Etiology, Diagnosis and Management of Persistent Pulmonary Hypertension of the Newborn in Resource-limited Settings.

Persistent Pulmonary Hypertension of the Newborn (PPHN) is more common in Low and middle income countries (LMICs) due to high incidence of sepsis, perinatal asphyxia and meconium aspiration syndrome. Presence of hypoxic respiratory faillure and greater than 5% difference in preductal and post ductal saturation increases clinical sucipision for PPHN. The availability of Inhaled nitric oxide and extracorporaeal membrane oxygenation is limited but pulmonary vasodilators such as sildenafil are readily available in most LMICs.

Early Outcome of Neonates Admitted with Meconium Aspiration Syndrome.

BACKGROUND: Meconium aspiration syndrome is one of the commonest cause of respiratory distress in neonates. The incidence is still high in developing world. This study aims to study the clinical characteristics and early outcome of neonates admitted for meconium aspiration syndrome. METHODS: This was a cross-sectional descriptive study done among neonates admitted to the neonatal Intensive Care Unit with a diagnosis of Meconium Aspiration syndrome. Relevant epidemiological, clinical and laboratory data were obtained. The early outcome of those neonate was studied. RESULTS: Out of 140 neonates with a mean birth weight of 2865 + 543 grams,73.6% were male, of which 76.4% were referred cases while 23.6% were inborn. Of them 69.3% had history of thin type of meconium while 30.7% had thick type of meconium during delivery. Of all mothers, 74.3% were primigravida, 4.3% had intrapartum fever of unknown source,11.4% suffered from urinary tract infection while 2.8% had hypertension. Premature rupture of membrane had occurred among 7.9% and oligohydramnios was found in 10%. Half of them (50.7%) had spontaneous vaginal delivery, 44.3% had caesarian section, while 4.8% had assisted delivery. Around one third of the neonates (37.1%) were given supplemental oxygen via nasal prongs, 25.7% via head box, 27.1% via continuous positive airway pressure and 10% intubated. Around half of the neonates (42.1%) had no complications. Complication noted were sepsis, birth asphyxia, seizures and polycythemia in 35%, 14.3%, 5.7% and 2.9% respectively. Mortality occurred among 5.0% of them. CONCLUSIONS: Meconium aspiration syndrome is one of the commonest cause of respiratory distress in a neonate which is associated with common maternal risk factors especially in primigravida which included Urinary tract infection, hypertension and oligohydramnios.

Outcomes of neonates born through meconium-stained amniotic fluid pre and post 2015 NRP guideline implementation.

A shift in the Neonatal Resuscitation Program (NRP) guidelines occurred in 2015 from routine intubation and endotracheal suctioning of all meconium-stained non-vigorous infants towards less aggressive interventions based on response to initial resuscitation. This study aims to examine the impact of this change on outcomes of non-vigorous infants born through meconium-stained amniotic fluid at a level III academic NICU encompassing years before and after the change in guideline. This single-center retrospective study compared NICU therapies and clinical outcomes of 117 non-vigorous newborns pre-guideline implementation to 106 non-vigorous newborns post-guideline implementation. Nearly two thirds of infants in the pre-guideline cohort received endotracheal suctioning with recovery of meconium compared to less than a third of infants in the post-guideline cohort (p<0.01). Though a higher proportion of the pre-guideline cohort were admitted to the NICU for respiratory issues compared to the post-guideline cohort, the two groups did not differ significantly with regard to morbidity and therapies. Despite a marked reduction in rates of intubation and endotracheal suctioning, there is no difference in outcomes between pre-guideline implementation vs post-guideline implementation in non-vigorous meconium-stained infants, supporting the recent NRP guideline change and highlighting the benefit of expectant management.

[The evolution of approach in the resuscitation of neonates born with meconium-stained amniotic fluid: a tale of two countries, China and U.S.A., in the past 60 years]. / 羊水胎粪污染新生儿复苏的前世今生：过去60年中美两国的演变史.

