End-tidal carbon monoxide levels in prematurely born infants developing bronchopulmonary dysplasia

Improving early diagnosis of bronchopulmonary dysplasia

INTRODUCTION

Bronchopulmonary disease (BPD) is associated with long-term neurodevelopmental and cardiorespiratory complications, often requiring significant use of resources. To reduce this healthcare burden, it is essential that those at high risk of BPD are identified early so that strategies are introduced to prevent disease progression. Our aim was to discuss potential methods for improving early diagnosis in the first week after birth.

AREAS COVERED

A narrative review was undertaken. The search strategy involved searching PubMed, Embase and Cochrane databases from 1967 to 2024. The results of potential biomarkers and imaging modes are discussed. Furthermore, the value of scoring systems is explored.

EXPERT OPINION

BPD occurs as a result of disruption to pulmonary vascular and alveolar development, thus abnormal levels of factors regulating those processes are promising avenues to explore with regard to early detection of high-risk infants. Data from twin studies suggests genetic factors can be attributed to 82% of the observed difference in moderate to severe BPD, but large genome-wide studies have yielded conflicting results. Comparative studies are required to determine which biomarker or imaging mode may most accurately diagnose early BPD development. Models which include the most predictive factors should be evaluated going forward.

Exhaled Volatile Organic Compounds for Early Prediction of Bronchopulmonary Dysplasia in Infants Born Preterm

OBJECTIVE(S)

To investigate the predictive performances of exhaled breath volatile organic compounds (VOCs) for development of bronchopulmonary dysplasia (BPD) in infants born preterm.

METHODS

Exhaled breath was collected from infants born <30 weeks' gestation at days 3 and 7 of life. Ion-fragments detected by gas-Chromatography-mass-spectrometry analysis were used to derive and internally validate a VOC prediction model for moderate or severe BPD at 36 weeks postmenstrual age. We tested the predictive performance of the National Institute of Child Health and Human Development (NICHD) clinical BPD prediction model with and without VOCs.

RESULTS

Breath samples were collected from 117 infants (mean gestation 26.8 [±1.5] weeks). Thirty-three percent of the infants developed moderate or severe BPD. The VOC model showed a c-statistic of 0.89 (95% confidence interval [CI] 0.80-0.97) and 0.92 (95% CI 0.84-0.99)) for the prediction of BPD at days 3 and 7, respectively. Adding the VOCs to the clinical prediction model in non-invasive supported infants resulted in significant improvement in discriminative power on both days (day 3: c-statistic 0.83 versus 0.92, p-value 0.04; day 7: c-statistic 0.82 versus 0.94, p-value 0.03).

CONCLUSIONS

This study showed that VOC profiles in exhaled breath of preterm infants on non-invasive support in the first week of life differ between those developing and not developing BPD. Adding VOCs to a clinical prediction model significantly improved its discriminative performance.

Clinical Factors Influencing Endogenous Carbon Monoxide Production and Carboxyhemoglobin Levels in Neonates

Carboxyhemoglobin (COHb) is an index of endogenous carbon monoxide formation during the hem degradation process and could be used to confirm hemolysis in neonates. The influence of other clinical factors on COHb values in neonates has not been fully investigated. We aimed to evaluate the influence of hemolysis, sepsis, respiratory distress, and postnatal age on COHb values. We retrospectively analyzed COHb measurements determined with a carbon monoxide-oximeter in 4 groups of term neonates: A-sepsis, B-respiratory distress, C-hemolysis, and D-healthy neonates. The mean COHb values were 1.41% (SD: 0.26), 1.32% (SD: 0.27), 2.5% (SD: 0.69), and 1.27% (SD: 0.19) (P<0.001) in groups A (n=8), B (n=37), C (n=16), and D (n=76), respectively. COHb in group C was significantly higher than in the other groups. There was a negative correlation between postnatal age and COHb in healthy neonates. A cut-off level of 1.7% had 93% (95% confidence interval [CI]: 89%-97%) sensitivity and 94% (95% CI: 90%-98%) specificity for diagnosis of hemolysis. COHb values were higher during the first days of life. We found that COHb levels in neonates with hemolysis were significantly higher and that the influence of sepsis and respiratory distress on COHb values was insignificant.

