Little known and less understood: the benefits of a lower hematocrit (~40%) in reconstituted blood for double volume exchange transfusion

A double volume exchange transfusion (DVET) is an important, if infrequently performed, intervention to acutely lessen the total serum bilirubin (TSB) and reduce the extravascular CNS bilirubin exposure when neonatal hyperbilirubinemia poses a neurotoxicity risk. The current analysis based on the seminal works of Valaes, and Sproul and Smith, predicts that a DVET blood product of lower hematocrit (~40%) via its greater plasma volume and corresponding higher albumin content optimizes the benefits of an DVET in several ways. First, by augmenting bilirubin clearance from the extravascular space and thereby further reducing the CNS bilirubin exposure, second, by favorably positioning the intravascular albumin-bilirubin binding capacity at DVET completion to accommodate additional bilirubin equilibration and rebound hyperbilirubinemia post-exchange, and third by correcting anemia if present.

ABO hemolytic disease of the newborn: a need for clarity and consistency in diagnosis

The diagnosis of ABO hemolytic disease of the newborn (ABO HDN) has been the subject of considerable debate and clinical confusion. Its use as an overarching default diagnosis for hyperbilirubinemia in all ABO incompatible neonates regardless of serological findings is problematic and lacks diagnostic precision. Data on hemolysis indexed by carbon monoxide (CO) levels in expired air (ETCOc) and blood (COHbc) support an essential role for a positive direct antiglobulin test (DAT) in making a more precise diagnosis of ABO HDN. A working definition that includes ABO incompatibility, significant neonatal hyperbilirubinemia, and a positive DAT is needed to gain clarity and consistency in the diagnosis of ABO HDN. Absent a positive DAT, the diagnosis of ABO HDN is suspect. Instead, a negative DAT in a severely hyperbilirubinemic ABO incompatible neonate should trigger an exhaustive search for an alternative cause, a search that may require the use of targeted gene panels.

Management of severe hyperbilirubinemia in the cholestatic neonate: a review and an approach

A review of the literature demonstrates that severe total hyperbilirubinemia (total serum bilirubin ≥ 20 mg/dL [340 µmol/L]) in some cholestatic term (≥37 weeks) and late-preterm (≥34^0/7-36^6/7 weeks) gestation neonates poses a risk for bilirubin-induced brain damage. When the direct bilirubin fraction is <50% of the total serum bilirubin this risk is associated with the total serum bilirubin alone and treatment decisions should be based on the total serum bilirubin. On the other hand, there are limited data on the risk of bilirubin-induced brain damage in the neonate with severe total hyperbilirubinemia and a direct bilirubin fraction that is equal to or exceeds 50% of the total serum bilirubin. When this rare combination occurs, efforts to keep the indirect bilirubin fraction from reaching severe levels might, nevertheless, be prudent.

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.

Emergency release uncross-matched packed red blood cells for immediate double volume exchange transfusion in neonates with intermediate to advanced acute bilirubin encephalopathy: timely but insufficient?

Given the urgency of double volume exchange transfusion (ExT) in an infant with intermediate to advanced stages of acute bilirubin encephalopathy (ABE), it has been suggested that emergency release uncross-matched packed red blood cells (ER-PRBC) be used. The efficacy of an ExT in removing bilirubin from the brain, however, is a direct function of the mass of albumin exchanged. The very low albumin content of ER-PRBC may fail to be neuroprotective. Predicted changes in total serum bilirubin (TSB), serum albumin, the bilirubin/albumin (B/A) ratio, plasma volume (PV), and bilirubin equilibration from the extravascular space during ER-PRBC ExT are described. ExT using ER-PRBC is efficacious in lowering the TSB. However, this result is falsely reassuring as significant concurrent serum albumin loss, resultant hypoalbuminemia, contraction of PV, limited bilirubin clearance from the extravascular space, and sustained B/A ratio elevations above recommended ExT treatment thresholds suggest that bilirubin neurotoxicity will continue.

Identification of risk for neonatal haemolysis

AIM

To identify neonates at risk of haemolytic hyperbilirubinaemia through near-concurrent measurements of total serum/plasma bilirubin (TB) or transcutaneous bilirubin (TcB) and end-tidal breath carbon monoxide (CO), corrected for ambient CO (ETCOc), an index of bilirubin production and haemolysis.

