Effects of Ruscus extract on muscarinic receptors: Is there a role for endothelium derived relaxing factors on macromolecular permeability protection and microvascular diameter changes?

BACKGROUND: Protective effects of Ruscus extract on macromolecular permeability depend on its capacity to stimulate muscarinic receptors on endothelial cells and induce the release of endothelium derived relaxing factors (EDRFs). OBJECTIVE: To investigate if these effects depend only on activation of muscarinic receptors or if EDRFs release are also necessary. We have also investigated the participation of Ruscus extract on muscarinic-induced release of EDRFs on microvascular diameters. METHODS: Hamsters were treated daily during two weeks with Ruscus extract (50, 150 and 450 mg/kg/day) and then macromolecular permeability induced by histamine and arteriolar and venular diameters after cyclooxygenase (COX) and nitric oxide synthase (NOS) inhibitors: indomethacin and Nω-Nitro-L-arginine (LNA), respectively applied topically at 10-8M, 10-6M and 10-4M were observed on the cheek pouch preparation. RESULTS: Ruscus extract decreased macromolecular permeability in a dose-dependent fashion and did not affect microvascular diameters. NOS and COX inhibitors enhanced its effect on microvascular permeability. NOS inhibition reduced arteriolar diameter and COX blocking decreased arteriolar and venular diameters at the lowest dose and increased them at higher doses of Ruscus extract. CONCLUSION: The protective effect of Ruscus extract on macromolecular permeability seems to be mediated only via muscarinic receptors. Muscarinic activation attenuated vasoconstrictive tone through cyclooxygenase-independent endothelium derived relaxing factors.

Thrombocytopathy and endotheliopathy: crucial contributors to COVID-19 thromboinflammation.

The core pathology of coronavirus disease 2019 (COVID-19) is infection of airway cells by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that results in excessive inflammation and respiratory disease, with cytokine storm and acute respiratory distress syndrome implicated in the most severe cases. Thrombotic complications are a major cause of morbidity and mortality in patients with COVID-19. Patients with pre-existing cardiovascular disease and/or traditional cardiovascular risk factors, including obesity, diabetes mellitus, hypertension and advanced age, are at the highest risk of death from COVID-19. In this Review, we summarize new lines of evidence that point to both platelet and endothelial dysfunction as essential components of COVID-19 pathology and describe the mechanisms that might account for the contribution of cardiovascular risk factors to the most severe outcomes in COVID-19. We highlight the distinct contributions of coagulopathy, thrombocytopathy and endotheliopathy to the pathogenesis of COVID-19 and discuss potential therapeutic strategies in the management of patients with COVD-19. Harnessing the expertise of the biomedical and clinical communities is imperative to expand the available therapeutics beyond anticoagulants and to target both thrombocytopathy and endotheliopathy. Only with such collaborative efforts can we better prepare for further waves and for future coronavirus-related pandemics.

Methemoglobin and the response to inhaled nitric oxide in persistent pulmonary hypertension of the newborn.

BACKGROUND: We aimed to investigate whether the change in methemoglobin levels (ΔMHb) predicts oxygenation response to inhaled nitric oxide (iNO) in persistent pulmonary hypertension of the newborn (PPHN) with lung disease, with or without pulmonary hypoplasia. METHODS: In this prospective observational study, infants were categorized based on ΔMHb and oxygenation response (ΔPaO2/FiO2) following iNO: ΔMHb ≤0 or ΔMHb>0, and ΔPaO2/FiO2 < 20 mmHg (Non-responder) or≥20 mmHg (Responder). ΔMHb levels were compared among infants with or without pulmonary hypoplasia. RESULTS: Among infants with pulmonary hypoplasia (n = 28), ΔMHb was not associated with an oxygenation response to iNO or survival without ECMO. Among infants without hypoplasia (n = 29), subjects with ΔMHb>0 following iNO (n = 21) had a greater ΔPaO2/FiO2 (median, 64 mmHg; IQR, 127; p < 0.01) and 100% survival without extracorporeal membrane oxygenation (ECMO) when compared to infants with ΔMHb ≤0 (n = 8; median 10 mmHg; IQR, 33). CONCLUSIONS: PPHN secondary to lung disease without hypoplasia with increased ΔMHb following iNO was associated with better oxygenation response and survival without ECMO compared to subjects without an increase in MHb.

Anti-inflammatory and endothelium protective effect of long-term pioglitazone intake in patients suffering from bronchial asthma concurrent with ischemic heart disease.

