Carl T. D'Angio

Atypical chronic lung disease patterns in neonates.

Objective. To determine, in the postsurfactant era, the incidence and clinical characteristics of infants with atypical versus traditionally defined bronchopulmonary dysplasia (BPD) among premature infants with birth weights <1251 g. Design. Retrospective cohort study. Setting. A single regional neonatal intensive care unit (level III/IV). Patients. Two hundred thirty-two premature infants <1251 g at birth consecutively admitted during a 2-year period. Main Outcome Measure. Incidence of classic BPD and atypical chronic lung disease (CLD) (occurring without preceding respiratory distress or after recovery from respiratory distress). Results. Among 177 infants <1251 g who survived to 28 days, 27 (15%) had atypical CLD and 61 (34.5%) had classic BPD. Atypical CLD infants were significantly heavier and more mature than classic BPD infants (mean birth weights, 922 ± 152 g vs 854 ± 173 g; and mean gestational age, 26.8 ± 1.3 weeks vs 26.1 ± 1.6 weeks). Median duration of ventilator support (31 days; range, 2 to 127 vs 42 days; range, 4–145 days) and oxygen therapy (30 days; range, 11 to 163 vs 48 days; range, 19–180 days) were shorter in atypical CLD infants than in classic BPD infants. Conclusion. Atypical CLD comprised 31% of total cases of CLD. Atypical CLD appears to be less severe than classic BPD. These data suggest that initial, acute lung injuries are not the sole antecedents of neonatal CLD.

Cytokines Associated With Bronchopulmonary Dysplasia or Death in Extremely Low Birth Weight Infants

OBJECTIVE. The goal was to develop multivariate logistic regression models for the outcome of bronchopulmonary dysplasia and/or death at postmenstrual age of 36 weeks by using clinical and cytokine data from the first 28 days. METHODS. For 1067 extremely low birth weight infants in the Neonatal Research Network of the National Institute of Child Health and Human Development, levels of 25 cytokines were measured in blood collected within 4 hours after birth and on days 3, 7, 14, and 21. Stepwise regression analyses using peak levels of the 25 cytokines and 15 clinical variables identified variables associated with bronchopulmonary dysplasia/death. Multivariate logistic regression analysis was performed for bronchopulmonary dysplasia/death by using variables selected through stepwise regression. Similar analyses were performed by using average cytokine values from days 0 to 21, days 0 to 3, and days 14 to 21. RESULTS. Of 1062 infants with available data, 606 infants developed bronchopulmonary dysplasia or died. On the basis of results from all models combined, bronchopulmonary dysplasia/death was associated with higher concentrations of interleukin 1β, 6, 8, and 10 and interferon γ and lower concentrations of interleukin 17, regulated on activation, normal T cell expressed and secreted, and tumor necrosis factor β. Compared with models with only clinical variables, the addition of cytokine data improved predictive ability by a statistically significant but clinically modest magnitude. CONCLUSIONS. The overall cytokine pattern suggests that bronchopulmonary dysplasia/death may be associated with impairment in the transition from the innate immune response mediated by neutrophils to the adaptive immune response mediated by T lymphocytes.

A Randomized Trial Comparing Long-term and Short-term Use of Umbilical Venous Catheters in Premature Infants With Birth Weights of Less Than 1251 Grams

BACKGROUND. Umbilical vein and percutaneous central venous catheters are often used in preterm infants, but they can lead to complications, including infection. OBJECTIVE. We hypothesized that long-term umbilical vein catheter use would result in fewer infections than short-term umbilical vein catheter use followed by percutaneous central venous catheter placement. DESIGN/METHODS. Infants ≤1250 g with umbilical vein catheters placed at admission were randomly assigned to a long-term (umbilical vein catheter up to 28 days) or short-term (umbilical vein catheter for 7–10 days followed by percutaneous central venous catheter) group. Catheter infection was defined as symptoms and ≥1 positive blood culture for definite pathogens or >1 positive culture for other organisms, with a catheter in place. Clinically significant echocardiogram findings were defined as thrombi threatening vascular occlusion, crossing/blocking heart valves, or otherwise felt to be significant by the cardiologist. The primary outcome was time from birth to catheter infection, analyzed by the log-rank test. RESULTS. There were 106 subjects in the short-term group and 104 in the long-term group with birth weights of 915 ± 198 and 931 ± 193 g and gestational ages of 27.8 ± 2.0 and 27.7 ± 2.2 weeks, respectively. The distribution of time to catheter infection did not differ between the groups. The overall incidence of catheter infection was 13% in the short-term group and 20% in the long-term group. Median age at catheter infection was 11.5 days in the short-term group and 14 days in the long-term group. There were 7.4 infections per 1000 catheter-days in the short-term group and 11.5 per 1000 in the long-term group. Seven infections in the short-term group were in umbilical vein catheters, and 18 infections in the long-term group were in umbilical vein catheter. Echocardiograms detected 4 infants in the short-term group and 7 infants in the long-term group with significant thrombosis. All significant thrombi were at the site of the umbilical vein catheter tip. No thrombus caused hemodynamic compromise, no child had clinical symptoms of thrombosis, and none required therapy. Of the 45 small-for-gestational-age infants in the study, 9 developed thrombi (short-term group, 4; long-term group, 5). The incidence of thrombi was higher in the small-for-gestational-age group (20%) versus other study subjects (9%). There were no differences in time to full feedings or to regain birth weight or in the incidence of necrotizing enterocolitis or death. CONCLUSIONS. Infection and complication rates were similar between infants managed with an umbilical vein catheter in place for up to 28 days compared with infants managed with an umbilical vein catheter replaced by a percutaneous central venous catheter after 7 to 10 days. Umbilical vein catheter durations beyond the current Centers for Disease Control and Prevention–recommended limit of 14 days may be reasonable.

