Anesthesia for Noncardiac Surgery in Children With Congenital Heart Disease

THE NATURAL HISTORY OF CONGENITAL HEART DISEASE (CHD) has been favorably altered over the past several decades by remarkable advances in medical and surgical care. These refinements have resulted in decreased morbidity and improvement in long-term outcomes in affected children. As survival rates further improve and life expectancy continues to increase, an escalating number of children with CHD will present for noncardiac surgery or other procedures unrelated to their heart disease. The care of these children is becoming more common in all diagnostic and surgical settings. As the trend for earlier palliation and corrective surgery for congenital cardiovascular malformations continues, children who have undergone these interventions represent the main patient group that an anesthesiologist is likely to encounter during elective, urgent, and emergent noncardiac surgery. In some cases, children may require noncardiac surgery before undergoing procedures to address their cardiovascular disease. In others, the cardiac condition may not require or be amenable to surgical intervention.

A variety of extracardiac anomalies have been described in children with CHD and the reported prevalence of associated malformations ranges between 10% and 33%. The organ systems most often affected include musculoskeletal, central nervous, renal-urinary, gastrointestinal, and respiratory. Although many extracardiac malformations are relatively minor and have limited or no clinical implications, a considerable number of children with CHD have significant noncardiac comorbidities. These pathologic and disease processes may necessitate surgical intervention. Other routine ailments may affect these children, requiring diagnostic procedures and/or surgical care. In addition, chromosomal syndromes and genetic disorders, well known to be associated with CHD, may lead to conditions that necessitate anesthesia care.

The challenges of caring for children with CHD for noncardiac surgery are magnified by the wide range of structural malformations, each with specific physiologic perturbations, hemodynamic consequences, and severity. This is further complicated by the variety of medical and surgical strategies available for management of these conditions. Many children, but particularly those with more than mild disease, require an individualized approach to anesthesia care.

Clinical outcomes for CHD depend on the nature of the structural abnormalities and the possibility of successful palliation or correction. The primary goal of palliative surgery is to favorably influence the natural history of the defect and decrease the likelihood of the severe consequences of the disease. However, these children continue to have abnormal cardiovascular anatomy and physiology, and their abnormal circulation is associated with an increased risk of perioperative adverse events. Reparative, corrective, or definitive procedures are expected to improve hemodynamics and cardiac function while minimizing long-term ill effects of an abnormal circulation, improving the overall clinical outcome. Although the pathology might have been surgically treated, the cardiovascular system should not be considered normal. Therefore, repair of a congenital cardiac lesion should not be equated with a cure for many children.

Despite these considerations, for children with good hemodynamic results, the risks associated with noncardiac surgery may not be significantly different from those of others without CHD. These children are considered to be doing well clinically, have a good functional status, require few or no medications, have no exercise restrictions, and undergo routine surveillance. They require minimal or no adjustment in perioperative care compared with that provided to children without CHD. In others, however, residual abnormalities exist. In some who are less fortunate, a pathologic process may remain or develop after cardiac surgery that is related to the primary disease or therapy. This may lead to severe cardiovascular or pulmonary impairment. These residua and sequelae may necessitate further medical or surgical interventions and can increase perioperative morbidity during noncardiac surgery. Management of these children is guided by several factors but to a significant extent by the residual problems of the disease and treatment and associated hemodynamic perturbations.

Many publications have examined the implications of anesthesia for patients with CHD undergoing noncardiac surgery ; however, only a limited number provide data on perioperative outcomes. In contrast to the extensive literature regarding perioperative cardiac assessment and risk stratification during noncardiac surgery in adults with heart disease, the availability of guidelines aimed at improving clinical outcomes, and the data regarding cardiac complications and cardiac risks of noncardiac surgery, the lack of rigorous scientific data on this subject for the pediatric age group or the patient with CHD has made an equivalent effort challenging.

Optimal anesthesia care for children with CHD requires a thorough understanding of the underlying cardiovascular anatomic abnormalities, pathophysiologic consequences of the defect, functional status, residua, sequelae, and expected long-term outcome, in addition to the planned procedure and potential complications. In this chapter, general principles of anesthesia practice are reviewed as they pertain to the care of children with CHD during noncardiac surgery. Unique perioperative considerations and issues applicable to high-risk patient groups are also addressed.

Preoperative Assessment

A detailed preoperative evaluation is indispensable for identifying and anticipating factors that may place a child with CHD at increased risk during anesthesia care ( Table 23.1 ). An important goal of this assessment is to gather information regarding the specifics of the cardiovascular disease and prior therapeutic interventions. A determination of functional status is based primarily on clinical data. The history and physical examination, in addition to the laboratory data and ancillary tests, provide complementary information about the structural cardiovascular malformations and hemodynamic status, enabling an overall risk assessment. Based on this clinical evaluation and consideration of the major pathophysiologic consequences of a particular condition, a systematic, detailed, organized plan is formulated for anesthesia and perioperative management. In some cases, the preoperative evaluation may establish the need to delay or defer elective noncardiac surgery, other interventions, or diagnostic procedures.

TABLE 23.1

Factors That Place Children With Congenital Heart Disease at Increased Risk During Anesthesia for Noncardiac Surgery

Anticoagulation therapy

Arrhythmias

Congestive heart failure

Emergent surgery

History of implanted device (pacemaker or defibrillator)

Hypoxemia

Long-standing cyanosis

Major noncardiac surgery

Older age at the time of cardiac intervention

Older type of cardiac surgical procedure

Pulmonary hypertension/pulmonary vascular disease

Significant outflow tract obstruction

Significant sequelae or residua

Single-ventricle physiology or complex defects

Syncope

Unrepaired pathology

Ventricular dysfunction

Young age (infancy)

An additional important aspect of the preoperative visit is that it provides an opportunity to initiate psychological preparation of parents and children before the planned intervention. Issues regarding expectations on the day of surgery in terms of premedication, the potential need for intravenous access, plans for induction of anesthesia, the estimated duration of the procedure, and postoperative recovery can be addressed at that time. In addition to the surgeon and anesthesia providers, other teams that may be part of this preoperative assessment may include the child's cardiologist, nursing, social work, child-life specialists, and other support services.

