What are the advantages of ether Anaesthesia?

Organic chemical compound

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Chemical compound

Diethyl ether, or simply ether, is an organic compound with the chemical formula (CH3CH2)2O, sometimes abbreviated as Et2O.[a] It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs to the ether class of organic compounds. It is a common solvent. It was formerly used as a general anesthetic.[8]

Production

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Most diethyl ether is produced as a byproduct of the vapor-phase hydration of ethylene to make ethanol. This process uses solid-supported phosphoric acid catalysts and can be adjusted to make more ether if the need arises:[9] Vapor-phase dehydration of ethanol over some alumina catalysts can give diethyl ether yields of up to 95%.[10]

2 CH3CH2OH &#; (CH3CH2)2O + H2O

Diethyl ether can be prepared both in laboratories and on an industrial scale by the acid ether synthesis.[11]

Uses

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The dominant use of diethyl ether is as a solvent. One particular application is in the production of cellulose plastics such as cellulose acetate.[9]

Laboratory solvent

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It is a common solvent for the Grignard reaction in addition to other reactions involving organometallic reagents.[12] These uses exploit its basicity. Diethyl ether is a popular non-polar solvent in liquid-liquid extraction. As an extractant, it is immiscible with and less dense than water.

Although immiscible, it has significant solubility in water (6.05 g/(100 ml) at 25 °C[2]) and dissolves 1.5 g/(100 g) (1.0 g/(100 ml)) water at 25 °C.[13]

Fuel

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Diethyl ether has a high cetane number of 85&#;96 and, in combination with petroleum distillates for gasoline and diesel engines,[14] is used as a starting fluid because of its high volatility and low flash point. Ether starting fluid is sold and used in countries with cold climates, as it can help with cold starting an engine at sub-zero temperatures. For the same reason it is also used as a component of the fuel mixture for carbureted compression ignition model engines.

Chemical reactions

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Triethyloxonium tetrafluoroborate is prepared from boron trifluoride, diethyl ether, and epichlorohydrin:[15]

4 Et2O·BF3 + 2 Et2O + 3 C2H3OCH2Cl &#; 3 [Et3O]+[BF4]&#; + B(OCH(CH2Cl)CH2OEt)3

Diethyl ether is a hard Lewis base that reacts with a variety of Lewis acids such as iodine, phenol, and trimethylaluminium, and its base parameters in the ECW model are EB = 1.80 and CB = 1.63. Diethyl ether is a common laboratory aprotic solvent.

Diethyl ether is susceptible to formation of hydroperoxides.

Metabolism

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A cytochrome P450 enzyme is proposed to metabolize diethyl ether.[16]

Diethyl ether inhibits alcohol dehydrogenase, and thus slows the metabolism of ethanol.[17] It also inhibits metabolism of other drugs requiring oxidative metabolism. For example, diazepam requires hepatic oxidization whereas its oxidized metabolite oxazepam does not.[18]

Safety, stability, regulations

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Diethyl ether is extremely flammable and may form explosive vapour/air mixtures.[19]

Since ether is heavier than air it can collect low to the ground and the vapour may travel considerable distances to ignition sources. Ether will ignite if exposed to an open flame, though due to its high flammability, an open flame is not required for ignition. Other possible ignition sources include &#; but are not limited to &#; hot plates, steam pipes, heaters, and electrical arcs created by switches or outlets.[19] Vapour may also be ignited by the static electricity which can build up when ether is being poured from one vessel into another. The autoignition temperature of diethyl ether is 160 °C (320 °F). The diffusion of diethyl ether in air is 9.18 × 10&#;6 m2/s (298 K, 101.325 kPa).[citation needed]

Ether is sensitive to light and air, tending to form explosive peroxides.[19] Ether peroxides have a higher boiling point than ether and are contact explosives when dry.[19] Commercial diethyl ether is typically supplied with trace amounts of the antioxidant butylated hydroxytoluene (BHT), which reduces the formation of peroxides. Storage over sodium hydroxide precipitates the intermediate ether hydroperoxides. Water and peroxides can be removed by either distillation from sodium and benzophenone, or by passing through a column of activated alumina.[20]

Due to its application in the manufacturing of illicit substances, it is listed in the Table II precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances as well as substances such as acetone, toluene and sulfuric acid.[21]

History

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The compound may have been synthesised by either Jābir ibn Hayyān in the 8th century[22] or Ramon Llull in .[22][23] It was synthesised in by Valerius Cordus, who called it "sweet oil of vitriol" (oleum dulce vitrioli) &#; the name reflects the fact that it is obtained by distilling a mixture of ethanol and sulfuric acid (then known as oil of vitriol) &#; and noted some of its medicinal properties.[22] At about the same time, Paracelsus discovered the analgesic properties of the molecule in dogs.[22] The name ether was given to the substance in by August Sigmund Frobenius.[24]

For more information, please visit 4,4′-dihydroxydiphenyl ether.

