Changes in von Willebrand Factor Multimers, Concentration, and Function During Pediatric Extracorporeal Membrane Oxygenation.

OBJECTIVES: To investigate changes in von Willebrand factor (VWF) concentration, function, and multimers during pediatric extracorporeal membrane oxygenation (ECMO) and determine whether routine monitoring of VWF during ECMO would be useful in predicting bleeding. DESIGN: Prospective observational study of pediatric ECMO patients from April 2017 to May 2019. SETTING: The PICU in a large, tertiary referral pediatric ECMO center. PATIENTS: Twenty-five neonates and children (< 18 yr) supported by venoarterial ECMO. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Arterial blood samples were collected within 24 hours pre-ECMO, daily for the first 5 days of ECMO, every second day until decannulation, and 24 hours post-ECMO. The STA R Max analyzer was used to measure VWF antigen (VWF:Ag) and ristocetin cofactor (VWF:RCo) activity. VWF collagen binding (VWF:CB) was measured using an enzyme-linked immunosorbent assay. VWF multimers were measured using the semi-automated Hydragel 11 VWF Multimer assay. Corresponding clinical data for each patient was also recorded. A total of 25 venoarterial ECMO patients were recruited (median age, 73 d; interquartile range [IQR], 3 d to 1 yr). The median ECMO duration was 4 days (IQR, 3-8 d) and 15 patients had at least one major bleed during ECMO. The percentage of high molecular weight multimers (HMWM) decreased and intermediate molecular weight multimers increased while patients were on ECMO, irrespective of a bleeding status. VWF:Ag increased and the VWF:RCo/VWF:Ag and VWF:CB/VWF:Ag ratios decreased while patients were on ECMO compared with the baseline pre-ECMO samples and healthy children. CONCLUSIONS: Neonates and children on ECMO exhibited a loss of HMWM and lower VWF:CB/VWF:Ag and VWF:RCo/VWF:Ag ratios compared with healthy children, irrespective of major bleeding occurring. Therefore, monitoring VWF during ECMO would not be useful in predicting bleeding in these patients and changes to other hemostatic factors should be investigated to further understand bleeding during ECMO.

Platelet Phenotype and Function Changes With Increasing Duration of Extracorporeal Membrane Oxygenation.

OBJECTIVES: To investigate platelet pathophysiology associated with pediatric extracorporeal membrane oxygenation (ECMO). DESIGN: Prospective observational study of neonatal and pediatric ECMO patients from September 1, 2016, to December 31, 2019. SETTING: The PICU in a large tertiary referral pediatric ECMO center. PATIENTS: Eighty-seven neonates and children (< 18 yr) supported by ECMO. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Arterial blood samples were collected on days 1, 2, and 5 of ECMO and were analyzed by whole blood flow cytometry. Corresponding clinical data for each patient was also recorded. A total of 87 patients were recruited (median age, 65 d; interquartile range [IQR], 7 d to 4 yr). The median duration of ECMO was 5 days (IQR, 3-8 d) with a median length of stay in PICU and hospital of 18 days (IQR, 10-29 d) and 35 days (IQR, 19-75 d), respectively. Forty-two patients (48%) had at least one major bleed according to a priori determined definitions, and 12 patients (14%) had at least one thrombotic event during ECMO. Platelet fibrinogen receptor expression decreased (median fluorescence intensity [MFI], 29,256 vs 26,544; p = 0.0005), while von Willebrand Factor expression increased (MFI: 7,620 vs 8,829; p = 0.0459) from day 2 to day 5 of ECMO. Platelet response to agonist, Thrombin Receptor Activator Peptide 6, also decreased from day 2 to day 5 of ECMO, as measured by binding with anti-P-selectin, PAC-1 (binds activated GPIIb/IIIa), and anti-CD63 monoclonal antibodies (P-selectin area under the curve [AUC]: 63.46 vs 42.82, respectively, p = 0.0022; PAC-1 AUC: 93.75 vs 74.46, p = 0.0191; CD63 AUC: 55.69 vs 41.76, p = 0.0020). CONCLUSIONS: The loss of platelet response over time may contribute to bleeding during ECMO. These novel insights may be useful in understanding mechanisms of bleeding in pediatric ECMO and monitoring platelet markers clinically could allow for prediction or early detection of bleeding and thrombosis.

