The role of phototherapy in the crash-cart approach to extreme neonatal jaundice

Bilirubin Encephalopathy

PURPOSE OF REVIEW

Hyperbilirubinemia is commonly seen in neonates. Though hyperbilirubinemia is typically asymptomatic, severe elevation of bilirubin levels can lead to acute bilirubin encephalopathy and progress to kernicterus spectrum disorder, a chronic condition characterized by hearing loss, extrapyramidal dysfunction, ophthalmoplegia, and enamel hypoplasia. Epidemiological data show that the implementation of universal pre-discharge bilirubin screening programs has reduced the rates of hyperbilirubinemia-associated complications. However, acute bilirubin encephalopathy and kernicterus spectrum disorder are still particularly common in low- and middle-income countries.

RECENT FINDINGS

The understanding of the genetic and biochemical processes that increase the susceptibility of defined anatomical areas of the central nervous system to the deleterious effects of bilirubin may facilitate the development of effective treatments for acute bilirubin encephalopathy and kernicterus spectrum disorder. Scoring systems are available for the diagnosis and severity grading of these conditions. The treatment of hyperbilirubinemia in newborns relies on the use of phototherapy and exchange transfusion. However, novel therapeutic options including deep brain stimulation, brain-computer interface, and stem cell transplantation may alleviate the heavy disease burden associated with kernicterus spectrum disorder. Despite improved screening and treatment options, the prevalence of acute bilirubin encephalopathy and kernicterus spectrum disorder remains elevated in low- and middle-income countries. The continued presence and associated long-term disability of these conditions warrant further research to improve their prevention and management.

Intensive phototherapy vs. exchange transfusion for the treatment of neonatal hyperbilirubinemia

Background:

Intensive phototherapy (IPT) and exchange transfusion (ET) are the main treatments for extreme hyperbilirubinemia. However, there is no reliable evidence on determining the thresholds for these treatments. This multicenter study compared the effectiveness and complications of IPT and ET in the treatment of extreme hyperbilirubinemia.

Methods:

This retrospective cohort study was conducted in seven centers from January 2015 to January 2018. Patients with extreme hyperbilirubinemia that met the criteria of ET were included. Patients were divided into three subgroups (low-, medium-, and high- risk) according to gestational week and risk factors. Propensity score matching (PSM) was performed to balance the data before treatment. Study outcomes included the development of bilirubin encephalopathy, duration of hospitalization, expenses, and complications. Mortality, auditory complications, seizures, enamel dysplasia, ocular motility disorders, athetosis, motor, and language development were evaluated during follow-up at age of 3 years.

Results:

A total of 1164 patients were included in this study. After PSM, 296 patients in the IPT only group and 296 patients in the IPT plus ET group were further divided into the low-, medium-, and high-risk subgroups with 188, 364, and 40 matched patients, respectively. No significant differences were found between the IPT only and IPT plus ET groups in terms of morbidity, complications, and sequelae. Hospitalization duration and expenses were lower in the low- and medium-risk subgroups in the IPT only group.

Conclusions:

In this study, our results suggest that IPT is a safe and effective treatment for extreme hyperbilirubinemia. The indication of ET for patients with hyperbilirubinemia could be stricter. However, it is necessary to have a contingency plan for emergency ET as soon as IPT is commenced especially for infants with risk factors. If IPT can be guaranteed and proved to be therapeutic, ET should be avoided as much as possible.

