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Extracorporeal membrane oxygenation (ECMO) provides support for the pulmonary or cardiovascular function of children in whom the predicted mortality risk remains very high. The inevitable host inflammatory response and activation of the coagulation cascade due to the extracorporeal circuit contribute to additional morbidity and mortality in these patients. Mixing nitric oxide (NO) into the sweep gas of ECMO circuits may reduce the inflammatory and coagulation cascade activation during ECMO support.
The purpose of this study is to test the feasibility and safety of mixing NO into the sweep gas of ECMO systems and assess its effect on inflammation and coagulation system activation through a pilot randomized controlled trial.
The Nitric Oxide on Extracorporeal Membrane Oxygenation in Neonates and Children (NECTAR) trial is an open-label, parallel-group, pilot randomized controlled trial to be conducted at a single center. Fifty patients who require ECMO support will be randomly assigned to receive either NO mixed into the sweep gas of the ECMO system at 20 ppm for the duration of ECMO or standard care (no NO) in a 1:1 ratio, with stratification by support type (veno-venous vs veno-arterial ECMO).
Outcome measures will focus on feasibility (recruitment rate and consent rate, and successful inflammatory marker measurements), the safety of the intervention (oxygenation and carbon dioxide control within defined parameters and methemoglobin levels), and proxy markers of efficacy (assessment of cytokines, chemokines, and coagulation factors to assess the impact of NO on host inflammation and coagulation cascade activation, clotting of ECMO components, including computer tomography scanning of oxygenators for clot assessments), bleeding complications, as well as total blood product use. Survival without ECMO and the length of stay in the pediatric intensive care unit (PICU) are clinically relevant efficacy outcomes. Long-term outcomes include neurodevelopmental assessments (Ages and Stages Questionnaire, Strength and Difficulties Questionnaire, and others) and quality of life (Pediatric Quality of Life Inventory and others) measured at 6 and 12 months post ECMO cannulation. Analyses will be conducted on an intention-to-treat basis.
The NECTAR study investigates the safety and feasibility of NO as a drug intervention during extracorporeal life support and explores its efficacy. The study will investigate whether morbidity and mortality in patients treated with ECMO can be improved with NO. The intervention targets adverse outcomes in patients who are supported by ECMO and who have high expected mortality and morbidity. The study will be one of the largest randomized controlled trials performed among pediatric patients supported by ECMO.
Australian New Zealand Clinical Trials Registry ACTRN12619001518156; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=376869
DERR1-10.2196/43760
Extracorporeal membrane oxygenation (ECMO) has gained widespread acceptance as a rescue treatment for refractory cardiovascular and respiratory failure among neonates, children, and adults [
These ECMO-related side effects expose patients to substantial morbidity and can lead to death or devastating long-term outcomes, even if the primary reason for requiring ECMO has been resolved. Importantly, some pediatric data show that more than 85% of patients who die during or after their ECMO run have developed either bleeding or clotting complications [
Nitric oxide (NO) mediates anti-inflammatory host responses and regulates both endothelial functions as well as microvascular inflammation. The mixing of NO into the sweep gas that runs into the oxygenator in neonates and children undergoing cardiopulmonary bypass has been investigated in several pilot studies with promising results, and a large randomized controlled trial (RCT) has recently been published [
The Nitric Oxide on Extracorporeal Membrane Oxygenation in Neonates and Children (NECTAR) study was designed to investigate in a randomized clinical trial whether mixing NO into the sweep gas in neonates and children treated with ECMO is feasible (recruitment, randomization, and protocol compliance) and safe (accurate NO delivery and methemoglobin levels). Efficacy will be tested by measuring ECMO-free days (the number of days that patients spend alive and free from ECMO is censored at 30 and 90 days) and by assessing the inflammatory host response and coagulation activation. We hereby describe the NECTAR trial protocol.
The NECTAR trial is an investigator-initiated, 50-patient, open-label, single-center, pilot RCT with neonates and children who require ECMO support.
A tertiary pediatric intensive care unit (PICU) in Australia with approximately 30 ECMO runs annually.