Effect of Nitric Oxide via Cardiopulmonary Bypass on Ventilator-Free Days in Young Children Undergoing Congenital Heart Disease Surgery: The NITRIC Randomized Clinical Trial.

Importance: In children undergoing heart surgery, nitric oxide administered into the gas flow of the cardiopulmonary bypass oxygenator may reduce postoperative low cardiac output syndrome, leading to improved recovery and shorter duration of respiratory support. It remains uncertain whether nitric oxide administered into the cardiopulmonary bypass oxygenator improves ventilator-free days (days alive and free from mechanical ventilation). Objective: To determine the effect of nitric oxide applied into the cardiopulmonary bypass oxygenator vs standard care on ventilator-free days in children undergoing surgery for congenital heart disease. Design, Setting, and Participants: Double-blind, multicenter, randomized clinical trial in 6 pediatric cardiac surgical centers in Australia, New Zealand, and the Netherlands. A total of 1371 children younger than 2 years undergoing congenital heart surgery were randomized between July 2017 and April 2021, with 28-day follow-up of the last participant completed on May 24, 2021. Interventions: Patients were assigned to receive nitric oxide at 20 ppm delivered into the cardiopulmonary bypass oxygenator (n = 679) or standard care cardiopulmonary bypass without nitric oxide (n = 685). Main Outcomes and Measures: The primary end point was the number of ventilator-free days from commencement of bypass until day 28. There were 4 secondary end points including a composite of low cardiac output syndrome, extracorporeal life support, or death; length of stay in the intensive care unit; length of stay in the hospital; and postoperative troponin levels. Results: Among 1371 patients who were randomized (mean [SD] age, 21.2 [23.5] weeks; 587 girls [42.8%]), 1364 (99.5%) completed the trial. The number of ventilator-free days did not differ significantly between the nitric oxide and standard care groups, with a median of 26.6 days (IQR, 24.4 to 27.4) vs 26.4 days (IQR, 24.0 to 27.2), respectively, for an absolute difference of -0.01 days (95% CI, -0.25 to 0.22; P = .92). A total of 22.5% of the nitric oxide group and 20.9% of the standard care group developed low cardiac output syndrome within 48 hours, needed extracorporeal support within 48 hours, or died by day 28, for an adjusted odds ratio of 1.12 (95% CI, 0.85 to 1.47). Other secondary outcomes were not significantly different between the groups. Conclusions and Relevance: In children younger than 2 years undergoing cardiopulmonary bypass surgery for congenital heart disease, the use of nitric oxide via cardiopulmonary bypass did not significantly affect the number of ventilator-free days. These findings do not support the use of nitric oxide delivered into the cardiopulmonary bypass oxygenator during heart surgery. Trial Registration: anzctr.org.au Identifier: ACTRN12617000821392.

Anticoagulation strategies and difficulties in neonatal and paediatric extracorporeal membrane oxygenation (ECMO).

OBJECTIVE: The aim of this review is to highlight an emerging problem with anticoagulation-related complications in neonatal and paediatric ECMO, to explore for flaws in the currently recommended anticoagulation management responsible for these problems and to discuss possible strategies mitigating further escalation of the issue. DATA SOURCES: Pertinent neonatal and paediatric literature on the topic of interest and international Extracorporeal Life Support Organisation (ELSO) registry data request. CONCLUSIONS: The international ELSO registry data reveals increasing rates of anticoagulation-related complications during neonatal and paediatric ECMO worldwide. The causes are multifactorial and the proposed solution to the problem is to match anticoagulation management to the pathophysiological complexity of haemostasis on ECMO.

Extracorporeal membrane oxygenation circuitry.

