Introduction
The incidence of congenital heart disease (CHD) is about 4–9 per 1000 live-born full-term infants. Recent advances in pediatric cardiology, surgery, and critical care have significantly improved the survival rates of even the most complex defects. Many children will require multiple cardiac surgeries or interventional procedures, starting in the neonatal period and continuing into adulthood. In addition, CHD is often (30 percent) associated with extracardiac anomalies, syndromes or significant comorbidities, potentially requiring further imaging studies and surgical interventions, especially in the first year of life. Given the current trend for early diagnosis and intervention, with increasingly sophisticated imaging and treatment modalities, all pediatric anesthesiologists, with or without specific cardiac training, will encounter more and more patients with repaired or unrepaired CHD and other cardiac diseases in their daily practice.
Several recent studies demonstrated an increased risk for patients with cardiac disease undergoing noncardiac surgery, notably for the younger age group (<2 years), complex lesions, and patients with preexisting pulmonary hypertension, congestive heart failure (CHF), or significantly decreased ventricular function [1–4].
This chapter introduces the pediatric anesthesiologist to a systematic approach for the preoperative assessment and preparation of neonates and infants with cardiac disease; discusses anesthetic considerations for the most common repaired and unrepaired defects; and also reviews the anesthetic management for specific procedures that are frequently performed within the first year of life.
Evaluation and Preparation of the Neonate and Infant With Cardiac Disease
It is beyond the scope of this chapter to discuss an anesthetic plan for all possible cardiac defects and their repairs or interventions. Every child must be evaluated on an individual basis, often a very demanding task that can be greatly facilitated by a systematic approach:
(1) preoperative assessment;
(2) endocarditis prophylaxis;
(3) prevention of paradoxical embolization;
(4) special considerations for monitoring and intravenous access;
(5) management of fluid status;
(6) risks and goals for hemodynamic and respiratory management;
(7) preoperative planning.
Preoperative Assessment
A thorough preoperative assessment includes an understanding of the anatomy and pathophysiology of the underlying defect or disease, the type and outcome of repairs, palliations or interventions, a review of potential extracardiac malformations or coexisting syndromes, as well as the evaluation of the current functional status and medications.
Anatomy and Pathophysiology of the Underlying Defect or Disease
Table 29.1 shows a simplified classification of the most common congenital heart defects according to appearance (cyanotic versus acyanotic) and basic pathophysiology (please refer to Chapter 28 for more details). For complex cases it is advisable to contact the primary cardiologist or cardiac surgeon and discuss specific details and implications for the upcoming procedure. Pediatric cardiologists are very involved in the care of their patients but may be unaware of the potential effects of anesthesia or certain surgical requirements (immobility, positioning, abdominal insufflation, etc.).
| Cyanotic | Acyanotic |
|---|---|
| Right-to-left shunts Tetralogy of Fallot (10 percent) Pulmonary atresia (1 percent) Tricuspid atresia (< 1 percent) | Left-to-right shunts Ventricular septal defect (20–25 percent) Atrial septal defect (5–10 percent) Endocardial cushion defect (AV canal) (4–5 percent) Patent ductus arteriosus (5–10 percent) |
| Complex “mixing” lesions Transposition of the great vessels (5 percent) Total anomalous pulmonary venous return (1 percent) Truncus arteriosus (1 percent) Hypoplastic left heart syndrome (1 percent) Double outlet right ventricle (< 1 percent) | |
| Obstructive lesions (right-sided) Pulmonary stenosis (5–8 percent) | Obstructive lesions (left-sided) Coarctation of the aorta (8–10 percent) Aortic stenosis (5 percent) |
Type and Outcome of Repairs, Palliations, and Interventions
In the past, surgical repairs were often differentiated into definitive and palliative procedures. Definitive procedures are intended to correct the defect and can either be anatomic, leading to a “normal” acyanotic serial circulation where the blood flows through two separate sequential circulations with the right ventricle supporting the pulmonary circulation and the left ventricle the systemic one, or “non-anatomic or functional” repairs where a serial circulation is established but the right ventricle or a single ventricle is supporting the systemic circulation (e.g., Mustard or Senning repair of transposition of the great arteries [d-TGA], Fontan). There are simple surgeries like patch repairs of ASDs, VSDs, or PDA ligations with an otherwise normal heart and a low likelihood of long-term complications, but also complex reconstructions with conduits and valves that will obstruct and calcify over time and often require lifelong follow-up and multiple interventions. Some of these repairs are therefore not so “definitive.”
