Magnesium sulphate as an alternative and safe treatment for severe persistent pulmonary hypertension of the newborn

Zinc attenuates monocrotaline-induced pulmonary hypertension in rats through upregulation of A20

Pulmonary hypertension (PH) is characterized by excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), in which inflammatory signaling caused by activation of the NF-κB pathway plays an important role. A20 is an important negative regulator of the NF-κB pathway, and zinc promotes the expression of A20 and exerts a protective effect against various diseases (e.g. COVID19) by inhibiting the inflammatory signaling. The role of A20 and intracellular zinc signaling in PH has been explored, but the extracellular zinc signaling is not well understood, and whether zinc has protective effects on PH is still elusive. Using inductively coupled plasma mass spectrometry (ICP-MS), we studied the alteration of trace elements during the progression of monocrotaline (MCT)-induced PH and found that serum zinc concentration was decreased with the onset of PH accompanied by abnormalities of other three elements, including copper, chromium, and magnesium. Zinc chloride injection with the dosage of 5 mg/kg intraperitoneally partially corrected this abnormality and inhibited the progression of PH. Zinc supplementation induced the expression of A20 in lung tissue and reduce the inflammatory responses. In vitro, zinc supplementation time-dependently upregulated the expression of A20 in PASMCs, therefore correcting the excessive proliferation and migration of cells caused by hypoxia. Using genetically encoded-FRET based zinc probe, we found that these effects of zinc ions are not achieved by entering cells, but most likely by activating cell surface zinc receptor (ZnR/GPR39). These results provide the first evidence of the effectiveness of zinc supplementation in the treatment of PH.

Magnesium Supplementation Attenuates Pulmonary Hypertension via Regulation of Magnesium Transporters

Pulmonary hypertension (PH) is characterized by profound vascular remodeling and altered Ca²⁺ homeostasis in pulmonary arterial smooth muscle cells (PASMCs). Magnesium ion (Mg²⁺), a natural Ca²⁺ antagonist and a cofactor for numerous enzymes, is crucial for regulating diverse cellular functions, but its roles in PH remains unclear. Here, we examined the roles of Mg²⁺ and its transporters in PH development. Chronic hypoxia and monocrotaline induced significant PH in adult male rats. It was associated with a reduction of [Mg²⁺]_i in PASMCs, a significant increase in gene expressions of Cnnm2, Hip14, Hip14l, Magt1, Mmgt1, Mrs2, Nipa1, Nipa2, Slc41a1, Slc41a2 and Trpm7; upregulation of SLC41A1, SLC41A2, CNNM2, and TRPM7 proteins; and downregulation of SLC41A3 mRNA and protein. Mg²⁺ supplement attenuated pulmonary arterial pressure, right heart hypertrophy, and medial wall thickening of pulmonary arteries, and reversed the changes in the expression of Mg²⁺ transporters. Incubation of PASMCs with a high concentration of Mg²⁺ markedly inhibited PASMC proliferation and migration, and increased apoptosis, whereas a low level of Mg²⁺ produced the opposite effects. siRNA targeting Slc41a1/2, Cnnm2, and Trpm7 attenuated PASMC proliferation and migration, but promoted apoptosis; and Slc41a3 overexpression also caused similar effects. Moreover, siRNA targeting Slc41a1 or high [Mg²⁺] incubation inhibited hypoxia-induced upregulation and nuclear translocation of NFATc3 in PASMCs. The results, for the first time, provide the supportive evidence that Mg²⁺ transporters participate in the development of PH by modulating PASMC proliferation, migration, and apoptosis; and Mg²⁺ supplementation attenuates PH through regulation of Mg²⁺ transporters involving the NFATc3 signaling pathway.

Assessing the efficacy and safety of magnesium sulfate for management of autonomic nervous system dysregulation in Vietnamese children with severe hand foot and mouth disease

Background

Brainstem encephalitis is a serious complication of hand foot and mouth disease (HFMD) in children. Autonomic nervous system (ANS) dysregulation and hypertension may occur, sometimes progressing to cardiopulmonary failure and death. Vietnamese national guidelines recommend use of milrinone if ANS dysregulation with Stage 2 hypertension develops. We wished to investigate whether magnesium sulfate (MgSO₄) improved outcomes in children with HFMD if used earlier in the evolution of the ANS dysregulation (Stage 1 hypertension).

