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Bypass considerations based on diagnosis 147

Case notes:

______________________________________________

Surgeon preferences:

______________________________________________

References

1 Mullins CE, Mayer DC eds. Congenital Heart Disease: A

Diagrammatic Atlas. Hoboken: John Wiley & Sons, Inc.; 1992.

2 Stark JF, de Leval MR, Tsang VT eds. Surgery for Congenital

Heart Defects, 3rd edition. Chichester: John Wiley & Sons,

Ltd; 2006.

BVF

Figure 6.62 Bulboventricular foramen in tricuspid atresia. Adapted

from Mullins and Mayer [1]. Reproduced with permission of John

Wiley & Sons.

Perfusion for Congenital Heart Surgery: Notes on Cardiopulmonary Bypass for a Complex Patient Population, First Edition. Gregory S. Matte.

148

Blood pressure higher than

expected

•Isthevalue accurate?Request that the patient arterial

linebeflushedandzeroed.

•Has the transducer been moved lower (bed rolled to

oneside)causinganartifactuallyhigh bloodpressure

reading?

•Isthebypasscircuitpressurealsohigh?

○

If the bypass circuit and patient pressures are both

high,thepressureismorelikelytobereal.

○

Ifthebypasscircuitpressureisnormal,theproblemis

morelikelytobewiththepatientarteriallinesystem

orwithcannulaposition(theflowmaybepreferential

totherightarmwitharightradialline,forexample).

•Isthepumpflowappropriate?

○

Whatisthecardiacindex?

■

Are the values for patient weight, height, and

BSAenteredintotheheart–lungmachine(HLM)

computercorrectly?

○

Isthepropertubingsizeselectedonthearterialpump

head(rollerpumps)?

○

Isthereanavailableflowprobetoensurearterialpump

headflowmatchesdeliveredflow?

■

euseofaowprobecanquicklydiagnosewhether

calculatedowanddeliveredowaredisparate.

•Isthepatientbloodpressurehighbecausethepatientis

stillejecting?

○

Increaseleftventricularventflowifoneisinuse.

○

Significant collateral/shunt flow to the left heart in

the presence of restrictive or absent septal defects

may result in continued ejection. Significant aortic

regurgitationcanleadtoasimilarresult.

•Isthesystemicvascularresistancehigh?

○

Areanymedicationsrunningintothepatientwhich

mayincreaseSVR?Patientsoncardiacmedsnormally

havethosemedicationsturnedoffonceonbypass.

○

Consultwiththeanesthesiologistandconsiderisoflu-

rane, phentolamine, nitroglycerin, nitroprusside or

milrinone,etc.

Otherconsiderations:

Notes on select issues during bypass

CHAPTER7

Данная книга находится в списке для перевода на русский язык сайта https://meduniver.com/

Notes on select issues during bypass 149

Blood pressure lower than expected

•Isthevalue accurate?Request that the patient arterial

linebeflushedandzeroed.

•Hasthetransducerbeenmovedhigher(bedrolledtoone

side)causinganartifactuallylowbloodpressurereading?

•Isthebypasscircuitpressurealsolow?

○

If the bypass circuit and patient pressures are both

low,theproblemis morelikely to be flowrelatedor

patientrelated(SVR).

○

If the bypass circuit pressure is unchanged or as

expected with a displayed low patient pressure, the

problemis more likelyto be with the patient arterial

linesystemitself.

•Isthepumpflowadequate?

○

Whatisthecardiacindex?

■

Arethe valuesforpatientweight,height,andBSA

enteredintotheHLMcomputercorrectly?

○

Isthepropertubingsizeselectedonthearterialpump

head(rollerpumps)?

○

Externalshunts

■

Are there any inadvertently open circuit shunts

(oxygenatorprime/purgeline)?

■

Isthe samplingmanifold open (if not needed for

in-linebloodgasmonitoring)?

■

Ifhemoconcentratorowispassivelysupplied,turn

itotoensuretheunitisnotallowingexcesssteal

fromthearterialcircuit.

■

If active hemoconcentrator ow from an arterial

source is being used, ensure it is owing at the

intendedrate(correcttubingsizeenteredintohead

controller).

○

Internalshunts

■

DoesthepatienthaveanuncontrolledPDA,surgically

placed systemic-to-pulmonary shunt (BTS/Sano),

aortopulmonarycollateralsoranAPwindow?

■

Isthereexcessive“steal”totheLVvent?

■

Internal shunts will require higher than predicted

pump ows until they are surgically controlled.

