Reversibility of acute intermediate phase bilirubin encephalopathy

Management challenges in the treatment of severe hyperbilirubinemia in low- and middle-income countries: Encouraging advancements, remaining gaps, and future opportunities

Neonatal jaundice (NJ) is common in newborn infants. Severe NJ (SNJ) has potentially negative neurological sequelae that are largely preventable in high resource settings if timely diagnosis and treatment are provided. Advancements in NJ care in low- and middle-income countries (LMIC) have been made over recent years, especially with respect to an emphasis on parental education about the disease and technological advancements for improved diagnosis and treatment. Challenges remain, however, due to lack of routine screening for SNJ risk factors, fragmented medical infrastructure, and lack of culturally appropriate and regionally specific treatment guidelines. This article highlights both encouraging advancements in NJ care as well as remaining gaps. Opportunities are identified for future work in eliminating the gaps in NJ care and preventing death and disability related to SNJ around the globe.

Models of bilirubin neurological damage: lessons learned and new challenges

OBJECTIVE

Jaundice (icterus) is the visible manifestation of the accumulation of bilirubin in the tissue and is indicative of potential toxicity to the brain. Since its very first description more than 2000 years ago, many efforts have been undertaken to understand the molecular determinants of bilirubin toxicity to neuronal cells to reduce the risk of neurological sequelae through the use of available chemicals and in vitro, ex vivo, in vivo, and clinical models. Although several studies have been performed, important questions remain unanswered, such as the reasons for regional sensitivity and the interplay with brain development. The number of new molecular effects identified has increased further, which has added even more complexity to the understanding of the condition. As new research challenges emerged, so does the need to establish solid models of prematurity.

METHODS

This review critically summarizes the key mechanisms of severe neonatal hyperbilirubinemia and the use of the available models and technologies for translational research.

IMPACT

We critically review the conceptual dogmas and models used for studying bilirubin-induced neurotoxicity. We point out the pitfalls and translational gaps, and suggest new clinical research challenges. We hope to inform researchers on the pro and cons of the models used, and to help direct their experimental focus in a most translational research.

Serum Bilirubin and Sperm Quality in Adult Population

The neurotoxicity of bilirubin has been extensively reported in numerous studies. However, the association between bilirubin and male fertility has not yet been studied. The main goal of this study was to investigate the association between serum total bilirubin and sperm quality in an adult population. In this cross-sectional study, 9057 participants who attended the MJ health examination (2010–2016) were enrolled. Sperm specimens were collected by masturbation, and sperm quality was analyzed in accordance with the WHO criteria. Serum total bilirubin levels were measured by an automatic biochemical profile analyzer. Thereafter, the associations between serum total bilirubin and sperm quality were determined by a multivariable linear regression. Serum total bilirubin was inversely associated with sperm concentration and normal morphology with β values of −13.82 (95% CI: −26.99, −0.64) and −18.38 (95% CI: −30.46, −6.29) after adjusting for covariables. The highest levels of serum total bilirubin were significantly associated with sperm concentration and normal morphology with β values of −14.15 (95% CI: −28.36, 0.06) and −21.15 (95% CI: −33.99, −8.30). Our study highlighted the potential impact of serum bilirubin on sperm quality in a male population. Additional longitudinal research is necessary to explore these findings and underlying mechanisms.

Magnetic Resonance Image of Neonatal Acute Bilirubin Encephalopathy: A Diffusion Kurtosis Imaging Study

Background and Objective: The abnormal T1-weighted imaging of MRI can be used to characterize neonatal acute bilirubin encephalopathy (ABE) in newborns, but has limited use in evaluating the severity and prognosis of ABE. This study aims to assess the value of diffusion kurtosis imaging (DKI) in detecting ABE and understanding its pathogenesis.

Method: Seventy-six newborns with hyperbilirubinemia were grouped into three groups (mild group, moderate group, and severe group) based on serum bilirubin levels. All the patients underwent conventional MRI and DKI serial, as well as 40 healthy full-term infants (control group). The regions of interest (ROIs) were the bilateral globus pallidus, dorsal thalamus, frontal lobe, auditory radiation, superior temporal gyrus, substantia nigra, hippocampus, putamen, and inferior olivary nucleus. The values of mean diffusivity (MD), axial kurtosis (AK), radial kurtosis (RK), and mean kurtosis (MK), and fractional anisotropy (FA), radial diffusivity (RD), and axis diffusivity (AD) of the ROIs were evaluated. All newborns were followed up and evaluated using the Denver Development Screening Test (DDST). According to the follow-up results, the patients were divided into the normal group, the suspicious abnormal group, and the abnormal group.

Result: Compared with the control group, significant differences were observed with the increased MK of dorsal thalamus, AD of globus pallidus in the moderate group, and increased RD, MK, AK, and RK value of globus pallidus, dorsal thalamus, auditory radiation, superior temporal gyrus, and hippocampus in the severe group. The peak value of total serum bilirubin was moderately correlated with the MK of globus pallidus, dorsal thalamus, and auditory radiation and was positively correlated with the other kurtosis value. Out of 76 patients, 40 finished the DDST, and only 9 patients showed an abnormality. Compared with the normal group, the AK value of inferior olivary nucleus showed significant differences (p < 0.05) in the suspicious abnormal group, and the MK of globus pallidus, temporal gyrus, and auditory radiation; RK of globus pallidus, dorsal thalamus, and auditory radiation; and MD of globus pallidus showed significant differences (p < 0.05) in the abnormal group.

