Plasma 3-nitrotyrosine is elevated in premature infants who develop bronchopulmonary dysplasia

OBJECTIVE

Premature infants are susceptible to bronchopulmonary dysplasia (BPD), a chronic lung disease of infancy that appears to be caused in part by oxidative stress from hyperoxia. To investigate the possible role of nitric oxide-derived oxidants such as peroxynitrite in the etiology of BPD, we measured levels of plasma 3-nitrotyrosine, which is produced by the reaction of peroxynitrite with proteins.

PATIENTS AND METHODS

Ten premature infants who developed BPD, defined as requiring supplemental oxygen beyond 36 weeks' postmenstrual age, were identified retrospectively from a group of subjects enrolled in a clinical trial of antenatal therapy. Serial plasma samples had been collected on these infants during the first month of life as part of the trial. Sixteen comparison premature infants were identified from the same population: 5 had no lung disease, 6 had respiratory distress syndrome that resolved, and 5 had residual lung disease at 28 days of life that resolved by 36 weeks' postmenstrual age. Plasma 3-nitrotyrosine levels were measured using a solid phase immunoradiochemical method.

RESULTS

All 3-nitrotyrosine values in infants without BPD were <0.25 ng/mg protein, and levels did not change with postnatal age. Plasma 3-nitrotyrosine concentrations were significantly higher in infants with BPD, increasing approximately fourfold during the first month of life. For the 20 infants who had blood samples available at 28 days of life, plasma 3-nitrotyrosine levels correlated with the fraction of inspired oxygen that the infant was receiving (r = 0.7).

CONCLUSION

Plasma 3-nitrotyrosine content is increased during the first month of life in infants who develop BPD. This suggests that peroxynitrite-mediated oxidant stress may contribute to the development of this disease in premature infants and that 3-nitrotyrosine may be useful as an early plasma indicator of infants at risk for developing BPD.

Interleukin-6, C-reactive protein, and abnormal cardiorespiratory responses to immunization in premature infants

OBJECTIVE

We report our experience with routine immunization of 89 premature infants in the neonatal intensive care unit because 1) a substantial number of them developed abnormal clinical signs, and 2) all but one of those who received diphtheria, tetanus, and whole-cell pertussis (DTwP) vaccine responded with elevations of interleukin-6 (IL-6) and C-reactive protein (CRP) concentrations that are otherwise characteristic of bacterial disease.

METHODOLOGY

We hypothesized that the elevated IL-6 and CRP levels were solely a response to immunization and that treatment with antibiotics was not necessary. We performed this study in two consecutive parts. In part 1, we prospectively evaluated 79 consecutive premature infants who were immunized with DTwP, Haemophilus b conjugate vaccine, hepatitis B vaccine, and inactivated polio vaccine, (Hib, HBV, and IPV). IL-6 and CRP were determined before immunization and every 12 hours on three occasions after immunization. In part 2, we studied an additional 10 infants who received acellular pertussis vaccine (DTaP) and who, 2 days later, received Hib, HBV, and IPV immunization simultaneously. We followed the same schedule of IL-6 and CRP determinations as in part 1.

RESULTS

In part 1, 24 infants (30%) developed abnormal cardiorespiratory signs within 24 hours after immunization. CRP and IL-6 values rose to abnormal levels after immunization in all but one infant; that infant was later shown to have a T-cell abnormality. In part 2, 3 infants had abnormal cardiorespiratory signs after simultaneous immunization with Hib, HBV, and IPV, but not after DTaP. IL-6 and CRP levels remained normal in all 10 infants.

CONCLUSIONS

Part 1 demonstrates clearly the temporal relationship between IL-6 and CRP increments after DTwP, Hib, HBV, and IPV vaccines. In part 2 (DTaP was substituted for DTwP), there were no elevations of IL-6 or CRP, thus indicating that whole-cell pertussis component of DTwP was responsible for IL-6 and CRP elevations. Abnormal cardiorespiratory signs occurred frequently after immunizations in part 1, but they were unrelated to the magnitude of IL-6 and CRP elevations. The frequency of cardiorespiratory difficulty and its occasional severity suggest a need to monitor premature infants for approximately 48 hours after routine immunization.