Carboxyhaemoglobin levels and free-radical-related diseases in prematurely born infants

BACKGROUND

Carboxyhaemoglobin (COHb) levels may reflect the level of early oxidative stress which plays a role in mediating free-radical-related diseases in prematurely born infants.

AIM

To assess the relationship of COHb levels in the first seven days of after birth to the development of bronchopulmonary dysplasia (BPD) and other free-radical-related diseases.

STUDY DESIGN

Retrospective analysis of routinely performed COHb via blood gas samples of infants born at less than 30 weeks of gestation admitted to a tertiary neonatal intensive care unit was undertaken.

SUBJECTS

One hundred and four infants were included with a median (range) gestational age of 27.4 (22.4-29.9) weeks and a birthweight of 865 (395-1710) grams.

OUTCOMES

The maximum COHb per infant per day was recorded for the first 28 days and BPD and other free-radical-related diseases including intraventricular haemorrhage (IVH) were noted. The severity of BPD, requirement for home oxygen on discharge and survival to discharge were also recorded.

RESULTS

Infants who developed BPD (n = 76) had significantly higher COHb levels in the first seven days [1.7% (0.3-6.8)] compared to those that did not develop BPD [1.6% (0.9-3.8); p = 0.001]. Higher COHb levels in the first seven days after birth were also observed in infants with grade three/four IVH [n = 20; 1.9% (1.0-6.8)] compared to those without [1.6% (0.3-5.6); p < 0.001]. COHb levels, however, were not associated with the duration of ventilation, BPD severity or survival to discharge.

CONCLUSION

Higher COHb levels in prematurely born infants were associated with the development of BPD and IVH.

Increased circulating cytokeratin 19 fragment levels in preterm neonates receiving mechanical ventilation are associated with poor outcome

Invasive mechanical ventilation and oxygen toxicity are postnatal contributors to chronic lung disease of prematurity, also known as bronchopulmonary dysplasia (BPD). Cyfra 21-1 is a soluble fragment of cytokeratin 19, which belongs to the cytoskeleton stabilizing epithelial intermediate filaments. As a biomarker of structural integrity, Cyfra 21-1 might be associated with airway injury and lung hypoplasia in neonates. Serum Cyfra 21-1 concentrations for 80 preterm and 80 healthy term newborns were measured within 48 h after birth. Preterm infants with the combined endpoint BPD/mortality had significantly higher Cyfra 21-1 levels compared with those without fulfilling BPD/mortality criteria (P = 0.01). Also, severe RDS (>grade III) was associated with higher Cyfra levels (P = 0.01). Total duration of oxygen therapy was more than five times longer in neonates with high Cyfra 21-1 levels (P = 0.01). Infants with higher Cyfra 21-1 values were more likely to receive mechanical ventilation (50% vs. 17.5%). However, the duration of mechanical ventilation was similar between groups. The median Cyfra value was 1.93 ng/mL (IQR: 1.68-2.53 ng/mL) in healthy term neonates and 8.5 ng/mL (IQR: 3.6-16.0 ng/mL) in preterm infants. Using ROC analysis, we calculated a Cyfra cutoff > 8.5 ng/mL to predict BPD/death with an AUC of 0.795 (P = 0.004), a sensitivity of 88.9%, and a specificity of 55%. Mortality was predicted with a cutoff > 17.4 ng/mL (AUC: 0.94; P = 0.001), a sensitivity of 100%, and a specificity of 84%. These findings suggest that Cyfra 21-1 concentration might be useful to predict poor outcome in premature infants.

Neonatal hyperbilirubinemia management: Clinical assessment of bilirubin production

The predominant cause of elevated total/plasma bilirubin (TB) levels is from an increase in bilirubin production primarily because of ongoing hemolysis. If undiagnosed or untreated, the risk for developing extreme neonatal hyperbilirubinemia and possibly bilirubin-induced neurological dysfunction (BIND) is increased. Since carbon monoxide (CO) and bilirubin are produced in equimolar amounts during the heme catabolic process, measurements of end-tidal CO levels, corrected for ambient CO (ETCOc) can be used as a direct indicator of ongoing hemolysis. A newly developed point-of-care ETCOc device has been shown to be a useful for identifying hemolysis-associated hyperbilirubinemia in newborns. This review summarizes the biology of bilirubin production, the clinical utility of a novel device to identify neonates undergoing hemolysis, and a brief introduction on the use of ETCOc measurements in a cohort of neonates in China.

