The role of fetal hemoglobin in the artificial placenta: A premature ovine model.

INTRODUCTION: A radical paradigm shift in the treatment of premature infants failing conventional treatment is to recreate fetal physiology using an extracorporeal Artificial Placenta (AP). The aim of this study is to evaluate the effects of changing fetal hemoglobin percent (HbF%) on physiology and circuit function during AP support in an ovine model. METHODS: Extremely premature lambs (n = 5) were delivered by cesarean section at 117-121 d estimated gestational age (EGA) (term = 145d), weighing 2.5 ± 0.35 kg. Lambs were cannulated using 10-14Fr cannulae for drainage via the right jugular vein and reinfusion via the umbilical vein. Lambs were intubated and lungs were filled with perfluorodecalin to a meniscus with a pressure of 5-8 cm H2O. The first option for transfusion was fetal whole blood from twins followed by maternal red blood cells. Arterial blood gases were used to titrate AP support to maintain fetal blood gas values. RESULTS: The mean survival time on circuit was 119.6 ± 39.5 h. Hemodynamic parameters and lactate were stable throughout. As more adult blood transfusions were given to maintain hemoglobin at 10 mg/dL, the HbF% declined, reaching 40% by post operative day 7. The HbF% was inversely proportional to flow rates as higher flows were required to maintain adequate oxygen saturation and perfusion. CONCLUSIONS: Transfusion of adult blood led to decreased fetal hemoglobin concentration during AP support. The HbF% was inversely proportional to flow rates. Future directions include strategies to decrease the priming volume and establishing a fetal blood bank to have blood rich in HbF.

Extracorporeal life support without systemic anticoagulation: a nitric oxide-based non-thrombogenic circuit for the artificial placenta in an ovine model.

BACKGROUND: Clinical translation of the extracorporeal artificial placenta (AP) is impeded by the high risk for intracranial hemorrhage in extremely premature newborns. The Nitric Oxide Surface Anticoagulation (NOSA) system is a novel non-thrombogenic extracorporeal circuit. This study aims to test the NOSA system in the AP without systemic anticoagulation. METHODS: Ten extremely premature lambs were delivered and connected to the AP. For the NOSA group, the circuit was coated with DBHD-N2O2/argatroban, 100 ppm nitric oxide was blended into the sweep gas, and no systemic anticoagulation was given. For the Heparin control group, a non-coated circuit was used and systemic anticoagulation was administered. RESULTS: Animals survived 6.8 ± 0.6 days with normal hemodynamics and gas exchange. Neither group had any hemorrhagic or thrombotic complications. ACT (194 ± 53 vs. 261 ± 86 s; p < 0.001) and aPTT (39 ± 7 vs. 69 ± 23 s; p < 0.001) were significantly lower in the NOSA group than the Heparin group. Platelet and leukocyte activation did not differ significantly from baseline in the NOSA group. Methemoglobin was 3.2 ± 1.1% in the NOSA group compared to 1.6 ± 0.6% in the Heparin group (p < 0.001). CONCLUSIONS: The AP with the NOSA system successfully supported extremely premature lambs for 7 days without significant bleeding or thrombosis. IMPACT: The Nitric Oxide Surface Anticoagulation (NOSA) system provides effective circuit-based anticoagulation in a fetal sheep model of the extracorporeal artificial placenta (AP) for 7 days. The NOSA system is the first non-thrombogenic circuit to consistently obviate the need for systemic anticoagulation in an extracorporeal circuit for up to 7 days. The NOSA system may allow the AP to be implemented clinically without systemic anticoagulation, thus greatly reducing the intracranial hemorrhage risk for extremely low gestational age newborns. The NOSA system could potentially be applied to any form of extracorporeal life support to reduce or avoid systemic anticoagulation.

The new frontier in ECLS: Artificial placenta and artificial womb for premature infants.