Methods

During a regional epidemic we conducted a randomized, double-blind, placebo-controlled trial of MgSO₄ in children with HFMD, ANS dysregulation and Stage 1 hypertension, at the Hospital for Tropical Diseases in Ho Chi Minh city. Study participants received an infusion of MgSO₄ or matched placebo for 72 h. We also reviewed data from non-trial HFMD patients in whom milrinone failed to control hypertension, some of whom received MgSO₄ as second line therapy. The primary outcome for both analyses was a composite of disease progression within 72 h - addition of milrinone (trial participants only), need for ventilation, shock, or death.

Results

Between June 2014 and September 2016, 14 and 12 participants received MgSO₄ or placebo respectively, before the trial was stopped due to futility. Among 45 non-trial cases with poorly controlled hypertension despite high-dose milrinone, 33 received MgSO₄ while 12 did not. There were no statistically significant differences in the composite outcome between the MgSO₄ and the placebo/control groups in either study (adjusted relative risk (95%CI) of [6/14 (43%) vs. 6/12 (50%)], 0.84 (0.37, 1.92), p = 0.682 in the trial and [1/33 (3%) vs. 2/12 (17%)], 0.16 (0.01, 1.79), p = 0.132 in the observational cohort). The incidence of adverse events was similar between the groups. Potentially toxic magnesium levels occurred very rarely with the infusion regime used.

Conclusion

Although we could not demonstrate efficacy in these studies, there were no safety signals associated with use of 30-50 mg/kg/hr. MgSO₄ in severe HFMD. Intermittent outbreaks of HFMD are likely to continue across the region, and an adequately powered trial is still needed to evaluate use of MgSO₄ in controlling hypertension in severe HFMD, potentially involving a higher dose regimen.

Trial registration

ClinicalTrials.gov Identifier: NCT01940250 (Registered 22 AUG 2013).

Trial sponsor: University of Oxford

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4356-x) contains supplementary material, which is available to authorized users.

Intravenous magnesium sulfate for the management of severe hand, foot, and mouth disease with autonomic nervous system dysregulation in Vietnamese children: study protocol for a randomized controlled trial

BACKGROUND

Over the last 15 years, hand, foot, and mouth disease (HFMD) has emerged as a major public health burden across the Asia-Pacific region. A small proportion of HFMD patients, typically those infected with enterovirus 71 (EV71), develop brainstem encephalitis with autonomic nervous system (ANS) dysregulation and may progress rapidly to cardiopulmonary failure and death. Although milrinone has been reported to control hypertension and support myocardial function in two small studies, in practice, a number of children still deteriorate despite this treatment. Magnesium sulfate (MgSO4) is a cheap, safe, and readily available medication that is effective in managing tetanus-associated ANS dysregulation and has shown promise when used empirically in EV71-confirmed severe HFMD cases.

METHODS/DESIGN

We describe the protocol for a randomized, placebo-controlled, double-blind trial of intravenous MgSO4 in Vietnamese children diagnosed clinically with HFMD plus ANS dysregulation with systemic hypertension. A loading dose of MgSO4 or identical placebo is given over 20 min followed by a maintenance infusion for 72 h according to response, aiming for Mg levels two to three times the normal level in the treatment arm. The primary endpoint is a composite of disease progression within 72 h defined as follows: development of pre-specified blood pressure criteria necessitating the addition of milrinone, the need for ventilation, shock, or death. Secondary endpoints comprise these parameters singly, plus other clinical endpoints including the following: requirement for other inotropic agents; duration of hospitalization; presence of neurological sequelae at discharge in survivors; and neurodevelopmental status assessed 6 months after discharge. The number and severity of adverse events observed in the two treatment arms will also be compared. Based on preliminary data from a case series, and allowing for some losses, 190 patients (95 in each arm) will allow detection of a 50 % reduction in disease progression with 90 % power at a two-sided 5 % significance level.

DISCUSSION

Given the large numbers of HFMD cases currently being seen in hospitals in Asia, if MgSO4 is shown to be effective in controlling ANS dysregulation and preventing severe HFMD complications, this finding would be important to pediatric care throughout the region.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01940250 (Registered 22 August 2013).

