Defect and Type of Repair

In an anatomic repair, the morphologic left ventricle is connected to the aorta, the morphologic right ventricle is connected to the pulmonary artery, the circulation is in series, and cyanosis is corrected. An anatomic repair may be categorized as either a simple or a complex reconstruction. In a simple anatomic repair, the heart is structurally normal, and correction for the most part is “curative” without long-term sequelae. Repair of uncomplicated, nonpulmonary hypertensive PDA, ASD, or VSD would fall into this category. In a complex anatomic repair, anatomic correction is achieved, but because of the complex nature of the surgical repair there may be significant long-term sequelae. Complex repairs comprise extensive (right and/or left) ventricular outflow tract reconstruction, placement of conduits or baffles, and atrioventricular valve repair. Examples include TGA, tetralogy of Fallot (TOF) with or without pulmonary atresia, severe aortic stenosis (AS), severe pulmonary stenosis (PS), atrioventricular septal defects, mitral stenosis, truncus arteriosus, and interrupted aortic arch. Although patients may report few symptoms or limitations to activities of daily living, significant limitations (e.g., reduced exercise or aerobic capacity, heart rate and blood pressure response to exercise) may be evident on objective testing.

In a physiologic repair, the circulation is in series and the cyanosis relieved, but the heart is either univentricular (single ventricle) or biventricular with the morphologic right ventricle being the systemic ventricle and the morphologic left ventricle being the pulmonary ventricle. Single-ventricle repairs result in connection of the systemic venous return directly to the pulmonary artery, thereby excluding the pulmonary ventricle. By relieving hypoxemia, single-ventricle repairs are “functionally corrective.” A physiologic biventricular repair is seen with the atrial switch operation (Mustard or Senning) for TGA, effectively resulting in a switch at the atrial level, with the right ventricle functioning as the systemic ventricle. One major clinical implication of a univentricular heart or systemic right ventricle is significant functional deterioration of the ventricle over time; progressive insufficiency of the systemic atrioventricular valve and dysrhythmias can be additional pathophysiologic features.

Anesthetic considerations: Patients with simple anatomic repairs who are asymptomatic have normal to near-normal hemodynamics and can generally be anesthetized in the same manner as patients with a structurally normal heart. Patients with complex anatomic repairs, because of the issues discussed later, are at increased perioperative risk. Physiologic repairs are always palliative and are associated with progressive ventricular dysfunction and other risk factors. Anesthetic management of patients with single-ventricle physiologic repairs is complex and can be associated with significant intraoperative problems if the pathophysiology is not well understood.

Shunting

A shunt is an abnormal communication between the systemic and pulmonary circulations, allowing blood to flow directly from one circulatory system to the other. A left-to-right shunt allows oxygenated pulmonary venous blood to return directly to the lungs rather than being pumped to the body, whereas a right-to-left shunt allows deoxygenated systemic venous blood to bypass the lungs and return to the body (Sommer et al., 2008). An increased workload is placed on the ventricles, with the degree (volume) of shunting determining the severity of symptoms. Factors influencing the direction and degree of shunting include the size of the shunt orifice, the pressure gradient between the chambers or arteries involved in the shunt, the relative compliance of the right and left ventricles, the ratio of pulmonary vascular resistance (PVR) to systemic vascular resistance (SVR), and the blood viscosity (hematocrit). Total pulmonary blood flow (Q_P) is the sum of effective pulmonary blood flow and recirculated pulmonary blood flow, whereas total systemic blood flow (Q_S) is the sum of effective systemic blood flow and recirculated systemic blood flow. Total Q_P and total Q_S do not have to be equal.

The lesions most likely to be encountered before repair that are associated with the potential for left-to-right shunting include large PDA, VSD, and atrioventricular canal defects; patients palliated with large, unobstructed modified Blalock-Taussig shunts (e.g., stage I repair of hypoplastic left heart syndrome) can behave similarly. Left-to-right shunting results in increased pulmonary blood flow, increased pulmonary vascular resistance, increased pulmonary artery pressures (PAP), increased left atrial volume or pressure, pulmonary edema, and volume overload of both the right and left ventricles leading to biventricular failure. Low aortic diastolic pressure accompanying large systemic-to-pulmonary artery shunts can lead to myocardial ischemia as well as organ hypoperfusion (e.g., bowel ischemia). Pulmonary overcirculation is associated with decreased lung compliance, increased airway resistance (Stayer et al., 2004), and airway compression (Berlinger et al., 1983). Alterations in pulmonary function lead to increased work of breathing (with increased energy expenditure), atelectasis, air trapping, and respiratory infections. The time course for developing pulmonary vascular occlusive disease (PVOD) with shunt reversal (right-to-left) and Eisenmenger’s syndrome depends on the size and site of the shunt and age at repair; patients with underlying anatomic or genetic predisposition to the development of pulmonary hypertension—for example, trisomy 21 children—can develop earlier, more severe PVOD for a given shunt (Chi and Krovetz, 1975; Gorenflo et al., 2002).