Exhaled carbon monoxide levels in infants and toddlers with episodic asthma

Objective:

There are few lung function tests available to evaluate bronchial asthma in infants and toddlers. The objective of this study was to test the hypothesis that the measurement of exhaled carbon monoxide (eCO) levels is applicable to evaluate infants and toddlers with stable asthma and during acute asthma attack.

Methods:

A one-way valve breath sampling bag was developed to collect the exhaled air of infants and toddlers. A total of 483 infants (under 2 years) and toddlers (2-5 years) were studied; 355 had an established diagnosis of asthma (182 suffering mild asthma attacks and 173 without active asthmatic symptoms), 119 had upper respiratory infection (URI) including acute bronchitis, and 9 were healthy.

Results:

In infants and toddlers, eCO levels of those with asthma attacks [median (interquartile range) = 2.0 (2.0-3.25) ppm, n=182] were significantly higher than those of subjects with asymptomatic asthma [2.0 (1.0-2.0) ppm, n=173, P < 0.0001], URI [2.0 (1.0-3.0) ppm, n=119, P < 0.0001], and healthy children [1.0 (0.0-1.0) ppm, n=9, P < 0.0001]. In 75 children with asthma petit mal, eCO levels during asthma attacks [3.0 (2.0-4.0) ppm] significantly decreased after therapy [1.0 (1.0-2.0) ppm, P < 0.0001]. In infants and toddlers with an established diagnosis of asthma (n=355), eCO cut-off >2 ppm discriminated asthma attack from an asymptomatic state with a sensitivity of 95.6%, a specificity of 43.3%, and an area under the curve (AUC) of 0.71 (95% CI: 0.65-0.76, P < 0.0001). In 401 infants and toddlers with some respiratory symptoms, of which 285 cases were finally diagnosed as asthma [eCO level = 2.0 (2.0-3.0) ppm] and 116 cases were not asthma [eCO level = 2.0 (1.0-3.0) ppm, P < 0.0001], eCO cut-off >3 ppm supported the final diagnosis of asthma with a sensitivity of 38.9%, a specificity of 74.1%, and AUC of 0.63 (95% CI: 0.56-0.69, P < 0.0001).

Conclusion:

The measurement of eCO by a novel method is applicable to evaluate asthmatic activity and treatment responsiveness, and to diagnose asthma in infants and toddlers.

The role of gasotransmitters in neonatal physiology

The gasotransmitters, nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO), are endogenously-produced volatile molecules that perform signaling functions throughout the body. In biological tissues, these small, lipid-permeable molecules exist in free gaseous form for only seconds or less, and thus they are ideal for paracrine signaling that can be controlled rapidly by changes in their rates of production or consumption. In addition, tissue concentrations of the gasotransmitters are influenced by fluctuations in the level of O₂ and reactive oxygen species (ROS). The normal transition from fetus to newborn involves a several-fold increase in tissue O₂ tensions and ROS, and requires rapid morphological and functional adaptations to the extrauterine environment. This review summarizes the role of gasotransmitters as it pertains to newborn physiology. Particular focus is given to the vasculature, ventilatory, and gastrointestinal systems, each of which uniquely illustrate the function of gasotransmitters in the birth transition and newborn periods. Moreover, given the relative lack of studies on the role that gasotransmitters play in the newborn, particularly that of H₂S and CO, important gaps in knowledge are highlighted throughout the review.

Biomarkers for Bronchopulmonary Dysplasia in the Preterm Infant

Bronchopulmonary dysplasia (BPD) is a chronic inflammatory lung disease of very-low-birth-weight (VLBW) preterm infants, associated with arrested lung development and a need for supplemental oxygen. Over the past few decades, the incidence of BPD has significantly raised as a result of improved survival of VLBW infants requiring mechanical ventilation. While early disease detection is critical to prevent chronic lung remodeling and complications later in life, BPD is often difficult to diagnose and prevent due to the lack of good biomarkers for identification of infants at risk, and overlapping symptoms with other diseases, such as pulmonary hypertension (PH). Due to the current lack of effective treatment available for BPD and PH, research is currently focused on primary prevention strategies, and identification of biomarkers for early diagnosis, that could also represent potential therapeutic targets. In addition, novel histopathological, biochemical, and molecular factors have been identified in the lung tissue and in biological fluids of BPD and PH patients that could associate with the disease phenotype. In this review, we provide an overview of biomarkers for pediatric BPD and PH that have been identified in clinical studies using various biological fluids. We also present a brief summary of the information available on current strategies and guidelines to prevent and diagnose BPD and PH, as well as their pathophysiology, risk factors, and experimental therapies currently available.

