Adapting nitric oxide: A review of its foundation, uses in austere medical conditions, and emerging applications.

Nitric oxide was first identified as a novel and effective treatment for persistent pulmonary hypertension of the newborn (PPHN), and has since been found to be efficacious in treating acute respiratory distress syndrome (ARDS) and pulmonary hypertension. Physicians and researchers have also found it shows promise in resource-constrained settings, both within and outside of the hospital, such as in high altitude pulmonary edema (HAPE) and COVID-19. The treatment has been well tolerated in these settings, and is both efficacious and versatile when studied across a variety of clinical environments. Advancements in inhaled nitric oxide continue, and the gas is worthy of investigation as physicians contend with new respiratory and cardiovascular illnesses, as well as unforeseen logistical challenges.

Inhaled Nitric Oxide in Neonatal Pulmonary Hypertension.

Pivotal trials investigating the use of inhaled nitric oxide (iNO) in the 1990s led to approval by the Food and Drug Administration in 1999. Inhaled nitric oxide is the only approved pulmonary vasodilator for persistent pulmonary hypertension of the newborn (PPHN). Selective pulmonary vasodilation with iNO in near-term and term neonates with PPHN is safe, and targeted use of iNO in less mature neonates with pulmonary hypertension (PH) can be beneficial. This review addresses a brief history of iNO, clinical features of neonatal PH, and the clinical application of iNO.

Clinical and echocardiography predictors of response to first-line acetaminophen treatment in preterm infants with hemodynamically significant patent ductus arteriosus.

OBJECTIVE: To assess clinical and echocardiography predictors of acetaminophen response for the treatment of patent ductus arteriosus (PDA) in preterm neonates. STUDY DESIGN: Retrospective cohort study of preterm infants born <30 weeks, with a diagnosis of hemodynamically significant PDA, who received 1st line treatment with intravenous acetaminophen during the first 2 postnatal weeks. Response was defined by PDA closure or improvement in PDA score of >50%. RESULTS: A total of 100 infants were included whose median weight and gestational age at birth were 663 grams and 24.6 weeks respectively. In total, 66 infants were classified as responders and were more likely to have intrauterine growth restriction, exposure to maternal hypertension and chorioamnionitis. Non-response was more common among infants with thrombocytopenia and anemia. CONCLUSION: Responders were more likely to be IUGR with echocardiography indices of lower preload. Response to 1st line intravenous acetaminophen therapy is comparable to non-steroidal drugs in preterm infants. Relationship of response to acetaminophen to perinatal characteristics requires further characterization.

Prostaglandin-E1 infusion in persistent pulmonary hypertension of the newborn.

BACKGROUND: Neonates with persistent pulmonary hypertension of the newborn (PPHN) can present with hypoxia and right ventricular dysfunction with resultant inadequate oxygen delivery and end-organ damage. This study describes the use of prostaglandin-E1 (PGE) for ductal patency to preserve right ventricular systolic function and limit afterload in newborns with PPHN. METHODS: This is a retrospective cohort study that follows the hemodynamics, markers of end-organ perfusion, length of therapeutics, and echocardiographic variables of 57 newborns who used prostglandin-E1 in the setting of PPHN. RESULTS: Tachycardia, lactic acidosis, and supplemental oxygen use improved following PGE initiation. Fractional area change (FAC), to assess right ventricular systolic function, and pulmonary arterial acceleration time indexed to right ventricular ejection time (PAAT/RVET), to assess right ventricular afterload, also improved over three time points relative to PGE use (before, during, and after). CONCLUSIONS: Overall, we described the safety and utility of PGE in newborns with severe PPHN for stabilization while allowing natural disease progression.

Impact of persistent pulmonary hypertension and oxygenation on brain injury in neonates with neonatal encephalopathy treated with therapeutic hypothermia.

