesia induction. [[Atropine]] in infants less than 6 months of age less than 45 minutes before induction reduces hypotension during in induction with inhaled anesthetics.

Induction of Anesthesia:

==History==
===Herbal derivatives===
The first [[herbalism|herbal]] anesthesia was administered in prehistory. [[Opium]] poppy capsules were collected in 4200 BC, and opium poppies were farmed in Sumeria and succeeding empires. The use of opium-like preparations in anaesthesia is recorded in the Ebers Papyrus of 1500 BC. By 1100 BC poppies were scored for opium collection in Cyprus by methods similar to those used in the present day, and simple apparatus for smoking of opium were found in a Minoan temple. Opium was not introduced to India and China until 330 BC and 600–1200 AD, but these nations pioneered the use of cannabis incense and [[aconitum]]. In the second century, according to the Book of Later Han, the physician Hua Tuo performed abdominal surgery using an anesthetic substance called ''mafeisan'' (麻沸散 "cannabis boil powder") dissolved in wine. Throughout Europe, Asia, and the Americas a variety of Solanum species containing potent [[tropane]] alkaloids were used, such as mandrake, [[henbane]], [[Datura metel]], and [[Datura inoxia]]. Classic Greek and Roman medical texts by Hippocrates, Theophrastus, Aulus Cornelius Celsus, Pedanius Dioscorides, and Pliny the Elder discussed the use of opium and Solanum species, and treatment with the combined alkaloids proved a mainstay of anaesthesia until the nineteenth century. In the Americas [[coca]] was also an important anaesthetic used in [[Trepanation|trephining]] operations. Incan shamans chewed [[coca]] leaves and performed operations on the skull while spitting into the wounds they had inflicted to anaesthetize the site. [[ethanol|Alcohol]] was also used, its [[vasodilation|vasodilatory]] properties being unknown. Ancient herbal anaesthetics have variously been called soporifics, [[anodyne]]s, and [[narcotic]]s, depending on whether the emphasis is on producing unconsciousness or relieving pain.

In Central Asia, in the 10th century work of Shahnameh, the author, Ferdowsi, describes a [[caesarean section]] performed on Rudaba when giving birth, in which a special wine agent was prepared as an anesthetic<ref>''Medicine throughout Antiquity''. Benjamin Lee Gordon. 1949. p.306</ref> by a Zoroastrian priest, and used to produce unconsciousness for the operation. Although largely mythical in content, the passage does at least illustrate knowledge of anesthesia in ancient Persia.

The use of herbal anaesthesia had a crucial drawback compared to modern practice — as lamented by Fallopus, "When soporifics are weak they are useless, and when strong, they kill." To overcome this, production was typically standardized as much as feasible, with production occurring from specific famous locations (such as opium from the fields of Thebes in ancient Egypt). Anaesthetics were sometimes administered in the spongia somnifera, a sponge into which a large quantity of drug was allowed to dry, from which a saturated solution could be trickled into the nose of the patient. At least in more recent centuries, trade was often highly standardized, with the drying and packing of [[opium]] in standard chests, for example. In the 19th century, varying [[aconitum]] alkaloids from a variety of species were standardized by testing with guinea pigs. Despite these refinements, the discovery of [[morphine]], a purified alkaloid that soon afterward could be injected by [[Hypodermic needle|hypodermic]] for a consistent dosage, was enthusiastically received and led to the foundation of the modern pharmaceutical industry.

Another factor affecting ancient anaesthesia is that drugs used systemically in modern times were often administered locally, reducing the risk to the patient. [[Opium]] used directly in a wound acts on peripheral [[opioid receptor]]s to serve as an analgesic, and a medicine containing willow leaves ([[salicylate]], the predecessor of [[aspirin]]) would then be applied directly to the source of inflammation.

In 1804, the Japanese surgeon Hanaoka Seishū performed general [[anaesthesia]] for the operation of a breast cancer ([[mastectomy]]), by combining Chinese herbal medicine know-how and Western [[surgery]] techniques learned through "Rangaku", or "Dutch studies". His patient was a 60-year-old woman called Kan Aiya.<ref>[http://www.general-anaesthesia.com/ Utopian surgery: Early arguments against anaesthesiain surgery, dentistry and childbirth]</ref> He used a compound he called Tsusensan, based on the plants Datura metel, Aconitum and others.

===Non-pharmacological methods===
[[Hypnosurgery|Hypnotism]] and [[acupuncture]] have a long history of use as anesthetic techniques. In China, Taoist medical practitioners developed anesthesia by means of [[acupuncture]]. Chilling tissue (e.g. with ice) can temporarily cause nerve fibers ([[axon]]s) to stop conducting sensation, while [[hyperventilation]] can cause brief alteration in conscious perception of stimuli including pain (see [[Lamaze]]).

In modern anesthetic practice, these techniques are seldom employed.

