Chapter 12. Anesthesia for Patients with Congenital Heart Disease

• The incidence of congenital heart defects is approximately 8 in 1000 births.1 Over the course of the past decades survival of children with congenital heart disease has improved. Today, adults can present following various cardiac surgical repairs, for routine general and obstetric anesthesia care. Unfortunately, the frequently multistaged surgical repairs necessary to improve survival in children often result in complications in adulthood. Knowledge of the anatomy of the original structural defect and the repairs undertaken is essential in the choice of appropriate monitoring and anesthetic techniques for otherwise routine procedures. Moreover, these patients may require heart surgery and/or cardiac transplantation later in life. This chapter highlights the anatomy and physiology of common congenital heart defects and outlines the repairs associated with them. In general, surgical repairs are directed at ensuring the delivery of oxygenated blood to the systemic tissues and eliminating communications between the right and left heart. Of course, for some congenital heart disease (CHD) patients the distinction of which is the right heart and which is the left heart may not be entirely clear. Consequently, when considering the CHD patient, tracing the flow of blood through the chambers of the heart into the circulation and back again provides the basis toward acquiring an understanding of CHD.

Atrial septal defects (ASD) are abnormal communications between the left (LA) and right atrium (RA). A patent foramen ovale (PFO) can be present in up to 25% of the population and produces a small interatrial communication as a consequence of failure of the septum primum and septum secundum to fuse. ASDs account for 6% to 10% of the CHD population and present in a variety of ways.2 Eighty percent of ASDs are of the ostium secundum type (Figure 12–1 and Videos 12–1A and 12–1B) located in the middle of the interatrial septum. Defects located lower in the atrial septum (toward the atrial-ventricular [AV] valves) are ostium primum ASDs and are at times associated with a ventricular septal defect (VSD) as well. Sinus venosus ASDs occur close to the junctions of the superior vena cava (SVC) or inferior vena cava (IVC) with the RA. Sinus venosus ASDs are often associated with pulmonary vein anomalies and anomalous return of oxygenated pulmonary vein blood to the right atrium.

ASDs generally produce a left-to-right shunt of blood across the defect. Thus, oxygenated blood is delivered into the right heart circulation to be returned to the lungs through the pulmonary artery. The oxygen saturation of the RA is increased and RA and right ventricular (RV) volume is increased. The amount of blood, which flows between the chambers, is dependent upon both the size of the defect and the pressure gradient between the chambers. A ratio of the pulmonary blood flow (Qp) to the systemic blood flow (Qs) less than 1.5 is often adequately tolerated; however, when the Qp/Qs ratio exceeds 3, symptoms secondary to overload of the pulmonary circulation appear.3 Over time, pulmonary artery hypertension can develop resulting in RV hypertrophy and failure. Eventually, right-sided pressures can exceed those of the left heart resulting in an Eisenmenger syndrome where deoxygenated venous blood flows in a right-to-left direction producing hypoxemia.

Over time many small defects of < 3 mm will close spontaneously; however, defects greater than 8 mm generally will not resolve spontaneously.4,5 Approximately 20% of ASDs will close during the first year of life and many go undetected even into adulthood. However, patients with ASDs are at risk for bacterial endocarditis and paradoxical right-to-left embolism and stroke. Larger ASDs often become manifest in the patient's third decade heralded by complaints of dyspnea, arrhythmias, and congestive heart failure (CHF).3

The indications for surgical or catheter-mediated repair of an ASD include:

• RV volume overload
• Qp/Qs > 2
• Elective closure prior to entering school

Although some ASDs will close spontaneously, those children with sinus venosus and ostium primum ASDs have no chance of resolution without intervention.

Surgical closure of ASDs requires the use of cardiopulmonary bypass (CPB). Depending upon the size of the defect being repaired surgeons can perform either a primary suture closure of the defect or use a pericardial or synthetic patch.

