Category:Anesthetics: Difference between revisions

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~~This category groups~~ medicines ~~belonging~~ to the [[~~Classes~~|~~Anesthetics~~]] class. ~~See~~ [[~~Classes~~]] for the ~~full taxonomy~~.

The anesthetics are the medicines that abolish pain and awareness for surgery,

and their arrival is one of the genuine turning points in the history of

medicine. For all of human history before the middle of the nineteenth

century, surgery meant pain: operations were brief, brutal, and dreaded, and

the skill most prized in a surgeon was speed. The discovery that a medicine

could render a patient wholly insensible, and then return them unharmed,

changed what surgery could be. The story is best told as a history of that

discovery and of the classes of medicine that followed from it.

== Before anesthesia ==

The wish to dull the pain of surgery is ancient. Opium, mandrake, henbane, and

alcohol were all pressed into service, and from roughly the ninth century the

"soporific sponge", a sponge steeped in such plant extracts and held to the

face, was used across medieval Europe and the Islamic world. These methods

were unreliable and dangerous: the dose that dulled pain and the dose that

killed were not far apart, and none produced anything like dependable

insensibility. For practical purposes, surgery remained an ordeal to be

survived.

== Ether Day and the birth of modern anesthesia ==

The decisive event took place on October 16, 1846, at the Massachusetts

General Hospital in Boston. The dentist William T. G. Morton publicly

administered [[Diethyl ether|diethyl ether]] to a surgical patient, and the surgeon John Collins

Warren removed a tumour from the patient's neck without the patient feeling

pain. Warren's remark to the watching audience, "Gentlemen, this is no

humbug", marked the moment the world changed: news of the demonstration spread

within months across Europe and beyond.<ref name="etherday">Haridas RP. A prelude to Ether Day 1846: Charles F Heywood's letter to William TG Morton. ''Anaesth Intensive Care''. 2025 Sep 13. PMID: 40945954.</ref> The room is remembered as the "Ether Dome".

Credit for the discovery is not Morton's alone. The physician Crawford Long had

used [[Diethyl ether|ether]] for surgery in Georgia as early as 1842 but did not publish his

results until years later; the dentist Horace Wells had demonstrated [[Nitrous oxide|nitrous oxide]] for a dental extraction in 1845, but the demonstration was judged a

failure at the time. It was Morton's 1846 demonstration that was public,

successful, and decisive. Soon afterward Oliver Wendell Holmes proposed the

words "anaesthesia" and "anaesthetic" for the new state and the agents that

produced it.

{{PendellsCorner

| quote = Ether is to alcohol as alcohol is to water: if alcohol is water and fire, ether is water, fire, and air.

| volume = Poeia

| page = 83

}}

The [[Diethyl ether|ether]] that revolutionized surgery had a long prior life. It had been

described in the sixteenth century, Paracelsus is said to have noted its

effect on animals, and by the early nineteenth century it was familiar enough

to be inhaled for amusement at "[[Diethyl ether|ether]] frolics". For a time in the nineteenth

century [[Diethyl ether|ether]] was also taken recreationally as a substitute for alcohol; the

novelist John Irving, whose ''The Cider House Rules'' centers on an

[[Diethyl ether|ether]]-addicted physician, called it "the perfect addiction for a

conservative", and the poet Allen Ginsberg wrote a poem, "Aether", recording

an [[Diethyl ether|ether]] experience.

{{PendellsCorner

| quote = There are stories of entire villages drinking and sniffing ether, of the streets smelling like hospital rooms.

| volume = Poeia

| page = 86

}}

== Chloroform, and the spread of anesthesia ==

Within a year of Ether Day a rival agent appeared. In 1847 the Scottish

obstetrician James Young Simpson introduced [[Chloroform|chloroform]], which acted faster than

[[Diethyl ether|ether]] and did not have its pungency. [[Chloroform]] spread quickly, and its

acceptance was helped by John Snow, the first physician to make anesthesia a

full-time practice, who administered it to Queen Victoria for the birth of two

of her children in the 1850s, which did much to quiet religious and medical

objections to the relief of labour pain. [[Chloroform]], however, carried a darker

risk than [[Diethyl ether|ether]]: it could cause sudden fatal disturbances of heart rhythm,

even in otherwise healthy patients, and over the following decades this slowly

drove it out of use in favour of safer agents.

{{PendellsCorner

| quote = 2. excitement: giggling, or shouting — the religious sing hymns, the abusive fight — some of us need to write

| volume = Poeia

| page = 84

}}

== Local anesthesia ==

The anesthetics so far described produced unconsciousness; a separate line of

discovery sought to abolish pain in one part of the body while the patient

remained awake. The opening came in 1884, when the Viennese ophthalmologist

Karl Koller found that [[Cocaine|cocaine]], applied to the eye, made eye surgery painless.

The discovery that a drug could block sensation in a region of the body

founded local and regional anesthesia. [[Cocaine]] itself was too toxic and too

liable to cause dependence for general use, and it was progressively replaced

by safer synthetic local anesthetics developed through the twentieth century,

the family that includes [[Procaine|procaine]], [[Lidocaine|lidocaine]], and [[Bupivacaine|bupivacaine]].

