临床麻醉学 英文版2.docx

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.PositivepressureventilationcanbeperformedviatheLMAprovidedthathighinflationpressureisavoided,otherwiseleakageoccurspastthecuff,reducingventilationandcausinggastricinflation.Aversionwithareinforcedtubeisalsoavailable.TheLMAisreusable,providedthatitissterilizedbetweeneachpatient.

Theuseofthelaryngealmaskovercomessomeoftheproblemsoftheprevioustechniques:

●itisnotaffectedbytheshapeofthepatient’sfaceortheabsenceofteeth;

●theanesthetistisnotrequiredtoholditinposition,avoidingfatigueandallowinganyotherproblemstobedealtwith;

●itreducestheriskofaspirationofregurgitatedgastriccontents,butdoesnoteliminateit.

Itsuseisrelativelycontraindicatedwherethereisanincreasedriskofregurgitation,forexampleinemergencycases,pregnancyandpatientswithahiatushernia.

Recently,thelaryngealmaskhasbeenshowntobeusefulintwootherareas:

1Indifficulttrachealintubationwhereitwilloftenallowmaintenanceoftheairway.Alternatively,asmalldiametertrachealtubeorintroducecanbepassedintothelarynxviatheLMA.

2Duringcardiopulmonaryresuscitation,ithasbeenshownthatnon-anesthetistsareabletoinsertanLMAmorerapidlyandsuccessfullythanatrachealtubeandachievemoreeffectiveventilationthanusingaself-inflatingbagandfacemask.ItislikelythatinthefuturetheLMAwillfindaroleinairwaymanagementduringresuscitation.

TECHNIQUEFORINSERTION

Thepatient’sreflexesmustbesuppressedtoalevelsimilartotherequiredfortheinsertionofanoropharyngealairwaytopreventcoughingorlaryngospasm.

●Thecuffisdeflatedandthemasklightlylubricated（Fig.3.5a）.

●Aheadtiltisperformed,thepatient’smouthopenedfullyandthetipofthemaskinsertedalongthelardpalatewiththeopensidefacingbutnottouchingthetongue（Fig.3.5b）.

●Themaskisthenfurtherinserted,usingtheindexfingertoprovidesupportforthetube（Fig.3.5c）.Eventually,resistancewillbefeltatthepointwherethetipofthemaskliesattheupperoesophagealsphincter（Fig.3.5d）.

●Thecuffisnowfullyinflatedusinganair-filledsyringeattachedtothevalveattheendofthepilottube（Fig.3.5e）.

●Thelaryngealmaskissecuredeitherbyalengthofbandageoradhesivestrappingattachedtotheprotrudingtube.

Trachealintubation

Thisisthebestmethodofprovidingandsecuringaclearairwayin-patientsduringanesthesiaandresuscitation,butsuccessrequiresabolitionofthelaryngealreflexes.Duringanesthesia,thisisusuallyachievedbytheadministrationofamusclerelaxant（seeChapter4）.Deepinhalationalanesthesiaorlocalanesthesiaofthelarynxcanalsobeused,buttheseareusuallyreservedforuseinthosepatientswheredifficultywithintubationisanticipated,forexampleinthepresenceofairwaytumorsorimmobilityofthecervicalspine.

COMMONINDICATIONSFORTRACHEALINTUBATION

●Wheremusclerelaxantsateusedtofacilitatesurgery（e.g.abdominalandthoracicsurgery）therebynecessitatingtheuseofmechanicalventilation.

●In-patientswithafullstomach,toprotectagainstaspirationofregurgitatedgastriccontents.

●Wherethepositionofthepatientwouldotherwisemakemaintenanceoftheairwaydifficult,forexamplethelateralorproneposition.

●Wherethereiscompetitionbetweensurgeonandanesthetistfortheairway（e.g.operationsontheheadandneck）.

●Inthosepatientsinwhomtheairwaycannotbesatisfactorilymaintainedbyanyothertechnique.

●Duringcardiopulmonaryresuscitationwhenintubationallows:

（a）ventilationwith100%oxygenwithoutleaks;

（b）suctionclearanceofinhaleddebris;

（c）aroutefortheadministrationofdrugs.

EQUIPMENTFORTRACHEALINTUBATION

Avarietyofequipmentexistsandthatchosenwillbedeterminedbythecircumstancesandbythepreferencesoftheindividualanesthetist.Thefollowingisalistofthebasicneedsforadultoralintubation.

●Laryngoscopewithacurved（Macintosh）bladeandfunctioninglight.

●Trachealtubesinavarietyofsizesandinwhichthecuffswork..Theinternaldiameterisexpressedinmillimetersandthelengthincentimeters.Theymaybelightlylubricated.

（a）Formales:

8.0–9.0mminternaldiameter,22–24cmlengths.

（b）Forfemales:

7.5–8.5mminternaldiameter,20–22cmlengths.

●syringetoinflatethecuffoncethetubeisinplace.

●Cathetermountsor‘elbow’toconnectthetubetotheanestheticsystemorventilatortubing.

●Suction,switchedonandimmediatelytohandincasethepatientvomitsorregurgitates.

●Extras:

asemi-rigidintroducertohelpmouldthetubetoaparticularshape;Magill’sforceps,designedtoreachintothepharynxtoremovedebrisordirectthetipofatube;bandageortapetosecurethetube.

Trachealtubes

●Theseweretraditionallymanufacturedfromredrubberandwe