临床麻醉学英文版2.docx
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临床麻醉学英文版2
CHAPTER3
ManagingtheAirway
Basictechniques,37Thelaryngealmaskairway,42Emergencyairway
Simpleadjuncts,39Trachealintubation,43techniques,50
Maintenanceofapatentairwayisanessentialprerequisiteforthesafeandsuccessfulconductofanesthesia.Inaddition,duringresuscitationpatientsoftenhaveanobstructedairwayeitherasthecauseorresultoftheirlossofconsciousness.Theskillofairwaymaintenanceshouldbeacquiredbyalldoctors,andnotsimplyregardedastheresponsibilityoftheanesthetist.Thedescriptionsofairwaymanagementtechniques,whichfollow,areintendedtosupplementpracticeeitheronamanikinorpreferablyonandanesthetizedpatientunderthedirectionofaskilledanesthetist.
Basictechniques
Anesthesiafrequentlyresultsinlossoftheairwayanditismosteasilyrestoredbyacombinationoftheheadtiltalongwithajawthrust(seeChapter2).Thelatterisprovidedbytheanesthetist’sfourthandfifthfingers(ofoneorbothhands)liftingtheangleofthemandible.Theoveralleffectdesiredisthatthepatient’smandibleis‘lifted’intothemaskratherthanthemaskbeingpushedintotheface(Fig.3.1).
FACEMASKS
●ThemostcommonlyusedtypeinadultsistheBOCanatomicalfacemask(Fig.3.2)whichisdesignedtofitthecontoursofthefacewiththeminimumofpressure.
●Leakageofanestheticgasesisminimizedbyanair-filledcuffaroundtheedge.
●Masksatemadeinavarietyofsizesandthesmallestone,whichprovidesagoodseal,shouldbeused(tominimizetheincreaseindeadspace,whichoccurs).
●TheAmbumask(Fig.3.2)hasatransparentbody—allowingidentificationofvomit–makingitpoplarforresuscitation.
●Allmasksmustbedisinfectedbetweeneachpatient.
Simpleadjuncts
Themostcommonlyandusedaretheoropharyngeal(Guedel)andnasopharyngealairways,insertedaftertheinductionofanesthesiatohelpmaintaintheairwayinconjunctionwiththetechniquesdescribedabove.
OROPHARYNGEALAIRWAY
●Thesearecurvedplastictubes,flattenedincross-sectionandflangedattheoralend,whichlieoverthetongue,preventingitfromfallingbackintothepharynx.
●Theyareavailableinavarietyofsizesfromneonatestolargeadults.Thecommonestsizesare2-4,forsmalltolargeadults,respectively.
●Aguidetothecorrectsizeisdeterminedbycomparingtheairwaylengthtotheverticaldistancefromthecornerofthepatient’smouthtotheangleofthemandible.
●Itisinitiallyinserted‘upsidedown’asfarasthebackofthehardpalate(Fig.3.3a),rotated180(Fig.3.3b)andfullyinsertedutiltheflangeliesinfrontoftheteethorgumsinanedentulouspatient(Fig.3.3c).
NASOPHARYNGEALAIRWAY
●Theseareround,malleableplastictubes,beveledatthepharyngealendandflangedatthenasalend.
●Theyaresizedontheirinternaldiameterinmillimeters,withlengthincreasingwithdiameter.Thecommonsizesinadultsare6-8mm,forsmalltolargeadults,respectively.
●Aguidetothecorrectsizeismadebycomparingthediametertotheexternalnaris.
●Priortoinsertion,thepatencyofthenostril(usuallytheright)shouldbecheckedandtheairwaylubricated.
●Theairwayisinsertedalongthefloorofthenose,withthebevelfacingmediallytoavoidcatchingtheturbinates(Fig.3.4).
●Asafetypinmaybeinsertedthroughtheflangetopreventinhalationoftheairway.
●Ifobstructionisencountered,forceshouldnotbeusedasseverebleedingmaybeprovoked.Instead,theothernostrilcanbetried.
PROBLEMSWITHAIRWAYS
Thepresenceofsnoring,indrawingofthesupraclavicular,suprasternalandintercastalspaces,useoftheaccessorymusclesorparadoxicalrespiratorymovement(see-sawrespiration)suggestthattheabovemethodsatefailingtomaintainapatentairway.Commonproblemsarisingusingthesetechniquesalongwithafacemaskduringanesthesiaare:
1inabilitytomaintainagoodsealbetweenthepatient’sfaceandthemask,particularlyinthosewithoutteeth;
2fatigue,whenholdingthemaskforprolongedperiods;
3theriskofaspiration,duetothelossofupperairwayreflexes;
4theanesthetistisnotfreetodealwithanyotherproblems,whichmayarise.
Thelaryngealmaskairway(LMA)ortrachealintubationmaybeusedtoovercometheseproblems.
Thelaryngealmaskairway
Thisdevicewasdesignedforuseinspontaneouslybreathingpatients.Itconsistsofa‘mask’,whichsitsoverthelaryngealopening,attachedtowhichisatube,whichprotrudesfromthemouthandconnectsdirectlytotheanestheticbreathingsystem.Ontheperimeterofthemaskisaninflatablecuff,whichcreatesasealandhelpstostabilizeit.TheLMAisproducedinavarietyofsizessuitableforallpatients,fromneonatestoadults,withsizes3and4beingthemostcommonlyusedinfemaleandmaleadults,respectively.Positivepressu