Hyperbilirubinemia and bilirubin toxicity in the late preterm infant

Assessment of Knowledge and Attitudes of Parents Regarding Neonatal Jaundice in Abia State Children's Specialist Hospital, Umuahia, Nigeria: A Cross-Sectional Study

Background Neonatal jaundice, characterized by the yellow discoloration of an infant's skin and eyes, is a common condition that affects newborns. It results from an elevated level of bilirubin in the blood and, when severe, if left untreated, can lead to complications such as acute bilirubin encephalopathy and kernicterus, which can cause permanent neurological damage or even death. In low-resource settings like Nigeria, delayed recognition and inadequate management of neonatal jaundice are significant contributors to neonatal morbidity and mortality. Parental knowledge and attitudes play a critical role in the early identification and timely intervention of neonatal jaundice. However, there is limited data on the awareness, understanding, and practices of parents regarding this condition in many regions, including Abia State, Nigeria.  Aim This study sought to assess the knowledge and attitudes of parents at Abia State Children's Specialist Hospital, Umuahia, Nigeria, to inform strategies for improving early detection and management of neonatal jaundice. Research methodology This descriptive cross-sectional study was conducted at Abia State Children's Specialist Hospital. The study population included 385 parents (fathers and mothers) of neonates attending the pediatric and neonatal units. A systematic random sampling technique was used to select participants. Data were collected using a structured questionnaire and analyzed using IBM SPSS Statistics for Windows, Version 25, (Released 2017; IBM Corp., Armonk, New York, United States). Results The study revealed that 226 (58.70%) of parents had heard about neonatal jaundice, with the main perceived cause being an immature liver (148, 38.44%). While 216 (56.10%) of the parents recognized neonatal jaundice as a serious condition when severe, only 72 (18.70%) were very confident in identifying its signs. Most parents (369, 95.84%) would seek medical help if they suspected jaundice in their baby, yet 288 (74.81%) believed in the effectiveness of traditional remedies. Educational level and gender were significantly associated with knowledge about neonatal jaundice (p = 0.002 and p = 0.001, respectively). Conclusion The findings highlight a moderate level of awareness but varying confidence in identifying neonatal jaundice among parents. The reliance on traditional remedies suggests a need for enhanced health education to improve knowledge of and attitudes toward neonatal jaundice management.

Combating the Hidden Health Disparity of Kernicterus in Black Infants: A Review

IMPORTANCE

Kernicterus is a devastating, permanently disabling neurologic condition resulting from bilirubin neurotoxicity. Black neonates account for more than 25% of kernicterus cases in the US, despite making up only approximately 14% of all births. This is a largely overlooked health disparity.

OBSERVATIONS

The black kernicterus health disparity exists despite a lower overall incidence of clinically significant hyperbilirubinemia among black neonates, a paradox recently explained by a previously unrecognized risk for hazardous hyperbilirubinemia. Aligned with national and global health initiatives to reduce or eliminate health disparities, this review highlights the multiple biologic and nonbiologic factors contributing to kernicterus risk in black infants and approaches to reduce this health disparity. This includes both parent-level and clinician-level kernicterus prevention strategies, with an emphasis on improving parental health literacy on neonatal jaundice and acute bilirubin encephalopathy and clinician awareness of the key factors that contribute to hazardous hyperbilirubinemia risk in this vulnerable group. Parent-level prevention strategies include efforts to improve their health literacy on neonatal jaundice and acute bilirubin encephalopathy and empower care seeking for jaundice. Clinician-level prevention strategies include efforts to eliminate community and institutional barriers that impede access to care, heighten clinician awareness of the factors that contribute to kernicterus risk in this vulnerable patient group, and strengthen newborn hyperbilirubinemia management and bilirubin surveillance.

CONCLUSIONS AND RELEVANCE

There are multiple opportunities for intervention to reduce black kernicterus risk. Although kernicterus is a rare disorder, the incidence among black infants is not a trivial matter nor are efforts to prevent kernicterus. While the multiple interacting biologic and nonbiologic contributors to increased kernicterus risk among black infants pose a considerable challenge to clinicians, there are opportunities for intervention to reduce this risk and health disparity. Continued study is imperative to understand the current scope of kernicterus and its occurrence in black neonates.

Influence of single nucleotide polymorphisms (SNPs) in immunoregulatory genes in the morbidity of preterm newborns

Background: Prematurity is the main cause of perinatal and neonatal morbidity and mortality worldwide. Single nucleotide polymorphisms (SNPs) have been associated with the pathogenesis of morbidities in preterm neonates. We aimed to investigate the association between SNPs in regulatory genes of innate immune response IL1B, IL6, IL6R, IL10, TNFA, TNFRII, TLR2 and TLR4 and neonatal/infant morbidities in preterm newborns.Methods: Oral swabs were collected from 272 newborns (91 preterm and 181 at term) seen at Botucatu Medical School, Unesp, between 2013 and 2014 and SNPs were identified using Taqman^® Genotyping Assays. Medical records were examined to obtain data regarding neonatal/infant morbidity. Stepwise binomial logistic regression models were used to explain the morbidities.Results: Minor neonatal morbidity was influenced by the clinical parameters of maternal age and newborn weight at birth and by the presence of the allele IL6R2 C (rs2228145) while major neonatal morbidity was only influenced by gestational age. Minor infant morbidity was associated with the allele TLR2 T (rs4696480) and major infant morbidity was associated with gestational age and presence of IL6R2 C.Conclusion: The presence of SNPs that exacerbate the inflammatory response increases the susceptibility to neonatal and infant morbidity.

Neonatal morbidity in late preterm small for gestational age neonates

INTRODUCTION

To compare neonatal respiratory morbidity among small for gestational age (SGA; birth weight less than 10th percentile for gestational age) versus appropriate for gestational age (AGA; BW at 10-90th percentile) neonates born in the late preterm period.

