Failure of supplementation with vitamin E to prevent bronchopulmonary dysplasia in infants less than 1,500 g birth weight

In a randomized trial to determine whether oral vitamin E reduced stages III and IV bronchopulmonary dysplasia (BPD) by 50%, 268 infants were randomly allocated, after stratification by birth weight and severity of disease, to receive vitamin E 25 units or an indistinguishable placebo. The experimental (E) group and the control (C) group were similar in weight, gestational ages, Apgar scores, severity of illness, and initial oxygen and ventilator exposure. Serum vitamin E levels were significantly different within 48 h of administration and remained well above normal adult levels from the first week of life in the experimental group. There was no difference in the rates of early death, BPD at 28 days, or mortality from BPD. Severity was similar and no difference was seen in the incidence of necrotizing enterocolitis or sepsis. There was no evidence that vitamin E supplementation offered protection against chronic lung disease in infants less than 1,500 g birth weight.

Sleep apnea and hypoxemia in recently weaned premature infants with and without bronchopulmonary dysplasia

Infants with bronchopulmonary dysplasia (BPD) experience significant hypoxemia. Apnea indices and oxygen saturation levels of ten infants with BPD were compared to ten healthy premature infants who were evaluated to rule out apnea or bradycardia prior to discharge from the hospital. Infants with BPD who had been recently (less than 7 days) weaned from supplemental oxygen were evaluated on and off supplemental oxygen. Premature controls had never received oxygen nor ventilation assistance. Infants with BPD were born significantly more prematurely (28.1 +/- 1.0 vs. 33.0 +/- 3.9 weeks; P = 0.0012) while chronologic ages at the time of evaluation, adjusted for prematurity, were equal (37.1 +/- 3.1 vs. 38.0 +/- 2.7 weeks). Comparisons of apnea densities (expressed as percent of sleep time) between BPD and non-BPD prematures revealed the following: neither the average obstructive apnea (0.15 +/- 0.36 vs. 0.14 +/- 0.31) nor periodic breathing densities (6.0 +/- 8.56 vs. 10.2 +/- 5.84) were different. Infants with BPD experienced significantly more central apnea (0.62 +/- 0.34 vs. 0.16 +/- 0.11; P = 0.003) than did non-BPD prematures. Average oxygen saturation levels were significantly less among BPD vs. non-BPD prematures (90.0 +/- 10.18% vs. 95.7 +/- 4.33%; P = 0.033). When supplemented with oxygen, BPD prematures had significantly higher saturation (X = 94.5%) than when breathing room air (X = 90.0%). Both central apnea and periodic breathing densities declined significantly with this improvement in saturation (0.64 vs. 0.04% and 6.0 vs. 1.4%, respectively). These data suggest that saturation status may indicate central respiratory stability in chronic lung disease.

Elevated levels of fetal hemoglobin synthesis in infants with bronchopulmonary dysplasia

A study was devised to determine whether levels of fetal hemoglobin (HbF) synthesis are elevated in infants with bronchopulmonary dysplasia (BPD) when compared with the levels of HbF synthesis found in normal control infants. Twelve infants with BPD, whose postconceptional ages ranged from 40 to 62 weeks, were studied. The mean (+/- SD) gestational age and birth weight was 29 +/- 1.9 weeks and 1289 +/- 376 g, respectively. Elevation infants matched for birth weight, gestational age, and postnatal age served as the control subjects. Blood samples were incubated in an amino acid mixture containing [14C]leucine. The adult hemoglobin and HbF were then separated by column chromatography on diethylaminoethyl-Sephadex. The results demonstrated that the mean (+/- SD) level of HbF synthesis in infants with BPD was significantly higher than that in the control infants (42.6 +/- 22.9% vs 18.8 +/- 12.8%; P less than .01). When levels of HbF synthesis in the infants with BPD and the control infants were compared with data previously reported in normal infants, 7 of the 12 infants with BPD, but none of the control infants, were synthesizing amounts of HbF greater than would be expected for their postconceptional age. The results suggest that cardiopulmonary insufficiency could stimulate HbF synthesis during the first year of life as a result of an erythropoietic response to hypoxemia.

