Welcome to the multidisciplinary critical care review course in pediatrics. This topic is on cardiac surgery and post-operative care of children with congenital heart disease undergoing cardiac surgery. My name is Ravi Theogarajan. I'm the chief of the Cardiac Intensive Care Unit at Boston Children's Hospital. Here are my disclosures. I want to acknowledge illustrations used in this presentation were the kind courtesy of Boston Children's Hospital Department of Cardiology Image Library. The objectives of this presentation is to review the general principles of post-operative care for children after cardiac surgery, and to specifically talk more about the post-operative management of children with single ventricle congenital heart disease. I'm going to start off with some general principles of post-operative care of children with congenital heart disease, and these principles apply broadly to all children undergoing cardiac surgery. Here are some general comments for the post-operative care of children after cardiac surgery for congenital heart disease. For the provider, it's really important for each operation to know how a circulation is arranged. For example, in a patient with Tetralogy of Fallot, it would be important to know if an atrial communication is present, so that if the RV should fail, there's an ability to decompress the right side of the heart and maintain cardiac output. It's important to recognize the unique physiological challenges each circulation or each type of circulation brings. For example, in a patient with Hyperplastic Leptart Syndrome who's undergone a stage one palliation operation with a BT shunt, it's important to know that elevation in systemic vascular resistance may reduce cardiac output. It's important to recognize low cardiac output and investigate and treat causes for low cardiac output. It's important to anticipate and manage complications. It's important to know the expected course for each operation, so that deviations from the expected course can prompt investigation for residual congenital heart disease and appropriate management. Many issues in the postoperative period in patients undergoing cardiac surgeries in cardiopulmonary bypass relate to the blood-prosthetic surface interaction and ischemia reperfusion injury following cardiopulmonary bypass. These include myocardial dysfunction, often manifest as cardiac failure, endothelial dysfunction, often manifest as capillary leak, third space fluid, edema, increased systemic vascular resistance, increased pulmonary vascular resistance, pulmonary dysfunction, end-organ injury. Rarely a vasoplegic state characterized by decreased SVR resistance to conventional vasoconstrictors may be seen. Stress response and bleeding related to the use of anticoagulants during cardiopulmonary bypass should be anticipated and treated. It is important to recognize the unique characteristics of the neonatal myocardium and its implication for neonatal myocardial function, given that a large proportion of patients undergo surgery in the neonatal period. The neonatal myocardium has a higher resting pressure and decreased force of myocardial contraction compared to the mature myocardium. Thus, the neonatal myocardium is less likely to tolerate increased preload and afterload. Reduced performance of the neonatal myocardium is because it contains less contractile tissue compared to adults. Furthermore, immaturity of the cytoplasmic reticulum results in less calcium availability for myocardial contractions. These issues, along with the higher resting pressure or higher end-diastolic pressure in the resting neonatal myocardium, result in a muted response to volume administration or increasing preload. Thus, stroke volume in neonates is fixed and cardiac output is dependent on heart rate. Neonates tend to tolerate bradycardia really poorly. As mentioned previously, there is also a limited reserve to increasing force of contraction against increasing afterload. The neonatal myocardium responds to increased afterload with dilation and dysfunction, and thus careful management of afterload is essential in newborn to ensure good cardiac output. This slide shows the effects of poster pressure mechanical ventilation on cardiac function. The table shows the effects of poster pressure mechanical ventilation on the right and the left ventricle. For the right ventricle, poster pressure mechanical ventilation reduces preload by increasing interthoracic pressure and reducing venous return from the SVC and the IVC coming back to the right atrium. Thus, right ventricle end-diastolic volume is reduced. Poster ventrothoracic pressure increases the afterload to the right ventricle, and as a consequence, pulmonary blood flow is decreased. This is particularly profound in patients with cabopulmonary connection circulations, such as following the bidirectional gland-in-the-fountain operations, where pulmonary blood flow into the pulmonary vasculature is passive. For the left side of the heart, preload to the left side of the heart is reduced as a consequence of reducing pulmonary blood flow based on the effects of poster pressure mechanical ventilation on the right heart. However, the afterload to the left ventricle is reduced, and the mechanism for this is provided in the additional material found at the end