256 SECTION IV Pediatric Critical Care Cardiovascular differing expectations for quality of life if survival is achieved Technical limitations are an inability to obtain vascular access secondary to t[.]
256 S E C T I O N I V Pediatric Critical Care: Cardiovascular differing expectations for quality of life if survival is achieved Technical limitations are an inability to obtain vascular access secondary to thrombosis, abnormal anatomy, or prior surgery 100 Percent 80 60 Critical Care Management During Extracorporeal Life Support Still waiting Removed from list Died DD transplant 40 20 0 12 24 26 Months post listing • Fig 28.5 Waitlist mortality statistics from the Scientific Registry of Transplant Recipients (SRTR) DD, Deceased donor A study merging UNOS and Pediatric Health Information Systems databases reported that children with CHD, particularly single-ventricle conditions, require substantially greater hospital resource utilization and have significantly worse outcomes during the first year after heart transplantation compared with other indications, emphasizing the importance of modifying patient risk factors with interventions such as pretransplantation conditioning with VAD support and cardiac rehabilitation.141 Malignant Dysrhythmias MCS can be lifesaving for pediatric patients with malignant dysrhythmias unresponsive to pharmacotherapy A subset of patients with acute fulminant myocarditis will present with refractory LCOS and ventricular tachycardia or high-degree heart block that further compromises end-organ perfusion In this scenario, MCS may be used to bridge patients to recovery following initiation of antiarrhythmic agents and/or electrophysiologic mapping with ablation therapy or transplantation Several potentially lethal arrhythmias—such as supraventricular tachycardia, junctional ectopic tachycardia, ventricular tachycardia, or torsades de pointes—can occur congenitally, can be acquired in the perioperative period, or manifest as a result of the ingestion of toxic substances or medications.142–144 Again, ECLS can allow time for resolution of the dysrhythmia with aggressive medical treatment and the subsequent recovery of cardiac function.145 Contraindications Although individual institutions may have variations to this list, the number of absolute contraindications to ECLS continues to decrease.146–149 Irreversible cardiac failure without the option for transplantation, irreversible lung failure, severe neurologic dysfunction, grade III/IV intracranial hemorrhage, uncontrolled bleeding, and lethal congenital anomalies/genetic syndromes are considered contraindications Each center should evaluate carefully the decision to provide ECLS to these patients Relative contraindications include prematurity (,34 weeks), weight less than kg, and grade II intraventricular hemorrhage.149–151 Cardiac arrest is not a contraindication if rapid effective CPR was initiated, the underlying etiology is deemed reversible, and time to cannulation is less than 60 minutes The challenge remains determining what is irreversible, shortened life span, poor prognosis, or severe, as these definitions have changed over time and with Patients who require MCS are critically ill by definition, often with multiple end-organ dysfunction Thus it is not surprising that complications occur with a greater frequency for this group than for other critically ill patients Basic management principles are discussed in this section Cardiac Output When assessing the hemodynamic state of a patient, one must consider to what degree conventional support (mechanical ventilation and vasoactive agents) is contributing to cardiac and pulmonary function versus the ECLS system The amount of flow provided by the ECLS system is measured through ultrasonic flow probes on the high-pressure side of the circuit beyond where any shunts (i.e., high-pressure to low-pressure connection through a hemofilter) may occur An approximation of flow generated by the pump can be calculated from the product of the revolutions per minute (RPMs) and circuit tubing diameter For most cardiac ECLS patients, flow is initiated at 120 to 150 mL/kg per minute However, it is important to note that flow should be adjusted to fit the physiologic needs of each patient Patients with septic shock may require higher flows, approaching 200 mL/kg per minute, to support their metabolic needs assuming that venous drainage is sufficient to yield such flows A precise measurement of the patient’s intrinsic CO (i.e., the amount of blood flow that is not passed through the ECLS circuit) is unobtainable However, indirect