Evidence for the safety of ascorbic acid administration to the premature infant

Ascorbic acid (AA), a plasma antioxidant, is maintained at high levels in premature fetal blood and declines rapidly postpartum. The sudden reduction in blood AA levels secondary to premature delivery may increase the risk of oxidant injury, that is, bronchopulmonary dysplasia and intraventricular hemorrhage. There is concern that administration of AA to premature infants, in an effort to increase antioxidant capacity, may cause hemolysis. We felt that the benefits of early AA administration and prevention of the immediate postnatal drop in blood AA levels, might outweigh the risks of erthrocyte damage. Fifty one high-risk premature infants were randomized to receive either normal saline or 100 mg/kg of AA, daily for the first week of life. Double-blind comparisons were made of hemoglobin, hematocrit, erythrocyte morphology, bilirubin, number of blood transfusions and days of phototherapy, renal function tests, the incidence of infection, bronchopulmonary dysplasia, and intraventricular hemorrhage during the first month of life. The administration of AA prevented the immediate postnatal drop in AA and was not associated with evidence of increased hemolysis. No significant differences in renal function, rate of infection, bronchopulmonary dysplasia, or intraventricular hemorrhage were seen between the two groups. This study suggests that AA administration to the premature infant is safe and supports the designing and performance of larger clinical studies of the antioxidant properties of AA.

Red blood cell glutathione and plasma sulfhydryls in chronic lung disease of the newborn

We compared the postnatal changes (days 1-28) in red blood cell glutathione and plasma sulfhydryl content in preterm babies developing chronic lung disease (CLD, n = 13) to those in babies with respiratory distress syndrome (RDS, n = 13) and control babies (n = 21). There were no initial differences in these measurements between the three groups. However, on day 28 in CLD and RDS the red blood cell glutathione was decreased compared to the control babies (p < 0.05). In CLD, there was a significant correlation between reduced/oxidized glutathione and (i) maximal FiO2 (r = -0.69, p < 0.05) and (ii) minimal a/A ratio (r = +0.73, p < 0.005). On day 28, although the plasma sulfhydryl level did not differ between the groups, the sulfhydryl/total protein ratio was decreased in CLD (p < 0.05). The late decrease in both glutathione and sulfhydryl/total protein ratio in babies with CLD suggests that oxidative stress is still ongoing at 28 days after birth and that the antioxidant capacity of their blood is still diminished at this time.

[Function of the hypothalamo-hypophyseal-adrenal axis to corticotropin-releasing hormone test in premature infants with bronchopulmonary dysplasia]

BACKGROUND

The purpose of this prospective study was to examine the hypothalamic-pituitary-adrenal axis using the corticotropin-releasing hormone stimulation test in 24 preterm infants (mean gestational age 27.4 +/- 1.4 weeks, mean birth weight 997 +/- 166 g) with bronchopulmonary dysplasia after completion of dexamethasone treatment.

METHODS

The CRH stimulation test was performed before and two days after the course of dexamethasone therapy in a dosage of 1 microgram/kg body weight. Blood samples were obtained before and 30 minutes after application of CRH. The blood values for cortisol and ACTH were measured by radioimmunoassay.

RESULTS

The mean basal cortisol level was significantly reduced from 338 +/- 283 nmol/l before dexamethasone treatment to 153 +/- 102 nmol/l after dexamethasone therapy. The site of HPA suppression was located to the pituitary gland as the mean basal ACTH level dropped from 9.5 +/- 5.2 pmol/l to 5.6 +/- 2.0 pmol/l after the dexamethasone course. In 9 infants there was only an insufficient increase of cortisol level after application of CRH as a possible sign of a reduced adrenal response. The patients with HPA-suppression did not differ in clinical aspects from infants without suppression of the HPA.

CONCLUSION

The results demonstrate a significant suppression of the adrenal and pituitary gland in very low birth weight infants with bronchopulmonary dysplasia after dexamethasone treatment. Before stressful situations like surgery we therefore recommend an investigation of the HPA.

Serum levels of magnesium at birth related to complications of immaturity

Magnesium is a natural calcium channel blocker inhibiting vasoconstriction in numerous vascular beds. Magnesium sulphate given prior to birth to pre-eclamptic mothers and mothers in preterm labour has in retrospect been found to be associated with a decreased incidence of both intraventricular haemorrhage and cerebral palsy. Little is known about the effect of normal variations of serum magnesium in the very preterm baby, where morbidity is closely related to rapid vascular changes. We have analysed the absolute levels and normal variations of magnesium concentration in cord blood and during the first 3 weeks after birth for 69 infants born before 32 gestational weeks of age. The results show an inverse relation between serum magnesium at birth and gestational age. Higher levels of serum magnesium at birth within normal variations were associated with a delayed closure of the ductus arteriosus, and mild but not severe peri- and intraventricular haemorrhage.