of this presentation. In general, patients with right heart failure are less likely to tolerate mechanical ventilation with high mean airway pressure, and those with isolated left heart failure may benefit from poster pressure mechanical ventilation, including those provided by non-invasive forms such as BiPAP because it reduces afterload to the left ventricle. This slide shows the relationship between lung volume and pulmonary vascular resistance. Lung volume here is depicted on the horizontal axis and pulmonary vascular resistance on the vertical axis, and as you can see, the pulmonary vascular resistance is lowest when the lung is filled to FRC, or functional residual capacity. If the lung is collapsed, as in adelaide disease, then pulmonary vascular resistance is high, related to both hypoxic pulmonary vasoconstriction as well as collapse of alveoli around pulmonary capillaries. Similarly, over-distension of the lung also results in elevated pulmonary vascular resistance because of stretch and compression of the pulmonary capillaries related to stretch. So for children recovering following cardiac surgery, if pulmonary vascular resistance is an issue, really ventilating them in and around or maintaining FRC is really a crucial aspect of their ventilatory care. This slide summarizes the effects of mechanical ventilation on cardiovascular function. Poster pressure mechanical ventilation is common following cardiac surgery, and therefore understanding the effects of mechanical ventilation on cardiovascular function is crucial for recovery of patients following cardiac surgery. We clearly know that mechanical ventilation provides cardiovascular support by decreasing oxygen consumption with decreasing work of breathing for respiration. It also provides cardiovascular support by decreasing LV afterload in patients with isolated left-sided heart failure. Maintaining FRC with the lowest mean airway pressure gets you the lowest level of pulmonary vascular resistance, especially in patients with right heart disease or right heart failure that require mechanical ventilation. Patients with right ventricular failure or cable pulmonary connection circulations, a high mean airway pressure can actually reduce cardiac output, and care should be taken to maintain FRC at the lowest mean airway pressure possible. It should also be said that ventilation should be adjusted based on physiology, and there's no one good mode of mechanical ventilation for children with heart disease. And it should be adjusted with the principles of interactions between mechanical ventilation and cardiac function in unique circulations to provide successful support for these patients. Post-operative low cardiac output is common in children undergoing cardiac surgery for general heart disease with cardiopulmonary bypass. It is most common in newborn and infants. It is estimated that 26% of infants undergoing cardiac surgery have low cardiac output. The onset of low cardiac output is usually 6 to 12 hours following the operation. 25% of children with post-operative low cardiac output have a cardiac index of less than 2 liters per minute per meter squared, and a cardiac output of less than 2 liters per minute per meter squared is associated with increased risk of mortality. Any child presenting with low cardiac output syndrome following cardiac surgery for correction of congenital heart disease should have residual defects ruled out. The usual manifestations of post-operative low cardiac output is cool extremities, poor perfusion, tachycardia, hypotension, reduced urine output, lactic acidosis, decreased mixed venous oxygen saturation, and organ dysfunction, such as dysfunction of the renal and hepatic dysfunction. Management of post-operative low cardiac output following cardiac surgery for congenital heart disease is common in our intensive care units. Principles of management include optimizing preload using central venous pressure measurements and replacing volume to an optimal central venous pressure, enhancing contractility of the myocardium using agents such as dopamine and epinephrine, reducing afterload to the ventricle using inodilators such as milrinone or vasodilators such as niprite, reducing oxygen consumption so that cardiac output is aligned to tissue metabolic needs. We can achieve this by gently cooling patients, providing them hypothermia or preventing fevers, providing sedation and mechanical ventilation such that the cardiac output that is generated by this heart is aligned with tissue metabolic needs. It's important to ensure sinus rhythm. AV synchrony provides a 10% to 20% increase in cardiac output, and ensuring sinus rhythm can happen in the forms of atrial pacing or management of arrhythmia. Like I previously mentioned, it's really imperative to rule out residual structural heart disease in children presenting with low cardiac output after cardiac surgery for congenital heart disease. A clinical study done in 2003 of use of prophylactic milrinone after cardiac surgery in infants was shown to reduce the incidence of low cardiac output, and milrinone is commonly used for this purpose. And finally, if medical management has been optimized and the patient continues to deteriorate with lactic acidosis and onset of end-organ injury, the use of mechanical circulatory