Chronic Auditory Toxicity in Late Preterm and Term Infants With Significant Hyperbilirubinemia

Detecting Hearing Loss Through Targeted Surveillance: Risk Registry and Surveillance Timeframe Recommendations

PURPOSE

The purpose of this study was to inform the revision of a targeted surveillance risk registry by identifying which risk factors predict postnatally identified hearing loss (PNIHL) in children who pass newborn hearing screening and to determine whether hearing surveillance beyond the age of 1 year is warranted.

METHOD

We used retrospective analysis of the audiological outcomes of children born in the state of Queensland, Australia, between January 1, 2010, and December 31, 2019, who passed the newborn hearing screen with risk factors.

RESULTS

Approximately one third of children were lost to follow-up and could not be included in the analysis. Risk factors that predicted PNIHL in the analyzed cohort were as follows: syndromes associated with hearing loss, craniofacial anomalies, perinatal infections, and family history of permanent childhood hearing loss. Severe asphyxia did not predict PNIHL but yielded some cases of significant bilateral hearing loss. Hearing loss in children with a history of prolonged ventilation was mild and/or unilateral in nature (except in cases where the hearing loss was due to an unrelated etiology). There were no cases of PNIHL in children with hyperbilirubinemia or neonatal bacterial meningitis. For the risk factors that predicted PNIHL, nearly all hearing losses were detected by 1 year of age, except for children with family history where one quarter of hearing losses had a later onset.

CONCLUSIONS

The four risk factors recommended for efficient postnatal identification of hearing loss are as follows: syndromes associated with hearing loss, craniofacial anomalies, perinatal infection, and family history of permanent childhood hearing loss. Hearing surveillance through to 1 year old is sufficient except for children with a family history, where a second phase assessment is indicated. Alternative targeted surveillance protocols and models of care are required to minimize loss to follow-up.

Unbound Bilirubin and Acute Bilirubin Encephalopathy in Infants Born Late Preterm and Term with Significant Hyperbilirubinemia

OBJECTIVE

To compare the association of unbound bilirubin (UB), total serum bilirubin (TSB), and bilirubin:albumin molar ratio (BAMR) with acute bilirubin encephalopathy (ABE), as assessed by bilirubin-induced neurologic dysfunction (BIND) score, in infants with significant hyperbilirubinemia (TSB ≥20 mg/dL or underwent exchange transfusion).

STUDY DESIGN

In this prospective cohort study, infants ≥34 weeks of gestational age with significant hyperbilirubinemia during the first 2 postnatal weeks were eligible, unless they had craniofacial malformations, chromosomal disorders, TORCH (toxoplasmosis, other infections, rubella, cytomegalovirus and herpes simplex) infections, surgery, or a family history of congenital deafness. TSB, serum albumin, and UB were measured at hospital admission using the colorimetric, bromocresol green, and modified peroxidase method, respectively. Infants were evaluated on admission for ABE using a standardized neurologic examination and assigned a BIND score by trained physicians. Infants with a total BIND score of 0 were deemed to not have ABE, whereas those with a score ≥1 were deemed to have ABE.

RESULTS

A total of 151 infants were studied, among whom 37 (24.5%) had ABE. Of these, 19 had mild ABE (BIND score 1-3) and 18 had moderate-to-severe ABE (BIND score 4-9). On logistic regression, UB, but not TSB or BAMR, was associated with ABE (aOR 1.64; 95% CI 1.17-2.3). On ordered logistic regression, UB, but not TSB or BAMR, was associated with severity of ABE (aOR 1.76; 95% CI 1.28-2.4).

CONCLUSIONS

Our findings of the association between UB and ABE indicate that BIND scoring may be useful for evaluation of ABE in infants ≥34 weeks of gestational age.