Use of methohexital for elective intubation in neonates

The effectiveness and safety of a short acting barbiturate, methohexital, was assessed for its use at the time of elective intubation in 18 newborn infants with severe respiratory or cardiac conditions. Evaluation included the speed of action and the degree of relaxation, sedation, and sleep in the first five minutes after administration. All newborn infants were intubated in a fully relaxed and somnolent state. In most infants recovery was completed within five minutes. A slight to moderate oxygen saturation drop was observed during the period of intubation, especially in patients with cyanotic heart disease. The side effects of the drug were twitching and a slight drop in blood pressure. In conclusion, methohexital seems to be a useful drug for short term anaesthesia in neonates, during which, short procedures like elective intubation can be safely performed.

[Evolution of the result of respiratory function studies in children with bronchopulmonary dysplasia]

BACKGROUND

Reports of short- and medium-term evolution of Lung Function Tests (LFT) in infants with bronchopulmonary dysplasia (BPD) are still scarce.

POPULATION AND METHODS

The results of the first (before 3 months of corrected age) and the second (between 3 and 9 months of corrected age) LFT in 22 premature infants with BPD (gestational age 31 +/- 2.5 weeks; birth weight: 1570 +/- 440 g; duration of mechanical ventilation: 46 +/- 24 days, total duration of oxygen therapy: 88 +/- 47 days) were compared to those obtained in 27 normal infants for the first LEF and 10 normal infants for the second LFT, similar to the patients for birth weight and corporeal index (CI).

RESULTS

In the first LFT, major abnormalities were an increased thoracic gaz volume (TGV) (16.5 +/- 42 vs 122 +/- 24 mL; P < 0.001) and TGV CI ratio (1.25 +/- 0.31 vs 0.89 +/- 0.17 ml/kg/m2; P < 0.0001) a decreased pulmonary compliance (2.49 +/- 1.46 vs 11.60 +/- 4.50 mL/cmH2O; P < 0.0001) and specific pulmonary compliance (0.015 +/- 0.10 vs 0.100 +/- 0.042 mL/cmH2O/mL de TGV; P < 0.0001), an increased total pulmonary resistance (20.4 +/- 12.1 vs 10.5 +/- 5.3 cmH2O/L/s; P < 0.001). In the second LFT, an increased TGV (235 +/- 62 vs 166 +/- 28 mL; P < 0.01) and TGV CI ratio (1.64 +/- 0.65 vs 0.98 +/- 0.11 ml/kg/m2; P < 0.05), a decreased pulmonary compliance (2.68 +/- 2.0 vs 15.2 +/- 5.7 mL/cmH2O; P < 0.0001) and specific pulmonary compliance (0.013 +/- 0.010 vs 0.106 +/- 0.050 mL/cmH2O/mL de TGV; P < 0.0001), an increased total pulmonary resistance (17.1 +/- 9.6 vs 8.6 +/- 4.9 cmH2O/L/s; P < 0.05) were noted when compared with the control group results. Major abnormalities of the blood gases were hypoxemia (63 +/- 10 vs 85 +/- 20 mmHg; P < 0.05), hypercapnia (38.5 vs 31 +/- 4 mmHg; P < 0.0001) during the first LFT. Hypoxemia (77 +/- 14 vs 90 +/- 14 mmHg and hypercapnia (37 +/- 4 vs 29 +/- 5 mmHg) continued in the second LFT. Thoracic distention and total pulmonary resistances in infants with BPD did not improve but their pulmonary compliance (P < 0.0001) and PaO2 (P < 0.01) between the first and second LFT did it. Infants who had been ventilated for a hyaline membrane disease (HMD) were more hypoxic on the second LFT (P < 0.05) than those who had been ventilated for other causes. Statistically significant relationships were found between thoracic distention and duration of positive inspiratory pressure (P < 0.05; r = 0.43), duration of positive expiratory pressure (P < 0.05, r = 0.45) total oxygen therapy duration; between total pulmonary resistance and duration of mechanical ventilation with high frequency (P < 0.05; r = 0.52); between hypoxemia and duration of oxygen therapy with FiO2 > or = 60% (P < 0.05; r = 0.54).

CONCLUSIONS

This study shows prolonged clinical and functional abnormalities of the respiratory functions requiring longer follow-up.