Risk factors and outcomes of persistent pulmonary hypertension of the newborn in neonatal intensive care unit of Al-minya university hospital in egypt

Background:

Persistent pulmonary hypertension of the newborn (PPHN) result from the failure of the normal fetal-to-neonatal circulatory transition is associated with substantial infant mortality and morbidity.

Objective:

To estimate the possible risk factors and assess the outcome of these cases.

Materials and Methods:

Prospective study was performed enrolling all full-term and post-term newborn admitted to the NICU from January 2009 to April 2012, All neonates were subjected to complete history and physical examination, laboratory data including a complete blood count, arterial blood gases, blood glucose, serum electrolytes, and blood culture to exclude sepsis. Cases with PPHN had a continuous pulse oximeter, blood pressure and electrocardiography monitoring. Chest X-ray and echocardiogarphy were carried out to verify shunt and exclude structural congenital heart disease.

Results:

Out of the studied 640 infants, 32 infants (5%) developed PPHN, Meconium aspiration, birth asphyxia, hyaline membrane diseases, neonatal septicemia, post-term birth being large for gestational age, cesarean section, maternal overweight, and diabetes mellitus were associated with an elevated risk for PPHN. All neonates treated with O₂, 10 neonates with Mg sulphate, 16 with oral sildenafil and 12 with mechanical ventilation. After 6 months follow-up, 12 (37.54%) improved and followed-up without sequelae, 4 (12.5%) developed some neurodevelopmental impairment, 8 (25%) died, 3 (9.3%) developed chronic lungs diseases, 2 (6.2%) developed hearing defects and another 3 (9.3%) missed follow-up.

Conclusion:

PPHN was found in 5% of the studied population. Meconium aspiration, birth asphyxia, neonatal septicemia, post-term were associated with an elevated risk for PPHN. As this is a unit based study, a comprehensive countrywide survey on PPHN in Egypt is recommended to determine any regional differences in disease incidence.

Randomized controlled trial of magnesium sulfate in women at risk of preterm delivery-neonatal cardiovascular effects

OBJECTIVE

Use of antenatal magnesium sulfate (MgSO(4)) may reduce cerebral palsy in infants born very preterm. Low systemic blood flow in the first day in very preterm infants has been associated with cerebral injury and adverse motor outcome. The aim was to determine the effect of MgSO(4) on systemic blood flow in preterm infants.

STUDY DESIGN

Randomized trial of MgSO(4) versus saline placebo given to mothers at risk of delivery before 30 weeks gestation. Echocardiographic monitoring performed at 3 to 5, 10 to 12 and 24 h.

RESULT

A total of 48 infants were exposed to MgSO(4) and 39 to placebo. Infants exposed to MgSO(4) were significantly more likely to receive volume expansion (42% versus 21%). Inotrope use did not differ significantly (40% versus 26%). There was no significant difference in mean lowest superior vena cava (SVC) flow or right ventricular output (RVO), or incidence of low SVC flow or RVO in the first 24 h. Infants exposed to MgSO(4) had a significantly higher heart rate and were more likely to have low SVC flow at 10 to 12 h but not other times.

CONCLUSION

Antenatal MgSO(4) produced no consistent cardiovascular effects in the infant in the first 24 h. There is no evidence from this study to suggest the mechanism by which antenatal MgSO(4) prevents cerebral palsy is through a cardiovascular effect in the newborn.

Persistent pulmonary hypertension of the newborn: a review

Persistent pulmonary hypertension of the newborn (PPHN) is a serious medical emergency in the neonatal period which occurs because of failure of transition of the foetal circulation into the normal circulation. The condition is characterised by persistently elevated pulmonary vascular pressures and despite numerous modalities of treatment available, the condition carries with it a high rate of mortality and morbidity. Early awareness of predisposing conditions and early diagnosis leads to better outcomes in PPHN.

Neurodevelopmental outcome of newborns with persistent pulmonary hypertension

BACKGROUND

Developmental disabilities have been reported in infants with persistent pulmonary hypertension of the newborn (PPHN) treated with inhaled nitric oxide (INO) or intravenous magnesium sulphate (MgSO(4)) and/or extracorporeal membrane oxygenation. This paper reports the rate of developmental disabilities at 2 years of age in a cohort of survivors of PPHN treated with INO, MgSO(4), or both during the neonatal period.