Children taken to surgery for ASD repair are premedicated with oral or intravenous midazolam. Invasive arterial pressure monitoring is employed. Anesthesia induction can be through the use of inhalational agents or intravenous agents. The intravenous induction of anesthetic may be slower as the concentration of induction agent is diluted by flow from the left atrium. Conversely, the recirculation of vapor rich blood from the left heart to the pulmonary circulation will raise the partial pressure of inhalational agent in the lungs and thus in the brain, speeding induction. A reduced fraction of inspired oxygen (FiO2) is suggested for patient management following control of the airway to maintain pulmonary vascular resistance (PVR) and thus decrease left-to-right shunt. Maintenance of anesthesia in the pediatric population is with a combination of opioids, inhalational agents, and muscle relaxants. Prior to cannulation for the initiation of CPB, heparin is administered as in the adult population. Often CPB times are relatively brief and the patients are generally separated from CPB with little need for inotropic support. Following repair of the ASD, pressure within the LA will increase and right atrial pressure (CVP) will decrease secondary to elimination of left-to-right flow into the RA. A left atrial pressure line can be placed by the surgeon to discern left ventricular preload.3 Surgical mortality is low and hospital length of stay generally less than 4 days.

Many ASDs can be closed with devices delivered by a cardiac catheter. These procedures are performed under fluoroscopic and echocardiographic guidance and eliminate the need for sternotomy and CPB. Patient selection is essential to identify those most amenable to catheter-mediated repairs. Ostium primum and sinus venosus ASDs generally are not correctable by catheter-based approaches due to the location of the defect and associated pathologies. The Amplatzer septal occluder system (AGA Medical Corporation, Golden Valley, Minnesota) consists of two attached circular discs. The larger of the two discs faces the LA while the smaller disc faces the RA (Figure 12–2). The device straddles the defect in the atrial septum after being introduced via a catheter placed in a femoral vein. Over time, heart tissue overgrows the device incorporating it into the heart and occluding the ASD. The procedure is usually performed under general anesthesia. Complications are rare but include: air embolization, device dislodgement into the left atrium, and device impingement onto the tricuspid and mitral valve. An antithrombotic regimen is required for 6 months or longer to prevent clot formation on the surface of the device. Additionally antibiotic prophylaxis is necessary prior to certain surgical procedures in patients following device placement.

Ventricular septal defects (VSDs) are abnormal communications between the left and the right heart through the ventricular septum (Video 12–2 and 12–3). VSDs represent 20% of congenital heart defects.6 VSDs are classified by their location along the ventricular septum7:

• Type I: 5% to 7% of VSDs are Type I or sub-arterial VSDs. They are also known as supracristal, outlet, subpulmonary, infundibular, conal, and doubly committed. They are present near the aortic and pulmonic valve (Figure 12–3). They can cause herniation of the right coronary cusp of the aortic valve into the VSD resulting in aortic insufficiency.
• Type II: Approximately 80% of VSDs are perimembranous VSDs. They are also known as infracrista, paramembranous, and conoventricular VSDs. The defect is in the membranous portion of the interventricular septum near the atrial ventricular valve (Figure 12–4). This defect is associated with septal malalignment, overriding aorta, subaortic stenosis, and tricuspid valve leaflet herniation into the septal defect.
• Type III: 5% to 8% of VSDs are inlet VSDs. These are also known as canal type VSDs or endocardial cushion defects. They are located inferior to the atrial ventricular (AV) valve.
• Type IV: 5% to 20% of VSDs are muscular VSDs and are found in the muscular part of the interventricular septum (Figure 12–5).

Many VSDs are small and will close spontaneously. Spontaneous closure occurs most frequently during the first year of life. Some small, restrictive VSDs result in a minimal trans-septal blood flow and limited risk.8 Others result in free communications between the ventricles and the degree to which blood is shunted across the septum is dependent upon the ratio of systemic to pulmonary vascular resistance. When pulmonary vascular resistance is low, flow from the left heart into the right is increased. The result is volume overload and congestive heart failure. Over time, pulmonary vascular resistance increases secondary to development of pulmonary vascular occlusive disease leading to reversal of the shunt (flow becomes right-to-left) so-called Eisenmenger syndrome.7 Approximately 10% of patients with an uncorrected VSD will develop Eisenmenger syndrome, which carries a high incidence of early death.