Altered platelet-activating factor levels and acetylhydrolase activities are associated with increasing severity of bronchopulmonary dysplasia

Lipid inflammatory mediators are thought to play an important role in the pathogenesis of neonatal lung injury and bronchopulmonary dysplasia (BPD). Because preliminary studies from the intensive care nursery of the University of Tennessee Medical Center, Knoxville, revealed linear increased in blood platelet-activating factor (PAF) levels in very low birthweight infants developing chronic lung disease and lower cord blood PAF acetylhydrolase activities in premature infants, it was theorized that altered platelet-activating factor levels and PAF acetylhydrolase activities are associated with increasing severity of BPD. Platelet-activating factor levels (blood and tracheal lavage) and PAF acetylhydrolase activities (blood and tracheal lavage) were measured over days 1 to 2, 3 to 5 and 6 to 7 in 16 ventilated infants and weekly in 9 infants with bronchopulmonary dysplasia. Platelet-activating factor values were normalized per nanogram of lavage blood urea nitrogen. Severity of bronchopulmonary dysplasia was estimated using the scoring system developed by Toce. Mean blood and lavage PAF levels and PAF acetylhydrolase activities were compared in infants developing bronchopulmonary dysplasia with those without the disease over the first seven days of life. Infants developing chronic lung disease were significantly smaller and of younger gestational age. In infants with bronchopulmonary dysplasia, higher PAF levels in blood were seen on days 3 to 5, along with increased lavage acetylhydrolase activities on days 1 to 2. Increased levels of PAF in lavage on days 3 to 5 were associated with increasing severity of bronchopulmonary dysplasia. Altered blood and lavage platelet-activating factor levels and PAF acetylhydrolase activities appear to be associated with the pathogenesis and severity of bronchopulmonary dysplasia.

Eliminating sleep-associated hypoxemia improves growth in infants with bronchopulmonary dysplasia

OBJECTIVE

Infants with bronchopulmonary dysplasia (BPD) have been previously reported to have a decrease in growth velocity after stopping supplemental oxygen (SO). SO was stopped after a short-term recording (20-30 minutes) of pulse oxygen saturation (Sao2) of 92% or greater in room air. Other studies have documented that Sao2 decreases further during feedings and sleep in infants with BPD. Two questions were asked: (1) whether short-term, awake Sao2 studies would reliably predict prolonged sleep Sao2; and (2) how Sao2 sustained at 88% to 91% vs 92% or greater in room air would impact growth velocity in infants with BPD.

METHODOLOGY

Short-term Sao2 studies were prospectively compared with prolonged sleep Sao2 (n = 63) and the growth velocity of infants who had SO discontinued after a prolonged sleep Sao2 recording of 88% to 91% (group 1; n = 14) versus 92% or greater (group 2; n = 34) in room air.

RESULTS

Failure to maintain Sao2 at predetermined levels occurred in 18 (29%) of 63 infants during their first prolonged sleep study. There was no correlation between short-term awake Sao2 and prolonged sleep Sao2 recordings (r = .02). Body weight, height, weight for height, and rate of weight gain were similar for all study infants before SO was stopped and remained constant for group 2 infants after SO was stopped. However, group 1 infants had a significant decrease in the rate of weight gain (17.3 +/- 13.1 vs 3.7 +/- 6.1 g/kg per day), and the mean z scores for weight gain and weight for height also decreased significantly for group 1 infants. Energy intake, incidence of acute infection, hematocrit values, and medication use did not differ before or after stopping SO in either group.

CONCLUSIONS

This study indicated that short-term, awake Sao2 measurements do not predict prolonged sleep Sao2, and overall, infants with BPD continued a positive growth trend when Sao2, remained greater than 92% during prolonged sleep.

Surfactant therapy prior to the interhospital transport of preterm infants

The risk-to-benefit ratio of surfactant treatment of outborn preterm infants prior, as opposed to after, transportation to a perinatal center is not known. The objective of this study was to document current practice and to examine clinical outcomes in North America. In phase I (December, 1991 to January, 1992) questionnaires were distributed to 114 perinatal centers in the United States and Canada. The centers returned 98 surveys. Over half (50.5%) of the centers report giving surfactant rescue prior to infant transport, but only a minority (9.5%) of the centers report doing so for prophylaxis. In phase II (January, 1992 to December, 1992), clinical outcomes of surfactant-eligible babies requiring interhospital transport at a university hospital were evaluated to determine which infants ultimately received surfactant and when. The infants were compared between groups and did not differ significantly in gestational age, birthweight, sex type, number of multiple births, five-minute Apgar scores, or whether antenatal steroids were used. In phase II, the 66 consecutive, ventilator-dependent, outborn infants with average, and median, gestational age of 28 weeks were compared. The infants receiving surfactant prior to transport, when compared to the infants that got it after transport (9 hours later), did not do any better. There was 6% more survival without bronchopulmonary dysplasia in the group receiving surfactant after transport (65.2% versus 59.3%, p = 0.665). The infants receiving surfactant after transport were off the ventilator sooner (95% C.I. 6.0-28.7 versus 11.8-25.9 days) and discharged from the perinatal center earlier (95% C.I. 37.8-70.8 versus 47.9-69.0 days). Furthermore, arterial blood gases before and after transport reveals that there were no short-term advantages in administering surfactant prior to transport when compared to waiting for reevaluation at the perinatal center. These findings suggest that surfactant can be used safely prior to the interhospital transport of preterm infants, but this treatment does not seem to confer benefit over waiting for reevaluation, and possible surfactant treatment, at the tertiary perinatal center.