History and Physical Examination

As for all children undergoing anesthesia, the history and physical examination are essential components of a thorough preoperative evaluation. In addition to the details regarding the present illness and planned procedure, the history should focus on the status of the cardiovascular system. Relevant information includes the type of cardiovascular disease and comorbid conditions, medications, allergies, prior hospitalizations, surgical procedures or other interventions, anesthesia experiences, and complications. Symptoms, including tachypnea, dyspnea, tachycardia, fatigue, and those related to rhythm problems, should be sought. Feeding difficulties and diaphoresis can represent significant symptoms in infants, whereas decreased activity level or exercise intolerance may be a concern for older children. Palpitations, chest pain, and syncope should be characterized. The history should include an assessment of growth and development because these may be affected in children with CHD. Failure to thrive suggests ongoing cardiorespiratory compromise. Those with decompensated disease, complex pathologies, associated genetic defects, or other syndromes may be particularly vulnerable. Recent illnesses such as intercurrent respiratory infections or pulmonary disease may increase the potential for perioperative complications and require careful appraisal of the risk/benefit ratio in elective cases.

The physical examination should include the child's weight and height. Vital signs, including heart rate, respiratory rate, and blood pressure, should be documented. If the child is known or suspected to have or has been treated for any form of aortic arch obstruction or has had any systemic-to-pulmonary artery shunt, upper and lower extremity and the right and left upper extremity blood pressure recordings and palpation of the quality of pulses should be documented. This assessment provides information about the patency of arterial beds and helps in the selection of blood pressure monitoring sites. The examination should explore suitable sites for vascular access (venous and arterial) and identify potential difficulties. Emphasis should be given to the airway and cardiovascular system, with particular attention to any changes from previous examination findings.

General assessment includes the child's level of activity, breathing pattern, level of distress (if any), and presence/degree of cyanosis. Respiratory evaluation focuses on the quality of the breath sounds and should indicate the presence or absence of labored breathing, intercostal retractions, wheezing, rales, or rhonchi. Abnormalities may suggest congestive symptoms or a pneumonic process. Cardiac auscultation should include assessment of heart sounds, pathologic murmurs, and gallop rhythms. The presence of a thrill, representing a palpable murmur, should be documented. The abdomen should be examined for the presence of hepatosplenomegaly. Assessment of the extremities should include examination of pulses, overall perfusion, capillary refill, cyanosis, clubbing, and edema. Noncardiac anomalies or pathology that may affect anesthesia care (e.g., specific syndrome complex, potentially difficult airway, gastroesophageal reflux) should be recorded.

An important objective of the preoperative evaluation is to identify children with functional cardiopulmonary limitations imposed by their cardiovascular disease. Symptoms and signs consistent with congestive heart failure, cyanosis, hypercyanotic episodes, and compromised functional status (i.e., significant exercise intolerance or syncopal episodes) should raise concerns about potential perioperative problems. The pediatric cardiologist should facilitate information about the nature and severity of the cardiovascular pathology, describe the child's overall clinical status, and assess prior complications. The cardiologist should identify those children who may be at increased risk and optimize their preoperative clinical condition. The perioperative care teams should be alerted to any concern that may affect the care of the child. The anesthesiologist should have a detailed understanding of the child's cardiac defect, pathophysiologic consequences, nature of the medical and surgical therapies applied, functional status, and implications for perioperative management. In patients at increased risk, pediatric anesthesia consultation is recommended before the procedure. In some cases, based on this assessment, an inpatient setting may be favored over an outpatient surgical facility. Although the surgical team may not have an in-depth understanding of the child's cardiovascular disease, by discussing the details of the surgical plan and potential issues with the perioperative care providers, problems can be anticipated and proactively addressed.

Ancillary Studies and Laboratory Data

The baseline systemic arterial saturation value should be determined by pulse oximetry (Sp o ₂ ) when the child is calm and, in most cases, while breathing room air. Acceptable values depend on many factors, including the specific cardiovascular defect(s), whether the child has a two- or a one-ventricle circulation, the preoperative versus postoperative status with respect to the cardiac pathology, and the stage in the palliative pathway for those undergoing such a strategy. Children who have undergone definitive (corrective) procedures should be expected to have normal to a near-normal Sp o ₂ value (at least 95%). After palliative interventions, Sp o ₂ values typically range between 75% and 85%.

The extent of preoperative laboratory testing largely depends on the status of the patient and the type, anticipated duration, and complexity of surgery. Studies most commonly obtained include hematocrit, hemoglobin, electrolytes, and coagulation tests. In cyanotic children, a complete blood cell count allows determination of polycythemia, anemia, and thrombocytopenia. Prothrombin time, partial thromboplastin times, and international normalized ratio (INR) provide an indication of clotting ability. Cyanotic children usually have increased red blood cell mass and relatively small plasma volumes. The collection of specimens for coagulation tests requires sampling tubes that adjust the amount or concentration of citrate to prevent artifactually prolonged values. For those receiving diuretic therapy, digoxin, or angiotensin-converting enzyme inhibitors (ACEIs), the determination of a basic metabolic panel can be useful. A comprehensive metabolic panel that assesses electrolyte and acid-base balance, the health of the kidneys and liver, as well as concentrations of blood glucose and blood proteins may be more appropriate in some cases. Blood typing and cross-matching should be performed depending on the anticipated need for blood administration.

A recent electrocardiogram (ECG) should be reviewed for any changes from prior studies (particularly regarding criteria consistent with chamber dilation or ventricular hypertrophy), the presence of rhythm abnormalities, and findings suggesting myocardial ischemia. If an arrhythmia is identified on the preoperative assessment, further evaluation is warranted because it may reflect an underlying hemodynamic abnormality that may affect the perioperative course. A continuous ECG recording (i.e., Holter monitor) and further evaluation may be indicated in the child with a history of rhythm disturbance, palpitations, or syncope or with an ECG suggesting significant ectopy or arrhythmia. An exercise tolerance test or treadmill study is warranted if there is concern about myocardial ischemia, as may be the case for the child with aortic stenosis, coronary artery anomalies, or exercise-induced arrhythmias.

