Jean-Louis Wayenberg

Nitrated plasma albumin as a marker of nitrative stress and neonatal encephalopathy in perinatal asphyxia

Reactive nitrogen species (RNS) have been shown to play a major role in the pathophysiology of hypoxic-ischemic cerebral injury. Using a novel sensitive ELISA allowing the quantification of nitrated albumin (nitroalbumin) in plasma, we tested the hypothesis that perinatal asphyxia increases nitrating RNS generation by verifying whether the concentration of one of its target proteins is correlated with the clinical outcome. We assayed nitroalbumin in 114 plasma samples collected during the first hour, at day 1, and at day 4 of life from 48 term newborns suffering from perinatal asphyxia and correlated this marker with neurological and systemic neonatal outcomes. Nitroalbumin levels at day 1, but not at days 0 and 4, were significantly increased in patients who developed moderate or severe encephalopathy compared to those who had a normal neurological evolution or developed mild encephalopathy (median: 14.4 ng/ml versus 7.3 ng/ml, respectively). In contrast, nitroalbumin concentration at day 1 was not associated with systemic complications. First-hour and fourth-day nitroalbumin concentrations did not differ with respect to the neonatal neurological course. At day 0, nitroalbumin levels also correlated with circulating leukocytes. We conclude that plasma nitroalbumin seems to be a specific marker of neurological injury after perinatal asphyxia and may serve as a secondary end-point in neuroprotective clinical trials.

Diagnosis of severe birth asphyxia and early prediction of neonatal neurological outcome in term asphyxiated newborns.

Ten indicators available during the first two hours of life, such as clinical criteria of neonatal distress and postnatal arterial blood gases, were compared with the neonatal neurological course in sixty full term newborns with significant birth asphyxia in order to test their value for the diagnosis and the short-term prognosis of severe birth asphyxia. Birth asphyxia was defined as severe when it was followed by symptoms of moderate or severe post-asphyxial encephalopathy. We calculated a sensitivity lower than fifty percent for clinical criteria such as delay in establishing regular respiration and Apgar scores. It was clear that normal delay in establishing regular respiration and normal Apgar scores do not exclude severe birth asphyxia. Arterial pH and base deficit at thirty minutes of life were found to be the best criteria for the diagnosis of severe birth asphyxia, but lacked positive predictive value. The best predictive tool for the short-term neurological prognosis of birth asphyxia was a single score established at 30 minutes of life and based on the evaluation of consciousness, respiration and neonatal reflexes. Some aspects of the pathophysiology of birth asphyxia and the rationale for treatment of post-asphyxial metabolic acidosis are discussed.

Threshold of metabolic acidosis associated with neonatal encephalopathy in the term newborn

Objective. To determine the threshold of metabolic acidosis associated with neonatal encephalopathy (NE) in the term newborn. Methods. Term patients were included on the basis of abnormal hemodynamic, respiratory or neurological signs still persisting 30 min after birth. Base deficit (BD30) was measured in arterial blood between the 30th and the 45th min of life and correlated with the occurrence of NE during the first days of life using receiver operating characteristics (ROC) methodology. Results. Moderate or severe NE occurred in 26% of patients whose BD30 was higher than 10 mmol/L and in 79% of patients whose BD30 was higher than 18 mmol/L. No infants developed moderate or severe NE when BD30 was less than 10 mmol/L. The apex of ROC curve related to moderate or severe NE corresponds to a BD30 of 14 mmol/L. At this threshold, the sensitivity of BD30 is 73.2% and the specificity 82%. Conclusion. The threshold of metabolic acidosis that provides the best combination of sensitivity and specificity in relation to the occurrence of moderate or severe NE was a BD30 higher than 14 mmol/L. Significant birth asphyxia should be considered if BD30 exceeds 10 mmol/L.