Right-to-left shunting results in decreased oxygen content of the systemic arterial blood, with the decrease in proportion to the volume of deoxygenated systemic venous blood mixing with the oxygenated pulmonary venous blood. Even with normal cardiac output, the decrease in tissue oxygen delivery limits exercise tolerance (Sommer et al., 2008).

Anesthetic considerations: Avoidance of air bubbles in intravenous catheters to prevent systemic embolization and attention to pulmonary vascular tone and its influence on the PVR-to-SVR ratio are important considerations. Factors influencing PVR are discussed later in the pulmonary hypertension section. In patients with left-to-right shunts, the major perioperative concerns are threats to already limited systemic blood flow. Routine clinical monitoring tools are unlikely to indicate an evolving problem in this regard until severe hypotension and evidence of myocardial ischemia ensue; in patients with shunt physiology, it is important both to maintain myocardial pump function (i.e., avoid myocardial depression) and to try to limit decreases in PVR. Such decreases (e.g., those that can be produced by hyperventilation or hyperoxia) can lead to a steal phenomenon with increased pulmonary blood flow (PBF). The major acute consequence will be decreased Q_S with increased risk for significant systemic hypotension and hypoperfusion; in the longer term, the increased Q_P that results can increase pulmonary congestion, lung water, and cardiac volume overload.

In patients who have or who are at risk for significant right-to-left shunting or who are dependent on a systemic-to-pulmonary artery shunt for pulmonary blood flow (e.g., after stage I repair of hypoplastic left heart syndrome [HLHS] or as the initial palliation for reduced blood flow lesions such a tricuspid atresia), primary management considerations are the maintenance of overall pump (cardiac) function and blood pressure and avoidance of factors that further increase PVR or decrease SVR (or both). It is important to note that the resultant arterial oxygen saturation in such patients will be affected by both the magnitude of the right-to-left shunting and the saturation of the shunted (essentially systemic venous return) blood.

Ventricular Dysfunction

Progressive ventricular dysfunction leading to congestive heart failure (CHF) is the most common cause of disability and death in patients with CHD (Warnes and Deanfield, 2001). The etiology is multifactorial and may result from the primary disease, many years of abnormal volume and pressure loading (which cause pathologic remodeling of numerous cardiomyocyte and nonmyocyte functions and processes), chronic hypoxemia, damage during surgical repair (inadequate myocardial preservation, scarring, poor repair, damage to coronary arteries), acquired disease (Graham, 1982), and arrhythmias (Shinbane et al., 1997; Deal, 2001). Ventricular volume overload occurs with intracardiac or extracardiac left-to-right shunts, valvular regurgitation, and single-ventricle lesions. The time course over which irreversible ventricular dysfunction develops is variable, but if surgical intervention to correct the volume overload is undertaken within the first year of life, residual dysfunction is uncommon (Cordell et al., 1976; Graham et al., 1976). Ventricular pressure overload results from residual or recurrent ventricular outflow obstruction or elevated PAP or PVR. The time to develop significant ventricular dysfunction is longer compared with a chronic volume load, so symptoms are uncommon unless the obstruction is severe and prolonged, or it is combined with a volume load (Graham, 1991). Chronic hypoxemia and cyanosis decrease ventricular oxygen supply and increase oxygen demand through increased work related to increases in pulmonary and systemic vascular resistance with associated polycythemia. Myocardial ischemia resulting from coronary artery anomalies or kinking or torsion after reimplantation may also cause ventricular dysfunction.