Outcomes for extremely low gestational age newborns (ELGANs), defined as <28 weeks estimated gestational age (EGA), remain disproportionately poor. A radical paradigm shift in the treatment of prematurity is to recreate the fetal environment with extracorporeal support and provide an environment for organ maturation using an extracorporeal VV-ECLS artificial placenta (AP) or an AV-ECLS artificial womb (AW). In this article, we will review clinical indications, current approaches in development, ongoing challenges, remaining milestones and ethical considerations prior to clinical translation.

Thoracoscopic Patch Repair of Congenital Diaphragmatic Hernia: Can Smaller Incisions Treat Larger Defects?

INTRODUCTION: Thoracoscopic CDH repair is increasingly performed for Type A and small Type B defects that are amenable to primary repair. However, the thoracoscopic approach is controversial for larger defects necessitating a patch due to technical complexity, intraoperative acidosis, and recurrence risk. We aim to compare clinical outcomes between thoracoscopic and open patch repair of Type B/C defects, using a standardized technique. METHODS: This is a single-center retrospective review of thoracoscopic and open CDH patch repairs January 2017-December 2021. We excluded primary repairs, Type D hernias, repairs on ECMO, recurrent repairs. Various preoperative, intraoperative, and postoperative variables were compared. Primary outcome was recurrence rate. Secondary outcomes included intraoperative pH and pCO2, operative time, and complication rates. RESULTS: Twenty-nine patients met inclusion criteria (open = 13, thoracoscopic = 16). The open cohort had lower o/e total fetal lung volume (29 vs 41.2%, p = 0.042), higher preoperative peak inspiratory pressures (24 vs 20 cm H2O, p = 0.007), were more frequently Type C defects (92.3 vs 31%, p = 0.002) and had liver "up" in left-sided hernias (46 vs 0%, p < 0.0001). Intraoperatively, median lowest pH and highest pCO2 did not differ; neither did overall median pH or pCO2. Operative times were similar (153 vs 194 min, p = 0.113). No difference in recurrence rates was identified, however postoperative complications were higher in the open group. There were no mortalities. CONCLUSIONS: Although we demonstrate higher disease severity of patients undergoing open repair, thoracoscopic patch repair for Type B/C defects is safe and effective in patients with favorable physiologic status, alleviating concerns for intraoperative acidosis, operative length, and risk of recurrence. LEVEL OF EVIDENCE: II.

Ethical challenges in first-in-human trials of the artificial placenta and artificial womb: not all technologies are created equally, ethically.

Artificial placenta and artificial womb technologies to support extremely premature neonates are advancing toward clinical testing in humans. Currently, no recommendations exist comparing these approaches to guide study design and optimal enrollment eligibility adhering to principles of research ethics. In this paper, we will explore how scientific differences between the artificial placenta and artificial womb approaches create unique ethical challenges to designing first-in-human trials of safety and provide recommendations to guide ethical study design for initial human translation.

Neonatal pneumothorax in congenital diaphragmatic hernia: Be wary of high ventilatory pressures.

Background: Patients with congenital diaphragmatic hernia (CDH) require invasive respiratory support and higher ventilator pressures may be associated with barotrauma. We sought to evaluate the risk factors associated with pneumothorax in CDH neonates prior to repair. Methods: We retrospectively reviewed newborns born with CDH between 2014 and 2019 who developed a pneumothorax, and we matched these cases to patients with CDH without pneumothorax. Results: Twenty-six patients were included (n=13 per group). The pneumothorax group required extracorporeal life support (ECLS) more frequently (85% vs 54%, p=0.04), particularly among type A/B defects (31% vs 7%, p=0.01). The pneumothorax group had higher positive end-expiratory pressure (PEEP) within 1 hour of birth (p=0.02), at pneumothorax diagnosis (p=0.003), and at ECLS (p=0.02). The pneumothorax group had a higher mean airway pressure (Paw) at birth (p=0.01), within 1 hour of birth (p=0.01), and at pneumothorax diagnosis (p=0.04). Using multiple logistic regression with cluster robust SEs, higher Paw (OR 2.2, 95% CI 1.08 to 3.72, p=0.03) and PEEP (OR 1.8, 95% CI 1.15 to 3.14, p=0.007) were associated with an increased risk of developing pneumothorax. There was no difference in survival (p=0.09). Conclusions: Development of a pneumothorax in CDH neonates is independently associated with higher Paw and higher PEEP. A pneumothorax increases the likelihood of treated with ECLS, even with smaller defect.

