Inhaled nitric oxide and gentle ventilation in the treatment of pulmonary hypertension of the newborn--a single-center, 5-year experience

Oxygen Targets in Neonatal Pulmonary Hypertension: Individualized, "Precision-Medicine" Approach

Oxygen is a specific pulmonary vasodilator. Hypoxemia causes pulmonary vasoconstriction, and normoxia leads to pulmonary vasodilation. However, hyperoxia does not enhance pulmonary vasodilation but causes oxidative stress. There are no clinical trials evaluating optimal oxygen saturation or Pao2 in pulmonary hypertension. Data from translational studies and case series suggest that oxygen saturation of 90% to 97% or Pao2 between 50 and 80 mm Hg is associated with the lowest pulmonary vascular resistance.

Complications associated with incorrect use of nasal CPAP

Nasal continuous positive airway pressure (nCPAP) is a safe, effective, non-invasive respiratory modality to deliver positive end expiratory pressure in neonates. Many studies have established its associated improved respiratory outcomes without increase in major morbidities associated with preterm neonates. In contrast, there is paucity in literature addressing complications such as nasal injury, abdominal distention, air leak syndromes (especially pneumothorax), hearing loss, heat and chemical burns, swallowing and aspiration of small components of the nasal interface and delay in escalation of respiratory support associated with the use of nCPAP, most frequently due to its incorrect use. This is a comprehensive review that seeks to address the different complications that are associated with the incorrect use of nCPAP highlighting that these are operator-related and not device-related.

Update on pre-ECMO evaluation and treatment for term infants in respiratory failure

The epidemiology, diagnostic and management approach to severe hypoxemic respiratory failure in the term and near-term neonate has evolved over time, as has the need for extracorporeal membrane oxygenation (ECMO) support in this patient population. Many patients who historically would have required ECMO support now respond to less invasive therapies, with patients requiring ECMO generally representing a higher risk and more heterogenous group of underlying diagnoses. This review will highlight these changes over time and the current available evidence for the diagnosis and management of these infants, as well as the current indications and relative contraindications to ECMO support when oxygen delivery cannot meet demand with less invasive management.

Milrinone Use in Persistent Pulmonary Hypertension of the Newborn

Failure of the normal transition from in utero to ex utero physiology leads to "persistent" pulmonary hypertension of the newborn (PPHN). PPHN is frequently associated with low systemic blood pressure and low cardiac output because of increased right ventricular afterload and myocardial dysfunction. The general management of newborns with PPHN is geared toward maintenance of normothermia, normal serum electrolytes, normal intravascular volume, correction of acidosis, adequate sedation/analgesia, adequate ventilation and oxygenation with optimal lung recruitment, and avoidance of hyperoxia. Inotropic and vasoactive agents are commonly initiated early to increase cardiac output, maintain adequate systemic blood pressure, and enhance oxygen delivery to the tissue. Unfortunately, there is not much evidence on the choice, timing of initiation, dosing, monitoring, and titrating of vasoactive agents in this patient population. In this review, we will discuss the pathophysiology of PPHN and review the use of inotropic, lusitropic, and vasoactive agents in the management of PPHN, with particular attention to milrinone.

Surf early to higher tides: surfactant therapy to optimize tidal volume, lung recruitment, and iNO response

Inhaled nitric oxide is approved by FDA for the management of hypoxemic respiratory failure in term and near-term infants. However, approximately a third of patients treated with inhaled nitric oxide fail to have a sustained improvement in oxygenation. Recruitment of the lung with surfactant enables optimal delivery of nitric oxide to the alveolar space leading to effective pulmonary vasodilation.