Eligible children will be identified during the clinical deterioration typically seen prior to ECMO support commencement, such as progressive respiratory, cardiovascular, and cardiorespiratory failure, including cardiopulmonary arrest. If the situation permits, prospective consent will be sought; otherwise, delayed consent or consent to continue the approach will be applied.
All infants and children (birth to ≤16 years) that are commenced on ECMO will be eligible for inclusion in the study if there is the ability to obtain prospective consent or consent to continue from parents or guardians. In addition, infants or children that are commenced on ECMO at the colocated Neonatal Intensive Care Unit will be eligible for inclusion in the study. Patients who are commenced on ECMO outside of these units will not be eligible for the study.
Neonates and children treated with ECMO who were retrieved to the PICU on ECMO, those with preexisting methemoglobinemia (methemoglobin [MetHb]>3%), and patients managed on a ventricular assist device only without an oxygenator were present in the ECMO circuit.
Treatment group allocation will be performed using a web-based REDCap electronic data capture tool hosted by The University of Queensland [
Prospective consent will be sought from the parents or guardians of any child for whom a decision to be commenced on ECMO has been made. Where possible, this consent will be obtained before the commencement of ECMO. However, due to parental stress and cognitive overload at the time of cannulation, consent can also be obtained following randomization under the consent to continue model (termed “delayed consent” previously) [
Blinding is not possible, as the NO delivery device makes a distinctive noise during standard operation. Further, the NO levels need to be adjusted depending on sweep flow, which requires nurses by the side to identify whether NO is being delivered or not.
Infants and children will be randomly assigned to receive either NO or standard care. Those allocated to the intervention (NO) will receive 20 ppm of NO mixed into the sweep gas running into the oxygenator during their ECMO run. The NO concentration will be maintained at 20 ppm using a NO delivery system (Sokinox, Maquet), or a similar device. Continuous sampling of NO and NO2 concentrations is performed by the Sokinox machine by gas aspiration after the NO injection site. Patients allocated to the standard study arm will receive the standard oxygen-air mix in the ECMO oxygenator as per institutional practice and protocol.
Apart from mixing NO into the sweep gas flow of the ECMO system, no other patient management parameters will be changed, and institutional practices and protocols will be followed. Methods and goals of anticoagulation will remain unchanged for any other ECMO management and treatments, such as decisions to decannulate, ventilation support, inotrope management, fluid intake, fluid removal practices, or antimicrobial or immunological treatments.
A data and safety monitoring board (DSMB) will monitor the conduct of the study and the accrual of data. The DSMB will consist of a chairperson (experienced in clinical trials), a pediatric intensivist, a cardiac surgeon, and a statistician. The DSMB will be independent of the study investigators and will monitor adverse events in the study as well as ensure the validity and timeliness of the data collection. The DSMB may advise the Chief Investigator to terminate the trial, which would necessitate safety concerns in this step. The DSMB is expected to meet at least 4 times during the study period.
The study team will be responsible for all documentation of the study nurse’s and the investigator’s training records and credentials. All consent forms will be reviewed by the study team. The perfusion data collection forms will be compared to the source documentation to ensure both the completeness and accuracy of the data. All severe adverse events will be recorded and reported to the local Human Research and Ethics Committee (HREC) as per the institutional guidelines.
