Sanjiv B. Amin

Expression of vascular endothelial growth factor and Flk-1 in developing and glucocorticoid-treated mouse lung.

Although the endothelial cell is the most abundant cell type in the differentiated lung, little is known about regulation of lung developmental vasculogenesis. Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen and angiogenic factor that has putative roles in vascular development. Mitogenic actions of VEGF are mediated by the tyrosine kinase receptor KDR/murine homologue fetal liver kinase Flk-1. HLF (hypoxia-inducible factor-like factor) is a transcription factor that increases VEGF gene transcription. Dexamethasone augments lung maturation in fetal and postnatal animals. However, in vitro studies suggest that dexamethasone blocks induction of VEGF. The objectives for the current study were to measure VEGF mRNA and Flk-1 mRNA in developing mouse lung and to measure the effects of dexamethasone treatment in vivo on VEGF and Flk-1 in newborn mouse lung. Our results show that VEGF and Flk-1 messages increase in parallel during normal lung development (d 13 embryonic to adult) and that the distal epithelium expresses VEGF mRNA at all ages examined. Dexamethasone (0.1–5.0 mg·kg−1·d−1) treatment of 6-d-old mice resulted in significantly increased VEGF, HLF, and Flk-1 mRNA. Dexamethasone did not affect cell-specific expression of VEGF, VEGF protein, or proportions of VEGF mRNA splice variants. These data suggest that the developing alveolar epithelium has an important role in regulating alveolar capillary development. In addition, unlike effects on cultured cells, dexamethasone, even in relatively high doses, did not adversely affect VEGF expression in vivo. The relatively high levels of VEGF and Flk-1 mRNA in adult lung imply a role for pulmonary VEGF in endothelial cell maintenance or capillary permeability.

Unbound bilirubin predicts abnormal automated auditory brainstem response in a diverse newborn population

Objective:The objective of this study was to determine if plasma unbound or ‘free’ bilirubin concentration (Bf) measured during the first 30 days of life is associated with subsequent abnormal hearing screening testing by automated auditory brainstem response (AABR) in a diverse population of newborns.Study Design:An observational study of newborns receiving AABR, plasma total bilirubin concentration (TBC) and Bf measurements and without underlying conditions known to affect hearing was conducted. Logistic regression was used to determine associations between abnormal AABR and Bf or TBC. The impacts of a variety of clinical factors on the regression model were also assessed.Result:A total of 191 patients with birth weights and gestations ranging from 406 to 4727 g and 24 to 42 weeks, respectively, were studied. Among them, 175 (92%) had normal (bilateral PASS) AABR and 16 had abnormal AABR (6 had unilateral REFER AABR, and 10 had bilateral REFER AABR). Mean TBC was not significantly different in babies with normal or abnormal AABR, but mean Bf was greater in the latter group (1.76 versus 0.93 μg per 100 ml, respectively, P=0.012). Bf, but not TBC, was associated with an abnormal AABR (Bf adjusted odds ratio 3.3, 95% CI 1.8 to 6.1). Comparing receiver-operating characteristics curves, the Bf/TBC ratio was a better predictor of an abnormal AABR than Bf alone. Intraventricular hemorrhage was the only confounding clinical variable.Conclusion:An abnormal AABR is associated with an elevated Bf or Bf/TBC ratio, but not the TBC alone. The prevalence of bilirubin neurotoxicity as a cause of audiological dysfunction may be underestimated if the TBC alone is used to assess the severity of newborn jaundice.

