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Anesthesia, or anaesthesia (see spelling differences; from Greek î�î�-, an-, "without"; and î�á��σî�î�σî�ς, aisthä�sis, "sensation"), has traditionally meant the condition of having sensation (including the feeling of pain) blocked or temporarily taken away. It is a pharmacologically induced reversible state of amnesia, analgesia, loss of responsiveness, loss of skeletal muscle reflexes and/or decreased stress response. This allows patients to undergo surgery and other procedures without the distress and pain they would otherwise experience. Another definition is a "reversible lack of awareness," whether this is a total lack of awareness (e.g. a general anesthetic) or a lack of awareness of a part of the body such as a spinal anesthetic or another nerve block would cause. The word was coined by Oliver Wendell Holmes, Sr. in 1846.^[1]

Types of anesthesia include local anesthesia, regional anesthesia and general anesthesia. In local anesthesia a specific location of the body is numbed, such as the hand. Regional anesthesia numbs a larger area of the body by administering anesthesia to a cluster of nerves. Two frequently used regional anesthesia are spinal anesthesia and epidural anesthesia. General anesthesia describes unconsciousness and lack of any awareness or sensation.^[2]

[edit] History

[edit] Plant derivatives

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. In 13th century Italy Theodoric Borgognoni used similar mixtures along with opiates to induce unconsciousness, and treatment with the combined alkaloids proved a mainstay of anesthesia until the nineteenth century. In the Americas coca was also an important anesthetic used in trephining operations. Incan shamans chewed coca leaves and performed operations on the skull while spitting into the wounds they had inflicted to anesthetize the site.^{[citation needed]} Alcohol was also used, its vasodilatory properties being unknown. Ancient herbal anesthetics have variously been called soporifics, anodynes, and narcotics, depending on whether the emphasis is on producing unconsciousness or relieving pain.

The use of herbal anesthesia had a crucial drawback compared to modern practice'as lamented by Fallopius, "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 locations (such as opium from the fields of Thebes in ancient Egypt). Anesthetics 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 for a consistent dosage, was enthusiastically received and led to the foundation of the modern pharmaceutical industry.

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.^[3] German surgeon August Bier (1861'1949) was the first to use cocaine for intrathecal anesthesia in 1898. A number of newer local anesthetic agents, many of them derivatives of cocaine, were synthesized in the 20th century, including procaine (1905), Eucaine (1900), Stovaine (1904), and lidocaine (1943).

The first published report on opioids for intrathecal anesthesia belongs to a Romanian surgeon, Nicolae Racoviceanu-Pite�ti (1860-1942), who presented his experience at Paris in 1901.^[4]

[edit] Early inhalational anesthetics

Anesthesia pioneer Crawford W. Long

Contemporary re-enactment of Morton's October 16, 1846, ether operation; daguerrotype by Southworth & Hawes

On 16 October 1846 William Thomas Green Morton, a Boston dentist was invited to the Massachusetts General Hospital to demonstrate his new technique for painless surgery. Surgeon John Collins Warren removed a tumor from the neck of Edward Gilbert Abbott after Morton had induced anesthesia. This first public demonstration of ether anesthesia occurred in the surgical amphitheater now called the Ether Dome. The previously skeptical Dr. Warren was impressed and stated "Gentlemen, this is no humbug." In a letter to Morton shortly thereafter, physician and writer Oliver Wendell Holmes, Sr. proposed naming the state produced "anesthesia", and the procedure an "anesthetic".^[5]

Morton at first attempted to hide the actual nature of his anesthetic substance, referring to it as Letheon. He received a US patent for his substance, but news of the successful anesthetic spread quickly by late 1846. Respected surgeons in Europe including Liston, Dieffenbach, Pirogoff, and Syme, quickly undertook numerous operations with ether. An American-born physician, Boott, encouraged London dentist, 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. Drawbacks with ether such as excessive vomiting and its flammability led to its replacement in England with chloroform.

Discovered in 1831, the use of chloroform in anesthesia is 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.

[edit] Non-pharmacological methods

There is a long history of the use of hypnotism as an anesthetic techniques.^{[citation needed]} Chilling tissue (e.g. with a mixture of salt and ice or a spray of ether or ethyl chloride) can temporarily inhibit the ability of nerve fibers (axons) to conduct sensation.^{[citation needed]} The hypocapnia that results from hyperventilation can temporarily inhibit the conscious perception of sensory stimuli, including pain (see Lamaze technique).^{[citation needed]} These techniques are seldom employed in modern anesthetic practice.