Neonates born through meconium-stained amniotic fluid (MSAF) may develop complications including meconium aspiration syndrome, persistent pulmonary hypertension of newborn and death. The approach to the resuscitation of these neonates has significantly evolved for the past few decades. Initially, under direct visualization technique, neonates with MSAF were commonly suctioned below the vocal cords soon after delivery. Since 2015, Neonatal Resuscitation Program (NRP®) of the American Academy of Pediatrics has recommended against "routine" endotracheal suctioning of non-vigorous neonates with MSAF but favored immediate resuscitation with positive pressure ventilation via face-mask bagging. However, the China neonatal resuscitation 2021 guidelines continue to recommend routine endotracheal suctioning of non-vigorous neonates born with MSAF at birth. This review article discusses the differences and the rationales in the approach in the resuscitation of neonates with MSAF between Chinese and American NRP® guidelines over the past 60 years.

Perinatal risk factors associated with the need for resuscitation in newborns born through meconium-stained amniotic fluid.

OBJECTIVE: The Neonatal Life Support 2020 guidelines emphasize that meconium-stained amniotic fluid (MSAF) remains a significant risk factor for a newborn to receive advanced resuscitation, especially if additional risk factors are present at the time of birth. However, these additional perinatal risk factors are not clearly identified. The purpose of this study was to evaluate the importance of additional independent ante- and intrapartum risk factors in the era of no routine endotracheal suctioning that determine the need for resuscitation in newborns born through MSAF. METHODS: This retrospective cohort study included deliveries ≥ 35 weeks' gestation associated with MSAF that occurred between January 1, 2017 and December 31, 2019. The newborns needing resuscitation (any intervention beyond the initial steps) were compared to those not needing resuscitation. Among newborns needing resuscitation, those needing advanced resuscitation (continuous positive airway pressure/ positive pressure ventilation or beyond) were compared to those not needing advanced resuscitation. RESULTS: Logistic regression analysis revealed that among various perinatal factors, primigravida, thick meconium, fetal distress, chorioamnionitis, rupture of membranes ≥ 18 hours, post-term (gestational age ≥ 42 weeks), cesarean section or shoulder dystocia independently significantly increased the odds of a meconium-stained newborn needing resuscitation. Among these factors, fetal distress, chorioamnionitis or cesarean section independently further increased the odds of needing advanced resuscitation. CONCLUSION: Risk stratification of perinatal factors associated with the need for newborn resuscitation and advanced resuscitation in the deliveries associated with MSAF may help neonatal teams and resources to be appropriately prioritized and optimally utilized.

Trends in Neonatal Extracorporeal Membrane Oxygenation During a Venovenous Cannula Shortage.

OBJECTIVES: To report temporal trends in venovenous extracorporeal membrane oxygenation (ECMO) use for neonatal respiratory failure in U.S. centers before and after functional venovenous cannula shortage due to withdrawal of one dual lumen venovenous cannula from the market in 2018. DESIGN: Retrospective cohort study. SETTING: ECMO registry of the Extracorporeal Life Support Organization. PATIENTS: Infants who received neonatal (cannulated prior to 29 d of age) respiratory ECMO at a U.S. center and had a record available in the ECMO registry from January 1, 2010 to July 20, 2021. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Primary outcome was receipt of venovenous ECMO (vs venoarterial or other), and secondary outcomes were survival to hospital discharge and adverse neurologic outcomes. Using an interrupted time series design, we fit multivariable mixed effects logistic regression models with receipt of venovenous ECMO as the dependent variable, treatment year modeled as a piecewise linear variable using three linear splines (pre shortage: 2010-2014, 2014-2018; shortage: 2018-2021), and adjusted for center clustering and multiple covariates. We evaluated trends in venovenous ECMO use by primary diagnosis including congenital diaphragmatic hernia, meconium aspiration, pulmonary hypertension, and other. Annual neonatal venovenous ECMO rates decreased after 2018: from 2010 to 2014, adjusted odds ratio (aOR) for yearly trend 0.98 (95% CI 0.92-1.04), from 2014 to 2018, aOR for yearly trend 0.90 (95% CI 0.80-1.01), and after 2018, aOR for yearly trend 0.46 (95% CI 0.37-0.57). We identified decreased venovenous ECMO use after 2018 in all diagnoses evaluated, and we failed to identify differences in temporal trends between diagnoses. Survival and adverse neurologic outcomes were unchanged across the study periods. CONCLUSIONS: Venovenous ECMO for neonatal respiratory failure in U.S. centers decreased after 2018 even after accounting for temporal trends, coincident with withdrawal of one of two venovenous cannulas from the market.

