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General anaesthetics are often defined as compounds that induce a loss of consciousness in humans or loss of righting reflex in animals. Clinical definitions are also extended to include an induced coma that causes lack of awareness to painful stimuli, sufficient to facilitate surgical applications in clinical and veterinary practice. General anaesthetics do not act as analgesics and should also not be confused with sedatives. General anaesthetics are a structurally diverse group of compounds whose mechanisms encompass multiple biological targets involved in the control of neuronal pathways. The precise workings are the subject of some debate and ongoing research.
Anesthesia or anaesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia, paralysis, amnesia, and unconsciousness. An individual under the effects of anesthetic drugs is referred to as being anesthetized.
Halothane, sold under the brand name Fluothane among others, is a general anaesthetic. It can be used to induce or maintain anaesthesia. One of its benefits is that it does not increase the production of saliva, which can be particularly useful in those who are difficult to intubate. It is given by inhalation.
Isoflurane, sold under the brand name Forane among others, is a general anesthetic. It can be used to start or maintain anesthesia; however, other medications are often used to start anesthesia, due to airway irritation with isoflurane. Isoflurane is given via inhalation.
Sevoflurane, sold under the brand name Sevorane, among others, is a sweet-smelling, nonflammable, highly fluorinated methyl isopropyl ether used as an inhalational anaesthetic for induction and maintenance of general anesthesia. After desflurane, it is the volatile anesthetic with the fastest onset. While its offset may be faster than agents other than desflurane in a few circumstances, its offset is more often similar to that of the much older agent isoflurane. While sevoflurane is only half as soluble as isoflurane in blood, the tissue blood partition coefficients of isoflurane and sevoflurane are quite similar. For example, in the muscle group: isoflurane 2.62 vs. sevoflurane 2.57. In the fat group: isoflurane 52 vs. sevoflurane 50. As a result, the longer the case, the more similar will be the emergence times for sevoflurane and isoflurane.
General anaesthesia (UK) or general anesthesia (US) is a method of medically inducing loss of consciousness that renders a patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general anaesthetic medications, which often act in combination with an analgesic and neuromuscular blocking agent. Spontaneous ventilation is often inadequate during the procedure and intervention is often necessary to protect the airway. General anaesthesia is generally performed in an operating theater to allow surgical procedures that would otherwise be intolerably painful for a patient, or in an intensive care unit or emergency department to facilitate endotracheal intubation and mechanical ventilation in critically ill patients. Depending on the procedure, general anaesthesia may be optional or required. Regardless of whether a patient may prefer to be unconscious or not, certain pain stimuli could result in involuntary responses from the patient that may make an operation extremely difficult. Thus, for many procedures, general anaesthesia is required from a practical perspective.
An anesthetic or anaesthetic is a drug used to induce anesthesia — in other words, to result in a temporary loss of sensation or awareness. They may be divided into two broad classes: general anesthetics, which result in a reversible loss of consciousness, and local anesthetics, which cause a reversible loss of sensation for a limited region of the body without necessarily affecting consciousness.
Awareness under anesthesia, also referred to as intraoperative awareness or accidental awareness during general anesthesia (AAGA), is a rare complication of general anesthesia where patients regain varying levels of consciousness during their surgical procedures. While anesthesia awareness is possible without resulting in any long-term memory of the experience, it is also possible for victims to have awareness with explicit recall, where they can remember the events related to their surgery.
Desflurane (1,2,2,2-tetrafluoroethyl difluoromethyl ether) is a highly fluorinated methyl ethyl ether used for maintenance of general anesthesia. Like halothane, enflurane, and isoflurane, it is a racemic mixture of (R) and (S) optical isomers (enantiomers). Together with sevoflurane, it is gradually replacing isoflurane for human use, except in economically undeveloped areas, where its high cost precludes its use. It has the most rapid onset and offset of the volatile anesthetic drugs used for general anesthesia due to its low solubility in blood.
Postoperative nausea and vomiting (PONV) is the phenomenon of nausea, vomiting, or retching experienced by a patient in the post-anesthesia care unit (PACU) or within 24 hours following a surgical procedure. PONV affects about 10% of the population undergoing general anaesthesia each year. PONV can be unpleasant and lead to a delay in mobilization and food, fluid, and medication intake following surgery.
