The use of a calcium-channel blocker, nicardipine, for severely asphyxiated newborn infants

Nicardipine for the Treatment of Neonatal Hypertension During Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is one of the primary reasons systemic hypertension is experienced in hospitalized neonates. Commonly used antihypertensive agents have resulted in significant adverse effects in neonatal and pediatric populations. Nicardipine is a desirable option because of its rapid and titratable antihypertensive properties and low incidence of adverse effects. However, data for use in neonatal ECMO are limited. We conducted a retrospective review of patients less than 44 weeks post-menstrual age who received a nicardipine infusion for first-line treatment of systemic hypertension while on ECMO at our institution between 2010 and 2016. Systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressures were evaluated for 48-h after nicardipine initiation. Eight neonates received a nicardipine infusion while on ECMO during the study period. Nicardipine was initiated at a mean dose of 0.52 ( ± 0.22) mcg/kg/min and titrated to a maximum dose of 1.1 ( ± 0.85) mcg/kg/min. The median duration of nicardipine use was 51 (range 4-227) hours. Significant decreases in SBP, DBP, and MAP occurred within one hour of initiation of nicardipine and were sustained through the majority of the 48-h evaluation period. No patients experienced hypotension. Prospective studies are warranted to evaluate the optimal dose, safety, and efficacy of nicardipine in neonates who require ECMO.

Brain resuscitation in the drowning victim

Drowning is a leading cause of accidental death. Survivors may sustain severe neurologic morbidity. There is negligible research specific to brain injury in drowning making current clinical management non-specific to this disorder. This review represents an evidence-based consensus effort to provide recommendations for management and investigation of the drowning victim. Epidemiology, brain-oriented prehospital and intensive care, therapeutic hypothermia, neuroimaging/monitoring, biomarkers, and neuroresuscitative pharmacology are addressed. When cardiac arrest is present, chest compressions with rescue breathing are recommended due to the asphyxial insult. In the comatose patient with restoration of spontaneous circulation, hypoxemia and hyperoxemia should be avoided, hyperthermia treated, and induced hypothermia (32-34 °C) considered. Arterial hypotension/hypertension should be recognized and treated. Prevent hypoglycemia and treat hyperglycemia. Treat clinical seizures and consider treating non-convulsive status epilepticus. Serial neurologic examinations should be provided. Brain imaging and serial biomarker measurement may aid prognostication. Continuous electroencephalography and N20 somatosensory evoked potential monitoring may be considered. Serial biomarker measurement (e.g., neuron specific enolase) may aid prognostication. There is insufficient evidence to recommend use of any specific brain-oriented neuroresuscitative pharmacologic therapy other than that required to restore and maintain normal physiology. Following initial stabilization, victims should be transferred to centers with expertise in age-specific post-resuscitation neurocritical care. Care should be documented, reviewed, and quality improvement assessment performed. Preclinical research should focus on models of asphyxial cardiac arrest. Clinical research should focus on improved cardiopulmonary resuscitation, re-oxygenation/reperfusion strategies, therapeutic hypothermia, neuroprotection, neurorehabilitation, and consideration of drowning in advances made in treatment of other central nervous system disorders.

Neurotrophin-induced migration and neuronal differentiation of multipotent astrocytic stem cells in vitro

Hypoxic ischemic encephalopathy (HIE) affects 2-3 per 1000 full-term neonates. Up to 75% of newborns with severe HIE die or have severe neurological handicaps. Stem cell therapy offers the potential to replace HIE-damaged cells and enhances the autoregeneration process. Our laboratory implanted Multipotent Astrocytic Stem Cells (MASCs) into a neonatal rat model of hypoxia-ischemia (HI) and demonstrated that MASCs move to areas of injury in the cortex and hippocampus. However, only a small proportion of the implanted MASCs differentiated into neurons. MASCs injected into control pups did not move into the cortex or differentiate into neurons. We do not know the mechanism by which the MASCs moved from the site of injection to the injured cortex. We found neurotrophins present after the hypoxic-ischemic milieu and hypothesized that neurotrophins could enhance the migration and differentiation of MASCs. Using a Boyden chamber device, we demonstrated that neurotrophins potentiate the in vitro migration of stem cells. NGF, GDNF, BDNF and NT-3 increased stem cell migration when compared to a chemokinesis control. Also, MASCs had increased differentiation toward neuronal phenotypes when these neurotrophins were added to MASC culture tissue. Due to this finding, we believed neurotrophins could guide migration and differentiation of stem cell transplants after brain injury.

