Congenital Cardiac Anesthesia Society
A Section of the the Society for Pediatric Anesthesia

{“questions”:{“jb8lj”:{“id”:”jb8lj”,”mediaType”:”image”,”answerType”:”text”,”imageCredit”:””,”image”:””,”imageId”:””,”video”:””,”imagePlaceholder”:””,”imagePlaceholderId”:””,”title”:”Author: Nicholas Houska, DO – University of Colorado, Children\u2019s Hospital Colorado \r\n\r\nA 2023 consensus statement endorsed by sixteen professional societies, including the Congenital Cardiac Anesthesia Society, recommends a two-tier classification of pediatric heart surgery programs. To optimize high-complexity pediatric heart surgery, what is the minimum number of congenital heart surgeons recommended for Comprehensive Care Centers? \r\n”,”desc”:”EXPLANATION \r\nThe Congenital Heart Surgeon\u2019s Society has recently developed consensus recommendations for centers performing pediatric cardiac surgery in the United States, which were endorsed by fifteen other societies representing healthcare professionals caring for children and adults with congenital heart disease. The current system of healthcare delivery for pediatric heart surgery in the United States consists of a multitude of centers with wide variability in location, volume, and case complexity. Pediatric cardiac surgical outcomes differ widely after low and high complexity procedures and when compared across different care centers. This is likely related to wide variability in staffing models, program structure, resources, and perioperative care practices and processes between centers. Numerous studies have shown an association between surgical volume and outcomes, with low volume centers having higher mortality. Furthermore, studies have shown that both high performing and low performing centers have the potential for improvement in outcomes. National efforts have been made to reduce variability and improve outcomes, including public reporting, quality improvement networks, disseminating best practices, and developing consensus-based standards and guidelines for care. \r\n\r\n\r\n\r\nThe consensus statement settled on two tiers of recommendations. The first tier is termed \u201cEssential\u201d and consists of recommendations for fundamental components to promote high-quality care for any pediatric heart surgery program. The second tier is termed \u201cComprehensive\u201d and consists of recommendations to optimize high-complexity pediatric heart surgery. Per the consensus statement, at least three surgeons are recommended in a Comprehensive Care Center to optimize high complexity pediatric cardiac surgery. The consensus statement also highlights that these are recommendations, and that individual center variability may be deemed necessary as appropriate. \r\n\r\n\r\n\r\n \r\nREFERENCES \r\n\r\nBacker CL, Overman DM, Dearani JA, et al. Recommendations for centers performing pediatric heart surgery in the United States. J Thorac Cardiovasc Surg <\/em>. 2023. https:\/\/doi.org\/10.1016\/j.jtcvs.2023.09.001 Published online September 2023 \r\n”,”hint”:””,”answers”:{“bowuy”:{“id”:”bowuy”,”image”:””,”imageId”:””,”title”:”A.\tTwo surgeons”},”eafl0″:{“id”:”eafl0″,”image”:””,”imageId”:””,”title”:”B.\tThree surgeons”,”isCorrect”:”1″},”j576o”:{“id”:”j576o”,”image”:””,”imageId”:””,”title”:”C.\tFive surgeons”}}}}}

{“questions”:{“y3nb7”:{“id”:”y3nb7″,”mediaType”:”image”,”answerType”:”text”,”imageCredit”:””,”image”:””,”imageId”:””,”video”:””,”imagePlaceholder”:””,”imagePlaceholderId”:””,”title”:”Author: Melissa Colizza, MD – Centre Hospitalier Universitaire Sainte-Justine – Montreal, Quebec \r\n\r\nA seven-day-old neonate with double outlet right ventricle with Taussig-Bing Anomaly is scheduled for an arterial switch operation. Which of the following preoperative anatomic features is MOST likely associated with an increase in early mortality after the arterial switch operation for Taussig-Bing Anomaly?