[edit] Anesthesia providers

Physicians specializing in perioperative care, development of an anesthetic plan, and the administration of anesthetics are known in the United States as anesthesiologists and in the United Kingdom and Canada as anaesthetists or anaesthesiologists. All anesthetics in the UK, Australia, New Zealand and Japan are administered by physicians. Nurse anesthetists also administer anesthesia in 109 nations.^[6] In the US, 35% of anesthetics are provided by physicians in solo practice, about 55% are provided by Anesthesia Care Teams (ACTs) with anesthesiologists medically directing Anesthesiologist Assistants or CRNAs, and about 10% are provided by CRNAs in solo practice.^{[7][8][9][10][11]}

[edit] Physicians

Anesthesia students training with a patient simulator

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

In the US, 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.^[12]

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, Fellowship of the Royal College of Anaesthetists (FRCA) is conferred upon medical doctors following completion of the written and oral parts of the Royal College's examination. 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 (or of the American Osteopathic Board of Anaesthesiology, for osteopathic physicians).

Specialists in intensive care medicine, pain medicine, emergency medicine and palliative medicine have usually done some training in anesthetics. The role of the anesthesiologist is changing. It is no longer limited to the operation itself. Many anesthesiologists perform well as perioperative physicians, and will involve themselves in optimizing the patient's health before surgery, performing the anesthetic, including specialized intraoperative monitoring (such as transesophageal echocardiography), following up the patient in the post anesthesia care unit and postoperative wards, and ensuring optimal analgesia throughout.

It is important to note that the term anaesthetist 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 refers to medical doctors who specialize in anesthesiology. Anesthesia providers are often trained using full scale human simulators. The field was an early adopter of this technology and has used it to train students and practitioners at all levels for the past several decades. Notable centers in the United States can be found at Harvard's Center for Medical Simulation,^[13] Stanford,^[14] The Mount Sinai School of Medicine HELPS Center in New York,^[15] and Duke University^[16]

[edit] Nurse anesthetists

In the United States, advanced practice nurses specializing in the provision of anesthesia care are known as Certified Registered Nurse Anesthetists (CRNAs). According to the American Association of Nurse Anesthetists, the 39,000 CRNAs in the US administer approximately 30 million anesthetics each year, roughly two thirds of the US total.^[17] 34% 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,^[18] and gain a masters degree in nurse anesthesia before passing the mandatory Certification Exam. Masters-level CRNA training programs range in length from 24 to 36 months.

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. CRNAs do not require anesthesiologist supervision in any state. Many states place restrictions on practice, and hospitals often regulate what CRNAs and other midlevel providers can or can not do based on local laws, provider training and experience, and hospital and physician preferences.^[19]

In the United States, the Centers for Medicare and Medicaid Services (CMS), a federal agency within the United States Department of Health and Human Services, determines the conditions for payment for all anesthesia services provided under the Medicare, Medicaid, and State Children's Health Insurance Program (SCHIP) programs. For the purposes of payment for anesthesiology services, CMS defines an anesthesia practitioner as a physician who performs the anesthesia service alone, a CRNA who is not medically directed, or a CRNA or AA who is medically directed.^[20] Under the QZ Anesthesia Claims Modifier, CMS allows payment to a CRNA for anesthesiology services provided under these programs without medical direction by a physician.^[20] Furthermore, under CMS regulations, anesthesia must be administered only by:

• a qualified doctor of medicine or osteopathy, dentist, oral surgeon, or podiatrist;
• a CRNA who, unless exempted, is under the supervision of the operating practitioner or of an anesthesiologist;
• an anesthesiologist's assistant who is under the supervision of an anesthesiologist.^[21]

The aforementioned exemption for CRNAs is the State exemption (also referred to as an "opt-out"). Under the State exemption, if the State in which the hospital is located submits a letter to CMS requesting exemption from physician supervision of CRNAs, and that letter has been signed by the Governor of that State, then hospitals within that State may be exempted from the requirement for physician supervision of CRNAs.^[21] In 2001, CMS established this exemption for CRNAs from the physician supervision requirement by recognizing a Governor's written request to CMS attesting that it is in the best interests of the State's citizens to exercise this exemption.^[22] As of July 2009, fifteen states (California, Iowa, Nebraska, Idaho, Minnesota, New Hampshire, New Mexico, Kansas, North Dakota, Washington, Alaska, Oregon, South Dakota, Wisconsin and Montana) have chosen to opt-out of the CRNA physician supervision regulation.^[22]

[edit] Anesthesiologist assistants

In the United States, anesthesiologist assistants (AAs) are graduate-level trained specialists who have undertaken specialized education and training to provide anesthesia care under the direction of an Anesthesiologist. AAs typically hold a masters degree and practice under Anesthesiologist supervision in 18 states through licensing, certification or physician delegation.^[23]

In the UK, a similar group of assistants are currently being evaluated. They are named Physician's Assistant (Anaesthesia) (PAAs). Their background can be nursing, Operating Department Practice, or another profession allied to medicine or a science graduate. Training is in the form of a postgraduate diploma and takes 27 months to complete. Once finished, a masters degree can be undertaken.^{[citation needed]}

[edit] Anesthesia technicians

Anesthesia technicians are specially trained biomedical technicians who assist anesthesiologists, nurse anesthetists, and anesthesiologist assistants with monitoring equipment, supplies, and patient care procedures in the operating room. Commonly these services are collectively called Perioperative services, and thus the term Perioperative Service Technician (PST) is used interchangeably with Anesthesia Technician.