Prevention of overcirculation in the pulmonary vasculature is essential to avoid pulmonary hypertension, right ventricular failure, and Eisenmenger syndrome. Initial anesthetic management for surgical closure of VSDs is similar to that described for ASD repair. However, nitric oxide (NO) along with infusions of the inotropic medications may be required to effectively separate from CPB. Conduction defects secondary to manipulation of the interventricular septum may occur necessitating temporary and at times permanent pacing following repair.

Defects in the atrioventricular canal or endocardial cushion can result in an ostium primum ASD, a cleft anterior leaflet of the mitral valve, and an inlet VSD. They represent approximately 2.9% of CHD patients. AV canal defects are associated with Down syndrome. Figure 12–6 demonstrates a so-called "partial" AV canal defect consisting of a primum ASD and a cleft mitral valve. Figure 12–7 reveals a complete AV canal defect with the addition of an inlet VSD. Patients develop an initial left-to-right shunt with associated congestive heart failure. If left untreated pulmonary hypertension develops much earlier leading to flow reversal from right to left. Surgical therapy often consists of not only closure of the atrial and ventricular septal defects but also correction of any abnormalities found in the patient's atrioventricular valves. Inotropic support, NO therapy, and temporary pacing are often necessary to successfully separate the AV canal patient from CPB.

VSDs can occur acutely in the adult population following myocardial infarction or secondary to iatrogenic mishap (eg, too much myocardium resected during hypertrophic cardiomyopathy (HCM) surgery. Patients are often quite unstable and are taken to surgery for attempts at salvage.

Tetralogy of Fallot (TOF) is the most common cyanotic heart disease representing 10% of all CHD patients (Video 12–4). TOF consists of four anatomic abnormalities:

1. Right ventricular outflow tract (RVOT) obstruction

2. RV hypertrophy

3. A large, unrestricted VSD

4. An aorta which overrides both the left and right ventricle receiving flow from both chambers (Figure 12–8).

Additionally, coronary artery abnormalities may present (5%-12%) with the left anterior descending coronary artery (LAD) branching from the right coronary artery (RCA). Other associated anomalies include: pulmonary valve atresia, ASD, persistent left superior vena cava, anomalous pulmonary vein connections, and dextrocardia.

The presentation of the TOF patient is dependent upon the degree of RVOT obstruction. Patients with significant RVOT obstruction will have a right-to-left shunt resulting in severe hypoxemia and cyanosis with saturations ranging from 70% to 80%. On the other hand, those with minimal obstruction "pink tet" will have VSD physiology with a left-to-right shunt. Often RVOT obstruction has a dynamic component leading to acute increases of obstruction and exacerbation of right-to-left shunting. Such episodes referred as "tet spells" may produce transient cerebral ischemia and loss of consciousness. These may occur secondary to infundibular spasm secondary to increased activity in the sympathetic nervous system as might occur with crying.9

Induction of anesthesia can produce a fall in systemic vascular resistance (SVR) leading to a worsening right-to-left shunt and hypoxemia. Should tet spells present in the perioperative period they can be relieved by:

• Hyperventilation with 100% FiO2
• Volume administration
• Phenylephrine
• Knee-chest position
• Increasing anesthetic depth

Ultimately, therapy is directed at increasing systemic vascular resistance, relieving infundibular spasm, and decreasing pulmonary vascular resistance.

The presence of chronic cyanosis can lead to polycythemia and the potential for embolic stroke across the VSD. Infectious vegetations are also a source of systemic emboli in TOF and other CHD patients at increased risk for endocarditis.