\r\n”,”desc”:”EXPLANATION \r\nDouble-outlet right ventricle (DORV) is a conotruncal defect in which both great arteries arise from the morphologic right ventricle, semilunar valves are not in fibrous continuity with either atrioventricular valve, and a ventricular septal defect (VSD) is commonly present (the only egress for blood to exit the left ventricle). The Society of Thoracic Surgeons (STS) Congenital Heart Surgery Nomenclature and Database Project Committee, the European Association of Cardiothoracic Surgery, and the European Association of Cardiologists have classified DORV into the following subtypes: \r\n(1) VSD type (DORV with subaortic or doubly committed VSD without right ventricular outflow obstruction (RVOTO); \r\n(2) Tetralogy of Fallot type (DORV with subaortic or doubly committed VSD with RVOTO); \r\n(3) Transposition of the Great Arteries (TGA) type (DORV with subpulmonary VSD with or without RVOTO\/Taussig-Bing Anomaly); \r\n(4) Remote VSD type (DORV with uncommitted VSD with or without RVOTO); \r\n(5) DORV and Atrioventricular septal defect. \r\n\r\nTypes 1 and 2 comprise approximately 65% of DORV while group 3 is present in approximately 25% of DORV. Group 4 and 5 make up the remainder of DORV. Associated defects seen with DORV include atrioventricular septal defects, aortic arch obstruction, ventricular hypoplasia, heterotaxy, mitral valve abnormalities, subaortic stenosis, pulmonary stenosis, and coronary artery anomalies. The position of a ventricular septal defect in relation to the great arteries and other associated anomalies determines the physiologic consequences of DORV, potential surgical repair, and dictates the appropriate anesthetic management. \r\n\r\nIn 1949, Taussig and Bing described a type of DORV with side-by-side position of the great arteries in which both great vessels arose from the right ventricle with supporting bilateral coni and a ventricular septal defect underlying both coni. The original definition has evolved over the years to include other variants of DORV with a subpulmonary VSD. In TGA type DORV\/ Taussig-Bing Anomaly (TBA), the aorta may be located slightly anterior and rightward (d-transposition) or side-by-side with the pulmonary artery. Thus, the great vessels are parallel to each other and do not spiral around each other, as with normal anatomy. As a consequence of great vessel position and septal malalignment, there is preferential blood flow from the left ventricle through the VSD to the pulmonary artery and thus TGA physiology. TBA is also frequently associated with aortic arch obstruction, often resulting in discrete aortic coarctation, aortic arch hypoplasia or interrupted aortic arch. \r\n\r\nPrimary arterial switch operation (ASO) has become the first-line treatment for TBA without RVOTO. However, mortality is estimated to be 5-6%, which remains higher than the ASO for d-TGA. A study by Vergnat and colleagues reported a mortality rate of 5.8% in 69 patients with TBA. Most children who died in the immediate post-operative period or within the first postoperative year had an abnormal coronary pattern, specifically a looping or extended\/prolonged course. Prolonged cardiopulmonary bypass (CPB) time was also a risk factor for mortality. These findings are like those reported in a 2023, single-institution study of 225 TBA patients by Gu et al. Overall 30-day mortality was 12.9%. Thirteen children died due to complications related to the coronary arteries (all within 48 hours after surgery). While intramural coronary anatomy did not reach statistical significance, it did tend to be a risk factor for mortality (adjusted OR 4.81, 95% CI 0.927-24.9, p = 0.062). In a sub-group analysis, a left circumflex artery originating from sinus two (Leiden convention) and looping behind the native pulmonary artery also tended to have a higher mortality. In normal coronary anatomy, the right coronary originates from sinus two and the left coronary artery originates from