Influence of gestational age on cord serum bilirubin binding studies

The effect of gestational age on bilirubin binding was studied using cord serum from 22 preterm infants and 13 term infants and serum from 17 adults. Using the peroxidase oxidation method, a bilirubin titration curve was obtained by adding bilirubin to serum and measuring the apparent unbound bilirubin concentration. The resultant curve was analyzed using the least-squares fit of the empiric equation Y = aXb. After correction for albumin concentration by plotting the apparent unbound bilirubin concentration against the molar ratio of total bilirubin/albumin, term and preterm infants had identical titration curves, which remained inferior to that of adults. In addition, the apparent primary bilirubin association constant Ka'1 was similar for all infants but was two to three times less than that for adults. We conclude that bilirubin binding by cord serum is equivalent regardless of gestational age. However, adult serum binds bilirubin qualitatively better than does serum from infants of all gestational ages. We suggest that the adverse effect of prematurity on bilirubin binding noted in previous studies may have reflected postnatal complications rather than gestational age as such.     

Effects of albumin infusion therapy on total and unbound bilirubin values in term infants with intensive phototherapy

BACKGROUND: The purpose of the present study was to evaluate the effect of intravenous albumin administration on the serum total and unbound bilirubin values in term non-hemolytic hyperbilirubinemic neonates during intensive phototherapy. METHODS: Fifty-eight infants (gestational age 39.4 +/- 1.4 weeks; birth weight 3,245 +/- 435 g) were given phototherapy with similar light energy. Twenty infants (control group) received only phototherapy, while 38 others (albumin-treated group) were also given human albumin at 1 g/kg bodyweight, i.v., during the first 2 h of phototherapy. RESULTS: When comparing changes in total and unbound bilirubin values 0, 2, 6 and 24 h after entering the study between the albumin-treated group and the control group, there was a significant reduction in the serum unbound bilirubin values at the end of albumin treatment and at 6 and 24 h. However, there was no significant reduction in total serum bilirubin values during the study period. In the albumin-treated group, the mean serum unbound bilirubin reduction from the baseline level at the end of albumin treatment and at 6 and 24 h was 0.40 +/- 0.19, 0.41 +/- 0.20 and 0.43 +/- 0.20 microg/dL, respectively. CONCLUSIONS: The results suggest that albumin priming may be effective for an immediate reduction in serum unbound bilirubin values, the fraction that is potentially neurotoxic.     

Hyperbilirubinemia in preterm infants in Japan: New treatment criteria

In 1992, Kobe University proposed treatment criteria for hyperbilirubinemia in newborns using total serum bilirubin and serum unbound bilirubin reference values. In the last decade, chronic bilirubin encephalopathy has been found to develop in preterm infants in Japan because it can now be clinically diagnosed based on an abnormal signal of the globus pallidus on T2‐weighted magnetic resonance imaging and abnormal auditory brainstem response with or without apparent hearing loss, along with physical findings of kinetic disorders with athetosis. We therefore revised the Kobe University treatment criteria for preterm hyperbilirubinemic infants in 2017. The three revised points are as follows: (i) newborns are classified under gestational age at birth or corrected gestational age, not birthweight; (ii) three treatment options were created: standard phototherapy, intensive phototherapy, and albumin therapy and/or exchange blood transfusion; and (iii) initiation of standard phototherapy, intensive phototherapy, and albumin therapy and/or exchange blood transfusion is decided based on the total serum bilirubin and serum unbound bilirubin reference values for gestational weeks at birth at <7 days of age, and on the reference values for corrected gestational age at ≥7 days of age. Studies are needed to establish whether chronic bilirubin encephalopathy can be prevented using the 2017 revised Kobe University treatment criteria for preterm infants in Japan.     

Bilirubin-albumin binding affinity and serum albumin concentration during intensive phototherapy (blue double light) in jaundiced newborn infants

Thirty newborn infants with normal birth weights and uncomplicated hyperbilirubinaemia were studied. Twenty three of these were treated continuously for 24h with intensive phototherapy (blue double light), and seven untreated infants served as controls. During the treatment the serum concentrations of total bilirubin and unbound bilirubin in diluted serum measured by the peroxidase method were markedly reduced. The binding affinity of bilirubin to its high affinity site on serum albumin was not affected. During the treatment a slight decrease of the serum albumin concentration occurred, and the possible causes of this observation are discussed.     