The majority of TOF patients are repaired in infancy except those whose pulmonary arteries are too underdeveloped.9,10 A palliative Blalock-Taussig (BT) shunt can be performed whereby the subclavian artery is anastomosed to the ipsilateral branch of the pulmonary artery (Figure 12–9). The BT shunt provides additional blood flow to the pulmonary vasculature to relieve cyanosis until a definitive repair can be completed. In those patients thought candidates for a complete surgical repair TOF surgery consists of:

• Ligation of any previous BT shunt
• Relief of RVOT obstruction through resection of excess muscle mass (Figure 12–10)
• Closure of the VSD
• Patch to enlarge subannular or transannular area of RVOT
• RV to PA conduit if pulmonary atresia or anomalous LAD are present

Perioperative anesthetic management of the TOF patient is centered upon promoting pulmonary blood flow and avoiding cyanosis. Dehydration should be avoided preoperatively. Oral midazolam can be given with the child appropriately monitored so to reduce perioperative anxiety, crying, and potentially the incidence of tet spells. An inhalational induction with sevoflurane is acceptable if intravenous access is not available. Nonetheless, limited pulmonary blood flow may slow an inhalational induction. The myocardial depressant effects of inhalational agents may be useful in limiting any infundibular spasm, RVOT obstruction, and right-to-left shunting across the VSD. On the other hand, systemic vasodilation and tachycardia caused by inhalational agents may increase right-to-left shunting and hypoxemia. If an IV is readily available etomidate, ketamine, and fentanyl used in combination with muscle relaxants and vasopressors can be employed. The presence of a right-to-left shunt may decrease the time for anesthetic effect following intravenous induction with some drug bypassing the lungs. Obviously, in any patient with right-to-left shunts in the heart all IV lines must be purged of air to prevent systemic air emboli perioperatively.

Systemic vascular resistance is maintained perioperatively with the use of phenylephrine and the patient's volume augmented with fluid boluses. Inotropes generally are not used in the peri-induction period as they might worsen infundibular spasm and promote right-to-left shunting. Should infundibular spasm be suspected small doses of esmolol could be given.

A radial artery catheter is placed opposite to that of any BT shunt since the shunt can "steal" blood from the patient's upper extremity. Central venous access is obtained to deliver fluids and other medications perioperatively.

Maintenance of anesthesia is achieved with combinations of narcotics, muscle relaxants, and inhalational agents. High airway pressures are avoided to minimize the impact of mechanical ventilation upon PVR.

Separation from CPB following surgical repair may require high right-sided filling pressures secondary to a generally poorly compliant RV in the TOF patient.11 RV dysfunction is common following TOF repair. Fluid loading, inotropic support, and afterload reduction are mainstays of therapy for weaning from CPB. Complete heart block and right bundle branch block are common perioperatively and temporary pacing is often necessary. Pressure-controlled ventilation with 100% oxygen and the lowest airway pressure to maintain a Paco2 of 25 to 33 mm Hg is employed. As such, PVR is minimized to the degree possible. The majority of patients are extubated within 12 hours and require 1 to 2 days of ICU care.

Unfortunately, many patients following TOF repair are at risk for a variety of long-term complications, which can complicate anesthetic management of these patients for noncardiac surgery. Residual VSD and pulmonic valvular incompetence are most unwelcome surgical sequelae. Those patients with hemodynamically significant VSD are at risk for developing pulmonary hypertension and should be reoperated to correct this defect.12 RV dysfunction can also complicate long-term management. Ventricular dysrhythmias are common and can emanate from various foci including the area of infundibular resection and areas near the VSD patch.13 Although isolated PVCs may be well-tolerated, potentially lethal ventricular rhythms can develop with the overall incidence of sudden death of 0.3% per patient an year after surgical repair.14 Anesthesiologists may be called upon to care for the patient following TOF repair undergoing electrophysiologic studies and placement of antiarrhythmia implantable devices. All patients with TOF whether repaired or not require endocarditis prophylaxis.15

Anesthetic management of the TOF patient requiring noncardiac surgery is similar to that described for cardiac surgical repair. Interventions are directed toward the maintenance of pulmonary blood flow and the avoidance of right-to-left shunting. Appropriate antibiotic prophylaxis must be given and the patient monitored as described above for any major surgical intervention.