Changing populations being treated with ECMO in the neonatal period - who are the others?

Extracorporeal life support via extracorporeal membrane oxygenation (ECMO) has served the sickest of neonates for almost 50 years. Naturally, the characteristics of neonates receiving ECMO have changed. Advances in care have averted the need for ECMO for some, while complex cases with uncertain outcomes, previously not eligible for ECMO, are now considered. Characterizing the disease states and outcomes for neonates on ECMO is challenging as many infants do not fall into classic categories, i.e. meconium aspiration syndrome (MAS), respiratory distress syndrome (RDS), or congenital diaphragmatic hernia (CDH). Since 2017, over one third of neonatal respiratory ECMO runs reported to the Extracorporeal Life Support Organization Registry are grouped as Other, a catch-all that encompasses those with a diagnosis not included in the classic categories. This review summarizes the historical neonatal ECMO population, reviews advances in therapy and technology impacting neonatal care, and addresses the unknowns in the ever-growing category of Other.

Prediction score for prolonged hospital stay in meconium aspiration syndrome: A multicentric collaborative cohort of south India.

BACKGROUND AND OBJECTIVE: With improved survival in neonates with meconium aspiration syndrome (MAS), the focus is currently on mitigating the morbidities. The objective of this study was to predict factors determining prolonged hospital stay in neonates with MAS. MATERIALS AND METHODS: It was a retrospective cohort from five centers of south India between 2018 and 2020. Neonates ≥35 weeks of gestation admitted to neonatal intensive care unit with the diagnosis of MAS and requiring oxygen beyond 24 h of life were included in the study. The morbidities in the neonates with stay ≤7 days (short stay) were compared with >7 days (prolonged stay). Logistic regression by the backward stepwise method was used for predictive score creation. RESULTS: Out of 347 neonates with MAS discharged home, 103 (29%) had a short stay and 244 (71%) had prolonged stay. The primary support beyond O2 (continuous positive airway pressure/mechanical ventilation) (42% vs. 83%, p < 0.001), fractional inspired oxygen (FiO2 ) at 1 h >30% (45% vs. 87%, p < 0.001), hypoxic ischemic encephalopathy (HIE) stage 2 or 3 (1% vs. 27%, p < 0.001), moderate-severe persistent pulmonary artery hypertension (PPHN) (3% vs. 31%, p < 0.001) were independent factors associated with prolonged stay on logistic regression. A prediction model was devised using weighted scores of these four associated morbidities. The clinical score thus developed had 83% sensitivity, 68% specificity for the prediction of prolonged stay (area under curve: 82%, 95% confidence interval [78-87], p < 0.001). CONCLUSION: More than two-thirds of neonates with MAS had prolonged stay. The primary support beyond oxygen, FiO2 requirement >30%, Moderate to severe PPHN, HIE stage 2 or 3 were predictive of prolonged stay in neonates with MAS.

Contemporary management of infants born through meconium stained amniotic fluid.

Delivery room management of infants delivered through meconium stained amniotic fluid has evolved over the past four decades. The burden of disease weighs more heavily in low- and middle-resource areas. Current information does not allow for precise prediction of infants that will require resuscitation at delivery versus those that need simple stabilization. Optimal care of newborns requires assessment of risk factors and obstetrical and pediatric team preparation to respond to the needs of the newborn.