Someaortopulmonarycollateralsmaynotbeacces-

sible, and therefore increased pump ows will be

required throughout the bypass run. e use of

NIRSmaybeparticularlyhelpfulindeterminingan

adequatepumpowtomaintaincerebralbloodow

wheninternalshuntsarenotcontrolled.epump

owshouldideally resultin adequate NIRS values

while not ooding the surgical eld. is is not

alwayspossible,andsoaggressiveeldsuction(and

venting)maybeneededtocompensate.

○

Physicalobstructiontoflow

■

Check for kinked tubing in the arterial circuit,

especially where the tubing enters and exits the

rollerhead.A reservoirlamporashlightcanbe

helpful with peering into the tubing guides to

checkthis.

○

Is there an available flow probe to ensure arterial

pumpheadflowmatchesdeliveredflow?

■

e use of a ow probe can quickly diagnose

whether calculated ow and delivered ow are

disparate.

■

Was the occlusion properly set (roller pumps)?

ere is the possibility that once the arterial

headtubingchangestemperatureduringthe case

(warming with constant ow, cooling with low

ow hypothermic bypass), the occlusion may

change.During a planned circulatory arrest or in

consultationwith the surgeon, one can come o

bypass,clampthearteriallimb,andpressurecheck

the system. If the system pressure falls dramati-

cally,theocclusioncanbe adjustedappropriately.

iscan be accomplished in just several seconds

obypass.

•Was cardiotomy suction blood from the chest intro-

ducedtothecircuit?

○

Suctioned mediastinal blood may contain activated

agentsthatcausetransienthypotension.

•Was stagnant blood in the hemoconcentrator intro-

ducedintothecircuit?

○

Stagnantcircuitbloodmaycontainactivatedagents

thatcausetransienthypotension.

•Is the systemic vascular resistance low? Consult with

anesthesia.

○

Maximizepumpflowinconsiderationof theopera-

tiveneedsandpatienttemperature.

○

Areanybloodpressuremedicationsrunningintothe

patient?Some surgeonsprefer to have nitroglycerin

empiricallyrunaftercrossclampremovaland/ordur-

ingrewarming.Thisdripmayneedadjustment.

○

Isisofluraneinuse?Consultwiththeanesthesiologist

andconsiderdecreasingorterminatingitsuse.

○

Consult with the anesthesiologist and consider an

alphaagonistsuchasphenylephrine.

150 Chapter7

○

Is the patientflushed (red faced)? Epinephrine and

diphenhydraminemaybeconsideredforasuspected

allergic reaction, especially when phenylephrine

doesn’twork.

•Isthehematocritadequate?

○

Some patients may normally exist with a high

hematocrit.A relatively low hematocritmay result

inalowsystemicbloodpressure.Considerincreasing

thehematocrit.

•Isthereapossibleaorticdissection?

Otherconsiderations:

Данная книга находится в списке для перевода на русский язык сайта https://meduniver.com/

Notes on select issues during bypass 151

Bypass circuit pressure higher

thanexpected

•Isthevalueaccurate?Zerothecircuitpressuretransducer.

•Isthepatientarterialbloodpressurealsohigh?

○

If the bypass circuit and patient pressures are both

high,theproblemismorelikelytobereal.

•Isthepatientarterialbloodpressurenormalorlowwith

ahighcircuitpressure?

○

Isthereakinkinthecircuitarteriallimb?

○

Isthearterialcannulakinked?

○

Isthearterialcannulaappropriatelysized?

○

Is the arterial cannula properly positioned (if no

bumper is used on the cannula, it is morelikely to

migratefromitsoriginallocation)?

○

Isthereapossibleaorticdissection?

•Isthepumpflowappropriateandaccurate?

○

Whatisthecardiacindex?

■

Arethe valuesforpatientweight,height,andBSA

enteredintotheHLMcomputercorrectly?

○

Isthepropertubingsizeselectedonthearterialpump

head(rollerpumps)?

○

Is there an available flow probe to ensure arterial

pumpheadflowmatchesdeliveredflow?

•IstheSVRhigh?

○

Consult with anesthesia and consider lowering

SVRwithisofluraneoranothermedication.

•Whatisthestatusofthearteriallinefilter?

○

Isthereevidenceofafilterdefectorclot?

○

Oxygenatorswithintegratedarteriallinefiltersgen-

erallyhave system pressuremonitoredpost-filter.If

thisisthecase,filterclotsmayonlybeevident,pres-

sure-wise,withasignificantchangeinpre-membrane

pressure(whichisn’talwaysmonitored).

Otherconsiderations:

152 Chapter7

Bypass circuit pressure lower

thanexpected

•Isthevalueaccurate?Zerothecircuitpressuretransducer.