Conclusion: DKI can reflect the subtle structural changes of neonatal ABE, and MK is a sensitive indicator to indicate the severity of brain damage.

Hyperbilirubinemia in the Term Infant: Re-evaluating What We Think We Know

This article attempts to highlight contemporary issues relating to term neonatal hyperbilirubinemia and to focus attention on controversial issues and concepts with the potential to effect change in clinical approach. On the one hand, the focus is bilirubin neurotoxicity, which is now known to encompass a wide, diverse spectrum of features. The various aspects of this spectrum are outlined and defined. On the other hand, bilirubin also possesses antioxidant properties. As such, mild hyperbilirubinemia is suggested as actually offering the neonate some protective advantage.

A greater awareness of children with glucose-6-phosphate dehydrogenase deficiency is imperative in western countries

AIM

This national retrospective Danish study described the characteristics of children diagnosed with glucose-6-phosphate dehydrogenase (G6PD) deficiency, an inherited X-linked recessive disorder that often affects children of Middle Eastern descent.

METHODS

We studied children born between 1 January 2000 and 31 December 2017 and diagnosed with G6PD deficiency. They were identified from the Danish National Hospital Discharge Register and the Danish Database of Extreme Neonatal Hyperbilirubinaemia.

RESULTS

There were 113 children diagnosed with G6PD deficiency, 67% were of Middle Eastern descent and they were frequently diagnosed before the onset of symptoms, based on known heredity. Of the 67 infants born in Denmark, 10% had extreme neonatal hyperbilirubinaemia and one developed kernicterus spectrum disorder, as did one child born in the Middle East. Most (61%) of the 33 children with jaundice received phototherapy, 12% had exchange transfusions and 18% received whole blood transfusions. After the neonatal period, 23% of the cohort had blood transfusions and 4% needed intensive care for acute haemolytic anaemia. The incidence of G6PD deficiency appeared to be severely underestimated.

CONCLUSION

Many families from countries where G6PD deficiency is endemic move to Denmark and other Western countries. Greater awareness is essential to avoid chronic and potentially lethal, consequences.

Improving Effectiveness of Phototherapy in an Academic Center: A Quality Improvement Project

Neonatal hyperbilirubinemia is a common cause of delayed discharge and readmissions in our institution. As previously published, the irradiance our phototherapy (PT) units provided was below the irradiance recommended by the AAP for intensive phototherapy (>30 µW/cm²/nm). We measured irradiance delivered by our PT units (Drager 4000) using a standardized footprint grid. By varying number of blue and white fluorescent PT lights, height of PT unit above the neonate and type of bed used (open bassinet versus isolette), we determined the optimal PT arrangement needed to deliver intensive PT (30 µW/cm²/nm). We then developed a standardized, multidisciplinary protocol specifying light arrangement and distance required needed to achieve the desired irradiance level. We were able to show improved irradiance following above changes. Onsite measurement of irradiance provided by local phototherapy units and development of a multidisciplinary, standardized protocol are necessary to assure delivery of recommended levels PT for neonates with hyperbilirubinemia.

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.

Early prediction of adverse outcomes in infants with acute bilirubin encephalopathy

OBJECTIVE

Acute bilirubin encephalopathy (ABE) remains one of the important causes of neonatal mortality and child disability, early identification, and intervention which could improve outcomes. The purpose of this study was to evaluate early predictors of adverse outcomes in infants with ABE.

METHODS

Newborns of gestational age ≥ 35 weeks and diagnosed with ABE were included in the study. Bilirubin-induced neurological dysfunction (BIND) score, total serum bilirubin (TSB) peak value, and serum albumin levels were determined. Adverse outcomes were defined as death or survival with auditory dysfunction and/or cerebral palsy.

RESULTS

Eighty-two infants were eligible for recruitment in the study. The outcome data from 76 ABE infants (92%) were used for analysis, of which 25 infants got adverse outcomes and 51 live a normal life. Univariate analysis for BIND score, TSB peak value, bilirubin-albumin ratio (B/A), albumin level, abnormal AABR, and neonatal sepsis was performed to elucidate the association with adverse outcomes. Bivariate logistic regression analysis showed B/A (OR 10.48, 95%CI: 1.55-70.81, P = 0.02) and BIND score (OR 3.68, 95%CI: 1.39-9.72, P = 0.01) were correlated with adverse outcomes. ROC curve analysis showed that B/A (≥8.9 mg/g), BIND score (≥6) could predict adverse outcomes of ABE separately; B/A in conjunction with BIND score could increase prediction sensitivity to 100%.

INTERPRETATION

Both B/A and BIND score can be used to predict adverse outcomes of ABE, and the combination of the two parameters can increase prediction sensitivity significantly.

Extreme neonatal hyperbilirubinemia and kernicterus spectrum disorder in Denmark during the years 2000-2015

OBJECTIVE

To determine the incidence and etiology of extreme neonatal hyperbilirubinemia, defined as total serum bilirubin (TSB) ≥450 µmol/L, and kernicterus spectrum disorder (KSD) in Denmark between 2000 and 2015.

STUDY DESIGN

We identified all infants born between 01.01.2000 and 31.12.2015 with TSB ≥450 µmol/L, ratio of conjugated to TSB <0.30, gestational age ≥35 weeks, and postnatal age ≤4 weeks, using Danish hospitals' laboratory databases.

RESULT

We included 408 infants. The incidence of extreme neonatal hyperbilirubinemia among infants with gestational age ≥35 weeks was 42/100,000 during the study period with a seemingly decreasing incidence between 2005 and 2015. Twelve of the 408 infants developed KSD, (incidence 1.2/100,000) Blood type ABO isohemolytic disease was the most common explanatory etiology.