Review of a recent chest radiograph, including a lateral view, provides information regarding cardiac size, chamber enlargement, and pulmonary vascularity. Prior studies such as echocardiograms, cardiac catheterizations, electrophysiologic procedures, magnetic resonance imaging, and computed tomography should be reviewed. In some cases, it may be necessary to obtain further diagnostic information before proceeding with the planned procedure if there are symptoms that merit additional investigations or issues of concern. These evaluations should be coordinated with the child's cardiologist. It is also important to consider whether the child would benefit from cardiac catheterization to undertake interventions addressing significant structural, functional, or hemodynamic abnormalities before the anticipated noncardiac procedure. In addition to providing potentially helpful information, the clinical status of the child can be substantially improved in many cases by catheter-based interventions. This may be of significant benefit when the planned procedure is of an elective nature and considered to be major.

One of the goals of the preoperative evaluation is to obtain the most diagnostic information with the fewest tests and the least risk, discomfort for the child, and expense. The anesthesiologist is particularly suited to determine which tests are appropriate for optimal perioperative planning and whether additional data are needed.

Informed Consent

The physicians involved in the care of the child should meet with the patient and family to discuss the anesthetic plan and answer any questions. The preoperative consultation provides the opportunity to alleviate patient and parental anxiety. At the same time, the possible benefits and risks involved should be discussed. Although anesthesia and surgery in children with CHD, particularly in those with uncorrected defects, may carry an increased risk, it may not be possible to define the specific contribution of each factor to the overall risk.

Fasting Guidelines

The optimal period of fasting for children before surgery has been the subject of debate. However, most centers follow guidelines established by their national societies to reduce the risk of aspiration. The same principles are applicable to children with CHD with a few additional considerations. Intake of clear fluids or the intravenous (IV) administration of maintenance fluids should be considered in some children to ensure adequate hydration if the fasting period is anticipated to be prolonged. This is particularly important in small infants and in children with obstructive pathology, cyanotic disease, or single-ventricle physiology. Maintenance of adequate hydration and ventricular preload may minimize potential detrimental hemodynamic changes associated with anesthesia and surgery.

Medications

Children with CHD may be taking medications on a regular basis. Although there may be an occasional exception, such as diuretic, vasodilator (e.g., ACEI), or anticoagulation therapy, there is usually no need to discontinue long-term medications before surgery. It is often important to continue these drugs until the time of surgery, and in most centers, children are allowed to take scheduled oral medications with small sips of water preoperatively.

Intraoperative Management

Anesthesia and surgery impose additional stresses on the cardiovascular system and provoke compensatory mechanisms to maintain homeostasis. It is important to assess the child's physiology and cardiovascular reserve to anticipate his or her ability to increase cardiac output to meet metabolic demands and procure optimal oxygen delivery. This information, along with the nature and complexity of the surgery, affects the extent of monitoring required and the selection of anesthetic agents and techniques. Prompt intervention is imperative if decompensation occurs. Good communication among the surgeon, cardiologist/intensivist, anesthesiologist, and nursing teams during the entire perioperative period is essential in treating children with complex disease.

General Considerations

Anesthesia Care Provider and Health Care Facility

Anesthesia care should be provided by individuals who are familiar with children with CHD, the planned operative procedure, and the surgeon's usual approach. Although many specialized centers that care for children have dedicated pediatric cardiac anesthesiologists, they may not be available at all facilities. Even if these providers are available, the number might be limited and they may not be able to support all noncardiac cases; in some instances, this type of advanced expertise may not be required. The most important factor that an anesthesiologist can offer a child with CHD is a comprehensive understanding of the anatomic abnormalities, pathophysiology of the cardiac malformation, and how this may be affected by the anesthetic and surgical procedure. Familiarity with the most likely residua and sequelae is essential. Adequate communication among all physicians involved enhances the likelihood of the best possible outcome.

Recent publications have addressed one of the ongoing controversies in CHD—namely, which medical facility should provide care for these patients during noncardiac surgery. Data regarding this specific issue and support for a strong recommendation are otherwise extremely limited. It has been suggested that high-risk children should be cared for at specialized centers. A recent outcome review concluded that procedures requiring general anesthesia could be performed safely in children from any of the three risk groups in a noncardiac center with the caveat that this requires close communication and careful planning among the various specialties. Further data in this regard are necessary.

Premedication

The use of premedication provides sedation and anxiolysis before most surgical procedures because some degree of fear or anxiety is expected. This facilitates parental separation, entry into the operating room, placement of monitors, and induction of anesthesia.

Commonly used premedications include oral or IV benzodiazepines, opioids, and small amounts of hypnotic agents. Drugs such as barbiturates and ketamine are occasionally used. Alternative routes for premedication include intramuscular, intranasal, and rectal. The cardiorespiratory effects of premedication in children can be influenced by the underlying systemic disease. Children with marginal clinical status or hemodynamic decompensation may require little or no premedication. Caution should also be exercised in children with a history of cardiovascular pathology associated with pulmonary hypertension because hypoventilation and hypoxemia can be detrimental. Conversely, children susceptible to hypercyanotic episodes or those with catecholamine-induced arrhythmias can benefit from heavy premedication. In selected children, for example those affected by cyanotic heart disease, oxygen saturation monitoring after premedication should be considered with the administration of supplemental oxygen as needed.

