Improved oxygenation in a randomized trial of inhaled nitric oxide for persistent pulmonary hypertension of the newborn

OBJECTIVE

To determine the effect of inhaled nitric oxide (NO) on clinical outcome in newborns with persistent pulmonary hypertension (PPHN).

DESIGN

A prospective, randomized trial of patients referred to a level 3 nursery in a single large center. Clinicians were not masked to group assignment. Crossover of patients from control to NO treatment was not permitted.

METHODS

We randomized 49 mechanically ventilated newborns, transferred to our center with clinical and echocardiographic evidence of severe PPHN (arterial oxygen tension [PaO2] <100; fractional inspired oxygen = 1) to treatment with or without NO. Patients with gestational age <34 weeks or with congenital heart disease or diaphragmatic hernia were excluded. High-frequency oscillatory ventilation was used but not allowed concomitantly with NO. Primary outcome variables were oxygenation, mortality, and use of extracorporeal membrane oxygenation (ECMO).

RESULTS

Meconium aspiration syndrome and isolated PPHN were the most common diagnoses (32/49) and were distributed equally between groups. The median age at the time of entry into the study was similar between groups, 25 hours for control patients and 18 hours for NO patients. Median baseline oxygenation index (OI) was similar in 23 control (OI = 29) and 26 NO (OI = 30) patients. Mortality (8%), use of ECMO (33%), median days on mechanical ventilation (9 days), and duration of supplemental oxygen (13 days) were not different between treatment groups. PaO2, oxygen saturation, and OI improved in the NO group compared with baseline and to control patients at 15 minutes. The median percent change in OI (-31%) in the NO group was significantly different from baseline and from the control group. The difference in oxygenation between treatment groups was still apparent 12 hours after baseline. Before cannulation for ECMO, oxygenation was better in the NO group compared with control patients. Among patients who were placed on ECMO, the median time from baseline to ECMO cannulation was 2.4 hours (range, 1 to 12 hours) among control patients and 3.3 hours (range, 2 to 68 hours) for those randomized to receive NO. There was a tendency to observe fewer adverse neurologic events (seizure and intracranial hemorrhage) in the NO group (4/26 vs 8/23). One child with alveolar capillary dysplasia confirmed by postmortem examination could not be weaned from 80 parts per million of NO and transiently developed methemoglobinemia (peak methemoglobin level = 17%). No other side effects were observed.

CONCLUSIONS

Although mortality and ECMO use were similar for both treatment groups using this study size and design, sustained improvement in oxygenation with NO and better oxygenation at initiation of ECMO may have important clinical benefits. We speculate that modification of treatment to include specific lung expansion strategies with NO treatment and recognition that early improvement of oxygenation may be sustained with NO may lead to reduced use of ECMO in NO treated patients compared with controls.

Impact of new treatments for neonatal pulmonary hypertension on extracorporeal membrane oxygenation use and outcome

OBJECTIVE

To determine the impact of new treatment modalities, including high-frequency oscillatory ventilation (HFOV) and inhaled nitric oxide (INO), on extracorporeal membrane oxygenation (ECMO) use and outcome of neonatal patients with persistent pulmonary hypertension of the newborn.

STUDY DESIGN

We reviewed the medical records of neonatal patients meeting established ECMO criteria from 1988 to 1995. Clinical data were gathered from this retrospective chart review. Comparison of ECMO experiences were made between the 1988-90 period (pre-HFOV and INO, or period 1) and the 1993-95 period (HFOV and INO fully established as treatment modalities, or period 2).

