Blood Cytokine Profiles Associated with Distinct Patterns of Bronchopulmonary Dysplasia among Extremely Low Birth Weight Infants.

OBJECTIVE: To explore differences in blood cytokine profiles among distinct bronchopulmonary dysplasia (BPD) patterns. STUDY DESIGN: We evaluated blood spots collected from 943 infants born at ≤1000 g and surviving to 28 days on postnatal days 1, 3, 7, 14, and 21 for 25 cytokines. Infants were assigned to the following lung disease patterns: (1) no lung disease (NLD); (2) respiratory distress syndrome without BPD; (3) classic BPD (persistent exposure to supplemental oxygen until 28 days of age); or (4) atypical BPD (period without supplemental oxygen before 28 days). Median cytokine levels for infants with BPD were compared with the IQR of results among infants with NLD. RESULTS: The distribution of enrolled infants by group was as follows: 69 (NLD), 73 (respiratory distress syndrome), 381 (classic BPD), and 160 (atypical BPD). The remaining 260 infants could not be classified because of missing data (104) or not fitting a predefined pattern (156). Median levels of 3 cytokines (elevated interleukin [IL]-8, matrix metalloproteinase-9; decreased granulocyte macrophage colony-stimulating factor) fell outside the IQR for at least 2 time points in both infants with atypical and classic BPD. Profiles of 7 cytokines (IL-6, IL-10, IL-18, macrophage inflammatory protein-1α, C-reactive protein, brain-derived neurotrophic factor, regulated on activation, normal T cell expressed and secreted) differed between infants with classic and atypical BPD. CONCLUSIONS: Blood cytokine profiles may differ between infants developing classic and atypical BPD. These dissimilarities suggest the possibility that differing mechanisms could explain the varied patterns of pathophysiology of lung disease in extremely premature infants.

Vascular Endothelial Growth Factor/Placental Growth Factor Heterodimer Levels in Preterm Infants with Bronchopulmonary Dysplasia.

BACKGROUND: Bronchopulmonary dysplasia (BPD) is associated with changes in pulmonary angiogenesis. However, the role of the vascular endothelial growth factor/placental growth factor (VEGF/PlGF) heterodimer, an antiangiogenic factor, remains unknown in this disease. OBJECTIVE: To compare VEGF/PlGF levels in preterm infants with and without BPD. METHODS: This study was approved by the Institutional Review Board. Preterm neonates with birth weight <2,000 g and gestational age ≤ 34 weeks were included. Exclusion criteria were: neonates transferred from other institutions after 72 hours of life; death before blood collection; presence of major congenital malformations, inborn errors of metabolism, and early sepsis; and mothers with multiple pregnancies, TORCH infections, HIV infection, or autoimmune diseases. BPD was defined as the need for oxygen therapy for a period equal to or greater than 28 days, accompanied by radiographic changes compatible with the disease. Blood was collected from neonates in the first 72 hours of life. VEGF/PlGF levels were measured using the enzyme-linked immunosorbent assay method. The chi-square test, t-test, Mann-Whitney test, analysis of variance, and Kruskal-Wallis test were used for statistical analysis. Variables found to be significant in the univariate analysis were included in the multivariate analysis. RESULTS: Seventy-three patients were included (19 with BPD, 43 without BPD, and 11 neonates who died in the first 28 days of life), with a mean (SD) gestational age of 30.32 (2.88) weeks and birth weight of 1,288 (462) g. Median VEGF/PlGF levels were higher in the groups with BPD and death in the first 28 days of life than in the group without BPD (16.46 [IQR, 12.19-44.57] and 20.64 [IQR, 13.39-50.22], respectively, vs. 9.14 [IQR, 0.02-20.64] pg/mL], p < 0.001). Higher VEGF/P1GF levels remained associated with BPD and death in the first 28 days of life in the multivariate analysis. CONCLUSION: Higher plasma VEGF/PlGF levels were found in preterm neonates with BPD and in those who died in the first 28 days of life, suggesting an important role of this substance in pulmonary vascular development.

Plasma asymmetric dimethylarginine levels are increased in neonates with bronchopulmonary dysplasia-associated pulmonary hypertension.