METHODS

Paired TB/TcB (mg/dL) and ETCOc (ppm) measurements were obtained in newborns (n = 283) at 20 to <60 hours of age in five nurseries. TB/TcB values were assigned TB/TcB percentile risk values using the Bhutani hour-specific nomogram. In infants having two serial TB/TcB measurements (n = 76), TB rate of rise (ROR, mg/dL/h) was calculated.

RESULTS

For the entire cohort (n = 283), 67.1% and 32.9% had TB/TcB<75th and ≥75th percentile, respectively. TB/TcB (5.79 ± 1.84 vs 9.14 ± 2.25 mg/dL) and ETCOc (1.61 ± 0.45 vs 2.02 ± 1.35 ppm, p = 0.0002) were different between the groups. About 36.6% of infants with TB/TcB ≥75th percentile had ETCOc ≥ 2.0 ppm. In the subcohort of infants with serial TB/TcB measurements (n = 76), 44.7% and 55.3% had TB/TcB<75th and ≥75th percentile, respectively. TB/TcB (5.28 ± 1.97 vs 9.53 ± 2.78 mg/dL), ETCOc (1.72 ± 0.48 vs 2.38 ± 1.89 ppm, p = 0.05) and TB ROR (0.011 ± 0.440 vs 0.172 ± 0.471 mg/dL/h) were different between the groups.

CONCLUSION

The combined use of TB/TcB percentile risk assessments and ETCOc measurements can identify infants with haemolytic hyperbilirubinaemia. The addition of TB ROR can identify those infants with elimination disorders.

Refractory Causes of Kernicterus in Developed Countries: Can We Eradicate G6PD Deficiency Triggered and Low-Bilirubin Kernicterus?

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) deficiency triggered and low-bilirubin kernicterus persist despite current prevention strategies.

OBJECTIVE

Review efforts to eradicate bilirubin induced brain injury in these two conditions including novel approaches to risk assessment and hyperbilirubinemia evaluation.

RESULT AND CONCLUSION

In the case of G6PD deficiency, a heightened awareness of populations at risk and an expanded kernicterus prevention strategy focused on intensified parental engagement, education and counselling on neonatal jaundice is needed. In the case of low-bilirubin kernicterus, a renewed focus on identifying infants with hypoalbuminemia and implementation of hyperbilirubinemia treatment thresholds based on the bilirubin/albumin ratio is needed. Bilirubin binding panels when commercially available will prove valuable.

Maternal Empowerment - An Underutilized Strategy to Prevent Kernicterus?

BACKGROUND

Kernicterus is a common cause of death and morbidity in many Low- Middle-income Countries (LMICs) and still occurs in affluent nations. In either case, the immediate cause is delayed treatment of severe hyperbilirubinemia. In the West, a provider driven "systems approach" has been widely adopted to identify babies at risk prior to discharge from birthing centers with follow up monitoring based on the serum bilirubin level at time of discharge. The situation is more complicated in regions of the world where kernicterus is endemic, especially in LMICs where Glucose-6-phosphate Dehydrogenase Deficiency (G6PDd) is common and the system of jaundice management is often fragmented.

OBJECTIVE

To examine reasons for errors in jaundice management leading to kernicterus and the potential beneficial role of enlisting more parental participation in management decisions.

METHOD

We searched world literature related to pitfalls in jaundice management including deficiencies in providers' and parents' knowledge and behavior. Perspectives from mothers of children with kernicterus supplemented the literature review.

RESULT

System failures contributing to kernicterus in affluent countries include a lack of follow up planning, bad advice by providers, and a delay in care seeking by parents. In many LMICs, the majority of births occur at home with unskilled attendants. Traditional practices potentiate hemolysis in G6PDd babies. The danger of severe jaundice is frequently underestimated both by parents and care providers, and cultural and economic barriers as well as ineffective therapies delay care seeking. The failure to provide parents information about identifying severe jaundice and knowledge about the risks and treatment of hyperbilirubinemia has contributed to delayed treatment in both affluent and low-middle-income countries. A recent non-randomized clinical trial, supports teaching all parents skills to monitor jaundice, signs of early neurotoxicity, the importance of breast feeding, avoidance of ineffective or dangerous practices, and when/where to seek help.

CONCLUSION

Empowering parents allow them to participate more fully in care decisions and to confront obstacles to care when provider services fail.

