Andersons pediatric cardiology 2297
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Accordingly,IVinductionofanesthesiafollowedbyendotrachealintubation
andmechanicalventilationisthepreferredapproachforpatientswithimpaired
ventricularfunction,elevatedpulmonaryarterypressures,severehypoxemia,
andneonateswithcomplexcongenitalcardiacdisease.Immobilityforimaging
ordiagnosticstudieswithlimitedpainfulstimulationcanbeachievedinolder
patientswithcontinuoussedationviaindwellingIVaccessorfollowing
inductionofgeneralanesthesiaandIVplacement.
Propofolhasbecomeapopularagentforinducingdeepsedationandgeneral
anesthesia.Inclinicallyrelevantplasmaconcentrations,propofolhasbeenfound
tohaveminimalnegativeinotropiceffectsinisolatedanimalcardiac
preparations23orinhumanadultatrialmusclestrips.24Inchildrenwithnormal
hearts,inductiondosesofpropofolconsistentlydecreasesystolicandmean
arterialpressureby5%to25%aswellasreducesystemicvascularresistance,
withoutchangesinheartrate,cardiacoutput,orpulmonaryvascularresistance.25
Inpatientswithintracardiacshunts,increasesinright-to-leftshuntanddecreases
inthepulmonarytosystemicflowratio(Qp:Qs)havebeenobserved,whichmay
resultinasignificantdecreaseinPaO2andSpO2.26Propofolshouldthereforebe
usedjudiciouslyinpatientswhocannottoleratesystemicafterloadreductionand
inpatientswhosepulmonarybloodflowdependsonbalancingtheirsystemic
andpulmonaryvascularresistances.However,ithasnosignificanteffecton
sinuatrialatrioventricularnodeconductionorontheabilitytoinduce
supraventriculartachycardia,renderingitdesirableastheprincipalanesthetic
agentforelectrophysiologystudiesandradiofrequencyablations.27Importantly,
however,itslong-termuseintheintensivecaresettingiscontraindicated,with
severalreportsoflacticacidosisandmyocardialfailurethoughttobedueto
disruptionoffattyacidoxidation28followingprolonged(>48hours)orhighdoseuseinpediatricpatients.29,30
Adrugfrequentlyusedtoinduceanesthesiainhemodynamicallyunstable
childrenisketamine.ThisN-methylD-aspartatereceptorantagonistisapotent
analgesicandprovidesdissociativeanesthesia.31Itincreasesheartrate,blood
pressure,andcardiacoutputthroughcentralnervoussystem–mediated
sympathomimeticstimulationandinhibitionofthereuptakeofcatecholamines.
Ithasbeenshowntohaveminimalornoeffectonpulmonaryarterypressuresor
pulmonaryvascularresistanceifoxygenationismaintained.32–34However,itisa
directmyocardialdepressantwhenstudiedinisolatedmyocytepreparations35
andinfailingadulthumanatrialandventricularmuscletrabeculae,16thoughtto
beduetoinhibitionofL-typevoltage-dependentCa2+channelsinthe
sarcolemmalmembrane.36Thismayexplainthemyocardialdepressionobserved
inpatientswhosesympathomimeticresponsesarealreadymaximallystimulated,
suchasindecompensatedheartfailure.Moreover,inpatientschronicallytreated
withβ-adrenergicagonists,catecholaminereceptorsmaybedownregulated,
resultinginadiminishedresponsetoendogenouslygeneratedcatecholamines.
Thisdirectmyocardial-depressingeffectisgreaterthanthatproducedby
etomidate.24Otherwell-recognizedsideeffectsassociatedwithketamineinclude
emergencedelirium,excessivesalivation,andincreasesincerebralmetabolism,
intracranialpressure,cerebralbloodflow,andcerebraloxygenconsumption.31
Etomidateisanimidazole-derivedhypnotic/sedativeagentwhoseanesthetic
effectsareproducedbystimulatinggamma-aminobutyricacidreceptors.Its
desirableeffectsincludeminimalmyocardialdepression,reductionsincerebral
bloodflow,cerebralmetabolicrateforoxygenconsumption(by30%to50%)
andintracranialpressure,aswellasminimalrespiratorydepression.16,24
Undesirableeffectsincludepainoninjection,myoclonicmovement,hiccups,
nauseaandvomiting,andadrenalsuppression.