evaluation of the patient’s CO is possible through an assessment of arterial systolic blood pressure, pulse pressure, HR, organ perfusion, SvO2, and lactic acid levels on a given flow rate Comparisons of these variables over time allow the clinician to make decisions regarding the adequacy of circulatory support or the readiness to wean from support An echocardiogram can also provide valuable information about cardiac filling and function and guide therapy, particularly when weaning from ECLS or during a trial off ECLS Svo2 is measured in the venous return portion of the circuit, with a goal of 65% to 80% However, if a left-to-right shunt exists, such as a left atrial vent, the Svo2 will be falsely elevated, particularly if the patient is receiving high Fio2 and PEEP Serial lactate measurements are often helpful to aid in the assessment of global end-organ perfusion Elevated lactate levels may occur in patients with ongoing hepatic dysfunction, sepsis, low CO, and end-organ hypoperfusion A rough approximation of the relative contributions of the patient and circuit pulmonary parameters is possible by analyzing serial patient and circuit blood gas assays (pH, partial pressure of arterial carbon dioxide, Pao2, Sao2) while taking into consideration the mechanical ventilation settings (including Fio2 and PEEP), circuit flow rate, gas sweep rate, and circuit O2 concentration Finally, shunts within the patient or the circuit must be taken into consideration Examples of right-to-left patient shunts include those with a patent ductus arteriosus, atrial septal defect, or ventricular septal defect in the setting of severe PAH Circuit left-toright shunts are generally limited to a left atrial vent, open bridge, the arteriovenous hemodialysis filter, and in vivo continuous arterial blood gas devices Total blood flow for the patient on MCS requires the addition of ECLS circuit flow with the patient’s native CO minus any shunt within the system as a whole CHAPTER 28 Cardiac Failure and Ventricular Assist Devices Troubleshooting Hemodynamic compromise often continues despite MCS Lowdose inotropes or inodilators can aid cardiac contractility to augment native CO and reduce afterload to both the right and left ventricles The most commonly used agents are dopamine (3–5 mg/kg per minute), epinephrine (0.03–0.05 µg/kg/min), dobutamine (5 µg/kg per minute), or milrinone (0.25–0.75 mg/kg per minute) Recall that while these are the typical modest range of doses in children, the presence of ECLS reduces the plasma level of these agents owing to the marked increase in the volume of distribution and circulating blood volume while on ECLS The use of catecholamines in high doses is detrimental to cardiac recovery and should be avoided by increasing circuit flow to provide adequate CO Likewise, the complete removal of any inotropic support is typically not suggested while on ECLS either, particularly when cardiac stun (lack of opening of the aortic valve during systole, which leaves the arterial line flat from only ECLS flow) is present Tachydysrhythmias and pulseless electrical activity requiring cardiopulmonary resuscitation occurs in 3% of neonatal and pediatric ECLS runs Pharmacologic/electrical cardioversion of any dysrhythmia should be attempted emergently even while on ECLS to prevent further deterioration in cardiac perfusion and function Cardiac pacing can also be used to optimize CO Hypovolemia Hypovolemia is a common occurrence during MCS for a variety of reasons Inadequate venous drainage secondary to cannula malposition, cardiac tamponade, tension pneumothorax, or hemothorax may occur and generally results in hypotension requiring immediate correction Ongoing evaporative losses from the oxygenator and bleeding secondary to coagulopathy can contribute to hypovolemia Initiation of ECLS activates a host of inflammatory mediators, resulting in capillary leak and hypovolemia.152 Finally, attempts at mobilizing the large amount of “third-spaced” fluid with either diuretics, hemofiltration, or through drains in pleural/peritoneal cavities can quickly cause either inadequate CO from the patient or inadequate venous drainage to the ECLS circuit Hypertension Hypertension secondary to neurohormonal dysregulation or pain/ agitation is one of the most common and unavoidable cardiovascular complications of ECLS Although hypertension has not been demonstrated to negatively impact patient survival, its presence can worsen bleeding or further impair cardiac function and thus should be promptly addressed.153 Cardiac Stun Cardiac stun, a term that describes reversible global