Optimal Oxygen Targets in Term Lambs with Meconium Aspiration Syndrome and Pulmonary Hypertension

Optimal oxygen saturation as measured by pulse oximetry (SpO2) in neonatal lung injury, such as meconium aspiration syndrome (MAS) and persistent pulmonary hypertension of newborn (PPHN), is not known. Our goal was to determine the SpO2 range in lambs with MAS and PPHN that results in the highest brain oxygen delivery (bDO2) and pulmonary blood flow (Qp) and the lowest pulmonary vascular resistance and oxidative stress. Meconium was instilled into endotracheal tubes in 25 near-term gestation lambs, and the umbilical cord was occluded to induce asphyxia and gasping, causing MAS and PPHN. Lambs were randomized into four groups and ventilated for 6 hours with fixed fraction of inspired oxygen (FiO2) = 1.0 irrespective of SpO2, and three groups had FiO2 titrated to keep preductal SpO2 between 85% and 89%, 90% and 94%, and 95% and 99%, respectively. Tissues were collected to measure nitric oxide synthase activity, 3-nitrotyrosine, and 8-isoprostanes. Throughout the 6-hour exposure period, lambs in the 95-99% SpO2 target group had the highest Qp, lowest pulmonary vascular resistance, and highest bDO2 but were exposed to higher FiO2 (0.5 ± 0.21 vs. 0.29 ± 0.17) with higher lung 3-nitrotyrosine (0.67 [interquartile range (IQR), 0.43-0.73] ng/mcg protein vs. 0.1 [IQR, 0.09-0.2] ng/mcg protein) and lower lung nitric oxide synthase activity (196 [IQR, 192-201] mMol nitrite/mg protein vs. 270 [IQR, 227-280] mMol nitrite/mg protein) compared with the 90-94% target group. Brain 3-nitrotyrosine was lower in the 85-89% target group, and brain/lung 8-isoprostane levels were not significantly different. In term lambs with MAS and PPHN, Qp and bDO2 through the first 6 hours are higher with target SpO2 in the 95-99% range. However, the 90-94% target range is associated with significantly lower FiO2 and lung oxidative stress. Clinical trials comparing the 90-94% versus the 95-99% SpO2 target range in term infants with PPHN are warranted.

Hemoglobin oxygen saturation targets in the neonatal intensive care unit: Is there a light at the end of the tunnel? 1

The optimal oxygenation target needed to prevent the extremes of hypoxia and oxygen toxicity in premature and sick newborns has been the subject of much research and debate. The advent of the pulse oximeter has allowed the continuous monitoring of oxyhemoglobin saturation and the delivery of oxygen with greater precision. Well-run, large clinical trials to determine the safest oxygen concentration have led to several revisions in guidelines for neonatal care. However, monitoring of oxyhemoglobin saturation has its limitations and does not provide a comprehensive assessment of tissue oxygenation. To identify optimal oxygen therapy, various other factors (partial pressure of arterial carbon dioxide, hemoglobin concentration, blood pH, and tissue metabolic demand) that influence perfusion and tissue oxygenation need to be considered.

Current trends in neonatal ECMO

Extracorporeal membrane oxygenation (ECMO) is a life-saving therapy for patients with respiratory and cardiac failure refractory to maximal medical management. The extracorporeal life support organization registry is the largest available resource for describing the population and outcomes of patients treated with this therapy. The use of ECMO for neonatal patients is decreasing in proportion to the total annual ECMO runs most likely due to advancements in medical management. Although the overall survival for neonatal ECMO has decreased, this is likely a reflection of the increasingly complex neonatal patients treated with this therapy. Although many patient and mechanical complications are decreasing over time, there remains a high percentage of morbidities and risks associated with ECMO. Continued refinements in management strategies are important to improving overall patient outcomes.

Persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is characterized by elevated pulmonary vascular resistance resulting in right-to-left shunting of blood and hypoxemia. PPHN is often secondary to parenchymal lung disease (such as meconium aspiration syndrome, pneumonia or respiratory distress syndrome) or lung hypoplasia (with congenital diaphragmatic hernia or oligohydramnios) but can also be idiopathic. The diagnosis of PPHN is based on clinical evidence of labile hypoxemia often associated with differential cyanosis. The diagnosis is confirmed by the echocardiographic demonstration of - (a) right-to-left or bidirectional shunt at the ductus or foramen ovale and/or, (b) flattening or leftward deviation of the interventricular septum and/or, (c) tricuspid regurgitation, and finally (d) absence of structural heart disease. Management strategies include optimal oxygenation, avoiding respiratory and metabolic acidosis, blood pressure stabilization, sedation and pulmonary vasodilator therapy. Failure of these measures would lead to consideration of extracorporeal membrane oxygenation (ECMO); however decreased need for this rescue therapy has been documented with advances in medical management. While trends also note improved survival, long-term neurodevelopmental disabilities such as deafness and learning disabilities remain a concern in many infants with severe PPHN. Funded by: 1R01HD072929-0 (SL).

