Cardiac History

A complete medical history with details of the underlying pathology, timing of each stage of palliation of the single-ventricle disease, additional surgeries to address arrhythmias (eg, pacemaker insertion), diaphragmatic plication, airway surgeries, cardiac catheterizations, and interventions must be reviewed. Residual lesions and physiologic burden of those procedures should be assessed. The most important information is gleaned from a patient’s cardiologist and the most recent cardiac catheterization report. Any recent changes in a patient’s exercise tolerance, functional ability, restriction of physical exercise, or escalation of therapy might indicate a worsening of cardiac dysfunction. Prior cardiac catheterization data, access sites, patency of veins and arteries, cardiac index, the integrity of the Fontan pathway, presence of a fenestration if any, pressures along the Fontan pathway, transpulmonary gradient, ventricular end-diastolic pressure, pulmonary vascular resistance, and status of the atrioventricular (AV) valve all are useful information.

Morphologically, the right and left ventricles are vastly different, with the right being thin walled and highly trabeculated and the left more muscular and conical shaped. The result is a right ventricle being apt to deal with volume loads and the left suited for ejecting against high pressures. Additionally, both the timing of the initial Fontan completion and the time since Fontan completion are important when considering risk. A study of long-term outcomes for patients with Fontan operations has shown that Fontan completion after age 7 (rather than ages 2–4 years) is associated with worse long-term complications. Delayed Fontan completion often is accompanied by formation of aortopulmonary collaterals, which serve as a source of persistent desaturation (right to left shunt). Additionally, patients with systemic left ventricles have improved outcomes (failure-free survival) compared with non-HLHS patients with systemic right ventricles. Patients with HLHS and, therefore, systemic right ventricles have significantly worse long-term outcomes compared with patients with non-HLHS systemic right ventricles. By comparison, the hazard ratio for Fontan failure is 3.8 (95% CI, 2.0–7.1) for patients with HLHS compared with single-LV Fontan patients.

For all Fontan patients, in particular those with HLHS, time since Fontan completion correlates with the rate of long-term complications and should be considered when conducting the preoperative evaluation. The 10-year freedom from failure rate was 79% for patients with HLHS compared with non-HLHS Fontan patients. There are several factors that contribute to long-term Fontan failure, discussed later.

Echocardiographic Assessment

The most recent echocardiogram should be reviewed with a specific focus on ventricular function as well as function of the AV and semilunar valves. Patients with cardiac failure as evidenced by poor or declining ventricular function are at greater risk of anesthesia-related complications.

Echocardiography should assess for systolic and diastolic ventricular dysfunction, AV valve and semilunar valve function, flow through the atrial septum and patency of pulmonary veins, cavopulmonary connections, and pulmonary arteries. Flow limitations at any level of the Fontan pathway have the potential to impede pulmonary blood flow as well as reduce effective cardiac output.

It must be considered that the single ventricle in the Fontan patient is not equivocal to the corresponding ventricle in a 2-ventricle patient in structure and function. In patients’ pre-Fontan years, the single ventricle is subjected to chronic myocardial hypoxia as well as volume overload, which leads to altered myocardial architecture and function. ^, Additionally, the geometric architecture of the single ventricle is vastly different when compared with the 2-ventricle inter-relationship. These factors contribute to increased systolic and diastolic dysfunction in the Fontan population, which can be exacerbated during periods of volume expansion and stress, such as the perioperative period. Ventricular assessment is important especially in patients with distant Fontan completion because function is known to decline over time. Similarly, valvulopathy places additional stress on the single ventricle and can be exacerbated during anesthesia. Moderate to severe AV valve or semilunar valve regurgitation and/or presence of pulmonary artery, pulmonary vein, or cavopulmonary anastomosis stenosis may require intervention prior to elective noncardiac surgery.

Arrythmia in Patients with Fontan Physiology

Patients with Fontan circuits are at high risk for several arrythmias, with the incidence correlating with the type of Fontan operation performed. ^, Generally, arrythmias in Fontan patients are atrial in origin with sinus node dysfunction. Supraventricular tachycardia is the most common although ventricular arrythmias may occur. Arrythmias may be due to conduction disturbance during surgical intervention or as a sequela of Fontan physiology. Patients with extracardiac conduits have less incidence of arrythmia compared with those with lateral tunnel connection and significantly fewer episodes than those with an atriopulmonary connection.