dyskinesia of the ventricle, was coined by Braunwauld and Kloner in 1982.154 Reversible cardiac dysfunction that results in the lack of antegrade LV ejection during systole resembles electromechanical dissociation, which has been observed frequently in patients following the initiation of VA ECLS Excluding conditions of physiologic tamponade from thoracic issues, blood, or air, an infant on ECLS should have sufficient cardiac function to generate a minimal pulse pressure of 10 mm Hg Evaluations of patients who experience cardiac stun upon initiation of ECLS defined this condition as the absence of aortic valve opening during systole, equalizing of the patient preductal and postmembrane circuit Pao2, and absence of pulse pressure in the aorta The etiology of cardiac stun is multifactorial and hypothesized to be the sequelae of acute ischemia followed by reperfusion or severe 257 electrolyte disturbances The incidence of stun on ECLS is 5% to 12% in neonates and, when present and prolonged (.24 hours), results in a significant increase in mortality for these patients Stun typically occurs during the initiation of bypass in patients who were hypoxic, hypercarbic, acidotic, and suffered a cardiac arrest prior to ECLS Important factors in trying to minimize cardiac stun upon the initiation of ECLS include correcting the pH and ionized calcium levels in the circuit and infusing calcium chloride to the patient upon commencing ECLS, followed by close monitoring of arterial blood gases and electrolytes with rapid correction of abnormalities.145 Echocardiography and Cardiac Catheterization Initial diagnostic and hemodynamic assessment should be attempted by transthoracic echocardiography, but imaging windows may be severely limited resulting in insufficient information TEE may improve diagnostic accuracy but may not be possible secondary to bleeding risks or patient size Even if adequate imaging is obtained, the specific hemodynamic state of the patient on ECLS must be taken into account when interpreting these studies Invariably, the loading conditions of the heart are markedly altered during ECLS The echocardiographer should actively interface with the ECLS team (to potentially modify flows, add volume, modify mechanical ventilator support, etc.) in order to obtain the most comprehensive assessment of cardiac function to inform clinical decisions regarding the continuation or removal of further ECLS Cardiac catheterization can be a useful tool for select patients who fail to wean from ECLS The specific loading conditions of the heart must be considered in the context of the acquired data in order to make sound clinical decisions Therapeutic interventions that might be performed in the catheterization lab include balloon or blade atrial septostomy to alleviate left atrial hypertension, balloon valvuloplasty or angioplasty of vascular obstructions, device closure of residual atrial or ventricular shunts, and/or coil embolization of aortopulmonary shunts.116 Correction of these types of residual defects in the catheterization laboratory or surgical correction in the operating room may be required to allow for separation from MCS.114 For patients with significant LV failure, it may be necessary to decompress the left heart to prevent or reverse pulmonary edema or hemorrhage, decrease mitral regurgitation and, importantly, improve coronary perfusion to increase the chances of myocardial recovery In this scenario, venting of the LV occurs through surgical placement of a cannula in the left atrial appendage connected to the venous drainage to the ECLS circuit This is accomplished in the operating room/ICU during or after transthoracic ECLS cannulation or in the catheterization laboratory through creation of an interatrial connection via balloon or blade septostomy This procedure can markedly improve LV function and increase the chances of survival.155,156 Single Ventricle Lower survival rates are universally found in this subset of patients, which may be attributed to an imbalance of the systemic and pulmonary circulations, volume burden to the single ventricle after complex palliative surgery, compromised single-ventricle function (particularly with RV morphology), and/or impaired coronary perfusion to the systemic ventricle when a systemic-topulmonary artery (PA) connection (i.e., modified Blalock-Taussig [BT] shunt) results in diastolic runoff from the aorta Despite these challenges, larger centers continue to report improved outcomes with the accumulation of experience and application of 258 S E C T I O N I V Pediatric Critical Care: Cardiovascular innovative