IsofluraneAnesthetics, InhalationAnesthesia, InhalationMethyl EthersDose-Response Relationship, DrugElectroencephalographyHemodynamicsEthersHalothaneAnestheticsNitrous OxideEnfluraneAnesthetics, IntravenousPropofolAnesthesia Recovery PeriodAnesthetics, CombinedHydrocarbons, FluorinatedAnesthesia, GeneralAnesthesiaAnesthesia, Closed-CircuitMonitoring, Intraoperative