[Status of glycolysis in newborns with hypoxia]

An incriase has been shown in the blood content of lactate, NADH2, pyruvate, activity of lactatedehydrogenase in hypoxic newborn infants, which fact is believed to have a positive character. Under conditions of deficient supply of tissues with oxygen activization of glycolysis is of compensatory character. The results obtained should be regarded as a positive factor aimed to make up for the fund of NADH2, a potential energy product securing ATP synthesis through aerobic mechanism.

Role of cAMP and K(+) channel-dependent mechanisms in piglet hypoxic/ischemic impaired nociceptin/orphanin FQ-induced cerebrovasodilation

This study was designed to determine the role of altered cAMP and K(+) channel-dependent mechanisms in impaired pial artery dilation to the newly described opioid, nociceptin/orphanin FQ (NOC/oFQ) following hypoxia/ischemia in newborn pigs equipped with a closed cranial window. Recent studies have observed that NOC/oFQ elicits pial dilation via release of cAMP, which, in turn, activates the calcium sensitive (K(ca)) and the ATP-dependent K(+) (K(ATP)) channel. Global cerebral ischemia (20 min) was induced via elevation of intracranial pressure, while hypoxia (10 min) decreased pO(2) to 35+/-3 mm Hg with unchanged pCO(2). Topical NOC/oFQ (10(-8), 10(-6) M) induced vasodilation was attenuated by ischemia/reperfusion (I+R) and reversed to vasoconstriction by hypoxia/ischemia/reperfusion (H+I+R) at 1 h of reperfusion (control, 9+/-1 and 16+/-1%; I+R, 3+/-1 and 6+/-1%; H+I+R, -7+/-1 and -12+/-1%). Such altered dilation returned to control values within 4 h in I+R animals and within 12 h in H+I+R animals. NOC/oFQ dilation was associated with elevated CSF cAMP in control animals but such biochemical changes were attenuated in I+R animals and reversed to decreases in cAMP concentration in H+I+R animals (control, 1037+/-58 and 1919+/-209 fmol/ml; I+R, 1068+/-33 and 1289+/-30 fmol/ml; H+I+R, 976+/-36 and 772+/-27 fmol/ml for absence and presence of NOC/oFQ 10(-6) M, respectively). Topical 8-Bromo cAMP (10(-8), 10(-6) M) pial dilation was unchanged by I+R but blunted by H+I+R (control, 10+/-1 and 20+/-1%; I+R, 11+/-1 and 20+/-2%; H+I+R, 0+/-1 and 0+/-2%). Pituitary adenylate cyclase activating polypeptide and cromakalim, adenylate cyclase and K(ATP) channel activators, respectively, elicited dilation that was blunted by both I+R and H+I+R while NS1619, a K(ca) channel activator, elicited dilation that was unchanged by I+R but blunted by H+I+R. These data indicate that impaired NOC/oFQ dilation following I+R results form altered adenylate cyclase and K(ATP) channel-dependent mechanisms. These data further indicate that impaired NOC/oFQ dilation following H+I+R results not only from altered adenylate cyclase and K(ATP) channel but also from altered cAMP and K(ca) channel-dependent mechanisms.

NMDA blockade attenuates caspase-3 activation and DNA fragmentation after neonatal hypoxia-ischemia

The aim was to study the effects of an NMDA receptor antagonist on caspase-3 activation and DNA fragmentation after hypoxia-ischemia (HI) in 7-day-old rats. Animals were treated with vehicle or MK-801 (0.5 mg/kg) directly after HI and sacrificed 8, 24 or 72h later. MK-801 reduced injury (by 53%), cells positive for active caspase-3 (by 39%) and DNA fragmentation (by 79%) in the cerebral cortex. Furthermore, MK-801 significantly decreased caspase-3 activity, and Western blots revealed a tendency towards decreased proteolytic cleavage of the caspase-3 proform. The data imply that NMDA receptors are involved in the activation of apoptotic processes in the immature brain after HI.

Detection of transitory myocardial ischemia secondary to perinatal asphyxia

Transitory myocardial ischemia (TMI) is seen as a complication of severe asphyxia. Its presentation is variable, ranging from tachypnea to cardiogenic shock, and it is often masked by the predominant disease. The objective of this study was to detect TMI secondary to perinatal asphyxia in a population of asphyxiated newborns (NB) in comparison with asphyxiated NB with no evidence of TMI. From April 1996 to December 1997, 43 asphyxiated (stressed) NB were studied. Three were excluded. Patients were placed into two groups: Group A with TMI (n = 33) and Group B without TMI (n = 7). No significant differences were found in gestational age, birth weight, extrauterine age, Apgar score, or total creatine phosphokinase values between the two groups. Differences were found in CPK-MB levels and in ischemic electrocardiographic changes and blockages, especially for Group A. In this group, only 24 (72.7%) were cardiovascularly symptomatic. We conclude that TMI secondary to perinatal asphyxia is more frequent than has been reported. Thus, it would be useful in all asphyxiated NB to measure CPK-MB isoenzyme activity and patients can then be submitted to an electrocardiogram for detection in order to offer opportune treatment when required.