CONCLUSIONS

Our study stresses the importance of a systematic approach to neonatal jaundice and ongoing surveillance of extreme neonatal hyperbilirubinemia and KSD.

Sixty years of phototherapy for neonatal jaundice - from serendipitous observation to standardized treatment and rescue for millions

A breakthrough discovery 60 years ago by Cremer et al. has since changed the way we treat infants with hyperbilirubinemia and saved the lives of millions from death and disabilities. "Photobiology" has evolved by inquiry of diverse light sources: fluorescent tubes (wavelength range of 400-520 nm; halogen spotlights that emit circular footprints of light; fiberoptic pads/blankets (mostly, 400-550 nm range) that can be placed in direct contact with skin; and the current narrow-band blue light-emitting diode (LED) light (450-470 nm), which overlaps the peak absorption wavelength (458 nm) for bilirubin photoisomerization. Excessive bombardment with photons has raised concerns for oxidative stress in very low birthweight versus term infants treated aggressively with phototherapy. Increased emphasis on prescribing phototherapy as a "drug" that is dosed cautiously and judiciously is needed. In this historical review, we chronicled the basic to the neurotoxic components of severe neonatal hyperbilirubinemia and the use of standardized interventions.

Review of bilirubin neurotoxicity II: preventing and treating acute bilirubin encephalopathy and kernicterus spectrum disorders

Previously in Part I of this two-part review, we discussed the current and recent advances in the understanding of the molecular biology and neuropathology of bilirubin neurotoxicity (BNTx). Here in Part II, we summarize current treatment options available to treat the severely jaundiced infants to prevent significant brain damage and improve clinical outcomes. In addition, we review potential novel therapies that are in various stages of research and development. We will emphasize treatments for both prevention and treatment of both acute bilirubin encephalopathy (ABE) and kernicterus spectrum disorders (KSDs), highlighting the treatment of the most disabling neurological sequelae of children with mild-to-severe KSDs whose "rare disease" status often means they are overlooked by the clinical research community at large. As with other secondary dystonias, treatment of the dystonic motor symptoms in kernicterus is the greatest clinical challenge.

Early Amplitude-Integrated Electroencephalography Predicts Long-Term Outcomes in Term and Near-Term Newborns With Severe Hyperbilirubinemia

BACKGROUND

We aimed to determine the predictive neurological prognostic value of early amplitude-integrated electroencephalography (aEEG) in term and near-term neonates with severe hyperbilirubinemia compared with cranial magnetic resonance imaging (MRI) and auditory brainstem response (ABR).

METHODS

Infants of ≥35 weeks of gestation with severe hyperbilirubinemia (total serum bilirubin [TSB] ≥340 μmol/L) or with hyperbilirubinemia (TSB ≥257 μmol/L) in association with bilirubin-induced neurological dysfunction were recruited. All the subjects had an aEEG after being admitted to the neonatal intensive care unit, whereas cranial MRI and ABR were performed when TSB had come down to the normal range. All the infants were followed up to 12 months.

RESULTS

During the study period, 77 of 83 infants were eligible, of which 71 had severe hyperbilirubinemia and six had hyperbilirubinemia in association with bilirubin-induced neurological dysfunction. Thirty-three infants were diagnosed with acute bilirubin encephalopathy (ABE), two of whom died of ABE, and 62 completed the follow-up, of which 12 infants had adverse outcomes. Sixty-four infants underwent aEEG, 40 infants had cranial MRI, and 39 infants had ABR. Logistic regression and the receiver-operator characteristic curve analysis showed that the ability of severely abnormal aEEG to predict adverse neurological outcomes in severe hyperbilirubinemia was no better than abnormal ABR, with a sensitivity of 35.7% versus 83.3%, a specificity of 92.0% versus 74.1%, a positive predictive value of 55.6% versus 58.8%, and a negative predictive value of 83.6% versus 90.9%.

CONCLUSIONS

Early aEEG could predict adverse neurodevelopmental outcomes in neonates with severe hyperbilirubinemia, although the sensitivity was lower than ABR.

Turkish Neonatal Society guideline to the approach, follow-up, and treatment of neonatal jaundice

Jaundice is one of the most common problems in the newborn. It is generally accepted as a physiologic condition; most cases are benign and transient. However, in a small portion of jaundiced newborn infants, serum bilirubin concentrations increase to a level at which irreversible brain damage can occur. The timely diagnosis and management of severe hyperbilirubinemia is essential to prevent acute bilirubin encephalopathy and kernicterus. Kernicterus still occurs although it is almost always preventable. The focus of this guideline is to reduce the incidence of severe hyperbilirubinemia and bilirubin encephalopathy. Therefore, a system-based approach using the recommendations of this guideline should be implemented in all birthing facilities and continued in ambulatory care of the newborn infants.

Emergency release uncross-matched packed red blood cells for immediate double volume exchange transfusion in neonates with intermediate to advanced acute bilirubin encephalopathy: timely but insufficient?

Given the urgency of double volume exchange transfusion (ExT) in an infant with intermediate to advanced stages of acute bilirubin encephalopathy (ABE), it has been suggested that emergency release uncross-matched packed red blood cells (ER-PRBC) be used. The efficacy of an ExT in removing bilirubin from the brain, however, is a direct function of the mass of albumin exchanged. The very low albumin content of ER-PRBC may fail to be neuroprotective. Predicted changes in total serum bilirubin (TSB), serum albumin, the bilirubin/albumin (B/A) ratio, plasma volume (PV), and bilirubin equilibration from the extravascular space during ER-PRBC ExT are described. ExT using ER-PRBC is efficacious in lowering the TSB. However, this result is falsely reassuring as significant concurrent serum albumin loss, resultant hypoalbuminemia, contraction of PV, limited bilirubin clearance from the extravascular space, and sustained B/A ratio elevations above recommended ExT treatment thresholds suggest that bilirubin neurotoxicity will continue.