OBJECTIVE: To test the hypothesis that levels of the endogenous inhibitor of nitric oxide production, asymmetric dimethylarginine (ADMA), would be greater in preterm infants with bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) than in infants with BPD alone. STUDY DESIGN: A case-control study of 23 patients with both BPD and PH (cases) and 95 patients with BPD but no evidence of PH (controls). Levels of ADMA were compared between cases and controls by t test. RESULTS: Patients with both BPD and PH had greater plasma levels of ADMA than patients with BPD alone (P = .04). In samples drawn before 28 days of life, greater levels of ADMA were again found in cases compared with controls (P = .02). The plasma arginine-to-ADMA ratio was lower in cases than in controls (P = .03), suggesting a greater likelihood of inhibition of nitric oxide production in patients with both BPD and PH than in patients with BPD alone. CONCLUSION: In this neonatal BPD cohort, ADMA levels are increased in patients with BPD who develop PH. We speculate that ADMA may be both a biomarker and a potential therapeutic target for preterm infants with BPD-associated PH.

Plasma pro-endothelin-1 and respiratory distress in newborn infants.

Plasma concentrations of the stable endothelin-1 precursor, C-terminal portion of the endothelin-1 precursor, determined prospectively in 293 newborn infants (gestational age, 24-41 weeks) at birth and on day 3 of life were unrelated to gestational age at birth, but strongly associated with respiratory distress when measured on day 3 of life.

Blood cytokines during the perinatal period in very preterm infants: relationship of inflammatory response and bronchopulmonary dysplasia.

OBJECTIVE: To evaluate the influence of chorioamnionitis (CA) on plasma cytokines and the cytokine-associated risk of bronchopulmonary dysplasia (BPD) during the perinatal period. STUDY DESIGN: Eleven cytokines from 128 very low gestational age infants were analyzed from cord blood and from plasma at ages 1 day and 7 days after birth. The diagnosis of CA was based on histology of the placenta, fetal membranes, and umbilical cord. Neonatal risk factors were recorded. RESULTS: In the 48 infants born with CA, high concentrations of inflammatory cytokines in cord blood decreased during the first postnatal day. Inflammatory cytokines in cord blood was associated with the severity of CA. At 1 day after birth, the concentration of interleukin (IL)-8 predicted the risk of BPD. For the 75 infants born without CA, cytokine concentrations increased after birth. For the 128 infants born with or without CA, at 1 day after birth, the concentrations of IL-8, granulocyte colony-stimulating factor, and anti-inflammatory IL-10 were associated with the risk of BPD, after adjustment for the duration of gestation and severity of respiratory distress during the first day. CONCLUSIONS: In infants exposed to CA, insufficient inhibition of high fetal inflammatory cytokine response shortly after birth may increase the risk of BPD.

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.

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.

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.

Effect of dexamethasone therapy on fibronectin and albumin levels in lung secretions of infants with bronchopulmonary dysplasia.

The influence of dexamethasone on levels of total fibronectin (tFn), cellular fibronectin (cFn), plasma fibronectin (pFn), and albumin in lung secretions was determined in tracheal aspirate samples collected from 45 infants with bronchopulmonary dysplasia during a 6-week course of dexamethasone therapy. Secretory component for IgA (SC) was used as a reference protein. Thirty-seven infants (82%) survived and had their endotracheal tubes successfully removed. Corticosteroid therapy was associated with a significant decrease in the cFn/SC ratio. There was also a significant decrease in albumin/SC and pFn/SC ratios, suggesting decreased capillary permeability with corticosteroid therapy. Four of the remaining infants did not improve while receiving corticosteroids and died of respiratory failure at 3 to 8 weeks of age. In these "no response" infants, tFn/SC, cFn/SC, pFn/SC, and albumin/SC ratios when corticosteroid therapy was initiated were threefold to fourfold greater (p < 0.01) than ratios in survivors. Another group of four infants initially responded to corticosteroids but subsequently died with severe pulmonary cystic degeneration at 4 to 6 months of age; in these infants, tracheal aspirate tFn/SC, cFn/SC, and albumin/SC ratios were significantly lower than in survivors and remained unchanged during corticosteroid therapy. The decrease in the concentrations of plasma fibronectin and albumin in tracheal aspirate samples from the survivors suggests that the rapid clinical improvement seen in infants with bronchopulmonary dysplasia after the initiation of dexamethasone therapy is due in part to improvement in the integrity of the alveolar-capillary barrier. In addition, the decrease in the aspirate levels of cFn suggests the potential for corticosteroids to limit pulmonary fibrosis in the surviving infants. The depressed levels of fibronectin observed in the infants with severe cystic lung disease may represent an impaired healing response to lung injury.

