71 Fontan Pathway From Birth Through Early Childhood
Third-Stage Reconstruction: The Modified Fontan Procedure
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the thoracic duct and carry lymph toward the central venous system in the thorax Lymphatic fluid contains, fats, lymphocytes, immunoglobin, and coagulation factors Any elevation of central venous pressure, as occurs as a predictable consequence of fUVH palliation, can produce relative obstruction to the normal drainage of lymphatic fluid into the central venous system and result in a chylothorax Although elevation of central venous pressure is an anticipated consequence of surgical palliation and early chylous drainage is common, this generally resolves after a day or two following SCPC palliation The terms chylothorax and chylous effusion generally refer to effusions or high output from a chest tube that persists for more than a week The first step in management is to rule out any anatomic abnormalities that can raise central venous pressure, such as obstruction of the superior cavopulmonary pathway, thrombus in the superior vena cava, or additional sources of pulmonary blood flow Direct injury to the thoracic duct can also result in chylothorax, which can result in chylothorax in the setting of an optimal anatomic result and favorable hemodynamics If there are no anatomic issues, a stepwise treatment plan is begun that starts with a low-fat diet to limit lymph production This can be escalated to NPO and TPN Additional medical therapies can be added, including octreotide, steroids, and aldactone.237 For recalcitrant effusions, thoracic duct ligation and pleurodesis can be considered In addition to taking steps to limit the drainage, treatment must also be directed at the pathophysiology of ongoing loss of chylous fluid Ongoing chest tube drainage can result in malnutrition due to loss of proteins and fat, development of hypercoagulability due to loss of coagulation factors, and immunocompromise due to loss of lymphocytes and immunoglobin Patients with prolonged effusions are at risk for these complications These complications can develop insidiously and exacerbate the clinical course For example, loss of coagulation factors can result in line-related thrombosis of a central line, which can further elevate central venous pressure and lead to even greater hydraulic stimulus to the formation of a chylous effusion Ongoing oral intake will result in increased chylous output and paradoxically worsen protein loss Making the patient NPO and beginning TPN will limit ongoing protein loss while supporting nutrition Replacement of chest tube output with fresh frozen plasma will limit the development of coagulopathy Anticoagulation with unfractionated heparin or low-molecular-weight heparin may limit thrombotic complications Family Support and Interstage II Surveillance and Monitoring After the Superior Cavopulmonary Connection Two of the most common stressors to families during the second interstage period (interstage II) is (1) the loss of the continuity and availability of the interstage monitoring team (see Chapter 72) and (2) the variability in practice regarding type and frequency of diagnostic studies and timing of the Fontan procedure.3,238 The SCPC physiology is significantly more stable than the multidistribution circulation, and the emphasis of care shifts from physiologic stability to a focus on growth and development This is also the time when any additional surgical procedures—either cardiac (e.g., valvuloplasty) or noncardiac (e.g., gastrointestinal, orthopedic, urologic)—are typically performed Family support frequently shifts from the dedicated interstage team to local and Internet-based support groups.239–241 Increasing numbers of centers have started lifelong programs specifically for patients with fUVH and their families.242 Additionally, families are increasingly participating in research and developing best-practice models along with clinicians.243–245 Third-Stage Reconstruction: The Modified Fontan Procedure The third stage of reconstruction and the ultimate goal for the patient with fUVH is the modified Fontan procedure Patients with tricuspid atresia and normally related great vessels were the impetus for developing the Fontan procedure.246,247 Experimental procedures and early reconstructive efforts were directed at bypassing the obstructed right side.248–254 Success in patients with tricuspid atresia was followed by application of Fontan palliation to a wide variety of fUVH anatomies Hydrodynamic studies determined that a smoothcaliber unobstructed Fontan pathway (rather than attempting to incorporate the pulsatile right atrium as a pumping chamber) minimized energy loss and improved output.255 The extracardiac Fontan simplified the procedure even further and permitted application to even broader anatomic variants.256 The modified Fontan procedure will relieve cyanosis by separating pulmonary and systemic venous return and will restore, as closely as possible, a normal in-series blood flow pattern (Box 71.7) All of the previous procedures are aimed at creating the best possible Fontan candidate—one with preserved systolic and diastolic single-ventricle function and well-developed pulmonary vasculature with low pulmonary arteriolar resistance (see Chapter 70) Box 71.7 Goals of the Fontan Procedure ■ Surgical baffling from the inferior vena cava to the pulmonary artery ■ Minimization/elimination of hypoxemia ■ Performance of additional procedures (e.g., pulmonary artery plasty, septectomy, valvuloplasty) Preoperative Evaluation To assess risk and guide surgical planning, the factors outlined in Table 71.9