Inhaled nitric oxide in congenital diaphragmatic hernia

Outcomes of neonatal congenital diaphragmatic hernia in a non-ECMO center in a middle-income country: a retrospective cohort study

BACKGROUND

Most studies examining survival of neonates with congenital diaphragmatic hernia (CDH) are in high-income countries. We aimed to describe the management, survival to hospital discharge rate, and factors associated with survival of neonates with unilateral CDH in a middle-income country.

METHODS

We retrospectively reviewed the medical notes of neonates with unilateral CDH admitted to a pediatric intensive care unit (PICU) in a tertiary referral center over a 15-year period, from 2003-2017. We described the newborns' respiratory care pathways and then compared baseline demographic, hemodynamic, and respiratory indicators between survivors and non-survivors. The primary outcome measure was survival to hospital discharge.

RESULTS

Altogether, 120 neonates were included with 43.3% (52/120) diagnosed antenatally. Stabilization occurred in 38.3% (46/120) with conventional ventilation, 13.3% (16/120) with high-frequency intermittent positive-pressure ventilation, and 22.5% (27/120) with high frequency oscillatory ventilation. Surgical repair was possible in 75.0% (90/120). The overall 30-day survival was 70.8% (85/120) and survival to hospital discharge was 66.7% (80/120). Survival to hospital discharge tended to improve over time (p > 0.05), from 56.0% to 69.5% before and after, respectively, a service reorganization. For those neonates who could be stabilized and operated on, 90.9% (80/88) survived to hospital discharge. The commonest post-operative complication was infection, occurring in 43.3%. The median survivor length of stay was 32.5 (interquartile range 18.8-58.0) days. Multiple logistic regression modelling showed vaginal delivery (odds ratio [OR] = 4.8; 95% confidence interval [CI] [1.1-21.67]; p = 0.041), Apgar score [Formula: see text] 7 at 5 min (OR = 6.7; 95% CI [1.2-36.3]; p = 0.028), and fraction of inspired oxygen (FiO₂) < 50% at 24 h (OR = 89.6; 95% CI [10.6-758.6]; p < 0.001) were significantly associated with improved survival to hospital discharge.

CONCLUSIONS

We report a survival to hospital discharge rate of 66.7%. Survival tended to improve over time, reflecting a greater critical volume of cases and multi-disciplinary care with early involvement of the respiratory team resulting in improved transitioning from PICU. Vaginal delivery, Apgar score [Formula: see text] 7 at 5 min, and FiO₂ < 50% at 24 h increased the likelihood of survival to hospital discharge.

Congenital diaphragmatic hernia: a narrative review of controversies in neonatal management

The consequences of most hernias can be immediately corrected by surgical repair. However, this isn't always the case for children born with a congenital diaphragmatic hernia. The derangements in physiology encountered immediately after birth result from pulmonary hypoplasia and hypertension caused by herniation of abdominal contents into the chest early in lung development. This degree of physiologic compromise can vary from mild to severe. Postnatal management of these children remains controversial. Although heavily studied, multi-institutional randomized controlled trials are lacking to help determine what constitutes best practice. Additionally, the results of the many studies currently within the literature that have investigated differing aspect of care (i.e., inhaled nitric oxide, ventilator type, timing of repair, role of extracorporeal membrane oxygenation, etc.) are difficult to interpret due to the small numbers investigated, the varying degree of physiologic compromise, and the contrasting care that exists between institutions. The aim of this paper is to review areas of controversy in the care of these complex kids, mainly: the use of fraction of inspired oxygen, surfactant therapy, gentle ventilation, mode of ventilation, medical management of pulmonary hypertension (inhaled nitric oxide, sildenafil, milrinone, bosentan, prostaglandins), the utilization of extracorporeal membrane oxygenation, and the timing of surgical repair.

A Novel Thoracic Ultrasound Measurement After Congenital Diaphragmatic Hernia Repair Identifies Decreased Diaphragmatic Excursion Associated With Adverse Respiratory and Surgical Outcomes

Background and Aim: Congenital diaphragmatic hernia (CDH) is a rare defect often associated with pulmonary hypoplasia and abnormal pulmonary vascular development. Even after successful hernia repair, pulmonary disease may persist into adulthood. Impaired diaphragmatic motility may lead to compromised respiratory function long after index repair. This study investigates whether a novel ultrasound measurement, the diaphragmatic excursion ratio, can be a simple and non-invasive method to evaluate routine diaphragmatic motion after CDH repair, and whether it correlates with adverse surgical and respiratory outcomes. Materials and Methods: A cross-sectional study was conducted in consecutive patients who presented at medium-term follow-up visit between December 2017 and December 2018 after CDH repair at single pediatric hospital. Transthoracic ultrasound was performed with craniocaudal diaphragmatic excursion measured bilaterally during routine breathing. Diaphragmatic excursion ratios (diaphragmatic excursion of repaired vs. unrepaired side) were calculated and retrospectively compared with clinical data including demographics, length of stay, respiratory adjuncts, oral feeding, and need for gastrostomy. Results: Thirty-eight patients (median age at ultrasound, 24 months, interquartile range 11-60) were evaluated. Nine patients underwent primary repair, 29 had non-primary repair (internal oblique muscle flap or mesh patch). Patients with a diaphragmatic excursion ratio below the median (0.54) had longer hospital stays (median 77 vs. 28 days, p = 0.0007) more ventilator days (median 16 vs. 9 days, p =0.004), and were more likely to have been discharged on oxygen (68 vs. 16%, p = 0.001). They were also less likely to be exclusively taking oral feeds at 1-year post-surgery (37 vs. 74%, p = 0.02) and more likely to require a gastrostomy tube in the first year of life (74 vs. 21%, p = 0.003). Conclusions: Transthoracic ultrasound after CDH repair is practical method to assess diaphragm motion, and decreased diaphragm excursion ratio is associated with worse respiratory outcomes, a longer length of stay, and dependence on gastrostomy tube feeding within 1 year. Further prospective studies may help validate this novel ultrasound measurement and offer prognostic value.

Inhaled Nitric Oxide Is Associated with Improved Oxygenation in a Subpopulation of Infants with Congenital Diaphragmatic Hernia and Pulmonary Hypertension

OBJECTIVES

To determine which patients with congenital diaphragmatic hernia (CDH) and pulmonary hypertension (PH) benefit from inhaled nitric oxide (iNO) treatment by comparing characteristics and outcomes of iNO responders to nonresponders.