RESULTS

One hundred three patients were treated with ECMO during the 8-year study period. After HFOV and INO were introduced in 1991 and 1992 respectively, the number of patients meeting established ECMO criteria who subsequently required ECMO therapy progressively declined, from 22.3 +/- 2.3 (mean +/- SD) patients per year during period 1 to 12 patients in 1991 when HFOV was introduced, 8 patients in 1992 when INO was introduced, and 5.3 +/- 2.9 patients per year in period 2. The number of patients referred for ECMO over time did not change. Survival after ECMO dropped from 84% during period 1 to 56% in period 2. Introduction of new pre-ECMO therapies has not delayed institution of ECMO, significantly increased the length of ECMO runs, or lengthened the hospital course of ECMO survivors. A comparison of the eight infants treated with ECMO in 1992 with the 10 infants treated with INO in 1993 showed a longer hospital stay and a larger average patient bill for the patients treated with ECMO.

CONCLUSION

New treatment approaches for severe persistent pulmonary hypertension have reduced ECMO use, shortened the duration of hospitalization, and reduced costs for those infants responding to HFOV and INO. However, survival of patients requiring ECMO therapy has decreased.

Inhaled nitric oxide enhances oxygenation but not survival in infants with alveolar capillary dysplasia

A complex vascular abnormality in the lungs, termed alveolar capillary dysplasia (ACD) and misalignment of the lung vessels, has been recently recognized in some infants with persistent pulmonary hypertension. These infants die despite maximal medical support including extracorporeal membrane oxygenation (ECMO). Inhaled nitric oxide has been reported to improve oxygenation in neonates with persistent pulmonary hypertension of the newborn, and may allow some infants to avoid the need for ECMO. We identified five infants who had received inhaled nitric oxide to treat refractory hypoxemia caused by persistent pulmonary hypertension of the newborn, and who subsequently died and had autopsy confirmation of ACD. Each infant received care at a different medical center. In each patient, inhaled NO increased the arterial partial pressure of oxygen dramatically. Despite initial clinical improvement, the response to NO was not sustained in any patient. As responsiveness was lost, each infant with ACD required inhaled NO concentrations of 80 ppm or higher to sustain oxygenation. Each infant died, four after extensive periods of ECMO support. This experience demonstrates that a short-term improvement after inhalation of nitric oxide does not lead to long-term survival in ACD. Further, in three infants the diagnosis of ACD was established by lung biopsy before death. Increasing awareness of this clinical entity may allow for the avoidance of costly, invasive procedures such as ECMO until more specific therapies become available.

[Congenital diaphragmatic hernia: an analysis of the results and prognostic factors prior to the development of an ECMO program]

BACKGROUND

Some neonates with congenital diaphragmatic hernia (CDH) and persistent pulmonary hypertension are not adequately oxygenated with conventional treatment. The extracorporeal membrane oxygenation (ECMO) has been successful in some of them as an alternative in their management.

PATIENTS AND METHODS

We studied the charts of 47 neonates with CDH, symptomatic within 24 hours of birth, treated in our institution during the last seven years (1987-1994). In all of them, conventional ventilation and hemodynamic support was used. In 12 patients high frequency ventilation (HFV) was used and two survived. In all patients we analyzed the following ventilatory and gasometric parameters: Oxygenation index (OI)*, ventilatory index (VI)** and postductal PCO2. In 15 neonates who did not survive, a necropsy was performed and a morphometric parameter, pulmonary index (PI)*** was studied.

RESULTS

The overall survival was 60%. VI and OI showed significant differences (p < 0.001) between survivors and non-survivors with values of 460.9 +/- 303 vs 1532 +/- 500.6, respectively for VI and 10.3 +/- 5.7 vs 46.2 +/- 37.8, respectively for IO. There were no significant differences in postductal PCO2. Mean PI in the 15 non-survivors was 0.0072 +/- 0.002 (normal > 0.015). Regression coefficients of PI with OI or VI were not significant. Neonates with VI < 1000 and OI < 40 survived. All patients with VI > 1000 and OI > 40 died. Some babies with VI > 1000 and OI < 40 (21.6%) survived.

