版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
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)whichisdesignedtofitthecontoursofthefacewiththe
minimumofpressure.
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:
inabilitytomaintainagoodsealbetweenthepatient’sfaceandthemask,particularlyinthosewithoutteeth;
fatigue,whenholdingthemaskforprolongedperiods;
theriskofaspiration,duetothelossofupperairwayreflexes;
theanesthetistisnotfreetodealwithanyotherproblems,whichmayarise.
Thelaryngealmaskairway(LMA)ortrachealintubationmaybeusedtoovercometheseproblems.
Thelaryngealmaskairway
Thisdevicewasdesignedforuseinspontaneouslybreathingpatients.Itconsistsofa‘mask’,whichsitsoverthelaryngealopening,attachedtowhichisatube,whichprotrudesfromthemouthandconnectsdirectlytotheanestheticbreathingsystem.Ontheperimeterofthemaskisaninflatablecuff,whichcreatesasealandhelpstostabilizeit.TheLMAisproducedinavarietyofsizessuitableforallpatients,fromneonatestoadults,withsizes3and4beingthemostcommonlyusedinfemaleandmaleadults,respectively.PositivepressureventilationcanbeperformedviatheLMAprovidedthathighinflationpressureisavoided,otherwiseleakageoccurspastthecuff,reducingventilationandcausinggastric
inflation.Aversionwithareinforcedtubeisalsoavailable.TheLMAisreusable,providedthatitissterilizedbetweeneachpatient.
Theuseofthelaryngealmaskovercomessomeoftheproblemsoftheprevioustechniques:
itisnotaffectedbytheshapeofthepatientsfaceortheabsenceofteeth;
theanesthetistisnotrequiredtoholditinposition,avoidingfatigueandallowinganyotherproblemstobedealtwith;
itreducestheriskofaspirationofregurgitatedgastriccontents,butdoesnoteliminateit.
Itsuseisrelativelycontraindicatedwherethereisanincreasedriskofregurgitation,forexampleinemergencycases,pregnancyandpatientswithahiatushernia.
Recently,thelaryngealmaskhasbeenshowntobeusefulintwootherareas:
Indifficulttrachealintubationwhereitwilloftenallowmaintenanceoftheairway.Alternatively,asmalldiametertrachealtubeorintroducecanbepassedintothelarynxviatheLMA.
Duringcardiopulmonaryresuscitation,ithasbeenshownthatnon-anesthetistsareabletoinsertanLMAmorerapidlyandsuccessfullythanatrachealtubeandachievemoreeffectiveventilationthanusingaself-inflatingbagandfacemask.ItislikelythatinthefuturetheLMAwillfindaroleinairwaymanagementduringresuscitation.
TECHNIQUEFORINSERTION
Thepatient’sreflexesmustbesuppressedtoalevelsimilartotherequiredfortheinsertionofanoropharyngealairwaytopreventcoughingorlaryngospasm.
Thecuffisdeflatedandthemasklightlylubricated(Fig.3.5a).
Aheadtiltisperformed,thepatient'smouthopenedfullyandthe
tipofthemaskinsertedalongthelardpalatewiththeopensidefacingbutnottouchingthetongue(Fig.3.5b).
Themaskisthenfurtherinserted,usingtheindexfingertoprovide
supportforthetube(Fig.3.5c).Eventually,resistancewillbefeltatthepointwherethetipofthemaskliesattheupperoesophagealsphincter(Fig.3.5d).
Thecuffisnowfullyinflatedusinganair-filledsyringeattachedto
thevalveattheendofthepilottube(Fig.3.5e).
Thelaryngealmaskissecuredeitherbyalengthofbandageor
adhesivestrappingattachedtotheprotrudingtube.
Trachealintubation
Thisisthebestmethodofprovidingandsecuringaclearairwayin-patientsduringanesthesiaandresuscitation,butsuccessrequiresabolitionofthelaryngealreflexes.Duringanesthesia,thisisusuallyachievedbytheadministrationofamusclerelaxant(seeChapter4).Deepinhalationalanesthesiaorlocalanesthesiaofthelarynxcanalsobeused,buttheseareusuallyreservedforuseinthosepatientswheredifficultywithintubationisanticipated,forexampleinthepresenceofairwaytumorsorimmobilityofthecervicalspine.