STUDY DESIGN

We performed a retrospective chart review of infants with CDH treated at our center between 2011 and 2016. In a subset of patients, iNO was initiated for hypoxemia or echocardiographic evidence of extrapulmonary right to left shunting. Initial post-treatment blood gases were reviewed, and patients were classified as responders (increased PaO₂ >20 mm Hg) or nonresponders. Baseline characteristics, echocardiograms and outcomes were compared between groups with Fisher exact tests and Mann-Whitney t tests, as appropriate.

RESULTS

During the study period, 95 of 131 patients with CDH (73%) were treated with iNO. All patients with pretreatment echocardiograms (n = 90) had echocardiographic evidence of PH. Thirty-eight (40%) patients met treatment response criteria. Responders had significant improvements in PaO₂ (51 ± 3 vs 123 ± 7 mm Hg, P < .01), alveolar-arterial gradient (422 ± 30 vs 327 ± 27 mm Hg, P < .01), and PaO₂ to FiO₂ ratio (82 ± 10 vs 199 ± 15 mm Hg, P < .01). Nonresponders were more likely to have left ventricular systolic dysfunction (27% vs 8%, P = .03) on echocardiogram. Responders were less likely to require extracorporeal membrane support (50 vs 24%, P = .02).

CONCLUSIONS

iNO treatment is associated with improved oxygenation and reduced need for ECMO in a subpopulation of patients with CDH with PH and normal left ventricular systolic function.

Initial oxygenation response to inhaled nitric oxide predicts improved outcome in congenital diaphragmatic hernia

BACKGROUND

Pulmonary hypertension (PH) is the most important complication of congenital diaphragmatic hernia (CDH) and still has a high mortality rate. The aim of this study was to evaluate the effectiveness of inhaled nitric oxide therapy in PH due to CDH.

METHODS

Hospital records of children who had undergone inhaled nitric oxide therapy for PH due to CDH between June 2009 and December 2011 were reviewed.

RESULTS

Twenty-nine patients had a diagnosis of CDH at the time of study, and eight of these patients underwent nitric oxide therapy because of failure of conventional ventilation techniques, which was successful in five of these patients. Patients who had a good overall outcome of nitric oxide therapy experienced rapid improvement (pretreatment, mean PaO2 = 44.8 mmHg; after the first hour of therapy, mean PaO2 = 96.8 mmHg), whereas patients with no response did not have a similar course (pretreatment, PaO2 = 37 mmHg; after the first hour, PaO2 = 54.6 mmHg).

CONCLUSION

Inhaled nitric oxide therapy seems to increase survival in PH due to CDH. No predictive parameters to orient patient selection could be identified; however, the early response seemed to predict the overall outcome. Good results in our series were attributed to routine use of sildenafil and dopamine, along with the nitric oxide inhalation.

Inhaled nitric oxide use in neonates with congenital diaphragmatic hernia

OBJECTIVE

To describe the use of inhaled nitric oxide (INO) in newborns with congenital diaphragmatic hernia (CDH).

METHODS

Pediatric Health Information System data were queried for newborns with CDH admitted at <8 days of age at tertiary care US pediatric hospitals between 2003 and 2011. INO treatment status and timing in relation to CDH repair were determined for each infant. Hospital-specific rates of INO use, extracorporeal membrane oxygenation (ECMO) use, and mortality were determined.

RESULTS

Data were analyzed for 1713 neonates with CDH admitted to 33 hospitals. More than half (57%) received INO during their inpatient stay, and utilization varied dramatically between hospitals (34% to 92%). Neonates treated with INO accumulated >$81 million in pharmacy charges. The proportion of infants receiving INO as well as their duration of therapy increased significantly during the study period. The rate of ECMO utilization and mortality did not change significantly during the study period. Hospital-specific mortality rates did not correlate with INO therapy, ECMO utilization, or case volume.

CONCLUSIONS

INO use in neonates with CDH is widespread, and has increased at many US tertiary pediatric hospitals without contemporaneous change in ECMO utilization or mortality. The improvement of evidence-based guidelines for the use of INO in newborns with CDH could lead to a reduction in health care costs for these patients.

Congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is defined by the presence of an orifice in the diaphragm, more often left and posterolateral that permits the herniation of abdominal contents into the thorax. The lungs are hypoplastic and have abnormal vessels that cause respiratory insufficiency and persistent pulmonary hypertension with high mortality. About one third of cases have cardiovascular malformations and lesser proportions have skeletal, neural, genitourinary, gastrointestinal or other defects. CDH can be a component of Pallister-Killian, Fryns, Ghersoni-Baruch, WAGR, Denys-Drash, Brachman-De Lange, Donnai-Barrow or Wolf-Hirschhorn syndromes. Some chromosomal anomalies involve CDH as well. The incidence is < 5 in 10,000 live-births. The etiology is unknown although clinical, genetic and experimental evidence points to disturbances in the retinoid-signaling pathway during organogenesis. Antenatal diagnosis is often made and this allows prenatal management (open correction of the hernia in the past and reversible fetoscopic tracheal obstruction nowadays) that may be indicated in cases with severe lung hypoplasia and grim prognosis. Treatment after birth requires all the refinements of critical care including extracorporeal membrane oxygenation prior to surgical correction. The best hospital series report 80% survival but it remains around 50% in population-based studies. Chronic respiratory tract disease, neurodevelopmental problems, neurosensorial hearing loss and gastroesophageal reflux are common problems in survivors. Much more research on several aspects of this severe condition is warranted.

Congenital diaphragmatic hernia: an overview of the etiology and current management

AIM

To review provide an overview of the etiology and current strategies in the management of congenital diaphragmatic hernia (CDH).

METHODS

We did a comprehensive review of research trends, evidence based studies and epidemiologic studies.

RESULTS

CDH is a life-threatening pathology in infants, and a major cause of death due to the pulmonary hypoplasia and pulmonary hypertension. There is much research related to elucidating the etiology of CDH and developing management strategies to improve the outcomes in these infants.

CONCLUSION

An early diagnosis with increased understanding of this disease is a crucial factor for a timely approach to managing the critically ill infant, and to offer the potential for improved outcomes and substantial reductions in morbidity.

