Congenital heart disease is one of the most common birth defects, and with 85% of these children now surviving into adulthood, an increasing number of patients require ongoing care. Many, but not all, will have had some corrective or palliative surgery in infancy or childhood and will require further surgery throughout their life. Approximately 40% of patients will have had curative treatment for a simple lesion and require little ongoing cardiac care. Only 20% will have complex disease that necessitates lifelong support. A comparison of pediatric and adult congenital heart disease (ACHD) defects is shown in Table 27.1 along with their relative incidence. In cardiac lesion cases, ACHD patients present for cardiac surgery for a number of reasons, including late diagnosis, worsening shunting, valvular disease, congenital coronary abnormalities, conduit revision, and pregnancy, which may unmask significant cardiac compromise. Arrhythmias are a common complication in ACHD patients and may necessitate catheter ablation or cardioversion requiring anesthesia. In addition, as their life expectancy increases, many individuals will present with noncardiac disease or traumatic injury requiring surgery.
| Pediatric Congenital Heart Disease | Adult Congenital Heart Disease | ||
|---|---|---|---|
| Defect | % | Defect | % |
| Ventricular septal defect | 35 | Atrial or ventricular septal defects | 22 |
| Atrial septal defect | 9 | Tetralogy of Fallot | 14 |
| Patent ductus arteriosus | 8 | Complex disease (eg, Fontan) | 13 |
| Pulmonary stenosis | 8 | Obstruction of the left ventricular outflow tract | 12 |
| Aortic stenosis | 6 | Transposition of the great arteries | 10 |
| Coarctation of the aorta | 6 | Obstruction of the right ventricular outflow tract | 8 |
| Tetralogy of Fallot | 5 | Coarctation of the aorta | 7 |
| Transposition of great vessels | 4 | Marfan syndrome | 5 |
| Atrioventricular septal defect | 3 | Corrected transposition of the great vessels | 4 |
| Other rarer conditions (eg, tricuspid atresia, bicuspid valves, univentricular heart) | 16 | Atrioventricular septal defect | 3 |
| Eisenmenger syndrome | 2 | ||
General Anesthesia for Cardiac Surgery
When general anesthesia is considered for a patient with ACHD, enough information must be collected from the best sources. A clear understanding of the functional anatomy is vital. Preoperative assessment of these patients is similar to that for any other surgical patient, with special attention directed toward anticoagulation and assessment of cardiorespiratory function, including the current level of exercise tolerance. Examination should be performed to establish the presence of congestive cardiac failure and cyanosis. In cases in which previous surgery has been undertaken, details of that surgical procedure are important because they will allow a better understanding of the patient’s anatomic and physiologic status. Investigations should be tailored to elucidate the cardiac anatomy and actively exclude or diagnose pulmonary hypertension, which is an independent risk factor for perioperative morbidity and mortality. Coronary angiography may be needed. The lateral chest radiograph, historically useful in assessing the relationship between the sternum and right ventricle, and particularly important in reoperation, has been superseded by magnetic resonance imaging, which is the radiologic imaging of choice. Special attention should be paid to renal, hepatic, and hematologic tests, particularly the presence of secondary erythrocytosis associated with chronic hypoxia.
In many cases, this will be “redo” surgery and provision must be made for rapid availability of blood and blood products if these are not immediately available on site. Adhesive external defibrillator pads should be used in patients who are undergoing second or subsequent cardiac surgery. The surgical challenges of reoperation in these patients should not be underestimated.
Sedative premedication may be prescribed (with supplemental oxygen), but care must be taken in cases of cyanotic heart disease or pulmonary hypertension in which hypercapnia can have profound deleterious effects on pulmonary vascular resistance.
