MODEL RELEASED. Portrait of an anaesthetist at work, showing her administering gas through a face mask to maintain general anaesthesia in a patient. General anaesthesia describes a state of unconsciousness, analgesia (pain relief) and relaxation of skeletal muscle. A combination of drugs is typically used: thiopentone (by injection) is used to induce anaesthesia; maintenance is achieved with a combination of inhalation (of halothane, enflurane or isoflurane), intravenous drugs, and muscle relaxants.