COMMONINDICATIONSFORTRACHEALINTUBATION
•Wheremusclerelaxantsateusedtofacilitatesurgery(e.g.abdominalandthoracicsurgery)therebynecessitatingtheuseofmechanicalventilation.
In-patientswithafullstomach,toprotectagainstaspirationof
regurgitatedgastriccontents.
Wherethepositionofthepatientwouldotherwisemake
maintenanceoftheairwaydifficult,forexamplethelateralorproneposition.
Wherethereiscompetitionbetweensurgeonandanesthetistfor
theairway(e.g.operationsontheheadandneck).
Inthosepatientsinwhomtheairwaycannotbesatisfactorily
maintainedbyanyothertechnique.
Duringcardiopulmonaryresuscitationwhenintubationallows:
ventilationwith100%oxygenwithoutleaks;
suctionclearanceofinhaleddebris;
aroutefortheadministrationofdrugs.
EQUIPMENTFORTRACHEALINTUBATION
Avarietyofequipmentexistsandthatchosenwillbedeterminedbythecircumstancesandbythepreferencesoftheindividualanesthetist.Thefollowingisalistofthebasicneedsforadultoralintubation.
Laryngoscopewithacurved(Macintosh)bladeandfunctioning
light.
Trachealtubesinavarietyofsizesandinwhichthecuffswork..The
internaldiameterisexpressedinmillimetersandthelengthincentimeters.Theymaybelightlylubricated.
Formales:8.0—9.0mminternaldiameter,22-24cmlengths.
Forfemales:7.5—8.5mminternaldiameter,20-22cm
lengths.
syringetoinflatethecuffoncethetubeisinplace.
Cathetermountsor‘elbow’toconnectthetubetotheanesthetic
systemorventilatortubing.
Suction,switchedonandimmediatelytohandincasethepatient
vomitsorregurgitates.
Extras:asemi-rigidintroducertohelpmouldthetubetoaparticular
shape;Magill’sforceps,designedtoreachintothepharynxtoremovedebrisordirectthetipofatube;bandageortapetosecurethetube.
Trachealtubes
•Theseweretraditionallymanufacturedfromredrubberandwerereusable.However,disposableplastic(PVC)onesarenowwidelyusedtoeliminatecross-infectionandarechemicallylessirritanttothelarynx
(Fig.3.6).
Tubesaresizedanaccordingtotheirinternaldiameterin
millimetersandaremanufacturedinhalf-millimeterintervals.Theyarelongenoughtobeusedorallyornasally.
Astandard15-mmconnectorisprovidedtoallowconnectiontothe
breathingsystem.
Inadultanesthesia,atrachealtubewithaninflatablecuffisusedto
preventleakageofanestheticgasesbackpastthetubewhenpositivepressureventilationisused.Thisalsohelpspreventaspirationofanyforeignmaterialintothelungs.
Thecuffisinflatedbyinjectingairfromasyringeviaa
small-diametertube,atthedistalendofwhichisaone-wayvalvetopreventdeflationandasmallpilotballoonwhichindicateswhenthecuffisinflated.
Awidevarietyofspecializedtubeshavebeendeveloped,examplesofwhichareshowninFig.3.6.
•Reinforcedtubesateusedtopreventkinkingandsubsequentobstructionofthetrachealtubeasaresultofthepositioningofthepatient’shead(Fig.3.6c).
Preformedtubesareusedduringsurgeryontheheadandneckand
aredesignedtotaketheconnectionsawayfromthesurgicalfield(Fig.3.6d).
Doublelumentubesareeffectivelytwotubesweldedtogetherside-by-side,withonetubeextendingdistallybeyondtheother.Theyareusedduringthoracicsurgery,andplacedsuchthatthedistaltubelieswithinonemainbronchus(endobronchial).Thisallowstheotherlungtobedeflatedtofacilitateviatheendobronchialportion(Fig.3.6E).
Inchildrenunderapproximately10yearsofage,uncuffedtubesare
usedasanaturalsealisprovidedbythenarrowinginthesubglotticregion(Fig.3.6F).
THETECHNIQUEOFORALINTUBATION
Thisrequiresabolitionofthelaryngealreflexesandappropriatemonitoringofthepatient.
Positioning
Thepatientispositionedwiththeneckflexedandtheheadextendedattheatlanto-occipitaljoint.Thisistheso-called‘sniffingthemorningair’position.Thepatient’smouthisfullyopenedusingtheindexfingerandthumboftherighthandinascissorsaction.