The extracorporeal membrane oxygenation circuit is made of a number of components that have been customized to provide adequate tissue oxygen delivery in patients with severe cardiac and/or respiratory failure for a prolonged period of time (days to weeks). A standard extracorporeal membrane oxygenation circuit consists of a mechanical blood pump, gas-exchange device, and a heat exchanger all connected together with circuit tubing. Extracorporeal membrane oxygenation circuits can vary from simple to complex and may include a variety of blood flow and pressure monitors, continuous oxyhemoglobin saturation monitors, circuit access sites, and a bridge connecting the venous access and arterial infusion limbs of the circuit. Significant technical advancements have been made in the equipment available for short- and long-term extracorporeal membrane oxygenation applications. Contemporary extracorporeal membrane oxygenation circuits have greater biocompatibility and allow for more prolonged cardiopulmonary support time while minimizing the procedure-related complications of bleeding, thrombosis, and other physiologic derangements, which were so common with the early application of extracorporeal membrane oxygenation. Modern era extracorporeal membrane oxygenation circuitry and components are simpler, safer, more compact, and can be used across a wide variety of patient sizes from neonates to adults.

Safety and feasibility of adjunct autologous cord blood stem cell therapy during the Norwood heart operation.

BACKGROUND: We conducted this phase I, open-label safety and feasibility trial of autologous cord blood (CB) stem cell (CBSC) therapy via a novel blood cardioplegia-based intracoronary infusion technique during the Norwood procedure in neonates with an antenatal diagnosis of hypoplastic left heart syndrome (HLHS). CBSC therapy may support early cardiac remodeling with enhancement of right ventricle (RV) function during the critical interstage period. METHODS: Clinical grade CB mononucleated cells (CBMNCs) were processed to NetCord-FACT International Standards. To maximize yield, CBSCs were not isolated from CBMNCs. CBMNCs were stored at 4 °C (no cryopreservation) for use within 3 days and delivered after each cardioplegia dose (4 × 15 mL). RESULTS: Of 16 patients with antenatal diagnosis, 13 were recruited; of these 13 patients, 3 were not treated due to placental abruption (n = 1) or conditions delaying the Norwood for >4 days (n = 2) and 10 received 644.9 ± 134 × 106 CBMNCs, representing 1.5 ± 1.1 × 106 (CD34+) CBSCs. Interstage mortality was 30% (n = 3; on days 7, 25, and 62). None of the 36 serious adverse events (53% linked to 3 deaths) were related to CBMNC therapy. Cardiac magnetic resonance imaging before stage 2 (n = 5) found an RV mass index comparable to that in an exact-matched historical cohort (n = 22), with a mean RV ejection fraction of 66.2 ± 4.5% and mean indexed stroke volume of 47.4 ± 6.2 mL/m2 versus 53.5 ± 11.6% and 37.2 ± 10.3 mL/m2, respectively. All 7 survivors completed stage 2 and are alive with normal RV function (6 with ≤mild and 1 with moderate tricuspid regurgitation). CONCLUSIONS: This trial demonstrated that autologous CBMNCs delivered in large numbers without prior cryopreservation via a novel intracoronary infusion technique at cardioplegic arrest during Norwood palliation on days 2 to 3 of life is feasible and safe.

Factors XI and XII in extracorporeal membrane oxygenation: longitudinal profile in children.

Background: Extracorporeal membrane oxygenation (ECMO) is used in children with cardiopulmonary failure. While the majority of ECMO centers use unfractionated heparin, other anticoagulants, including factor XI and factor XII inhibitors are emerging, which may prove suitable for ECMO patients. However, before these anticoagulants can be applied in these patients, baseline data of FXI and FXII changes need to be acquired. Objectives: This study aimed to describe the longitudinal profile of FXI and FXII antigenic levels and function before, during, and after ECMO in children. Methods: This is a prospective observational study in neonatal and pediatric patients with ECMO (<18 years). All patients with venoarterial ECMO and with sufficient plasma volume collected before ECMO, on day 1 and day 3, and 24 hours postdecannulation were included. Antigenic levels and functional activity of FXI and FXII were determined in these samples. Longitudinal profiles of these values were created using a linear mixed model. Results: Sixteen patients were included in this study. Mean FXI and FXII antigenic levels (U/mL) changed from 7.9 and 53.2 before ECMO to 6.0 and 34.5 on day 3 and they recovered to 8.8 and 39.4, respectively, after stopping ECMO. Function (%) of FXI and FXII decreased from 59.1 and 59.0 to 49.0 and 50.7 on day 3 and recovered to 66.0 and 54.4, respectively. Conclusion: This study provides the first insights into changes of the contact pathway in children undergoing ECMO. FXI and FXII antigen and function change during ECMO. Results from this study can be used as starting point for future contact pathway anticoagulant studies in pediatric patients with ECMO.