Extreme neonatal hyperbilirubinemia, acute bilirubin encephalopathy, and kernicterus spectrum disorder in children with galactosemia

BACKGROUND

Galactosemia has not been recognized as a cause of extreme neonatal hyperbilirubinemia, although growing evidence supports this association.

METHODS

In a retrospective cohort study, we identified children with galactosemia due to GALT deficiency using the Danish Metabolic Laboratory Database. Among these, we identified children with extreme neonatal hyperbilirubinemia or symptoms of ABE. Extreme neonatal hyperbilirubinemia was defined as maximum total serum bilirubin (TSB_max)) level ≥450 µmol/L and a ratio of conjugated serum bilirubin/TSB <0.30.

RESULTS

We identified 21 children with galactosemia (incidence:1:48,000). Seven children developed extreme neonatal hyperbilirubinemia (median [range] TSB_max level: 491 [456-756] µmol/L), accounting for 1.7% of all extreme neonatal hyperbilirubinemia cases. During the first 10 days of life, hyperbilirubinemia was predominantly of unconjugated type. Four children developed symptoms of intermediate/advanced ABE. One additional child had symptoms of intermediate/advanced ABE without having extreme neonatal hyperbilirubinemia. On follow-up, one child had KSD.

CONCLUSIONS

Galactosemia is a potential cause of extreme neonatal hyperbilirubinemia, ABE, and KSD. It is crucial that putative galactosemic children are treated aggressively with phototherapy to prevent ABE and KSD. Thus it is important that galactosemia is part of the work up for unconjugated hyperbilirubinemia.

Follow-up of Children with Kernicterus in Kano, Nigeria

INTRODUCTION

Acute bilirubin encephalopathy (ABE) is associated with long-term sequelae (kernicterus). It continues to be a significant issue in our region of Nigeria, accounting for much morbidity and mortality. Herein we report the outcome of neonates with ABE seen at our centre.

METHODOLOGY

We established a surveillance of children who had ABE and returned to follow-up from prospective cases of ABE (2012-2014). ABE was diagnosed based on a bilirubin-induced neurologic dysfunction score of ≥ 1. Kernicterus was subsequently established based on a history of developmental delays, hearing impairments and abnormal physical and neurologic examinations at follow-up age ≥3 months.

RESULT

Five hundred fifty-one neonates had hyperbilirubinaemia of whom 104 (18.8%) had ABE. Mean transcutaneous bilirubin using the Ingram icterometer was 18.3 mg/dl  ±  SD 1.9 [(12.5-19.1), total serum bilirubin of 18.1 ± 10.9] (range: 10.3-64 mg/dl). Sixty-five infants returned for follow-up (41 males and 24 females); mean age 9 months (22 days to 17 months). Most (58 of 65; 89.2%) had abnormal neurological findings and 15 (25.9%) had probable kernicterus.

CONCLUSION

There is a critical need for a National Kernicterus Registry to document all cases of kernicterus and formulate an effective treatment and prevention policy.

Double versus single intensive phototherapy with LEDs in treatment of neonatal hyperbilirubinemia

OBJECTIVE

We investigate whether double phototherapy reduces total serum bilirubin concentration faster than single light during intensive phototherapy with high levels of irradiance using light-emitting diodes.

STUDY DESIGN

Eighty-three infants with gestational age ⩾33 weeks and uncomplicated hyperbilirubinemia were randomized to either double (n=41) or single phototherapy (n=42) for 24 h. The mean irradiance was 64.8 μW cm^-2 nm^-1 from above and 39 μW cm^-2 nm^-1 from below.

RESULTS

The percentage decreases of total serum bilirubin after 12 h of double vs single phototherapy were (mean (95% confidence interval (CI))) 39% (37 to 42) vs 30% (27 to 32), respectively (P<0.001). After 24 h, the decreases were 58% (56 to 61) vs 47% (44 to 50), respectively (P<0.001). The results were still significant after adjustment for confounding. The only side effect was loose stools.

CONCLUSION

Even with intensive phototherapy increasing spectral power by increasing the irradiated body surface area, the efficacy of phototherapy is improved.

A Pharmacologic View of Phototherapy

A pharmacologic view of phototherapy for neonatal jaundice is presented. By considering the photons of therapy light as molecules of a drug, this view connects therapeutic efficacy with photon wavelength, photon dose, dose rate and regimen, efficiency of photon absorption by bilirubin, quantum yields of photoproducts, and their metabolic courses. Based on this view, recommendations to ultimately improve efficacy and safety are presented. Special attention is given to phototherapy regimens for low gestational age, low birthweight infants.

Biology of Bilirubin Photoisomers

Phototherapy is the main treatment for neonatal hyperbilirubinemia. In acute treatment of extreme hyperbilirubinemia, intensive phototherapy may have a role in 'detoxifying' the bilirubin molecule to more polar photoisomers, which should be less prone to crossing the blood-brain barrier, providing a 'brain-sparing' effect. This article reviews the biology of bilirubin isomers. Although there is evidence supporting the lower toxicity of bilirubin photoisomers, there are studies showing the opposite. There are methodologic weaknesses in most studies and better-designed experiments are needed. In an infant acutely threatened by bilirubin-induced brain damage, intensified phototherapy should be used expediently and aggressively.

