End-tidal carbon monoxide is predictive for neonatal non-hemolytic hyperbilirubinemia

End-tidal carbon monoxide concentrations measured within 48 hours of birth predict hemolytic hyperbilirubinemia

OBJECTIVES

To determine, among neonates at-risk for hyperbilirubinemia, whether measuring end-tidal carbon monoxide concentration (ETCOc) twice before 48 hours could identify those who would develop hyperbilirubinemia and differentiate hemolytic vs. non-hemolytic causes.

METHODS

Prospective study on neonates meeting criteria "at-risk for hyperbilirubinemia." Routine bilirubin measurements and 10-day follow-up were used to categorize neonates as; (1) normal (no hyperbilirubinemia, all bilirubins <95th percentile of Bhutani nomogram), (2) having hemolytic hyperbilirubinemia (bilirubin ≥95th percentile, DAT+, elevated retic, or G6PD+), or (3) having non-hemolytic hyperbilirubinemia.

RESULTS

386 neonates were enrolled. 321 (83%) did not develop hyperbilirubinemia and 65 (17%) did, of which 29 were judged hemolytic and 36 non-hemolytic. High ETCOc differentiated the hemolytic group (p < 0.001). First-day ETCOc correlated with bilirubin and with reticulocyte count (r = 0.896 and 0.878) and sensitivity and specificity for predicting hyperbilirubinemia were excellent (83% and 95%).

CONCLUSIONS

ETCO measurement in the first 48 hours after birth predicts hemolytic hyperbilirubinemia.

Breath Biomarkers in Diagnostic Applications

The detection of chemical compounds in exhaled human breath presents an opportunity to determine physiological state, diagnose disease or assess environmental exposure. Recent advancements in metabolomics research have led to improved capabilities to explore human metabolic profiles in breath. Despite some notable challenges in sampling and analysis, exhaled breath represents a desirable medium for metabolomics applications, foremost due to its non-invasive, convenient and practically limitless availability. Several breath-based tests that target either endogenous or exogenous gas-phase compounds are currently established and are in practical and/or clinical use. This review outlines the concept of breath analysis in the context of these unique tests and their applications. The respective breath biomarkers targeted in each test are discussed in relation to their physiological production in the human body and the development and implementation of the associated tests. The paper concludes with a brief insight into prospective tests and an outlook of the future direction of breath research.

Ppt level carbon monoxide detection based on light-induced thermoelastic spectroscopy exploring custom quartz tuning forks and a mid-infrared QCL

In this paper, we report on an ultra-highly sensitive light-induced thermoelastic spectroscopy (LITES)-based carbon monoxide (CO) sensor exploiting custom quartz tuning forks (QTFs) as a photodetector, a multi-pass cell and a mid-infrared quantum cascade laser (QCL) for the first time. The QCL emitting at 4.58 µm with output power of 145 mW was employed as exciting source and the multi-pass cell was employed to increase the gas absorption pathlength. To reduce the noise level, wavelength modulation spectroscopy (WMS) and second harmonic demodulation techniques were exploited. Three QTFs including two custom QTFs (#1 and #2) with different geometries and a commercial standard QTF (#3) were tested as photodetector in the gas sensor. When the integration time of the system was set at 200 ms, minimum detection limits (MDLs) of 750 part-per-trillion (ppt), 4.6 part-per-billion (ppb) and 5.8 ppb were achieved employing QTF #1 #2, and #3, respectively. A full sensor calibration was achieved using the most sensitive QTF#1, demonstrating an excellent linear response with CO concentration.

Hemolysis during and after 21 days of head-down-tilt bed rest

Hemoconcentration is observed in bed rest studies, descent from altitude, and exposure to microgravity. Hemoconcentration triggers erythrocyte losses to subsequently normalize erythrocyte concentration. The mechanisms of erythrocyte loss may involve enhanced hemolysis, but has never been measured directly in bed rest studies. Steady‐state hemolysis was evaluated by measuring two heme degradation products, endogenous carbon monoxide concentration [CO] and urobilinogen in feces, in 10 healthy men, before, during, and after two campaigns of 21 days of 6° head‐down‐tilt (HDT) bed rest. The subjects were hemoconcentrated at 10 and 21 days of bed rest: mean concentrations of hemoglobin (15.0 ± 0.2 g/L and 14.6 ± 0.1 g/L, respectively) and erythrocytes (5.18 ± 0.06E6/μL and 5.02 ± 0.06E6/μL, respectively) were increased compared to baseline (all Ps < 0.05). In contrast, mean hemoglobin mass (743 ± 19 g) and number of erythrocytes (2.56 ± 0.07E13) were decreased at 21 days of bed rest (both Ps < 0.05). Indicators of hemolysis mean [CO] (1660 ± 49 ppb and 1624 ± 48 ppb, respectively) and fecal urobilinogen concentration (180 ± 23 mg/day and 199 ± 22 mg/day, respectively) were unchanged at 10 and 21 days of bed rest compared to baseline (both Ps > 0.05). A significant decrease in [CO] (−505 ppb) was measured at day 28 after bed rest. HDT bed rest caused hemoconcentration in parallel with lower hemoglobin mass. Circulating indicators of hemolysis remained unchanged throughout bed rest supporting that enhanced hemolysis did not contribute significantly to erythrocyte loss during the hemoconcentration of bed rest. At day 28 after bed rest, decreased hemolysis accompanied the recovery of erythrocytes, a novel finding.