METHODS

A secondary analysis of a multicenter randomized trial of antenatal corticosteroids for women at risk for late preterm birth. Singleton, nonanomalous, AGA or SGA births that delivered at 34-36 weeks were included. Women were excluded if they delivered after 37 weeks or had a large for gestational age baby (LGA; weight over 90th for gestational age). The primary outcome was a composite of any of the following: respiratory support by 72 h (continuous positive airway pressure or high flow nasal cannula ≥2 h, oxygen with a fraction of inspired oxygen of ≥30% for ≥4 h, extra corporeal membrane oxygenation or mechanical ventilation) or neonatal death. The secondary outcomes included several neonatal and maternal morbidities. Multivariable Poisson regression models were used to examine the association between neonatal weight and outcomes (using adjusted relative risk [aRR] and 95% confidence intervals [CI]).

RESULTS

Of the 2831 women in the parent trial, 2315 (82%) women met inclusion criteria; among them, 426 (18%) of the neonates were SGA. There was no significant difference in the risk of the primary outcome between SGA and AGA (13.1 versus 15.1%, aRR 0.85, 95% CI 0.66-1.10). SGA, however, was associated with an increased risk for neonatal intensive care unit admission (68 versus 45%, aRR 1.60, 95% CI 1.47-1.74), hypothermia (12.2 versus 8.8%, aRR 1.36, 95% CI 1.01-1.83), feeding problems (47.2 versus 36.9%, aRR 1.24, 95% CI 1.07-1.45) and a decreased risk of neonatal hyperbilirubinemia (7.5 versus 12.7%, aRR 0.59, 95% CI 0.41-0.84), when compared to AGA.

CONCLUSION

In this cohort of late preterm birth, there was no significant difference in the rate of composite respiratory morbidity between SGA and AGA newborns.

Plasma proteome changes in cord blood samples from preterm infants

OBJECTIVE

In the presented study, we aimed to systematically analyze plasma proteomes in cord blood samples from preterm infants stratified by their gestational age to identify proteins and related malfunctioning pathways at birth, possibly contributing to the complications observed among preterm infants.

STUDY DESIGN

Preterm newborns were enrolled of three subgroups with different gestation age: newborns born ≤26 (group 1), between 27 and 28 (group 2) and between 29 and 30 (group 3) weeks of gestation, respectively, and compared to the control group of healthy, full-term newborns in respect to their plasma proteome composition.

RESULT

Preterm delivery is associated with multiple protein abundance changes in plasma related to a plethora of processes, including inflammation and immunomodulation, coagulation, and complement activation as some key features.

CONCLUSION

Plasma proteome analysis revealed numerous gestation-age-dependent protein abundance differences between term and preterm infants, which highlight key dysregulated pathways and potential new protein treatment targets.

Risk Factors Associated with Neonatal Jaundice: A Cross-Sectional Study from Iran

BACKGROUND

Neonatal jaundice is one of the main causes of the patient's admission in the neonatal period and is potentially linked to morbidity.

AIM

This study aimed to determine the possible risk factors for neonatal jaundice.

METHODS

We investigated the case of infants who were admitted to the neonatal department of Ziyaeian hospital and Imam Khomeini Hospital for jaundice. Simple random sampling was used to evaluate variables related to maternal and neonatal predisposing factors based on the medical records and clinical profiles. All variables in this study were analysed using SPSS software.

RESULTS

In this study, about 200 mothers and neonates were examined. Our findings depicted that mother's WBC, Hb, PLT, and gestational age were associated with jaundice (P < 0.05). Furthermore, there were significant relationships between different degrees of bilirubin with TSH, T4 levels and G6PD (P < 0.05). In fact, TSH, T4 levels and G6PD were found to be linked to neonatal hyperbilirubinemia. The risk factors for jaundice in our study population comprise some predisposing factors such as WBC, Hb, PLT, gestational age, TSH, and T4 levels, as well as G6PD. Neonates at risk of jaundice are linked to some maternal and neonatal factors that can provide necessary interventions to reduce the burden of the disease. Therefore, identification of associated factors can facilitate early diagnosis, and reduce subsequent complications.

CONCLUSION

Neonatal jaundice should be considered as the main policy in all health care settings of the country. Therefore, identification of factors affecting the incidence of jaundice can be effective in preventing susceptible predisposing factors in newborns and high-risk mothers.

Point-of-Care Testing for G6PD Deficiency: Opportunities for Screening

Glucose-6-phosphate dehydrogenase (G6PD) deficiency, an X-linked genetic disorder, is associated with increased risk of jaundice and kernicterus at birth. G6PD deficiency can manifest later in life as severe hemolysis, when the individual is exposed to oxidative agents that range from foods such as fava beans, to diseases such as typhoid, to medications such as dapsone, to the curative drugs for Plasmodium (P.) vivax malaria, primaquine and tafenoquine. While routine testing at birth for G6PD deficiency is recommended by the World Health Organization for populations with greater than 5% prevalence of G6PD deficiency and to inform P. vivax case management using primaquine, testing coverage is extremely low. Test coverage is low due to the need to prioritize newborn interventions and the complexity of currently available G6PD tests, especially those used to inform malaria case management. More affordable, accurate, point-of-care (POC) tests for G6PD deficiency are emerging that create an opportunity to extend testing to populations that do not have access to high throughput screening services. Some of these tests are quantitative, which provides an opportunity to address the gender disparity created by the currently available POC qualitative tests that misclassify females with intermediate G6PD activity as normal. In populations where the epidemiology for G6PD deficiency and P. vivax overlap, screening for G6PD deficiency at birth to inform care of the newborn can also be used to inform malaria case management over their lifetime.

Diagnosis Accuracy of Transcutaneous Bilirubinometry in Very Preterm Newborns

BACKGROUND

Transcutaneous bilirubin (TcB) is a validated test for systematic screening of neonatal hyperbilirubinemia and monitoring term and near-term infants under phototherapy.

OBJECTIVES

To evaluate TcB diagnostic accuracy for very preterm neonates.

METHODS

Total serum bilirubin (TSB) and TcB measurements were performed prospectively in a multicenter sample of newborns <30 weeks of gestational age (GA). TcB sensitivity, specificity, predictive values, and likelihood ratios for the detection of neonates requiring phototherapy were calculated over the first 15 days of life, with or without phototherapy, with the expectation of achieving a detection rate of hyperbilirubinemia of over 95%. The potential influence of neonatal characteristics on the discordance between TcB and TSB in very preterm newborns was analyzed using multivariate multilevel logistic regression analyses.

