Halogenated ether
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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. Technically, the element astatine is also a halogen, but due to a number of factors it is rarely, if ever, used in organic chemistry.
Perhaps the most common use of halogenated ethers has been in anesthesiology. The first widely used inhalation anesthetic was diethyl ether, which is not a halogenated ether, but it enabled surgeons to perform painful surgeries without the patient being conscious. Unfortunately for doctors of that era, diethyl ether has the disadvantage of being extremely flammable and in some cases, explosive. Occasionally, this led to fires or explosions during surgery, and is one of the reasons that diethyl ether is no longer used in hospital settings. It is still commonly used as a solvent in organic chemistry labs, though with caution. In some countries, diethyl ether was eventually replaced with non-flammable (but more toxic) halogenated hydrocarbons such as chloroform and trichloroethane. Much later, safer halogenated hydrocarbon anesthetics such as halothane were developed.
Halogenated ethers have replaced most other compounds for use as inhalation anesthetics. Halogenated ethers have the advantages of being non-flammable as well as less toxic than earlier general anesthetics. Halogenated ethers differ from other ethers because they contain at least one halogen atom in each molecule. Examples of halogenated ethers include the general anethetics isoflurane, desflurane, and sevoflurane.
Currently, all inhalation anesthetics except for halothane are halogenated ethers, and when used, are always mixed with oxygen or air and then inhaled by the patient before or during surgery. In most surgical situations, other drugs such as opiates are used for pain and skeletal muscle relaxants are used to cause temporary paralysis. Additional drugs such as midazolam may be used to produce amnesia during surgery.
Newer intravenous anesthetics (such as propofol) have increased the options of anesthesiologists, but halogenated ethers remain a mainstay of general anesthesia.