METHODS

Sixteen survivors of PPHN were prospectively followed up. These infants were treated with intravenous MgSO(4) and/or INO during the neonatal period. Neurodevelopmental assessment was carried out at 2 years of age using the Bayley Scales of Infant Development 2nd Edition by a developmental psychologist. Eleven (68.8%) infants completed the 2-year follow-up.

RESULTS

The median mental developmental index (MDI) and physical developmental index scores were 85 (interquartile range, IQR = 27) and 87 (IQR = 33), respectively. Two infants (18.2%) had developmental disability (MDI scores <70).

CONCLUSION

Survivors of PPHN are at risk of developmental disabilities. Early intervention programme and long-term follow-up should be integrated in the management of these infants.

Pulmonary hypertension and the asphyxiated newborn

Persistent pulmonary hypertension of the newborn may occur with perinatal asphyxia, either because of direct effects of hypoxia/ischemia on pulmonary arterial function or indirectly because both are associated with meconium aspiration syndrome or perinatal sepsis/pneumonia. Therapies for persistent pulmonary hypertension of the newborn have the potential to affect cerebral function and cerebral perfusion in infants with hypoxic ischemic encephalopathy. Our literature review concludes that hyperventilation should be avoided, bicarbonate therapy is unproven, and hypoxia and hyperoxia should both be avoided. Nitric oxide improves pulmonary artery pressure and systemic perfusion. The effects of inotropic agents on cerebral perfusion or outcomes are uncertain.

Current and future therapeutic options for persistent pulmonary hypertension in the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a potentially life-threatening condition that is characterized by supra-systemic pulmonary vascular resistance causing right-to-left shunting through the ductus arteriosus and/or foramen ovale, leading to a vicious cycle of hypoxemia, acidosis and further pulmonary vasoconstriction. Advances in neonatology including surfactant instillation, high-frequency ventilation, extracorporeal membrane oxygenation and, most importantly, inhaled nitric oxide (INO), have revolutionized the management of PPHN. However, given that INO does not improve oxygenation in a significant proportion (30-40%) of cases, there is an urgent need to consider other therapeutic options for PPHN. The issue is more important for developing nations with a higher PPHN-related health burden and limited resources. This article discusses the evidence about INO in term and preterm neonates in brief, and focuses mainly on the potential alternative drugs in the management of PPHN.

Pharmacotherapy for meconium aspiration

In this article we have attempted to review the current pharmacological treatment options for infants with meconium aspiration syndrome with or without persistent pulmonary hypertension. These treatments include ventilatory support, surfactant treatment and inhaled nitric oxide (INO), in addition to older and newer pharmacological treatments. These include sedatives, muscle relaxants, alkali infusion, antibiotics and the newer vasodilators. Many aspects of treatment, including ventilatory care, surfactant treatment and the use of INO, are reviewed in great detail in this issue. On the other hand, many newer pharmacological modalities of treatment described here have not been evaluated with randomized control trials. We have given an overview of these emerging therapies.

Uso de milrinona no tratamento da hipertensão pulmonar persistente do recém-nascido

OBJETIVO: Descrever uma série de casos de recém-nascidos com hipertensão pulmonar persistente grave, que receberam milrinona para promover a vasodilatação pulmonar. MÉTODOS: Análise retrospectiva de prontuários de 28 pacientes com diagnóstico de hipertensão pulmonar persistente do recém-nascido (HPPRN). Após o diagnóstico, todos os pacientes receberam uma dose de ataque de 50mcg/kg de milrinona, seguida por 0,75mcg/kg/min. O índice de oxigenação (IO) foi calculado no início da infusão e 72 horas após o início da medicação. RESULTADOS: Todos os neonatos receberam milrinona e o sildenafil foi associado em 54%. O uso de dopamina assegurou a manutenção da pressão arterial em nível adequado em todos os casos. Sedação contínua, alcalinização e surfactante foram medidas coadjuvantes no tratamento. Durante a internação, sete pacientes (25%) evoluíram a óbito e todos eles apresentaram aumento do IO, com elevação da média de 25 para 38 com a milrinona. Os sobreviventes, com exceção de um neonato, apresentaram redução do IO em uso de milrinona, com queda da média de 19 para 7. CONCLUSÕES: O uso da milrinona parece ser uma alternativa para o tratamento da HPPRN, na ausência do óxido nítrico. A redução do IO com a medicação foi fator determinante da boa evolução dos pacientes. O índice de falha no tratamento com a milrinona nesta casuística foi semelhante ao encontrado na literatura para o uso de óxido nítrico.

