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Address correspondence to John Richard McNamara, MB, BCh, BAO, Department of Anaesthesiology and Intensive Care Medicine, Mater Misericordiae University Hospital, Dublin, Ireland.
The Fontan circulation is the single-ventricle approach to surgical palliation of complex congenital heart disease wherein biventricular separation and function cannot be safely achieved. Incremental improvements in this surgical technique, along with improvements in the long-term medical management of these patients, have led to greater survival of these patients and a remarkably steady increase in the number of adults living with this unusual circulation and physiology. This has implications for healthcare providers who now have a greater chance of encountering Fontan patients during the course of their practice. This has particularly important implications for anesthesiologists because the effects of their interventions on the finely balanced Fontan circulation may be profound.
The American Heart Association and American College of Cardiology recommend that, when possible, elective surgery should be performed in an adult congenital heart disease center, although this may not be feasible in the provision of true emergency care. This review article summarizes the pathophysiology pertinent to the provision of anesthesia in this complex patient group and describes important modifications to anesthetic technique and perioperative management.
THE FONTAN procedure first was described in 1971 by Fontan when he published a case series of its application in three patients with tricuspid atresia, two of whom survived.
The Fontan procedure today is the most widely applied surgical palliation for a range of congenital heart defects with a single functional ventricle or in conditions for which a biventricular repair is impossible or unfavorable (eg, hypoplastic left-sided heart syndrome, tricuspid atresia, and unbalanced atrioventricular [AV] canal).
The procedure involves the creation of a pathway to transmit the whole vena caval blood flow to the lungs, allowing only oxygenated blood to return from the lungs to the heart and a single functional ventricle (Fig 1). The procedure usually is carried out in three stages, ultimately achieving an anastomosis from the vena cavae to the pulmonary arteries. A functional right or subpulmonic ventricle thereby is bypassed or eliminated from the pulmonary circulation, resulting in pulmonary arteries that receive nonpulsatile blood flow directly from the vena cavae, rather than pulsatile blood flow from a functional right ventricle. This nonpulsatile pulmonary blood flow driven by pressure gradient, from the relatively high-pressure vena cavae to a lower-pressure left or common atrium, is a major departure from normal biventricular physiology and has significant clinical sequelae.
Fig 1Representation of the Fontan circulation in its following three potential forms: (A) the classic atriopulmonary connection, (B) the lateral tunnel, and (C) the extracardiac conduit.
Over time, incremental improvements in patient selection, surgical technique, and perioperative management of patients for Fontan surgery have occurred. This, combined with improvements in the long-term medical management of these patients, have resulted in improved survival, with survival into adulthood now being the norm. This has resulted in an ever-increasing population of adult patients living with Fontan circulation. Rychik et al. estimated that patients who undergo surgery today may hope for a 30-year survival of >80%. Up to 70,000 patients may be alive worldwide today with Fontan circulation, and this population is expected to double in the next 20 years.
The Australian and New Zealand Fontan Registry Report from 2018 illustrated well the growing use of Fontan surgery and the remarkably steady increase in the population of those living with Fontan circulation (Fig 2).
Fig 2This graph demonstrates the steadily increasing number of individuals living with Fontan circulation over time. Abbreviations: AP, atriopulmonary connection; ECC, extracardiac conduit; LT, lateral tunnel. With permission, from The Australian & New Zealand Fontan Registry.
The ever-increasing population of Fontan patients naturally presents themselves with increasing frequency to healthcare professionals for a range of interventions.
The growth of this challenging patient cohort justifies a comprehensive review of their perioperative anesthetic management, particularly in light of the publication in recent years of several guidelines relating to perioperative care of this cohort.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
This review outlines key concepts relevant to the provision of anesthetic care for this complex patient population, outlining the physiology of Fontan circulation, the deleterious effects of anesthesia on this circulatory system, the unique pattern of chronic organ dysfunction seen, and its effect on preoperative assessment and planning with reference to the current literature and guidelines.
Fontan Physiology
In the absence of a subpulmonary ventricle, Fontan circulation is characterized by chronically elevated systemic venous pressures and decreased cardiac output (CO). These two features are responsible for much of the widespread systemic organ dysfunction seen in Fontan patients.
However, the systemic consequences of Fontan circulation also should be considered in the context of a patient born with major congenital cardiac anomalies, abnormal circulation since in utero, frequent episodes of hemodynamic compromise in early life, chronic cyanosis, and the need for multiple major surgical interventions requiring cardiopulmonary bypass.
The pattern of organ dysfunction is nuanced and repetitious. Pervasive respiratory, renal, hepatic, neurologic, gastrointestinal, immunologic, and endocrine dysfunction occur widely, in addition to the expected cardiac dysfunction. This is discussed in greater detail herein according to the organ system, with a particular focus on details that either influence the delivery of anesthesia or are affected significantly by the dynamic conditions experienced by patients undergoing anesthesia and surgery.