Pharmacological neuroprotection after perinatal hypoxic-ischemic brain injury

Perinatal hypoxia-ischemia (HI) is an important cause of neonatal brain injury. Recent progress in the search for neuroprotective compounds has provided us with several promising drugs to reduce perinatal HI-induced brain injury. In the early stage (first 6 hours after birth) therapies are concentrated on prevention of the production of reactive oxygen species or free radicals (xanthine-oxidase-, nitric oxide synthase-, and prostaglandin inhibition), anti-inflammatory effects (erythropoietin, melatonin, Xenon) and anti-apoptotic interventions (nuclear factor kappa B- and c-jun N-terminal kinase inhibition); in a later stage stimulation of neurotrophic properties in the neonatal brain (erythropoietin, growth factors) can be targeted to promote neuronal and oligodendrocyte regeneration. Combination of pharmacological means of treatment with moderate hypothermia, which is accepted now as a meaningful therapy, is probably the next step in clinical treatment to fight post-asphyxial brain damage. Further studies should be directed at a more rational use of therapies by determining the optimal time and dose to inhibit the different potentially destructive molecular pathways or to enhance endogenous repair while at the same time avoiding adverse effects of the drugs used.

The management of hypertensive emergencies in children after stem cell transplantation

AIM OF THE REVIEW

This work presents a short overview on the available data about drugs that are currently used to treat hypertensive emergencies in children with a focus on incidents after stem cell transplantation. It shows that the pediatric use of all hypotensive agents appears to be mainly based on personal experience of the attending physicians rather than on convincing clinical trials.

METHOD

A literature search was performed in MEDLINE, through PubMed, using the medical subject headings (MeSH) hypertensive emergencies, nifedipine, nicardipine, and children. Further articles were identified by checking cross-references of articles and books.

RESULTS

Hypertensive emergencies in children after stem cell transplantation usually have a renal etiology, because of the treatment with the calcineurin inhibitors cyclosporine and tacrolimus. In these severe cases an immediate action is necessary to avoid possible appearance or exacerbation of endorgan damage. Because of their mechanism of action and a potential nephroprotective effect calcium channel blockers may be particularly suitable in cases of hypertensive emergencies. An intravenous application of nifedipine may compensate the difficulties of accurate dosing, but keeping in mind possible severe side effects and the lack of published experience its use in children is at least questionable. Nicardipine appears to be the hypotensive agent of first choice. In adults, the treatment of hypertensive emergencies with intravenous nicardipine is well-documented, but for an evaluation of safety in pediatric use, the published studies and case reports appear to be barely adequate.

CONCLUSION

The actual treatment approaches vary widely, demonstrating the lack of hard science on which current treatment of hypertensive emergencies in children is based. The hypotensive agent for the individual situation should be chosen considering the properties, side effects, the limited experiences with its use and the patient's anamnesis.

Hypothermia for the treatment of infants with hypoxic-ischemic encephalopathy

Neonatal encephalopathy affects 2 to 5 of every 1000 live births and represents a major cause of mortality and long-term morbidity in affected infants. Hypoxic ischemic encephalopathy (HIE) is the major cause of encephalopathy in the neonatal period. Until recently, management of a newborn with encephalopathy has consisted largely of supportive care to restore and maintain cerebral perfusion, provide adequate gas exchange and treat seizure activity. Recent randomized controlled trials have shown that mild therapeutic hypothermia (cooling) initiated within 6 h of birth reduces death and disability in these infants. Cooling can be accomplished through whole-body cooling or selective head cooling. Meta-analysis of these trials suggests that for every six or seven infants with moderate to severe HIE who are treated with mild hypothermia, there will be one fewer infant who dies or has significant neurodevelopmental disability. In response to this evidence, major policy makers and guideline developers have recommended that cooling therapy be offered to infants with moderate to severe HIE. The dissemination of this new therapy will require improved identification of infants with HIE and regional commitment to allow these infants to be cared for in a timely manner.

Therapeutic hypothermia for neonatal hypoxic ischaemic encephalopathy

There is now a strong evidence base supporting therapeutic hypothermia for infants with moderate or severe neonatal hypoxic ischaemic encephalopathy. Experimental and clinical data indicate that induced hypothermia reduces cerebral hypoxic ischaemic injury and randomized clinical trials in newborns with hypoxic ischaemic encephalopathy confirm improved neurological outcomes and survival at 18 months of age with therapeutic hypothermia. Studies are on-going to confirm whether these benefits are maintained in later childhood. Efforts are now focused on optimal implementation of therapeutic hypothermia in clinical practice: training in the assessment of severity of encephalopathy; initiation and maintenance of hypothermia before admission to a cooling facility; care of the infant during cooling; and appropriate investigation and follow-up are crucial for optimizing neurological outcomes. The establishment of registries of infants with hypoxic ischaemic encephalopathy and audit are important for guiding clinical practice.