In Utero Iron Status and Auditory Neural Maturation in Premature Infants as Evaluated by Auditory Brainstem Response

OBJECTIVE To determine whether cord ferritin (CF) concentration, an index of in utero iron status, is associated with auditory neural maturation in premature infants. STUDY DESIGN A prospective cohort study was performed to compare auditory neural maturation in infants with latent iron deficiency (CF 11-75 ng/mL) and infants with normal iron status (CF > 75 ng/mL) at birth. Our inclusion criteria were infants of 27-33 weeks gestational age who were admitted to the neonatal intensive care unit between July 2007 and November 2008 within 12 hours after birth and had cord blood collected. Infants with TORCH infections (toxoplasmosis, other infections, rubella, cytomegalovirus infection, and herpes simplex), chromosomal disorders, craniofacial anomalies, culture-proven sepsis, and/or unstable conditions were excluded. CF level was measured using a chemiluminescence immunoassay method. Bilateral monaural auditory brainstem evoked response (ABR) was assessed using 80-dB nHL click stimuli at a repetition rate of 29.9/seconds within 48 hours after birth. RESULTS Of the 80 infants studied, 35 had latent iron deficiency. After controlling for confounders, the infants with latent iron deficiency had significantly prolonged absolute wave latencies I, III, and V and decreased frequency of mature ABR waveforms compared with the infants with normal iron status. CONCLUSION Premature infants with in utero latent iron deficiency have abnormal auditory neural maturation compared with infants with normal in utero iron status.

Auditory neuropathy spectrum disorder in late preterm and term infants with severe jaundice.

OBJECTIVE To evaluate if severe jaundice is associated with acute auditory neuropathy spectrum disorder in otherwise healthy late preterm and term neonates. METHODS In a prospective observational study, all neonates who were admitted with severe jaundice at which exchange transfusion may be indicated as per American Academy of Pediatrics guidelines had comprehensive auditory evaluation performed before discharge to home. Neonates with infection, perinatal asphyxia, chromosomal disorders, cranio-facial malformations, or family history of childhood hearing loss were excluded. Comprehensive auditory evaluations (tympanometry, oto-acoustic emission tests, and auditory brainstem evoked responses) were performed by an audiologist unaware of the severity of jaundice. Total serum bilirubin and serum albumin were measured at the institutional chemistry laboratory using the Diazo and Bromocresol purple method, respectively. RESULTS A total of 13 neonates with total serum bilirubin concentration at which exchange transfusion is indicated as per American Academy of Pediatrics were admitted to the Neonatal Intensive Care Unit over 3 month period. Six out of 13 neonates (46%) had audiological findings of acute auditory neuropathy spectrum disorder. There was no significant difference in gestational age, birth weight, hemolysis, serum albumin concentration, peak total serum bilirubin concentrations, and peak bilirubin:albumin molar ratio between six neonates who developed acute auditory neuropathy and seven neonates who had normal audiological findings. Only two out of six infants with auditory neuropathy spectrum disorder had clinical signs and symptoms of acute bilirubin encephalopathy. CONCLUSIONS Our findings strongly suggest that auditory neuropathy spectrum disorder is a common manifestation of acute bilirubin-induced neurotoxicity in late preterm and term infants with severe jaundice. Our findings also suggest that comprehensive auditory evaluations should be routinely performed in neonates with severe jaundice irrespective of the presence of clinical findings of acute bilirubin encephalopathy.

Morphological changes in serial auditory brain stem responses in 24 to 32 weeks' gestational age infants during the first week of life.

OBJECTIVE The purpose of this investigation was to describe and quantify the sequential morphological changes in the auditory brain stem response (ABR) during the first postnatal week of life in very premature infants < or = 32 wk gestational age. These normative data could be useful in predicting neurological outcome in infants with perinatal risk factors. DESIGN Sequential ABRs were recorded on a total of 135 infants on 5 out of the first 7 days of life. For analysis, data were grouped by gestational age in 2 wk intervals. In addition, a unique system was devised to categorize waveform response types in premature infants: type 1, a response with normal morphology and replicable waves III and V; type 2, a replicable response with either a wave III or wave V; type 3, a replicable response with neither a wave III or wave V; type 4, a response with no replicable waveform. RESULTS The frequency of detection of waves improves over the first week of life with the detectability of waves III and V being more frequent than wave I at all gestational ages. There was a gradual improvement in response types in infants > 26 wk with the greatest improvement occurring during the 28 to 29 wk gestation. ABRs were predominantly types 3 and 4 at 24 to 25 wk, type 3 at 26 to 27 wk, type 2 at 28 to 29 wk, and types 1 and 2 at 30 to 31 wk. Absolute wave latencies and interwave latencies also progressively decreased during the first postnatal week. In some infants there was a transient increase in latencies or worsening of response type on the second to third test day. CONCLUSIONS There is progressive improvement in frequency of detection of waves I, III, and V with increasing gestational age. Response types gradually mature over the first postnatal week, particularly in premature infants 28 to 32 wk gestational age.

