Luc J. I. Zimmermann

Non-Invasive Markers for Early Diagnosis and Determination of the Severity of Necrotizing Enterocolitis

Objectives:To improve diagnosis of necrotizing enterocolitis (NEC) by noninvasive markers representing gut wall integrity loss (I-FABP and claudin-3) and gut wall inflammation (calprotectin). Furthermore, the usefulness of I-FABP to predict NEC severity and to screen for NEC was evaluated. Methods:Urinary I-FABP and claudin-3 concentrations and fecal calprotectin concentrations were measured in 35 consecutive neonates suspected of NEC at the moment of NEC suspicion. To investigate I-FABP as screening tool for NEC, daily urinary levels were determined in 6 neonates who developed NEC out of 226 neonates included before clinical suspicion of NEC. Results:Of 35 neonates suspected of NEC, 14 developed NEC. Median I-FABP, claudin-3, and calprotectin levels were significantly higher in neonates with NEC than in neonates with other diagnoses. Cutoff values for I-FABP (2.20 pg/nmol creatinine), claudin-3 (800.8 INT), and calprotectin (286.2 &mgr;g/g feces) showed clinically relevant positive likelihood ratios (LRs) of 9.30, 3.74, 12.29, and negative LRs of 0.08, 0.36, 0.15, respectively. At suspicion of NEC, median urinary I-FABP levels of neonates with intestinal necrosis necessitating surgery or causing death were significantly higher than urinary I-FABP levels in conservatively treated neonates.Of the 226 neonates included before clinical suspicion of NEC, 6 developed NEC. In 4 of these 6 neonates I-FABP levels were not above the cutoff level to diagnose NEC before clinical suspicion. Conclusions:Urinary I-FABP levels are not suitable as screening tool for NEC before clinical suspicion. However, urinary I-FABP and claudin-3 and fecal calprotectin are promising diagnostic markers for NEC. Furthermore, urinary I-FABP might also be used to predict disease severity.

Histological chorioamnionitis and respiratory outcome in preterm infants.

A considerable body of human and animal experimental evidence links antenatal inflammation to both accelerated maturation and adverse development of the lung. Initial reports suggest that in preterm infants histological chorioamnionitis is associated with a decreased incidence of respiratory distress syndrome (RDS), while the incidence of bronchopulmonary dysplasia (BPD) is increased. Considerable variation exists in the findings of subsequent human studies, largely dependent on differences in inclusion and exclusion criteria. Taking these differences into account, recent studies generally seem to confirm the effect of chorioamnionitis on RDS incidence, while no effect on BPD is seen. The increased use of antenatal steroids and the diminished effects of secondary pro-inflammatory hits seem to explain part of this change. Additional research is needed to explore these complex interactions and their underlying mechanisms, and evaluate the long term pulmonary effects of antenatal inflammation.

Chorioamnionitis: a multiorgan disease of the fetus?

The bacterial infection of chorion and amnion is a common finding in premature delivery and is referred to as chorioamnionitis. As the mother rarely shows symptoms of a systemic inflammation, the course of chorioamnionitis is frequently asymptomatic and chronic. In contrast, the fetal inflammatory response syndrome represents a separate phenomenon, including umbilical inflammation and increased serum levels of proinflammatory cytokines in the fetus. Ascending maternal infections frequently lead to systemic fetal inflammatory reaction. Clinical studies have shown that antenatal exposure to inflammation puts the extremely immature neonates at a high risk for worsening pulmonary, neurological and other organ development. Interestingly, the presence of chorioamnionitis is associated with a lower rate of neonatal mortality in extremely immature newborns. In the following review, the pathogeneses of inflammation-associated perinatal morbidity are outlined. The concept of fetal multiorganic disease during intrauterine infection is introduced and discussed.