Anesthetic considerations: The chronic presence or potential to develop or exacerbate low systemic cardiac output is probably the single most important consideration in approaching the care of patients with CHD. Attempts to correlate clinical status and functional myocardial reserve can be unreliable. No single parameter or test is best to assist with this assessment. Rather, one is advised to carefully integrate historical, physical, and diagnostic test information pertaining to myocardial performance to arrive at an integrated assessment of the degree of ventricular dysfunction, as well as the potential for further decompensation that can occur as a result of anesthetic choices and procedural factors. Although there is no single recipe, key aspects of successful management include appropriate fluid administration, usually with maintenance of normal to modestly increased preload, and selection of suitable anesthetic induction and maintenance techniques most likely to maintain contractile function and hemodynamic stability. These techniques should also be chosen to minimize the possibility of airway obstruction and hypoventilation. Of note, positive pressure ventilation is likely to improve the function of a dysfunctional systemic ventricle according to Laplace’s law, by the effect of increased intrathoracic pressure to decrease transmural myocardial pressure and hence decrease ventricular afterload. In instances of significant myocardial dysfunction, prophylactic inotrope administration before or soon after induction and also during the procedure may be beneficial.

Hypoxemia and Cyanosis

Cyanosis is associated with decreased pulmonary blood flow or intracardiac mixing lesions, or both. Prior to repair, cyanotic lesions include tricuspid atresia, pulmonary atresia, tetralogy of Fallot, transposition of the great arteries, and truncus arteriosus; tricuspid atresia, pulmonary atresia, and TOF are all lesions that typically have reduced PBF. Increased PBF occurs in truncus arteriosus. In lesions with intracardiac mixing (e.g., TGA), cyanosis can occur with decreased or increased PBF depending on whether there is obstruction to the PBF. Cyanosis may also be found in the setting of very low cardiac output, increased arteriovenous oxygen difference, and respiratory disease. With the advent of early infant repair, chronic hypoxemia is now most frequently encountered in the young child undergoing staged repair, and in the adult with unrepaired or palliated CHD. Indeed, one stimulus for early, definitive repair is to eliminate hypoxemia and the compensatory polycythemia, with its rheologic, neurologic, hemostatic, renal, and metabolic consequences. Although the analyses are limited and imperfect for obvious reasons, the data that does exist suggests that chronic hypoxemia during infancy and early childhood is a significant risk factor for reduced cognitive performance. As blood viscosity increases, systemic (including coronary) and pulmonary vascular resistances increase markedly. Hemostatic abnormalities that can result from cyanosis and polycythemia include thrombocytopenia, platelet dysfunction, shortened platelet survival, disseminated intravascular coagulation, decreased production of coagulation factors, and primary fibrinolysis (Tempe and Virmani, 2002; Odegard et al., 2003, 2009). Sludging of red blood cells increases the risk for thromboembolism and stroke, particularly when the hemoglobin approaches or exceeds, 20 g/dL, and in conjunction with dehydration. Phlebotomy regimens are being used less frequently in the absence of symptoms, as they may be associated with an increased risk for cerebrovascular events (Ammash and Warnes, 1996). The duration and degree of hypoxemia and polycythemia are important historical factors in the evaluation of possible long-term residual cardiac muscle blood flow abnormalities.

Anesthetic considerations: It is important to maintain adequate preoperative hydration by encouraging liberal clear fluid intake in accordance with fasting guidelines or placement of an intravenous catheter and administration of maintenance fluids. Although the data are scant, preoperative hydration may be especially important as the hemoglobin concentration exceeds, 20 g/dL, and some consideration should be given to reducing red cell mass (pheresis, normovolemic phlebotomy) at higher hemoglobin values, perhaps particularly before more complicated procedures. There is an increased risk of bleeding in association with increased tissue vascularity, hemostatic abnormalities, and anticoagulants, and the risks of regional anesthesia in the presence of a hemostatic abnormality should be carefully considered. Of note, the effect of anemia on oxygen-carrying capacity is exaggerated as hemoglobin values “within the normal range” in cyanotic patients may represent a significant deficit. Other aspects of anesthetic management should be based on the underlying pathophysiology, as discussed later.

Rhythm and Conduction Abnormalities

Arrhythmias and conduction defects have a major impact on the prognosis and management of patients who have undergone palliation or repair of CHD (Warnes and Deanfield, 2001). Rhythm disturbances that may be well tolerated in a structurally normal heart may be life threatening in a structurally or functionally abnormal heart. The etiology is multifactorial and includes damage to the arterial supply or direct injury to the sinoatrial node, atrioventricular (AV) node, and conduction system, atrial or ventricular scarring, chamber dilation or hypertrophy with resultant pathologic remodeling, and myocardial ischemia.