Palliative procedures like arterio-pulmonary shunts or pulmonary artery banding are used to temporarily improve severe cyanosis or pulmonary overcirculation if the baby is premature, too small, or too sick for a complete neonatal repair.
Many cardiac defects are corrected or palliated during interventions in the cardiac catheterization suite: device closures of ASDs, VSDs, or PDAs, balloon dilations and stent placements for obstructions, or coil embolization of aortopulmonary collaterals or shunts are just a few examples (see also Chapter 28). Parents should be specifically asked about recent cardiac catheterizations. These can be an indication of residual postoperative problems but are often “downplayed” as diagnostic tests and not mentioned during the initial interview.
Obviously, the outcome after a surgical procedure or an intervention is another important question. Classic complications like complete heartblock after a VSD patch repair or coronary injury and ventricular dysfunction after an outflow tract reconstruction have to be distinguished from residual defects (subvalvular obstruction, valve regurgitation, residual VSDs, pulmonary hypertension, etc.) or altered physiology (single ventricle or systemic right ventricle).
Extracardiac Malformations and Genetic Syndromes Associated With Congenital Heart Disease
Approximately 25–30 percent of neonates with CHDs have additional extracardiac malformations or associated syndromes that may require further workup or interventions prior to the cardiac repair.
Moreover, they can have significant implications for the anesthetic management: difficult airway or tracheoesophageal fistulas, metabolic and endocrine problems, immunodeficiency (requiring irradiated blood products), or limb abnormalities with limited intravenous access. Table 29.2 is a short list of the most common syndromes associated with CHD. Unfamiliar syndromes should be carefully reviewed in major pediatric or cardiology textbooks.
| Syndrome | Commonly associated CHD | Other anesthetic implications |
|---|---|---|
| CHARGE association (Coloboma, congenital Heart defects, choanal Atresia, Renal abnormalities, Genital hypoplasia, Ear deformities) | 65 percent conotruncal anomalies, aortic arch anomalies | Difficult airway and intubation, renal dysfunction |
| DiGeorge syndrome (chromosome 22 deletion, CATCH 22) | Interrupted aortic arch, truncus arteriosus, VSD, PDA, ToF | Hypocalcemia, immunodeficiency, need for irradiated blood products |
| Duchenne muscular dystrophy | Cardiomyopathy | Hyperkalemic cardiac arrest with succinylcholine, rhabdomyolysis with inhalational agents |
| Ehler–Danlos syndrome | Aneurysm of aorta and carotid vessels | Difficult IV, increased bleeding |
| Ellis–van Creveld syndrome (chondro-ectodermal dysplasia) | 50 percent common atrium | Possible difficult intubation |
| Fetal alcohol syndrome | 25–30 percent VSD, PDA, ASD, ToF | Difficult airway, renal disease |
| Friedreich’s ataxia | Cardiomyopathy | Progressive neurological degeneration, glucose intolerance |
| Glycogen storage disease II (Pompe) | Cardiomyopathy | |
| Holt–Oram syndrome | ASD, VSD | Upper limb abnormalities |
| Leopard syndrome (cardio-cutaneous syndrome) | PS, long PR interval, cardiomyopathy | Growth retardation, possible difficult intubation |
| Long QT syndromes: – Jervell and Lange Nielsen – Romano–Ward | Long QT interval, ventricular tachyarrhythmia | Congenital deafness |
| Marfan syndrome | Aortic aneurysm, AR and/or MR | Spontaneous pneumothorax, cervical spine instability |
| Mucopolysaccharidosis: – Hurler (type I) – Hunter (type II) – Morquio (type III) | AR and/or MR, coronary artery disease, cardiomyopathy | Difficult airway, atlantoaxial instability, kyphoscoliosis |
| Noonan syndrome | PS (dystrophic valve), LVH, septal hypertrophy | Possible difficult intubation, platelet dysfunction, renal dysfunction |
| Tuberous sclerosis | Myocardial rhabdomyoma | Seizure disorder, renal dysfunction |
| Shprintzen syndrome (velocardiofacial, 22q11.2 deletion) | Conotruncal anomalies, ToF | Difficult airway |
| VACTERL association | VSD, conotruncal anomalies (ToF, truncus arteriosus, etc.) | Vertebral anomalies, Anal atresia, Cardiac defects, Tracheoesophageal fistula, Esophageal atresia, Renal anomalies, Limb defects |
| Williams syndrome | Supravalvular AS, PA stenosis | Developmental delay, occasional difficult airway, renal dysfunction |
| Zellweger syndrome (cerebrohepatorenal syndrome) | PDA, VSD, ASD | Neonatal jaundice, kidney and liver dysfunction, coagulopathy, hypotonia |