Perinatal asphyxia induces region-specific long-term changes in mRNA levels of tyrosine hydroxylase and dopamine D(1) and D(2) receptors in rat brain

To study the effects of neonatal asphyxia on gene expression of the dopaminergic systems, we determined quantitatively the mRNA levels of tyrosine hydroxylase, dopamine transporter, dopamine D(1) and D(2) receptors in substantia nigra/ventral tegmental area, striatum and limbic area. The mRNA levels were determined at one and 4 weeks after asphyxia by a quantitative reverse transcription polymerase chain reaction method. Spontaneously and Caesarean section born rats showed similar mRNA levels with the exception of an increase of tyrosine hydroxylase mRNA levels in the limbic area of 4-week-old animals. Five min of asphyxia did not change the mRNA levels in any region compared to that in the spontaneously born rats. Fifteen and twenty min of asphyxia induced region-specific alterations in mRNA levels. In SN/VTA an increase of tyrosine hydroxylase mRNA levels in the 1-week-old rats and in striatum an increase of D(1) and D(2) dopamine receptor mRNA levels in the 4-week-old rats were observed. Fifteen min of asphyxia induced a selective increase of D(1) and D(2) dopamine receptor mRNA levels in the limbic area of 4-week-old rats. These observations indicate that neonatal asphyxia triggers a cascade of gene expressions for tyrosine hydroxylase and D(1) and D(2) dopamine receptors. In 1-week-old rats, the gene expression of tyrosine hydroxylase increased in the cell body region substantia nigra/ventral tegmental area. This change may increase the D(1) and D(2) dopamine receptor expression in the target regions striatum and limbic area during further development.

Relation between brain tissue pO2 and dopamine synthesis of basal ganglia--a 18FDOPA-PET study in newborn piglets

Perinatal hypoxic-ischemic cerebral injury is a major determinant of neurologic morbidity and mortality in the neonatal period and later in childhood. There is evidence that the dopaminergic system is sensitive to oxygen deprivation. However, the respective enzyme activities have yet not been measured in the living neonatal brain. In this study, we have used 18F-labelled 6-fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) together with positron emission tomography (PET) to estimate the activity of the aromatic amino acid decarboxylase (AADC), the ultimate enzyme in the synthesis of dopamine, in the brain of newborn piglets under normoxic and moderate asphyxial conditions. The study was performed on 8 newborn piglets (2-5 days old). In each piglet PET studies were performed under control conditions and during 2-hour asphyxia. Simultaneously, brain tissue pO2 was recorded, cerebral blood flow (CBF) was measured with colored microspheres and cerebral metabolic rate of oxygen (CMRO2) was determined. Asphyxia was induced by lowering the inspired fraction of oxygen from 0.35 to 0.10 and adding about 6% CO2 to the inspired gas. Asphyxia elicited a more than 3-fold increase of the CBF (p < 0.01) so that CMRO2 remained unchanged throughout the asphyxial period. Despite this, brain tissue pO2 was reduced from 19 +/- 4 mm Hg to 6 +/- 3 mm Hg (p < 0.01). Blood-brain transfer of FDOPA as well as permeability-surface area product (PS) from striatum were unchanged. Striatal synthesis rate of fluoro-dopamine from FDOPA (k3) was, however, significantly increased (p < 0.01). This increase of the AADC activity is associated with reduced brain tissue pO2. Asphyxia-induced CBF increase impedes an alteration of brain oxidative metabolism.

Transient nonketotic hyperglycinemia in an asphyxiated patient with pyridoxine-dependent seizures

An asphyxiated neonate with pyridoxine-dependent seizures and associated transient nonketotic hyperglycinemia is reported. Frequent seizures and their resultant hypoxic-ischemic insult may have led to the elevation of the cerebrospinal fluid glycine level in this patient. Early diagnosis and treatment of pyridoxine-dependent seizures is essential for an improved neurologic outcome.