support such as ECMO may be useful in rescuing these patients. It is estimated that 2% to 7% of children undergoing cardiac surgery for correction of congenital heart defects may have postoperative pulmonary hypertension. Cardiopulmonary bypass-induced pulmonary endothelial dysfunction can cause increased pulmonary vascular resistance, but this dissolves over time. Pulmonary hypertension often complicates the management of some high-risk patients, and these include neonates undergoing cardiac surgery for congenital heart disease, patients who have preoperative pulmonary vascular disease or elevated pulmonary vascular resistance, patients with tribosomate 21 undergoing a late repair of septal defects, patients who have pulmonary vein obstruction such as newborn with obstructed total anomalous pulmonary venous return, patients with left atrial hypertension as a result of diseases such as mitral valve disease or mitral stenosis, and left atrial hypertension may have pulmonary hypertension in the postoperative period, and patients who have residue or left-to-right shunt after correction of a septal defect may have pulmonary hypertension. Pulmonary hypertension or pulmonary hypertensive crisis are often precipitated by certain inciting events, and these include pain, anxiety, tracheal suctioning for clearing of secretions from the endotracheal tube, metabolic acidosis, hypoxia, or respiratory insufficiency or hypoventilation may precipitate a pulmonary hypertensive crisis. Pulmonary hypertensive crisis is characterized by an acute increase in pulmonary vascular resistance and PA pressure that results in an acute afterload to the right ventricle, resulting in right ventricular failure. The consequence of right ventricular failure is an acute distention of the RV, an elevation of RV and diastolic pressure and volume. Acute distention of the RV shifts the intraventricular septum into the left ventricular outrotract, resulting in low output from the left ventricle or low cardiac output and hypotension. This along with the increased RV and diastolic pressure results in RV ischemia, and then if these events are not treated, eventually will result in cardiac arrest. Clinical features of pulmonary hypertensive crisis include an acute elevation of right-sided pressures. So there's an acute increase or abrupt increase in RA pressure or CVP. If a pulmonary artery catheter is present, then an acute increase in PA pressure accompanied with hypotension and low cardiac output and wheezing related to bronchoconstriction. The pulmonary hypertensive crisis has to be recognized promptly, and patients should be rescued from pulmonary hypertensive crisis because the estimated mortality for postoperative pulmonary hypertensive crisis is about 20%. Management includes providing adequate ventilation and oxygenation, and this often requires hand ventilation with 100% oxygen to provide adequate FRC and 100% oxygen, and oxygen here is used as a pulmonary vasodilator. If a patient is agitated and has previous history of elevated pulmonary vascular resistance, sedation paralysis is needed. If there's metabolic acidosis, correction of acidosis is required. Use of specific pulmonary hypertensive therapies such as nitric oxide or other pulmonary vasodilators may be useful. It may be useful to support the function of the right ventricle using inotropic support, either epinephrine or dopamine. And then if all of these things fail to reverse pulmonary hypertensive crisis and the patient's approaching cardiac arrest, then rescue with ECMO may be warranted. Postoperative bleeding is common in children undergoing cardiac surgery. Bleeding may be due to surgical bleeding from suture lines, presence of residual heparin effects from cardiopulmonary bypass, coagulopathic process or DIC, platelet dysfunction as a result of exposure to cardiopulmonary bypass, and the use of hypothermia. Management of bleeding requires prompt attention to both assessing the quantity of bleeding and following over time to make sure that the bleeding events are resolving. Management of bleeding also includes performing coagulation tests so that coagulopathic processes can be diagnosed and blood products can be used to reverse coagulopathic processes and contain bleeding. If a heparin effect is thought to be present, then reversal with the use of protamine may be useful in some cases. Other hemostatic agents such as antifibrinolytics, such as epsilon amino caproic acid or Amocar, or tranexamic acid more commonly used these days, and factor VIIa may be useful. If a postoperative patient is bleeding, it is important to involve the surgical team early on so that they can follow along with the primary team caring for the patient in the ICU and promptly intervene surgically if that's necessary. So close communication and contact with your surgical colleagues is really important. Cardiac tamponade in the postoperative period is an acute emergency that requires prompt attention and quick resolution. Cardiac tamponade may be caused by collection of blood or serous fluid in the parochial space, resulting in compression of the heart. Cardiac tamponade can be seen in patients who've had a bleeding event, and it's important to suspect cardiac tamponade if there's been a sudden cessation of chest strain output in a patient who's