OBJECTIVE: To investigate the effects of persistent pulmonary hypertension (PPHN) and oxygenation on outcome of neonates with neonatal encephalopathy (NE) treated with therapeutic hypothermia (TH). STUDY DESIGN: We compared the outcome of neonates with NE treated with TH with or without PPHN. RESULTS: 384 neonates with NE were treated with TH; 24% had PPHN. The fraction of inspired oxygen was higher in the first 4 days of life (p < 0.001) in neonates with PPHN. They had a significantly lower arterial partial pressure of oxygen in the first 4 days of life (p = 0.005) and higher on days 3-4 of life (p < 0.001). They were more often intubated (p < 0.001) and more often had concomitant hypotension (p < 0.001). They had higher mortality (p = 0.009) and more often developed brain injury (p = 0.02). CONCLUSION: PPHN occurred frequently in neonates with NE treated with TH and was associated with a higher incidence of adverse outcome.

Novel scoring tool of hypoxemic respiratory failure and pulmonary hypertension for defining severity of persistent pulmonary hypertension of newborn.

OBJECTIVE: To obtain preliminary validity data for a hypoxemic respiratory failure/pulmonary hypertension (HRF/PH) score for classifying persistent pulmonary hypertension of the newborn (PPHN). STUDY DESIGN: Retrospective chart review of 100 consecutive neonates admitted to a Children's hospital from 2016-2021 with PPHN, gestational age ≥34 weeks, and echocardiograms in the first week. We assessed the correlation between HRF/PH score and short-term outcomes using linear and logistic regressions. RESULTS: HRF/PH scores ranged 2-12 (mean 8.5), and were classified mild (0-5), moderate (6-10), and severe (11-15), with 6%, 77% and 17% infants in respective categories. HRF/PH score category correlated with invasive ventilation, nitric oxide, high frequency ventilation, vasoactive infusions, extracorporeal life support and death. HRF/PH score category did not correlate with duration of support or length of stay. CONCLUSION: The HRF/PH score offers a promising representation of disease severity for PPHN. The tool requires further validation in prospective studies and evaluation for long-term outcomes.

Comparison of the efficacy of inhaled versus infused milrinone in the management of persistent pulmonary hypertension of the newborn in resource-limited settings: A randomized clinical trial.

BACKGROUND: The standard treatment for persistent pulmonary hypertension of the newborn (PPHN) is inhaled nitric oxide (iNO), which is not available in Iran. Consequently, other drugs, such as milrinone, are prescribed. So far, no study has investigated the effectiveness of inhaled milrinone in the management of PPHN. The present study aimed to improve the management of PPHN in the absence of iNO. METHODS: In this randomized clinical trial, neonates with PPHN, admitted to the neonatal intensive care unit of Hazrat Ali-Asghar and Akbar-Abadi hospitals, were treated with intravenous dopamine infusion and randomly divided into two groups, receiving milrinone through inhalation or infusion rout. The neonates were evaluated by Doppler echocardiography, clinical examinations, and oxygen demand test. The neonates were also evaluated for the clinical symptoms and mortality in the follow-up. RESULTS: A total of 31 infants, with a median age of 2 days (interquartile range = 4), were included in this study. There was a significant decrease in the peak systolic and mean pulmonary arterial pressure in both inhalation and infusion groups following milrinone administration, with no significant difference between the groups (p = 0.584 and p = 0.147, respectively). There was no significant difference between the two groups regarding the mean systolic blood pressure before and after treatment. Additionally, diastolic blood pressure was significantly lower in the infusion group after treatment (p = 0.020); however, the amount of reduction was not significantly different between the groups (p = 0.928). Overall, 83.9% of the participants achieved full recovery, 75% of whom were in the infusion group and 93.3% in the inhalation group (p = 0.186). CONCLUSION: Milrinone inhalation can have similar effects to milrinone infusion as an adjunct treatment in the management of PPHN. Also, infusion and inhalation of milrinone showed similar safety.