strategies For example, initial efforts to balance the systemic and pulmonary circulations on ECLS included either completely or partially occluding the aortopulmonary shunt, which has now been demonstrated to increase mortality The use of smaller-size BT shunts or the use of the Sano modification (RV to PA nonvalved conduit for stage one hypoplastic left heart palliation) has contributed to decreasing the recirculation that would otherwise occur Of note, higher ECLS with flows approaching 200 mL/kg per minute may be required to provide adequate systemic and pulmonary support when the shunt is left open.157,158 Anticoagulation Strategies ECLS requires meticulous management of hemostasis to limit patient morbidities Hemorrhagic and thrombotic complications are a major concern for patients during ECLS, particularly after cardiac surgery Bleeding can manifest at surgical sites (arterial/ venous cannulation sites, surgical repair sites [atriotomy, ventriculotomy, aortotomy sites], sternal incision, indwelling catheter sites, etc.) or may be masked in areas such as the thorax, intracranial vault, or the gastrointestinal tract A meta-analysis of observational studies, including 1763 patients on VA ECMO, reported a 33% incidence of bleeding that was mostly correlated to the heparin monitoring strategy.159 Prevention strategies that target reduction of hematologic complications focus on maintenance of the hemostatic regulatory mechanisms as close to normal as possible.160–163 Patients placed on ECLS following cardiac surgery represent a unique population at risk for hemorrhagic management since they often have multiple surgical sites, dilutional coagulopathy, and abnormal coagulation patterns Apart from single-center experience, no well-defined consensus or protocol is available for pediatric and neonatal ECLS The patient’s age, diagnosis, clinical status in conjunction with the specific details of the ECLS device, and, finally, the flow through the circuit will dictate which anticoagulation strategy should be employed The most commonly used agent for anticoagulation on ECLS is continuously infused unfractionated heparin (UH) Most centers measure platelet counts, hematocrit, prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, specific factor levels (i.e., anti-factor Xa, antithrombin III [ATIII]), quantitative heparin levels, and activated clotting time (ACT) The ACT is the most commonly measured test for coagulation, as it can be performed quickly at the bedside, though other coagulation tests are available at the point of care (i.e., PTT).164,165 Despite this advantage, ACT results vary markedly based on the technique used and are a nonspecific measure of coagulation because they measure the total time for a clot to form after ex vivo activation The ACT is a global composite of the different individual components of coagulation; thus, more specific tests (listed earlier) must be used in concert to ascertain which specific component in the coagulation cascade is affected No single test is currently used to guide the anticoagulation regimen; rather, a panel of tests must be obtained and analyzed in concert Increasingly, many centers have reported on the effective use of thromboelastography (TEG) in determining patient coagulation status.166 When “adequately anticoagulated on a continuous unfractionated heparin infusion,” the target ACT should be between 180 and 220 seconds when the ECLS pump is flowing at full flow (i.e., 150 mL/kg per minute) This goal can be decreased to 160 seconds on full flow if significant bleeding is present, particularly in the immediate postoperative period UH is metabolized via two mechanisms: at low doses, via a saturable mechanism representing clearance by the reticuloendothelial system and endothelial cells to which heparin binds with high affinity, and at high doses, via a nonsaturable mechanism represented by renal excretion Thus, close monitoring during ECLS must be followed when a patient’s urinary output is oscillating between oliguria and polyuria Newer treatment strategies include the use of additional agents such as ATIII in either bolus or infusion form to correct abnormalities in the clotting cascade ATIII is an a2-glycoprotein serine protease inhibitor that inactivates a number of enzymes from the coagulation system, including the activated forms of factors II, VII, IX, X, XI, and XII Replacement of ATIII is controversial, with some centers replacing it only when the level is low (,30%) and heparin infusion rates are increasing without a concomitant increase in ACT or PTT,167,168 while other centers