had a previous bleeding event. Tamponade is usually manifest by tachycardia, lobe hypotension, decreased pulse pressure or pulsus paradoxus, and increase in filling pressures, either the CVP or right atrial pressure or left atrial pressure. Echocardiography will demonstrate diastolic right atrial collapse. If pulsus paradoxus is present and a patient is hypotensive, quick and prompt opening of the chest or draining of the pericardial effusion or the pericardial fluid collection with pericardiocentesis should be undertaken immediately. Volume expansion to increase intravascular volume can potentially temporize whilst the opening of the chest or pericardiocentesis is being orchestrated. Residual lesions after congenital heart surgery are common and need to be promptly attended to. The manifestations of residual lesions after congenital heart surgery may be nonspecific, such as a manifestation as low cardiac output or congestive heart failure, that's refractive medical management, left atrial or pulmonary hypertension, presence of pulmonary edema, ascites, rhythm disturbances, or need for prolonged mechanical venomation. The usual tools available for diagnosis of residual lesions after congenital heart surgery include diagnosis with an echocardiogram or cardiac catheterization. If a residual lesion is present and the patient is symptomatic, then these require early reinvention, such as either with a cath-based intervention or a surgical intervention. It's estimated that about 6% of patients receiving mechanical venomation following cardiac surgery to correct congenital heart disease result in extubation failure. The slide here shows reasons for extubation failure following congenital cardiac surgery, along with the usually applicable reasons for any patient receiving mechanical venomation, such as airway-related issues, secretion-related issues, sedation, respiratory events. There are some issues that are specific to patients recovering from cardiac surgery after congenital heart disease. These require careful evaluation and management to get a patient successfully extubated. Some causes that are common to children with congenital heart disease include presence of residual lesions, as previously mentioned, diaphragmatic paralysis of phrenic nerve injury, restrictive chest wall, and diuretic-induced contraction alkalosis. These conditions need to be carefully evaluated and treated. Phrenic nerve injury during cardiac surgery can result in diaphragmatic paralysis and extubation failure in children undergoing cardiac surgery for congenital heart disease. In a recent publication from the Society of Thoracic Surgeons, it was estimated that diaphragm paralysis occurred in 1.2% of all cardiac surgical procedures. They also demonstrated that diaphragm paralysis was associated with increased mortality and increased mobility that included increased use of tracheostomy and increased and prolonged duration of mechanical ventilation. The diagnosis of diaphragm paralysis can be made on plain chest x-ray film but care should be taken not to use positive pressure ventilation while imaging these patients. And the x-ray here shows that the right hemidiaphragm is elevated compared to the left hemidiaphragm suggesting that the diaphragm is moved upwards from paralysis. Other ways of confirming the diagnosis include fluoroscopy to demonstrate paradoxical upward movement of the diaphragm during inspiration or more recently ultrasound has also been used to make a diagnosis of diaphragm paralysis. The management of diaphragm paralysis include plication of the diaphragm and then subsequent liberation that can subsequently help liberate patients from mechanical ventilation. Post-operative arrhythmias can occur after cardiac surgery for congenital heart disease. The incidence is estimated to be about 15% and factors associated with post-operative arrhythmias include scotch and suture lines, type of surgery, myocardial dysfunction, electrolyte abnormality from diuretic use, residual defects, pain and fever, and hyperadrenergic state. Supraventricular tachycardia are the most common type of arrhythmia seen in the post-operative period. Management of post-operative arrhythmia includes patient assessment as well as making a rhythm diagnosis and consulting with an electrophysiologist to choose the right modality of treatment. Patient assessment includes assessing as to whether a patient is stable or unstable in the arrhythmia and the hemodynamic impact of the arrhythmia on circulatory physiology. It's also important to assess certain correctable causes which include acidosis, electrolyte disturbances such as hypokalemia or hypocalcemia or hypomagnesemia. If there's presence of fever or agitation, those could be treated as an adjunct to arrhythmia management. Junctional ectopic tachycardia is a rare tachycardia that's seen in children after cardiac surgery for congenital heart disease. Junctional ectopic tachycardia or JET is an automatic ectopic tachycardia that originates at the level of the atrioventricular node or the atrioventricular junction or the level of the bundle of PIS. Heart rates are generally about 170. There's AV dissociation and there are more ventricular complexes than atrial complexes and the QRS duration of the ventricular complexes are the same QRS duration as