Histologic chorioamnionitis, fetal involvement, and antenatal steroids: effects on neonatal outcome in preterm infants

OBJECTIVE The objective of the study was to study the effects of histologic chorioamnionitis (HC) with or without fetal involvement and antenatal steroid (AS) exposure on neonatal outcome in a prospective cohort of preterm infants. STUDY DESIGN The clinical characteristics and placental histology were prospectively collected in 301 infants born at a gestational age 32.0 weeks or less in the Erasmus University Medical Center. RESULTS In univariable analyses, HC without fetal involvement (n=53) was associated with decreased severe respiratory distress syndrome (RDS) (11% vs 28%; P<.05), whereas HC with fetal involvement infants (n=68) had more necrotizing enterocolitis (9% vs 2%; P<.05), intraventricular hemorrhage (IVH) (25% vs 12%; P<.05), and neonatal mortality (19% vs 9%; P<.05). In HC without fetal involvement infants, AS reduced the incidences of RDS (43% vs 85%; P<.05) and IVH (5% vs 39%; P<.01). In multivariable analyses, HC without fetal involvement was associated with decreased severe RDS (odds ratio, 0.22; 95% confidence interval, 0.05-0.93; P<.05) and increased early-onset sepsis (odds ratio, 2.22; 95% confidence interval, 1.02-4.83; P<.05). CONCLUSION In a prospective cohort of preterm infants, multivariable analyses reveal only a modest association between histologic chorioamnionitis and neonatal outcome.

Chorioamnionitis Alters the Response to Surfactant in Preterm Infants

OBJECTIVE To study the association between antenatal exposure to chorioamnionitis and the neonatal response to surfactant. STUDY DESIGN Prospective observational cohort of 301 preterm infants of gestational age < or = 32.0 weeks, 146 of whom received surfactant according to standardized criteria. Fraction of inspired oxygen (FiO(2)) requirement (using analysis of variance) and time to extubation (using Kaplan-Meier and Cox regression analyses) were compared between groups based on the presence of histological chorioamnionitis (HC) with or without fetal involvement (HC-, n = 88; HC + F-, n = 25; HC + F+, n = 33) and between infants who developed bronchopulmonary dysplasia (BPD) or died (n = 57) and BPD-free survivors (n = 89). Multiple logistic regression was performed to investigate the association between HC and BPD. RESULTS Compared with HC- infants, HC + F+ infants had significantly greater FiO(2) requirement and prolonged time to extubation postsurfactant, not accounted for by differences in gestational age and birth weight. Infants with BPD/death had a strikingly similar pattern of increased FiO(2) requirement postsurfactant. Moreover, in infants who received surfactant, HC + F+ status was associated with increased risk for BPD (odds ratio [OR] = 3.40; 95% confidence interval [CI] = 1.02-11.3; P = .047) and for BPD/death (OR = 2.72; 95% CI = 1.00-7.42; P = .049). CONCLUSIONS An impaired surfactant response was observed in preterm infants with severe chorioamnionitis and may be involved in the association between chorioamnionitis, mechanical ventilation, and the development of BPD.

Prospective evaluation of surfactant composition in bronchoalveolar lavage fluid of infants with congenital diaphragmatic hernia and of age-matched controls.

OBJECTIVES Infants with congenital diaphragmatic hernia may have biochemically immature lungs. However, normal lecithin/sphingomyelin ratios and phosphatidylglycerol concentrations have been reported in the amniotic fluid of congenital diaphragmatic hernia patients. We hypothesized that if the lungs of congenital diaphragmatic hernia patients are surfactant deficient, that this condition would be reflected in an altered surfactant composition in the bronchoalveolar lavage fluid compared with that composition in age-matched controls. DESIGN Prospective, controlled study. SETTING Surgical intensive care unit in a Level III pediatric university hospital. PATIENTS Four groups were studied: two groups of congenital diaphragmatic hernia patients (conventionally ventilated, n = 13; treated with extracorporeal membrane oxygenation, n = 5); and two control groups (conventionally ventilated, n = 13; extracorporeal membrane oxygenation, n = 6). INTERVENTIONS Bronchoalveolar lavage, using a blind, standardized technique, was performed in conventionally ventilated congenital diaphragmatic hernia patients, extracorporeal membrane oxygenation-treated congenital diaphragmatic hernia patients, age-matched conventionally ventilated controls without pulmonary abnormalities, and extracorporeal membrane oxygenation-treated infants without congenital diaphragmatic hernia. MEASUREMENTS AND MAIN RESULTS The concentrations of different surfactant phospholipids and the fatty acid composition of phosphatidylcholine in bronchoalveolar lavage fluid were measured. No significant differences between the concentrations of phosphatidylcholine and phosphatidylglycerol, and the lecithin/sphingomyelin ratios, were found between the four groups. The fatty acid composition of phosphatidylcholine in conventionally ventilated patients showed a median percentage of palmitic acid within the normal range for age in both groups: 68% in congenital diaphragmatic hernia patients and 73% in controls (p < .001). CONCLUSIONS Our findings indicate that the concentrations of different phospholipids are similar in congenital diaphragmatic hernia patients and controls without congenital diaphragmatic hernia. A primary surfactant deficiency is unlikely in infants with congenital diaphragmatic hernia. However, secondary surfactant deficiency after respiratory failure may be involved.