Statistical analysis plan for the NITric oxide during cardiopulmonary bypass to improve Recovery in Infants with Congenital heart defects (NITRIC) trial.

Background: The NITric oxide during cardiopulmonary bypass (CPB) to improve Recovery in Infants with Congenital heart defects (NITRIC) trial, a 1320-patient, multicentre, randomised controlled trial, is aiming to improve survival free of ventilation after CPB by using nitric oxide delivered into the oxygenator of the CPB. Objective: To provide a statistical analysis plan before completion of patient recruitment and data monitoring. Final analyses for this study will adhere to this statistical analysis plan, which details all key pre-planned analyses. Stata scripts for analyses have been prepared alongside this statistical analysis plan. Methods: The statistical analysis plan was designed collaboratively by the chief investigators and trial statistician and builds on the previously published study protocol. All authors remain blinded to treatment allocation. Detail is provided on statistical analyses including cohort description, analysis of primary and secondary outcomes and adverse events. Statistical methods to compare outcomes are planned in detail to ensure methods are verifiable and reproducible. Results: The statistical analysis plan developed provides the trial outline, list of mock tables, and analysis scripts. The plan describes statistical analyses on cohort and baseline description, primary and secondary outcome analyses, process of care measures, physiological descriptors, and safety and adverse event reporting. We define the pre-specified subgroup analyses and the respective statistical tests used to compare subgroups. Conclusion: The statistical analysis plan for the NITRIC trial establishes detailed pre-planned analyses alongside Stata scripts to analyse the largest trial in the field of neonatal and paediatric heart surgery. The plan ensures standards for trial analysis validity aiming to minimise bias of analyses. Trial registration: ACTRN12617000821392.

Reference values for kaolin-activated thromboelastography in healthy children.

BACKGROUND: The hemostatic system of children changes with age and differs significantly from the hemostatic system of adults. Age-specific reference values are therefore required for most hemostatic variables. Thromboelastography (TEG) is a point-of-care coagulation test that may provide superior evaluation and management of coagulopathies after cardiac surgery, when large-dose unfractionated heparin is administered for cardiopulmonary bypass. In this study, we established reference values for kaolin-activated TEG in healthy children, to facilitate accurate interpretation of pediatric TEG results. METHODS: Kaolin-activated TEG was performed on 100 healthy children undergoing elective day surgery and 25 healthy adult volunteers. The following TEG variables were recorded: reaction time, coagulation time, alpha angle, maximum amplitude, percentage lysis 30 min after maximum amplitude was reached, and the coagulation index. Differences between age-groups were evaluated using analysis of variance. RESULTS: Age-specific reference values for kaolin-activated TEG in healthy children between 1 mo and 16 yr of age are presented. No significant differences between children and adults were observed. CONCLUSIONS: TEG results, from a particular clinical setting, must be compared to age-specific, as well as analyzer- and activator-specific, reference values to allow for correct interpretation of the results. Reference values provided here will be of use in acute clinical situations where a practical monitor of hemostasis is required.

Postoperative support with the centrifugal pump ventricular assist device (VAD).

Centrifugal pump left ventricular assist device is a useful adjunct in pediatric cardiac surgery, as a bridge to recovery, or in some cases, to transplantation. This form of circulatory support may not have the universal applicability of extracorporeal membrane oxygenation, but it is equally or more effective in properly selected patients. The technology for centrifugal pump support is now quite standardized, and the advantages well documented. In this chapter we discuss the problems of indications, case selection, technical aspects of the circuit, and general clinical management. Results since 1989 are also presented.

