Indomethacin promotes germinal matrix microvessel maturation in the newborn beagle pup

Prophylactic indomethacin and the risk of serious pulmonary hemorrhages in preterm infants less than 28 weeks' gestation

OBJECTIVE

To determine if prophylactic indomethacin (PINDO) decreases serious pulmonary hemorrhages in infants <28 weeks.

STUDY DESIGN

Intention-to-treat analysis of 615 consecutively admitted infants during four alternating protocol-driven epochs of PINDO or expectant patent ductus arteriosus (PDA) management.

RESULTS

41/615 (6.7%) developed serious pulmonary hemorrhage at 2 (1, 3) days (median (IQR)). In unadjusted and adjusted multivariable models, infants born in a PINDO epoch had significantly lower incidences of pulmonary hemorrhage and pulmonary hemorrhage or death before 7 days. There were less moderate/large PDA during PINDO epochs. The associations between PINDO and pulmonary hemorrhage and pulmonary hemorrhage/death were no longer significant when presence of a PDA was included in the analyses. There was no apparent association between PINDO epochs and the incidence of serious intraventricular hemorrhages.

CONCLUSION

Even though PINDO no longer appears to affect the incidence of sIVH it still is associated with a lower incidence of pulmonary hemorrhage.

The importance of laminin at the blood-brain barrier

The blood-brain barrier is a unique property of central nervous system blood vessels that protects sensitive central nervous system cells from potentially harmful blood components. The mechanistic basis of this barrier is found at multiple levels, including the adherens and tight junction proteins that tightly bind adjacent endothelial cells and the influence of neighboring pericytes, microglia, and astrocyte endfeet. In addition, extracellular matrix components of the vascular basement membrane play a critical role in establishing and maintaining blood-brain barrier integrity, not only by providing an adhesive substrate for blood-brain barrier cells to adhere to, but also by providing guidance cues that strongly influence vascular cell behavior. The extracellular matrix protein laminin is one of the most abundant components of the basement membrane, and several lines of evidence suggest that it plays a key role in directing blood-brain barrier behavior. In this review, we describe the basic structure of laminin and its receptors, the expression patterns of these molecules in central nervous system blood vessels and how they are altered in disease states, and most importantly, how genetic deletion of different laminin isoforms or their receptors reveals the contribution of these molecules to blood-brain barrier function and integrity. Finally, we discuss some of the important unanswered questions in the field and provide a "to-do" list of some of the critical outstanding experiments.

Ductus arteriosus and the preterm brain

As the approach to the patent ductus arteriosus (PDA) in the preterm infant remains controversial, the potential consequences of a significant ductal shunt on the brain should be evaluated. In this population at high risk of adverse outcomes, including intraventricular haemorrhage and white matter injury, as well as longer-term neurodevelopmental impairment, it is challenging to attribute sequelae to the PDA. Moreover, individual patient characteristics including gestational age and timing of PDA intervention factor into risks of brain injury. Haemodynamic assessment of the ductus combined with bedside neuromonitoring techniques improve our understanding of the role of the PDA in neurological injury. Effects of various PDA management strategies on the brain can similarly be investigated. This review incorporates current understanding of how the PDA impacts the developing brain of preterm infants and examines modalities to measure these effects.

Effects of prophylactic indomethacin on intraventricular hemorrhage and adverse outcomes in neonatal intensive care unit

OBJECTIVE

To identify the relationship between prophylactic indomethacin (PI) administration and incidence of intraventricular hemorrhage.

STUDY DESIGN

A retrospective analysis of extremely premature infants <27 weeks gestational age born between January 2014 and September 2020.

RESULTS

A total of 421 infants were included from three of Nationwide Children's Hospital delivery centers. Of those 255 (61%) received PI. After adjustment by inverse proportionality treatment weighting (IPTW), no differences were found in incidence of intraventricular hemorrhage (IVH) at the time of the first ultrasound, 31% vs. 33% in PI and control groups respectively (p = 0.68). The rate of rise of serum creatinine from baseline to day of life four was significantly higher in the PI group (0.14 mg/dl PI and 0.03 mg/dl control, p < 0.001).

CONCLUSION

PI was not associated with any benefit in prevention of IVH, but is associated with adverse effects including acute rise in creatinine.

Periventricular- intraventricular hemorrhage in the premature infant- A historical perspective

The objective of this chapter is to trace the evolution of intraventricular hemorrhage in the premature infant highlighting the importance of the germinal matrix, a critical role for cerebral blood flow changes in the genesis of hemorrhage, clinical factors that increase the bleeding risk, and potential preventative strategies. In 1976, neuropathological studies demonstrated capillary rupture within the germinal matrix as the precursor of hemorrhage. In 1980, introduction of cranial ultrasound facilitated diagnosis of intraventricular hemorrhage. In 1979, loss of cerebral autoregulation in sick newborn infants was demonstrated. In the 1980's, studies demonstrated the importance of intravascular factors in provoking hemorrhage. In 1983, the association of cerebral blood flow velocity fluctuations and subsequent hemorrhage was demonstrated. In 1994, antenatal steroids use to accelerate lung development was recommended. This was associated with an unanticipated reduction in hemorrhage. In the mid 1990's early indomethacin administration was associated with a reduction of severe hemorrhage.

Development of an integrated risk scale for prediction of shunt placement after neonatal intraventricular hemorrhage

OBJECTIVE

Neonatal intraventricular hemorrhage (IVH) is a major cause of mortality and morbidity, particularly following premature birth. Even after the acute phase, posthemorrhagic hydrocephalus is a long-term complication, frequently requiring permanent ventriculoperitoneal shunt (VPS) placement. Currently, there are no risk classification methods integrating the constellation of clinical data to predict short- and long-term prognosis in neonatal IVH. To address this need, the authors developed a two-part machine learning approach for predicting short- and long-term outcomes after diagnosis of neonatal IVH. Integrating both maternal and neonatal characteristics, they developed a binary classifier to predict short-term mortality risk and a clinical scale to predict the long-term risk of VPS placement.

METHODS

Neonates with IVH were identified from the Optum Clinformatics Data Mart administrative claims database. Matched maternal and childbirth characteristics were obtained for all patients. The primary endpoints of interest were short-term (30 day) mortality and long-term VPS placement. Classification of short-term mortality risk was evaluated using 5 different machine learning approaches and the best-performing method was validated using a withheld validation subset. Prediction of long-term shunt risk was performed using a multivariable Cox regression model with stepwise variable selection, which was subsequently converted to an easily applied integer risk scale.

RESULTS

A total of 5926 neonates with IVH were identified. Most patients were born before 32 weeks' gestation (67.2%) and with low birth weight (81.2%). Empirical 30-day mortality risk was 10.9% across all IVH grades and highest among grade IV IVH (34.3%). Among the neonates who survived > 30 days, actuarial 12-month postdiagnosis risk of shunt placement was 5.4% across all IVH grades and 31.3% for grade IV IVH. The optimal short-term risk classifier was a random forest model achieving an area under the receiver operating characteristic curve of 0.882 with important predictors ranging from gestational age to diverse comorbid medical conditions. Selected features for long-term shunt risk stratification were IVH grade, respiratory distress syndrome, disseminated intravascular coagulation, and maternal preeclampsia or eclampsia. An integer risk scale, termed the Shunt Prediction After IVH in Neonates (SPAIN) scale, was developed from these 4 features, which, evaluated on withheld cases, demonstrated improved risk stratification compared with IVH grade alone (Harrell's concordance index 0.869 vs 0.852).

CONCLUSIONS

In a large cohort of neonates with IVH, the authors developed a two-pronged, integrated, risk classification approach to anticipate short-term mortality and long-term shunt risk. The application of such approaches may improve the prognostication of outcomes and identification of higher-risk individuals who warrant careful surveillance and early intervention.