Neonatal jaundice and associated factors in public hospitals of southern Ethiopia: A multi-center cross-sectional study

Background

Neonatal jaundice is one of the most prevalent problems, affecting over a million newborns globally every year. It increases the likelihood of hospitalization, lifetime disability, and death, particularly in low and middle-income countries. Despite its impact and diverse risk factors, neonatal jaundice remains underappreciated in developing nations such as Ethiopia. As a result, this study aimed to determine the magnitude and associated factors of jaundice in newborns admitted to public hospitals in south Ethiopia.

Methods

A facility-based cross-sectional study was conducted among 417 newborns from October 1, 2020, to April 30, 2021. The data was collected using pretested interviewer-administered questionnaire and checklist. Jaundice and its severity were assessed using the physician's diagnosis and the Kramer scale. Open data kit tools and Stata version 16.0 were used for data collection and analysis, respectively. Bivariable and multivariable analyses were used to identify factors associated with neonatal jaundice. An odds ratio with a 95 % confidence interval was used to assess the direction and strength of the association.

Results

Out of the newborns, 24.46 % [95 % CI: 20.42-28.88] encountered neonatal jaundice. Being male [AOR: 1.81, 95 % CI: 1.06, 3.12], birth injuries [AOR: 3.01, 95 % CI: 1.27, 7.12], perinatal asphyxia [AOR: 2.10, 95 % CI: 1.18, 3.76], hyaline membrane disease [AOR: 2.16, 95 % CI: 1.16, 4.00], sepsis [AOR: 3.30, (95 % CI: 1.67, 6.54], the combined effect of low birth weight and prematurity [AOR: 1.88, 95 % CI: 1.06, 3.35], and maternal alcohol abuse during pregnancy [AOR: 2.46, 95 % CI: 1.02, 5.94] were significantly associated with neonatal jaundice.

Conclusion

The burden of neonatal jaundice was high in the hospitals studied. Early detection and treatment of neonatal problems, counseling pregnant women to avoid consuming any level of alcohol, strict monitoring of labor and delivery, improving antenatal care utilization, and pre-discharge universal bilirubin screening of newborns are essential to reduce the incidence and complications of jaundice. The findings of this study will be used as input to initiate interventions and conduct further studies.

The pyroptosis mechanism of ototoxicity caused by unconjugated bilirubin in neonatal hyperbilirubinemia

When activated by unconjugated bilirubin (UCB), inflammatory mediators such as IL - 18 and TNF contribute to the neurotoxicity and ototoxicity observed in severe neonatal hyperbilirubinemia. However, in cell and molecular level, the regulation and mechanism of UCB-induced ototoxicity are remained unclear. In this study, 7-day-old mammary rats were exposed to various concentrations of UCB to imitate the infant auditory damage. The auditory brainstem response result (ABR) indicated severe hearing loss, which occurred with increasing concentration. Morphological analysis of organotypic cochlear cultures treated with different concentrations of UCB indicated that auditory nerve fibers (ANF) were demyelinated and the density of spiral ganglion neurons (SGN) were decreased. In addition, HEI-OC1 cells treated with different concentrations of UCB showed severe necrosis by Flow Cytometry. The morphologic feature of pyroptosis has been observed by scanning electronic microscope. Cleaved Caspase-1, GSDMD and NLRP3 expression were significantly increased in cochlear explants with UCB-induced. To further clarify the molecular mechanism of UCB-induced inner ear cell pyroptosis, specific inhibitors of pyroptosis were applied, the protein associated with pyrotosis such as Cleaved Caspase-1, GSDMD, ASC, IL-18 and NLRP3 were significantly lower than the group with UCB alone. All the data above indicated that ERK /NLRP3/GSDMD signaling pathway involved in UCB-induced ototoxicity.

Effects of bilirubin on the development and electrical activity of neural circuits

In the past several decades, bilirubin has attracted great attention for central nervous system (CNS) toxicity in some pathological conditions with severely elevated bilirubin levels. CNS function relies on the structural and functional integrity of neural circuits, which are large and complex electrochemical networks. Neural circuits develop from the proliferation and differentiation of neural stem cells, followed by dendritic and axonal arborization, myelination, and synapse formation. The circuits are immature, but robustly developing, during the neonatal period. It is at the same time that physiological or pathological jaundice occurs. The present review comprehensively discusses the effects of bilirubin on the development and electrical activity of neural circuits to provide a systematic understanding of the underlying mechanisms of bilirubin-induced acute neurotoxicity and chronic neurodevelopmental disorders.