===Early gases and vapours===
The works of Greek authors such as [[Dioscorides]] were well-known in the Islamic Empire, and physicians such as al-Razi, [[Avicenna]], and Abu al-Qasim wrote medical textbooks of great importance in the development of medicine in Europe and the Middle East. Muslim [[anesthesiologist]]s were the first to utilize oral as well as [[Inhalational anaesthetic|inhalant anesthetics]]. In Islamic Spain, Abu al-Qasim (Abulcasis) and Ibn Zuhr (Avenzoar), among other Muslim surgeons, performed hundreds of [[Surgery|surgeries]] under inhalant anesthesia with the use of [[narcotic]]-soaked sponges which were placed over the face. Abulcasis and Ibn Sina (Avicenna) wrote about anasthesia in their influential medical encyclopedias, the ''al-Tasrif'' and ''[[The Canon of Medicine]]''.<ref>Dr. Kasem Ajram (1992). ''Miracle of Islamic Science'', Appendix B. Knowledge House Publishers. ISBN 0911119434.</ref><ref>[[Sigrid Hunke]] (1969), ''Allah Sonne Uber Abendland, Unser Arabische Erbe'', Second Edition, p. 279-280: {{quote|"The science of medicine has gained a great and extremely important discovery and that is the use of general anaesthetics for surgical operations, and how unique, efficient, and merciful for those who tried it the Muslim anaesthetic was. It was quite different from the drinks the Indians, Romans and Greeks were forcing their patients to have for relief of pain. There had been some allegations to credit this discovery to an Italian or to an Alexandrian, but the truth is and history proves that, the art of using the anaesthetic sponge is a pure Muslim technique, which was not known before. The sponge used to be dipped and left in a mixture prepared from cannabis, opium, hyoscyamus and a plant called Zoan."}} ([[cf.]] Prof. Dr. M. Taha Jasser, [http://www.islamset.com/hip/i_medcin/taha_jasser.html Anaesthesia in Islamic medicine and its influence on Western civilization], Conference
on Islamic Medicine)</ref>

[[Image:Southworth & Hawes - First etherized operation (re-enactment).jpg|thumb|right|300px|Contemporary re-enactment of Morton's October 16, 1846, ether operation; daguerrotype by Southworth & Hawes.]]

In the West, the development of effective anesthetics in the 19th century was, with Listerian techniques, one of the keys to successful surgery. Henry Hill Hickman experimented with [[carbon dioxide]] in the 1820s. The anesthetic qualities of [[nitrous oxide]] (isolated in 1773 by Joseph Priestley) were discovered by the British chemist Humphry Davy about 1799 when he was an assistant to Thomas Beddoes, and reported in a paper in 1800. But initially the medical uses of this so-called "laughing gas" were limited — its main role was in entertainment. It was used on 30 September 1846 for painless tooth extraction upon patient Eben Frost by American [[dentist]] William Thomas Green Morton. Horace Wells of Connecticut, a traveling dentist, had demonstrated it the previous year 1845, at Massachusetts General Hospital. Wells made a mistake, in choosing a particularly sturdy male volunteer, and the patient suffered considerable pain. This lost the colorful Wells any support. Later the patient told Wells he screamed in shock and not in pain. A subsequently drunk Wells died in jail, by cutting his femoral artery, after allegedly assaulting a prostitute with sulfuric acid.

Another dentist,William E. Clarke, performed an extraction in January 1842 using a different chemical, [[diethyl ether]] (discovered by Valerius Cordus in 1540). In March 1842 in Danielsville, Georgia, Dr. Crawford Long was the first to use anaesthesia during an operation, giving it to a boy (John Venables) before excising a cyst from his neck; however, he did not publicize this information until later.

On October 16, 1846, another dentist, William Thomas Green Morton, invited to the Massachusetts General Hospital, performed the first public demonstration of diethyl ether (then called sulfuric ether) as an anesthetic agent, for a patient (Edward Gilbert Abbott) undergoing an excision of a vascular tumor from his neck. In a letter to Morton shortly thereafter, Oliver Wendell Holmes, Sr. proposed naming the procedure ''anæsthesia''.
[[Image:CrawfordLong.jpg|left|thumb|180px|Anesthesia pioneer Crawford W. Long]]
Despite Morton's efforts to keep "his" compound a secret, which he named "Letheon" and for which he received a US patent, the news of the discovery and the nature of the compound spread very quickly to Europe in late 1846. Here, respected surgeons—including Liston, Dieffenbach, Pirogoff, and Syme—undertook numerous operations with [[ether]].
An American-born physician, Boott — who had traveled to London — encouraged a leading dentist, Mr James Robinson, to perform a dental procedure on a Miss Lonsdale. This was the first case of an operator-anesthetist. On the same day, 19 December 1846 in Dumfries Royal Infirmary, Scotland, a Dr. Scott used ether for a surgical procedure. The first use of anesthesia in the Southern Hemisphere took place in Launceston, Tasmania, that same year. Ether has a number of drawbacks, such as its tendency to induce [[vomiting]] and its flammability. In England it was quickly replaced with [[chloroform]].