•Isthepatientbloodpressurealsolow?

○

If the bypass circuit and patient pressures are both

low,theproblemis morelikely to be flowrelatedor

patientrelated(SVR).

○

Ifthebypasscircuitpressureislowwithanormalor

highpatientpressure,theproblemismorelikelytobe

withthebypasscircuittransducersystem.Checkthe

zero and considering changing the transducer. You

can also briefly attach the bypass circuit pressure

dometoadifferenttransducer(i.e., the cardioplegia

transducer)toverifythevalue.

•Pumpflow

○

Whatisthecardiacindex?

■

Arethe valuesforpatientweight,height,andBSA

enteredintotheHLMcomputercorrectly?

○

Isthepropertubingsizeselectedonthearterialpump

head(rollerpumps)?

○

Externalshunts

■

Are there any inadvertently open circuit shunts

(oxygenatorprime/purgeline)?

■

Isthe samplingmanifold open (if not needed for

in-linebloodgasmonitoring)?

■

Ifhemoconcentratorowispassivelysupplied,turn

itotoensuretheunitisnotallowingexcesssteal

fromthearterialcircuit.

■

If active hemoconcentrator ow from an arterial

source is being used, ensure it is owing at the

intendedrate (correct tubingsizeenteredintohead

controller).

○

Internalshunts

■

DoesthepatienthaveanuncontrolledPDA,surgically

placed systemic-to-pulmonary shunt (BTS/Sano),

aortopulmonarycollaterals,oranAPwindow?

■

Isthereexcessive“steal”totheLVvent?

■

Internalshuntswillrequirehigherthanpredicted

pumpflowsuntil they aresurgically controlled.

Some aortopulmonary collaterals may not be

accessibleand so increased pumpflows will be

requiredthroughoutthe bypass run.Theuse of

NIRSmaybeparticularlyhelpfulindetermining

an adequate pump flow to maintain cerebral

blood flow when internal shunts are not con-

trolled. The pump flow should ideally result in

adequate NIRS values while not flooding the

surgicalfield.Thisisnotalwayspossibleandso

aggressive field suction (and venting) may be

neededtocompensate.

○

Physicalobstructiontoflow

■

Ifthearterialpumpheaddisplayisyourowindicator,

checkforkinkedtubinginthearterialcircuitproximal

tothepressuremonitoringsite,especially where the

tubingenters and exits the roller head. A reservoir

lamporashlightcanbehelpfulwithpeeringintothe

tubingguidestocheckthis.

○

Is there an available flow probe to ensure arterial

pumpheadflowmatchesdeliveredflow?

■

euseofaowprobecanquicklydiagnosewhether

calculatedowanddeliveredowaredisparate.

■

Was the occlusion properly set (roller pumps)?

ereis the possibilitythat once the arterialhead

tubing changes temperature during the case

(warmingwithconstantow,coolingwithlowow

hypothermic bypass), the occlusion may change.

Duringaplannedcirculatoryarrestorinconsulta-

tion with the surgeon, one can come o bypass,

clamp the arterial limb, and pressure check the

system.Ifthesystempressurefallsdramatically,the

occlusioncanbeadjustedappropriately.iscanbe

accomplishedinjustseveralsecondsobypass.

•Is the systemic vascular resistance low? Consult with

anesthesia.

○

Maximizepumpflowinconsiderationof theopera-

tiveneedsandpatienttemperature.

○

Areanybloodpressuremedicationsrunningintothe

patient?Some surgeonsprefer to have nitroglycerin

empiricallyrunaftercrossclampremovaland/ordur-

ingrewarming.Thisdripmayneedadjustment.

○

Isisofluraneinuse?Consultwiththeanesthesiologist

andconsiderdecreasingorterminatingitsuse.

○

Consult with the anesthesiologist and consider an

alphaagonistsuchasphenylephrine.

○

Is the patient flushed (red faced)? Epinephrine

and diphenhydramine may be considered for a

suspectedallergicreaction,especiallywhenphen-

ylephrinedoesn’twork.

•Isthehematocritadequate?

○

Somepatientsmaynormallyexistwithahighhematocrit.

Arelativelylowhematocritmayresultina lowsystemic

bloodpressure.Considerincreasingthehematocrit.

Otherconsiderations:

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Notes on select issues during bypass 153

Central venous pressure elevated

•Isthe valueaccurate? Request that the central line be

flushedandzeroed.

○

Isthecentrallineinaccuratebecauseitisinthecaval

snare?

•IsthebedrotatedwiththeCVPtransducerpositionedlower?