Current Functional Status and Medications
A detailed history, physical examination, and review of recent imaging studies are important to assess the current functional status. Specific questions regarding signs and symptoms of CHF, pulmonary hypertension, or severe ventricular dysfunction, episodes of syncope or palpitations, cyanotic “spells” with or without agitation, feeding difficulties, recurrent infections, and recent changes in medications will help to stratify the risk for anesthesia. In addition to a careful airway, cardiac and pulmonary examination, the physical examination should include the assessment of peripheral pulse quality, capillary refill, clubbing, hepatomegaly, potential blood pressure gradients between the extremities, and access sites for intravenous or arterial lines. All available recent cardiac studies or diagnostic tests should be reviewed and if necessary discussed with the cardiologist. Many cardiac medications can have significant implications for anesthetic management and may warrant preoperative laboratory studies. For example, diuretics can be associated with intravascular volume depletion and electrolyte disturbances, ACE inhibitors with severe hypotension after induction of anesthesia, digoxin with increased toxicity triggered by electrolyte and fluid shifts, beta blockers can mask the heart rate response to pain and stress, and platelet inhibitors increase the risk for bleeding. A complete list of current medications should be compiled during the preoperative evaluation and the perioperative continuation or discontinuation decided on an individual basis. All cyanotic patients will need a complete blood count to assess for polycythemia and the need for preoperative hydration or admission to prevent spontaneous thromboembolism due to severely elevated hematocrit levels (>55–60 percent). A normal hematocrit in a cyanotic patient is usually a sign of anemia, often caused by iron deficiency. Coagulation tests can be helpful to evaluate platelet and factor deficiencies that are often associated with severe cyanosis. Table 29.3 summarizes the important aspects of the preoperative evaluation.
Table 29.3 Important aspects for the preoperative evaluation
| History | • Signs and symptoms of CHF: – Failure to thrive, poor feeding, tachypnea, sweating – Recurrent pulmonary infections (secondary to congestion) – Decreased activity level and fatigue in older patients • Palpitations or syncope • Additional congenital anomalies (e.g., airway, genitourinary) • Recent and current medications (e.g., diuretics, digoxin, ACE inhibitors) • Review of previous surgeries and interventional procedures • Last follow-up with the patient’s pediatric cardiologist |
| Physical examination | • Characteristic heart murmur, precordial thrill, arrhythmias • Tachypnea, increased work of breathing, rales • Poor peripheral perfusion, delayed capillary refill • Bounding or diminished pulses • Cool extremities, mottled skin, sweating • Hepatomegaly • Peripheral edema, puffy eye lids |
| Laboratory studies | • CBC: polycythemia (secondary to cyanosis), anemia (secondary to malnutrition) • Electrolytes: hypokalemia, hyponatremia (secondary to diuretic therapy) • Coagulation profile |
| Additional tests | • Echocardiography: cardiac function and intracardiac anatomy • EKG: rhythm, signs of atrial or ventricular hypertrophy • CXR: cardiomegaly, pulmonary edema, or infiltrates |
| Specific studies | • Cardiac catheterization: anatomy, pressure gradients, saturations, shunts • Cardiac MRI: anatomy, pulmonary blood flow, right and left ventricular function |
Endocarditis Prophylaxis
In 2007, the American Heart Association [6] published their latest update of the guidelines for endocarditis prophylaxis. The focus was shifted toward cardiac conditions that are associated with the highest risk for adverse outcomes from endocarditis. Currently, endocarditis prophylaxis is only recommended for all dental procedures involving manipulations of gingival tissue or oral mucosa and the following conditions:
prosthetic cardiac valve or prosthetic material used for cardiac valve repair;
previous endocarditis;
Congenital heart disease:
– unrepaired cyanotic CHD, including palliative shunts and conduits;
– completely repaired CHD with prosthetic material or device, whether placed by surgery or catheter intervention, during first six months after the repair;
– repaired CHD with residual defects in the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibits endothelialization);
cardiac transplantation recipients who develop cardiac valvulopathy.