Conjunctival Icterus - An Important but Neglected Sign of Clinically Relevant Hyperbilirubinemia in Jaundiced Neonates

BACKGROUND

Conjunctival icterus is a largely neglected physical sign that may be helpful in identifying neonates with clinically relevant hyperbilirubinemia by practitioners in the hospital and outpatient clinic or parents at home.

OBJECTIVE

A recent NICU based study reported that conjunctival icterus is often a sign of significant (TSB ≥ 17 mg/dl) hyperbilirubinemia and TSB levels ≥ 76th-95th percentile on the Bhutani nomogram. In contrast, others report that conjunctival icterus, although frequently present at high TSB levels, may also be detected at lower TSB concentrations; suggesting instead that its absence may help to rule out significant hyperbilirubinemia.

RESULT AND CONCLUSION

The current review details the nature of conjunctival icterus and presents new data on its clinical occurrence in relation to TSB levels that re-affirm its correlation with elevated TSB concentrations and use to trigger TSB measurement in the jaundiced neonate.

A Hypothesis for Using Pathway Genetic Load Analysis for Understanding Complex Outcomes in Bilirubin Encephalopathy

Genetic-based susceptibility to bilirubin neurotoxicity and chronic bilirubin encephalopathy (kernicterus) is still poorly understood. Neonatal jaundice affects 60–80% of newborns, and considerable effort goes into preventing this relatively benign condition from escalating into the development of kernicterus making the incidence of this potentially devastating condition very rare in more developed countries. The current understanding of the genetic background of kernicterus is largely comprised of mutations related to alterations of bilirubin production, elimination, or both. Less is known about mutations that may predispose or protect against CNS bilirubin neurotoxicity. The lack of a monogenetic source for this risk of bilirubin neurotoxicity suggests that disease progression is dependent upon an overall decrease in the functionality of one or more essential genetically controlled metabolic pathways. In other words, a “load” is placed on key pathways in the form of multiple genetic variants that combine to create a vulnerable phenotype. The idea of epistatic interactions creating a pathway genetic load (PGL) that affects the response to a specific insult has been previously reported as a PGL score. We hypothesize that the PGL score can be used to investigate whether increased susceptibility to bilirubin-induced CNS damage in neonates is due to a mutational load being placed on key genetic pathways important to the central nervous system's response to bilirubin neurotoxicity. We propose a modification of the PGL score method that replaces the use of a canonical pathway with custom gene lists organized into three tiers with descending levels of evidence combined with the utilization of single nucleotide polymorphism (SNP) causality prediction methods. The PGL score has the potential to explain the genetic background of complex bilirubin induced neurological disorders (BIND) such as kernicterus and could be the key to understanding ranges of outcome severity in complex diseases. We anticipate that this method could be useful for improving the care of jaundiced newborns through its use as an at-risk screen. Importantly, this method would also be useful in uncovering basic knowledge about this and other polygenetic diseases whose genetic source is difficult to discern through traditional means such as a genome-wide association study.

Bilirubin-Induced Neurotoxicity in the Preterm Neonate

Bilirubin-induced neurotoxicity in preterm neonates remains a clinical concern. Multiple cellular and molecular cascades likely underlie bilirubin-induced neuronal injury, including plasma membrane perturbations, excitotoxicity, neuroinflammation, oxidative stress, and cell cycle arrest. Preterm newborns are particularly vulnerable secondary to central nervous system immaturity and concurrent adverse clinical conditions that may potentiate bilirubin toxicity. Acute bilirubin encephalopathy in preterm neonates may be subtle and manifest primarily as recurrent symptomatic apneic events. Low-bilirubin kernicterus continues to be reported in preterm neonates, and although multifactorial in nature, is often associated with marked hypoalbuminemia.

Bilirubin Concentrations in Jaundiced Neonates with Conjunctival Icterus

OBJECTIVES

To assess the total serum bilirubin (TSB) levels at which conjunctival icterus is observed in neonates of ≥34 weeks gestation during the first week of life.

STUDY DESIGN

Two convenience samples of neonates were examined for conjunctival icterus within 4 hours of TSB measurements. A concurrent assessment of cephalopedal cutaneous icterus was performed and the TSB characterized using the Bhutani hour-specific risk zone nomogram.