RESULTS

Altogether, 481 measurements were analyzed in 167 preterm patients. Mean GA was 27.6 ± 1.6 weeks. The rates of newborns requiring phototherapy were 52% in the first 3 days, 16% from the 4th to the 7th day, and 2% during the second week. Diagnostic performance was similar among babies with or without phototherapy. TcB sensitivity decreased over time from 100% (93.9-100.0) to 50% (1.3-98.7). Specificity showed an inverse evolution from 14.8% (7.0-26.2) to 80.7% (72.2-89.2). The best performance was that of negative predictive values which varied from 95.5 to 100.0. False negatives were rare throughout the study (0.8% of measurements). In a multivariate analysis, the only factor significantly influencing discordance between TcB and TSB was postnatal age. We did not find any impact of GA and skin color.

CONCLUSION

Among very preterm babies, TcB measurements might be useful for screening for neonatal jaundice in the first 2 weeks of life. In case of a TcB value below the phototherapy threshold, invasive TSB quantification could be unnecessary, with potential avoidance of blood drawing.

The Preterm Infant: A High-Risk Situation for Neonatal Hyperbilirubinemia Due to Glucose-6-Phosphate Dehydrogenase Deficiency

Prematurity and glucose-6-phosphate dehydrogenase (G6PD) deficiency are risk factors for neonatal hyperbilirubinemia. The 2 conditions may interact additively or synergistically, contributing to extreme hyperbilirubinemia, with the potential for bilirubin neurotoxicity. This hyperbilirubinemia is the result of sudden, unpredictable, and acute episodes of hemolysis in combination with immaturity of bilirubin elimination, primarily of conjugation. Avoidance of contact with known triggers of hemolysis in G6PD-deficient individuals will prevent some, but not all, episodes of hemolysis. All preterm infants with G6PD deficiency should be vigilantly observed for the development of jaundice both in hospital and after discharge home.

Cadmium and arsenic override NF-κB developmental regulation of the intestinal UGT1A1 gene and control of hyperbilirubinemia

Humanized UDP-glucuronosyltransferase (UGT)-1 (hUGT1) mice encode the UGT1 locus including the UGT1A1 gene. During neonatal development, delayed expression of the UGT1A1 gene leads to hyperbilirubinemia as determined by elevated levels of total serum bilirubin (TSB). We show in this report that the redox-sensitive NF-κB pathway is crucial for intestinal expression of the UGT1A1 gene and control of TSB levels. Targeted deletion of IKKβ in intestinal epithelial cells (hUGT1/Ikkβ(ΔIEC) mice) leads to greater neonatal accumulation of TSB than observed in control hUGT1/Ikkβ(F/F) mice. The elevation in TSB levels in hUGT1/Ikkβ(ΔIEC) mice correlates with a reduction in intestinal UGT1A1 expression. As TSB levels accumulate in hUGT1/Ikkβ(ΔIEC) mice during the neonatal period, the increase over that observed in hUGT1/Ikkβ(F/F) mice leads to weight loss, seizures and eventually death. Bilirubin accumulates in brain tissue from hUGT1/Ikkβ(ΔIEC) mice inducing an inflammatory state as shown by elevated TNFα, IL-1β and IL-6, all of which can be prevented by neonatal induction of hepatic or intestinal UGT1A1 and lowering of TSB levels. Altering the redox state of the intestines by oral administration of cadmium or arsenic to neonatal hUGT1/Ikkβ(F/F) and hUGT1/Ikkβ(ΔIEC) mice leads to induction of UGT1A1 and a dramatic reduction in TSB levels. Microarray analysis following arsenic treatment confirms upregulation of oxidation-reduction processes and lipid metabolism, indicative of membrane repair or synthesis. Our findings indicate that the redox state in intestinal epithelial cells during development is important in maintaining UGT1A1 gene expression and control of TSB levels.

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.

A national survey of admission practices for late preterm infants in England

Background

Infants born at 34⁺⁰ to 36⁺⁶ weeks gestation are defined as ‘late preterm’ infants. It is not clear whether these babies can be managed on the postnatal ward (PNW) or routinely need to be admitted to the neonatal unit after birth.

Aim

To conduct a national survey of admission practice for late preterm and low birth weight infants directly to the PNW after birth in England.

Methods

All neonatal units were identified from the Standardised Electronic Neonatal Database (SEND). Individual units were contacted and data collected on their admission practice.

Results

All 180 neonatal units in England responded. 49, 84 and 47 Units were Special Care Units (SCUs), Local Neonatal Units (LNUs) and Neonatal Intensive Care Units (NICUs) respectively. 161 units (89%) had written guidelines in relation to direct PNW admission for late preterm infants.

The mean gestational age of infants admitted directly to the PNW was significantly lower in LNUs compared to SCUs and NICUs compared to LNUs. Mean birth weight limit for direct PNW admission was significantly lower in NICUs compared to SCUs.

72 units had PNW nursery nurses. There was no significant difference in gestational age or birth weight limit for direct PNW admission in the presence of PNW nursery nurses.

Conclusions

Admission practices of late preterm infants directly to the PNW varies according to designation of neonatal unit in England. Further studies are needed to establish the factors influencing these differences.

Short-term respiratory outcomes in late preterm infants

Objective

To evaluate short-term respiratory outcomes in late preterm infants (LPI) compared with those of term infants (TI).

Methods

A retrospective study conducted in a single third level Italian centre (2005–2009) to analyse the incidence and risk factors of composite respiratory morbidity (CRM), the need for adjunctive therapies (surfactant therapy, inhaled nitric oxide, pleural drainage), the highest level of respiratory support (mechanical ventilation – MV, nasal continuous positive airway pressure – N-CPAP, nasal oxygen) and the duration of pressure support (hours in N-CPAP and/or MV).