Magnesium sulfate for persistent pulmonary hypertension of the newborn

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) occurs in approximately 1.9 per 1000 newborns and may be more frequent in developing countries. There is strong evidence for the use of inhaled nitric oxide (iNO) and extra corporeal membrane oxygenation (ECMO) in the treatment of PPHN. However, many developing countries do not have access or the technical expertise required for these expensive therapies. Magnesium sulfate is a potent vasodilator and hence has the potential to reduce the high pulmonary arterial pressures associated with PPHN. If magnesium sulfate were found to be effective in the treatment of PPHN, this could be a cost effective and potentially life-saving therapy.

OBJECTIVES

To evaluate the use of magnesium sulfate compared with placebo or standard ventilator management alone, sildenafil infusion, adenosine infusion, or inhaled nitric oxide on mortality or the use of backup iNO or ECMO in term and near-term newborns (> 34 weeks gestational age) with PPHN.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group (CNRG) was used. No language restrictions was applied. The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2006) and MEDLINE (1966 to April 20, 2007) were searched for relevant randomized and quasi-randomized trials. In addition the reference lists of retrieved articles were reviewed and known experts were contacted to obtain unpublished data.

SELECTION CRITERIA

All randomised or quasi-random studies were eligible where one of the treatment groups received magnesium sulfate for PPHN.

DATA COLLECTION AND ANALYSIS

Standard methods of the Cochrane Collaboration and the CNRG were used, including independent assessment of trial quality and extraction of data by each author.

MAIN RESULTS

No eligible trials were found

AUTHORS' CONCLUSIONS

On the basis of the current lack of evidence, the use of magnesium sulphate cannot be recommended in the treatment of PPHN. Randomised controlled trials are recommended.

Neurodevelopmental outcome of infants with birth asphyxia treated with magnesium sulfate

BACKGROUND

A neuroprotective effect of MgSO(4) has been shown in some animal models of perinatal hypoxic-ischemic brain damage. The aim of the present paper was to determine whether postnatal MgSO(4) infusion (250 mg/kg per day i.v. for 3 days, in combination with dopamine) is safe in infants with severe birth asphyxia, and also observe effects on neurodevelopmental outcome at 18 months.

METHODS

Inclusion criteria were clinical history consistent with perinatal asphyxia; gestational age at least 37 weeks; 5 min Apgar score < or =6; failure to initiate spontaneous respiration within 10 min after birth; and symptoms of encephalopathy. On each day MgSO(4) was infused over 1 h in combination with dopamine (5 microg/kg per min). Changes in vital signs, clinical course of encephalopathy, laboratory variables, and adverse events were monitored. Infants were followed for 18 months.

RESULTS

Thirty infants were studied. Mean birthweight was 2878 g; mean gestational age, 39.6 weeks, and median 5 min Apgar score, 3. All required endotracheal intubation for resuscitation. Median age at MgSO(4) initiation was 5 h. All infants had moderate or severe hypoxic-ischemic encephalopathy. Mean serum Mg(2+) concentration remained at least 1.3 mmol/L. MgSO(4) caused no change in physiological variables including mean arterial pressure. Two infants died as neonates, while six of 28 survivors had severe neurodevelopmental disability at 18 months; the remaining 22 had no neurodevelopmental disability.

CONCLUSION

Postnatal infusion of MgSO(4) with dopamine caused no change in physiological variables. Deaths and severe sequelae were less frequent than in reported cases with the same grade of hypoxic-ischemic encephalopathy severity, and this treatment may improve neurodevelopmental outcome in infants with severe birth asphyxia.

