Lydia Cassorla · 2019. 11. 1. · Asplenia Right isomerism, bilateral right sidedness AVSD Atrioventricular septal defect, “AV canal,” an endocardial cushion defect. Characterized

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the need for a careful methodology for preoperative assess-ment. Specific factors include an increase in the number ofpatients with CHD undergoing surgery, diagnostic advances,a trend toward corrective procedures performed on small,potentially unstable infants, and the frequency of surgeryperformed on the day of hospital admission.

Demographics

Due to improved diagnosis and outcome, the population ofpatients with CHD undergoing surgery in the USA is grow-ing (see Chapter 1). Increasingly, patients survive to adult-hood following corrective or palliative surgery, includingthose with complex structural lesions.1,2 Anesthesia for non-cardiac surgery in patients with CHD is therefore becomingmore common in all surgical venues, including outpatientsurgery centers and labor and delivery suites (see Chapters13 & 26). In addition, new mothers with CHD are much morelikely to have offspring with cardiac defects than the popu-lation at large. A 16% incidence of CHD is reported in the children of women with CHD, irrespective of whether themother’s lesion was unoperated, palliated, or corrected.3 Thiscontrasts with an overall incidence of CHD of 0.5–1.2% of livebirths.4,5 Immigration brings older children and adults withuncorrected CHD to US medical centers as well.

Diagnostic tools

Diagnostic tools are continually evolving and provide abroad range of preoperative information for assessment.Echocardiography, computerized tomography (CT), andnuclear cardiology now create stunningly detailed images.Fetal diagnosis of CHD is commonplace and has facilitatedthe coordination of resources at congenital heart surgery centers and improved outcomes.6 The anesthesiologist mustbe able to utilize the information derived from each majordiagnostic modality. The potential utility of intraoperativetransesophageal echocardiography (see Chapter 9) may alsobe identified, as small sized probes permit intraoperativeassessment of nearly all pediatric patients.

Introduction

Assessment of the patient with congenital heart disease(CHD) is a unique challenge for the anesthesiologist due to awide range of anatomic lesions and the need for in-depthunderstanding of each patient’s physiologic abnormalities.An interdisciplinary approach is recommended to optimizethe contributions of all members of the perioperative team.Regular pre-surgical meetings attended by representativesfrom pediatric cardiac surgery, pediatric cardiology, pedi-atric cardiac anesthesiology, radiology, and pediatric inten-sive care facilitate patient assessment and provide a forum toreview each case and view diagnostic studies prior to electivesurgeries. Most patients have already undergone extensiveanatomic evaluation; however, each specialist contributes aunique perspective to the comprehensive plan for periopera-tive care and ensures that major concerns are communi-cated. An effective system to organize and exchange patientinformation is a key element of success, as in many cases the primary preoperative challenge the anesthesiologist faces isthe integration of a great deal of data. The anesthesiologistmust correlate the information, optimize the preoperativecondition of the patient, and prepare for anticipated intra-operative challenges.

It is assumed that the reader is familiar with general prin-ciples of pre-anesthetic assessment for both pediatric and adultpatients. The focus of this chapter is upon: What is specialabout the assessment of a patient who has CHD? The goal isto formulate a rational, customized anesthetic plan. Given thewide variety of lesions, important keys lie in understandingCHD terminology, and in a method to classify patients basedupon their physiology. These tools are discussed below as thefirst and second goals of the preoperative assessment.

Impact of current trends on thepreoperative assessment

Current trends in congenital heart surgery further reinforce

Preoperative evaluation and preparation:A physiologic approach

Lydia Cassorla

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structures. Among others Lev, Van Praagh, Anderson et al.,and de la Cruz and Nadal-Ginard8 –12 have made importantcontributions in this field. While there is currently no con-sensus opinion from national or international organizationsregarding anatomic terms for CHD there is a movement to do so. A summary of commonly used terms is presented inTable 11.1.

Segmental approach

For practical purposes it is useful to consider the heart ascomposed of three types of segmentsaatria, ventricles, andgreat arteries.10,13–15 During normal development they divideinto right- and left-sided structures, each side having charac-teristic morphologic features. Segments may be described asright- or left-sided to define their location relative to othercardiac structures, or morphologically right or left to describetheir anatomic features. Normal anatomy is the standard fordefining morphologic features. Therefore a morphologicallyright structure is normally right-sided, but may be left-sided,and vice versa.16 Basic morphologic characteristics of eachnormal segment are described in Table 11.2.

Atrial sidedness or situs

Situs describes the laterality of asymmetric structures withinthe cardiovascular, respiratory, and gastrointestinal systems.From a cardiac standpoint it is based upon the location of the atria. The usual arrangement, situs solitus, is one of aright-sided, morphologically right atrium, and a left-sided,morphologically left atrium. Note that the venous connec-tions are not definitive, as there can be anomalous drainage of the systemic or pulmonary veins.

Conditions of abnormal situs include situs inversus, iso-merism, and indeterminate situsasitus ambiguous. These aresome of the most complex of congenital abnormalities andare discussed in Chapter 22. Situs inversus exists when mor-phologically right- and left-sided structures lie in a mirrorimage of the normal arrangement. Isomerism is present when both the right- and left-sided atria are mirror images ofthe same morphological type. Right isomerism exists whenthe right-sided and left-sided atria are mirror images of amorphologically right atrium, and left isomerism exists whenboth atria are mirror images of a morphologically left atrium.Bronchi, pulmonary segments, abdominal great vessels, andabdominal organs show characteristics of the atrial situs.17

Right isomerism is usually associated with absence of thespleen and therefore is often called asplenia. Left isomerismis termed polysplenia due to the potential for multiplespleens. When isomerism is present, the heart and stomach areoften on opposite sides (visceroatrial heterotaxy). Heterotaxyis therefore often used as a synonym for isomerism althoughis not strictly equal. Both isomerism and indeterminate situsare also called situs ambiguous.14,16–18

Surgical and non-invasive approach

Rapid and ongoing evolution of surgery for CHD has had ahuge impact on the preoperative preparation required for the pediatric cardiac anesthesiologist. Improved surgical out-comes and a focus upon structural correction in the neonatalperiod has tremendously increased the number of major procedures performed in the first days and weeks of life (see Chapters 1 & 12). The development of non-surgical techniques has widened the therapeutic arena to include the interventional cardiac catheterization laboratory as well.Examples include device closure of septal defects, balloondilation of stenotic valves and vessels, and placement of coilsand stents (see Chapter 25).

Preoperative stabilization of the neonate

In nearly all cases the neonate can be stabilized to permitthorough preoperative assessment and preparation of thesurgical team. Important therapies include administration ofprostaglandin E1 (PGE1) to maintain patency of the ductusarteriosus, balloon atrial septostomy to enhance mixing ofpulmonary and systemic venous return, and red blood celltransfusion to optimize hemoglobin levels for patients withmarginal oxygen transport. Pulmonary vascular resistance(PVR) may be manipulated with alterations of inspired oxygen concentration, carbon dioxide level, and nitric oxidetherapy. Inotropic and/or vasodilator support may enhancethe ability of the neonatal heart to meet cardiac output (CO)demands (see Chapters 14 & 27). In nearly all cases, therefore,the anesthesiologist has time to perform a careful review ofthe available data and surgical plan.

Surgery on the day of hospital admission

Most elective surgeries and interventional procedures arecurrently performed on the day of hospital admission for eco-nomic reasons. The logistics of the preoperative evaluation of this most challenging group of patients must be carefullycoordinated to avoid suboptimal patient assessment or lastminute cancellations.

Preoperative goal no. 1: Understandcongenital heart disease terminology

Terminology and segmental approach to anatomy

In order to understand and communicate information regard-ing CHD, the anesthesiologist must first make sense of theterminology. The first modern attempt to classify CHD waspublished in 1936 by Dr Maude E. Abbott.7 Since that timeadditional nomenclature published by multiple authors hasled to more than one term for many similar conditions and

PART 3 Preoperative considerations

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Table 11.1 Commonly used anatomic terms for congenital heart disease.

ASD Atrial septal defect

Asplenia Right isomerism, bilateral right sidedness

AVSD Atrioventricular septal defect, “AV canal,” an endocardial cushion defect. Characterized by a single atrioventricular

ring, with both a primum ASD and a VSD in complete defects

Balanced ventricles A pair of ventricles of nearly equal size. Often used to describe the ventricles of a patient with AVSD. Balanced ventricles are

more easily separated during surgery to achieve a two-ventricle repair

Bulb A ventricular structure that gives rise to a great vessel but that has no inlet valve. The orifice connecting it to the

other ventricle is a bulbo-ventricular-foramen

Concordance Connection of two structures of identical morphologic sidedness, e.g. morphologically right-to-right, or left-to-left.

Used to describe atrioventricular or ventriculoarterial connections. Does not describe position of structures within

the body or position with respect to other cardiac structures

Dextrocardia A right-sided heart, or a heart with a rightward base–apex axis

Discordance Connection of a morphologically right-sided structure to a morphologically left-sided structure at the atrioventricular

or ventriculoarterial level. See concordance

d-loop ventricles Looping describes the internal organization of the ventricles. First described by Van Praagh in 1964, “right-handed”

or d-loop is the result of normal looping of the heart in formation. Consistent with the illustration of an imaginary

right hand placed with its palm against the septal surface of the right ventricle, the thumb extending back through

the atrioventricular valve toward the atrium, and the fingers extending toward the right ventricular outflow tract

and pulmonary valve. With d-looping the left hand would be similarly positioned only for the left ventricle

Dominant ventricle A ventricle that is much larger than its companion, often a double inlet, or double outlet ventricle, or part of an

unbalanced atrioventricular septal defect. See unbalanced ventricles

Double inlet ventricle A ventricle into which both atrioventricular valves flow

Double outlet ventricle A ventricle which gives rise to both great vessels. This term is usually applied when at least half of the second outlet

valve lies over the ventricle

d-related great vessels Aortic valve to the right of the pulmonary valve. The normal arrangement is a right-posterior aorta with respect to the

pulmonary trunk. (Previously thought to represent ventricular looping, however this is an unreliable marker. Many

references have used the term d-transposition, for example, as synonymous for complete transposition with d-looped

ventricles and l-transposition as synonymous with corrected transposition with l-looped ventricles. This is now

generally considered incorrect usage of the term)

