Effects of Soybean Lipid Infusion on Unbound Free Fatty Acids and Unbound Bilirubin in Preterm Infants

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.

Effect of reduced versus usual lipid emulsion dosing on bilirubin neurotoxicity and neurodevelopmental impairment in extremely preterm infants: study protocol for a randomized controlled trial

BACKGROUND

Bilirubin neurotoxicity (BN) occurs in premature infants at lower total serum bilirubin levels than term infants and causes neurodevelopmental impairment. Usual dose lipid infusions in preterm infants may increase free fatty acids sufficiently to cause bilirubin displacement from albumin, increasing passage of unbound bilirubin (UB) into the brain leading to BN and neurodevelopmental impairment not reliably identifiable in infancy. These risks may be influenced by whether cycled or continuous phototherapy is used to control bilirubin levels.

OBJECTIVE

To assess differences in wave V latency measured by brainstem auditory evoked responses (BAER) at 34-36 weeks gestational age in infants born ≤ 750 g or < 27 weeks' gestational age randomized to receive usual or reduced dose lipid emulsion (half of the usual dose) irrespective of whether cycled or continuous phototherapy is administered.

METHODS

Pilot factorial randomized controlled trial (RCT) of lipid dosing (usual and reduced) with treatment groups balanced between cycled or continuous phototherapy assignment. Eligible infants are born at ≤ 750 g or < 27 weeks' gestational age enrolled in the NICHD Neonatal Research Network RCT of cycled or continuous phototherapy. Infants will randomize 1:1 to reduced or usual dose lipid assignment during the first 2 weeks after birth and stratified by phototherapy assignment. Free fatty acids and UB will be measured daily using a novel probe. BAER testing will be performed at 34-36 weeks postmenstrual age or prior to discharge. Blinded neurodevelopmental assessments will be performed at 22-26 months. Intention-to-treat analyses will be performed with generalized linear mixed models with lipid dose and phototherapy assignments as random effects covariates, and assessment for interactions. Bayesian analyses will be performed as a secondary analysis.

DISCUSSION

Pragmatic trials are needed to evaluate whether lipid emulsion dosing modifies the effect of phototherapy on BN. This factorial design presents a unique opportunity to evaluate both therapies and their interaction. This study aims to address basic controversial questions about the relationships between lipid administration, free fatty acids, UB, and BN. Findings suggesting a reduced lipid dose can diminish the risk of BN would support the need for a large multicenter RCT of reduced versus usual lipid dosing.

TRIAL REGISTRATION

Clinical Trials.gov, NCT04584983, Registered 14 October 2020, https://clinicaltrials.gov/ct2/show/NCT04584983 Protocol version: Version 3.2 (10/5/2022).

Effect of Reduced Versus Usual Lipid Emulsion Dosing on Bilirubin Neurotoxicity and Neurodevelopmental Impairment in Extremely Preterm Infants: Study Protocol for a Randomized Controlled Trial

Background : Bilirubin neurotoxicity ( BN ) occurs in premature infants at lower total serum bilirubin levels than term infants and causes neurodevelopmental impairment. Usual dose lipid infusions in preterm infants may increase free fatty acids sufficiently to cause bilirubin displacement from albumin, increasing passage of unbound bilirubin ( UB ) into the brain leading to BN and neurodevelopmental impairment not reliably identifiable in infancy. These risks may be influenced by whether cycled or continuous phototherapy is used to control bilirubin levels. Objective : To assess differences in wave V latency measured by brainstem auditory evoked responses ( BAER ) at 34-36 weeks gestational age in infants born ≤750 g or <27 weeks' gestational age randomized to receive usual or reduced dose lipid emulsion (half of the usual dose) irrespective of whether cycled or continuous phototherapy is administered. Methods : Pilot factorial randomized controlled trial ( RCT ) of lipid dosing (usual and reduced) with treatment groups balanced between cycled or continuous phototherapy assignment. Eligible infants are born at ≤750 g or <27 weeks' gestational age enrolled in the NICHD Neonatal Research Network RCT of cycled or continuous phototherapy. Infants will randomize 1:1 to reduced or usual dose lipid assignment during the first 2 weeks after birth and stratified by phototherapy assignment. Free fatty acids and UB will be measured daily using a novel probe. BAER testing will be performed at 34-36 weeks postmenstrual age or prior to discharge. Blinded neurodevelopmental assessments will be performed at 22-26 months. Intention-to-treat analyses will be performed with generalized linear mixed models with lipid dose and phototherapy assignments as random effects covariates, and assessment for interactions. Bayesian analyses will be performed as a secondary analysis. Discussion : Pragmatic trials are needed to evaluate whether lipid emulsion dosing modifies the effect of phototherapy on BN. This factorial design presents a unique opportunity to evaluate both therapies and their interaction. This study aims to address basic controversial questions about the relationships between lipid administration, free fatty acids, UB, and BN. Findings suggesting a reduced lipid dose can diminish the risk of BN would support the need for a large multicenter RCT of reduced versus usual lipid dosing. Trial Registration : Clinical Trials.gov, NCT04584983, Registered 14 October 2020, https://clinicaltrials.gov/ct2/show/NCT04584983 Protocol Version : Version 3.2 (10/5/2022).