Endocarditis prophylaxis is no longer recommended for routine gastrointestinal or genitourinary procedures.
Prevention of Paradoxical Embolization
All newborns and many cardiac patients, especially those with single ventricle lesions, complete atrioventricular canals, or preexisting right-to-left shunts, are at risk for paradoxical embolization and sudden or worsening cyanosis. Changes in pulmonary vascular resistance or loading conditions can lead to increased pressures in the right side of the heart and open the only functionally closed fetal shunt connections (PFO and PDA), which can worsen existing right-to-left shunting or reverse preexisting left-to- right shunts. Air or thrombotic material from the venous circulation can directly enter the arterial system and cause limb ischemia or ischemic infarcts in the brain or intestinal organs. Many neonatal cardiac repairs involve fenestrated patch closures to allow for decompression of the right ventricle during the initial recovery period. Decreased right ventricle function, perioperative episodes of pulmonary hypertension, or increased right ventricle afterload with breath holding and coughing during emergence from anesthesia can result in severe cyanosis. Careful evaluation of all cardiac patients for potential intracardiac shunt connections and appropriate anesthetic management including prophylactic use of air filters whenever possible and meticulous avoidance of air entrapment in stopcocks and injection ports are important measures to decrease the risk for paradoxical embolization.
Special Considerations for Monitoring and Intravenous Access
A five-lead ECG with ST segment analysis is recommended for all cardiac patients at risk for ischemia, especially before and after stage 1 palliation and for hypertrophied ventricles. Patients with modified Blalock–Taussig (BT) shunts (steal effect) or known vascular occlusions can have decreased blood pressure readings on the respective extremities and the noninvasive BP cuff should be placed accordingly. Depending on the procedure, the complexity of the cardiac defect and the functional status of the patient, invasive monitoring with an arterial line and central venous access might be indicated. Capnography is well known to be inaccurate to assess the adequacy of ventilation in defects with right-to-left shunting, compromised pulmonary blood flow or “unbalanced” single ventricle physiology [7]. Direct blood pressure monitoring will not only allow for close monitoring of hemodynamic changes, but also ventilator adjustments based on arterial blood gases. Anticipation of hemodynamic instability and the need for inotropic support or monitoring of mixed venous saturations may warrant placement of a central venous line. After a long hospitalization peripheral intravenous access can be very difficult and limited to small cannulas. Central venous access is often the only reliable choice. A careful preoperative evaluation and examination of all potential access sites, including blood pressure measurements on all four extremities to assess for gradients as well as a review of previous surgeries and catheterization reports for known occlusions, shunts, subclavian flaps, or surgical cut-downs, is very important. For “frequent flyers,” such as patients with Tetralogy of Fallot and pulmonary atresia (ToF/PA), if at all possible, the femoral vessels should be spared for future access in the catheterization lab.
Management of Fluid Status
Many cardiac patients will benefit from a small fluid bolus (5–10 ml kg–1) prior to or shortly after induction. Intravascular volume depletion due to chronic diuretic therapy, loss of sympathetic tone, and vasodilation, as well as decreased preload with onset of positive pressure ventilation, can lead to significant hypotension. Some patients are especially preload dependent, such as patients with right ventricle hypertrophy and pulmonary hypertension (PH), bidirectional Glenn physiology, or hypertrophic cardiomyopathy. Cyanotic patients with polycythemia are at risk for spontaneous thrombosis. NPO times should be either kept to a minimum or, alternatively patients can be admitted the day before for adequate hydration.
On the other hand, there are a group of cardiac patients who will not tolerate rapid fluid administration, like the 25 ml kg–1 usually given during short day surgery cases. Patients with pulmonary vein stenosis (for example after TAPVR repair), mitral stenosis, or diastolic dysfunction can easily decompensate with rapid fluid administration and develop severe pulmonary edema.