Laryngoscopy
Thelaryngoscopeisalwaysheldinthelefthandandthebladeisintroducedintothemouthalongtheright-handsideofthetongue,displacingittotheleft.Thebladeisadvanceduntilthetipliesinthegapbetweenthebaseofthetongueandtheepiglottis,thevallecula.Forceisthenappliedinthedirectioninwhichthehandleofthelaryngoscopeispointing,theeffortcomingfromtheupperarmnotthewrist,toliftthetongueandepiglottistoexposethelarynx.Thisshouldbeseenasa
triangularopening,withtheapexanteriorlyandthewhitishcoloredtruecordslaterally(Fig.3.7).
Intubation
Thetrachealtubeisintroducedintotherightsideofthemouth,advancedandseentopassthroughthecordsuntilthecuffliesjustbelowthecords.Thetubeisthenheldfirmlybythefingersoftherighthandandthelaryngoscopeiscarefullyremoved.Thecuffistheninflatedsufficientlytopreventanyleakduringventilation.Finallythepositionofthetubeisconfirmedbylisteningforbreathsoundsinbothaxillaeanditisthensecuredinplace.
Fornasotrachealintubation;awell-lubricatedtubeisintroducedusuallyviatherightnostrilalongthefloorofthenosewiththebevelpointingmediallytoavoiddamagetotheturbinates.Itisadvancedintotheoropharynx,whereitisusuallyvisualizedusingalaryngoscopeinthemannerdescribedabove.Itcantheneitherbeadvanceddirectlyintothelarynxbypushingontheproximalend,orthetippickedupwithMagill’sforceps(whicharedesignednottoimpairtheviewofthelarynxanddirectedintothelarynx.Theprocedurethencontinuesasfororalintubation.
DIFFICULTINTUBATION
Occasionally,intubationofthetracheaismadedifficultbecauseofaninabilitytovisualizethelarynx.Thismayhavebeenpredictedatthepreoperativeassessmentormaybeunexpected.Avarietyoftechniqueshavebeendescribedtohelpsolvethisproblemandincludethefollowing:
manipulationofthethyroidcartilagebydownwardsandupwardspressurebyanassistanttotryandbringthelarynxoritsposterioraspectintoview;
atlaryngosopy,agumelasticbougie,60cmlong,isinsertedintothetrachea,overwhichthetrachealtubeis‘railroaded’intoplace;
afibreopticbronchoscopeisintroducedintothetracheaviathemouthornoseandisusedasaguideoverwhichatubecanbepassedintothetrachea.Thistechniquehastheadvantagethatitcanbeusedineitheranesthetizedorawakepatients.
COMPLICATIONSOFTRACHEALINTUBATION
Thefollowingisonemethodsofcategorizingthem,butitisnotanattempttocoveralloccurrences.
Hypoxia
Oesophagealintubation.Thisisbestdetectedbymeasuringthecarbondioxideinexpiredgas;lessthan0.2%indicatesoesophagealintubation.Analternativeistoattacha50ml‘bladder’syringetothetrachealtubeandwithdrawtheplungerrapidly(Wee’soesophagealdetector).Ifthetrachealtubeisintheesophagus,resistanceisfeltandaircannotbeaspirated;ifitisinthetrachea,airiseasilyaspirated.Lessreliablesignsate‘burping’soundsasgasescapes,diminishedbreathsoundsonauscultation,anddecreasedchestmovementonventilationandgurglingsoundsovertheepigastrium.Pulseoximetryonlychangeslate,particularlyifthepatienthasbeenpreoxygenated.
NB.Ifthereisanydoubtaboutthepositionofthetubethenitshouldberemovedandthepatientventilatedviaafacemask..
Failedintubationandinabilitytoventilatethepatients.Thisisusuallyaresultofabnormalanatomyorairwaypathology.Manycasesarepredictableatthepreoperativeassessment(seepage6).
Failedventilationafterintubation.Possiblecausesincludethetubebecomingkinked,disconnected,orinsertedtoofarandpassingintoonemainbronchus,severebronchospasmandtensionpneumothorax.
Aspiration.Regurgitatedgastriccontentscancauseblockageoftheairwaysdirectlyorsecondarytolaryngealspasmandbronchospasm.Cricoidpressurecanbeusedtoreducetheriskofregurgitationpriortointubation(seebelow).