Prophylactic cyclo-oxygenase inhibitor drugs for the prevention of morbidity and mortality in preterm infants: a network meta-analysis

BACKGROUND

Patent ductus arteriosus (PDA) is associated with significant morbidity and mortality in preterm infants. Cyclooxygenase inhibitors (COX-I) may prevent PDA-related complications. Controversy exists on which COX-I drug is the most effective and has the best safety profile in preterm infants.

OBJECTIVES

To compare the effectiveness and safety of prophylactic COX-I drugs and 'no COXI prophylaxis' in preterm infants using a Bayesian network meta-analysis (NMA).

SEARCH METHODS

Searches of Cochrane CENTRAL via Wiley, OVID MEDLINE and Embase via Elsevier were conducted on 9 December 2021. We conducted independent searches of clinical trial registries and conference abstracts; and scanned the reference lists of included trials and related systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that enrolled preterm or low birth weight infants within the first 72 hours of birth without a prior clinical or echocardiographic diagnosis of PDA and compared prophylactic administration of indomethacin or ibuprofen or acetaminophen versus each other, placebo or no treatment.

DATA COLLECTION AND ANALYSIS

We used the standard methods of Cochrane Neonatal. We used the GRADE NMA approach to assess the certainty of evidence derived from the NMA for the following outcomes: severe intraventricular haemorrhage (IVH), mortality, surgical or interventional PDA closure, necrotizing enterocolitis (NEC), gastrointestinal perforation, chronic lung disease (CLD) and cerebral palsy (CP).

MAIN RESULTS

We included 28 RCTs (3999 preterm infants). Nineteen RCTs (n = 2877) compared prophylactic indomethacin versus placebo/no treatment, 7 RCTs (n = 914) compared prophylactic ibuprofen versus placebo/no treatment and 2 RCTs (n = 208) compared prophylactic acetaminophen versus placebo/no treatment. Nine RCTs were judged to have high risk of bias in one or more domains.We identified two ongoing trials on prophylactic acetaminophen. Bayesian random-effects NMA demonstrated that prophylactic indomethacin probably led to a small reduction in severe IVH (network RR 0.66, 95% Credible Intervals [CrI] 0.49 to 0.87; absolute risk difference [ARD] 43 fewer [95% CrI, 65 fewer to 16 fewer] per 1000; median rank 2, 95% CrI 1-3; moderate-certainty), a moderate reduction in mortality (network RR 0.85, 95% CrI 0.64 to 1.1; ARD 24 fewer [95% CrI, 58 fewer to 16 more] per 1000; median rank 2, 95% CrI 1-4; moderate-certainty) and surgical PDA closure (network RR 0.40, 95% CrI 0.14 to 0.66; ARD 52 fewer [95% CrI, 75 fewer to 30 fewer] per 1000; median rank 2, 95% CrI 1-2; moderate-certainty) compared to placebo. Prophylactic indomethacin resulted in trivial difference in NEC (network RR 0.76, 95% CrI 0.35 to 1.2; ARD 16 fewer [95% CrI, 42 fewer to 13 more] per 1000; median rank 2, 95% CrI 1-3; high-certainty), gastrointestinal perforation (network RR 0.92, 95% CrI 0.11 to 3.9; ARD 4 fewer [95% CrI, 42 fewer to 137 more] per 1000; median rank 1, 95% CrI 1-3; moderate-certainty) or CP (network RR 0.97, 95% CrI 0.44 to 2.1; ARD 3 fewer [95% CrI, 62 fewer to 121 more] per 1000; median rank 2, 95% CrI 1-3; low-certainty) and may result in a small increase in CLD (network RR 1.10, 95% CrI 0.93 to 1.3; ARD 36 more [95% CrI, 25 fewer to 108 more] per 1000; median rank 3, 95% CrI 1-3; low-certainty). Prophylactic ibuprofen probably led to a small reduction in severe IVH (network RR 0.69, 95% CrI 0.41 to 1.14; ARD 39 fewer [95% CrI, 75 fewer to 18 more] per 1000; median rank 2, 95% CrI 1-4; moderate-certainty) and moderate reduction in surgical PDA closure (network RR 0.24, 95% CrI 0.06 to 0.64; ARD 66 fewer [95% CrI, from 82 fewer to 31 fewer] per 1000; median rank 1, 95% CrI 1-2; moderate-certainty) compared to placebo. Prophylactic ibuprofen may result in moderate reduction in mortality (network RR 0.83, 95% CrI 0.57 to 1.2; ARD 27 fewer [95% CrI, from 69 fewer to 32 more] per 1000; median rank 2, 95% CrI 1-4; low-certainty) and leads to trivial difference in NEC (network RR 0.73, 95% CrI 0.31 to 1.4; ARD 18 fewer [95% CrI, from 45 fewer to 26 more] per 1000; median rank 1, 95% CrI 1-3; high-certainty), or CLD (network RR 1.00, 95% CrI 0.83 to 1.3; ARD 0 fewer [95% CrI, from 61 fewer to 108 more] per 1000; median rank 2, 95% CrI 1-3; low-certainty). The evidence is very uncertain on effect of ibuprofen on gastrointestinal perforation (network RR 2.6, 95% CrI 0.42 to 20.0; ARD 76 more [95% CrI, from 27 fewer to 897 more] per 1000; median rank 3, 95% CrI 1-3; very low-certainty). The evidence is very uncertain on the effect of prophylactic acetaminophen on severe IVH (network RR 1.17, 95% CrI 0.04 to 55.2; ARD 22 more [95% CrI, from 122 fewer to 1000 more] per 1000; median rank 4, 95% CrI 1-4; very low-certainty), mortality (network RR 0.49, 95% CrI 0.16 to 1.4; ARD 82 fewer [95% CrI, from 135 fewer to 64 more] per 1000; median rank 1, 95% CrI 1-4; very low-certainty), or CP (network RR 0.36, 95% CrI 0.01 to 6.3; ARD 70 fewer [95% CrI, from 109 fewer to 583 more] per 1000; median rank 1, 95% CrI 1-3; very low-certainty). In summary, based on ranking statistics, both indomethacin and ibuprofen were equally effective (median ranks 2 respectively) in reducing severe IVH and mortality. Ibuprofen (median rank 1) was more effective than indomethacin in reducing surgical PDA ligation (median rank 2). However, no statistically-significant differences were observed between the COX-I drugs for any of the relevant outcomes.

AUTHORS' CONCLUSIONS

Prophylactic indomethacin probably results in a small reduction in severe IVH and moderate reduction in mortality and surgical PDA closure (moderate-certainty), may result in a small increase in CLD (low-certainty) and results in trivial differences in NEC (high-certainty), gastrointestinal perforation (moderate-certainty) and cerebral palsy (low-certainty). Prophylactic ibuprofen probably results in a small reduction in severe IVH and moderate reduction in surgical PDA closure (moderate-certainty), may result in a moderate reduction in mortality (low-certainty) and trivial differences in CLD (low-certainty) and NEC (high-certainty). The evidence is very uncertain about the effect of acetaminophen on any of the clinically-relevant outcomes.

Use of Prophylactic Indomethacin in Preterm Infants: A Systematic Review and Meta-Analysis

BACKGROUND

Prophylactic indomethacin has been widely used as an effective intervention for reducing mortalities and morbidities in preterm infants including the cardiopulmonary and neurodevelopmental morbidities such as intraventricular hemorrhage (IVH), but many studies have reported contradictory outcomes regarding its significance. Therefore, we aim to systematically review and meta-analyze the data of prophylactic indomethacin on preterm infants.

METHODS

Our systematic search included the following databases: Pubmed, Google Scholar, Scopus, Web of Science, The New York Academy of Medicine (NYAM), Virtual health library (VHL), and the System for Information on Grey Literature in Europe (SIGLE) to include studies that assessed the use of prophylactic indomethacin in preterm infants until 12 August 2021.