Bispectral index (BIS) is one of several technologies used to monitor depth of anesthesia. BIS monitors are used to supplement Guedel's classification system for determining depth of anesthesia. Titrating anesthetic agents to a specific bispectral index during general anesthesia in adults allows the anesthetist to adjust the amount of anesthetic agent to the needs of the patient, possibly resulting in a more rapid emergence from anesthesia. Use of the BIS monitor could reduce the incidence of intraoperative awareness during anaesthesia. The exact details of the algorithm used to create the BIS index have not been disclosed by the company that developed it.
An inhalational anesthetic is a chemical compound possessing general anesthetic properties that is delivered via inhalation. They are administered through a face mask, laryngeal mask airway or tracheal tube connected to an anesthetic vaporiser and an anesthetic delivery system. Agents of significant contemporary clinical interest include volatile anesthetic agents such as isoflurane, sevoflurane and desflurane, as well as certain anesthetic gases such as nitrous oxide and xenon.
A halogenated ether is a subcategory of a larger group of chemicals known as ethers. An ether is an organic chemical that contains an ether group—an oxygen atom connected to two (substituted) alkyl groups. A good example of an ether is the solvent diethyl ether. What differentiates a halogenated ether from other types of ethers is the substitution (halogenation) of one or more hydrogen atoms with a halogen atom. Halogen atoms include fluorine, chlorine, bromine, and iodine.
Minimum alveolar concentration or MAC is the concentration, often expressed as a percentage by volume, of a vapour in the alveoli of the lungs that is needed to prevent movement in 50% of subjects in response to surgical (pain) stimulus. MAC is used to compare the strengths, or potency, of anaesthetic vapours. The concept of MAC was first introduced in 1965.
Postoperative cognitive dysfunction (POCD) is a decline in cognitive function that may last from 1–12 months after surgery, or longer. In some cases, this disorder may persist for several years after major surgery. POCD is distinct from emergence delirium. Its causes are under investigation and occurs commonly in older patients and those with pre-existing cognitive impairment.
Veterinary anesthesia is a specialization in the veterinary medicine field dedicated to the proper administration of anesthetic agents to non-human animals to control their consciousness during procedures. A veterinarian or a Registered Veterinary Technician administers these drugs to minimize stress, destructive behavior, and the threat of injury to both the patient and the doctor. The duration of the anesthesia process goes from the time before an animal leaves for the visit to the time after the animal reaches home after the visit, meaning it includes care from both the owner and the veterinary staff. Generally, anesthesia is used for a wider range of circumstances in animals than in people not only due to their inability to cooperate with certain diagnostic or therapeutic procedures, but also due to their species, breed, size, and corresponding anatomy. Veterinary anesthesia includes anesthesia of the major species: dogs, cats, horses, cattle, sheep, goats, and pigs, as well as all other animals requiring veterinary care such as birds, pocket pets, and wildlife.
Guedel's classification is a means of assessing the depth of general anesthesia introduced by Arthur Ernest Guedel (1883–1956) in 1920.
Flurothyl (Indoklon) is a volatile liquid drug from the halogenated ether family, related to inhaled anaesthetic agents such as diethyl ether, but having the opposite effects, acting as a stimulant and convulsant. A clear and stable liquid, it has a mild ethereal odor whose vapors are non-flammable. It is excreted from the body by the lungs in an unchanged state.
Total intravenous anesthesia (TIVA) refers to the intravenous administration of anesthetic agents to induce a temporary loss of sensation or awareness. The first study of TIVA was done in 1872 using chloral hydrate, and the common anesthetic agent propofol was licensed in 1986. TIVA is currently employed in various procedures as an alternative technique of general anesthesia in order to improve post-operative recovery.
The effects of early-life exposures to anesthesia on the brain in humans are controversial. Evidence from nonhuman primate research suggests significant developmental neurotoxicity and long-term social impairment, with a dose–response relationship where repeated exposures cause a more severe impact than single ones. Research in humans has not found conclusive clinical evidence of cognitive impairment; however, systematic reviews imply the possibility of greater behavioural impairments in children exposed to anesthesia before the age of three than control subjects.