Umbilical Cord Blood Acid-Base Parameters and Lactate as Predictors of Subsequent Meconium Aspiration Syndrome in Neonates.

Meconium aspiration syndrome (MAS) in neonates born through meconium-stained amniotic fluid (MSAF) causes significant morbidity and mortality. Early recognition of at-risk neonates could help optimize treatment. The aim was to determine predictive characteristics of cord blood pH, base deficit and lactate with subsequent MAS. Receiver operating characteristic (ROC) curves with area under curve (AUC) were estimated. Among 231 MSAF complicated pregnancies, 25 (10.8%) had MAS. Mean cord pH was significantly lower in neonates with MAS compared to those without MAS (7.15 ± 0.11 vs. 7.26 ± 0.07; p < 0.001). Median lactate between the two groups [5.6 (7.5, 3.7) vs. 2.7 (4.5, 2.0)] and base deficit [-10.6 (-13.2, -4.2) vs. -3.7 (-6.3, -2.6)] also differed significantly (p = 0.01). ROC curve area for cord lactate, pH, and base deficit were 0.81, 0.79, and 0.75, respectively. The predictive cutoff values for pH, lactate, and base deficit were 7.20, 3.55 mmol/L, and -5.3 mmol/L, respectively.

A retrospective cohort study of tracheal intubation for meconium suction in nonvigorous neonates. / æ— æ´»åŠ›æ–°ç”Ÿå„¿æ°”ç®¡æ’ç®¡å¸å¼•èƒŽç²ªçš„å›žé¡¾æ€§é˜Ÿåˆ—ç ”ç©¶.

OBJECTIVES: To study the feasibility of tracheal intubation for meconium suction immediately after birth of nonvigorous neonates born through meconium-stained amniotic fluid (MSAF). METHODS: A retrospective cohort study was performed on nonvigorous neonates born through MSAF who were admitted to the Department of Neonatology, Zhecheng People's Hospital. The neonates without meconium suction who were admitted from July 1, 2017 to June 30, 2018 were enrolled as the control group. The neonates who underwent meconium suction from July 1, 2018 to June 30, 2019 were enrolled as the suction group. The two groups were compared in terms of the mortality rate and the incidence rates of neonatal meconium aspiration syndrome (MAS), persistent pulmonary hypertension of the newborn, pneumothorax, and pulmonary hemorrhage. RESULTS: There were 80 neonates in the control group and 71 in the suction group. There were no significant differences between the two groups in the incidence rates of MAS (11% vs 7%), persistent pulmonary hypertension of the newborn (5% vs 4%), pneumothorax (3% vs 1%), and death (0% vs 1%). Compared with the control group, the suction group had a significantly lower proportion of neonates requiring oxygen inhalation (16% vs 33%, P<0.05), noninvasive respiratory support (25% vs 41%, P<0.05) or mechanical ventilation (10% vs 23%, P<0.05) and significantly shorter duration of noninvasive ventilation [(58±24) hours vs (83±41) hours, P<0.05] and length of hospital stay [6(4, 8) days vs 7(5, 10) days, P<0.05]. CONCLUSIONS: Although tracheal intubation for meconium suction immediately after birth may shorten the duration of respiratory support for mild respiratory problems, it cannot reduce the incidence rate of MAS, mortality rate, or the incidence rate of serious complications in nonvigorous infants born through MSAF.

Neonatal outcomes of non-vigorous neonates with meconium-stained amniotic fluid before and after change in tracheal suctioning recommendation.