High-intensity light-emitting diode vs fluorescent tubes for intensive phototherapy in neonates

BACKGROUND

Special blue fluorescent tubes are recommended by the American Academy of Pediatrics (AAP) as the most effective light source for lowering serum bilirubin. A high-intensity light-emitting diode ('super LED') could render intensive phototherapy more effective than the above conventional methods. This study compared the efficacy and safety of a high-intensity light-emitting diode bed vs conventional intensive phototherapy with triple fluorescent tube units as a rescue treatment for severe unconjugated neonatal hyperbilirubinaemia.

METHOD

This was a randomised, prospective trial. Two hundred jaundiced neonates ≥ 35 weeks gestation who met the criteria for intensive phototherapy as per AAP guidelines were randomly assigned to be treated either with triple fluorescent tube units (group 1, n = 100) or a super LED bed (group 2, n = 100). The outcome was the avoidance of exchange transfusion by successful control of hyperbilirubinaemia.

RESULTS

Statistically significant higher success rates of intensive phototherapy were achieved among neonates treated with super LED (group 2) than in those treated conventionally (group 1) (87% vs 64%, P = 0.003). Significantly higher 'bilirubin decline' rates were reported in both haemolytic and non-haemolytic subgroups treated with the super LED bed compared with a similar sub-population in the conventionally treated group. Comparable numbers of neonates in both groups developed rebound jaundice (8% vs 10% of groups 1 and 2, respectively). Side-effects were mild in both groups, but higher rates of hyperthermia (12% vs 0%, P = 0.03), dehydration (8% vs 2%, P = 0.26) and skin rash (39% vs 1%, P = 0.002) were reported in the fluorescent tubes-treated group compared with the LED group.

CONCLUSIONS

Super LED is a safe rescue treatment for severe neonatal hyperbilirubinaemia, and its implementation may reduce the need for exchange transfusion.

A decision-making tool for exchange transfusions in infants with severe hyperbilirubinemia in resource-limited settings

Late presentation and ineffective phototherapy account for excessive rates of avoidable exchange transfusions (ETs) in many low- and middle-income countries. Several system-based constraints sometimes limit the ability to provide timely ETs for all infants at risk of kernicterus, thus necessitating a treatment triage to optimize available resources. This article proposes a practical priority-setting model for term and near-term infants requiring ET after the first 48 h of life. The proposed model combines plasma/serum bilirubin estimation, clinical signs of acute bilirubin encephalopathy and neurotoxicity risk factors for predicting the risk of kernicterus based on available evidence in the literature.

Predictors of Repeat Exchange Transfusion for Severe Neonatal Hyperbilirubinemia

OBJECTIVES

To identify the predictors of repeat exchange transfusion among infants with severe hyperbilirubinemia.

DESIGN

Retrospective cross-sectional study.

SETTING

A referral children's hospital in inner-city Lagos, Nigeria.

PATIENTS

Infants who received exchange transfusion for severe hyperbilirubinemia from January 2012 to December 2014.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

The predictors of repeat exchange transfusion were identified among all infants who had at least one exchange transfusion using multivariable logistic regression. A total of 352 infants with mean peak total serum bilirubin of 26.32 ± 7.96 mg/dL received exchange transfusion; of these, 49 (13.9%) with mean peak total serum bilirubin of 32.85 ± 10.54 mg/dL had repeat exchange transfusion. More than two thirds of infants who received exchange transfusion and repeat exchange transfusion were male, and at least one third had ABO incompatibility. No infant had more than two exchange transfusions. The mean age of admission was approximately 5 days (range, 1-14 d). Peak total serum bilirubin greater than or equal to 30 mg/dL (odds ratio, 2.88; 95% CI, 1.46-5.70) and acute bilirubin encephalopathy (odds ratio, 2.37; 95% CI, 1.18-4.77) were predictive of repeat exchange transfusion.

CONCLUSIONS

Acute bilirubin encephalopathy and excessive total serum bilirubin levels at least 30 mg/dL are predictive of repeat exchange transfusion. A risk assessment framework that combines total serum bilirubin levels, acute bilirubin encephalopathy status, and risk factors of neurotoxicity should be considered for the timely detection and monitoring of infants at risk of repeat exchange transfusion.

Early formation of bilirubin isomers during phototherapy for neonatal jaundice: effects of single vs. double fluorescent lamps vs. photodiodes

BACKGROUND

In neonatal jaundice, phototherapy converts bilirubin to more polar photoisomers which can be excreted without conjugation. We measured changes in the concentration of bilirubin Z,E-photoisomer during the first 4 h of intensive phototherapy using single fluorescent lights as a reference, compared to double fluorescent lights, and a single unit of photodiodes.

METHODS

Neonates (N = 42; birth weight: 1,200-4,690 g; gestational age: 28-42 wk) were studied during phototherapy. Infants were randomized to: (i) single, or (ii) double fluorescent phototherapy; or (iii) single unit photodiodes. Irradiance was measured. Serum bilirubin (by cooximetry) and Z,E bilirubin (by high-pressure liquid chromatography) were measured at 0,15, 30, 60, 120, and 240 min after the start of phototherapy. Data were analyzed with a linear mixed model.

RESULTS

There was a highly significant increase of Z,E-bilirubin over time (P < 0.0001), starting at 15 min. Photoisomers reached ~25% of total bilirubin concentration after 4 h. However, there were no significant differences between the three randomized groups in spite of significantly higher irradiance using double fluorescent lights vs. single fluorescent or photodiodes.

