Neonatal pulmonary manifestations due to prolonged amniotic leak

Oligohydramnios and associated fetal complications

During intrauterine life the fetus is bathed in amniotic fluid which provides a low resistance space for free movement and a buffer against external trauma. This fluid is produced in early pregnancy largely as a maternal dialysate, then as a fetal transudate. Fetal urine is the most important source of amniotic fluid after 16 weeks gestation. The control of amniotic fluid is complex and poorly understood; it arises from secondary partitioning of water within the fetoplacental extracellular space and reflects fetal fluid balance.

Characteristics of pulmonary hypertension in preterm neonates

OBJECTIVE

Characteristics of preterm infants who develop pulmonary hypertension (PHT) and their response to inhaled nitric oxide (iNO) are not well described. Our objective was to identify risk factors for PHT in infants <37 weeks gestational age (GA) and to evaluate their response to iNO.

STUDY DESIGN

A retrospective chart review was conducted in infants <37 weeks GA born from July/2000 to October/2005 who had an echocardiographic diagnosis of PHT in the first 4 weeks of life. A comparison non-PHT group was generated matched for GA and birth date. Data on prenatal and postnatal characteristics, response to iNO and mortality were collected.

RESULTS

Low Apgar scores, preterm premature rupture of membranes, oligohydramnios, pulmonary hypoplasia and sepsis were independently predictive of PHT. Mortality was significantly higher in the PHT group (26.2% versus 4.1%; P<0.0001) compared to the control group. Low birth weight, severe intraventricular hemorrhage and male sex were significantly associated with death in infants with PHT. Thirty-seven percent (23/61) of infants with PHT were treated with inhaled NO. Infants < 29-week GA had poor response to iNO and the response to iNO increased with GA (P<0.02).

CONCLUSIONS

Low Apgar scores, oligohydramnios and pulmonary hypoplasia are associated with the development of PHT in premature infants. The percentage of infants responding to iNO increases with advancing GA.

Nitric oxide in preterm infant with pulmonary hypoplasia

Premature infants with hypoplastic lungs may have elevated pulmonary vascular resistance with right to left shunt across ductus arteriosus and/or foramen ovale. Inhaled nitric oxide (NO) being selective pulmonary vasodilator without significant effects on systemic circulation can potentially reverse this shunt. The authors herewith report a case of a premature infant with severe hypoxemic respiratory failure after preterm premature prolonged rupture of membranes leading to oligohydramnios and pulmonary hypoplasia that was treated successfully with NO and describe the neurodevelopmental outcome at 1 year of age.

Prenatal prediction of pulmonary hypoplasia: clinical, biometric, and Doppler velocity correlates

OBJECTIVES

To determine the value of pulmonary artery Doppler velocimetry relative to fetal biometric indices and clinical correlates in the prenatal prediction of lethal lung hypoplasia (LH) in prolonged (>1 week) oligohydramnios.

METHODS

Forty-two singleton pregnancies with oligohydramnios associated with premature rupture of membranes ([PROM]; n = 31) or bilateral renal pathology (n = 11) were examined using color-coded Doppler ultrasound in a cross-sectional study design. Mean gestational age was 28.0 +/- 4.3 weeks (range: 20-36 weeks). Thoracic, cardiac, and abdominal circumference and the largest vertical amniotic fluid pocket were measured. Pulsed Doppler measurements of the arterial pulmonary branches were made at the level of the cardiac 4-chamber view. Diagnosis of LH was based on clinical, radiologic, and pathologic criteria. Clinicians were blinded to the prenatal measurements.

RESULTS

The prevalence of lethal LH was 43%. In the PROM subset, combination of onset of PROM at <or =20 weeks, duration of oligohydramnios at > or =8 weeks, and degree of oligohydramnios at < or =1 cm presented the highest clinical prediction rate for lethal LH. For both the total group and the PROM subset, the highest prediction rate for lethal LH was presented by thoracic circumference/abdominal circumference ratio, peak systolic velocity in the proximal branch, and time-averaged and end-diastolic velocity in the middle branch of the pulmonary artery. In the PROM subset, the combination of all 3 clinical, biometric, and Doppler parameters revealed the most favorable combination to predict lethal LH (positive predictive value: 100%; accuracy: 93%; and sensitivity: 71%).

CONCLUSION

Doppler velocimetry may detect changes in pulmonary artery waveforms in the presence of LH but fails to be the ultimate test for the prenatal prediction of lethal LH. The best prediction can be achieved by combining clinical, biometric, and Doppler parameters.

Inhaled nitric oxide for oligohydramnios-induced pulmonary hypoplasia: a report of two cases and review of the literature

We describe the clinical courses of two premature infants, a male born at 29(4/7) weeks' gestational age after an 8-week period of rupture of membranes (ROM) and severe oligohydramnios, and a female infant born at 31 weeks' gestational age after an 18-week period of ROM and severe oligohydramnios. Within hours after birth, despite intubation and aggressive ventilation, both infants developed fulminant hypoxic respiratory failure. Their clinical courses were consistent with pulmonary hypertension and both infants were transferred for trials of inhaled nitric oxide (iNO). Both infants had dramatic responses to iNO, suggesting that the pulmonary disease seen after prolonged oligohydramnios may have a component of nitric oxide-sensitive pulmonary hypertension. The goals of this article are to (1) review oligohydramnios-induced pulmonary hypoplasia, (2) discuss patients at highest mortality risk, and (3) describe the effects of iNO on pulmonary hypertension in infants with hypoxemia following prolonged ROM and severe oligohydramnios.