Chorioamnionitis as a risk factor for necrotizing enterocolitis: a systematic review and meta-analysis.

OBJECTIVE To accumulate available evidence regarding the association between antenatal inflammation and necrotizing enterocolitis (NEC). STUDY DESIGN A systematic literature search was performed using Medline, Embase, Cochrane Library, ISI Web of Knowledge, and reference hand searches. Human studies published in English that reported associations between chorioamnionitis or other indicators of antenatal inflammation and NEC were eligible. Relevant associations were extracted and reported. Studies reporting associations between histological chorioamnionitis (HC) and NEC, HC with fetal involvement and NEC, and clinical chorioamnionitis and NEC were pooled in separate meta-analyses. RESULTS A total of 33 relevant studies were identified. Clinical chorioamnionitis was significantly associated with NEC (12 studies; n = 22 601; OR, 1.24; 95% CI, 1.01-1.52; P = .04; I(2) = 12%), but the association between HC and NEC was not statistically significant (13 studies; n = 5889; OR, 1.39; 95% CI, 0.95-2.04; P = .09; I(2) = 49%). However, HC with fetal involvement was highly associated with NEC (3 studies; n = 1640; OR, 3.29; 95% CI, 1.87-5.78; P ≤ .0001; I(2) = 10%). Selection based on study quality did not affect the results. No indications of publication bias were apparent. Multivariate analyses in single studies generally attenuated the reported associations. Several associations between other markers of antenatal inflammation and NEC are reported. CONCLUSION Currently available evidence supports a role for antenatal inflammation in NEC pathophysiology. This finding emphasizes the need to further study the underlying mechanisms and evaluate potential interventions to improve postnatal intestinal outcomes.

Endotoxin induced chorioamnionitis prevents intestinal development during gestation in fetal sheep.

Chorioamnionitis is the most significant source of prenatal inflammation and preterm delivery. Prematurity and prenatal inflammation are associated with compromised postnatal developmental outcomes, of the intestinal immune defence, gut barrier function and the vascular system. We developed a sheep model to study how the antenatal development of the gut was affected by gestation and/or by endotoxin induced chorioamnionitis. Chorioamnionitis was induced at different gestational ages (GA). Animals were sacrificed at low GA after 2d or 14d exposure to chorioamnionitis. Long term effects of 30d exposure to chorioamnionitis were studied in near term animals after induction of chorioamnionitis. The cellular distribution of tight junction protein ZO-1 was shown to be underdeveloped at low GA whereas endotoxin induced chorioamnionitis prevented the maturation of tight junctions during later gestation. Endotoxin induced chorioamnionitis did not induce an early (2d) inflammatory response in the gut in preterm animals. However, 14d after endotoxin administration preterm animals had increased numbers of T-lymphocytes, myeloperoxidase-positive cells and gammadelta T-cells which lasted till 30d after induction of chorioamnionitis in then near term animals. At early GA, low intestinal TLR-4 and MD-2 mRNA levels were detected which were further down regulated during endotoxin-induced chorioamnionitis. Predisposition to organ injury by ischemia was assessed by the vascular function of third-generation mesenteric arteries. Endotoxin-exposed animals of low GA had increased contractile response to the thromboxane A2 mimetic U46619 and reduced endothelium-dependent relaxation in responses to acetylcholine. The administration of a nitric oxide (NO) donor completely restored endothelial dysfunction suggesting reduced NO bioavailability which was not due to low expression of endothelial nitric oxide synthase. Our results indicate that the distribution of the tight junctional protein ZO-1, the immune defence and vascular function are immature at low GA and are further compromised by endotoxin-induced chorioamnionitis. This study suggests that both prematurity and inflammation in utero disturb fetal gut development, potentially predisposing to postnatal intestinal pathology.