It was considered to be a sulfur compound until the idea was disproved in about .[25]

The synthesis of diethyl ether by a reaction between ethanol and sulfuric acid has been known since the 13th century.[25]

Anesthesia

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The first use of ether in dental surgery, by Ernest Board. Panel from Ether Monument in Boston commemorating Morton's demonstration of ether's anesthetic use.

William T. G. Morton participated in a public demonstration of ether anesthesia on October 16, , at the Ether Dome in Boston, Massachusetts. Morton had called his ether preparation, with aromatic oils to conceal its smell, "Letheon" after the Lethe River (Λήθη, meaning "forgetfulness, oblivion"). [26] However, Crawford Williamson Long is now known to have demonstrated its use privately as a general anesthetic in surgery to officials in Georgia, as early as March 30, , and Long publicly demonstrated ether's use as a surgical anesthetic on six occasions before the Boston demonstration.[27][28][29] British doctors were aware of the anesthetic properties of ether as early as where it was widely prescribed in conjunction with opium.[30] Diethyl ether was preferred by some practitioners over chloroform as a general anesthetic due to ether's more favorable therapeutic index, that is, a greater difference between an effective dose and a potentially toxic dose.[31]

Diethyl ether does not depress the myocardium but rather it stimulates the sympathetic nervous system leading to hypertension and tachycardia. It is safely used in patients with shock as it preserves the baroreceptor reflex.[32] Its minimal effect on myocardial depression and respiratory drive, as well as its low cost and high therapeutic index allows it to see continued use in developing countries.[33] Diethyl ether could also be mixed with other anesthetic agents such as chloroform to make C.E. mixture, or chloroform and alcohol to make A.C.E. mixture. In the 21st century, ether is rarely used. The use of flammable ether was displaced by nonflammable fluorinated hydrocarbon anesthetics. Halothane was the first such anesthetic developed and other currently used inhaled anesthetics, such as isoflurane, desflurane, and sevoflurane, are halogenated ethers.[34] Diethyl ether was found to have undesirable side effects, such as post-anesthetic nausea and vomiting. Modern anesthetic agents reduce these side effects.[27]

An illustration depicting ether's effects, s&#;s

Prior to , it was on the World Health Organization's List of Essential Medicines for use as an anesthetic.[35][36]

Medicine

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Ether was once used in pharmaceutical formulations. A mixture of alcohol and ether, one part of diethyl ether and three parts of ethanol, was known as "Spirit of ether", Hoffman's Anodyne or Hoffman's Drops. In the United States this concoction was removed from the Pharmacopeia at some point prior to June ,[37] as a study published by William Procter, Jr. in the American Journal of Pharmacy as early as showed that there were differences in formulation to be found between commercial manufacturers, between international pharmacopoeia, and from Hoffman's original recipe.[38] It is also used to treat hiccups through instillation into the nasal cavity.[39]

Recreational abuse

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The recreational use of ether also took place at organised parties in the 19th century called ether frolics, where guests were encouraged to inhale therapeutic amounts of diethyl ether or nitrous oxide, producing a state of excitation. Long, as well as fellow dentists Horace Wells, William Edward Clarke and William T. G. Morton observed that during these gatherings, people would often experience minor injuries but appear to show no reaction to the injury, nor memory that it had happened, demonstrating ether's anaesthetic effects.[40]

In the 19th century and early 20th century ether drinking was popular among Polish peasants.[41] It is a traditional and still relatively popular recreational drug among Lemkos.[42] It is usually consumed in a small quantity (kropka, or "dot") poured over milk, sugar water, or orange juice in a shot glass. As a drug, it has been known to cause psychological dependence, sometimes referred to as etheromania.[43][medical citation needed]

See also

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• The Great Moment &#; film about William T.G. Morton and ether

Explanatory notes

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1. ^

   CH3CH2

   which is often written as

   C2H5

   (see

   Et stands for monovalent ethyl group which is often written as(see pseudoelement symbol

References

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Historical perspectives

The discovery of ether for the use as an anesthetic was in which marked the birth of a modern age in anesthesiology. Although its use has been abandoned in the developed world, ether was safely and effectively used as an inhalation anesthetic for over one hundred years. Prior to the middle of the 19th century and the discovery of ether, surgery was a rare and gruesome procedure. One of the most common operations was extremity amputation. There the surgeon used saws and knives to remove an appendage and scalding irons to cauterize the wound. Before the discovery of anesthesia, the sound of patients thrashing and screaming vibrated throughout the operating rooms [2]. They resorted to a variety of methods to control the patient&#;s pain including alcohol, opiates, ice, and various distractions.