Acute Neonatal Respiratory Failure

Acute respiratory failure requiring assisted ventilation is one of the most common reasons for admission to the neonatal intensive care unit. Respiratory failure is the inability to maintain either normal delivery of oxygen to the tissues or normal removal of carbon dioxide from the tissues. It occurs when there is an imbalance between the respiratory workload and ventilatory strength and endurance. Definitions are somewhat arbitrary but suggested laboratory criteria for respiratory failure include two or more of the following: PaCO₂ > 60 mmHg, PaO₂ < 50 mmHg or O₂ saturation <80 % with an FiO₂ of 1.0 and pH < 7.25 (Wen et al. 2004).

The pulmonary circulation in neonatal respiratory failure

The pulmonary circulation rapidly adapts at birth to establish lungs as the site of gas exchange. Abnormal transition at birth and/or parenchymal lung disease can result in neonatal hypoxemic respiratory failure. This article reviews the functional changes in pulmonary hemodynamics and structural changes in pulmonary vasculature secondary to (1) normal and abnormal transition at birth, and (2) diseases associated with neonatal hypoxemic respiratory failure. Various management strategies to correct respiratory failure are also discussed.

Respiratory support in meconium aspiration syndrome: a practical guide

Meconium aspiration syndrome (MAS) is a complex respiratory disease of the term and near-term neonate. Inhalation of meconium causes airway obstruction, atelectasis, epithelial injury, surfactant inhibition, and pulmonary hypertension, the chief clinical manifestations of which are hypoxaemia and poor lung compliance. Supplemental oxygen is the mainstay of therapy for MAS, with around one-third of infants requiring intubation and mechanical ventilation. For those ventilated, high ventilator pressures, as well as a relatively long inspiratory time and slow ventilator rate, may be necessary to achieve adequate oxygenation. High-frequency ventilation may offer a benefit in infants with refractory hypoxaemia and/or gas trapping. Inhaled nitric oxide is effective in those with pulmonary hypertension, and other adjunctive therapies, including surfactant administration and lung lavage, should be considered in selected cases. With judicious use of available modes of ventilation and adjunctive therapies, infants with even the most severe MAS can usually be supported through the disease, with an acceptably low risk of short- and long-term morbidities.

PPHN: is sildenafil the new nitric? A review of the literature

Persistent pulmonary hypertension of the newborn (PPHN) is a life-threatening neonatal pathology resulting from poor hemodynamic and respiratory transition to extrauterine life. Inhaled nitric oxide (iNO) is a current, commonly used treatment of PPHN. However, some infants with PPHN do not respond to iNO therapy. Because of the significant morbidity and mortality associated with PPHN, it is useful to look at other possible therapies. This article explores the use of sildenafil in the treatment of PPHN, either as a supplement to iNO or as an alternative to iNO. Current research, including a case study, is reviewed. An emphasis is placed on the administration and efficacy of sildenafil in synergy with, and in lieu of, current iNO therapy in the treatment of PPHN.

Hyperventilation versus standard ventilation for infants in postoperative care for congenital heart defects with pulmonary hypertension

PURPOSE

In infants undergoing surgery for cardiac defects with left-to-right shunt, a hyperventilation strategy has been applied to prevent pulmonary hypertensive crisis (PHC). Hyperventilation with a large tidal volume and/or higher airway pressure, however, may be detrimental to the lung. This randomized study compared the effects of hyperventilation versus standard ventilation.

METHODS

We enrolled 22 infants with a preoperative pulmonary-to-systemic blood pressure ratio of more than 0.7. Hyperventilation, with a tidal volume of 10-12 ml x kg(-1) to keep Pa(CO2) between 30 and 35 mmHg, was randomly applied in 11 patients for 16 h or more. The other 11 patients were randomly assigned to standard ventilation, with a 6- to 8- ml x kg(-1) tidal volume.