Correlation of ABO blood groups with treatment response and efficacy in infants with persistent pulmonary hypertension of the newborn treated with inhaled nitric oxide.

OBJECTIVE: Not all infants with persistent pulmonary hypertension of the newborn (PPHN) respond to inhaled nitric oxide (iNO) therapy, as it is known to improve oxygenation in only 50% to 60% of cases. In this study, we investigated whether ABO blood groups were a relevant factor affecting the improvement of oxygenation by nitric oxide (NO) therapy in infants with PPHN. METHODS: This study was a retrospective, multicenter, and cohort-controlled trial that involved 37 medical units. Infants with PPHN who met the inclusion criteria and were treated with NO (a vasodilator) alone from July 1, 2015, to June 30, 2020, were selected and assigned into three groups: blood type A, blood type B, and blood type O (there were only 7 cases of blood type AB, with a small number of cases, and therefore, blood type AB was excluded for further analysis). The response to iNO therapy was defined as an increase in the ratio of the partial pressure of arterial oxygen (PaO2)/fraction of inspired oxygen (FiO2) > 20% from the basal value after treatment. Oxygenation was assessed mainly based on the two values, oxygenation index (OI) and PaO2/FiO2. The correlation of ABO blood groups with responses to iNO therapy and their influence on the efficacy of iNO therapy was analyzed based on the collected data. RESULTS: The highest proportion of infants with PPHN who eventually responded to iNO therapy was infants with blood type O. Infants with blood type O more readily responded to iNO therapy than infants with blood type B. Oxygenation after iNO treatment group was optimal in the blood type O group and was the worst in the blood type A group among the three groups. Infants with blood type O showed better efficacy than those with blood types A and B. CONCLUSION: ABO blood groups are correlated with responses to iNO therapy in infants with PPHN, and different blood groups also affect the efficacy of NO therapy in infants with PPHN. Specifically, infants with blood type O have a better response and experience the best efficacy to iNO therapy.

Management of neonatal pulmonary hypertension-a survey of neonatal intensive care units in India.

BACKGROUND: Persistent pulmonary hypertension of the newborn (PPHN) is a common neonatal condition associated with significant morbidity and mortality. First-line diagnostic and treatment options such as echocardiography and inhaled nitric oxide (iNO) are not routinely available in resource limited settings and alternative treatment modalities need to be utilized. This study was conducted to assess current diagnostic and management strategies used for PPHN in Indian neonatal intensive care units (NICUs). METHODS: A questionnaire in multiple choice question format was sent to practising neonatologists in India via an online survey tool between July to August 2021. Information pertaining to demographic data, diagnostic criteria and management strategies of PPHN was requested. The responses were collated and information processed. RESULTS: There were 118 respondent NICUs (response rate 74%). The majority of neonatal units (65%) admitted an average of 1-3 patients of PPHN per month. Targeted neonatal echocardiography (TnECHO) was practised in 80% of the units. Most common management strategies being followed were pulmonary vasodilators (88.1%), inotropes (85.6%), conventional ventilation (68.6%) and high frequency ventilation (59.3%). The most preferred pulmonary vasodilator was sildenafil (79%) and inotropic agent was milrinone (32%). Only 25% of respondents reported use of iNO. None of the participating units used extracorporeal membrane oxygenation. CONCLUSION: We found wide variability in management practices of PPHN across Indian NICUs. Non-selective pulmonary vasodilators are more widely used than iNO. There is an urgent need for structured TnECHO training programs and evidence based national guidelines for standardized management of PPHN as per availability of resources in India. Additional research on low cost alternative therapies to iNO in Indian settings might be helpful.

Milrinone Versus Sildenafil in Treatment of Neonatal Persistent Pulmonary Hypertension: A Randomized Control Trial.