CONCLUSIONS

In our experience, the use of HFV did not improve the prognosis of these patients, but we believe that the use of ECMO in those patients with VI > 1000, and overall, patients with VI > 1000 and OI < 40 would improve the survival rates of this congenital malformation. *QI = FiO2 x MAP/PO2 postductal x 100. (MAP = Median airway pressure). **VI = VR x MAP (VR = Ventilatory rate). ***PI = Pulmonary weight/Body weight.

Survivors of extracorporeal membrane oxygenation at 1 year of age: the relationship of primary diagnosis with health and neurodevelopmental sequelae

OBJECTIVE

Although extracorporeal membrane oxygenation (ECMO) has been responsible for the improved survival of infants with cardiorespiratory failure, its use over the last decade has raised concern as to the health of the survivors and the severity of neurodevelopmental sequelae. Though infants meeting ECMO criteria have a variety of reasons prompting the use of this therapy, most studies to date have simply reported outcome on the entire population that has survived without regard to the original nature of the child's illness. The purpose of this study was to determine the type and extent of health-related problems and neurodevelopmental sequelae in infants requiring ECMO therapy and the association of these findings with the infants' primary diagnosis.

METHODS

Eighty-two neonates required ECMO therapy between May 1990 and December 1993. The most common diagnosis prompting ECMO therapy included 26% with meconium aspiration syndrome, 34% with congenital diaphragmatic hernia (CDH), 16% with persistence of the fetal circulation, and 9% with sepsis. Information concerning the hospital course was obtained through chart review, and the infants were seen at 6 and 12 months of age for medical and neurodevelopmental follow-up. Data were analyzed using descriptive statistics and Fisher's exact test, t-tests, and analysis of variance where appropriate. Assessment of hospital course and discharge data focused on the four main diagnostic groups, whereas follow-up data were further limited to the two most frequently encountered groups (meconium aspiration syndrome and CDH).

RESULTS

Overall survival was 79%. Significant differences in survival were noted based on primary diagnostic category. Those with CDH fared the worst, with an overall survival rate of 68% and a more complicated hospital course with a longer duration of ECMO. At discharge, the CDH group demonstrated a greater incidence of bronchopulmonary dysplasia, gastroesophageal reflux, feeding dysfunction, and hypotonia. No significant differences were noted in the incidence of intraventricular hemorrhage, cerebral infarction, extra-axial fluid collection, or seizures. Hearing loss was uncommon. During the first year of life, although no differences were noted in growth rate, infants in the CDH group continued to experience a higher incidence of gastroesophageal reflux (43%) and feeding dysfunction, with 36% of this group requiring tube feedings for nourishment. Although 40% of the entire ECMO population was diagnosed with bronchopulmonary dysplasia before initial discharge, by 1 year of age, 50% of those with CDH versus 17% of those with meconium aspiration syndrome continued to be clinically symptomatic. Although the ECMO population as a whole scored in the normal range developmentally, CDH infants had significantly lower motor and slightly lower cognitive scores at 1 year of age. Despite finding abnormal muscle tone in a high percentage of the entire ECMO population at discharge, most demonstrated resolution by 1 year of age. Of the CDH infants, however, 75% continued to evidence some degree of hypotonicity, which affected acquisition and quality of gross motor skills.

CONCLUSION

Despite the impact that ECMO has had on the survival of infants with severe respiratory failure, the efficacy of ECMO cannot be assessed accurately without an analysis of the extent and morbidity in the surviving population. Most centers are reporting relatively low morbidity for the entire ECMO population. However, upon separating this population into primary diagnostic categories, we found that the CDH population encountered a greater number of neurodevelopmental, respiratory, and feeding abnormalities during the first year of life. The reasons for these differences are unclear but may be related to the severity of the primary illness itself or the variables associated with prolonged ECMO therapy. Stratifying outcome by primary diagnosis gives the health care provider more information to improve

Orthotopic transplantation for total anomalous pulmonary venous connection associated with complex congenital heart disease

BACKGROUND

When total anomalous pulmonary venous connection is associated with other complex cardiac malformations, early and late postsurgical morbidity and mortality are excessive.