RESULTS

The final list of our included studies is comprised of 23 randomized trials and cohort studies. Among all the studies outcomes, significant favorable outcome was lowering the rate of PDA, surgical PDA ligation (P < 0.001) and severe IVH (P = 0.008) while no significance was recorded with BPD, pulmonary hemorrhage, intraventricular hemorrhage, necrotizing enterocolitis, intestinal perforation, mortality, and length of hospital stay.

CONCLUSION

Since the meta-analysis results regarding effectiveness of prophylactic indomethacin varied based on the study design particularly with regard to outcomes such as surgical PDA ligation and severe IVH, this warrants the need for more evidence regarding the effectiveness of prophylactic indomethacin in very low birth weight infants.

Germinal Matrix-Intraventricular Hemorrhage: A Tale of Preterm Infants

Germinal matrix-intraventricular hemorrhage (GM-IVH) is a common intracranial complication in preterm infants, especially those born before 32 weeks of gestation and very-low-birth-weight infants. Hemorrhage originates in the fragile capillary network of the subependymal germinal matrix of the developing brain and may disrupt the ependymal lining and progress into the lateral cerebral ventricle. GM-IVH is associated with increased mortality and abnormal neurodevelopmental outcomes such as posthemorrhagic hydrocephalus, cerebral palsy, epilepsy, severe cognitive impairment, and visual and hearing impairment. Most affected neonates are asymptomatic, and thus, diagnosis is usually made using real-time transfontanellar ultrasound. The present review provides a synopsis of the pathogenesis, grading, incidence, risk factors, and diagnosis of GM-IVH in preterm neonates. We explore brief literature related to outcomes, management interventions, and pharmacological and nonpharmacological prevention strategies for GM-IVH and posthemorrhagic hydrocephalus.

Neuroprotective effect of indomethacin in normal perfusion pressure breakthrough phenomenon

Loss of cerebral autoregulation in normal perfusion pressure breakthrough (NPPB) phenomenon has been reported in other Central Nervous System diseases such as neonatal intraventricular haemorrhage. Several studies have demonstrated that low-dose indomethacin prevents this latter condition. A previous rat model was used to resemble NPPB phenomenon. Study animals were distributed in 4 groups that received 3 doses of indomethacin at different concentrations prior to fistula occlusion 60 days after its creation. Control animals received saline solution. Intracranial pressure (ICP) increased in all groups following fistula creation, whereas mean arterial pressure (MAP) and cerebral perfusion pressure (CPP) decreased as a manifestation of cerebral hypoperfusion and intracranial hypertension. The administration of indomethacin was associated with raised MAP and CPP, as well as decreased ICP. Sodium fluorescein extravasation was slight in study animals when comparing with control ones. Histological analysis evidenced diffuse ischaemic changes with signs of neuronal apoptosis in all brain layers in control animals. These findings were only focal and slight in study animals. The results suggest the usefulness of indomethacin to revert, at least partially, the haemodynamic effects of NPPB phenomenon in this experimental model, as well as to reduce BBB disruption and histological ischemia observed in absence of indomethacin.

Assessing haemorrhage-critical values of cerebral blood flow by modelling biomechanical stresses on capillaries in the immature brain

The development of intraventricular haemorrhages (IVH) in preterm newborns is triggered by a disruption of the vessels responsible for cerebral microcirculation. Analysis of the stresses exerted on vessel walls enables the identification of the critical values of cerebral blood flow (CBF) associated with the development of IVH in preterm infants. The purpose of the present study is the estimation of these critical CBF values using the biomechanical stresses obtained by the finite element modelling of immature brain capillaries. The properties of the endothelial cells and basement membranes employed were selected on the basis of published nanoindentation measurements using atomic force microscopes. The forces acting on individual capillaries were derived with a mathematical model that accounts for the peculiarities of microvascularity in the immature brain. Calculations were based on clinical measurements obtained from 254 preterm infants with the gestational age ranging from 23 to 30 weeks, with and without diagnosis of IVH. No distinction between the affected and control groups with the gestational age of 23 to 26 weeks was possible. For infants with the gestational age of 27 to 30 weeks, the CBF value of 17.03 ml/100 g/min was determined as the critical upper value, above which the likelihood of IVH increases.

The developing brain by trimester

Transient anatomical entities play a role in the maturation of brain regions and early functional fetal networks. At the postmenstrual age of 7 weeks, major subdivisions of the brain are visible. At the end of the embryonic period, the cortical plate covers the neopallium. The choroid plexus develops in concert with it, and the dorsal thalamus covers about half the diencephalic third ventricle surface. In addition to the fourth ventricle neuroepithelium the rhombic lips are an active neuroepithelial production site. Early reciprocal connections between the thalamus and cortex are present. The corticospinal tract has reached the pyramidal decussation, and the arteries forming the mature circle of Willis are seen. Moreover, the superior sagittal sinus has formed, and at the rostral neuropore the massa commissuralis is growing. At the viable preterm age of around 24 weeks PMA, white matter tracts are in full development. Asymmetric progenitor division permits production of neurons, subventricular zone precursors, and glial cells. Myelin is present in the ventral spinal quadrant, cuneate fascicle, and spinal motor fibers. The neopallial mantle has been separated into transient layers (stratified transitional fields) between the neuroepithelium and the cortical plate. The subplate plays an important role in organizing the structuring of the cortical plate. Commissural tracts have shaped the corpus callosum, early primary gyri are present, and opercularization has started caudally, forming the lateral fissure. Thalamic and striatal nuclei have formed, although GABAergic neurons continue to migrate into the thalamus from the corpus gangliothalamicum. Near-term PMA cerebral sublobulation is active. Between 24 and 32 weeks, primary sulci develop. Myelin is present in the superior cerebellar peduncle, rubrospinal tract, and inferior olive. Germinal matrix disappears from the telencephalon, except for the GABAergic frontal cortical subventricular neuroepithelium.

Recent advances in perinatal neuroprotection

Perinatal brain injury is a major cause of neurological disability in both premature and term infants. In this review, we summarize the evidence behind some established neuroprotective practices such as administration of antenatal steroids, intrapartum magnesium for preterm delivery, and therapeutic hypothermia. In addition, we examine emerging practices such as delayed cord clamping, postnatal magnesium administration, recombinant erythropoietin, and non-steroidal anti-inflammatory agents and finally inform the reader about novel interventions, some of which are currently in trials, such as xenon, melatonin, topiramate, allopurinol, creatine, and autologous cord cell therapy.

A single-dose indomethacin prophylaxis for reducing perinatal brain injury in extremely low birth weight infants: a non-inferiority analysis

OBJECTIVE

To evaluate whether rates of perinatal brain injury among extremely low birth weight infants are comparable between two treatments: single-dose indomethacin prophylaxis (SGL-IP) (0.2 mg/kg, given once) vs. standard-dose indomethacin prophylaxis (STD-IP) (0.1 mg/kg/day, 3 days).

METHODS

In this retrospective study, the primary outcome was perinatal brain injury (neuro-imaging evidence of intraventricular hemorrhage or periventricular leukomalacia) or death before discharge. A non-inferior efficacy of an SGL-IP regimen compared with a STD-IP regimen was determined by calculating the adjusted difference in the risk of the primary outcome using a multivariable logistic regression model. A 10-percentage point non-inferiority margin was favored.

RESULTS

Prevalence rates of primary outcome were 41.7% in the SGL-IP group (n = 403) and 42.5% in the STD-IP group (n = 509) (adjusted risk difference: -1.2, 95% CI: -7.6 to +5.2, p = 0.71).

CONCLUSION

Use of a single prophylactic indomethacin dose was as effective as a standard regimen in preventing perinatal brain injury.