Results

During the study period 14,515 infants were delivered. There were 856 (5.9%) LPI and 12,948 (89.2%) TI. CRM affected 105 LPI (12.4%), and 121 TI (0.9%), with an overall rate of 1.6%. Eighty-four LPI (9.8%) and 73 TI (0.56%) received respiratory support, of which 13 LPI (1.5%) and 16 TI (0.12%) were ventilated. The adjusted OR for developing CRM significantly increased from 3.3 (95% CI 2.0-5.5) at 37 weeks to 40.8 (95% CI 19.7-84.9%) at 34 weeks. The adjusted OR for the need of MV significantly increased from 3.4 (95% CI 1.2-10) at 37 weeks to 34.4 (95% CI 6.7-180.6%) at 34 weeks. Median duration of pressure support was significantly higher at 37 weeks (66.6 h vs 40.5 h). Twin pregnancies were related to a higher risk of CRM (OR 4.3, 95% CI 2.6-7.3), but not independent of gestational age (GA). Cesarean section (CS) was associated with higher risk of CRM independently of GA, but the OR was lower in CS with labour (2.2, 95% CI 1.4-3.4 vs 3.0, 95% CI 2.1-4.2).

Conclusions

In this single third level care study late preterm births, pulmonary diseases and supportive respiratory interventions were lower than previously documented. LPI are at a higher risk of developing pulmonary disease than TI. Infants born from elective cesarean sections, late preterm twins in particular and 37 weekers too might benefit from preventive intervention.

Metyrapone, an inhibitor of cytochrome oxidases, does not affect viability in a neuroblastoma cell model of bilirubin toxicity

Background

Unconjugated hyperbilirubinemia may cause brain damage in infants, and globally remains a source of neonatal morbidity and mortality. A significant inter-individual variability in vulnerability to bilirubin toxicity remains largely unexplained. An enzyme located in mitochondria oxidizes bilirubin. We hypothesized that inhibiting bilirubin oxidation in human neuronal cell cultures exposed to bilirubin would increase cell death.

Methods

The ability of mitochondrial membranes from CHP-212 human neuroblastoma cells to oxidize bilirubin was verified by spectrophotometry. Intact cells in culture were exposed to bilirubin (75 μM) with or without metyrapone (250 μM) for 24 h, stained with Annexin-V and Propidium iodide and analyzed for apoptosis and necrosis by flow cytometry.

Results

Bilirubin caused a significant reduction of viability, from 84 ± 2.0% (mean ± SEM) vs 67 ± 2.7% (p < 0.05), but adding metyrapone to the bilirubin-exposed cells did not further impact cell viability. Metyrapone alone did not influence cell viability.

Conclusion

Herein we have shown that metyrapone does not increase cell death in neuroblastoma cells in culture exposed to bilirubin. Our results question the relationship between the oxidative mechanism evaluated by spectrophotometry and cell viability. Our findings add to the discussion on whether bilirubin oxidation represents a potentially important protective mechanism in neurons challenged by hyperbilirubinemia.

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Neonatal jaundice may cause brain damage in newborn infants.

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Oxidation of bilirubin in the brain has been proposed as a protective mechanism.

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In a cell model, blocking the enzyme responsible for bilirubin oxidation did not increase toxicity.

Management of breastfeeding during and after the maternity hospitalization for late preterm infants

Among infants born moderately and late preterm or early term, the greatest challenge for breastfeeding management is the late preterm infant (LPI) who is cared for with the mother in the maternity setting. Breastfeeding failure among LPIs and their mothers is high. Evidence-based strategies are needed to protect infant hydration and growth, and the maternal milk supply, until complete feeding at breast can be established. This article reviews the evidence for lactation and breastfeeding risks in LPIs and their mothers, and describes strategies for managing these immaturity-related feeding problems. Application to moderately and early preterm infants is made throughout.

Moderately preterm, late preterm and early term infants: research needs

In spite of increased appreciation that all preterm infants and early term infants are at higher risk for mortality and morbidities compared with their term counterparts, there are many knowledge gaps affecting optimal clinical care for this vulnerable population. This article presents a research agenda focusing on the systems biology, epidemiology, and clinical and translational sciences on this topic.

Hospital readmissions and emergency department visits in moderate preterm, late preterm, and early term infants

The increased vulnerability of late preterm infants is no longer a novel concept in neonatology, with many studies documenting excess morbidity and mortality in these infants during the birth hospitalization. Because outcomes related to gestational age constitute a continuum, it is important to analyze data from the gestational age groups that bookend late preterm infants infants-moderate preterm infants (31-32 weeks) and early term infants (37-38 weeks). This article evaluates hospital readmissions and emergency department visits in the first 30 days after discharge from birth hospitalization in a large cohort of infants greater than or equal to 31 weeks' gestation.

Incidence of and risk factors for neonatal jaundice among newborns in southern Nepal

OBJECTIVE

To quantify the incidence of and risk factors for neonatal jaundice among infants referred for care from a rural, low-resource, population-based cohort in southern Nepal.

METHODS

Study participants were 18,985 newborn infants born in Sarlahi District in southern Nepal from May 2003 through January 2006 who participated in a cluster-randomised, placebo-controlled, community-based trial to evaluate the effect of newborn chlorhexidine cleansing on neonatal mortality and morbidity. Jaundice was assessed based on visual assessment of the infant by a study worker and referral for care. Adjusted relative risks (RR) were estimated to identify risk factors for referral for neonatal jaundice using Poisson regression.

RESULTS

The incidence of referral for neonatal jaundice was 29.3 per 1000 live births (95% confidence interval: 26.9, 31.7). Male sex, high birth weight, breastfeeding patterns, warm air temperature, primiparity, skilled birth attendance, place of delivery, prolonged labour, oil massage, paternal education and ethnicity were significant risk factors (P-values < 0.01). After multivariable adjustment, sex, birth weight, difficulty feeding, prolonged labour, primiparity, oil massage, ambient air temperature and ethnicity remained important factors. Among infants with difficulty feeding, exclusive breastfeeding was a risk factor for neonatal jaundice, whereas exclusive breastfeeding was protective among infants with no report of difficulty feeding.

CONCLUSIONS

Several known risk factors for neonatal jaundice in a low-resource setting were confirmed in this study. Unique observed associations of jaundice with ambient air temperature and oil massage may be explained by the opportunity for phototherapy based on the cultural practices of this study population. Future research should investigate the role of an infant's difficulty in feeding as a potential modifier in the association between exclusive breastfeeding and jaundice.