baseline EKG. Junctional ectopic tachycardia can cause significant hemodynamic perturbations and require careful management. Because junctional ectopic tachycardia may be worsened by hyperadrenergic state, providing sedation and paralysis and reducing the amount of inotropic support where possible is useful in the management of these rhythms. If the heart rate is less than 170, atrial pacing above the junctional ectopic tachycardia rate would be useful in restoring AV synchrony. Centers vary about the choice of antiarrhythmic agents and the use of hypothermia and the management of junctional ectopic tachycardia. The two agents that are commonly used in the management of junctional ectopic tachycardia include amiodarone or prokinamide. The good news about junctional ectopic tachycardia is that it's a self-limiting arrhythmia that is likely to resolve over time. However, it causes enough hemodynamic perturbations that careful attention to the management of these rhythms is crucial in making progress with a patient in the rhythm. Consultation with another electrophysiologist is crucial in making a diagnosis as well as managing antiarrhythmic therapy in these patients. Now that we've reviewed general principles in the postoperative care of children with congenital heart disease recovering after cardiac surgery, this section focuses on postoperative care of patients with single ventricle congenital heart disease recovering following palliative congenital heart surgery. To illustrate the principles of postoperative care of children with single ventricle congenital heart disease, we will use the example of staged palliation for hyperplastic left heart syndrome. As you've heard from the previous lecture on congenital cardiac malformations, hyperplastic left heart syndrome is a condition where this hyperplasia of the left side of structures and the right ventricle becomes the future systemic ventricle. This hyperplastic left heart syndrome is palliated in stages. And stage one palliation consists of constructing a systemic outflow tract for the right ventricle and providing a source of pulmonary blood flow. And the glen and the fontan, which is stage two and stage three procedures, consists of separation of the systemic venous and systemic arterial circulation. So coming back to stage one palliation for hyperplastic left heart syndrome consists of creating a systemic outflow tract for the right ventricle. And this is achieved by disconnecting the main pulmonary artery from the branch pulmonary arteries and using that to reconstruct the right ventricular outflow tract, which then becomes a systemic outflow tract, reconstruction of the aortic arch, and then providing a source of pulmonary blood flow using either a systemic to pulmonary artery shunt or using a right ventricle to pulmonary artery conduit and then atrial septectomy. In the stage one palliation operation, the right ventricle ejects blood both to the pulmonary and systemic circulation. Thus, success with this procedure requires balancing of pulmonary and systemic circulation. In stage one palliation operation, the systemic arterial saturation predicts the balance of QPQS, and those can be calculated showing the formula here. In a patient who has a SVC saturation of 60 percent, a systemic arterial saturation of 80 percent, and an assumed pulmonary vein saturation of 100 percent, QPQS is 80 minus 60 divided by 100 minus 80, which is a QPQS of one. Systemic arterial saturation predicts the balance of QPQS in patients with stage one palliation. The higher the saturation, the more pulmonary blood flow and less systemic blood flow, and those patients have reduced cardiac output. And therefore, managing oxygen saturations to reflect a QPQS of one to 1.5 is really important, and this can be achieved by balancing pulmonary and systemic vascular resistances. Postoperative management of stage one palliation, as previously mentioned, requires careful balance of pulmonary and systemic blood flow, and this is achieved by carefully managing systemic vascular resistance. Postoperative management includes reduction in systemic vascular resistance and encouraging systemic outflow or cardiac output using agents such as milrinone or niprite, providing myocardial support when necessary using dopamine and epinephrine, and avoiding hyperventilation or exposure to high quantities of IL-2, which may reduce pulmonary vascular resistance. It is important to recognize that elevations of systemic vascular resistance decrease QS and thus decrease cardiac output, and careful attention needs to be paid to this. Maneuvers to increase PVR, such as exposure to carbon dioxide or hypoxic gas mixtures, do not have any effect on QS. In patients with a BT shunt, because there's diastolic flow reversal in the aortic arch, coronary steel may occur. In patients with single ventricle palliation, right ventricular volume load is common and requires diuresis and careful management of QP to prevent volume overload. This table shows some scenarios for troubleshooting the stage 1 palliation circulation. If your systemic oxygen saturation is 80% and if you have a normal mixed venous saturation or SVC saturation, a normal lactate and a normal blood pressure, then your circulation is balanced. If your saturations are greater than 90% and your SVC