Stannsoporfin with phototherapy to treat hyperbilirubinemia in newborn hemolytic disease

OBJECTIVE

To evaluate the efficacy and safety of tin mesoporphyrin (SnMP) in neonates with hyperbilirubinemia (HB) due to hemolysis.

STUDY DESIGN

This multicenter, placebo-controlled phase 2b study (NCT01887327) randomized newborns (35-42 weeks) with hemolysis started on phototherapy (PT) to placebo (Ctrl), SnMP 3.0 mg/kg, or SnMP 4.5 mg/kg given once IM within 30 min of initiation of PT.

RESULTS

In all, 91 patients were randomized (Ctrl: n = 30; 3 mg/kg SnMP: n = 30; 4.5 mg/kg SnMP: n = 31). At 48 h TSB significantly increased in Ctrl by 17.5% (95% CI 5.6-30.7; p = 0.004) and significantly decreased by -13% (95% CI -21.7 to -3.2; p = 0.013) in the 3.0 mg/kg and by -10.5% (95% CI -19.4 to -0.6; p = 0.041) in the 4.5 mg/kg group. Decreases in SnMP groups were significant (p < 0.0001) vs Ctrl.

CONCLUSION

SnMP with PT significantly reduced TSB by 48 h. SnMP may be useful as a treatment for HB in neonates with hemolysis.

Neonatal hyperbilirubinemia and the role of unbound bilirubin

BACKGROUND

Neonatal jaundice occurs in more than 80% of newborn infants. Although mild jaundice is physiologic and possibly neuroprotective, severe hyperbilirubinemia can lead to neurologic dysfunction and death. Hyperbilirubinemia is due to an imbalance between bilirubin production and the developing excretory capacity in the first days of life. Management utilizes total serum bilirubin (TSB) levels, although recent advances suggest a role for unbound bilirubin.

GOALS

The goal of this review is to examine bilirubin biology, toxicology, and clinical effects, discuss preventive and therapeutic measures, describe neurodevelopmental consequences, and propose that, with the advent of new technology, unbound bilirubin is the optimal measurement for the management.

METHODS

Comprehensive review on neonatal hyperbilirubinemia.

RESULTS

Neonatal hyperbilirubinemia can be prevented by tin mesoporphyrin to limit heme oxygenase activity, a key enzyme in bilirubin production, or restricting bilirubin's absorption from the gastrointestinal tract. Treatment modalities include removing bilirubin from the body by exchange transfusion, binding to immunoglobulin, or converting it to a water-soluble isomer with phototherapy. While these approaches have evolved during the past decades, the diagnosis, intervention indications, and prognosis have consistently relied on TSB concentration despite its poor ability to predict an outcome.

CONCLUSIONS

Total serum bilirubin is inadequate to optimize care of the term and preterm infant with hyperbilirubinemia. A rapid, accurate, and more effective indicator of bilirubin neurotoxicity is needed to manage jaundiced infants and for the universal screening of newborn infants. Future measurements of free bilirubin unattached to albumin will improve the management of neonatal hyperbilirubinemia.

