药物诱导的麻醉

药物诱导的麻醉第一页，共二十二页，2022年，8月28日PRINCIPLESOFTHEADMINISTRATIONOFGENERALANAESTHETICSUptakeandDistributionofinhalationalgeneralanestheticsDepthofAnesthesia-Tensionofanaestheticagentinbrain-controls-ratesofinductionandrecoveryTensionandpartialpressureareinterchangeableterms第二页，共二十二页，2022年，8月28日Tensioninthearterialbloodandbrainaresameandaredeterminedby:ConcentrationoftheanaestheticintheinspiredairdependsonrateofventilationTransferofthegasfromthealveolitothebloodDecreasedindisease(ex.emphysema)Rateoftransferisdeterminedby:Solubility(Bloodgaspartitioncoefficient.)Rateofbloodflow(directlyproportionaltotheC.O.Partialpressuresoftheagentinarterialandmixedvenousblood.Lossoftheagentfromthearterialbloodtoallthetissueofthebody第三页，共二十二页，2022年，8月28日ANAESTHESIAMACHINESAredevicesbywhichtheanesthesiologistisabletodeliverMeasuredquantitiesofanaestheticgasesandoxygenthroughaccurateflowmetersandwiththeuseofspecialvaporizersitispossibletoaddthevaporofvolatileanestheticliquidtothegasstream.ThemixtureofoxygenandanaestheticagentisthendeliveredtoabreathingcircuitforadministrationbyInhalation.第四页，共二十二页，2022年，8月28日GeneralAnestheticsarethemostdangerousdrugs

Therapeuticindexrangesbetween2-42-3timesdosecausescirculatoryfailure第五页，共二十二页，2022年，8月28日OraldosedeliversthetotaldoseWhengasorvaporisinhaledonlyasmallamountisabsorbedWhereastherestisexhaledoutinnext1-2secondsThedrugreachesthebrainbyleavingthebloodAnaestheticbloodlevelsofthesecannotbemeasuresaccuratelyConcentrationsinthelungscanbeeasilyfrequentlyandaccuratelybemeasuredThepartialspressuresoftheanaestheticinthelungandthebrainarealmostequalatequilibrium第六页，共二十二页，2022年，8月28日MinimumAlveolarConcentrationMACisthemeasureofpotencyofgeneralanestheticsItistheminimumalveolarconcentration(MAC)atoneatmosphericpressurethatproducesimmobilityin50%patientsoranimalsexposedtonoxiousstimuli第七页，共二十二页，2022年，8月28日ELIMINATIONOF

GENERALANAESTHETICSFreegasesandvaporswashoutofthelungs:Thearterialbloodtensiondeclinesfirst.Followedbythatinthetissueswheretheanaestheticagentpersistsforalongertime.Tissuehavinglowbloodflow(muscle)relievetheagentmuchslowly.OTHERROUTES:Theseagentsarealsoeliminatedinsmallerquantitiesfromskin,mucousmembraneandthekidneys第八页，共二十二页，2022年，8月28日StagesofGeneralAnaesthesia第九页，共二十二页，2022年，8月28日DEPTHOFGENERALANAESTHESIAOCCURSINSTAGESSTAGE-1ANALGESIASTAGE-2DELERIUMSTAGE-3SURGICALANESTHESIASTAGE-4MEDULLARYPARALYSES第十页，共二十二页，2022年，8月28日APPROACHESFORTESTINGDEPTHOFANAESTHESIA