sinus one, eventually dividing into the left circumflex and left anterior descending coronary arteries. Prolonged CPB time was also noted to be a risk factor for mortality. \r\n\r\nReintervention remains common after the ASO in patients with DORV and TBA, with a reported incidence between 25 to 55% at 15 years. Most reinterventions are related to either RVOTO (neopulmonary) or left ventricular outflow tract obstruction (LVOTO). Right-sided reinterventions are mostly related to the subneopulmonary conus or pulmonary artery stenosis. On the left side, subneoaortic stenosis from muscular tissue, residual aortic arch obstruction and neo-aortic valve regurgitation are reported as the main reasons for reintervention. Several risk factors have been identified in the literature and seem to vary across studies for reintervention. These include aortic arch obstruction, preoperative subaortic RVOTO, side-by-side arteries and aortic to pulmonary artery (PA) size mismatch. Aortic arch obstruction may result in a higher pulmonary artery-to-aorta diameter ratio and a dilated neo-aortic root with a higher risk of neo-aortic insufficiency. However, neither side-by-side arteries, nor obstruction along the LVOT have been reported as risk factors for mortality in TBA patients. \r\n\r\n\r\n\r\n \r\nREFERENCES \r\nMavroudis, C., Backer, C.L. and Anderson, R.H. . Double-Outlet Right Ventricle. In Mavroudis C, Backer CL. Eds. Pediatric Cardiac Surgery<\/em>. 5th Edition. John Wiley & Sons Ltd. 2023. Pp. 499-537 \r\nSpaeth JP. Perioperative Management of DORV. Semin Cardiothorac Vasc Anesth<\/em>. 2014;18(3):281-289. doi: 10.1177\/1089253214528048 \r\nVergnat M, Baruteau AE, Houyel L, et al. Late outcomes after arterial switch operation for Taussig-Bing anomaly. J Thorac Cardiovasc Surg<\/em>. 2015;149(4):1124-1132. doi: 10.1016\/j.jtcvs.2014.10.082 \r\n\r\nFricke TA, Konstantinov IE. Arterial Switch Operation: Operative Approach and Outcomes. Ann Thorac Surg<\/em>. 2019;107(1):302-310. doi: Fricke TA, Konstantinov IE. Arterial Switch Operation: Operative Approach and Outcomes. Ann Thorac Surg<\/em>. 2019;107(1):302-310. doi: 10.1016\/j.athoracsur.2018.06.002\r\n\r\n\r\nGu M, Hu J, Dong W, et al. Mid-Term Outcomes of Primary Arterial Switch Operation for Taussig-Bing Anomaly. Semin Thorac Cardiovasc Surg<\/em>. 2023;35(3):562-571. doi: 10.1053\/j.semtcvs.2022.06.001\r\n\r\n\r\nAlsoufi A, Cai S, Williams WG, Coles JG et al. Improved results with single-stage total correction of Taussig-Bing Anomaly. Eur J Cardiothorac Surg<\/em>. 2008;33(3) 244-250. doi: 10.1016\/j.ejcts.2007.11.017\r\n\r\n”,”hint”:””,”answers”:{“x1pj2”:{“id”:”x1pj2″,”image”:””,”imageId”:””,”title”:”A.\tSubaortic right ventricular outflow tract obstruction”},”egl9v”:{“id”:”egl9v”,”image”:””,”imageId”:””,”title”:”B.\tSide-by-side great arteries”},”5q8ok”:{“id”:”5q8ok”,”image”:””,”imageId”:””,”title”:”C.\tCoronary artery anomalies”,”isCorrect”:”1″}}}}}

{“questions”:{“sol9q”:{“id”:”sol9q”,”mediaType”:”image”,”answerType”:”text”,”imageCredit”:””,”image”:””,”imageId”:””,”video”:””,”imagePlaceholder”:””,”imagePlaceholderId”:””,”title”:”Author: Melissa Colizza, MD – Centre Hospitalier Universitaire Sainte-Justine – Montreal, Quebec \r\n\r\nA seven-year-old, 23 kg male has a left ventricular-assist device (LVAD) due to dilated cardiomyopathy. Which of the following devices is associated with the HIGHEST risk of thromboembolic complications?