Fontan Circulation
Gradient-driven pulmonary blood flow is feasible because the pulmonary vascular bed normally provides low resistance to blood flow. However, the pulmonary vasculature is reactive and pulmonary vascular resistance (PVR) can change abruptly (eg, because of changes in partial pressure of oxygen [pO2], partial pressure of carbon dioxide [pCO2], and pH). Without the reactive right ventricle to compensate for such changes, pulmonary blood flow can be reduced dramatically by an increase in PVR. Reduction in pulmonary blood flow will result in reduced preload returning to the left or common atrium and systemic ventricle, thereby directly reducing CO.
In addition to changes in PVR, reductions in central venous pressure (CVP) will reduce the pressure gradient driving pulmonary blood flow, again resulting in reduced blood return to the systemic ventricle and, thereby, reduced CO. Therefore, CO in the Fontan patient can be affected dramatically by changes in capacitance or filling within the systemic venous side of the circulation and by changes in PVR.
Anatomic obstructions in the pulmonary vasculature, elevation of PVR, AV valve stenosis or regurgitation, elevation of ventricular end-diastolic pressure, or rhythm disturbances with loss of AV synchrony may impede pulmonary blood flow.
A fenestration often is incorporated into the Fontan circulation through the creation of a small window from the right atrium, lateral tunnel, or extracardiac conduit into the common atrium. This has two potential advantages. First, it results in a lower systemic venous pressure as this system is decompressed somewhat by an amount of flow bypassing the pulmonary circulation and directly entering the common atrium. Second, it acts as a fail-safe in the event of acute increases in PVR, preserving some blood return to the systemic circulation even when pulmonary blood flow is acutely reduced, thereby protecting CO at the expense of desaturation.
Fenestration has the disadvantage of a persistent right-to-left shunt, with resulting deoxygenation, and providing a potential means for emboli such as air or thrombus to pass from right to left, increasing the risk of systemic embolization. In Fontan patients with fenestration, acute desaturation may suggest excessive flow across the fenestration and may be the first sign of an acute increase in PVR.
Sinus node dysfunction occurs in up to 45% of adults long term after Fontan surgery, and has been associated with a reduction in preload to the single ventricle and heart failure sequelae. Atrial tachyarrhythmias occur in up to 60% of adults with Fontan circulation, often are poorly tolerated, and are associated with significant morbidity and mortality.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
One large Fontan series showed that only 24% of patients remained free from arrhythmia at 30 years postoperatively, with 5% of patients having sudden cardiac death likely explained by arrhythmia.
Management of arrhythmias may be difficult in Fontan patients, with some articles suggesting high rates of complications from antiarrhythmic drugs, such as dofetilide causing torsades de pointes
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
Standard decision-making strategies about rhythm control and thromboprophylaxis used in patients with acquired heart disease and atrial fibrillation do not apply to patients with Fontan circulation, for whom rhythm control and anticoagulation are of far greater importance.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
The assessment of cardiac function is challenging in Fontan patients, with standard tests and measures of cardiac function more difficult to apply and interpret. The process of heart failure with Fontan circulation is heterogeneous and complex.
Systolic and diastolic dysfunction, structural cardiac or valvular abnormalities, rhythm disorders, and impediments to flow through the pulmonary circulation each contribute to heart failure and decompensation.
Fontan failure may lead to AV valve dysfunction and arrhythmia or may result from it.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
Other markers of failure include liver dysfunction; renal failure; and, more specific to this population, cyanosis, growth failure, protein-losing enteropathy (PLE), and plastic bronchitis (PB).
ACHD patients often adapt to chronically reduced functional capacity by self-restricting activity, and often will report that their functional status is unchanged or fine when questioned. Subjective assessment of functional capacity, therefore, may be misleading. Exercise testing can more objectively measure functional capacity and cardiac reserve in these patients, providing important information for diagnosis and prognostication. These patients may demonstrate reduced maximal oxygen uptake, an early anaerobic threshold, and a reduced maximal heart rate. Such testing may unmask significant cardiorespiratory dysfunction and exercise intolerance not otherwise apparent, and allow for more accurate preoperative risk assessment and a better-informed consent process, particularly in the elective setting.
Echocardiography has a central role in the assessment of cardiac function in this population but has significant limitations. It allows for quantification of chamber size, ventricular systolic and diastolic functions, and assessment of AV and semilunar valve structure and function. Fontan patients with a systemic left ventricle may more reasonably have their systolic function expressed relative to typical measures of systolic function such as left ventricular ejection fraction, but there is a lack of consensus on assessment of a systemic right ventricle.
