哈尔滨医科学临床麻醉学小儿麻醉.ppt

PediatricAnesthesia,DepartmentofanesthesiologyCuiXiaoGuang,Theprovisionofsafeanesthesiaforpediatricpatientsdependsonaclearunderstandingofthephysiologic,pharmacologic,andpsychologicaldifferencesbetweenchildrenandadults.,Neonates:01monthsInfants:112monthsToddlers:13yearssmallchildren:412years,DEVELOPMENTALPHYSIOLOGYOFTHEINFANT,Thepulmonarysystem1,TherelativelylargesizeoftheinfantstongueThelarynxislocatedhigherintheneckTheepiglottisisshapeddifferently,beingshortandstubbyThevocalcordsareangledTheinfantlarynxisfunnelshaped,thenarrowestportionoccurringatthecricoidcartilage:uncuffedendotrachealtubes;patientsyoungerthan6years.,Thepulmonarysystem2,Alveoliincreaseinnumberandsizeuntilthechildisapproximately8yearsold.Functionalresiduralcapacity(FRC):thesamewithadult;inductionandpalinesthesiaofanesthesiaisrapidA-aDO2islarger:functionalairwayclosureLimitsoxygenreserves:hypoxemia.Theworkofbreathing:(Inprematureinfants)threetimesofadults,increasedbycoldstressorsomedegreeofairwayobstruction.RR:twotimesofadults,Thepulmonarysystem3,Tidalvolume(VT)islittle;physiologicaldeadspaceis30%ofVTAirwayresistanceincreasing:secretion,upperairwayinfectionDiaphragmaticandintercostalmusclesdonotachievetheadultconfigurationoftypeImusclefibersuntilthechild2yearsold:apneaorcarbondioxideretentionandrespiratoryfailure.Infantshaveoftenbeendescribedasobligatenasalbreathers:5monthsofage.,TheCardiovascularSystem1,Inuterus:foramenovale,ductusarteriosus(rightleft)Atbirth:thefetalcirculationbecomesanadult-typecirculation.-transitionalcirculationProlongedtransitionalcirculation:prematurity,infection,acidosis,pulmonarydiseaseresultinginhypercarbiaorhypoxemia(aspirationofmeconium),hypothermia,congenitalheartdisease.,TheCardiovascularSystem2,Themyocardialstructureoftheheartislessdeveloped,producelesscompliantventriclesThisdevelopmentalmyocardialimmaturity:sensitivitytovolumeloading,poortoleranceofincreasedafterload,heartrate-dependentcardiacoutput.,TheCardiovascularSystem3,Bradycardiaandprofoundreductionsincardiacoutput:activationoftheparasympatheticnervoussystemhypoxiaanestheticoverdoseThesympatheticnervoussystemandbaroreceptorreflexesarenotfullymature.,TheKidneys,Renalfunctionismarkedlydiminishedinneonatesandfurtherdiminishedinpretermbabiesbecauseoflowperfusionpressureandimmatureglomerularandtubularfunction.Nearlycompletematuration:approximately20weeksafterbirthCompletematuration:about2yearsofagedehydration,TheLiver1,Thefunctionalmaturityoftheliverissomewhatincomplete.Mostenzymesystemsfordrugmetabolismaredevelopedbutnotyetinduced(stimulated)bythedrugsthattheymetabolize.Jaundice:decreasedbilirubinbreakdown,TheLiver2,Aprematureinfantsliverhasminimalglycogenstoresandisunabletohandlelargeproteinloads:hypoglycemiaacidemiafailuretogainweightwhenthedietcontainstoomuchprotein.Thelowerthealbuminvalue,thelessproteinbindingandthegreaterthelevelsoffreedrug.,TheGastrointestinalSystem,Atbirth,gastricpHisalkalotic;afterbirththesecondday,pHisinthenormalTheabilitytocoordinateswallowingwithrespirationdoesnotfullymatureuntiltheinfantis4to5monthsofage:gastroesophagealrefluxIfadevelopmentalproblemoccurswithinthegastrointestinalsystem,symptomswilloccurwithin24to36hoursofbirth.Upper-vomitingandregurgitation;Lower-abdominaldistentionandfailuretopassmeconium.,Thermoregulation,Thinskin,lowfatcontent,andahighersurfacerelativetoweightallowgreaterheatlosstotheenvironmentinneonates.保温Thermogenesis:shiveringandnonshivering(metabolismofbrownfat).Generalanesthesiaaffectsthemetabolismofbrownfat.-hypothermiaHypothermia:delayedawakeningfromanesthesia,cardiacirritability,respiratorydepression,increasedpulmonaryvascularresistance,andaltereddrugresponses.,Centralnervoussystem,MorefatisinthecentralnervoussystemPermeabilityofBloodbrainbarrierisgreat:opioiddecrementbilirubinkernicterusMAC,PharmacologicalDifferences,Theresponsetomedications:bodycomposition,proteinbinding,bodytemperature,distributionofcardiacoutput,functionalmaturityoftheheart,maturationoftheblood-brainbarrier,therelativesize(aswellasfunctionalmaturity)oftheliverandkidneys,thepresenceorabsenceofcongenitalmalformations,Alterationsinbodycompositionhaveseveralclinicalimplicationsforneonates,adrugthatiswatersoluble:largervolumeofdistributionandlargerinitialdose(e.g.,succinylcholine);lessfat:adrugthatdependsonredistributionintofatforterminationofitsactionwillhavealongerclinicaleffect(e.g.,thiopental);adrugthatredistributesintomuscle:longerclinicaleffect(e.g.,fentanyl);Others,InhaledAnesthetics,NitrousoxideHalothaneEnfluraneIsofluraneSevofluraneDesflurane,Nitrousoxide,lowerdissolubility:含气间隙的体积增大neonate:pneumothorax,emphysemacongenitaldiaphragmaticherniaoracromphalusnecroticenteritis,Enflurane,Intheintroductionofanesthesia:breathholding,cough,laryngospasmAfteranesthesia:seizure-likeactivity,Isoflurane,Introductionofanesthesiaandanalepsia:rapidrespiratorydepression,coughing,laryngospasmAfterextubate:incidenceoflaryngospasm1MABL:bloodtransfusion;,VolumeofPRBCs,(DesiredHctPresentHct)EBVBW(kg)VolumeofPRBCs(ml)=HematocritofthePRBCs(60%),FreshFrozenPlasma,PT15sorPTT60s:Freshfrozenplasma,Platelets,Thrombocytopenia:15109/Lidiopathicthrombocytopenicpurp