Petukhov P, Kurilova OV, Ilinsky VV, Trakhtman PE, Dadali EL, Samokhodskaya LM, Kamalov AA, Kost OA. Blood ACE Phenotyping for Personalized Medicine: Revelation of Patients with Conformationally Altered ACE

Background: The angiotensin-converting enzyme (ACE) metabolizes a number of important peptides participating in blood pressure regulation and vascular remodeling. Elevated blood ACE is a marker for granulomatous diseases and elevated ACE expression in tissues is associated with increased risk of cardiovascular diseases. Objective and Methodology: We applied a novel approach -ACE phenotyping-to find a reason for conformationally impaired ACE in the blood of one particular donor. Similar conformationally altered ACEs were detected previously in 2-4% of the healthy population and in up to 20% of patients with uremia, and were characterized by significant increase in the rate of angiotensin I hydrolysis. Principal findings: This donor has (1) significantly increased level of endogenous ACE inhibitor in plasma with MW less than 1000; (2) increased activity toward angiotensin I; (3) M71V mutation in ABCG2 (membrane transporter for more than 200 compounds, including bilirubin). We hypothesize that this patient may also have the decreased level of free bilirubin in plasma, which normally binds to the N domain of ACE. Analysis of the local conformation of ACE in plasma of patients with Gilbert and Crigler-Najjar syndromes allowed us to speculate that binding of mAbs 1G12 and 6A12 to plasma ACE could be a natural sensor for estimation of free bilirubin level in plasma. Totally, 235 human plasma/sera samples were screened for conformational changes in soluble ACE. Conclusions/Significance: ACE phenotyping of plasma samples allows us to identify individuals with conformationally altered ACE. This type of screening has clinical significance because this conformationally altered ACE could not only result in the enhancement of the level of angiotensin II but could also serve as an indicator of free bilirubin levels.

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.

Effects of lipid emulsions on unbound bilirubin and response to phototherapy in preterm infants

OBJECTIVE

Bilirubin-induced neurotoxicity is mediated by the fraction of total serum bilirubin (TSB) not bound to albumin (Bf). Unbound free fatty acids (FFAu) generated from lipid emulsions compete with bilirubin for albumin binding, increasing Bf. Soy-based (IL) and soy-MCT-olive-fish oil-based (SMOF) lipid emulsions contain different fatty acids with distinct albumin binding affinities. IL increases Bf in preterm infants, but the effects of SMOF on Bf are not known. Our objective was to compare changes in TSB, Bf, FFAu, and response to phototherapy in preterm infants receiving SMOF and IL. We hypothesized that SMOF would be associated with lower Bf and better response to phototherapy than IL.

METHODS

Very preterm and low birth weight infants (<1500 g, <32 weeks) were infused with IL (n = 20) or SMOF (n = 20) as prescribed by providers. Phototherapy was prescribed using the standard care practice. FFAu profiles and levels, TSB, and Bf were measured on 0, 1, 2, and 3 g/kg/day of lipid infusion and at the initiation and termination of phototherapy. TSB was analyzed in the clinical laboratory using the diazo technique. FFAu and Bf were measured using fluorescent probes.

RESULTS

Escalating doses of IL and SMOF increased FFAu levels and Bf, but not TSB. Phototherapy did not significantly decrease Bf for infants receiving either lipid. IL-treated infants had higher levels of unbound linoleic acid, and SMOF-treated infants had higher unbound arachidonic, oleic, and docosahexaenoic acids.

CONCLUSIONS

IL and SMOF both increase Bf similarly, and phototherapy does not significantly affect Bf for infants receiving them.