INTRODUCTION: Treatment of co-morbidities, including bronchial asthma (BA) and coronary heart disease (CHD), is a relevant issue of modern therapy. The aim of the research is to study the impact of long-term intake of pioglitazone on the development of inflammation and ED in patients with BA concurrent with CHD. MATERIAL AND METHODS: The clinical study involved 50 people aged 40-75 who suffered from asthma concurrent with CHD. On the first day of the study, blood samples were collected and clinical examinations were performed, after which patients were randomized and divided into the control group who continued to receive only the standard therapy, and the study group, who received pioglitazone (Pioglar, Ranbaxy, India) 15 mg once a day along with comprehensive therapy. Re-examination was carried out in 6 months. RESULTS: It has been found that inclusion of pioglitazone in the course of standard therapy in patients with asthma concurrent with coronary heart within 6 months is a more efficient scheme than the course of standard therapies. According to the data obtained from the patients, there was a significant decrease in respiratory rate (p<0.01), levels of systolic blood pressure (p<0.001) and diastolic blood pressure (p<0.001). Administering pioglitazone contributed to the improvement of respiratory function and airflow obstruction, increased FEV1 performance (p<0.01) and Tiffeneau index (p<0.05). In patients of the study group, intake of pioglitazone helped to reduce angina. Intake of pioglitazone showed a significant decrease in the frequency of angina pectoris FC II (p<0.05) and a significant increase in the frequency of angina FC I (p<0.05), increase in the rate of threshold load power (p<0.05). In assessing endothelium-dependent vasodilation of the brachial artery, it has been noted that intake of pioglitazone by patients with asthma concurrent with coronary heart disease resulted in a statistically significant increase in the diameter of the brachial artery by an average of 4% (p<0.0001), the maximum blood flow velocity (TAMX) by an average of 40 % (p<0.0001), Δ% diameter increase in the brachial artery (p<0.0001), and achieved positive indicators of RI (p<0.0001). In assessing endothelium-dependent vasodilation of brachial artery in patients treated with pioglitazone, there was a significant increase in the diameter of brachial artery on average by 5% (p<0.0001) after taking nitroglycerin, an increase in ?% diameter of brachial artery (p<0.0001) and RI (p<0.0001). Inclusion of pioglitazone in the complex therapy for 6 months resulted in a significant decrease in the index of systemic inflammation hs-CRP (p<0.0001) and adhesion marker sVCAM-1 (p<0.0001), total cholesterol (p<0.001), triglycerides (p<0.001). CONCLUSION: Thus, these data demonstrate the anti-inflammatory and endothelium protective effects of pioglitazone against the background of standard therapy in patients with BA concurrent with CHD within 6 months, which may enhance the clinical efficacy in the treatment of these diseases.

Intestinal perforation in the premature infant.

OBJECTIVE: To compare demographic data, prenatal and postnatal characteristics, laboratory data, and outcomes in a cohort of premature infants with spontaneous ileal perforation (SIP), surgical necrotizing enterocolitis (sNEC) and matched controls. METHODS: A retrospective case-control study of infants with intestinal perforation with a birth weight (BW) less than 2,000 grams and gestational age (GA) less than 34 weeks and infants without perforation matched for BW (±150 grams) and GA (±1week). RESULTS: 130 premature infants were included, 30 infants with SIP, 35 infants with sNEC and 65 control infants. The median age of onset was 5 days postnatal age in SIP versus 25 days in sNEC (p < 0.001) and the peak onset was at 26 weeks corrected GA for SIP and 30 weeks corrected GA for sNEC. Infants with perforation had significantly higher rates of mortality (p < 0.001) and common morbidities associated with prematurity. Administration of corticosteroids and indomethacin did not differ among groups. SIP was more common among infants born to young mothers (p = 0.04) and less common in infants receiving caffeine (p = 0.02). sNEC was less common among infants receiving early red cell transfusion (p = 0.01). Perforation and sNEC trended towards less common in infants receiving inhaled nitric oxide. CONCLUSION: SIP and sNEC are distinct clinical entities. Potential protective effects of caffeine, inhaled nitric oxide, and early transfusion should be further studied.

Enhanced tumor therapy via drug co-delivery and in situ vascular-promoting strategy.