Trial of vitamin A supplementation in very low birth weight infants at risk for bronchopulmonary dysplasia.

We performed a randomized, double-blind, controlled trial to determine whether vitamin A supplementation in a group of very low birth weight infants would reduce the incidence of bronchopulmonary dysplasia. Forty-nine infants (birth weight 700 to 1100 gm) requiring mechanical ventilation and supplemental oxygen at 96 hours age were randomly assigned to receive either 2000 IU retinyl palmitate (n = 27) or saline placebo (n = 22) intramuscularly every other day for up to 14 doses. There were no differences between treatment groups in the incidences of bronchopulmonary dysplasia at 31 days of postnatal age (vitamin A group 48%, placebo group 55%; p = 0.776), supplemental oxygen requirement at 34 weeks of postconceptional age, or other complications of prematurity. The vitamin A group had higher mean plasma vitamin A concentrations than the placebo group, but mean plasma vitamin A concentrations were greater than 20 micrograms/dl (suggesting sufficiency) in both groups after the first study week. By study day 28, only one fourth of the infants in either group had plasma vitamin A concentrations less than 20 micrograms/dl. In contrast to an earlier report, we found no change in the incidence of BPD with vitamin A supplementation. Our findings may reflect a low baseline incidence of vitamin A deficiency in the study population and recent changes in the respiratory care of very low birth weight infants. The latter may have lessened the potential impact of vitamin A deficiency on lung disease.

Double-blind, placebo-controlled trial of alternate-day furosemide therapy in infants with chronic bronchopulmonary dysplasia.

To test the hypothesis that alternate-day administration of furosemide will result in a sustained improvement in pulmonary function without causing alterations in electrolyte or mineral homeostasis, we conducted a randomized, double-blind, placebo-controlled study of 11 hospitalized, oxygen-dependent, spontaneously breathing infants with chronic bronchopulmonary dysplasia. Infants were randomly selected to receive either furosemide, 4 mg/kg in two divided doses on alternate days orally, or placebo for 8 days, followed by crossover to the alternate-therapy for an additional 8-day period. The two study periods were separated by a 48-hour washout period. Dynamic compliance, total pulmonary resistance, the concentration of electrolytes in serum, and the concentrations of calcium and creatinine in urine were measured on nontreatment days. Alternate-day furosemide therapy increased dynamic lung compliance by 76 +/- 112% and decreased total pulmonary resistance by 20 +/- 39%, compared with placebo (both variables p = 0.032). Alternate-day furosemide therapy did not result in increased urine output, electrolyte abnormalities, or increased urinary calcium excretion. We conclude that this simplified treatment regimen may be useful in the management of infants with chronic bronchopulmonary dysplasia. The results support our previous speculation that furosemide improves pulmonary function by mechanisms unrelated to its diuretic properties.

Plasma retinol-binding protein response to vitamin A administration in infants susceptible to bronchopulmonary dysplasia.

We hypothesized that changes in plasma retinol-binding protein (RBP) concentration in response to vitamin A administration might be useful for evaluating vitamin A status of very low birth weight infants susceptible to bronchopulmonary dysplasia. We prospectively studied 24 consecutively admitted neonates (birth weight less than 1350 gm, gestational age less than 31 weeks, ventilator dependent for greater than 24 hours after birth), who were eligible to receive 2000 IU supplemental vitamin A by intramuscular injection on postnatal day 1 and on alternate days thereafter for 28 days. In addition to serial assessment of vitamin A status, we measured plasma RBP just before and 1, 3, and 6 hours after an intramuscular injection of vitamin A (2000 IU/kg retinyl palmitate) on days 1 and 28. The percent increase in plasma RBP (delta-RBP) was high (mean +/- SD: 61 +/- 37%) and plasma vitamin A and RBP values were low on day 1, indicative of vitamin A deficiency. Supplemental vitamin A improved vitamin A status of all infants as shown by low delta-RBP (mean +/- SD: 8 +/- 9%) and normal plasma vitamin A and RBP values on day 28. Bronchopulmonary dysplasia was diagnosed in 12 of 24 infants. Infants with bronchopulmonary dysplasia had a higher mean (+/- SD) delta-RBP on day 28 than those without bronchopulmonary dysplasia (13 +/- 10% vs 3 +/- 3%, p less than 0.01), indicative of persistence of low vitamin A status in infants with lung disease despite supplementation. We conclude that the plasma RBP response to vitamin A is a useful indicator of vitamin A status in very low birth weight infants. Although vitamin A supplementation at the dosage used in this study normalizes conventional plasma indexes of vitamin A in very low birth weight infants, the plasma RBP response to vitamin A may continue to reflect persistence of low vitamin A status in the more immature infants with significant lung disease. We suggest that the plasma RBP response to vitamin A may be a useful functional test in such infants.