METHODS

In an attempt to modify this outcome, twelve children (4 days to 6.8 years of age) with total anomalous pulmonary venous connection and various congenital cardiac defects were treated with orthotopic heart transplantation. Associated cardiac diagnoses included the following: hypoplastic left heart syndrome (n = 2), unbalanced atrioventricular canal with pulmonary atresia (n = 2), and single ventricle with severe pulmonary stenosis (n = 3) or atresia (n = 5). Two patients had situs inversus, and two had dextrocardia with situs ambiguous. Eight patients had asplenia and one had polysplenia. Palliative pretransplantation procedures in five patients included the following: systemic to pulmonary artery shunt (n = 5), atrioventricular valve annuloplasty (n = 1) and classical Glenn shunt (n = 1). The donor left atrium was anastomosed directly to a common pulmonary venous pool in nine patients; whereas three children required complex reconstruction to baffle the pulmonary venous flow to the donor left atrium.

RESULTS

There was one operative death related to an oversized heart and vena caval thrombosis. Follow-up ranged from 16 months to 4.5 years (average 3 years). In two patients (18%) pulmonary venous obstruction developed 3 and 4 months after transplantation. Reoperation to relieve the obstruction was successful in one patient. The second patient underwent three such reoperations and died of sepsis 10 months after orthotopic heart transplantation.

CONCLUSION

Orthotopic transplantation is a viable option for children with complex total anomalous pulmonary venous connection that precludes a biventricular repair. Transplantation may improve the dismal prognosis of those children, but it does not eliminate the potential for late pulmonary venous obstruction.

Robust Bayesian methods for monitoring clinical trials

Bayesian methods for the analysis of clinical trials data have received increasing attention recently as they offer an approach for dealing with difficult problems that arise in practice. A major criticism of the Bayesian approach, however, has focused on the need to specify a single, often subjective, prior distribution for the parameters of interest. In an attempt to address this criticism, we describe methods for assessing the robustness of the posterior distribution to the specification of the prior. The robust Bayesian approach to data analysis replaces the prior distribution with a class of prior distributions and investigates how the inferences might change as the prior varies over this class. The purpose of this paper is to illustrate the application of robust Bayesian methods to the analysis of clinical trials data. Using two examples of clinical trials taken from the literature, we illustrate how to use these methods to help a data monitoring committee decide whether or not to stop a trial early.

The effect of on-site extracorporeal membrane oxygenation on the therapy choice and outcomes of neonates with persistent pulmonary hypertension

The effect of on-site extracorporeal membrane oxygenation (OS-ECMO) and selection criteria on the utilization rate of this technology is unknown. We retrospectively studied 55 neonates who were admitted to Arkansas Children's Hospital from 1985 to 1993. We compared the ECMO utilization, mortality, and morbidity rates for outborn neonates with moderate and severe persistent pulmonary hypertension (PPHN) before and after the establishment of an ECMO program with guidelines for its use at our institution. The rate of ECMO use was three times higher and the mortality rate was 13 times lower in the period after OS-ECMO compared with the period when ECMO was available only at other institutions. No differences were observed in the morbidity rates between the two periods. Physician decisions to initiate ECMO involved more than guidelines, since 37% of the increased ECMO use was not associated with use of the guidelines. Possible reasons for noncompliance with the guidelines are discussed. Neonates who had received medical therapy only and who had an oxygenation index > or = 30 and < 40 had no mortality. Our findings suggest that the need for ECMO in this group of neonates is low.