Hemitruncus Right or left pulmonary artery arising directly from the aorta

Heterotaxy An abnormality in left–right arrangement. Includes isomerism syndromes, discordance, and imbalance of

morphologically left- and right-sided structures

Levocardia A left-sided heart, or a heart with a leftward base–apex axis

l-loop ventricles Abnormal, “left-handed” ventricular looping. Consistent with the illustration of an imaginary left hand placed with its

palm against the septal surface of the morphologic right ventricle, the thumb extending back through the atrioventricular

valve toward the atrium, and the fingers extending toward the right ventricular outflow tract and pulmonary valve. With

l-looping the right hand would be similarly positioned only for the morphologic left ventricle. See d-loop ventricles

l-related great vessels Aortic valve to the left of the pulmonary valve. (Previously thought to represent l-looped ventricles, however now known

to be an unreliable marker. See d-related great vessels)

Malalignment A malposition of the atrial or ventricular septum that results in an overriding valve. The malposition may be lateral, rotational

or both

Mesocardia A centrally located heart, or a heart with an inferior base–apex axis

Overriding valve Biventricular emptying of an atrioventricular valve or biventricular emptying of a semilunar valve. Associated with

malalignment VSD

Polysplenia Left isomerism, bilateral left sidedness

Semilunar valve Ventriculoarterial outlet valve

Continued p. 178

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Table 11.1 (cont’d)

Single outlet Single great vessel arising from the heart. Diagnoses include aortic atresia, pulmonary atresia, common arterial trunk

(truncus arteriosus), or a solitary arterial trunk (without evidence of pulmonary or aortic atresia)

Single ventricle Technically, the presence of only one anatomic ventricle. Term usually applied to patients with one functional ventricle

and often to those with single ventricle physiology—complete mixing of the systemic and pulmonary venous return.

May be associated with one or two great vessels

Situs ambiguous Indeterminate sidedness. Includes isomerism

Situs inversus Mirror image sidedness with respect to normal with a morphologically right atrium on the left side and a morphologically

left atrium on the right side

Situs solitus Normal sidedness

Straddling valve Anomalous insertion of atrioventricular valve cords into both sides of the interventricular septum. Severe straddling may

preclude a two-ventricular repair

TGA or TGV Transposition of the great arteries (vessels). Ventriculoarterial discordance

Truncus arteriosus A single semilunar valve and annulus that gives rise to a single common arterial vessel from which both the systemic and

the pulmonary circulations branch. May be associated with a truncal valve of more than three, and rarely two, cusps.

Always associated with a VSD just below the truncal valve

Unbalanced ventricles A pair of ventricles of unequal size. Often used to describe the ventricles of a patient with AVSD. When significantly

unbalanced, the ability of the smaller ventricle to perform adequately if separated from its companion is called into

question. See balanced ventricles

Univentricular Both atria are connected to one ventricle via two valves (double inlet ventricle) or absence of the right or left atrioventricular

atrioventricular connection connection (single atrioventricular connection)

VSD Ventricular septal defect

Table 11.2 Characteristic morphologic features of major cardiac structures.

Right atrium The most consistent morphologic features are its broad-based appendage, presence of pectinate muscles in the vestibule, and

a well-defined crista terminalis. Normal venous connections include the superior and inferior vena cavae and the coronary sinus;

however, it is the morphology of the appendage that is the arbiter of atrial morphology

Left atrium A narrow-based appendage is characteristic. Pectinate muscles are limited to the appendage. There is no crista terminalis.

Normal venous connections include the four pulmonary veins; however, their drainage may be anomalous

Right ventricle Coarse trabeculations in the apical portion of the ventricular are the most characteristic feature in malformed hearts. Association

with a tricuspid atrioventricular valve is present in hearts with two ventricles and two atrioventricular valves. See tricuspid valve

Left ventricle The apex of the ventricle has finer trabeculations than the morphologically right ventricle. Associated with a morphologic mitral

atrioventricular valve in hearts with two ventricles and two atrioventricular valves. The septal surface is “bald,” meaning without

septal cordal attachments to the atrioventricular valve. See mitral valve

Tricuspid valve Features include three leaflets (septal, inferior or mural, and anterior) and multiple cordal attachments to the ventricular septal surface

Mitral valve Features include two leaflets with two papillary muscles. Each papillary muscle supports adjacent parts of both leaflets. Fibrous

continuity of the septal (anterior) leaflet with the leaflets of the aortic valve is present, and there is absence of cordal attachments to

the ventricular septum

Pulmonary artery Branches soon after its origin into the right and left pulmonary arteries. Anomalous origin of individual pulmonary arteries from the

aorta is sometimes seen

Aorta Normally gives rise to the coronary arteries and the systemic arterial tree. Anomalous origin of individual coronary arteries is sometimes

seen. The first vessel after the coronaries, the innominate artery, branches to the side contralateral to the aortic arch

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(apex leftward) with a left-sided heart. Mesocardia (apex caudad) is associated with isomerisim. Dextrocardia (apexrightward) may or may not be associated with situs inversus.Note that a heart may displaced toward the right chest andstill demonstrate levocardia.18

Right and left

The usage of “right” and “left” to denote morphologic struc-tures as well as sidedness and relation has been reviewedabove. A third usage of these terms relates to shunting. Whendescribing a shunt, conventional rules apply and the “right”circulation is that which consists of systemic venous blood,either in the veins, heart, or pulmonary arterial tree. “Left”circulation describes blood draining from the lungs in thepulmonary veins, heart, or systemic arterial tree. Therefore a right-to-left shunt is systemic venous admixture into thesystemic arterial circulation and not necessarily shunting ofblood from a right-sided or morphologically right structureto a “left” structure. A fourth use of “right” and “left” refers toright- and left-handed ventricular looping19 and is describedunder d-loop and l-loop in Table 11.1.

Preoperative goal no. 2: Understand thecardiac pathology and physiology

Once familiar with basic anatomic terminology and the segmental approach, one is ready to classify the cardiacpathology. Congenital heart disease can be classified from anembryologic, anatomic, and a physiologic perspective.20 Thepediatric cardiologist may prefer an approach that beginswith clinical findings at presentation and assists in the diag-nosis of the lesion, or one that follows along anatomic lines.Even after hundreds of cases, however, unfamiliar variationsof anatomy may be encountered. In most cases anestheticmanagement and risks follow from the patient’s physiologicstate rather than their specific anatomy. In other words, adiverse number of anatomic lesions may lead to a similarphysiologic condition and therefore merit similar anestheticmanagement strategies.

It is more pragmatic, therefore, for the anesthesiologist togroup patients based upon the physiologic consequences oftheir anatomy.21 This step, which represents the most uniqueaspect of the preoperative assessment of CHD patients,allows the anesthesiologist to devise a rational anestheticplan and predict potential intraoperative problems. One crit-icism of this approach is the fact that the physiologic state ofan individual patient may change. For example an “acyan-otic” patient may demonstrate cyanosis if conditions such asPVR or blood pressure change. However it is precisely theability of the anesthesiologist to recognize that the physio-logic situation has changed, understand the implications inthe context of the patient’s disease, and respond in a dynamic

When working with patients with isomerism, it is espe-cially important for the anesthesiologist to keep in mind therelationship of the pulmonary and bronchial anatomy toatrial situs. A patient with right isomerism will have bilateral,mirror-imaged “right” lungs. Each lung will have right-sided morphology, including three lobes, a short mainstembronchus and an upper lobe bronchus that separates beforethe pulmonary artery crosses (eparterial branching pattern).18

When left isomerism is present both lungs will have mirroredleft-sided morphology.

Connections

There are two series of connections. Atria are connected toventricles by atrioventricular (AV) valves, which “go withthe ventricle.” That is to say an AV valve generally has rightmorphological characteristics when opening into a morpho-logically right ventricle and left morphological character-istics when opening into a morphologically left ventricle. Theventriculoarterial (VA) connections are semilunar valves.Concordance or discordance is described at both the AV andthe VA level. Connections are concordant when the morpho-logic characteristics of the segments they connect are botheither right or left. Connections are discordant when a mor-phologically right structure is connected to a morphologicallyleft structure or vice versa.10,11,16,18 Two variations of trans-position of the great arteries (TGA) illustrates these principles:

Transposition of the great arteries = ventriculoarterial discordance:• TGA with AV concordance = “complete transposition.”

Pulmonary venous blood passes from the left atrium to leftventricle and enters the pulmonary artery. The patient iscyanotic and requires stabilization and surgery in theneonatal period as oxygen transport is dependent uponbidirectional shunting at the atrial and ductal levels.

• TGA with AV discordance = “corrected transposition.”Pulmonary venous blood passes from the left atrium toright ventricle and enters the aorta. In this situation the two discordant connections balance or “correct” the circulatoryabnormality. There is no oxygen desaturation or need forurgent surgery, although the anatomic right ventricle isprone to failure in later life as it is charged with pumpingto the systemic circulation.

Position of the heart

Two issues are pertinent regarding the position of the heartathe orientation of the base to apex axis, and the location of theheart within the chest. The terms levocardia, dextrocardia,and mesocardia are used to describe both, resulting in someconfusion; however, they most often refer to the direction ofthe apex. It is best to communicate a clear description of therelation of the heart within the thorax independently fromthe base to apex axis. The normal arrangement is levocardia

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predominant flow abnormality is the passage of blood from the left to right. Some degree of right-to-left shunting is usually detectable. (Large communications permit varyingdegrees of bidirectional shunting, or mixing.) A patent ductus arteriosus (PDA) will result in an acyanotic patientwhen pulmonary arterial pressure remains below systemicarterial pressure throughout the cardiorespiratory cycle.

Physiologic abnormalities and risksThe primary physiologic abnormalities that may result fromlesions that permit left-to-right shunting are increased volumeloading of one or more of the cardiac chambers, decreasedsystemic CO, and increased intracardiac and/or pulmonaryvascular pressures. Congestive heart failure (CHF) may resultif the work of the heart exceeds compensatory mechanismsand reserve. Deterioration in gas exchange may result frompulmonary congestion.

Patients with substantial left-to-right shunting often demon-strate pulmonary hypertension. It is desirable to determinewhether elevated pulmonary pressures are present, andwhether they are due to augmented flow, resistance, or both.While echocardiography may be helpful to estimate pulmon-ary pressure and relative pulmonary to systemic flow, it isnot possible to determine the resistance in the pulmonaryarterial circulation without cardiac catheterization.