Safety of Intracoronary Human Cord Blood Stem Cells in a Lamb Model of Infant Cardiopulmonary Bypass.

BACKGROUND: One potential approach for advancing univentricular heart surgical palliation outcomes is by stem cell therapy to augment right ventricular function and muscle mass. Whether the stem cell-inclusive cord blood mononuclear cells (CBMNCs) are safe to perfuse into the coronary vasculature during neonatal cardiopulmonary bypass (CPB) is unknown. We evaluated the acute safety, functional effects, and fate of human CBMNCs in a novel model of coronary vasculature delivery in a lamb model of infant CPB. METHODS: Neonatal lambs were randomized in blinded fashion to receive control (n = 5) or human CD45(+) CBMNCs (8 × 10(6) cells/kg body weight, n = 7) treatments during CPB. Aortic cross-clamp time was 40 minutes, with maintenance blood cardioplegia delivered every 10 minutes. Pressure-volume indices were used to measure left ventricular function before CPB and 60 minutes after CPB. CBMNCs were assessed by flow cytometry and immunohistochemistry. RESULTS: CBMNC-treated lambs were hemodynamically stable after CPB, with a decline in left ventricular pressure-volume indices similar to controls. The coronary vasculature was patent on microscopy, without evidence of cell aggregates or clots. Human CD45(+) cells were distributed in high abundance within all cardiac regions, predominantly the right atrium and ventricles, and trafficked beyond endothelial cell layers and between myocytes. CD45(+) cells localized at low incidence in the spleen, liver, lungs, and kidneys, but rarely remained in the circulation (<0.1% of infused cells). CONCLUSIONS: Coronary delivery of human CBMNCs during blood-cardioplegic arrest in a lamb model of CPB results in highly abundant myocardial distribution of cells without acute adverse effects on vascular patency and post-CPB cardiac function.

Amplitude-integrated electroencephalography and brain injury in infants undergoing Norwood-type operations.

BACKGROUND: Perioperative brain injury is common in infants undergoing cardiac surgery. Amplitude-integrated electroencephalography (aEEG) provides real-time neurologic monitoring and can identify seizures and abnormalities of background cerebral activity. We aimed to determine the incidence of perioperative electrical seizures, and to establish the background pattern of aEEG, in neonates undergoing Norwood-type palliations for complex congenital heart disease in relation to outcome at 2 years. METHODS: Thirty-nine full-term neonates undergoing Norwood-type operations underwent aEEG monitoring before and during surgery and for 72 hours postoperatively. The perfusion strategy included full-flow moderately hypothermic cardiopulmonary bypass with antegrade cerebral perfusion. Amplitude-integrated electroencephalography tracings were reviewed for seizure activity and background pattern. Survivors underwent neurodevelopmental outcome assessment using the Bayley Scales of Infant Development (3rd edition) at 2 years of age. RESULTS: Thirteen (33%) infants had electrical seizures, including 9 with intraoperative seizures and 7 with postoperative seizures. Seizures were associated with significantly increased mortality, but not with neurodevelopmental impairment in survivors. Delay in recovery of the aEEG background beyond 48 hours was also associated with increased mortality and worse motor development. CONCLUSIONS: Perioperative seizures were common in this cohort. Intraoperative seizures predominantly affected the left hemisphere during antegrade cerebral perfusion. Delayed recovery in aEEG background was associated with increased risk of early mortality and worse motor development. Ongoing monitoring is essential to determine the longer-term significance of these findings.

The influence of bypass temperature on the systemic inflammatory response and organ injury after pediatric open surgery: a randomized trial.