The evolution of neonatology

In 1960, the terms "neonatology" and "neonatologist" were introduced. Thereafter, an increasing number of pediatricians devoted themselves to full-time neonatology. In 1975, the first examination of the Sub-Board of Neonatal-Perinatal Medicine of the American Board of Pediatrics and the first meeting of the Perinatal Section of the American Academy of Pediatrics were held. One of the most important factors that improved the care of the neonate was the miniaturization of blood samples needed to determine blood gases, serum electrolytes, glucose, calcium, bilirubin, and other biochemical measurements. Another factor was the ability to provide nutrition intravenously, and the third was the maintenance of normal body temperature. The management of respiratory distress syndrome improved with i.v. glucose and correction of metabolic acidosis, followed by assisted ventilation, continuous positive airway pressure, antenatal corticosteroid administration, and the introduction of exogenous surfactant. Pharmacologic manipulation of the ductus arteriosus, support of blood pressure, echocardiography, and changes in the management of persistent pulmonary hypertension, including the use of nitric oxide and extracorporeal membrane oxygenation, all have influenced the cardiopulmonary management of the neonate. Regionalization of neonatal care; changes in parent-infant interaction; and technological changes such as phototherapy, oxygen saturation monitors, and brain imaging techniques are among the important advances reviewed in this report. Most remarkable, a 1-kg infant who was born in 1960 had a mortality risk of 95% but had a 95% probability of survival by 2000. However, errors in neonatology are acknowledged, and potential directions for the future are explored.

Pulmonary hypertension in the newborn

Pulmonary hypertension of the newborn occurs in 1.9 per 1000 live births and affected infants are hypoxaemic because of right-to-left shunts through the ductus arteriosus and foramen ovale. Pulmonary hypertension of the newborn may be primary, or secondary to a variety of conditions including intrapartum asphyxia, infection, pulmonary hypoplasia, congenital heart disease or drug therapy. It may occur in association with a normal number (maladaptation) or a decreased number of arteries (for example with pulmonary hypoplasia). Few strategies used in infants with pulmonary hypertension of the newborn have been subjected to rigorous evaluation. Inhaled nitric oxide has been shown to reduce the need for extracorporeal membrane oxygenation but not mortality, in term or near term born infants. Preliminary evidence suggests that other vasodilators given by the inhaled route may improve oxygenation and new vasodilators have become available; appropriately designed trials with long-term outcomes are required to test such therapies.

Effect of increasing doses of magnesium in experimental pulmonary hypertension after acute pulmonary embolism

OBJECTIVE

To investigate the dose-related effects of magnesium on pulmonary vascular resistance and associated changes in cardiac output in porcine micro-embolic pulmonary hypertension.

DESIGN

Prospective, interventional animal study.

SETTING

University animal laboratory.

SUBJECTS

Forty anaesthetised and ventilated piglets.

INTERVENTIONS

Right heart catheterisation for the measurement of cardiac output, pulmonary artery pressure, central venous pressure and pulmonary capillary wedge pressure; arterial cannulation for measurement of arterial pressures and ionised magnesium levels; calculation of pulmonary and systemic vascular resistance before and after induction of acute pulmonary micro-embolism, and without or with the administration of magnesium (0.5, 1.0, 2.0 mmol/kg bolus and 1 mmol/kg bolus followed by 1 mmol/kg per h continuous infusion).

MEASUREMENTS AND MAIN RESULTS

The bolus administration of increasing doses of magnesium (0.5, 1.0, 2.0 mmol/kg) was associated with an increase in ionised serum magnesium levels and a dose-dependent decrease of mean pulmonary arterial pressure, an increase of cardiac output and a decrease of pulmonary vascular resistance. This effect was sustained after bolus administration (1 mmol/kg) followed by a continuous infusion of magnesium (1 mmol/kg per h).

CONCLUSIONS

Magnesium has a directly dose-dependent beneficial effect on the circulation in acute embolic pulmonary hypertension and improves cardiocirculatory impairment in massive pulmonary embolism (PE).

New approaches for persistent pulmonary hypertension of newborn

The management of PPHN entered a new era with the development of inhaled NO therapy for the relief of pulmonary hypertension. The wider application of INO therapy and improved ventilation strategies led to a decrease in the need for invasive life-sustaining therapies such as ECMO. The remarkable advances in the understanding and treatment of PPHN were made possible by the extensive investigations in the laboratory using animal models. Further decreases in morbidity and mortality are possible with specific strategies targeted to correct the alterations in NO and prostacyclin biology and strategies to reduce lung injury. Further research is needed to understand the basis for the biologic susceptibility of some infants to environmental insults such as intra-uterine stressor exposure to NSAIDs in utero.