High-Power DFB Diode Laser-Based CO-QEPAS Sensor: Optimization and Performance

A highly sensitive carbon monoxide (CO) trace gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) was demonstrated. A high-power distributed feedback (DFB), continuous wave (CW) 2.33 μm diode laser with an 8.8 mW output power was used as the QEPAS excitation source. By optimizing the modulation depth and adding an optimum micro-resonator, compared to a bare quartz tuning fork (QTF), a 10-fold enhancement of the CO-QEPAS signal amplitude was achieved. When water vapor acting as a vibrational transfer catalyst was added to the target gas, the signal was further increased by a factor of ~7. A minimum detection limit (MDL) of 11.2 ppm and a calculated normalized noise equivalent absorption (NNEA) coefficient of 1.8 × 10-5 cm-1W/√Hz were obtained for the reported CO-QEPAS sensor.

Cord Blood Alkaline Phosphatase as an Indicator of Neonatal Jaundice

BACKGROUND

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

OBJECTIVES

The purpose of this study was to examine the validity of cord blood alkaline phosphatase level for predicting neonatal hyperbilirubinemia.

PATIENTS AND METHODS

Between October and December 2013 a total of 102 healthy term infants born to healthy mothers were studied. Cord blood samples were collected for measurement of alkaline Phosphatase levels immediately after birth. Neonates were followed-up for the emergence of jaundice. Newborns with clinical jaundice were recalled and serum bilirubin levels measured. Appropriate treatment based on serum bilirubin level was performed. Alkaline phosphatase levels between the non-jaundiced and jaundiced treated neonates were compared.

RESULTS

The incidence of severe jaundice that required treatment among followed-up neonates was 9.8%. The mean alkaline phosphatase level was 309.09 ± 82.51 IU/L in the non-jaundiced group and 367.80 ± 73.82 IU/L in the severely jaundiced group (P = 0.040). The cutoff value of 314 IU/L was associated with sensitivity 80% and specificity 63% for predicting neonatal hyperbilirubinemia requiring treatment.

CONCLUSIONS

The cord blood alkaline phosphatase level can be used as a predictor of severe neonatal jaundice.

Icterus Neonatorum in Near-Term and Term Infants: An overview

Neonatal jaundice is the yellowish discoloration of the skin and/or sclerae of newborn infants caused by tissue deposition of bilirubin. Physiological jaundice is mild, unconjugated (indirect-reacting) bilirubinaemia, and affects nearly all newborns. Physiological jaundice levels typically peak at 5 to 6 mg/dL (86 to 103 μmol/L) at 72 to 96 hours of age, and do not exceed 17 to 18 mg/dL (291-308 μmol/L). Levels may not peak until seven days of age in Asian infants, or in infants born at 35 to 37 weeks' gestation. Higher levels of unconjugated hyperbilirubinaemia are considered pathological and occur in a variety of conditions. The clinical features and management of unconjugated hyperbilirubinaemia in healthy near-term and term infants, as well as bilirubin toxicity and the prevention of kernicterus, are reviewed here. The pathogenesis and aetiology of this disorder are discussed separately.

Risk assessment strategy for prediction of pathological hyperbilirubinemia in neonates

OBJECTIVE

To evaluate combined ability of clinical risk factors and transcutaneous bilirubin (TcB) in predicting pathological hyperbilirubinemia (PHB) needing treatment during first week of life in healthy term and late preterm neonates.