Decreased systemic blood flow in the presence of left-to-right shunt is often due to excess flow to the pulmonary bed,often called pulmonary “over circulation”. In this setting leftatrial pressure (LAP) is usually elevated as a result of aug-mented pulmonary venous return. Diastolic blood pressuremay be compromised if systemic CO is reduced or there is a low-resistance vascular bed, such as a large anomalous pulmonary vessel or ductus arteriosus, branching from theproximal aorta. Coronary ischemia without coronary diseaseor anomalies may result from the combination of high CO,elevated LAP and low diastolic blood pressure.

When a large systemic-to-pulmonary shunt is present at theventricular or arterial level the systolic pressure in the pul-monary artery will equal that in the aorta because they are inparallel with the same head of pressure. A large VSD or PDAare examples. One rule of thumb is to anticipate equalizationof pressures when the diameter of the communication exceeds75% of a normal aortic annulus diameter. If the pulmonaryand systemic beds are exposed to equivalent pressure, thepulmonary to systemic flow ratio (Q· p : Q· s) is inverselyrelated to the relative vascular resistances. Ohm’s law can betransformed to its cardiovascular equivalent to understand asimplified relationship between pressure, flow, and resistance.

I = current flow (amperes) Q· = flow

E = electromotive force (volts) P = pressure

R = resistance (Ohms) R = vascular resistance

I =E

R��Ohm’s Law

setting that are the hallmarks of appropriate care. The follow-ing pathophysiologic classification is outlined in Table 11.3.

Acyanotic congenital heart disease

With left-to-right shunt

EtiologiesAtrial septal defect (ASD), ventricular septal defect (VSD),selected patients with atrioventricular septal defect (AVSD or “AV canal”), and partial anomalous pulmonary venousreturn are examples of acyanotic CHD with left-to-right shunt.At both the atrial and ventricular level pressure on the leftside of the heart normally exceeds that on the right side over the great majority of the cardiac cycle. In the presence of a relatively small intracardiac communication, therefore, the


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Table 11.3 Physiologic classification of congenital heart disease.

I Acyanotic congenital heart disease

A With left-to-right shunt

1 ASD

2 VSD

3 PDA

4 AVSD (may also be cyanotic)

5 Tetralogy of Fallot (may also be cyanotic)

6 Partial anomalous pulmonary venous return

B Without left-to-right shunt

1 Valvular heart disease

2 Subvalvular or supravalvular obstruction

3 Cor triatriatum

4 Double chambered right ventricle

5 Cardiomyopathies

II Cyanotic congenital heart disease

A Pulmonary blood flow dependent upon the ductus arteriosus

1 Tetralogy of Fallot, with severe right ventricular outflow obstruction

2 Pulmonary atresia or severe stenosis

3 Tricuspid atresia with pulmonary stenosis

4 Ebstein’s anomaly, severe

B Systemic blood flow dependent upon the ductus arteriosus

1 Hypoplastic left heart syndrome

2 Severe coarctation or interruption of the aorta

C Mixing lesions without duct-dependent circulation

1 Large ASD or VSD

2 AVSD with large communication

3 Double inlet ventricle

4 Double outlet ventricle

5 Truncus arteriosus

6 Tricuspid atresia without pulmonary stenosis

7 Total anomalous pulmonary venous return

8 Transposition of the great arteries (may be dependent upon the ductus

for mixing and oxygen transport)

ASD, atrial septal defect; AVSD, atrioventricular septal defect; PDA, patent

ductus arteriosus; VSD, ventricular septal defect.

cardiovascularequivalent

Q̇ = PR

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particularly low diastolic blood pressure. It is therefore use-ful to ensure that monitoring devices display diastolic bloodpressure prominently, rather than a mean value.

Without left-to-right shunt

EtiologiesAcyanotic lesions without left-to-right shunt consist primar-ily of valvular heart disease or cardiomyopathy. Subvalvularor supravalvular obstruction, cor triatriatum, and double-chambered right ventricle are also in this category.

Physiologic abnormalities and risksThe primary potential physiologic consequences are decreasedsystemic CO, and excess pressure and/or volume in one ormore of the cardiac chambers. Obstructive lesions limit COby mechanically interfering with forward flow. Regurgitantlesions limit forward flow by introducing pump inefficiency.Cardiomyopathies result in pump failure or obstruction dueto hypertrophy. Elevated intracardiac pressures, congestivefailure, and pulmonary hypertension may occur. Patientswith substantial obstruction to left-sided flow, such as thosewith severe mitral stenosis, aortic stenosis, or subaortic stenosis are at particular risk for induction of anesthesia andmay not tolerate an inhalation technique (see Chapter 19).They should be identified preoperatively and scheduled with care as prolonged fasting may further compromise theirreserve. In selected cases preoperative intravenous fluidsmay add to the safety of fasting.

Compensatory mechanismsIf the obstruction is at the ventricular outlet, concentrichypertrophy results, with a salient effect on ventricular wallstress. An undesirable side effect of ventricular hypertrophy,however, is diastolic dysfunction. A high end-diastolic fillingpressure is often present long before systolic dysfunction and pump failure occurs. In pediatric patients, subvalvularstenosis is a common variant, with the potential for adynamic component to outflow obstruction. In these pati-ents tachycardia, hypovolemia, and positive inotropes maybe deleterious.

Regurgitant lesions result in excess volume work for theventricle involved. With chronic regurgitation, chamberenlargement results. Eccentric hypertrophy mitigates the elevated wall stress associated with ventricular dilation.Additional compensatory mechanisms include tachycardiaand elevated filling pressures. Diastolic dysfunction precedessystolic pump failure in this situation as well.

Signs of limited reservePatients may demonstrate signs of inadequate systemic out-put due to low CO. Poor feeding and growth, tachycardia,hypotension, decreased capillary refill, acidosis, organ hypo-perfusion, and signs of right- or left-sided congestive failure

Compensatory mechanismsExcess pulmonary blood flow returns to the left atrium andmust again be ejected by the heart. The primary compensat-ory mechanisms to maintain an elevated CO include tachy-cardia, eccentric ventricular hypertrophy, and enlargementof all chambers receiving excess flow. If systemic blood flowis compromised, systemic vascular resistance (SVR) mayincrease to maintain blood pressure.

Signs of limited reservePulmonary congestion may result in increased work ofbreathing. Patients may tire easily while feeding, and demon-strate dyspnea, diaphoresis, and lengthy feeding. Failure tothrive with poor weight gain is often an indication of inade-quate systemic flow. Signs include poor growth, tachycardia,hypotension, decreased capillary refill, acidosis, and organhypoperfusion. Systemic congestion may also be present.Toward the end of the first month of life the elevated PVR ofthe neonatal period decreases toward normal. If a large com-munication is present between the pulmonary and systemiccirculations, a patient with CHF may deteriorate at this timeas the decline in PVR further augments pulmonary bloodflow. Ventilation–perfusion mismatch, hypoxemia, and frankpulmonary edema may result.

Stabilizing therapies Stabilizing therapies include digoxin and diuretics for pati-ents with systemic or pulmonary congestion, supplementaloxygen and ventilatory support for patients with pulmonarydysfunction, and afterload reduction for those with poor systemic perfusion. Inotropes may be useful to stabilizepatients with severe congestive failure. If oxygen transport to the tissues is marginal due to low CO, blood transfusion to increase arterial oxygen content may also be a useful pre-operative therapy.

A word of caution about oxygen and ventilatory therapy is in order. It is critical for the anesthesiologist to identifypatients who may be at risk for deterioration if supplementaloxygen or controlled ventilation is instituted. Due to the pulmonary vasodilating effects of increased PAO2 and/ordecreased PACO2, patients with large left-to-right shunts atthe ventricular or great vessel level may experience a suddenincrease in pulmonary blood flow if alveolar oxygen con-centration or ventilation is increased. Systemic hypotensionoften accompanies reduced resistance of the pulmonary vascular bed in this setting. The combination of high left-atrial filling from excess pulmonary blood flow and systemichypotension may precipitate a rapid downward spiral due tolow coronary perfusion pressure and myocardial ischemia.Cardiac failure or even cardiac arrest may soon follow.Patients with a significant pulmonary shunt at the level of thegreat vessels (such as a large PDA) are most vulnerable tocoronary ischemia due to ongoing pulmonary runoff duringthe diastolic phase of the cardiac cycle and the potential for

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physiology and to estimate a desired value for SpO2. Optimalsaturation for patients with complete mixing of pulmonaryand systemic venous return, for example, is not the maxi-mum achievable value. A 1 : 1 relationship between pul-monary and systemic flow is generally considered optimal,and usually results in arterial oxygen saturation between 75%and 85%. When pulmonary blood flow is limited, incremen-tal increases in the ratio have a relatively large positive effecton arterial saturation. However when the ratio exceeds 1 : 1further increases in pulmonary blood flow have a diminish-ing effect upon saturation.22 The benefits of an increased arte-rial saturation are more than outweighed by the cost of over-circulation to the pulmonary bed. Another way of looking atthis problem is that the risk of high output cardiac failureincreases while the incremental gains in oxygen content ofthe blood diminish. This relationship is illustrated in Fig. 11.1.

Classification of cyanotic heart disease

Cyanotic patients may be divided into three broad physio-logic categories based upon the role of the ductus arteriosus.Each is discussed separately below.

Cyanotic heart disease with duct-dependent pulmonaryblood flow

EtiologiesDuctus-dependent pulmonary blood flow is primarily asso-ciated with obstruction to right ventricular inflow or outflow.Examples include pulmonary stenosis or atresia, tetralogy of Fallot with severe right ventricular outflow obstruction,tricuspid atresia, and Ebstein’s anomaly.

Physiologic abnormalities and risksPatients are primarily at risk for decreased pulmonary blood

may occur depending upon the site of obstruction, regurgita-tion, or myocardial failure.

Stabilizing therapiesStabilizing therapies are similar to those for patients with left-to-right shunts, and include digoxin and diuretics forpatients with systemic or pulmonary congestion, supple-mental oxygen or positive pressure ventilation for patientswith pulmonary dysfunction, and afterload reduction forpatients with poor systemic perfusion due to valvularinsufficiency or dilated cardiomyopathy. Inotropes may beuseful to stabilize patients with severe congestive failure. If oxygen transport to the tissues is marginal due to low CO, blood transfusion to optimize hemoglobin and arterialoxygen content may also be a useful preoperative therapy.

