Andersons pediatric cardiology 1865

Elevated TPG CVP: low Atrial pressure: low Elevated pulmonary vascular resistance Pulmonary venous obstruction Hypovolemia CVP, Central venous pressure, measured in the Fontan baffle, superior caval vein, or pulmonary artery; TPG, transpulmonary gradient The necessary management strategies to treat low cardiac output depend on their fundamental causes and may range from volume resuscitation, chest drainage, antiarrhythmic medications, pulmonary vasodilators, vasoactive support, catheter interventions, and so forth Broad recommendations are therefore not helpful in the scenario of low cardiac output in this population The key to appropriate management is identification of the cause It is important for the management team to first and foremost have knowledge of the preoperative status of the patient, including pulmonary artery size and pressure, PVR, ventricular end-diastolic pressure, ventricular and AV valve function, and so forth Next, the team providing postoperative care must have a complete understanding of the procedure and course in the operating room The most important data during the early postoperative period is that obtained from intravascular catheters in the central venous compartment and the common atrium, comparing those values to the preoperative and intraoperative values An echocardiogram will further assess ventricular function as well an AV valve regurgitation and evaluate for extracardiac fluid Postoperative acoustic access may be quite limited, and cardiac catheterization may be necessary to confirm hemodynamic findings and evaluate the surgical anastomoses and pulmonary arterial tree Management strategies are then tailored to the specific anatomy, physiology and cause of low cardiac output In refractory cases, the Fontan operation may need to be “taken down” to a SCPC or systemic-to-pulmonary artery shunt; this occurs in 1% to 4% of cases with high early and late mortality rates.296–299 Rhythm Disturbances Postoperative rhythm disturbances following the Fontan are common and occur in approximately 30% of patients.300–303 The most common early arrhythmias are sinus node dysfunction, junctional ectopic rhythm, and atrial tachycardias It is important for optimization of postoperative hemodynamics to maintain atrioventricular synchrony in the early postoperative period In the case of a junctional ectopic tachycardia, measures to control the rate of accelerated junctional rhythm primarily include minimization of endogenous (pain and agitation) and exogenous (vasoactive medications) catecholamines and pharmacologic therapy Although whole-body cooling has been utilized in other patient populations, this requires neuromuscular blockade to prevent shivering and thus mechanical ventilation, which further compromises hemodynamics (Counterintuitively, extubating the patient with an accelerated nodal rhythm may actually improve hemodynamics and slow the junctional rate, allowing for atrial pacing or return of sinus rhythm Should this approach be tried, equipment needed for prompt reintubation should be available.) Pharmacologic therapies for junctional ectopic tachycardia include amiodarone, procainamide, and dexmedetomidine Once the rate of the junctional rhythm has been controlled, AV synchrony may be achieved with temporary atrial pacing Temporary pacing maneuvers may also be helpful for sinus node dysfunction Atrial tachycardias may be terminated with rapid atrial pacing maneuvers via temporary pacing wires when available or cardioversion when appropriate Effusions/Chylothorax Chylothorax, requiring chest tubes greater than 1 week, is a common complication following a Fontan, occurring in up to 25%.236 Both causes and management are similar to the situation after a superior cavopulmonary anastomosis Elevation of central venous pressure is a predictable consequence of palliation for fUVH and can impair normal drainage of lymphatic fluid into the central venous system, resulting in a chylothorax As a consequence, chylous drainage is common after a Fontan and of slightly longer duration than after a superior cavopulmonary anastomosis, but it generally resolves in 4 to 5 days The first step in the management of chylothorax is to rule out any anatomic abnormalities that could raise central venous pressure, such as obstruction of the Fontan or significant aortopulmonary collateral burden If there are no anatomic issues, a stepwise treatment plan is begun that starts with a low-fat diet to limit stimulating lymph production This can be escalated to NPO and TPN Additional medical therapies can be added, including octreotide, steroids, and aldactone.237 Unlike the situation after the superior cavopulmonary anastomosis following the Fontan procedure, all or nearly all the cardiac output must traverse the pulmonary vascular bed and any elevation of PVR will add arithmetically to the central venous pressure Pulmonary vasodilators such as inhaled nitric oxide or sildenafil may be useful in lowering the transpulmonary gradient and thereby the central venous pressure Pleurodesis can be considered Again, treatment must also be directed at the pathophysiology of ongoing loss of chylous fluid Patients with prolonged effusions are at risk for malnutrition, infection, and thrombotic complications Eliminating oral intake to decrease lymph production combined with TPN should be considered early as both a treatment of the chylothorax and to avoid ongoing protein loss and malnutrition A portion of the chest tube output should be replaced with fresh frozen plasma to ameliorate loss of coagulation factors