Preliminary observations of a system for determination of phototherapy exposure over a neonate body shape

While it is possible to determine the irradiance and spectral content for a given neonatal phototherapy device at various locations over a neonate's surface, this does not allow estimation of the total rate of energy delivery within a specific spectral range over the neonate's exposed body surface. A series of 192 blue wavelength enhanced silicon photodiodes was distributed over the surface of a commercially available newborn body shape and connected to a specially designed interface circuit. Placement of photosensors over the surface of the baby shape was determined with consideration of the surface area of twelve specific anatomical areas where each was allocated 16 individual photodiodes. Calibration of detection channels for specific wavelength intervals was undertaken using a Bentham dmc150 spectroradiometer system and also a separate hand held spectroradiometer. This made it possible to estimate the effective integrated dose rate in Watts for specific wavelength intervals such as 460 nm to 490 nm as identified by the American Academy of Pediatrics for phototherapy lamp devices. This allowed identification of dose rate contributions from specific anatomical areas. Initial observations are reported for a range of phototherapy lamp systems and the findings are discussed in terms of their predicted relative clinical effectiveness. Options are also discussed in relation to the future development of the reported measurement system.

Can exchange transfusion be replaced by double-LED phototherapy?

Phototherapy is a conventional treatment for neonatal jaundice and widely considered as a safe procedure. Recent developments in light-emitting diode (LED) phototherapy devices have made more effective treatments possible. Exchange transfusion (ET) is typically applied for cases of refractory severe hyperbilirubinemia despite its risk of various complications. Since the therapeutic effect of phototherapy is correlated with its irradiance, ET may be avoided by performing phototherapy with higher irradiation. Recently, we adopted double-LED phototherapy as a bridging treatment to ET to treat a case of severe hyperbilirubinemia. In this case, the continual increase of bilirubin levels was suppressed immediately after its administration, and ET was not required. Throughout the treatment, no complications or increase in oxidative stress was observed. In addition, neurodevelopment was appropriate for the patient’s age at the 1-year follow-up, and no findings of kernicterus, including physical and magnetic resonance imaging findings, were observed. We hypothesized that double-LED phototherapy may be a good treatment strategy to replace ET for infants with severe hyperbilirubinemia; however, further investigations regarding safety issues including acute and long-term complications are needed before clinical adaptation.

Acute bilirubin encephalopathy: Some lessons learned

Acute bilirubin encephalopathy (ABE) is still an insufficiently addressed cause of mortality and long-term morbidity in low- and middle-income countries (LMICs). This article highlights that delayed or incorrect medical advice, inaccurate bilirubin measurements as well as ineffective phototherapy are some of the relevant causes predisposing jaundiced newborns to develop extreme hyperbilirubinemia [EHB, total serum/plasma bilirubin (TB) ≥ 25 mg/dL (428 µmol/L)] and subsequent ABE. Obstacles preventing state of the art management of such infants are also discussed. Prevention of ABE cannot occur without a system-based approach tailored to suit the needs and available resources of each community. Clear set protocols, rigorous training, monitoring, and accurate documentation together with simple innovative affordable technologies that can be locally produced, are essential to observe the change desired.

Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn

Bilirubin is the end product of heme catabolism formed during a process that involves oxidation-reduction reactions and conserves iron body stores. Unconjugated hyperbilirubinemia is common in newborn infants, but rare later in life. The basic physiology of bilirubin metabolism, such as production, transport, and excretion, has been well described. However, in the neonate, numerous variables related to nutrition, ethnicity, and genetic variants at several metabolic steps may be superimposed on the normal physiological hyperbilirubinemia that occurs in the first week of life and results in bilirubin levels that may be toxic to the brain. Bilirubin exists in several isomeric forms that differ in their polarities and is considered a physiologically important antioxidant. Here we review the chemistry of the bilirubin molecule and its metabolism in the body with a particular focus on the processes that impact the newborn infant, and how differences relative to older children and adults contribute to the risk of developing both acute and long-term neurological sequelae in the newborn infant. The final section deals with the interplay between the brain and bilirubin and its entry, clearance, and accumulation. We conclude with a discussion of the current state of knowledge regarding the mechanism(s) of bilirubin neurotoxicity.