Intraventricular Hemorrhage: Risk Factors and Association With Patent Ductus Arteriosus Treatment in Extremely Preterm Neonates

Objectives: To assess maternal and neonatal risk factors for intraventricular hemorrhage (IVH). To examine the association of patent ductus arteriosus (PDA) and its treatment, with IVH and its severity. Study design: In this retrospective cohort study, we included preterm neonates born at <29 weeks, admitted to a tertiary level III Neonatal Intensive Care Unit in Calgary, Canada, between 2013 and 2016, who had a head ultrasound in the first 7 days of life. A subset analysis included neonates who also had cardiac ultrasound in the first 3 days of life. Results: Of the 495 neonates, 121 (24.4%) had IVH of any grade and 48 (9.7%) had severe IVH. Identified risk factors were small birth gestation and weight, lack of antenatal corticosteroids, maternal chorioamnionitis, Apgar score <5 at 5 min, umbilical cord pH < 7, respiratory distress syndrome, early onset sepsis, hypercapnia, pCO2 fluctuations, prolonged intubation, inhaled nitric oxide, inotropes or normal saline boluses, metabolic derangements, opioids infusions, and bicarbonate/THAM therapy. In a primary analysis of the total cohort, when the decision to treat a PDA was used as a surrogate marker of its clinical significance, a PDA requiring treatment was associated with a higher risk of IVH. There was no significant difference in the incidence of IVH between neonates with early treatment of a clinically significant PDA compared to late, however early indomethacin treatment was associated with reduced severity of IVH. In the subset analysis, the presence of a hemodynamically significant PDA (hs-PDA) was not associated with a higher probability of IVH. Of those with severe IVH, 18 (55%) had a hs-PDA; this is clinically but not statistically significant. Conclusions: Identified risk factors should be the target of IVH reduction bundles. Early indomethacin treatment for a clinically significant PDA may reduce IVH severity.

Peri-intraventricular hemorrhage and oxidative and inflammatory stress markers in very-low birth weight newborns

OBJECTIVES

To evaluate the association between oxidative and inflammatory stress markers with peri-intraventricular hemorrhage (PIVH) in very-low birth weight newborns.

METHODS

This was a prospective study conducted in a level III neonatal unit. Basal and stimulated reactive oxygen intermediates (ROIs), reduced glutathione (GSH), and interleukin-6 (IL-6) levels were measured in umbilical cord blood. Newborns underwent serial ultrasound at the bedside, at 6, 12, 24, and 72hours of life and at seven days for the diagnosis of PIVH, classified as grades I to IV. Two groups were assessed, those with and without PIVH; maternal and neonatal control variables were used for comparison. Univariate and multiple regression analyses were applied.

RESULTS

A total of 125 newborns were assessed. PIVH incidence rate was 12.0%. In the univariate analysis, basal ROI, the use of two or more doses of corticosteroids, birth weight<1,000g, ventilatory support use, and SNAPPE II value ≥ 22 were significantly associated with PIVH. However, in the multivariate analysis, only antenatal steroid use was independently associated with the disease (OR 0,194; 95% CI: 0,048 to 0,773; p=0,02).

CONCLUSION

ROI, GSH, and IL-6 levels were not associated with the occurrence of PIVH in very-low birth weight infants.

Pathogenesis and prevention of intraventricular hemorrhage

Intraventricular hemorrhage (IVH) is a major neurologic complication of prematurity. Pathogenesis of IVH is attributed to intrinsic fragility of germinal matrix vasculature and to the fluctuation in the cerebral blood flow. Germinal matrix exhibits rapid angiogenesis orchestrating formation of immature vessels. Prenatal glucocorticoid exposure remains the most effective means of preventing IVH. Therapies targeted to enhance the stability of the germinal matrix vasculature and minimize fluctuation in the cerebral blood flow might lead to more effective strategies in preventing IVH.

Indomethacin prophylaxis to prevent intraventricular hemorrhage: association between incidence and timing of drug administration

OBJECTIVE

To test the hypothesis that administration of indomethacin prophylaxis before 6 hours of life results in a lower incidence of intraventricular hemorrhage (IVH) compared with administration after 6 hours of life, and that the effects of early prophylaxis depend on gestational age (GA) and sex in very low birth weight infants (birth weight <1250 g).

STUDY DESIGN

Very low birth weight infants admitted to our neonatal intensive care unit between 2003 and 2010 who received indomethacin prophylaxis were analyzed retrospectively. Exclusion criteria included unknown time of indomethacin prophylaxis, death at <12 hours of life, congenital anomalies, and unavailable head ultrasound report. Infants were dichotomized based on the timing of indomethacin prophylaxis (<6 hours or >6 hours of life) to compare incidence of IVH all grades and severe (grade 3-4) IVH. Secondary analyses examined the effects of the time of indomethacin prophylaxis initiation by GA and sex on the incidence of IVH.

RESULTS

A total of 868 infants (431 males and 437 females) met the criteria for analysis. Indomethacin prophylaxis was given at <6 hours of life in 730 infants and at >6 hours of life to 168 infants. The 2 groups differed with respect to antenatal steroid exposure, GA, outborn prevalence, and pneumothoraces. After multivariate analysis, there were no between-group differences in all-grade or severe IVH. However, females, but not males, treated at <6 hours of life had a lower incidence of severe IVH (P < .05), particularly at lower GAs.

CONCLUSION

Prophylactic indomethacin administered before 6 hours of life is not associated with lower incidence of IVH.

Infantile posthemorrhagic hydrocephalus

INTRODUCTION

Intraventricular/germinal matrix hemorrhage affects 7-30% of premature neonates, 25-80% of whom (depending on the grade of the hemorrhage) will develop hydrocephalus requiring shunting. Predisposing factors are low birth weight and gestational age.

MATERIAL

There is increasing evidence for the role of TGF-β1 in the pathogenesis of hydrocephalus, but attempts to develop treatment modalities to clear the cerebrospinal fluid (CSF) from blood degradation products have not succeeded so far. Ultrasound is a valuable screening tool for high-risk infants and magnetic resonance imaging is increasingly utilized to differentiate progressive hydrocephalus from ex vacuo ventriculomegaly, evaluate periventricular parenchymal damage, decide on the surgical treatment of hydrocephalus, and follow up these patients in the long term. Treatment of increasing ventriculomegaly and intracranial hypertension in the presence of hemorrhagic CSF can involve a variety of strategies, all with relative drawbacks, aiming to drain the CSF while gaining time for it to clear and the neonate to reach term and become a suitable candidate for shunting. Eventually, patients with progressive ventriculomegaly causing intracranial hypertension, who have reached term and their CSF has cleared from blood products, will need shunting.

CONCLUSION

Cognitive long-term outcome is influenced more by the effect of the initial hemorrhage and other perinatal events and less by hydrocephalus, provided that this has been addressed timely in the early postnatal period. Shunting can have many long-term side effects due to mechanical complications and overdrainage. In particular, patients with posthemorrhagic hydrocephalus are more susceptible to multiloculated hydrocephalus and encysted fourth ventricle, both of which are challenging to treat.

Should we definitively abandon prophylaxis for patent ductus arteriosus in preterm new-borns?

Although the prophylactic administration of indomethacin in extremely low-birth weight infants reduces the frequency of patent ductus arteriosus and severe intraventricular hemorrhage, it does not appear to provide any long-term benefit in terms of survival without neurosensory and cognitive outcomes. Considering the increased drug-induced reduction in renal, intestinal, and cerebral blood flow, the use of prophylaxis cannot be routinely recommended in preterm neonates. However, a better understanding of the genetic background of each infant may allow for individualized prophylaxis using NSAIDs and metabolomics.