Effects of Two Different Exogenous Surfactant Preparations on Serial Peripheral Perfusion Index and Tissue Carbon Monoxide Measurements in Preterm Infants with Severe Respiratory Distress Syndrome

BACKGROUND

Administration of an exogenous surfactant may affect both ventilatory and hemodynamic parameters in preterm infants with respiratory distress syndrome (RDS). Peripheral perfusion may be expected to be influenced, and serial perfusion index (PI) values may show this effect. Noninvasive transcutaneous carbon monoxide (TCO) monitoring may show RDS severity, oxidative and inflammatory stress, and response to surfactant treatment.

METHODS

This randomized controlled nonblinded study was performed in 30 preterm infants with RDS, treated with poractant alfa (n = 15) or beractant (n = 15); 18 preterm infants without RDS served as a control group. Oxygenation and hemodynamic parameters were recorded and compared through the first 6 hours of treatment. PI and TCO values were measured prior to (Tp), immediately after (T0), and at 5 minutes (T5), 30 minutes (T30), 60 minutes (T60), and 360 minutes (T360) after the bolus surfactant administration. The mean arterial pressure, oxygenation index, pH, and lactate levels were recorded simultaneously.

RESULTS

Both study groups had lower Tp PI and higher Tp TCO levels than controls. Both surfactant preparations improved the PI, TCO, mean arterial pressure, oxygenation index, pH, and lactate levels at the end point of T360. However, the median Tp PI value of 1.3 first decreased to 0.86 at T0 (P < 0.001), and then it increased to 0.99 at T5 (p < 0.001) and to 1.25 at T30 (p = 0.037). The median Tp TCO value of 3 decreased to 2, 1.5, 0, and 0 at T0, T5, T30, and T60, respectively (p < 0.001). PI more quickly recovered to Tp values (30 minutes vs. 60 minutes) and reached the control group values (30 minutes vs. 360 minutes) with beractant compared to that with poractant alfa. TCO recovered to Tp values in both groups at the same time (5 minutes vs. 5 minutes), but reached the control group values more quickly (5 minutes vs. 30 minutes) with poractant alfa than with beractant.

CONCLUSION

Patients with RDS had poor perfusion, and PI improved with both surfactant preparations only following a short decline in the 1(st) minute. The expected improvement of PI occurred earlier in the beractant subgroup. TCO declined in both groups, showing lung improvement and decreased oxidative/inflammatory stress, and it was normalized earlier with poractant alfa.

Carboxyhemoglobin Formation in Preterm Infants Is Related to the Subsequent Development of Bronchopulmonary Dysplasia

OBJECTIVE

To evaluate the usefulness of carboxyhemoglobin (CO-Hb) levels as a biomarker to predict the development and severity of bronchopulmonary dysplasia (BPD).

METHODS

Twenty-five infants born at <33 wk of gestational age or with a birth weight of <1,500 g were enrolled. CO-Hb levels were measured between postnatal days 5 and 8, 12 and 15, 19 and 22, and 26 and 29. Urinary levels of 8-hydroxydeoxyguanosine (8-OHdG), advanced oxidation protein products, and Nε-(hexanoyl) lysine were measured between postnatal days 5 and 8 and 26 and 29. Receiver operating characteristic (ROC) analysis was used to compare the biomarkers' predictive values.

RESULTS

Compared with infants in the no-or-mild BPD group, infants with moderate-to-severe BPD exhibited higher CO-Hb levels during the early postnatal period and higher 8-OHdG levels between postnatal days 5 and 8. Using ROC analysis to predict the development of moderate-to-severe BPD, the area under the curve (AUC) for CO-Hb levels between postnatal days 5 and 8 was higher than AUCs for the urinary markers.

CONCLUSIONS

CO-Hb levels during the early postnatal period may serve as a practical marker for evaluating oxidative stress and the severity of subsequently developing BPD.