Erythropoietin therapy in neonates at risk of having bronchopulmonary dysplasia and requiring multiple transfusions

OBJECTIVES

To determine whether treatment with recombinant human erythropoietin (r-HuEPO) reduces transfusion requirements in premature neonates at risk of having bronchopulmonary dysplasia and requiring multiple transfusions.

STUDY DESIGN

A double-blind, randomized, controlled trial.

SUBJECTS

Fifty-five infants appropriate in weight for gestational age (less than 1250 gm birth weight) who, at 10 days of age, were predicted to have a greater than 75% probability of having bronchopulmonary dysplasia. This criterion had previously been shown to identify infants requiring multiple transfusions. Twenty-seven infants were randomly assigned to receive r-HuEPO therapy and 28 to a control group. r-HuEPO was administered in a dosage of 20 U/kg body weight, subcutaneously, three times a week for 6 weeks. Control infants received sham treatment.

RESULTS

Infants treated with r-HuEPO required significantly fewer transfusions than control infants during their entire hospital stay (mean 3.48 +/- 1.58 vs 5.68 +/- 2.30; p = 0.0001) and had a higher mean reticulocyte count (p < or = 0.0005) and a higher mean hemoglobin concentration (p < or = 0.005) during the treatment period. At follow-up, 4 months after term, there were no significant differences between the groups in mean reticulocyte count (p = 0.86) or mean hemoglobin concentration (p = 0.56). However, two infants in each group had low serum ferritin values indicative of depleted iron stores.

CONCLUSIONS

Treatment with r-HuEPO effectively stimulated erythropoiesis in premature infants at high risk of having bronchopulmonary dysplasia and requiring multiple transfusions; the result was a reduction in transfusion requirements. This treatment, together with other strategies to reduce the need for transfusions, is appropriate in this population. Unrelated to r-HuEPO treatment, these infants may be at risk of having iron deficiency later in infancy.

Effect of long-chain n-3 fatty acid supplementation on visual acuity and growth of preterm infants with and without bronchopulmonary dysplasia

Healthy preterm infants fed formula with long-chain n-3 fatty acids (n-3 LCFAs) from marine oil have better early visual acuity but lower plasma phosphatidylcholine (PC) arachidonic acid (AA) and growth than infants fed formula containing linolenic acid (LLA) as the sole n-3 fatty acid. This randomized, double-blind trial was designed to study the effects of a different source of n-3 LCFAs and a shorter feeding interval on visual acuity (by Teller Acuity Card) and growth of preterm infants (n = 59; 747-1275 g birth wt), some of whom required long periods of supplemental oxygen and developed bronchopulmonary dysplasia (BPD). Infants were studied at 0, 2, 4, 6, 9, and 12 mo past term. Plasma PC AA, and normalized weight, length, and head circumference were not influenced by BPD or n-3 LCFAs except that n-3 LCFA-supplemented infants weighed less at 6 (P<0.05) and 9 (P<0.01) mo and had smaller head circumferences at 9 mo (P<0.05). Compared with control infants, however, those fed n-3 LCFAs had lower weight-for-length at 2, 6, 9, and 12 mo (P<0.0003, P<0.0114, P<0.0008, and P<0.006, respectively). n-3 LCFAs improved early (2-mo) but not later acuity among infants without BPD (P<0.02). Regardless of diet, infants with BPD had poorer grating acuity at 2 (P<0.0002) and 4 (P<0.04) mo but not thereafter.

Prediction of early outcome in resolving chronic lung disease of prematurity after discharge from hospital

In an attempt to identify those infants with resolving chronic lung disease of prematurity (CLD) at greatest risk of sudden infant death syndrome or acute life threatening event (SIDS/ALTE), or readmission to hospital following discharge, recordings of arterial oxygen saturation were made on 35 infants. Recordings were collected while the infants were breathing room air. Movement artefact was excluded and the data analysed to provide the mean individual arterial oxygen saturation (MSaO2), and the variability of the mean individual oxygen saturation (delta MSaO2). These data were related to clinical outcome recorded over the three months following investigation. A MSaO2 less than 90% on discharge predicted hospital admission within three months with a sensitivity of 1 and a specificity of 0.76, and SIDS/ALTE with a sensitivity of 1 and a specificity of 0.75. A delta MSaO2 greater than 6% predicted SIDS/ALTE with a sensitivity 0.88 and specificity of 1. Infants with resolving chronic lung disease of prematurity who are at risk of increased morbidity and mortality can be assessed by accurate measurement of mean arterial saturation.