○

Rotationofthebedwhichaffectsrelativetransducer

heightcanartifactuallyaffecttheCVPreading.

•Wasthebedlowereddecreasingthekineticpotentialbet-

weenthe heart andvenous reservoir?Consider raising

thebedorloweringthevenousreservoirifpossible.

•IstheCVPacutelyelevated?

○

Check venous line for physical obstructionson and

offthesurgicalfield.

○

Checkforanairlock.

○

Asksurgeonaboutvenouscannula(e)position.

■

Venouscannulasideportsagainstchamberorvessel

wall?

■

SVCcannulainsertedtoofar?Innominateblocked?

•HastheCVPprogressivelybecomeelevated?

○

Ask surgeon about cannula position (per above

considerations).

○

Considerationshouldbegiventothepossibilityofa

luminalobstructioncausedbysomethinginthecava/

atriumorclotformationwithinthecannula[1,2].

•HavetheNIRSvaluesalsochanged?

○

StableNIRSmayfavorartifactintheCVPreading.

○

Decreasing NIRS may indicate the elevated CVP is

real.

•Isthepumpflowappropriate?

○

Whatisthecardiacindex?

■

Arethevaluesforpatientweight,height,andBSA

enteredcorrectly?

○

Isthepropertubingsizeselectedonthearterialpump

head(rollerpumps)?

○

Is there an available flow probe to ensure arterial

pumpheadflowmatchesdeliveredflow?

■

euseofaowprobecanquicklydiagnosewhether

calculatedowanddeliveredowaredisparate.

•Considerdecreasingpumpflowinatemperatureappro-

priatemanner.Targettemperaturemayneedadjustment

aswell.

Otherconsiderations:

154 Chapter7

Heat exchange issue (slow cooling

orwarming)

•Arethe water lines properly connected at the heater-

coolerandtheoxygenator?

○

Verifyheater-coolerwatersupplyis directed to oxy-

genatorwaterinlet.

○

Are the water lines appropriately sized so as not to

impedeflow?

○

Arethewaterlinesofappropriatelength?Longerlines

willdecreaseperformanceinasystem.

•Isthepatientobese?

○

Fat does not warm or cool as efficiently as muscle

whichhasmoreblood flow.Obesepatientswill take

longertocoolandwarm.

•Isthereacoarctationoftheaorta?

○

Thiswillhamperlowerbodycooling(withcentralcan-

nulation),butrewarmingshouldbenormalafterrepair.

•Isthepatientsignificantlyvasoconstricted?

○

ConsultwithanesthesiaandconsiderloweringSVRwith

isofluraneoranothermedication.

○

Phentolamine,nitroprusside,nitroglycerin,milrinone,

andotheragentsmaybeusedtodecreaseSVRinorder

toaidcoolingandwarming.Somecliniciansallowfor

a lowerblood pressure if it aids in cooling/warming

andtheNIRSareacceptable.

•Whatisthepumpflowrate?

○

Increasedpumpflowratesareafirst-linetreatmentto

increasethermalexchange.

○

Heatexchangeefficiencydropsoffasflowrateincreases.

Ifanoxygenatorisbeingusednearitsmaximumrated

flow,heatexchangeefficiencywilldecrease.

•Whatis the water flow rate through the heater-cooler

system?

○

Heatexchange performanceis in part driven by

the counter flow principle (water and blood flows

are opposing to maximize thermal transfer) and by

the absolute water flow through the system. If the

waterflow rate is below normal, check for kinks in

thewatertubing.

■

Consider a backup unit if the water ow rate is

belownormal.

Other

considerations:

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Notes on select issues during bypass 155

NIRS values lower than expected

TheperfusionistshouldmonitortheNIRSvaluesduring

theprebypassperiod.Thesevaluesshouldbecomparedto

bypassvaluesthroughouttherun and aremostoftenan

excellentindicatorofcerebralperfusion.IftheNIRSvalues

arelowerthanexpectedonbypass,oreven worse,lower

than prebypass values, consideration should be given to

thefollowing:

•Isthevalueaccurate?VerifyNIRSprobeplacementwith

the anesthesiologist and concern about the current

value.

•Isthepumpflowadequate?

○

Whatisthecardiacindex?

■

Arethe valuesforpatientweight,height,andBSA

enteredintotheHLMcomputercorrectly?

○

Isthepropertubingsizeselectedonthearterialpump

head(rollerpumps)?

○

Externalshunts

■

Are there any inadvertently open circuit shunts

(oxygenatorprime/purgeline)?

■

Isthe samplingmanifold open (if not needed for

in-linebloodgasmonitoring)?