This protocol and the informed consent document, and any subsequent modifications, have been reviewed and approved by the human research ethics committee (reference number HREC/18/QCHQ/49018). This study will be conducted in compliance with this version of the protocol. Any change to the protocol document or informed consent document that affects the scientific intent, study design, patient safety, or anything that may affect a participant’s willingness to continue in the study is considered an amendment, and therefore will be written and filed as an amendment to this protocol or the informed consent document. All protocol deviations will be reported to the principal investigator, recorded in REDCap, and reported to HREC. Protocol deviations and violations will be assessed for clarification by the principal investigator. The study was approved by the local HREC (HREC/18/QCHQ/49018) and has been registered with the Australian New Zealand Clinical Trials Registry (ACTRN12619001518156). The NECTAR trial commenced recruitment in August 2020
The NECTAR trial is a pilot RCT with the main focus on feasibility, safety, and exploration of efficacy. A sample size of 50 patients has been chosen in line with the recommendations for pilot studies that anticipate a medium effect size for a continuous primary outcome for the main trial [
Baseline variables (demographics, primary diagnosis, comorbidities including syndromes), precannulation disease severity, precannulation surgery (such as cardiac surgery), cannulation technique, primary and secondary end points, as well as predetermined physiological variables of interest, will be recorded and entered prospectively into a purpose-built REDCap database [
Participant data confidentiality will be ensured by the study coordinator, the research staff, and the institution sponsoring the trial. All data, as well as the study protocol and any other information that this trial may generate, will be held in strict confidence.
Blood samples for inflammatory and coagulation pathway activation will be collected prior to cannulation, as well as at 1, 12, and 24 hours post commencement of ECMO. These samples will be frozen using standard operating procedures and batch tested.
The NECTAR trial is a pilot RCT; hence, it will focus on safety and feasibility outcomes in addition to exploring efficacy outcomes as described in
Feasibility outcomes
Monthly recruitment rate
Randomized to screened patient ratio
Compliance with the study protocol (with particular focus on the timing of the initiation of nitric oxide (NO) and the maintenance of NO for the duration of the study)
Safety outcomes
Failure rate of gas delivery
Carbon dioxide control of patients
Methemoglobin levels
Efficacy outcomes
Host systemic inflammation levels at 1, 12, and 24 hours
Coagulation system activation and consumption
Clotting and bleeding complications
Rate of clotting and bleeding events
Survival without extracorporeal membrane oxygenation (ECMO), censored at 30 and 90 days post randomization. Patients dying within 30 and 90 days of presentation will be considered as 0 days, to account for the competing effect of mortality on ECMO-free survival.
Survival free of pediatric intensive care unit (PICU; censored at 30 and 90 days)
Hospital length of stay post randomization
Median daily blood product usage
Complement system activation
Child neurodevelopment, function, and quality of life at 6 and 12 months, as measured by:
Ages and Stages Questionnaire (<5 years of age) OR Strength and Difficulties Questionnaire (>5 years of age)
Pediatric Quality of Life Inventory
Pediatric Emotional Distress Scale (2-5 years) OR Children’s Revised Impact of Events Scale (>5 years)
Behavior Rating Index of Executive Functioning – Preschool (2-5 years) OR Behavior Rating Index of Executive Functioning – 2 (>5 years)
Vineland Adaptive Behavior Scale
Parent functioning at 6 and 12 months, as measured by:
Parenting Stress Index – Short Form
Kessler-6
Primary Caregiver – Post Traumatic Stress Disorder Scale
The focus will be on the monthly recruitment rate, the randomized to screened patient ratio, and protocol adherence, that is, how many blood collection points, computer tomography scans of oxygenators, and daily indirect oxygenator clot measurements (by extracorporeal life support assessment monitor) were completed.
There will be a focus on sweep gas delivery failure related to NO administration. Specifically, an arterial oxygen saturation of less than 80 due to a sweep gas interruption related to NO administration or carbon dioxide control outside of 30 to 50 mm Hg due to NO administration will be recorded as a safety event. The methemoglobin (MetHb) levels during the time of ECMO will be measured, and events above 3% related to NO administration will be noted.