\r\n”,”desc”:”EXPLANATION \r\nHeart failure affects 0.7-7.4 children per 10,000 globally. The mortality rate is 7-15% in patients with severe heart failure in the United States. Although heart transplantation is a definitive treatment, the number of patients on the heart transplant waiting list exceeds the number of donor hearts available. Thus, mechanical support with extracorporeal membrane oxygenation (ECMO) or ventricular assist devices (VADs) has been utilized as a bridge-to-recovery, bridge-to-transplant, or destination therapy. VAD placement prior to the onset of end-organ dysfunction reduces waitlist mortality, but there are still significant complications associated with VADs. Appropriate VAD selection in the pediatric population remains challenging. Patient size (body surface area) and anticipated duration of support are the primary considerations when choosing a particular device. The ideal device would account for the physiologic differences in pediatric versus adult patients with minimal risk of hemolysis or thromboembolism.\r\n\r\n\r\nThe Berlin Heart EXCOR (BHE), a paracorporal pulsatile flow device, has been used in the pediatric population since the 1990s and is the only FDA-approved VAD for children with a body surface area (BSA) less than 0.6 m^{2<\/sup>. The volume capacity of the BHE pneumatic pump and set heart rate determine cardiac output. The BHE has been used successfully as a bridge to recovery and bridge to transplantation in children. However, BHE implantation is associated with a higher rate of thrombosis and adverse neurological events compared to the continuous-flow devices. A 2018 literature review (including 27 studies) analyzing antithrombotic therapies and thromboembolic complications in 558 children with different types of VADs (87% BHE and 1.8% Heartware HVAD) by Huang et al reported an overall incidence of thromboembolic events in 26% of patients. The overall incidence of thromboembolic complications ranged from 22 to 56% in patients with the BHE the studies included. \r\n\r\n\r\nConversely, there is a lower rate of thromboembolic events with continuous-flow devices. Rates of thromboembolic events in patient cohorts with the Heartmate II (HM2) in the early 2010s were reported at less than 15%. The newer generation, Heartmate III (HM3), is another continuous-flow device with magnetically levitated bearings and intrinsic pulsatility, allowing ejection through the aortic valve thereby decreasing the shear stress and compressive forces on blood which is known to lead to thrombosis. It has been the only FDA-approved long-term continuous-flow device for children since the recall of the Heartware (HVAD) in 2021. A 2020 study by O’Connor and colleagues investigated outcomes in 35 pediatric and adult congenital cardiac patients who had undergone HM3 implantation. They reported no episodes of pump thrombosis, pump dysfunction requiring exchange, or stroke. While the recommended patient body surface area for HM3 implantation is greater than 1.4 m2<\/sup>, successful implantation has been reported in a patient with a BSA of 0.78 m2<\/sup>. A 2022 meta-analysis by George and colleagues (using twelve papers) investigated the complications associated with different types of VADs placed in infants and children. The study demonstrated that the BHE was associated with the highest risk of thromboembolic complications compared with the HVAD and HM3 (continuous flow devices). The authors postulate that this increased risk may be related to the more complex design of pulsatile VADs, such as one-way valves, which create areas of stagnant flow. In contrast, with continuous-flow devices, thrombosis may be caused by increased shear stress and heat generated by the pump. Although the HeartWare HVAD was commonly used in older children, it was withdrawn from the markets in 2021 due to an increased risk of neurological complications and technical failure related to the battery. \r\n\r\n\r\nThe HM3 seems to be the most promising mechanical support device with respect to safety and freedom from thromboembolic events. However, the BHE remains the only FDA approved device that is available on the market for neonates, whom are intrinsically at a higher risk for both thromboembolic and hemorrhagic complications. Notably, it is important to remember that anticoagulation protocols vary between individual patients, devices, and institutions. \r\n\r\n \r\nREFERENCES \r\n\r\nHorton SB, Skinner A, Landa AB, Stayer SA, Motta P. Mechanical Circulatory Support. In Andropoulos DB, Mossad EB, Gottlieb EA, eds. Anesthesia for Congenital Heart Disease <\/em>.Fourth edition. John Wiley & Sons, Inc.; 2023. pp. 996-1025.