Conventional tumor starving therapy by reducing its vessel density may be effective at early treatment but potentially contributes to tumor hypoxia, drug resistance and metastasis. A new strategy through enhancing tumor angiogenesis in combination with effective chemotherapeutic drugs, has shown successful tumor growth and spread inhibition. To achieve in situ release of angiogenic and antitumor drugs in tumor, we designed a precise ratiometric polymeric hybrid micelle system for co-delivering nitric oxide and paclitaxel. The hybrid micelles could accumulate in tumor via the long blood circulation and enhanced permeability and retention (EPR) effect, promote the drug accumulation and penetration in tumor by in situ increased vascular permeability, blood perfusion and vessel density, achieve the synergistic antitumor effect of nitric oxide and paclitaxel through modified tumor microenvironment, overcome multidrug resistance and inhibit metastasis. This study presents a combinational therapy against tumor progression and spread, which shows great potential in cancer therapy of the future.

Methemoglobin and nitric oxide therapy in Ugandan children hospitalized for febrile illness: results from a prospective cohort study and randomized double-blind placebo-controlled trial.

BACKGROUND: Exposure of red blood cells to oxidants increases production of methemoglobin (MHb) resulting in impaired oxygen delivery to tissues. There are no reliable estimates of methemoglobinemia in low resource clinical settings. Our objectives were to: i) evaluate risk factors for methemoglobinemia in Ugandan children hospitalized with fever (study 1); and ii) investigate MHb responses in critically ill Ugandan children with severe malaria treated with inhaled nitric oxide (iNO), an oxidant that induces MHb in a dose-dependent manner (study 2). METHODS: Two prospective studies were conducted at Jinja Regional Referral Hospital in Uganda between 2011 and 2013. Study 1, a prospective cohort study of children admitted to hospital with fever (fever cohort, n = 2089 children 2 months to 5 years). Study 2, a randomized double-blind placebo-controlled parallel arm trial of room air placebo vs. 80 ppm iNO as an adjunctive therapy for children with severe malaria (RCT, n = 180 children 1-10 years receiving intravenous artesunate and 72 h of study gas). The primary outcomes were: i) masimo pulse co-oximetry elevated MHb levels at admission (>2 %, fever cohort); ii) four hourly MHb levels in the RCT. RESULTS: In the fever cohort, 34 % of children admitted with fever had elevated MHb at admission. Children with a history of vomiting, delayed capillary refill, elevated lactate, severe anemia, malaria, or hemoglobinopathies had increased odds of methemoglobinemia (p < 0.05 in a multivariate model). MHb levels at admission were higher in children who died (n = 89) compared to those who survived (n = 1964), p = 0.008. Among children enrolled in the iNO RCT, MHb levels typically plateaued within 12-24 h of starting study gas. MHb levels were higher in children receiving iNO compared to placebo, and MHb > 10 % occurred in 5.7 % of children receiving iNO. There were no differences in rates of study gas discontinuation between trial arms. CONCLUSIONS: Hospitalized children with evidence of impaired oxygen delivery, metabolic acidosis, anemia, or malaria were at risk of methemoglobinemia. However, we demonstrated high-dose iNO could be safely administered to critically ill children with severe malaria with appropriate MHb monitoring. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01255215 (Date registered: December 5, 2010).

Elevated plasma ADMA contributes to development of endothelial dysfunction in children with acute lymphoblastic leukemia.

BACKGROUND: Childhood acute lymphoblastic leukemia (ALL) survivors are at higher cardiovascular risk than the general population, which may result from anthracycline-related endothelial dysfunction (ED). However, a few studies indirectly show that ED may appear in ALL children before treatment begins. Hence, in this study we intended to verify the hypothesis that ED is part of the ALL phenotype. PATIENTS/METHODS: Twenty-eight ALL children and 14 healthy age-matched control children were recruited. The study group was examined at baseline, then at the 33rd and 78th day of treatment. At each step of the protocol endothelial vasodilative function was assessed by a laser Doppler flowmeter, which was followed by blood collecting for subsequent analyses. RESULTS: Compared to controls, the study group at baseline was characterized by significantly lower endothelial vasodilative responsiveness, accompanied by elevated asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) concentrations, which were correlated with lactate dehydrogenase (LDH) and aspartate transaminase (AST). Initial ALL treatment restored endothelial function, which followed changes in ADMA and LDH concentrations. DISCUSSION: This is the first demonstration that functionally assessed ED is present in ALL children at the diagnosis and results from elevated ADMA and parallel inflammatory ED.