Intravenous Access

Secure IV access is mandatory for administration of fluids and medications during anesthesia care in children with CHD. In most, IV access is established after an inhalational induction. In those considered at great risk, such as children with severe ventricular outflow tract obstruction, moderate to severe cardiac dysfunction, pulmonary hypertension, or potential for hemodynamic compromise, consideration should be given for placement of IV access before induction of anesthesia or very early in the process. The size of the IV catheter should be determined by the anticipated fluid/transfusion requirements. If peripheral access is poor, central venous access may be necessary, particularly if there is potential for large intravascular volume shifts and to allow monitoring of central venous pressure. Placement of a central venous catheter is assisted by two-dimensional ultrasound imaging or audio Doppler (see Chapter 49 ). In the small infant with single-ventricle physiology, central venous cannulation with catheter placement in the superior vena cava may be undesirable in view of concerns about potential vascular complications that may affect pulmonary blood flow or subsequent surgical palliation. In these children, a small catheter or alternative approach (e.g., femoral venous access) should be considered. In children with an existent or potential right-to-left shunt, all air must be removed from IV infusion tubing. Air filters can be difficult to use in the operating room because they potentially restrict the rate at which IV fluids or blood may be administered in emergency situations. They can be more useful in the preoperative and postoperative periods.

Emergency Drugs

Hemodynamic instability can occur in children with CHD under any circumstance and at any time. Therefore drugs for emergency situations should be prepared in advanced or be immediately available to the anesthesiologist providing care.

Monitoring

A fundamental principle of intraoperative monitoring is to use techniques or devices that provide useful information to facilitate clinical decision making and to avoid monitors that are distracting or redundant. Basic monitoring involves observation of the child, including skin color, capillary refill, respiration, pulse palpation, events on the surgical field, and color of shed blood. Standard noninvasive monitors used during most surgical interventions include oscillometric blood pressure assessment, electrocardiography, pulse oximetry, capnography, and temperature recordings. A precordial stethoscope can be extremely helpful for monitoring changes in heart tones that may suggest early hemodynamic compromise. In the child with CHD, relatively sophisticated and invasive monitoring may be needed.

Arterial Blood Pressure Assessment

Blood pressure monitoring begins with pulse palpation. An automated blood pressure measurement is used in most children. The selection of monitoring site is influenced by vascular anomalies (e.g., aortic arch pathology, aberrant origin and course of aortic arch vessels) or prior surgical interventions (e.g., Blalock-Taussig shunt, arterial cutdown). Direct blood pressure monitoring by an indwelling arterial catheter may be necessary for beat-to-beat assessment and for blood gas analysis. In most children, this is accomplished after induction of anesthesia. Percutaneous arterial cannulation can be achieved in most cases with a low risk of complications (see Chapter 49 ). The radial artery usually is preferred over the ulnar artery because avoiding the ulnar artery allows preservation of a larger contributor of blood supply to the hand. The ulnar artery often is the larger vessel and it can be cannulated if required. However, some centers have a policy that the ulnar artery should never be cannulated. This policy ensures that there is always at least one vessel (ulnar artery) available to perfuse the hand should the radial vessel be compromised. Ultrasound guidance with two-dimensional imaging or audio Doppler can facilitate cannulation. The need for invasive monitoring is largely based on the child's clinical condition and nature of the surgical procedure.

Electrocardiography

The ECG provides a surface recording of the electrical myocardial activity and is used to monitor heart rate, cardiac rhythm, and ST-segment analysis. One or multiple leads typically are displayed. Arrhythmias can occur because of hypoxia, electrolyte imbalances, acid-base abnormalities, intravascular or intracardiac catheters, and surgical manipulations near or around the thorax. Ischemia may be evident on direct examination of the ECG or ST-segment analysis. Although in adults this is associated with worsened outcome, the implication for the pediatric population is unknown.

Pulse Oximetry

Placement of an oximeter probe is well tolerated, even by uncooperative children, and it is usually one of the earliest monitors applied during induction of anesthesia. Monitoring arterial oxygen saturation by pulse oximetry is particularly useful in infants, cyanotic children, and those with complex anatomy or significant hemodynamic compromise. In addition to providing continuous assessment of oxygen-hemoglobin saturation and heart rate, the pulse oximeter waveform can indicate the adequacy of peripheral perfusion and cardiac output. Other parameters that can be reflected by the Sp o ₂ include intracardiac or great artery–level shunting and pulmonary blood flow.

Capnography

Capnography confirms proper tracheal tube placement, helps to assess the adequacy of ventilation, and aids in the recognition of pathologic conditions such as bronchospasm, airway obstruction, and malignant hyperthermia. Capnography is also useful in spontaneously breathing, sedated children receiving supplemental oxygen through a nasal cannula; a prospective, observational study in children undergoing cardiac catheterization with sedation administered by nonanesthesiologists found that exhaled carbon dioxide values (P etco ₂ ) provided a reasonable estimate of arterial blood CO ₂ values. Although the absolute value for P etco ₂ may not be as reliable as in the presence of a tracheal tube, the capnograph waveform confirms the presence or absence of respirations and air exchange. End-tidal CO ₂ monitoring also provides a gross index of pulmonary blood flow. In children with cyanotic heart disease, P etco ₂ values can underestimate arterial carbon dioxide tension (Pa co ₂ ) measurements owing to altered pulmonary blood flow and ventilation-perfusion mismatch.

Temperature Monitoring

Temperature should be routinely monitored during most procedures. Although temperature swings are usually not profound, some children, particularly small neonates, may become hypothermic because of the large body surface area/body weight ratio and decreased amount of subcutaneous tissue. This can influence oxygen delivery (i.e., increased oxygen consumption) and emergence from anesthesia, cause detrimental changes in hemodynamics, and affect hemostasis. The neonate or small infant with CHD can be particularly vulnerable to the effects of hypothermia.

Urinary Output Measurements

The production of urine is a useful index of the adequacy of renal perfusion and cardiac output. Urine output is usually monitored during cases involving major fluid shifts or blood loss or when the surgical procedure is expected to be prolonged. No specific value for intraoperative urine output is predictive of good renal function in the postoperative period.

Echocardiography

Numerous publications have documented the utility of transesophageal echocardiography in general anesthesia practice and as a monitoring device in high-risk adults undergoing noncardiac procedures. Sporadic reports have demonstrated the utility of this imaging approach in children undergoing noncardiac surgery. However, the application of this imaging modality in the pediatric age group or contributions in this particular setting has not been well defined and deserves further investigation.

