Neonatal jaundice--what now?

Unbound bilirubin levels in phototherapy-treated preterm infants receiving soy-based lipid emulsion

BACKGROUND

Phototherapy is an effective treatment for neonatal jaundice. Treatment indication uses total serum bilirubin (TSB), although unbound bilirubin (Bf) more accurately predicts disability risk. The goals of this investigation were to examine the response of Bf and TSB to phototherapy in preterm infants, and we hypothesized that (i) TSB and Bf respond differently; (ii) the relationship between TSB and Bf is altered; and (iii) unexpected Bf elevations are found.

METHODS

One hundred and seventeen preterm infants <2 kg at birth and receiving (IL) were enrolled; and measurements of TSB and Bf were obtained. TSB was measured by the diazo method and Bf with a fluorescent Bf sensor BL22P1B11-Rh.

RESULTS

Initial mean (± SD) TSB and Bf levels (41.4 ± 6.9 h) were 8.0 ± 9.0 mg/dL and 16.9 ± 12.4 nmol/L (P < 0.05). The rates of rise (ROR) were 0.21 ± 0.10 mg/dL/h for TSB and 0.38 ± 0.33 nmol/L/h for Bf. Phototherapy reduced TSB from 8.0 ± 9.0 to 5.8 ± 9.4 mg/dL (P = 0.068) but Bf did not change (16.9 ± 12.4 to 14.1 ± 9.4 nmol/L P = n.s.). Bf levels were >11 nmol/L in 64, >17 nmol/L in 18, and >22 nmol/L in 7 infants.

CONCLUSIONS

Bf and TSB responded differently. While TSB and Bf correlated well before phototherapy, they did not correlate during phototherapy. TSB showed a trend toward a reduction with treatment, Bf did not. While TSB ROR information is not helpful, ROR Bf data can be utilized to anticipate treatment. Potentially high Bf levels existed before and after phototherapy and the mean Bf level at phototherapy termination remained elevated in a significant proportion of infants.

Incidence and causes of neonatal hyperbilirubinemia in a center of Catania

Aim and scope:

We conducted this study to estimate the incidence of hyperbilirubinemia in a small neonatal care unit in Catania, Italy, and to determine the underlying causes, which would be of value in identifying and implementing strategies to prevent morbidity from this condition.

Background:

Management of hyperbilirubinemia remains a challenge for neonatal medicine because of the risk for serious neurological complications related to the toxicity of bilirubin.

Methods:

From January 2006 to January 2007, we screened 525 newborns born at the Neonatal Care Unit of Valsalva Hospital in Catania, Italy. Infants aged 3–5 days and with unconjugated hyperbilirubinemia were included for assessment if they had a peak serum total bilirubin level exceeding 6 mg/dl (102 μmol/L). Sex, birth weight, gestational age, breast feeding, type of birth, presence of facial bruising (including cephalohematoma) and ABO group were noted. Patients with Toxoplasma or Cytomegalovirus infection, hepatic insufficiency, or suspected drug-induced hyperbilirubinemia were excluded from more detailed analysis.

Results:

Our year-long nursery sample examined otherwise healthy-appearing term infants for the prevalence of hyperbilirubinemia (defined as bilirubin levels exceeding 6 mg/dL [11mol/L]). We found hyperbilirubinemia in 19% (100/525). Among the patients with hyperbilirubinemia, almost all (99%) had peak levels of bilirubin <20 mg/dL, levels which are generally considered to be potentially neurotoxic.

Conclusions:

In our clinic experience, hyperbilirubinemia was generally a serious medical issue and one whose etiology can usually be well defined.

Erythroid apoptosis in idiopathic neonatal jaundice

OBJECTIVES

The objectives of this study were to evaluate the contribution of erythroid apoptosis to neonatal idiopathic pathologic jaundice and to determine whether a measurement of the erythroid apoptosis value at birth could predict the development of hyperbilirubinemia during the first 15 days of life.