Surface colonization with coagulase-negative staphylococci in premature neonates

To follow the emergence of surface colonization with coagulase-negative staphylococci in neonates, we sampled four surface sites (axilla, ear, nasopharynx, and rectum) in 18 premature infants during the first 4 weeks of life. Swabs were obtained on the first day of life, twice weekly for 2 weeks, and weekly thereafter. Isolates were characterized by species, biotype, antibiotic susceptibility patterns, and slime production. Over 4 weeks the percentage of infants with Staphylococcus epidermidis as the only surface coagulase-negative staphylococci rose from 11% to 100%. Predominance of a single S. epidermidis biotype increased from none to 89%. Multiple antibiotic resistance rose from 32% to 82% of isolates, and the prevalence of slime production increased from 68% to 95%. This microbiologic pattern was established by the end of the first week of life and persisted throughout the month of study. In three infants, S. epidermidis sepsis developed with organisms identical to their predominant surface isolate. We conclude that species, multiple antibiotic resistance, and slime production appear to confer a selective advantage for the surface colonization of premature newborn infants in the intensive care nursery environment. Infants so colonized may be at greater risk for subsequent infection with these strains of coagulase-negative staphylococci.

Bcl-2 Family Gene Expression during Severe Hyperoxia Induced Lung Injury

Exposure of the lung to severe hyperoxia induces terminal transferase dUTP end-labeling (TUNEL) indicative of DNA damage or apoptosis and increases expression of the tumor suppressor p53 and of members of the Bcl-2 gene family. Because cell survival and apoptosis are regulated, in part, by the relative abundance of proteins of the Bcl-2 family, we hypothesized that lung cells dying during exposure would show increased expression of pro-apoptotic members, such as Bax, whereas surviving cells would have increased expression of anti-apoptotic members, such as Bcl-XL. The hypothesis is tested in the current study by determining which Bcl-2 genes are regulated by hyperoxia, with specific focus on correlating expression of Bax and Bcl-XL with morphologic evidence of apoptosis or necrosis. Adult mice exposed to greater than 95% oxygen concentrations for 48 to 88 hours had increased whole-lung mRNA levels of Bax and Bcl-XL, no change in Bak, Bad, or Bcl-2, and decreased levels of Bcl-w and Bfl-1. In situ hybridization revealed that hyperoxia induced Bax and Bcl-XL mRNA in uniform and overlapping patterns of expression throughout terminal bronchioles and parenchyma, coinciding with TUNEL staining. Electron microscopy and DNA electrophoresis, however, suggested relatively little classical apoptosis. Unexpectedly, Western analysis demonstrated increased Bcl-XL, but not Bax, protein in response to hyperoxia. Bax and Bfl-1 were not altered by hyperoxia in p53 null mice; however, oxygen toxicity was not lessened by p53 deficiency. These findings suggest that oxygen-induced lung injury does not depend on the relative expression of these Bcl-2 members.

Three-year follow-up of vaccine response in extremely preterm infants

Objective. To assess whether the adequate antibody response observed in former extremely premature infants after the primary series of immunizations is sustained after the first booster vaccines. Subjects and Methods. Sixteen former extremely premature (<29 weeks, <1000 g at birth) and 17 former full-term (>37 weeks) infants had sera obtained for antibody titer measurement at 3 to 4 years of age. All had received the primary series and first booster vaccines for diphtheria, pertussis, tetanus, polio, andHaemophilus influenzae type b. Twelve preterm and 14 full-term children had completed the hepatitis B vaccine series. Results. At 3 to 4 years of age, former preterm and full-term children had similar geometric mean titer (GMT) values of antibodies to tetanus, diphtheria, and pertussis. Preterm children had a lower GMT value of Haemophilus polyribosylribitol phosphate (PRP) antibody than did full-term children (0.99 vs 3.06 μg/mL). Fifty percent of preterm and 88% of full-term children had PRP antibody >1.0 μg/mL; 100% of preterm and 94% of full-term children had anti-PRP titers >0.15 μg/mL. GMT values of neutralizing antibodies to polio serotypes 1 and 2 were similar, with 94% to 100% of both groups above protective levels (≥1:8). The difference in GMT values of polio serotype 3 approached significance (29 vs 73); fewer preterm children had protective titer values (75% vs 100%). Among children vaccinated against hepatitis B, 75% of preterm and 71% of full-term children were protected (10 mIU/mL). Conclusions. Preterm children immunized at the recommended chronological ages displayed antibody responses similar to those for full-term children for most immunizing antigens. Responses to PRP and polio serotype 3 were less robust than those of full-term children.