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.

Changes in vasopressin, atrial natriuretic factor, and water homeostasis in the early stage of bronchopulmonary dysplasia

Arginine vasopressin (AVP), atrial natriuretic factor, and water balance were examined in the infants with or without bronchopulmonary dysplasia (BPD) during the first 4 wk of life. Fourteen premature infants, nine in the early stage of BPD secondary to respiratory distress syndrome (BPD infants) and five healty low birth wt infants (LBW infants), were the subjects of this study. The water and sodium balance, renal function, and plasma AVP and atrial natriuretic factor concentrations were determined during the first 4 wk of life. Plasma AVP and atrial natriuretic factor levels of BPD infants at the 4th wk of life were higher than those of LBW infants at the corresponding age. Urine osmolality was higher and free water clearance was lower in BPD infants at the 4th wk of life when compared with each parameter in LBW infants, respectively. Paco2 of BPD infants at the 4th wk of life was more elevated than that of LBW infants. These results suggest that elevated plasma AVP level may be related with pulmonary abnormalities and that atrial natriuretic factor may hence compensate the water retention resulted from the functionally activated AVP in the early stage of BPD.

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.

Neonatal pulse oximetry: accuracy and reliability

Pulse oximetry has gained widespread use in neonatal oxygen monitoring. However, because specific morbidity in neonates has been related to abnormal levels of oxygen partial pressure (PaO2), it is essential to demonstrate that pulse oxygen saturation values (SpO2) are highly accurate and reflect with precision the simultaneous PaO2. In this report, data is presented that describe the accuracy of the Ohmeda Biox 3700 pulse oximeter. SpO2 was highly correlated with arterial blood oxygen saturation (r = .99) measured on arterial (catheter) blood using a two-wavelength Radiometer OSM2 Hemoximeter. When compared with PaO2, SpO2 values of 92% +/- 3% (mean +/- range) excluded all of the measured PaO2 values less than 45 mm Hg and greater than 100 mm Hg. SpO2-tcPO2 (transcutaneous PO2) and SpO2-PaO2 (catheter or percutaneous arterial PO2) correlations showed that bronchopulmonary dysplasia, percutaneous arterial sampling, and nipple feeding skewed the tcPO2 but not the PaO2 correlations with SpO2, indicating that SpO2 is not sensitive to peripheral factors that affect tcPO2. SpO2-PaO2 correlation was not affected by gestational age. A high degree of accuracy of SpO2 values and SpO2 prediction of normal appearing PaO2 values are defined by these results.

Accuracy of two wavelength pulse oximetry in neonates and infants

In 60 neonates (gestational age, 26.5-40 weeks; postnatal age, 1-14 days) and in 11 infants (gestational age, 26-33 weeks; postnatal age, 4.5-38 weeks), the accuracy of two wavelength pulse oximetry was examined. A total of 112 comparisons between transcutaneous pulse oximetry saturation (StcO2, NELLCOR N-100) and arterial oxygen saturation (SaO2, OSM2 RADIOMETER) were obtained. SaO2 ranged from 80 to 100%. Criteria for comparison between StcO2 and SaO2 were standardized: patients in behavioral state 1, StcO2 stable for 2 min, and arterial samples drawn from an indwelling arterial line. StcO2 was significantly related to SaO2 (P less than 0.01), but the difference, StcO2 - SaO2, significantly increased when SaO2 decreased [StcO2 - SaO2(%) = -0.39 SaO2(%) + 37.95; r = -0.64, P less than 0.01]. No significant relationship was found between StcO2 - SaO2 and either bilirubinemia (range, 5-222 mumol/L) or fetal hemoglobin (HbF) (range, 12-95%). We conclude that StcO2 overestimates SaO2 when SaO2 decreases, and this overestimation is not due to high levels of bilirubin or HbF.