Cooling the newborn after asphyxia - physiological and experimental background and its clinical use

Many years of experimental work on hypoxic-ischaemic injury have supported the hypothesis that cooling the body and brain after the primary injury offers permanent neuroprotection. Clinically, the question of how late cooling can start after the insult and still have a protective effect is important and not fully investigated. Pilot studies in human adults initiated cooling after 10-18 h (trauma, stroke), however animal data suggest cooling is not effective if started later than 6 h. There might be a threshold for 'cooling dose' - by depth or duration - to achieve permanent protection. Hypothermia must be administered with understanding of the extensive physiological effects. Different enzymes have different sensitivity to changes in temperature, hence some effects may be beneficial and some deleterious. Hypothermia and cardiovascular responses and coagulation needs careful monitoring.

Novel treatments after experimental brain injury

Perinatal hypoxic-ischaemic encephalopathy(HIE) is being studied in laboratory models that allow the delayed cascade of events triggered by the energetic insult to be examined in detail. The concept of the 'excitotoxic cascade' provides a conceptual framework for thinking about the pathogenesis of HIE. Major events in the cascade triggered by hypoxia-ischaemia include overstimulation of N-methyl-D-aspartate type glutamate receptors, calcium entry into cells, activation of calcium-sensitive enzymes such as nitric oxide synthase, production of oxygen free radicals, injury to mitochondria, leading in turn to necrosis or apoptosis. New experimental approaches to salvaging brain tissue from the effects of HIE include inhibition of neuronal nitric oxide synthase, administration of neuronal growth factors, and inhibition of the caspase enzymes that execute apoptosis. Recent experimental work suggests that these approaches may be effective during a longer 'therapeutic window' after the insult, because they are acting on events that are relatively delayed. Application of modest hypothermia may allow these agents to be neuroprotective at even longer intervals after hypoxia-ischaemia.

Selection of babies for intervention after birth asphyxia

Based on animal experiments, the therapeutic window for neonates with signs of perinatal hypoxia-ischaemia is probably less than 6 h, and early selection of patients is of utmost importance. In term neonates, fetal heart rate and blood flow patterns, the Apgar score, and other clinical scoring systems are insufficient to select patients for intervention, whereas umbilical artery pH<7.0 combined with umbilical arteriovenous differences in PCO(2), lactate/pyruvate ratios in cord blood, and CSF interleukin-1beta have a better predictive value. At present, neurophysiological methods such as (amplitude-integrated) EEG and evoked potentials have the best predictive value. In preterm neonates, lactate/pyruvate and uric acid measurements in cord blood, as well as neurophysiology appear to be helpful to predict brain injury, and might be used to select patients for intervention.

C-fos gene expression in rat brain around birth: effect of asphyxia and catecholamines

At birth, the mammalian nervous system must adapt rapidly to the new conditions it encounters in the extra-uterine environment. One aspect of this adaptation, known as arousal, is mediated by catecholamines, the levels of which in the brain increase rapidly after birth. The pattern of gene expression also changes. Shortly after birth, expression of the immediate early gene c-fos, known to reflect general neural activity, is up-regulated. Furthermore, asphyxia often occurs in connection with birth. In order to examine the effects of this phenomenon on the expression of c-fos, as well as on the rate of noradrenaline (NA) turnover, asphyxia was induced in rat pups delivered by caesarean section. Northern blot analysis and in situ hybridization revealed that the increase in expression of c-fos in certain areas of the brain was greatly enhanced by asphyxia of moderate duration; whereas more prolonged asphyxia lowered the level of c-fos mRNA. Asphyxia had a similar effect on the rate of NA turnover. Adrenergic receptor antagonists administered prior to birth attenuated the birth-related induction of c-fos mRNA. However, the potentiation of c-fos expression by asphyxia was not altered by these antagonists. Therefore, we propose that while catecholamines play an important role in the induction of c-fos in the brain at birth, the effects of asphyxia involve a different mechanism.

Glucose transporters, hexokinase, and phosphofructokinase in brain of rats with perinatal asphyxia

Transport by glucose transporters from blood to the brain during hypoxic-ischemic conditions is well studied. However, the recent availability of a clinically related animal model of perinatal asphyxia and the fact that no concomitant determination of glucose transporters, parameters for glucose utilization, brain glucose, and cerebral blood flow (CBF) have been reported and the early phase of perinatal asphyxia has never been studied led us to perform the following study. Cesarean section was performed on full-term pregnant rats. The obtained pups within patent uterus horns were placed into a water bath at 37 degrees C from which they were subsequently removed after 5-20 min of graded asphyxia. Brain pH, brain tissue glucose, CBF, mRNA and activity of hexokinase and phosphofructokinase, and mRNA and protein of the glucose transporters GLUTI and GLUT3 were determined. Brain pH decreased and brain tissue glucose and CBF increased with the length of the asphyctic period; hexokinase and phosphofructokinase mRNA and activity were unchanged during the observation period. The mRNA and protein of both glucose transporters were comparable between normoxic and asphyctic groups. We show that glucose transport and utilization are unchanged in the early phase of perinatal asphyxia at a time point when CBF and brain glucose are already significantly increased and severe acidosis is present.