Correlation of serum KL-6 and CC16 levels with neurodevelopmental outcome in premature infants at 12 months corrected age

The aim of this study was to evaluate KL-6 and CC16 levels and their correlation with neurodevelopmental outcome among very low birth weight pre-term infants at 12 months corrected age. This prospective cohort study was performed from 2011 to 2013 by enrolling pre-term neonates of gestational age ≤ 32 weeks and birth weight ≤ 1500 g. Serum KL-6 and CC16 levels were determined 7 days after birth and their correlation with neurodevelopment was evaluated using Gesell Mental Developmental Scales. Of the 86 eligible pre-term infants, 63 completed follow-up, of which 15 had bronchopulmonary dysplasia. At 12 months corrected age, 49 infants had favorable outcomes and 14 infants had poor neurodevelopmental outcome. KL-6 levels were higher and CC16 levels were lower in infants with poor neurodevelopmental outcome compared with those infants who had favourable neurodevelopmental outcome. Serum KL-6 levels less than 90.0 ng/ml and CC16 levels greater than 320.0 pg/ml at 7 days of life were found to be predictive of a favourable outcome at 12 months corrected age. These biological markers could predict neurodevelopmental outcome at 12 months corrected age in very low birth weight premature infants, and help the clinician plan early therapeutic interventions to minimize or avoid poor neurodevelopmental outcome.

Unmyelinated white matter loss in the preterm brain is associated with early increased levels of end-tidal carbon monoxide

Objective

Increased levels of end-tidal carbon monoxide (ETCOc) in preterm infants during the first day of life are associated with oxidative stress, inflammatory processes and adverse neurodevelopmental outcome at 2 years of age. Therefore, we hypothesized that early ETCOc levels may also be associated with impaired growth of unmyelinated cerebral white matter.

Methods

From a cohort of 156 extremely and very preterm infants in which ETCOc was determined within 24 h after birth, in 36 infants 3D-MRI was performed at term-equivalent age to assess cerebral tissue volumes of important brain regions.

Results

Linear regression analysis between cerebral ventricular volume, unmyelinated white matter/total brain volume-, and cortical grey matter/total brain volume-ratio and ETCOc showed a positive, negative and positive correlation, respectively. Multivariable analyses showed that solely ETCOc was positively related to cerebral ventricular volume and cortical grey matter/total brain volume ratio, and that solely ETCOc was inversely related to the unmyelinated white matter/total brain volume ratio, suggesting that increased levels of ETCOc, associated with oxidative stress and inflammation, were related with impaired growth of unmyelinated white matter.

Conclusion

Increased values of ETCOc, measured within the first 24 hours of life may be indicative of oxidative stress and inflammation in the immediate perinatal period, resulting in impaired growth of the vulnerable unmyelinated white matter of the preterm brain.

Early end-tidal carbon monoxide levels, patency of the ductus arteriosus and regional cerebral oxygenation in preterm infants

BACKGROUND

Carbon monoxide (CO), a relaxant regulator of muscle tone and marker of oxidative stress and inflammation, can be measured in exhaled air by determination of end-tidal CO corrected for CO in ambient air (ETCOc).

OBJECTIVE

Increased endogenous production of CO may influence patency of the ductus arteriosus, cerebral perfusion and, subsequently, cerebral oxygenation. The aim was to study the relation between early ETCOc levels, hemodynamically significant patent ductus arteriosus (hsPDA) and cerebral oxygenation (rScO2) in preterm infants <32 weeks' gestational age and determine predictive values of ETCOc for hsPDA.

METHODS

ETCOc was measured in 91 infants within the first 24 h after birth. A hsPDA was diagnosed according to echocardiographic indices. In 78/91 infants, rScO2 was monitored with near-infrared spectroscopy to assess cerebral oxygenation.

RESULTS

ETCOc values were significantly higher in infants who subsequently developed hsPDA (2.3 ± 0.7 ppm) vs. no-hsPDA (1.7 ± 0.6 ppm), p < 0.001. With a cut-off value of 2.5 ppm, positive and negative predictive values of ETCOc for hsPDA were 55 and 88%, respectively. rScO2 values were not different between the two groups (64 ± 1 vs. 65 ± 3%, NS).

CONCLUSIONS

The higher ETCOc values in hsPDA infants early after birth reflect the early relaxant state of ductal muscular tone. ETCOc <2.5 ppm within 24 h after birth may predict the subsequent absence of hsPDA. ETCOc showed no correlation with cerebral oxygenation in both groups.