RESULTS

Two hundred forty neonates were studied of which 76 had conjunctival icterus. Conjunctival icterus was always accompanied by cutaneous jaundice to at least the chest and more often than not a TSB >14.9 mg/dL (255 umol/L) consistently in the 76th%-95th% to >95th% range on the Bhutani nomogram. Only a few infants with TSB in the range of 10-14.9 mg/dL (171-255 umol/L) had conjunctival icterus.

CONCLUSIONS

Conjunctival icterus was observed in a subset of jaundiced neonates and associated with elevated hour-specific TSB levels frequently >95th% on the Bhutani nomogram. Conjunctival icterus is a sign of clinically relevant hyperbilirubinemia that merits a TSB measurement and evaluation of the infant.

Common hematologic problems in the newborn nursery

"Common red blood cell disorders encountered in the normal newborn nursery include hemolytic disease of the newborn and resultant hyperbilirubinemia, anemia, and polycythemia. A less frequent clinically relevant hematologic issue in newborns to be covered herein is thrombocytopenia."

Are the neuromotor disabilities of bilirubin-induced neurologic dysfunction disorders related to the cerebellum and its connections?

Investigators have hypothesized a range of subcortical neuropathology in the genesis of bilirubin-induced neurologic dysfunction (BIND). The current review builds on this speculation with a specific focus on the cerebellum and its connections in the development of the subtle neuromotor disabilities of BIND. The focus on the cerebellum derives from the following observations: (i) the cerebellum is vulnerable to bilirubin-induced injury; perhaps the most vulnerable region within the central nervous system; (ii) infants with cerebellar injury exhibit a neuromotor phenotype similar to BIND; and (iii) the cerebellum has extensive bidirectional circuitry projections to motor and non-motor regions of the brainstem and cerebral cortex that impact a variety of neurobehaviors. Future study using advanced magnetic resonance neuroimaging techniques have the potential to shed new insights into bilirubin's effect on neural network topology via both structural and functional brain connectivity measurements.

Magnetic resonance imaging of bilirubin encephalopathy: current limitations and future promise

Infants with chronic bilirubin encephalopathy often demonstrate abnormal bilateral, symmetric, high-signal intensity on T2-weighted magnetic resonance imaging of the globus pallidus and subthalamic nucleus, consistent with the neuropathology of kernicterus. Early magnetic resonance imaging of at-risk infants, while frequently showing increased T1-signal in these regions, may give false-positive findings due to the presence of myelin in these structures. Advanced magnetic resonance imaging including diffusion-weighted imaging, magnetic resonance spectroscopy, and diffusion tensor imaging with tractography may shed new insights into the pathogenesis of bilirubin-induced brain injury and the neural basis of long-term disability in infants and children with chronic bilirubin encephalopathy.

The enigma of low bilirubin kernicterus in premature infants: why does it still occur, and is it preventable?

Low bilirubin kernicterus in preterm neonates, though rare, remains an unpredictable and refractory form of brain injury. Hypoalbuminemia, co-morbid CNS insult(s), infection, and inflammation are contributing causes that, in many cases, appear to interact in potentiating bilirubin neurotoxicity. Despite compulsive attention to serum bilirubin levels, and clinical and laboratory indices of neurotoxicity risk, low bilirubin kernicterus continues to be seen in contemporary NICUs. While efforts to refine and improve current treatment guidelines are certainly needed, such revision(s) will also have to take into account the risks and benefits of any intervention, including phototherapy.

Apnea in acute bilirubin encephalopathy

Central apnea, defined as cessation of breathing for ≥20s, is frequent in premature infants born at <34 weeks׳ gestation but uncommon among healthy late preterm (34(0/7)-36(6/7) weeks׳ gestation) and term (≥37 weeks׳ gestation) infants, where it is usually a clinical manifestation of a neurological or metabolic problem. There is growing evidence that marked unconjugated hyperbilirubinemia is associated with central apnea in neonates. This article explores the reported association between acute bilirubin encephalopathy and symptomatic apneic events in newborns and the possible mechanisms involved in the pathogenesis of this phenomenon. The prevalence of symptomatic apneic events in reports of acute bilirubin encephalopathy suggests this clinical finding should be considered a sign of bilirubin neurotoxicity.

