Haloalkanes consist of a Hydrogen and Carbon mix with one or more Halogen atoms (such as Fluorine or Chlorine) attached. The HC atom mix is called an Alkane, and the halogen atom replaces a hydrogen atom. These chemical compounds are used widely in industry and medicine, although recent discoveries in their composition have shown them to be damaging to the environment.
Probably the most famous Halokane used as an anesthetic is Chloroform, a natural or synthetic compound which sends a patient into a deep sleep or coma, depending on the dosage. Chloroform is not widely used in proper medicine today, instead being a common industrial chemical, but is very well-known in popular culture and is an instantly recognizable example of a "knockout drug." Chloroform depresses the nervous system, keeping pain signals from reaching the brain, but it can cause toxic buildup and dose-related damage.