Early biomarkers as predictors for bronchopulmonary dysplasia in preterm infants: a systematic review

BACKGROUND

Bronchopulmonary dysplasia (BPD) is usually diagnosed in preterm infants at least 28 days after birth. Great interest lies in the potential to identify biomarkers that predict development of the disease and future neurodevelopmental outcomes. We have reviewed the existing literature on early biomarkers as predictors for BPD in preterm infants.

METHODS

Two reviewers independently searched the databases of PubMed, EMBASE, and Google Scholar for studies pertaining to biomarkers for BPD. Studies were assessed using Quality Assessment of Diagnostic Accuracy Studies criteria.

RESULTS

We identified 46 relevant articles that are summarized in the review. These studies assessed over 30 potential biomarkers. Sensitivity and specificity of biomarkers were reported or could be calculated for only 16 articles, and ranged from 0 to 100 %. Based on the nine highest quality studies, serum KL-6, CC16, neutrophil gelatinase-associated lipocalin, and end-tidal carbon monoxide (etCO) perform extremely well in predicting the early diagnosis of established BPD, highlighting these biomarkers as promising candidates for future research.

CONCLUSIONS

Published data from studies on serum biomarkers and etCO suggest that biomarkers may have great potential to predict the subsequent BPD and neurodevelopmental outcomes. These biomarkers need validation in larger studies, and the generalizability of biomarkers for predicting BPD, as well as the neurodevelopmental outcomes, needs to be further explored.

Exhaled carbon monoxide levels in preschool-age children with episodic asthma

BACKGROUND

The concentration of exhaled carbon monoxide (eCO) in young children with stable asthma and during acute asthma attack is not known.

METHODS

A sampling bag was developed to collect the exhaled air of preschool children. A total of 257 preschool-age children (≥ 3 years and ≤ 6 years old) were studied; 111 had a diagnosis of asthma (43 suffering a mild asthma attack and 68 without active asthmatic symptom), 99 had upper respiratory infection (URI) and 47 were healthy.

RESULTS

In preschool-age children, eCO levels of those with asthma attacks (mean ± SE, 2.7 ± 0.3 p.p.m., n= 43) were significantly higher than those of subjects with asymptomatic asthma (0.5 ± 0.1 p.p.m., P < 0.05), URI (0.8 ± 0.1 p.p.m., P < 0.05) and healthy children (0.4 ± 0.1 p.p.m., P < 0.05). A multivariate linear regression model showed that eCO was higher in children with asthma attacks independent of age and gender. In 33 asthmatic children followed before and after treatment, eCO levels during asthma attacks significantly decreased after inhalation therapy with a combination of salbutamol and sodium cromoglycate (before therapy, 2.9 ± 0.4 p.p.m.; after therapy, 0.6 ± 0.1 p.p.m., P < 0.0001).

CONCLUSIONS

The measurement of eCO using a novel collecting system is useful in the recognition of asthma in preschool children.

Early end-tidal carbon monoxide levels and neurodevelopmental outcome at 3 years 6 months of age in preterm infants

AIM

Increased end-tidal carbon monoxide (ETCOc) and cytokines in preterm infants are related to bronchopulmonary dysplasia and intraventricular haemorrhages. The aim was to study the predictive value of ETCOc and cytokine levels for long-term outcome.

METHODS

This study comprised 105 very preterm infants (57 males, 48 females; gestational age range 25 wks 5d-31 wks 4d; birthweight 610-2100 g) who were admitted to a neonatal intensive care unit between 1 February and 31 December 2002. ETCOc, plasma tumour necrosis factor alpha (TNF-α) and interleukins (IL) 6 and 8, and malondialdehyde (MDA, a marker of lipid peroxidation), were measured at days 1, 3, and 5 of life and related to outcome at 3 years 6 months of age (Griffiths Mental Developmental Scales).

RESULTS

Of the 105 infants, 69 were eligible for follow-up (37 males; 32 females; bronchopulmonary dysplasia, n = 12). ETCOc at 0 to 24 hours was higher in infants with adverse outcome (Griffiths developmental quotient <85, n = 15) compared with favourable outcome (2.7SD 0.7 vs 2.0SD 0.5; p < 0.05). MDA and cytokines did not differ between groups. Regression analysis with bootstrapping of independent variables (gestational age, birthweight, ETCOc, TNF-α, IL-6, IL-8, and bronchopulmonary dysplasia) showed that ETCOc was the only parameter that correlated with outcome. The sensitivity and negative predictive value of ETCOc for adverse outcome were 93% and 85% respectively.