OBJECTIVE: Systemic cooling for cardiopulmonary bypass is widely used to attenuate the systemic inflammatory response syndrome and organ injury in children after open surgery. We compared the effects of moderate (24 °C) and mild (34 °C) hypothermia during bypass on markers of the systemic inflammatory response syndrome and organ injury, and on clinical outcome after corrective surgery for congenital heart disease. METHODS: Sixty-six children (mean age, 6.8 ± 5.7 months; mean weight, 6.2 ± 2.3 kg) were randomized to 24 °C or 34 °C bypass temperature during cardiac surgery. Perfusion strategies were otherwise strictly identical. Clinical data and blood samples were collected before bypass, 5 minutes after aortic crossclamp release, and 4, 24, and 48 hours after bypass. Patients were followed up until discharge from the hospital. RESULTS: In the 54 children with outcome data, bypass temperature did not influence the duration of mechanical ventilation between the 24 °C group and the 34 °C group (median [interquartile range] 22 [13-40] hours vs 14 [8-40] hours, P = .14), intensive care unit stay (43 [24-49] hours vs 29 [23-47] hours, P = .79), blood loss (29 [20-38] mL/kg vs 23 [13-38] mL/kg, P = .36), or incidence of postoperative infection (9% vs 11%, P = 1.0). There was no evidence of an influence of bypass temperature on the markers of acute inflammation, innate immune response, organ injury, coagulation, or hemodynamics. CONCLUSIONS: There is no evidence that the systemic inflammatory response syndrome and organ injury after pediatric open surgery are influenced by bypass temperature. The routine use of hypothermic bypass may not be warranted in the pediatric population.

Integrated Oxygenator FX05.

In recent years, there has been a trend to incorporate arterial filters into cardiopulmonary bypass (CPB) oxygenators. The FX oxygenators are the first examples of integrating a filter around the fibers of the oxygenator. To assess the efficacy of the FX05 oxygenator, in comparison with our existing CPB setup (RX05 oxygenator + arterial filter), we randomly assigned 40 patients undergoing CPB, with calculated flows <1.5 L/min, to FX05 or RX05 + arterial filter (19 FX and 21 RX). Embolic load was assessed using the emboli detection and classification quantifier, with sensors placed prefilter and postfilter/oxygenator at identical distances for both devices. A total of 6,270 FX readings and 6,183 RX readings were obtained. Because of the extremely skewed nature of the data, the prefilter embolic volumes were divided into deciles, and each decile was analyzed separately. Our results show that the devices perform similarly; both filter out a high percentage of the prefilter embolic load. Our data support that in the clinical setting, the FX05 is as effective at removing emboli as the RX05 with an arterial filter (CXAF02) which, in conjunction with the prime volume reduction and circuit simplification, has warranted our conversion to the FX series of oxygenators.

Improved outcomes of paediatric extracorporeal support associated with technology change.

This study aims to evaluate the impact of a change in extracorporeal membrane oxygenation (ECMO) technology on patient and circuit outcomes. A retrospective single-centre study of all ECMO runs from 1988 to 2006 was performed. Predictors of survival to hospital discharge (primary outcome measure) were evaluated in the entire cohort by univariate and multivariate analysis. A detailed subgroup univariate and multivariate analysis was performed in the cardiac and respiratory groups to identify predictors of survival to hospital discharge. A total of 275 patients underwent 294 extracorporeal support runs at a median (interquartile range) age of 40 (3-639) days and weight of 4.0 (3.1-10) kg. The primary indications for support were respiratory (41.8%), cardiac (45.6%) and sepsis (12.6%). Between the initial (Era 1) and most recent era (Era 3), cardiac support became the predominant ECMO indication (26 of 127 vs. 59 of 107; P<0.001). Survival to decannulation, intensive care and hospital discharge for the entire cohort and Era 3 patients were 50.0%, 48.9%, 44.4% and 71.7%, 55.6%, 52.6% (P<0.003), respectively. Treatment in Era 3 was associated with increased survival to intensive care discharge (P=0.02) for all ECMO patients. Cardiac survival was associated with treatment in Era 3 (P=0.04) and a lower complexity score (P<0.001). There was a significant reduction in mechanical circuit complications in the respiratory ECMO subgroup. A significant improvement in patient survival outcomes and reduction in mechanical circuit complications was noted in the current era. This improvement was associated with a change in ECMO technology.