CONCLUSION

Formation of bilirubin photoisomers is rapid, and occurs early during intensive phototherapy for neonatal jaundice. The rate and level of photoisomerization was not influenced by irradiance and light source.

Ex vivo (1)H nuclear magnetic resonance spectroscopy reveals systematic alterations in cerebral metabolites as the key pathogenetic mechanism of bilirubin encephalopathy

BACKGROUND

Bilirubin encephalopathy (BE) is a severe neurologic sequelae induced by hyperbilirubinemia in newborns. However, the pathogenetic mechanisms underlying the clinical syndromes of BE remain ambiguous. Ex vivo (1)H nuclear magnetic resonance (NMR) spectroscopy was used to measure changes in the concentrations of cerebral metabolites in various brain areas of newborn 9-day-old rats subjected to bilirubin to explore the related mechanisms of BE.

RESULTS

When measured 0.5 hr after injection of bilirubin, levels of the amino acid neurotransmitters glutamate (Glu), glutamine (Gln), and γ-aminobutyric acid (GABA) in hippocampus and occipital cortex significantly decreased, by contrast, levels of aspartate (Asp) considerably increased. In the cerebellum, Glu and Gln levels significantly decreased, while GABA, and Asp levels showed no significant differences. In BE 24 hr rats, all of the metabolic changes observed returned to normal in the hippocampus and occipital cortex; however, levels of Glu, Gln, GABA, and glycine significantly increased in the cerebellum.

CONCLUSIONS

These metabolic changes for the neurotransmitters are mostly likely the result of a shift in the steady-state equilibrium of the Gln-Glu-GABA metabolic cycle between astrocytes and neurons, in a region-specific manner. Changes in energy metabolism and the tricarboxylic acid cycle may also be involved in the pathogenesis of BE.

Apnea in acute bilirubin encephalopathy

Central apnea, defined as cessation of breathing for ≥20s, is frequent in premature infants born at <34 weeks׳ gestation but uncommon among healthy late preterm (34(0/7)-36(6/7) weeks׳ gestation) and term (≥37 weeks׳ gestation) infants, where it is usually a clinical manifestation of a neurological or metabolic problem. There is growing evidence that marked unconjugated hyperbilirubinemia is associated with central apnea in neonates. This article explores the reported association between acute bilirubin encephalopathy and symptomatic apneic events in newborns and the possible mechanisms involved in the pathogenesis of this phenomenon. The prevalence of symptomatic apneic events in reports of acute bilirubin encephalopathy suggests this clinical finding should be considered a sign of bilirubin neurotoxicity.

Age-dependent pattern of cerebellar susceptibility to bilirubin neurotoxicity in vivo in mice

Neonatal jaundice is caused by high levels of unconjugated bilirubin. It is usually a temporary condition caused by delayed induction of UGT1A1, which conjugates bilirubin in the liver. To reduce bilirubin levels, affected babies are exposed to phototherapy (PT), which converts toxic bilirubin into water-soluble photoisomers that are readily excreted out. However, in some cases uncontrolled hyperbilirubinemia leads to neurotoxicity. To study the mechanisms of bilirubin-induced neurological damage (BIND) in vivo, we generated a mouse model lacking the Ugt1a1 protein and, consequently, mutant mice developed jaundice as early as 36 hours after birth. The mutation was transferred into two genetic backgrounds (C57BL/6 and FVB/NJ). We exposed mutant mice to PT for different periods and analyzed the resulting phenotypes from the molecular, histological and behavioral points of view. Severity of BIND was associated with genetic background, with 50% survival of C57BL/6‑Ugt1^−/− mutant mice at postnatal day 5 (P5), and of FVB/NJ-Ugt1^−/− mice at P11. Life-long exposure to PT prevented cerebellar architecture alterations and rescued neuronal damage in FVB/NJ-Ugt1^−/− but not in C57BL/6-Ugt1^−/− mice. Survival of FVB/NJ-Ugt1^−/− mice was directly related to the extent of PT treatment. PT treatment of FVB/NJ-Ugt1^−/− mice from P0 to P8 did not prevent bilirubin-induced reduction in dendritic arborization and spine density of Purkinje cells. Moreover, PT treatment from P8 to P20 did not rescue BIND accumulated up to P8. However, PT treatment administered in the time-window P0–P15 was sufficient to obtain full rescue of cerebellar damage and motor impairment in FVB/NJ-Ugt1^−/− mice. The possibility to modulate the severity of the phenotype by PT makes FVB/NJ-Ugt1^−/− mice an excellent and versatile model to study bilirubin neurotoxicity, the role of modifier genes, alternative therapies and cerebellar development during high bilirubin conditions.

William A Silverman lecture

This is the text of the William A Silverman lecture given by Dr David K Stevenson at the Pediatric Academic Societies Annual Meeting in Washington, DC, May 4-7, 2013.

Neurobehavior of term neonates with neonatal hyperbilirubinemia

Objective:

To find the effect of neonatal hyperbilirubinemia on neurobehavior of term infants.

Materials and Methods:

This study was undertaken in the neonatal unit of our tertiary care hospital. Term neonates who developed jaundice with serum bilirubin value of above 15 mg/dl within 1^st week of life were enrolled in the study. Peak total serum bilirubin (PSB) levels of cases were recorded. Age and sex matched normal controls were assigned to every case. Both the groups were assessed by Brazelton′s neurobehavioral assessment scale (NBAS) and the scores of the individual clusters were compared.