Postnatal management and long-term outcome for survivors with congenital diaphragmatic hernia

Significant advances in the postnatal management of patients with congenital diaphragmatic hernia (CDH) have resulted in a remarkable improvement in survival rates over the past two decades. The success of current postnatal management of CDH patients has rendered fetal intervention to be limited to the most severe cases, and the role for prenatal treatment of CDH patients remains unclear. The adoption of lung-preserving strategies including high-frequency oscillatory ventilation (HFOV) and extracorporeal membrane oxygenation (ECMO) have improved CDH outcomes especially in those patients with significant ventilatory or circulatory compromise. Survival rates of up to 90% are being reported in some high-volume centers. However, the increased survival in CDH patients has been accompanied by an increase in neurological, nutritional and musculoskeletal morbidity among the long-term survivors. This has resulted in the need to provide resources for the long-term follow-up and support of this patient population. In this article, the postnatal management strategies and primary and secondary outcomes of high-volume international pediatric surgical centers will be reviewed. Finally, the role of a multidisciplinary management team for the follow-up of long-term CDH survivors will be discussed.

Management of pulmonary hypertension in congenital diaphragmatic hernia: nitric oxide with prostaglandin-E1 versus nitric oxide alone

AIM

Prostaglandin-E1 (PGE1) is used at most centers for treating pulmonary hypertension (PH) in congenital diaphragmatic hernia (CDH) because it has been regarded as effective. The aim of this study was to investigate the role of PGE1 for treating PH in CDH.

METHODS

We reviewed 49 CDH cases with echocardiography-proven PH. PH was treated with PGE1 and nitric oxide (NO) and high frequency oscillatory ventilation (HFOV) from 1997 to 2001 (PG + NO; n = 19) and with NO and HFOV from 2002 to 2007 (NO; n = 30).

RESULTS

Subject demographics, severity of PH, and presence of other anomalies were not significantly different between the two groups. In the PG + NO group, 12/19 (63.2%) survived (PG + NO-s) and 7/19 (36.8%) died (PG + NO-d). In the NO group, 21/30 (70.0%) survived (NO-s) and 9/30 (30.0%) died (NO-d). Survival rates were not significantly different. In the NO-s group, spontaneous closure of the ductus arteriosus (DA) was significantly earlier compared with the PG + NO-s group (P < 0.01; 4.0 +/- 0.9 vs. 9.5 +/- 2.2 days after birth). DA diameters were significantly larger in groups that died compared with groups that survived (P < 0.01), and PH persisted in groups that died. In the NO-s group, surgery was possible significantly earlier compared with the PG + NO-s group (P < 0.01; 3.75 +/- 0.67 vs. 6.12 +/- 0.78 days after birth). No NO-s case developed a PH crisis even though PGE1 was not used. Hospital stay was significantly shorter in the NO-s group compared with the PG + NO-s group (P < 0.05; 39.9 +/- 19 vs. 53.2 +/- 23 days).

CONCLUSION

Nitric oxide alone would appear to simplify the management of CDH with PH and provide better outcome.

Mid- and long-term effects on pulmonary perfusion, anatomy and diaphragmatic motility in survivors of congenital diaphragmatic hernia

The aim of the present study was to evaluate the pulmonary sequelae and diaphragmatic motility in infant, adolescent and adult patients (pts) who had undergone the repair of a congenital diaphragmatic hernia. Thirty-one (81.5%) out of 38 survivors after left side CDH repair, without using a patch, were followed-up. They were subdivided in two groups. Group A (mid-term follow-up): 12 pts (39%) (5 males, 7 females) with a mean age of 4.5 years; Group B (long-term follow-up): 19 pts (61%) (9 males, 10 females) with a mean age of 21.0 years. All pts underwent physical examination, chest X-ray, diaphragmatic ultrasonographic (US) examination, pulmonary perfusion scintigraphy. Patients of the group B were also submitted to spirometry. All pts had a normal life-style and no one complained of respiratory symptoms. The chest X-ray revealed pathologic findings in 12 pts (39%). 8 pts (26%) showed chest wall alterations. The profile of the left diaphragmatic dome appeared irregular in 9 pts (29%). In all pts M-mode sonography disclosed a reduced diaphragmatic motility on the treated side. The mean pulmonary perfusion scintigraphy value on the affected side was 39.2+/-0.7%. The spirometric study showed normal values. We noted that the lung perfusion significantly and rapidly improved after CDH repair even the apparently hypoplastic and small lungs, the diaphragm maintained a good contractility during forced respiration.

New approaches to managing congenital diaphragmatic hernia

A number of new techniques have been studied for managing newborns with congenital diaphragmatic hernia and respiratory insufficiency. Among these have been the techniques of delayed approach to the repair of the diaphragmatic hernia; permissive hypercapnia; nitric oxide and surfactant administration; intratracheal pulmonary ventilation; liquid ventilation; perfluorocarbon-induced lung growth; and lung transplantation. These interventions are at various stages of development and evaluation of effectiveness. All, however, are being explored in the hopes of improving outcome in patients with congenital diaphragmatic hernia who continue to have significant morbidity and mortality in the newborn period.

Inhaled nitric oxide with early surgery improves the outcome of antenatally diagnosed congenital diaphragmatic hernia

BACKGROUND/PURPOSE

The outcome of antenatally diagnosed congenital diaphragmatic hernia (CDH) has remained poor despite aggressive therapeutic strategies. Since 1996, the authors have used a new approach including early surgery and inhaled nitric oxide (iNO). The aim of this study is to determine whether early surgery in combination with iNO improves the clinical outcome of antenatally diagnosed CDH.

METHODS

From 1988, 40 consecutive neonates with antenatally diagnosed CDH were admitted to the authors' hospital. Ten cases of fatal chromosomal anomalies or major cardiac anomalies were excluded from this study. From 1988 through 1995 (period 1: n = 13), delayed surgery was used in high-risk CDH. From 1996 through 2000 (period 2: n = 17), early surgery in combination with iNO was used. The severity of lung hypoplasia was evaluated using the fetal lung/thorax transverse area ratio (L/T). High-frequency oscillatory ventilation (HFOV) was used routinely during the study periods, and extracorporeal membrane oxygenation (ECMO) was used on basis of conventional entry criteria. The authors compared the clinical outcome, use of ECMO, and the L/T between the 2 periods retrospectively.

RESULTS

Patients in the 2 periods were comparable in terms of birth weight, gestational age, and the L/T. The mean age at surgery was 3.1 +/- 4.9 days in period 1, and 0.8 +/- 1.1 days in period 2. Fewer infants in period 2 compared with period 1 were treated with ECMO (period 1, 62% v period 2, 6%; P <.01). There was significant difference in the survival rate between the 2 periods (period 1, 38% v period 2, 94%; P <.01).