Is auditory neuropathy an appropriate term? A systematic literature review on its aetiology and pathogenesis

To clarify the aetio-pathogenesis of Auditory Neuropathy Spectrum Disorder (ANSD), a total of 845 papers were divided into four categories: Review, Audiology, Treatment and Aetiology. Aetiology was the topic analysed categorising papers as: Genetics, Histopathology, Imaging and Medical diseases. Isolated ANs were in relation to Otoferlin, Pejvakin and DIAPH3 deficiency, and the syndromes were mainly Charcot Marie Tooth, Friedreich Ataxia, mitochondrial disorders and those associated with optic neuropathies. In histopathology papers, important information was available from analyses on human premature newborns and on some syndromic neuropathies. From cochlear dysmorphism to cerebral tumours associated with ANs, these are described in what is identified as the Imaging area. Finally, the prevalent clinical pathology was bilirubinopathy, followed by diabetes. In conclusion, AN/ANSDs do not refer to a clear pathological condition, but to an instrumental pattern without any evidence of auditory nerve involvement, except in a few conditions. The terms AN/ANSD are misleading and should be avoided, including terms such as “synaptopathy” or “dis-synchrony”.

High levels of unbound bilirubin are associated with acute bilirubin encephalopathy in post-exchange transfusion neonates

BACKGROUND

Although it is known that unbound bilirubin can enter the brain, there is little evidence of its association with the development of acute bilirubin encephalopathy. Here, we investigated this potential relationship in neonates who had undergone exchange transfusion.

METHODS

Data from 46 newborns who underwent exchange transfusion between 2016 and 1-1 to 2018-12-31 at the First People's Hospital of Changde City in China were analyzed. The unbound bilirubin level was taken as the independent variable and the development of the acute bilirubin encephalopathy as the dependent variable. The covariates were age, birth weight, sex, red blood cell count, blood glucose, hemolytic disease, and whether the infant had received phototherapy.

RESULTS

The mean age and gestational age of the neonates were 146.5 ± 86.9 h and 38.6 ± 1.3 weeks [38.7(34.6-41.1) weeks] old, respectively; 52.17% were male. Binary logistic regression analysis after adjustment for covariates showed a positive association between the levels of unbound bilirubin and the development of acute bilirubin encephalopathy (odds ratio = 1.41, 95% confidence intervals 1.05-1.91, P = < 0.05).

CONCLUSION

There is a significant association between unbound bilirubin levels and the development of acute bilirubin encephalopathy in neonates. Further investigations are required to explore the mechanisms.

Acetaminophen elevates unbound bilirubin levels by the glucose oxidase-peroxidase method

BACKGROUND

Acetaminophen is widely administered to neonates but its effect on unbound bilirubin (UB) levels remains unclear. The aim of this study was to clarify whether administration of acetaminophen is related to an elevation of UB levels.

METHOD

Infants with a birthweight of ˂1,500 g admitted to our neonatal intensive care unit between January 2017 and April 2020 were retrospectively reviewed. Seventy-one infants were enrolled, five of whom had received acetaminophen. Clinical data were analyzed when the highest UB value (UB peak) in each infant was recorded. Demographic data and information on treatment within the 24 h before the UB peak were also collected. UB was determined by the glucose oxidase-peroxidase (GOD-POD) method. Infants were categorized according to the presence or absence of acetaminophen administration (acetaminophen and no acetaminophen groups) within 24 h of the UB peak. The relationship between UB values and various clinical variables was then compared.

RESULTS

Both the peak UB value and the ratio of gastrointestinal disease were higher in the acetaminophen group than in the no acetaminophen group. Univariate analysis revealed that a total of seven variables were potentially correlated with UB peak values (P < 0.10). Multivariate analysis showed that acetaminophen and direct bilirubin were independently associated with UB peak values.

CONCLUSION

Our study suggests that administration of acetaminophen is related to higher UB levels by the GOD-POD method. UB values measured by the GOD-POD method should not be used in infants treated with acetaminophen for evaluation of bilirubin neurotoxicity avoidance.

Preterm Neonatal Mortality and its predictors in Tikur Anbessa Specialized Hospital, Addis Ababa, Ethiopia: a retrospective cohort study

BACKGROUND

Preterm neonatal death is a global problem. In Ethiopia, it is still high, and the trend in reduction is slower as compared to child mortality. Preterm neonatal birth is the leading cause. The magnitude and associated factors are also not well documented. Therefore, this study aimed to estimate the incidence of mortality and its predictors among preterm neonates in Tikur Anbesa Specialized Hospital (TASH).