Pulmonary hypertension associated with acute or chronic lung diseases in the preterm and term neonate and infant. The European Paediatric Pulmonary Vascular Disease Network, endorsed by ISHLT and DGPK.

Persistent pulmonary hypertension of the newborn (PPHN) is the most common neonatal form and mostly reversible after a few days with improvement of the underlying pulmonary condition. When pulmonary hypertension (PH) persists despite adequate treatment, the severity of parenchymal lung disease should be assessed by chest CT. Pulmonary vein stenosis may need to be ruled out by cardiac catheterisation and lung biopsy, and genetic workup is necessary when alveolar capillary dysplasia is suspected. In PPHN, optimisation of the cardiopulmonary situation including surfactant therapy should aim for preductal SpO2between 91% and 95% and severe cases without post-tricuspid-unrestrictive shunt may receive prostaglandin E1 to maintain ductal patency in right heart failure. Inhaled nitric oxide is indicated in mechanically ventilated infants to reduce the need for extracorporal membrane oxygenation (ECMO), and sildenafil can be considered when this therapy is not available. ECMO may be indicated according to the ELSO guidelines. In older preterm infant, where PH is mainly associated with bronchopulmonary dysplasia (BPD) or in term infants with developmental lung anomalies such as congenital diaphragmatic hernia or cardiac anomalies, left ventricular diastolic dysfunction/left atrial hypertension or pulmonary vein stenosis, can add to the complexity of the disease. Here, oral or intravenous sildenafil should be considered for PH treatment in BPD, the latter for critically ill patients. Furthermore, prostanoids, mineralcorticoid receptor antagonists, and diuretics can be beneficial. Infants with proven or suspected PH should receive close follow-up, including preductal/postductal SpO2measurements, echocardiography and laboratory work-up including NT-proBNP, guided by clinical improvement or lack thereof.

Pulmonary hypertension in the intensive care unit. Expert consensus statement on the diagnosis and treatment of paediatric pulmonary hypertension. The European Paediatric Pulmonary Vascular Disease Network, endorsed by ISHLT and DGPK.

Acute pulmonary hypertension (PH) complicates the course of several cardiovascular, pulmonary and other systemic diseases in children. An acute rise of RV afterload, either as exacerbating chronic PH of different aetiologies (eg, idiopathic pulmonary arterial hypertension (PAH), chronic lung or congenital heart disease), or pulmonary hypertensive crisis after corrective surgery for congenital heart disease, may lead to severe circulatory compromise. Only few clinical studies provide evidence on how to best treat children with acute severe PH and decompensated RV function, that is, acute RV failure. The specific treatment in the intensive care unit should be based on the underlying pathophysiology and not only be focused on so-called 'specific' or 'tailored' drug therapy to lower RV afterload. In addition therapeutic efforts should aim to optimise RV preload, and to achieve adequate myocardial perfusion, and cardiac output. Early recognition of patients at high risk and timely initiation of appropriate therapeutic measures may prevent the development of severe cardiac dysfunction and low cardiac output. In patients not responding adequately to pharmacotherapy, (1) novel surgical and interventional techniques, temporary mechanical circulatory support with extracorporeal membrane oxygenation, (2) pumpless lung assist devices (3) and/or lung or heart-lung transplantation should be timely considered. The invasive therapeutic measures can be applied in a bridge-to-recovery or bridge-to-lung transplant strategy. This consensus statement focuses on the management of acute severe PH in the paediatric intensive care unit and provides an according treatment algorithm for clinical practice.

Treatment of children with pulmonary hypertension. Expert consensus statement on the diagnosis and treatment of paediatric pulmonary hypertension. The European Paediatric Pulmonary Vascular Disease Network, endorsed by ISHLT and DGPK.

Treatment of children and adults with pulmonary hypertension (PH) with or without cardiac dysfunction has improved in the last two decades. The so-called pulmonary arterial hypertension (PAH)-specific medications currently approved for therapy of adults with PAH target three major pathways (endothelin, nitric oxide, prostacyclin). Moreover, some PH centres may use off-label drugs for compassionate use. Pulmonary hypertensive vascular disease (PHVD) in children is complex, and selection of appropriate therapies remains difficult. In addition, paediatric PAH/PHVD therapy is vastly based on experience and trial data from adult rather than paediatric studies; however, the first randomised paediatric PAH trials have been conducted recently. We present consensus recommendations for the treatment of children with PH. Class of recommendation and level of evidence were assigned based on paediatric data only or on adult studies that included >10% children. After a systematic literature search and analysis of the published data, we developed treatment strategies and algorithms that can guide goal-oriented PH therapy. We discuss early combination therapy (double, triple) in patients with PAH in functional class II-IV and in those with inadequate response to the initial pharmacotherapy. In those children with progressive, severe PAH and inadequate response, advances in drug development, and interventional and surgical approaches provide promising new strategies to avoid, reverse or ameliorate right heart failure and left ventricular compression. In particular, first follow-up data indicate that Potts shunt (left pulmonary artery to descending aorta anastomosis) may be an alternative destination therapy, or bridge to bilateral lung transplantation, in end-stage paediatric PAH.