Transposition of the great arteries (TGA) essentially means ventricular arterial discordance. These lesions represent 5% to 7% of all CHD and have a high mortality within the first year of life.16 Complete transposition describes a patient with appropriate atrioventricular concordance but ventriculo-arterial discordance. As such, the right atrium is connected to the right ventricle via the tricuspid valve but the right ventricle is connected to the systemic artery, the aorta (Figure 12–11). The left atrium is likewise connected via the mitral valve to the left ventricle, which in turn is connected incorrectly to the pulmonary artery. The coronary arteries emerge from the aorta. Consequently, without other defects in the heart, deoxygenated blood would only be delivered to systemic circulation as blood flow is in parallel and not in series. However, this condition is associated with other defects including a patent ductus arteriosus (PDA), patent foramen ovale (PFO), and VSD (Figure 12–12). Consequently, oxygenated and deoxygenated blood intermix permitting transient survival until surgical repair can be undertaken. Without mixing of blood secondary to other structural defects life would not be possible. In patients with TGA and a VSD mixing occurs in the ventricle. In those patients born with an intact interventricular septum blood mixing is dependent upon a PFO, ASD, or PDA. Prostaglandin E1 infusions are at times needed to preserve PDA blood flow. Likewise, balloon atrial septostomy in the catheterization laboratory can be performed to increase the connection between the systemic and pulmonary circulations at the atrial level (Figure 12–13). Other patients may be given a BT shunt to improve pulmonary blood flow (Figure 12–14).

Definitive surgical repair is the arterial switch or Jatene operation. Both the ascending aorta and pulmonary artery are transected above their respective valves. The pulmonary artery is attached to the right ventricular outflow tract (RVOT) and the aorta to the left ventricular outflow tract (LVOT) (Figure 12–15). The coronary arteries that follow the aorta during development must be explanted from the region of the RVOT and reimplanted into the aorta. Twisting of the coronary arteries during performance of the Jatene procedure can lead to myocardial ischemia and ventricular dysfunction. The Rastelli (Figure 12–16) and Damus-Kaye-Stansel procedures are employed when an arterial switch is not possible. Following these procedures oxygenated blood is directed into the systemic circulation while deoxygenated venous blood enters the lungs.

The direction of oxygenated and deoxygenated blood can also be changed at the atrial level.17 Atrial switch procedures (Mustard and Senning) by creating intra-atrial baffle direct systemic venous blood to the mitral valve (MV), LV, and pulmonary artery. Conversely, pulmonary venous return is directed to the tricuspid valve (TV), RV, and aorta (Figure 12–17). The RV remains the systemic pumping chamber, TV faces systemic pressure, and over time TV regurgitation and RV failure may occur. Likewise, many patients experience varying degrees of arrhythmias.

In rare cases of TGA so-called congenitally corrected TGA can occur. In this arrangement the right atrium is connected to the mitral valve and the left ventricle, which in turn pumps blood into the pulmonary artery. The left atrium is connected to the tricuspid valve and the right ventricle, which in turn is connectedto the systemic artery, the aorta. Consequently, in congenitally corrected TGA a morphological right ventricle becomes the systemic pumping chamber of the heart; however, because of the serial connections in the circulation deoxygenated blood reaches the lungs and oxygenated blood is pumped into the systemic circulation. This TGA variant can remain asymptomatic for some time (third-fifth decade) until the RV fails as the systemic pumping chamber of the heart, tricuspid regurgitation develops, or conduction abnormalities ensue.18

Anesthetic management of patients undergoing TGA surgeries is complicated and requires a thorough knowledge of the patient's circulation. Inotropes and vasodilators might be needed following arterial switch when the low pressure left ventricle assumes its proper role as the systemic pumping chamber of the heart. Signs of myocardial ischemia secondary to coronary arteries occlusion after their reimplantation have to be sought. Patients whose right ventricle must serve as the systemic ventricles are prone to ventricular failure and tricuspid valve regurgitation. All patients are prone to different kinds of dysrhythmias.