Discovered in 1831, the use of chloroform in anesthesia is usually linked to James Young Simpson, who, in a wide-ranging study of organic compounds, found chloroform's efficacy on 4 November 1847. Its use spread quickly and gained royal approval in 1853 when John Snow gave it to Queen Victoria during the birth of Prince Leopold. Unfortunately, chloroform is not as safe an agent as ether, especially when administered by an untrained practitioner (medical students, nurses, and occasionally members of the public were often pressed into giving anesthetics at this time). This led to many deaths from the use of chloroform that (with hindsight) might have been preventable. The first fatality directly attributed to chloroform anesthesia (Hannah Greener) was recorded on 28 January 1848.

John Snow of London published articles from May 1848 onwards 'On Narcotism by the Inhalation of Vapours' in the London Medical Gazette. Snow also involved himself in the production of equipment needed for inhalational anesthesia.

The surgical amphitheatre at Massachusetts General Hospital, or "ether dome" still exists today, although it is used for lectures and not surgery. The public can visit the amphitheater on weekdays when it is not in use.

===Early local anesthetics===
The first effective local anesthetic was [[cocaine]]. Isolated in 1859, it was first used by Karl Koller, at the suggestion of Sigmund Freud, in ophthalmic surgery in 1884. Before that doctors had used a salt and ice mix for the numbing effects of cold, which could only have limited application. Similar numbing was also induced by a spray of ether or ethyl chloride. A number of cocaine derivatives and safer replacements were soon produced, including [[procaine]] (1905), Eucaine (1900), Stovaine (1904), and [[lidocaine]] (1943).

[[Opioid]]s were first used by Racoviceanu-Piteşti, who reported his work in 1901.

==Anesthesia providers==

Physicians specialising in peri-operative care, development of an anesthetic plan, and the administration of anesthetics are known in the United States as anesthesiologists and in the UK and Canada as anaesthetists or anaesthesiologists. All anaesthetics in the UK, Australia, New Zealand and Japan are administered by physicians. Nurse anesthetists also administer anesthesia in 109 nations.<ref>{{cite web | title = Nurse anestheisa worldwide: practice, education and regulation | url = http://ifna-int.org/ifna/e107_files/downloads/Practice.pdf| format = PDF | publisher = International Federation of Nurse Anesthetists | accessdate = 2007-02-08}}</ref> In the US, 35% of anesthetics are provided by physicians in solo practice, about 55% are provided by ACTs with anesthesiologists medically directing Anesthesiologist Assistants, CRNAs, and about 10% are provided by CRNAs in solo practice. <ref>{{cite web | date = [[2007-02-01]] | title = Is Physician Anesthesia Cost-Effective? | url = http://www.anesthesia-analgesia.org/cgi/content/full/98/3/750#R7-138848 | format = html | publisher = Anesth Analg | accessdate = 2007-02-15}}</ref> <ref>{{cite web | date = [[2007-02-01]] | title = When do anesthesiologists delegate? | url = http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&list_uids=2725080&dopt=Abstract | format = html | publisher = Med Care | accessdate = 2007-02-15}}</ref> <ref>{{cite web | title = Nurse anestheisa worldwide: practice, education and regulation | url = http://ifna-int.org/ifna/e107_files/downloads/Practice.pdf| format = PDF | publisher = International Federation of Nurse Anesthetists | accessdate = 2007-02-08}}</ref>
- <ref>{{cite web | date = [[2007-02-25]] | title =Surgical mortality and type of anesthesia provider | url = http://www.aana.com/news.aspx?ucNavMenu_TSMenuTargetID=171&ucNavMenu_TSMenuTargetType=4&ucNavMenu_TSMenuID=6&id=1606&terms=medical+direction+percent&searchtype=1&fragment=True | format = html | publisher = AANA | accessdate = 2007-02-25}}</ref>
- <ref>{{cite web | date = [[2007-02-25]] | title = Anesthesia Providers, Patient Outcomes, and Cost | url = http://nursing.fiu.edu/anesthesiology/COURSES/Semester%203/NGR%206760%20ANE%20Prof%20Aspects/PROF%20Readings/Abenstein.pdf | format = pdf | publisher = Anesth Analg | accessdate = 2007-02-25}}</ref>

===Physician anesthesiologists/anaesthetists/anaesthesiologists===

In the US, medical doctors who specialize in anesthesiology are called anesthesiologists. Such physicians in the UK and Canada are called anaesthetists or anaesthesiologists.