CONCLUSION

Our data suggest that early surgery and iNO improves the outcome and reduces the requirement of ECMO in the treatment of antenatally diagnosed CDH.

Inhaled nitric oxide in the neonatal period

Pulmonary hypertension of the newborn is an important cause of hypoxaemia, particularly in the at term or near term neonate. It can occur as a primary condition or secondary to a variety of other diseases. Endogenous nitric oxide is an important modulator of vascular tone in pulmonary circulation. Initial uncontrolled studies indicated that inhalation of nitric oxide resulted in a reduction in pulmonary hypertension, with improvement in oxygenation, but no change in the systemic vascular resistance. There have now been a number of randomised trials performed exploring the efficacy of inhaled nitric oxide. These trials have demonstrated that in at term or near term infants, inhaled nitric oxide reduces the combined end point of death or the need for extracorporeal membrane oxygenation. The significant effect seems due to the reduced extracorporeal membrane oxygenation requirement. No such beneficial effect has been consistently reported in infants with congenital diaphragmatic hernia. Randomised trials have failed to highlight long-term positive results in preterm infants. Inhaled nitric oxide has side effects, although those due to nitrogen dioxide and methaemoglobin formation can be minimised by appropriate nitric oxide delivery. It is important to use the smallest effective nitric oxide dose, continuous nitric oxide and nitrogen dioxide monitoring and frequent methaemoglobin analyses. Careful patient selection should be undertaken, avoiding those at high risk of haemorrhagic complications. Longer term follow-up studies are required to determine the real risk:benefit ratio of inhaled nitric oxide treatment.

Pulmonary barotrauma in congenital diaphragmatic hernia: a clinicopathological correlation

BACKGROUND/PURPOSE

The high mortality rate in congenital diaphragmatic hernia (CDH) has been ascribed to pulmonary hypoplasia and persistent pulmonary hypertension of the newborn (PPHN). One of the principal treatment strategies has been the use of hyperventilation to reverse ductal shunting, but the wisdom of this approach is being questioned because of parenchymal lung injury from high inflation pressures. The authors hypothesize that the use of hyperventilation to reverse or prevent ductal shunting would result in ventilator-induced lung injury, which would be evident on postmortem examination. A retrospective review of clinical and autopsy information was conducted.

METHODS

Clinical and autopsy information gathered for a previously published series of 223 infants with CDH presenting in the first 24 hours of life was reviewed. Autopsy and clinical data were analyzed from 68 of 101 nonsurvivors who died with severe hypoxemia.

RESULTS

Sixty-two of 68 cases (91%) had evidence of diffuse alveolar damage and hyaline membrane formation, which was more evident in the ipsilateral lung. Forty-four (65%) infants had pneumothoraces, and 4 infants had interstitial fibrosis. Pulmonary hemorrhage was seen in 35 cases (50 maximum peak inspiratory pressure [mean +/- SD] was 40.4+/-7.9 cm H2O and lowest modified ventilatory index [respiratory rate x peak airway pressure] was 2323+/-836). The degree of pulmonary hypoplasia was evaluated by lung weight with the ratio of the observed combined lung weight to the expected lung weight based on birth weight and gestational age. The ratio based on birth weight was 57%+/-25%, and the ratio based on gestational age was 60%+/-26%. Twenty-one infants (35%) had nonpulmonary anomalies. The most significant was a 10% incidence of congenital heart disease. Apart from this, lethal nonpulmonary anomalies were rare.

CONCLUSION

These results suggest that lung injury secondary to mechanical ventilation plays an important role in the mortality rate of patients with CDH, which may become increasingly significant when there is underlying pulmonary hypoplasia.

Role of inhaled nitric oxide as a selective pulmonary vasodilator in pediatric cardiac surgical practice

Our aim was to assess the role of inhaled nitric oxide (NO) therapy in post operative cases of congenital heart defects who developed pulmonary arterial hypertensive (PAH) crisis and had no response with conventional management. From February '95 to January '97, inhaled NO therapy was used in 21 children. Age ranged from 2 months to 9 years (mean 5.6 years) and duration of therapy ranged from 1 to 13 days. Of 21 patients, 17 responded well with 5-20 ppm while 4 did not. The preoperative mean pulmonary systolic pressure was 88 mm Hg against mean systemic pressure of 96 mm Hg. Post operatively, their PA pressure reduced to 62 mm Hg, with systemic pressure of 98 mm Hg. After using inhaled NO, PA pressure dropped to 24 mm Hg (mean systolic) (p < 0.007), after excluding the non responders. Of 4 non responders, two died due to irreversible pulmonary vascular disease and remaining two died due to residual defects. The study shows that inhaled NO is a selective pulmonary vasodilator, which is useful in postoperative PAH crisis and also reduces the transpulmonary gradient in single ventricle repair cases. It is safe and effective for prolonged use. It is very useful in Indian perspective, when more number of cases with congenital heart defects (CHD) along with severe PAH are encountered routinely.

Inhaled nitric oxide in persistent pulmonary hypertension of the newborn refractory to high-frequency ventilation

BACKGROUND: This study was designed to evaluate the effect of nitric oxide (NO) on the management of neonates with severe persistent pulmonary hypertension refractory to high-frequency oscillatory ventilation. METHODS: The birth weight and the gestational age of infants were 3125.5 +/- 794 g (mean +/- SD) and 39 +/- 2.4 weeks, respectively. All neonates were ventilated for an average of 137.5 min (range 90-180 min) prior to NO therapy. The mean oxygenation index (OI) of all neonates prior to NO was 46.3 +/- 5 (mean +/- SEM). NO was initially administered at 20 parts per million (ppm) for at least 2 h and increased gradually by 2 ppm to a maximum of 80 ppm. RESULTS: Eighteen infants (75%) responded and six (25%) did not respond to the treatment. Three neonates died in the responding group, while all the non-responders died (P = 0.0001). The survival rate was 62.5% among all neonates. NO significantly decreased OI (P < 0.0001) and improved the arterial/alveolar (a/A) oxygen ratio (P < 0.0001) within the first 2 h of NO therapy in 61.1% of the responders. However, the OI and the a/A oxygen ratio remained almost the same throughout the treatment in the non-responders and the non-survivors. CONCLUSION: Inhaled NO at 20 ppm, following adequate ventilation for 2 h without significant response, could be used to identify the majority of the non-responders in order to seek other alternatives.