Absidia corymbifera Infections in Neonates

We report the first two documented cases of neonatal zygomycosis caused by Absidia corymbifera. A premature infant developed disseminated disease from a cutaneous site with pulmonary, gastrointestinal, and cerebral involvement. The infant died despite amphotericin B therapy and surgical debridement. The second case occurred in a full-term infant with congenital heart disease and fungal pneumonitis. Zygomycosis was not suspected because of underlying cardiac disease and a complicated postoperative course, and this infant also died. Absidia joins a growing list of opportunistic fungal pathogens of the compromised neonate.

Transient Bilirubin Encephalopathy and Apnea of Prematurity in 28 to 32 Weeks Gestational Age Infants

OBJECTIVE:Apnea of prematurity (AoP) is, in part, a reflection of brainstem-mediated respiratory control system maturation. We previously demonstrated changes in brainstem function in relation to hyperbilirubinemia (bilirubin encephalopathy, (BE)) as evaluated by auditory brainstem evoked responses (ABR) in infants 28 to 32 weeks gestational age (GA). We hypothesized that in this population, as bilirubin increases and causes auditory brainstem dysfunction, respiratory control system may also be adversely affected leading to increased frequency of AoP.STUDY DESIGN:We studied 100, 28 to 32 weeks GA infants and identified 66 with normal and 34 with abnormal ABR progression in temporal relation to hyperbilirubinemia (BE). The abnormal ABR progression was associated with elevated bilirubin, specifically elevated unbound bilirubin levels. A blinded, retrospective chart review quantified the amount of weekly apnea and bradycardia events during the hospital stay, total duration of methylxanthine treatment, total duration of mechanical ventilation, CPAP, and/or nasal cannula, and risk factors for apnea (sepsis, IVH grade >II, asphyxia). Since mechanical ventilation confounds the identification of apnea, infants requiring mechanical ventilation were excluded from further review (n=60; 21 with BE and 39 with normal ABR progression). Data from the remaining 40 infants were analyzed. Students t-test was used to analyze continuous variables if the distribution was normal otherwise Wilcoxon-ranked-sum test was used. χ2 was used to analyze nominal variables. A p≤0.05 was considered significant.RESULTS:There was no difference in risk factors between infants with and without BE. BE was identified on day 3 (median; range 1 to 6 days). Patients with BE had significantly more apneic events (15 vs 2, p=0.0009), bradycardic events (14 vs 1, p=0.02), and required more prolonged treatment with CPAP (2.2 vs 0.5 days, p=0.007), nasal cannula (6.6 vs 2.2 days, p=0.02), and methylxanthines (9.5 vs. 1.9 days, p=0.002) than those with normal ABR progression. The difference in the incidence of apnea and bradycardia between infants with and without BE was most pronounced during the first week.CONCLUSIONS:Premature infants with transient bilirubin encephalopathy as defined by abnormal ABR progression in relation to hyperbilirubinemia have more concurrent apneic events and require more prolonged respiratory support and medications.

Latent Iron Deficiency In Utero Is Associated with Abnormal Auditory Neural Myelination in ≥35 Weeks Gestational Age Infants