Host inflammation and complement components will be assessed before cannulation and at 1, 12, and 24 hours post cannulation by determining serum concentrations of C-reactive protein, procalcitonin, IL-1b, IL-6, IL-8, IL-10, and TNF-
Coagulation system measurements
Change in granule (soluble CD40 ligand and P-selectin) and chemokine (platelet factor 4) levels released by activated platelets
ADAMTS13 release
Change in van Willebrand factor concentrations during and after the extracorporeal membrane oxygenation (ECMO) run
Changes in inflammatory and complement system activation
Change in C-reactive protein, procalcitonin, interleukin (IL)-1b, IL-6, IL-8, IL-10, and tumor necrosis factor
The secondary clinical outcomes include mortality at 30 and 90 days. ECMO-free and PICU-free survival censored at 30 and 90 days post randomization, length of stay at the hospital post randomization, average daily blood product usage, complement system activation with measurements of complement (C)1q, C5a, C9, C3, C4, complement factor B, complement factor H, and Mannose-binding Lectin, as well as neurodevelopmental function and quality of life at 6 and 12 months, will be considered (
Cardiac, respiratory, and extracorporeal membrane oxygenation–assisted cardiopulmonary resuscitation outcomes (proportions alive at 30 and 90 days for each group)
Circuit duration (time to decannulation or time to circuit change) per treatment group
Renal function measured as creatinine and urine output changes during extracorporeal membrane oxygenation (ECMO) per treatment group
Renal replacement treatment on ECMO (type of renal replacement therapy, duration of slow continuous ultrafiltration, type of filter, and duration of filter viability)
Incidence of seizures diagnosed during ECMO or up to 48 hours after decannulation
Transmembrane oxygenator pressure assessment every 24 hours
Oxygenator clot volume as assessed by the extracorporeal life support assessment monitor
Oxygenator clot volume (by computer tomography imaging)
Hemolysis (plasma-free hemoglobin) per treatment group
Mean daily heparin dose per kg required to meet target anticoagulation per treatment group
We will further investigate the oxygenator’s function and structure. The former will be done by postoxygenator blood gas sampling, and the latter by oxygenator clot volume assessment by computer tomography scanning. Outcomes by age group (<28 days, 28 to 365 days, and greater than 365 days) will be analyzed.
Descriptive statistics will be used to report the baseline characteristics of the total study cohort and each subgroup. The primary efficacy outcome measure investigating days free of ECMO will be analyzed using quantile regression incorporating treatment group and VA or VV support (stratification variable) as fixed effects, with the treatment group effect estimate and 95% CI reported (assuming the data is abnormally distributed). Exploratory subgroup analysis by cardiac, respiratory, and ECMO-assisted cardiopulmonary resuscitation support will be performed. Analysis of secondary outcomes includes comparisons of measurements and proportions, with confidence intervals of differences as the major method of presentation. The primary analysis will be by intention-to-treat. If appropriate, per-protocol analyses will be performed as well and compared to the intention-to-treat. Statistical significance will be set at the .05 level and no adjustment for multiple comparisons will be made, noting the exploratory nature of the analysis. CIs will be generated using quantile regression for abnormally distributed continuous data, a 2-sided
Neurodevelopmental and functional outcomes (using phone interviews and web-based questionnaires) will be documented at baseline (assessment of premorbid function during PICU admission) using the test battery described in
The neurodevelopmental outcomes will be reported separately from the main study.
Long-term outcome measures at 6 and 12 months after pediatric intensive care unit discharge.
Measure | <5 years of age | ≥5 years of age |
Neurodevelopment | Ages and Stages Questionnaire (ASQ) | Strengths and Difficulties Questionnaire (SDQ) |
Quality of life | Pediatric Quality of Life Inventory | Pediatric Quality of Life Inventory |
Distress | Pediatric Emotional Distress Scale (2-4 years) (PEDS) | Children’s Revised Impact of Events Scale (≥5 years) (CRIES) |
Executive functioning | Behavior Rating Index of Executive Functioning for Preschoolers (2-4 years) (BRIEF-P) | Behavior Rating Index of Executive Functioning (≥5 years) (BRIEF) |
Adaptive behavior | Vineland Adaptive Behavior Scale (VABS) | VABS |
Functioning | Functional Status Score (FSS), Pediatric Cerebral Performance Category (PCPC), and Pediatric Outcome Performance Category (POPC) | FSS, PCPC, and POPC |
Parent outcomes | Kessler (K6), Primary Carer – Post Traumatic Stress Disorder (PC-PTSD), and Parenting Stress Index – Short Form (PSI-4-SF) | K6, PC-PTSD, and PSI-4-SF |
Given the severity of the underlying disease leading to the requirement for ECMO, patients are expected to have a high rate of adverse events unrelated to the study intervention. Events that are in the expected range of adverse events during standard treatment will therefore not be reported as related to the study intervention, as previously described [
The NECTAR trial will be the first RCT to assess the effect of NO on bleeding, clotting, and inflammatory complications in neonates and children supported on ECMO. It will establish the feasibility and safety of the procedure to allow the design of a trial powered for patient-centered outcomes.
