Brain injury in preterm infants--what can the obstetrician do?

The role of glucocorticoid receptors in dexamethasone-induced apoptosis of neuroprogenitor cells in the hippocampus of rat pups

Background. Dexamethasone (Dex) has been used to reduce inflammation in preterm infants with assistive ventilation and to prevent chronic lung diseases. However, Dex treatment results in adverse effects on the brain. Since the hippocampus contains a high density of glucocorticoid receptors (GCRs), we hypothesized that Dex affects neurogenesis in the hippocampus through inflammatory mediators. Methods. Albino Wistar rat pups first received a single dose of Dex (0.5 mg/kg) on postnatal day 1 (P1) and were sacrificed on P2, P3, P5, and P7. One group of Dex-treated pups (Dex-treated D1D2) was given mifepristone (RU486, a GCR antagonist) on P1 and sacrificed on P2. Hippocampi were isolated for western blot analysis, TUNEL, cleaved-caspase 3 staining for cell counts, and morphological assessment. Control pups received normal saline (NS). Results. Dex reduced the developmental gain in body weight, but had no effect on brain weight. In the Dex-treated D1D2 group, apoptotic cells increased in number based on TUNEL and cleaved-caspase 3 staining. Most of the apoptotic cells expressed the neural progenitor cell marker nestin. Dex-induced apoptosis in P1 pups was markedly reduced (60%) by pretreatment with RU486, indicating the involvement of GCRs. Conclusion. Early administration of Dex results in apoptosis of neural progenitor cells in the hippocampus and this is mediated through GCRs.

[Assessment of preterm children's early development]

Preterm birth is an event that affects the child's healthy development. Several studies have addressed the evaluation of children born preterm and the influence that multiple risk factors have on the course of their development. This study performed a systematic review of the literature from 2000 to 2005 about the evaluation of the development of children born preterm until the age of 24 months. The biological risk factors were present in every study, with highlights on intraventricular hemorrhage, necrotizing enterocolitis, chronic pulmonary disease, and retardation of intrauterine development as the most studied risks. The child's motor development was the most studied area. In terms of age, the first evaluations focused on the first six months of life. Neonatal risk, low birth weight, baby boys, cerebral injuries, and first-week abnormal spontaneous movements were predicting factors of preterm child development at the age of two years.

Anti-inflammatory and immunomodulatory strategies to protect the perinatal brain

Infection and inflammation contribute to perinatal brain damage, particularly to the white matter. Although combating perinatal inflammation can be dangerous, because inflammation might have beneficial effects for mother and fetus, it is worthwhile reviewing potential anti-inflammatory neuroprotective compounds, along with their potential adverse effects. Further research on the possible neuroprotective roles of existing medications and substances is necessary.

Dexamethasone treatment differentially affects the oxidative energy metabolism of rat brain mitochondria in developing and adult animals

We studied the effect of repeated exposure to dexamethasone (Dex) treatment on rat brain mitochondrial oxidative energy metabolism in developing rats at different postnatal ages, i.e. 2-5 week and in adults. The animals were injected with a dose of 2 mg of Dex/kg body weight at around 7:00 a.m. for three alternative days prior to the day of sacrifice; the control group animals received saline vehicle. We measured rates of respiration with different substrates, viz. glutamate, pyruvate+malate, succinate and ascorbate+TMPD; the contents of individual cytochromes and the dehydrogenases and ATPase activities. Dex treatment, in general, stimulated the state 3 rates of respiration rates in young animals in age-dependent and substrate-specific manner except for the 3 week group, whereas in the adults there was substantial inhibition of the respiration. The pattern of dehydrogenases activities matched with respiration rates. Dex treatment also resulted in uncoupling of the second and third site of phosphorylation in 3-week-old animals and in the adults. The contents of cytochrome aa3, b and ATPase activities decreased significantly after Dex treatment in all the age groups. The results thus emphasize that exposure to repeated Dex treatment can significantly influence the oxidative energy metabolism of brain mitochondria in young growing animals as well as in adults.