Persistent pulmonary hypertension of the newborn

Pulmonary hypertension refers to the elevation of the pulmonary artery pressure above normal. In utero a raised pulmonary arterial pressure in the baby is normal; at birth there is a marked decrease in pulmonary vascular resistance allowing the lung to establish gas exchange. Persistent pulmonary hypertension of the newborn (PPHN; Figure 1) occurs when this decrease fails to occur.

Update on extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) consists of the application of intermediate-term cardiopulmonary bypass for the treatment of potentially reversible heart and/or lung failure in the neonate, child, and adult. Applications in the neonate include congenital diaphragmatic hernia, pulmonary hypertension, meconium aspiration syndrome, and pre- and post-operative congenital heart surgery support. In the older child, myocarditis, infections, and respiratory failure (RSV and ARDS) are the most frequent indications, in addition to peri-operative cardiac surgical support. A review of the institutional experiences at the University of Louisville spanning a 15-year period and comparison international data will be presented, along with a pertinent review of the literature. Technical considerations, complications, and long-term outcomes will be reviewed, and the potential interface between ECMO and other, less invasive technologies, i.e., high-frequency ventilation, replacement surfactant, and nitric oxide, will be discussed.

Inhaled nitric oxide applications in paediatric practice

The nitric oxide pathway plays a pivotal, yet diverse, role in human physiology, including modulation of vascular tone, neural transmission and inflammation. Inhaled nitric oxide is a selective pulmonary vasodilator that has emerged rapidly as an important therapeutic agent. It finds its best applications in paediatrics; the use of iNO in term neonates with hypoxaemic respiratory failure, in the assessment of pulmonary vascular reactivity and in the treatment of postoperative pulmonary hypertension in congenital heart disease is well recognised and accepted. This review details the delivery and monitoring aspects of inhaled nitric oxide, its potential toxic and side effects and its applications in several cardiopulmonary disorders in paediatrics.

Developmental change in magnesium sulfate-induced relaxation of rabbit pulmonary arteries

Magnesium causes a variety of vascular smooth muscle to relax. The present study was designed to determine whether there is a developmental change in the magnesium-induced response of pulmonary vasculature. Isolated pulmonary arteries (PA) of newborn (1- to 3-day-old) and juvenile (4- to 6-wk-old) rabbits were suspended in organ chambers filled with modified Krebs-Ringer bicarbonate solution (95% O(2)-5% CO(2), 37.0 degrees C), and their isometric tension was recorded. In arteries preconstricted with endothelin-1 to a similar tension level, MgSO(4) caused greater relaxation of juvenile rabbit PA than that of the newborn rabbit PA. Verapamil, a voltage-dependent Ca(2+) channel blocker, attenuated magnesium-induced relaxation in juvenile rabbit PA but not in newborn PA. The uptake of Ca(2+) of juvenile rabbit PA was inhibited by MgSO(4), and the inhibition was attenuated by verapamil. The uptake of Ca(2+) of newborn rabbit PA was smaller than that of the juvenile PA and was not significantly affected by MgSO(4) and verapamil. These results demonstrate that there is a developmental increase in the dilator effect of MgSO(4) in rabbit PA. In newborn rabbit PA, an incomplete maturation of the voltage-dependent Ca(2+) channels may contribute to the smaller vasodilation induced by MgSO(4).

Strategies for reduction of neonatal mortality

Infant mortality rates in developed countries have shown significant decreases in recent years. Two-thirds of infant mortality still occurs in the neonatal period and our aim in this study was to review the causes of these neonatal deaths and see where further improvements may be possible. A 6-yr review of all neonatal deaths of live-born infants over 500 g birthweight from 1991 to 1996 was made. The 1989 amended Wigglesworth classification was used to categorize cause of death and other perinatal variables were also recorded. Results show there were 34,375 births and 153 neonatal deaths. Classification of these deaths by Wigglesworth found 78 (51 per cent) due to congenital malformations, 58 (38 per cent) due to prematurity, 6 (4 per cent) due to asphyxia and 11 (7 per cent) due to specific other causes. The corrected neonatal mortality was 2.18. Neural tube defects alone accounted for 10 per cent of the total neonatal mortality. Fifty-five out of 58 infants who died due to prematurity had birthweight < 1000 g and survival rates in this group compared well to international standards. We conclude that a reduction in neonatal mortality is possible but is most likely to result from community focused measures such as increased use of pre- and peri-conceptional folate.