The TOBY Study. Whole body hypothermia for the treatment of perinatal asphyxial encephalopathy: a randomised controlled trial

BACKGROUND

A hypoxic-ischaemic insult occurring around the time of birth may result in an encephalopathic state characterised by the need for resuscitation at birth, neurological depression, seizures and electroencephalographic abnormalities. There is an increasing risk of death or neurodevelopmental abnormalities with more severe encephalopathy. Current management consists of maintaining physiological parameters within the normal range and treating seizures with anticonvulsants. Studies in adult and newborn animals have shown that a reduction of body temperature of 3-4 degrees C after cerebral insults is associated with improved histological and behavioural outcome. Pilot studies in infants with encephalopathy of head cooling combined with mild whole body hypothermia and of moderate whole body cooling to 33.5 degrees C have been reported. No complications were noted but the group sizes were too small to evaluate benefit.

METHODS/DESIGN

TOBY is a multi-centre, prospective, randomised study of term infants after perinatal asphyxia comparing those allocated to "intensive care plus total body cooling for 72 hours" with those allocated to "intensive care without cooling".Full-term infants will be randomised within 6 hours of birth to either a control group with the rectal temperature kept at 37 +/- 0.2 degrees C or to whole body cooling, with rectal temperature kept at 33-34 degrees C for 72 hours. Term infants showing signs of moderate or severe encephalopathy +/- seizures have their eligibility confirmed by cerebral function monitoring. Outcomes will be assessed at 18 months of age using neurological and neurodevelopmental testing methods.

SAMPLE SIZE

At least 236 infants would be needed to demonstrate a 30% reduction in the relative risk of mortality or serious disability at 18 months. Recruitment was ahead of target by seven months and approvals were obtained allowing recruitment to continue to the end of the planned recruitment phase. 325 infants were recruited.

PRIMARY OUTCOME

Combined rate of mortality and severe neurodevelopmental impairment in survivors at 18 months of age. Neurodevelopmental impairment will be defined as any of:* Bayley mental developmental scale score less than 70* Gross Motor Function Classification System Levels III - V* Bilateral cortical visual impairments

TRIAL REGISTRATION

Current Controlled Trials ISRCTN89547571.

A review of calcium channel antagonists in the treatment of pediatric hypertension

All children aged > or = 3 years should have an annual blood pressure (BP) measurement taken during a routine physical examination. Physicians should become familiar with recommended pediatric normative BP tables. BP above the 95th percentile may require drug therapy. There are several categories of antihypertensives available to the clinician. Calcium channel antagonists (CCAs) are a class of drugs that exert their antihypertensive effect by inhibiting the influx of calcium ions across the cell membranes. This results in dilatation of peripheral arterioles. When given orally, CCAs are metabolised in the liver by cytochrome P450 (CYP) enzyme CYP3A4; hence, some CCAs will affect the half-life of drugs that share this enzyme system for their metabolism. CCAs can be safely used in children with renal insufficiency or failure and as a general rule there is no need to modify drug dosage in this population. CCAs are generally well tolerated; most adverse effects appear to be dose related. Headache, flushing, gastrointestinal upset, and edema of the lower extremities are the most common symptoms reported with the use of CCAs. Pediatric data regarding safety and efficacy of CCAs have mostly been obtained from retrospective analyses. Extended-release nifedipine and amlodipine are the two most commonly used oral CCAs in the management of pediatric hypertension. These drugs can be given once a day, although many children require twice-daily administration. Extended-release nifedipine has to be swallowed whole; hence, its use in younger children who cannot swallow pills is limited. Amlodipine can be made into a solution without compromising its long duration of action; therefore, it is the CCA of choice for very young children. Oral short-acting nifedipine and intravenous nicardipine are safe and effective CCAs for the management of hypertensive crisis in children. Short-acting nifedipine can cause unpredictable changes in BP; hence, it should be used cautiously and in low doses. Intravenous nicardipine has a rapid onset of action and a short half-life. Intravenous infusion of nicardipine can be titrated for effective control of BP. Intravenous nicardipine has been used safely in hospitalized children and newborns for the management of hypertensive crisis, and for controlled hypotension during surgery. CCAs are a class of antihypertensives that are safe and effective in pediatric patients. They have relatively few adverse effects and are well tolerated by children. This article reviews CCAs as antihypertensives in the management of pediatric hypertension.