Newer Technologies

Of significant interest over the past several years has been the use of point-of-care ultrasonography in various settings, including the perioperative period. This is an evolving field that is receiving increasing attention during noncardiac surgery. Continuous noninvasive cardiac output assessment represents an area of ongoing investigation in children using a variety of techniques. These monitoring modalities are likely to further enhance the practice of pediatric anesthesia in the future.

Selection of Techniques and Agents

Several anesthetic regimens have been used in children with CHD undergoing noncardiac surgery and studies or procedures that require deep sedation or immobility. Although no single formula or protocol is recommended, the anesthetic techniques and agents used for a particular situation should be selected in consideration of the procedure, the child's disease process and functional status, and the impact of the hemodynamic effects of the anesthetic and procedure on the pathophysiologic process. Factors such as age, physical characteristics, and preferences of the anesthesiologist must be considered. The primary goals of anesthesia management with respect to the cardiovascular system are to optimize systemic oxygen delivery, maintain myocardial performance within expected parameters for the patient, and ensure the adequacy of cardiac output. A potentially limited cardiovascular reserve, reduced tolerance for perioperative stress, and detrimental alterations of the balance between pulmonary and systemic blood flow during anesthesia and surgery should be considered. A carefully titrated anesthetic, regardless of the specific agent or drug, should be the goal.

Anesthesia Technique

General anesthesia has the advantages of wide acceptance, ease of application, and certainty of effect. It is the appropriate choice for most children undergoing noncardiac surgery. Disadvantages include a greater potential for wide fluctuations in the hemodynamics and a prolonged recovery period. The IV route allows for rapid induction of anesthesia. If IV access is not available, inhalational induction can be performed. Inhalational anesthetics dilate vascular beds and reduce sympathetic responsiveness. These are desirable goals for most children, even those with heart disease, because adequate myocardial function and a reactive sympathetic nervous system are usual. However, sick children, and in particular those with ventricular dysfunction, may require an increased resting sympathetic tone to maintain systemic perfusion. Potent inhalational agents in this setting can further impair myocardial function, decrease sympathetic tone, and potentially lead to cardiovascular decompensation. These children and others with a relatively fixed cardiac output frequently require a technique that combines several medications (i.e., balanced technique) to achieve anesthesia while minimizing the risk of hemodynamic compromise. A combined opioid, amnestic agent, and muscle relaxant technique minimizes myocardial depression and tends to leave sympathetic responsiveness intact while providing analgesia, amnesia, and immobility.

Regional anesthesia has been used safely and shown to be effective in children with CHD (see Chapters 42 and 43 ). Advantages of regional anesthesia, such as epidural and spinal techniques, include an effect largely limited to the surgical site, decreased number of systemic medications, a potentially brief recovery period, and usually a more pleasant experience for the child. Use of these techniques, however, may not always be effective. Regional anesthesia retains the potential for hemodynamic alterations, particularly in hypovolemic children or those with a fixed cardiac output. It is also contraindicated in those with coagulation defects. The administration of agents such as local anesthetics, opioids, or other adjuvants (e.g., clonidine) into the caudal space can attenuate the sympathetic outflow associated with surgical manipulation and noxious stimuli and facilitate postoperative pain management.

The choice of technique affects the termination of anesthesia and emergence. Anesthesia performed with fewer agents is inherently simpler, usually easier, and more predictable to terminate. The availability of ultra-short-acting opioids (e.g., remifentanil) and other agents (e.g., dexmedetomidine) has avoided the need for postoperative ventilation solely related to residual effects of depressant drugs. Ventricular function and the presence of intracardiac shunts can significantly affect uptake and distribution of inhalational anesthetics and the kinetics of IV medications (see Chapter 7 ).

Inhalational Agents

Inhalational anesthesia has been at the forefront of pediatric anesthesia practice for many years. Sevoflurane was introduced in the mid-1990s, replacing halothane for inhaled induction in many centers. A study on the safety and efficacy of inhaled agents in infants and children with CHD during cardiac surgery demonstrated twice as many episodes of hypotension, moderate bradycardia, and emergent drug use in those who received halothane compared with those given sevoflurane. These data, combined with those from other studies that demonstrated the potential benefits of sevoflurane on hemodynamic stability and minimal impact on myocardial performance, led to sevoflurane becoming the preferred anesthetic agent for children, particularly those with heart disease. Nonetheless, in some jurisdictions and under some conditions, halothane may remain the primary anesthetic for children. After an inhalational induction with sevoflurane, agents such as isoflurane or desflurane might be used to maintain anesthesia.

Intravenous Agents

Propofol is one of the most frequently used medications for IV sedation and general anesthesia. It has been used in children with CHD in numerous settings. The hemodynamic effects of propofol have been investigated in children with normal hearts and in those with cardiovascular disease. An echocardiographic study in infants with normal hearts undergoing elective surgery demonstrated that propofol did not alter heart rate, shortening fraction, rate-corrected velocity of circumferential fiber shortening, or cardiac index after IV induction. However, propofol decreased arterial blood pressure to a greater extent than thiopental, an effect attributed to a reduction in afterload. A comparison of propofol and ketamine during cardiac catheterization found that propofol caused a transient decrease in mean arterial pressure and mild arterial oxygen desaturation in some children. In view of the significantly faster recovery, propofol was identified as a practical alternative to ketamine for elective cardiac catheterization in children.

Another investigation in 30 children with CHD undergoing cardiac catheterization demonstrated significant decreases in mean arterial blood pressure and systemic vascular resistance during propofol administration. No changes in heart rate, mean pulmonary artery pressure, or pulmonary vascular resistance were observed. In children with intracardiac shunts, the net result of propofol was a significant increase in the right-to-left shunt, a decrease in the left-to-right shunt, and a decreased pulmonary/systemic blood flow ratio, resulting in a statistically significant decrease in the Pa o ₂ and arterial oxygen saturation (Sa o ₂ ), as well as reversal of the shunt direction from left-to-right to right-to-left in two patients. It was also shown that propofol could lead to further arterial desaturation in children with cyanotic heart disease. A recent study examined the effects of propofol on cerebral oxygenation in children with CHD. Propofol sedation was associated with increased cerebral tissue oxygenation despite a significant decrease in mean arterial pressure, stroke volume, cardiac output, and cardiac index. The authors reported that the hemodynamic changes were not considered clinically relevant and none required intervention.