In the U.S., a physician specializing in anesthesiology completes 4 years of college, 4 years of medical school, 1 year of internship, and 3 years of residency. According to the American Society of Anesthesiologists, anesthesiologists provide or participate in more than 90 percent of the 40 million anesthetics delivered annually.<ref>{{cite web | title = ASA Fast Facts: Anesthesiologists Provide Or Participate In 90 Percent Of All Annual Anesthetics | url = http://www.asahq.org/PressRoom/homepage.html | format = html | publisher = ASA | accessdate = 2007-03-22}}</ref>

In the UK this training lasts a minimum of seven years after the awarding of a medical degree and two years of basic residency, and takes place under the supervision of the [[Royal College of Anaesthetists]]. In Australia and New Zealand, it lasts five years after the awarding of a medical degree and two years of basic residency, under the supervision of the Australian and New Zealand College of Anaesthetists. Other countries have similar systems, including Ireland (the Faculty of Anaesthetists of the Royal College of Surgeons in Ireland), Canada and South Africa (the College of Anaesthetists of South Africa).

In the UK, completion of the examinations set by the Royal College of Anaesthetists leads to award of the Diploma of Fellowship of the Royal College of Anaesthetists (FRCA). In the US, completion of the written and oral Board examinations by a [[physician]] [[anesthesiologist]] allows one to be called "Board Certified" or a "Diplomate" of the American Board of Anesthesiology.

Other specialties within medicine are closely affiliated to anaesthetics. These include [[intensive care medicine]] and [[Pain management|pain medicine]]. Specialists in these disciplines have usually done some training in anaesthetics. The role of the anaesthetist is changing. It is no longer limited to the operation itself. Many anaesthetists consider themselves to be peri-operative physicians, and will involve themselves in optimizing the patient's health before surgery (colloquially called "work-up"), performing the anaesthetic, following up the patient in the [[post anesthesia care unit]] and post-operative wards, and ensuring optimal [[analgesia]] throughout.

It is important to note that the term ''anesthetist'' in the United States usually refers to registered nurses who have completed specialized education and training in nurse anesthesia to become certified registered nurse anesthetists (CRNAs). As noted above, the term ''anaesthetist'' in the UK and Cananda refers to medical doctors who specialize in anesthesiology.

===Nurse Anesthetists===
In the United States, advance practice nurses specializing in the provision of anesthesia care are known as Certified Registered Nurse Anesthetists (CRNAs). CRNAs provide 27 million hands-on anesthetics each year, roughly two thirds of the US total and are the sole providers of anesthesia in more than 70 percent of rural area hospitals. According to the American Association of Nurse Anesthetists, the 36,000 CRNAs in the US administer approximately 27 million anesthetics each year.[[http://aana.com/aboutaana.aspx?ucNavMenu_TSMenuTargetID=127&ucNavMenu_TSMenuTargetType=4&ucNavMenu_TSMenuID=6&id=38]] CRNAs are the sole providers of anesthesia in more than 70 percent of rural area hospitals. Thirty-four percent of nurse anesthetists practice in communities of less than 50,000. CRNAs start school with a bachelors degree and at least 1 year of acute care nursing experience[[http://aana.com/BecomingCRNA.aspx?ucNavMenu_TSMenuTargetID=18&ucNavMenu_TSMenuTargetType=4&ucNavMenu_TSMenuID=6&id=1018]], and gain a masters degree in nurse anesthesia before passing the mandatory Certification Exam. The average CRNA student has 5-7 years of nursing experience before entering a 27-36 month masters level anesthesia program.<ref>{{cite web | date = [[2006-02-01]] | title = Television conferencing: Is it as effective as "in person" lectures for nurse anesthesia education? | url = http://www.aana.com/uploadedFiles/Resources/Publications/AANA_Journal_-_Public/2006/February_2006/p19-21.pdf | format = PDF | publisher = AANA Journal | accessdate = 2007-02-05}}</ref>

CRNAs may work with podiatrists, dentists, anesthesiologists, surgeons, obstetricians and other professionals requiring their services. CRNAs administer anesthesia in all types of surgical cases, and are able to apply all the accepted anesthetic techniques -- general, regional, local, or sedation. Nurse Anesthetists are licensed to practice anesthesia independently, as well as in Anesthesia Care Teams.<ref>{{cite web | title = Anethesiology Care Team | url = http://www.durhamregional.org/healthlibrary/behind_the_scenes/20060518173014802 | format = html | publisher = durhamregional.org | accessdate = 2007-02-11}}</ref> CRNAs may also practice in parallel with their physician colleagues in certain institutions, both types of provider caring for their own patients independently and consulting whenever collaboration is appropriate to patient outcome. CRNAs may also practice in parallel with their physician colleagues in certain institutions, both types of provider caring for their own patients independently and consulting whenever collaboration is appropriate to patient outcome.