[Comparison of arterial and transcutaneous oxygen partial pressure in infants with bronchopulmonary dysplasia]

Transcutaneous PO2 (PTCO2) (Radiometer electrode heated to 44 degrees C) was compared to arterial PO2 (PaO2) in 19 infants with bronchopulmonary dysplasia: 12 infants were tested once, at the mean postnatal age of 14 weeks (range 4-43 weeks), the other 7 infants were studied longitudinally from 5 weeks (range 2-8 weeks) to 12 weeks (range 6-18 weeks) of postnatal age. The protocol was standardized: measurement during behavioral stage 1, using a peripheral arterial line. Twenty-eight comparisons between PTCO2 and PaO2 were obtained. PTCO2 was significantly related to PaO2 [PTCO2 (mmHg) = 0.81 PaO2 + 5.2, r = 0.73, p less than 0.01]. The mean difference PTCO2 - PaO2 was -7.2 mmHg (range: -34.5 to + 33); in the studied age range the PTCO2 - PaO2 was not significantly related to postnatal age (r = -0.24; p greater than 0.1).

Oxygen toxicity in the infant rhesus monkey: effects on regulatory peptides in lung and blood

A total of ten 6-month-old male rhesus monkey (Macaca mulatta) infants, born full-term, were positive-pressure ventilated with greater than 95% oxygen or room air (controls). A protocol was used which closely simulated pediatric intensive care. To test if regulatory peptides were affected by the oxygen treatment, and to search for an early marker of oxygen toxicity, lung tissue samples and systemic mixed venous blood were collected at 6, 12 and 24 hours after onset of treatment. The peptides, gastrin releasing peptide (GRP), calcitonin gene-related peptide (CGRP), peptide YY (PYY), vasoactive intestinal peptide (VIP) and somatostatin (SOM), were quantitated in lung tissue extracts and plasma using radioimmunoassay. Lung tissue GRP, CGRP, and PYY levels appeared to decrease gradually with time, perhaps as a result of the positive pressure ventilation procedure. GRP and CGRP levels decreased less among monkey infants ventilated with oxygen, thus they were significantly higher at 24 hours than in air ventilated controls. VIP levels were significantly lower among tests compared to controls at that time. Blood peptide levels did not change with oxygen treatment. These results suggest that tissue concentrations of certain pulmonary regulatory peptides can become altered by ventilation with greater than 95% oxygen. A blood borne peptide marker was not identified.

Pulmonary vascular extraction of circulating norepinephrine in infants with bronchopulmonary dysplasia

Although the pulmonary circulation in infants with advanced bronchopulmonary dysplasia (BPD) is characterized by abnormal structure and vasoreactivity, metabolic lung functions have not been studied in these infants. To test the hypothesis that patients with severe BPD may have abnormal metabolic lung function, we assessed the pulmonary vascular extraction of circulating norepinephrine in six children with BPD during cardiac catheterization. Plasma norepinephrine levels were measured from simultaneously drawn mixed venous (main pulmonary artery) and left atrium or femoral artery samples. In comparison with four infants with mild heart disease without pulmonary hypertension, we found that infants with BPD extract proportionately less norepinephrine than non-BPD infants [-7 +/- 50% (BPD) versus +27 +/- 6% (non-BPD); P less than 0.001, t test]. Three infants with BPD had higher arterial than mixed venous concentrations of plasma norepinephrine, suggesting net production across the lung. Plasma catecholamine levels and percent extraction correlated poorly with cardiac index and systemic and pulmonary vascular resistance indices. However, this study group was characterized by a high incidence of pulmonary (6/6) and systemic (4/6) hypertension, left ventricular hypertrophy (4/6), and subsequent death (3/6). We conclude that infants with severe BPD and pulmonary hypertension have decreased pulmonary vascular clearance or net production of circulating norepinephrine, but links between altered pulmonary catecholamine metabolism and pulmonary hypertension, or other cardiovascular abnormalities associated with BPD, remain speculative.