The etiology and prior treatment of arrythmias should be assessed in the perioperative evaluation. A detailed assessment of the therapies used, such as antiarrhythmics, electrophysiology studies and ablation of pathways, cardioversions, and pacemaker insertion, should be performed. If a patient has an implantable pacemaker or automated implantable cardioverter-defibrillators, the device location, mode of function, and response to tachycardia should be determined. Smaller pediatric patients often have epicardial pacemakers with generators located in the subcostal/abdominal region. Generator location, baseline setting, and response to overlying magnet should be considered. The anesthesia provider should notify the surgeon as to the presence of an intra-abdominal pacemaker so that damage to the unit or leads does not inadvertently occur during a procedure. A conversation with the patient’s electrophysiologist should incorporate discussion regarding the status and perioperative reprogramming of the pacemaker to mitigate the effects of interference by electrocautery.

Functional Assessment of the Fontan Patient

Preoperative assessment should elicit signs and symptoms suggestive of cardiac dysfunction and include assessment of underlying exercise capacity and baselines of blood pressure and oxygen saturation. Poor or worsening exercise tolerance and/or dyspnea with exertion may suggest ventricular dysfunction. Poor growth (height) and increasing weight are suggestive of chronically reduced cardiac output and ascites formation, respectively. New-onset or increased frequency of arrythmia may be suggestive of chronic ventricular failure and atrial dilatation.

Oxygen saturation should be assessed in the context of the type of Fontan operation that was performed. Although persistent desaturation may be due to presence of a fenestration, desaturation also may be suggestive of elevated pulmonary venous pressures, collateral formation, and/or ventricular dysfunction.

Although most Fontan patients do not require routine anticoagulation, the risk of stopping these medications must be considered on a case-by-case basis, specifically for patients with persistent arrythmia at risk for thrombogenesis.

Fontan patients with AV valve regurgitation and arrythmia often are managed using diuretic and afterload reduction agents as well as antiarrhythmics, respectively. These medications should be continued perioperatively. Fontan patients lack a ventricle to provide pulmonary blood flow and are reliant on passive flow to the lungs, therefore, adequate preload is critical in maintaining cardiac output. With prolonged nil per os (NPO) times, however, patients may become excessively volume depleted. Long NPO times should be avoided when possible and/or the patients should be started on intravenous fluid to maintain intravascular volume homeostasis.

Preoperative Laboratory Assessment of the Fontan Patient

Laboratory studies should be used to help determine a patient’s physiologic status and ability to tolerate the proposed surgical procedure. Typically, a complete blood cell count, chemistry panel, and type and screen suffice for most procedures that are minor. Evaluation of renal and hepatic function should be considered, particularly for those with distant Fontan corrections.

Patients with Fontan physiology are prone to chronic hypoxemia and, therefore, tend to have higher hematocrit levels than normal values. Baseline hemoglobin and hematocrit should be assessed and maintained perioperatively. Fontan patients are prone to excessive surgical bleeding from persistently high venous pressures, anticoagulant therapy, liver involvement, and intrinsic coagulation factor abnormalities. These patients should have cross-matched blood available for surgeries with anticipated blood loss, especially because they might have antibodies that make cross-matching difficult in an urgent situation.

Fontan patients, in particular those with chronically elevated venous pressures, are at risk for Fontan-associated liver disease (FALD). FALD may range from mild hepatic fibrosis to end-stage liver disease and potentially the development of hepatocellular carcinoma. Basic tests of liver function tests, such alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as well as γ-glutamyl transferase, often are elevated. With prolonged hepatic congestion, worsening liver fibrosis can lead to hepatic failure and the sequalae of end-stage liver disease. Testing for coagulopathy should be considered in patients with features suggestive of advanced liver disease.

Patients with Fontan circulation also are at risk for multifactorial chronic kidney disease; the incidence increases with age. Reduced cardiac output, use of nephrotoxic medications, and repeated episodes of cardiopulmonary bypass result in increased incidence of renal dysfunction after the Fontan operation. ^, Baseline renal function should be assessed in Fontan patients prior to elective surgery. Adequate hydration, avoidance of prolonged NPO times, and avoidance of hypotension are crucial in perioperative management.