OBJECTIVE: To evaluate the short-term outcomes of non-vigorous infants born through meconium-stained amniotic fluid (MSAF) before and after implementation of no-tracheal suctioning guidelines. STUDY DESIGN: Single-center retrospective study of ≥36-week gestation neonates with MSAF. RESULTS: During routine-suction era (9/2013-12/2014), 280/2306 neonates (12%) were born through MSAF and 39 (14%) were non-vigorous. Thirty (77%) of non-vigorous infants underwent tracheal suctioning. In the no-suction era (1/2017-12/2018), 282/2918 neonates (9.7%) were born through MSAF and 30 (10.6%) were non-vigorous and one needed intubation. Admissions for meconium aspiration syndrome (15% vs 53%) and respiratory distress (18% vs 57%) were significantly higher among non-vigorous infants in the no-suction era. CONCLUSIONS: In this single-center study, non-vigorous infants born through MSAF without routine-tracheal suctioning had a higher incidence of NICU admission for MAS and respiratory distress compared to the routine-suction era. Multicenter randomized trials evaluating tracheal suction in non-vigorous infants with MSAF are warranted.

Lung ultrasound for the assessment of lung recruitment in neonates with massive pneumothorax during extracorporeal membrane oxygenation: a case report.

Bedside lung ultrasound may be an effective method for the assessment of lung recruitment in newborns with extracorporeal membrane oxygenation (ECMO). We report a case of a neonate who had severe hypoxemia with persistent pulmonary hypertension and massive pneumothorax due to meconium aspiration syndrome and was treated with ECMO. Positive pressure mechanical ventilation resulted in persistent massive air leakage from the disrupted pulmonary tissue. When ECMO was initiated, a "total lung rest" ventilation strategy was used to facilitate healing of the lung rupture and absorption of the pneumothorax. After complete absorption of the pneumothorax, lung recruitment was performed by progressively increasing the positive end-expiratory pressure under the guidance of lung ultrasound. Bedside lung ultrasound was successfully used to assess pneumothorax absorption and improvement of pulmonary inflammation and successfully guided the recruitment of collapsed alveoli and the withdrawal of ECMO.

Síndrome de aspiración meconial: revisión de la fisiopatología y estrategias de manejo / Meconium aspiration syndrome: review of the pathophysiology and management strategies

El síndrome de aspiración meconial, es una condición clínica caracterizada por insuficiencia respiratoria que ocurre en neonatos nacidos a través de líquido amniótico teñido de meconio, y que puede presentarse como una enfermedad grave con riesgo vital. Su incidencia ha disminuido gracias a mejores prácticas obstétricas y atención perinatal y se ha observado una mejoría en la sobrevida, gracias a mejores prácticas en la UCI neonatal. Sin embargo, el abordaje más adecuado sigue siendo un tema de debate, dado que hasta el momento se basa sólo en medidas de soporte, sin que existan medidas que actúen sobre los mecanismos de daño. Por otro lado, la morbilidad a largo plazo entre los sobrevivientes sigue siendo una preocupación importante. Esta revisión ofrece una visión general actualizada de la epidemiología, la fisiopatología, el diagnóstico, el manejo terapéutico, la prevención y el pronóstico de los pacientes que presentan este cuadro.

Meconium aspiration syndrome is a clinical condition characterized by respiratory failure that occurs in neonates born through meconium-stained amniotic fluid and can present as a serious life-threatening disease. Its incidence has decreased thanks to better obstetric practices and perinatal care, and an improvement in survival has been observed, thanks to better practices in the neonatal ICU. However, the most appropriate approach is still a matter of debate, given that so far it is based only on support measures, without any measures that act on the damage mechanisms. On the other hand, long-term morbidity among survivors remains a major concern. This review offers an updated overview of the epidemiology, pathophysiology, diagnosis, therapeutic management, prevention, and prognosis of patients with this condition.

The clinical effects of high-frequency oscillatory ventilation in the treatment of neonatal severe meconium aspiration syndrome complicated with severe acute respiratory distress syndrome.