\r\n\r\n\r\n\r\nHuang JY, Monagle P, Massicotte MP, VanderPluym CJ. Antithrombotic therapies in children on durable ventricular assist devices: A literature review. Thromb Res <\/em>.2018; 172:194-203. DOI: 10.1016\/j.thromres.2018.02.145\r\n\r\n\r\nGeorge AN, Hsia TY, Schievano S, Bozkurt S. Complications in children with ventricular assist devices: systematic review and meta-analyses. Heart Fail Rev <\/em>.2022;27(3):903-913. doi: 10.1007\/s10741-021-10093-x\r\n\r\n\r\nSchweiger M, Hussein H, de By TMMH, et al. Use of Intracorporeal Durable LVAD Support in Children Using HVAD or HeartMate 3-A EUROMACS Analysis. J Cardiovasc Dev Dis <\/em>.2023;10(8):351. Published 2023 Aug 17. doi: 10.3390\/jcdd10080351\r\n\r\n\r\nO’Connor MJ, Lorts A, Davies RR, et al. Early experience with the HeartMate 3 continuous-flow ventricular assist device in pediatric patients and patients with congenital heart disease: A multicenter registry analysis. J Heart Lung Transplant <\/em>.2020;39(6):573-579. 10.1016\/j.healun.2020.02.007\r\n\r\n”,”hint”:””,”answers”:{“511xz”:{“id”:”511xz”,”image”:””,”imageId”:””,”title”:”A.\tBerlin Heart EXCOR”,”isCorrect”:”1″},”g5foa”:{“id”:”g5foa”,”image”:””,”imageId”:””,”title”:”B.\tHeartMate III”},”udpwk”:{“id”:”udpwk”,”image”:””,”imageId”:””,”title”:”C.\tHeartware HVAD”}}}}}}

{“questions”:{“pk7hz”:{“id”:”pk7hz”,”mediaType”:”image”,”answerType”:”text”,”imageCredit”:””,”image”:””,”imageId”:””,”video”:””,”imagePlaceholder”:””,”imagePlaceholderId”:””,”title”:”Author: Melissa Colizza – CHU Sainte-Justine – Montreal, Quebec \r\n\r\nWhich of the following types of circulatory support requires the LOWEST level of systemic anticoagulation during combined heart-liver transplantation?\r\n”,”desc”:”EXPLANATION \r\nCombined heart-liver transplantation (CHLT) was first performed in 1984 and has become more frequent in the last decade. Indications have evolved to include metabolic diseases resulting in cardiomyopathy and end-stage liver disease leading to secondary heart failure. The most common indication for CHLT in the last decade was congenital heart disease with secondary liver disease. This was largely due to the growing number of patients palliated with a Fontan surviving to adulthood with concomitant Fontan-associated liver disease (FALD).\r\n\r\nCHLT is most commonly performed in sequential manner with cardiac transplantation on CPB first, followed by weaning from bypass and subsequent liver transplantation. Heparin may or may not be fully reversed prior to liver transplantation. Sequential cardiac then liver transplantation leads to hemodynamic derangements and additional stress on the cardiac allograft, particularly during inferior vena cava clamping and hepatic reperfusion. Several circulatory support strategies have been utilized to minimize central venous hypertension and optimize systemic cardiac output, including venovenous bypass and venoarterial extracorporeal membrane oxygenation (ECMO). \r\n\r\nVenovenous bypass (VVB) is the process during which blood is diverted from the infrahepatic IVC and portal vein and returned to the right heart via the axillary, subclavian, or internal jugular veins. The VVB circuit consists of heparin-bonded access catheters, a nonheparinized circuit, a centrifugal pump, and a blood warmer. There are options for an oxygenator and renal support. Anticoagulation management varies greatly across centers; VVB without anticoagulation has been described in the 1980s in circuits without an oxygenator, although more recent reports describe ACT targets like those used in VA ECMO. VA ECMO offers the benefits of full circulatory support of the heart and lungs, at the cost of greater levels of anticoagulation. The exact strategy for CHLT will depend on patient anatomy, cardiac allograft function, hemodynamic response to IVC test clamping and institutional preference.