Induction of anesthesia may need to be undertaken with invasive arterial pressure monitoring in situ. All standard induction agents have been used safely in these patients. Some practitioners prefer etomidate for induction because the extent of systemic vasodilation is lessened. Ketamine may confer some hemodynamic advantage but is limited by the frequency of dysphoric reactions. Of greater importance than the choice of agent is the speed and overall dose administered. Many of these patients have slow circulation times, and consequently there is a risk of overdose if the induction drug is injected too rapidly. Some practitioners titrate the induction agent until loss of the lash reflex and then supplement the induction with an opiate (eg, fentanyl). Neuromuscular blockade can be achieved with any nondepolarizing muscle relaxant, although many practitioners avoid atracurium because hypotension after histamine release may have a more marked hemodynamic effect in patients reliant on afterload to avoid shunting. Maintenance with an oxygen-air mixture and an inhalational agent is acceptable, as is total intravenous anesthesia. Nitrous oxide should be avoided because it causes myocardial depression. It is seldom necessary or advisable to ventilate with 100% oxygen.
Monitoring should include electrocardiography, saturation, core temperature, and ventilator parameters (eg, end-tidal carbon dioxide and inspired oxygen concentration). Central venous pressure measurements are essential, but the route of access should be discussed with reference to the surgical approach, and care should be taken with univentricular circulations in which thrombotic and embolic events are more common. Pulmonary artery catheters are rarely used because interpretation may be misleading in the presence of significant shunting, and the calculation of cardiac output by thermodilution is inaccurate in this setting. In all cases, meticulous attention must be paid during line insertion to prevent air emboli, which can be disastrous in patients with intracardiac defects. Transesophageal echocardiography is an essential additional monitor for the surgical procedure itself and adds additional information that may assist the anesthetist. Real-time interpretation allows rapid response to changing hemodynamic conditions.
Every effort should be made in the preoperative period to prevent postoperative hypothermia (shivering increases myocardial work) and hyperglycemia (which may worsen cerebral outcome).
All these patients should receive level 2 or 3 postoperative care (high dependency or intensive care). Detailed handover and discussion between cardiac surgeons, cardiac anesthetists, and intensivists help to ensure that appropriate care is maintained throughout the perioperative period. The length and complexity of the surgery often necessitate postoperative ventilation, but care must be taken to ensure that the deleterious effects of intermittent positive-pressure ventilation do not worsen cardiac function. Early extubation is preferred and may be associated with an improved outcome.
Fluid management should be carefully guided by hemodynamic response because many of these patients are particularly susceptible to congestive cardiac failure. Current trends in medical management with regard to fluid resuscitation and oxygen delivery may not apply to this population.
Guidelines from the National Institute for Health and Clinical Excellence recommend that routine antibiotic prophylaxis is not beneficial. This view is shared by the British Cardiovascular Society and European Society of Cardiology. However, prophylaxis should be considered in accordance with local guidelines, bearing in mind that postoperative sepsis and infective endocarditis carry higher mortalities than in the general population. Good oral hygiene and regular dental review are recommended for these patients.
Adequate analgesia must be provided. It not only forms part of standard postsurgical care but also reduces the likelihood of pulmonary hypertension in susceptible patients.
Pulmonary Hypertension
Pulmonary hypertension is defined as mean pulmonary artery pressures in excess of 25 mmHg at rest. The presence of pulmonary hypertension may be a surrogate marker of the severity of the associated cardiac disease. Its presence is associated with higher mortality rates. Every effort should be made to avoid iatrogenic rises in pulmonary artery pressure, from, for example, sympathetic stimulation (light anesthesia, pain), acidosis, hypoxia, hypercarbia, hypothermia, increased intrathoracic pressures, and excessive positive end-expiratory pressure. In severe pulmonary hypertension, standard ventilator maneuvers may be of limited value and may worsen the hemodynamics. A useful strategy is moderate hyperventilation, utilizing a shorter inspiratory time, longer expiratory time, and accepting higher peak airway pressures.
It is advisable to use a specialist physician to assist in the preoperative care of patients with known pulmonary hypertension and to continue that care into the postoperative period, when pulmonary hypertensive crises are more common. All the pulmonary hypertension targeted therapies used by the patient preoperatively should continue throughout the perioperative period.