METHODS

This prospective cohort study included healthy neonates with gestation ≥35 wk and birth weight ≥2000 g. TcB was measured with a multi-wavelength transcutaneous bilirubinometer (Bilichek®) at 30 ± 12 h of postnatal age. Follow-up was conducted as per American Academy of Pediatrics guidelines. For diagnosis of PHB, TcB was measured at each follow-up visit. Serum bilirubin was measured if TcB was >15 mg/dL or within 2 mg/dL of phototherapy cut-off.

RESULTS

Among 462 neonates [birth weight (g; mean ± SD): 2711 ± 431, gestation (wk; median, IQR): 38 (37-39), male: 52%] enrolled in the study, 392 (84.9%) completed followup and PHB was observed in 65 (16.6%) neonates. Discriminant ability of risk model, including both clinical risk factors and TcB, was better than the risk models with clinical risk factors or TcB alone (c-statistic: 0.86 vs. 0.74 vs. 0.77). On logistic regression analysis risk factors found significant were TcB (OR: 1.65, 95% CI: 1.4-1.9), gestation at birth (OR: 0.6, 95% CI: 0.50-0.77) and primiparity (OR: 2.1, 95% CI: 1.1-3.9). A risk prediction score was developed with these three risk factors as ordinal/dichotomous variables. Negative and positive predictive values for score <8 and >12 were 97% and 46%, respectively.

CONCLUSIONS

Risk score consisting of TcB, gestation at birth and parity status was able to accurately predict pathological hyperbilirubinemia in derivation cohort of healthy term and late preterm north Indian neonates.

Single breath CO measurements normalized to 5% CO2in Coombs' test positive neonates

A portable, prototype instrument that measures peak CO, CO2 and H2 concentrations of breath samples was evaluated on 58 antibody positive, blood group incompatible infants. The reproducibility of 108 duplicate breath CO determinations improved when the result was normalized (CO(n)) for the simultaneously measured CO2 concentration (r = 0.97 versus r = 0.87). The average CO(n) for 18 antibody positive, ABO incompatible infants who received phototherapy was 1.2 ppm higher than the average for 32 who did not receive phototherapy (p < 0.001). There was a positive correlation between CO(n) and the duration of phototherapy (r = 0.75). Sodium acetate infusion and breath H2 did not affect the CO(n) results. In antibody positive infants, single breath CO to CO2 ratios provided more reproducible results than CO determinations that were not adjusted for the CO2 concentration. Therefore, a portable instrument that measures both gases on the same aliquot of exhaled air and that is not affected by H2 should have clinical utility as an indicator of heme catabolism and bilirubin production that is not distorted by hyper- or hypoventilation.

Membrane conductance in trained and untrained subjects using either steady state or single breath measurements of NO transfer

The aim of this work was to define the relationship between membrane conductance for NO (Dm) and physical activity by using either the steady state NO transfer (T(LNO)SS) or the single breath method (T(LNO)SB), making the hypothesis that NO transfer is only limited by the membrane. Alterations in T(LNO)SS with lung volume during tidal ventilation were measured in six subjects at rest and during steady exercise at 30, 60, and 80% of maximal aerobic power (MAP). A fast responding chemoluminescent NO analyser was used. Two calculation methods were used by sampling NO: (1) at mid-tidal volume, (2) in the middle of the alveolar plateau. T(LNO)SB at rest and maximal oxygen consumption (V(.-)O(2)max) were also measured in 18 other subjects. At rest T(LNO)SS with method 2 was 192% of the value given by method 1. T(LNO)SS with method 1 increased by 50% with 80% MAP as it did not change with method 2. Method 2 seemed inaccurate. T(LNO)SB at rest, which is closely related to Dm, was correlated to age and V(.-)O(2)max, T(LNO)SB=182-1.2 age+24.3 V(.-)O(2) max(l min(-1)) (p<0.01, r(2)=0.72). The T(LNO)SS and T(LNO)SB versus lung volume relationships suggest an influence of the breathing pattern on Dm. Dm can be estimated either by these two NO transfer methods, however the use of the T(LNO)SS method is highly sensitive to the alveolar sampling level. Dm increase during exercise is a function of MAP. Dm at rest decreases with age as it increases with MAP.

