Unbound bilirubin measurements in term and late-preterm infants

How should hyperbilirubinemia be considered in the definition of the hearing screening protocol for neonates at risk?

PURPOSE

To analyze hyperbilirubinemia as an indicator for the definition of risk protocol in newborn hearing screening (NHS) and in auditory monitoring in full-term and preterm neonates.

METHODS

This is an observational, cross-sectional and retrospective study. A total of 554 children born in a public maternity hospital were included and divided into two groups: (G1) with 373 full-terms neonates; (G2) with 181 preterm neonates. Data were collected from the participant's medical records to obtain information regarding the result of the NHS, performed by recording the automated auditory brainstem response (AABR), birth conditions, clinical characteristics, interventions performed, and results of the first test of total bilirubin (TB) and indirect bilirubin (IB) as well as the peak of TB and IB. A descriptive statistical analysis of the results was performed, and the level of significance adopted was 5%.

RESULTS

On the NHS test, quotes of retest referral rates were smaller in G1 when compared to G2. There was no significant difference between the groups regarding type of delivery, gender, presence of Rh and ABO incompatibility, G6PD enzyme deficiency, and performance of phototherapy. TB and IB levels at the first exam and at peak time did not differ between neonates with "pass" and "fail" results on the NHS test in both groups.

CONCLUSION

Bilirubin levels in the neonatal period below the recommended values for indication of exchange transfusion are not directly related to the "fail" result on the NHS tests in term and preterm neonates.

Current status of neonatal jaundice management in Japan

BACKGROUND

This nationwide survey aimed to determine the status of jaundice management in Japan.

METHODS

A questionnaire about bilirubin level measurements and neonatal jaundice treatment was sent to 330 institutions providing neonatal care. The responses were analyzed according to institution level.

RESULTS

Of 330 institutions, 172 responded (52.1% response rate). Total bilirubin levels were measured in the central laboratory using spectrophotometry at 134 institutions and a blood gas analyzer at 81 institutions. Unbound bilirubin (UB) levels were measured by 79 institutions, while transcutaneous bilirubin measurements were taken at 63 institutions. There was no association between institution level and UB or transcutaneous bilirubin measurement. For phototherapy criteria, the Murata-Imura criteria were adopted by 67 institutions, Nakamura criteria by 36, and Morioka criteria by 39. Light-emitting diodes (LED) were used by 160 institutions versus fluorescent lights by 31. When a blue LED was used, 119 institutions used the high mode. There is no standard for increasing light intensity. No association was found between institution level and phototherapy criteria. UB was measured in 14 of 63 institutions using the Murata-Imura criteria.

CONCLUSIONS

There is a large variation in the management and treatment of neonatal jaundice among institutes in Japan.

Effects of lipid emulsions on unbound bilirubin and response to phototherapy in preterm infants

OBJECTIVE

Bilirubin-induced neurotoxicity is mediated by the fraction of total serum bilirubin (TSB) not bound to albumin (Bf). Unbound free fatty acids (FFAu) generated from lipid emulsions compete with bilirubin for albumin binding, increasing Bf. Soy-based (IL) and soy-MCT-olive-fish oil-based (SMOF) lipid emulsions contain different fatty acids with distinct albumin binding affinities. IL increases Bf in preterm infants, but the effects of SMOF on Bf are not known. Our objective was to compare changes in TSB, Bf, FFAu, and response to phototherapy in preterm infants receiving SMOF and IL. We hypothesized that SMOF would be associated with lower Bf and better response to phototherapy than IL.

METHODS

Very preterm and low birth weight infants (<1500 g, <32 weeks) were infused with IL (n = 20) or SMOF (n = 20) as prescribed by providers. Phototherapy was prescribed using the standard care practice. FFAu profiles and levels, TSB, and Bf were measured on 0, 1, 2, and 3 g/kg/day of lipid infusion and at the initiation and termination of phototherapy. TSB was analyzed in the clinical laboratory using the diazo technique. FFAu and Bf were measured using fluorescent probes.