Protein-losing enteropathy (PLE) has been reported in up to 12% of patients with Fontan palliation and is a major source of morbidity. ^, Although the exact etiology is unknown, it is suspected that lymphatic congestion results from both reduced cardiac output and chronic venous congestion. The loss of protein in PLE can lead to ascites, hypotension (from oncotic pressure reduction), malabsorption, and intestinal failure. Diffuse ascites and hypoalbuminemia may suggest PLE. The management of PLE is incredibly challenging and should be deferred to centers that routinely provide care to complex congenital heart patients.

Plastic bronchitis (PB) is reported in up to 5% of Fontan patients and characterized by production of thick casts within the airway. ^, These protein and lymphatic-rich casts, when expectorated from the airway, are thought to result from elevated venous and lymphatic pressure similar to that occurring in PLE. The presence of PB is suggestive of Fontan failure with management similarly deferred to congenital heart disease centers. PB leads to airway inflammation, chronic cough, and hypoxemia and is a major source of morbidity and mortality for these patients.

Home Medications

These patients often receive multiple medications, cardiac and others, as part of their multidisciplinary medical care. In addition, some patients take herbal medications. It is important to review all medications in detail and determine drug interactions with commonly used anesthetic drugs. Common medications include diuretics, angiotensin-converting enzyme (ACE) inhibitors, inotropes, pulmonary vasodilators, antihypertensives, anticoagulants, antiarrhythmic drugs, antibiotics, and psychotropic medications. Some patients might require oxygen therapy at home. Diuretics probably are best withheld on the morning of surgery to preempt the risk of dehydration. Other medications should be continued based on the cardiologist’s recommendations. Generally, ACE inhibitors are withheld on the day of surgery due to concern for refractory hypotension.

Anesthesia and the Fontan Patient

Recent illnesses

Recovery from recent upper respiratory and gastrointestinal illnesses must be optimized prior to elective noncardiac surgery, even if it means surgery is delayed. Because pulmonary blood flow and hence systemic cardiac output are dependent on the transpulmonary gradient, laryngospasm and bronchospasm associated with an intercurrent upper respiratory illness in patients with Fontan physiology can precipitate both respiratory failure and cardiac failure. It is best to wait at least 4 weeks after a patient becomes asymptomatic to schedule elective, noncardiac surgery. Gastrointestinal illnesses with loss of fluid from the gastrointestinal tract leaves a Fontan patient dehydrated, with inadequate preload. Achieving and maintaining adequate intravascular volume aids the anesthetic course in these patients, and it is prudent to ensure full recovery from acute gastrointestinal processes prior to elective surgery.

The anesthetic care of the Fontan patient should be planned with consideration of the surgery required in conjunction with the patient-specific aberrations, as discussed previously. Prolonged NPO times should be avoided because these may lead to dehydration, reduced pulmonary venous return, decreased cardiac output, and exaggerated hypotension with induction of anesthesia. Children demonstrating normal function of the Fontan circuit may be suitable for inhalation induction. When performing intravenous induction of anesthesia, underlying aberrations must be considered (eg, ventricular function, AV valve regurgitation, and pulmonary hypertension). Although all medications have been used, benzodiazepines, ketamine, opioids, and dexmedetomidine often are administered in combination. Additionally, induction of anesthesia can be met with exaggerated hypotension from reduced pulmonary venous return. Although intravenous hydration is appropriate, aggressive fluid administration may be poorly tolerated, particularly in patients with underlying diastolic dysfunction. Due to chronically high venous pressures, Fontan patients generally have ample sites for peripheral venous access. Central venous access should be performed with caution with consideration for femoral access to avoid direct catherization of the cavopulmonary anastomosis.

Ventilation can have exaggerated effects on patients with Fontan physiology. In particular, large tidal volumes, rapid respiratory rates, high positive end-expiratory pressures, and long inspiratory times all contribute to reduced pulmonary venous return. Similarly, factors contributing to elevated pulmonary vascular resistance, especially in patients with underlying pulmonary hypertension, should be avoided ( Table 2 ). Although preexisting pulmonary hypertension may preclude the Fontan completion, over time, multifactorial changes to the pulmonary vasculature often result in elevated pulmonary pressures.

Table 2

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

Modernizing Education of the Pediatric Anesthesiologist Regional Anesthesia Pediatric Anesthesia Outside the Operating Room Sustainability in the Operating Room Trends in Pediatric Pain Using Electroencephalography (EEG) to Guide Propofol and Sevoflurane Dosing in Pediatric Anesthesia

Stay updated, free articles. Join our Telegram channel

Join