Cyanotic heart disease

Physiology of cyanotic heart disease

Arterial desaturation and cyanosis are the result of venousadmixture to the systemic circulation, called right-to-leftshunting. With normal cardiac anatomy this occurs mostoften in the lungs due to alveolar collapse or vascular shunts.In the context of structural heart disease right-to-left shunt-ing is usually accompanied by some element of left-to-rightshunting, however whenever significant arterial oxygendesaturation is present the patient is considered to have cyan-otic heart disease. As noted above, when describing a shuntthe systemic venous blood is “right” and pulmonary venousblood is “left,” regardless of the location or morphologiccharacteristics of the structures involved.

When venous admixture is significant, the relative volumeand saturation of systemic venous and pulmonary venousblood determine arterial saturation. Therefore, systemic arte-rial saturation will depend to some extent upon factors thatdetermine systemic venous oxygen saturation in addition tothe normal determinants of pulmonary venous oxygen satu-ration. These are outlined in Table 11.4. Arterial saturationwill fluctuate with changes in pulmonary function and shuntfraction, but also with changes in hemoglobin, temperature,and CO. If the systemic circulation supplies an importantsource of pulmonary blood flow, arterial saturation will varywith systemic blood pressure as well. Examples of this situation include PDA, aortopulmonary collateral vessels,and any prosthetic shunt from the aorta or its branches to the pulmonary artery.

Importance of Q· p : Q· sWhile all patients with cyanotic heart disease have venousadmixture, they do not all have decreased pulmonary bloodflow. Many are at risk for excess pulmonary blood flow. Animportant goal of the preoperative assessment is to interpretthe patient’s arterial saturation in terms of the individual


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Table 11.4 Factors determining arterial oxygen saturation (SaO2) with

right-to-left shunt.

1 Determinants of pulmonary venous oxygen saturation

(a) PAO2

(b) Gas exchange

(c) Alveolar ventilation

2 Determinants of systemic venous oxygen saturation*

(a) V·O2

(b) Hemoglobin

(c) Cardiac output

(d) Factors affecting the oxyhemoglobin dissociation curve

3 Pulmonary to systemic blood flow ratio (Q·p : Q· s)*

*Normally, these factors do not play a significant role in determining SaO2.

PAO2, pulmonary alveolar oxygen tension; Q·p : Q· s, pulmonary to systemic

blood flow ratio; V·O2, oxygen consumption

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Stabilizing therapiesProstaglandin E1 is usually effective to maintain a low resist-ance in the ductus. Potential complications of PGE1 includetachycardia, hypotension, apnea, hyperpyrexia, and seizures.Additional therapies to reduce PVR such as supplementaloxygen, respiratory and/or metabolic alkalosis, phosphodi-esterase inhibitors, and nitrate or nitric oxide therapy may behelpful. Systemic blood pressure and CO must be maintainedto provide adequate perfusion pressure to the ductus. If pul-monary blood flow remains critically low, blood transfusionto a hemoglobin level of approximately 17 g/dL may aug-ment the oxygen content of the pulmonary venous blood andenhance oxygen transport. Inotropic support may be helpful.Sedation must be used with caution and carefully assessedfor its potential effect on SVR and blood pressure.

Cyanotic heart disease with duct-dependent systemicblood flow

EtiologiesObstructions or limitations to flow through the aortic valve or proximal aorta are associated with duct-dependent sys-temic blood flow. Examples include hypoplastic left heartsyndrome, interrupted aortic arch, and severe coarctation ofthe aorta with persistent flow through the ductus arteriosus.

Physiologic abnormalities and risksThis group of patients is at risk for increased pulmonaryblood flow and decreased systemic perfusion. Surgical goalsare to stabilize the blood flow to the body and limit bloodflow to the lungs, as pulmonary blood flow is usually abovenormal when systemic blood flow is dependent upon theductus arteriosus. Arterial oxygen saturation is usually ade-quate; however, patients remain at risk for decreased oxygendelivery due to anatomic obstruction to systemic flow ratherthan diminished oxygen content of the blood. Saturation inthe descending aorta may be lower than that in the ascendingaorta due to differential perfusion from the right and lefthearts.

Compensatory mechanismsBecause the pulmonary vasculature is usually receiving morethan normal flow, the heart receives excess pulmonary venousreturn. Tachycardia is necessary to maintain an elevated COin the volume-loaded neonatal heart as the ability to augmentstroke volume is limited. Systemic vascular resistance is oftenelevated in response to decreased systemic perfusion.

Signs of limited reservePatients may demonstrate acidosis due to inadequate systemic perfusion. Excess pulmonary flow may result inundesirable effects such as pulmonary congestion or edema.Reduced coronary perfusion pressure and myocardial dys-function may occur, particularly if diastolic blood pressure is

flow and cyanosis. Most require surgery to provide a stablesupply of blood to the lungs. With an important componentof pulmonary blood flow provided via the aorta and ductusarteriosus, flow to the lungs depends upon the systemicblood pressure, resistance in the ductus, and PVR. Systemicblood pressure, in turn, depends upon CO and SVR.

Compensatory mechanismsSystemic vascular resistance is a key determinant of the perfusion pressure to the duct, and therefore must be main-tained. Increased hemoglobin also augments the oxygen- carrying capacity of the pulmonary blood flow and improvesoxygen transport. Acidosis, if present, results in an aug-mented respiratory drive and a chronic respiratory alkalosis,augmenting the alveolar PO2.

Signs of limited reserveUntil patients undergo surgical intervention they are critic-ally dependent upon the ductus arteriosus for pulmonaryblood flow and oxygen transport. Severe hypoxemia may bedemonstrated if ductal flow is marginal. Acidosis may besevere due to combined respiratory and metabolic compon-ents. If compensatory mechanisms and stabilizing measuresare exhausted patients may develop myocardial dysfunctionleading to further decreases in CO and blood pressure.Pulmonary blood flow is pressure dependent (via the ductus)therefore hypotension will result in a tandem downward spiral of arterial saturation and cardiac function.

060

70

80

90

100

Q.p : Q

.s ratio

1 : 1 2 : 1 3 : 1 4 : 1

Mixed Venous Oxygen Sat = 70%

Mixed Venous Oxygen Sat = 50%

Sys

tem

ic A

rter

ial O

xyge

n S

atur

atio

n %

Fig. 11.1 The effect of variable Q·p : Q· s ratio on expected arterial oxygen

saturation when systemic and pulmonary venous blood are completely

mixed. A pulmonary venous oxygen saturation of 100% is assumed. Note

that the incremental increase improvement in systemic arterial saturation

diminishes at high Q·p : Q· s ratios. Two mixed venous saturations are

illustrated, 50% and 70%. Mixed venous oxygen saturation will vary with

hemoglobin concentration, cardiac output, and oxygen consumption.22

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the effect of arterial desaturation on hemopoietin and redblood cell production. If pulmonary blood flow is elevated,additional pulmonary venous return may create additionalvolume work for the heart. Tachycardia and increased SVRmay occur to maintain CO and blood pressure.

Signs of limited reserveDepending upon whether the systemic or pulmonary circula-tion is more tenuous, patients may demonstrate signs of limited pulmonary or systemic blood flow. Patients with evidence of pulmonary congestion due to pulmonary over-circulation are among the most difficult to manage duringtransport to the operating room and during the pre-bypassperiod. Supplemental oxygen and hyperventilation maycause a detrimental increase pulmonary blood flow and CHF.On the other hand, if pulmonary congestion is already pre-sent hypoventilation and decreases in FIO2 may be equallyintolerable as intrapulmonary shunting and hypoxemia mayrapidly occur.

Stabilizing therapiesTherapy must be individualized depending upon the specificphysiology. If, for example, dynamic pulmonary stenosis ispresent, β-blockers may improve pulmonary flow. If sys-temic flow is compromised due to excess pulmonary bloodflow, strategies to increase PVR and maintain coronary perfu-sion pressure, as outlined above, may be useful.

Summary—physiologic classification

To facilitate the preoperative evaluation, patients may begrouped into acyanotic and cyanotic categories. Acyanoticpatients may or may not have left-to-right shunting with augmented pulmonary blood flow. Cyanotic patients havesome degree of right-to-left shunt, however not all havedecreased pulmonary blood flow. They may be physiologic-ally grouped according to the role of the ductus arteriosus. Ifeither the pulmonary or systemic circulation is dependentupon the ductus, PGE1 therapy is initiated until surgery isperformed. Patients with ductal dependence of the pulmon-ary blood flow usually have reduced pulmonary blood flow.Those with ductal dependent systemic blood flow usuallyhave increased pulmonary blood flow and may have limitedsystemic perfusion. Patients with intracardiac shunting with-out dependence upon the ductus have variable pulmonaryand systemic blood flow and varying degrees of bidirectionalshunting. Those with large left-to-right shunts are at risk foracute pulmonary congestion, poor systemic perfusion andsudden deterioration if interventions such as supplementaloxygen or increased ventilation cause PVR to decline. It isimportant to identify this category of patients preoperativelyas they must be managed very carefully upon transport to theoperating room and before cardiopulmonary bypass (CPB).

low in the setting of elevated LAP, as described above in thesection on acyanotic disease with left-to-right shunt.

Stabilizing therapiesAs for patients with duct-dependent pulmonary blood flow,ductal patency must be maintained with PGE1. In this cir-cumstance, however, the goal is to ensure systemic bloodflow. Additional strategies are aimed at increasing PVR tolimit pulmonary congestion and improve systemic blood flow.Pulmonary vascular resistance may be increased with an FIO2of less than 0.21, and/or intentional respiratory acidosis viapermissive alveolar hypercapnia or inspired carbon dioxide.Because flow to the periphery is compromised, attention tohemoglobin concentration is warranted to optimize systemicoxygen transport. Inotropic support may assist in maintain-ing CO in the face of excess pulmonary venous return.

Cyanosis due to mixing lesions

EtiologiesThe third group of cyanotic patients includes those withintracardiac right-to-left or bidirectional shunting withoutduct-dependent pulmonary or systemic flow. Examples inthis category include large VSD, AVSD, and double inlet oroutlet ventricle, single AV valve, total anomalous pulmonaryvenous return, and truncus arteriosus. Truncus arteriosusmay be considered in this grouping as ductal patency is veryrare unless interruption of the aorta is also present. Beforesurgery, TGA may be considered a mixing lesion with thepotential for inadequate mixing. When feasible, surgicalgoals include the separation of the pulmonary and systemiccirculations and correction of any obstructions to systemic orpulmonary blood flow.