References
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{{cite web}}: CS1 maint: archived copy as title (link) - ↑ Sikich, N; Lerman, J (2004). "Development and psychometric evaluation of the pediatric anesthesia emergence delirium scale". Anesthesiology. 100 (5): 1138–45. doi: 10.1097/00000542-200405000-00015 . PMID 15114210. S2CID 25599011.
- ↑ Traube, C.; Silver, G.; Kearney, J.; Patel, A.; Atkinson, T. M.; Yoon, M. J.; Halpert, S.; Augenstein, J.; Sickles, L. E.; Li, C.; Greenwald, B. (2014). "Cornell Assessment of Pediatric Delirium: A valid, rapid, observational tool for screening delirium in the PICU". Critical Care Medicine. 42 (3): 656–663. doi:10.1097/CCM.0b013e3182a66b76. PMC 5527829 . PMID 24145848.
- 1 2 Vlajkovic, Gordana P.; Sindjelic, Radomir P. (2007). "Emergence Delirium in Children: Many Questions, Few Answers". Anesthesia & Analgesia. 104 (1): 84–91. doi: 10.1213/01.ane.0000250914.91881.a8 . PMID 17179249. S2CID 7315961.
- ↑ Lo, S. S.; Sobol, J. B.; Mallavaram, N.; Carson, M.; Chang, C.; Grieve, P. G.; Emerson, R. G.; Stark, R. I.; Sun, L. S. (2009). "Anesthetic-specific electroencephalographic patterns during emergence from sevoflurane and isoflurane in infants and children". Pediatric Anesthesia. 19 (12): 1157–1165. doi:10.1111/j.1460-9592.2009.03128.x. PMID 19708912. S2CID 23663252.
- ↑ Welborn, Leila G.; Hannallah, Raafat S.; Norden, Janet M.; Ruttimann, Urs E.; Callan, Clair M. (November 1996). "Comparison of Emergence and Recovery Characteristics of Sevoflurane, Desflurane, and Halothane in Pediatric Ambulatory Patients". Anesthesia & Analgesia. 83 (5): 917–920. doi: 10.1213/00000539-199611000-00005 . PMID 8895263.
- ↑ Miller, David; Lewis, Sharon R; Pritchard, Michael W; Schofield-Robinson, Oliver J; Shelton, Cliff L; Alderson, Phil; Smith, Andrew F (21 August 2018). "Intravenous versus inhalational maintenance of anaesthesia for postoperative cognitive outcomes in elderly people undergoing non-cardiac surgery". Cochrane Database of Systematic Reviews. 2018 (8): CD012317. doi:10.1002/14651858.CD012317.pub2. PMC 6513211 . PMID 30129968.
- ↑ Saczynski, J. S.; Marcantonio, E. R.; Quach, L.; Fong, T. G.; Gross, A.; Inouye, S. K.; Jones, R. N. (2012). "Cognitive Trajectories after Postoperative Delirium". The New England Journal of Medicine. 367 (1): 30–39. doi:10.1056/NEJMoa1112923. PMC 3433229 . PMID 22762316.
- ↑ Kunicki, Zachary J.; Ngo, Long H.; Marcantonio, Edward R.; Tommet, Douglas; Feng, Yi; Fong, Tamara G.; Schmitt, Eva M.; Travison, Thomas G.; Jones, Richard N.; Inouye, Sharon K. (2023). "Six-Year Cognitive Trajectory in Older Adults Following Major Surgery and Delirium". JAMA Internal Medicine. 183 (5): 442–450. doi:10.1001/jamainternmed.2023.0144. PMC 10028541 . PMID 36939716.
- ↑ Mason, LJ (2004). "Pitfalls of Pediatric Anesthesia: Emergence Delirium" (PDF). Richmond, Virginia: Society for Pediatric Anestheisa. Archived from the original (PDF) on 2016-03-27. Retrieved 2012-06-21.
- ↑ Card, E.; Tomes, C.; Lee, C.; Wood, J.; Nelson, D.; Graves, A.; Shintani, A.; Ely, E.W.; Hughes, C.; Pandharipande, P. (2015). "Emergence from general anaesthesia and evolution of delirium signs in the post-anaesthesia care unit". British Journal of Anaesthesia. 115 (3): 411–417. doi:10.1093/bja/aeu442. PMC 4533730 . PMID 25540068.