Brain RNA polymerase and nucleolar structure in perinatal asphyxia of the rat

Ribosomes are integral constitutens of the protein synthesis machinery. Polymerase I (POL I) is located in the nucleolus and transcribes the large ribosomal genes. POL I activity is decreased in ischemia but nothing is known so far on POL I in perinatal asphyxia. We investigated the involvement of POL I in a well-documented model of graded systemic asphyxia at the level of activity, mRNA, protein, and morphology. Caeserean section was performed at the 21st day of gestation. Rat pups still in the uterus horns were immerged in a water bath for asphyctic periods from 5-20 min. Brain was taken for measurement of pH, nuclear POL I activity, and mRNA steady state, and protein levels of RPA40, an essential subunit of POL I and III. Silver staining and transmission electron microscopy with morphometry when appropriate were used to examine the nucleolus. Brain pH and nuclear POL I activity decreased with the length of the asphyctic period while POL-I mRNA and protein levels were unchanged. Accompanying the decrease in brain pH we found significant changes of nucleolar structure in the course of perinatal asphyxia at the light and electron microscopic level. As early as ten min following the asphyctic insult, morphological disintegration of the nucleolus was observed. The changes became more dramatic with longer duration of perinatal asphyxia. We conclude that severe acidosis may be responsible for decreased POL activity and for disintegration of nucleoli in neurons. This condition may lower the ribosome content in neonatal neurons and impair protein synthesis.

Correlation of basal ganglia magnetic resonance spectroscopy with Apgar score in perinatal asphyxia

BACKGROUND

Brain metabolite levels are measured by proton magnetic resonance spectroscopy (1H MRS) and include N-acetylaspartate (NAA), creatine (Cr), choline (Cho), and lactate and the ratios NAA to Cho and Cr (NAA-ChoCr), NAA-Cr, NAA-Cho, and Cho-Cr. Brain metabolite levels may correlate with the degree of neonatal asphyxia.

OBJECTIVE

To determine which brain metabolite ratios have the strongest correlation with the Apgar scores in infants with possible asphyxia; whether the correlation is stronger with basal ganglia (BG) or anterior border-zone metabolites; and whether a combined approach using routine MR imaging (MRI), diffusion-weighted MRI, and MRS can be used to evaluate the severity of neonatal asphyxia.

METHODS

Twenty infants with 1-minute Apgar scores of 6 or less were studied at 2 to 28 days of age. The MRS variables were compared with routine and diffusion-weighted brain MRI. Clinical variables and MRS findings were subjected to factor analysis and stepwise multiple regressions to determine interrelationships.

RESULTS

The BG region NAA-Cho and NAA-ChoCr ratios correlated with the 1-minute (P<.001) and 5-minute (P = .01 for NAA-Cho; P = .006 for NAA-ChoCr). There was no correlation between metabolite levels and the 10-minute Apgar scores. The stongest predictions exist between the 1-minute Apgar scores and the NAA-Cho and NAA-ChoCr ratios. In the anterior border zone, the only correlation was between the 1-minute Apgar score and the NAA-Cho ratio, but there was a strong age effect in these data. Lactate was found in the BG of 3 infants, all of whom had 5-minute Apgar scores of 6 or less. Three patients had focal lesions on MRI; 2 of these had elevated lactate levels in the abnormal region; and the third, who had an intrauterine stroke, had no lactate in the region.

CONCLUSIONS

Correlations between NAA-Cho and NAA-ChoCr ratios and the 1- and 5-minute Apgar scores are stronger in the BG region than in the frontal border zone. The presence or absence of lactate may indicate the severity of the brain insult, and the combination of MRS, MRI, and diffusion-weighted MRI may assist in localizing and predicting a long-term brain injury.

[Study on the relationship between perinatal hypoxia and concentration of endothelin-1 in amniotic fluid]

OBJECTIVE

To investigate the relationship between endothelin-1 (ET-1) concentration in amniotic fluid (AF) and perinatal hypoxia.

METHODS

161 cases were measured for amniotic fluid(AF) ET-1 levels by radioimmunoassay. 110 cases of normal pregnancy were included in control group among which 30 term pregnancies were simultaneously measured for maternal and umbilical plasma ET-1. 51 cases of intrauterine hypoxia were the study group.