INTERPRETATION

Adverse neurodevelopmental outcome is associated with increased endogenous carbon monoxide. ETCOc less than 2.0 ppm during the first day indicates a favourable outcome.

Dermal carbon monoxide excretion in neonatal rats during light exposure

Total body, head, and trunk carbon monoxide (CO) excretion rates were measured separately by gas chromatography in 1- to 7-d-old Wistar rat pups exposed to the dark and to mixed blue (one Special Blue-F20T12/BB) and white (two Cool White-F20T12/CW) fluorescent light or blue light emitting diode (LED) sources. During 48-min cycled exposures to the dark and to either light source, total body CO excretion rapidly increased 1.9- and 1.4-fold, respectively, over dark control levels. When CO excretion rates from the head and trunk were measured separately during exposure to either light source, CO excretion from the head did not change significantly; however, a large mean 4.4-fold increase in CO excretion from the trunk was observed. When light intensity delivered by the blue LED source was varied, we found that trunk CO excretion increased with increasing light intensities. In the presence of riboflavin (10 micromol/kg), total body CO excretion increased 2.8- and 2.1-fold during exposure to the mixed fluorescent light and blue LED sources, respectively. We conclude that light-induced elevations in total body CO excretion may be caused by transdermally excreted CO, which is most likely produced through endogenous photosensitizer-mediated photooxidation of dermal biomolecules.

Neonatal jaundice: a critical review of the role and practice of bilirubin analysis

Neonatal jaundice is common, and usually harmless, because of physiological jaundice or breast-feeding. In some neonates unconjugated bilirubin concentration, coupled with other risk factors, is sufficient to allow free bilirubin to cross the blood-brain barrier and cause kernicterus. Another subgroup of infants is jaundiced because of elevated conjugated bilirubin; a marker for a number of pathological conditions. Bilirubin measurement must identify those infants at risk. Transcutaneous bilirubin measurement is increasingly used in healthy infants, especially before early discharge or at home, to assess the need for laboratory bilirubin measurement. Transcutaneous measurements are not covered by laboratory quality assessment schemes. Guidelines on management of neonatal jaundice utilize age in hours and other risk factors to define bilirubin action thresholds, which may be as low as 100 μmol/L for sick premature infants, whereas early discharged babies may only present after bilirubin concentrations are extremely high. Hence, there is a requirement for accurate total bilirubin measurement from <100 to >500 μmol/L, with sufficient precision to assess the rate of bilirubin change with time. Babies presenting with late jaundice always require conjugated bilirubin measurement. It is of concern that many total and direct bilirubin automated kit methods suffer from haemolysis interference, while use of in-house methods or modification of commercial methods has virtually disappeared. External quality assessment has a vital role in providing data on different methods' performance, including accuracy, precision and susceptibility to interference. Laboratories should consider whether their adult bilirubin methods are suitable for neonates.

Use of carbon monoxide as a therapeutic agent: promises and challenges

As a by-product of heme catabolism by the heme oxygenase system, carbon monoxide (CO) has been neglected for many years, and only recently has its role as an essential signaling molecule been appreciated. In the past decade, the use of CO gas in pre-clinical experimental models of disease has produced some remarkable data indicating that its therapeutic delivery to mammals could alleviate inflammatory processes and cardiovascular disorders. However, the inherent toxic nature of CO cannot be ignored, knowing that inhalation of uncontrolled amounts of this gas can ultimately lead to serious systemic complications and neuronal derangements. From a clinical perspective, a key question is whether a safe and therapeutically effective threshold of CO can be reached locally in organs and tissues without delivering potentially toxic amounts through the lung. The advent of CO-releasing molecules (CO-RMs), a group of compounds capable of carrying and liberating controlled quantities of CO in cellular systems, appears a plausible alternative in the attempt to overcome the limitations of CO gas. Although in its infancy and far from being used for clinical applications, the CO-RMs technology is supported by very encouraging biological results and reflected by the chemical versatility of these compounds and their endless potential to be transformed into CO-based pharmaceuticals.