Use of the intramuscular relative-dose-response test to predict bronchopulmonary dysplasia in premature infants

We tested the hypothesis that an intramuscular relative dose response (IM-RDR) on day 1 of life would more accurately predict which premature infants would develop bronchopulmonary dysplasia (BPD) than single measurements of retinol, retinyl palmitate (RP), or retinol binding protein (RBP). Seventy-five premature infants < or = 32 wk gestation had the IM-RDR on day 1 of life. An RDR > or = 25% occurred in 6 of 37 infants who did not develop BPD compared with 15 of 38 infants who developed BPD (P = 0.025). Retinol, RP, and RBP on day 1 were not different between the groups. BPD infants who received postnatal dexamethasone during their hospital course had a higher day-28 baseline retinol concentration (1.19 +/- 0.15 mumol/L) than did the group with no BPD (0.82 +/- 0.06 mumol/L) (P = 0.03). However, the effect of postnatal dexamethasone on serum retinol was biphasic, rising initially, and then declining after 8-12 d. RP values at time 0 and 5 h on day 28 were higher than day 1 values in both infants without BPD and infants with BPD who did not receive dexamethasone. Retrospective analysis also revealed a significant correlation between a day-1 RDR > or = 25% and the incidence of intraventricular hemorrhage in these premature infants. Because the IM-RDR is more helpful in predicting the development of BPD than single serum retinol and RP analyses, this test could be useful in determining which premature infants might benefit from supplemental vitamin A for BPD.

The relationship of selenium status to respiratory outcome in the very low birth weight infant

OBJECTIVE

To examine the relationship between plasma and erythrocyte selenium and glutathione peroxidase (GPx) levels in premature infants and outcome measures.

DESIGN

Prospective observational longitudinal study.

SETTING

Two regional neonatal intensive care units in the South Island of New Zealand, an area with low soil selenium.

PATIENTS

Seventy-nine infants with birth weights less than 1500 g or gestation less than 32 weeks admitted within 48 hours of birth from November 1992 through November 1993.

MAIN OUTCOME MEASURES

Oxygen requirement at 28 days (chronic lung disease), or 36 weeks postmenstrual age and for all or most of the time from birth (bronchopulmonary dysplasia), total days in oxygen, retinopathy of prematurity, periventricular hemorrhage, or ventricular dilatation.

RESULTS

Initial infant plasma selenium and GPx levels were about two thirds of maternal levels and fell a further 30% in 28 days. In contrast to adults, there was a poor correlation in infant plasma between selenium and GPx at birth and 28 days. Plasma selenium at 28 days was significantly lower in infants with chronic lung disease and bronchopulmonary dysplasia. After controlling for gestational age and age when fully fed orally, 28-day plasma selenium was significantly associated with the log of total days of oxygen requirement, each drop of 0.1 mumol/L in 28-day selenium being associated with a 58% increase in days of oxygen dependency. No significant associations of other parameters of selenium status and respiratory outcome were found, and there were no significant associations of any parameters of selenium status with other outcome measures.

CONCLUSIONS

This study demonstrates for the first time in human infants that low plasma selenium levels are significantly associated with an increased respiratory morbidity. Whether selenium deficiency is etiologically important in determining the respiratory outcome or the result of sickness in the infant should be investigated in a randomized, controlled trial.

Comparison of secretory component for immunoglobulin A with albumin as reference proteins in tracheal aspirate from preterm infants

OBJECTIVES

To determine whether the concentration of secretory component (SC) in tracheal aspirate samples is less altered by changes in alveolar-capillary permeability and thus is a more reliable reference standard than albumin for the measurement of other components obtained by saline lavage in preterm infants.

METHODS

A total of 1229 tracheal aspirate and 1530 blood samples were collected from 195 neonates to evaluate the effects of advancing postnatal and gestational age, resolution of acute respiratory distress syndrome (RDS), steroid therapy for chronic lung disease, and acute sepsis on tracheal aspirate SC and albumin levels. The tracheal aspirate and blood samples were analyzed by enzyme-linked immunosorbent assay techniques for SC and albumin concentrations.