Intervention strategies for neonatal hypoxic-ischemic cerebral injury

BACKGROUND

Accumulating evidence points to an evolving process of brain injury after intrapartum hypoxia-ischemia that initiates in utero and extends into a recovery period. It is during this recovery period that the potential for neuroprotection exists.

OBJECTIVE

This discussion briefly reviews the cellular characteristics of hypoxic-ischemic cerebral injury and the current and future therapeutic strategies aimed at ameliorating ongoing brain injury after intrapartum hypoxia-ischemia.

METHODS

As part of the Newborn Drug Development Initiative, the National Institute of Child Health and Human Development and the US Food and Drug Administration cosponsored a workshop held March 29 and 30, 2004, in Baltimore, Maryland. Information for this article was gathered during that workshop. Literature searches of MEDLINE (Ovid) and EMBASE (1996-2005) were also conducted; search terms included newborn, infant, hypoxia-ischemia, hypoxic-ischemic encephalopathy, asphyxia, pathogenesis, treatment, reperfusion injury, and mechanisms, as well as numerous interventions (ie, therapeutic hypothermia, magnesium, and barbiturates).

RESULTS

The acute brain injury results from the combined effects of cellular energy failure, acidosis, glutamate release, intracellular calcium accumulation, lipid peroxidation, and nitric oxide neurotoxicity that serve to disrupt essential components of the cell, resulting in death. Many factors, including the duration or severity of the insult, influence the progression of cellular injury after hypoxia-ischemia. A secondary cerebral energy failure occurs from 6 to 48 hours after the primary event and may involve mitochondrial dysfunction secondary to extended reactions from primary insults (eg, calcium influx, excitatory neurotoxicity, oxygen free radicals, or nitric oxide formation). Some evidence suggests that circulatory and endogenous inflammatory cells/mediators also contribute to ongoing brain injury. The goals of management of a newborn infant who has sustained a hypoxic-ischemic insult and is at risk for injury should include early identification of the infant at highest risk for evolving injury, supportive care to facilitate adequate perfusion and nutrients to the brain, attempts to maintain glucose homeostasis, and consideration of interventions to ameliorate the processes of ongoing brain injury. Recent evidence suggests a potential role for modest hypothermia (ie, a reduction in core body temperature to -34 degrees C) administered to high-risk term infants within 6 hours of birth. Either selective (head) or systemic (body) cooling reduces the incidence of death and/or moderate to severe disability at 18-month follow-up. Additional strategies-including the use of oxygen free radical inhibitors and scavengers, excitatory amino acid antagonists, and growth factors; prevention of nitric oxide formation; and blockage of apoptotic pathways-have been evaluated experimentally but have not been replicated in a systematic manner in the human neonate. Other avenues of potential neuroprotection that have been studied in immature animals include platelet-activating factor antagonists, adenosinergic agents, monosialoganglioside GM1, insulin-like growth factor-1, and erythropoietin.

CONCLUSIONS

Much progress has been made toward understanding the mechanisms contributing to ongoing brain injury after intrapartum hypoxia-ischemia. This should facilitate more specific pharmacologic intervention strategies that might provide neuroprotection during the reperfusion phase of injury.

Transplantation of multipotent astrocytic stem cells into a rat model of neonatal hypoxic–ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) in neonates results in long-term disabilities. Stem cell therapy may offer an attractive treatment for HIE. Multipotent astrocytic stem cells (MASCs) from mice transplanted into a rat model of hypoxia-ischemia (HI) survived the transplantation and showed signs of migration towards the injured cortex. Some MASCs around the injured cortex differentiated into neuronal and astrocytic phenotypes. MASCs transplanted into non-ischemic pups survived but retained their astrocytic phenotype. These data suggest that transplanted MASCs can survive and differentiate into neurons and astrocytes in the post-injury milieu of the neonatal brain injured by HI.