\r\n\r\nThere are case reports of simultaneous cardiac and liver transplantation while on full cardiopulmonary bypass (CPB). The benefits of performing both on CPB include the following, 1) a single period of reperfusion, 2) greater level of hemodynamic stability, particularly during liver reperfusion, 3) shorter cold ischemic time for the liver allograft, and 4) hemodynamic support of the newly transplanted heart with decreased venous congestion of the liver. However, en bloc liver and heart transplantation exposes patients to longer CPB duration and higher heparin doses.\r\n\r\nAnesthetic management of CHLT is challenging and has been comprehensively reviewed by Smeltz and colleagues. Patient preparation should include large bore venous access for fluid administration and blood product transfusion, arterial line placement in location(s) with consideration of the bypass cannulation plan, and central venous access above the IVC clamping site. If VVB is planned, central venous access should include the femoral vein in addition to a return cannula to the superior vena cava. Patients undergoing CHLT often have elevated pulmonary vascular resistance (PVR) secondary to cardiac disease or portopulmonary hypertension, which is a risk factor for right ventricular dysfunction. Thus, vasoactive agents with minimal effects on pulmonary vascular resistance, such as vasopressin and norepinephrine, and pulmonary vasodilators are advantageous. Significant vasoplegia and bleeding are expected along with administration of large quantities of blood products. Frequent laboratory assessment of hemostasis with point of care testing is necessary, especially in patients palliated with a Fontan and heavy collateral burden. Ideally, there must be a balance between adequate tissue perfusion and avoidance of volume overload, pulmonary edema, and right ventricular dysfunction. Thus, there should be major consideration of factor concentrate use to manage coagulopathy. \r\n\r\nVenovenous bypass requires the least amount of anticoagulation, especially with heparin-bonded circuits. VA ECMO generally requires higher levels of anticoagulation, but not as high as the anticoagulation required for full CPB.\r\n\r\n\r\n \r\nREFERENCES \r\nReardon LC, Lin JP, VanArsdell GS, et al. Orthotopic Heart and Combined Heart Liver Transplantation: the Ultimate Treatment Option for Failing Fontan Physiology. Curr Transplant Rep<\/em>. 2021;8(1):9-20. doi: 10.1007\/s40472-021-00315-4 \r\nTracy KM, Matsuoka LK, Alexopoulos SP. Update on combined heart and liver transplantation: evolving patient selection, improving outcomes, and outstanding questions. Curr Opin Organ Transplant<\/em>. 2023;28(2):104-109. doi: 10.1097\/MOT.0000000000001041 \r\nHofer RE, Christensen JM, Findlay JY. Anesthetic considerations for combined heart–liver transplantation in patients with Fontan-associated liver disease. Curr Opin Organ Transplant<\/em>. 2020;25(5):501-505. doi: 10.1097\/MOT.0000000000000800 \r\nGriffith BP, Shaw BW Jr, Hardesty RL, Iwatsuki S, Bahnson HT, Starzl TE. Veno-venous bypass without systemic anticoagulation for transplantation of the human liver. Surg Gynecol Obstet<\/em>. 1985;160(3):270-272. \r\nBarbara DW, Rehfeldt KH, Heimbach JK, Rosen CB, Daly RC, Findlay JY. The perioperative management of patients undergoing combined heart-liver transplantation. Transplantation<\/em>. 2015;99(1):139-144. doi: 10.1097\/TP.0000000000000231 \r\nSmeltz AM, Kumar PA, Arora H. Anesthesia for combined heart and liver transplantation. J Cardiothorac Vasc Anesth<\/em>. 2021; 35:3350-3361. doi.org\/10.1053\/j.jvca.2020.12.005\r\n”,”hint”:””,”answers”:{“3rcjj”:{“id”:”3rcjj”,”image”:””,”imageId”:””,”title”:”A.\tVenovenous bypass “,”isCorrect”:”1″},”3b6ps”:{“id”:”3b6ps”,”image”:””,”imageId”:””,”title”:”B.\tVenoarterial extracorporeal membrane oxygenation”},”papds”:{“id”:”papds”,”image”:””,”imageId”:””,”title”:”C.\tCardiopulmonary bypass”}}}}}