Physiologic abnormalities and risksPure right-to-left shunt is rare and is associated with rightventricular inflow or outflow obstruction that is mild enoughto permit survival without the duct. “Mixing” or bidirec-tional shunting of blood is usually present. Pulmonary bloodflow may be low, normal, or high. Therefore, signs of eitherinadequate systemic or inadequate pulmonary flow may bepresent. In some conditions complete mixing of all pul-monary and systemic venous blood is obligatory. Examplesinclude double inlet or double outlet ventricle or conditionswith single AV valves. In this situation arterial saturation is a helpful guide to the relative pulmonary and systemic flow. With normal hemoglobin and oxygen consumption anarterial oxygen saturation of 75–85% generally indicates wellbalanced pulmonary and systemic flow. In many cases, how-ever, the degree of mixing or streaming of blood is unknownunless cardiac catheterization is performed.

Compensatory mechanismsGiven time, hemoglobin concentrations will increase due to


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demonstrated in this condition. Due to immunologic depres-sion, banked blood products are irradiated to prevent graft-vs.-host disease for patients known to have DiGeorgesyndrome and for patients in high risk groups mentionedabove. Complete transposition, on the other hand, is usuallyan isolated cardiac defect without associated anomalies.Vascular anomalies, especially abnormal origin of the sub-clavian artery, are important to the anesthesiologist, as theymay impact the site of optimal monitoring and vascularaccess. The anesthesiologist must be aware of associatedanomalies in CHD patients and assess their pertinence toanesthetic management on a case-by-case basis.

Growth and development

A relationship between CHD and growth impairment hasbeen documented for decades.28–30 Infants with more com-plex lesions are significantly smaller than normal while thosewith isolated defects such as ASD and VSD are generally normal in weight. It is therefore important to assess growth,functional, neurologic, and cognitive milestones, and notewhether they are at or below par. While cyanosis appears to be a factor in growth impairment and developmentaldelay, there is not a direct correlation with degree of hyp-oxemia. Patients who remain cyanotic after surgery, however,continue to make slower progress.30–32 Poor growth afterbirth often results from fatigue during feeding. Other causesof feeding difficulties may also be present. Previous aorticarch surgery (repair of interrupted arch or Norwood recon-struction) may result in esophageal dysfunction. Patientswith associated neurologic conditions or cleft lip or palatemay not feed normally.28 The anesthesiologist should beespecially aware of developmental abnormalities and noteany areas that may overlap with potential anesthetic complications.

Congestive heart failure

Congestive heart failure (CHF) is classically defined as theinability of the heart to meet systemic needs for CO and oxygen transport. In the setting of CHD where primary pumpfailure is rare, it is usually due to a structural lesion thatresults in either volume or pressure overload of a ventricle, or both.33,34 The term congestive heart failure is also used to describe excess pulmonary blood flow without gross in-adequacies of systemic flow. This ambiguity sometimes leadsto confusion regarding the nature of a problem described as“congestive heart failure.”

Causes of CHF in infants include volume overload due tolarge shunts or severe valvular regurgitation, obstructiveconditions and cardiac muscle diseases such as endocardialfibroelastosis, and CHF secondary to non-cardiac condi-tions.33 Patients with systemic right ventricles are particu-larly at risk. Patients with large shunts typically do not

Initial questions for physiologic classification:• Is the patient cyanotic?• Is there a left-to-right, right-to-left, or mixed shunt?• Is either the pulmonary or systemic circulation dependent

upon the ductus?• Is there a pressure or volume overload on any of the

cardiac chambers?• What compensatory mechanisms or stabilizing therapies

are in place?• What is the current degree of cardiopulmonary reserve?• Is there a risk of deterioration if FIO2 or ventilation is

increased?

Preoperative goal no. 3: Review additional history, physical exam, and studies

History and physical examination

A complete medical history and a focused physical examina-tion are performed.

Most patients have undergone evaluation by pediatric,pediatric cardiology, and pediatric cardiac surgery specialistsbefore surgery is scheduled. The anesthesiologist’s assess-ment adds important information in two areas. First, condi-tions apart from the surgical diagnosis that are of particularinterest to anesthetic management may be detected. Theseinclude airway abnormalities, bronchospasm, gastroesoph-ageal reflux, and issues pertaining to vascular access. Second,meeting the patient preoperatively provides an opportun-ity for the anesthesiologist to become familiar with specificdetails of the physical examination and to form a first-handimpression of the patient’s condition and state of reserve. Thephysical examination should include the measurement ofSpO2, blood pressure, and assessment of pulses in all extremit-ies. Previous anesthetic records and operative reports areparticularly valuable to answer questions. The side of previ-ous modified Blalock–Taussig shunts should be known priorto induction of anesthesia as arterial pressure may be unreli-able in the ipsilateral arm.

Congenital heart disease is often accompanied by addi-tional defects, many of which are genetic.5,23 –25 In theBaltimore–Washington Infant Heart Study of 1981–1989,nearly 28% of patients had associated anomalies or syn-dromes.26 The most common is Down’s syndrome (9%), however a large number of defects are represented. With thegrowth of genetic science, specific chromosomal etiologiesare defined with increasing frequency.

Patients with conotruncal abnormalities, including pul-monary atresia, truncus arteriosus, and interrupted aorticarch are at an increased risk for chromosome 22q11 dele-tion, known as velocardiofacial syndrome or diGeorge’s syndrome.27 Hypocalcemia and an absent thymus are often

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Patients with pacemakers

Cardiac pacemakers sense bradycardia, tachycardia, or both.Bradycardia sensing pacemakers are usually placed for sinusnode dysfunction or high grade AV conduction defects andrespond by pacing the selected chambers (see Chapter 15)Most tachycardia sensing devices today are implantable cardioverter defibrillators (ICDs) and respond by deliveringelectrical energy aimed at cardioversion. Newer ICDs havebradycardia sensing and pacing capabilities as well. Othersmay also have the capability to terminate some tachydys-rhythmias with rapid pacing, a function that was previouslyavailable without ICD capability.41

Whenever a patient has a permanent pacemaker in place,the indications for pacing, underlying rhythm, device typeand its functional status must be researched preoperatively.This may present a significant challenge, especially withexpanding indications for pacing, mobility of patients, andthe development of many new and sophisticated devices. Inall cases, a preoperative electrocardiogram (ECG) is indi-cated. If atrial or ventricular pacing is continuous the under-lying rhythm may be unknown without previous medicalrecords. If no pacing is demonstrated, current pacer functionmay be in question. Consultation with specialists in electro-physiology may be indicated if information is lacking.Electronic interrogation of device settings and reprogram-ming may be required; however, one must first know themanufacturer of the device.

During surgery, electrocautery may inhibit bradycardiadetection and lead to asystole if bradyarrhythmia or conduc-tion block is present. Continuous application of an externalmagnet over bradycardia sensing pacemakers usually revertsfunction to a fixed rate, asynchronous pacing mode. A deci-sion to reprogram the pacemaker during the perioperativeperiod should be made on a case-by-case basis. It is essentialto know if tachycardia sensing is part of the pacemaker cap-abilities to determine appropriate perioperative management.

All tachycardia sensing capabilities should be disabledprior to surgery, as electrocautery or supraventricular tachy-arrhythmias may trigger defibrillation.42,43 This may be per-formed by reprogramming the device or with externalapplication of a magnet. Unfortunately, the action and dura-tion of magnet application to switch off tachycardia sensingdiffers among major device manufacturers. Regardless ofmanufacturer, however, an externally applied magnet willnot convert bradycardia sensing devices to an asynchronouspacing mode if the device has tachycardia sensing capability.The anesthesiologist must therefore carefully assess the needfor intraoperative pacing for any patient with a device that hasboth pacing and ICD capabilities. If the patient relies uponthe pacemaker for ventricular pacing it is prudent to repro-gram the device to an asynchronous mode prior to surgery aselectrocautery is likely to inhibit sensing of bradycardia and a

develop heart failure until the PVR falls in the third or fourthweek of life, at which time the pulmonary circulation receivesa disproportionately high share of blood flow. Rarely, tachy-or bradyarrhythmias may lead to heart failure.35

Difficulty feeding, excessive perspiration, and poor growthare the most common symptoms of CHF in infants. Findingsinclude cardiomegaly (cardiothoracic ratio > 0.5), tachycar-dia, tachypnea, and pulmonary congestion. Hepatomegaly, agallop rhythm, pulmonary edema and vascular collapse maybe seen. Respiratory rates of greater than 45 and heart rategreater than 150 are suggestive. Mottling and slow capillaryrefill in the extremities are severe signs. Pharmacologic ther-apy for CHF includes digoxin, diuretics, afterload reduction,and inotropes for critically ill patients. Supplemental oxygenor respiratory support may be necessary if pulmonary con-gestion or pulmonary edema is severe.33,34

Pulmonary hypertension

The pulmonary circulation is thick-walled and has a highresistance in the fetus. Beginning with the first minutes of life PVR drops dramatically in response to distension of thevessels with aeration of the lungs, increased PAO2, and multi-ple endogenous vasodilating factors. The majority of thedecrease in PVR is completed by the first 3 weeks of life.Larger pulmonary vessels continue to regress over severalmonths.22 In patients with CHD the pressure and resistanceof the pulmonary circulation often do not decline normally.Structural disease, depressed pulmonary venous saturation,and excess flow are all potential factors.36

Systolic pulmonary artery pressures (PAPs) are often estimated by Doppler echocardiography and are measured at cardiac catheterization if anatomically possible. The term“pulmonary hypertension” is ambiguous with regard to eti-ology. The anesthesiologist must correlate knowledge aboutpulmonary vascular flow to interpret whether pulmonaryhypertension, if present, is due to elevated flow, elevatedresistance, or both. If pressure is elevated in proportion toexcess flow one may anticipate a rapid decline in pulmonarypressure when the source of shunt is repaired. Once struc-tural pulmonary vascular changes develop, however, eleva-tions in PVR may be irreversible.37 Many patients havereactive pulmonary hypertension and demonstrate reducedPVR when exposed to elevated alveolar oxygen concentra-tions, alkalosis,38 or nitric oxide.37 For patients scheduled for bidirectional Glenn or Fontan surgeries the assessment of PVR is a key determinant of eligibility for the procedure, as the pulmonary blood flow will be dependent on passiveflow through the pulmonary circulation.39,40 Whenever pul-monary hypertension is present, special attention to the function of the pulmonary ventricle and its valves is meritedas well, as secondary changes may have diminished reserveor resulted in cor pulmonale.