maintain levels near 100% Bivalirudin is a direct thrombin inhibitor that works independent of antithrombin on both circulating and clot-bound thrombin It is currently approved for use during percutaneous coronary intervention and heparin-induced thrombocytopenia It has a quick onset of action and a short half-life Bivalirudin infusions have been reported in a small number of pediatric patients on ECLS.169–171 At our institution, we have successfully used bivalirudin in patients with suspected heparin-induced thrombocytopenia, heparin resistance, risk of major bleeding, and/or evidence of thrombosis while on heparin Ranucci et al demonstrated that the use of bivalirudin in ECMO was associated with less total blood loss and fewer transfusion needs in postcardiotomy patients requiring ECMO.172 There is wide variability on the dosing strategies, but at our institution we start the infusion at 0.15 to 0.20 mg/kg per hour without the administration of a bolus and titrate to goal PTT 60 to 80 seconds Anticoagulation with Coumadin, clopidogrel, low-molecular-weight heparin, and aspirin individually or in combination can be considered with certain MCS devices other than ECLS.173 Heparin-induced thrombocytopenia (HIT) is a relatively rare but serious complication of heparin administration caused by antibodies binding to a complex of heparin and platelet factor that leads to large-vessel thrombosis and increased mortality A drop in platelet count by more than 50% of the highest previous value should raise suspicion of HIT and trigger investigation Treatment includes discontinuing heparin administration and initiating direct thrombin inhibitor therapy (i.e., argatroban) if continued anticoagulation is needed.160,174 The lysine analogs tranexamic acid and ε-aminocaproic acid are antifibrinolytic agents that have been shown to reduce bleeding in ECLS patients undergoing surgical procedures However, prophylactic administration failed to reduce the incidence of intracranial hemorrhage in neonates.162,175 Profound abnormalities in many components of the coagulation cascade commonly occur in postoperative cardiac patients on ECLS With this in mind, an attempt to normalize components of coagulation not impacted by heparin is important Platelets are consumed at surgical bleeding sites, sequestered by the membrane oxygenator; thus, transfusions are required to maintain counts greater than 100,000/mm3 in bleeding patients or patients at high risk However, lower transfusion thresholds can be set to avoid excessive exposure to blood products in the nonbleeding patient Administration of fresh-frozen plasma to broadly increase multiple coagulation factors activity is also common When hypofibrinogenemia occurs, cryoprecipitate infusion can be used owing to the high concentrations of fibrinogen in the low volume of the cryoprecipitate unit The availability of plasma protein concentrate allows administration of highly concentrated factors in a CHAPTER 28 Cardiac Failure and Ventricular Assist Devices substantially reduced volume, decreasing the volume burden associated with conventional therapy Although rare, the application of heparin-free ECLS has been reported.176,177 Ventilation Strategies Ventilator management during ECLS remains controversial Although data exist to guide clinicians regarding prevention of barotrauma, volutrauma, and O2 toxicity for mechanically ventilated patients with acute respiratory distress syndrome in general, there is a lack of controlled clinical trials and consensus for pediatric patients on ECLS.178–180 Lung collapse strategies used for respiratory support on ECLS are not used by most cardiac centers Goals continue to target the prevention of atelectasis with utilization of appropriate PEEP in order to maximize oxygenation of nonbypassed blood returning to the left atrium, which then is ejected by the LV to perfuse the coronary arteries In addition, providing modest levels of ventilator support can be achieved with either a pressure- or volume-limited mode of ventilation targeting a delivered tidal volume of ,6 mL/kg Respiratory rates between 10 and 25 are set depending on the age and rest strategy being employed and the degree that the patient’s lungs are required for gas exchange Optimizing Pao2 to the patient and circuit by blending Fio2 to keep the Fio2 below 0.6 reduces free radical formation and O2 toxicity, providing adequate oxygenation to decrease pulmonary hypertension and optimize myocardial Do2 Chest radiographs are routinely performed to assess and guide strategies to optimize lung volume so that volutrauma and barotrauma are