Patent ductus arteriosus of the preterm infant

A persistently patent ductus arteriosus (PDA) in preterm infants can have significant clinical consequences, particularly during the recovery period from respiratory distress syndrome. With improvement of ventilation and oxygenation, the pulmonary vascular resistance decreases early and rapidly, especially in very immature infants with extremely low birth weight (<1000 g). Subsequently, the left-to-right shunt through the ductus arteriosus (DA) is augmented, thereby increasing pulmonary blood flow, which leads to pulmonary edema and overall worsening of cardiopulmonary status. Prolonged ventilation, with the potential risks of volutrauma, barotrauma, and hyperoxygenation, is strongly associated with the development and severity of bronchopulmonary dysplasia/chronic lung disease. Substantial left-to-right shunting through the ductus may also increase the risk of intraventricular hemorrhage, necrotizing enterocolitis, and death. Postnatal ductal closure is regulated by exposure to oxygen and vasodilators; the ensuing vascular responses, mediated by potassium channels, voltage-gated calcium channels, mitochondrial-derived reactive oxygen species, and endothelin 1, depend on gestational age. Platelets are recruited to the luminal aspect of the DA during closure and probably promote thrombotic sealing of the constricted DA. Currently, it is unclear whether and when a conservative, pharmacologic, or surgical approach for PDA closure may be advantageous. Furthermore, it is unknown if prophylactic and/or symptomatic PDA therapy will cause substantive improvements in outcome. In this article we review the mechanisms underlying DA closure, risk factors and comorbidities of significant DA shunting, and current clinical evidence and areas of uncertainty in the diagnosis and treatment of PDA of the preterm infant.

Intraventricular hemorrhage in premature infants: mechanism of disease

Intraventricular hemorrhage (IVH) is a major complication of prematurity. IVH typically initiates in the germinal matrix, which is a richly vascularized collection of neuronal-glial precursor cells in the developing brain. The etiology of IVH is multifactorial and is primarily attributed to the intrinsic fragility of the germinal matrix vasculature and the disturbance in the cerebral blood flow (CBF). Although this review broadly describes the pathogenesis of IVH, the main focus is on the recent development in molecular mechanisms that elucidates the fragility of the germinal matrix vasculature. The microvasculature of the germinal matrix is frail because of an abundance of angiogenic blood vessels that exhibit paucity of pericytes, immaturity of basal lamina, and deficiency of glial fibrillary acidic protein (GFAP) in the ensheathing astrocytes endfeet. High VEGF and angiopoietin-2 levels activate a rapid angiogenesis in the germinal matrix. The elevation of these growth factors may be ascribed to a relative hypoxia of the germinal matrix perhaps resulting from high metabolic activity and oxygen consumption of the neural progenitor cells. Hence, the rapid stabilization of the angiogenic vessels and the restoration of normal CBF on the first day of life are potential strategies to prevent IVH in premature infants.

The diagnosis, management, and postnatal prevention of intraventricular hemorrhage in the preterm neonate

Intraventricular hemorrhage (IVH) occurs in 20% to 25% of very low birthweight preterm neonates and may be associated with significant sequelae. Infants who have IVH are at risk for posthemorrhagic hydrocephalus and periventricular leukomalacia; as many as 75% of those who have parenchymal involvement of hemorrhage suffer significant neurodevelopmental disability. Because of the prevalence of IVH and the medical and societal impact of this disease, many postnatal pharmacologic prevention strategies have been explored. Randomized clinical prevention trials should provide long-term neurodevelopmental follow-up to assess the impact of preterm birth, injury, and pharmacologic intervention on the developing brain.

Maturational changes in laminin, fibronectin, collagen IV, and perlecan in germinal matrix, cortex, and white matter and effect of betamethasone

Germinal matrix is selectively vulnerable to hemorrhage in premature infants, and use of prenatal betamethasone is associated with a lower occurrence of germinal matrix hemorrhage. Because the major components of extracellular matrix of the cerebral vasculature-laminin, fibronectin, collagen IV, and perlecan-provide structural stability to blood vessels, we examined whether the expression of these molecules was decreased in the germinal matrix and affected by betamethasone. In both human fetuses and premature infants, fibronectin was significantly lower in the germinal matrix than in the cortical mantle or white matter anlagen. Conversely, laminin alpha1 gene expression was greater in the human germinal matrix compared with the cortical mantle or white matter. Expression of alpha1- and alpha2(IV) collagen chains increased with advancing gestational age. Low-dose prenatal betamethasone treatment enhanced fibronectin level by 1.5-2-fold whereas a high dose reduced fibronectin expression by 2-fold in rabbit pups. Because fibronectin provides structural stability to the blood vessels, its reduced expression in the germinal matrix may contribute to the fragility of germinal matrix vasculature and the propensity to hemorrhage in premature neonates.

A pilot study of changes in cerebral blood flow velocity, resistance, and vital signs following a painful stimulus in the premature infant

PURPOSE

The purpose of this pilot study was to determine the cerebral blood flow velocity and resistance changes and vital signs following a painful stimulus in the premature infant.

SUBJECTS

A convenience sample of 12 infants was randomly assigned to one of 2 treatment groups. In the final analysis, there were 10 infants younger than 24 hours of age and between 25 and 32 weeks' gestational age.

DESIGN

A randomized 2-period, 2-group, crossover design was used.

METHODS

Cerebral blood flow velocity and resistance were measured via a Doppler head ultrasound transducer placed over the anterior fontanel. Vital signs were measured with a cardiorespiratory monitor. The infant then received the heel stick procedure or the sham procedure (heel preparation with no heel puncture). Each infant served as his or her own control. After each procedure, there was ultrasound and vital sign measurement at 15, 60, 120, 180, 240, and 300 seconds. Thereafter, the alternate treatment was used and 6 more measurements were taken.

MAIN OUTCOME MEASURES

Cerebral values: peak systolic velocity (PSV) and resistive index (RI); vital signs: heart rate, respiratory rate, oxygen saturation (SpO2), and blood pressure.

RESULTS

Treatment groups were similar at baseline except for gestational age. There were no carryover or period effects in the crossover design for the primary outcomes except for SpO2. There was a significant group effect (heel stick compared with sham) (P = .009) for peak systolic velocity; however, there were no significant differences between groups at each time point. Two subjects had a distinctive pattern based on simultaneous changes in flow and resistance: when flow velocity increased, resistance decreased. This may be reflective of risk for intraventricular hemorrhage (IVH). Mean arterial blood pressure (MAP) was not significant. However, heart rate was significantly different between stick and sham at 15 seconds (P = .022); respiratory rate was significant at 180 seconds (P = .029); and SpO2 was significant at 3 different time points. There were no significant correlations between PSV and mean arterial blood pressure and PSV and SpO2 when comparing stick to sham.

CONCLUSIONS

This is a study based on a small sample size. However, the Doppler-measured peak systolic velocity increases significantly after a painful stimulus. The clinical implication of this finding needs to be established.

Immunolocalization of tight junction proteins in blood vessels in human germinal matrix and cortex

Brain development occurs in a specialized environment maintained by a blood-brain barrier (BBB). An important structural element of the BBB is the endothelial tight junction (TJ). TJs are present during the embryonic period, but BBB impermeability accrues over an extended gestational interval. In studies of human premature infants, we used immunomicroscopy to determine if amounts of the TJ proteins ZO-1, claudin and occludin increase with gestational age in vessels of germinal matrix (GM) and cortex. By 24 weeks postconception (PC), TJ proteins were present in both GM and cortical vessels, but immunoreactivity in the GM of the youngest subjects was less than in older subjects. At 24 weeks PC, TJ protein immunoreactivity in GM vessels was less than in cortical vessels suggesting that TJ maturation progresses along a superficial to deep brain axis. This concept correlates with conclusions from previous analyses of the expression of brain endothelial cell alkaline phosphatase (AP) activity. AP appears in cortical vessels before appearing in deep white matter and GM vessels. Together, these data indicate that differentiation of some functional specializations is still in progress in GM vessels during the third trimester. This maturation could relate to the pathogenesis of germinal matrix hemorrhage-intraventricular hemorrhage.

Prolonged indomethacin exposure is associated with decreased white matter injury detected with magnetic resonance imaging in premature newborns at 24 to 28 weeks' gestation at birth

OBJECTIVES

Newborns delivered before 28 weeks' gestation commonly have white matter lesions on MRI that are associated with adverse neurodevelopmental outcomes. Our objective was to determine the risk factors for MRI-detectable white matter injury in infants delivered before 28 weeks' gestation who were treated with prophylactic indomethacin.