Hemoptysis is a serious complication in this patient group. Smaller hemorrhages may herald larger, catastrophic events, although this is uncommon. Management strategies involve interventional radiology and, again, pulmonary hypertension physicians.
A pulmonary hypertensive crisis is a medical emergency with a very high mortality rate. It is often difficult to diagnose immediately and may present in a variety of ways, largely determined by factors such as mode of ventilation and level of consciousness. If suspected, rapid treatment must be instituted if there is to be any chance of survival. Correction of any of the precipitants listed earlier should be undertaken, and pharmacologic treatment may include epoprostenol, intravenous nitrates, isoprenaline, phosphodiesterase inhibitors, opiates, sildenafil (which may not be widely available in an intravenous form), and inhaled nitric oxide. Mechanical support with intraaortic balloon counterpulsation or right ventricular assist devices remains a last resort. Despite all these maneuvers, mortality remains high.
Univentricular Heart and the Fontan Operation Patient
For functionally univentricular hearts, the mainstay of treatment remains the Fontan operation or one of its modifications. The procedure essentially directs venous blood into the pulmonary artery, bypassing the single chamber, which in turn serves as a pump to the systemic circulation. Pulmonary blood flow, which determines cardiac output, is thus completely passive and highly dependent on adequate preload, low pulmonary vascular resistance, and good systemic ventricular function. Lateral tunnels or extracardiac conduits are more recent modifications of the Fontan procedure, but a high percentage of older patients had the atriopulmonary type of Fontan operation.
Preoperative anesthetic assessment should aim to identify those patients at higher risk. These patients include those with ventricular dysfunction, increased pulmonary vascular resistance, abnormal pulmonary anatomy, atrioventricular valve abnormalities, and history of sustained arrhythmia.
Fundamental to the anesthetic management of these patients is the maintenance of low pulmonary artery pressures and adequate venous return, which both dictate eventual cardiac output. Sinus rhythm is clearly desirable.
In addition to standard anesthetic monitoring, central venous pressure may be monitored (and will reflect pulmonary artery pressure after surgical treatment), but great care must be taken to avoid air emboli and protect against the higher than usual risk of intracardiac venous thrombosis.
Positive-pressure ventilation has a profound deleterious effect on these patients, with high intrathoracic pressures severely limiting or abolishing venous return. Early extubation or spontaneous respiration is desirable.
Low cardiac output is usually multifactorial in these patients. Causes include inadequate preload, elevated pulmonary vascular resistance, physical obstruction in the pulmonary or systemic pathway, arrhythmias, and pump failure. These patients are often resistant to standard inotropic support, particularly if the ventricle is hypertrophied and underfilled.
Arrhythmias are common and poorly tolerated. Treatment may include intraoperative pacing, amiodarone, and cardioversion, the latter being the treatment of choice if there are any signs of hemodynamic compromise.
Other common complications include hypoxia (especially in the presence of fenestrated baffles), which may be unresponsive to conventional ventilatory maneuvers, pleural and pericardial effusions, ascites, and thrombosis.
Arrhythmias
Arrhythmias represent one of the most common reasons for admission among ACHD patients. Any arrhythmia may occur, but commonly they include supraventricular tachycardias (notably in patients who have undergone atrial surgery and in the Fontan circulation), ventricular tachycardias, and the most common of all, reentrant intraatrial tachycardias. Most of these arrhythmias may be hard to manage with medications, and the changes in rhythm can cause serious hemodynamic disturbances in patients with poor cardiac reserve. This means that a common procedure necessitating general anesthesia is urgent/emergency cardioversion, with or without concomitant echocardiography to exclude thrombus. These patients require slow induction and may need intubation if transesophageal echocardiography is to be performed. Remifentanil by infusion is one technique allowing both echocardiography and cardioversion while maintaining cardiac stability. Beware of profound hemodynamic compromise on induction in patients with univentricular hearts. External pacing must be immediately available because there may be no direct venous access to the ventricle in these complex patients.
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