== The twentieth century: intravenous and modern inhalational agents ==

For a long time [[Diethyl ether|ether]] and [[Chloroform|chloroform]], later joined by other agents, remained

the mainstays. The twentieth century transformed the field along two lines.

The first was intravenous induction. In 1934 the barbiturate [[Thiopental|thiopental]] was

introduced, allowing anesthesia to be induced by injection: a rapid and far

more comfortable passage into unconsciousness than the slow inhalation of a

pungent vapour. [[Thiopental]] became the standard induction agent for decades and

was, much later, largely displaced by [[Propofol|propofol]], introduced in the 1980s, which

allows both rapid induction and rapid, clear-headed recovery and is now the

most widely used intravenous induction agent.<ref name="modernagents">Robinson DH, Toledo AH. Historical development of modern anesthesia. ''Journal of Investigative Surgery''. 2012 Jun;25(3):141-9. PMID: 22583009.</ref>

The second was a generation of better inhalational agents. In 1956 [[Halothane|halothane]]

was introduced; it was potent, pleasant to breathe, and, importantly, not

flammable, which removed the ever-present danger of operating-room fires that

[[Diethyl ether|ether]] had carried. [[Halothane]] was in time succeeded by the halogenated ethers

in use today, [[Isoflurane|isoflurane]], [[Sevoflurane|sevoflurane]], and [[Desflurane|desflurane]].<ref name="modernagents" />

A third strand made modern surgery possible: the use of medicines to relax or

paralyse the muscles. In 1942 the anesthetist Harold Griffith introduced

[[Curare|curare]], long known as a South American arrow poison, into anesthetic practice,

so that surgical muscle relaxation could be achieved without deepening

unconsciousness to dangerous levels.<ref name="griffith">Sykes K. Harold Griffith Memorial Lecture. The Griffith legacy. ''Canadian Journal of Anaesthesia''. 1993 Apr;40(4):365-74. PMID: 8485797.</ref> These agents, the

[[:Category:Neuromuscular blockers|neuromuscular blockers]], are covered as a

class on their own page. Their arrival completed what is now called "balanced

anesthesia": the modern practice of combining separate medicines for the

distinct goals of unconsciousness, pain relief, and muscle relaxation, rather

than relying on a single agent to do everything.

== Members ==

The anesthetics are best understood as several distinct groups, gathered by a

shared purpose rather than a shared chemistry. The '''inhalational

anesthetics''' are the volatile agents and gases, among them the modern

halogenated ethers [[Isoflurane|isoflurane]], [[Sevoflurane|sevoflurane]], and [[Desflurane|desflurane]], and the gas

[[Nitrous oxide|nitrous oxide]]. The '''intravenous (general) anesthetics''' are the injected

induction agents, chief among them [[Propofol|propofol]], together with [[Thiopental|thiopental]],

[[Etomidate|etomidate]], and others. The '''local anesthetics''' block sensation in a part

of the body, and include [[Lidocaine|lidocaine]], [[Bupivacaine|bupivacaine]], and their relatives. The

'''dissociative anesthetics''', notably [[Ketamine|ketamine]], produce a distinctive

trance-like state and are discussed more fully under their own grouping; some

are also used outside anesthesia. The neuromuscular blockers, used alongside

anesthetics to relax muscle, are a separate class with their own page. The

list is not exhaustive, and some agents are used in more than one role.

== Mechanisms ==

How the general anesthetics work is, remarkably, still not fully understood,

and it is one of the genuine open questions of pharmacology. It is established

that the inhalational and intravenous general anesthetics act on the brain to

produce reversible unconsciousness, and that many of them are understood to do

so in part by enhancing the activity of inhibitory signalling in the nervous

system, particularly at the GABA-A receptor, the receptor for the brain's

principal inhibitory neurotransmitter. Several agents act at other targets as

well: [[Nitrous oxide|nitrous oxide]] and the dissociative anesthetics, for instance, are

understood to act substantially by blocking the NMDA receptor, a receptor for

excitatory signalling. The local anesthetics work by an entirely different and

better-understood mechanism: they block the sodium channels that nerves use to

carry electrical signals, so that a nerve in contact with the medicine cannot

transmit the message of pain. That these medicines have these actions is well

established; how, exactly, the general anesthetics convert those molecular

actions into the disappearance of conscious awareness remains incompletely

answered.

== Safety ==

Modern anesthesia is, by any historical measure, remarkably safe: serious harm

directly attributable to anesthesia is now an uncommon event, where once it

was a real risk of every operation. That safety is the achievement not only of

better medicines but of monitoring, training, and the rise of anesthesiology

as a specialty in its own right. Risk is not absent. The anesthetics are

medicines with a narrow margin between the intended effect and dangerous

depression of breathing and circulation, which is why they are given by

trained practitioners with continuous monitoring. Particular hazards include

malignant hyperthermia, a rare and dangerous inherited reaction to certain

anesthetic agents; postoperative nausea and vomiting; and, debated and still

under study, questions about the effects of anesthesia on the very young and

the very old. The local anesthetics, if enough reaches the bloodstream, can

affect the heart and nervous system. As with all medicines, figures for these

risks are population estimates that vary between studies, and individual

response varies considerably between people.

== References ==

[[Category:MedCategory]]

[[Category:MedCategoryFull]]

[[Category:Pharmaceutical]]

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