AnalgesiaAnalgesia, EpiduralAnalgesics, OpioidAnesthesia, GeneralReceptors, Opioid, muAnesthesiaAnalgesia, ObstetricalReceptors, OpioidAnesthesia, LocalAnesthesia, EpiduralReceptors, Opioid, deltaAnesthesia, SpinalAnalgesia, Patient-ControlledReceptors, Opioid, kappaAnesthesia, ConductionAnesthesia, InhalationAnesthesia, IntravenousAnesthesia, ObstetricalOpioid PeptidesPain, PostoperativeMorphineAnesthetics, LocalFentanylBupivacainePain MeasurementAnesthesia Recovery PeriodAnesthesia, DentalNarcotic AntagonistsNaloxoneAnalgesicsAdjuvants, AnesthesiaPainNerve BlockAnesthetics, IntravenousAcupuncture AnalgesiaAnesthetics, InhalationAnesthetics, CombinedPropofolSufentanilNitrous OxideLidocaineMeperidineNaltrexoneMethyl EthersOpioid-Related DisordersIsofluraneAnesthesiologyInjections, SpinalKetamineEnkephalinsAnestheticsNarcoticsAnesthesia, CaudalMonitoring, IntraoperativeEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Double-Blind MethodLabor PainConscious SedationCesarean SectionAmbulatory Surgical ProceduresDrug ToleranceTramadolPostoperative Nausea and VomitingAlfentanilPreanesthetic MedicationEndorphinsAmidesHalothaneBuprenorphineAnalgesics, Non-NarcoticAnesthesia and AnalgesiaEnkephalin, D-Penicillamine (2,5)-HydromorphoneLabor, ObstetricAnesthetics, DissociativePain ThresholdDynorphinsHypnotics and SedativesEnkephalin, LeucineDose-Response Relationship, DrugAnesthesia, Closed-CircuitMepivacainebeta-EndorphinButorphanolAnesthetics, GeneralThiopentalPiperidinesProspective StudiesPrilocaineXylazineAnesthesia Department, HospitalPentobarbitalEnkephalin, Leucine-2-AlaninePain ManagementKetorolacPregnancyIntraoperative PeriodMorphinansNalbuphineIntubation, Intratracheal