Delayed repair of congenital diaphragmatic hernia with early high-frequency oscillatory ventilation during preoperative stabilization

PURPOSE

The authors reviewed their experience in the management of CDH after the introduction of early high-frequency oscillatory ventilation (HFOV) during the preoperative stabilization period and delayed CDH repair.

METHODS

This is a retrospective analysis of 24 consecutive infants with CDH treated at University of California, Irvine Medical Center (UCIMC) during a 36-month period from January 1993 to December 1996.

RESULTS

Two patients were excluded from the study: one fetus with a prenatal diagnosis was referred for fetal surgery; one infant received CDH repair at another institution 2 weeks before transfer to UCIMC. Eight (36%) infants were inborn, and nine (41%) had a prenatal diagnosis of CDH. Median gestational age was 40 weeks (range, 29 to 42 weeks). Median birth weight was 3,019 g (range, 1,205 to 4,337 g). The defect was left sided in 18 infants (86%). Twenty-one infants were intubated within 5 hours of life, 15 had an AaDO2 greater than 610, 11 had an oxygenation index greater than 40, and 11 had a pH of less than 7.2. The median ratio of pulmonary artery pressure to systemic blood pressure was 0.93 (range, 0.51 to 1.15) in 12 infants. Eighteen infants were placed on HFOV within a median of 1 hour of life. Nitric oxide was given to six infants and surfactant to eight. Four infants were referred for extracorporeal membrane oxygenation (ECMO). Repair of CDH was performed on infants at a median age of 33.5 hours (range, 5.5 to 322). Six (30%) received a prosthetic patch. Overall 18 of 22 infants survived (81%); three survivors received ECMO. Two infants of the survivor group had congenital heart anomalies: one ventricular septal defect (VSD) and one double-outlet right ventricle with a VSD. Of the four nonsurvivors, one had lethal cardiac anomalies and bilateral CDH, two had severe bilateral pulmonary hypoplasia (one received ECMO), and one infant was a 29-week premature baby who did not qualify for ECMO.

CONCLUSION

We report a survival rate of 81% (18 of 22) with the management of CDH by delayed surgical repair, early postnatal HFOV, and selective referral for ECMO.

Effect of dexamethasone on endothelial nitric oxide synthase in experimental congenital diaphragmatic hernia

AIMS

To study the effect of prenatal glucocorticoid treatment on endothelial nitric oxide synthase (eNOS) expression in rats with congenital diaphragmatic hernia (CDH).

METHODS

CDH was induced in fetal rats by the maternal administration of nitrofen on day 9.5 of gestation. Dexamethasone was administered on days 18.5 and 19.5 before delivery of the fetuses on days 20.5 and 21.5. Pulmonary eNOS protein expression was studied by western immunoblotting and immunohistochemistry.

RESULTS

On day 20.5, eNOS expression was significantly reduced in CDH pups compared with normal control rats. Dexamethasone treated CDH pups had eNOS concentrations equivalent to those of normal animals. By day 21.5, however, there was no detectable difference in eNOS expression between the experimental groups.

CONCLUSIONS

eNOS is deficient in near term (day 20.5) CDH rats. Dexamethasone restores eNOS expression in these animals to that seen in normal rat lungs. At term, the precise role of eNOS in the pathophysiology of CDH remains uncertain.

Antenatal glucocorticoid therapy suppresses angiotensin-converting enzyme activity in rats with nitrofen-induced congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Neonates with congenital diaphragmatic hernia (CDH) have a high morbidity and mortality rate caused by pulmonary hypoplasia associated with pulmonary hypertension (PH). In experimental CDH, antenatal glucocorticoid therapy improves surfactant biochemical immaturity, enhances lung compliance, and induces morphological maturation in CDH rats. The effects of steroid therapy on preventing or treating PH in this condition have not been studied. Angiotensin converting enzyme (ACE), which is produced by the vascular endothelium, is implicated in the pathogenesis of pulmonary hypertension. The aim of this study was to evaluate the effect of antenatal glucocorticoid therapy on ACE activity and expression in CDH rat lungs.

METHODS

CDH was induced in fetal rats by the maternal administration of 100 mg nitrofen on day 9.5 of gestation (term, day 22). Dexamethasone (Dex) (0.25 mg/kg) was given by intraperitoneal injection on days 18.5 and 19.5 before delivery of the fetuses by cesarean section on day 21.5. Control animals received olive oil (OO) by gavage and normal saline (NS) as vehicle injection. ACE activity was measured spectrophotometrically in the lungs of rats from four treatment groups: CDH-NS, non-CDH-NS, CDH-Dex, and OO-NS controls. Total lung ACE activity (mU per lung) was significantly lower in CDH-NS (P = .002) and CDH-Dex (P = .004) rats compared with non-CDH-NS and OO-NS controls (9.1 +/- 1.0 and 10.7 +/- 1.3 v 16.2 +/- 1.6 and 15.4 +/- 1.7). When specific ACE activity (mU/mg protein) was derived by expressing ACE activity per milligram of lung protein, CDH-NS animals showed elevated specific ACE activity (P = .05) compared with OO-NS controls (6.31 +/- 1.1 v 4.4 +/- 0.4). CDH-Dex animals had a significantly lower specific ACE activity (P = .01) compared with CDH-NS and Non-CDH-NS rats (4.0 +/- 0.4 v 6.31 +/- 1.1 and 5.83 +/- 0.54). The specific ACE activity levels of CDH-Dex rats were equivalent to those seen in the lungs of OO-NS controls (P = .24).

CONCLUSION

Antenatal steroid therapy, by suppressing pulmonary ACE activity, may reduce the risk of pulmonary hypertension developing in human newborns with antenatally diagnosed CDH.

Perioperative assessment of respiratory compliance and lung volume in infants with congenital diaphragmatic hernia: prediction of outcome

BACKGROUND/PURPOSE

Infants who have congenital diaphragmatic hernia (CDH) have high mortality and morbidity. The aim of this study was to determine the relative ability of the results of serial measurements of compliance of the respiratory system (CRS) and lung volume (functional residual capacity (FRC)) to predict poor outcome: death or oxygen dependency at 28 days. In addition, the authors wished to document the evolution of any lung function abnormalities during the perioperative period.