Increased intracranial pressure in a neonate with citrullinaemia

Sir: Citrullinaemia is a rare disorder of the urea cycle involving an arginino-succinate synthetase deficiency. Although increased intracranial pressure (ICP) has been suspected in neonatal onset urea cycle enzyme deficiencies, it has never been demonstrated. A neonate with citrullinaemia and ICP is described. This 2,900 g female full-term newborn underwent an uneventful delivery after a normal pregnancy. She was the first child of first cousin North African parents. On the 2nd day of life she exhibited poor feeding and jitteriness. She was hypertonic and presented episodes of chewing and ocular revulsion. Apar t f rom slight hypernatraemia (151mEq/1), basal screening and cerebrospinal fluid analysis were normal. Cerebral CAT scan showed periventricular hypodensities suggesting ischaemia. Further neurological deterioration occurred in the next few hours with grade II

Non-invasive measurement of intracranial pressure in the newborn and the infant: the Rotterdam teletransducer.

Knowledge of intracranial pressure may be important in many clinical situations in neonates and young infants. The best way to obtain this information would be a non-traumatic procedure. In order to test the reliability of a new fontanometer, the Rotterdam teletransducer, 25 simultaneous measurements of cerebrospinal fluid (CSF) pressure and anterior fontanelle pressure (AFP) were performed. Mean (SD) difference between CSF pressure and AFP was -0.2 (1.8) mm Hg (95% confidence interval from -0.48 to -0.88 mm Hg). The AFP was also measured in 60 healthy children (15 premature, 30 term newborn babies, and 15 infants). The different aspects of AFP were analysed and normal values computed. These results suggest that the Rotterdam teletransducer gives reliable continuous information about intracranial pressure and can be used in clinical practice. Interpretation of AFP plots must take the influence of postconceptional age and the physiological occurrence of pressure waves into account.

Early transient hypoglycemia is associated with increased albumin nitration in the preterm infant

Background: The clinical significance of early transient hypoglycemia (ETH), a frequent event in preterm newborns, is a highly controversial issue. In experimental models, hypoglycemia has been reported to cause oxidative stress. Among the reactive species, early generated peroxynitrite is responsible for protein nitration and lipid peroxidation, a process referred to as nitrative stress. Objectives: The aim of the present study is to investigate whether ETH is associated with protein nitration in the preterm newborn. Methods: Using a novel highly sensitive ELISA, we quantified plasma nitroalbumin (PNA) as a marker of peroxynitrite generation in 72 preterm newborns (28–36 weeks), among which 25 had a glycemia level of <2.5 mmol/l during the first hour of life (H1). Results: PNA was significantly higher in ETH than in normoglycemic infants at H1 [median = 6.3 (3.8–8.8) vs. 3.4 ng/ml (2.1–5.1), p = 0.027] and at day 1 [median = 6.6 (5.6–15.3) vs. 3.9 ng/ml (2.3–4.6), p = 0.014]. PNA was inversely correlated with glycemia at H1 (r = –0.30, p = 0.01) and at day 1 (r = –0.63, p = 0.001). In ETH infants, lactatemia was inversely correlated with PNA. At day 1, PNA was higher in ETH infants treated by gavage than in those treated with intravenous dextrose [median = 8.9 ng/ml (7.1–10.4) vs. 4.4 ng/ml (2.6–5.7), p = 0.008]. Conclusions: These results indicate that ETH is associated with increased peroxynitrite generation resulting in systemic protein nitration in premature newborns. Treatment of ETH with intravenous dextrose is associated with lower PNA levels than gavage.

Anterior fontanelle pressure monitoring for the evaluation of asymptomatic infants with increased head growth rate

We studied non-invasive intracranial pressure monitoring in 20 asymptomatic infants with increased head growth rate. Both basal anterior fontanelle pressure (AFP) traces and occurrence of pressure waves were analysed and compared with normal range values previously established. Eight recordings were classified as pathological; cerebral imaging showed subdural collections or ventricular dilatation in all cases. Five out of these eight infants further developed neurological deficits and/or increase of the ventricular size, and required neurosurgical procedures. Twelve infants had normal AFP traces; six of these had normal cerebral imaging and six showed enlargement of subarachnoid spaces with normal ventricles. All of these 12 patients normalised their head growth rate and remained asymptomatic. This observation suggests that AFP monitoring may be helpful in asymptomatic infants with increased head growth rate to identify a progressive intracranial process and the potential need for a neurosurgical procedure.