Ceftriaxone effect on bilirubin-albumin binding

The effect of ceftriaxone on bilirubin-albumin binding was measured in vitro using the peroxidase method with human serum albumin and a dialysis rate method with adult and newborn serum. Ceftriaxone competes with bilirubin for binding to human serum albumin; the displacement constant is 1.5 X 10(4) L/mol. Therapeutic levels of ceftriaxone decrease the reserve albumin concentration in newborn serum by 39%. These results indicate that ceftriaxone may increase the risk of bilirubin encephalopathy in jaundiced premature infants.     

Deposition of bilirubin acid in the central nervous system--a hypothesis for the development of kernicterus

On the basis of the concentration of unconjugated bilirubin and available albumin for the binding of bilirubin it is possible to calculate the level of unbound bilirubin in a serum sample. The solubility of bilirubin can further be calculated when the pH is known. In cases of threatened kernicterus the free bilirubin concentration in serum samples from newborn infants surpasses the solubility by a factor close to one hundred. It is hypothesized that deposition of bilirubin in tissues takes place as an ongoing event, the deposited pigment being eliminated by bilirubin oxidase in healthy infants. Kernicterus results when the rate of deposition becomes overwhelming as a result of high bilirubin concentration, low albumin reserve, low pH, after administration of a displacing drug, or if the bilirubin oxidase system has been compromised by preceding birth asphyxia or other forms of central nervous system injury.     

Deposition of Bilirubin Acid in the Central Nervous System–A Hypothesis for the Development of Kernicterus

ABSTRACT. On the basis of the concentration of unconjugated bilirubin and available albumin for the binding of bilirubin it is possible to calculate the level of unbound bilirubin in a serum sample. The solubility of bilirubin can further be calculated when the pH is known. In cases of threatened kernicterus the free bilirubin concentration in serum samples from newborn infants surpasses the solubility by a factor close to one hundred. It is hypothesized that deposition of bilirubin in tissues takes place as an ongoing event, the deposited pigment being eliminated by bilirubin oxidase in healthy infants. Kernicterus results when the rate of deposition becomes overwhelming as a result of high bilirubin concentration, low albumin reserve, low pH, after administration of a displacing drug, or if the bilirubin oxidase system has been compromised by preceding birth asphyxia or other forms of central nervous system injury.     

早产儿早期静脉营养耐受性的探讨

目的 探讨早产儿生后1～2d对静脉营养的耐受性。方法 将不能完全耐受肠道营养的早产儿34例(胎龄29～36周，体重900～1800g)，随机分为两组，实验组于生后48h内添加氨基酸及脂肪乳；对照组采用传统的静脉营养方法，即生后第3天应用氨基酸，第5天应用脂肪乳，同时均根据病情尽早经口微量喂养。两组患儿均于生后第1天及第7天采血，监测血清游离脂肪酸、总胆红素、直接胆红素、白蛋白、甘油三脂、总胆固醇，每天监测体重、微量血糖及经皮胆红素值。比较两组患儿恢复出生体重的时间、血清游离脂肪酸、胆红素及血脂的变化。结果 1)实验组患儿恢复出生体重的时间较对照组短；2)两组患儿生后相同日龄测得血清游脂肪酸、总胆红素、直接胆红素、甘油三脂、总胆固醇及血清游离脂肪酸与白蛋白的摩尔比均无显著差异。结论 早产儿生后1～2d可耐受全或部分肠道外营养。     

Increase in bilirubin binding to albumin with correction of neonatal acidosis.

Twenty-six serial measurements of free bilirubin concentration and apparent association constant of bilirubin for albumin (Ka) at a bilirubin: albumin molar ratio of 0.8 were performed and compared with baseline values in 11 newborn infants with acidosis before treatment and during recovery from acidosis. When arterial pH was corrected from 7.12 +/- 0.02 (Mean +/- S.EM.) to 7.34 +/- 0.02, there was a significant decrease in serum free bilirubin concentration and a significant increase in the Ka at molar ratio 0.8. The data offer in vivo evidence that correction of acidosis in the neonate results in an improvement of the apparent bilirubin binding affinity of albumin.     