Use of tocolytics: what is the benefit of gaining 48 hours for the fetus?

Preterm birth remains one of the serious problems in perinatal medicine and is associated with an increased risk of neonatal complications and long-term morbidity. Although each day that delivery is delayed between 22 and 28 weeks of gestation increases survival by 3%, since most spontaneous preterm labour occurs between 28 and 34 weeks of gestation, this is of secondary concern; the primary goal of delay is to improve the function of certain systems in the fetus and to balance the risks of a hostile intrauterine environment with the complications of extrauterine preterm life. Although there is a lack of definitive evidence that tocolytic drugs improve outcome following spontaneous preterm labour and preterm birth, there is ample evidence that tocolysis delays delivery for long enough to permit administration of a complete course of antepartum glucocorticoids and to facilitate in utero transfer to a tertiary care unit where neonatal care will be optimal. Both these measures have been associated with improved outcomes; antepartum glucocorticoids reduce the incidence of respiratory distress syndrome, intraventricular haemorrhage, periventricular leucomalacia and necrotising enterocolitis, and in utero transfer is associated with decreased morbidity and mortality and less hospital-based intervention compared with postnatal transportation. Consequently, women who are more likely to benefit from tocolysis are those at early gestational ages, those needing transfer to a hospital that can provide neonatal intensive care and those who have not yet received a full course of antepartum glucocorticosteroids. In these cases, delaying labour for at least 48 hours with drugs such as atosiban should be considered, since it offers clear advantages for the fetus.

Guidelines for the management of spontaneous preterm labor

Preterm birth is defined as delivery at <37 completed weeks of pregnancy (World Health Organization). Spontaneous preterm birth (SPB) includes preterm labor, preterm spontaneous rupture of membranes, preterm premature rupture of membranes (PPROM) and cervical weakness; it does not include indicated preterm delivery for maternal or fetal conditions. Early SPB (<32 weeks' gestation) is associated with an increased higher perinatal mortality rate, inversely proportional to gestational age. The pathophysiologic events that trigger SPB are largely unknown but include decidual hemorrhage (abruption), mechanical factors (uterine overdistention or cervical incompetence), and hormonal changes (perhaps mediated by fetal or maternal stress). In addition, several cervicovaginal infections have been associated with preterm labor. SPB is also the leading cause of long-term morbidity, including neurodevelopmental handicap, cerebral palsy, seizure disorders, blindness, deafness and non-neurological disorders, such as bronchopulmonary dysplasia and retinopathy of prematurity. Delaying delivery may reduce the rate of long-term morbidity by facilitating the maturation of developing organs and systems. The benefits of administration of antepartum glucocorticosteroids to reduce the incidence and severity of respiratory distress syndrome may be exploited by delay. Delay may also permit transfer of the fetus in utero to a center with neonatal intensive care unit facilities. There is considerable variation in the way that spontaneous preterm labor (SPTL) is diagnosed, managed and treated internationally. The development of clinical guidelines requires an evidence-based approach to improve outcome and allow more efficient use of resources. With recent advances in our understanding of the etiology and mechanisms of SPTL and the availability of safer, more specific tocolytics, it was felt that guidelines should be developed to achieve, if possible, an European consensus in patient diagnosis, management and treatment.

Brain injury in the infant: the old, the new, and the uncertain

Although neonatal brain injury occurs most frequently after a perinatal hypoxic-ischemic insult, recently studies have noted that variable causes such as metabolic and reperfusion events can result in, or aggravate, a brain insult. Current data suggest that about 2 to 5 of 1,000 live births in the United States and more so in developing countries experience a brain injury Approximately 20% to 40% of infants who survive the brain injury develop significant neurological and developmental impairments. The resulting impact on the child, family, and society presents a formidable challenge to health care professionals. Although several important insights have been gained in the last several years about the epidemiology, diagnosis, and mechanism of brain injury, management remains mostly a cocktail of controversial trials. This article provides a comprehensive review of the pathology, clinical manifestations, and timely management of infants with brain injury.