saturation is lower, you have lactic acidosis and have hypotension, then your QP is greater than your QS. It's possible that the systemic vascular resistance may be elevated and you may want to consider an ion or dilator in these patients. It's also important to avoid hyperventilation or exposure of patients to higher levels of FiO2 that may reduce pulmonary vascular resistance in these patients. One anatomical feature that can cause elevated QP with low cardiac output is development of aortic arch obstruction. And if there's aortic arch obstruction, you're likely to have increased QP greater than QS because pulmonary blood flow is driven by the anatomical obstruction in the aortic arch. These patients may need full blood pressure measurements and echocardiography and an intervention to correct the arch obstruction. In patients with stage 1 palliation who have an acute desaturation episode, hypotension and an acute loss in entire CO2 have shunt obstruction, either obstruction of the BT shunt or obstruction of the RVDPA conduit. And these patients need emergency intervention to reestablish pulmonary blood flow. In patients with stage 1 palliation who have saturations in the expected range 70 to 80%, who present with low mixed venous saturation, lactic acidosis and hypotension, may have low cardiac output and may need inotropic support or inobasal dilator support. It's essential that an echocardiography is obtained in these patients to rule out atrioventric valve regurgitation or arch obstruction because both these conditions can present as low cardiac output with saturations in the expected range. The bidirectional glen operation is the second stage of single ventricle palliation and is usually undertaken at three to six months of age. In the bidirectional glen operation, the superior vena cava is the nastiest to the pulmonary arteries, bringing the cerebral and pulmonary circulations in sequence. Therefore, any increase in cerebral blood flow will bring increased blood flow into the pulmonary arteries and therefore increase oxygen saturation. Gentle hypoventilation and mild carbon dioxide retention by causing cerebral vasodilation may improve saturations in the bidirectional glen operation, whereas hypoventilation and reduction in carbon, reduction in PCO2 may cause cerebral vasoconstriction and reduce oxygen saturations. The bidirectional glen patients are best managed with early extubation where possible, and because the cerebral venous pressure is increased by anastomosing the SVC previously connected to the right atrium, which is low pressure to a high pressure pulmonary artery, results in systemic hypertension as a compensatory mechanism to maintain cerebral perfusion pressure. The systemic hypertension may require management in the postoperative period and is likely to resolve over time. This table provides a simple guide to troubleshooting hypoxemia after a bidirectional glen operation. Hypoxemia after a bidirectional glen operation may occur because of low cardiac output or low mixed venous oxygen saturation, and the usual causes for that are ventricular dysfunction or AV valve or atrioventricular valve regurgitation, and this can be ruled out by echocardiogram. You can have hypoxemia related to lung disease, and you can have hypoxemia related to lung disease, or you can have hypoxemia because the overall pulmonary blood flow is decreased. Decrease in pulmonary blood flow can occur if the SVC is decompressed into the IVC through veins such as the azygous vein that was not ligated in the operation, or there's obstruction to flow at the level of the glen anastomosis or increased pulmonary vascular resistance. These conditions should be diagnosed and appropriately managed. The Fontan operation, usually undertaken at about two years of age, is the final step in single ventricle palliation. The Fontan operation achieves separation of the systemic venous and systemic arterial circulation and creates a venous and arterial circulation in series. The Fontan operation consists of anastomosis of the inferior vena cava to the pulmonary arteries, either using a conduit in the right atrium, and this is called a lateral tunnel Fontan, or using a conduit that's outside the heart or an extracardiac Fontan. For the Fontan circulation to be efficient and successful, you need adequate preload to drive blood into the pulmonary arteries. You want no obstruction, both in terms of the size of the pulmonary artery or anatomical obstruction to the pulmonary artery that allows blood from the IVC and SVC to flow freely into the pulmonary arteries. You want no obstruction of the level of the lung, either from elevated pulmonary vascular resistance or mechanical ventilation that increases mean airway pressure that impedes blood flowing into the lungs. You want the blood returning from the lungs into the systemic atrium to be unimpeded and therefore a good systemic function of the single ventricle, low end diastolic pressure, and no level of systemic outflow tract obstruction. So all of these conditions need to be met to keep a Fontan circulation efficient, and any inefficiencies in these areas will result in an inefficient Fontan circulation or a patient that struggles after a Fontan operation. Most centers create a fenestration in the Fontan baffle that connects the