Results:

Habituation, range of state, autonomic regulation and regulation of state clusters were significantly altered in the case group, while motor organization cluster was mainly affected in neonates with severe jaundice (PSB > 25 mg/dl). No differences were noted in the reflex and orientation NBAS clusters.

Conclusion:

Neonatal hyperbilirubinemia causes definite alteration in the neonatal neurobehavior.

Bilirubin induces auditory neuropathy in neonatal guinea pigs via auditory nerve fiber damage

Bilirubin can cause temporary or permanent sensorineural deafness in newborn babies with hyperbilirubinemia. However, the underlying targets and physiological effects of bilirubin-induced damage in the peripheral auditory system are unclear. Using cochlear functional assays and electron microscopy imaging of the inner ear in neonatal guinea pigs, we show here that bilirubin exposure resulted in threshold elevation in both compound action potential (CAP) and auditory brainstem response (ABR), which was apparent at 1 hr and peaked 8 hr after drug administration. The threshold elevation was associated with delayed wave latencies and elongated interwave intervals in ABR and CAP. At 72 hr postinjection, these measures returned to control levels, except for the CAP amplitude. Cochlear microphonics remained unchanged during the experiment. Morphological abnormalities were consistent with the electrophysiological dysfunction, revealing fewer auditory nerve fibers (ANFs) in the basal turn, myelin sheath lesions of spiral ganglion neurons (SGNs) and ANFs, and loss of type 1 afferent endings beneath inner hair cells (IHCs) without loss of hair cells at 8 hr posttreatment. Similar to the electrophysiological findings, morphological changes were mostly reversed 10 days after treatment, except for the ANF reduction in the basal turn. These results suggest that hyperbilirubinemia in neonatal guinea pigs impaired auditory peripheral neuromechanisms that targeted mainly the IHC synapses and the myelin sheath of SGNs and their fibers. Our observations indicate a potential connection between hyperbilirubinemia and auditory neuropathy.

Phototherapy to prevent severe neonatal hyperbilirubinemia in the newborn infant 35 or more weeks of gestation

OBJECTIVE

To standardize the use of phototherapy consistent with the American Academy of Pediatrics clinical practice guideline for the management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation.

METHODS

Relevant literature was reviewed. Phototherapy devices currently marketed in the United States that incorporate fluorescent, halogen, fiber-optic, or blue light-emitting diode light sources were assessed in the laboratory.

RESULTS

The efficacy of phototherapy units varies widely because of differences in light source and configuration. The following characteristics of a device contribute to its effectiveness: (1) emission of light in the blue-to-green range that overlaps the in vivo plasma bilirubin absorption spectrum (~460-490 nm); (2) irradiance of at least 30 μW · cm(-2) · nm(-1) (confirmed with an appropriate irradiance meter calibrated over the appropriate wavelength range); (3) illumination of maximal body surface; and (4) demonstration of a decrease in total bilirubin concentrations during the first 4 to 6 hours of exposure. RECOMMENDATIONS (SEE APPENDIX FOR GRADING DEFINITION): The intensity and spectral output of phototherapy devices is useful in predicting potential effectiveness in treating hyperbilirubinemia (group B recommendation). Clinical effectiveness should be evaluated before and monitored during use (group B recommendation). Blocking the light source or reducing exposed body surface should be avoided (group B recommendation). Standardization of irradiance meters, improvements in device design, and lower-upper limits of light intensity for phototherapy units merit further study. Comparing the in vivo performance of devices is not practical, in general, and alternative procedures need to be explored.

Prevention of neurodevelopmental sequelae of jaundice in the newborn

Although its cause, jaundice in the newborn, is extremely common, the disabling neurological disorder kernicterus is very rare. Kernicterus may be prevented by selecting those infants who are at risk of extreme jaundice or who may be particularly vulnerable to bilirubin neurotoxicity. Because the tools for achieving that goal are inadequate, a secondary strategy is needed. This involves a plan for emergency treatment of severely jaundiced infants, in particular those who present with neurological symptoms. In this paper I review the strategies for preventing extreme jaundice, and for reversing neurotoxicity in those infants for whom the principal strategies fail. Briefly, the tools for prevention include measurement of bilirubin while the infant is staying in the maternity unit, plotting the value on an hour-specific chart, assessing other risk factors for jaundice, and educating the parents. Emergency treatment should include immediate, high-irradiance phototherapy, consideration of intravenous immune globulin, and preparation for an exchange transfusion.

Neonatal screening for glucose-6-phosphate dehydrogenase deficiency: biochemical versus genetic technologies

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, a commonly occurring genetic condition, is associated in neonates with severe hemolytic episodes, extreme hyperbilirubinemia, and bilirubin encephalopathy. Neonatal screening programs for the condition should increase parental and caretaker awareness, thereby facilitating early access to treatment with resultant diminished mortality and morbidity. However, screening for G-6-PD deficiency is not widely performed. Although G-6-PD-deficient males may be accurately identified, females are more difficult to categorize because many in this group may be heterozygotes with phenotype overlap between normal homozygotes, heterozygotes, and deficient homozygotes. Screening methodologies include biochemical qualitative assays, quantitative enzymatic activity measurements and DNA-based polymerase chain reaction molecular screening. The appropriateness of any of these technologies for any particular population group or geographic area must be assessed before setting up a screening program. The pros and cons of each method, including ease of testing, cost, need for sophisticated laboratory equipment and degree of personnel training, as well as the ability to identify females, are discussed.