Milestones for clinical translation of the artificial placenta.

Despite significant advances in the treatment of prematurity, premature birth results in significant mortality and morbidity. In particular, extremely low gestational age newborns (ELGANs) defined as <28 weeks estimated gestational age (EGA) suffer from disproportionate mortality and morbidity. A radical paradigm shift in the treatment of prematurity is to recreate fetal physiology using an extracorporeal VV-ECLS artificial placenta (AP) or an AV-ECLS artificial womb (AW). Over the past 15 years, tremendous advances have been made in the laboratory confirming long-term support and organ protection and ongoing development. The major milestones to clinical application are miniaturization, anticoagulation, clinical risk stratification, specialized critical care protocols, a regulatory path and a strategy and platform to translate technology to the bedside. Currently, several groups are addressing the remaining milestones for clinical translation.

Updates in Neonatal Extracorporeal Membrane Oxygenation and the Artificial Placenta.

Extracorporeal life support, initially performed in neonates, is now commonly used for both pediatric and adult patients requiring pulmonary and/or cardiac support. Data suggests the clinical feasibility of Extracorporeal Membrane Oxygenation for premature infants (29-33 weeks estimated gestational age [EGA]). For extremely premature infants less than 28 weeks EGA, an artificial placenta has been developed to recreate the fetal environment. This approach is investigational but clinical translation is promising. In this article, we discuss the current state and advances in neonatal and "preemie Extracorporeal Membrane Oxygenation" and the development of an artificial placenta and its potential use in extremely premature infants.

Care Levels for Fetal Therapy Centers.

Fetal therapies undertaken to improve fetal outcome or to optimize transition to neonate life often entail some level of maternal, fetal, or neonatal risk. A fetal therapy center needs access to resources to carry out such therapies and to manage maternal, fetal, and neonatal complications that might arise, either related to the therapy per se or as part of the underlying fetal or maternal condition. Accordingly, a fetal therapy center requires a dedicated operational infrastructure and necessary resources to allow for appropriate oversight and monitoring of clinical performance and to facilitate multidisciplinary collaboration between the relevant specialties. Three care levels for fetal therapy centers are proposed to match the anticipated care complexity, with appropriate resources to achieve an optimal outcome at an institutional and regional level. A level I fetal therapy center should be capable of offering fetal interventions that may be associated with obstetric risks of preterm birth or membrane rupture but that would be very unlikely to require maternal medical subspecialty or intensive care, with neonatal risks not exceeding those of moderate prematurity. A level II center should have the incremental capacity to provide maternal intensive care and to manage extreme neonatal prematurity. A level III therapy center should offer the full range of fetal interventions (including open fetal surgery) and be able manage any of the associated maternal complications and comorbidities, as well as have access to neonatal and pediatric surgical intervention including indicated surgery for neonates with congenital anomalies.

Hepatic Function in Premature Lambs Supported by the Artificial Placenta and Total Parenteral Nutrition.

The artificial placenta (AP) promotes organ development and reduces organ injury in a lamb model of extreme prematurity. This study evaluates hepatic outcomes after AP support with total parenteral nutrition (TPN) administration. Premature lambs (116-121 days estimated gestational age; term = 145) were cannulated for 7 days of AP support. Lambs received TPN with SMOFlipid (n = 7) or Intralipid (n = 5). Liver function and injury were compared between the two groups biochemically and histologically. Groups were compared by ANOVA with Tukey's multiple comparisons or linear-mixed effects models. From baseline to day 7, total bilirubin (Intralipid 2.6 ± 2.3 to 7.9 ± 4.4 mg/dl; SMOFlipid 0.3 ± 0.1 to 5.5 ± 2.3 mg/dl), alanine aminotransferase, and gamma-glutamyl transferase increased in both groups ( p < 0.001 for all). Direct bilirubin (0.3 ± 0.2 to 1.8 ± 1.4 mg/dl; p = 0.006) and AST (27 ± 5 to 309 ± 242 mg/dl; p < 0.001) increased in SMOFlipid group (not measured in Intralipid group). On liver histology, Intralipid showed more cholestasis than SMOFlipid; both groups showed more than tissue controls. The Intralipid group alone showed hepatocyte injury and had more congestion than controls. Lambs supported by the AP with TPN administration maintain normal hepatic function and sustain minimal hepatic injury. SMOFlipid is associated with decreased cholestasis and hepatic injury versus Intralipid.