right atrium into the systemic atrium, and this allows the Fontan circulation to decompress desaturated blood into the systemic atrium and thereby maintaining cardiac output even if the Fontan circulation is inefficient. The fenestrations are usually useful in the early postoperative course and are in general closed using cardiac catheterization and a device to close the fenestration at about a year of age. Based on the description of the Fontan circulation and efficiencies and inefficiencies of the Fontan circulation, postoperative management of patients after Fontan operations require maintenance of an adequate preload, maintaining an open fenestration, mechanical ventilation to maintain FRC to keep your pulmonary vascular resistance as low as possible, but using a low mean airway pressure, afterload reduction to improve the efficiency of the single ventricle. So these are usually what is necessary to keep a Fontan circulation efficient. And as previously mentioned, ensuring a sinus rhythm and therefore AV synchrony can keep the systemic atrial pressure as low as possible so that the blood returning from the pulmonary venous circulation can empty into the atrium without any impediment. Most Fontans should be extubated early. Negative pressure ventilation or spontaneous breathing creating negative pleural pressure increases venous return into the pulmonary circulation and therefore makes the Fontan more efficient. So the goal should be early extubation for a Fontan operation just like the bidirectional glen. This table provides a general guidance to troubleshooting the Fontan circulation. Most patients recovering after a Fontan operation have intravascular catheters that measure pressures in the various parts of the Fontan pathway. Pressures measured in the Fontan baffle may be from the CVP or right-sided pressures. Pressures measured on the left side of the heart or in the systemic atrium are usually placed the pulmonary vein into the systemic atrium. A difference in the right and the left-sided pressures gives you a trans-pulmonary gradient which is a measure of efficiency of transit of blood from the Fontan circulation through the pulmonary arteries and the lung and return to the left atrium. Patients who have low cardiac output related to low right-sided pressures and low left-sided pressures with a normal trans-pulmonary gradient have reduced preload, may be hypovolemic, and attention needs to be paid to improving preload to improve cardiac output. Patients who have elevated right-sided pressures but a low left-sided pressure and an elevated trans-pulmonary gradient have a defect in transit of blood from the Fontan pathway into the left atrium and these may include elevation of pulmonary vascular resistance, anatomical obstruction to the pulmonary arteries, or mechanical ventilation with high mean airway pressure. In patients who have an elevated right-sided pressure, low left-sided pressure, and elevated trans-pulmonary gradient who are fully saturated have occlusion of the fenestration and the Fontan is unable to decompress the Fontan baffle or the Fontan pathway into the left side of the heart because the fenestration is occluded and this makes the Fontan circulation inefficient and low cardiac output is related to inability to decompress the Fontan into the left side of the heart. Fenestration occlusions can be diagnosed using echocardiography and can be intervened upon in the cardiac catheterization lab. Patients who have elevated right-sided and left-sided pressure with a normal trans-pulmonary gradient may have tamponade and tamponade should be ruled out. In patients who do not have tamponade, then elevated right and left-sided pressure may be related to systemic ventricle dysfunction and either elevated end-diastolic pressure or related to systemic outflow tract obstruction or poor function of the systemic ventricle. In patients who have lost AV synchrony or in a junctional rhythm, the left-sided pressures may be elevated because the ATM is dis-synchronous with the ventricle and restoring AV synchrony may make the Fontan circulation more efficient. So using pressures to evaluate the Fontan pathway to diagnose the cost of low cardiac output is really essential to move the Fontan patient forward. Thank you very much for your attention. I hope this talk provides you an overview of post-operative management of children with congenital heart disease after cardiac surgery. I've also provided you some additional material that addresses vital sign interpretation, a few tips on physiology, restrictive RVs physiology and management, and troubleshooting arrhythmias and pacing. Thank you very much for your attention. Management of patients with Tetralogy of Fallot and restrictive RV physiology includes maintaining higher filling pressures for RV function, maintaining functional residual capacity to maintain PVR at the lowest level possible. But this has to be achieved, as previously mentioned, with a low mean airway pressure, enhancing right ventricular contractility in the presence of systolic dysfunction, and the use of pulmonary vasodilators to reduce PVR. Creation of an atrial septum.

post-operative care

congenital heart disease

cardiac surgery

single ventricle

physiological challenges

complications

pulmonary hypertension

communication