Factors affecting bilirubin levels during first 48 hours of life in healthy infants

OBJECTIVE

To investigate the relationship of delivery type, maternal anesthesia, feeding modalities, and first feeding and meconium passage times with early bilirubin levels of healthy infants.

METHODS

Cord, 24 hours' and 48 hours' total bilirubin levels were measured in 388 study infants.

RESULTS

Infants born with cesarean section were fed later and more often had mixed feeding. First meconium passage was delayed with general anesthesia. Cord, 24 and 48 hours' bilirubin levels were not correlated with first feeding time, meconium passage time, mode of delivery, existence and type of anesthesia, and feeding modalities. Being in high intermediate risk zone at 72 hours of Bhutani's nomogram was only related to first feeding time and high cord bilirubin level. Late preterm infants were more frequently born with cesarean section and offered supplementary formula. Therefore, first meconium passage times and bilirubin levels were similar in the late preterm and term infants.

CONCLUSIONS

Type of delivery or anesthesia, late prematurity, feeding modalities, and first meconium passage time were not related to early bilirubin levels in healthy neonates, but delayed first feeding and high cord bilirubin levels were related to be in higher risk zone for later hyperbilirubinemia.

NEONATAL OUTCOMES FOLLOWING LATE PRETERM BIRTH

It is well recognised that birth before 32 weeks of gestation is associated with substantial neonatal morbidity and mortality and these risks have been extensively reported. The focus of perinatal research for many years has therefore been very preterm and extremely preterm delivery, since the likelihood and severity of adverse neonatal outcomes are highest within this group. In contrast, until recently, more mature preterm infants have been understudied and indeed, almost ignored by researchers.

Developmental physiology of late and moderate prematurity

This is a brief review of the developmental physiology of selected organ and functional systems in moderate and late preterm infants. This outline provides a discussion of the physiological underpinnings for some of the clinical conditions seen in this group of infants, including hypothermia, hypoglycemia, respiratory distress syndrome, transient tachypnea, severe respiratory failure, apnea, feeding difficulties, jaundice, and increased susceptibility to infections.

Therapeutic potential of heme oxygenase-1/carbon monoxide in lung disease

Heme oxygenase (HO), a catabolic enzyme, provides the rate-limiting step in the oxidative breakdown of heme, to generate carbon monoxide (CO), iron, and biliverdin-IXα. Induction of the inducible form, HO-1, in tissues is generally regarded as a protective mechanism. Over the last decade, considerable progress has been made in defining the therapeutic potential of HO-1 in a number of preclinical models of lung tissue injury and disease. Likewise, tissue-protective effects of CO, when applied at low concentration, have been observed in many of these models. Recent studies have expanded this concept to include chemical CO-releasing molecules (CORMs). Collectively, salutary effects of the HO-1/CO system have been demonstrated in lung inflammation/acute lung injury, lung and vascular transplantation, sepsis, and pulmonary hypertension models. The beneficial effects of HO-1/CO are conveyed in part through the inhibition or modulation of inflammatory, apoptotic, and proliferative processes. Recent advances, however, suggest that the regulation of autophagy and the preservation of mitochondrial homeostasis may serve as additional candidate mechanisms. Further preclinical and clinical trials are needed to ascertain the therapeutic potential of HO-1/CO in human clinical disease.

Reduced expression of UGT1A1 in intestines of humanized UGT1 mice via inactivation of NF-κB leads to hyperbilirubinemia

BACKGROUND & AIMS

Bilirubin is a natural and potent antioxidant that accumulates in the blood of newborn children and leads to physiological jaundice. Breastfed infants have higher serum levels of bilirubin than formula-fed infants and are at risk for bilirubin-induced neurological dysfunction (BIND). Clearance of bilirubin requires the expression of uridine diphosphate glucuronosyltransferase (UGT) 1A1; we investigated its role in the association between breast feeding with jaundice in mice.

METHODS

We studied mice in which the original Ugt1 locus was disrupted and replaced with the human UGT1 locus (hUGT1 mice); these mice spontaneously develop neonatal hyperbilirubinemia and BIND. We fed human breast milk or formula to neonatal hUGT1 mice and examined activation of the intestinal xenobiotic receptors pregnane X receptor and constitutive androstane receptor. We also examined inflammatory signaling pathways in mice with disruptions in IκB-kinase-α and IκB kinase-β in the intestinal epithelium.

RESULTS

hUGT1 mice that were fed breast milk developed severe hyperbilirubinemia because of suppression of UGT1A1 in the gastrointestinal tract. Formula-fed hUGT1 mice had lower serum levels of bilirubin, which resulted from induction of UGT1A1 in the gastrointestinal tract. hUGT1/Pxr-null mice did not develop severe hyperbilirubinemia, whereas hUGT1/Car-null mice were susceptible to BIND when they were fed breast milk. Breast milk appeared to suppress intestinal IκB kinase α and β, resulting in inactivation of nuclear factor-κB and loss of expression of UGT1A1, leading to hyperbilirubinemia.

CONCLUSIONS

Breast milk reduces expression of intestinal UGT1A1, which leads to hyperbilirubinemia and BIND; suppression of this gene appears to involve inactivation of nuclear factor-κB. Hyperbilirubinemia can be reduced by activation of pregnane X receptor, constitutive androstane receptor, or nuclear factor-κB.

Neonatal morbidity in singleton late preterm infants compared with full-term infants

AIM

The aim of this study was to test the hypothesis that singleton late preterm infants (34 0/7 to 36 6/7 weeks of gestation) compared with full-term infants have a higher incidence of short-term morbidity and stay longer in hospital.

METHODS

In this retrospective, multicentre study, electronic data of children born at five hospitals in Switzerland were recorded. Short-term outcome of late preterm infants was compared with a control group of full-term infants (39 0/7 to 40 6/7 weeks of gestation). Multiple gestations, pregnancies complicated by foetal malformations, maternal consumption of illicit drugs and infants with incomplete documentation were excluded. The results were corrected for gender imbalance.