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 in very low birth weight infants with acute and chronic lung disease

With improved survival of very low birth weight infants, the incidence of bronchopulmonary dysplasia has significantly increased. Pulse oximetry appears to be an adequate alternative to transcutaneous PO2, for continuous arterial oxygen saturation (SaO2) monitoring in neonates; however, its usefulness has not been very well documented in very low birth weight infants. We studied 68 patients with birth weight less than 1,250 g; 44 neonates had respiratory distress syndrome and 24 had bronchopulmonary dysplasia. Using a Nellcor N-100 pulse oximeter, we compared transcutaneous oxygen saturation with simultaneous arterial samples analyzed for SaO2 (range 78% to 100%) using an IL 282 co-oximeter. Fetal hemoglobin was measured in 66 patients. We also evaluated the accuracy of transcutaneous PO2 in reflecting arterial PO2 in patients with bronchopulmonary dysplasia. Over a wide range of PO2, PCO2, pH, heart rate, BP, hematocrit, and fetal hemoglobin, linear regression analysis revealed a close correlation between pulse oximeter values and co-oximeter measured SaO2 in patients with acute (r = .88, Y = 19.41 + 0.79X) and chronic (r = .90, Y = 9.72 + 0.92X) disease. Regression analysis of transcutaneous v arterial PO2 in infants with bronchopulmonary dysplasia showed an r value of .78. In addition, in these patients with chronic disease, the mean difference between pulse oximeter SaO2 and co-oximeter measured SaO2 was 2.7 +/- 1.9% (SD); whereas the mean difference between transcutaneous and arterial PO2 was -14 +/- 10.7 mm Hg. Our findings indicate that pulse oximetry can be used reliably in very low birth weight infants with acute and chronic lung disease, for SaO2 values greater than 78%.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of antioxidant enzymes to trace metals in premature infants

Serum levels of the trace metals copper, zinc, and selenium were measured in premature infants. White blood cell glutathione peroxidase and superoxide dismutase levels were measured in conjunction with the trace metals. Three groups of infants were evaluated: group I was relatively healthy, group II were infants with stage 2 bronchopulmonary dysplasia (BPD) or less, group III were infants with stage 3 BPD or worse. Zinc and selenium levels declined in all groups during conventional parenteral nutrition (TPN) regimens, while copper remained stable. Copper did decline in groups I and II coincident with an acceleration in growth rate. An expected rise in antioxidant enzyme levels in infants with pulmonary oxygen toxicity was not seen. This study suggests that supplemental selenium as well as an increased zinc intake over current recommendations for premature infants receiving TPN may be indicated.

Short-term dexamethasone therapy for bronchopulmonary dysplasia: acute effects and 1-year follow-up

Eight ventilator-dependent infants with bronchopulmonary dysplasia (BPD) were treated with dexamethasone (0.5 mg/kg/day). Therapy was initiated at 19.3 +/- 3.9 days of age, continued at the initial dose for 7 days, then tapered over 2 weeks. The clinical course of these infants with BPD was compared to that of 8 similar ventilator-dependent infants with uncomplicated hyaline membrane disease (HMD). At study entry, the BPD patients had significantly higher ventilator rates, peak inspiratory pressures, mean airway pressures, alveolar-arterial oxygen gradients and fraction of inspired oxygen (FiO2) values. After 7 days of dexamethasone therapy, ventilator rates, peak inspiratory pressures, mean airway pressures, FiO2 values and alveolar-arterial oxygen gradients improved significantly. At this time, ventilator rates, peak inspiratory pressures and FiO2 values were similar to those of patients with uncomplicated HMD. BPD patients were extubated after 6.5 +/- 2.4 days of therapy. The incidences of septicemia, rickets and retinopathy of prematurity were similar in the BPD and uncomplicated HMD patients. Most dexamethasone-treated patients developed arterial hypertension during the first 48 h of therapy. Blood pressures returned to normal within 7 days of stopping therapy. All BPD patients had cosyntropin responses tested 5.5 +/- 2.6 weeks after stopping therapy. Six were normal. Two had inadequate responses. At 1 year adjusted age, the dexamethasone-treated BPD infants and HMD infants had similar radiographic bone ages, similar growth patterns and similar scores on the Bayley infant development scale. Dexamethasone was useful in the treatment of early BPD. Used as short-term therapy, the drug had minimal complications and no long-term sequelae.

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.