Arrhythmias may occur in the postoperative period or many years after surgery, and they tend to vary with the type of underlying heart disease and surgical procedures that have been performed (Vetter, 1991). Supraventricular tachycardias (atrial flutter/intraatrial reentrant tachycardia, atrial fibrillation) and sinoatrial node dysfunction (bradycardia, tachy-brady syndrome, exit block, sinus arrest) are more common in lesions that required extensive intraatrial surgery or have residual elevations in right atrial pressure, such as the atrial switch (Mustard or Senning) procedure for TGA, the Fontan procedure, and TOF repair. Isolated right bundle branch block is frequent after ventriculotomy. The QRS duration may be an independent predictor of arrhythmia, right ventricular dysfunction, and sudden death risk in patients after TOF repair (Gatzoulis et al., 2000a). Whether aberrant conduction and ventricular dyssynchrony are independent causes of ventricular dysfunction and, consequently, whether using biventricular pacing to restore normal activation-contraction patterns can prevent or reverse ventricular function in patients with dyssynchrony is currently under investigation (Cecchin et al., 2009). Ventricular arrhythmias are more common in lesions with residual ventricular pressure or volume load, as in aortic stenosis, hypertrophic cardiomyopathy, and TOF repair. Tachyarrhythmias and ventricular dysfunction are a dangerous combination and a cause of late sudden death (Vetter, 1991).

Anesthetic considerations: Any new onset of palpitations or syncope should be investigated before elective surgery. Consultation with a pediatric electrophysiologist can be very helpful to understanding the risk factors and causes for various rhythm disturbances in the CHD population, the need for additional diagnostic procedures, and the preferred pharmacologic and electrical approaches to the rhythm disturbances likely to arise. Such discussions help ensure availability and appropriate use of antiarrhythmic agents and cardioversion/defibrillation devices. The availability of similar expertise consultation during procedures is also advisable. In patients with tachyarrhythmias, there is at least theoretical reason to avoid agents with vagolytic or sympathetic-stimulating properties (e.g., pancuronium). The electrophysiologic impact of most inhaled or intravenous agents is probably modest.

Existing pacemakers should be checked preoperatively and the appropriate precautions taken in patients with complete AV block. There is the need for preoperative evaluation and temporary resetting or shutting down of pacemakers and implantable cardioverter defibrillators (Practice advisory, 2005), as well as backup pacing (transcutaneous pacing) in the event of pacemaker malfunction. For high-risk patients, an external pacing or defibrillator unit should be in the operating room and pads applied around the time of induction of anesthesia. The need for and use of electrocautery (monopolar versus bipolar) in pacemaker-dependent patients should be discussed with both the surgeon and electrophysiologist. Implanted pacemakers and cardioverter defibrillators typically need to be interrogated and reprogrammed after the surgical procedure. The electrophysiologist may also be helpful for patient optimization. For example, consideration should be given to temporary pacing in select unpaced patients with bradycardia, as well as to radiofrequency catheter ablation in patients with amenable tachyarrhythmias, especially before major procedures.

Pulmonary Hypertension

In the unrepaired child, unrestricted left-to-right shunting with increased pulmonary blood flow produces a volume load on the heart and structural changes in the pulmonary vascular bed (medial hypertrophy progressing to necrotizing arteritis [Heath and Edwards, 1958]), leading to decreased myocardial function and pulmonary hypertension (mean PAP greater than 25 mm Hg). The time course for developing PVOD depends on the size and site of the shunt and age at surgery. Progression is more rapid when both the volume and the pressure load on the pulmonary circulation are increased, such as with a large VSD. For the majority of infants with an unrestrictive shunt, repair of the defect in the first year of life is usually associated with regression of the pulmonary vascular changes. Pulmonary hypertension develops more slowly with increased pulmonary blood flow in the absence of elevated pulmonary artery pressures, as with an ASD, where the absence of pulmonary hypertension into the third decade or beyond is not uncommon. Eisenmenger’s syndrome is characterized by irreversible PVOD and cyanosis related to reversal of the left-to-right shunt (Wood, 1958).