Trauma
Directlyduringlaryngoscogyandinsertionofthetubetolips,teeth,gongue,pharynx,larynx,trachea,andnoseandnasopharynxduringnasalintubation;causingsofttissueswellingorbleeding.
Indirectlytothemandible(dislocation),andthecervicalspineandcord,particularlywherethereispre-existingdegenerativediseaseortrauma.
Reflexactivity
Hypertensionanddysrhythmias.Thisoccursinresponsetointubationandmayjeopardizepatientswithcoronaryarterydisease,aorticorintracranialaneurysms,In-patientsatrisk,specificactionistakentoattenuatetheresponse,forexamplepretreatmentwithB-blockers.Potentanalgesics(fentanyl.Alfentanil)orintravenouslignocaine.
Vomiting.Thismaybestimulatedwhenlaryngoscopyisattemptedin-patientswhoareinadequatelyanesthetized.Itismorefrequentwhenthereismaterialinthestomach;forexampleinemergencieswhenthepatientisnotstarved,inpatientswithintestinalobstruction,orwhengastricemptyingisdelayed,asafteropiateanalgesicsorfollowingtrauma.
Laryngealspasm.Reflexadductionofthevocalcordsasaresultofstimulationoftheepiglottisorlarynx.
CRICOIDPRESSURE(SELLICK’SMANOEUVRE)
Thecricoidcartilageistheonlycompleteringifcartilageinthelarynx.Pressureexerteduponitanteroposteiorlyforcesthewholeringposteriorly,compressingtheesophagusagainstthebodyofthesixthcervicalvertebra,therebypreventingpassiveregurgitation.Itisperformedbyanassistantusingthethumbandfirsttwofingerstoapplythepressurewhilsttheotherhandisplacedbehindthepatient’snecktostabilizeit(Fig.3.8).Pressureisappliedasthepatientlosesconsciousnessandmaintaineduntilthetubehasbeensuccessfullyinserted,thecuffinflatedandtubespositionconfirmed.Ifthepatientstartstoactivelyvomit,pressureshouldbereleasedduetotheriskoftheesophagusrupturing,andthepatientshouldbeturnedontotheirsidetominimizeaspiration.
Emergencyairwaytechniques
Thesemustonlybeusedwhenallothertechniqueshavefailedtosecureandmaintainanairwayandoxygenationineitherananesthetizedpatientoroneundergoingresuscitation.
Needlecricothyroidotomy.Thecricothyroidmembraneisidentifiedandpuncturedusingalargeborecannula(12-14gauge)attachedtoasyringe.Aspirationofairconfirmsthatthecannulalieswithinthetrachea.Thecannulaisthenangledtoabout45caudallyandadvancedofftheneedleintothetrachea(Fig.3.9).Ahigh-flowoxygensupplyisthenattachedtothecannulaandinsufflatedfor1secondfollowedbya4-secondrest.Expirationoccursviatheupperairwayasnormal.Thistechniqueonlyoxygenatesthepatientanddoesnoteliminatecarbondioxide.Itisthereforelimitedtoabout30minutesusewhileadefinitiveairwayiscreated.
Surgicalcricothyroidotomy.Thisinvolvesmakinganincisionthroughthecricothyroidmembranetoallowtheintroductionofa5.0-6.0mmdiametertracheostomytubeortrachealtube(Fig.3.10).Itismoredifficulttoperform.Andresultsinsignificantlymorebleeding,thantheabove.Theadvantagesarethatonceatubeofthisdiameterhasbeeninserted,thepatientcanbeadequatelyventilated,ensuringoxygenation,eliminationofcarbondioxideandtheairwaysuctionedtoremoveanybloodordebris.
CHAPTER4
DrugsAssociatedWithAnesthesia
Intravenousanesthetic Neuromuscularblocking Analgesicsin
anesthesia,71
(induction)agents,53drugsandtheir Furtherreading,77
Inhalationalinduction,56antagonism,64
Inhalationalagentsandintravenousinfusions,57
Theanesthetisthastobefamiliarwithawiderangeofdrugstofacilitatethesafeandeffectiveconductofanesthesia.Unlikemostotherbranchesofmedicine,thesearealmostalwaysadministeredpaenterally;eitherintravenouslyorviainhalation.Unfortunately,aswellastheirdesiredeffectonthecentralnervoussystem,thesedrugshaveundesirableactionsonmanyotherbodysystemsofwhichtheanesthetistmustbefullyaware.