Mitral inflow velocities and tissue deformation indices can be used to identify diastolic dysfunction. Again, there is a lack of consensus regarding normal cutoff values in the univentricular heart, but worsening diastolic dysfunction may be identified readily with serial echocardiography over time.
Cardiac magnetic resonance imaging (MRI) is used widely in this cohort and holds some advantages over echocardiography, including detailed determination of vascular anatomy and myocardial tissue viability. Cardiac MRI allows for accurate estimation of AV valve regurgitation fraction, stroke volume, ejection fraction, end-diastolic volume (a strong predictor of death), and total venous flow return (another described MRI marker of Fontan decompensation).
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
Cardiac MRI and computed tomography (CT) imaging also are useful in assessing thrombosis; intracardiac shunts; and pulmonary vasculature, including branch pulmonary artery (PA) obstruction, pulmonary arteriovenous malformations, and collateral burden.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
Systemic-to-pulmonary artery collaterals frequently develop in cyanotic Fontan patients. They can result in pulmonary hypertension, which will contribute to failure and are a potential source of bleeding during cardiac surgery. When identified, such collaterals can be treated with endovascular coiling.
Current MRI and CT imaging techniques have significantly reduced the requirement for invasive cardiac catheterization in these patients.
Respiratory
Significant respiratory dysfunction is common among Fontan patients and may be a direct consequence of their primary congenital cardiac condition or because of complications from the surgical and medical management of their congenital heart disease.
Restrictive respiratory physiology is common among ACHD patients in general, with Fontan patients demonstrating the highest prevalence at 89%.
There are several contributors to this restrictive pattern, with both extrinsic restriction and intrinsic lung parenchymal pathology seen. Restrictive thoracic spine deformities, including scoliosis and kyphosis, and phrenic nerve palsy, leading to diaphragmatic paralysis, can be identified readily on chest x-ray. Generalized respiratory and skeletal muscle weakness are common in young adults with complex congenital heart disease (CHD) and contribute to the restrictive picture.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
Intrinsic lung restriction in Fontan patients may relate to pulmonary hypoplasia from decreased pulmonary blood flow in utero or to pulmonary toxicity from long-term amiodarone use.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
Pulmonary function tests may reveal the restrictive respiratory pattern. Diffusing capacity for carbon monoxide may help identify amiodarone-related lung disease, and high-resolution CT may be useful for further characterization.
In addition to restrictive lung disease, Fontan patients may experience recurrent pneumonia, pulmonary embolism (PE), pleural effusion, and PB. PB refers to cast formation in the small airways from the accumulation of leaked proteinaceous material as a result of high venous and lymphatic pressures. It occurs in <5% of Fontan patients. The casts can lead to bronchial blockage and can be a marker of cardiac failure. Symptoms may include chronic cough or wheeze not responsive to bronchodilators, and expectoration or bronchoscopic removal of casts is diagnostic. T2-weighted MRI may identify a site of lymphatic spillage into airway lumen and can guide catheter-based lymphatic intervention to occlude abnormal decompression channels. The condition may be alleviated by treatment of Fontan failure (eg, with pulmonary vasodilators, diuretics, or transplantation). Cast clearance and symptoms may be assisted by bronchodilators, chest physiotherapy, inhaled steroids, nebulized mucolytics, or tissue plasminogen activator. If significant hypoxia or airway obstruction occurs, bronchoscopy may allow for cast extraction.
Decreased glomerular filtration rate, proteinuria, and albuminuria are common in Fontan patients. At 13 years of age, 10% of these patients have mild renal dysfunction. This increases to more than 50% by 26 years of age.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
The causes of renal injury in these patients are multiple and including acute illness, chronic hypoxia, impaired CO, venous congestion, and multiple cardiac surgeries with the attendant requirement for cardiopulmonary bypass. Renal function should be assessed routinely because impairment usually is silent but is associated with worse surgical outcomes and increased mortality.
Findings from elective surveillance liver biopsy indicate that all patients with Fontan circulation have some degree of liver fibrosis present, and the severity increases with age and time from Fontan surgery.
In addition to the progressive pattern of congestive liver disease, viral hepatitis and drug toxicity are important considerations. The incidence of hepatitis C virus exposure in patients with CHD who underwent heart surgery before 1992 is 8.6%, and the incidence of chronic infection is 4%-to-5%.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
Mild derangement of biochemical liver markers is common, but ultrasound, cross-sectional imaging and elastography offer greater sensitivity for assessing liver disease
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
The majority of Fontan patients are prothrombotic, with a number of contributing factors including protein C deficiency, enhanced platelet activation and thrombin formation, impaired fibrinolysis, and polycythemia as a result of chronic cyanosis.