avoided Fluid, Nutrition, and Renal Fluid overload and electrolyte disturbances such as high or low serum levels of potassium, calcium, magnesium, and phosphorus are common and need correction Most cardiac patients on ECLS receive total parenteral nutrition owing to the increased risk of gastrointestinal complications in patients with cardiac defects, umbilical artery catheters, poor perfusion, or other bowel abnormalities A select subset may tolerate trophic enteral feedings; whenever possible, even a small amount of enteral feeds should be provided Diuretics—commonly, furosemide—are often employed to provide optimal fluid balance in patients with significant capillary leak and fluid retention Optimization of fluid status is essential to weaning and eventual separation from ECLS For anuric or oliguric patients, early placement of an in-line hemofilter into the ECLS circuit with or without countercurrent dialysate or a complete continuous renal replacement therapy device is recommended Still, the management decisions that balance the use and timing of diuretics versus hemofiltration are center specific The indications for initiation of dialysis are the same as for other critically ill patients with renal failure Multiple retrospective reviews of patients supported by ECLS have found that fluid overload and AKI are risk factors for increased mortality.181–183 Analgesia and Sedation Adequate analgesia and sedation are essential for both safety and comfort and to decrease metabolic demands in patients with circulatory compromise in the early postoperative recovery period While an opiate and a benzodiazepine class drug have been used historically, a multimodal approach is increasingly preferred, which could include other agents such as dexmedetomidine, ketamine, or propofol Current oxygenators can bind many drugs, including opioids, depending on the lipophilic and proteinbinding qualities of the specific drug Thus dosing amounts are 259 usually significantly higher while on ECLS.178,184 In this study, ECMO circuits were set up using Quadrox-iD pediatric oxygenators primed with whole blood to represent a 5-kg patient Hydromorphone and fentanyl were injected (also, mycophenolate and tacrolimus) and serial blood samples were taken over 12 hours In this ex vivo model, hydromorphone hydrochloride was not as significantly sequestered compared with fentanyl (mycophenolic acid and tacrolimus serum concentrations were stable) Benzodiazepine infusions may be used with cautious monitoring, as toxicity from propylene glycol (lorazepam), other solvents (midazolam), or long-acting toxic metabolites (diazepam) have been reported in critically ill neonates, infants, and children.185 Recent studies are finding an increase in delirium when benzodiazepines are used in critically ill pediatric patients; thus, some centers are beginning to limit their administration Neuromuscular blockade should largely be avoided to limit the development of critical care neuromyopathy, allow for regular evaluation of the central nervous system, and limit soft-tissue fluid accumulation Central nervous system infarcts, hemorrhage, or seizures are all known complications of ECLS For infants with an open fontanel, a daily head ultrasound should be performed early in the course of treatment and with any change in clinical neurologic status For older patients, a significant change in their neurologic status has a high likelihood of heralding major intracranial pathology, which needs to be promptly diagnosed by computed tomography in order to guide treatment and determine patient viability Several centers have reported a new approach in which older patients are supported without the need of continuous analgesia and sedation and without the need of mechanical ventilation This awake ECLS modality has been used as bridge to recovery, bridge to VAD, or bridge to transplantation.186,187 Infection It is not surprising that patients on ECLS are at a high risk of developing nosocomial bloodstream infections (BSIs) Identified risk factors include the duration of ECLS,188 open versus closed chest cannulation, the presence of central venous lines, and undergoing a major procedure prior to or while on ECLS It appears that older patients on ECLS for respiratory failure may be at higher risk of healthcare-associated infection than neonates or cardiac patients BSIs during ECLS for both pediatric cardiac patients post-CPB and neonates with cardiac or respiratory failure have been associated with a poor outcome The diagnosis of sepsis is difficult in patients supported with ECLS Although variable degrees of