Risks and Goals for Hemodynamic and Respiratory Management
Depending on the underlying pathophysiology, the goals and potential risks of alterations in the hemodynamic or respiratory status have to be carefully assessed. Patients with severe CHF from pulmonary overcirculation, pulmonary hypertension, restricted pulmonary blood flow, obstructive or regurgitant valvular defects, or single ventricle physiology will require very different hemodynamic and ventilatory strategies. Optimization of the current status and avoidance of detrimental changes with induction of anesthesia, positioning, fluid shifts, or surgical instrumentation/stimulation are important and can often be facilitated by a preoperative team discussion between anesthesiologist, surgeon, and cardiologist. A quick review of the individual arrhythmia risk for the specific defect or procedure will help with preparing appropriate antiarrhythmic medications and equipment (defibrillator, pacing devices). In complex cases, a preoperative consultation with an electrophysiology specialist can be very valuable. Specific goals and potential problems for individual congenital heart defects will be discussed in the section “Considerations for specific cardiac diseases.”
Preoperative Planning
Anesthesiologists play an important role in perioperative care. Evaluating the need for preoperative consultations with cardiology, new updated imaging studies (echo, chest X-ray) as well as timing of the procedure (e.g., first case of the day) and possible coordination with other procedures are important tasks. In preparation for the case, the appropriate location (satellite facility versus main campus), staffing, and level of support has to be selected and all necessary material and equipment organized such as additional syringe pumps for inotropic agents, difficult airway cart, defibrillator, or antiarrhythmic medications. Finally, the right venue for the initial postoperative recovery and further observation has to be chosen. Depending on the complexity of the cardiac disease and/or the surgical procedure, this can range from a specialized cardiac intensive care unit to the recovery room, followed by admission to a regular floor or cardiac ward, or even a day surgery unit. Once again, a preoperative team discussion can be a valuable tool to make timely arrangements and avoid unnecessary waiting periods in the operating or recovery room.
Considerations for Specific Cardiac Diseases
It is beyond the scope of this chapter to describe the detailed management of all cardiac defects and cardiac diseases for potential procedures and interventions in the first year of life, so the following section will highlight the most important anesthetic considerations for common CHD and diseases. Various anesthetic agents and techniques have been used successfully. More details can be found in recent review articles and Chapter 28 [8–10].
Ventricular Septal Defect
Ventricular septal defects (VSDs) are the most common form of CHD, affecting 20–25 percent of CHD patients. Thirty to forty percent of VSDs will close spontaneously within the first year of life.
Pathophysiology
The resulting left-to-right shunt is dependent on the size of the defect and the pressure gradient across the septum, which is determined by left and right ventricle pressures, pulmonary vascular resistance (PVR), and systemic vascular resistance (SVR). Large left-to right shunts lead to pulmonary overcirculation, CHF, and poor cardiac output.
Associated Anomalies
Less than 5 percent of VSDs are associated with chromosomal abnormalities such as trisomy 13, 18, and 21.
Anesthetic Considerations
Small VSD with no obvious CHF:
– Careful inhalation induction possible; be aware of reduced cardiac reserve
– “Bubble” precautions
– Risk of shunt reversal (see below)
Large VSD with significant CHF:
– “Bubble” precautions
– Careful intravenous induction aiming for a stable PVR/SVR ratio and normoventilation
– Avoidance of hyperventilation and high FiO2: a high PaO2 and low PaCO2 can decrease PVR, which will increase left-to-right shunting and decrease systemic cardiac output
– Avoidance of potent negative inotropic anesthetic agents in the volume overloaded, failing ventricle with poor reserve and compliance; low-dose inotropic support often beneficial
– Risk of shunt reversal (right-to-left) with severe hypotension or increases in PVR due to loss of airway during induction, bronchospasm, hypoxia or acidosis, coughing, or breath holding during emergence.
Considerations for Patients With Repaired VSDs
Dysrhythmias and conduction defects such as right bundle branch block (RBBB), ventricular arrhythmias, and heart block
Residual ventricular dysfunction, especially after severe CHF or repairs requiring ventriculotomy.
Residual pulmonary hypertension or exaggerated pulmonary vascular reactivity, which is sometimes associated with a late repair, high altitude, or syndromes like trisomy 21.
Patent Ductus Arteriosus
The ductus arteriosus is a normal fetal structure that connects the main pulmonary artery and the upper descending aorta. In utero, approximately 60 percent of right ventricular output bypasses the lungs via the ductus arteriosus.
