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== Anesthesia and the Brain ==▼
{{Short description|Medically induced coma}}▼
{{Use dmy dates|date=January 2019}}Anesthesia has little to no effect on brain function, unless there is an existing brain disruption. Barbiturates, or the drugs used to administer anesthesia do not effect auditory brain stem response.<ref>{{Cite journal |last=Smith |first=D.I. |last2=Mills |first2=J.H. |date=May 1989 |title=Anesthesia effects: auditory brain-stem response |url=http://dx.doi.org/10.1016/0013-4694(89)90047-3 |journal=Electroencephalography and Clinical Neurophysiology |volume=72 |issue=5 |pages=422–428 |doi=10.1016/0013-4694(89)90047-3 |issn=0013-4694}}</ref> An example of a brain disruption would be a concussion.<ref>{{Cite journal |last=Rasouli |first=Mohammed R. |last2=Kavin |first2=Michelle |last3=Stache |first3=Stephen |last4=Mahla |first4=Michael E. |last5=Schwenk |first5=Eric S. |date=February 2020 |title=Anesthesia for the patient with a recently diagnosed concussion: think about the brain! |url=https://pubmed.ncbi.nlm.nih.gov/31257815 |journal=Korean Journal of Anesthesiology |volume=73 |issue=1 |pages=3–7 |doi=10.4097/kja.19272 |issn=2005-7563 |pmc=7000285 |pmid=31257815}}</ref> It can be risky and lead to further brain injury if anesthesia is used on a concussed person. Concussions create ionic shifts in the brain that adjust the neuronal transmembrane potential. In order to restore this potential more glucose has to be made to equal the potential that is lost. This can be very dangerous and lead to cell death. This makes the brain very vulnerable in surgery. There are also changes to cerebral blood flow. The injury complicates the oxygen blood flow and supply to the brain.▼
{{More citations needed|date=February 2015}}
{{Infobox medical intervention
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== History ==
{{Main|History of general anesthesia}}
{{Further|History of tracheal intubation}}
Attempts at producing a state of general anaesthesia can be traced throughout recorded history in the writings of the ancient [[Sumer]]ians, [[Babylonia]]ns, [[Assyria]]ns, [[Ancient Egypt|Egyptians]], [[Ancient Greece|Greeks]], [[Ancient Rome|Romans]], [[Indus Valley civilisation|Indians]], and [[History of China#Ancient China|Chinese]]. During the [[Middle Ages]], scientists and other scholars made significant advances in the [[Eastern world]], while their European counterparts also made important advances.
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== Purpose ==
General anaesthesia has many purposes and routinely used in almost all surgical procedures. An appropriate surgical anesthesia should include the following goals:
# Hypnosis/Unconsciousness (loss of awareness)
# Analgesia (loss of response to pain)
# Amnesia (loss of memory)
# Immobility (loss of motor reflexes)
# Paralysis (skeletal muscle relaxation and normal muscle relaxation)<ref name
== Biochemical mechanism of action ==
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Benzodiazepines are the most commonly used class of drugs for premedication. The most commonly utilized benzodiazepine is [[Midazolam]], which is characterized by a rapid onset and short duration. Midazolam is effective in reducing [[Preoperational anxiety|preoperative anxiety]], including [[Separation anxiety disorder|separation anxiety]] in children.<ref>{{Cite journal |last=El Batawi |first=Hisham Yehia |date=2015 |title=Effect of preoperative oral midazolam sedation on separation anxiety and emergence delirium among children undergoing dental treatment under general anesthesia |journal=Journal of International Society of Preventive & Community Dentistry |volume=5 |issue=2 |pages=88–94 |doi=10.4103/2231-0762.155728 |issn=2231-0762 |pmc=4415335 |pmid=25992332}}</ref> It also provides mild sedation, sympathicolysis, and anterograde amnesia.<ref name=":11" />
[[Melatonin]] has been found to be effective as an anaesthetic premedication in both adults and children because of its [[hypnotic]], [[anxiolytic]], [[Sedation|sedative]], [[Nociception|analgesic]], and [[anticonvulsant]] properties. Recovery is more rapid after premedication with melatonin than with midazolam, and there is also a reduced incidence of post-operative [[Psychomotor agitation|agitation]] and delirium.<ref name="Naguib2007">{{cite journal | vauthors = Naguib M, Gottumukkala V, Goldstein PA | title = Melatonin and anesthesia: a clinical perspective | journal = Journal of Pineal Research | volume = 42 | issue = 1 | pages = 12–21 | date = January 2007 | pmid = 17198534 | doi = 10.1111/j.1600-079X.2006.00384.x | doi-access = free }}</ref> Melatonin has been shown to have a similar effect in reducing perioperative anxiety in adult patients compared to benzodiazepine.<ref>{{cite journal | vauthors = Madsen BK, Zetner D, Møller AM, Rosenberg J | title = Melatonin for preoperative and postoperative anxiety in adults | journal = The Cochrane Database of Systematic Reviews | volume = 2020 | pages = CD009861 | date = December 2020 | issue = 12 | pmid = 33319916 | pmc = 8092422 | doi = 10.1002/14651858.CD009861.pub3 }}</ref>