RESULTS

The peak inspiratory pressure was higher (20 +/- 3 vs 18 +/- 2 cmH2O; P = 0.018), and Pa(CO2) (34 +/- 5 vs 42 +/- 7 mmHg; P = 0.003) and positive end-expiratory pressure (3 +/- 0 vs 5 +/- 0; P < 0.0001) were significantly lower in the hyperventilation than in the standard ventilation group. The Pa(CO2)/inspiratory fraction of oxygen Pa(CO2) ratio decreased from 244 +/- 160 mmHg at the onset of postoperative ventilation, to 177 +/- 96 mmHg at 24 h (P = 0.038) in the hyperventilation group, versus a decrease from 240 +/- 89 to 220 +/- 97 mmHg in the standard ventilation group not significant (NS). Serum interleukin (IL)-6 level, measured at 24 h postoperatively, was significantly lower (P = 0.02) in the standard ventilation than in the hyperventilation group, suggesting an attenuated postoperative systemic inflammatory response. A single patient in each group developed PHC.

CONCLUSION

Hyperventilation may cause lung injury and systemic inflammation in infants with pulmonary hypertension undergoing corrective heart surgery.

Developmental outcomes in persistent pulmonary hypertension treated with nitric oxide therapy

BACKGROUND

The aim of the present study was to assess 3 year auditory and neurodevelopmental outcomes of persistent pulmonary hypertension of the newborn (PPHN) before and after introducing inhaled nitric oxide (i-NO) therapy, and to detect the clinical factors affecting poor outcome.

METHODS

A retrospective historical cohort study of 26 survivors with PPHN with oxygenation index (OI) >or=25 (13 infants without i-NO therapy, control group; 13 with i-NO therapy, i-NO group) was performed. Auditory brainstem response (ABR) at 6 and 12 months and neurodevelopmental outcomes at 3 years of age were evaluated.

RESULTS

ABR abnormalities at 6 months were observed in one infant in the i-NO group and six in the control group (P = 0.04). At 1 year, one infant in the i-NO group and two of six infants in the control group still had ABR abnormality. In the i-NO group, two children had abnormal neurodevelopmental outcomes, as compared with five children in the control group at 3 year follow up. Two children in the control group and no children in the i-NO group had hearing loss at 3 years of age. Hypocapnea (P = 0.04) and elevated creatine phosphokinase (P = 0.04) were found to be most predictive for neurodevelopmental abnormality.

CONCLUSION

Avoidance of excessive hypocapnea via introduction of i-NO therapy might reduce both ABR and neurodevelopmental abnormalities.

Continuous positive airway pressure and conventional mechanical ventilation in the treatment of meconium aspiration syndrome

Meconium aspiration syndrome (MAS) is a complex syndrome that ranges in severity from mild respiratory distress to severe respiratory failure, persistent pulmonary hypertension of the newborn and sometimes death. Understanding of the syndrome's complicated pathophysiology will help determine the appropriate treatment strategy, including the use of continuous positive airway pressure (CPAP), conventional mechanical ventilation (CMV) and other therapies. Approximately 30 to 50% of infants diagnosed with MAS will require CPAP or mechanical ventilation. The optimum modes of ventilation for MAS are not known. Very few studies have been conducted to determine 'best' ventilatory strategies. Despite the introduction, over the last two decades, of innovative ventilatory treatments for this disease (for example, surfactant, high-frequency ventilation, inhaled nitric oxide, extracorporeal membrane oxygenation), the majority of infants can be successfully managed with CPAP or mechanical ventilation alone.