In full-term infants, functional closure (i.e., smooth muscle contraction) usually occurs 10–15 hours after birth, but can be delayed by many factors. Permanent closure (fibrosis) is usually completed by the first 2–3 weeks of life. Patent ductus arteriosus (PDA) represents about 10 percent of congenital heart defects. In preterm infants, the overall incidence is 20–30 percent.
Pathophysiology
The degree of shunting via the PDA depends on the size of the PDA and the ratio of PVR to SVR.
With declining PVR, large PDAs can result in significant left-to-right shunting, left ventricle volume overload, CHF, and pulmonary hypertension.
Associated Anomalies
A PDA is often essential for pulmonary or systemic blood flow in patients with complex cardiac lesions. In preterm infants, the cardiovascular changes associated with a PDA can exacerbate conditions like necrotizing enterocolitis, intracranial hemorrhage, or respiratory distress syndrome.
Anesthetic Considerations
Ductal Dependent Lesions (e.g., hypoplastic left heart, transposition of the great arteries with intact ventricular septum, critical aortic stenosis, and interrupted aortic arch). Usually maintenance of ductal patency with prostaglandin E1 infusion (PGE1).
Second IV access for medication and fluid bolus, potentially difficult access (“doughy” tissue)
Side-effects of PGE1 therapy: dose-dependent apnea, platelet dysfunction, gastric mucosal hyperplasia, etc.
Ratio of PVR to SVR will determine adequacy of pulmonary or systemic blood flow
ICU admission for apnea monitoring.
Isolated PDA. Shunt direction and degree of shunting dependent on size of PDA and ratio of PVR to SVR. Presentation can range from very sick neonates or infants in CHF and on inotropic support to completely asymptomatic infants awaiting cardiac intervention or surgery.
“Bubble” precautions
Potential episode of cyanosis during emergence if coughing or breath holding, etc.
For symptomatic patients in CHF, please see recommendations for “large VSD” above.
Considerations for Patients With Repaired PDAs
Recurrent laryngeal nerve injury
Pulmonary hypertension and ventricular dysfunction if late repair
Coarctation of the Aorta
Coarctation of the aorta is present in 5–10 percent of patients with CHD. Most patients have a discrete stenosis of the upper thoracic aorta, opposite the insertion of the ductus arteriosus, but the anatomic spectrum can range from a long tubular hypoplasia of the transverse arch to band-like strictures in the descending aorta.
Pathophysiology
The hemodynamic picture is highly dependent on the severity of the stenosis and the presence of associated cardiac defects and collateral circulation. For instance, a newborn with critical stenosis may decompensate acutely when the ductus arteriosus closes. Or the patient may develop severe CHF and pulmonary overcirculation within the first 1–2 weeks of life if associated with a large VSD.
Associated Anomalies
Coarctation of the aorta is often associated with other congenital anomalies: 50 percent of patients have an additional intracardiac lesion, such as a large VSD, aortic stenosis, or hypoplastic left ventricle; 85 percent have a bicommissural aortic valve. In addition, variations of the brachiocephalic vessels with an abnormal origin of the subclavian arteries may occur, and 3–5 percent of patients have berry aneurysms of the circle of Willis. Patients with Turner syndrome have a high incidence of coarctation; other congenital malformations are present in 25 percent of patients.
Anesthetic Considerations
Maintain ductal patency with prostaglandin infusion, use second intravenous access for other drugs and bolus administration
Newborns and infants in CHF: Usually careful IV induction and narcotic-based maintenance
Patients with large VSD, at risk for pulmonary overcirculation: Avoid hyperventilation and high FiO2.
Consider inotropic support if severe CHF
Invasive BP monitoring in the right radial artery (preductal, unless there are arch anomalies like an anomalous right subclavian artery)
Consider additional BP monitoring and pulse oximetry in lower extremities
Considerations for Patients With Repaired Coarctation
Atrial Septal Defect
In its isolated form, atrial septal defect (ASD) comprises 5–10 percent of congenital heart defects, but is part of more complex cardiac defects in 30–50 percent of CHD patients.
Pathophysiology
Left-to-right shunt with slowly progressive right atrium and right ventricle dilation, and eventually development of pulmonary hypertension late in life. Eighty percent of all ASDs, especially those <8 mm, will close spontaneously within the first two years of life.