Ether (diethyl ether) was first prepared in by Valerius Cordus, a Prussian botanist. Cordus produced the compound, known as &#;sulfuric ether&#; at the time, by distilling sulfuric acid (oil of vitriol) with fortified wine to make an &#;oleum vitrioli dulce&#; (sweet oil of vitriol) [3]. Despite this early synthesis, ether was rarely used over the next three decades. In fact, it&#;s only routine consumption was as a recreational drug among poor Britians who sometimes drank an ounce of ether when traditional alcohol was not available. American students adopted a variation of this practice in the &#;ether frolics&#; of the early s to achieve a feeling of euphoria. Participants would hold ether soaked towels to their faces until losing consciousness.

Ether was first made use of as a general anesthetic by Dr. Crawford Williamson Long on March 30, . Long was a physician and pharmacist who learned about ether while studying medicine in college. In , Long removed a tumor from the neck of a patient who was under the effects of ether anesthesia. Unfortunately, the successful and unprecedented use of anesthesia during surgery was not credited to Long due to his laxity in publishing the results of the surgery until several years later.

The first true demonstration of ether as an inhalation anesthetic was on October 16, by William T.G. Morton, a Boston dentist. He discovered the anesthetic properties of ether in his search to provide patients with relief from painful dental procedures [4]. Prior to , anesthesia was not used during surgical procedures and patients often avoided surgical intervention at all cost. Additionally, prior to the monumental events of , Morton attended a public demonstration of the anesthetic properties of nitrous oxide given by Horace Wells. Wells, also a dentist, administered nitrous oxide to a patient and then extracted a wisdom tooth. Unfortunately, the patient did not appear to be fully anesthetized and the public deemed the demonstration to be a failure.

The exhibition furthered Morton&#;s interest in inhalation anesthetics and led him to consult a professor of chemistry at Harvard Medical School, Charles A. Jackson [4]. Jackson recommended a trial of sulfuric ether as an alternative to nitrous oxide, commonly known as &#;laughing gas&#;. Morton began experimenting with the ether and learned that a drop on the skin produced local analgesia. Further investigation with inhaled ether revealed that the agent was more versatile than inhaled nitrous oxide. As opposed to nitrous oxide, bottles of ether could be transported easily and the volatility of the drug permitted effective inhalation. In addition, the concentration of the drug required for surgical anesthesia was so low that the patients did not become hypoxic when breathing ether vaporized in air which is an advantage compared to nitrous oxide. Morton, who had entrepreneurial aspirations, quickly became convinced that ether was a suitable surgery anesthetic for hospital surgery and knew the significance of ether as a surgical anesthetic. He also knew that since ether has been available for centuries, it could not be patented, so Morton added some odor-masking impurities to ether, and called the concoction Letheon.

As a result of Morton&#;s &#;success&#;, he began to promote the use of ether in his dental practice. His success also prompted a demonstration at Harvard Medical School. On October 16, , Morton publicly administered inhaled ether to a patient at Massachusetts General Hospital which took place in an amphitheater now known as the &#;Ether Dome&#;. The patient was successfully anesthetized and the surgeon, Dr. John Warren, removed a tumor from Mr. Gilbert Abbot&#;s neck. The patient had muttered as if in a semi-conscious state during the operation and after the surgery was complete, he stated that the pain was considerable, though mitigated. On the following day, the vapor was administered to another patient with complete success [4]. The public demonstration of ether anesthesia signaled the birth of the field of anesthesiology as a specialty. Ether anesthesia was adopted rapidly around the world and surgical anesthesia and analgesia became an accepted standard in surgical care.

Morton kept the true composition of Letheon a secret with the hopes of becoming wealthy. However, it was not long before surgeons recognized the smell of Letheon and associated it with ether. Morton attempted to fight the widespread use of ether which even included petitioning Congress for two decades to award him as the discoverer of ether. Nonetheless, Congress was knowledgeable of ether&#;s ancient origins and no monetary reward was given to Morton.

Oliver Wendell Holmes Sr. created the term anesthesia that was derived from the Greek word anaisthēsia meaning &#;lack of sensation&#; [5]. Holmes was a professor of anatomy and physiology at Harvard and had rejoiced saying that &#;The knife is searching for disease, the pulleys are dragging back dislocated limbs, nature herself is working out the primal curse which doomed the tenderest of her creatures to the sharpest of her trials, but the fierce extremity of suffering has been steeped in the waters of forgetfulness, and the deepest furrow in the knotted brow of agony has been smoothed forever [6].&#;

Ether was safe, easy to use, and remained the standard general anesthetic until the s when the fluorinated hydrocarbons (halothane, enflurane, isofluorane and sevoflurane) came into common use. Although these newer agents reduced the postoperative nausea, vomiting and flammability that were problematic with ether, they were expensive to produce and included a host of undesirable side effects.

Anesthetics used today are almost unrecognizable from anesthetics used in the late s. Ether has been replaced completely by newer inhalation agents and open drop delivery systems have been exchanged for complicated vaporizers and monitoring systems. Anesthesia in the developing world, however, where lack of financial stability has halted the development of the field, still closely resembles primitive anesthetics.

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