Pulmonary hypertension and increased PVR can be reactive, fixed, or a combination of the two. The reactivity of the pulmonary vascular bed is determined during cardiac catheterization by the changes in PAP and PVR in response to vasodilators such as oxygen and nitric oxide (NO). Factors increasing PVR include hypoxemia, hypercarbia, acidemia, extremes of lung volume, hypothermia, and sympathetic stimulation associated with stress or light anesthesia. Acute dramatic increases in PAP or PVR result in increased RV afterload with decreased RV stroke volume; in addition, resultant RV dilation can cause a leftward shift of the interventricular septum, with further impairment of left ventricular (LV) function and filling, and decreased cardiac output. The ensuing hypotension can result in myocardial ischemia (particularly of the RV), bradycardia, and cardiac arrest. If an intracardiac communication (patent foramen ovale [PFO], ASD, VSD) is present, increases in PAP lead to right-to-left shunting and desaturation, albeit with better maintenance of LV filling and systemic cardiac output.

Anesthetic considerations: Severe pulmonary hypertension appears to impart major anesthetic risk, even for minor procedures (Ammash and Warnes, 1996; Raines et al., 1996; Daliento et al., 1998; Martin et al., 2002; Carmosino et al., 2007). This topic has been the subject of recent reviews (Subramaniam and Yared, 2007; Friesen and Williams, 2008). Suprasystemic pulmonary artery pressure is a significant predictor of major complications in children with pulmonary hypertension undergoing noncardiac surgery (Carmosino et al., 2007). It is not possible to recommend a specific anesthetic technique as all anesthetic techniques have been used successfully. Of note, many perioperative deaths occur in the postoperative period (Lyons et al., 1995; Martin et al., 2002). In older patients with Eisenmenger’s syndrome, most deaths appear to occur either as a result of the surgical procedure and not of anesthesia, or in the postoperative period because of complications such as atelectasis, pneumonia, worsening hypoxemia, or other end-organ dysfunction (Martin et al., 2002). Preoperative knowledge of the degree of pulmonary hypertension, pulmonary vascular reactivity, right ventricular dysfunction, and the presence of an intracardiac communication is imperative. For example, patients with severe pulmonary arterial hypertension, significant RV dysfunction, and no “pop-off” communication (i.e., right-to-left shunt) are probably the most at risk.

Acute right ventricular dysfunction and resultant low systemic cardiac output are the major pathophysiologic consequences of acute exacerbations in pulmonary artery pressure. The overall goals of anesthesia, therefore, are to provide adequate analgesia and anesthesia while minimizing increases in PVR and depression of myocardial function (Friesen and Williams, 2008). Likely methods include providing adequate preoperative sedation, high inspired oxygen, hyperventilation (respiratory alkalosis) if possible, adequate depth of anesthesia, maintenance of a normal to increased preload, early use of an inotrope to support RV function and systemic blood pressure (i.e., RV perfusion), and use of induction and maintenance agents that do not significantly reduce contractility or systemic blood pressure. Endotracheal intubation as a potential mechanical trigger of pulmonary vasoreactivity should be recognized; this also applies to extubation on emergence from anesthesia. In addition to adequate anesthetic depth, lidocaine spray to the vocal cords and trachea may offer some degree of protection. Noninvasive ventilation may be an attractive alternative to support adequate gas exchange during anesthesia and surgery under some conditions. Although allowing better control of oxygenation and ventilation, positive pressure ventilation increases RV afterload and decreases RV filling so that excessive inspiratory pressures and volumes, and positive end-expiratory pressure (PEEP), should be avoided. It is critical that pulmonary vasodilator therapy not be interrupted perioperatively, particularly prostacyclin (Flolan) infusions, whose discontinuation can result in severe rebound pulmonary hypertension in as little as 10 to 15 minutes. With severe pulmonary hypertension and known responsiveness of the pulmonary vasculature to NO, it is advisable to have NO available for immediate or even prophylactic administration. The use of invasive monitoring (e.g., arterial blood pressure) is usually determined by the nature of the surgical procedure. Because of the significant morbidity and mortality of anesthesia and surgery for the patient with severe pulmonary hypertension, a risk-benefit analysis involving the cardiologist, surgeon, and anesthesiologist is essential before performing elective procedures.