Image-based prenatal predictors correlate with postnatal survival, extracorporeal life support use, and defect size in left congenital diaphragmatic hernia.

OBJECTIVE: To evaluate the association between prenatal imaging predictors of patients with left-sided congenital diaphragmatic hernia (LCDH) and postnatal outcomes. STUDY DESIGN: CDH study group data were reviewed for LCDH infants born 2015-2019. Prenatal ultrasound (US) and magnetic resonance imaging (MRI) data were collected and correlated with postnatal information including CDHSG defect size (A through D or non-repair (NR)). RESULTS: In total, 929 LCDH patients were included. Both US and MRI imaging predictors correlated with postnatal survival (72.2%) and ECLS use (29.6%). Logistic regression models confirmed increased survival and decreased ECLS use with larger values for all predictors. Importantly, all prenatal values evaluated showed no significant difference between defect size D and NR patients. CONCLUSIONS: This is the largest cohort of LCDH patients and demonstrates that prenatal imaging factors correlate with postnatal outcomes and confirms that patients in the non-repair group are prenatally similar to type D defects.

A single institution's experience with the management of peripheral bronchial atresia.

PURPOSE: Peripheral bronchial atresia is a pulmonary abnormality diagnosed on postnatal computed tomography after prenatal imaging reveals a congenital lung lesion. Debate regarding management of this abnormality prompted us to review our institution's practice patterns and outcomes. METHODS: All patients diagnosed with bronchial atresia were assessed from 6/2014 to 7/2020. Pediatric radiologists were surveyed to delineate computed tomography criteria used to diagnose peripheral bronchial atresia. Criteria were applied in an independent blinded review of postnatal imaging. Data for patients determined to have peripheral bronchial atresia and at least an initial pediatric surgical evaluation were analyzed. RESULTS: Twenty-eight patients with bronchial atresia received at least an initial pediatric surgical evaluation. Expectant management was planned for 22/28 (79%) patients. Two patients transitioned from an expectant management strategy to an operative strategy for recurrent respiratory infections; final pathology revealed bronchial atresia in both. Six patients were initially managed operatively; final pathology revealed bronchial atresia (n = 3) or congenital lobar overinflation (n = 3). CONCLUSIONS: Peripheral bronchial atresia can be safely managed expectantly. A change in symptoms is suspicious for alternate lung pathology, warranting further workup and consideration for resection. LEVEL OF EVIDENCE: Level IV.

Switching to centrifugal pumps may decrease hemolysis rates among pediatric ECMO patients.

Recent advances in ECLS technology have led to the adoption of centrifugal pumps for the majority of patients worldwide. Despite several advantages of centrifugal pumps, they remain controversial because a number of studies have shown increased rates of hemolysis. The aim of this study was to assess the impact of transitioning from roller to centrifugal pumps on hemolysis rates at our center. A retrospective analysis of all pediatric ECMO patients at a single center between 2005 and 2017 was undertaken. Hemolysis was defined as a plasma free hemoglobin >50 mg/dL. Multivariable logistic regression was performed correcting for several factors to determine risk factors for hemolysis and analyze outcomes among patients with hemolysis. Significant findings were those with p < 0.05. A total of 590 patients were identified during the study period. Multivariable logistic regression for risk factors for hemolysis showed roller pumps (OR 1.92, CI 1.11-3.33) and ECMO duration (OR 1.002 per hour, CI 1.00-1.01) to be significant factors. Rates of hemolysis significantly improved following conversion from roller to centrifugal pumps, with significantly lower rates of hemolysis in 2012, 2015, 2016, and 2017 when compared to the historical average with roller pumps from 2005 to 2009 (34.7%). Additionally, hemolysis was associated with an increased risk of death (OR 3.59, CI 2.05-6.29) when correcting for other factors. These data suggest decreasing rates of hemolysis with centrifugal pumps compared to roller pumps. Since hemolysis was also associated with increased risk of death, these data support the switch from roller to centrifugal pumps at ECMO centers.