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The degree of pulmonary vascular markings and lungwater are of principal importance as they may indicateincreased pulmonary vascular pressures or congestion. Thehighest risk category for CHF includes non-cyanotic patientswith left-to-right shunt, patients with duct-dependent sys-temic blood flow, and those with mixing lesions and unre-stricted pulmonary blood flow. In cyanotic patients, therefore,the pulmonary vasculature will be normal or decreased unlessa coexisting left-to-right shunt is present. Cardiomegaly asevidenced by a cardiothoracic ratio greater than 0.5 is a use-ful sign of CHF or pericardial effusion in spite of structurallesions and cardiac malposition. Cardiomegaly is usuallyproportionate to pulmonary arterial vascularity unless coarctation of the aorta or myocardial disease is present.49

Regional lung disease may also result from CHD. Com-pression of one or more pulmonary veins, or bronchi mayresult in lobar congestion or hyperinflation. Patients withtetralogy of Fallot with absent pulmonary valve are par-ticularly at risk due to an enlarged pulmonary artery. Theanesthesiologist should specifically look at the image of the tracheobronchial tree on the preoperative chest film.Anomalies of situs will include mirror imaging (isomerism)of normal tracheobronchial structures, which may be im-portant if endotracheal intubation is planned. If pulmonaryproblems occur intraoperatively, advance knowledge of thebronchial anatomy is key to proper interpretation of bron-choscopy findings.

Inspection of the lateral chest film for evidence of reducedspace between the sternum and the heart is important forpatients undergoing repeat sternotomy. When the retroster-nal space is reduced an increased risk of inadvertent dis-ruption of anterior cardiac or prosthetic structures duringsurgical dissection through scarred tissue is present. Mostcommonly the right heart, pulmonary artery, or prostheticright ventricular outflow conduit is involved. The anesthesiateam may wish to tailor their plans regarding intravenousaccess and blood availability prior to CPB in view of thisheightened risk. The surgical and perfusion teams will needto prepare for alternative cannulation sites and the potentialfor urgent institution of CPB. In selected cases the surgeonmay elect to dissect or cannulate the femoral vessels prior todissection and sternotomy.

For older patients with coarctation of the aorta, rib notch-ing may be present. This indicates well-developed collateralarterial flow and a reduced risk of ischemia to organs distal tothe coarctation site if the aorta is cross-clamped.

Echocardiography

Currently, the anatomic pathology for which congenital heartsurgery is scheduled is most often defined by echocardio-graphy. It has proved such a powerful tool that pediatric cardiologists express concern that their auscultatory skill

magnet will have no therapeutic effect. Intraoperative appli-cation of external pacing/defibrillator pads is appropriate forall patients with cardiac pacemaker devices.

Preoperative studies

Laboratory studies

Appropriate laboratory studies include complete blood count(CBC), blood urea nitrogen (BUN), creatinine, electrolytes,coagulation studies, a screen for antibodies, and a crossmatchfor appropriate blood products. Unless blood loss or trans-fusion has recently occurred, an elevated hemoglobin level isa valuable indicator of chronic cyanosis. Diuretic therapymay result in dehydration, hypochloremic metabolic alkalo-sis, or hypokalemia. Although polycythemic patients mayhave abnormal coagulation,44,45 they may also have abnormalcoagulation study results if the laboratory is unaware of theirhematocrit, as fractional serum volume is reduced and dis-torts test results. Patients with extremely elevated hemoglobinconcentrations (hematocrit > 65%) may have poor capillaryflow due to hyperviscosity, which can reduce oxygen trans-port and lead to intravascular coagulation.46,47 Additionalstudies include serum glucose in infants and critically ill patients, and ionized calcium in infants and in patients sus-pected or known to have diGeorge’s syndrome. Blood typeand antibody screen is performed in all patients and blood is crossmatched as indicated by patient age, condition, andproposed procedure.

Electrocardiogram

The ECG should be reviewed for signs of abnormal rhythm,conduction, chamber hypertrophy, and as a baseline for post-operative comparison. Its interpretation is complicated bythe abnormal position of many structures. ST-segment and T-wave abnormalities may indicate ventricular strain orischemia. Dysrhythmias are discussed in Chapter 15.

Chest radiograph

The clinical relevance of the preoperative chest radiograph tothe anesthesiologist is primarily the lung fields and tracheo-broncheal tree. Determination of situs may also be assisted by identifying the laterality of the stomach, liver, and theirrelation to the position of the heart within the thorax. His-torically, the chest radiograph has played an important rolein the differential diagnosis of many congenital heart lesions.The ability to discern pulmonary vascularity, cardiac size, posi-tion, shape, and associated vascular, bronchial and skeletalanomalies are all helpful, however echocardiography hasproven a more powerful and convenient preoperative diag-nostic tool.48

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is diminishing due to lack of use! Prior to 1988 nearly all congenital heart surgery patients underwent preoperativecardiac catheterization. Today cardiac catheterization is mostoften performed to answer remaining physiologic questionsfollowing an echocardiographic diagnosis or to furtherdefine structures with angiography that are difficult to imagewith echo. Many patients undergo complete repair of majorcongenital heart defects without cardiac catheterization.50

Advantages of echocardiography include its non-invasivenature, relative lack of biologic effects, ample acoustic win-dows in infants (due to the paucity of bony structures), andthe ability to use high frequency, high-resolution transducersin small patients due to the proximity of cardiac structures tothe body surface. Technologic advances now permit stun-ningly clear images that may be transmitted digitally withoutloss of detail (Fig. 11.2). Disadvantages of echocardiographyinclude the inability to obtain absolute rather than relativehemodynamic data, and the high degree of technical skillrequired to obtain optimal studies and a certain degree ofsubjective interpretation of spatial relations.

The vast majority of preoperative echocardiographic stud-ies are pre-cordial (transthoracic) rather than transesophagealdue to the greater number of available acoustic windows, andthe need for general anesthesia in infants and children tofacilitate transesophageal studies. It is therefore importantfor the pediatric cardiac anesthesiologist to become familiarwith pre-cordial views and the range of information that can be derived. Normal acoustic windows for pre-cordialecho in infants include suprasternal, parasternal, apical, andsubcostal approaches. The plane of the transducer may be oriented in line with the three orthogonal planes of the body:sagittal, coronal, and transverse. More commonly it is to beoriented along the planes of the heart in short axis, or in longaxis in the “four chamber” or “two chamber” cross sections.The short and long axis of the heart is normally not in linewith the orthogonal planes of the body, however, as the apexis situated to the left and anterior to the base.51,52 Examples ofparasternal short axis and the “ductus cut” views are illus-trated in Fig. 11.2.

The preoperative assessment of congenital heart surgerypatients usually consists of a complete echocardiographicexamination including two-dimensional imaging, spectral(pulse and continuous wave) and color Doppler interroga-tion of cardiac inflow and outflow, as well as imaging ofpathologic flow, and associated structures of interest. Imag-ing information is obtained regarding cardiac and great vessel anatomy, as well as myocardial and valvular function.Quantitative echocardiography is useful to calculate shunts,estimate intracardiac pressures and to evaluate the severityof myocardial or valvular dysfunction. If tricuspid regur-gitation is present, pulmonary arterial systolic pressure can usually be estimated.

Ideally, the anesthesiologist should review the pre-operative echo study images for optimal understanding and


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Fig. 11.2 (a) Hypoplastic left heart syndrome—aortic arch. “Ductus cut”

view. This view is achieved via the suprasternal notch and is useful for

imaging the ductus arteriosus, coarctation of the aorta, and other aortic

arch anomalies. Note the small ascending aorta compared to the

descending component. The innominate artery is not seen as it lies outside

the plane of the transducer. The left common carotid and subclavian arteries

are clearly visualized as well as the large difference in diameter of the

ascending and descending aortic arch components. Note that the size of the

right pulmonary artery exceeds that of the ascending aorta. (b) Hypoplastic

left heart syndrome—pulmonary artery. Parasternal short axis view. The

pulmonary trunk and branch pulmonary arteries are usually easily visualized

with pre-cordial echocardiography. This image demonstrates the large size

discrepancy between the ascending aorta and the pulmonary artery as well

as a clear view of the ductus connecting to the descending aorta. The right

pulmonary artery is better visualized than the left pulmonary artery in this

view. Asc. Ao, ascending aorta; Desc. Ao, descending aorta; LA, left atrium;

LCA, left coronary artery; LPA, left pulmonary artery; LSCA, left subclavian

artery; PA, pulmonary artery; RA, right atrium; RPA, right pulmonary artery;

RVOT, right ventricular outflow tract. All images are courtesy of the Pediatric

Echocardiography Laboratory at the University of California, San Francisco.

(a)

(b)

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Many patients undergo cardiac catheterization to assessthe anatomy and resistance of the pulmonary vascula-ture. If patients have left-to-right shunting and pulmonaryhypertension, interventions in the cardiac catheterizationlaboratory may be undertaken to assess the reactivity of thepulmonary vasculature. Typically 100% oxygen or vasodila-tor therapy including nitric oxide response is utilized whileintracardiac and great vessel pressure and saturation meas-urements are repeated. If the PVR does not decline, thepatient may have fixed pulmonary vascular obstructive disease and not benefit from surgical correction.

Pressure and saturation information from cardiac catheter-ization may be codified in a graphic form for preliminary orfinal reports. An example is illustrated in Fig. 11.3. The anesthesiologist should be familiar with the format used fordisplaying preliminary information at their institution, asformal reports may not be available preoperatively if surgeryfollows soon after cardiac catheterization.