RESULTS

Data from 530 late preterm and 1686 full-term infants were analysed. Compared with full-term infants, late preterm infants had a significant higher morbidity: respiratory distress (34.7% vs. 4.6%), hyperbilirubinaemia (47.7% vs. 3.4%), hypoglycaemia (14.3% vs. 0.6%), hypothermia (2.5% vs. 0.6%) and duration of hospitalization (mean, 9.9 days vs. 5.2 days). The risk to develop at least one complication was 7.6 (95% CI: 6.2-9.6) times higher among late preterm infants (70.8%) than among full-term infants (9.3%).

CONCLUSION

Singleton late preterm infants show considerably higher rate of medical complications and prolonged hospital stay compared with matched full-term infants and therefore need more medical and financial resources.

Selective vulnerability of rat brain regions to unconjugated bilirubin

Hippocampus is one of the brain regions most vulnerable to unconjugated bilirubin (UCB) encephalopathy, although cerebellum also shows selective yellow staining in kernicterus. We previously demonstrated that UCB induces oxidative stress in cortical neurons, disruption of neuronal network dynamics, either in developing cortical or hippocampal neurons, and that immature cortical neurons are more prone to UCB-induced injury. Here, we studied if immature rat neurons isolated from cortex, cerebellum and hippocampus present distinct features of oxidative stress and cell dysfunction upon UCB exposure. We also explored whether oxidative damage and its regulation contribute to neuronal dysfunction induced by hyperbilirubinemia, considering neurite extension and ramification, as well as cell death. Our results show that UCB induces nitric oxide synthase expression, as well as production of nitrites and cyclic guanosine monophosphate in immature neurons, mainly in those from hippocampus. After exposure to UCB, hippocampal neurons presented the highest content of reactive oxygen species, disruption of glutathione redox status and cell death, when compared to neurons from cortex or cerebellum. In particular, the results indicate that cells exposed to UCB undertake an adaptive response that involves DJ-1, a multifunctional neuroprotective protein implicated in the maintenance of cellular oxidation status. However, longer neuronal exposure to UCB caused down-regulation of DJ-1 expression, especially in hippocampal neurons. In addition, a greater impairment in neurite outgrowth and branching following UCB treatment was also noticed in immature neurons from hippocampus. Interestingly, pre-incubation with N-acetylcysteine, a precursor of glutathione synthesis, protected neurons from UCB-induced oxidative stress and necrotic cell death, preventing DJ-1 down-regulation and neuritic impairment. Taken together, these data point to oxidative injury and disruption of neuritic network as hallmarks in hippocampal susceptibility to UCB. Most importantly, they also suggest that local differences in glutathione content may account to the different susceptibility between brain regions exposed to UCB.

Neonatal outcomes in a population of late-preterm infants

The late-preterm infants are a group of premature steadily increasing, different from term infants as immature in terms of respiratory, metabolic, neurological, and immunological features. They may present at birth and during the first week of life various diseases and brain lesions echographically evident. We analyzed the neonatal outcomes of 417 late-preterm infants, born in our Department of Neonatology in a period of two and a half years, evaluating respiratory problems (RDS, transient tachypnea, pneumonia, pneumothorax, and apnea), metabolic problems (hypoglycemia, hypomagnesemia, hypo-hypernatremia, dehydration, hypocalcemia, and hyperbilirubinemia), infections, neurological symptoms associated with electrolyte disturbances, the disease patterns observed by ultrasound examination of the brain, the kidney ultrasound images, genital malformations.

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.

Transcutaneous bilirubin levels in late preterm neonates

OBJECTIVE

To examine transcutaneous bilirubin (TcB) levels in late preterm neonates.

STUDY DESIGN

Between July 2006 and December 2009, we performed 4387 TcB measurements with a BiliCheck bilirubinometer in 793 healthy late preterm neonates at designated times up to 120 postnatal hours. TcB percentiles are presented on an hour-specific nomogram. Mean increment TcB rates and the rates of increase for different percentiles are calculated as well.

RESULTS

We present a percentile-based nomogram that reflects the natural history of TcB in late preterm neonates up to the fifth day of life. TcB levels demonstrated a different pattern of increase in neonates who developed significant hyperbilirubinemia compared with those who did not. However, the rates of TcB increase were quite similar up to age 48 hours, with a substantial overlap of TcB values between the two groups.

CONCLUSIONS

We developed of a TcB nomogram designated for hour-specific evaluation of hyperbilirubinemia in neonates born between 35(0/7) and 37(6/7) weeks' gestation.

Hyperbilirubinemia in African American neonates: clinical issues and current challenges

African American neonates evidence a low incidence of hyperbilirubinemia yet account for more than 25% of the reported kernicterus cases in the USA. Glucose-6-phosphate dehydrogenase (G6PD) deficiency accounts for approximately 60%, and late preterm gestation and ABO hemolytic disease approximately 40% of these cases. Females heterozygous for G6PD A- harbor a population of G6PD-deficient red blood cells and are at risk for hyperbilirubinemia. Pre-discharge bilirubin measurement coupled with gestational age enhances the identification of neonates at hyperbilirubinemia risk. Parental education at the time of birth hospitalization discharge combined with timely follow-up may help to reduce the risk of developing hazardous hyperbilirubinemia.

Signal processing system to extract serum bilirubin concentration from diffuse reflectance spectrum of human skin

Neonatal jaundice is a medical condition which occurs in newborns as a result of an imbalance between the production and elimination of bilirubin. Excess bilirubin in the blood stream diffuses into the surrounding tissue leading to a yellowing of the skin. The extra-vascular bilirubin act as interfering signal that limits the estimation of serum bilirubin from reflectance spectrum of human skin. This is particularly an issue for neonates who are being subjected to phototherapy (a common treatment for neonatal jaundice). Unfortunately, analytical models developed to study the light transport in human skin do not consider the effects of extra-vascular bilirubin (and other absorbing chromophores). A biomedical signal processing method that estimates serum bilirubin in presence of confounding signals such as melanin and extra-vascular bilirubin concentrations is presented. The new system model and nonlinear solver have been successful in estimating the serum bilirubin concentration on simulated spectral databases within an average error of 15%.