Treatment of MAS with PPHN using combined therapy: SLL, bolus surfactant and iNO

The objective of the study was to compare the effectiveness of surfactant treatment either by bolus or surfactant lung lavage followed by inhaled nitric oxide (iNO) therapy in infants with meconium aspiration syndrome (MAS) complicated by persistent pulmonary hypertension (PPHN). In this study, thirteen infants with diagnosis of MAS and PPHN were first treated with conventional respiratory support. Then between 2 and 22h of life they were randomized either to bolus surfactant treatment (n=6) or surfactant lung lavage (SLL, n=7) treatment. Then all infants were treated with iNO therapy. The groups were compared with regard to their clinical course: changes in PaO(2), FiO(2), MAP, OI, A-a oxygen gradient, duration of iNO therapy, length of ventilation and hospitalization. Complications and mortality were also compared. The results showed that infants treated with SLL had significant improvements in oxygenation, decreases in MAP and A-a gradients. But there were no significant differences in duration of ventilation, iNO treatment, length of hospitalization or complications. In conclusion these data show no advantage of SLL therapy over bolus surfactant treatment in infants with MAS complicated by PPHN.

Hypoxic respiratory failure: etiology and outcomes at one referral center 2000 through 2005

OBJECTIVE

We calculated in a referral population of term and near-term infants with hypoxic respiratory failure (HRF) as a primary presenting problem the overall survival rate, the need for extracorporeal membrane oxygenation (ECMO) and the incidence of apparently irreversible disorders.

STUDY DESIGN

All infants >or=36-week gestation admitted at <or=72 h of age from 2000 through 2005 were identified. The worst (highest) oxygen index (OI) was calculated and outcomes were noted.

RESULTS

A total of 630 infants were reviewed and 315 infants were identified with primary diagnosis of HRF; four infants died before discharge. One hundred seventy-seven infants had OI <or=14; 71 had OI of 15 to 25; and 67 had OI of >25. A total of 32 infants received ECMO, including all four who died, two with histologic evidence of pulmonary malformations and two with septic shock.

CONCLUSION

Term or near-term infants with isolated HRF are likely to survive, given the low incidence of pulmonary disorders not supportable by inhaled nitric oxide or ECMO.

Persistent pulmonary hypertension of the newborn: pathogenesis, etiology, and management

Persistent pulmonary hypertension of the newborn (PPHN) is characterized by severe hypoxemia shortly after birth, absence of cyanotic congenital heart disease, marked pulmonary hypertension, and vasoreactivity with extrapulmonary right-to-left shunting of blood across the ductus arteriosus and/or foramen ovale. In utero, a number of factors determine the normally high vascular resistance in the fetal pulmonary circulation, which results in a higher pulmonary compared with systemic vascular pressure. However, abnormal conditions may arise antenatally, during, or soon after birth resulting in the failure of the pulmonary vascular resistance to normally decrease as the circulation evolves from a fetal to a postnatal state. This results in cyanosis due to right-to-left shunting of blood across normally existing cardiovascular channels (foramen ovale or ductus arteriosus) secondary to high pulmonary versus systemic pressure. The diagnosis is made by characteristic lability in oxygenation of the infant, echocardiographic evidence of increased pulmonary pressure, with demonstrable shunts across the ductus arteriosus or foramen ovale, and the absence of cyanotic heart disease lesions. Management of the disease includes treatment of underlying causes, sedation and analgesia, maintenance of adequate systemic blood pressure, and ventilator and pharmacologic measures to increase pulmonary vasodilatation, decrease pulmonary vascular resistance, increase blood and tissue oxygenation, and normalize blood pH. Inhaled nitric oxide has been one of the latest measures to successfully treat PPHN and significantly reduce the need for extracorporeal membrane oxygenation.

Inhaled nitric oxide therapy might reduce the need for hyperventilation therapy in infants with persistent pulmonary hypertension of the newborn

AIM

To determine whether inhaled nitric oxide might reduce the need for excessive respiratory alkalosis to maintain systemic oxygenation in infants with persistent pulmonary hypertension of the newborn (PPHN).

MATERIALS AND METHODS

A retrospective historical cohort study of 34 infants with PPHN with oxygenation index (OI) of 25 or more, including 19 infants without inhaled nitric oxide (i-NO) therapy (control group) and 15 infants with inhaled nitric oxide therapy (i-NO group) was performed. The initial dose of 10 ppm of i-NO was administered and no responders received the maximum dose of 25 ppm. We evaluated the mortality rate and the change of OI index and PaCO(2) during the first 6 days.