RESULTS

Escalating doses of IL and SMOF increased FFAu levels and Bf, but not TSB. Phototherapy did not significantly decrease Bf for infants receiving either lipid. IL-treated infants had higher levels of unbound linoleic acid, and SMOF-treated infants had higher unbound arachidonic, oleic, and docosahexaenoic acids.

CONCLUSIONS

IL and SMOF both increase Bf similarly, and phototherapy does not significantly affect Bf for infants receiving them.

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.

[The Role of Nrf2 Pathway Activation in Hippocampal Neuron Injury of Neonatal Rats with Bilirubin Encephalopathy]

OBJECTIVE

To explore the effect of nuclear factor-erythroid 2-related factor (Nrf2) pathway activation on hippocampal neuron damage in neonatal rats with bilirubin encephalopathy.

METHODS

Neonatal rats were randomly assigned to a control group (Control), a model group (Model) and an Nrf2 activator TBHQ (tert-Butylhydroquinone) group (TBHQ), with 20 rats in each group. Bilirubin solution was injected through the cerebellomedullary cistern to establish the neonatal rat model of bilirubin encephalopathy. Neurobehavioral changes were observed in rats and the water content of the brain tissue was measured. Nissl staining was done to observe the damage of hippocampal neurons. TUNEL staining was used to observe the apoptosis of hippocampal neurons. Colorimetric analysis was done to determine the Caspase-3 activity in the hippocampus. The content of malondialdehyde (MDA) and reduced glutathione (GSH) and the activity of superoxide dismutase (SOD) in the hippocampus were examined by chemical analysis. qRT-PCR and Western blot were done to measure the expression of Nrf2 and heme oxygenase-l (HO-1) mRNA and proteins in the hippocampus.

RESULTS

After injection of bilirubin into the cerebellomedullary cistern, the young rats in the Model group and the TBHQ group showed different degrees of neurological abnormalities, while those in the control group showed no significant neurobehavioral abnormalities. Compared with the Control group, the Model group had severe neuronal damage, and the water content of brain tissue, the apoptosis of hippocampal neurons, the activity of Caspase-3 and the content of MDA content significantly increased ( P<0.01), while the SOD activity, GSH content, the expression of Nrf2 and HO-1 mRNA and proteins significantly decreased ( P<0.05). Compared with the Model group, neuronal damage was improved in the TBHQ group, and the water content of brain tissue, apoptosis of hippocampal neurons, activity of Caspase-3 and MDA content were all significantly reduced ( P<0.01), while SOD activity, GSH content and the expression of Nrf2 and HO-1 mRNA and proteins were significantly increased ( P<0.05).

CONCLUSION

Activation of the Nrf2 pathway can improve hippocampal neuronal damage in neonatal rats with bilirubin encephalopathy and inhibit neuronal apoptosis and the oxidation reaction.

Curcumin Prevents Cerebellar Hypoplasia and Restores the Behavior in Hyperbilirubinemic Gunn Rat by a Pleiotropic Effect on the Molecular Effectors of Brain Damage

Bilirubin toxicity to the central nervous system (CNS) is responsible for severe and permanent neurologic damage, resulting in hearing loss, cognitive, and movement impairment. Timely and effective management of severe neonatal hyperbilirubinemia by phototherapy or exchange transfusion is crucial for avoiding permanent neurological consequences, but these therapies are not always possible, particularly in low-income countries. To explore alternative options, we investigated a pharmaceutical approach focused on protecting the CNS from pigment toxicity, independently from serum bilirubin level. To this goal, we tested the ability of curcumin, a nutraceutical already used with relevant results in animal models as well as in clinics in other diseases, in the Gunn rat, the spontaneous model of neonatal hyperbilirubinemia. Curcumin treatment fully abolished the landmark cerebellar hypoplasia of Gunn rat, restoring the histological features, and reverting the behavioral abnormalities present in the hyperbilirubinemic rat. The protection was mediated by a multi-target action on the main bilirubin-induced pathological mechanism ongoing CNS damage (inflammation, redox imbalance, and glutamate neurotoxicity). If confirmed by independent studies, the result suggests the potential of curcumin as an alternative/complementary approach to bilirubin-induced brain damage in the clinical scenario.