Models of bilirubin neurological damage: lessons learned and new challenges

OBJECTIVE

Jaundice (icterus) is the visible manifestation of the accumulation of bilirubin in the tissue and is indicative of potential toxicity to the brain. Since its very first description more than 2000 years ago, many efforts have been undertaken to understand the molecular determinants of bilirubin toxicity to neuronal cells to reduce the risk of neurological sequelae through the use of available chemicals and in vitro, ex vivo, in vivo, and clinical models. Although several studies have been performed, important questions remain unanswered, such as the reasons for regional sensitivity and the interplay with brain development. The number of new molecular effects identified has increased further, which has added even more complexity to the understanding of the condition. As new research challenges emerged, so does the need to establish solid models of prematurity.

METHODS

This review critically summarizes the key mechanisms of severe neonatal hyperbilirubinemia and the use of the available models and technologies for translational research.

IMPACT

We critically review the conceptual dogmas and models used for studying bilirubin-induced neurotoxicity. We point out the pitfalls and translational gaps, and suggest new clinical research challenges. We hope to inform researchers on the pro and cons of the models used, and to help direct their experimental focus in a most translational research.

Hypertriglyceridemia in Preterm Infants

Preterm and critically ill infants are at risk for hypertriglyceridemia (HTG). Common risk factors for HTG include prematurity, intravenous lipid emulsion dose and oil composition, reduced lipoprotein lipase activity, fetal growth restriction, sepsis, and renal failure. Despite these risk factors, clinicians lack a universally agreed upon definition for HTG and evidence-based approach to HTG management. This review provides a detailed overview of triglyceride and intravenous lipid emulsion metabolism and how this relates to specific HTG risk factors, along with some practical considerations for managing HTG in the neonatal population.

The effect of different intravenous lipids on free bilirubin levels in premature infants

BACKGROUND

Intravenous lipid emulsions are commonly used as a part of parenteral nutrition in premature infants. The potential bilirubin-displacing effects of high free fatty acid (FFA) levels during lipid infusions are known. Levels of free bilirubin (FB) predict the risk of bilirubin neurotoxicity more accurately than indirect serum bilirubin levels. In the present study, we decided to compare the effect of two different lipid solutions on free bilirubin and free fatty acids levels in premature infants.

METHODS

Infants were grouped into two groups according to intravenous lipid preparations: Infants in Group 1 received lipid emulsion containing olive oil + soybean oil and Group 2 received containing olive oil + soybean oil + fish oil. The blood samples were gained when lipid intake was 3.5 g/kg/day and FFA and FB levels were analyzed.

RESULTS

Serum FFA and FB levels were similar in groups (p = 0.26 and 0.69 respectively). There were significant correlation between serum FFA and FB levels in Group 1 (r = 0.74, p < 0.001) and in Group 2 (r = 0.92, p < 0.001).

CONCLUSION

Both lipid preparations seem to have similar effects on free bilirubin and free fatty acid levels in premature newborns.

An Evaluation to Establish the Acceptable Serum Triglyceride Levels in Neonates Receiving Intravenous Fat Emulsion Infusion in a Multicenter Retrospective Study

OBJECTIVE

This study aimed to establish neonatal serum triglyceride (TG) level reference ranges during lipid infusion and correlate peak TG with neonatal outcomes.

STUDY DESIGN

This is a retrospective review of 356 neonates with 696 TG measures obtained in four neonatal intensive care units between 2015 and 2017. TG was evaluated collectively to establish a reference range and a threshold limit. To analyze the effects of a higher TG threshold, neonates were categorized by their peak TG: <180 (TG<180), 180 to 400 (TG180-400), and > 400 mg/dL (TG>400). Univariable and multivariable regression models were constructed to compare peak TG to patient characteristic and clinical outcomes.

RESULTS

The frequency of TG > 400 mg/dL was 5% and found only in neonates weighing < 1.5 kg. Neonates in the TG180-400 (n = 91) group were significantly lower in birth weight and gestational age, had lower 5-minute APGAR scores, and had increased ventilatory requirement when compared with neonates in the TG<180 (n = 240) group (all p < 0.001). The TG180-400 group had increased risk of severe intraventricular hemorrhage (p = 0.02) and bronchopulmonary dysplasia (p = 0.03). Elevated TG was associated with mortality (odds ratio [OR]: 14.4, p < 0.001) in univariable analysis, but the relationship weakened (OR: 4.4, p = 0.05) after adjusting for comorbidities in multivariable logistic regression.