ABSTRACT: Persistent pulmonary hypertension of the newborn (PPHN) is a condition caused by failure of pulmonary vascular adaptation at birth, resulting in severe hypoxia. Several therapeutic modalities are being tried in developing countries where established therapies (inhaled nitric oxide and extracorporeal membrane oxygenation) are widely unavailable. This study aimed to assess the efficacy of milrinone versus sildenafil as available alternative therapeutics in treating PPHN. Forty neonates (>34 weeks) admitted to neonatal intensive care units with evidence of PPHN were randomly allocated to receive either oral sildenafil (0.5-2 mg/kg/6 hours) or intravenous milrinone (0.25-0.75 mic/kg/min). Primary outcomes included improvements in systolic pulmonary artery pressure and oxygen saturation index (OSI) at 24 and 48 hours after treatment. Secondary outcomes included the duration of hospitalization and mechanical ventilation. The ClinicalTrials identifier is NCT04391478. Both groups showed significant improvement in the post-treatment hemodynamic variables compared with pretreatment levels ( P < 0.05 for all parameters). Systolic pulmonary artery pressure and OSI values significantly improved in both study groups compared with baseline ( P < 0.001). The 24-hour and 48-hour post-treatment OSI values were much lower in the milrinone group than those in the sildenafil group ( P < 0.05). The length of hospital stay was significantly shorter in the milrinone group than that in the sildenafil group ( P < 0.05). There were no significant differences in the duration of mechanical ventilation, incidence of intracranial hemorrhage and pulmonary hemorrhage, or mortality between the 2 groups ( P > 0.05). In conclusion, milrinone and sildenafil are effective and well-tolerated in neonates with PPHN, particularly when inhaled nitric oxide and extracorporeal membrane oxygenation are not available. Milrinone is superior to sildenafil in improving oxygenation without lowering blood pressure parameters.

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OBJECTIVES: To evaluate the early risk factors for death in neonates with persistent pulmonary hypertension of the newborn (PPHN) treated with inhaled nitric oxide (iNO). METHODS: A retrospective analysis was performed on 105 infants with PPHN (gestational age ≥34 weeks and age <7 days on admission) who received iNO treatment in the Department of Neonatology, Children's Hospital of Nanjing Medical University, from July 2017 to March 2021. Related general information and clinical data were collected. According to the clinical outcome at discharge, the infants were divided into a survival group with 79 infants and a death group with 26 infants. Univariate and multivariate Cox regression analyses were used to evaluate the risk factors for death in infants with PPHN treated with iNO. The receiver operating characteristic (ROC) curve was used to calculate the cut-off values of the factors in predicting the death risk. RESULTS: A total of 105 infants with PPHN treated with iNO were included, among whom 26 died (26/105, 24.8%). The multivariate Cox regression analysis showed that no early response to iNO (HR=8.500, 95%CI: 3.024-23.887, P<0.001), 1-minute Apgar score ≤3 points (HR=10.094, 95%CI: 2.577-39.534, P=0.001), a low value of minimum PaO2/FiO2 within 12 hours after admission (HR=0.067, 95%CI: 0.009-0.481, P=0.007), and a low value of minimum pH within 12 hours after admission (HR=0.049, 95%CI: 0.004-0.545, P=0.014) were independent risk factors for death. The ROC curve analysis showed that the lowest PaO2/FiO2 value within 12 hours after admission had an area under the ROC curve of 0.783 in predicting death risk, with a sensitivity of 84.6% and a specificity of 73.4% at the cut-off value of 50, and the lowest pH value within 12 hours after admission had an area under the ROC curve of 0.746, with a sensitivity of 76.9% and a specificity of 65.8% at the cut-off value of 7.2. CONCLUSIONS: Infants with PPHN requiring iNO treatment tend to have a high mortality rate. No early response to iNO, 1-minute Apgar score ≤3 points, the lowest PaO2/FiO2 value <50 within 12 hours after admission, and the lowest pH value <7.2 within 12 hours after admission are the early risk factors for death in such infants. Monitoring and evaluation of the above indicators will help to identify high-risk infants in the early stage.