Persistent pulmonary hypertension of the newborn infant. Comparison of conventional versus extracorporeal membrane oxygenation in neonates fulfilling Bartlett's criteria

Persistent pulmonary hypertension of the newborn (PPHN) is a challenge for the neonatologist and a common indication for treatment with extracorporeal membrane oxygenation (ECMO) when medical management fails. We observed 132 neonates born between January 1985 and December 1988 with the diagnosis of persistent pulmonary hypertension of the newborn: 73 (55%) met the Bartlett criteria for treatment with ECMO with 80% predicted mortality; 21 (29%) deteriorated despite conventional medical treatment, were thought to be dying, and were sent for ECMO. Among the 52 patients who were medically treated 40 (77%) survived, a marked difference compared with a predicted 20% survival. All ECMO-treated neonates survived. Although conventionally treated infants showed a trend toward less dependence on supplemental oxygen at > 28 days of life, this study failed to detect a significant difference between those two groups. We conclude that mortality was lower for ECMO-treated infants than for those who were medically treated (0 of 21 vs 12 of 52, p < 0.05); mortality for infants with persistent pulmonary hypertension of the newborn who met Bartlett's criteria and were medically treated was lower than published data; and there was no significant difference in oxygen dependence at > 28 days between the survivors who received ECMO and those who received medical therapy.

High frequency oscillatory ventilation and extracorporeal membrane oxygenation in severe persistent pulmonary hypertension of the newborn

We report on 50 term and near-term neonates (birth weight greater than 1800 g, gestational age greater than 33 weeks) with severe persistent pulmonary hypertension of the newborn (PPHN), referred to us from January 1987 to July 1991 after failure of maximum conventional treatment. All infants had paO2 less than 45 mm Hg when ventilated with peak inspiratory pressure greater than 38 cm H2O and FiO2 = 1.0, hence meeting entry criteria for extracorporeal membrane oxygenation (ECMO). High frequency oscillatory ventilation (HFOV) was tried in all patients. If sufficient oxygenation could not be achieved (paO2 less than 40 mm Hg for at least 2 h), ECMO therapy was begun, which was the case in 25 children. Neonates responding to HFOV (n = 25) were of a slightly younger gestational age (37.0 weeks vs 38.8 weeks, P less than 0.05), had higher Apgar scores and were less hypoxaemic before HFOV (paO2 36.6 mm Hg vs 28.8 mm Hg, P less than 0.01); during HFOV there was a significant rise in paO2 (greater than 150 mm Hg; P less than 0.001) and a fall in pCO2 to 21.6 mm Hg (P less than 0.001). Due to air leaks, which was the main complication of HFOV (52%), ECMO therapy had to be begun in two additional infants after an initial positive effect. HFOV tended to be successful in cases of primary PPHN, meconium aspiration and sepsis, but not in infants with lung hypoplasia as a result of diaphragmatic hernia or other reasons. Success or failure of HFOV could not be reliably predicted by any parameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Survival of infants with persistent pulmonary hypertension without extracorporeal membrane oxygenation

A retrospective evaluation was performed of the survival after conservative therapy of infants with persistent pulmonary hypertension who met the published criteria of Bartlett et al (Pediatrics. 1985;76:479-487) or Short et al (Clinics in Perinatology. 1987;14:737-748) for extracorporeal membrane oxygenation (ECMO) therapy. An 80% to 90% mortality rate can be predicted with these criteria, which are based on historical data, if ECMO is not used. The records of infants with the diagnosis of persistent pulmonary hypertension, weighing greater than 2 kg at birth and who were treated during two time periods, January 1980 to December 1981 [23 patients] and January 1986 to December 1988 [17 patients], were reviewed. During the earlier period, hyperventilation was the mainstay of our therapy, whereas during the later period, a more conservative approach (avoidance of hyperventilation) was adopted. In 1980 to 1981, 1 of the 6 patients (17%) who were eligible for ECMO by criteria of Bartlett et al survived, which is consistent with the published data. However, in 1986 to 1988, 9 of 10 ECMO-eligible patients (90%) survived (P less than .02). The corresponding survival figures using the alveolar-arterial oxygen difference criteria of Short et al were 0 of 5 survivors (0%) in 1980 to 1981 and 8 of 9 (89%) in 1986 to 1988 (P less than .006). These data indicate that approximately 90% of patients who are candidates for ECMO now survive in our institution without the use of that therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Historical controls for extracorporeal membrane oxygenation in neonates