METHODS

Daily measurements of CRS and FRC were made in the first week of life and subsequently during week 2 in 16 infants who had a median gestational age of 38 weeks and birth weight of 3.2 kg.

RESULTS

Seven infants had a poor outcome: five died and two others remained oxygen dependent beyond 28 days. The infants who had a poor outcome were characterized on day 1 by a significantly lower CRS, but not FRC (P < .05). In comparison with results from day 1, the median CRS of the infants overall had significantly improved only by week 2 (P < .05), there was no such significant change in FRC with increasing postnatal age. At week 2, only the CRS results differed significantly between those infants who had and who did not have poor outcome (P < .05).

CONCLUSION

The results of serial measurements of CRS, rather than FRC are the more useful predictor of outcome in infants who have CDH.

Nitric oxide in respiratory failure in the newborn infant

Nitric oxide given as an inhalation (INO) is a novel selective pulmonary vasodilator without effects on the systemic circulation. Preliminary observations indicated that INO treatment was associated with improvements in oxygenation in near-term newborn infants with hypoxic respiratory failure and persistent pulmonary hypertension of the newborn (PPHN). Subsequently, at least eight prospective randomized controlled trials evaluating the use of INO in the near-term neonate with hypoxic respiratory failure have been presented or published. A meta-analysis of these trials has provided evidence that INO improves the PaO2 in the INO-treated infants by 52.8 mm Hg (weighted mean difference) compared with controls (95% CI, 38.2, 67.4), and significantly decreases the oxygenation index by 16.9 compared with controls (95% CI, -22.2, -11.6). The incidence of death or need for ECMO is significantly reduced by treatment with INO, relative risk 0.71 compared to control (95% CI, 0.57, 0.87), with the majority of the improvement observed in the reduction in the need for ECMO. A single study of infants with congenital diaphragmatic hernia (CDH) did not show a benefit for early INO therapy, with treated infants having a greater requirement for ECMO (P = .043). At present, there are no long-term evaluations of infants who have received INO as part of these prospective trials. INO improves oxygenation and reduces the need for ECMO in the near-term hypoxic neonate, but further research is required to evaluate the ultimate safety and benefit of this therapy.

Inhaled nitric oxide and hypoxic respiratory failure in infants with congenital diaphragmatic hernia. The Neonatal Inhaled Nitric Oxide Study Group (NINOS)

OBJECTIVE

We designed and conducted a randomized, double-masked, controlled multicenter study to determine whether inhaled nitric oxide (INO) in term and near-term infants with congenital diaphragmatic hernia (CDH) would reduce the occurrence of death and/or the initiation of extracorporeal membrane oxygenation (ECMO).

PATIENTS AND METHODS

Infants of 34 weeks gestation or more, <14 days of age with CDH, without known structural heart disease, requiring assisted ventilation for hypoxemic respiratory failure with two oxygenation indices (OIs) of 25 or more at least 15 minutes apart, were eligible for this trial. Infants were centrally randomized and then received masked treatment with 20 ppm NO or 100% oxygen as control. Infants with less than a full response to 20 ppm NO (increase in PaO2 > 20 Torr) after 30 minutes were evaluated at 80 ppm NO/control study gas.

RESULTS

The 28 control and 25 treated infants enrolled by the 13 participating centers were not significantly different at randomization for any of the measured variables including prerandomization therapies and initial OIs (45.8 +/- 16.3 for controls, 44.5 +/- 14.5 for INO). Death at <120 days of age or the need for ECMO occurred in 82% of control infants compared with 96% of INO infants (ns). Death occurred in 43% of controls and 48% of the INO group (ns), and ECMO treatment was used for 54% of control and 80% of INO-treated infants. There was no significant improvement in PaO2 (delta PaO2 7.8 +/- 19.8 vs 1.1 +/- 7.6 Torr, ns) nor significant reduction in OI (-2.7 +/- 23.4 vs 4.0 +/- 14.8, ns) associated with INO treatment. Mean peak nitrogen dioxide (NO2) concentration was 1.9 +/- 1.3 ppm and the mean peak methemoglobin was 1.6 +/- 0.8 mg/dL. No infant had study gas discontinued for toxicity. There were no differences between the control and INO groups for the occurrence of intracranial hemorrhage, specific grades of intracranial hemorrhage, periventricular leukomalacia, brain infarction, and pulmonary or gastrointestinal hemorrhages.

CONCLUSIONS

Although the immediate short-term improvements in oxygenation seen in some treated infants may be of benefit in stabilizing responding infants for transport and initiation of ECMO, we conclude that for term and near-term infants with CDH and hypoxemic respiratory failure unresponsive to conventional therapy, inhaled NO therapy as used in this trial did not reduce the need for ECMO or death.

Congenital diaphragmatic hernia--a tale of two cities: the Toronto experience

PURPOSE

The optimal therapy for congenital diaphragmatic hernia (CDH) is evolving. This study analyzes the results of treatment of CDH in a large tertiary care pediatric center using conventional and high-frequency oscillatory ventilation (HFOV) without extracorporeal membrane oxygenation (ECMO) contrasting these with a parallel study from a similar large urban center using conventional ventilation with ECMO.

METHODS

Between 1981 and 1994, 223 consecutive neonates who had CDH diagnosed in the first 12 hours of life were referred for treatment before repair. Conventional ventilation was used with conversion to HFOV for refractory hypoxemia or hypercapnia, and a predicted near 100% mortality rate. ECMO was used in only three patients, all of whom died. A retrospective database was collected. Thirty-one clinical variables were tested for their association with the outcome. Common ventilatory and oxygenation indices were tested for their prognostic capability.

RESULTS

Apgar scores, birth weight, right-sided defects, pneumothorax, total ventilatory time, and the use of high frequency oscillatory ventilation were the only variables associated with outcome. A modified ventilatory index and postductal A-aDo2 were strong prognostic indicators. From 1981 to 1984 surgery was performed on an emergency basis. Since 1985 surgery was deferred until stabilization had been achieved. This resulted in a shift in the mortality from postoperative to preoperative with no change in total survival. HFOV did not alter the overall survival. Results of autopsies performed (70%) showed significant pulmonary hypoplasia and barotrauma as the primary causes of death. The survival was 54.7%.

CONCLUSION

Conventional ventilation with HFOV produced equal survival to conventional ventilation with ECMO in two comparable series. Pulmonary hypoplasia was the principle cause of death. This continued high mortality at both centers suggests that new therapies are required to improve outcomes.