The effects of propofol have been examined in children undergoing electrophysiologic testing and radiofrequency catheter ablation for tachyarrhythmias. The drug has no significant effect on sinoatrial or atrioventricular (AV) node function or accessory pathway conduction in Wolff-Parkinson-White syndrome. However, another study documented that ectopic atrial tachycardia can be suppressed during propofol administration in children.

Collectively, these data support the judicious use of propofol in children with adequate cardiovascular reserve who can tolerate mild decreases in myocardial contractility and heart rate and mild to moderate decreases in systemic vascular resistance. Given the effects of propofol on the direction and magnitude of intracardiac shunts, this might be an important consideration in children with cyanotic heart disease and can influence the hemodynamic assessment of those undergoing evaluation of pulmonary/systemic blood flow ratios in the cardiac catheterization laboratory.

Sodium thiopental, a rapid-onset short-acting barbiturate, was used for many years for induction of anesthesia. The last company to market sodium thiopental in the United States stopped production of the drug in early 2011. Several investigations documented the cardiovascular responses to this agent; in children with normal hearts, the cardiac index remained unchanged, although the shortening fraction decreased along with alterations in load-independent parameters of contractility. The data regarding myocardial depressant properties of barbiturates and its effects on venodilation and peripheral blood pooling suggested that the administration of thiopental in a subset of children could cause hemodynamic instability. Thus it was recommended that thiopental should be used with caution, particularly in those with limited reserve or increased sympathetic tone.

Etomidate, a carboxylated imidazole derivative, has anesthetic and amnestic properties but is devoid of analgesic effects. This agent demonstrates favorable qualities over other IV drugs because of its lack of effect on hemodynamics. This, combined with laboratory and clinical data that support minimal effects on myocardial contractility, makes this drug a particularly desirable agent in critically ill individuals and in those with limited cardiovascular reserve. Despite these benefits, several undesirable adverse effects are associated with etomidate, including pain on IV administration, myoclonic movements that may mimic seizure activity, and inhibition of adrenal steroid synthesis perioperatively. Although used primarily as an induction agent, etomidate has been administered for sedation of children during cardiac catheterization and in other settings.

Ketamine is a dissociative anesthetic agent administered by the IV, intramuscular, nasal, rectal, and oral routes. Because its sympathomimetic effects result in an increased heart rate, blood pressure, and cardiac output, this drug has been widely used in children with heart disease, particularly in young infants. The effects of this agent on systemic vascular resistance make it a suitable choice in children with right-to-left shunts because pulmonary blood flow is enhanced. This contrasts with inhalational agents, which by causing systemic vasodilation can decrease pulmonary blood flow in the presence of an intracardiac communication and potentially worsen the degree of cyanosis. In clinical use, however, arterial oxygen saturation typically increases with both agents. Additional favorable properties include intense analgesia at subanesthetic doses and a lack of respiratory depressant effects.

Several investigations have addressed the concern of potential detrimental changes in pulmonary vascular tone resulting from ketamine, although no significant effects have been reported on pulmonary arterial pressures and pulmonary vascular resistance at the usual clinical doses. Regarding its effect on myocardial performance, in vitro investigations have shown a direct myocardial depressant effect in animal species and the failing adult human heart. This is considered to be the result of inhibition of L-type voltage-dependent calcium channels in the sarcolemmal membrane and may be a consideration in the critically ill infant with a severely impaired cardiac reserve. Additional undesirable effects of ketamine include emergence reactions, excessive salivation, vomiting, and increased intracranial pressure.

Dexmedetomidine is a selective α ₂ -adrenergic agonist agent being increasingly used in the pediatric age group. Compared with clonidine, the drug exhibits greater specificity for the α ₂ -adrenergic receptor over the α ₁ -adrenergic receptor. Favorable effects of the drug include sedation, anxiolysis, and analgesia. This medication provides hemodynamic stability, although adverse effects have been reported, including bradycardia, hypertension, and hypotension. A study of the hemodynamic effects in children undergoing dexmedetomidine sedation for radiologic imaging demonstrated modest decreases in heart rate and blood pressure. These changes in response to moderate doses were independent of age, required no pharmacologic interventions, and did not result in any adverse events; however, high-dose dexmedetomidine can be associated with significant bradycardia. In addition, treatment of dexmedetomidine-induced bradycardia with glycopyrrolate (5 µg/kg) has been associated with severe persistent hypertension.

Dexmedetomidine is used as a premedication agent during diagnostic studies and procedural sedation, to reduce emergence delirium, in the treatment of symptoms associated with opioid withdrawal, and as an adjuvant agent in the operating room and postoperative settings. In children with CHD, its benefits have been reported during monitored anesthesia care, diagnostic and interventional cardiac catheterization, intraoperative sedation, after cardiac and thoracic surgery, as a primary agent during invasive procedures, and in the treatment of perioperative atrial and junctional tachyarrhythmias. The drug has also been used in children with pulmonary hypertension with good results.

Known electrophysiologic effects of dexmedetomidine in children include significant depression of sinus and AV nodal function. Other findings include a reduction in the heart rate and increases in arterial blood pressure. Although dexmedetomidine has been described as an undesirable agent for electrophysiologic studies because it could be associated with adverse effects in patients at risk for bradycardia or AV block, another study reported that dexmedetomidine was not associated with any significant or atypical ECG interval abnormalities, except for a trend toward a decrease in heart rate in children with CHD. Until additional data are available, it may be prudent to exercise caution when considering the use of dexmedetomidine in children with conduction abnormalities. Although experience suggests an overall safety profile in children with CHD, fragile patients may not tolerate the heart rate and blood pressure fluctuations associated with dexmedetomidine; significant adverse effects include severe bradycardia progressing to asystole.