Pulmonary vasodilator strategies in neonates with acute hypoxemic respiratory failure and pulmonary hypertension.

The management of acute hypoxemic respiratory failure (AHRF) in newborns continues to be a clinical challenge with elevated risk for significant morbidities and mortality, especially when accompanied with persistent pulmonary hypertension of the newborn (PPHN). PPHN is a syndrome characterized by marked hypoxemia secondary to extrapulmonary right-to-left shunting across the ductus arteriosus and/or foramen ovale with high pulmonary artery pressure and increased pulmonary vascular resistance (PVR). After optimizing respiratory support, cardiac performance and systemic hemodynamics, targeting persistent elevations in PVR with inhaled nitric oxide (iNO) therapy has improved outcomes of neonates with PPHN physiology. Despite aggressive cardiopulmonary management, a significant proportion of patients have an inadequate response to iNO therapy, prompting consideration for additional pulmonary vasodilator therapy. This article reviews the pathophysiology and management of PPHN in term newborns with AHRF while highlighting both animal and human data to inform a physiologic approach to the use of PH-targeted therapies.

Paracetamol Treatment for Patent Ductus Arteriosus, an Apparent Association with Acute Hemolysis in Three Preterm Infants: Case Series.

We report three preterm infants who were treated with paracetamol for hemodynamically significant patent ductus arteriosus and developed acute hemolysis. No other apparent cause of acute hemolysis was found during Neonatal Intensive Care Unit hospitalization. All three infants were born within 1 year. As this side effect of paracetamol has not been reported previously and many preterm infants receive paracetamol for PDA closure, we advocate awareness. We cannot be sure whether the hemolysis occurred due to an underlying cause that was augmented by paracetamol or whether the drug itself caused acute hemolysis in these preterm infants.

Using real-world data in pediatric clinical trials: Lessons learned and future applications in studies of persistent pulmonary hypertension of the newborn.

Persistent pulmonary hypertension of the newborn (PPHN) is a complication of term birth, characterized by persistent hypoxemia secondary to failure of normal postnatal reduction in pulmonary vascular resistance, with potential for short- and long-term morbidity and mortality. The primary pharmacologic goal for this condition is reduction of the neonate's elevated pulmonary vascular resistance with inhaled nitric oxide, the only approved treatment option. Various adjunctive, unapproved therapeutics have been trialed with mixed results, likely related to challenges with recruiting the full, intended patient population into clinical studies. Recently, real-world data and subsequent derived evidence have been utilized to improve the efficiency of various pediatric clinical trials. We aim to provide recent perspectives regarding the use of real-world data in the planning and execution of pediatric clinical trials and how this may facilitate more streamlined assessment of future therapeutics for the treatment of PPHN and other neonatal conditions.

Pulmonary hypertension and oxidative stress: Where is the link?

Oxidative stress can be associated with hyperoxia and hypoxia and is characterized by an increase in reactive oxygen (ROS) and nitrogen (RNS) species generated by an underlying disease process or by supplemental oxygen that exceeds the neutralization capacity of the organ system. ROS and RNS acting as free radicals can inactive several enzymes and vasodilators in the nitric oxide pathway promoting pulmonary vasoconstriction resulting in persistent pulmonary hypertension of the newborn (PPHN). Studies in animal models of PPHN have shown high ROS/RNS that is further increased by hyperoxic ventilation. In addition, antioxidant therapy increased PaO2 in these models, but clinical trials are lacking. We recommend targeting preductal SpO2 between 90 and 97%, PaO2 between 55 and 80 mmHg and avoiding FiO2 > 0.6-0.8 if possible during PPHN management. This review highlights the role of oxidative and nitrosative stress markers on PPHN and potential therapeutic interventions that may alleviate the consequences of increased oxidant stress during ventilation with supplemental oxygen.