METHODS

This was a prospective cohort study conducted at the intensive care nursery at University of California San Francisco Children's Hospital. Patients included 57 premature newborns between 24 and 27 (+6 days) weeks' gestation at birth (October 1998 to October 2004). We identified perinatal and neonatal risk factors associated with moderate-severe "white matter injuries" (T1 signal abnormalities >2 mm or >3 areas of T1 abnormality) and moderate-severe "brain abnormality" (moderate-severe white matter injuries, any degree of ventriculomegaly, or severe intraventricular hemorrhage) on MRI. Infants were studied with MRI at 31.1 weeks' postmenstrual age (median).

RESULTS

Moderate-severe white matter injuries were detected in 12 (21%) of 53 preterm newborns, and 20 (35%) of 57 had moderate-severe brain abnormality. Prolonged indomethacin exposure was the only risk factor independently associated with a lower risk of white matter injury or brain abnormality, even when adjusting for the presence of a hemodynamically significant PDA, gestational age at birth, prenatal betamethasone, systemic infection, and days of mechanical ventilation.

CONCLUSIONS

In this observational study, a longer duration of indomethacin exposure was associated with less white matter injury in infants delivered before 28 weeks' gestation. A randomized trial of prolonged indomethacin treatment is needed to determine whether indomethacin can decrease white matter injury and neurodevelopmental abnormalities.

Modeling the neurovascular niche: VEGF- and BDNF-mediated cross-talk between neural stem cells and endothelial cells: An in vitro study

Neural stem cells (NSCs) exist in vascularized niches. Although there has been ample evidence supporting a role for endothelial cell-derived soluble factors as modulators of neural stem cell self-renewal and neuronal differentiation there is a paucity of data reported on neural stem cell modulation of endothelial cell behavior. We show that co-culture of NSCs with brain-derived endothelial cells (BECs) either in direct contact or separated by a porous membrane elicited robust vascular tube formation and maintenance, mediated by induction of vascular vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF) and activation of vascular VEGFR2 and TrkB by NSC NO. Nitric oxide (NO) scavengers and sequestration of VEGF and BDNF blunted this induction of tube formation, whereas addition of exogenous NO donor, rBDNF and rVEGF rescued the induction of tube formation. Further, rBDNF enhanced NSC eNOS activation and NO generation, suggesting an inducible positive feed-back signaling loop between NSCs and BECs, providing for homeostasis and responsiveness of the resident NSCs and BECs comprising the neurovascular niche. These findings show the importance of reciprocal modulation of NSCs and BECs in induction and maintenance of the neurovascular niche and underscores their dynamic interactions.

Prophylactic ibuprofen for the prevention of intraventricular hemorrhage among preterm infants: a multicenter, randomized study

OBJECTIVE

Ibuprofen enhances cerebral blood flow autoregulation and was shown to protect neurologic functions after oxidative stresses in an animal model. For these reasons, we hypothesized that the prophylactic use of ibuprofen would reduce the occurrence of intraventricular hemorrhage (IVH) and its worsening toward grades 2 to 4 among preterm infants. To confirm this hypothesis, we planned the present prospective study.

METHODS

This was a double-blind, randomized, controlled trial in which preterm infants with gestational ages of <28 weeks received ibuprofen or placebo within the first 6 hours of life. The infants were assigned randomly, at 7 neonatal care units, to receive ibuprofen (10 mg/kg, followed by 5 mg/kg after 24 and 48 hours) or placebo. Serial echoencephalography was performed 24 and 48 hours after the initial cerebral ultrasound study, on postnatal days 7, 15, and 30, and at 40 weeks' postconceptional age. Grade 1 IVH or no IVH was considered a successful outcome, whereas grade 2 to 4 IVH represented failure. The rates of ductal closure, side effects, and complications were recorded.

RESULTS

We studied 155 infants. Grade 2 to 4 IVH developed for 16% of the ibuprofen-treated infants and 13% of the infants in the placebo group. The occurrence of patent ductus arteriosus was less frequent only on day 3 of life in the ibuprofen group. There were no significant differences with respect to other complications or adverse effects.

CONCLUSIONS

Our study demonstrated that prophylactic ibuprofen is ineffective in preventing grade 2 to 4 IVH and that its use for this indication cannot be recommended.

Intraventricular hemorrhage in the premature neonate

Intraventricular hemorrhage in the premature neonate has been and continues to be a cause of morbidity and mortality in NICUs around the globe. Much information is available concerning the etiology and preventative and treatment strategies to reduce the incidence of IVH in this patient population. As neonatal caregivers are struggling to care for and protect infants who are surviving despite extreme prematurity, this survival is complicated by the infant's cerebral vasculature, which is very susceptible to hemorrhage; by respiratory problems that require the use of lifesaving, but potentially harmful, ventilation interventions; and by the infant's compromised ability to self-regulate vascular responses to stress. The preventative treatments being explored and proposed may come with debilitating and potentially lethal sequelae. Research continues, however. New recommendations are being proffered, and perhaps, in the near future, the incidence of IVH and its associated morbidity and mortality will decline dramatically.

Morphometric assessment of collagen accumulation in germinal matrix vessels of premature human neonates

Germinal matrix haemorrhage in premature neonates is commonly attributed to vascular immaturity, possibly related to an abbreviated process of angiogenesis. Terminal steps in the progression of angiogenesis are the formation of a subendothelial basal lamina containing collagen IV and an extracellular matrix containing collagens I and III. Immature vessels would predictably be deficient in these collagen subtypes. We analysed germinal matrix (GM), cortical, and white matter (WM) vessels with antibodies specific for collagens I, III and IV to test the hypothesis that GM vessels are immature. Brains were collected during post-mortem from prematurely born human neonates ranging in age from 17 weeks to 36 weeks postconception. All GM vessels were immunoreactive for collagen subtypes I, III and IV. Using digital image analysis, collagen IV immunoperoxidase-labelling was measured in vessels in GM, cortex and WM. Intensity values in GM and WM were normalized relative to cortical intensity within the same subject. At week 17 of gestation, GM vessels exhibited a higher concentration of collagen IV than did WM or cortical vessels. Regression analysis demonstrated that collagen intensity in GM was greater than that in cortex and WM at all stages. We conclude that GM vessels in even the youngest, prematurely born, viable neonates do not exhibit evidence of structural immaturity. The high incidence of GM haemorrhage in premature neonates may be related to factors other than a deficiency in accumulated collagen.

Age-dependent cerebral hemodynamic effects of indomethacin in the newborn piglet

With recent discussions in the literature regarding prophylactic use of early (within the first 12 h after birth), low-dose indomethacin to reduce the incidence and severity of intraventricular hemorrhage, knowledge pertaining to the cerebral hemodynamic effects of indomethacin in this age group is of significant interest. The cerebral circulation is known to undergo significant changes during the first few days of postnatal life. In the present study, we have investigated the hypothesis that postnatal adaptive changes influence the cerebral hemodynamic response to indomethacin in an age-dependent manner. Near-infrared spectroscopy with indocyanine green was used to measure cerebral hemodynamics, cerebral metabolic rate of oxygen, and cerebral oxygen extraction fraction in 39 newborn piglets. Piglets were grouped by age and received either 0.2 mg/kg indomethacin (14 were <13 h of age and 12 were >13 h of age) or saline (8 were <13 h of age and 5 were >13 h of age) infusions. In a subgroup of indomethacin-treated piglets (9 less than and 7 greater than 13 h of age), Doppler flow ultrasound was used to diagnose and monitor the presence and persistence of patent ductus arteriosus. Age was a significant factor in the cerebral hemodynamic response to indomethacin with piglets <13 h of age exhibiting delayed increases in cerebral blood flow and cerebral blood volume at 150 min post-indomethacin infusion.

