Andersons pediatric cardiology 1851

anesthesia,temperature,cerebralperfusionpressure,andoverallmetabolicstate.
PatientssuspectedofhavingaclinicalseizureshouldundergocontinuousEEG
monitoringalongwithbrainimaging.
NovelNoninvasiveAlgorithmsBasedonHigh-FidelityContinuous
PhysiologicData.
Computeralgorithmsbasedonhigh-fidelityphysiologicdatasuchastheiDO2
indexdescribedearlierhavebecomeimportantadjunctsinthepostoperative
managementfollowingpalliation.AnacuteorsustainedriseintheiDO2indexis
associatedwithinadequateDO2andmaybeanearlyindicatorofimpending
myocardialfailure.Thesealgorithmsmayprovetobeofparticularvaluein
detectingimpendingcardiovascularcollapsefollowinginterventionssuchas
sternalclosure.
UrinaryCatheters.
Thoughnottraditionallyconsideredamonitoringdeviceperse,theurinary
catheterprovidesacontinuousassessmentofurineoutput,whichisanimportant
surrogateforcardiacoutputaswellasrenalfunction.Giventheriskfor
infection,urinarycathetersareoftendiscontinuedassoonasasteady
physiologicstateisachieved,astheriskofthecontinuousmonitoringofurine
outputcanbemitigatedbysimpleintermittentmonitoringofurineoutput
withoutanindwellingcatheter.
TemperatureMonitors.
Continuousmonitoringofcorebodytemperatureisanimportantcomponentof
postoperativecare.Themaintenanceofnormothermiaormildhypothermia
minimizesoxygendemandontherecoveringmyocardium.Temperatureprobes
maybeinsertedintotheesophagus,bladder,orrectum.Althoughriskof
mucosalinjuryissmall,continuoustemperatureprobesaretypicallyremovedas
soonasasteadyphysiologicstateisreached.Comparisonofthecore
temperaturetoaperipheraltemperature(e.g.,atthetoe)isahelpfuladditional
surrogateforcardiacoutput.

Bleeding

Maturationofthehemostaticsystemcontinuesthroughoutthefirstyearoflife;
thissystemdiffersfromthatinadults.Thelevelsofmanyclottingfactorsand


inhibitorsarelowandcancontributethechallengesofachievinghemostasis
followingsurgeryintheneonateandinfant.111,112Itisessentialtoachieve
hemostasisatthecompletionofanycardiacprocedurebutisespecially
importantinthepatientundergoingneonatalpalliationwithacontinued
multidistributioncirculation.Volumelossandanemiawillresultindecreased
totalcardiacoutputandworseninghypoxemia.Ongoingbleedingcanresultin
cardiactamponadeandcardiovascularcollapse.Inmostclosedprocedures—
suchaspulmonaryarterybanding,creationofasystemic-to-pulmonaryartery
shunt,orcoarctationrepair—bleedingisuncommon.Inthesecases,bleedingis
nearlyalwayssurgical—thatis,itisnotduetoadefectinthecoagulation
system.AftercasesusingcardiopulmonarybypasssuchasaDKS,especially
whencombinedwithhypothermia,asinaNorwoodprocedure,bleedingis
commonandduetobothsurgicalsitebleedingandthecoagulopathiceffectof
cardiopulmonarybypass,especiallywhencombinedwithhypothermia.
Reactionsinthecoagulationcascadearetemperature-dependent,anditis
essentialthatnormothermiabeachievedpriortoweaningfrombypass.Calcium
isanimportantcofactorinhemostasisandessentialfornormalcardiomyocyte
function;itshouldthereforebenormalizedpriortoweaningfrombypass.
Heparinisusedforanticoagulationduringcardiopulmonarybypass,andonce
thepatienthasbeensuccessfullyweanedfromit,completereversalofheparin
withprotamineisthefirststepinachievinghemostasis.Toachievestableclot
formation,bothplateletsandfibrinogenarenecessaryandshouldbetargetsfor
supplementation.113,114Althoughindividualsupplementationofthesefactors
basedonmeasureddeficiencywouldbeideal,practicallythemostcommon
approachisempiricsupplementationofplateletsandfibrinogenusingeither
freshfrozenplasmaorcryoprecipitate.Althoughplateletsandfibrinogenare