Magnetic resonance imaging

Improved technology in magnetic resonance imaging (MRI)and magnetic resonance angiography (MRA) has followedthe tremendous advances of echocardiography in the diagno-sis and assessment of CHD. Application thus far has beenpredominately for lesions that are difficult to evaluate byechocardiography, such as coarctation of the aorta, branchpulmonary arterial stenosis, pulmonary venous connections,vascular rings, and complex three-dimensional relationships.However increasingly refined techniques and the ability toperform functional assessment of ejection fraction and regur-gitant volumes position MRI for continued expansion in itsrole regarding preoperative assessment of CHD patients.Technologic advances including fast imaging have enhancedimage detail and permitted quantification of shunts, valvularregurgitation, and relative flow to the right and left pulmon-ary arteries.56 – 61

Advantages of MRI over other imaging techniques includethe absence of ionizing radiation or contrast agents. The effectiveness of echocardiography also decreases as childrengrow due to more limited acoustic windows. Therefore MRImay be an alternative as well as a complementary techniquein older children and adults with CHD.62 Magnetic reson-ance imaging is particularly successful for evaluation of someareas that traditionally difficult to assess with echocardio-graphy, such as right ventricular function and pulmonaryflow.56,58,60,61,63 Future perioperative applications include anaugmented role in determining the desirability and timing ofsurgery. For example the ability to assess right ventricularfunction may assist in the difficult question of timing for pulmonary valve replacement following initial correction of tetralogy of Fallot.64,65 Patients considered for the Fontanoperation also benefit from assessment of the dimensions ofthe right and left pulmonary arteries, which is facilitated with

potential comparison with intraoperative and postoperativeechocardiography. As a minimum, all preoperative echocar-diogram reports should be available for review and a pediatricechocardiographer should review any studies from outsidehospitals to determine the adequacy of the study and inter-pretation of the pathology.53 Preoperative echocardiographicassessment should be completed before admission to theoperating room and not rely upon an intraoperative trans-esophageal examination, as the acoustic windows are morelimited and physiologic conditions may be significantlyaltered by general anesthesia and positive pressure ventilation.

Cardiac catheterization

While the indications for cardiac catheterization have de-creased in tandem with the rise of other diagnostic modalit-ies, whenever preoperative cardiac catheterization has beenperformed the anesthesiologist should review the report. Itwill include measurements of pressure and oxygen satura-tion from some or all of the cardiac chambers. From thesedata pressure gradients, systemic and PVRs, and shunts maybe quantified. Systemic and pulmonary flow may be calcu-lated as absolute quantities or as a relative ratio, the Q· p : Q· s.A ratio of greater than 1 indicates left-to-right shunting whilea ratio of less than 1 indicates right-to-left shunting. Note thata ratio of close to 1 : 1 does not by itself rule out bidirectionalshunt. The Fick method is used for quantification of pul-monary and systemic flow, using oxygen consumption as the“indicator.” While actual oxygen consumption can be mea-sured, it is often estimated from tabled data. Angiography isusually performed to further define any anatomic structuresin question.54,55

Interpretation of data from patients with structural heartdisease is a challenge for the beginner; however, the basicprinciples for measurement and calculation are readilyunderstood. It is useful to follow the sequence of pressuresand saturations in a flow-directed pathway to detect evid-ence of obstruction or shunt. Normal values for newbornsand older children are presented in Chapter 25 (see Table 25.1,p. 411). Note that oxygen saturation is normally stable fromthe right ventricle to the pulmonary artery, and from the left atrium to the aorta. Deviations indicate intracardiacshunting. Pressures are normally equal on both sides of theAV valves at the end of diastole. Peak ventricular systolicpressure normally equals the peak systolic pressure in thecorresponding great vessel. Pressure gradients indicateobstruction at or near the valves. Pulmonary venous desatu-ration may indicate intrapulmonary shunt from lung disease,pulmonary arteriovenous malformation, or may result fromhypoventilation due to sedation for the procedure. Arterialdesaturation indicates right-to-left shunt in the heart, lungsor the great vessels. Formulae used to calculate flows, shunts,and resistances are presented in Chapter 25 (see Table 25.2, p. 412).

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Fig. 11.3 Cardiac catheterization diagram. Data from a 4-month-old patient with tricuspid and

pulmonary atresia are shown. This is a concise, convenient, one-page summary of the patient’s anatomy,

history, physiology, and catheterization data. It can be stored in paper or digital format and easily

projected for surgical case conference. Numbers followed by percentages are measured oxygen

saturations; plain numbers are pressure values. a, atrial a-wave pressure; ABG, arterial blood gas; BSA,

body surface area; BT, Blalock–Taussig; LPA, left pulmonary artery; LSVC, presence of a left superior vena

cava; m, mean pressure; McGoon, McGoon ratio of pulmonary artery to aorta size; PAR, pulmonary artery

vascular resistance; PVWP, pulmonary venous wedge pressure; Qp, pulmonary blood flow; Qs, systemic

blood flow; RLLPA, right lower lobe pulmonary artery; RPA, right pulmonary artery; Rp : Rs, ratio of

pulmonary to systemic vascular resistance; v, atrial v-wave pressure; VO2 cons, oxygen consumption.

MRI.66,67 Unlike echocardiography, it is rarely performed toestablish the primary cardiac diagnosis.

The MRI technique used to generate morphologic imagesis primarily sliced spin-echo images through the heart and

thorax. Imaging slices typically have a thickness of 5 mmwith a 1 mm gap between slices. Thinner slices and increasedexcitation may be used for areas of interest. Compensationfor cardiac and respiratory motion is achieved by synchro-

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191

Computerized tomography

While utilized less frequently than MRI, the use of contrast-enhanced conventional or spiral CT imaging has a distinctrole in the assessment of CHD patients, particularly thosewith vascular rings, aortic abnormalities, and pericardial disease.70 Ultra-fast CT scanning and electron-beam tomo-graphy acquire images more quickly than MRI and can beECG triggered to eliminate motion artifact. Therefore, somepediatric patients may tolerate ultra-fast CT scanning with-out the sedation that is normally required for more lengthyMRI examinations. When contrast is added to ECG-triggeredelectron beam tomographic images, fine resolution permits

nization with the ECG signal and a sensor on the patient’sabdomen. As multiple cardiac cycles are required to com-plete the image of each slice, the time to complete a study is somewhat dependent upon heart rate. When possible,breath holding or apnea is employed to eliminate respir-atory motion. For increased spatial resolution of vascularstructures gadolinium-enhanced MRA is performed. Three-dimensional reconstruction can also be performed using this technology, creating striking images (Figs 11.4 & 11.5).Physiologic information is derived from additional tech-niques including gated fast gradient-echo sequences andvelocity-encoded cine MRI. Blood flow can be calculatedfrom velocity and cross-sectional measurements.56,68 As ex-perience and technology grow, the role of MRI and MRA inthe management of CHD patients is very likely to expand.59,69

Fig. 11.4 Oblique sagittal T1-weighted magnetic resonance image

of the thorax in a 13-year-old boy showing moderate to severe aortic

coarctation (arrows). Dilation of the ascending aorta is also present.

Fig. 11.5 Oblique sagittal volume rendered image from a contrast

enhanced magnetic resonance angiography in a 15-year-old boy showing

severe aortic coarctation (arrows) just distal to the origin of the left

subclavian artery. Large collateral vessels are seen on the posterior superior

aspect of the thorax. Enlarged internal mammary arteries are also present

(arrowheads).

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catheterization is performed less often than in the past due toadvances in echocardiography and MRI.50,56,72 Because manyCHD patients are evaluated in outside medical centers priorto surgery, it is particularly helpful to review available infor-mation regarding elective cases several days in advance. Thisprovides time to obtain valuable data, reduces unnecessaryrepetition of tests, and allows for preparation of the patientand the perioperative team.

Preoperative goal no. 5: Prepare the patientand family

Patient and family education, and informedconsent

A detailed discussion of the role of the anesthesiologist in the upcoming surgery is required, incorporating informedconsent guidelines. The plans for premedication, monitoring,induction and maintenance of anesthesia, blood transfusion,and postoperative care are discussed. If the patient is oldenough to understand, he or she should be included in appro-priate sections of this discussion, reassured, and told what to expect. Particular emphasis should be placed on specificinstructions. Patients and their families receive a great deal of new information prior to congenital heart surgery. It is anatural time of apprehension for all concerned. For patientsbeing admitted on the day of surgery, instructions regardingeating and drinking, specific medications, and logistics mustbe communicated clearly and given to the patient and theirfamily in writing whenever possible.

diagnosis of intracardiac defects, pulmonary vascular anomal-ies, cardiac muscle mass and motion.71,72 However, the use ofionizing radiation and intravenous contrast remain (Fig. 11.6).

Preoperative goal no. 4: Determine if thepatient information is adequate

During a busy day caring for critically ill patients, the tempta-tion to accept available preoperative information as completemust be questioned continually. A critical approach is advoc-ated, with an eye open for key information that is not evident.Are the anatomic pathology and the proposed procedureclarified? The indication for surgery, impetus for its timing,and expected outcome for the individual patient must beunderstood. How does the proposed surgery fit into the long-term plan? Is the upcoming surgery palliative, corrective, orpart of a staged series of procedures? Is it urgent or elect-ive? Only when these questions have been answered can the anesthesiologist determine if the available information isadequate.

Generally, a recent ECG, echocardiogram, chest radiograph,and laboratory examination as outlined above are performed.A summary of information expected in the preoperativeassessment is found in Table 11.5. As mentioned, cardiac


192

Fig. 11.6 Severe aortic coarctation in a 19-year-old man diagnosed with

aortic coarctation using narrow collimation contrast enhanced multislice

computed tomography. The axial computed tomography image shows

severe aortic coarctation. The main pulmonary artery is seen branching into

the right and left pulmonary arteries. The ascending aorta is imaged in cross

section alongside the pulmonary artery. In comparison, the black arrow

indicates the severely narrowed proximal descending thoracic aorta.

Enlarged internal mammary arteries (double white arrows) and numerous

enlarged collateral vessels (arrowheads) are also present.

Table 11.5 Preoperative assessment.

All cases As indicated

History and physical exam X

Pulse oximetry X

Chest radiograph X

ECG X

CBC, electrolytes, BUN, creatinine X

Glucose, calcium X

Coagulation studies X

Blood type and antibody screen X

Blood crossmatch X

Echocardiogram: complete two-dimensional, X

spectral, and color Doppler study

Cardiac catheterization X

MRI/MRA X

Computerized tomography X

BUN, blood urea nitrogen; CBC, complete blood count; ECG,

electrocardiogram; MRA, magnetic resonance angiography; MRI, magnetic

resonance imaging.