There are many pathologic conditions which give rise to single ventricle (SV) physiology. In one subset of patients such as the majority of those with tricuspid atresia (Figure 12–18) pulmonary blood flow is inadequate and oxygenation of the blood becomes possible only through flow via the PDA. Such patients often present with cyanosis. Other patients (eg, those with hypoplastic left heart syndrome [HLHS]) have an undeveloped left (systemic) ventricle and an ascending aorta and subsequently inadequate systemic perfusion. Systemic circulation is provided by flow through a PDA into the aorta (Figure 12–19). Consequently, HLHS patients have systemic hypoperfusion but pulmonic hyperperfusion. Depending upon the anatomic variant, SV patients can have either too much or too little pulmonary blood flow. If too much blood flow the patient will manifest signs of pulmonary congestion and systemic hypoperfusion. If there is too little pulmonary blood flow the patient can become cyanotic. The initial management of the SV patient is centered upon the resuscitation of the affected newborn. The goal of management is to bring into balance the patient's Qs and Qp which should approach a ratio of 1.19 Prostaglandin E1 infusion is used to maintain ductal patency.

Irrespective of the anatomic lesions, palliation of the SV patient is usually accomplished over two to three stages during infancy and early childhood. The goals are to dedicate SV to the systemic circulation and direct systemic venous return to the pulmonary arteries. In patients with decreased pulmonary blood flow a systemic artery to pulmonary artery shunt (BT shunt) is performed to relieve cyanosis (Figure 12–20). In those patients with pulmonary hyperperfusion and systemic hypoperfusion, initial management include the placement of pulmonary artery (PA) band to prevent excessive pulmonary blood flow.

The anesthetic management of patients for initial SV palliation depends upon the degree of pulmonary hypo- or hyperperfusion encountered. The patient with pulmonary hyperperfusion for PA banding requires maintenance of pulmonary vascular resistance so to prevent further "steal" of blood from the systemic to the pulmonary circulation. Inotropic support is often needed secondary to SV volume overload. Patients requiring BT shunts for pulmonary hypoperfusion require high-inspired oxygen concentrations and controlled hyperventilation to reduce PVR. Both BT shunt and PA banding procedures can be performed without the use of CPB.

Patients with HLHS are treated by the Norwood procedure (Figure 12–21). A new aorta is created from the hypoplastic aorta and the main pulmonary artery. The RV becomes the systemic pumping chamber and pulmonary blood flow is provided by a BT shunt or Sano shunt.20 A combination of pulmonary artery banding and radiologically guided stenting of the PDA can also be performed for newborns with HLHS21 (Fig 12–22). In this hybrid approach the pulmonary arteries are banded to reduce pulmonary hyperperfusion and the PDA is stented to provide systemic perfusion from the SV into the aorta.

The second stage of palliative procedures for the SV patient generally involves creation of a Glenn shunt. In the Glenn procedure venous return from the SVC is directed into the pulmonary artery (Figure 12–23). Cyanosis is not corrected by the Glenn procedure since inferior vena cava (IVC) flow still returns to the SV and is ejected into the systemic circulation. As patients grow, flow from the IVC increases gradually decreasing the patient's arterial saturation. The bidirectional Glenn shunt (BDG) delivers SVC flow to both the right and left lungs. However, IVC flow is not delivered to the lungs resulting in the potential for developing pulmonary arterio-venous malformations (AVMs). It is believed to be secondary to the absence of hepatic venous factor delivered directly to the lungs.22

The third stage of palliation for the SV patient is the Fontan procedure.23 The Fontan procedure completes the process by which the SV is dedicated exclusively to the systemic circulation. The goal of the procedure is to direct all SVC and IVC venous return to the pulmonary vasculature, bypass the function of the right ventricle, and establish the single ventricle as the systemic pumping chamber of the heart. The Fontan procedure today creates a total cavopulmonary connection (TCPC) as a lateral tunnel (Figure 12–24) or extracardiac conduit (Figure 12–25).