Rare and de novo variants in 827 congenital diaphragmatic hernia probands implicate LONP1 as candidate risk gene.

Congenital diaphragmatic hernia (CDH) is a severe congenital anomaly that is often accompanied by other anomalies. Although the role of genetics in the pathogenesis of CDH has been established, only a small number of disease-associated genes have been identified. To further investigate the genetics of CDH, we analyzed de novo coding variants in 827 proband-parent trios and confirmed an overall significant enrichment of damaging de novo variants, especially in constrained genes. We identified LONP1 (lon peptidase 1, mitochondrial) and ALYREF (Aly/REF export factor) as candidate CDH-associated genes on the basis of de novo variants at a false discovery rate below 0.05. We also performed ultra-rare variant association analyses in 748 affected individuals and 11,220 ancestry-matched population control individuals and identified LONP1 as a risk gene contributing to CDH through both de novo and ultra-rare inherited largely heterozygous variants clustered in the core of the domains and segregating with CDH in affected familial individuals. Approximately 3% of our CDH cohort who are heterozygous with ultra-rare predicted damaging variants in LONP1 have a range of clinical phenotypes, including other anomalies in some individuals and higher mortality and requirement for extracorporeal membrane oxygenation. Mice with lung epithelium-specific deletion of Lonp1 die immediately after birth, most likely because of the observed severe reduction of lung growth, a known contributor to the high mortality in humans. Our findings of both de novo and inherited rare variants in the same gene may have implications in the design and analysis for other genetic studies of congenital anomalies.

Development of an artificial placenta for support of premature infants: narrative review of the history, recent milestones, and future innovation.

Over 50 years ago, visionary researchers began work on an extracorporeal artificial placenta to support premature infants. Despite rudimentary technology and incomplete understanding of fetal physiology, these pioneering scientists laid the foundation for future work. The research was episodic, as medical advances improved outcomes of premature infants and extracorporeal life support (ECLS) was introduced for the treatment of term and near-term infants with respiratory or cardiac failure. Despite ongoing medical advances, extremely premature infants continue to suffer a disproportionate burden of mortality and morbidity due to organ immaturity and unintended iatrogenic consequences of medical treatment. With advancing technology and innovative approaches, there has been a resurgence of interest in developing an artificial placenta to further diminish the mortality and morbidity of prematurity. Two related but distinct platforms have emerged to support premature infants by recreating fetal physiology: a system based on arteriovenous (AV) ECLS and one based on veno-venous (VV) ECLS. The AV-ECLS approach utilizes only the umbilical vessels for cannulation. It requires immediate transition of the infant at the time of birth to a fluid-filled artificial womb to prevent umbilical vessel spasm and avoid gas ventilation. In contradistinction, the VV-ECLS approach utilizes the umbilical vein and the internal jugular vein. It would be applied after birth to infants failing maximal medical therapy or preemptively if risk stratified for high mortality and morbidity. Animal studies are promising, demonstrating prolonged support and ongoing organ development in both systems. The milestones for clinical translation are currently being evaluated.

Fetal hemoglobin levels in premature newborns. Should we reconsider transfusion of adult donor blood?