{“questions”:{“4zthb”:{“id”:”4zthb”,”mediaType”:”image”,”answerType”:”text”,”imageCredit”:””,”image”:””,”imageId”:””,”video”:””,”imagePlaceholder”:””,”imagePlaceholderId”:””,”title”:”Author: Melissa Colizza – CHU Sainte-Justine – Montreal, Quebec \r\n\r\nA one-year-old male has a cardiac arrest secondary to near drowning in a bathtub. After resuscitation and return of spontaneous circulation at the scene, the patient is intubated several hours after arrival to the intensive care unit due to rapidly evolving pulmonary edema and acute respiratory distress syndrome. Despite maximal mechanical ventilatory support, the patient is placed on veno-arterial extracorporeal membrane oxygenation (VA ECMO) via the right neck due to worsening arterial blood gases and hemodynamics. Twenty-four hours after VA ECMO initiation, the systemic oxygen saturation has decreased to 88% from 95% in all four limbs over several hours. Which of the following clinical factors is the MOST likely explanation for the decrease in systemic oxygen saturation?”,”desc”:”EXPLANATION \r\nExtra-corporal membrane oxygenation (ECMO) has been used since the 1970s for children with cardiopulmonary failure, in particular, post cardiotomy cardiac failure and respiratory failure due to congenital diaphragmatic hernia. Over the years, perfusion techniques and anticoagulation strategies have improved, which has led to an increased number of indications for ECMO and a recommendation for earlier ECMO initiation. Veno-arterial ECMO (VA-ECMO) is typically used for acute cardiac failure with or without respiratory failure, whereas veno-venous ECMO (VV-ECMO) is used for hypoxic or hypercarbic respiratory failure with preserved cardiac function despite maximal mechanical ventilatory support.\r\n\r\nThere are several VA ECMO cannulation strategies in use. In adults, adolescents, and larger children, femoral artery and femoral vein cannulation is most often used in the non-surgical setting due to the ease of vessel accessibility. In children less than 30 to 40 kilograms, neck cannulation via the internal jugular vein and the carotid artery is generally preferred, as the femoral vessels are smaller and do not accommodate cannulas large enough to generate adequate flows to provide full circulatory support. \r\n\r\nDuring VA-ECMO support, the patient\u2019s cardiopulmonary and systemic circulation are in a parallel configuration with the ECMO circuit. The blood supplied to the patient from the ECMO circuit via the arterial cannula originates from the oxygenator and is full saturated with oxygen unless set otherwise. Depending on the proportion of total systemic venous return draining to the ECMO venous reservoir, the remaining venous blood will pass through the lungs, return to the left atrium and then be ejected from the left ventricle into the aorta to mix with blood flow from the ECMO arterial cannula. In the presence of significant pulmonary pathology, there is likely significant pulmonary venous desaturation resulting in a systemic oxygen saturation (SpO2) less than 100%. With VA ECMO via carotid arterial cannulation, such as the one described in the stem, mixing occurs at the level of the carotid artery and ascending aorta. Therefore, the SpO2 will be lower than 100% in all four limbs. Management of this problem includes the following: (1) adjusting the mechanical ventilator settings to improve pulmonary gas exchange if possible; (2) increasing the ECMO flow rate such that a greater percentage of the total blood volume passes through the oxygenator and, (3) increasing the inspired concentration of oxygen in the ECMO sweep gas. \r\n\r\nNorth-South syndrome, or Harlequin phenomenon, is a condition in which the lower body systemic saturation is higher than the