CONCLUSION

It is unclear if the adverse outcomes seen in neonates with higher peak TG were due to elevated TG alone, or whether illness severity predicted the increased TG. More prospective studies are needed to further delineate the relationships.

Curcumin Prevents Cerebellar Hypoplasia and Restores the Behavior in Hyperbilirubinemic Gunn Rat by a Pleiotropic Effect on the Molecular Effectors of Brain Damage

Bilirubin toxicity to the central nervous system (CNS) is responsible for severe and permanent neurologic damage, resulting in hearing loss, cognitive, and movement impairment. Timely and effective management of severe neonatal hyperbilirubinemia by phototherapy or exchange transfusion is crucial for avoiding permanent neurological consequences, but these therapies are not always possible, particularly in low-income countries. To explore alternative options, we investigated a pharmaceutical approach focused on protecting the CNS from pigment toxicity, independently from serum bilirubin level. To this goal, we tested the ability of curcumin, a nutraceutical already used with relevant results in animal models as well as in clinics in other diseases, in the Gunn rat, the spontaneous model of neonatal hyperbilirubinemia. Curcumin treatment fully abolished the landmark cerebellar hypoplasia of Gunn rat, restoring the histological features, and reverting the behavioral abnormalities present in the hyperbilirubinemic rat. The protection was mediated by a multi-target action on the main bilirubin-induced pathological mechanism ongoing CNS damage (inflammation, redox imbalance, and glutamate neurotoxicity). If confirmed by independent studies, the result suggests the potential of curcumin as an alternative/complementary approach to bilirubin-induced brain damage in the clinical scenario.

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.

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.

Effects of soybean lipid infusion on triglyceride and unbound free fatty acid levels in preterm infants

Objective: To determine the plasma triglyceride (TG) and unbound free fatty acid (FFAu) levels in infants treated with increasing dosages of soybean lipid, intralipid (IL), infusion. Study design: TG and FFAu levels were measured in 78 preterm infants (BW 500-2000 g; GA 23-34 weeks) using the fluorescent probe ADIFAB2 and enzymatic method. Results: The infants' BW was 1266.2 ± 440.7 g and GA 28.8 ± 3.1 weeks. TG levels were 77.4 ± 50 mg/dL, 140.2 ± 188 mg/dL (p < .04 compared to levels during low dose IL infusion) and 135.6 ± 118 mg/dL (p < .004), respectively during increased IL rates. FFAu levels were 17.7 ± 13 nM, 47.3 ± 102.8 nM (p = .07) and 98 ± 234 nM (p = .03). TG levels correlated with IL dose, the rate of IL administration, and FFAu levels. TG and FFAu levels were higher in infants below 28 weeks' gestation Conclusions: Increasing dosage of IL is associated with increasing levels of TG and FFAu, especially in infants below 29 weeks of gestation. The increased level of FFAu suggests inefficient cellular utilization.

A multi-center evaluation of a device for measurement of bilirubin binding capacity in neonates: the effects of gestational age, Intralipid exposure and illness severity

OBJECTIVE

Measure daily bilirubin-binding capacity (BBC) variation using an automated, not as-yet FDA approved, Point-of-Care hematofluorometer. Measure the effects of prematurity, clinical instability and exposure to Intralipid on BBC.

SUBJECTS

Convenience sample of 109 infants from well-baby and intensive care nurseries. Gestational ages 28-41 weeks. 261 specimens obtained from postnatal ages 1-4 days. Unstable neonates were defined by need for at least noninvasive respiratory support and FiO2 ≥ 0.25.

RESULTS

Median interday variation was 2.9 ± 5.1 mg/dL. BBC (0.254 mg/dL/wk) and albumin (0.037 g/dL/wk) increased for each week of gestation. BBC was lower in unstable compared to well infants (26.1 ± 7.6 mg/dL v 28.6 ± 6.3 mg/dL). BBC was not significantly different in infants receiving or not receiving IL.

CONCLUSIONS

BBC measurements using the device had acceptable intraspecimen reproducibility and interday variability. BBC may be helpful in guiding the assessment of aggressive versus conservative management decisions in preterm and sick infants with hyperbilirubinemia.