PATIENTS AND METHODS

Three groups were defined: group 1 (n = 101), healthy newborns whose erythroid apoptosis value and serum total bilirubin levels were detected from birth to day 15; group 2 (n = 24), newborns who were hospitalized for jaundice (serum total bilirubin level: > 12.9 mg/dL) without any identifiable pathologic cause; and group 3 (control group, n = 24), healthy newborns whose serum total bilirubin levels were < or = 12.9 mg/dL. Erythroid apoptosis value was assessed by flow cytometry using an annexin-V fluorescein isothiocyanate kit.

RESULTS

In group 1, there was no correlation between the erythroid apoptosis value and serum total bilirubin levels obtained at birth and at the fourth and 15th days of life; the erythrocyte apoptosis value obtained at birth was not significantly different between the neonates whose serum total bilirubin levels were > 12.9 and < or = 12.9 mg/dL and who had prolonged and nonprolonged jaundice during follow-up. The erythroid apoptosis value differed significantly between the newborns in groups 2 and 3. There was no significant correlation between the erythroid apoptosis value and serum total bilirubin levels of the infants in groups 2 and 3.

CONCLUSIONS

The erythroid apoptosis value obtained at birth could not predict the development of hyperbilirubinemia in neonates, but it was increased significantly in jaundiced neonates whose serum total bilirubin levels were > 12.9 mg/dL. In these infants, increase in the erythroid apoptosis value may be a result of the toxic effect of bilirubin or of a protective mechanism of neonates to increase heme turnover and bilirubin production to diminish oxidative stress.

The effects of bilirubin on evoked potentials and long-term potentiation in rat hippocampus in vivo

Neonatal jaundice is a common condition that could potentially lead to severe neurotoxicity. In this electrophysiological study we observed the effects of a short-term bilirubin injection on evoked potentials (population spike, PS) and long-term potentiation (LTP) in the hippocampal CA3 region of Sprague Dawley rats in vivo. The animal received a bolus i.v. injection of either 60 mg/kg, or 30 mg/kg of bilirubin, or an equivalent volume of bilirubin-free vehicle in 5 min. The results showed that both bilirubin-treated groups had a dose-independent prolongation of peak latencies and decrease of slopes of the PS at all measured time points following injection (1, 3, 5, 10, 15, 30, 45, 60, 90, 120 min), while the amplitudes of the PS did not change significantly. The peak latency, slope, and the amplitude of PS stayed unchanged in the control group. Furthermore, while LTP could be induced by high-frequency stimulation in control animals, this phenomenon was absent in both bilirubin-treated groups. The amplitudes of the PS in the two treated groups after stimulation were also smaller than those of the control animals at every time points. These findings are in accordance with previous observations showing significant depressive effects of bilirubin on the nervous system. Our novel finding that short-term exposure to bilirubin can inhibit the induction of LTPs in the hippocampus, is compatible with the suggestion that neonatal hyperbilirubinemia can impact on learning and memory.

Developmental follow-up of breastfed term and near-term infants with marked hyperbilirubinemia

OBJECTIVE

In recent years, the increased prevalence of breastfeeding in conjunction with early discharge practices has increased the risk for marked hyperbilirubinemia in neonates. This has resulted in the potential for bilirubin brain injury in affected infants. The purpose of this study was to identify all infants >/=36 weeks' gestational age with bilirubin levels >25 mg/dL and evaluate them for early and late evidence of bilirubin brain injury.

METHODS

We reviewed the charts of all infants (from 1993-1996) >/=36 weeks' gestational age who were readmitted to the hospital during the first week of life with bilirubin levels >25 mg/dL. Readmission records were reviewed for early signs of bilirubin encephalopathy. Magnetic resonance imaging (MRIs) and Brainstem auditory-evoked responses (BAERs) were reviewed for evidence of bilirubin toxicity. At follow-up, study infants had a complete neurodevelopmental examination, repeat MRIs, and behavioral hearing evaluations.