Nitric oxide dose response during moderate and severe hypoxia in swine

BACKGROUND

Elucidation of factors that influence the dose response to inhaled nitric oxide is crucial to optimizing its therapeutic benefit. We investigated whether severity of hypoxia is one such factor.

METHODS

Seven Yorkshire swine underwent 14 triphasic experiments: (1) control period of mechanical ventilation (fractional concentration of oxygen = 0.3); (2) induction of hypoxic pulmonary hypertension (fractional concentration of oxygen = 0.1 to 0.15); and (3) inhaled nitric oxide at 5, 10, 20, 40, and 80 parts per million (ppm). Hemodynamics and arterial blood gases were measured by pulmonary and systemic arterial catheters.

RESULTS

Experiments were divided into two groups of seven based on hypoxia severity: severe (arterial oxygen tension, 25 to 40 mm Hg) and moderate (arterial oxygen tension, 41 to 60 mm Hg). The percent changes in mean pulmonary artery pressure after each dose were compared within each group by repeated measure analysis of variance and each dose was compared between the two groups by Student's t test. A statistically significant dose response existed in both groups (p < 0.02). Low doses resulted in significantly less vasodilation in the severe versus the moderate hypoxia group (5 ppm, 59% +/- 6% versus 94% +/- 7%, p = 0.003; 10 ppm, 69% +/- 8% versus 99% +/- 8%, p = 0.017).

CONCLUSIONS

Lower doses are significantly less effective in achieving maximal pulmonary vasodilation during severe hypoxia. Therefore, the degree of hypoxia is a determinant of the inhaled nitric oxide dose response.

Mortality among infants with high-risk congenital diaphragmatic hernia in Singapore

Several factors suggested to predict mortality in congenital diaphragmatic hernia (CDH) have not always been applicable in different centers. A retrospective review was conducted of 19 consecutive neonates in Singapore in whom CDH was diagnosed within 12 hours of birth to identify factors associated with mortality. Of the 19 cases, 15 (79%) were diagnosed using antenatal ultrasonography. Eight (42%) underwent primary repair at a median age of 23 hours (range, 12 to 50 hours). Of the 19 infants, 15 died (mortality rate, 79%). Survivors until hospital discharge were compared with nonsurvivors. Antenatal diagnosis and stomach position in left-sided defects had no effect on outcome, although polyhydramnios tended to be associated with nonsurvival. Significant postnatal factors associated with mortality included a low arterial pH level, low initial arterial-alveolar oxygen ratio, high initial alveolar-arterial oxygen gradient, as well as high oxygenation and ventilation indices. These results reflect difficulty in oxygenation because of pulmonary hypoplasia despite evidence of adequate ventilation. There was no difference between survivors and nonsurvivors in either their initial or best postductal blood gases. The "Bohn quadrants" did not aid in predicting survival of infants who underwent repair because all eight such infants had best postductal carbon dioxide values of less than 40 mm Hg and ventilation indices of less than 1,000. Yet only four (50%) survived until hospital discharge. Large-scale evaluation of these factors may be required in the future to demonstrate their validity and reliability because of changing management strategies for CDH.

Prediction of morbidity during infancy after repair of congenital diaphragmatic hernia

Recent studies have suggested there may be a high incidence of pulmonary and extrapulmonary sequelae among infants who have undergone repair of congenital diaphragmatic hernia (CDH). The aim of this study was to identify factors that predict high-risk cases to facilitate counseling of parents. Morbidity, defined as conditions requiring treatment and/or hospitalization during follow-up, was documented. Only five of 15 cases that had been diagnosed antenatally (at 16 to 26 weeks' gestation) and underwent surgical repair after preoperative stabilization were without morbidity at the time of follow-up. Respiratory problems were identified in seven (chylothorax in 3, recurrent infections in 4) and failure to thrive in four; three infants required further gastrointestinal surgery. A comparison of infants with and without morbidity showed that the only significant difference between the groups was in the duration of respiratory support. A requirement for respiratory support for more than 10 days had 90% sensitivity, 100% specificity, and a positive predictive value for morbidity at follow-up of 100%.

Sustained pulmonary vasodilation after inhaled nitric oxide for hypoxic pulmonary hypertension in swine

It has been shown that pulmonary vasodilation is sustained after discontinuation of inhaled nitric oxide (INO) during moderate hypoxic pulmonary hypertension (HPH) in swine. The present investigations demonstrated how INO dose, hypoxia duration, and endogenous NO production influence this important phenomenon. Fifteen adolescent Yorkshire swine were randomly assigned to three groups (n = 5 each) and underwent the following phasic experimental protocol: (I) Baseline ventilation (FIO2 = .3); (II) Initiating HPH (FIO2 = .16 to .18, PaO2 = 45 to 55 mm Hg); (III) INO at 10 ppm; (IV) Posttreatment observation; (V) INO of 80 ppm; and (VI) Posttreatment observation. Phase II (pretreatment hypoxia) lasted 30 minutes in group A (short hypoxia) and 120 minutes in group B (long hypoxia). N-nitro-L-arginine methyl ester (NAME) was used to inhibit nitric oxide synthase (NOS) throughout the experiment in group C (short hypoxia + NAME). Hemodynamics and blood gases were monitored by systemic and pulmonary artery catheters placed by femoral cutdown. Analysis of variance with post-hoc adjustment was used to compare groups at each phase, and the paired t test was used for comparisons within a group. With respect to baseline mean pulmonary artery pressure (MPAP) and pulmonary vascular resistance (PVR), there were no significant differences among the three groups. MPAP and PVR were significantly higher in group C than in group A during phase II, (MPAP, 76% +/- 8% v 33% +/- 2%; PVR, 197% +/- 19% v 78% +/- 10%; P < .05). There were no significant differences in MPAP or PVR during phases III through VI. When MPAP was expressed as percent dilation, 80 ppm caused significantly more dilation than did 10 ppm in all three groups. Groups A and C had significantly higher sustained pulmonary artery dilation after 80 ppm than after 10 ppm (A, 82% +/- 31% v 17% +/- 11%; C, 68% +/- 10% v 42% +/- 12%; both P < .05), but group B did not (43% +/- 15% v 30% +/- 9%; P = .25). High dose results in stronger vasodilation than low dose during and after INO for moderate HPH of short duration. Long hypoxia blunts this high-dose advantage. Endogenous NO inhibition augments HPH but does not decrease pulmonary vasodilation during or after INO.

