Inhalational anaesthetic substances are either volatile liquids or gases, usually delivered using an anaesthesia machine composing a mixture of oxygen, anaesthetics and ambient air, delivering it to the patient and monitoring patient and machine parameters. Liquid anaesthetics are vaporized in the machine. Many compounds have been used for inhalation anaesthesia, but only a few are still in widespread use. Desflurane, isoflurane, and sevoflurane are the volatile anaesthetics most widely used today. They are often combined with nitrous oxide. Older volatile anesthetics, such as halothane, enflurance and methoxyfluraneless are less popular. Researchers are also actively exploring the use of xenon as an anaesthetic. Injection anaesthetics are used for induction and maintenance of a state of unconsciousness. Anaesthetists prefer to use intravenous injections as they are faster, generally less painful and more reliable than intramuscular or subcutaneous injections. Among the most widely used drugs are: * Propofol * Etomidate * Barbiturates such as methohexital and thiopentone/ thiopental * Benzodiazepines such as midazolam and diazepam * Ketamine is used in the UK as "field anaesthesia", for instance at a road traffic incident, and is more frequently used in the operative setting in the US. The volatile anaesthetics are a class of general anaesthetic drugs composed of gasses and liquids which evaporate easily for administration by inhalation. All of these agents share the property of being quite hydrophobic (i.e., as liquids, they are not freely miscible with in water, and as gases they dissolve in oils better than in water).[information sourced and edited from Wikipedia "General Anaesthetic"]