RESULTS

The mean values for the concentrations of aspirate and plasma SC did not vary significantly during an 8-week study period (n = 100) and did not vary with either gestational age (23 to 36 weeks) or postnatal age. Albumin concentration significantly decreased in aspirate samples from 1.67 +/- 0.77 mg/dl at week 1 to 0.41 +/- 0.21 mg/dl at week 8 (p < 0.001), whereas serum levels increased from 2.65 +/- 0.36 to 2.99 +/- 0.54 gm/dl (p < 0.001), suggesting a decrease in alveolar-capillary leakage with advancing postnatal age. The concentration of SC in aspirate samples from 51 infants who received dexamethasone remained constant during the first week of therapy, whereas the concentration of albumin decreased from 1.33 +/- 0.91 mg/dl at the initiation of therapy to 0.51 +/- 0.34 mg/dl on treatment day 7 (p < 0.001). The onset of sepsis (n = 40) was not accompanied by a significant change in either aspirate SC or albumin levels. However, in infants who had a deterioration in respiratory status concomitant with the onset of sepsis (n = 10), the levels of aspirate albumin increased whereas serum levels decreased (p < 0.001), suggesting an increase in alveolar-capillary leakage; the levels of aspirate SC remained unaltered.

CONCLUSIONS

Secretory component may serve as a more valid reference protein for the standardization of tracheal aspirate collection in preterm infants during evaluation of changes in inflammatory mediators in disease states and therapeutic interventions that alter alveolar-capillary integrity.

Sequential evaluation of plasma retinol-binding protein response to vitamin A administration in very-low-birth-weight neonates

Vitamin A (retinol) deficiency is associated with impaired healing from lung injury in very-low-birth-weight (VLBW) neonates susceptible to bronchopulmonary dysplasia (BPD). Vitamin A supplementation from birth may ameliorate this adverse outcome. We hypothesized that plasma retinol-binding protein (RBP) response to vitamin A administration, which provides a dynamic measure to vitamin A status, might be useful for early recognition of vitamin A deficiency in VLBW neonates at risk for BPD. We prospectively studied 20 VLBW neonates (inclusion criteria: birth weight < 1300 g, gestational age < 30 weeks, need for supplemental oxygen and mechanical ventilation for > 24 h after birth) who were eligible to receive vitamin A supplementation. In addition to sequential assessment of vitamin A status, we measured plasma RBP just before and 3 and 6 h after an intramuscular injection of vitamin A (2000 IU/kg retinyl palmitate) on Postnatal Days 1, 7, 15, 21, 29, and 43. The percentage increase in plasma RBP (delta-RBP) was calculated. A high plasma delta-RBP value ( > 8%) is indicative of vitamin A deficiency. Based on pulmonary outcome, the infants were divided into two groups: BPD (n = 12) and No BPD (n = 8). Mean vitamin A intake ranged from 1414 to 2114 IU/kg/day and did not differ between infant groups. Mean plasma vitamin A concentration increased from baseline levels on Postnatal Day 1 to levels within the desired range of 1.05-2.10 mumol/liter (30.0-60.0 micrograms/dl) during supplementation period in both infant groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygen saturation in premature neonates with bronchopulmonary dysplasia in a hammock

Premature neonates with bronchopulmonary dysplasia (BPD) frequently present borderline hypoxemia and the risk for oxygen desaturation may increase in relation to the posture. Our aim was to see if infants with BPD experience severe hypoxemia (SaO2 < 85%) in a hammock, a 'containing' posture considered advantageous to neuromotor and relational development of the preterm. Fifteen pulse oximetry recordings (Ohmeda B105 3760 Pulse Oximeter) were obtained in 15 subjects (range of gestational age and postnatal age 27-30 and 33-48 weeks, respectively; range of birth weight and body weight at entrance to the study 0.64-1.35 and 0.97-2.24 kg, respectively) before, during and after placement in a hammock; each testing period lasted 15 min, and each baby served as his or her own control. BPD preterm infants were receiving oxygen therapy by continuous flow standard nasal cannulas (FiO2 > 25%, < 40%). The analysis of the data, that have a rough gaussian distribution, indicates a worsening of SaO2 in the hammock position. In fact, mean +/- SEM, median and range of the SaO2 values in pre- and posthammock position are comparable, but are significantly different at 99.9% confidence level (CL) in prehammock vs. hammock posture and at 98% CL in posthammock vs. hammock posture. Moreover, the percent of time with SaO2 < 85% during the periods recorded increased about 10 +/- 5% in a hammock (24 +/- 4%), in comparison to pre- (14 +/- 3%) and posthammock position (15 +/- 3%). These results suggest that oxygen-dependent BPD preterm infants in the hammock posture may experience severe hypoxemia that in part limits the possible advantages of the 'containment'.