In addition to the hypercoagulable biochemical picture, these patients have heightened endothelial injury and the relative stasis of blood flow completing the classic Virchow's triad of conditions contributing to thrombosis.
Thrombosis occurs in 8%-to-33% of patients with Fontan physiology and is an important cause of morbidity and mortality, particularly when it leads to pulmonary embolism or stroke.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
Hemodynamic consequences of pulmonary embolus in this group may be dire, and fenestration creates a pathway for paradoxical embolization. The risk may be predicted by disease complexity but not by CHA2DS2-VASC scores.
Risk increases further with disturbance of the coagulation system through excessive factor loss from PLE or synthetic impairment from severe liver fibrosis or cirrhosis.
Defining coagulation abnormalities with standard laboratory testing is difficult, with prothrombin time and partial thromboplastin time often prolonged despite a procoagulant state.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
There is evidence that thromboprophylaxis reduces thrombotic complications in Fontan patients. Current guidelines suggest that aspirin is a reasonable first choice, with warfarin reserved for those with additional risk factors, previous thrombosis, or older age.
Comparative trial of the use of antiplatelet and oral anticoagulant in thrombosis prophylaxis in patients undergoing total cavopulmonary operation with extracardiac conduit: Echocardiographic, tomographic, scintigraphic, clinical and laboratory analysis.
Chronic venous hypertension, low CO, increased mesenteric vascular resistance, endothelial dysfunction, and inflammation lead to loss of intestinal cell membrane integrity. Diarrhea may occur, and the consequences of protein loss include edema from hypoalbuminemia and clotting and immune dysfunction from loss of factors and immunoglobulin.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
Because venous hypertension and reduced cardiac output are the drivers of PLE in Fontan patients, it occurs with progressive failure of Fontan circulation and is one of the potential indications for heart transplantation in this group, but those with PLE have a higher perioperative risk when transplanted.
Assessment and planning should occur well in advance of elective surgery to allow time for optimization of the patient's condition and potential transfer to an appropriate setting.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
A study by Maxwell et al. reviewed ACHD cases from the Closed Claims Project in the United States and found that inadequate preoperative assessment and optimization accounted for up to 40% of adverse events in ACHD patients undergoing noncardiac surgery.
Factors contributing to adverse perioperative events in adults with congenital heart disease: A structured analysis of cases from the closed claims project.
A thorough review of the patient's previous cardiac surgeries and current physiology are needed to guide perioperative management by the anesthesiologist. The presence or absence of a patent fenestration should be noted. Surgeries that intentionally sacrifice a subclavian artery (eg, classic Blalock-Taussig shunt) should be considered when selecting the site of noninvasive blood pressure measurement and arterial line placement in order to avoid spurious measurements.
Fontan patients generally are on antiplatelet or anticoagulant medications. The risk of thrombotic and embolic events is high, with potential for devastating consequences. Thrombotic risk must be balanced carefully with concerns about bleeding when withholding antiplatelet or anticoagulant drugs is being considered.
Management of Hemodynamics
In addition to standard perioperative monitoring requirements, invasive blood pressure measurement generally is indicated. In addition to its obvious and important role in real-time identification of rapid hemodynamic changes, an arterial line will facilitate the intermittent measurement of pH, pO2, and pCO2, which are important modifiable determinants of PVR and, therefore, CO in the Fontan patient (Table 1).
Factors contributing to adverse perioperative events in adults with congenital heart disease: A structured analysis of cases from the closed claims project.
Gradient-driven pulmonary blood flow, and, therefore, CO, in these patients is very volume- dependent. Dehydration should be avoided by minimizing fasting times
or administration of intravenous fluid. Wide-bore access to facilitate rapid administration of volume will allow the anesthesiologist to intraoperatively compensate for hypovolemia or venodilation. A central venous catheter (CVC) may be required in some situations, but this requirement should be considered with the significant risks borne in mind. There is an increased risk of thrombus and greater potential fallout from embolism of any thrombus formed around a CVC. Patients who require a CVC intraoperatively may benefit from early removal. Air filters and meticulous attention are required to avoid air emboli.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
When a CVC is in place, transduction of CVP may help to guide intraoperative management of hemodynamics. Isolated values of CVP in these patients may be even more difficult to interpret than in the general population, but changes in CVP over time likely are indicative of important clinical changes and may help characterize any such change and guide intervention.
As previously described, atrial tachycardias are prevalent, seen in 60% of adult Fontan patients.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
A group from the Mayo Clinic studied retrospectively the incidence of complications among 154 adult Fontan patients undergoing 538 noncardiac procedures under anesthesia or sedation. They found nine procedures (2%) were complicated by intraoperative arrhythmia requiring treatment. All were atrial arrhythmias, including five atrial flutter and four unspecified atrial arrhythmias.