RESULTS

There were no significant differences in characteristics between groups. Two of 15 in the i-NO group and 6 of 19 infants in the control group died during the first 48 h. Baseline OI, PaCO(2) and arterial pH were similar in the two groups. OI in the i-NO group was significantly higher than in the control group between 12 and 96 h. PaCO(2) in the i-NO group was higher than in the control group between 24 and 144 h.

CONCLUSION

i-NO therapy for PPHN might improve systemic oxygenation without excessive hypocapnia. However there was no reduction in duration of ventilation support or oxygen supply.

Milrinone improves oxygenation in neonates with severe persistent pulmonary hypertension of the newborn

BACKGROUND

Many neonates with severe persistent pulmonary hypertension of the newborn (PPHN) are nonresponders to inhaled nitric oxide (iNO). Milrinone is a promising adjunctive therapy because of its pulmonary vasodilator properties and cardiotropic effects.

DESIGN

Case series of neonates with severe PPHN (defined as oxygenation index [OI] >20, failure of iNO therapy, and echocardiographic confirmation of PPHN).

SETTING

Tertiary neonatal intensive care unit.

SUBJECTS

Full-term (> or =37 weeks) neonates with severe PPHN who received intravenous milrinone.

MEASUREMENTS

The primary end point was the effect of intravenous milrinone on OI and hemodynamic stability over a 72-hour study period. Secondary end points examined included duration of iNO and degree of cardiorespiratory support.

RESULTS

Nine neonates at a mean gestation of 39.25 +/- 2.76 weeks, birth weight of 3668 +/- 649.1 g, and baseline OI of 28.1 +/- 5.9 received milrinone treatment after a poor initial response to iNO treatment. Intravenous milrinone was commenced at a median age of 21 hours (range, 18-49 hours), and patients were treated for median of 70 hours (range, 23-136). Oxygenation index was significantly reduced after milrinone treatment, particularly in the immediate 24 hours of treatment (8.0 +/- 6.6, P < .001). There was a significant improvement in heart rate (179 +/- 15.2 vs 149.6 +/- 22.4, P < .001) over the same period. Infants who received milrinone did not develop systemic hypotension; in fact, there was a nonsignificant trend toward improved blood pressure.

CONCLUSIONS

Intravenous milrinone produces early improvements in oxygenation without compromising systemic blood pressure.

Extracorporeal membrane oxygenation in infants with meconium aspiration syndrome: a decade of experience with venovenous ECMO

BACKGROUND

Despite the emergence of new therapies for respiratory failure of the newborn with meconium aspiration syndrome (MAS), extracorporeal membrane oxygenation (ECMO) has a significant role as a rescue modality in these infants. Our objective was to compare the use of venovenous (VV) vs venoarterial (VA) ECMO in newborns with MAS who need ECMO and to ascertain the impact of new therapies in these infants during the last decade. We also evaluated how disease severity or time of ECMO initiation affected mortality and morbidity.

METHODS

A report of 12 years experience (1990-2002) of a single center, comparing VV and VA ECMO, is given. Venovenous ECMO was the preferred rescue modality for respiratory failure unresponsive to maximal medical therapy. Venoarterial ECMO was used only when the placement of a VV ECMO 14-F catheter was not possible; 128 patients met ECMO criteria, 114 were treated with VV ECMO, and 12 with VA ECMO. Two patients were converted from VV to VA ECMO.