RESULTS

(1) The AF ET-1 levels showed increasing trend after 14 weeks (P < 0.01). (2) Fetal plasma ET-1 levels were significantly higher than that of maternal plasma ET-1 levels, but lower than those of AF ET-1 (P < 0.01). The ET-1 levels of umbilical plasma had positive correlation with those of AF ET-1 (r = 0.952, P < 0.01), but there is no correlation with levels of maternal plasma ET-1 (r = 0.338, P < 0.05). (3) In study group, the level of AF ET-1 was elevated with severity of hypoxia, the average level of AF ET-1 in cases of intrauterine hypoxia was (30.654 +/- 5.832) ng/L. In cases of severe neonatal asphyxia it was (960.650 +/- 236.698) ng/L.

CONCLUSIONS

The ET-1 exists in AF and gradually increases while pregnancy advanced. AF ET-1 levels can be served as a marker to predict perinatal hypoxia.

Induced brain hypothermia in asphyxiated human newborn infants: a retrospective chart analysis of physiological and adverse effects

OBJECTIVE

To assess the physiological effects and adverse side-effects of induced hypothermia in asphyxiated newborn infants as a base for future controlled, randomized trials.

DESIGN

Retrospective chart analysis with historical controls.

SETTING

Tertiary neonatal intensive care unit of the University of Cape Town, South Africa.

PATIENTS

Twenty-one asphyxiated newborns treated with induced hypothermia between September 1997 and February 1998 were compared to 15 asphyxiated newborn infants admitted during March to August 1997. The two groups of infants did not differ in patient characteristics or severity of asphyxia (comparison group vs hypothermia group: Apgar at 5 min 5.3 +/- 3.1 vs 5.2 +/- 2.3; base deficit 15.6 +/- 6.3 vs 11.5 +/- 7.2 and Thompson neurological score 10.1 +/- 4.0 vs 9.1 +/- 3.6).

INTERVENTIONS

Hypothermia was induced by placing a cap formed from coolpacks, at a temperature of about 10 degrees C, around the head of asphyxiated newborn infants to maintain the nasopharyngeal temperature between 34 and 35 degrees C. Hypothermia was maintained for 3 days.

MEASUREMENTS AND RESULTS

In the comparison group 4/15 infants died and in the hypothermia group 4/21 died. Hypothermia was induced at a median of 6.0 h (range 45 min to 53 h) post-partum, maintained for an average of 80 h (median 77.5 h, range 22 to 185 h) and resulted in an average nasopharyngeal temperature of 34.6 +/- 0.5 degrees C. Hypothermia reduced abdominal skin temperature from 36.3 +/- 0.5 degrees C to 35.1 +/- 0.35 degrees C (p = 0.0001), heart rate from 139 +/- 21 to 121 +/- 13 beats/min (p < 0.0001) and respiratory rate from 67 +/- 11 to 56 +/- 9 breaths/min (p = 0.005). Neither episodes of bradycardia nor dysrhythmias, apnea, clinical signs of bleeding diathesis in the hypothermia group nor differences in the frequency of hypoglycaemia and urinary output, blood in urine or tracheal secretion between the two groups were observed. In the survivors the neurological score, assessed at day 2 and day 5, fell from 10.9 +/- 3.5 to 8.1 +/- 4.5 in the hypothermia group and rose from 8.1 +/- 2. 5 to 9.0 +/- 3.1 in the comparison group (p = 0.003).

CONCLUSIONS

Adverse effects of mild hypothermia induced for 3 days in asphyxiated newborns were significantly less than expected from previous reports on neonates with accidental hypothermia.

Nitric oxide and nitric oxide synthase in the early phase of perinatal asphyxia of the rat

The role of nitric oxide, a compound involved in neurotransmission and regulation of cerebral blood flow, in cerebral ischemia is still not fully elucidated yet. Although well studied in adult systems of cerebral ischemia/hypoxia, information on nitric oxide in perinatal asphyxia is limited and, in particular, no direct evidence for its generation has been provided. We therefore decided to study nitric oxide generation in brain of asphyctic rat pups by biophysical and biochemical methods. We used a simple, non-invasive rat model resembling the clinical situation in perinatal asphyxia: rat pups delivered by Caesarean section were placed into a water bath at 37 degrees C still in patent membranes for various asphyctic periods (up to 20 min). Brain pH, cerebral blood flow, neuronal nitrix oxide synthase messenger RNA (by northern and dot blot analysis), immunoreactive protein (by western blot analysis) and nitric oxide synthase activity were determined; generation of nitric oxide was evaluated directly by electron paramagnetic resonance spectroscopy. Neuronal nitric oxide synthase messenger RNA activity and nitric oxide generation were unaffected, whereas neuronal nitric oxide synthase-immunoreactive protein of 150,000 mol. wt was decreased and of 136,000 mol. wt was increased with the length of the asphyctic period. This is the first report on direct evidence for the generation of nitric oxide in perinatal asphyxia and we demonstrate that nitric oxide production remains unaffected even by 20 min of asphyxia, at a time-point when cerebral blood flow was increased four-fold and severe acidosis was present. However, it was found that levels of immunoreactive neuronal nitric oxide synthase of 136,000 mol. wt were increased paralleling the length of asphyxia. Levels of the 150,000 mol. wt immunoreactive neuronal nitric oxide synthase protein decreased, suggesting a different regulation pattern. Thus, the present biochemical and biophysical results form the basis for further investigations on nitric oxide in perinatal asphyxia.