Heart rate variability during sleep in infants with bronchopulmonary dysplasia. Effects of mild decrease in oxygen saturation

We sought to determine whether abnormal heart rate modulation by the autonomic nervous system occurs in patients with severe bronchopulmonary dysplasia (BPD) in relation to sleep stages and mild changes in arterial oxygen saturation SaO2. On 10 oxygen-dependent 7- to 29-month-old infants with BPD, polygraphic recordings, including heart and respiratory rate and body movement detection, were performed. Heart rate variability was evaluated in high (HF), mid, and low (LF) frequency bands. Parameters were analyzed in two ranges of SaO2: normal range, (SaO2 greater than 95%), and mild decrease in (SaO2, values of 90 to 94%). In contrast to what is normally observed, LF at normal SaO2 was less marked in rapid eye movement, (REM) sleep than in non-rapid eye movement (NREM) sleep stage 2. A mild decrease in SaO2, as compared with a normal SaO2 value, was associated with: (1) a heart and respiratory rate acceleration, (2) a decrease in HF in REM sleep (p < 0.02); (3) an increase in LF in NREM sleep stage 2 (p < 0.02), intensifying the change observed in a normal SaO2 level. These data show that a mild decrease in SaO2 increases modifications of autonomic control observed in infants with severe BPD.

Absence of ventilatory responses to alternating breaths of mild hypoxia and air in infants who have had bronchopulmonary dysplasia: implications for the risk of sudden infant death

Infants who have had bronchopulmonary dysplasia (BPD) are at an increased risk of sudden infant death syndrome. Because failure of the cardiorespiratory response to hypoxia is suggested to play a key role in sudden infant death syndrome, we tested the hypothesis that infants who have had BPD have a reduced respiratory chemoreflex response to hypoxia. We examined the reflex respiratory responses to breath-by-breath alternations in fractional inspired oxygen concentration in eight infants who had had BPD (mean gestation = 27 wk, mean postnatal age = 93 d) who were no longer on supplemental oxygen and compared the responses with those of 12 preterm infants who had not required supplemental oxygen or been mechanically ventilated since birth (mean gestation = 30 wk, mean postnatal age = 38 d). For test runs we alternated fractional inspired oxygen concentration through two gas delivery lines between 0.21 and 0.16 on a breath-by-breath basis, and for control runs we alternated the inspirate between the two gas lines with a fractional inspired oxygen concentration of 0.21 in each. Respiration was measured using inductance plethysmography infants with BPD showed no significant differences between test and control responses for any respiratory variable. In contrast, all respiratory variables in the preterm infants showed test responses significantly greater than control. We speculate that the "blunted" chemoreflex respiratory response seen in infants with BPD may predispose them to subsequent respiratory failure, but we do not known which component of the chemoreflex is impaired.

Influence of dexamethasone on lymphocyte proliferation in whole blood cultures of neonates

The lymphocyte proliferative response to mitogen stimulation was measured in cord blood cultures of term and preterm neonates. The lymphocyte proliferative response increased 150- to 400-fold above baseline after stimulation with mitogens. Dexamethasone suppressed the lymphocyte proliferative response in a concentration-dependent manner with considerable suppression at concentrations applied during treatment of preterm neonates for bronchopulmonary dysplasia (BPD). Dexamethasone and other corticosteroids tested in equipotent glucocorticoid concentrations suppressed the lymphocyte proliferative response to the same extent. We conclude that dexamethasone treatment for BPD may well compromise immune functions of preterm neonates.

A randomized, double-blind, placebo-controlled trial of recombinant erythropoietin in treatment of the anemia of bronchopulmonary dysplasia

Because anemia in patients with bronchopulmonary dysplasia is characterized by inappropriately low serum concentrations of erythropoietin but increased in vitro sensitivity of erythroid progenitors to erythropoietin, we speculated that administration of human recombinant erythropoietin would correct this anemia. Fifteen infants with the anemia of bronchopulmonary dysplasia were randomly assigned to receive erythropoietin or placebo subcutaneously for 10 days. Changes in reticulocyte count, hematocrit, blood lactate concentration, neutrophil count, platelet count, heart rate, oxygen requirement, weight gain, and number of transfusions were assessed. In the 10 erythropoietin recipients (99 +/- 12 days of age), hematocrit values increased from 0.325 +/- 0.006 to 0.381 +/- 0.013 (mean +/- SEM; p < 0.005) and reticulocyte counts from 122 +/- 20 to 446 +/- 48 x 10(3)/microliters (p < 0.005); lactate values remained unchanged. In the five placebo recipients (91 +/- 12 days of age), hematocrits and reticulocyte counts remained unchanged, and lactate values increased from 0.73 +/- 0.14 to 1.34 +/- 0.25 mumol/gm (p < 0.05). During the 30 days after the treatment period, one erythropoietin recipient and four placebo recipients were given transfusions. Other measured variables remained unchanged in both groups. We conclude that erythropoietin is effective in treatment of the anemia of bronchopulmonary dysplasia.