Hypoxic regulation of the fetal cerebral circulation

Fetal cerebrovascular responses to acute hypoxia are fundamentally different from those observed in the adult cerebral circulation. The magnitude of hypoxic vasodilatation in the fetal brain increases with postnatal age although fetal cerebrovascular responses to acute hypoxia can be complicated by age-dependent depressions of blood pressure and ventilation. Acute hypoxia promotes adenosine release, which depresses fetal cerebral oxygen consumption through action of adenosine on neuronal A1 receptors and vasodilatation through activation of A2 receptors on cerebral arteries. The vascular effect of adenosine can account for approximately half the vasodilatation observed in response to hypoxia. Hypoxia-induced release of nitric oxide and opioids can account for much of the adenosine-independent cerebral vasodilatation observed in response to hypoxia in the fetus. Direct effects of hypoxia on cerebral arteries account for the remaining fraction, although the vascular endothelium contributes relatively little to hypoxic vasodilatation in the immature cerebral circulation. In contrast to acute hypoxia, fetal cerebral blood flow tends to normalize during acclimatization to chronic hypoxia even though cardiac output is depressed. However, uncompensated chronic hypoxia in the fetus can produce significant changes in brain structure and function, alteration of respiratory drive and fluid balance, and increased incidence of intracranial hemorrhage and periventricular leukomalacia. At the level of the fetal cerebral arteries, chronic hypoxia increases protein content and depresses norepinephrine release, contractility, and receptor densities associated with contraction but also attenuates endothelial vasodilator capacity and decreases the ability of ATP-sensitive and calcium-sensitive potassium channels to promote vasorelaxation. Overall, fetal cerebrovascular adaptations to chronic hypoxia appear prioritized to conserve energy while preserving basic contractility. Many gaps remain in our understanding of how the effects of acute and chronic hypoxia are mediated in fetal cerebral arteries, but studies of adult cerebral arteries have produced many powerful pharmacological and molecular tools that are simply awaiting application in studies of fetal cerebral artery responses to hypoxia.

Topiramate prevents excitotoxic damage in the newborn rodent brain

Brain lesions induced in newborn mice by the glutamatergic agonists ibotenate (acting on NMDA and metabotropic receptors) and S-bromowillardiine (acting on AMPA-kainate receptors) mimic some aspects of white matter cysts and transcortical necrosis observed in human perinatal brain damage. Topiramate (TPM), already used in children to manage newly diagnosed and refractory epilepsy, has potential neuroprotective effects that may be useful in human perinatal brain lesions. In the excitotoxic newborn mouse model, TPM provided dose-dependent and long-lasting protection of developing white matter and cortical plate against S-bromowillardiine. TPM had no significant effect on ibotenate-induced brain lesions. TPM-induced neuroprotection potentially involved increased survival of pre-oligodendrocytes, decreased neuronal apoptosis, inhibition of microglial activation and astrogliosis, and decreased seizure activity. Diazepam, phenytoin, and carbamazepine had no neuroprotective effect in this model. The present study provides experimental support for the consideration of TPM as a candidate therapy for excitotoxic perinatal brain lesions.

Brain injury in the term infant

Perinatal brain injury in the term infant is a relatively uncommon event. The principal lesions are intracranial hemorrhage including subarachnoid, subdural, intraparenchymal, intraventricular, focal cerebral infarction and hypoxic ischemic cerebral injury secondary to intrapartum hypoxia-ischemia. Both intracranial hemorrhage and focal cerebral infarction are invariably identified at the time of clinical symptoms, ie, seizures or apnea. This clearly limits the potential for prevention. The mechanisms contributing to brain injury secondary to intrapartum hypoxia-ischemia have become more clearly defined. Secondary or reperfusion injury is potentially amenable to neuroprotective strategies. Modest hypothermia is one such therapy that has been studied in high-risk newborn infants with some initial success. Future studies need to focus on additional neuroprotective strategies.

Hypoxic-ischemic brain injury in the term infant-current concepts

An enhanced understanding of the cellular characteristics contributing to ongoing brain injury following intrapartum hypoxia-ischemia has resulted in the implementation of targeted neuroprotective strategies in the newborn period. This review briefly covers the pathogenesis of hypoxic-ischemic injury with an emphasis on reperfusion injury; the role of magnetic resonance imaging in the detection of such injury, and focuses on potential strategies both supportive and neuroprotective to prevent ongoing injury with a specific emphasis on modest hypothermia.

Low Apgar scores and the definition of birth asphyxia

Nonreassuring fetal heart rate patterns, prolonged labor, meconium-stained fluid, a low 1-minute Apgar score, and mild to moderate acidemia have no predictive value for long-term neurologic injury without signs of encephalopathy and seizures. It is important to provide proper resuscitation, support infants, and allow time for evaluation. We have time and the tools to provide fairly predictive information to the families. It is important to use this knowledge wisely in communicating honestly with families, because difficult decisions undoubtedly will arise.

The postnatal management of the asphyxiated term infant

Investigations in animal models of hypoxic-ischemic injury have not translated into clinical trials of success because of the complex pathology of hypoxic-ischemic brain injury in neonates, the difficulty in defining the onset and duration and severity of the injury, the underlying predisposing disorders of the mothers or the infant, the side effects of many of the investigational drugs precluded clinical use, and many of the investigational agents interfered with only one step of the cascade of events that lead to brain injury. It is possible that a combination of therapeutic agents, including those that affect different levels of the cascade to cell death, will have the greatest neuroprotective effects. Modest hypothermia postpones secondary energy failure and can prolong the window while pharmacotherapeutic agents can be used. It is possible that in the future, sequential administration of agents or strategies that are initiated in the intrapartum period and continued postnatally will be the optimum method for treating infants who are at highest risk for brain injury following acute hypoxic-ischemic asphyxia.