Adding insult to injury: autoimmune haemolytic anaemia complicated by pulmonary embolism.

Autoimmune haemolytic anaemia (AIHA) is a disease characterised by the production of pathological antibodies that attach to the surface of a patient's own red blood cells, resulting in haemolysis. It can present in either an acute or a chronic manner. In addition to the obvious consequence of anaemia, there are other potentially deadly complications that can arise from AIHA, such as venous thromboembolism (VTE) and pulmonary hypertension. We report a case of a 52-year-old woman who developed a pulmonary embolism (PE) soon after being diagnosed with AIHA. Despite having a very small pulmonary venous clot burden, she developed profound haemodynamic compromise with severe right ventricular dysfunction, which quickly reversed with inhaled nitric oxide treatment. This case makes an interesting observation of cell-free haemoglobin-associated nitric oxide scavenging as a mechanism of pulmonary hypertension and highlights the possible benefit of nitric oxide in treatment.

Pulmonary Hypertension and Vascular Abnormalities in Bronchopulmonary Dysplasia.

Despite advances in the care of preterm infants, these infants remain at risk bronchopulmonary dysplasia (BPD), which results in prolonged need for supplemental oxygen, recurrent respiratory exacerbations, and exercise intolerance. Recent investigations have highlighted the important contribution of the developing pulmonary circulation to lung development, showing that these infants are also at risk for pulmonary vascular disease (PVD), including pulmonary hypertension (PH) and pulmonary vascular abnormalities. Several epidemiologic studies have delineated the incidence of PH in preterm infants and the impact on outcomes. These studies have also highlighted gaps in the understanding of PVD in BPD.

Nitric oxide (NO): an emerging target for the treatment of glaucoma.

The predominant risk factor for the progression of glaucoma is an increase in IOP, mediated via a reduction in aqueous outflow through the conventional (trabecular meshwork and Schlemm's canal) outflow pathway. Current IOP lowering pharmacological strategies target the uveoscleral (nonconventional) outflow pathway or aqueous humor production; however, to date no therapy that primarily targets the conventional pathway exists. Nitric oxide (NO) is an intracellular signaling molecule produced by endogenous NO synthases, well-known for its key role in vasodilation, through its action on smooth muscle cells. Under physiological conditions, NO mediates a multitude of diverse ocular effects, including maintenance of IOP. Nitric oxide donors have been shown to mediate IOP-lowering effects in both preclinical models and clinical studies, primarily through cell volume and contractility changes in the conventional outflow tissues. This review is focused on evaluating the current knowledge of the role and mechanism of action of endogenous NO and NO donors in IOP regulation. Data on key additional functions of NO in glaucoma pathology (i.e., ocular blood flow and effects on optic neuropathy) are also summarized. The potential for future therapeutic application of NO in the treatment of glaucoma is then discussed.

The effect of inhaled nitric oxide therapy on thromboelastogram in newborns with persistent pulmonary hypertension.

UNLABELLED: Studies about the effects of inhaled nitric oxide (iNO) on bleeding time and platelet aggregation in newborns are limited in number and have inconclusive results. Thromboelastogram (TEG) shows the combined effects of coagulation factors and platelet functions. In this preliminary study, we aimed to evaluate the effects of iNO on coagulation using TEG in newborns with persistent pulmonary hypertension (PPH). TEG assays were performed in 10 term infants receiving iNO treatment for PPH and 32 healthy term infants. Samples of the iNO group were collected before and during iNO. Clot reaction time (R), clot kinetics (K), maximum amplitude (MA), and alpha angle were obtained from the TEG tracing. TEG-R values were statistically higher during iNO treatment (7.75 ± 3.34) when compared to the values before iNO (4.83 ± 1.38) and the healthy controls (3.75 ± 0.98). The alpha angle was lower in iNO treated infants at both periods (before iNO, 55.33 ± 8.58; during iNO, 42.90 ± 18.34) compared to the control group (64.95 ± 6.88). MA values before iNO treatment were the lowest (44.43 ± 14.09) and improved with the iNO treatment (48.40 ± 9.49) despite still being lower compared to the controls (53.67 ± 5.56). CONCLUSION: Both PPH and iNO may negatively effect in vitro coagulation tests. Therefore, newborns with PPH requiring iNO treatment should be closely monitored for coagulation problems.