Plasma unbound free fatty acid profiles in premature infants before and after intralipid infusion

Background: Unbound free fatty acids (FFAu) are the bioactive fraction of plasma free fatty acids (FFA). Most plasma FFA are bound to albumin. Only when FFA dissociate from albumin, do they become biologically active.Objective: To measure the first FFAu profiles in human infants and to measure these profiles before and during intravenous administration of the soybean lipid, intralipid (IL).Study design: The study population was 16 premature infants, from a parent study of 130 infants with birth weights 500-2000 g and gestational age 23-34 weeks. The infants chosen had plasma samples of ≥120 µL (volume needed for each FFAu profile measurement) in the first day of life. Infants received IL infusions starting in the second day of life at 1 g/kg/day, increasing by 1-g/kg/day daily up to 3 g/kg/day. FFAu profiles were determined during IL infusion when plasma was available. Profiles are the concentrations of the nine most abundant long-chain FFAu and were determined using novel fluorescent probes.Results: Before intralipid infusion unbound myristic acid was the dominant FFAu, as high as 78% of the total FFAu (sum of the 9 FFAu). In contrast, unbound linoleic acid was 0% in all infants. With increasing infusion of IL to 3 g/kg/day, unbound linoleic increased to 26% of the total FFAu, with unbound oleic, myristic, and linolenic acid the second, third and fourth most abundant. The average total FFAu concentration also increased from 4 nM before intralipid to 53 nM at 3 g/kg/day. During IL infusion the FFAu profiles approached the fatty acid composition of intralipid at 3 g/kg/day.Conclusions: This first study of FFAu profiles in neonates revealed that before IL infusion unbound linoleic acid was zero in all 16 infants and levels of myristic acid were exceptionally large, as much as 78% of the total FFAu profile. These results suggest important and previously unrecognized roles of lipid metabolism in early development. Zero unbound linoleic acid before IL infusion may help promote closure of the ductus arteriosus but after IL infusion, synthesis of arachidonic from linoleic acid may tend to promote patency. The high levels of unbound myristate may be needed for immediate neonatal energy needs.

Association of intralipid intake in extremely low birthweight infants with neurodevelopmental outcomes

AIM

To determine whether high intake of intralipid (IL) in extremely low birthweight (ELBW) neonates is associated with higher rates of neuroimpairment and Bayley III scores at two years of corrected age.

METHODS

Quartiles of IL received by 389 ELBW infants were linked to neurodevelopmental outcomes. Logistic regression analyses, adjusted for confounders, were performed to determine the association between IL dose and neuroimpairment. Linear regression analyses were performed to predict Bayley III scores.

RESULTS

No association was found between IL dose and neuroimpairment A significant association was found between higher IL intake and lower Bayley Cognitive, motor and language scores. Adding breast milk intake to the linear regression eliminated the associations.

CONCLUSION

Higher IL intake was associated with lower cognitive, motor and language scores. Breast milk intake eliminated the latter associations, which underscores the important role of breast milk in developmental outcome.

Unbound bilirubin measurements by a novel probe in preterm infants

BACKGROUND

Hyperbilirubinemia occurs in over 80% of newborns and severe bilirubin toxicity can lead to neurological dysfunction and death, especially in preterm infants. Currently, the risk of bilirubin toxicity is assessed by measuring the levels of total serum bilirubin (TSB), which are used to direct treatments including immunoglobulin administration, phototherapy, and exchange transfusion. However, free, unbound bilirubin levels (Bf) predict the risk of bilirubin neurotoxicity more accurately than TSB.

OBJECTIVE

To examine Bf levels in preterm infants and determine the frequency with which they exceed reported neurotoxic thresholds.

METHODS

One hundred thirty preterm infants (BW 500-2000 g; GA 23-34 weeks) were enrolled and Bf levels measured during the first week of life by the fluorescent Bf sensor BL22P1B11-Rh. TSB and plasma albumin were measured by standard techniques. Bilirubin-albumin dissociation constants (K_d) were calculated based on Bf and plasma albumin.

RESULTS

Five hundred eighty samples were measured during the first week of life, with an overall mean Bf of 13.6 ± 9.0 nM. A substantial number of measurements exceeded potential toxic thresholds levels as reported in the literature. The correlation between Bf and TSB was statistically significant (r² 0.17), but this weak relationship was lost at high Bf levels. Infants <28-week gestations had more hearing screening failures than infants ≥28-week gestation.

CONCLUSIONS

Unbound (free) bilirubin values are extremely variable during the first week of life in preterm infants. A significant proportion of these values exceeded reported neurotoxic thresholds.