Carbon Monoxide: Endogenous Production, Physiological Functions, and Pharmacological Applications

Over the last decade, studies have unraveled many aspects of endogenous production and physiological functions of carbon monoxide (CO). The majority of endogenous CO is produced in a reaction catalyzed by the enzyme heme oxygenase (HO). Inducible HO (HO-1) and constitutive HO (HO-2) are mostly recognized for their roles in the oxidation of heme and production of CO and biliverdin, whereas the biological function of the third HO isoform, HO-3, is still unclear. The tissue type-specific distribution of these HO isoforms is largely linked to the specific biological actions of CO on different systems. CO functions as a signaling molecule in the neuronal system, involving the regulation of neurotransmitters and neuropeptide release, learning and memory, and odor response adaptation and many other neuronal activities. The vasorelaxant property and cardiac protection effect of CO have been documented. A plethora of studies have also shown the importance of the roles of CO in the immune, respiratory, reproductive, gastrointestinal, kidney, and liver systems. Our understanding of the cellular and molecular mechanisms that regulate the production and mediate the physiological actions of CO has greatly advanced. Many diseases, including neurodegenerations, hypertension, heart failure, and inflammation, have been linked to the abnormality in CO metabolism and function. Enhancement of endogenous CO production and direct delivery of exogenous CO have found their applications in many health research fields and clinical settings. Future studies will further clarify the gasotransmitter role of CO, provide insight into the pathogenic mechanisms of many CO abnormality-related diseases, and pave the way for innovative preventive and therapeutic strategies based on the physiologic effects of CO.

Effect of hematocrit on exhaled carbon monoxide in healthy newborn infants

OBJECTIVE

We tested the hypothesis that, the red blood cell (RBC) mass, estimated by hematocrit (HCT) or hemoglobin (Hb) level, influences the carbon monoxide (CO) production rate.

STUDY DESIGN

The relationship between end tidal CO corrected for ambient carbon monoxide level (ETCOc) and the RBC mass have been studied in 58 full-term infants at the mean age 4.9 hours.

RESULTS

Mean ETCOc was 1.88 ppm (1.3 to 3.4 ppm). ETCOc correlated significantly with HCT (R 2=10.1%, p=0.015) and with Hb (R 2=11%, p=0.011). Infants with a capillary HCT >65% had significantly higher ETCOc (mean 1.99+/-0.49 ppm) than infants with a capillary HCT <65% (1.74+/-0.39 ppm), p=0.035. When CO production was corrected for HCT (ETCOc/HCT), this difference did not longer exist.

CONCLUSIONS

In newborn infants ETCOc significantly correlates with RBC mass. Comparing different infant's CO generation rate one should take into consideration their initial RBC level. In order to adjust for the existing differences in RBC, we suggest the use of the ETCOc/HCT index.

Is there a causal relationship between the receipt of blood transfusions and the development of chronic lung disease of prematurity?

The number and total volume of blood transfusions received by premature babies is, after gestational age and birth weight a good predictor of the likelihood of developing chronic lung disease of prematurity (CLD) and retinopathy of prematurity (ROP). Oxidative damage, inflammation and pulmonary infections are also strongly associated with the development of CLD. It is currently not clear whether there is a causal relationship between the receipt of blood transfusions and oxidative damage, infection, inflammation and CLD in these babies. Strong arguments may be made both for and against a causal relationship. The babies who receive blood transfusions are usually smaller than those who do not, and are ventilated, often with high oxygen levels, for a longer period of time. The longer the baby is on a ventilator the more likely it is to develop pulmonary infection and inflammation. All these factors will promote free radical production and oxidative damage irrespective of the receipt of blood transfusion. This would argue against a causal relationship. On the other hand, an argument may be presented which is based on iron promoted free radical generation, infection and fibrosis consequent to the breakdown of haeme released from transfused erythrocytes. Haeme is broken down by haeme oxygenase (HO) to iron, CO and bilirubin. Under normal circumstances the products of HO activity are beneficial to the organism, but when HO activity is excessive, the products are potentially damaging. Free iron, (in the Fe2+ form) if not sequestered with protein or urate, will generate highly toxic free radicals via the Fenton and Heber-Wiess reactions, predispose the tissue to infection and promote fibrosis. The iron chelating ability of the premature baby appears to be limited so that it would be difficult to deal with any increase in free iron production. Free iron will in turn induce HO activity leading to a potentially serious positive feedback process. The lung is particularly sensitive to iron induced HO activity. In addition, HO activity may be enhanced by other events occurring in the premature lung such as the production of proinflammatory cytokines and the reduced level of glutathione. Thus, the possibility of a causal relationship clearly exists and needs to be examined. This can be attempted by measuring the products of HO activity in relation to the receipt of blood transfusions.