RESULTS

From 1993 to 1996, we identified 6 term and near-term infants readmitted to the hospital within the first week of life with peak bilirubin values ranging from 26.4 mg/dL (451 micromol/L) to 36.9 mg/dL (631 micromol/L). Five of 6 infants had bilirubin values >30 mg/dL (513 micromol/L). All were exclusively breastfed or fed a combination of breast and bottle feedings. Five of 6 infants presented with abnormal neurologic signs. Four infants had initial MRIs, 3 of whom had increased signal intensity in the basal ganglia consistent with kernicterus. Two infants had abnormal BAERs; both also had abnormal MRIs. Five of 6 infants received exchange transfusions and all were treated with phototherapy and intravenous fluids. Follow-up examinations between 3 months and 2 years showed resolution of clinical signs in all but 1 infant. Four infants had a subsequent normal MRI and 1 had residual hearing impairment. One infant demonstrated severely abnormal developmental evaluations, as well as both an abnormal initial MRI and BAERs. Follow-up MRI showed evidence of encephalomalacia with changes not characteristic of kernicterus.

CONCLUSIONS

We observed transient neurologic abnormalities in 5 of 6 infants readmitted to the hospital during the first week of life with marked hyperbilirubinemia. The abnormalities resolved following aggressive management using hydration, phototherapy, and exchange transfusion and may not correlate with long-term prognosis. Less aggressive therapy may be associated with residual neurologic abnormalities. We speculate that inadequate establishment of breastfeeding coupled with early discharge practices may play a role in the development of marked hyperbilirubinemia in these infants.

Carbon monoxide and bilirubin production in neonates

Neonatal hyperbilirubinemia is a normal postnatal phenomenon resulting from a transitional imbalance between the production and elimination of bilirubin in the neonate. Bilirubin has been shown to be not only a potent antioxidant, but also toxic at excessive concentrations. As a result, the biology of bilirubin, its production, regulation, and measurements have been the focus of extensive studies. Bilirubin, carbon monoxide, and iron are derived from the degradation of heme, a ubiquitous two-step pathway catalyzed by the enzyme, heme oxygenase. It has been shown that these metabolically active products from the heme catabolic pathway may, in turn, influence many other biologic processes. This report provides a brief overview of these interrelationships in the hope that it may provide insight into the central role this pathway plays in the existence of most organisms.

Issues in newborn care

During the provision of newborn care, the primary care provider must identify any apparent or potential health concerns, while at the same time dealing with the concerns of new mothers and other members of the now expanded family. Efficiently managing outpatient problems such as colic, dysfunctional sleep, skin disorders, neonatal jaundice, feeding problems, and newborn circumcision is the purpose of this article.

Zinc Protoporphyrin: A Metabolite with a Mission

Zinc protoporphyrin (ZnPP) is a normal metabolite that is formed in trace amounts during heme biosynthesis. The final reaction in the biosynthetic pathway of heme is the chelation of iron with protoporphyrin. During periods of iron insufficiency or impaired iron utilization, zinc becomes an alternative metal substrate for ferrochelatase, leading to increased ZnPP formation. Evidence suggests that this metal substitution is one of the first biochemical responses to iron depletion, causing increased ZnPP to appear in circulating erythrocytes. Because this zinc-for-iron substitution occurs predominantly within the bone marrow, the ZnPP/heme ratio in erythrocytes reflects iron status in the bone marrow. In addition, ZnPP may regulate heme catabolism through competitive inhibition of heme oxygenase, the rate-limiting enzyme in the heme degradation pathway that produces bilirubin and carbon monoxide. Physiological roles, especially relating to carbon monoxide and possibly nitric oxide production, have been suggested for ZnPP. Clinically, ZnPP quantification is valuable as a sensitive and specific tool for evaluating iron nutrition and metabolism. Diagnostic determinations are applicable in a variety of clinical settings, including pediatrics, obstetrics, and blood banking. ZnPP analytical methodologies for clinical studies are discussed. In addition to diagnostic tests and metabolic studies, ZnPP has a potential therapeutic application in controlling bilirubin formation in neonates as a preventive measure for hyperbilirubinemia. Biochemical research techniques, both in vivo and in vitro, are described for further studies into the role of ZnPP in metabolism and physiology.