beingsupplemented,theoperativefieldshouldbeevaluatedforsurgical
bleeding.Ifbleedingpersistsdespitesupplementationofplateletsandfibrinogen
andimportantsurgicalbleedinghasbeenruledout,additionalhemostaticagents
maybeconsidered.
Avarietyoftopicalagentsareusedtohelpachievehemostasis.Theseinclude
agentswithalargesurfaceareaofmaterialthatactivatesthecontactactivation
system,suchasgelatinfoams,oxidizedcellulose,andmicrofibrillarcollagen.
Theseagentsareoftencombinedwiththrombin,eitherbovinederivedor
recombinanthumantypes.Manyfibrinsealants(e.g.,TisseelandEvicel)are
commerciallyavailable;thesecombinefibrinogenandthrombinatthebleeding
site,creatingafibrinclot.Theseagentsarecommonlyappliedtobleedingsites,


venousoozingfromrawareasorsutureslines.Theexternallyappliedmaterials
createaclotmatrixthatslowsbleedingfromthesourceandaugmentslocal
hemostaticmechanismsatthebleedingsite.Morecohesivebiologicsealantscan
beusedonsuturelinesinadvanceofbleeding,suchaspolyethyleneglycol
hydrogels(e.g.,Coseal),glutaraldehydecross-linkedcollagen(e.g.,Bioglue),or
polyaldehydecross-linkedbovineserumalbumin(e.g.,Preveleak).Allofthese
agentsareabsorbableandinsmallquantitiescanbeleftinplace.Theyare
frequentlycombinedtotakeadvantageofdifferentmechanismsofhemostasis.
Gelatinfoams,oxidizedcellulose,microfibrillarcollagen,andfibrinsealantscan
allswellandcompromiseflowinvascularstructures.Ifthebiologicsealantsare
placedcircumferentiallyaroundvascularstructures,theycancause
constriction.115,116
Inadditiontobloodcomponentreplacement,intravascularagentscanbeused
toinhibitfibrinolysisoracceleratethecoagulationsystem.Thesecanbedivided
intotwogroups:(1)prophylacticagents,specificallyantifibrinolyticsincluding
aprotinin,tranexamicacid,andepsilon-aminocaproicacid,and(2)agentsgiven
totreatexcessivebleeding,includingrecombinantfactorVIIaandprothrombin

complexconcentrates.Antifibrinolyticsarecommonlyusedincardiacsurgery,
typicallyinitiatedatthebeginningofthecaseandcontinueduntilafterheparin
reversalwithprotamine.Withthepossibleexceptionofaprotinin,whichisno
longeravailableintheUnitedStates,theantifibrinolyticsarelowrisk,modestly
effective,anddonotincreasetheriskofmortality.117Agentsgiventotreat
excessivebleedingincluderecombinantactivatedfactorVIIaandprothrombin
complexconcentrates.RecombinantactivatedfactorVIIaisaformofblood
factorVIImanufacturedviarecombinanttechnologyforthetreatmentof
hemophilia;ithasbeenusedtotreathemorrhageinavarietyofsettings
includingcongenitalheartsurgery.118RecombinantactivatedfactorVIIa
augmentstheintrinsicpathwayofcoagulationandactslocally,atthesiteof
endothelialdamage,bybindingtotissuefactor.Thisleadstothrombin
generation,fibrinclotformation,andtheactivationofplatelets.Prothrombin
complexconcentratesareamixtureofpurifiedhumanplasma–derivedvitamin
K-dependentfactorsII,VII,IX,andXandproteinsCandS.119Both
recombinantactivatedfactorVIIaandprothrombincomplexconcentratescanbe
veryhelpfulinachievinghemostasis,buttheyarealsoassociatedwithan
increaseinthromboticcomplicationsandshouldbeusedwithcaution.120–122