Blinkingofeyelidsonstrikingtheeyelashes.SwallowingRegularityanddepthofrespiration.IncreaseinrespiratoryrateandB.P.onincisionTightnessofjawmuscles.Aboveresponsesfadeondeepeningoftheanesthesia.DeepanesthesiaLeedsto:RespiratorydepressionApneaLoweringofB.P.Asystole第十一页，共二十二页，2022年，8月28日PREANAESTHETICMEDICATIONDecreaseanxietywithoutdrowsinessAmnesiaRelievepreoperativepainDecreaserequirementforaninhalationalagent.Minimisingundesirableeffectsofanesthetics.(salivation,decreaseinheartrate,coughing,vomiting)Decreasevolumeandacidityofthegastriccontents.Decreasestressresponseinpreoperativeperiod第十二页，共二十二页，2022年，8月28日PREANAESTHETICMEDICATION2-3drugsareusedconcomitantly: SedativesHypnotics Antianxietydrugs Opoids Antiemetics H-2antagonists Gastrokineticagents Anticholinergics第十三页，共二十二页，2022年，8月28日 DRUGSUSEDIN

PREANAESTHETICMEDICATIONSBenzodiazepines:Diazepam,Lorazepam,Midazolam.Barbibiturates:Pentobarbitone,secobarbitone.Antihistamines:Hydroxyzine,Diphenhydramine.Phenothiazines:Promethazine.Butyrophenones:Droperidol.Opoids:Morphine,fentanyl,meperidine.Anticholinergics:atropine,scopolamine,glycopyrrolate.Antiemetics:OndansetronDrugsdecreasinggastricacidity: H-2antagonists. Antacids. Gastrokineticagents.第十四页，共二十二页，2022年，8月28日

MECHANISMOFACTIONSOFGENERALANAESTHETICSAlldrugsbelongtodiversegroupsInertgasesasxenonInorganic/OrganiccompdsasNitrousoxideandChloroform.ComplexOrganicMoleculesHalogenatedAlkanesandethersTheModeofactioniswithoutanysatisfactoryexplanation.POSTULATIONS:Influencesynaptictransmission.Axonalconductionisunaffected.Potentiatereleaseofinhibitoryneurotransmitters.Inhibitexcitatorysynapses.第十五页，共二十二页，2022年，8月28日 MECHANISMOFACTIONSOFGENERALANAESTHETICSActionoftheseagentsisonLipidbilayerand/orproteinlipidinterfaceORIONCHANNELS(Na/K/Ca)ORLigandgatedChannelsl-Glutamate.NMDANAChRGABA-A第十六页，共二十二页，2022年，8月28日Atthemolecularlevel,anestheticsprobablyexerttheireffectsbydirectinteractionswithproteinsratherthanbydisturbingthematrixofthelipidbilayerasearlierpostulated.AnestheticsMaybindtohydrophobicpocketsorclefts,producingsmallchangesinproteinConformationalertingreceptorofchannelfunction.ItisalsopossiblethatspecializedareasOfthemembranesuchastheboundarylipidssurroundingmembraneProteinsareimportantsitesofanaestheticbindingandaction. MECHANISMOFACTIONSOFGENERALANAESTHETICS第十七页，共二十二页，2022年，8月28日 MECHANISMOFACTION:Theexactmechanismbywhichinhalationalanestheticsfunctionisnotknown.Thereappearstobeacorrelationbetweenanestheticpotencyandlipidsolubility(Meyer-Overtontheory),suggestingthattheseanestheticslikelyaffectthelipidmatrixofnervecellmembranesinthebrain.Furthermore,NMRandelectronspinresonancestudiesindicatethatanestheticscausealocaldisorderingofthelipidmembranematrix,possiblydecreasingthenumberofmoleculesthatalternatesimultaneouslybetweenthegelandcrystallinestates,andtherebyalteringmembranefunction.第十八页，共二十二页，2022年，8月28日 NEUROLEPTANALGESIA-Stateofquiescence-Reducedmotoractivity-Reducedanxiety-Indifferencetothesurroundingswithoutlossof

consciousnessThepatientrespondstocommands.Drugs:aneuroleptcompd(Droperidol)plusanopoidanalgesic(fentanyl)Neuroleptanalgesiamaybeconvertedintoneuroleptanaesthesiabyconcominantadministrationof65%nitrousoxide第十九页，共二十二页，2022年，8月28日

DISSOCIATIVEANAESTHESIAastateofsedatio