Effect of nuclear factor κB inhibition on serotype 9 adeno-associated viral (AAV9) minidystrophin gene transfer to the mdx mouse

Gene therapy studies for Duchenne muscular dystrophy (DMD) have focused on viral vector-mediated gene transfer to provide therapeutic protein expression or treatment with drugs to limit dystrophic changes in muscle. The pathological activation of the nuclear factor (NF)-κB signaling pathway has emerged as an important cause of dystrophic muscle changes in muscular dystrophy. Furthermore, activation of NF-κB may inhibit gene transfer by promoting inflammation in response to the transgene or vector. Therefore, we hypothesized that inhibition of pathological NF-κB activation in muscle would complement the therapeutic benefits of dystrophin gene transfer in the mdx mouse model of DMD. Systemic gene transfer using serotype 9 adeno-associated viral (AAV9) vectors is promising for treatment of preclinical models of DMD because of vector tropism to cardiac and skeletal muscle. In quadriceps of C57BL/10ScSn-Dmd(mdx)/J (mdx) mice, the addition of octalysine (8K)-NF-κB essential modulator (NEMO)-binding domain (8K-NBD) peptide treatment to AAV9 minidystrophin gene delivery resulted in increased levels of recombinant dystrophin expression suggesting that 8K-NBD treatment promoted an environment in muscle tissue conducive to higher levels of expression. Indices of necrosis and regeneration were diminished with AAV9 gene delivery alone and to a greater degree with the addition of 8K-NBD treatment. In diaphragm muscle, high-level transgene expression was achieved with AAV9 minidystoophin gene delivery alone; therefore, improvements in histological and physiological indices were comparable in the two treatment groups. The data support benefit from 8K-NBD treatment to complement gene transfer therapy for DMD in muscle tissue that receives incomplete levels of transduction by gene transfer, which may be highly significant for clinical applications of muscle gene delivery.

Systemic delivery of NEMO binding domain/IKKγ inhibitory peptide to young mdx mice improves dystrophic skeletal muscle histopathology

The activation of nuclear factor κB (NF-κB) contributes to muscle degeneration that results from dystrophin deficiency in human Duchenne muscular dystrophy (DMD) and in the mdx mouse. In dystrophic muscle, NF-κB participates in inflammation and failure of muscle regeneration. Peptides containing the NF-κB Essential Modulator (NEMO) binding domain (NBD) disrupt the IκB kinase complex, thus blocking NF-κB activation. The NBD peptide, which is linked to a protein transduction domain to achieve in vivo peptide delivery to muscle tissue, was systemically delivered to mdx mice for 4 or 7 weeks to study NF-κB activation, histological changes in hind limb and diaphragm muscle and ex vivo function of diaphragm muscle. Decreased NF-κB activation, decreased necrosis and increased regeneration were observed in hind limb and diaphragm muscle in mdx mice treated systemically with NBD peptide, as compared to control mdx mice. NBD peptide treatment resulted in improved generation of specific force and greater resistance to lengthening activations in diaphragm muscle ex vivo. Together these data support the potential of NBD peptides for the treatment of DMD by modulating dystrophic pathways in muscle that are downstream of dystrophin deficiency.

Improvement of the mdx mouse dystrophic phenotype by systemic in utero AAV8 delivery of a minidystrophin gene

Duchenne muscular dystrophy (DMD) is a devastating primary muscle disease with pathological changes in skeletal muscle that are ongoing at the time of birth. Progressive deterioration in striated muscle function in affected individuals ultimately results in early death due to cardio-pulmonary failure. As affected individuals can be identified before birth by prenatal genetic testing for DMD, gene replacement treatment can be started in utero. This approach offers the possibility of preventing pathological changes in muscle that begin early in life. To test in utero gene transfer in the mdx mouse model of DMD, a minidystrophin gene driven by the human cytomegalovirus promoter was delivered systemically by an intraperitoneal injection to the fetus at embryonic day 16. Treated mdx mice studied at 9 weeks after birth showed widespread expression of recombinant dystrophin in skeletal muscle, restoration of the dystrophin-associated glycoprotein complex in dystrophin-expressing muscle fibers, improved muscle pathology, and functional benefit to the transduced diaphragm compared with untreated littermate controls. These results support the potential of the AAV8 vector to efficiently cross the blood vessel barrier to achieve systemic gene transfer to skeletal muscle in utero in a mouse model of muscular dystrophy, to significantly improve the dystrophic phenotype and to ameliorate the processes that lead to exhaustion of the skeletal muscle regenerative capacity.