leukopenia have been documented for neonates supported with ECLS, an increase in phagocytosis and intracellular killing by neutrophils also occurs Temperature is controlled by the circuit’s heat exchanger; thus, infection is generally not manifested by fever in these patients Hypotension or thrombocytopenia may occur for a variety of reasons In view of this observation, the standard of care in many ECLS centers has been to perform routine surveillance cultures and provide prophylactic antibiotics However, management strategies to limit infectious risks continue to evolve Owing to lack of a proven benefit and concerns regarding the long-term impact of broad-spectrum antibiotics on local bacterial resistance profiles, an increasing number of centers now perform daily blood cultures without the routine use of prophylactic antibiotics Additional retrospective data may suggest that routine surveillance cultures may not be warranted.189 Further investigation is needed to determine the impact of prophylactic antibiotic use on the incidence of BSI, local antimicrobial flora, length of stay, survival, and cost.190 260 S E C T I O N I V Pediatric Critical Care: Cardiovascular Intrahospital Transport Crucial situations exist for patients supported with ECLS that require intrahospital transport This can include mobilization from the intensive care unit to a variety of locations, such as the catheterization laboratory, radiology suite, or the operating theater Reluctance to perform diagnostic or therapeutic interventions is often driven by fear of potentially disastrous complications during transport, yet these fears are largely unfounded Guidelines designed to promote the establishment of an organized, efficient transport process supported by appropriate equipment and personnel have been recognized and are increasingly used in hospitals Intrahospital transport for patients on ECLS is a labor-intensive process that should be approached in a coordinated effort with specific focus on the preparatory phase, the transfer phase, and the posttransport phase Simulation practice with the various teams is now standard practice, resulting in safe intrahospital transport for patients on ECLS.191–193 Ventricular Assist Devices The two main types of VADs are pulsatile pumps and continuousflow pumps Although the initial types of VADs were pulsatile, continuous-flow pumps have been gaining popularity worldwide both for adult and pediatric patients (eTable 28.3) because of their decreased incidence of thromboembolic complications, smaller size, and ability to discharge patients home Most VADs share similar basic principles, and based on the pump-patient interface, devices can be classified as intracorporeal or paracorporeal Cannulation depends on the type of support required The right atrium (systemic venous drainage) and PA (arterial return) are cannulated for a right ventricular assist device (RVAD), and the LV (pulmonary venous drainage) and aorta (arterial return) are cannulated for a left ventricular assist device (LVAD) A combination of both right and left ventricular assist devices is termed a biventricular assist device (BiVAD) For children with complex CHD, including single-ventricle physiology, placement of the inflow and outflow cannulas can be varied and complex The pump is connected to a controller and power supply and other monitoring sensors A comparison of ECLS and VADs is listed in eTable 28.4 Pulsatile Ventricular Assist Devices Pulsatile VADs function on the principle of positive displacement by trapping a fixed amount of blood and then forcing (displacing) that trapped volume into an exit cannula Since the early report of pneumatically driven, pulsatile, paracorporeal VADs in children, the pediatric experience with pulsatile devices has continued to grow.194,195 Advantages of these devices include the ability to support infants and toddlers, provide long-term support (weeks to months), provide biventricular support without an oxygenator, increase patient mobility, and provide pulsatile flow to the body that more closely mimics the normal output of the heart The external position of the pump allows device exchange in case of malfunction or thrombus formation Disadvantages include a propensity for thromboembolic complications and the need for exteriorization of the cannulae Infection is a serious complication, though immobilization of the cannulas close to the exit site can decrease its incidence These devices have a special silicone system that connects the blood pump to the body.196,197 Most times, LVAD insertion may be sufficient for bridging patients