Update on PPHN: mechanisms and treatment.

Persistent pulmonary hypertension of the newborn (PPHN) is a syndrome of failed circulatory adaptation at birth, seen in about 2/1000 live born infants. While it is mostly seen in term and near-term infants, it can be recognized in some premature infants with respiratory distress or bronchopulmonary dysplasia. Most commonly, PPHN is secondary to delayed or impaired relaxation of the pulmonary vasculature associated with diverse neonatal pulmonary pathologies, such as meconium aspiration syndrome, congenital diaphragmatic hernia, and respiratory distress syndrome. Gentle ventilation strategies, lung recruitment, inhaled nitric oxide, and surfactant therapy have improved outcome and reduced the need for extracorporeal membrane oxygenation (ECMO) in PPHN. Newer modalities of treatment discussed in this article include systemic and inhaled vasodilators like sildenafil, prostaglandin E1, prostacyclin, and endothelin antagonists. With prompt recognition/treatment and early referral to ECMO centers, the mortality rate for PPHN has significantly decreased. However, the risk of potential neurodevelopmental impairment warrants close follow-up after discharge for infants with PPHN.

Ischemia-reperfusion injury: influencing the microcirculatory and cellular environment.

Ischemia-reperfusion injury forms the basis of tissue damage and cellular apoptosis in many pathologic and traumatic processes. The tissue damage follows a natural progression of cellular and metabolic events initiated by an ischemic episode. Ischemia causes intracellular/extracellular changes principally resulting in increased intracellular calcium, pH changes, and adenosine triphosphate depletion that end in cell death if the process is not interrupted. This interruption takes the form of reperfusion, characterized by a "flushing" of tissues with toxic metabolites, principally reactive oxygen species. The immediate effect is mitochondrial pore permeability, complement activation, cytochrome release, cytokine activation, inflammation, edema, neutrophil platelet adhesion, capillary plugging, and thrombosis. This sets the stage for the long recognized "no-reflow" phenomenon and progressive tissue death. Current recognition of cellular "cross-talk" and molecular events have introduced new logical strategies to sequentially combat the events occurring in relation to ischemia-reperfusion injury. These include mechanical preconditioning and pharmacological preconditioning and postconditioning strategies. It is likely that success in reversing or limiting tissue damage will be found in a sequential multitargeted approach using a combination of these strategies-clinical trials in this regard are sorely needed.

Variation in the management of persistent pulmonary hypertension of the newborn: a survey of physicians in Canada, Australia, and New Zealand.

BACKGROUND: Despite advances in management of persistent pulmonary hypertension of the newborn (PPHN), the risk of mortality and adverse neurological sequelae remains high. Characterizing variation in practices is a crucial step toward improved patient outcome. OBJECTIVE: Evaluate intensive care practices in Canada and the Australia-New Zealand region (AUS-NZ). METHODS: A prospective cross-sectional online survey of neonatologists was conducted. A 35-item questionnaire was developed, validated, and piloted to collect information on diagnosis, inhaled nitric oxide (iNO) practices, alternative vasodilators or cardiotropes, and echocardiography. Variation among survey respondents as well as intergroup comparison was performed. RESULTS: Data were collected from 217 respondents. Echocardiography and arterial blood gas were the most common diagnostic tests to assess the severity of PPHN. iNO administration is more frequently scrutinized in Canada (36% versus 10% [AUS-NZ], p < 0.001). Canadian physicians reported higher use of intravenous milrinone (p < 0.001), vasopressin (p = 0.02), and inhaled prostacyclin (p = 0.02), but lower use of sildenafil (p = 0.01) for refractory pulmonary hypertension. A greater proportion of neonatologists in AUS-NZ were trained to perform echocardiography (p < 0.001) to optimize treatment decisions. CONCLUSION: Wide variation exists in the management of PPHN. There is a need to provide more guidance regarding principles of management in PPHN, while recognizing the dynamic nature of cardiopulmonary physiology in individual patients.