INCREASE IN BILIRUBIN BINDING TO ALBUMIN WITH CORRECTION OF NEONATAL ACIDOSIS

Abstract. Twenty-six serial measurements of free bilirubin concentration and apparent association constant of bilirubin for albumin (Ka) at a bilirubin: albumin molar ratio of 0.8 were performed and compared with baseline values in 11 newborn infants with acidosis before treatment and during recovery from acidosis. When arterial pH was corrected from 7.12±0.02 (Mean±S.E.M.) to 7.34±0.02, there was a significant decrease in serum free bilirubin concentration and a significant increase in the Ka at molar ratio 0.8. The data offer in vivo evidence that correction of acidosis in the neonate results in an improvement of the apparent bilirubin binding affinity of albumin.     

Usefulness of the bilirubin/albumin ratio for predicting bilirubin-induced neurotoxicity in premature infants

Unconjugated hyperbilirubinaemia occurs in almost all premature infants and is potentially neurotoxic. Treatment is based on total serum bilirubin (TSB), but treatment thresholds are not evidence based. Free bilirubin (Bf)-that is, not bound to albumin, seems a better parameter for bilirubin neurotoxicity, but measurements of Bf are not available in clinical practice. The bilirubin/albumin (B/A) ratio is considered a surrogate parameter for Bf and an interesting additional parameter in the management of hyperbilirubinaemia. This paper reviewed the evidence supporting the use of B/A ratios for predicting bilirubin-induced neurological dysfunction (BIND) including neurodevelopmental delay in jaundiced premature infants (gestational age less than 32 weeks). A literature search was performed and six publications reviewed regarding B/A ratios in the management and outcome of jaundiced premature infants. No prospective clinical trials had been undertaken to show whether bilirubin-induced neurotoxicity is reduced or whether unnecessary treatment is avoided by using the B/A ratio in addition to TSB. Recently, a randomised controlled trial evaluating the effect of the additional use of the B/A ratio on neurodevelopmental outcome in jaundiced premature infants has been initiated. Based on the prevailing evidence many authorities suggest that the additional use of the B/A ratio may be valuable when evaluating jaundiced premature infants.     

Bilirubin binding in the plasma of newborns: critical evaluation of a fluorescence quenching method and comparison to the peroxidase method

Bilirubin binding affinities and capacities and apparent unbound ("free") bilirubin levels were determined in serum samples from 47 high-risk newborns, in 22 samples of cord serum, and in serum samples from 15 Greek children with marked hyperbilirubinemia, by both fluorescence quenching and peroxidase methods. The free fatty acid:albumin molar ratio was also determined for serum samples from high-risk newborns. In vitro and in vivo measurements suggest that free fatty acids are rarely present at levels that produce significant displacement of bilirubin, which is in agreement with previous studies. The two bilirubin binding assays showed only fair correlation with sizable discrepancies for many specimens. Technical difficulties inherent in the fluorescence quenching method and possible sources of error are discussed. Our observations suggest that routine application of these two assays as the primary criterion for therapeutic intervention (e.g., exchange transfusion) is premature.     

BILIRUBIN, RESERVE ALBUMIN FOR BINDING OF BILIRUBIN AND pH IN PLASMA DURING PHOTOTHERAPY (ORDINARY AND DOUBLE LIGHT) OF TERM NEWBORN INFANTS

ABSTRACT. Ebbesen, F. (Department of Neonatology, Rigshospitalet, Copenhagen, Denmark). Bilirubin, reserve albumin for binding of bilirubin and pH in plasma during phototherapy (ordinary and double light) of term newborn infants. Acta Paediatr Scand, 70:223, 1981. –Forty-five term newborn infants with uncomplicated hyperbilirubinaemia were treated continuously with phototherapy for 24 hours. Twenty-eight infants received double light treatment and 17 infants ordinary phototherapy. During both treatments a significant decrease in the serum unconjugated bilirubin concentration, a significant increase in the serum reserve albumin concentration for binding of bilirubin determined by the [¹⁴C] MADDS method, and a significant decrease in the index of serum bilirubin toxicity occurred. The changes in these parameters were significantly greater during the double light treatment than during the ordinary phototherapy. During the treatment the fall in index was constant. No significant change in plasma pH was seen. Thus, the study gives further evidence that the risk of bilirubin encephalopathy is reduced by phototherapy and that double light treatment is in the respect superior to ordinary phototherapy. Prior to phototherapy the molar ratio in serum of unconjugated bilirubin plus reserved albumin for binding of bilirubin to albumin was only 0.60, on average, and during the treatment the increase in the serum reserve albumin concentration was less than the decrease in the serum bilirubin concentration. This can be explained either by the presence in infant serum of an unknown ligand interfering competitively or allosterically in the binding of MADDS and bilirubin to albumin, or by the existence of a foetal albumin with a lower affinity for MADDS than adult albumin.     