Review of bilirubin neurotoxicity II: preventing and treating acute bilirubin encephalopathy and kernicterus spectrum disorders

Previously in Part I of this two-part review, we discussed the current and recent advances in the understanding of the molecular biology and neuropathology of bilirubin neurotoxicity (BNTx). Here in Part II, we summarize current treatment options available to treat the severely jaundiced infants to prevent significant brain damage and improve clinical outcomes. In addition, we review potential novel therapies that are in various stages of research and development. We will emphasize treatments for both prevention and treatment of both acute bilirubin encephalopathy (ABE) and kernicterus spectrum disorders (KSDs), highlighting the treatment of the most disabling neurological sequelae of children with mild-to-severe KSDs whose "rare disease" status often means they are overlooked by the clinical research community at large. As with other secondary dystonias, treatment of the dystonic motor symptoms in kernicterus is the greatest clinical challenge.

High unbound bilirubin for age: a neurotoxin with major effects on the developing brain

Neonatal hyperbilirubinemia is one of the most frequent diagnoses made in neonates. A high level of unconjugated bilirubin that is unbound to albumin is neurotoxic when the level exceeds age-specific thresholds or at lower levels in neonates with neurotoxic risk factors. Lower range of unbound bilirubin results in apoptosis, while moderate-to-high levels result in neuronal necrosis. Basal ganglia and various brain stem nuclei are more susceptible to bilirubin toxicity. Proposed mechanisms of bilirubin-induced neurotoxicity include excessive release of glutamate, mitochondrial energy failure, release of proinflammatory cytokines, and increased intracellular calcium concentration. These mechanisms are similar to the events that occur following hypoxic-ischemic insult in neonates. Severe hyperbilirubinemia in term neonates has been shown to be associated with increased risk for autism spectrum disorders. The neuropathological finding of bilirubin-induced neurotoxicity also includes cerebellar injury with a decreased number of Purkinje cells, and disruption of multisensory feedback loop between cerebellum and cortical neurons which may explain the clinical characteristics of autism spectrum disorders. Severe hyperbilirubinemia occurs more frequently in infants from low- and middle-income countries (LMIC). Simple devices to measure bilirubin, and timely treatment are essential to reduce neurotoxicity, and improve outcomes for thousands of neonates around the world.

Light-induced morphological transition between unconjugated bilirubin photoisomers

Morphology switching by an external stimulus creates the possibility to detect and control the activity and functionality of bio-molecules. Unconjugated bilirubin (UCB), a waste product resulting from heme catabolism, is highly sensitive towards blue light induced configurational conversion from (4Z,15Z) to (4Z,15E)-bilirubin. UCB has a distinct elongated nanostructure which is readily photoswitchable to spherical by external blue light (470 nm) irradiation. Herein, the morphology alteration by blue light was nicely correlated with the photoisomerisation of UCB, using different microscopic and spectroscopic techniques. To restrict the other photo-incidents during phototreatment on UCB, a suitable time frame was calibrated by monitoring the absorption, HPLC, lifetime distribution and ¹H NMR studies. Furthermore, by the help of this morphological transition as a marker, UCB early stage photoisomerisation has also been triggered by two-photon irradiation (940 nm).

Bilirubin binding in jaundiced newborns: from bench to bedside?

BACKGROUND

Bilirubin-induced neurologic dysfunction (BIND) is a spectrum of preventable neurological sequelae in jaundiced newborns. Current total plasma bilirubin (B_T) concentration thresholds for phototherapy and/or exchange transfusion poorly predict BIND.

METHODS

The unbound (free) bilirubin (B_f) measured at these B_T thresholds provides additional information about the risk for BIND. B_f can be readily adapted to clinical use by determining B_f population parameters at current B_T thresholds. These parameters can be established using a plasma bilirubin binding panel (BBP) consisting of B_T, B_f, and two empiric constants, the maximum B_T (B_Tmax) and the corresponding equilibrium association bilirubin constant (K).