upper body. This differential hypoxemia occurs specifically in patients on VA ECMO with femoral cannulation and is caused by mixing of 100% oxygenated and relatively deoxygenated blood in the aorta. With femoral cannulation, 100% oxygenated blood from the femoral arterial cannula flows to the upper body via the thoracic aorta, aortic arch and ascending aorta in a retrograde fashion and mixes with the blood ejected from the left ventricle. In the setting of poor left ventricular (LV) function and low cardiac output, there is negligible mixing of retrograde blood from arterial cannula with antegrade blood via native cardiac output. However, in the setting of improving myocardial function\/cardiac output and poor pulmonary function, an increasing amount of blood is ejected from the left ventricle, which is relatively desaturated in comparison to blood from the femoral arterial cannula. Thus, 100% oxygenated blood from the ECMO arterial cannula will combine with blood ejected from the LV at a mixing zone in the aorta, called \u201cNorth-South\u201d line. Blood from \u201cSouth\u201d region will have a higher oxygen saturation than blood from the \u201cNorth\u201d region. The anatomic location of the North-South line will depend on ECMO flow rate, native ventricular function\/cardiac output, and systemic vascular resistance. Management of North-South syndrome usually involves adding an additional cannula to the ECMO circuit that delivers blood with 100% oxygen saturation to the superior vena cava\/right atrium. North-South syndrome is unlikely in the patient described in stem because there are carotid arterial and jugular venous cannulas present rather than femoral arterial and femoral venous cannulas. \r\n\r\nRecirculation is a clinical scenario that occurs during VV ECMO when a large proportion of the oxygenated blood from the outflow cannula is recycled through the inflow cannula and returns to the ECMO circuit without circulating through the patient. Most of the blood passing through the lungs and left ventricle will not have passed through the oxygenator and will be desaturated. However, the pre- and post-oxygenator blood will be bright red with a high oxygen saturation. The degree of recirculation depends on cannula type and position, ECMO pump flow, and cardiac output. Dual-lumen cannulas or long cannulas lying near each other increase the risk of recirculation. Right ventricular dysfunction\/low cardiac output also puts the patient at risk, as there is less forward blood flow. Additionally high pump flows may cause the inflow cannula to draw blood in from the outflow cannula and lead to recirculation. This is not possible in the patient described in the stem as the patient is on VA ECMO. \r\n\r\n\r\n\r\n\r\n \r\nREFERENCES \r\nGajkowski EF, Herrera G, Hatton L, Velia Antonini M, Vercaemst L, Cooley E. ELSO Guidelines for Adult and Pediatric Extracorporeal Membrane Oxygenation Circuits. ASAIO J<\/em>. 2022;68(2):133-152. doi:10.1097\/MAT.0000000000001630\r\n\r\nFalk L, Sallisalmi M, Lindholm JA, et al. Differential hypoxemia during venoarterial extracorporeal membrane oxygenation. Perfusion<\/em>. 2019;34(1_suppl):22-29. doi:10.1177\/0267659119830513\r\n\r\nXie A, Yan TD, Forrest P. Recirculation in venovenous extracorporeal membrane oxygenation. J Crit Care<\/em>. 2016; 36:107-110. \r\n\r\nMeyer RJ, Theodorou AA, Berg, RA. Childhood drowning. Pediatr Rev<\/em>. 2006; 27(5): 163-168. \r\n\r\nKim K II, Lee WY, Kim HS, Jeong JH, Ko HH. Extracorporeal membrane oxygenation in near-drowning patients with cardiac or pulmonary failure. Scan J Trauma Resusc Emerg Med<\/em>. 2014; 12: 77. \r\n\r\n”,”hint”:””,”answers”:{“tqatx”:{“id”:”tqatx”,”image”:””,”imageId”:””,”title”:”A)\tNorth-South Syndrome”},”rx1pe”:{“id”:”rx1pe”,”image”:””,”imageId”:””,”title”:”B)\tRecirculation”},”ylf0a”:{“id”:”ylf0a”,”image”:””,”imageId”:””,”title”:”C)\tImproved myocardial function”,”isCorrect”:”1″}}}}}