Dexmedetomidineisanimidazolederivativeandaselectiveα2adrenergic
receptoragonistwithsedative,analgesic,andanxiolyticproperties.Itis
increasinglyusedasasedativefornoninvasiveimagingstudies37aswellas
intraoperativelyandpostoperativelytohelpbluntthesympatheticstress
response,todecreaseanestheticrequirements,andtocontrolpostoperative
pain.38,39Itssideeffectsincludeadose-dependentdecreaseinheartrate,
hypotensionorhypertension,andpotentiationofopioidandsedativedrugs.40Of
note,dexmedetomidineclearanceisdecreasedinprematureandfull-term
neonates,necessitatinglowerdosesinthisagegroupandheightenedmonitoring
forsideeffects.41
MonitoringandVascularAccess
InadditiontothestandardnoninvasivemonitoringrequiredbytheAmerican
SocietyofAnesthesiologists,whichincludepulseoximetry,noninvasiveblood
pressuremeasurement,ECG,temperature,andcapnography,ifavailable,
invasivemonitoringisfrequentlyutilizedforpediatriccardiacsurgical
procedures.Thesemayincludeinvasivearterialandcentralvenouscatheters,
intracardiaclines,ortransesophagealechocardiography,andutilizationvaries
substantiallybyinstitution.Neonatesfrequentlyhaveumbilicalarterialand
venouscathetersplacedeitherintheintensivecareunit(ICU)oruponarrivalto
theOR.Thesecathetersprovideaccuratepressuremonitoringandreliable
vascularaccess,respectively,andallowothervascularsitestobepreservedfor
futureanticipatedsurgicalproceduresandcatheterizations.Ifumbilicalarterial
accessisnotavailable,radial,ulnar,orfemoralarterialaccessisobtainedprior
totheoperation.Posteriortibialanddorsalispedisarterialpressuremonitoring
areoftenunreliablefollowingcardiopulmonarybypassordeephypothermic
circulatoryarrest.Moreover,useofthebrachialandaxillaryarteriesarenot
commonlyemployedduetotheriskfordistallimbischemia.Consideration
regardinglateralityisgiventopriororanticipatedsystemictopulmonaryartery
shuntsordescendingaorticcross-clamping,whichaffecttheabilitytomeasure
hemodynamicsdistally.Modalityofarterialcannulationisdependenton
providerleveloftrainingandfamiliaritywithinsertiontechniques,suchas
palpation,Dopplerorultrasoundguidance,orcut-downwithdirectvisualization
ofthevessel.ArecentCochranereviewdemonstratedhigherfirst-attempt
successratesandlowercomplicationrateswithultrasoundguidanceforarterial
lineplacementinthepediatricpopulationcomparedwithpalpationorDoppler
auditoryassistance.42
Theuseofpercutaneouscentralvenouscathetersvariesamonginstitutions.
Whileacentralvenouscathetermayprovidecentralvenouspressuremonitoring,
accessforvasoactiveinfusions,andlarge-borecentralaccessforrapidvolume
delivery,theirplacementcanaddsignificanttimetothepre-bypassperiodand
placementcarriestheriskofpneumothorax,hematoma,inadvertentarterial
puncture,infection,andcentralveinthrombosis,whichmaybeparticularly
deleteriousininfantsinthesingle-ventriclepathway.Ifumbilicalvenousaccess
isnotavailable,internaljugularorsubclavianvenousaccessareusually
preferred,althoughfemoralveinaccessmaybeadvantageousinchildrenwith