Signal processing system to quantify bilirubin in the jaundice clinical model spectra

Neonatal jaundice is a medical condition which occurs in newborns as a result of an imbalance between the production and elimination of bilirubin. Excess bilirubin in the blood stream diffuses into the surrounding tissue leading to a yellowing of the skin. An optical system integrated with a signal processing system is used as a platform to noninvasively quantify bilirubin concentration through the measurement of diffuse skin reflectance. Initial studies, based on simulated skin reflectance spectra have lead to the generation of a clinical model for neonatal jaundice which, generates spectral reflectance data for jaundiced skin with varying levels of bilirubin concentration in the tissue. The spectral database built using the jaundice clinical model is then used as a test database to validate the signal processing system in real time. This evaluation forms the basis for understanding the translation of this research to human trials. The new jaundice clinical model and signal processing system have been successful validated using a porcine model as a surrogate for neonatal skin tissue. Samples of pig skin were soaked in bilirubin solutions of varying concentrations to simulate jaundice skin conditions. The resulting skins samples were analyzed with our skin reflectance systems producing bilirubin concentration values that show a high correlation (R(2) = 0.96) to concentration of the bilirubin solution that each porcine tissue sample was soaked in‥

Feeding challenges in the late preterm infant

A late preterm infant is defined as one born between 34 and 36 6/7 weeks of completed gestation. The rate of late preterm births has risen 18 percent since the late 1990s. Data are beginning to emerge concerning morbidity rates and the risks these newborns face with regard to feeding difficulties, temperature instability, hypoglycemia, and hyperbilirubinemia. Feeding challenges place these vulnerable infants at risk for prolonged hospital stays and readmission after discharge. To better address the unique needs of late preterm infants, providers should establish individual feeding orders. This article offers research-based suggestions for caring for these infants in the newborn nursery and the postpartum unit as well as parent teaching guidelines.

So, he's a little premature...what's the big deal?

Health care providers have recently recognized that a large segment of the morbidity associated with preterm birth is disproportionately due to the late preterm infant (LPI). One explanation is that this population is the fastest-growing sector of all preterm births. This article describes the epidemiology and etiology of the LPI, and discusses why the LPI is at an increased risk for complications, such as thermal instability, hypoglycemia, feeding difficulties, respiratory distress, hyperbilirubinemia, and sepsis. The need for emergency department visits after hospital discharge and what is currently known regarding neurodevelopmental outcomes are also presented.

Influência da icterícia obstrutiva na capacidade reprodutiva, desenvolvimento fetal e morfologia ovariana em ratas

OBJETIVO: Estudar a influência da icterícia obstrutiva sobre a capacidade reprodutiva e desenvolvimento fetal em ratas. MÉTODOS: Foram utilizadas 60 ratas sexualmente maduras e sabidamente férteis distribuídas em dois grupos: grupo 1 (n=30)- submetidas a ligadura do ducto biliopancreático e grupo 2 (n=30) -controles. A partir do 23? dia pós-operatório, as ratas foram acasaladas e seus ciclos estrais avaliados diariamente por meio de esfregaços vaginais, que permitiram determinar o dia da cópula e a idade gestacional em que foram mortas. Realizou-se estudo histológico dos corpos lúteos nos ovários de todas as ratas e analisou-se macroscopicamente a morfologia externa dos fetos. RESULTADOS: Observou-se que 23 ratas controle (92%) e 11 ratas ictéricas (39,3%) desenvolveram prenhez (p=0,0002). As 17 ratas com hiperbilirrubinemia e sem prenhez (60,7%) apresentaram somente corpos lúteos com aspecto involutivo em seus ovários e sofreram modificações em seus ciclos estrais, permanecendo vários dias em proestro ou estro. As ratas prenhes com hiperbilirrubinemia não apresentaram alterações em seus corpos lúteos, porém os seus fetos eram anormais. CONCLUSÃO: Em presença de hiperbilirrubinemia, a fertilização é viável, a capacidade reprodutiva é muito reduzida, os ciclos estrais tornam-se irregulares, o epitélio vaginal permanece cornificado, os corpos lúteos ovarianos regridem, os corpos lúteos gravídicos não são alterados aumentando progressivamente durante a prenhez e o desenvolvimento fetal é gravemente alterado.

Identification of neonates at risk for hazardous hyperbilirubinemia: emerging clinical insights

Hyperbilirubinemia is the most common condition requiring evaluation and treatment in neonates. Identifying among all newborns those few at risk to develop marked hyperbilirubinemia is a clinical challenge. Clinical, epidemiologic, and genetic risk factors associated with severe hyperbilirubinemia include late preterm gestational age, exclusive breastfeeding, glucose-6-phosphate dehydrogenase deficiency, ABO hemolytic disease, East Asian ethnicity, jaundice observed in the first 24 hours of life, cephalohematoma or significant bruising, and history of a previous sibling treated with phototherapy. It is increasingly apparent that the etiopathogenesis of severe hyperbilirubinemia is often multifactorial, and emerging evidence suggests that combining risk factor assessment with measurement of predischarge total serum or transcutaneous bilirubin levels will improve hyperbilirubinemia risk prediction.

Exchange transfusion for neonatal hyperbilirubinemia with glucose-6-phosphate-deficient blood

Evaluation of: Samanta S, Kumar P, Kishore SS, Garewal G, Narang A: Donor blood glucose-6-phosphate dehydrogenase deficiency reduces the efficacy of exchange transfusion in neonatal hyperbilirubinemia. Pediatrics 123, E96–E100 (2009). Intravascular hemolysis following transfusion with glucose-6-phosphate dehydrogenase (G-6-PD)-deficient blood has been documented, although it is not routine to screen donor blood for this condition prior to exchange transfusion. Samanta et al. studied the effect of exchange transfusion with G-6-PD-deficient donor blood on neonates with moderate hyperbilirubinemia to determine the effectiveness of the exchange, postexchange serum total bilirubin levels, the duration of phototherapy and the need for repeat exchange transfusion. A total of 21 newborns were exchanged with G-6-PD-deficient donor blood and 114 with G-6-PD normal blood. Although the percentage decrease in serum total bilirubin from pre-exchange values immediately following the exchange was similar between the groups, during the postexchange period the percentage decrease became less in those exchanged with G-6-PD-deficient blood. Similarly, the duration of postexchange phototherapy and the number of babies requiring repeat exchange transfusion, were higher in those transfused with G-6-PD-deficient blood. The authors recommend that in areas where G-6-PD deficiency is prevalent, donor blood should be screened for G-6-PD deficiency prior to exchange transfusion use.