Myocardial Ischemia

Coronary artery anomalies (e.g., intramural coronary, anomalous origin from the other sinus or pulmonary artery) or problems associated with coronary reimplantation in the arterial switch operation can result in myocardial ischemia. More commonly, in many patients with congenital defects and normal coronary arteries, ischemia is secondary to imbalances in myocardial oxygen supply and demand. There is some evidence, in lesions associated with abnormal load, including ones where the RV is the systemic ventricle, that coronary angiogenesis and capillary supply may not keep pace with increased muscle mass. This creates a relative supply-demand inequity. Subendocardial perfusion is largely determined by coronary perfusion pressure, which is the aortic diastolic pressure minus the ventricular end-diastolic pressure. In addition, the time interval available for perfusion (predominately diastole) is critical. As a result, the relationship between diastolic blood pressure, ventricular end-diastolic pressure, and heart rate determines whether subendocardial ischemia occurs. These three factors place patients with CHD at risk for ischemia in the following situations: (1) the systolic pressure in the ventricles is abnormally elevated (in some cases, the pulmonary ventricle may have suprasystemic pressures), thereby requiring elevated perfusion pressure; (2) the aortic diastolic pressure is compromised by diastolic runoff of aortic blood into the lower resistance pulmonary circuit in ductal-dependent and systemic-to-pulmonary artery shunts (coronary perfusion is further compromised if the coronary ostia are perfused with desaturated blood, as in patients with HLHS); (3) elevated ventricular end-diastolic pressure, which may be the result of impaired systolic function, impaired diastolic function (reduced ventricular compliance and relaxation, as seen with ventricular pressure overload), increased ventricular end-diastolic volume (volume overload), or a combination of these; and (4) increases in heart rate, which geometrically reduce the duration of diastole (the duration of systole stays relatively constant) so that the time available for coronary perfusion falls and consequently a higher diastolic pressure is necessary to maintain the same degree of subendocardial perfusion. In particular, the combination of a high heart rate and low diastolic blood pressure can produce significant ischemia.

Anesthetic considerations: Standard principles are followed to ensure that myocardial oxygen supply exceeds demand apply. In particular, maintaining aortic perfusion pressures, in combination with avoiding excessive tachycardia, frequently appears to be critical. With cyanotic lesions, a hemoglobin level above the normal acceptable range may be necessary.

Infective Endocarditis

The most recent guidelines of the American Heart Association concluded that only an extremely small number of cases of infective endocarditis could be prevented by antibiotic prophylaxis for dental procedures (Wilson et al., 2007). As a result, infective endocarditis prophylaxis for dental procedures is recommended only for patients with underlying cardiac conditions (Box 21-2) associated with the highest occurrence and risk for adverse outcome from infective endocarditis. Prophylaxis in this group is recommended for all dental procedures that involve manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa. The antibiotic is administered in a single dose before the procedure (Table 21-1). Administration of antibiotics solely to prevent endocarditis is not recommended for patients who undergo a genitourinary or gastrointestinal tract procedure.

Rarely, patients scheduled for an invasive procedure have endocarditis, in which case the results of blood cultures should guide antibiotic therapy.

End-Organ Dysfunction and Injury

Unrestricted left-to-right shunting, in addition to increasing PAP and PVR, produces alterations in lung mechanics and airway compression. The primary effects on lung mechanics are a decrease in lung compliance and an increase in airway resistance (Bancalari et al., 1977; Stayer et al., 2004). Decreased compliance will necessitate higher than expected airway pressures, with care being taken not to insufflate the stomach during mask ventilation. Airway compression can result from dilated pulmonary arteries, left (or right) atrial dilation, massive cardiomegaly, or intraluminal bronchial obstruction (Berlinger et al., 1983). The pulmonary lymphatics are also compressed in these circumstances, perhaps explaining an increased incidence of pulmonary infectious symptoms in patients with large left-to-right shunts.

Neurologic injury and adverse neurodevelopmental outcome in CHD patients are multifactorial, with various contributions from genetic, lesion, and procedural elements (Newburger and Bellinger, 2006). Relatively pervasive issues include hyperactivity, diminished executive function, and various other neurocognitive abnormalities, especially in areas pertaining to speech and language and executive functions. Less commonly seen in the current era are seizures, stroke, and choreoathetosis. Structural brain abnormalities have been found with magnetic resonance imaging (MRI) in infants with CHD before any intervention, as well as after surgery or balloon atrial septostomy (Mahle et al., 2002; McQuillen et al., 2006; McQuillen et al., 2007; Miller et al., 2007; Andropoulos et al., 2010). Complex CHD may have anywhere from a mild to a profound impact on a child’s psychosocial development (Horner et al., 2000). These issues necessitate additional sensitivity with the family, altering the amount of detail discussed in front of the child when obtaining informed consent, and precluding certain sedation or regional anesthetic techniques.