Prophylactic indomethacin reduces grades III and IV intraventricular hemorrhages when compared to early indomethacin treatment of a patent ductus arteriosus

OBJECTIVE

To determine the relative risk of severe intraventricular hemorrhage (IVH) between two very early indomethacin treatment strategies.

STUDY DESIGN

Retrospective chart review of infants <29 weeks gestation and <1350 g who received either indomethacin prophylaxis or very early echocardiography with indomethacin treatment only if the ductus arteriosus was patent.

RESULTS

A total of one hundred and two infants received prophylactic indomethacin (pINDO). Echochardiography was performed on 158 infants, of whom 117 received indomethacin. Infants receiving pINDO had lower gestational age, but similar birth weight, gender, race, antenatal steroid exposure, delivery mode, Apgar scores, and need for resuscitation as infants evaluated by echocardiography. Grades III to IV IVH was observed less frequently in infants who received pINDO (OR 0.27, 95% CI 0.10 to 0.77, p=0.014). Frequency of side effects and recurrent patent ductus arteriosus did not differ between treatment groups.

CONCLUSION

pINDO reduces severe IVH when compared to an early echocardiography strategy.

Cost-effectiveness of prophylactic indomethacin in very-low-birth-weight infants

OBJECTIVE

To perform cost-effectiveness analysis to facilitate the decision-making process surrounding use of indomethacin in preterm infants to lower the incidence of patent ductus arteriosus (PDA), intraventricular hemorrhage (IVH), and death.

METHODS

A MEDLINE literature search from 1966 to July 2000 was performed to identify relevant randomized, controlled trials (RCTs), as well as cohort and retrospective case-control studies. A decision tree was built representing the choice to use or not use indomethacin, and the potential outcome costs. Probabilities of being in each chance node were obtained from this search. Where data probabilities were not clear, a sensitivity analysis was conducted.

RESULTS

There was no difference in the expected survival per year; however, there was a significant difference when effectiveness was measured as quality-adjusted life years (QALYs), resulting in 11 and 10 years for the indomethacin and control groups, respectively. The indomethacin treatment cost was $95,157 and that of the control groups was $99,955. The cost effectiveness per life expectancy of being in the indomethacin and control groups was $7142 and $7727, respectively. The sensitivity analysis for PDA closure and prevention of IVH for infants eventually developing PDA versus those without PDA showed no difference. The cost-effectiveness analysis per QALY was $8443 for the indomethacin treatment and $9168 for the control group.

CONCLUSIONS

The prophylactic use of indomethacin is less costly and more effective within an important range of certainty. However, this analysis does not include several potentially confounding factors, such as antenatal steroid use or indomethacin-induced renal toxicity. Depending on the frequency with which these factors arise, economic projections may be considerably altered against the early use of indomethacin.

Astrocyte-derived VEGF mediates survival and tube stabilization of hypoxic brain microvascular endothelial cells in vitro

Chronic sublethal hypoxia has been associated with changes in neurovascular behavior, mediated, in part, by induction of vascular endothelial growth factor-A (VEGF-A(165)). In this report we demonstrate that RBE4 cells (derived from rodent cerebral microvasculature), when cultured in three-dimensional collagen gels: (1) Are induced to undergo increased tube formation in response to VEGF-A(165) in a dose-dependent manner; (2) undergo apoptosis under mild hypoxic conditions; (3) are rescued from the effects of hypoxia by the addition of exogenous VEGF-A(165) in a dose-dependent and inhibitable manner or by co-culture with primary newborn rat astrocytes, which are induced to express increased amounts of VEGF-A in hypoxic conditions. Further, we demonstrate that: (4) The observed astrocyte-produced, VEGF-mediated protection from apoptosis (survival) is inhibitable with soluble recombinant VEGF receptor-1 (sFlt), and is associated with a robust induction of MAPK tyrosine phosphorylation. These findings illustrate the importance of VEGF in the process of neurovascular survival in response to injury in developing brain and provide insight into the signaling pathways involved.

Intraventricular haemorrhage and posthaemorrhagic hydrocephalus: pathogenesis, prevention and future interventions

Intraventricular haemorrhage (IVH) is still a major complication of preterm birth with serious disability resulting. The fragile blood vessels in the germinal matrix below the ventricular lining and the instability of blood flow to this highly vascular area are the main mechanisms behind IVH. There is good evidence that corticosteroid therapy before preterm delivery reduces mortality and IVH substantially with a trend towards a reduction in disability. There is good evidence that postnatal indomethacin reduces IVH but no evidence that mortality or disability is reduced. There is evidence that stabilizing cerebral blood flow with pancuronium in infants with respiratory distress reduces IVH in the minority of infants with marked fluctuations. There is limited evidence that postnatal vitamin E and ethamsylate reduce IVH but insufficient evidence of reduced mortality or disability. Hydrocephalus following IVH results initially from multiple small blood clots throughout the CSF channels impeding circulation and re-absorption. Transforming growth factor beta is released into the CSF and there is mounting evidence that this cytokine stimulates the laying down of extracellular matrix proteins such as laminin and fibronectin which produce permanent obstruction to the CSF pathways. Interventions such as early lumbar punctures, diuretic drugs to reduce CSF production and intraventricular fibrinolytic therapy have been tested and, not only fail to prevent shunt dependence, death or disability, but have significant adverse effects. Surgical interventions such as subcutaneous reservoir and external drain have not been subject to controlled trial. Ventriculoperitoneal shunt is not feasible in the early phase after IVH but, despite the problems with blockages and infections, remains the only option for infants with excessive head expansion over periods of weeks. New treatment approaches aimed at preventing hydrocephalus are needed.

Circulating neutrophil concentration and respiratory distress in premature infants

BACKGROUND

The acute disappearance of neutrophils from the circulation can be associated with pulmonary leukostasis, lung injury, and respiratory distress.

OBJECTIVE

To determine whether a low concentration of mature neutrophils in the peripheral blood soon after birth is associated with an increase in subsequent respiratory distress in premature infants.

DESIGN

A cohort study performed by chart review at a tertiary medical center.

SUBJECTS

Premature infants (birth weight 500 to 1250 g) who had a complete blood count obtained within 2 hours of delivery (n = 237). Patients in the lowest quartile of mature neutrophil concentrations (early neutropenia, < or =0.90 x 10(9) neutrophils/L blood) were compared with patients in the remaining 3 quartiles (control group).

RESULTS

Low neutrophil concentrations were transient in the early neutropenia group. The concentration of mature circulating neutrophils rose from 0.49 +/- 0.25 x 10(9) cells/L at an average of 1 hour after delivery to 2.8 +/- 2.2 x 10(9) cells/L within 6 to 8 hours in the early neutropenia group and from 4.6 +/- 4.8 x 10(9) cells/L to 8.2 +/- 8. 0 x 10(9) cells/L in the control group during the same time period. Respiratory support immediately after birth was similar in both groups of infants, but by 12 hours patients who had early neutropenia required significantly greater inflation pressures and concentrations of inspired oxygen. By 1 week after birth patients who had early neutropenia were more likely to require mechanical ventilation and supplemental oxygen. Pulmonary interstitial emphysema, serious intraventricular hemorrhage, and chronic lung disease occurred more frequently in patients with early neutropenia.

CONCLUSION

A low concentration of mature neutrophils in the systemic circulation of premature infants within 2 hours of birth is associated with more severe respiratory distress during the first postnatal week and with an increased risk of serious complications of prematurity.

Outcome of children in the indomethacin intraventricular hemorrhage prevention trial

BACKGROUND

For preterm infants, intraventricular hemorrhage (IVH) may be associated with adverse neurodevelopmental outcome. We have demonstrated that early low-dose indomethacin treatment is associated with a decrease in both the incidence and severity of IVH in very low birth weight preterm infants. In addition, we hypothesized that the early administration of low-dose indomethacin would not be associated with an increase in the incidence of neurodevelopmental handicap at 4.5 years of age in our study children.