Another example of anaesthetic premedication is the preoperative administration of [[Adrenergic beta-antagonist|beta adrenergic antagonists]], which reduce the burden of arrhythmias after cardiac surgery. However, evidence also has shown an association of increased adverse events with beta-blockers in non-cardiac surgery.<ref>{{cite journal | vauthors = Blessberger H, Kammler J, Domanovits H, Schlager O, Wildner B, Azar D, Schillinger M, Wiesbauer F, Steinwender C | display-authors = 6 | title = Perioperative beta-blockers for preventing surgery-related mortality and morbidity | journal = The Cochrane Database of Systematic Reviews | volume = 2018 | issue = 3 | pages = CD004476 | date = March 2018 | pmid = 29533470 | pmc = 6494407 | doi = 10.1002/14651858.CD004476.pub3 | collaboration = Cochrane Anaesthesia Group }}</ref> Anaesthesiologists may administer one or more [[antiemetic]] agents such as [[ondansetron]], [[droperidol]], or [[dexamethasone]] to prevent postoperative nausea and vomiting.<ref name=":11" /> NSAIDs are commonly used analgesic premedication agent, and often reduce need for [[opioid]]s such as [[fentanyl]] or [[sufentanil]]. Also [[Prokinetic agent|gastrokinetic]] agents such as [[metoclopramide]], and [[histamine antagonist]]s such as [[famotidine]].<ref name=":11" />
Non-pharmacologic preanaesthetic interventions include playing cognitive behavioral therapy, music therapy, aromatherapy, hypnosis [[massage]], pre-operative preparation video, and guided imagery relaxation therapy, etc.<ref>{{Cite journal |last1=Wang |first1=Rulin |last2=Huang |first2=Xin |last3=Wang |first3=Yuan |last4=Akbari |first4=Masod |date=2022-04-11 |title=Non-pharmacologic Approaches in Preoperative Anxiety, a Comprehensive Review |journal=Frontiers in Public Health |volume=10 |pages=854673 |doi=10.3389/fpubh.2022.854673 |issn=2296-2565 |pmc=9035831 |pmid=35480569|doi-access=free }}</ref> These techniques are particularly useful for children and patients with [[intellectual disability|intellectual disabilities]]. Minimizing sensory stimulation or distraction by video games may help to reduce anxiety prior to or during induction of general anaesthesia. Larger high-quality studies are needed to confirm the most effective non-pharmacological approaches for reducing this type of anxiety.<ref name="Manyande2015">{{cite journal | vauthors = Manyande A, Cyna AM, Yip P, Chooi C, Middleton P | title = Non-pharmacological interventions for assisting the induction of anaesthesia in children | journal = The Cochrane Database of Systematic Reviews | volume = 2015 | issue = 7 | pages = CD006447 | date = July 2015 | pmid = 26171895 | pmc = 8935979 | doi = 10.1002/14651858.CD006447.pub3 }}</ref> Parental presence during premedication and induction of anaesthesia has not been shown to reduce anxiety in children.<ref name="Manyande2015" /> It is suggested that parents who wish to attend should not be actively discouraged, and parents who prefer not to be present should not be actively encouraged to attend.<ref name="Manyande2015" />
▲== Anesthesia and the Brain ==
▲{{Short description|Medically induced coma}}
▲{{Use dmy dates|date=January 2019}}Anesthesia has little to no effect on brain function, unless there is an existing brain disruption. Barbiturates, or the drugs used to administer anesthesia do not effect auditory brain stem response.<ref>{{Cite journal |last=Smith |first=D.I. |last2=Mills |first2=J.H. |date=May 1989 |title=Anesthesia effects: auditory brain-stem response |url=http://dx.doi.org/10.1016/0013-4694(89)90047-3 |journal=Electroencephalography and Clinical Neurophysiology |volume=72 |issue=5 |pages=422–428 |doi=10.1016/0013-4694(89)90047-3 |issn=0013-4694}}</ref> An example of a brain disruption would be a concussion.<ref>{{Cite journal |last=Rasouli |first=Mohammed R. |last2=Kavin |first2=Michelle |last3=Stache |first3=Stephen |last4=Mahla |first4=Michael E. |last5=Schwenk |first5=Eric S. |date=February 2020 |title=Anesthesia for the patient with a recently diagnosed concussion: think about the brain! |url=https://pubmed.ncbi.nlm.nih.gov/31257815 |journal=Korean Journal of Anesthesiology |volume=73 |issue=1 |pages=3–7 |doi=10.4097/kja.19272 |issn=2005-7563 |pmc=7000285 |pmid=31257815}}</ref> It can be risky and lead to further brain injury if anesthesia is used on a concussed person. Concussions create ionic shifts in the brain that adjust the neuronal transmembrane potential. In order to restore this potential more glucose has to be made to equal the potential that is lost. This can be very dangerous and lead to cell death. This makes the brain very vulnerable in surgery. There are also changes to cerebral blood flow. The injury complicates the oxygen blood flow and supply to the brain.
== Stages of anaesthesia ==
[[Guedel's classification]], described by [[Arthur Ernest Guedel]] in 1937,<ref name = "Hewer_1937" /> describes four stages of anaesthesia. Despite newer anaesthetic agents and delivery techniques, which have led to more rapid onset of—and recovery from—anaesthesia (in some cases bypassing some of the stages entirely), the principles remain.
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