The fetal lung. 2: Pulmonary hypoplasia

This review describes the pathogenesis of pulmonary hypoplasia and highlights its clinical, radiological and pathologic features, with emphasis on oligohydramnios-related pulmonary hypoplasia. Since pulmonary hypoplasia may lead to severe respiratory distress immediately after birth and even to neonatal death, an accurate and patient-friendly prenatal test for early detection and distinction between lethal and non-lethal pulmonary hypoplasia is still highly desirable. An extended overview of the proposed methods for the prenatal prediction of pulmonary hypoplasia is presented.

Inhaled nitric oxide for premature infants after prolonged rupture of the membranes

We evaluated the use of inhaled nitric oxide in eight premature infants (520 to 1440 gm, 24 to 31 weeks of gestation) who failed to respond to conventional management and who had prolonged rupture of the membranes and oligohydramnios. All infants had a significant improvement in oxygenation and a fall in mean airway pressure with inhaled nitric oxide. Further studies are required to determine the safety and efficacy of this form of therapy.

High-dose versus low-dose bovine surfactant treatment in very premature infants

The aim of the study was to determine if high-dose bovine surfactant (Alveofact, initially 100 mg/kg birth weight) would improve oxygenation compared with low-dose surfactant (50 mg/kg birth weight) administered intratracheally within 1 h after birth. Inclusion criteria included gestational age 24-29 weeks and birth weight 500-1500 g, intubation and mechanical ventilation, absence of congenital malformations and bacterial infections. Retreatment was considered if the fraction of inspired oxygen (FiO2) was > 0.4 (dose 50 mg/kg birth weight). The primary endpoint was level of oxygenation (PaO2/FiO2) 2 h after treatment. The study design was a sequential analysis using a triangular test with alpha = 0.05 and 95% power to detect a 25% improvement in the endpoint. Oxygenation was improved significantly with high-dose (n = 42) compared to low-dose treatment (n = 48): 30.9 +/- 15.0 kPa (231.5 +/- 112.7 mmHg) versus 24.1 +/- 15.7 kPa (180.6 +/- 118.0 mmHg) (mean +/- SD). The survival rate was 83% in both groups and the incidence of pulmonary interstitial emphysema was 33% versus 14% with the high-dose treatment. We conclude that high-dose surfactant significantly improved oxygenation and reduced lung barotrauma. An initial dose greater than 50 mg/kg birth weight of surfactant is required for optimal acute response.

Can Prenatal Ultrasound Predict Pulmonary Hypoplasia?

Pulmonary hypoplasia is often associated with sonographically detectable conditions: oligohydramnios, prolonged premature rupture of membranes, and, not infrequently, fetal anomalies. In their efforts to improve prenatal sonographic diagnosis of this condition, investigators have used an array of different sonographic biometric measurements and fetal behavioral patterns. Definitions of these measurements and their respective successes in predicting pulmonary hypoplasia are presented. The sonographic parameters that have been of most value in the prediction of pulmonary hypoplasia are chest circumference, direct measurements of the lung, lung length, lung span to hemithorax diameter, and more complex formulas, such as lung area/heart area x 100/chest area. Although fetal measurements may help predict pulmonary hypoplasia, no single sonographic finding consistently leads to a prediction of the presence of pulmonary hypoplasia. Therefore, obstetric management (i.e., nonintervention) cannot currently be altered with the finding of abnormal biometric parameters unless a known lethal anomaly is observed.

Early treatment of respiratory distress syndrome with bovine surfactant in very preterm infants: a multicenter controlled clinical trial

OBJECTIVE

To determine the effect of bovine surfactant (SF-RI 1, Alveofact) administered during the first hour following birth to very premature infants [gestational age (GA), 25-30 weeks] in a multicenter, controlled trial.

HYPOTHESIS

Survival without bronchopulmonary dysplasia (BPD; definition: ventilator dependency or FiO2 greater than 0.3 during spontaneous respiration) at day 28 is increased in surfactant-treated infants (sequential analysis).

PATIENTS AND METHODS

Thirty-four infants [GA 28.0 +/- 1.5 SD weeks, birth weight (BW), 1,048 +/- 299 g] received 50 mg/kg BW surfactant, whereas 35 infants (GA, 27.6 +/- 1.5 weeks, BW 969 +/- 269 g) served as controls. Retreatment with surfactant (up to three identical doses) 12-24 hours after the previous dose was permitted if FiO2 was greater than 0.5.

RESULTS

Survival without BPD was significantly higher in surfactant treated infants (26/34) compared to controls (14/35; P = 0.003), but in the incidence of pulmonary air leaks, patent ductus arteriosus, intracranial hemorrhage, and nosocomial infections they were not different.