A retrospective review of all patients cared for who met Loe's criteria for extracorporeal membrane oxygenation (ECMO) was conducted covering the 3-yr period 1983 through 1985. There were five out of 3,726 admissions who met criteria for ECMO (three of 127 outborn admissions). All infants were greater than 2 kg birth weight and met criteria based on alveolar-arterial oxygen pressure difference (P[A-a]O2), barotrauma criteria, or both P(A-a)O2 and barotrauma criteria. All infants had persistent pulmonary hypertension. Two patients also had hyaline membrane disease and one also had asphyxia and meconium aspiration. All patients were treated with conventional therapy and all survived. There were no patients who met criteria for ECMO and died and there were no patients referred for ECMO during this period. Published criteria for ECMO estimate a control group mortality rate of 80% to 94%. Mortality for this series was 0%. (Ninety-five percent confidence interval for mortality in a group of five survivors is 0% to 45%.) Controlled trials of ECMO were not done initially because it was considered unethical. This series shows that historical mortality rates are no longer valid and that controlled trials must be done.

High-frequency jet ventilation in neonatal pulmonary hypertension

To determine if high-frequency jet ventilation is beneficial in neonates with persistent pulmonary hypertension, we compared the ventilator settings, blood gas concentrations, and outcome of infants who met established criteria for a high predictive mortality. During a six-year period, 14 neonates who had severe respiratory failure and hypoxemia while receiving conventional ventilation were treated with high-frequency jet ventilation. Twenty-three comparable infants meeting the same criteria were treated exclusively with conventional ventilation. After initiation of high-frequency jet ventilation there was a significant reduction in mean airway pressure and partial pressure of arterial carbon dioxide (PaCO2). In contrast, neonates treated exclusively with conventional ventilation continued to have higher airway pressures and PaCO2. However, there was no difference in the alveolar-to-arterial oxygen gradient, air leakage, incidence of bronchopulmonary dysplasia, or duration of assisted ventilation or oxygen supplementation. Furthermore, mortality was comparable in both groups of infants. These preliminary observations suggest that high-frequency jet ventilation can reduce airway pressure and PaCO2 in neonates with persistent pulmonary hypertension but does not appear to improve outcome.

Extracorporeal membrane oxygenation in the newborn and beyond

Extracorporeal membrane oxygenation (ECMO) has gained notoriety recently as a treatment of last resort for neonates at term or near term who suffer from pulmonary failure. Because of serious inherent risks, the procedure is at present reserved for infants with reversible pulmonary disease who have failed conventional or high-frequency ventilation and who meet the prognostic criterion of 80 percent mortality.

Outcome of persistent pulmonary hypertension in relation to severity of presentation

Since the initial description of persistent pulmonary hypertension of the newborn (PPHN), the management of these infants has been controversial. A variety of therapeutic modalities, such as extracorporeal membrane oxygenation, have been utilized. Early recognition of a group of patients with PPHN who might require aggressive therapy would be clinically useful. Highest alveolar-arterial oxygen gradient at or near diagnosis was evaluated retrospectively in 53 patients with PPHN in relation to survival, aggressiveness of management, and frequency of pulmonary complications (air leak and broncho-pulmonary dysplasia). Highest alveolar-arterial oxygen gradient was a good early predictor of nonsurvival and was significantly higher in nonsurvivors compared with survivors (mean [+/- SD], 618 +/- 23 mm Hg vs 521 +/- 128 mm Hg). Values of 600 mm Hg or greater were more frequent in the nonsurvivors compared with the survivors (92% vs 37%). Air leak also proved to be a good predictor of nonsurvival.