The role of phototherapy in the crash-cart approach to extreme neonatal jaundice

Extreme neonatal jaundice occurs infrequently but carries a high risk of permanent sequelae (kernicterus) when it does. Rapid therapeutic intervention has the potential to reduce this risk in some infants. Several case reports of infants with acute intermediate to advanced bilirubin encephalopathy shows that reversal may be possible. Phototherapy can be instituted at the flip of a switch, whereas other therapeutic measures necessarily involve delays. Therefore, high-intensity phototherapy must be regarded as an emergency measure in infants presenting with extreme jaundice and even more so in the presence of neurological symptoms. The principal and well-described effect of phototherapy involves conversion of bilirubin IXα (z, z) to more polar isomers, which are excreted in bile and urine. When care is taken to maximize the spectral power of phototherapy lights, and whenever possible with measures added to reduce the enterohepatic circulation of bilirubin, very rapid reductions in total serum bilirubin levels are possible. A hypothesis has been advanced that conversion of bilirubin to more polar photoisomers, which can reach relative concentrations of 20%-25% of total serum bilirubin within 1-2 hours, might have a direct neuroprotective effect. This theory posits that because polar molecules generally require a transporter to cross the blood-brain barrier, bilirubin photoisomers should be less prone to enter the brain. Although this theory has some support in in vitro toxicity studies, the evidence is controversial. Until further experimental support can be gained, photoconversion of bilirubin does not constitute a viable argument against instituting further measures against bilirubin neurotoxicity, such as intravenous immune globulin (when indicated) and exchange transfusion. Conversely, neither is the state of evidence an argument against immediate and effective phototherapy in the medical emergency of extreme neonatal jaundice.

National guidelines for treatment of jaundice in the newborn

Jaundice is the most common reason for instituting treatment in otherwise healthy as well as sick newborn infants. Herein, we describe the process employed in Norway to forge agreement on a set of treatment guidelines that are now used across the country. The Norwegian Pediatric Association was a key resource in this process, which involved contacts with all paediatric departments in Norway. We have also performed an international survey regarding the use of such national guidelines, showing that the majority of those queried confirm having national guidelines. The evidence base for any neonatal jaundice guideline is weak; therefore, it is not surprising that the various guidelines differ both in format and in specifics. In the Norwegian guidelines, treatment indications are based on bilirubin concentrations and related to birth weight. Postnatal age is also factored in because jaundice develops gradually during the first 3-4 days before it levels off.

CONCLUSION

Following the introduction of these guidelines, fewer babies in Norway receive phototherapy, and no cases of chronic kernicterus have been reported during this period.

Severe neonatal hyperbilirubinemia and kernicterus: are these still problems in the third millennium?

Despite efforts to eliminate permanent and irreversible brain damage due to bilirubin encephalopathy and kernicterus, these conditions continue to accompany us into the third millennium. This phenomenon occurs not only in developing countries with emerging medical systems, but in Westernized countries as well. Comprehensive guidelines to detect newborns with jaundice and treat those in whom hyperbilirubinemia has already developed have been formulated in several countries, but have not been successful in completely eliminating the problem. In this appraisal of the situation we review selected aspects of bilirubin encephalopathy and/or kernicterus. We highlight recent reports of severe hyperbilirubinemia and kernicterus, discuss some of the factors responsible for the continuing appearance of these conditions, and briefly review what can be done to decrease bilirubin-related morbidity and mortality to the minimum.

Phototherapy for neonatal jaundice--therapeutic effects on more than one level?

Phototherapy for jaundice is a common treatment in neonatal medicine and is used to prevent the neurotoxic effects of bilirubin. Studies have assessed the optimal wavelength of phototherapy light, the importance of irradiance and spectral power, and the types of light source, including the use of single versus multiple light sources. Outcome measures have been duration of need for phototherapy or rate of reduction of serum bilirubin over a given time. An apparent resurgence of kernicterus in recent years has forced us to focus on the emergency management of severely jaundiced infants. Several studies have shown that very rapid reductions of total serum bilirubin levels are possible. The speed with which photoisomers are formed appears to be important both from this perspective and theoretically may also be neuroprotective because of the more polar nature of the photoisomers. This work reviews the evidence concerning the speed of photoisomer formation, as well as the evidence regarding the relative neurotoxicity of bilirubin isomers.

Early isomerization of bilirubin in phototherapy of neonatal jaundice

Neonatal jaundice is usually treated with phototherapy that converts bilirubin to more polar stereoisomers. These should theoretically be less able to cross the blood-brain barrier. The rates of photoisomer formation and concentrations accumulating in the circulation may have a bearing on the risk of kernicterus. The purpose of this study was to determine the rate of appearance of the major 4Z, 15E photoisomer of bilirubin during the early stages of phototherapy. Twenty jaundiced neonates were treated with phototherapy, and blood samples were drawn before and at approximately 15, 30, 60, and 120 min (10 infants) or at approximately 15, 60, 120, and 240 min (10 infants) after beginning phototherapy. Blood samples were analyzed for total serum bilirubin (TSB) and the 4Z, 15E photoisomer of bilirubin. Significant (p<0.0001) formation of the 4Z, 15E photoisomer was detectable within 15 min. The change in TSB from time 0 was insignificant at 120 min but reached significance at 240 min (p<0.001). The 4Z, 15E bilirubin constituted up to 20-25% of TSB at 2 h and may not have peaked by 4 h. Further studies are needed to determine whether this early shift in balance between bilirubin isomers with different polarities may impact the risk of bilirubin encephalopathy even before TSB starts to fall.