Influence of intravenous fat emulsion on serum bilirubin in very low birthweight neonates.

Thirty nine very low birthweight neonates (with a birth weight of 820 to 1500 g and gestation of 27 to 34 weeks) who required total parenteral nutrition were randomly assigned to one of three regimens of administration of fat emulsion for a period of eight days. Groups 1 and 2 received the emulsion at a constant rate over 24 and 16 hours, respectively, beginning with a daily dosage of 1 g/kg and increasing daily by 1 g/kg to a maximum of 4 g/kg. Group 3 received the emulsion at a constant rate of 4 g/kg a day over 24 hours. Plasma concentrations of free fatty acids and serum concentrations of total bilirubin, apparent unbound bilirubin, and albumin were measured at regular intervals. Effects of the three regimens on serum bilirubin measurements were determined. The regimen of fat infusion and rate of infusion seemed to have no effect on serum concentrations of total and apparent unbound bilirubin, although there was a trend towards greater variability in apparent unbound concentrations with the intermittent regimen.     

Incidence and predicting factors of hypozincemia in very-low-birth-weight infants at near-term postmenstrual age

We prospectively investigated serum zinc (Zn) concentrations and clinical factors in 118 very-low-birth-weight infants with a gestational age of 29.5 +/- (SD) 2.5 weeks and a birth weight of 1,194 +/- 254 g at near-term postmenstrual age. The 25th percentile of the serum Zn concentration was 7.0 micromol/l. The infants whose serum Zn concentrations were less than 7.0 micromol/l (defined as hypozincemia) did not have apparent symptoms of Zn deficiency. Multivariate logistic regression analyses demonstrated that hypozincemia was associated with factors such as weight gain (1-g/kg/day increase of weight; OR 1.1762, 95% CI 1.0414-1.3286) and serum albumin concentration (1-g/dl increase of serum albumin; OR 0.0816, 95% CI 0.0152-0.4372). The types of milk feeding did not affect the serum Zn concentrations in the study subjects. This study suggests that hypozincemia in very-low-birth-weight infants at near-term postmenstrual age is associated with greater weight gain and lower serum albumin concentration. Nutritional supply of Zn by human milk fortifier and preterm formula does not appear to meet the demands of rapidly growing very-low-birth-weight infants.     

Influence of Drugs on Albumin and Bilirubin Interaction

Twenty-eight drugs, including cephem antibiotics and anti-inflammatory agents currently used or considered potentially useful in neonatal intensive care nurseries in Japan, were examined to determine their influence on albumin and bilirubin interaction by means of a glucose oxidase - peroxidase method, using an automated analyzer (Arrows) for unbound bilirubin (U.B.). The apparent binding constant for drugs to the high-affinity site on albumin (KD) was determined. Of cephem. antibiotics, latamoxef sodium (LMOX) and cefazolin sodium (CEZ) were found to displace bilirubin from albumin (K_D= 5.9 times 10³ M-¹ and 4.5 times 10³ M-¹, respectively) as strongly as Na salicylate (K_D= 6.8 times 10³ M^-1). Mephenamate and indomethacin, which are used for medical closure of patent ductus arteriosus in premature infants, were also found to be stronger bilirubin displacers (Kn = 1.3 times 10⁵ M^-1 and 1.2 times 10⁵ M-¹, respectively) than sulfisoxazole (K_D= 1.6 times 10⁴ M-¹). Maximal displacement factors (MDF's) were also estimated in reference to protein binding (%) and effective serum concentration (M) of each drug in human adults. Of these drugs, mephenamate showed a higher risk of bilirubin displacement (MDF = 3.79) than sulfisoxazole (MDF = 2.58) and LMOX had a higher risk of displacement (MDF = 1.97) than Na salicylate (MDF = 1.85). On the other hand, indomethacin and CEZ showed minimal effects on displacement at therapeutic levels (MDF = 1.03 and 1.00, respectively). At therapeutic serum levels, mephenamate and LMOX may possess the potential for displacing bilirubin from albumin and increasing the risk of bilirubin encephalopathy, in a manner similar to sulfisoxazole.     

