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Bypass considerations based on diagnosis 97

• These patients, especially those allowed to have a lower

hematocrit to prevent blood transfusion, may require

increased flow early in the case (for hypotension or low

NIRS values) and the use of vasoconstrictors may be

needed.

• pH-stat blood gas management for cases is performed at

30 °C or below. Alpha-stat blood gas management is

performed for adults and patients with suspected

vascular disease.

• When the repair is anticipated to require a short bypass

run, the anesthesiologist may request that anesthetic

gas be delivered through the circuit for the duration

ofCPB.

Figure 6.11 Primum ASD with cleft mitral valve. Adapted from

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

Wiley & Sons.

Figure 6.10 Secundum atrial septal defect. From Mullins and Mayer [1].

Reproduced with permission of John Wiley & Sons.

Figure 6.12 Sinus venosus ASD with PAPVR (right pulmonary veins

returning to the SVC/RA junction). From Mullins and Mayer [1].

Reproduced with permission of John Wiley & Sons.

Figure 6.13 Example of persistent LSVC with unroofed coronary sinus.

From Stark et al. [2]. Reproduced with permission of John Wiley & Sons.

98 Chapter 6

Case notes:

______________________________________________

Surgeon preferences:

______________________________________________

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Bypass considerations based on diagnosis 99

Cardiomyopathy requiring

orthotopic heart transplantation

Basics:

Heart transplantation may be indicated for unrepaired

complex congenital cardiac defects, failed primary

complete or palliative surgical procedures and heart failure

caused by various forms of cardiomyopathy (CMO).

Restransplantation for early and late organ failure also

remains as an indication. Transplantation involves excising

the native heart and implanting the donor organ. The new

heart is commonly implanted by sewing the following

vessels in this particular order: left atrium, inferior vena

cava, superior vena cava, aorta, and pulmonary artery.

Some cardiomyopathy patients receive an LVAD or BiVAD

as a bridge to transplantation.

Bypass notes:

• Maximum anticipated flow for equipment selection:

3.0 L/min/m

2

.

• FFP may be administered either preoperatively or in the

prime for VAD patients on anticoagulant therapy.

• Cardioplegia is not normally needed. The donor heart

receives cardioplegia immediately before harvesting. If

the time before reperfusion of the donor heart in the

recipient is greater than 4–5 h, the surgeon may elect to

administer cardioplegia, either cold or warm, prior to

reperfusion of the donor heart.

• The cross-clamp time for heart transplants refers to the

time from cross clamping the donor heart to reperfusion of

the donor heart in the recipient. Here, the cross-clamp

time may be longer than the cardiopulmonary bypass time.

• Cardioplegia is not administered to the native heart but

the perfusionist must still be vigilant of the bypass

system pressure during application of the aortic cross

clamp.

• Steroids are frequently administered to the circuit at the

beginning of the bypass run and immediately before

reperfusion of the donor heart.

• Bicaval cannulation is required.

• Left ventricular vent is common.

• Target temperature is 26–32 °C. Lower target tempera-

tures may be used to help prevent rewarming the donor

organ before reperfusion.

• Minimum dilutional hematocrit is 25–30%.

• pH-stat blood gas management for cases is performed at

30 °C or below. Alpha-stat blood gas management is

performed for adults and patients with suspected

vascular disease.

• It is prudent to monitor the myocardial reperfusion time

since it is common for the surgeon to request updates

during the rewarming/assessment period.

• It is important to know the surgeon’s preference for

maximum aortic pressure whenever the aorta has been

opened surgically, especially when allowing for ejection.

• Heart failure frequently negatively impacts the

pulmonary vasculature. Inhaled nitric oxide is com-

monly available for the post-bypass period to treat

pulmonary hypertension.

Case notes:

______________________________________________

Surgeon Preferences:

______________________________________________

100 Chapter 6

Coarctation of the aorta

Basics:

Coarctation of the aorta (CoA) is a condition where the

aortic blood flow path is restricted, usually in the area of

the ductus arteriosus insertion (or ligamentum arteriosum

for older patients). This restriction can impair lower body

perfusion and increase the workload on the heart. If this

defect requires surgical correction in isolation, it is fre-

quently done without cardiopulmonary bypass. Other

associated cardiac anomalies increase the probability of

using bypass for correction. Surgical correction on bypass

may include excision of the affected area with end to end

anastomosis of the aorta, patch repair (especially when

associated with arch hypoplasia), or subclavian flap repair

(the subclavian artery is transected and folded down over

the affected area that is opened to receive the SCA take-off ).

Severe CoA may be associated with arch hypoplasia

requiring long-segment repair of the aortic arch. Here,

regional perfusion may be used. Regional perfusion

can be provided with several different strategies. The

overall goal with regional perfusion is to provide,

at least, cerebral blood flow during the aortic arch

repair.Additionally, continuous or intermittent myocar-

dial and/or lower body perfusion can be incorporated

aswell (see section “Flow rates, regional perfusion, and

hypothermic circulatory arrest” in Chapter 3).

Bypass notes:

• Maximum anticipated flow for equipment selection:

3.0 L/min/m

2

.