Anesthetic management of the second and third stages of SV palliation can be quite challenging. The SV, which was exposed to volume overload at the time of systemic to pulmonary artery shunt or other circumstances of parallel circulation, is prone to ventricular failure. Pulmonary vascular resistance should be low in Fontan candidates, but can be underestimated resulting in the impedance of blood flow through the lungs. Anesthetic induction can be achieved with inhalational or intravenous agents. Direct arterial pressure monitoring is obtained as well as adequate venous access for resuscitation in children who most likely have already had one to two prior sternotomies. At times surgeons will cannulate both the femoral artery and femoral vein to establish femoral-femoral CPB in the event of exsanguination upon sternal opening. Anesthetic maintenance is with combinations of narcotics, inhalational agents, muscle relaxants, and neuraxial narcotics for postoperative pain control to facilitate early extubation.24 Fontan repair can be completed with or without the use of CPB.25

Following surgical repair, anesthetic management is directed at reducing PVR and promoting passive pulmonary blood flow. Patients are maintained on high-inspired FiO2 and ventilated to produce a moderate hypocarbia with low inspiratory pressures. Nitric oxide or inhaled prostacyclin may be needed to decrease PVR and improve pulmonary blood flow. Monitoring of both venous pressure and atrial pressure are helpful in perioperative management. The central venous pressure measures pressure within the venous system delivering deoxygenated blood to the pulmonary arteries bypassing the heart. The atrial pressure reflects the pressure in the single atrium receiving oxygenated blood via the pulmonary veins to be ejected into the systemic circulation by the SV. Ideally, the CVP is 15 mm Hg with an atrial pressure of 8 mm Hg. If the atrial pressure measured by a surgically placed transthoracic atrial line is elevated, dysfunction of the single ventricle or AV valve regurgitation should be suspected. SV dysfunction can be treated by inotropes and afterload reduction. However, if the atrial pressure is normal and the central venous pressure increased, then increased PVR is suggested and nitric oxide therapy is initiated. Positive pressure ventilation increases PVR and decreases pulmonary blood flow. Pulmonary flow in the Fontan patient is improved by maintenance of a short inspiratory time, prolonged expiratory time, larger tidal volume, slower respiratory rate, and low plateau pressures. The benefits of positive end-expiratory pressure (PEEP) in promoting alveolar recruitment must be balanced against the potential to increase intrathoracic pressure and decrease pulmonary blood flow. Early extubation and spontaneous ventilation are encouraged when tolerated, since negative transthoracic pressure augments pulmonary blood flow and increases cardiac output.

Adult patients following Fontan palliation should be managed in a manner similar to that for the child undergoing Fontan creation. Spontaneous ventilation is encouraged as is the use of anesthetic techniques with minimal negative inotropic effects. Sufficient intravascular volume is necessary to perfuse the pulmonary vasculature and preserve the cardiac output.

Specific anesthetic techniques must be designed for each individual patient following review of the patient's records and discussion with their primary physicians. The degree to which a patient's underlying defect has or has not been corrected needs to be discerned. Generally, management is directed toward:

• Avoiding air or other emboli in patients with shunts present
• Avoiding myocardial depression
• Reducing airway pressure
• Balancing pulmonary and systemic flow ratio

Even the most straightforward simple congenital lesions can be associated with a number of long-term complications including:

• Pulmonary hypertension
• Ventricular dysfunction
• Dysrhythmias
• Conduction defects
• Residual shunts
• Valvular lesions
• Arteriovenous malformations and vascular lesions

Pulmonary hypertension can be present in patients secondary to long-standing large, nonrestrictive defects resulting in an initial left-to-right shunt and pulmonary hyperperfusion when Qp>>>Qs. Congenital mitral valvular disease and ventricular failure can also lead to increases in pulmonary artery pressures. Eisenmenger syndrome occurs with less frequency today due to early surgical interventions. Elective surgery should be carefully considered in patients with Eisenmenger syndrome. In patients with pulmonary hypertension increases in PVR are avoided by:

• Minimizing sympathetic stimulation
• Preventing hypoxia and hypercarbia
• Maintaining normal airway pressures if possible
• Employing pulmonary vasodilators (eg, NO) when necessary

Sudden increases in PVR may precipitate right heart failure, oxygen desaturation, and reduced systemic cardiac output. Regional techniques can be employed where indicated.