Pathogenesis of hypoxic-ischemic cerebral injury in the term infant: current concepts

Multiple, biochemical cascades contribute to the pathogenesis of neonatal hypoxic-ischemic brain injury. This article summarizes experimental evidence that supports the role of excitatory amino acids, calcium, free radicals, nitric oxide, proinflammatory cytokines, and bioactive lipids. Specific vulnerabilities that distinguish the response of the immature brain from that of the mature brain are highlighted. These include increased susceptibility to excitotoxicity and free radical injury, greater tendency to apoptotic death, and heightened vulnerability of developing oligodendrocytes. Available supportive evidence from human studies is also included. Implications for clinical neuroprotective strategies are discussed.

Clinical trials of treatments after perinatal asphyxia

Following critical hypoxia-ischemia during labor and delivery, there is a window of therapeutic opportunity during hypoxic-ischemic encephalopathy. Meta-analysis of three randomized trials of prophylactic barbiturate therapy for neonatal hypoxic-ischemic encephalopathy showed no significant effect on death or disability. One randomized trial of allopurinol showed short-term benefits but was too small to test death or disability. No adequate trials of dexamethasone, calcium channel blockers, or magnesium sulphate have yet been completed, but pilot studies in infants have shown the cardiovascular risks of magnesium sulphate and calcium channel blockers. There is considerable evidence from animal studies that posthypoxic mild hypothermia reduces brain injury. One small randomized trial of mild hypothermia found no adverse effects but was too small to examine death or disability. One large randomized trial of selective head cooling has finished recruitment and a number of large trials of systemic mild hypothermia are ongoing. As time is critical with post-hypoxic interventions, the delay involved in obtaining informed parental consent for such trials might obscure a clinically important therapeutic effect.

Up-regulation of Ca(2+) channels in vas deferens after chronic treatment of newborn rats with nifedipine

Radioligand binding and contraction techniques were used to verify if L-type Ca(2+) channels are modified in rat vas deferens after treatment with the blocker nifedipine (15 microg), injected at 7, 14, 21 and 28 days after birth. Vas deferens tissue was used 10, 30 and 90 days after the last injection, to verify if modifications are persistent. Binding studies with cell membranes, using [(3)H]isradipine, showed an increase of the density (B(max)) of Ca(2+) channels by more than 60%, after 10 and 30 days, without changes of affinity (K(d)). Maximal contractions (E(max)) of KCl, were increased by 106% and 37%, respectively, after 10 and 30 days, without changes of apparent affinity (pD(2)). After 90 days, the values of B(max), K(d), E(max) and pD(2) were not different from the controls. Differences were also not found for rats injected when adult. It is concluded that treatment of newborn, but not of adult, rats with nifedipine produced a long-lasting, though reversible, up-regulation of L-type Ca(2+) channels.

Safety of the newer antihypertensive agents in children

Hypertension is relatively uncommon in children and few children receive antihypertensive medications. This article reviews the safety of calcium channel blockers, angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists in children with hypertension. While the newer antihypertensive agents appear to be well-tolerated by children, further studies are needed to determine the safety profile across the developmental continuum, with chronic dosing and in children with complex hypertension.

Recent advances in neonatology

This update focuses on recent neonatal research of potential interest to obstetricians. Accurate information on outcomes for infants born at the edges of viability is critical to informing management decisions. New research, population based, gives guidance on short-term survival and long-term neurodevelopmental outcome. Recent research has also highlighted the variation in attitudes to end-of-life decision-making and important influences on this that cross different boundaries. Although research is dominated by issues related to prematurity, some important developments relevant to term infants will be covered. There is accumulating evidence that challenges the traditional approach of using 100% O2 in resuscitation. For infants suffering intrapartum asphyxia there are new approaches to neuroprotection actively being explored. Therapeutic interventions such as extracorporeal membrane oxygenation and inhaled nitric oxide, available for some time, are having their place in neonatal intensive care more clearly defined.