METHODS

An institution-based retrospective cohort study was conducted among 604 preterm neonates admitted to Tikur Anbesa Specialized Hospital. Data were collected by reviewing patient charts using systematic sampling with a checklist. The data entry was done using EpiData version 4.2, and analysis was done using Stata Version 14.1. Kaplan-Meier and log-rank tests were used to estimate the survival time and to compare it. Cox proportional hazard was also fitted to identify major predictors. Hazard Ratios (HRs) with 95% Confidence Intervals (CI) were used to assess the relationship between factors associated with the occurrence of death. Finally, statistical significance was declared at p-value < 0.05.

RESULTS

In this study, a total of 604 patient charts were reviewed; of these, 571 met the inclusion criteria and were recruited to the study. A total of 170(29.7%) preterm neonates died during the follow-up period. The median follow-up time of preterm neonate under the cohort was 21 days (IQR: 4, 27). The incidence rate was 39.1 per 1000-person day. Rural residency (AHR: 1.45 (95% CI: 1.1,4.8)), Maternal diabetic Mellitus (AHR:2.29 (95%CI: 1.43,3.65), neonatal sepsis (AHR:1.62 (95% CI: 1.11,2.37), respiratory distress (AHR:1.54 (95% CI:1.03, 2.31), extreme prematurity (AHR:2.87 (95% CI:1.61, 5.11), and low APGAR score (AHR:3.11 (95% CI:1.79, 5.05) was found to be predictors.

CONCLUSION

The rate of preterm neonatal mortality is still an important problem. Having maternal gestational Diabetic Mellitus, neonatal sepsis, respiratory distress, and low Apgar score were major predictors for preterm neonatal mortality. Therefore, efforts have to be made to reduce the incidence of death and for timely management of mothers with Diabetic Mellitus. Healthcare professionals should also work on early diagnosis and treatment of preterm neonate with sepsis, respiratory distress, and low Apgar score.

Neonatal Jaundice in Preterm Infants with Bilirubin Encephalopathy

INTRODUCTION

The aim of this study is to clarify bilirubin parameters and its treatment in preterm infants with bilirubin encephalopathy (pBE).

METHODS

We asked the responders to an earlier nationwide Japanese survey on pBE to provide additional information. pBE was diagnosed based on the criteria used in the nationwide survey. We collected data on serum total bilirubin (TB), direct bilirubin (DB), albumin, and unbound bilirubin (UB) levels during the first 8 weeks of life, and on phototherapy and exchange transfusion treatments.

RESULTS

We obtained clinical data from 75 patients with pBE from 58 hospitals (response rate of 59%), who were born between 2002 and 2016. The average peak TB level was 12.6 mg/dL (215 μmol/L), and the average age at peak attainment was 19.7 days after birth. Albumin level was <2.5 g/dL in 44 patients, and the peak DB level was ≥2 mg/dL (34.2 μmol/L) in 20 patients. The average peak bilirubin/albumin (B/A) (mg/g) ratio was 3.8 (molar ratio of 0.475), and the average age at peak attainment was 18.6 days. The average peak UB level was 0.67 μg/dL (11.5 nmol/L). The median duration of phototherapy was 6 days, and the median day of the last session was 12. The peak TB level occurred after the last day of phototherapy in 30 of the 61 patients available for comparison.

CONCLUSIONS

Most patients with pBE lacked marked elevations in serum TB levels and the B/A ratio, the peaks of which were sometimes delayed to >4 weeks after birth.

Changes in auditory function in premature children: A prospective cohort study

OBJECTIVES

To analyze the age-specific pattern of auditory function in preterm children as a function of their gestational age at birth.

STUDY DESIGN

longitudinal cohort study.