Cyanosis following CHD repairs usually reflects residual right-to-left shunting. Long-standing cyanosis results in a compensatory erythrocytosis yielding an increase in blood viscosity and the propensity for thrombosis. Iron deficiency may accompany erythrocytosis making red cells less deformable further promoting clot formation. Perioperatively patients should be adequately hydrated when fasted.

CHD patients whether corrected or not are at risk for varying degrees of both systolic and diastolic right and left heart failure. Regimens used to treat left and right heart failure are applied in the CHD patient as they are in the general population. Similarly, many patients with CHD have various atrial and ventricular arrhythmias. Anesthesiologists can from time to time encounter CHD patients in electrophysiology laboratories when they present for ablative therapy.

CHD patients are at risk for endocarditis. The American Heart Association (AHA) provides guidelines to assist physicians in determining when prophylaxis is needed.15 As many patients following repair of CHD lesions have various shunts, baffles, and conduits the potential for infection should never be discounted. As these guidelines often change, practitioners should frequently review the AHA's recommendations.

With CHD patients evermore surviving into adulthood, an increasing number of pregnancies can be expected amongst women with repaired CHD.26 Moreover, acquired valvular or ischemic heart disease can necessitate surgical or catheter-mediated interventions in the rare pregnant patient.

The physiologic changes associated with pregnancy include:

• Decreased systemic vascular resistance
• Increased cardiac output
• Decreased pulmonary vascular resistance
• Decreased systolic and diastolic blood pressure
• Increased oxygen consumption
• Anemia
• Decreased functional residual capacity
• Airway edema and potential for difficult intubation

Patients with impaired ventricular or valvular function may be unable to adapt to the normal physiology of pregnancy, leading to hemodynamic collapse.

Patients with repaired CHD may be candidates for vaginal or cesarean delivery depending upon their medical conditions. Ventricular function should be assessed during the prenatal period and the history of previous repairs reviewed. Limited ventricular reserve as might be seen in patients with Fontan circulation may prevent the patient from responding to the hemodynamic challenges of delivery. Additionally, many CHD patients are taking Coumadin, which can lead to spontaneous abortion and birth defects. Conversion to heparin is necessary during pregnancy; however, it is generally advised not to become pregnant while on Coumadin therapy. An elective delivery is generally preferred as heparin anticoagulation where required can be transiently discontinued to permit the use of neuraxial anesthetics. Cesarean section is generally not mandated unless indicated for obstetrical purposes. The volume shifts associated with labor analgesia, and delivery may not be tolerated by the CHD patient with impaired ventricular function leading to hemodynamic collapse and heart failure. Invasive monitoring may be employed on an individual basis as indicated.

From time to time, anesthesiologists can take care of a pregnant patient who must undergo heart surgery requiring the use of CPB. Although cardiac surgery can be safe for the mother, there are numerous perioperative risks for fetal survival.27 Fetal heart rate monitoring can be employed after 22 weeks' gestational age. Fetal bradycardia is associated with hemodilution, sustained uterine contraction, hypotension, and medications. High flows (> 2.4 L/min/m2), CPB pressures of > 70 mm Hg, and normothermia have been suggested to improve fetal viability. Expeditious surgical times and avoidance of hyperkalemia secondary to repeated doses of cardioplegia solution are also recommended. Heparin and protamine do not cross the placenta. Since coagulation is enhanced during pregnancy, anti-fibrinolytic agents are avoided in the pregnant patient requiring CPB. Left uterine displacement should be done by placing a wedge under the right hip to avoid aorto-caval compression. A hematocrit > 25% is likewise suggested during CPB.

Review of TEE examinations of patients with CHD both before and after surgical repair can be challenging for adult echocardiographers at all levels. The basic echocardiographer should be able to recognize the abnormal structure of the CHD patient's heart. Basic echocardiographers should seek the assistance of individuals with specific experience with the CHD patient when bringing these patients to surgery.