Neonatal Jaundice in Preterm Infants with Bilirubin Encephalopathy

Sustained lower bilirubin-binding affinity of albumin in extremely preterm infants

BACKGROUND

Elevated albumin-free or unbound bilirubin (UB) levels beyond the first week of life have been associated with the development of bilirubin encephalopathy in preterm infants. However, the mechanism(s) that induces this prolonged unbound bilirubinemia has remained unknown. We hypothesized that it may due to a sustained lower bilirubin-binding affinity of albumin in extremely premature infants.

METHODS

Twenty-two very preterm infants born at 28-31 weeks' gestational age (GA) (VPT Group) and 21 extremely preterm infants born at 22-27 weeks' GA (EPT Group) were retrospectively studied. On days 14, 21, and 28, bilirubin-binding affinity of albumin was assessed by calculating of the UB/total bilirubin ratio, bilirubin-albumin molar ratio (BAMR), and binding affinity (Ka).

RESULTS

On days 14, 21, and 28, significantly higher UB/total bilirubin ratios were found in the EPT than in the VPT Group. Although BAMRs were comparable, significantly lower Ka values on days 14, 21, and 28 were observed in the EPT than those in the VPT Group (56.1 vs. 70.9 L/μmol, p < 0.001; 55.2 vs. 74.7 L/μmol, p < 0.001; 53.0 vs. 86.5 L/μmol, p < 0.001, respectively).

CONCLUSIONS

EPT infants have a sustained lower bilirubin-binding affinity of albumin beyond the first week of life.

IMPACT

Bilirubin encephalopathy is still reported in extremely preterm (EPT) infants. EPT infants often have prolonged unbound bilirubinemia beyond the first week of life. Sustained lower bilirubin-binding affinity of albumin, regardless of the bilirubin-albumin molar ratio (BAMR), is observed in EPT infants. BAMRs should not be used as a surrogate marker of unbound bilirubinemia, especially in EPT infants at a later postnatal period.

Impact of Protein Binding Capacity and Daily Dosage of a Drug on Total Serum Bilirubin Levels in Susceptible Infants

Hyperbilirubinemia is a common pathological condition in neonates. Free bilirubin can penetrate the blood-brain barrier (BBB), which can lead to bilirubin neurotoxicity. In the context of predicting the risk of bilirubin neurotoxicity, although the specificity and sensitivity of free bilirubin levels are higher than those of total serum bilirubin (TSB), free bilirubin is not widely monitored in clinical practice. The threshold TSB levels at which phototherapy must be administered have been established previously. However, TSB levels are not well correlated with neurodevelopmental outcomes. Currently, TSB levels are commonly used to guide phototherapy for neonatal hyperbilirubinemia. Some clinical drugs can displace bilirubin from its albumin-binding sites, and consequently upregulate plasma bilirubin. Daily dosages play a vital role in regulating bilirubin levels. A drug with both a high protein binding capacity and high daily dosage significantly increases bilirubin levels in infants. Premature or very low birth weight (VLBW) infants are vulnerable to the upregulation of bilirubin levels as they exhibit the lowest reserve albumin levels and consequently the highest bilirubin toxicity index. Because bilirubin is involved in maintaining the balance between pro-oxidant and antioxidant agents, the downregulation of bilirubin levels is not always desirable. This review provides insights into the impact of protein binding capacity and daily dosage of drugs on the bilirubin levels in susceptible infants.

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.

Risk factors for neonatal hyperbilirubinemia: a systematic review and meta-analysis

BACKGROUND

Hyperbilirubinemia is the most common cause of neonatal hospitalization and, although it generally has a good prognosis, a significant percentage of neonatal patients maintain a high bilirubin level, which can lead to severe complications, including lifelong disability such as growth retardation, encephalopathy, autism and hearing impairment. The study of risk factors for neonatal hyperbilirubinemia has been controversial. Therefore, we evaluated the risk factors of neonatal hyperbilirubinemia using a meta-analysis.

METHODS

Relevant English and Chinese studies that discussed risk factors for neonatal hyperbilirubinemia were retrieved from the PubMed, EMBASE, Medline, Central, China National Knowledge Infrastructure (CNKI), Wanfang and China Science Digital Library (CSDL). The literature took newborns as the research object, set up a control group, and observed the relationship between exposure factors and neonatal hyperbilirubinemia. The combined effect size was expressed by odds ratio (OR) and 95% confidence interval (CI). The Chi-square test was used to test heterogeneity of the studies, and if it existed, subgroup analyses were used to explore the source of heterogeneity, and the random-effects model was selected for the combined analysis. The fixed-effects model was chosen for the combined analysis if there was no heterogeneity. Publication bias was assessed using Egger's test and funnel plot.

RESULTS

Risk factors for neonatal hyperbilirubinemia were exclusive breastfeeding (BF: OR =1.74, 95% CI: 1.42, 2.12, Z=5.43, P<0.00001); glucose-6-phosphate dehydrogenase deficiency (G6PD: OR =1.62, 95% CI: 1.44, 1.81, Z=8.39, P<0.00001); maternal-fetal ABO blood group incompatibility (OR =1.64, 95% CI: 1.42, 1.89, Z=6.75, P<0.00001); and preterm birth (PTB: OR =1.31, 95% CI: 1.17, 1.47, Z=4.60, P<0.00001); there was no heterogeneity or publication bias among the studies (BF: χ²=5.34, P=0.25, I²=25%; G6PD: χ²=4.40, P=0.49, I²=0%; ABO: χ²=1.91, P=0.75, I²=0%; PTB: χ²=0.81, P=0.67, I²=0%).

CONCLUSIONS

Exclusive breastfeeding, G6PD deficiency, ABO incompatibility and premature birth were confirmed as risk factors for neonatal hyperbilirubinemia. Pregnant women with risk factors should be monitored more closely and clinical intervention should be given in a timely manner.