Genes involved in the pathophysiology of perinatal asphyxia

Mechanisms in the pathogenesis of perinatal asphyxia (PA) at the gene level are only beginning to be elucidated, although gene hunting using differential display has revealed differences in gene expression between hypoxic and normoxic cells in vitro. As no information on gene expression was available from in vivo studies, we decided to use a non-invasive and clinically relevant animal model of PA for mRNA hunting applying the subtractive hybridization method. mRNAs from normoxic rat brain and brain of rat pups with 20 min of asphyxia were isolated and compared by this technique. The resulting subtracted mRNAs were converted to cDNA, sequenced and identified by gene bank data. A series of transcripts representing transcription factors, transporters, metabolic factors, were found to be up- or downregulated providing insight into mechanisms of PA, and on the other hand, genes with unknown functions could be given a preliminary role i.e. in PA. Results obtained with this powerful tool are now challenging quantitative determination of these genes and gene products at the protein and activity level to confirm their role in PA.

Oxidative stress, brain white matter damage and intrauterine asphyxia in fetal lambs

In order to examine the role of oxidative stress in asphyxia-induced perinatal brain damage, near-term fetal lambs were subjected to umbilical cord occlusion for approximately 60min until fetal arterial pH diminished to less than 6.9 and base excess to less than -20 meq/l. The levels of superoxide, hydrogen peroxide, glutathione (GSH) and thiobarbiturate-reactive substances (TBARS) within brain grey and white matter were determined at 72h to correlate with morphological changes. Although the topography and extent of brain damage varied somewhat from case to case, ranging from focal infarction in grey or white matter to subtle and patchy alterations of white matter, the telencephalic white matter appeared to bear the brunt of damage as compared to other regions. The parietal white matter, in particular was often the seat of early pathological changes that could be seen in isolation. These white matter changes were accompanied by significant increases in hydrogen peroxide and TBARS levels as compared to those in grey matter. In another set of experiments, 8 different brain regions were assayed for TBARS, GSH and superoxide dismutase (SOD). A highly significant rise in the levels of TBARS was again noted in the parietal and frontal white matter. SOD levels were higher in the frontal and parietal white matter, basal ganglia and cerebellum. Cerebral cortical and hippocampal neurons were relatively unaffected until accompanied by more severe damage to grey and white matter at other sites. These results suggest that the developing telencephalic white matter appears to be most vulnerable to the effects of intrauterine fetal asphyxia and that oxidative stress may be a major contributing factor in the pathogenesis of perinatal hypoxic-ischemic encephalopathy.

Resuscitation with room-air or oxygen supplementation

An accumulating body of data indicates that optimal newborn resuscitation is not performed with 100% oxygen. On the contrary, ambient air seems to have several advantages compared with supplemental oxygen. Present guidelines on newborn resuscitation should be critically reviewed and revised according to scientific evidence.

Persistent increases in cerebral lactate concentration after birth asphyxia

In this prospective study proton magnetic resonance spectroscopy (1H MRS) was used to test the hypothesis that lactate can be detected later than 1 mo after birth in the brains of infants who display severe neurodevelopmental impairment 1 y after transient perinatal hypoxia-ischemia. Data were obtained from three groups of infants: 1) eight infants suffering birth asphyxia followed by perinatal encephalopathy and abnormal neurodevelopmental outcome at 1 y of age (defined as major neurologic impairment, Griffiths quotient <85%, and low optimality score); 2) 10 infants with signs of perinatal hypoxia-ischemia but normal neurodevelopmental outcome at 1 y; and 3) six control infants with uneventful perinatal courses and normal neurodevelopment at 1 y. Between one and four examinations (median 1) were performed at median (range) 11 (4-68) wk after birth, and the cerebral concentration ratio of lactate to creatine plus phosphocreatine (Cr) calculated from each spectrum. Lactate was detected later than the 1st mo after birth in seven of eight infants with abnormal neurodevelopmental outcome [maximum detected lactate/Cr was median (range) 0.44 (0.24-0.67)]. No lactate was detected later than the 1st mo after birth in infants with normal neurodevelopmental outcome, nor in five of six control subjects, although a small amount of lactate was detected in one control infant (lactate/Cr=0.04). These results suggest that the pathologic postasphyxial process, indicated by persistent cerebral lactate, may not be confined to the period immediately after injury.