Intravenousanesthetic(induction)agents
Thesesaredrugswhichareusedtostart(induce)anesthesia.Afterintravenous(i.v.)administration,consciousnessislostinlittlemorethanthetimeittakesforthesedrugstogetfromthesiteofadministrationtothebrain(onearm-braincirculationtime).Generally,consciousnessisregainedbyredistributionfromthebraintoothertissues.Currently,onlypropofolisalsousedtomaintainanesthesia.Anesthesiacanalsobeinducedbytheinhalationofanincreasingconcentrationofavolatileagent.
Becauseoftheadverseeffectsofthei.v.agentsonthecardiovascularsystem,muchlowerdosesshouldbeadministeredinelderly,frailorshockedpatients.
SODIUMTHIOPENTONE(INTRAVAL)
Thisisshortactingbarbiturate,thedoserequiredforinductionisusuallybetween2and7mg/kg.Inductionofanesthesiaisrapidandsmooth,takingabout15-20seconds,exceptinthosewhosecirculationisdelayed,forexamplepatientswhoareelderly,hypovolemic,orhavecardiacdisease.Patientsmaycommentonbeingabletotasteonionsorgarlicduringadministration.Consciousnessusuallyreturnsafter4-10minutesastheresultofredistribution,followedbyaprolongedperiod(=24hours)ofmetabolismbytheliverandexcretionbythekidneys.Repeateddosesareassociatedwithaccumulationanddelayedrecovery.
Systemiceffects
Hypotensionoccurssecondarytomyocardialdepressionandvenodilation.Thisisexaggeratedinthosewhoarehypovolemicorhavealimitedcardiovascularreserve.
Ashortperiodofbreathholdingoccursfollowedbydepressionofventilation.
Sodiumthiopentoneisapotentanticonvulsant.Cerebralmetabolism,bloodflowandintracranialpressurearereduced.
Aswithallbarbiturates,administrationmayexacerbateporphyria.PROPOFOL(DIPRIVAN)
Propofolispreparedasanemulsion.Thedoserequiredtoinduceanesthesiaisusuallybetween1.5and2.5mg/kg.Thirtytofortypercentofpatientscomplainofpainorburningoninjection.Inductionofanesthesiaisrapidbutlessdefinitethanwiththiopentone.Involuntarymovementsaresometimesseen.After4-7minutes,thereisarapid,fullrecoveryofconsciousness,apropertythathasmadepropofolpopularforday-casesurgery.Postoperativenauseaandvomitingareuncommon.Repeatdoses(oraconstantinfusion)canbeusedtomaintainanesthesia.
Systemiceffects
Hypotensioniscommon,secondarytovasodilatation.
Apneaiscommonafteraninductiondoseandmaylastfor40-50seconds.
Ventilationandtheresponsetocarbondioxidearedepressed.laryngealreflexesappeartobedepressed,laryngealspasmuncommon.
Cerebralmetabolismandbloodflowarereducedalongwithintracranialpressure.
Musclerelaxationinmorepronouncedafterpropofol,particularlywhenusedasaconstantinfusiontomaintainanesthesia.
ETOMIDATE(HYPNOMIDATE)
Thedoseforinductionofanesthesiais0.2-0.3mg/kg.Painoninjectioniscommon.Inductionisrapid,butisfrequentlyassociatedwithmuscletwitchingandinvoluntarymovement.Recoveryoccursafter4-8minutes,followingredistributionfromthebrain.Etomidateisnon-cumulative,evenafterseveraldoses.
Systemiceffects
Causesaslightfallincardiacoutputandminimalvasodilatation.Bloodpressureisbettermaintainedthanwithotheragents,makingitpopularforuseinsickpatients.
Causesdose-dependentdepressionofventilationandadecreasedventilatoryresponsetocarbondioxide.
Reducescerebralmetabolism,bloodflowandintracranialpressure,anditisanticonvulsant.
Itdoesnotcausehistaminereleaseandallergicreactionsareextremelyrare.
Despitebeingnon-cumulative,prolongedusesuppressesadrenocorticalfunction,impairingrecoveryincriticallyillpatients.