to heart transplantation, even in the presence of significant preoperative RV dysfunction Adequate unloading of the LV reduces the LV end-diastolic pressure and, in turn, reduces RV afterload, which may improve RV systolic function If there is a significant burden of tachyarrhythmia, severe RV dysfunction at baseline, or failure of the RV to recover despite LVAD placement, BiVAD support should be considered Some of the early devices include the Thoratec Ventricular Assist System (Thoratec Corp.), which is a pneumatically driven, polyurethane sac enclosed in a plastic housing designed for intermediate and long-term use (weeks to years) The Thoratec VAD has a stroke volume of 65 mL and can be operated at rates up to 100 beats per minute, providing blood flow rates of almost L/ minute There are two Thoratec VAD systems, one paracorporeal (PVAD) and one implantable (IVAD) The Thoratec Paracorporeal Pneumatic VAD (PVAD) is indicated as a bridge to transplantation or bridge to recovery system It can provide acute or intermediate uni- or biventricular support Furthermore, it can be used in smaller patients who are poor candidates for implantable devices, with the smallest reported patient weighing 17 kg (body surface area [BSA] 0.73 m2) The Thoratec IVAD is a smaller, intracorporeal device with the same features as the Thoratec PVAD except that it is used when longer support is anticipated The device has been FDA approved since 2004 for circulatory assistance as a bridge to transplant or bridge to recovery.198,199 The long-term pulsatile device that has had the best outcomes in comparison with ECMO is the Berlin Heart EXCOR It is currently the most commonly used and accepted VAD and is the only labeled VAD available for long-term support of neonates and infants This device, first approved for use in Europe in the late 1990s, is a paracorporeal pulsatile pneumatic pump with polyurethane valves and a transparent chamber through which the adequacy of filling and emptying can be assessed and evaluated for thrombus formation This pump can be used to support left, right, or both ventricles The blood-contacting surfaces of the pump are heparin coated, reducing anticoagulation requirements Because it is available in a wide range of sizes, the Berlin Heart EXCOR VAD provides circulatory support options for pediatric patients ranging from 2.5 kg to adolescents The Berlin Heart EXCOR was specially designed and developed for pediatric patients The pump sizes vary between 10 mL and 60 mL The 10-mL and 15-mL pumps are suitable for neonates, infants, and young toddlers The 25-mL and 30-mL pumps can be used in children usually younger than 10 years (BSA m2) Adult-size pumps (50 mL, 60 mL) can be implanted in older children Sizes are adopted based on the ability to provide cardiac index of greater than 2.5L/min per m2 with the VAD rate preferably below 120 beats/min for non–singleventricle physiology support All Berlin Heart EXCOR cannulae exit the body through the upper abdominal wall (Fig 28.6) Survival with the Berlin EXCOR in the pediatric population has been reported across multiple centers internationally, with survival to discharge at 60% to 80% in children from weeks up to age 16 years Survival is significantly better in patients with myocarditis and dilated cardiomyopathy than for patients with CHD Neurologic complications vary between 25% and 30%.136,200–202 The Berlin Heart EXCOR pediatric VAD multicenter trial was published in 2012, which led to its approval by the FDA Although data from the trial suggest that 90% of children can be bridged to transplantation with the EXCOR, with a stroke risk of 29%, the primary cohort captured only one-fourth of all US children implanted with the EXCOR during the 3-year study period and did not include patients in whom the device was implanted as compassionate use In a later publication, Almond et al examined EXCOR outcomes in all 204 children implanted during the study period.200 Overall survival in this unselected ... myocardial recovery In this scenario, venting of the LV occurs through surgical placement of a cannula in the left atrial appendage connected to the venous drainage to the ECLS circuit This is accomplished... blade septostomy This procedure can markedly improve LV function and increase the chances of survival.155,156 Single Ventricle Lower survival rates are universally found in this subset of patients,... resulting in capillary leak and hypovolemia.152 Finally, attempts at mobilizing the large amount of “third-spaced” fluid with either diuretics, hemofiltration, or through drains in pleural/peritoneal