RESULTS

Venovenous and VA ECMO patients had comparable birth weight (mean +/- SEM, 3.48 +/- 0.05 vs 3.35 +/- 0.15 kg) and gestational age (40.3 +/- 0.1 vs 40.7 +/- 0.3 weeks). Before ECMO, there was no difference between VV and VA ECMO patients in oxygenation index (60 +/- 3 vs 63 +/- 8), mean airway pressure (19.5 +/- 0.4 vs 20.8 +/- 1.5 cm H2O), alveolar-arterial O2 gradient (630 +/- 2 vs 632 +/- 4 torr), ECMO cannulation age (median [25th-75th percentiles], 23 [14-47] vs 26 [14-123] hours), or in the % of patients who needed vasopressors/inotropes (98% vs 100%). From November 1994, inhaled nitric oxide (NO) was available. Before VV ECMO, 67% of the patients received NO, 24% received surfactant, and 48% were treated with high-frequency ventilation (HFV). There was no significant difference between VV and VA ECMO patients in survival rate (94% vs 92%), ECMO duration (88 [64-116] vs 94 [55-130] hours), time of extubation (9 [7-11] vs 14 [9-15] days), age at discharge (23 [18-30] vs 27 [15-41] days), or incidence of short-term intracranial complications (5.3% vs 16.7%). For the total cohort of 126 infants, indices of disease severity (oxygenation index, alveolar-arterial O 2 gradient, mean airway pressure) did not correlate with outcome measures. Delay in ECMO initiation (> 96 hours) was associated with prolonged mechanical ventilation and hospitalization (P < .01). New therapies (NO, HFV, surfactant) in the second part of the decade were associated with a longer ECMO duration (98 [80-131] vs 87 [60-116] hours; P < .05), no delay in ECMO initiation time (23 [10-40] vs 24 [14-52] hours), and no significant change in survival (97% vs 92.5%). No patient was treated with VA ECMO after 1994.

CONCLUSIONS

Venovenous ECMO is as reliable as VA ECMO in newborns with MAS in severe respiratory failure who need ECMO. Delay in ECMO initiation may result in prolonged mechanical ventilation and increased length of hospital stay. The emergence of new conventional therapies (NO, HFV, surfactant) and particularly increased experience enable sole use of VV ECMO with no significant change in survival in infants with MAS.

Bench-to-bedside review: Ventilator strategies to reduce lung injury -- lessons from pediatric and neonatal intensive care

As in the adult with acute lung injury and acute respiratory distress syndrome, the use of lung-protective ventilation has improved outcomes for neonatal lung diseases. Animal models of neonatal respiratory distress syndrome and congenital diaphragmatic hernia have provided evidence that 'gentle ventilation' with low tidal volumes and 'open-lung' strategies of using positive end-expiratory pressure or high-frequency oscillatory ventilation result in less lung injury than do the traditional modes of mechanical ventilation with high inflating pressures and volumes. Although findings of retrospective studies in infants with respiratory distress syndrome, congenital diaphragmatic hernia, and persistent pulmonary hypertension of the newborn have been similar to those of the animal studies, prospective, randomized, controlled trials have yielded conflicting results. Successful clinical trial design in these infants and in children with acute lung injury/acute respiratory distress syndrome will require an appreciation of the data supporting the modern ventilator management strategies for infants with lung disease.

Controversies in the treatment of meconium aspiration syndrome

MAS remains an infrequent but challenging condition confronting neonatologists. Avoidance of postterm pregnancies, improved intrapartum monitoring,and amnioinfusion have been beneficial. Studies have not demonstrated conclusively that any form of ventilation is superior to others, but strategies that recruit alveoli are desirable. Surfactant lavage or replacement may be beneficial. When hypoxic respiratory failure progresses, iNO may improve oxygenation and avoid ECMO.

Phosphodiesterase inhibitors for persistent pulmonary hypertension of the newborn: a review

Persistent pulmonary hypertension of the newborn (PPHN) is a complex syndrome with multiple causes, with an incidence of 0.43-6.8/1,000 live births and a mortality of 10-20%. Survivors have high morbidity in the forms of neurodevelopmental and audiological impairment, cognitive delays, hearing loss, and a high rate of rehospitalization. The optimal approach to the management of PPHN remains controversial. Inhaled nitric oxide (iNO) is currently regarded as the gold standard therapy, but with as many as 30% of cases failing to respond, has not proven to be the single magic bullet. Given the complex pathophysiology of the disease, any such magic bullet is unlikely. A number of recent studies have suggested a role for specific phosphodiesterase (PDE) inhibitors in the management of PPHN. Sildenafil, a specific PDE5 inhibitor, appears the most promising of such agents. We aim to review the current status and limitations of iNO and the potential of PDE inhibitors in the management of PPHN. The reasons why caution is warranted before specific PDE5 inhibitors like sildenafil are labelled as potential magic bullets for PPHN will be discussed. The need for randomized-controlled trials to determine the safety, efficacy, and long-term outcome following treatment with sildenafil in PPHN is emphasized.