• Cardioplegia common with traditional bypass.

Alternately, left heart bypass may be used with the circuit

bypassing the affected area and running from the LA to

the descending aorta for isolated coarctation repair.

• Single venous cannulation (dual stage if available) may

be used.

• The presence of septal defects normally requires the use

of bicaval cannulation.

• Left ventricular vent common if bicaval cannulation is

used.

• Target temperature is 24–28

°C. Target temperature

must consider that lower body perfusion may be inter-

rupted during the repair. Arch augmentation commonly

requires a target temperature of 18 °C.

• An ice wrap applied to the head to prevent warming is

common for procedures 25 °C and below.

• Minimum dilutional hematocrit is 25–30%.

• pH-stat blood gas management for cases is performed at

30 °C or below. Alpha-stat blood gas management is

performed for adults and patients with suspected

vascular disease.

• The pump flows during traditional bypass may needto

be reduced during the repair if the aorta is clamped

around the coarctation since the pump will only be

providing flow to the upper body (with limited descend-

ing aortic flow from collateral vessels). Regional perfu-

sion techniques generally have pump flows of 20–60 mL/

kg/min depending on whatis being perfused, the NIRS

value, and blood pressure.

• An isolated coarctation repair may employ a simple

left atrial-to-femoral artery pump circuit. Here, the

heart provides pulsatile blood flow to the upper

body, while the LA-FA circuit provides continuous

flow to the lower body during the coarctation repair.

Ideally, upper and lower body arterial blood pressure

lines are used to monitor and control flow between

the two systems.

• A right radial arterial line is preferred if only one line

is to be used since it allows for pressure monitoring

during the repair since femoral and left sided pressures

will not be useful during the coarctation repair in most

cases (some regional perfusion techniques may pro-

vide lower body flow).

• If bypass is needed, extra attention must be paid to

the rate of cooling for the lower body since flow may

be impeded depending on the degree of coarctation.

Higher pump flows may be helpful to assist with

cooling.

• Some level of metabolic acidosis is expected if a cross

clamp is used on the descending aorta during the repair

without lower body perfusion.

• Increased vigilance during rewarming applies as well

since any impediment to cooling the lower body that

existed should be alleviated after the repair. The surgeon

should be notified if the rate of lower body rewarming is

below expected values.

• Topical cooling with a recirculating blanket may be

especially helpful for these patients.

• It is important to know the surgeon’s preference for

maximum aortic pressure whenever the aorta has

been opened surgically, especially when allowing for

ejection.

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Bypass considerations based on diagnosis 101

Case notes:

______________________________________________

Surgeon preferences:

______________________________________________

Figure 6.14 Coarctation of the aorta. From Mullins and Mayer [1].

Reproduced with permission of John Wiley & Sons.

102 Chapter 6

Common atrioventricular canal

defect; same as complete

atrioventricular canal, atrioventricular

septal defect or endocardial cushion

defect

Basics:

A common atrioventricular canal (CAVC) results when

there is insufficient formation of endocardial tissue

(cushions), which normally comes together to form both

AV valves (tricuspid and mitral) and the atrial and ven-

tricular septa. This insufficiency creates a single or

“common” pathway between both atria and both ventri-

cles with essentially one valve between the two, an

atrioventricular valve (AV valve). The AV canal defect is

additionally classified as balanced or unbalanced. Canal

defects are balanced when the common AV valve is seated

roughly evenly above the ventricular chambers. Canal

defects are unbalanced when the common AV valve is

seated such that it favors one ventricle over the other.

This is an important distinction since an unbalanced

anatomy is more likely to result in underdevelopment of

the unfavored ventricle. Ventricular size is an important

consideration with unbalanced defects since significant

hypoplasia of one ventricle may preclude biventricular

repair. CAVC can lead to heart failure due to a significant

left-to-right shunt. Surgical correction is aimed at cre-

ating two functional AV valves (tricuspid and mitral) and

closing the atrial and ventricular septal defects.

Partial atrioventricular canal defect (PAVC) exists as

well. Here, there is insufficient primum septum that can

extend to the mitral valve creating both a primum ASD

and MR due to a cleft in the mitral valve. PAVC is synony-

mous with a Primum ASD.

Bypass notes:

• Maximum anticipated flow for equipment selection:

3.0

L/min/m

2

.

• Cardioplegia is required.

• Bicaval cannulation is required.

• Left ventricular vent is common.

• Target temperature is 24–28 °C.

• An ice wrap applied to the head to prevent warming is

common for procedures 25 °C and below.

• Minimum dilutional hematocrit is 25–30%.

• pH-stat blood gas management for cases is performed at

30 °C or below. Alpha-stat blood gas management is

performed for adults and patients with suspected

vascular disease.

• PAVC may simply require suture closure of the mitral

cleft and patch closure of the primum ASD.

• CAVC repair requires the common AV valve to be

divided into two. This usually requires valve testing

solution to be used during the reconstruction. The valve

testing solution is usually saline and should primarily be

sent to a cell saver or wall sucker.

• Excessive valve testing solution returned to the pump

will require sodium bicarbonate for buffering. The

patient’s sodium may rise if bicarbonate administration

is regular.