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worsened by premedication unless pulmonary blood flow orlung function is affected. The anesthesiologist is generallypresent during and after premedication. Pulse oximetry maybe employed to monitor the effect on saturation with admin-istration, and supplemental oxygen should be immediatelyavailable. Judicious dosing is warranted in sicker patients,however, as transient decreases in saturation may occur76

and pulse oximetry is less accurate in lower ranges of satura-tion.77 Most patients are admitted on the day of surgery anddo not have an intravenous line in place. A variety of medica-tions have been used with success for sedation and anxiolysisin congenital heart surgery patients. General guides are thatpatients under 1 year of age rarely require premedication,oral medication is preferred to nasal, and injections are universally disliked.

Oral midazolam 0.5–1.0 mg/kg is usually an effective anxiolytic. Generally, no more than 20 mg of midazolam isadministered orally. If patients will not take an oral medica-tion, nasal midazolam 0.3 mg/kg can be rapidly injectedusing a short intravenous catheter or slip-tip syringe. A concentration of 5 mg/mL is recommended to minimize volume, although it is irritating to the nasal mucosa. Rarely, achild or developmentally delayed adult presents a particularchallenge with regard to premedication. In such cases keta-mine, 4–5 mg/kg with glycopyrrolate 10–20 µg/kg and mida-zolam 0.1 mg/kg can be injected intramuscularly. This mayalso be the agent of choice for induction patients in whom an inhalation induction is deemed risky. Oral ketamine mayalso be employed in doses of 2–10 mg/kg in combinationwith midazolam 0.5–1.0 mg/kg.75,78 Rectal administration of benzodiazepines and barbiturates is also reasonable forpatients 1–3 years of age.

Preoperative intravenous placement

Older children may express a preference for an intravenousinduction of anesthesia. Many have had ample experiencewith intravenous lines and phlebotomy. Premedication andplacement of a topical anesthetic cream is usually helpful;however, bravery often falters as anxiety mounts on the dayof surgery.

Communicate essential findings and plan

Both written and verbal communication are important com-ponents of the preparation for surgery. Because a great dealof information is often available for congenital heart surgerypatients, an appropriate summary focused upon the patho-physiology and issues pertinent to the anesthetic plan isappropriate. Anatomic findings that impact potential vascularaccess or monitoring, such as occluded vessels or anomalousorigin of the subclavian artery, are valuable parts of this sum-mary. Use of acronyms and names of rare syndromes shouldbe minimized in favor of clear, descriptive terminology. Any

Fasting, premedication, and preoperative orders

Preoperative fasting

Guidelines for fasting do not differ from other surgeries.Clear liquids are generally considered safe for small childrenand older patients up to 2 hours prior to surgery. Patientswith swallowing difficulties, gastroesophageal reflux, abnor-mal gastric motility, or neurologic disease may merit longerfasting times. Special attention is warranted to avoid dehy-dration in children scheduled for surgery later in the day,particularly those with cyanotic heart disease. If a patient ispolycythemic, taking diuretics, or has significant systemicoutflow obstruction, consideration should be given to admin-istering intravenous fluid preoperatively as the potential riskof dehydration is increased and the time of surgery may beunpredictable.

Medications

General principles apply regarding administration of regularmedications on the day of surgery, and most medications are given. It is especially important to continue inhalers forpatients with bronchospasm. Exceptions include diuretics in selected patients, and insulin in diabetic patients. Someexperienced clinicians withhold digoxin therapy for 1 dayprior to surgery with CPB as it is felt to represent a risk factorfor malignant ventricular arrhythmias associated with potas-sium fluctuations following bypass.34

Antibiotic prophylaxis for bacterial endocarditis

Prophylactic antibiotics for dental, oral, respiratory tract, gas-trointestinal, and genitourinary procedures are indicated inpatients with cardiac defects for prevention of endocarditis.Patients who have had congenital heart repairs should alsoreceive antibiotic prophylaxis with the exception of thosewho have had closure of a secundum ASD, VSD or PDA morethan 6 months previously. Patients with residual leaks shouldbe treated. The risk of postoperative endocarditis appears tobe greatest in patients with prosthetic valves, conduits, andgrafts as well as those with tetralogy of Fallot and aorticstenosis. The regimens recommended by the American HeartAssociation for antibiotic dosage are listed in Chapter 26.73

Premedication

The time of separation of the patient from his or her family isparticularly stressful for all concerned. Generous premedica-tion is usually helpful to reduce patient anxiety and facilitateseparation. If the structural facilities permit induction withthe family present, this may also be helpful. Cyanosis fromcardiac disease is not a general contraindication to premedi-cation.74,75 Desaturation due to intracardiac shunt will not be

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3 Whittemore R, Hobbins JC, Engle MA. Pregnancy and its out-come in women with and without surgical treatment of congen-ital heart disease. Am J Cardiol 1982; 50: 641–51.

4 Hoffman JI. Incidence, mortality and natural history. In: AndersonRH, Barker EJ, Macartney FJ et al., eds. Paediatric Cardiology, vol. 1.Edinburgh: Churchill Livingstone, 2002: 111–21.

5 Berry CL. Incidence, nature and etiology of malformations of theheart in man. Proc R Soc Med 1974; 67: 353–4.

6 Brick DH, Allan LD. Outcome of prenatally diagnosed congenitalheart disease: An update. Pediatr Cardiol 2002; 23; 449–53.

7 Abbott ME. Atlas of Congenital Cardiac Disease. New York: Amer-ican Heart Association, 1936.

8 Lev M. Pathologic diagnosis of positional variations in cardiacchambers in congenital heart disease. Lab Invest 1954; 3: 71–82.

9 Van Praagh R. Diagnosis of complex congenital heart disease;morphologic–anatomic method and terminology. CardiovascIntervent Radiol 1984; 7: 115–20.

10 Anderson RH, Becker AE, Freedom RM et al. Sequential segmentalanalysis of congenital heart disease. Pediatr Cardiol 1984; 5: 281–8.

11 de la Cruz MV, Nadal-Ginard B. Rules for the diagnosis of vis-ceral situs, truncoconal morphologies and ventricular inversions.Am Heart J 1972; 84: 19–32.

12 de la Cruz MV, Barrazueta JR, Arteaga M et al. Rules for diagnosisof atrioventricular discordances and spatial identification of ventricles. Br Heart J 1976; 38: 341–54.

13 Anderson RH, Wilcox BR. How should we optimally describecomplex congenitally malformed hearts? Ann Thorac Surg 1996;62: 710–16.

14 Edwards WD. Classification and terminology of cardiovascularanomalies. In: Allen HD, Gutgesell HP, Clark EB, Driscoll DJ, eds.Moss and Adams’ Heart Disease in Infants, Children, and Adolescents,6th edn. Philadelphia, PA: Lippincott, Williams & Wilkins, 2001:118–42.

15 Van Praagh R. The segmental approach to diagnosis in congenitalheart disease. In: Bergsma D, ed. Birth Defects Original ArticleSeries, vol. VIII, no. 5. Baltimore, MD: The National Foundationa

March of Dimes. Williams & Wilkins, 1972: 4–23.16 Anderson RH. Anatomy. In: Anderson RH, Barker EJ, Macartney

FJ et al., eds. Paediatric Cardiology, vol. 1. Edinburgh: ChurchillLivingstone, 2002: 37–55.

17 Edwards WD. Congenital heart disease. In: Schoen FJ, ed. Inter-ventional and Surgical Cardiovascular Pathology; Clinical Correlationsand Basic Principles. Philadelphia, PA: Saunders, 1989: 281–367.

18 Anderson RH. Terminology. In: Anderson RH, Barker EJ,Macartney FJ et al., eds. Paediatric Cardiology, vol. 1. Edinburgh:Churchill Livingstone, 2002: 19–36.

19 Bargeron LM. Angiography relevant to complicating features. In:Becker AE, Losekoot TG, Marcelletti C, Anderson RH, eds. PaediatricCardiology, vol. 3. Edinburgh: Churchill Livingstone, 1981: 33–47.

20 Rowe RD, Freedom RM, Mehrizi A et al. The Neonate with Con-genital Heart Disease. Philadelphia, PA: Saunders, 1981: 137–65.

21 Meliones JN, Kern FH, Schulman SR et al. Pathophysiologicaldirected approach to congenital heart disease: A perioperativeperspective. In: Society of Cardiovascular Anesthesiologists.Perioperative Management of the Patient with Congenital Heart Disease.Baltimore, MD: Williams & Wilkins, 1996: 1–42.

22 Rudolph AM. Congenital Diseases of the Heart: Clinical–PhysiologicConsiderations in Diagnosis and Management. Chicago: Year Book,1974.

important findings in the history or condition of the patientthat are not evident in the surgical assessment must be com-municated to the surgical team as early as possible, especiallyif they may impact the readiness of the patient for surgery as planned. When working with such complex patients, it is particularly helpful to speak with the surgical team pre-operatively when questions about the anatomic implications,therapeutic approach, or surgical plan remain.

Summary

The preoperative evaluation of patients prior to congenitalheart surgery is a special challenge because of the wide rangeof potential anatomic and physiologic abnormalities. An inter-disciplinary approach to assessment and review of diag-nostic studies is optimal for the preparation of the patient andthe perioperative team. The pediatric cardiac anesthesiolo-gist requires a working knowledge of pediatric cardiologyterminology and commonly used diagnostic modalities tointerpret the large amount of patient information that is accumulated for most cases. With these tools the physiologicconsequences of the malformed heart may be appreciatedalong with the remaining degree of cardiopulmonaryreserve.

A system for physiologic classification utilizing non-cyanotic and cyanotic categories with an emphasis on the roleof the ductus arteriosus is recommended. Anesthetic strat-egy follows from the physiologic category and condition ofthe patient rather than their specific anatomy in most cases.Attention should be paid to compensatory mechanisms andexisting therapies as they must be maintained during thepreparation for anesthesia and the pre-bypass period.

Patients at particular risk for deterioration at the outset of anesthetic care include those with left-sided obstructivelesions, such as aortic stenosis, and those with excess pul-monary blood flow for whom supplemental oxygen andmechanical ventilation may present new dangers. These individuals must be identified preoperatively and managedaccordingly. For most children over 1 year of age, includingthose with cyanosis, routine premedication is appropriateand safe with pulse oximetry and supplemental oxygenavailable.

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