Understanding severe hyperbilirubinemia and preventing kernicterus: Adjuncts in the interpretation of neonatal serum bilirubin

The serum total bilirubin concentration at any point in time represents the amount of bilirubin being produced minus that being excreted. Hyperbilirubinemia develops when bilirubin production exceeds the body's capacity to excrete it, primarily by conjugation. When extreme, hyperbilirubinemia may lead to the development of free bilirubin, that form of bilirubin which may cross the blood-brain barrier and enter and damage the basal nuclei of the brain. This rare, though devastating complication, may result in irreversible bilirubin induced brain damage termed kernicterus. In this paper, adjuncts to the interpretation of the serum total bilirubin are discussed, with the purpose of singling out those few neonates in real danger of bilirubin encephalopathy. Interpretation of the serum total bilirubin should be performed in conjunction with factors unique to the particular infant being evaluated. Understanding the mechanisms and dangers of severe neonatal hyperbilirubinemia should facilitate recognition of an emergency situation and optimize the speed with which bilirubin testing is performed and blood for exchange transfusion prepared. Hyperbilirubinemia is a condition of major importance and a source of concern to all involved in the management of the newborn. Its prevention and management should be based on the recently revised American Academy of Pediatric guidelines, with special attention paid to neonates manifesting risk factors for kernicterus. Close cooperation between the clinical laboratory and the medical team managing the newborn is an essential component in the management of a hyperbilirubinemic baby.

An evidence-based review of important issues concerning neonatal hyperbilirubinemia

This article is adapted from a published evidence report concerning neonatal hyperbilirubinemia with an added section on the risk of blood exchange transfusion (BET). Based on a summary of multiple case reports that spanned more than 30 years, we conclude that kernicterus, although infrequent, has at least 10% mortality and at least 70% long-term morbidity. It is evident that the preponderance of kernicterus cases occurred in infants with a bilirubin level higher than 20 mg/dL. Given the diversity of conclusions on the relationship between peak bilirubin levels and behavioral and neurodevelopmental outcomes, it is apparent that the use of a single total serum bilirubin level to predict long-term outcomes is inadequate and will lead to conflicting results. Evidence for efficacy of treatments for neonatal hyperbilirubinemia was limited. Overall, the 4 qualifying studies showed that phototherapy had an absolute risk-reduction rate of 10% to 17% for prevention of serum bilirubin levels higher than 20 mg/dL in healthy infants with jaundice. There is no evidence to suggest that phototherapy for neonatal hyperbilirubinemia has any long-term adverse neurodevelopmental effects. Transcutaneous measurements of bilirubin have a linear correlation to total serum bilirubin and may be useful as screening devices to detect clinically significant jaundice and decrease the need for serum bilirubin determinations. Based on our review of the risks associated with BETs from 15 studies consisting mainly of infants born before 1970, we conclude that the mortality within 6 hours of BET ranged from 3 per 1000 to 4 per 1000 exchanged infants who were term and without serious hemolytic diseases. Regardless of the definitions and rates of BET-associated morbidity and the various pre-exchange clinical states of the exchanged infants, in many cases the morbidity was minor (eg, postexchange anemia). Based on the results from the most recent study to report BET morbidity, the overall risk of permanent sequelae in 25 sick infants who survived BET was from 5% to 10%.

Neonatal hyperbilirubinemia in Japanese neonates: analysis of the heme oxygenase-1 gene and fetal hemoglobin composition in cord blood

Neonatal hyperbilirubinemia is frequent and severe in Japanese infants. Although the G71R mutation of the bilirubin uridine diphosphate-glucuronosyltransferase gene is associated with severe neonatal hyperbilirubinemia in this population, it accounts for only half of the neonates with severe hyperbilirubinemia. It was suggested that increased bilirubin production would also be associated with severe neonatal hyperbilirubinemia in Japanese infants. To elucidate the genetic factors causing severe hyperbilirubinemia in these patients, we studied two notable factors associated with bilirubin production: heme oxygenase-1, a key enzyme of heme metabolism, and fetal Hb composition, a factor possibly associated with heme load in neonates. We first determined the sequences of promoter and all coding regions of the heme oxygenase-1 gene in Japanese neonates who had undergone phototherapy, but found no mutation except for the polymorphic (GT)n repeats in the promoter region. These repeats modulate the transcription of the heme oxygenase-1 gene, and the longer repeat sequences are known to reduce the transcription. We detected a significant difference in the allele frequencies of each number of (GT)n repeats between Japanese and German populations. However, we could not find a relation between those polymorphisms and neonatal hyperbilirubinemia. We next analyzed the state of Hb switching of the gamma- to beta-globin chain and the phenotype of gamma-globin chain isoforms in cord blood. We found no relation between fetal Hb composition and neonatal hyperbilirubinemia. Further studies are required to elucidate genetic or environmental factors in neonatal hyperbilirubinemia in Japanese infants.