• Consideration should be given to informing the surgeon

of the sodium load when the patient’s sodium level rises

above 150

mmol/L.

• Aggressive conventional ultrafiltration may be helpful

in maintaining the hematocrit.

• Dilutional ultrafiltration (DUF) or zero-balance ultrafil-

tration (ZBUF) may be helpful in adjusting the sodium

level when large volumes of test solution are returned to

the pump.

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Bypass considerations based on diagnosis 103

Case notes:

______________________________________________

Surgeon preferences:

______________________________________________

Figure 6.15 Complete atrioventricular canal. From Mullins and Mayer [1].

Reproduced with permission of John Wiley & Sons.

104 Chapter 6

Cor triatriatum

Basics:

Cor triatriatum literally means a heart with three atria.

Here, there is a membrane within one of the atria that sepa-

rates it into two. This occurs more commonly in the left

atrium, resulting in a pulmonary venous (upper/proximal)

chamber and a supramitral (lower/distal) chamber. The size

of the communication between the chambers determines

the severity of the disease. A significant membrane

impeding pulmonary venous return to the left ventricle can

lead to heart failure. If the membrane is small and the com-

munication to the left ventricle adequate, cor triatriatum

may be an incidental finding during the repair of other

defects. Cor triatriatum less commonly is found on the right

side. Surgical correction is aimed at excising the membrane

within the affected atrium.

Bypass notes:

• Maximum anticipated flow for equipment selection:

3.0 L/min/m

2

.

• Cardioplegia is required.

• Bicaval cannulation is required.

• Left ventricular vent is common.

• Target temperature is 28–30 °C.

• Minimum dilutional hematocrit is 25–30%.

• pH-stat blood gas management for cases is performed

at 30 °C or below. Alpha-stat blood gas management

is performed for adults and patients with suspected

vascular disease.

Upper chamber

Lower chamber

Left atrial

appendage

MV

LV

Figure 6.16 Cor triatriatum. From Stark et al. [2]. Reproduced with

permission of John Wiley & Sons.

Case notes:

______________________________________________

Surgeon preferences:

______________________________________________

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Bypass considerations based on diagnosis 105

Corrected transposition of the great

arteries (L-TGA, Levo-TGA, or C-TGA)

or congenitally corrected TGA

Basics:

Corrected TGAs (CCTGAs) can be confusing at first study

because the great arteries are indeed not transposed as with

dextro-TGA. The aorta arises on the left side and the

pulmonary artery arises on the right side as one would nor-

mally expect. The difference with L-TGA is that the ventri-

cles rotated differently (leftward or levo) in utero with the

result being that the morphologic left ventricle is right sided

and the morphologic right ventricle is left sided. Therefore,

the right-sided left ventricle pumps venous blood to the

lungs and the left-sided right ventricle pumps arterial blood

to the body. The ventricular position and discordance with

its associated great vessel is how this defect is classified. The

Van Praagh segmental classification for this defect would be

the set {S,L,L) since the atria are situs, the ventricles rotated

left, and there is ventriculoarterial discordance.

Associated defects (VSD, TR) with cyanosis may lead to

early identification of this defect. However, L-TGA may

exist with no symptomology until later in later life. The

left-sided right ventricle can fail because it is not

designed to provide systemic support. Surgical correc-

tion is aimed at making the morphologic right ventricle

provide pulmonary blood flow and the morphologic left

ventricle provide systemic blood flow. Most commonly,

this is done with a double-switch procedure: atrial and

arterial-level switches. This results in right-sided venous

blood flowing to the left-sided right ventricle and on to

the pulmonary artery. The left-sided pulmonary venous

blood flows to the right-sided left ventricle and on to

the aorta.

Bypass notes:

• Maximum anticipated flow for equipment selection:

3.5 L/min/m

2

.

• Cardioplegia is required. An additional cardioplegia

dose should be available since this procedure may have

an extended cross clamp time. Induced ventricular

fibrillation may be used during the initial intracardiac

assessment and the atrial switch procedure.

• Bicaval cannulation is required.

• Left ventricular vent is common.

• Target temperature is 22–30 °C.

• An ice wrap applied to the head to prevent warming is

common for procedures 25 °C and below.

• Minimum dilutional hematocrit is 25–30%. An

increased hematocrit before coming off bypass must

beconsidered for sick myocardium.

• pH-stat blood gas management for cases is performed at

30 °C or below. Alpha-stat blood gas management is

performed for adults and patients with suspected

vascular disease.

• It is important to know the surgeon’s preference for

maximum aortic pressure whenever the aorta has been

opened surgically, especially when allowing for ejection.

Morphologic RV

Morphologic LV

Figure 6.17 Congenitally corrected transposition of the great arteries

with VSD. From Mullins and Mayer [1]. Reproduced with permission of

John Wiley & Sons.

106 Chapter 6

Case notes:

______________________________________________

Surgeon preferences:

______________________________________________

Morphologic RV

Morphologic LV

Figure 6.18 Congenitally corrected transposition of the great arteries

with IVS. From Mullins and Mayer [1]. Reproduced with permission of

John Wiley & Sons.

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