RESULTS

B_Tmax and K provide the variables needed to accurately estimate B_f at B_T < B_Tmax to obtain B_f at threshold B_T in patient samples. Once B_f population parameters are known, the BBP in a newborn can be used to identify poor bilirubin binding (higher B_f at the threshold B_T compared with the population) and increased risk of BIND.

CONCLUSION

The BBP can also be used in jaundice screening to better identify the actual B_T at which intervention would be prudent. The BBP is used with current B_T thresholds to better identify the risk of BIND and whether and when to intervene.

Filtered sunlight versus intensive electric powered phototherapy in moderate-to-severe neonatal hyperbilirubinaemia: a randomised controlled non-inferiority trial

BACKGROUND

Kernicterus resulting from severe neonatal hyperbilirubinaemia is a leading cause of preventable deaths and disabilities in low-income and middle-income countries, partly because high-quality intensive phototherapy is unavailable. Previously, we showed that filtered-sunlight phototherapy (FSPT) was efficacious and safe for treatment of mild-to-moderate neonatal hyperbilirubinaemia. We aimed to extend these studies to infants with moderate-to-severe hyperbilirubinaemia.

METHODS

We did a prospective, randomised controlled non-inferiority trial in Ogbomoso, Nigeria-a simulated rural setting. Near-term or term infants aged 14 days or younger who were of 35 weeks or more gestational age and with total serum bilirubin concentrations at or above the recommended age-dependent treatment levels for high-risk neonates were randomly assigned (1:1) to either FSPT or intensive electric phototherapy (IEPT). Randomisation was computer-generated, and neither clinicians nor the parents or guardians of participants were masked to group allocation. FSPT was delivered in a transparent polycarbonate room lined with commercial tinting films that transmitted effective phototherapeutic light, blocked ultraviolet light, and reduced infrared radiation. The primary outcome was efficacy, which was based on assessable treatment days only (ie, those on which at least 4 h of phototherapy was delivered) and defined as a rate of increase in total serum bilirubin concentrations of less than 3·4 μmol/L/h in infants aged 72 h or younger, or a decrease in total serum bilirubin concentrations in those older than 72 h. Safety was defined as no sustained hypothermia, hyperthermia, dehydration, or sunburn and was based on all treatment days. Analysis was by intention to treat with a non-inferiority margin of 10%.

FINDINGS

Between July 31, 2015, and April 30, 2017, 174 neonates were enrolled and randomly assigned: 87 to FSPT and 87 to IEPT. Neonates in the FSPT group received 215 days of phototherapy, 82 (38%) of which were not assessable. Neonates in the IEPT group received 219 treatment days of phototherapy, 67 (31%) of which were not assessable. Median irradiance was 37·3 μW/cm²/nm (IQR 21·4-56·4) in the FSPT group and 50·4 μW/cm²/nm (44·5-66·2) in the IEPT group. FSPT was efficacious on 116 (87·2%) of 133 treatment days; IEPT was efficacious on 135 (88·8%) of 152 treatment days (mean difference -1·6%, 95% CI -9·9 to 6·7; p=0·8165). Because the CI did not extend below -10%, we concluded that FSPT was not inferior to IEPT. Treatment was safe for all neonates.

INTERPRETATION

FSPT is safe and no less efficacious than IEPT for treatment of moderate-to-severe neonatal hyperbilirubinaemia in near-term and term infants.

FUNDING

Thrasher Research Fund and National Center for Advancing Translational Sciences.

Prediction of 3- to 5-Month Outcomes from Signs of Acute Bilirubin Toxicity in Newborn Infants

OBJECTIVE

To evaluate the ability of the bilirubin-induced neurologic dysfunction (BIND) score to predict residual neurologic and auditory disability and to document the relationship of BIND score to total serum bilirubin (TSB) concentration.

STUDY DESIGN

The BIND score (assessing mental status, muscle tone, and cry patterns) was obtained serially at 6- to 8-hour intervals in 220 near-term and full-term infants with severe hyperbilirubinemia. Neurologic and/or auditory outcomes at 3-5 months of age were correlated with the highest calculated BIND score. The BIND score was also correlated with TSB.