Is inhaled nitric oxide a miraculous molecule? The analysis of nitric oxide use in newborns with persistent pulmonary hypertension of the newborn.

AIM: The aim of this study was to establish a set of hospitalised patients with persistent pulmonary hypertension of the newborn (PPHN) by using retrospective analysis according to gestational age, position during childbirth, type of childbirth, dosage and length of the treatment by inhaled nitric oxide (NO) and application of inotropic agents as well as interindividual specifics and the background of PPHN. RESULTS: Our cohort consisted of 11 newborns who were hospitalised in Neonatal Department of Intensive Medicine between 1st January 2017 and 31st December 2019. Four of these patients were born prematurely. Only two out of eleven patients were born vaginally. Nine of the newborns were diagnosed with secondary PPHN, in three of these cases it was caused by infection. The highest dose of inhaled nitric oxide used was 40 ppm. CONCLUSION: The focus of this paper was the therapeutic use of nitric oxide, its various applications and the effect of it on pulmonary circulation of the newborn. Inhaled NO is a selective pulmonary vasodilator used as a therapeutic agent for PPHN of the newborn. The conclusions of this paper can be beneficial in the development of better therapeutic strategies for patients with PPHN in the future (Tab. 3, Fig. 1, Ref. 40).

Vasopressin for refractory persistent pulmonary hypertension of the newborn in preterm neonates - a case series.

OBJECTIVE: To describe the clinical outcomes following treatment with vasopressin for a sub-cohort of critically ill preterm neonates who have refractory persistent pulmonary hypertension of the newborn (PPHN). DESIGN: Case series. SETTING: Tertiary neonatal intensive care unit, Toronto, Canada. POPULATION: Neonates born <37 weeks gestational age (GA) who received vasopressin for refractory PPHN (lack of response to inhaled nitric oxide) over a 4-year period. MEASUREMENTS: Changes in physiological indices of cardio-pulmonary stability during vasopressin therapy were analyzed using one-way repeated measures ANOVA, compared to pretreatment values. Data regarding survival to discharge and neurodevelopmental outcomes at 18-24 months were described. MAIN RESULTS: Thirteen neonates with a mean GA of 31.4 ± 3.3 weeks were included. Vasopressin was initiated at 28.5 ± 4.5 h of age. Overall, oxygenation and hemodynamic variables improved significantly following vasopressin therapy (p < .05 at 24 h vs. pretreatment). Oxygenation failure resolved in 8 cases, of which 7 patients survived (6 without disability). Among the 5 cases where oxygenation failure persisted despite vasopressin, 4 died while one survived with disability. CONCLUSIONS: Vasopressin offers promise as a therapy for preterm neonates with refractory PPHN and hemodynamic instability, but prospective investigation is needed.

Worsened short-term clinical outcomes in a cohort of patients with iNO-unresponsive PPHN: a case for improving iNO responsiveness.

OBJECTIVES: To identify distinguishing characteristics of neonates with persistent pulmonary hypertension of the newborn (PPHN) unresponsive to inhaled nitric oxide (iNO) and evaluate the use of milrinone in this cohort. STUDY DESIGN: Retrospective chart review of 99 neonates with PPHN treated with iNO over a five-year period at a quaternary neonatal intensive care unit. RESULTS: Neonates with iNO-unresponsive PPHN had an increased number of ventilator days (10 vs 7 days, p = 0.02), greater length of hospital stay (30 vs 22 days, p = 0.02), and increased risk of death or ECMO than iNO-responsive neonates (p = 0.03). Inhaled NO non-responders treated with milrinone had improved oxygenation (p < 0.03) and no change in systemic hemodynamics. CONCLUSION: Neonates with iNO-unresponsive PPHN had worse clinical outcomes than iNO responders. Milrinone may be a safe and effective adjuvant therapy, although large-scale studies are lacking. Identifying early predictors of iNO response and novel strategies to enhance iNO responsiveness should be prioritized.