Perinatal brain injury: from pathogenesis to neuroprotection

Brain injury secondary to hypoxic-ischemic disease is the predominant form of all brain injury encountered in the perinatal period. The focus of this article is the most recent research developments in this field and especially those developments that should lead to the most profound effects on interventions in the first years of the new millennium. Neuronal injury is the predominant form of cellular injury in the term infant. The principal mechanisms leading to neuronal death after hypoxia-ischemia/reperfusion are initiated by energy depletion, accumulation of extracellular glutamate, and activation of glutamate receptors. The cascade of events that follows involves accumulation of cytosolic calcium and activation of a variety of calcium-mediated deleterious events. Notably this deleterious cascade, which evolves over many hours, may be interrupted even if interventions are instituted after termination of the insult, an important clinical point. Of the potential interventions, the leading candidates for application to the human infant in the relative short-term are mild hypothermia, inhibitors of free radical production, and free radical scavengers. Promising clinical data are available for the use of mild hypothermia.

Post-resuscitative management of the asphyxiated term and preterm infant

Up until the recent past, the treatment for perinatal asphyxia included only supportive measures. Babies were resuscitated and then observed for signs of multi-organ system dysfunction. Apart from standard supportive management, a new arsenal of potential neuroprotective strategies have emerged over the past years, in order to decrease the severity of brain injury following asphyxia. Today, several neuroprotective therapies are being evaluated in human infants.

Early biochemical indicators of hypoxic-ischemic encephalopathy after birth asphyxia

Hypoxic-ischemic encephalopathy (HIE) after perinatal asphyxia is a condition in which serum concentrations of brain-specific biochemical markers may be elevated. Neuroprotective interventions in asphyxiated newborns require early indicators of brain damage to initiate therapy. We examined brain-specific creatine kinase (CK-BB), protein S-100, and neuron-specific enolase in cord blood and 2, 6, 12, and 24 h after birth in 29 asphyxiated and 20 control infants. At 2 h after birth, median (quartiles) serum CK-BB concentration was 10.0 U/L (6.0-13.0 U/L) in control infants, 16.0 U/L (13.0-23.5 U/L) in infants with no or mild HIE, and 46.5 U/L (21.4-83.0 U/L) in infants with moderate or severe HIE. Serum protein S-100 was 1.6 microg/L (1.4-2.5 microg/L) in control infants, 2.9 microg/L (1.8-4.7 microg/L) in asphyxiated infants with no or mild HIE, and 17.0 microg/L (3.2-34.1 microg/L) in infants with moderate or severe HIE 2 h after birth. No significant difference was detectable in serum neuron-specific enolase between infants with no or mild and moderate or severe HIE 2 and 6 h after birth. A combination of serum protein S-100 (cutoff value, 8.5 microg/L) and CK-BB (cutoff value, 18.8 U/L) 2 h after birth had the highest predictive value (83%) and specificity (95%) of predicting moderate and severe HIE. Cord blood pH (cutoff value, <6.9) and cord blood base deficit (cutoff value, >17 mM) increase the predictive values of protein S-100 and CK-BB. We conclude that elevated serum concentrations of protein S-100 and CK-BB reliably indicate moderate and severe HIE as early as 2 h after birth.

Systematic review of therapy after hypoxic-ischaemic brain injury in the perinatal period

Objectives were to identify and to evaluate controlled trials of interventions for term infants developing hypoxic-ischaemic encephalopathy. Five randomized trials concerning prophylactic anticonvulsant therapy for neonatal HIE were identified. There were methodological problems with all of them, and meta-analysis of barbiturate prophylaxis showed no significant effect on death or disability. One randomized trial of allopurinol showed short-term benfits, but was too small to test death or disability. One small randomized trial of hypothermia found no adverse effects, but was too small to examine death or disability. No adequate trials of dexamethasone, calcium channel blockers, magnesium sulphate, or naloxone have yet been completed, but pilot studies in infants have shown the risks of magnesium sulphate and calcium channel blockers.

Hypoxic-ischemic brain damage in perinatal age group

Cerebral hypoxia-ischemia in the perinatal period continues to be a major contributor to chronic neurologic impairment in children worldwide. Extensive research conducted in the past several years has led to a better understanding of the mechanisms involved in hypoxic-ischemic brain injury. Based on this understanding, the major potential therapeutic approaches being studied include antagonists of excitatory amino acids, calcium channel antagonists, free-radical scavengers, nitric oxide synthase inhibitors, anti-inflammatory agents, trophic factors, and hypothermia. Several agents are in clinical trial phases in adults. However, safety concerns and close relationship between pathomechanisms of hypoxic-ischemic cerebral injury and normal developmental processes have contributed to the slow pace in the neonatal trials. Large multicenter trials including an adequate number of infants will be needed to evaluate efficacy of therapeutic interventions in this particular age group. A large number of risk factors that predispose to hypoxic ischemic injury have been identified. It is important to control these factors and prevent brain damage in the first place. This is especially true for developing countries where resources for treatment with newer agents (when they become available) are likely to be limited. Recent information regarding mechanisms of injury and potential therapeutic measures related to perinatal age are presented in this paper.