CONCLUSION

Bovine surfactant treatment improves survival without BPD in very premature infants at risk for neonatal respiratory distress syndrome (RDS).

Biochemical and morphometric analyses in hypoplastic lungs

We report the results of biochemical and morphometric studies on lungs of infants with bilateral lung hypoplasia either with or without oligohydramnios (OH or NOH) in comparison with findings in normally grown lungs. The OH and NOH lungs were equally hypoplastic in terms of DNA content but OH lungs had a significantly lower disaturated phosphatidylcholine (DSPC) concentration than NOH or normal lungs, apart from a subgroup with gastrointestinal or airway obstruction. Hydroxyproline concentration in OH lungs was higher than that in NOH or normal lungs. Desmosine concentrations did not differ significantly between groups despite the obvious lack of elastin in the septal crests of the OH group on histology. Morphometry revealed low lung volume, low radial alveolar counts, low alveolar numbers, and low alveolar surface area in both OH and NOH groups. Alveoli and alveolar ducts constituted a higher proportion of lung volume in NOH than in OH lungs. The similarity of most morphometric indices in the two groups implies that maturation does not depend on quantitative elaboration of airways and alveoli. The finding of impaired epithelial maturation despite the high hydroxyproline concentration in the OH lungs suggests an abnormality in epithelial-mesenchymal interaction that is not present in the equally small lungs of the NOH group.

Comparison of six different ultrasonographic methods for predicting lethal fetal pulmonary hypoplasia

Nomograms of six different ultrasonographic fetal parameters were established by studying uncomplicated, singleton pregnancies, with well-established dates, between 16 and 40 weeks of gestation. The studied parameters could reflect fetal lung mass and included the following: chest circumference (CC), chest area (CA), chest area minus heart area (CA - HA), chest circumference/abdominal circumference ratio (CC X 100/AC), chest area/heart area ratio (CA/HA), and chest area minus heart area divided by chest area ratio [(CA - HA) X 100/CA]. The effect of ruptured membranes on these six ultrasonographic parameters was assessed by studying patients who had premature rupture of the membranes of less than 1 week's duration. It was found that premature rupture of the membranes is associated with increased frequency of CC, CA, and CA - HA measurements at or below the 5th percentile. However, in patients with premature rupture of the membranes all measurements were within the normal range for the three ratios. The efficacy of each of the six parameters was determined by studying 13 fetuses at high risk for development of lethal pulmonary hypoplasia. The (CA - HA) X 100/CA parameter had the best diagnostic accuracy (sensitivity 85%, specificity 85%, positive predictive value 83%, and negative predictive value 85%).

Treatments of preterm premature rupture of the membranes: a meta-analysis

The objective of this overview was to critically evaluate published randomized controlled trials on treatments in preterm premature rupture of the membranes. The Oxford data base on perinatal trials, MEDLINE, Excerpta Medica, and Index Medicus were searched. Through primary and secondary review with preset inclusion criteria, two independent judges identified 27 randomized controlled trials, of which 13 met inclusion criteria. The quality of these randomized controlled trials was scored. Five randomized controlled trials regarding antenatal use of corticosteroids to prevent respiratory distress syndrome could be combined meta-analytically and showed a reduction in respiratory distress syndrome in the treatment group (p = 0.001). However, no significant reduction in respiratory distress syndrome (p = 0.286) was found after one study, with the lowest quality score, was excluded. A significant increase in endometritis and a trend toward an increase in neonatal infections and cesarean section rates were noted with treatment. Tocolysis, prophylactic antibiotics, and other interventions studied were not found to be of proved benefit and therefore should not be used outside of a randomized controlled trial.

Pulmonary hypoplasia testing in clinical obstetrics

An ultrasound-based diagnostic test for predicting pulmonary hypoplasia antenatally by measurements of fetal chest circumference was applied prospectively to 45 patients at risk for developing this disorder. The outcome for the newborn infant and the autopsy findings were correlated with the antenatal prediction. The results of this test demonstrated a sensitivity and a specificity of 88% and 96%, respectively. The application of this test to clinical practice is recommended.

Ultrasonic ratio of fetal thoracic to abdominal circumference: an association with fetal pulmonary hypoplasia

Real time ultrasound was used in pregnant women who were considered to be at risk for development of pulmonary hypoplasia (n = 26). The population consisted of women who had either premature rupture of membranes (n = 16) or oligohydramnios (n = 10). The ratio calculated by comparing the fetal thoracic circumference to abdominal circumference was obtained in all cases within 10 days of delivery. This ratio correlated strongly with neonatal outcome. Multivariate regression models of neonatal outcome were developed to analyze the relationship of gestational age at which premature membrane rupture occurred, the duration of premature rupture, date of birth, and prenatal diagnosis. The addition of the thoracic circumference to the abdominal circumference ratio increased significantly the proportion of explained variability. Application of this ratio should be considered in evaluating fetal status in oligohydramnios and in the expectant management of premature rupture of membranes.