===Anesthesiology assistants===

In the US, anesthesiologist assistants (AAs) are physician assistants who have undertaken specialized education and training to provide anesthesia care. AAs typically hold a masters degree and practice under physician supervision in sixteen states through licensing, certification or physician delegation.<ref>{{cite web |title = Five facts about AAs| url = http://www.anesthetist.org/content/view/14/38/ | format = HTML | publisher = American Academy of Anesthesiologist Assistants | accessdate = 2007-02-08}}</ref>

In the UK, a similar group of assistants are currently being evaluated. In Scotland they are named Physician's Assistant - Anaesthesia and in the rest of the UK, they are called anaesthesia practitioners. Their background can be nursing, operating department professional or another profession allied to medicine or a science graduate. Training takes 27 months and to date, the first five have graduated in England.

Anesthesiology Assistants should be distinguished from Anesthesia Technicians.

===Anesthesia technicians===
Anesthesia technicians are specially trained biomedical technicians who assist anesthesiologists, nurse anesthetists, and anesthesiology assistants with monitoring equipment, supplies, and patient care procedures in the operating room.

In New Zealand, anaesthetic technicians complete a course of study recognized by the New Zealand Association of Anaesthetic Technicians and Nurses.

In the United Kingdom, personnel known as ODPs ([[operating department practitioner]]s) or anaesthetic nurses provide support to the physician anaesthetist (anaesthesiologist).

===Veterinary Anesthetists/anesthesiologists===
{{main|Veterinary anesthesia}}
Veterinary anesthetists utilize much the same equipment and drugs as those who provide anesthesia to human patients. In the case of animals, the anesthesia must be tailored to fit the species ranging from large land animals like horses or elephants to birds to aquatic animals like fish. For each species there are ideal, or at least less problematic, methods of safely inducing anesthesia. For wild animals, anesthetic drugs must often be delivered from a distance by means of remote projector systems ("dart guns") before the animal can even be approached. Large domestic animals, like cattle, can often be anesthetized for standing surgery using only local anesthetics and sedative drugs. While most clinical veterinarians and veterinary technicians routinely function as anesthetists in the course of their professional duties, veterinary anesthesiologists in the U.S. are veterinarians who have completed a two-year residency in anesthesia and have qualified for certification by the American College of Veterinary Anesthesiologists.

==Anesthetic agents==
===Local anesthetics===
{{main|Local anesthetic}}
* [[procaine]]
* [[Tetracaine|amethocaine]]
* [[cocaine]]
* [[lidocaine]]
* [[prilocaine]]
* [[Bupivacaine|bupivicaine]]
* [[levobupivacaine]]
* [[ropivacaine]]
* [[Cinchocaine|dibucaine]]

Local anesthetics are agents which prevent transmission of nerve impulses without causing unconsciousness. They act by binding to fast [[sodium channels]] from within (in an open state). Local anesthetics can be either [[ester]] or [[amide]] based.

Ester local anesthetics (e.g., procaine, amethocaine, cocaine) are generally unstable in solution and fast-acting, and allergic reactions are common.

Amide local anesthetics (e.g., lidocaine, prilocaine, bupivicaine, levobupivacaine, ropivacaine and dibucaine) are generally heat-stable, with a long shelf life (around 2 years). They have a slower onset and longer half-life than ester anaesthetics, and are usually [[racemic]] mixtures, with the exception of levobupivacaine (which is S(-) -bupivacaine) and ropivacaine (S(-)-ropivacaine). These agents are generally used within regional and epidural or spinal techniques, due to their longer duration of action, which provides adequate analgesia for surgery, labor, and symptomatic relief.

Only preservative-free local anesthetic agents may be injected [[intrathecal]]ly.

====Adverse effects of local anaesthesia====
Adverse effects of local anesthesia are generally referred to as [[Local Anesthetic Toxicity]].

Effects may be localized or systemic.

Examples of systemic effects of local anesthesia:

Local anesthetic drugs are toxic to the heart (where they cause [[arrhythmia]]) and brain (where they may cause unconsciousness and [[seizures]]). Arrhythmias may be resistant to [[defibrillation]] and other standard treatments, and may lead to loss of heart function and death.

The first evidence of local anesthetic toxicity involves the nervous system, including agitation, confusion, dizziness, blurred vision, tinnitus, a metallic taste in the mouth, and nausea that can quickly progress to seizures and cardiovascular collapse.

Toxicity can occur with any local anesthetic as an individual reaction by that patient. Possible toxicity can be tested with pre-operative procedures to avoid toxic reactions during surgery.

An example of localized effect of local anesthesia:

Direct infiltration of local anesthetic into [[skeletal muscle]] will cause temporary paralysis of the muscle.

===Current inhaled general anesthetic agents===
{{main|General anaesthesia}}
*[[Nitrous oxide]]
*[[Halothane]]
*[[Enflurane]]
*[[Isoflurane]]
*[[Sevoflurane]]
*[[Desflurane]]
*[[Xenon]] (rarely used)

Volatile agents are specially formulated organic liquids that evaporate readily into vapors, and are given by inhalation for induction and/or maintenance of general anesthesia. Nitrous oxide and xenon are gases at room temperature rather than liquids, so they are not considered volatile agents. The ideal anesthetic vapor or gas should be non-flammable, non-explosive, lipid-soluble, and should possess low blood gas solubility, have no end organ (heart, liver, kidney) toxicity or side-effects, should not be metabolized, and should be non-irritant when inhaled by patients.