Recognition and management of pulmonary hypertension

Pulmonary hypertension (mean pulmonary arterial pressure > 20mm Hg at rest or > 30mm Hg during exercise) occurs (i) as primary pulmonary hypertension (no known underlying cause), (ii) as persistent pulmonary hypertension of the newborn or (iii) secondary to a variety of lung and cardiovascular diseases. In the last 10 to 15 years there have been significant advances in the medical management of this debilitating and life-threatening disorder. The main drugs in current use are anticoagulants (warfarin, heparin) and vasodilators, especially oral calcium antagonists, intravenous prostacyclin (prostaglandin I2; epoprostenol) and inhaled nitric oxide. Calcium antagonists, (e.g. nifedipine, diltiazem) are used chiefly in primary pulmonary hypertension. They are effective in patients who give a pulmonary vasodilator response to an acute challenge with a short acting vasodilator (e.g. prostacyclin, nitric oxide or adenosine), and are used in doses greater than are usual in the treatment of other cardiovascular disorders. Prostacyclin, given by continuous intravenous infusion, is effective in patients even if they do not respond to an acute vasodilator challenge. The long term benefit in these patients is thought to reflect the antiproliferative effects of the drug and/or its ability to inhibit platelet aggregation. It is used either as long term therapy or as a bridge to transplantation. Inhaled nitric oxide, which is used mainly in persistent pulmonary hypertension of the newborn, has the particular benefit of being pulmonary selective, due to its route of administration and rapid inactivation. Anticoagulants have a specific role in the treatment of pulmonary thromboembolic pulmonary hypertension and are also used routinely in patients with primary pulmonary hypertension. Nondrug treatments for pulmonary hypertension include (i) supplemental oxygen (> or = 15 h/day), which is the primary therapy in patients with pulmonary hypertension secondary to chronic obstructive pulmonary disease and (ii) heart-lung or lung transplantation, which nowadays is regarded as a last resort. Different types of pulmonary hypertension require different treatment strategies. Future advances in the treatment of pulmonary hypertension may come from the use of drug combinations, the development of new drugs, such as endothelin antagonists, nitric oxide donors and potassium channel openers, or the application of gene therapy.

Severe transient neonatal lactic acidosis during prophylactic zidovudine treatment

Zidovudine (ZDV) treatment during pregnancy, delivery and the postnatal period is effective in reducing the maternal-infant transmission of the human immunodeficiency virus. Reported adverse effects in the neonate during this longterm treatment are bone marrow suppression and elevation in aspartate aminotransferase activity. We report a case of severe ZDV-associated lactic acidosis in a neonate, which resolved rapidly following discontinuation of ZDV. The mechanisms leading to this side effect are poorly understood.

Role of magnesium sulfate in seizure prevention in patients with eclampsia and pre-eclampsia

Eclampsia is a leading cause of maternal mortality. The prevention of seizure activity in pre-eclampsia and recurrent seizures in eclamptic patients is an essential aspect of management. Many drugs with anticonvulsant properties have been used to treat patients with pre-eclampsia and eclampsia. Magnesium sulfate is a significantly better drug than either diazepam or phenytoin for preventing recurrent seizures in eclamptic patients. Magnesium sulfate has diverse cardiovascular and neurological effects and also alters calcium metabolism. Although the drug crosses the placenta and may affect the fetus, these effects are clinically small and fetal morbidity has been shown to be reduced in randomised studies comparing magnesium sulfate to either phenytoin or benzodiazepines. Dosage regimens of magnesium sulfate are empirical. Because adverse effects of this agent are related to toxicity, the establishment of greater efficacy by using higher dosage regimens needs to be tested against a greater risk of adverse effects. The most serious toxicity related to magnesium sulfate use is magnesium sulfate use is neuromuscular blockade that may result in respiratory arrest. Magnesium sulfate is now the drug choice for treating eclamptic patients. However, further studies are required to establish the role of this agent as a prophylactic agent in the prevention of eclampsia.