Total serum bilirubin levels during cyclooxygenase inhibitor treatment for patent ductus arteriosus in preterm infants

AIM

To determine whether ibuprofen use in VLBW infants is associated with increased serum bilirubin levels and impaired neurodevelopmental outcome at 2 years of age compared to indomethacin.

METHODS

We retrospectively evaluated bilirubin data and outcome parameters of 178 VLBW infants treated with COX inhibitors for a haemodynamically relevant patent ductus arteriosus (PDA) between 1998 and 2003 in a single institution. In our department ibuprofen replaced indomethacin for PDA treatment in 2001, while clinical and echocardiographic criteria for the indication of PDA invention have remained unchanged.

RESULTS

Ibuprofen and indomethacin therapy groups did not differ in their baseline clinical profile. Peak serum bilirubin concentration was 10.2 mg/dL in the ibuprofen group and 8.6 mg/dL in the indomethacin group (p < 0.01), while phototherapy duration did not differ. At 2 years of age neurodevelopmental outcome was similar in both groups. In a single case analysis, four cases of adverse neurodevelopmental outcome despite inconspicuous clinical course were identified in the ibuprofen group.

CONCLUSION

In VLBW infants with PDA, ibuprofen treatment was associated with higher bilirubin levels than indomethacin.

Complications of the late preterm infant

One of the goals of Healthy People 2010 (set in 1998) was to reduce preterm birthrates from 11.6% to 7.6%. However, in 2004, the preterm birthrate of 12.5% was actually higher than the rate in 1998. Approximately 65% of this increase in prematurity rate is attributed to the increasing birthrate of the late preterm infant. Care of the late preterm infant is far more complicated than many hospital policies and clinical guidelines imply. It cannot be stressed enough to frontline clinicians that late preterm infants are not full-term infants. Their care should not be defined by the same policies and practices that govern term infants. The purpose of this article is to explore the complications that accompany late preterm birth. The following complications will be discussed: thermoregulation challenges, feeding difficulty, late neonatal sepsis, prolonged physiologic jaundice, hypoglycemia, possible neurodevelopmental differences, and respiratory problems.

Serial brain MRI and ultrasound findings: relation to gestational age, bilirubin level, neonatal neurologic status and neurodevelopmental outcome in infants at risk of kernicterus

AIMS

To describe cranial ultrasound (cUS) and magnetic resonance imaging (MRI) findings in neonates at risk of kernicterus, in relation to gestational age (GA), total serum bilirubin (TSB), age at imaging and neurodevelopmental outcome.

PATIENTS AND METHODS

Neonates with peak TSB > 400 micromol/L and/or signs of bilirubin encephalopathy. Review of neonatal data, cUS, preterm, term and later MRI scans and neurodevelopmental outcome.

RESULTS

11 infants were studied, two < 31, four 34-36 and five 37-40 weeks GA. TSB levels: 235-583 micromol/L (preterms); 423-720 micromol/L (terms). Neonatal neurological examination was abnormal in 8/10. cUS showed increased basal ganglia (BG) in 4/9 infants and white matter (WM) echogenicity, lenticulostriate vasculopathy (LSV) and caudothalamic hyperechogencity/cysts (GLCs) in 5/9 infants. MRI showed abnormal signal intensity (SI) in the globus pallidum (GP) in 1/2 preterm, 8/9 term and 9/11 later scans. Abnormal WM SI occurred in 2 preterm, 7 term and 10/11 later scans. Seven infants developed athetoid/dystonic cerebral palsy (CP) and 6 hearing loss (HL). Adverse outcome was associated with abnormal BG on cUS (3/4 CP, 4/4 HL), with high SI in GP (7/9 CP, 6/9 HL) on late T2-weighted MRI (all GA) and on T1/T2-weighted term MRI, mainly in term-born infants. WM abnormalities, GLCs and LSV did not correlate with outcome.

CONCLUSIONS

Severe CP occurred with relatively low TSB levels in preterms but only at high levels in full-terms; HL was difficult to predict. Early scans did not reliably predict motor deficits whilst all children with CP had abnormal central grey matter on later scans. Abnormal WM was seen early suggesting primary involvement rather than change secondary to grey matter damage. Why characteristic central grey matter MRI features of kernicterus are not seen early remains unexplained.

[Effect of jaundice on fertility, ovarian morphology and fetal development in rats]

The effect of jaundice on the reproductive capacity, ovarian morphology and fetal development in rats was assessed in 53 sexually mature rats divided into two groups: group 1 (n = 28) -- submitted to ligature of the biliopancreatic duct and group 2 (n = 25) - control -- submitted only to sham operation. In jaundice rats fertilization is viable, the reproductive capacity is intensive reduced, the estrus cycles becomes irregular, the corpi lutea is presented in regression, the gravidic lutea is not modified increasing gradually during the pregnancy and the fetal development is seriously impaired.

Highly sensitive method for quantitative determination of bilirubin in biological fluids and tissues

Unconjugated bilirubin (UCB) exhibits potent antioxidant and cytoprotective properties, but causes apoptosis and cytotoxicity at pathologically elevated concentrations. Accurate measurement of UCB concentrations in cells, fluids and tissues is needed to evaluate its role in redox regulation, prevention of atherosclerotic and malignant diseases, and bilirubin encephalopathy. In the present study, we developed and validated a highly sensitive method for tissue UCB determinations. UCB was extracted from rat organs with chloroform/methanol/hexane at pH 6.2 and then partitioned into a minute volume of alkaline buffer that was subjected to HPLC using an octyl reverse phase (RP) column. Addition of mesobilirubin as an internal standard corrected for losses of UCB during extraction. Recoveries averaged 75+/-5%. The detection limit was 10pmol UCB/g wet tissue. Variance was +/-2.5%. When used to measure UCB concentrations in tissues of jaundiced Gunn rats, this procedure yielded UCB levels directly comparable to published methods, and accurately determined very low tissue bilirubin concentrations (</=40pmol UCB/g tissue) in non-jaundiced rats.