Cerebral excitatory amino acids and Na+,K+-ATPase activity during resuscitation of severely hypoxic newborn piglets

We tested the hypothesis that early brain recovery in hypoxic newborn piglets is improved by resuscitating with an O2 supply close to the minimum level required by the newborn piglet brain. Severely hypoxic 2-5-d-old anaesthetized piglets were randomly divided into three resuscitation groups: hypoxaemic (n = 8), 21% O2 (n = 8), and 100% O2 groups (n = 8). The hypoxaemic group was mechanically ventilated with 12-18% O2 adjusted to achieve a cerebral venous O2 saturation of 17-23% (baseline; 45 +/- 1%, mean +/- SEM). During the 2h resuscitation period, extracellular aspartate and glutamate concentrations in the cerebral striatum were higher during hypoxaemic resuscitation (p = 0.044 and p = 0.055, respectively) than during resuscitation with 21% O2 or 100% O2, suggesting an unfavourable accumulation of potent excitotoxins during hypoxaemic resuscitation. The cell membrane Na+,K+-ATPase activity of cerebral cortical tissue after 2 h resuscitation was similar in the three groups (p = 0.30). In conclusion, hypoxaemic resuscitation did not normalize early cerebral metabolic recovery as efficiently as resuscitation with 21% O2 or 100% O2. Resuscitation with 21% O2 was as efficient as resuscitation with 100% O2 in this newborn piglet hypoxia model.

The effect of antioxidative combination therapy on post hypoxic-ischemic perfusion, metabolism, and electrical activity of the newborn brain

Reoxygenation and reperfusion after severe hypoxia and ischemia (HI) contribute substantially to birth asphyxia-related brain injury. Excess production of free radicals via metabolization of arachidonic acid, xanthine oxidase, and non-protein-bound iron play an important role. Cerebral reperfusion injury is characterized by a decrease in perfusion, oxygen consumption, and electrical activity of the brain. Reduction of free radical production may attenuate these features. We therefore induced severe HI in 35 newborn lambs, and upon reperfusion the lambs received a placebo [control (CONT), n = 7], the cyclooxygenase inhibitor indomethacin (INDO, 0.3 mg/kg/i.v., n = 7), the xanthine oxidase inhibitor allopurinol (ALLO, 20 mg/kg/i.v., n = 7), the iron chelator deferoxamine (DFO, 2.5 mg/kg/i.v., n = 7), or a combination of these drugs (COMB, n = 7). In each group changes (%) from pre-HI values were investigated for brain perfusion [measured by carotid artery flow (Qcar, mL/min)], (relative) cerebral O2 metabolism (CMR(O2)), and electrocortical brain activity (ECBA, microV) at 15, 60, 120, and 180 min post-HI. Qcar decreased significantly at 120 and 180 min post-HI in CONT (p < 0.05), but not in INDO, ALLO, DFO, and COMB groups. CMR(O2) decreased significantly in CONT at 60 min post-HI (p < 0.05), remained stable in DFO and INDO, and was significantly higher in ALLO and COMB (p < 0.05) at 120 and 180 min post-HI. ECBA was significantly lower in CONT during the whole post-HI period (p < 0.05), ECBA in INDO and COMB were significantly decreased at 60 and 120 min post-HI (p < 0.05), but recovered afterward, whereas DFO and ALLO remained stable during the post-HI period. In conclusion preservation of Qcar and CMR(O2), and recovery of ECBA occurred after treatment with INDO, ALLO, and DFO; combination of these drugs did not have an additional positive effect.

Resuscitation of asphyxiated newborn infants with room air or oxygen: an international controlled trial: the Resair 2 study

OBJECTIVE

Birth asphyxia represents a serious problem worldwide, resulting in approximately 1 million deaths and an equal number of serious sequelae annually. It is therefore important to develop new and better ways to treat asphyxia. Resuscitation after birth asphyxia traditionally has been carried out with 100% oxygen, and most guidelines and textbooks recommend this; however, the scientific background for this has never been established. On the contrary, theoretic considerations indicate that resuscitation with high oxygen concentrations could have detrimental effects. We have performed a series of animal studies as well as one pilot study indicating that resuscitation can be performed with room air just as efficiently as with 100% oxygen. To test this more thoroughly, we organized a multicenter study and hypothesized that room air is superior to 100% oxygen when asphyxiated newborn infants are resuscitated.