KETAMINE(KETALAR)
Thei.v.doseis1-2mg/kg,followingwhichconsciousnessislostover1minute,lastingfor10-20minutes.Ketaminecanalsobeadministeredintramuscularlytoinduceanesthesia.Theintramuscular(i.m.)doseis5-10
mg/kganditmaytake8-10minutestoloseconsciousness.Thesubsequentdurationofactionisvariable.Repeatbolusesoraninfusioncanbeadministeredtomaintainanesthesia.Vividhallucinationsarecommonduringrecoveryandcanbeminimizedbytheconcurrentuseofabenzodiazepine(e.g.midazolam).
Systemiceffects
Heartrate,bloodpressureandcardiacoutputarewellmaintainedeveninshockedpatients,makingitusefulduringemergencysurgery.
Thereisminimaldepressionofventilation.
Laryngealreflexesarealsomaintainedbetterthanwithotheragentsandbronchodilatationoccurs.
Advantages
Theabilitytoadministerketaminebyi.m.injectionisusefulwhenvenousaccessisdifficult.Theprofoundanalgesiceffectscanbeobtainedatsubanestheticdoses.Thispropertyisutilizedwhenpatients,oftenchildren,undergorepeatedminorpainfulprocedures,forexampleburnsdressings.Itisoccasionallyusedasthesoleagentinsoleagentinadversecircumstances,forexampleinprehospitalcaretofacilitateextricationofseverelyinjuredvictims.
METHOHEXITONE(BRIETAL)
Thisisashorteractingbarbituratethanthiopentone.Itwasoriginallypopularforshortproceduresanddaycasesbecauseoftheimprovedrecoverycomparedwiththiopentone.Ithasnowlargelybeensupersededbypropofol.
MIDAZOLAM
Thisisashort-acting,water-solublebenzodiazepine.Itisnotatrueinductionagentasitdoesnotproducearapidlossofconsciousness.Thedoserequiredtoinduceanesthesiaisbetween0.1and0.3mg/kg.Itmaytake30-45secondsbeforeconsciousnessislostwiththeend-pointbeingveryindistinct.Recoveryoccursafter10-15minutesandisassociatedwithalongerperiodofamnesia.
Systemiceffects
Causesrelativelylittlecardiovasculardepression.
Itisapotentrespiratorydepressant,particularlyintheelderly.
Ithasmildanticonvulsantandmusclerelaxantproperties.
Inhalationalinduction
Thismaybeusedwheni.v.inductionofanesthesiaisnotpractical,forexampleinanuncooperativechildorapatientwithalackofsuitableveins.Anesthesiaisinducedrelativelyslowlyandrespirationispreserved.Thisisthereforeausefultechniquein-patientswithairwaycompromise,whenani.v.agentmaycauseapnea,andventilationandoxygenationbecomeimpossiblewithcatastrophicresults.
Thepatientbreathesanincreasingconcentrationofaninhalationalagentinoxygen(ifthereisairwaycompromise),orinamixtureofoxygenandnitrousoxide.Adequacyofanesthesiaisassessed(andoverdosageavoided)basedonclinicalsignsor‘stagesofanesthesia’.TheoriginaldescriptionofthesestagesbyA.E.Guedelwasbasedonusingether,butthemainfeaturescanstillbeseen
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 2024年度农产品出口贸易合同
- 2024年度物流服务合同:二零二四年跨境电商物流配送服务协议
- 2024年度建筑工程二级建造师专项服务合同
- 管道龙头栓市场发展现状调查及供需格局分析预测报告
- 玫瑰油市场发展现状调查及供需格局分析预测报告
- 纸巾市场发展预测和趋势分析
- 2024年度娄桂离婚法律咨询服务合同
- 2024年度成都二手房产买卖合同范本
- 空气凝结器市场需求与消费特点分析
- 2024年度化工企业原材料采购合同
- 膝关节骨性关节炎(膝痹病)病程模板
- 概述卡诺循环
- 一年级上册汉字注音练习
- FMEA潜在失效模式及分析标准表格模版
- 三级动火许可证
- 辅助器具的使用指导.ppt
- 某单桩承载力及桩基沉降计算表格
- 石膏固定PPT课件
- 领导干部接访下访制度文档
- 大学物理下学期知识点总结Word版
- 【报告】管道脱脂检测报告
评论
0/150
提交评论