In New Zealand, an anaesthetic technician completes a course of study recognized by the New Zealand Anaesthetic Technicians Society.^[24]

[edit] Operating Department Practitioners

In the United Kingdom, Operating Department Practitioners provide close assistance and support to the anaesthetist (anaesthesiologist).^{[citation needed]} They can also assist with surgical procedures alongside the surgeon and provide postoperative Care to patients emerging from anesthesia. ODPs can be found in the Operating Department, Accident and Emergency (providing advanced airway assistance), Intensive Care Unit, High Dependency Unit and for specialist MRI scanners which require anesthetic cover. They also work with organ retrieval teams in transplant surgery and attend pre hospital care to injury victims in the community and will undertake specialist training to carry out this work. They are state registered in the UK and their title, Operating Department Practitioner is a protected title. The ODP is not a technician but a practitioner of perioperative care. ODPs also work in the field of teaching as lecturers, resuscitation trainers and work in senior positions in management of operating theatre departments.

[edit] Veterinary anesthetists/anesthesiologists

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.

[edit] Anesthetic agents

An anesthetic agent is a drug that brings about a state of anesthesia. A wide variety of drugs are used in modern anesthetic practice. Many are rarely used outside of anesthesia, although others are used commonly by all disciplines. Anesthetics are categorized in to two categories: general anesthetics cause a reversible loss of consciousness (general anesthesia), while local anesthetics cause reversible local anesthesia and a loss of nociception.

[edit] Anesthetic 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, anesthetic agents and vapors, medical breathing circuits and the variety of anesthetic machines (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. The risk of transmission of infection by anesthetic equipment has been a problem since the beginnings of anaesthesia. Although most equipment that comes into contact with patients is disposable, there is still a risk of contamination from the anaesthetic machine itself^[25] or because of bacterial passage through protective filters.^[26]

[edit] Anesthetic monitoring

Patients being treated under general anesthetics must be monitored continuously to ensure the patient's safety. In the UK the Association of Anaesthetists (AAGBI) have set minimum monitoring guidelines for General and Regional Anaesthesia. For minor surgery, this generally includes monitoring of heart rate (via ECG or pulse oximetry), oxygen saturation (via pulse oximetry), noninvasive blood pressure, inspired and expired gases (for oxygen, carbon dioxide, nitrous oxide, and volatile agents). For moderate to major surgery, monitoring may also include 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 anesthetics which might impair the health of operating room personnel.

[edit] Anesthesia record

The anesthesia record is the medical and legal documentation of events during an anesthetic.^[27] 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). An AIMS is any information system that is used as an automated electronic anesthesia record keeper (i.e., connection to patient physiologic monitors and/or the anesthetic machine) and which also may allow the collection and analysis of anesthesia-related perioperative patient data gathered from patient monitors and/or anesthesia machine. These systems typically run on medical-grade hardware in the operating room. AIMS can be stand-alone systems or integrated modules of a clinical information system (CIS). A recent study showed that in the US, AIMS have become increasingly installed in US academic anesthesia departments since 2007 ^[28]. AIMS have several benefits to the anesthesia departments as well to the hospital administration as documented in the scientific literature:

• Reducing Anesthesia-Related Drug Costs^[29]
• Increased anesthesia billing and capture of anesthesia-related charges^[30]
• Increased hospital reimbursement through improved hospital coding^[31][32]
• Improvement of the data quality of the intraoperative anesthesia record^[33][34]
• Support training and education of the anesthesia workforce^[35]
• Support of clinical decision-making^[36]
• Support of patient care and safety^[37]
• Enhancement of clinical studies^[38]
• Enhancement of clinical quality improvement programs^[39]
• Support of clinical risk management^[40]
• Monitoring for diversion of controlled substances^[41]

[edit] See also

• Anesthesia awareness
• Allergic reactions during anesthesia
• ASA physical status classification system
• Cardiothoracic anesthesiology
• EEG measures during anesthesia
• Geriatric anesthesia
• Patient safety
• Perioperative mortality
• Second gas effect

[edit] References

[edit] External links

• American Association of Nurse Anesthetists
• American Society of Anesthesiologists
• International Federation of Nurse Anesthetists
• British Anaesthetic & Recovery Nurses Association
• La SFAR Société Française d'Anesthésie et de Réanimation
• DGF Online: Deutsche Gesellschaft Für Fachkrankenpflege E.V
• Schweizerische Interessengemeinschaft für Anästhesiepflege - Fédération Fédération suisse des infirmiers anesthésistes (Swiss Federation of Nurse Anesthesists)
• Nederlandse Vereniging Van Anesthesie Medewerkers
• Riksföreningen för anestesi och intensivvård (Swedish Association of Nurse Anesthetists and Intensive Care Nurses)
• International Anesthesia Research Society
• Online ABG calculator for anaesthesia