METHODS

a prospective cohort study involved 271 preterm children aged from 6 months to 15 years old. Children were divided into two groups: 70 children with a gestational age at birth of 32-36 weeks (Group 1) and 201 children with a gestational age of 22-31 weeks (Group 2). Hearing was assessed by ABR, ASSR, OAE, behavioral audiometry, and pure tone audiometry. Additionally, for some children, CT, MRI, and GBJ2 evaluations were performed. Assessments of hearing impaired children were performed 3-4 times a year for children under 2 years of age; 2-3 times a year for children from 2 to 5 years of age; and 1-2 times a year for children over 5 years of age. Infants without any hearing problems were examined 2-3 times during their first year of life, followed by annual examinations as they aged.

RESULTS

The initial hearing examination identified SNHL and ANSD in 18 children (25.7%) and 64 children (31.8%) in Group 1 and Group 2, respectively. No significant difference in the occurrence of auditory impairment in the two groups was found at the initial assessment (p > 0.05). Further long-term follow-up revealed changes in hearing in 16 children: 15 from Group 2 and only one child from Group 1. Four different kinds of hearing changes were noted: hearing recovery to normal levels in children with ANSD; late onset hearing loss; the transformation of ANSD to SNHL, and vice versa. The age, factors, and possible mechanisms of such changes are discussed in the article.

CONCLUSION

The auditory function in prematurely born children tends to be unstable, especially at a very early age. In very preterm infants, it may either deteriorate or improve. Infants born before 31 weeks' gestation require long-term follow-up at least until they are 3-4 years of age. Caution is advised regarding very early cochlear implantation for children born before 32 weeks of gestation age.

Does riboflavin depletion cause auditory neuropathy spectrum disorder in at risk neonates?

We present a new hypothesis for the pathogenesis of auditory neuropathy spectrum disorder (ANSD) in at risk neonates involving depletion of riboflavin. The association between neonatal hyperbilirubinemia and ANSD is well recognized, yet causation has not been proven. The risk of ANSD does not correlate clearly with severity of hyperbilirubinemia and ASND only occurs in a small proportion of hyperbilirubinemic neonates. Additional, perhaps co-dependent, factors are therefore likely to be involved in pathogenesis. The metabolism of bilirubin consumes riboflavin and levels of riboflavin are depleted further by phototherapy. The neonate may also be deficient in riboflavin secondary to maternal deficiency, and reduced intake or impaired absorption. We propose that riboflavin depletion may be a significant contributor to development of ANSD in at risk neonates. The basis of this hypothesis is the recent recognition that impairment of riboflavin metabolism caused by genetic mutations (SLC52A2 or AIMF1) also causes ANSD.

Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn

Bilirubin is the end product of heme catabolism formed during a process that involves oxidation-reduction reactions and conserves iron body stores. Unconjugated hyperbilirubinemia is common in newborn infants, but rare later in life. The basic physiology of bilirubin metabolism, such as production, transport, and excretion, has been well described. However, in the neonate, numerous variables related to nutrition, ethnicity, and genetic variants at several metabolic steps may be superimposed on the normal physiological hyperbilirubinemia that occurs in the first week of life and results in bilirubin levels that may be toxic to the brain. Bilirubin exists in several isomeric forms that differ in their polarities and is considered a physiologically important antioxidant. Here we review the chemistry of the bilirubin molecule and its metabolism in the body with a particular focus on the processes that impact the newborn infant, and how differences relative to older children and adults contribute to the risk of developing both acute and long-term neurological sequelae in the newborn infant. The final section deals with the interplay between the brain and bilirubin and its entry, clearance, and accumulation. We conclude with a discussion of the current state of knowledge regarding the mechanism(s) of bilirubin neurotoxicity.

Identification of Perinatal Risk Factors for Auditory Neuropathy Spectrum Disorder

OBJECTIVES/HYPOTHESIS

To identify medical risk factors associated with auditory neuropathy spectrum disorder (ANSD).

STUDY DESIGN

Retrospective case-control study.