Innovative neonatal ventilation and meconium aspiration syndrome

Respiratory failure remains a major cause of morbidity and mortality in the neonatal population. Infants with hypoxemic respiratory failure because of meconium aspiration syndrome (MAS), persistent pulmonary hypertension of the newborn (PPHN), and pneumonia/sepsis have a potential for increased survival with extracorporeal membrane oxygenation (ECMO). Other treatment options previously limited to inotropic support, conventional ventilatory management, respiratory alkalosis, paralysis and intravenousvasodilators have been replaced by high-frequency oscillatory ventilation (HFOV), surfactant, and inhaled nitric oxide (iNO). HFOV has been advocated for use to improve lung inflation while potentially decreasing lung injury through volutrauma. Other reports describe enhanced efficacy of HFOV when combined with iNO. Subsequent to studies reporting surfactant deficiency or inactivation may contribute to neonatal respiratory failure exogenous surfactant therapy has been implemented with apparent success. Recent studies have shown that iNO therapy in the neonate with hypoxemic respiratory failure can result in improved oxygenation and decreased need for ECMO. In this article, the authors place in context of a system-based strategy the prenatal, natal and postnatal management of babies delivered through meconium stained amniotic fluid (MSAF) so that adverse outcomes are minimized, and the least number of babies require innovative ventilatory support. At Pennsylvania Hospital, over a six-year period (1995 to 2000), 14.5% (3370/23,175 of live births babies were delivered with MSAF. These data show that 4.6% (155/3370) of babies with MSAF sustained MAS. Overall, 26% (40/155) of babies with MAS needed ventilatory support (or 0.17% of all live-births); of these only 20% (8/40 or 0.035% of live births) needed innovative ventilatory support. None died or needed ECMO. These data describe the impact of a system-based approach to prevent and manage adverse outcomes related to MSAF at regional Level III perinatal center.

Inhaled nitric oxide in the treatment of moderate persistent pulmonary hypertension of the newborn: a randomized controlled, multicenter trial

OBJECTIVE

Inhaled nitric oxide (iNO) improves oxygenation and reduces the need for extracorporeal membrane oxygenation in infants with severe persistent pulmonary hypertension of the newborn (PPHN). The effectiveness of iNO in the treatment of moderate PPHN has not been adequately defined. We therefore conducted a randomized, prospective multicenter study to assess whether iNO in patients with moderate PPHN would improve arterial p(a)O(2), prevent progression to severe PPHN, and improve outcomes.

METHODS

Infants > or = 34 weeks gestation with moderate pulmonary hypertension (alveolar-arterial oxygen gradient (AaDO(2)) 500-599 Torr) were randomly assigned to continue standard medical therapy (control group) or standard medical therapy plus iNO (iNO group). For each patient in the iNO group, iNO concentration was increased in steps of 10-20 ppm every 30 minutes until there was no further improvement in arterial p(a)O(2). This concentration of iNO was then maintained while all other ventilatory support, including inspired oxygen concentration, was weaned according to a predefined protocol.

RESULTS

In all, 27 of 40 control patients (58%) compared to six of 40 infants (15%) in the iNO group failed assigned therapy and developed severe PPHN (p<0.0005). Arterial p(a)O(2) improved from 112+/-48 to 133+/-100 (p=0.132) in control infants compared to an increase from 101+/-29 to 208+/-118 (p<0.0005) in iNO-treated patients. For the first 36 hours after study, entry AaDO(2) levels and ventilatory support were significantly lower in iNO-treated infants compared to control patients.

CONCLUSION

In patients with moderate PPHN, treatment with iNO improves arterial p(a)O(2), reduces the amount of ventilatory support needed, and prevents progression to severe PPHN.