Predicting survival in infants with persistent pulmonary hypertension of the newborn

Since persistent pulmonary hypertension of the newborn (PPHN) often occurs as a life-threatening illness, it would be advantageous to identify the highest-risk infants within the first 24 hours of life so that transfer to centers with extracorporeal membrane oxygenation (ECMO) or high-frequency ventilation can be facilitated. Fifty-three infants with PPHN were evaluated retrospectively. A multivariate discriminant analysis of risk factors determined that lowest pH, critical PaCO2, highest inspiratory pressure (PI), maximum ventilator rate, and 5-minute Apgar score were significantly different between the 35 survivors (66%) and the 18 infants (34%) who had died when examined within the first 24 hours of life. A clinical scoring system was designed based on these five criteria, which predicted outcome accurately in 93% of infants. A logistic regression analysis was performed as a check on these results and found that lowest pH, critical PaCO2, and PI predicted outcome with great accuracy. These results suggest that the use of these scoring systems within the first 24 hours of age may help predict outcome in infants with PPHN.

Criteria for extracorporeal membrane oxygenation in a population of infants with persistent pulmonary hypertension of the newborn

Extracorporeal membrane oxygenation (ECMO) has been available since 1975 as a therapy of last resort to provide adequate oxygenation for term infants with acute lung disorders that do not respond to maximal medical therapy. Virtually all term infants with serious lung disease have persistent pulmonary hypertension of the newborn (PPHN) characterized by significant right-to-left shunting of blood and severe diffusion defects manifested as increased alveolar-arterial oxygen gradients (AaDO2). Criteria for initiation of ECMO therapy have been developed in several institutions but at the present time there are no universal criteria applicable to all infants with PPHN. We have attempted to establish entry criteria that may be used for different populations of infants with PPHN. Based on a retrospective review of 30 infants with PPHN in our institution, we have defined standards of maximal medical therapy. An alveolar-arterial oxygen difference (AaDO2) of greater than or equal to 610 for 8 hours has been shown to be associated with 79% mortality in this population. This AaDO2/time interval is established as a major criterion for institution of extracorporeal membrane oxygenation.

Correction of congenital diaphragmatic hernia in utero. IV. An early gestational fetal lamb model for pulmonary vascular morphometric analysis

Infants born with congenital diaphragmatic hernia (CDH) often have specific pathologic abnormalities of the pulmonary microcirculation that result in high pulmonary vascular resistance and extrapulmonary right-to-left shunting after birth. In an attempt to make an animal model with similar vascular changes, we created CDH in fetal lambs at 60 to 63 days gestation, repaired some at 100 to 113 days gestation, and subsequently performed morphometric analysis of the pulmonary vasculature. Creation of CDH at this early gestational age resulted in a high fetal mortality rate. In the unrepaired CDH lambs, the pulmonary vascular abnormalities were more severe in the left lung. Similar to human CDH, diaphragmatic hernia in the fetal lamb resulted in a decrease in the total size of the pulmonary vascular bed, a decrease in the number of vessels per unit area lung, and increased muscularization of the arterial tree. Fetal surgical repair of CDH restored the pulmonary arterial bed towards normal.

Management of infants with severe respiratory failure and persistence of the fetal circulation, without hyperventilation

The successful management of 15 infants suffering from persistence of fetal pulmonary circulation and in severe respiratory failure is presented. The treatment regimen focused on minimizing barotrauma. Infants were intubated nasotracheally and ventilated with intermittent mandatory ventilation. Peak inspiratory pressures were determined by the clinical assessment of chest excursion. Ventilator settings and fractional inspiratory oxygen (FiO2) were selected to maintain a PaO2 between 50 and 70 mm Hg; PaCO2 was not a controlling parameter and was allowed to increase as high as 60 mm Hg. Hyperventilation and muscle relaxants were not used. High ventilator rate was used in ten infants who required high inspiratory pressure to maintain chest excursion, with a favorable response in five. Tolazoline was given to 14 infants of whom ten showed an improvement in oxygenation; dopamine was given to three infants who were oliguric. All infants survived, and only one infant developed chronic lung disease which was defined by the infant's need for supplemental oxygen beyond 30 days of life.