METHODS

During a 2-year period (2013-2014) patients with newly diagnosed ANSD were identified at a tertiary care facility. Twenty-two patients (n = 22) were identified aged 0.5 to 8.1 years. There were 15 males and seven females. Sixteen had bilateral, four had left-sided, and two had right-sided ANSD. Two age-matched, side-matched, and gender-matched control groups were then collected. The first group was 22 normal-hearing children (n = 22). The second was 22 children with sensorineural hearing loss (SNHL) (n = 22) who did not meet the criteria for ANSD. The chart of each subject was reviewed for the following five-predictor variables: prematurity, low birth weight, jaundice, use of mechanical ventilation, and administration of ototoxic medications. Analysis of variance was performed to analyze the prevalence of perinatal risk factors among the three groups. Multivariate linear regression was then applied.

RESULTS

When comparing the ANSD group to both the normal-hearing and SNHL groups, the subjects with ANSD had statistically significant higher rates of prematurity, low birth weight, jaundice, and mechanical ventilation. Multiple regression analysis was performed to identify predictors of ANSD compared to each control group individually. Jaundice in the first month of life approached significance when comparing the ANSD group to the normal-hearing group, and was the only medical risk factor found to be statistically significant when comparing the ANSD group to the SNHL group.

CONCLUSIONS

A history of neonatal hyperbilirubinemia was significantly more common in children with ANSD compared to children with severe SNHL.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:671-674, 2021.

Effect of Hyperbilirubinemia on Medial Olivocochlear System in Newborns

OBJECTIVES

To evaluate medial olivocochlear efferent system of babies with hyperbilirubinemia with normal auditory brain stem responses.

MATERIALS AND METHODS

This was a prospective study in a tertiary referral hospital. The study involved 40 hyperbilirubinemic and 44 healthy newborns. Cochlear and auditory activity of participants was evaluated by transient otoacoustic emissions (TOAEs) and brainstem auditory evoked response components (BAER). Medial olivocochlear (MOC) reflex was evoked with contralateral acoustic stimulation and recorded with TOAEs.

RESULTS

A comparison of the MOC reflex activity between two groups with Mann Whitney U test revealed that MOC reflex activity were significantly decreased in the hyberbilirubinemic group for both ears (p<.05). This difference was significant for all frequencies in both ears. There was no significant relation between total serum bilirubin level and MOC reflex activity.

CONCLUSION

Hyperbilirubinemic newborns had decreased MOC reflex activity. This may be indicative of future problems in speech discrimination and effective hearing in noisy background. Additional long cohort studies are needed to evaluate the clinical importance of MOC reflex measurements in this group. MOC reflex measurement has the potential to form part of the audiologic evaluation of newborns with hyperbilirubinemia in the future.

High unbound bilirubin for age: a neurotoxin with major effects on the developing brain

Neonatal hyperbilirubinemia is one of the most frequent diagnoses made in neonates. A high level of unconjugated bilirubin that is unbound to albumin is neurotoxic when the level exceeds age-specific thresholds or at lower levels in neonates with neurotoxic risk factors. Lower range of unbound bilirubin results in apoptosis, while moderate-to-high levels result in neuronal necrosis. Basal ganglia and various brain stem nuclei are more susceptible to bilirubin toxicity. Proposed mechanisms of bilirubin-induced neurotoxicity include excessive release of glutamate, mitochondrial energy failure, release of proinflammatory cytokines, and increased intracellular calcium concentration. These mechanisms are similar to the events that occur following hypoxic-ischemic insult in neonates. Severe hyperbilirubinemia in term neonates has been shown to be associated with increased risk for autism spectrum disorders. The neuropathological finding of bilirubin-induced neurotoxicity also includes cerebellar injury with a decreased number of Purkinje cells, and disruption of multisensory feedback loop between cerebellum and cortical neurons which may explain the clinical characteristics of autism spectrum disorders. Severe hyperbilirubinemia occurs more frequently in infants from low- and middle-income countries (LMIC). Simple devices to measure bilirubin, and timely treatment are essential to reduce neurotoxicity, and improve outcomes for thousands of neonates around the world.

