Unbound bilirubin and risk assessment in the jaundiced newborn: possibilities and limitations

Unbound bilirubin measurements in term and late-preterm infants

Background: Hyperbilirubinemia occurs in over 80% of newborns, and severe bilirubin toxicity can lead to neurological dysfunction and death. Unbound bilirubin (Bf) levels predict the risk of neurodevelopmental handicap, although total serum bilirubin (TSB) is used to manage care.Objective: To measure Bf levels in healthy infants, its relationship to TSB, and its response to phototherapy. We hypothesize unexpectedly high Bf levels, poor correlation with TSB and unpredictable response to phototherapy.Design/methods: Healthy infants were studied with simultaneous TSB and Bf measurements. The clinical data recorded included ethnicity, gender, birth weight, gestational age, and mode of delivery, Apgar scores, breast/formula feeds, and phototherapy.Results: One hundred thirty-two infants (3248.9 ± 509.2g, GA 38.7 ± 1.4 weeks), at mean age of the initial sample of 28.5 ± 15.6 h, had a TSB of 7.9 ± 2.7 mg/dl, and a Bf of 5.2 ± 3.2 nM. The correlation between Bf and TSB was significant but not between Bf and TSB for TSB >12 mg/dl. Bf >11nm were in 22.7% and >17 nM in 3.8% of infants. Post-phototherapy TSB and Bf levels were similar to those before treatment.Conclusions: The relationship between TSB and Bf in healthy infants is complex, with the inability of one to predict the other's level in infants with elevated TSB. The mechanism of bilirubin-related neurotoxicity suggests that the management of jaundice in healthy infants requires Bf measurements. Management of jaundice with TSB may result in more infants exposed to phototherapy. However, unexpected elevations of Bf occur in an apparently healthy population.

Immunizations, neonatal hyperbilirubinemia and animal-induced injuries

PURPOSE OF REVIEW

To report recent research findings and new recommendations on immunizations, neonatal hyperbilirubinemia, and animal-induced injuries.

RECENT FINDINGS

Vaccines against rotavirus and human papilloma virus have entered clinical use. Varicella outbreaks among previously vaccinated children have prompted the recommendation for a two-dose varicella vaccine series. Broader coverage for influenza vaccination is now recommended in the US and Canada. Diagnosis and treatment of neonatal hyperbilirubinemia uses population and hour-based norms for total serum bilirubin and assessment of risk factors. Delayed cord clamping is not apparently a risk factor for jaundice but warrants more study. Universal predischarge screening shows promise but is not yet officially recommended. New treatments for hyperbilirubinemia are being evaluated. Dogs are the chief cause of animal bites in children and the largest reservoir for rabies worldwide. In North America and Europe, cats and wild animals cause most human rabies. Postexposure prophylaxis should follow region-appropriate guidelines.

SUMMARY

New vaccines are available against rotavirus and human papilloma virus. Changes have been made to official immunization recommendations. Appropriate vaccine use can reduce the pediatric disease burden further. Hyperbilirubinemia is the subject of ongoing study, which may lead to improved diagnosis and treatment protocols and reduce the incidence of acute bilirubin encephalopathy. The best tool for rabies prevention after an animal bite is prompt postexposure prophylaxis.