■

Ifhemoconcentratorowispassivelysupplied,turn

itotoensuretheunitisnotallowingexcesssteal

fromthearterialcircuit.

■

If active hemoconcentrator ow from an arterial

source is being used, ensure it is owing at the

intendedrate(correcttubingsizeenteredintohead

controller).

○

Internalshunts

■

DoesthepatienthaveanuncontrolledPDA,sur-

gically placed systemic-to-pulmonary shunt

(BTS/Sano),aortopulmonarycollateralsor anAP

window?

■

Isthereexcessive“steal”totheLVvent?

■

Internalshuntswill require higher than predicted

pumpowsuntiltheyaresurgicallycontrolled.

○

Physicalobstructiontoflow

■

If the arterial pump head display is your ow

indicator, check for kinked tubing in the arterial

circuit,especiallywherethetubingentersandexits

therollerhead.A reservoirlamporashlightcan

be helpful with peering into the tubing guides to

checkthis.

○

Is there an available flow probe to ensure arterial

pumpheadflowmatchesdeliveredflow?

•Bloodpressure

○

Maintain at prescribed level with consideration for

tryingahigherpressure.

○

Isthebloodpressureaccurate(zeroedandnotinflu-

encedbycannulationorsurgicalclamps)?

•Gassupply

○

Isthepropergassourceselected?

■

IncreaseFiO

ifpossible.

○

Gasflowrate(thisislesslikelytoaffectoxygenation

butshouldbeverifiednonetheless)

■

Isthe setgasowreaching the patient?Verifythe

gas system is intact from the source to the

oxygenator.

■

Consider changing the ow meter.Some systems

mayaccumulatedebrisinthegas tubes leading to

inaccuratereadings.

■

Consider trialing a standalone source of 100%

oxygentoreadilyverifysourceandowonadif-

ferentsystem.

■

Is the pump anesthetic gas vaporizer sealed with

tightinletandoutletconnections?

■

Isthegasowratewithinthemanufacturerrecom-

mendedrange?

○

IsthePaO

asexpected?MaximizePaO

whileidenti-

fyingthecauseofthelowNIRSvalues.

○

IsthePaCO

asexpected?ConsiderpH-statifnotin

useoratleasttry increasing the PaCO

temporarily.

Somecongenitalpatientsmayhavebypass-significant

aortopulmonarycollateralsthatarenotalwaysdocu-

mentedbyimagingstudies.Increasingcerebralblood

flow with pH-stat management may improve the

NIRS.

○

Chronic CO

 retainers may require a PaCO

 value

closertotheirnorm.Consultwithanesthesiologist.

•HastheCVPprogressivelybecomeelevated?

○

Asksurgeonaboutvenouscannula(e)position.

■

Venous cannula side ports against chamber or

vesselwall?

■

SVC cannula inserted too far? Innominate

blocked?

○

HowdoesthecurrentCVPcomparetotheprebypass

andpostcannulationvalues?

○

Empirically,increasingpumpflowtoimproveNIRS

valuesmaybecounterproductive.Ifdrainageofthe

headistheissue,increasingpumpflowmayincrease

theCVPandpossiblydecreasethe cerebralperfu-

sionpressure,resultinginworseningNIRSvalues.

156 Chapter7

○

Considerationshouldbegiventothepossibilityofa

luminal obstruction caused by something in the

atriumorclotformationwithinthecannula[1,2].

•Hematocrit

○

Considerraisingthehematocrittothepatient’snormal

orevenabovetoseeifthereisaresponsewiththeNIRS.

•Temperature

○

Is the pump flow rate appropriate for the current

temperature?

•In-linebloodgasmonitoring

○

Dothein-linevaluesreasonablymatchthelabvalues?

○

Considerrecalibratingthein-linebloodgasmonitor?

•Anesthesiaconsiderations

○

Haveanesthesiologistcheckthefaceforsignsofinad-

equatedrainageofthehead.

○

Isthepatientshiveringduetoinadequateneuromus-

cular

 blockade? Is the level of anesthesia adequate?

Didthemedicationsgettothe patient?Consider an

additionaldosetorulethisout.

○

If isoflurane is integral with the circuit, is there a

chanceofmalignanthyperthermia?Isthelactatelevel

increasedwith risingpatient temperatureand a low

venoussaturation(atleastlowerthanexpectedgiven

the pumpparameters)? Evenif the vaporizer is off,

considerremovingthevaporizerfromthesystemand

changingthedownstreamtubing.

○

Did the anesthesiologist expect anesthetic gas on

bypassforprimaryanesthesia?

○

Isthereanestheticagentinthevaporizer?

Otherconsiderations:

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