Andersons pediatric cardiology 1826

—limitsafullunderstandingofthenuancesofthecomplexcirculationandmay
negativelyaffectassessmentandmanagementatthebedside.Infact,asour
understandingofthiscomplexphysiologyimproves,increasinglycomplex
modelshaverecentlybeenproposed(usingacombinationoflocalidentifiability,
Bayesianestimationandmaximumaposteriorisimplexoptimization)46aswell
asane-simulationmodel.47,48

“Single-VentriclePhysiology”
Theterm“single-ventriclephysiology”hasoccasionallybeenused
interchangeablybeforeandafterallthreeplannedstagesofsurgical
management.However,thecirculatorypatternsintheneonateandinfantbefore
andaftertheneonatalpalliation,superiorcavopulmonaryconnection(stageIIor
Glennprocedure)andtotalcavopulmonary(stageIIIorFontanoperation)areall
extremelydifferent(seelater).Usingasingletermsuchassingle-ventricle
physiologyacrossthesurgicalspectruminallofthesesituationsisbothirrational
andinaccurate.Instead,weproposeusingamorepreciseshorthand
nomenclature,suchasthe(1)multidistributioncirculation,(2)theGlenn
circulation,and(3)theFontancirculation.TheGlenncirculationisaseries
circulation,albeitwithanobligate40%to60%right-to-leftshuntfromthe
inferiorcavalveintotheventricle,andtheFontancirculationisalsoaseries
circulation,withthegreatmajorityofsystemicvenousreturnenteringthe
pulmonaryvascularbedinserieswiththesystemicvascularbed.However,in
contrasttotheseriescirculationinpatientswithtwoventricles,thereareunique
featuresofboththeGlennandFontancirculations,particularlywithrespectto
thecentralvenouspressure,whichisdiscussedlater.


PhysiologicEffectsofStaged
ReconstructioninthePatientWitha
FunctionallyUniventricularHeart
UndergoingSuperiorCavopulmonary

ConnectionandSubsequentFontan
Procedure
Thegeneralphysiologicaimsandmanagementstrategiesofthemultidistribution
circulationintheneonateandinfantdetailedinTable70.2andFig.70.2pertain
topostoperativecareaswellandarediscussedinmoredetailinChapter71.
Duringeachofthethreeplannedstagesofsurgicalmanagement,therearea
numberofimportantphysiologicchangesthatfollowsurgery,someofwhichare
temporary,whereasothersareplannedconsequencesofthesurgicalprocedure
itself(Table70.3).
Table70.2
GeneralPrinciplesofSurgicalPalliationintheNewbornandBeyond
FundamentalManagement
ShortTerm
LongerTerm
Principles
1.Provideunobstructedsystemic Preservesystemicoxygenandnutrient
Minimizetheseverityof
bloodflow
delivery
ventricularhypertrophy
Preserveventricularfunction
2.Providelimited/restricted
Provideadequategasexchange
Minimizetheriskofelevated
pulmonarybloodflowwithout
pulmonaryvascularresistance
pulmonaryarterydistortion
Minimizepulmonarystenosis
andhypoplasia
3.Ensureunobstructed

Minimizeriskofhypoxemia
Minimizetheriskofpulmonary
pulmonaryvenousreturn
Avoidpulmonaryedema
venoushypertensionandelevated
pulmonaryvascularresistance
4.Ensureunobstructedsystemic
Minimizeriskofcentralvenous
Lowercentralvenouspressure
venousreturn
hypertensionleadingto
Improvecardiacoutput
chylothorax,effusions,and
thrombosis
Minimizeriskofpostoperative
lowcardiacoutput
5.Minimizeatrialincisions
Reduceriskofperioperative
Reduceriskoflong-term
arrhythmiasandsinusnode
supraventriculararrhythmiasand
dysfunction
sinusnodedysfunction


6.Minimizethedurationand
severityofvolumeand
pressureload

Reduceriskofventriculardysfunction

andatrioventricularvalveregurgitation

Minimizeseverityofventricular
hypertrophy
Minimizeinefficientcirculatory
effectsofregurgitantfraction
Preserveventricularfunction

Table70.3
AcuteandChronicPhysiologicChangesDuringStaged
Reconstruction
Transientphysiologiceffectsof
surgery,cardiopulmonary
bypass,andanesthesia

Expectedchangesinloading
conditionsfromsurgical
procedures

■Rapidchangesinintravascularvolumeduetobleeding
■Decreaseinventricularoutputandmyocardialfunction
■Increaseinsystemicvascularresistance
■Increaseinpulmonaryvascularresistance
■Fluidretentionduetocapillaryleakand/orrenaldysfunction
■Decreaseinsurfactantproduction
■Pulmonaryedema
■Decreaseinpulmonaryvenoussaturation
■Changesinoxygen-carryingcapacityduetoanemiaand/orhemoglobin
affinityforoxygen
■Changesinoxygenconsumptionduetotemperature,pain,agitation,sedation,

andanalgesia
■Intheneonate,therearevariablechangesinpreload(combinedsystemicand
pulmonaryvenousreturn)thatoccurfromtheunoperatedtotheoperated
state.
■Ingeneral,thereisapostoperativedecreaseinvolumeloadingcompared
withthepreoperativestatebecausethepulmonarybloodflowisdecreased
withmostneonatalsurgicalinterventions.
■Intheinfantfollowingsuperiorcavopulmonaryconnection,thereis:
■Adecreaseinpulmonarybloodflow
■Adecreaseinvolumework(preload)
■Commonlyanincreaseinafterload(postoperativehypertension)
■Adecreaseinventricularfunction,whichtypicallyrecoversover2–6
months
■Anelevatedcentralvenouspressureintheupperhalfofthebody
■Followingthetotalcavopulmonary(Fontan)connection,thereis:
■Decreasedventricularfillingandcardiacoutput
■Elevatedcentralvenouspressureintheupperandlowerpartsofthebody
■Increasedlymphproduction
■Followingrepairofatrioventricularvalveregurgitation(atanystage),thereis
a:
■Decreaseinvolumework(preload)
■Increaseinafterload
■Decreaseinventricularfunction,whichtypicallyrecoversover2–6months

SuperiorCavopulmonaryConnection
(BidirectionalGlenn)