OBJECTIVE: To explore the efficacy and safety of high-frequency oscillatory ventilation (HFOV) in the treatment of severe meconium aspiration syndrome (MAS) complicated with severe acute respiratory distress syndrome (ARDS). METHODS: A total of 65 infants with severe MAS complicated with severe ARDS were included in the study. The clinical efficacy of treatment for the HFOV group (n = 31) and the conventional mechanical ventilation (CMV) group (n = 34) was retrospectively analysed. The partial pressure of oxygen (PaO2), partial pressure of carbon dioxide (PaCO2), PaO2/fraction of inspired oxygen (FiO2), and oxygen index values before and at 6, 12, 24, 48, and 72 h after mechanical ventilation, the mechanical ventilation time, oxygen inhalation time, incidence of complications, and outcomes of the two groups were compared. RESULTS: At 6, 12, 24, and 48 h after mechanical ventilation, the PaO2 in the HFOV group was significantly higher than in the CMV group, while the PaCO2 in the HFOV group was significantly lower than in the CMV group (P < 0.05). At 6, 12, 24, 48, and 72 h after mechanical ventilation, PaO2/FiO2 in the HFOV group was significantly higher than in the CMV group, and the OI in the HFOV group was significantly lower than in the CMV group (P < 0.05). Mechanical ventilation time, oxygen inhalation time, and the incidence of air leakage were significantly lower in the HFOV than in the CMV group (P < 0.05). CONCLUSIONS: Overall, HFOV can effectively improve lung ventilation and oxygenation function, shorten ventilator treatment time, and reduce the incidence rate of air leakage for neonatal MAS, making it a safe and effective treatment option.

Clinical features and prognosis of severe meconium aspiration syndrome with acute respiratory distress syndrome. / é‡åº¦èƒŽç²ªå¸å ¥ç»¼åˆå¾å¹¶å‘æ€¥æ€§å‘¼å¸çª˜è¿«ç»¼åˆå¾ä¸´åºŠç‰¹å¾åŠè½¬å½’åˆ†æž.

OBJECTIVES: To study the clinical features and prognosis of neonates with severe meconium aspiration syndrome (MAS) and acute respiratory distress syndrome (ARDS). METHODS: A retrospective analysis was performed on the medical data of 60 neonates with severe MAS who were admitted from January 2017 to December 2019. According to the presence or absence of ARDS, they were divided into two groups: ARDS (n=45) and non-ARDS (n=15). Clinical features and prognosis were compared between the two groups. RESULTS: Among the 60 neonates with severe MAS, 45 (75%) developed ARDS. Arterial blood gas analysis showed that the ARDS group had a significantly higher median oxygenation index within 1 hour after birth than the non-ARDS group (4.7 vs 2.1, P<0.05), while there was no significant difference between the two groups in white blood cell count, C-reactive protein (CRP), and interleukin-6 (IL-6) on admission and the peak values of procalcitonin, CRP, and IL-6 during hospitalization (P>0.05). The ARDS group had a significantly higher incidence rate of shock than the non-ARDS group (84% vs 47%, P<0.05). There was no significant difference between the two groups in the incidence rates of persistent pulmonary hypertension, pneumothorax, pulmonary hemorrhage, hypoxic-ischemic encephalopathy, intracranial hemorrhage, and disseminated intravascular coagulation (P>0.05). The ARDS group required a longer median duration of mechanical ventilation than the non-ARDS group (53 hours vs 3 hours, P<0.05). In the ARDS group, 43 neonates (96%) were cured and 2 neonates (4%) died. In the non-ARDS group, all 15 neonates (100%) were cured. CONCLUSIONS: Neonates with severe MAS and ARDS tend to develop respiratory distress earlier, require a longer duration of mechanical ventilation, and have a higher incidence rate of shock. During the management of children with severe MAS, it is recommended to closely monitor oxygenation index, give timely diagnosis and treatment of ARDS, evaluate tissue perfusion, and actively prevent and treat shock. Citation.

A randomized single-center controlled trial of synchronized intermittent mandatory ventilation with heliox in newborn infants with meconium aspiration syndrome.