Opioids and benzodiazepines are widely used medications in pediatric anesthesia practice. Opioids attenuate the neuroendocrine stress response associated with anesthesia and surgery. After repair of CHD, these medications blunt the stress response in the pulmonary circulation elicited by airway manipulations. Morphine administration can cause histamine release and vasodilation. The synthetic opioids are devoid of these effects and provide excellent hemodynamic stability with minimal changes in heart rate and blood pressure in children with CHD. The primary concern about opioid administration is their central respiratory depressant effects because their primary cardiovascular manifestations are minimal. Benzodiazepines provide sedation and amnesia during the perioperative period. Midazolam may allow a reduction in the inspired concentration of inhalational anesthetic agents, which is a desirable feature in children with labile hemodynamics or in those considered at great risk for the myocardial depressant properties of inhalational anesthetics. Studies of the effects of benzodiazepines in children with CHD are limited.

Neuromuscular blocking drugs facilitate tracheal intubation and prevent reflex movement during surgery if the anesthetics alone are insufficient. All inhalational anesthetics potentiate the effects of nondepolarizing muscle relaxants. These medications have various onsets and durations of action and diverse hemodynamic effects. The cardiovascular and autonomic effects of muscle relaxants have been characterized mainly in adults with acquired cardiovascular disease (see also Chapter 7 ). Drug selection is based on the need to facilitate tracheal intubation and surgical relaxation, hemodynamic side effects, and the anticipated duration of surgery.

Induction of Anesthesia

Induction of anesthesia in children with CHD most commonly can be accomplished using the inhaled or IV route. The intramuscular route (i.e., ketamine administration) may be preferable in some cases, particularly in an uncooperative, developmentally delayed, or combative child. Less common induction techniques include subcutaneous, intranasal, and rectal administration of induction or sedative agents. These various approaches may also be used in combination (see Chapter 4 ).

An IV induction is preferable in some children in view of its potentially greater safety margin. In addition to the ability to titrate medications and rapidly correct hemodynamic alterations, other benefits include the speed of effect, although this may be slowed in children with large left-to-right shunts owing to recirculation of the drug in the lungs. Left-to-right shunting decreases the concentration of anesthetic agents reaching the brain and delays its onset of action. In contrast, right-to-left shunts speed IV inductions because a significant portion of the medication bypasses the lungs (where it is degraded) and directly enters the systemic circulation, reaching the brain more rapidly than with an intact circulation.

If IV access is not available, an inhalational induction is performed in most cases. A carefully titrated inhalational induction and early placement of an IV catheter usually is safe, even in children with moderate hemodynamic disturbances, particularly after premedication has been given. This produces loss of consciousness, with acceptable conditions for establishing IV access. Inhalational induction can be delayed in cyanotic children and those with right-to-left shunts, particularly for anesthetics with reduced blood solubility, because the decreased pulmonary blood flow limits the rate of increase in the concentration of the anesthetic in the systemic arterial blood. The rapidity of an inhalational induction is increased in the presence of a reduced cardiac output because the anesthetic partial pressure in the alveoli increases more rapidly as less anesthetic is removed by the smaller pulmonary blood flow (see Chapter 7 ). Left-to-right intracardiac shunts have limited effects on the speed of induction of inhaled anesthetics.

Maintenance of Anesthesia

After induction, anesthesia can be maintained using an inhalational, IV, or combined inhalational and IV technique. In children with CHD, anesthesia can result in hemodynamic changes regardless of the technique, agents, or experience of the anesthesiologist. Some children may not tolerate even minor alterations in hemodynamics. Factors that may lead to cardiovascular collapse in the marginally compensated child include hypovolemia, relative anesthetic overdose, increased vagal tone, positive-pressure ventilation, hypoxemia, airway obstruction, alterations in Pa co ₂ or other factors that influence the balance between systemic and pulmonary blood flow, myocardial ischemia, arrhythmias, and anaphylaxis. The anesthesiologist should be prepared to manage these rare but occasionally unavoidable occurrences at any time.

Emergence From Anesthesia

Most children undergoing noncardiac surgical interventions are expected to awaken immediately at the completion of the procedure or shortly thereafter. This usually involves reducing and then discontinuing IV or inhalational anesthetics, antagonizing neuromuscular blockade, and extubating the trachea. Ensuring the return of protective reflexes and monitoring the adequacy of the airway and respirations are important considerations.

Postoperative Care

The postoperative management of the child with CHD involves many of the same physiologic principles applicable to intraoperative care. The extent of the postoperative care, optimal place for recovery, and need for monitoring and hospitalization depend in large part on the child's clinical condition and type and extent of the procedure. Immediately after surgery, most children awaken from anesthesia and recover from neuromuscular blockade, which may impose various stresses and hemodynamic changes. Adequate oxygenation and ventilation along with airway protection must be ensured and may need to be provided if the child cannot manage these functions on his or her own. Significant hypoventilation must be avoided during this time because it may negatively affect pulmonary vascular tone and overall hemodynamics in vulnerable children with CHD. Adequate pain control and, sometimes, sedation are important postoperatively. This may be a challenging issue for the child who requires noncardiac surgery soon after a prolonged hospitalization in view of the increased likelihood for tolerance to analgesic and sedative drugs.

Observation and physical examination provide much information about the child's respiratory status, cardiac function, and systemic perfusion during the postoperative period. Adequacy of oxygenation and ventilation can also be assessed with noninvasive monitoring and blood gas analysis. Monitoring urine output can be helpful.

Hemoglobin or hematocrit values are monitored as a measure of oxygen-carrying capability in cases in which significant blood loss or the administration of fluids might have occurred. Serum electrolytes are screened if fluid shifts have taken place during the surgical and/or postoperative periods. Although digoxin is now used less frequently, attention should be given to the avoidance of hypokalemia in children receiving this drug. Serum glucose concentrations should be followed in neonates and small infants and dextrose-containing IV solutions administered as appropriate. Determination of ionized calcium (iCa ⁺ ⁺ ) levels is indicated for patients with a history of DiGeorge syndrome because of a propensity toward hypocalcemia. Fluid replacement is dictated by the child's heart defect, type of surgery performed, and volume losses (see Chapters 9 and 12 ).