METHODOLOGY

In a prospective, international, controlled multicenter study including 11 centers from six countries, asphyxiated newborn infants with birth weight >999 g were allocated to resuscitation with either room air or 100% oxygen. The study was not blinded, and the patients were allocated to one of the two treatment groups according to date of birth. Those born on even dates were resuscitated with room air and those born on odd dates with 100% oxygen. Informed consent was not obtained until after the initial resuscitation, an arrangement in agreement with the new proposal of the US Food and Drug Administration's rules governing investigational drugs and medical devices to permit clinical research on emergency care without the consent of subjects. The protocol was approved by the ethical committees at each participating center. Entry criterion was apnea or gasping with heart rate <80 beats per minute at birth necessitating resuscitation. Exclusion criteria were birth weight <1000 g, lethal anomalies, hydrops, cyanotic congenital heart defects, and stillbirths. Primary outcome measures were death within 1 week and/or presence of hypoxic-ischemic encephalopathy, grade II or III, according to a modification of Sarnat and Sarnat. Secondary outcome measures were Apgar score at 5 minutes, heart rate at 90 seconds, time to first breath, time to first cry, duration of resuscitation, arterial blood gases and acid base status at 10 and 30 minutes of age, and abnormal neurologic examination at 4 weeks. The existing routines for resuscitation in each participating unit were followed, and the ventilation techniques described by the American Heart Association were used as guidelines aiming at a frequency of manual ventilation of 40 to 60 breaths per minute.

RESULTS

Forms for 703 enrolled infants from 11 centers were received by the steering committee. All 94 patients from one of the centers were excluded because of violation of the inclusion criteria in 86 of these. Therefore, the final number of infants enrolled in the study was 609 (from 10 centers), with 288 in the room air group and 321 in the oxygen group. Median (5 to 95 percentile) gestational ages were 38 (32.0 to 42.0) and 38 (31.1 to 41.5) weeks (NS), and birth weights were 2600 (1320 to 4078) g and 2560 (1303 to 3900) g (NS) in the room air and oxygen groups, respectively. There were 46% girls in the room air and 41% in the oxygen group (NS). Mortality in the first 7 days of life was 12.2% and 15.0% in the room air and oxygen groups, respectively; adjusted odds ratio (OR) = 0.82 with 95% confidence intervals (CI) = 0.50-1.35. Neonatal mortality was 13.9% and 19.0%; adjusted OR = 0. 72 with 95% CI = 0.45-1.15. Death within 7 days of life and/or moderate or severe hypoxic-ischemic encephalopathy (primary outcome measure) was seen in 21.2% in the room air group and in 23.7% in the oxygen group; OR = 0.94 with 95% CI = 0.63-1.40. (ABSTRACT TRUNCATED)

Perinatal hypoxic/ischemic encephalopathy: clinical challenge and experimental implications

Perinatal asphyxia is an important cause of neonatal mortality and subsequent sequelae. Striatum, richly innervated by nigrostriatal dopaminergic projections, is susceptible to perinatal insults. Measuring the cerebral cortical oxygen pressure and striatal extracellular dopamine in the striatum in piglets under different kinds and degrees of hypoxia/ischemia insult, the changes of extracellular striatal dopamine were found to be more related to the changes in blood pressure than with cortical oxygen pressure. After asphyxia, cortical oxygen pressure was significantly higher in piglets breathing 100% O2 than in those breathing 21% O2. Two hours after reoxygenation, there was a secondary release of more dopamine in piglets ventilated with 100% O2 than in those with 21% O2. Although 100% FiO2 after asphyxia increases more cortical oxygenation, it also results in poorer recovery in dopamine metabolism and higher secondary release of striatal dopamine, which may exacerbate post-hypoxic cerebral injury. Striatal lesions may strongly be related with levels of extracellular dopamine during different degrees and kinds of insults. The study of the urine 1H-NMR spectra in newborns within six hours after birth demonstrated that the lactate/creatinine ratio in newborns with subsequent hypoxic-ischemic encephalopathy was significantly higher than in those with perinatal distress only and in normal newborns. The urine lactate/creatinine ratio in newborns with perinatal distress only was also significantly higher than that in normal newborns. The levels of urinary lactate/creatinine by 1H-NMR spectroscopy within six hours after birth correlates well with subsequent hypoxic-ischemic encephalopathy. The characteristics of urine 1H-NMR spectra can be sensitively and specifically used to identify early after birth for the asphyxiated newborns with potential subsequent hypoxic-ischemic encephalopathy.