No anesthetic agent currently in use meets all these requirements. The agents in widespread current use are [[isoflurane]], [[desflurane]], [[sevoflurane]], and [[nitrous oxide]]. [[Nitrous oxide]] is a common adjuvant gas, making it one of the most long-lived drugs still in current use. Because of its low potency, it cannot produce anesthesia on its own but is frequently combined with other agents. Halothane, an agent introduced in the 1950s, has been almost completely replaced in modern anesthesia practice by newer agents because of its shortcomings.<ref name="town">{{cite book | last = Townsend | first = Courtney | title = Sabiston Textbook of Surgery | publisher = Saunders | location = Philadelphia | pages = Chapter 17 – Anesthesiology Principles, Pain Management, and Conscious Sedation | year = 2004 | isbn = 0721653685 }}</ref> Partly because of its side effects, enflurane never gained widespread popularity. <ref name="town"/>

In theory, any inhaled anesthetic agent can be used for induction of general anesthesia. However, most of the halogenated anesthetics are irritating to the airway, perhaps leading to coughing, laryngospasm and overall difficult inductions. For this reason, the most frequently used agent for inhalational induction is sevoflurane. All of the volatile agents can be used alone or in combination with other medications to maintain anesthesia (nitrous oxide is not potent enough to be used as a sole agent).

As of 2007, research into the use of [[xenon]] as an anesthetic is underway, but the gas is very expensive to produce and requires special equipment for delivery, as well as special monitoring and scavenging of waste gas.

Volatile agents are frequently compared in terms of potency, which is inversely proportional to the [[minimum alveolar concentration]]. Potency is directly related to lipid solubility. This is known as the [[Minimum alveolar concentration|Meyer-Overton hypothesis]]. However, certain pharmacokinetic properties of volatile agents have become another point of comparison. Most important of those properties is known as the blood:gas partition coefficient. This concept refers to the relative solubilty of a given agent in blood. Those agents with a lower blood solubility (i.e., a lower blood–gas partition coefficient; e.g., desflurane) give the anesthesia provider greater rapidity in titrating the depth of anesthesia, and permit a more rapid emergence from the anesthetic state upon discontinuing their administration. In fact, newer volatile agents (e.g., sevoflurane, desflurane) have been popular not due to their potency (minimum alveolar concentration), but due to their versatility for a faster emergence from anesthesia, thanks to their lower blood–gas partition coefficient.

===Current intravenous anesthetic agents (non-opioid)===
While there are many drugs that can be used intravenously to produce anesthesia or sedation, the most common are:
*[[Barbiturates]]
**[[Thiopental]]
**[[Methohexital]]
*[[Benzodiazepines]]
**[[Midazolam]]
**[[Lorazepam]]
**[[Diazepam]]
*[[Propofol]]
*[[Etomidate]]
*[[Ketamine]]

The two barbiturates mentioned above, thiopental and methohexital, are ultra-short-acting, and are used to induce and maintain anesthesia.<ref name="miller">{{cite book | last = Miller | first = Ronald | title = Miller's Anesthesia | publisher = Elsevier/Churchill Livingstone | location = New York | year = 2005 | isbn = 0443066566 }}</ref> However, though they produce unconsciousness, they provide no [[analgesia]] (pain relief) and must be used with other agents.<ref name="miller"/> Benzodiazepines can be used for sedation before or after surgery and can be used to induce and maintain general anesthesia.<ref name="miller"/> When benzodiazepines are used to induce general anesthesia, midazolam is preferred.<ref name="miller"/> Benzodiazepines are also used for sedation during procedures that do not require general anesthesia.<ref name="miller"/> Like barbiturates, benzodiazepines have no pain-relieving properties.<ref name="miller"/> Propofol is one of the most commonly used intravenous drugs employed to induce and maintain general anesthesia.<ref name="miller"/> It can also be used for sedation during procedures or in the ICU.<ref name="miller"/> Like the other agents mentioned above, it renders patients unconscious without producing pain relief.<ref name="miller"/> Because of its favorable physiological effects, "etomidate has been primarily used in sick patients".<ref name="miller"/> Ketamine is infrequently used in anesthesia practice because of the unpleasant experiences which sometimes occur upon emergence from anesthesia, which include "vivid dreaming, extracorporeal experiences, and illusions."<ref>Garfield JM, Garfield FB, Stone JG, et al: A comparison of psychologic responses to ketamine and thiopental-nitrous oxide-halothane anesthesia. Anesthesiology 1972; 36:329-338.</ref> However, like etomidate it is frequently used in emergency settings and with sick patients because it produces fewer adverse physiological effects.<ref name="miller"/> Unlike the intravenous anesthetic drugs previously mentioned, ketamine produces profound pain relief, even in doses lower than those which induce general anesthesia.<ref name="miller"/> Also unlike the other anesthetic agents in this section, "patients who receive ketamine alone appear to be in a cataleptic state, unlike other states of anesthesia that resemble normal sleep. Ketamine-anesthetized patients have profound analgesia but keep their eyes open and maintain many reflexes."<ref name="miller"/>