早产儿生后早期血清降钙素原生理变化规律的研究

目的探讨生后不同时间和不同胎龄的早产儿血清降钙素原(PCT)生理变化规律。方法无感染新生儿217例,其中足月儿115例,早产儿102例,后者依据胎龄分为3个亚组:30～32周(30例)、33～34周(35例)、35～36周(37例),分别研究其生后0～12 h、13～24 h、25～36 h、37～48 h、49～72 h、73～96 h、97～120 h、121～144 h PCT水平变化规律。结果新生儿生后随着时间推移,PCT逐渐升高,24 h左右达高峰,其后逐渐下降,生后96 h左右降至儿童正常值。早产儿组PCT峰值晚于足月儿组,约在生后36 h出现,此后缓慢下降,96 h左右降至和足月儿数据相当。30～32周早产儿生后PCT数值维持低浓度水平,37～48 h逐渐升高,升高时间晚于33～34周及35～36周早产儿。结论新生儿在生后早期PCT有一个先增高后下降的动态变化过程,其中早产儿分泌高峰要迟于足月儿。32周以前早产儿生后36 h之内PCT水平较低。     

Salicylate saturation index in neonatal jaundice.

30 serum samples from premature and newborn infants with non-haemolytic hyperbilirubinaemia were analyzed to prove the accuracy of determination of albumin binding capacity for bilirubin. The salicylate method of Odell was used to determine the saturation index of albumin indicated by a decrease in optical density through displaced bilirubin. Bilirubin is stoichometrically displaced from albumin by the addition of salicylate. The values of the sautration index correspond to free binding sites. Analysis of our data demonstrated that there is no direct correlation between the saturation index (SI) and total serum bilirubin/albumin concentration quotient. Methodical errors, problems in statistics and other theoretical concepts are discussed. The salicylate method is not suitable for accurate determination of albumin binding capacity for bilirubin.     

POSTNATAL CHANGES IN THE ABILITY OF PLASMA ALBUMIN TO BIND BILIRUBIN

ABSTRACT. The plasma concentrations of total albumin, unconjugated bilirubin and reserve albumin for bilirubin binding were determined in 407 healthy infants of various age up to eight days. The albumin reserve was measured using monoacetyldiaminodiphenyl-sulfone (MADDS) as a deputy ligand for bilirubin. The fraction of albumin capable of binding bilirubin was calculated as the sum of the concentrations of bilirubin and reserve albumin, divided by the total albumin concentration. Our data showed that this fraction was low (average 0.36) and did not change during the first 24 hours of life, and in this period it was independent of the maturity of the infant, as expressed by its birth weight or gestational age. From about 24 hours of life, the fraction began to increase. This increase came to an end about 60 hours after birth, and no further changes were seen during the following five days. The level of the bilirubin-binding fraction reached 60 hours after birth was related to the maturity of the infant: It increased with increasing birth weight up to 3000 g and with increasing gestational age up to 275 days, when on an average it was about 0.58. The fraction of binding albumin was independent of the sex.     

Postnatal changes in the ability of plasma albumin to bind bilirubin

The plasma concentrations of total albumin, unconjugated bilirubin and reserve albumin for bilirubin binding were determined in 407 healthy infants of various age up to eight days. The albumin reserve was measured using monoacetyldiaminodiphenyl-sulfone (MADDS) as a deputy ligand for bilirubin. The fraction of albumin capable of binding bilirubin was calculated as the sum of the concentrations of bilirubin and reserve albumin, divided by the total albumin concentration. Our data showed that this fraction was low (average 0.36) and did not change during the first 24 hours of life, and in this period it was independent of the maturity of the infant, as expressed by its birth weight or gestational age. From about 24 hours of life, the fraction began to increase. This increase came to an end about 60 hours after birth, and no further changes were seen during the following five days. The level of the bilirubin-binding fraction reached 60 hours after birth was related to the maturity of the infant: It increased with increasing birth weight up to 3000 g and with increasing gestational age up to 275 days, when on an average it was about 0.58. The fraction of binding albumin was independent of the sex.