A 2018 consensus article published by the European Society of Cardiology provides detailed guidance including the acute management of arrhythmias in congenital heart disease. These guidelines suggested that before the treatment of acute arrhythmia, consideration must be given to potential coexisting factors such as sinus node dysfunction, AV block, ventricular dysfunction, and other comorbidities. They recommended electrical cardioversion in unstable supraventricular tachycardia. For AV node-dependent supraventricular tachycardia, they recommend adenosine unless it is contraindicated. In hemodynamically stable patients, they recommended rate control with intravenous beta-blockers or calcium channel blockers but caution against their use when ventricular function is impaired. They also suggested sideeffects of pharmacologic management may be avoided by atrial overdrive pacing, which is an effective alternative strategy for the treatment of atrial flutter and macroreentrant atrial tachycardia and can be delivered via transesophageal pacing.
Arrhythmias in congenital heart disease: A position paper of the European Heart Rhythm Association (EHRA), Association for European Paediatric and Congenital Cardiology (AEPC), and the European Society of Cardiology (ESC) Working Group on grown-up congenital heart disease, endorsed by HRS, PACES, APHRS, and SOLAECE.
Other hemodynamic problems may manifest as arrhythmia; therefore, a thorough review of circulation and ventricular performance should be considered if arrhythmias arise.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
Many Fontan patients will have a pacemaker. Consideration of device position is required before surgery, to avoid damage or infection, and chest x-ray may be useful in this regard. Epicardial pacemakers located below the diaphragm generally are used in this group because endocardial leads are very challenging to place with Fontan anatomy and provide additional risk of thromboembolism.
Arrhythmias in congenital heart disease: A position paper of the European Heart Rhythm Association (EHRA), Association for European Paediatric and Congenital Cardiology (AEPC), and the European Society of Cardiology (ESC) Working Group on grown-up congenital heart disease, endorsed by HRS, PACES, APHRS, and SOLAECE.
Devices should be checked and reprogrammed to safe surgical modes. Surgical diathermy has the potential to cause electrical interference. In patients who are pacing-dependent intraoperatively, a nonsensing or asynchronous mode should be used.
The American Heart Association scientific statement on the management of adults with congenital heart disease suggested that reprogramming to slightly higher rates may be desirable.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
Even though the statement cited no evidence for this suggestion, it seems a logical and pragmatic approach to help maintain adequate CO in patients with no intrinsic ability to increase heart rate, at a time when multiple other mechanisms may impair CO.
When vasopressors, inotropes, and pulmonary vasodilators are required, familiarity with Fontan physiology and the individual patient's hemodynamic status will assist in the choice of appropriate agents. No randomized controlled trials have compared different inotropes or different vasopressors within this group. Such a study would not be feasible given the heterogeneity of Fontan patients who may have a systemic left or right ventricle, preserved or impaired ventricular function, and myriad other variables relating to their circulatory physiology and the procedure for which they require anesthesia. A number of studies that examined choice of agent during and immediately after Fontan completion surgery have been published, and these may provide some assurance regarding the utility and safety of certain agents.
There is evidence for the safety of vasopressin in the postoperative care of patients immediately after Fontan completion.
Vasopressin has the theoretical advantage over noradrenaline in that it avoids pulmonary vasoconstriction, which can impede pulmonary blood flow and cardiac output.
Individual patient factors must be considered, and care should be taken when manipulating systemic vascular resistance; increasing afterload may be detrimental to a failing systemic ventricle.
Many sources advocate for milrinone as the inotropic agent of choice for Fontan patients.
The perspective of the intensivist on inotropes and postoperative care following pediatric heart surgery: An international survey and systematic review of the literature.
World J Pediatr Congenit Heart Surg.2018; 9: 10-21
Because the maintenance of low PVR is an important intraoperative goal of management, any long-term pulmonary vasodilator therapy, such as sildenafil or bosentan, should not be acutely withdrawn. Hypothermia also carefully must be avoided because it will increase PVR. Inhaled nitric oxide is an important tool for the management of high PVR and the resultant reduction in CO seen in Fontan patients, and its availability should be ensured when perioperatively managing a Fontan patient.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
Heart-lung interactions in this group are more pronounced than in the general population. Even though the same physiologic principles apply, they require greater consideration and some modifications to ventilatory strategies.
The change from negative-pressure spontaneous ventilation to intermittent positive-pressure ventilation initially will reduce pulmonary blood flow and CO. Ventilator settings should be modified in order to minimize the impediment to pulmonary blood flow.
In the first instance, low positive end-expiratory pressure and low mean airway pressures are desirable. Low mean airway pressures may be facilitated by prolongation of expiratory time.