Selenium deficiency in low birth weight neonates: an unrecognized problem.

To determine whether selenium deficiency is common among low birth weight infants in our neonatal intensive care unit, we surveyed blood samples from healthy full-term and preterm infants born in our hospital over a 3-month period. Selenium was measured by electrothermal atomic absorption spectrometry. Glutathione peroxidase was measured in plasma by an automated method. Baseline (less than 72 hours postnatal) selenium concentration and glutathione peroxidase activity were significantly lower in low birth weight infants than in full-term babies. Sequential selenium analyses were obtained in 16 sick low birth weight neonates who remained in the intensive care nursery for up to 6 weeks because of lung disease. All were fed parenterally without supplemental selenium, with or without oral intake, for periods varying from 3 to 60 days. All had a marked decrease from baseline selenium levels, and values below the detection limit of our assay were found in seven infants. Selenium deficiency is much more common in small infants than is generally realized, but the clinical significance in neonates is poorly understood.

Clinical trial of vitamin A supplementation in infants susceptible to bronchopulmonary dysplasia.

We conducted a randomized, double-blind, controlled trial to determine whether vitamin A supplementation from early postnatal life could reduce the morbidity associated with bronchopulmonary dysplasia in very low birth weight (VLBW) neonates. Forty VLBW neonates (700 to 1300 g birth weight, 26 to 30 weeks gestational age), who were oxygen dependent and required mechanical ventilation for at least 72 hours after birth, were given by the intramuscular route either supplemental vitamin A (retinyl palmitate 2000 IU) or 0.9% saline solution on postnatal day 4 and every other day thereafter for a total of 14 injections over 28 days. The study groups were comparable in gestational maturity, clinical characteristics, initial lung disease, and vitamin A status at entry into the trial. Vitamin A administration resulted in significantly higher mean plasma concentrations of vitamin A and retinol-binding protein in treated infants compared with controls. Bronchopulmonary dysplasia was diagnosed in nine of 20 infants given vitamin A supplement and in 17 of 20 control infants (P less than 0.008). Four of 19 infants in the vitamin A group and 11 of 20 in the control group required mechanical ventilation on study day 28 (P less than 0.029). The need for supplemental oxygen, mechanical ventilation, and intensive care was reduced in infants given vitamin A supplement compared with controls. Airway infection and retinopathy of prematurity were less frequent in the vitamin A group. We conclude that vitamin A supplementation at the dosage used in this trial in VLBW neonates not only improves their vitamin A status but also appears to promote regenerative healing from lung injury, as evidenced by a decrease in the morbidity associated with bronchopulmonary dysplasia.

Pulse oximetry for continuous oxygen monitoring in sick newborn infants.

We studied 54 neonates with acute cardiorespiratory illness and 21 infants with bronchopulmonary dysplasia, to evaluate the accuracy of a nonheated pulse oximeter in predicting arterial oxygen saturation (SaO2). We also studied the accuracy of transcutaneous oxygen tension (tcPO2) in estimating arterial oxygen tension (PaO2) in infants with bronchopulmonary dysplasia. We compared pulse oximeter SaO2 with simultaneously measured SaO2 (range 78% to 100%) using a co-oximeter. Over a wide range of values for heart rate, blood pressure, hematocrit, PO2, PCO2, and pH, linear regression analysis revealed a close correlation between in vivo pulse oximeter readings and in vitro SaO2 measurements in patients with acute (r = 0.86, Y = 29.64 + 0.68X) and chronic (r = 0.91, Y = 6.29 + 0.96X) disease. Regression analysis of tcPO2 versus PaO2 showed an r value of 0.76 in infants with bronchopulmonary dysplasia. In these patients the mean difference between pulse oximeter SaO2 and in vitro SaO2 was 2.9% +/- 1.8% (SD), whereas the mean difference between tcPO2 and PaO2 was -14.5 +/- 11.1 mm Hg. Fetal hemoglobin ranged from 4.3% to 95%. We conclude that pulse oximetry is an appropriate alternative to tcPO2 for continuous oxygen monitoring in newborn infants with acute cardiorespiratory illnesses and chronic lung disease.