Biomarker reproducibility in exhaled breath condensate collected with different condensers

Optimal collection and analysis of exhaled breath condensate (EBC) are prerequisites for standardisation and reproducibility of assessments. The present study aimed to assess reproducibility of EBC volume, hydrogen peroxide (H2O2), 8-isoprostane and cytokine measurements using different condensers, including a newly developed glass condenser. At four points in time, 30 healthy subjects performed sequential EBC collections randomly using the following four condensers: glass, silicone, EcoScreen® (Erich Jaeger GmbH, Hoechberg, Germany) and an optimised glass condenser. In small EBC samples, H2O2 was measured by spectrophotometer, 8-isoprostane by enzyme immunoassay, and cytokines by multiplexed xMAP® technology (Luminex Corporation, Austin, TX, USA). The optimised glass condenser yielded significantly more EBC volume (median 2,025 µL, interquartile range 1,600–2,525). The reproducibility of EBC volume, yielded by the new glass condenser, was comparable with EcoScreen® (19–20 coefficients of variation (CV)%), but was significantly better compared with silicone and glass (29–37 CV%). The new condenser was associated with significantly more detections of H2O2, 8-isoprostane, interleukin-2, -4, -5 and -13, and tumour necrosis factor-α. Isoprostane concentrations were significantly higher using the new condenser, whereas H2O2 and cytokine concentrations were not. Reproducibility of biomarkers was equally variable for all condenser types. In conclusion, significantly more exhaled breath condensate volume and biomarker detections were found using the optimised glass condenser, including higher 8-isoprostane levels. However, biomarker reproducibility in exhaled breath condensate in healthy adults was not influenced by the type of condenser.

Endogenous surfactant metabolism in critically ill infants measured with stable isotope labeled fatty acids

Little is known about endogenous surfactant metabolism in infants, because radioactive isotopes used for this purpose in animals cannot be used in humans. We developed a novel and safe method to measure the endogenous surfactant kinetics in vivo in humans by using stable isotope labeled fatty acids. We infused albumin-bound [U-13C]palmitic acid (PA) and [U-13C]linoleic acid (LLA) for 24 h in eight critically ill infants (mean ± SD; weight: 3.7 ± 1.3 kg; age: 51.3 ± 61.6 d) who required mechanical ventilation. The 13C enrichment of PA and LLA in surfactant phosphatidylcholine (PC), obtained from tracheal aspirates, was measured by gas chromatography combustion interface-isotope ratio mass spectrometry. We measured a significant incorporation of both 13C-PA and 13C-LLA into surfactant PC. PC-PA and PC-LLA became enriched after 8.7 ± 4.9 h (range: 3.4-17.3) and 10.0 ± 7.2 h (range: 3.0-22.4), respectively; the times at maximum enrichment were 49.2 ± 8.9 and 45.6 ± 19.3 h, respectively. The fractional synthesis rate of surfactant PC-PA ranged from 0.4 to 3.4% per h, whereas the fractional synthesis rate of PC-LLA ranged from 0.5 to 3.8% per h. The surfactant PC-PA and PC-LLA half-lives ranged from 16.8 to 177.7 and 23.8 to 144.4 h, respectively. This method provides new data on surfactant metabolism in infants requiring mechanical ventilation. We found that synthesis of surfactant from plasma PA and LLA is a slow process and that there were marked differences in PC kinetics among infants. This variability could be related to differences in lung disease and could affect the clinical course of the respiratory failure.