After consideration of the immediate mechanical effects of intrathoracic pressures on pulmonary blood flow, the need for intermittent positive-pressure ventilation (IPPV) to target chemical determinants of PVR (ie, pO2, pCO2, and pH) must be addressed. Choice of positive end-expiratory pressure must balance the objective of reducing intrathoracic pressures with that of optimizing functional residual capacity and preventing atelectasis, compression/collapse of pulmonary blood vessels, and the pulmonary vasoconstriction that occurs in response to resultant hypoxia and hypercarbia.
The same balance of risk applies to the application of higher minute ventilation targeting carbon dioxide (CO2) clearance, ideally to normal values of pCO2 and pH despite the requisite increase in vigor of mechanical ventilation.
Depending on the surgery required and the clinical condition of the patient, IPPV could be avoided altogether by maintaining spontaneous ventilation (eg, by use of a supraglottic airway device and careful titration of anesthesia) or by use of a regional anesthetic technique.
These approaches to excluding the effects of IPPV come at the expense of losing tight control over ventilation and pCO2. When IPPV is required, early extubation may be beneficial but only when spontaneous ventilation is sufficient to achieve acceptable oxygenation and CO2 clearance.
Intraoperative positioning has exaggerated hemodynamic consequences for Fontan patients. Head-down positioning will worsen respiratory compliance, and any resultant hypoxia or hypercarbia can increase PVR. Lateral positioning may cause ventilation/perfusion mismatch, which also increases PVR. Head-up positioning may dramatically reduce systemic venous return, as will prone positioning, which results in abdominal compression. Reduced venous return will be poorly tolerated but can be somewhat ameliorated with lower limb compression stockings, intravascular volume expansion, and vasopressor administration, and care with prone positioning when it is required to ensure minimal abdominal compression.
The closed claims case review by Maxwell et al. found that 50% of perioperative adverse events in ACHD patients undergoing noncardiac surgery occur in the postoperative period.
Factors contributing to adverse perioperative events in adults with congenital heart disease: A structured analysis of cases from the closed claims project.
In addition to a greater incidence of complications in Fontan patients, the effect of even simple complications may be more pronounced in these physiologically vulnerable patients. Bleeding, fever, thromboembolism, infection, and pulmonary edema are poorly tolerated.
Careful management of volume status, bearing in mind the sensitivity to reduced preload, may require titration of fluid boluses or diuresis of any excess volume administered in the operating room. An effective strategy to prevent and treat postoperative nausea and vomiting will facilitate return to enteral intake, allowing for a patient's autoregulation of fluid intake and the early recommencement of important medications such as pulmonary vasodilators. Effective pain management is important in order to normalize breathing patterns and avoid significant respiratory depression.
The reinstitution of antiplatelet or anticoagulant drugs postoperatively must balance bleeding concerns with the significant thrombotic risk in these patients. Unfractionated heparin offers the benefit of reversibility. Early ambulation and pneumatic compression may help reduce the risk of venous thromboembolism.
The postoperative care setting depends on the surgery performed and the clinical status of the patient, but admission to a high-dependency or intensive care setting is more often warranted.
Laparoscopic surgery is associated with less postoperative pain, less pulmonary dysfunction, and a shorter hospital stay compared with open surgery but carries some ramifications, which are of greater consequence in Fontan patients. Peritoneal insufflation with CO2 will compress intra-abdominal vasculature to impede venous return, reduce pulmonary compliance by diaphragmatic splinting, and increase pCO2 by absorption from the peritoneum, leading to increased PVR and reduced CO.
In addition, the potential for CO2 embolization and the use of steep head-up or head-down positioning may be poorly tolerated by these patients.
Multiple case reports describe laparoscopic surgery in Fontan patients. A number of measures may help counter the deleterious effects previously outlined. Invasive blood pressure monitoring will allow for immediate identification of reduced CO on insufflation and positioning as well as quantifying CO2 absorption. Volume administration may compensate somewhat for the impediment to venous return. Lower insufflation pressures reduce the magnitude of disturbance, with case reports suggesting acceptable risk if intra-abdominal pressures are limited to <10 mmHg in Fontan patients.
Cautious positioning, effective communication with the surgeon, and a low threshold to convert to open procedure are essential.
Regional Anesthesia
Regional anesthesia is a useful technique for the management of Fontan patients in certain circumstances. Even though a general discussion on the benefits and pitfalls of regional anesthesia is well outside the scope of this review article, the particular benefits in relation to the Fontan patient relate to the avoidance of IPPV, early ambulation with potential advantages in a prothrombotic patient, and effective analgesia facilitating a normal breathing pattern postoperatively and the potential to reduce requirement for respiratory-depressant narcotic analgesia.