RESULTS

Follow-up neurologic and auditory examinations were performed for 145/202 (72%) surviving infants. All infants with severe acute bilirubin encephalopathy (BIND scores 7-9) either died or suffered residual neurologic and auditory impairment. Of 24 cases with moderate encephalopathy (BIND 4-6), 15 (62.5%) resolved following aggressive intervention and were normal at follow-up. Three of 73 infants with mild encephalopathy (BIND scores 1-3) but severe jaundice (TSB ranging 33.5-38 mg/dL; 573-650 µmol/L) had residual neurologic and/or auditory impairment. A BIND score ≥4 had a specificity of 87.3% and a sensitivity of 97.4% for predicting poor neurologic outcomes (receiver operating characteristic analysis). BIND scores trended higher with severe hyperbilirubinemia (r² = 0.54, P < .005), but 5/39 (13%) infants with TSB ≥36.5 mg/dL (624 µmol/L) had BIND scores ≤3, and normal outcomes at 3-5 months.

CONCLUSIONS

The BIND score can be used to evaluate the severity of acute bilirubin encephalopathy and predict residual neurologic and hearing dysfunction.

Biology of Bilirubin Photoisomers

Phototherapy is the main treatment for neonatal hyperbilirubinemia. In acute treatment of extreme hyperbilirubinemia, intensive phototherapy may have a role in 'detoxifying' the bilirubin molecule to more polar photoisomers, which should be less prone to crossing the blood-brain barrier, providing a 'brain-sparing' effect. This article reviews the biology of bilirubin isomers. Although there is evidence supporting the lower toxicity of bilirubin photoisomers, there are studies showing the opposite. There are methodologic weaknesses in most studies and better-designed experiments are needed. In an infant acutely threatened by bilirubin-induced brain damage, intensified phototherapy should be used expediently and aggressively.

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.

Neonatal death suspected to be from sepsis was found to be kernicterus with G6PD deficiency

We cared for a term male infant born to Burmese immigrants. At about 24 hours a total serum bilirubin (TSB) was 9.3 mg/dL, and phototherapy was begun. It was stopped 48 hours later, with a TSB of 10.9 mg/dL, and he was discharged from the hospital with an appointment for a repeat TSB check 48 hours later. A few hours before the appointment he became listless and apneic, and his parents took him to the emergency department of the regional children's hospital, where sepsis was suspected. The TSB was 41 mg/dL. He died 4 hours later, despite intensive care efforts, with opisthotonus and refractory hypotension. Blood drawn before the exchange transfusion had low glucose-6-phosphate dehydrogenase (G6PD) enzymatic activity, and sequencing of the G6PD gene revealed the G6PD Mahidol mutation (c.487G>A). Cultures and postmortem examination did not demonstrate an infectious process, but kernicterus was present. Acute kernicterus can mimic septic shock.

Fundamentals of phototherapy for neonatal jaundice

Phototherapy is the use of visible light for the treatment of hyperbilirubinemia in the newborn. This relatively common therapy lowers the serum bilirubin level by transforming bilirubin into water-soluble isomers that can be eliminated without conjugation in the liver. The dose of phototherapy is a key factor in how quickly it works; dose in turn is determined by the wavelength of the light, the intensity of the light (irradiance), the distance between the light and the baby, and the body surface area exposed to the light. Commercially available phototherapy systems include those that deliver light via fluorescent bulbs, halogen quartz lamps, light-emitting diodes, and fiberoptic mattresses. Proper nursing care enhances the effectiveness of phototherapy and minimizes complications. Caregiver responsibilities include ensuring effective irradiance delivery, maximizing skin exposure, providing eye protection and eye care, careful attention to thermoregulation, maintaining adequate hydration, promoting elimination, and supporting parent-infant interaction.

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.