OBJECTIVE: This study aimed to investigate the beneficial effects of synchronized intermittent mandatory ventilation (SIMV) with heliox in newborn infants with meconium aspiration syndrome (MAS). METHODS: Seventy-one newborn infants with MAS in the neonatal intensive care unit (NICU) of Daping Hospital of Army Medical University were enrolled in the trial. Infants treated with SIMV were randomized and divided into the heliox group (n = 35) and control group (n = 36). The heliox group received heliox for 6 h followed by air-oxygen mixed gas, and the control group received air-oxygen mixed gas. The primary outcome measures were PaO2 /FiO2 (P/F) and the extubation time. The secondary outcome measures were the incidence of mechanical ventilation complications, hospital length of stay in the NICU, blood gas analysis, and inflammation markers. RESULTS: The P/F in the heliox group was significantly better than that in the control group (p < .001). The extubation time and hospital length of stay in the NICU in the heliox group were shorter than those in the control group (p < .001). The inflammation markers at 6 h and myocardial injury markers at 24 h were decreased compared with those at 0 h, and those in the heliox group were more significantly decreased than those in the control group ([interleukin {IL}-6/IL-8/tumor necrosis factor α] p < .001, [C-reaction protein] p = .012; [creatine kinase] p < .001, [CK-MB] p = .041). CONCLUSION: Heliox appears to be more effective in reducing the length of ventilation and increasing carbon dioxide eliminations than an air-oxygen mixture in infants with MAS under the support of SIMV.

Morbidity of conversion from venovenous to venoarterial ECMO in neonates with meconium aspiration or persistent pulmonary hypertension.

BACKGROUND: Outcomes in neonates receiving extracorporeal membrane oxygenation (ECMO) for meconium aspiration syndrome (MAS) and/or persistent pulmonary hypertension (PPHN) are favorable. Infants with preserved perfusion are often offered venovenous (VV) support to spare morbidities of venoarterial (VA) ECMO. Worsening perfusion or circuit complications can prompt conversion from VV-to-VA support. We examined whether outcomes in infants requiring VA ECMO for MAS/PPHN differed if they underwent VA support initially versus converting to VA after a VV trial, and what factors predicted conversion. METHODS: We reviewed the Extracorporeal Life Support Organization registry from 2007 to 2017 for neonates with primary diagnoses of MAS/PPHN. Propensity score analysis matched VA single-runs (controls) 4:1 against VV-to-VA conversions based on age, pre-ECMO pH, and precannulation arrests. Primary outcomes were complications and survival. Data were analyzed using Mann-Whitney U and Fisher's exact testing. Multivariate regression identified independent predictors of conversion for VV patients. RESULTS: 3831 neonates underwent ECMO for MAS/PPHN, including 2129 (55%) initially requiring VA support. Of 1702 patients placed on VV ECMO, 98 (5.8%) required VV-to-VA conversion. Compared with 364 propensity-matched isolated VA controls, conversion runs were longer (190 vs. 127 h, P < 0.001), were associated with more complications, and decreased survival to discharge (70% vs. 83%, P = 0.01). On multivariate regression, conversion was more likely if neonates on VV ECMO did not receive surfactant (OR = 1.7;95%CI = 1.1-2.7;P = 0.03) or required high-frequency ventilation (OR = 1.9;95%CI = 1.2-3.3;P = 0.01) before ECMO. CONCLUSION: Conversion from VV-to-VA ECMO in infants with MAS/PPHN conveys increased morbidity and mortality compared to similar patients placed initially onto VA ECMO. VV patients not receiving surfactant or requiring high-frequency ventilation before cannulation may have increased risk of conversion. While conversions remain rare, decisions to offer VV ECMO for MAS/PPHN must be informed by inferior outcomes observed should conversion be required. LEVEL OF EVIDENCE: Level of evidence 3 Retrospective comparative study.