The majority of Fontan patients will be on long-term antiplatelet or anticoagulant drugs, but discontinuation of these in preparation for surgery may allow for a window for regional anesthesia to be safely performed. Regular guidelines and practice regarding regional techniques and anticoagulant medications should be followed.
Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy: American Society of Regional Anesthesia and Pain Medicine evidence-based guidelines (fourth edition).
There are no published guidelines available to direct the use of regional anesthesia in Fontan or ACHD patients in general. The New York School of Regional Anesthesia recommends a number of pragmatic modifications to standard techniques. A reduction in the total dose of local anesthetic administered will reduce the potential for cardiac toxicity and arrhythmia. Avoidance of sedation will eliminate the attendant respiratory depression. When narcotic analgesia or pharmacologic anxiolysis is used, careful titration to the desired effect may help to avoid hypoxia and hypercarbia and the associated increase in PVR.
Neuraxial blockade leads to sympathectomy, peripheral vasodilation, and reduced venous return, with troublesome effects on the Fontan patient. Epidural, combined spinal-epidural, or spinal catheter may allow for more gradual application of regional anesthesia than the single-shot subarachnoid blockade. Neuraxial blockade with these methods will allow for careful titration of block with simultaneous fluid loading and continuous monitoring of hemodynamics.
Obstetrics
Some of the physiologic effects of pregnancy will have more pronounced negative effects on the Fontan parturient. The prothrombotic conditions of pregnancy are added to the already thrombus-prone Fontan patient.
Diaphragmatic splinting can result in hypercarbia. Furthermore, the Fontan cardiovascular system, which is exquisitely sensitive to impaired venous return, will not tolerate aortocaval compression.
Addition of an anesthetic to the physiologic milieu of pregnancy and Fontan circulation requires careful consideration and expertise, necessitating obstetric care in a specialized center familiar with the management of these complex patients.
Method of delivery generally should be determined by obstetrical considerations. Only those Fontan patients with severe heart failure necessitate Caesarean delivery for medical reasons. Vaginal delivery is preferable because it is associated with less blood loss, less risk of infection, and fewer thromboembolic events.
The second stage of labor is troublesome because the Valsalva maneuver decreases venous return, and this phase can be shortened by assisted delivery, often facilitated by epidural analgesia.
To preserve CO and, thereby, placental blood flow, the sinus rhythm, ventricular function, systemic venous return, and low PVR must be maintained. Continuous electrocardiography monitoring, wide-bore intravenous access, and an arterial line are useful whether vaginal or Caesarean delivery is planned. Central venous access may be needed if there is a likely requirement for inotrope or vasopressor infusions.
Small fluid boluses should be titrated to maintain preload and CO, and left uterine displacement by wedge or tilt is of pressing importance.
Neuraxial anesthesia has a number of advantages for the Fontan patient, including analgesia, facilitating instrumental delivery to avoid Valsalva and shorten the second stage of labor, and access for surgical anesthesia should Caesarean section be required. Neuraxial anesthesia for Caesarean section will avoid the deleterious effects of positive intrathoracic pressure and myocardial depression from anesthetic drugs.
A functional understanding of moderate to complex congenital heart disease and the impact of pregnancy. Part II: Tetralogy of Fallot, Eisenmenger's syndrome and the Fontan operation.
Subarachnoid blockade is not favored because of the sudden reduction in systemic vascular resistance and venous return. Before any neuraxial technique is performed, the patient's coagulation status and use of antiplatelet or anticoagulant drugs must be determined.
Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy: American Society of Regional Anesthesia and Pain Medicine evidence-based guidelines (fourth edition).
When general anesthesia is required, hemodynamically stable induction agents such as ketamine and etomidate should be considered. At the time of delivery, endocarditis prophylaxis is indicated in Fontan patients.
An excellent recent systematic review by Ropero et al. provided the most comprehensive data set describing the course of 255 Fontan patients in pregnancy.
There was a high rate of miscarriage (45%) and elective termination of pregnancy (7%). Of the 115 live births, 59% were premature and 5% died in the neonatal period. The observed Caesarean section rate was 57.1%. The most common cardiovascular complications reported were supraventricular arrhythmia (8.4%), heart failure (3.9%), and systemic embolism (1.7%). The most common obstetric complications were postpartum hemorrhage (14%), retroplacental hematoma (2.5%), and premature rupture of membranes (1.9%). It is worth noting that the reported incidence of postpartum hemorrhage was much greater (at nearly 50%) in two of the larger included case series. Even though underlying liver dysfunction and the use of anticoagulant or antiplatelet drugs may have contributed, it is suggested that uterine atony was a major factor as a result of the withholding of uterotonic drugs because of concern about the sideeffects of tachycardia, hypotension, and fluid retention in this group, but these drugs have been shown to be safe in parturients with heart disease.