Inhaled nitric oxide for children with congenital heart disease and pulmonary hypertension

BACKGROUND

Endothelium-derived nitric oxide (NO) is a potent vasodilator and a major mediator of pulmonary vascular tone.

METHODS

Five infants underwent a trial of inhaled NO with hemodynamic monitoring in the operating room after atrioventricular canal repair. An additional 15 patients with congenital heart disease and refractory pulmonary hypertension were treated with inhaled NO for 1 day to 10 days postoperatively.

RESULTS

In the 5 infants with atrioventricular canal, corrective surgical intervention and conventional therapy (hyperventilation, inspired oxygen fraction of 0.80, and inotropic agents) lowered mean pulmonary artery pressure from 49.5 +/- 10.5 to 20.0 +/- 2.2 mm Hg (p < 0.001). Adding inhaled NO further decreased mean pulmonary artery pressure to 18.0 +/- 2.8 mm Hg (p = not significant). Inhaled NO had no effect on ventricular function curves (inflow occlusion) in this group. In the 15 patients with refractory postoperative pulmonary hypertension, 11 had a favorable response to inhaled NO, with a decrease in mean pulmonary artery pressure from 30.9 +/- 5.8 to 23.1 +/- 5.4 mm Hg (p < 0.01) in 8 patients with pulmonary artery catheters.

CONCLUSIONS

These studies demonstrate that inhaled NO has minimal beneficial effect on pulmonary artery pressure or cardiac output in infants after repair of atrioventricular canal. Inhaled NO is effective in decreasing PAP postoperatively in select patients with congenital heart disease and pulmonary hypertension refractory to conventional therapeutic modalities.

Timing of repair of congenital diaphragmatic hernia requiring extracorporeal membrane oxygenation support

Treatment of congenital diaphragmatic hernia (CDH) has undergone a revolutionary change in philosophy, from previous urgent repair to the present practice of stabilization and delayed repair. However, when extracorporeal membrane oxygenation (ECMO) is required, many people believe that the risk of postoperative pulmonary hypertension (PPHN) mandates hernia repair while on ECMO. This report details the experience in two ECMO centers with stabilization, ECMO if required, and CDH repair post-ECMO. All CDH patients symptomatic in the first hour of life with a gestational age of at least 34 weeks during the period were reviewed retrospectively. Standard criteria were used to select patients for ECMO. High-frequency jet or oscillating ventilators and nitric oxide were not routinely available throughout the study period, but were used in some of the more recent patients. A total of 60 patients presented to the two centers; 24 cases were stabilized with conventional management, repair of the CDH was done elective, and survival was 100%. Eight patients were referred after having repair elsewhere; six survived (75%). The two deaths were attributable to associated lethal lesions--complex cyanotic heart disease and alveolar capillary dysplasia. Eight patients who required ECMO were managed with the intention of repairing the defect on ECMO. Four survived (50%). Two patients died before repair. Twenty patients were managed with ECMO, with the intention of repairing the defect after decannulation. Overall survival was 13 (65%), deaths were caused by pre-ECMO hypoxia, pulmonary insufficiency, and associated cardiac disease. No patient had recurrent pulmonary hypertension after late repair.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitric oxide. Novel biology with clinical relevance

OBJECTIVE

The author provides the reader with a view of the regulation and function of nitric oxide (NO), based on the three distinct enzyme isoforms that synthesize NO.

SUMMARY BACKGROUND DATA

Nitric oxide is a short-lived molecule exhibiting functions as diverse as neurotransmission and microbial killing. Recent advances in the characterization of the enzymes responsible for NO synthesis and in the understanding of how NO interacts with targets have led to new insights into the many facets of this diverse molecule.

METHODS

Nitric oxide is produced by one of three enzyme isoforms of NO synthesis. These enzymes vary considerably in their distribution, regulation, and function. Accordingly, the NO synthesis or lack of NO production will have consequences unique to that isoform. Therefore, this review summarizes the regulation and function of NO generated by each of the three isoforms.

RESULTS

Nitric oxide exhibits many unique characteristics that allow this molecule to perform so many functions. The amount, duration, and location of the NO synthesis will depend on the isoform of NO synthase expressed. For each isoform, there probably are disease processes in which deficiency states exist. For induced NO synthesis, states of overexpression exist.

CONCLUSIONS

Understanding the regulation and function of the enzymes that produce NO and the unique characteristics of each enzyme isoform is likely to lead to therapeutic approaches to prevent or treat a number of diseases.

Pathophysiology of congenital diaphragmatic hernia. X: Localization of nitric oxide synthase in the intima of pulmonary artery trunks of lambs with surgically created congenital diaphragmatic hernia

The pathophysiology of congenital diaphragmatic hernia (CDH) results from a combination of pulmonary hypoplasia, pulmonary hypertension, and surfactant deficiency. Previously we demonstrated that inhaled nitric oxide (NO), a known vasodilator, only improves oxygenation and decreases pulmonary artery pressures when the lamb model of CDH is pretreated with exogenous surfactant. Nitric oxide synthase (NOS) in endothelial cells is responsible for the production of NO, a mediator of smooth muscle cell relaxation. Pulmonary hypertension in CDH may result from a defect in the endogenous production of NO. Our aim was to determine whether the main pulmonary artery trunks in CDH lambs have NOS immunoreactivity. Cryostat sections of paraformaldehyde-fixed specimens of pulmonary artery and aortic rings from 10 CDH lambs and five control lambs were processed for NADPH-diaphorase activity. Immunolocalization of NOS was studied in paraformaldehyde-fixed sections and compared with serially cut specimens from identical rings that were tested for NADPH-diaphorase activity. Intense NADPH-diaphorase staining was present in the intimal layer (endothelial lining) of the pulmonary artery and aortic rings of both the CDH and control lambs. This activity colocalized with NOS immunoreactivity in all specimens. Both NOS immunoreactivity and NADPH-diaphorase staining were lacking in cartilage, which were used as negative controls. NOS is present in the main pulmonary artery trunks of CDH lambs. To our knowledge, this is the first report of NOS immunoreactivity in CDH. We can only speculate whether this activity is preserved in other areas of the vascular tree in CDH, ie, pulmonary capillaries and veins. Perhaps the pulmonary hypertension in CDH is not caused by an NOS deficiency.