Developmental influence of unconjugated hyperbilirubinemia and neurobehavioral disorders

Bilirubin-induced brain injury in the neonatal period has detrimental effects on neurodevelopment that persist into childhood and adulthood, contributing to childhood developmental disorders. Unconjugated bilirubin is a potent antioxidant that may be useful for protecting against oxidative injuries, but it becomes a potent neurotoxin once it crosses the blood brain barrier. Because bilirubin toxicity involves a myriad of pathological mechanisms, can damage most types of brain cells, and affects brain circuits or loops that influence cognition, learning, behavior, sensory, and language, the clinical effects of bilirubin-induced neurotoxicity are likely to be manifold. One possible effect that several experts have identified is bilirubin-induced neurological dysfunction (subtle kernicterus). However, the underlying biological mechanisms or pathways by which subtle kernicterus could lead to developmental disorders has not been elucidated previously. Our aim in this review is to describe a spectrum of developmental disorders that may reflect subtle kernicterus and outline plausible biological mechanisms for this possible association. We review existing evidence that support or refute the association between unconjugated hyperbilirubinemia and developmental disorders, and limitations associated with these studies.

Prolonged furosemide exposure and risk of abnormal newborn hearing screen in premature infants

BACKGROUND

At very high doses, furosemide is linked to ototoxicity in adults, but little is known about the risk of hearing loss in premature infants exposed to furosemide.

AIMS

Evaluate the association between prolonged furosemide exposure and abnormal hearing screening in premature infants.

STUDY DESIGN

Using propensity scoring, infants with prolonged (≥28 days) exposure to furosemide were matched to infants never exposed. The matched sample was used to estimate the impact of prolonged furosemide exposure on the probability of an abnormal hearing screen prior to hospital discharge.

SUBJECTS

A cohort of infants 501-1250 g birth weight and 23-29 weeks gestational age discharged home from 210 neonatal intensive care units in the United States (2004-2013).

OUTCOME MEASURES

We defined abnormal hearing screen as a result of either "fail" or "refer" for either ear.

RESULTS

Altogether, 1020 infants exposed to furosemide for ≥28 days were matched to 790 unique infants never exposed, yielding a total of 1042 matches due to sampling with replacement and propensity score ties. Matching resulted in a population similar in baseline characteristics. After adjusting for covariates, the proportion of infants with an abnormal hearing screen in the furosemide-exposed group was not significantly higher than the never-exposed group (absolute difference 3.0% [95% CI -0.2-6.2%], P = 0.07).

CONCLUSIONS

Prolonged furosemide exposure was associated with a positive, but not statistically significant, difference in abnormal hearing screening in premature infants. Additional studies with post-hospital discharge audiology follow-up are needed to further evaluate the safety of furosemide in this population.

Bilirubin binding in jaundiced newborns: from bench to bedside?

BACKGROUND

Bilirubin-induced neurologic dysfunction (BIND) is a spectrum of preventable neurological sequelae in jaundiced newborns. Current total plasma bilirubin (B_T) concentration thresholds for phototherapy and/or exchange transfusion poorly predict BIND.

METHODS

The unbound (free) bilirubin (B_f) measured at these B_T thresholds provides additional information about the risk for BIND. B_f can be readily adapted to clinical use by determining B_f population parameters at current B_T thresholds. These parameters can be established using a plasma bilirubin binding panel (BBP) consisting of B_T, B_f, and two empiric constants, the maximum B_T (B_Tmax) and the corresponding equilibrium association bilirubin constant (K).

RESULTS

B_Tmax and K provide the variables needed to accurately estimate B_f at B_T < B_Tmax to obtain B_f at threshold B_T in patient samples. Once B_f population parameters are known, the BBP in a newborn can be used to identify poor bilirubin binding (higher B_f at the threshold B_T compared with the population) and increased risk of BIND.

CONCLUSION

The BBP can also be used in jaundice screening to better identify the actual B_T at which intervention would be prudent. The BBP is used with current B_T thresholds to better identify the risk of BIND and whether and when to intervene.