Cardiac surgery and heart transplantation in Fontan patients are complicated by factors in addition to those discussed thus far in the present review article.
Fontan circulation usually is achieved with a course of three sequential surgeries in early childhood. The risk of injury to mediastinal structures upon resternotomy is a pressing concern. Preoperative CT or MRI is useful in identifying any structures adherent to the sternum.
When such anatomy is present, using peripheral cannulation and commencement of cardiopulmonary bypass before sternotomy is a relatively safe approach. The systemic-to-pulmonary artery collaterals often seen in Fontan patients also contribute to bleeding and, preoperatively, may be identified and embolized.
Previous cardiac catheterizations and CHD surgeries can result in thrombosis of vessels, leading to difficulty with access; therefore, preoperative imaging of arterial and venous access points may be useful.
Heart transplantation is a potential treatment option for the patient with failing Fontan. It is well-tolerated physiologically in this population, assisted by the low PVR that usually is present in these patients. The surgery, however, is more difficult than in non-CHD patients,
Outcomes of adult patients with congenital heart disease after heart transplantation: Impact of disease type, previous thoracic surgeries, and bystander organ dysfunction.
Longer times for access with repeat sternotomy may result in prolonged graft ischemic time if organ retrieval and recipient preparation are not precisely choreographed. Prolonged graft ischemia contributes to graft dysfunction and worse outcomes.
As previously discussed, Fontan-associated liver disease is common in the failing Fontan, and when liver dysfunction is advanced, heart-only transplantation may be contraindicated. Higher Model for End-Stage Liver Disease Excluding INR scores have been associated with increased mortality after heart transplantation. Some small single-center case series have reported good outcomes from combined heart-liver transplantation in these patients, but additional data are required, and, presently, the need for combined heart-liver transplantation is decided on a case-by-case basis.
The population of Fontan patients has continued to grow since the first description of this surgical palliation in 1971. This patient cohort is physiologically complex and provides many challenges for the anesthesiologist tasked with perioperative care of these patients. As this population grows, the experience dealing with these patients and the body of evidence that guides practice slowly expand.
An understanding of Fontan physiology and the associated pathologies and organ system dysfunctions is essential to the safe delivery of anesthesia and perioperative care. Careful preoperative assessment and planning is warranted, and care of these patients should be undertaken in a center and by individuals experienced in the management of this group.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
Careful monitoring and manipulation of Fontan hemodynamics, particularly manipulation of pulmonary blood flow, are essential to maintaining CO and require ready access to, and understanding of, the various tools and drugs that may be applied.
Despite the expanding population of Fontan patients, encounters with these patients will remain a very rare occurrence for the majority of anesthesiologists. The care of these patients will be delivered best by those with significant experience, supported by colleagues in a specialized center. The evidence basis for perioperative management remains relatively sparse, and there are many questions that remain unanswered.
Tools for the objective assessment of thrombotic risk and the ideal mode of prevention remain to be determined. It remains to be seen whether transplantation increasingly will be applied for the management of a failing Fontan patient. Despite poorer outcomes currently, perhaps improvements in device technology, technical approach, and patient selection may lead to an expanding role for mechanical circulatory support in the management of a failing Fontan patient, helping to further improve the long-term survival of these patients in the future. It remains to be seen when the efforts to improve long-term survival of these patients will plateau.
2018 AHA/ACC guideline for the management of adults with congenital heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
Diagnosis and management of noncardiac complications in adults with congenital heart disease: A scientific statement from the American Heart Association.
Comparative trial of the use of antiplatelet and oral anticoagulant in thrombosis prophylaxis in patients undergoing total cavopulmonary operation with extracardiac conduit: Echocardiographic, tomographic, scintigraphic, clinical and laboratory analysis.
Factors contributing to adverse perioperative events in adults with congenital heart disease: A structured analysis of cases from the closed claims project.
Arrhythmias in congenital heart disease: A position paper of the European Heart Rhythm Association (EHRA), Association for European Paediatric and Congenital Cardiology (AEPC), and the European Society of Cardiology (ESC) Working Group on grown-up congenital heart disease, endorsed by HRS, PACES, APHRS, and SOLAECE.
The perspective of the intensivist on inotropes and postoperative care following pediatric heart surgery: An international survey and systematic review of the literature.
World J Pediatr Congenit Heart Surg.2018; 9: 10-21
Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy: American Society of Regional Anesthesia and Pain Medicine evidence-based guidelines (fourth edition).
A functional understanding of moderate to complex congenital heart disease and the impact of pregnancy. Part II: Tetralogy of Fallot, Eisenmenger's syndrome and the Fontan operation.
Outcomes of adult patients with congenital heart disease after heart transplantation: Impact of disease type, previous thoracic surgeries, and bystander organ dysfunction.
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