METHODS

To test this hypothesis, we provided neurodevelopmental follow-up for the 384 very low birth weight survivors of the Multicenter Randomized Indomethacin IVH Prevention Trial. Three hundred thirty-seven children (88%) were evaluated at 54 months' corrected age, and underwent neurodevelopmental examinations, including the Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R), the Peabody Picture Vocabulary Test-Revised (PPVT-R), and standard neurologic examinations.

RESULTS

Of the 337 study children, 170 had been randomized to early low-dose indomethacin therapy and 167 children had received placebo. Twelve (7%) of the 165 indomethacin children and 11 (7%) of the 158 placebo children who underwent neurologic examinations were found to have cerebral palsy. For the 233 English-monolingual children for whom cognitive outcome data follow, the mean gestational age was significantly younger for the children who received indomethacin than for those who received placebo. In addition, although there were no differences in the WPPSI-R or the PPVT-R scores between the 2 groups, analysis of the WPPSI-R full-scale IQ by function range demonstrated significantly less mental retardation among those children randomized to early low-dose indomethacin (for the indomethacin study children, 9% had an IQ <70, 12% had an IQ of 70-80, and 79% had an IQ >80, compared with the placebo group, for whom 17% had an IQ <70, 18% had an IQ of 70-80, and 65% had an IQ >80). Indomethacin children also experienced significantly less difficulty with vocabulary skills as assessed by the PPVT-R when compared with placebo children.

CONCLUSIONS

These data suggest that, for preterm neonates, the early administration of low-dose indomethacin therapy is not associated with adverse neurodevelopmental function at 54 months' corrected age.

Intravenous indomethacin for preventing mortality and morbidity in very low birth weight infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

Indomethacin is used to treat symptomatic patent ductus arteriosus and may prevent or limit intraventricular haemorrhage in the neonatal period. This review examines the effectiveness of prophylactic intravenous indomethacin in reducing the mortality and morbidity associated with these conditions in infants weighing less than 1750 grams at birth.

SEARCH STRATEGY

A literature search from January 1980 to October 1994 was made in three computerised data bases: Medline; Embase; and the Oxford Database of Perinatal Trials. The search was updated in February 1997.

SELECTION CRITERIA

Strict selection criteria were applied to clinical trials: the population had to be newborn infants of birth weight < 1751 grams; the intervention had to be prophylactic intravenous indomethacin; the trial had to be randomised and controlled; and at least one of several prespecified outcomes had to be reported in the results.

DATA COLLECTION AND ANALYSIS

The methodological quality of each study was assessed using explicit criteria. Data on relevant outcome measures were extracted on two separate occasions and, where appropriate, the results of individual trials were combined using meta-analysis techniques to provide a pooled estimate of effect.

MAIN RESULTS

There is a trend towards reduced neonatal mortality in infants receiving prophylactic indomethacin, pooled relative risk (RR) = 0. 85 [95% CI 0.66 to 1.09]. The incidence of symptomatic patent ductus arteriosus is significantly reduced in treated infants, pooled RR = 0.35 [0.26 to 0.47] but there is no evidence that treatment affects respiratory outcomes. Prophylactic indomethacin significantly reduces the incidence of Grade 3 and 4 intraventricular haemorrhage in treated infants, pooled RR = 0.60 [0.43 to 0.83]. There is no evidence to suggest prophylactic indomethacin is associated with any long term adverse effect although there is a trend in treated infants towards an increased incidence of necrotizing enterocolitis, and some evidence that treatment may transiently impair renal function. There is no evidence that haemostasis is disturbed.

REVIEWER'S CONCLUSIONS

Prophylactic treatment with indomethacin has a number of immediate benefits, in particular a reduction in symptomatic patent ductus arteriosus and severe intraventricular haemorrhage. There is no evidence at present of long-term harm. Further trials are needed to assess more precisely the effects, both beneficial and harmful, on short and long-term outcomes.

Indomethacin improves oxygen-induced retinopathy in the mouse

Retinopathy of prematurity is a disease commonly affecting extremely premature babies. Indomethacin is widely used in the perinatal period. The goal of the present study was to test the hypothesis that indomethacin will improve retinopathy in a mouse model when administered during the period of injury (hyperoxia exposure) to the developing retinal vasculature. C57BL6 mice pups were exposed to 75% oxygen from postnatal d 7 through 12. Indomethacin was administered along with the oxygen exposure as a single subcutaneous dose of 0.5 mg/kg/d for 5 d. Animals were killed on postnatal d 17 through 20. The severity of retinopathy was assessed by a retinopathy scoring system of fluorescein-conjugated dextran-perfused retinal flat mounts and by quantitation of extraretinal nuclei by use of periodic acid-Schiff-stained retinal sections. Animals that received indomethacin during hyperoxia exposure had a significantly lower median (25th, 75th quartile) retinopathy score 5 (4.5, 6) compared with animals that received oxygen [8 (7.5, 10)]. Animals given indomethacin during hyperoxia exposure had a significantly lower extraretinal nuclei count per section (13.3 +/- 4.6) (mean +/- SD) compared with animals that were oxygen exposed (41.9 +/- 14.7). Indomethacin did not affect the normal development of the retinal vasculature or the growth of the animals. The data show that indomethacin improves oxygen-induced retinopathy when administered concurrently with the injury phase without affecting the normal retinal development or growth of the animals.

Distinct signal transduction pathways are utilized during the tube formation and survival phases of in vitro angiogenesis

Angiogenesis, the formation of new blood vessels from pre-existing ones, occurs during development, wound healing and cancer and involves stages that orchestrate a network of cooperative interactions. Peptide growth factors and extracellular matrix (ECM) components are two major groups of angiogenesis mediators. Among the different ECM proteins, collagens have been well-associated with in vivo angiogenesis. Using human umbilical vein endothelial cells (HUVEC) grown in 3-D collagen gels we show that: (1) HUVEC do not survive well in 3-D collagen gels due to rapid induction of apoptosis. (2) VEGF, a potent in vivo angiogenic factor, fails to induce tube formation. (3) PMA was effective in inducing tube formation and survival in HUVEC dispersed in 3-D collagen gels, activating MAP kinase, phosphoinositide 3-OH kinase (PI-3-kinase) and Akt/PKB (protein kinase B) pathways. (4) VEGF was effective in preventing PMA-induced tube-like structure regression after PMA-withdrawal by (5) activating the mitogen activated protein kinase (MAPK), rather than the Akt/PKB, signaling pathway.

Posthemorrhagic hydrocephalus and brain injury in the preterm infant: dilemmas in diagnosis and management

Advances in neonatal critical care have reduced the incidence of intraventricular hemorrhage (IVH) in the newborn. Paradoxically, however, the prevalence of the complications of IVH including posthemorrhagic hydrocephalus (PHHC) has increased. By virtue of its association with long-term neurodevelopmental disability, posthemorrhagic hydrocephalus is an ominous diagnosis in the premature infant. Animal models have demonstrated that ventricular distention may cause direct cerebral parenchymal injury. Evidence for secondary parenchymal injury in the premature infant with PHHC is by necessity indirect. The precise impact of secondary parenchymal injury on the overall neurological outcome of premature infants with PHHC remains unclear in large part because of the vulnerability of the immature brain to other forms of injury (e.g., periventricular leukomalacia) that may be difficult to distinguish from injury due to distention. Furthermore, parenchymal injury due to PVL may cause ventricular enlargement that does not benefit from CSF diversion. Because these primary and secondary mechanisms of injury may operate concurrently, the precise or dominant cause of ventricular enlargement is often difficult to establish with certainty in the neonatal period. These diagnostic dilemmas have in turn impeded the development and evaluation of therapies specifically aimed at reversing ventricular distention and preventing secondary parenchymal injury. This article focuses on the current dilemmas in diagnosis and management of this potentially reversible form of injury as well as on potential future strategies for its prevention.