Vascular Endothelial Growth Factor in Pulmonary Lavage Fluid from Premature Infants: Effects of Age and Postnatal Dexamethasone

Corticosteroids are used to ameliorate bronchopulmonary dysplasia (BPD). They also affect normal development, including the expression of growth factors such as vascular endothelial growth factor (VEGF). Deep pulmonary lavage specimens were collected on days 1, 3, 7 and 28 of life in 40 infants of <34 weeks of gestation at birth during a randomized controlled trial of two doses of dexamethasone (DEX) at 12 and 24 h of age for BPD prophylaxis. VEGF was measured by enzyme-linked immunosorbent assay. The 18 DEX and 21 control subjects had similar gestations, birth weights and oxygen requirements at study entry. Lavage VEGF tripled between day 1 and 3 in both groups. The day 7 levels were higher in DEX subjects than in controls. DEX and control values were similar on day 28. Higher lavage VEGF levels on days 1 and 3 were also correlated with lower gestational age at birth. Lavage VEGF levels were not associated with the development of BPD. We speculate that these DEX- and age-associated changes in VEGF may affect pulmonary angiogenesis.

Renal tubular dysfunction in methylmalonic acidaemia

Renal tubular function was assessed in seven patients with methylmalonic acidaemia not responsive to vitamin B12. Five patients failed to concentrate their urine normally and in these patients the glomerular filtration rate was also reduced. Fractional excretion of sodium was increased in four patients, fractional excretion of potassium in one patient and in three there was a decreased tubular reabsorption of phosphate. Although possibly representing primary tubular damage these findings were thought to be consistent with adaptive changes secondary to the reduced glomerular filtration rate. Two patients had evidence of a defect of urinary acidification and several had a degree of hyporeninaemic hypoaldosteronism suggesting type 4 renal tubular acidosis. In one patient with a mild variant no renal disease was detected. Decreased renal function and tubular abnormalities were common in patients with methylmalonic acidaemia. It is likely that they are linked and essentially secondary to the tubulo-interstitial nephritis that is histologically demonstrable on renal biopsy. The failure of urinary concentrating ability and the disturbed urine acidification will contribute to the metabolic derangement during episodes of decompensation.

Chemokine mRNA Alterations in Newborn and Adult Mouse Lung During Acute Hyperoxia

Chemokines play a major role in the recruitment of inflammatory cells during acute lung injury. Adult and newborn C57BL/6 mice were exposed to > 95% oxygen for up to 72 hours and 7 days, respectively. Chemokine mRNA abundance was evaluated in whole lung RNA by ribonuclease protection assay and in tissue sections by in situ hybridization. Monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-2, and interferon gamma-induced protein (IP)-10 mRNAs were present in whole newborn lung by 4 days of hyperoxia and were markedly elevated by 7 days. Levels of mRNA for MCP-1, MIP-1 alpha, and MIP-2 were elevated to a lesser extent by 72 hours of hyperoxia in adults. MCP-1 mRNA abundance was moderately elevated in scattered areas of perivascular tissue, peribronchiolar tissue, and the alveolar interstitium in 4-day hyperoxic newborns and markedly upregulated diffusely throughout the peripheral airspaces in 7-day hyperoxic newborns. MCP-1 mRNA abundance was limited to scattered perivascular areas and airspaces in 72-hour hyperoxic adults. These differences in the intensity, timing, and distribution of chemokine mRNA abundance between adult and newborn mice may help to explain the marked differences in their susceptibility to oxygen injury.

Animal models of bronchopulmonary dysplasia. The preterm and term rabbit models

Bronchopulmonary dysplasia (BPD) is an important lung developmental pathophysiology that affects many premature infants each year. Newborn animal models employing both premature and term animals have been used over the years to study various components of BPD. This review describes some of the neonatal rabbit studies that have contributed to the understanding of BPD, including those using term newborn hyperoxia exposure models, premature hyperoxia models, and a term newborn hyperoxia model with recovery in moderate hyperoxia, all designed to emulate aspects of BPD in human infants. Some investigators perturbed these models to include exposure to neonatal infection/inflammation or postnatal malnutrition. The similarities to lung injury in human premature infants include an acute inflammatory response with the production of cytokines, chemokines, and growth factors that have been implicated in human disease, abnormal pulmonary function, disordered lung architecture, and alveolar simplification, development of fibrosis, and abnormal vascular growth factor expression. Neonatal rabbit models have the drawback of limited access to reagents as well as the lack of readily available transgenic models but, unlike smaller rodent models, are able to be manipulated easily and are significantly less expensive than larger animal models.