1093 Hypoglycemia Induces a Nitro-Oxidative Stress in Preterm Newborns

Recent data suggest that free radical injury occurs in the neonatal brain after hypoglycemia in animal models. We developed an ELISA allowing the quantitative determination of nitrated plasma albumin (nitroalbumin, PNA) as a biomarker of peroxynitrite generation and investigated the potential nitro-oxidative stress induced by hypoglycemia (< 2.5 mmol/L) in premature newborns. We measured PNA concentrations at days 0, 1 and 4 of life in 72 preterm infants without any other obvious cause of nitro-oxidative stress such as infection, asphyxia and hyperglycemia. Glucose levels were monitored every 3–4 hours using a strip method. For each patient, we calculated the AUCs for glycaemia measured during the 12, 18 and 24 hours preceding blood sampling as an index of the severity, the number and the duration of hypoglycemic events during the first day of life. Statistical analysis was performed using non-parametric tests. PNA concentrations were significantly higher in hypoglycaemic than in normoglycemic infants at days 0, 1 and 4. A significant inverse correlation was found between PNA at D1 and AUGs. PNA concentration at D1 is related to the number of hypoglycemic events. Gender, term, oxygen exposure, respiratory and hemodynamic parameters were not correlated with PNA concentrations. Thus, low glycemia levels during the first day of life are specifically associated with increased albumin nitration in preterm newborns, especially in case of recurrent hypoglycemia. This suggests the occurrence of systemic nitro-oxidative stress implying a risk of end-organ damage due to protein nitration, lipid peroxidation and DNA damage, in particular to the brain.

1092 Neonatal Hypoglycemia is Associated with Increased Albumin Nitration in Small for Gestational Age Term Newborns

Background and Aims Neonatal hypoglycemia is a frequent event in small for gestational age (SGA) term newborns. Its clinical significance is a highly controversial issue but in experimental models, hypoglycemia has been reported to cause oxidative stress. Among the reactive species, peroxynitrite is responsible for protein nitration, lipid peroxydation and DNA damage, a process referred to as nitro-oxidative stress which can induce apoptosis. The aim of the present study was to investigate whether hypoglycemia is associated with plasma albumin nitration as a marker of nitro-oxidative stress in SGA term newborns. Methods Using a highly sensitive ELISA we quantified plasma nitroalbumin (PNA) as a marker of peroxynitrite generation in 26 SGA term newborns with close glucose monitoring. We compared PNA concentrations in 9 normoglycemic (glycemia ≥2.5mmol/L) newborns and in 17 hypoglycemic (glycemia < 2.5 mmol/L) newborns. Results PNA measured during the first hours of life was inversely correlated with glycemia (r= –0.63, p=0.01) and significantly higher in hypoglycemic compared to normoglycemic patients (7.4ng/mL [5.0–7.9] in normoglycemic patients vs. 20.8ng/mL [9.9–77.7] in hypoglycemic patients, n=14, p<0.01). PNA measured at day 1 of life was significantly higher in patients with recurrent hypoglycemia compared to patients with transient hypoglycemia and normoglycemic patients. We observed significant correlations between PNA at day 1 and the area under the curve of the glycemia measured before PNA sampling for several threshold values of glycemia. Conclusions These results indicate that recurrent hypoglycemia is associated with systemic protein nitration in SGA term newborns, suggestive of a significant nitro-oxidative stress.

The logistic score: A criterion for hypothermia after perinatal asphyxia?

Objective. To identify during the first hour of life the asphyxiated term neonates who further develop moderate or severe neonatal encephalopathy. Methods. In 75 asphyxiated term infants, we measured postnatal arterial base deficit (BD30), assigned an early neurological score (ENS) according to their level of consciousness, respiration pattern and neonatal reflexes at 30 min of life and calculated the logistic score (LS) = (0.33 × BD30) – ENS. The receiver operating characteristics (ROC) methodology was applied to analyze the ability of the LS to correctly classify patients into two groups: normal or mild encephalopathy (60 patients) versus moderate or severe encephalopathy (15 patients). Results. The area under the ROC curve of the LS for moderate or severe encephalopathy (± standard error) was 94.4 ± 3.6%. At the threshold value of 1.2, the LS provided 87.5% sensitivity and 73.7% positive predictive value (PPV). The PPV of LS reaches 100% for a value >3.2, but this threshold allowed only 53.3% sensitivity. Conclusions. The LS is predictive of the neonatal neurological evolution after birth asphyxia and may help to select the high risk patients who are potential candidates for hypothermia therapy.