===Current intravenous opioid analgesic agents===
While opioids can produce unconsciousness, they do so unreliably and with significant side effects.<ref>Philbin DM, Rosow CE, Schneider RC, et al: Fentanyl and sufentanil anesthesia revisited: how much is enough?. Anesthesiology 1990; 73:5-11.</ref><ref>Streisand JB, Bailey PL, LeMaire L, Ashburn MA, Tarver SD, Varvel J, Stanley TH: Fentanyl-induced rigidity and unconsciousness in human volunteers. Incidence, duration, and plasma concentrations. Anesthesiology 1993; 78:629-634.</ref> So, while they are rarely used to induce anesthesia, they are frequently used along with other agents such as intravenous non-opioid anesthetics or inhalational anesthetics.<ref name="miller"/> Furthermore, they are used to relieve pain of patients before, during, or after surgery. The following opioids have short onset and duration of action and are frequently used during general anesthesia:
*[[Fentanyl]]
*[[Alfentanil]]
*[[Sufentanil]]
*[[Remifentanil]]

The following agents have longer onset and duration of action and are frequently used for post-operative pain relief:
*[[Buprenorphine]]
*[[Butorphanol]]
*[[Heroin|Diamorphine]], (diacetyl morphine, also known as [[heroin]], not available in U.S.)
*[[Hydromorphone]]
*[[Levorphanol]]
*[[Meperidine]], also called '''pethidine''' in the UK, New Zealand, Australia and other countries
*[[Methadone]]
*[[Morphine]]
*[[Nalbuphine]]
*[[Oxycodone]], (not available intravenously in U.S.)
*[[Oxymorphone]]
*[[Pentazocine]]

===Current muscle relaxants===
Muscle relaxants do not render patients unconscious or relieve pain. Instead, they are sometimes used after a patient is rendered unconscious (induction of anesthesia) to facilitate [[intubation]] or surgery by paralyzing skeletal muscle.

*Depolarizing muscle relaxants
**[[Succinylcholine]] (also known as '''suxamethonium''' in the UK, New Zealand, Australia and other countries)
*Non-depolarizing muscle relaxants
**Short acting
***[[Mivacurium]]
***[[Rapacuronium]]
**Intermediate acting
***[[Atracurium]]
***[[Cisatracurium]]
***[[Vecuronium]]
***[[Rocuronium]]
**Long acting
***[[Pancuronium]]
***Metocurine
***d-[[Tubocurarine]]
***[[Gallamine]]
***[[Alcuronium]]
***[[Doxacurium]]
***[[Pipecuronium bromide|Pipecuronium]]

====Adverse effects of muscle relaxants====
Succinylcholine may cause [[hyperkalemia]] if given to burn patients, or paralyzed (quadraplegic, paraplegic) patients. The mechanism is reported to be through upregulation of [[Acetylcholine receptor|acetylcholine receptors]] in those patient populations. Succinylcholine may also trigger [[malignant hyperthermia]] in susceptible patients.

Another potentially disturbing complication can be '[[anesthesia awareness]]'. In this situation, patients paralyzed with muscle relaxants may awaken during their anesthesia, due to decrease in the levels of drugs providing sedation and/or pain relief. If this fact is missed by the anaesthesia provider, the patient may be aware of his surroundings, but be incapable of moving or communicating that fact. Neurological monitors are becoming increasingly available which may help decrease the incidence of awareness. Most of these monitors use proprietary algorithms monitoring brain activity via evoked potentials. Despite the widespread marketing of these devices many case reports exist in which awareness under anesthesia has occurred despite apparently adequate anesthesia as measured by the neurologic monitor.

===Current intravenous reversal agents===
*[[Naloxone]], reverses the effects of opioids
*[[Flumazenil]], reverses the effects of benzodiazepines
*[[Neostigmine]], reverses the effects of non-depolarizing muscle relaxants
* Suggamadex, more effectively reverses [[rocuronium]] and [[norcuronium]]

==Anesthetic equipment==
{{main|Anaesthetic equipment}}
In modern anesthesia, a wide variety of medical equipment is desirable depending on the necessity for portable field use, surgical operations or intensive care support. Anesthesia practitioners must possess a comprehensive and intricate knowledge of the production and use of various '''medical gases''', anaesthetic agents and '''vapours''', medical '''[[breathing circuits]]''' and the variety of [[anaesthetic machine]]s (including vaporizers, ventilators and pressure gauges) and their corresponding safety features, hazards and limitations of each piece of equipment, for the safe, clinical competence and practical application for day to day practice.