Perioperative Problems and Special Considerations

Several potential problems may be encountered during the perioperative period in children with CHD undergoing noncardiac interventions. This section highlights some of these issues to serve as a framework and outlines selected considerations in these children.

Hypotension

Hypotension can be related to hypovolemia owing to prolonged fasting, volume loss, arrhythmia, anesthetic agents, myocardial dysfunction, or mechanical influences associated with the operative procedure. A practical diagnostic approach to the hypotensive patient is to consider factors that may affect ventricular preload, contractility, afterload, and the assessment of cardiac rhythm. Although the management of hypotension should be guided primarily by the causative factor, acutely increasing blood pressure by the administration of volume and an appropriate vasopressor, if indicated, often restores adequate perfusion while definitive therapy is instituted. Ensuring adequate intravascular volume with a fluid challenge often helps to restore perfusion and blood pressure, especially in hypovolemic patients. A pure α-adrenergic agent such as phenylephrine increases systolic blood pressure without further increases in heart rate. Some children are unable to tolerate any degree of myocardial depression or reduction in sympathetic outflow and require continuous inotropic support or vasopressor infusions throughout and after the operative procedure.

Cyanosis

Cyanosis is a common finding in children with defects characterized by reduced pulmonary blood flow or intracardiac mixing. As surgical management strategies evolve to target the youngest of infants, the chronic effects of cyanosis may be limited in these children. However, in those requiring delayed surgery, palliation, or staged correction of their defects, the effects of cyanosis can be long lasting. Chronic hypoxemia affects all major organ systems. Compensatory mechanisms that attempt to provide adequate systemic oxygen delivery in the presence of chronic hypoxemia include polycythemia (related to secondary erythrocytosis), increases in blood volume, alterations in oxygen uptake and delivery, and neovascularization. Despite the favorable effects of the adaptive responses, these alterations can be detrimental. Polycythemia, the most significant compensatory response, is associated with increases in blood viscosity and red cell sludging. The common occurrence of iron-deficiency anemia in cyanotic children further enhances hyperviscosity and the unfavorable consequences of this condition. Several hemostatic abnormalities (e.g., thrombocytopenia, altered platelet function, and clotting factor abnormalities) have been described as a result of hypoxemia and erythrocytosis that may affect the coagulation system and increase perioperative risks. This is compounded by increased tissue vascularity, with a larger number of blood vessels per unit of tissue.

The increased blood viscosity in children with cyanosis is associated with stasis and a risk for thrombotic events. If the hematocrit exceeds 65% preoperatively, some clinicians advocate phlebotomy to reduce the hematocrit to 60% to 65%. This limits sludging of red blood cells and increases oxygen delivery to tissues. If blood is removed by preoperative phlebotomy, it may be saved for autologous transfusion in the perioperative period.

During the perioperative period, adequate hydration should be maintained in children with cyanotic CHD, and care should be taken to avoid prolonged venous stasis. Cyanotic children are at risk for paradoxical embolic events, mandating meticulous attention to IV lines during fluid or drug administration. This is a reasonable routine approach for all children with CHD, regardless of the nature of the structural abnormalities. The use of air filters to IV tubing should not replace vigilance.

Tetralogy Spells

Hypercyanotic episodes in children with tetralogy of Fallot (i.e., tet spells) may be the result of significant dynamic right ventricular outflow tract (RVOT) obstruction leading to acute reductions in pulmonary blood flow. Tet spells are rare during noncardiac surgery, probably because general anesthesia attenuates the triggers. Occasionally, however, increased cyanosis may occur without warning in response to obscure stimuli. Whatever the cause, worsening cyanosis implies increases in dynamic obstruction and exacerbation of ventricular-level right-to-left shunting. Factors that decrease systemic blood pressure and systemic vascular resistance, such as hypovolemia and extreme vasodilation, should be avoided. Therapy consists of increasing blood volume and systemic vascular tone, the latter using either a phenylephrine bolus of 5 µg/kg IV initially and if needed, 0.1 to 2 µg/kg per minute by continuous infusion, norepinephrine 0.5 µg/kg IV initially, and then 0.05 to 2 µg/kg per minute by continuous infusion or metaraminol 0.01 mg/kg IV initially and then 0.05 to 0.5 µg/kg per minute by continuous infusion. Vasopressin infusion (0.02–0.04 units/kg per hour) may be an alternative agent. Increasing the inspired oxygen concentration and reducing inspiratory ventilatory pressures may also produce clinical improvement. Additional therapies include increasing the level of sedation or anesthetic depth and β-adrenergic blockade (esmolol [starting dose 50 µg/kg per minute] has largely replaced propranolol in this setting) (see also Chapters 16 and 17 ). Pulmonary vascular tone does not play a major role in the physiology of hypercyanotic episodes in tetralogy of Fallot; however, it is reasonable to limit additional afterload stresses to the right ventricle.

Heart Failure

In infants, congestive heart failure is most often due to ventricular volume overload resulting from ventricular or great artery–level communications. Heart failure can also result from severe valvar regurgitation, obstructive disease, or intrinsic myocardial disease (e.g., cardiomyopathy). Structural defects can lead to heart failure as a result of poor myocardial contractility, compromising cardiac output and the ability of the cardiovascular system to meet systemic demands.

In children with significant pulmonary vascular congestion, positive-pressure mechanical ventilation may be necessary before and after surgery. In cases of elective noncardiac surgery, it can be of significant benefit to optimize medical therapy or address the cardiovascular defect(s) before the planned procedure.

In a retrospective review of 21 children with severe heart failure who underwent 28 general anesthetics, 10% had a cardiac arrest requiring unplanned postoperative admission to the intensive care unit, and 96% required perioperative inotropic support. The investigators concluded that general anesthesia for children with severe heart failure is associated with a significant complication rate.

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