OBJECTIVE To determine whether cord serum ferritin level is associated with auditory brainstem evoked response interpeak latencies, an index of auditory neural myelination, in infants at ≥ 35 weeks gestational age (GA). STUDY DESIGN This prospective study compared auditory neural myelination in infants with latent iron deficiency (cord serum ferritin, 11-75 ng/mL) and infants with normal iron status (cord serum ferritin, >75 ng/mL) at birth. Our inclusion criteria were infants born at ≥ 35 weeks GA who had cord blood collected soon after birth and had 1 or more of the following risk factors for poor in utero iron status: maternal diabetes mellitus, pregnancy-induced hypertension, and intrauterine growth restriction. Cord serum ferritin level was measured using the chemiluminescence immunoassay method. Auditory brainstem evoked response was measured using 80-dB normal hearing level click stimuli at a rate of 69.9/second within 48 hours after birth to evaluate interpeak latencies, a measure of nerve conduction velocity or myelination. RESULTS Of the 45 infants studied, 12 had latent iron deficiency. On repeated-measures ANCOVA using interpeak latencies I-III, III-V, and I-V as multiple outcomes, infants with latent iron deficiency had significantly prolonged interpeak latencies (P = .01) compared with infants with normal iron status after controlling for confounders. CONCLUSION In utero latent iron deficiency is associated with abnormal auditory neural myelination at birth in infants born at ≥ 35 weeks GA.

Effect of free fatty acids on bilirubin-albumin binding affinity and unbound bilirubin in premature infants.

BACKGROUND The author has previously shown that intravenous lipid intake may be associated with an increase in unbound bilirubin in infants < or =28 weeks gestational age. The objective of this study was to evaluate whether this increase in unbound bilirubin is mediated by free fatty acids and to examine the secondary effect of free fatty acids on bilirubin-albumin binding affinity. METHODS A prospective study was conducted to include 26 infants < or =32 weeks gestational age with indirect hyperbilirubinemia and receiving intravenous lipids during the first 10 postnatal days. Blood samples were collected for unbound bilirubin, binding affinity, and free fatty acid measurement at varying intravenous lipid intakes (1-3 g/kg/d). Regression analyses were performed to evaluate the roles of free fatty acids and binding affinity as mediators. RESULTS Intravenous lipid intake was significantly associated with an increase in free fatty acids and unbound bilirubin in infants < or =28 weeks but not >28 weeks gestational age. In infants < or =28 weeks gestational age, each unit increase in free fatty acids was significantly associated with a decrease in binding affinity, which was significantly associated with an increase in unbound bilirubin. CONCLUSIONS In infants < or =28 weeks gestational age, intravenous lipid intake may be associated with an increase in unbound bilirubin, and this is mediated by an increase in free fatty acids and a secondary decrease in binding affinity. In infants >28 weeks gestational age, higher intravenous lipid intake may be used because it is unassociated with increases in free fatty acids and unbound bilirubin.

Hyperbilirubinemia and Language Delay in Premature Infants

OBJECTIVE. Our goal was to evaluate whether language delay at 3 years in premature infants is associated with previous exposure to hyperbilirubinemia during the first 2 weeks after birth. PATIENTS AND METHODS. We performed a retrospective case-control study of infants admitted to the NICU between January and October 2003. Inclusion criteria included a birth weight of ≤1500 g and follow-up to age 3 years. Exclusion criteria included genetic disorders and hearing loss or recurrent ear infections. Peak total serum bilirubin levels during the first 2 weeks and duration of hyperbilirubinemia (days with total serum bilirubin level at >8 mg/dL) were determined. Infants with language delay and who were receiving speech therapy by 3 years were identified through developmental clinic charts and a tracking program and compared with infants who had normal language development. RESULTS. A total of 125 infants with birth weight of ≤1500 g were admitted to the NICU between January and October 2003. Fifteen infants died, and 110 were discharged from the hospital. A total of 102 (93%) of 110 infants had follow-up to the age of 3 years. Four infants were excluded (1 genetic disorder, 3 delayed hearing loss or recurrent ear infections). Twenty-four infants had a language delay and received speech therapy, whereas 74 infants had normal language development. There was no significant difference in peak total serum bilirubin level and duration of hyperbilirubinemia between the 2 groups. On logistic regression, only bronchopulmonary dysplasia was associated with language delay. CONCLUSIONS. Hyperbilirubinemia, defined as peak total serum bilirubin level or duration of elevated bilirubin in days, is not associated with language delay in premature infants. However, this issue deserves investigation, because other measures of bilirubin, such as unbound bilirubin, may be associated with language delay.