==Anesthetic monitoring==
Patients being treated under general anesthetics must be monitored continuously to ensure the patient's safety. For minor surgery, this generally includes monitoring of [[heart rate]] (via [[ECG]] or [[pulse oximetry]]), [[oxygen saturation]] (via [[pulse oximetry]]), non-invasive [[blood pressure]], inspired and expired gases (for [[oxygen]], [[carbon dioxide]], [[nitrous oxide]], and volatile agents). For moderate to major surgery, monitoring may also include [[body temperature|temperature]], urine output, invasive blood measurements ([[arterial blood pressure]], [[central venous pressure]]), pulmonary artery pressure and pulmonary artery occlusion pressure, cerebral activity (via [[EEG]] analysis), neuromuscular function (via [[peripheral nerve]] stimulation monitoring), and [[cardiac output]]. In addition, the operating room's environment must be monitored for temperature and humidity and for buildup of exhaled [[Inhalational anaesthetic|inhalational anesthetics]] which might impair the health of operating room personnel.

==Anesthesia record==
The anesthesia record is the medical and legal documentation of events during an anesthetic.<ref>Stoelting RK, Miller RD: Basics of Anesthesia, 3rd edition, 1994.</ref> It reflects a detailed and continuous account of drugs, fluids, and blood products administered and procedures undertaken, and also includes the observation of cardiovascular responses, estimated blood loss, urinary body fluids and data from physiologic monitors (Anesthetic monitoring, see above) during the course of an anesthetic. The anesthesia record may be written manually on paper; however, the paper record is increasingly replaced by an electronic record as part of an Anesthesia Information Management System (AIMS).

==Anesthesia Information Management System (AIMS)==
An AIMS refers to any information system that is used as an automated electronic anesthesia record keeper (i.e., connection to patient physiologic monitors and/or the [[Anaesthetic machine]]) and which also may allow the collection and analysis of anesthesia-related perioperative patient [[data]].

==See also==
* [[ASA score]]
* [[EEG measures during anesthesia]]
* [[Patient safety]]
* [[Perioperative mortality]]
* [[Anaesthetic Technician]]
* [[Anaesthesia awareness]]
* [[Allergic reactions during anaesthesia]]

==References==
22. {Apfelbaum JL, Caplan RA, Connis RT, Epstein BS, Nickinovich DG, Warner MA. An Updated Report by the American Society of Anesthesiologists Committee on Standards and Practice Parameters. Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures. Anesthesiology 2011:114 (3): 495-511.

23. Cote CJ: Preoperative preparation and premedication. Br J Anaesth 83:16-28.

24. Hackel A, Gregory, GA. Committee on Pediatric Anesthesiology. Providing Anesthesia for Pediatric Patients. American Society of Anesthesiolgists. 2005: 69 (3): https://www.asahq.org/For-Members/Publications-and-Research/Newsletter-Articles/2005/March2005/providing-anesthesia-for-pediatric-patients.aspx

25. Miller BR, Friesen RH. Oral atropine premedication in infants attenuates cardiovascular depression during halothane anesthesia. Anesth. Analg 1988: 67:180-185{reflist|2}}

==External links==
* [http://www.nda.ox.ac.uk/wfsa/ World Anaesthesia Online] International resource of anaesthetic articles
* [http://www.iars.com/default/default.asp International Anesthesia Research Society]
* [http://ifna-int.org/ifna/page.php International Federation of Nurse Anesthetists]

{{General anesthetics}}
{{Local anesthetics}}
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{{Major Drug Groups}}

[[Category:anesthesia]]
[[Category:anesthetic equipment]]
[[Category:Surgery]]

[[ar:تخدير]]
[[ast:Anestesioloxía y reanimación]]
[[bn:অবেদন]]
[[ca:Anestèsia]]
[[cs:Anestezie]]
[[da:Anæstesi]]
[[de:Anästhesie]]
[[es:Anestesia]]
[[eo:Anestezo]]
[[fr:Anesthésie]]
[[gd:Cion-faireachdain]]
[[io:Anestezio]]
[[id:Anestesi]]
[[it:Anestesia]]
[[he:הרדמה]]
[[nl:Anesthesie]]
[[ja:麻酔]]
[[no:Anestesi]]
[[pl:Znieczulenie]]
[[pt:Anestesiologia]]
[[qu:Puñuchiq hampikamayuq]]
[[ru:Анестезия]]
[[simple:Anesthetic]]
[[sr:Анестезиологија]]
[[fi:Anestesia]]
[[sv:Anestesi]]
[[vi:Gây mê]]
[[tr:Anestezi]]
[[uk:Анестезія]]
[[zh:麻醉學]]

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