Chronic cyanosis, low systemic cardiac output, or high venous pressures (Damman et al., 2009) may over time contribute to the development of renal and hepatic insufficiency. This may not be evident on routine laboratory tests (e.g., serum creatinine or liver enzymes) but may predispose to perioperative dysfunction in response to relatively minor changes in organ perfusion and oxygen delivery, or to otherwise relatively mild toxic stresses (e.g., ketorolac). Cardiac catheterization (contrast nephropathy) increases the risk for perioperative renal dysfunction (Briguori et al., 2007).

Extracardiac Anomalies

Extracardiac anomalies occur in 25% of infants seen during the first year of life in patients with cardiac disease (Greenwood et al., 1975). The anomalies are often multiple and may result from chromosomal, genetic, teratogenic, or unknown causes.

Anesthetic considerations: A focused airway examination and thorough assessment of all organ systems is essential.

Heart Transplant Recipients

The worldwide annual transplant rate in children is around 400, with the major indications being cardiomyopathy and congenital heart disease (Kirk et al., 2008). Factors to consider in this population are cardiac physiology and functional status, cardiac allograft vasculopathy, rejection, the side effects of immunosuppressive agents, and the development of renal dysfunction, hypertension, and malignancy. Efferent denervation results in a resting tachycardia (withdrawal of vagal tone) and impaired chronotropic response to stress. Afferent denervation results in lack of angina during myocardial ischemia and alterations in cardiac baroreceptors and mechanoreceptors. Cardiac physiology is restrictive, with mildly elevated filling pressures and a low-normal ejection fraction (Cotts and Oren, 1997). There may be sinus node dysfunction and there is a shift from β₁ to β₂ receptors.

Anesthetic considerations (see Chapter 20, Anesthesia for Congenital Heart Surgery, for a more complete discussion): The response to hemodynamic instability is slower (dependence on circulating catecholamines) and less robust. The denervated heart is preload dependent, with a reduced chronotropic response to hypotension or sympathetic stimulation. Restrictive physiology, particularly with rejection, increases the risk for pulmonary edema when fluid administration is not judicious. Sensitivity is increased to direct-acting catecholamines, β-blockers, adenosine, and verapamil, and it is decreased to digoxin and indirect-acting sympathomimetic agents. Myocardial ischemia is an ever-present threat from coronary artery vasculopathy. A new onset of dysrhythmias or heart block is ominous, suggesting rejection or myocardial ischemia. Immunosuppression requires strict aseptic technique, and the hypertension and nephrotoxicity associated with some agents and possible need for stress-dose corticosteroids need to be addressed.

History and Physical Examination

As the history may be incomplete or misleading with complex CHD (Colman, 2003), close collaboration with the patient’s cardiologist is valuable. Additionally, the cardiologist can help identify patients at high risk, clarify pathophysiologic issues, establish if the current clinical status is the best possible, and provide the findings of recent cardiologic studies. The focus of the history should be on the type of lesion and factors listed in Box 21-1, prior surgical and catheterization procedures and complications thereof, anesthetic experience, medications, allergies, and current functional status. Specific symptoms that should be sought are feeding difficulties and sweating in infants, poor growth, cyanotic spells, decreased activity level such as inability to keep up with healthy peers, fatigue, dyspnea, palpitations, chest pain, and syncope. New or worsening symptoms require cardiology consultation. Recent respiratory tract infections can cause changes in pulmonary vascular resistance and airway reactivity, increasing anesthetic risk in the setting of decreased pulmonary compliance, pulmonary hypertension, systemic-to-pulmonary artery shunts, and cavopulmonary anastomosis.

The physical examination should include general appearance, level of activity, presence of distress, and vital signs. Arterial oxygen saturation (SpO₂) varies with clinical status, but is expected to be above 94% after definitive procedures and in the range of 75% to 85% after palliative interventions that create shunted or intracardiac mixing circulations. Evidence of tachycardia, cyanosis, tachypnea, labored breathing, congestive heart failure, and poor peripheral perfusion should be sought. Airway assessment is important, because extracardiac anomalies may be present in up to one quarter of patients with CHD (Friedman, 1997). Peripheral pulses and four extremity blood pressures should be assessed in the setting of known or suspected aortic arch obstruction, previous or present Blalock-Taussig shunts, or after multiple cardiac catheterizations.