Children requiring ECMO support continue to have a very high mortality risk. Both bleeding and clotting events are significantly associated with mortality and morbidity in this group of patients, and—in combination with inflammatory activation—they continue to pose a challenge to which no therapeutic answer has been found to date. The addition of NO to the sweep gas to reduce bleeding, clotting, and inflammatory complications is a promising therapeutic approach that has so far only been tested in vitro, in historical comparisons, or in RCTs on cardiopulmonary bypass settings rather than ECMO. Given the anticipated high safety of the intervention, the approach has the potential to improve patient-centered short- and long-term outcomes.
The patient group requiring ECMO is very heterogeneous, and due to the pilot study size, achieving a normal distribution of risk factors in the 2 study groups may be unlikely. In addition, this pilot trial is not powered to assess associations between the intervention and clinical outcomes such as ECMO-free survival. It is designed to test the feasibility, safety, and efficacy of such an intervention and the conduct of such a study while exploring clinical and laboratory data in relation to the study groups.
Inflammatory and coagulation system activation of patients during ECMO support remains a major contributor to ECMO-related morbidity and mortality. NO may be an effective treatment for children supported on ECMO to mitigate inflammation and coagulation system activation. Data from the NECTAR pilot study will inform the design of a larger, definitive trial.
activated partial thromboplastin time
data and safety monitoring board
extracorporeal membrane oxygenation
Human Research and Ethics Committee
interleukin
international normalized ratio
methemoglobin
Nitric Oxide on Extracorporeal Membrane Oxygenation in Neonates and Children
nitric oxide
pediatric intensive care unit
prothrombin time
randomized controlled trial
thromboelastography
tumor necrosis factor
veno-arterial
veno-venous
The authors acknowledge the input from Warwick Butt, Senior Intensivist Royal Children’s Hospital Melbourne, John Fraser, Director Intensive Care Unit St Andrew’s Hospital, Emma Haisz, and the Extracorporeal membrane oxygenation Clinical Nurse Consultant (ECMO CNC) as well as nurse educators for setup and training of staff. Further, the ECMO specialists are acknowledged, without whom the trial would not have been possible. Lastly, the study team would like to acknowledge the patients and parents who are willing to participate in the trial. This work was supported by grants from the Children’s Hospital Foundation, Brisbane, Australia, and by a grant from the Thrombosis and Hemostasis Society of Australia. LS has been supported by a National Health and Medical Research Council (NHMRC) Practitioner Fellowship and by the Children's Hospital Foundation, Brisbane, Australia. AS has been supported by a NHMRC Practitioner Fellowship and by the Children`s Hospital Foundation, Brisbane, Australia. AB acknowledges support through an Australian Research Council Future Fellowship (FT220100487) and by the Frazer Institute, The University of Queensland. The funding sources had no involvement in study design, analyses, or interpretation of the results. Air Liquide will provide nitric oxide (NO) delivery devices as well as NO to study centers but has no involvement in study design, conduct, analyses, or interpretation of the findings.
Deidentified participant data will be shared upon reasonable request after the publication of the original paper. Data will be available for use if the request is approved by the appropriate institutional review board and the Trial Steering Committee and a signed data access agreement is in place.
The first draft of the protocol was written by ACM and LS. KG wrote the section on statistical analyses. The final study protocol was established with input from LS, ACM, KJ, KG, JR, AB, PSV, DL, and AS. ACM prepared the final protocol manuscript, which was reviewed and approved by all authors.
ACM, LS, DL, KJ, KG, JR, and AB have no conflicts of interest to declare. AS has received grants from Fisher and Paykel.