PURPOSE: The aim of this study was to assess the percent decrease in fetal hemoglobin (HbF) after transfusion of adult-derived donor packed red blood cell (pRBC) units in extremely low gestational age newborns (ELGANs). METHODS: Control percent fetal hemoglobin (%HbF) levels were measured in newborn cord blood or peripheral blood samples in non-transfused patients prior to elective surgery. ELGANs were followed prospectively and %HbF was measured on residual post-test complete blood count (CBC) specimens. ELGAN %HbF values were compared to the control population and transfusions were recorded. RESULTS: Initial mean %HbF in ELGANs (n=16) was 92.2±1.3% (range 90.2-95.1%), which is similar to the control group (n=25). Mean levels dropped to 61.1±11.1% (range 34.2-73.2%) after a single pRBC transfusion (n=9) and to a mean of 35.6±6.3% after an additional transfusion (n=5). %HbF levels trended upwards if no additional transfusions were given, but levels still remained lower than expected for gestational age through discharge (n=85 samples). CONCLUSIONS: Percent fetal hemoglobin concentrations in ELGANs decrease precipitously after transfusion with adult donor pRBCs. Further studies are needed to evaluate the benefit of maintaining higher fetal hemoglobin concentrations in these patients and whether administration of HbF rather than adult donor pRBCs would improve patient outcomes.

Fetal Surgery in the Primate 4.0: A New Technique 30 Years Later.

INTRODUCTION: Open fetal surgery requires a hemostatic hysterotomy that minimizes membrane separation. For over 30 years, the standard of care for hysterotomy in the gravid uterus has been the AutoSuture Premium Poly CS*-57 stapler. OBJECTIVE: In this study, we sought to test the feasibility of hysterotomy in a rhesus monkey model with the Harmonic ACE®+7 Shears. METHODS: A gravid rhesus monkey underwent midgestation hysterotomy at approximately 90 days of gestation (2nd trimester; term = 165 ± 10 days) using the Harmonic ACE®+7 Shears. A two-layer uterine closure was completed and the dam was monitored by ultrasound intermittently throughout the pregnancy. At 58 days after hysterotomy (near term), a final surgery was performed to evaluate the uterus and hysterotomy site. RESULTS: A 3.5-cm hysterotomy was completed in 2 min 7 s. The opening was hemostatic and the membranes were sealed. Immediately after closure and throughout the pregnancy, ultrasound revealed intact membranes without separation and normal amniotic fluid levels. At term, the scar was well healed without signs of thinning or dehiscence. CONCLUSIONS: The Harmonic ACE®+7 Shears produced a hemostatic midgestation hysterotomy with membrane sealing in the rhesus monkey model. Importantly, healing was acceptable.

Predicting lethal pulmonary hypoplasia in congenital diaphragmatic hernia (CDH): Institutional experience combined with CDH registry outcomes.

BACKGROUND: The Severe Pulmonary Hypoplasia and Evaluation for Resuscitative Efforts (SPHERE) protocol was developed to attempt to identify CDH patients with likely lethal pulmonary hypoplasia. We present our experience with this protocol and utilize the CDH Registry to critically assess the protocol. METHODS: SPHERE patients identified based on prenatal imaging (10/2009-1/2018) were offered ECMO if meeting postnatal physiologic criteria, while others received comfort measures. Within the CDH Registry, patients with suspected severe CDH were identified and separated into "passed" (lowest pCO2 ≤100) versus "failed" (lowest pCO2 >100) groups. RESULTS: Of 23 SPHERE patients, 57% (13/23) passed criteria for ECMO and survival was 46% (6/13) in that cohort. Of 4912 patients in the CDH Registry, 265 met criteria. There was no difference in survival rates between those that "passed" (122/227; 54%) versus "failed" (18/38; 47%). However, the latter had longer ECMO runs and more required ventilator/ECMO support at 30 days. Amongst survivors, the "failed" group had longer hospital stays and more frequently required tube feeds at discharge. CONCLUSIONS: The SPHERE protocol did not predict mortality in the CDH Registry. However, our data suggest resource utilization is significant when unable to reach pCO2 ≤100 despite resuscitation. Morbidity remains high in this group. LEVEL OF EVIDENCE: Level III ANNOTATION OF CHANGES: Institutional Review Board Approval at University of Michigan (HUM00031524 and HUM00044010) TYPE OF STUDY: Retrospective Review.