Associated Anomalies
Atrial septal defects may be associated with virtually any congenital anomaly. The most commonly associated cardiovascular defects include pulmonary stenosis, partial anomalous venous return, and VSD. There is a higher incidence of secundum ASDs in patients with Holt–Oram, Noonan, Marfan, and Turner syndromes.
Anesthetic Considerations
Careful removal of all air bubbles from lines to prevent paradoxical air embolus
Higher incidence of perioperative dysrhythmias
Inhalation induction is usually well tolerated (except in sick infants with CHF).
Consideration for Patients With Repaired ASDs
Perioperative dysrhythmias
Occasionally persistent right ventricle dilation or pulmonary hypertension (associated syndromes).
Tetralogy of Fallot
Between 5 and 10 percent of all CHDs are classified as ToF. It is by far the most common cyanotic lesion. There is a wide anatomic spectrum ranging from the classical form with pulmonary stenosis to pulmonary atresia and variations without evidence of right ventricular outflow obstruction (“pink Tet”).
Pathophysiology
The most important pathophysiological aspect of ToF is the obstruction to pulmonary blood flow; this leads to a right-to-left shunt via the VSD and subsequent hypoxemia and cyanosis. The obstruction can be an anatomically fixed stenosis at the level of the valve or pulmonary artery and/or a dynamic narrowing of the infundibular area due to thickened muscle bundles and septal malalignment.
Associated Anomalies
Tetralogy of Fallot is often associated with other cardiac anomalies. Some of these are of special concern for the surgical approach:
Right-sided aortic arch (20–25 percent): Affects surgical approach for shunts and repair of tracheoesophageal fistula
Coronary anomalies (5–8 percent): Abnormal origin or coronary branch crossing the right ventricular outflow tract (RVOT).
There is also an important association with noncardiac anomalies; only 68 percent of ToF are isolated cardiac lesions:
Chromosomal abnormalities (11.9 percent): Trisomy 13, 18, and 21.
Genetic syndromes (7.2 percent):
– DiGeorge Syndrome/velocardiofacial or Shprintzen syndrome (22q deletion syndromes)
– CHARGE association
– VATER/VACTERL
Anesthetic Considerations
Dehydration and long fasting periods should be avoided due to polycythemia
Consider admission and hydration overnight if severely polycythemic (Hct > 55 percent)
Preinduction fluid bolus is often beneficial
Careful removal of all air bubbles from lines to avoid systemic air embolism
Medications for treatment of “hypercyanotic spells” should be immediately available (see Table 29.4)
If previously shunted, note site of previous shunt as pressure monitoring may provide an unreliable reading
Generally, an IV induction using ketamine is used to maintain SVR and preload; in mild forms, careful inhalation induction is possible (watch for delayed induction with right-to-left shunt).
Considerations for Patients With Repaired Tetralogy of Fallot
Residual VSD
Residual RVOT obstruction – mostly mild, but severe in 10 percent of cases
Pulmonic regurgitation and right ventricle dilation after transannular patch repair
Arrhythmias and right ventricle dysfunction may occur after ventriculotomy and infundibular patch repair due to scarring and fibrosis
Left ventricle dysfunction (anomalous coronaries and ischemic injury)
| ■ “Knee–chest position” or abdominal compression |
| ■ Supplemental oxygen |
| ■ Sedation |
| ○ Morphine: 0.1 mg kg–1 IM/SC or ketamine 1–2 mg kg–1 IV/IM |
| ■ Volume expansion: 10–20 ml kg–1 crystalloid |
| ■ Phenylephrine IV |
| ○ 0.5–1–2 μg kg–1 bolus, 0.1–0.5 μg kg–1 min–1 infusion |
| ■ Propranolol 0.1 mg kg–1 IV |
| ■ Esmolol: 50–300 μg kg–1 min–1 ± loading dose 100–500 μg kg–1 IV |
| ■ Bicarbonate IV |
Atrioventricular Septal Defect
Between 4 and 5 percent of CHD are endocardial cushion defects, which can be divided into several types: partial, transitional, and complete atrioventricular (AV) canals. The most extensive form, the complete AV canal (CAVC), consists of a primum ASD with a common AV valve orifice, bridging leaflets, and a moderate to large inlet VSD.
Pathophysiology
Large left-to right shunt with AV regurgitation leading to pulmonary overcirculation, CHF, and early onset of pulmonary hypertension. Increasing cyanosis is often the first sign of pulmonary hypertension.
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