Special Investigations

The extent of laboratory testing depends on the child’s clinical status and the complexity of the planned procedure. General recommendations for blood testing include the following: (1) hematocrit or hemoglobin if the child is pale, cyanotic, or undergoing a procedure with the potential for significant blood loss; (2) serum electrolytes for patients with renal dysfunction or those receiving diuretics, angiotensin-converting enzyme inhibitors, or digoxin (although preoperative electrolyte disturbances in children and young adults presenting for cardiac surgery are uncommon [Hastings et al., 2008]); (3) platelet count and coagulation studies for cyanotic children or those on anticoagulants or antiplatelet agents; and (4) blood typing and cross-matching if significant blood loss is anticipated. A chest radiograph should be obtained with new cardiorespiratory symptoms or abnormal findings on clinical examination, or if dictated by the surgical procedure. Cardiologic studies should be coordinated with the child’s cardiologist, because some tests will have been recently completed, and investigations such as cardiac catheterization, Holter monitoring, exercise stress tests, and cardiac MRI mandate the cardiologist’s input. The electrocardiogram is reviewed for rhythm abnormalities, impaired conduction, chamber enlargement, and ischemia. Changes from prior studies need to be explained before proceeding. Preoperative consultation with the cardiologist is essential for patients with pacemakers, with evaluation of the pacemaker and a clear plan made for appropriate adjustment on the day of surgery (see earlier) (Practice advisory, 2005). In all but the simplest lesions, recent echocardiography is probably useful to document the current status of anatomy and ventricular function.

Procedure Scheduling

Institutional practices vary in the provision of anesthetic care for the highest-risk children with CHD. The aging of the CHD population has also resulted in adults with CHD undergoing noncardiac procedures at pediatric institutions (Warnes et al., 2001). In some institutions, anesthesia is provided by those who routinely practice pediatric cardiac anesthesia, and in others (including our own) pediatric anesthesiologists who do not practice cardiac anesthesia provide the care (Walker et al., 2009). The important point is that the case be assigned to an anesthesiologist who will understand the cardiac pathophysiology and know how to prevent and promptly deal with cardiac-related complications.

Ideally, patients with significant CHD should be scheduled for surgery early in the day. Clinical advantages include minimizing the effects of dehydration on hemodynamic function (particularly in infants and in cases of obstructive lesions, shunt-dependent circulations, cyanotic disease, single-ventricle physiology), possible reduction in the increased myocardial oxygen consumption associated with prolonged anxiety, provision of additional time to monitor patients in the postanesthesia care unit if discharge to home is being considered, greater availability of additional support if necessary, and avoidance of multiple care teams.

Premedication

The younger child will usually benefit from oral premedication before placement of an intravenous catheter. Premedication is especially beneficial for children with cyanotic CHD, particularly those with hypercyanotic spells, catecholamine-induced arrhythmias, and preexcitation syndromes. Although the potential effects of hypoventilation and hypoxemia on PVR need to be considered in the setting of pulmonary hypertension, sympathetic stimulation in a distressed patient may have a more deleterious effect.

Midazolam, 0.5 to 0.75 mg/kg orally, is usually sufficient, but for patients who have had multiple surgeries and catheterizations and thus are likely to be more anxious and perhaps more tolerant to sedative medications, it is often necessary to increase the dose to 1 mg/kg (Masue et al., 2003); sometimes oral ketamine, 3 to 10 mg/kg, is added as well (Auden et al., 2000; Funk, et al., 2000). Troublesome ketamine-stimulated secretions can usually be controlled with glycopyrrolate once intravenous access is established. If the patient has intravenous access in situ or after placement, a small bolus of midazolam, 0.05 mg/kg, repeated as necessary, will provide anxiolysis and facilitate separation from the parents. Intramuscular sedation with ketamine, 3 to 5 mg/kg, with or without midazolam, 0.05 to 0.1 mg/kg, may be necessary for the uncooperative or combative child who will not accept oral premedication and for whom an intravenous induction is most desirable. A combination of oral meperidine and pentobarbital for heavy premedication of CHD patients has been used with a substantial track record of safety and success (Nicolson et al., 1989), but insufficient effect and rage-like reactions (most likely attributable to pentobarbital) are known side effects. After any heavy premedication, the anesthesiologist should remain with the patient, and, particularly for patients with cyanotic CHD, oxygen saturation should be monitored and oxygen administered as needed (Stow et al., 1988; DeBock et al., 1990).

Anesthetic Technique