Intravenous nicardipine in hypertensive preterm infants

Eight preterm infants were given intravenous nicardipine, a calcium channel blocker, to treat systemic hypertension (renal artery thrombosis (n = 3); dexamethasone for management of bronchopulmonary dysplasia (n = 2); unexplained (n = 3). Nicardipine doses ranged from 0.5 to 2.0 micrograms/kg/min and were given for three to 36 days (mean (SD) 15.9 (10.3) days). Systolic blood pressure had significantly decreased after 12 and 24 hours of nicardipine treatment (-17 (17)% and -21 (10)%, respectively). Diastolic blood pressure significantly decreased after 24 hours of treatment (-22 +/- 16%). The decrease in blood pressure remained significant over the subsequent days of treatment. No hypotension or other clinical side effects were observed. It is concluded that intravenous nicardipine could be a first line treatment for hypertension in preterm infants.

Posthypoxic cooling of neonatal rats provides protection against brain injury

AIM

To determine whether moderate hypothermia, applied after a hypoxic-ischaemic insult in neonatal rats, reduces cerebral damage.

METHOD

Unilateral hypoxic-ischaemic brain damage was induced in 7 day old rats by left carotid ligation, followed by 120 minutes of normothermic exposure to 8% O2, followed by random selection to three hours of hypothermia (rectal temperature, mean (SD), 32.5 (0.4) degrees C) or normothermia (38.3 (0.4) degrees C). One hundred and one animals were used for brain temperature or blood chemistry studies and 24 for survival studies (7 days) with neuropathology, including cell counting as outcome measures.

RESULTS

Thirty sections from each brain were histologically examined with respect to distribution and pattern of damage and given a score from 0 to 4. Animals treated with hypothermia had significantly less damage than normothermic animals (score 0.5 (0.3) vs 1.8 (0.5)).

CONCLUSIONS

Posthypoxic hypothermia reduces brain damage in awake, unrestrained 7 day old rats.

Predictive value of early neuroimaging, pulsed Doppler and neurophysiology in full term infants with hypoxic-ischaemic encephalopathy

To evaluate their prognostic value, five different non-invasive techniques were used on 34 full term infants with hypoxic-ischaemic encephalopathy (HIE) within six hours of delivery. Cranial ultrasonography, the resistance index (RI) of the middle cerebral artery obtained with Doppler ultrasonography, somatosensory evoked potentials (SEPs), visual evoked potentials (VEPs) and the cerebral function monitor (CFM) were used. According to the criteria of Sarnat, 11 infants developed mild, seven moderate, and 16 severe encephalopathy. The CFM had the highest positive (PPV 84.2%) and negative predictive value (NPV 91.7%). All but one of the infants with a continuous pattern had a good outcome. The CFM of 11 cases with a suppression-burst pattern changed to a continuous pattern over 24 to 48 hours in four infants, and was associated with a normal outcome in three. All five cases with an isoelectric CFM died. The SEPs also provided useful information (PPV 81.8%; NPV 91.7%). VEPs were often delayed during the first hours or life and did not carry a poor prognosis in five of 14 cases (PPV 77.3%). Both ultrasonography and Doppler RI were of little value, as they were almost always normal at this early stage. In 34 full term infants with HIE, studied within 6 hours of life, the CFM and SEPs provided the most useful information about the expected course of encephalopathy and subsequent neurodevelopmental outcome.

Effect of calcium antagonist, nicardipine, on cerebral blood flow in postasphyxial newborn piglets

An experiment was carried out in nine piglets within 24 h after birth (control group: four, nicardipine group: five) for the purpose of evaluating the effects of a calcium antagonist, nicardipine, on cerebral blood flow changes induced by asphyxia neonatorum. Under respiratory control with a mechanical ventilator, the animals were exposed to hypoxia. The inspiratory oxygen level was lowered at 15 min intervals from 0.08 to 0.06 and then to 0.05. When bradycardia (heart rate; 60/min or less) was observed, 100% oxygen, adrenaline, and sodium bicarbonate were administered for resuscitation. Nicardipine was administered at a dosage of 10 micrograms/kg via bolus injection 30 min after the resuscitation. It was administered thereafter at a rate of 10 micrograms/kg per h. The cerebral blood flow was measured using a laser Doppler velocimeter. The cerebral blood flow, electroencephalograph (EEG), blood pressure, and heart rate were continuously measured for 120 min after the resuscitation. In the control group, the mean arterial pressure 35 min after the resuscitation was 60 mmHg or more. However, the cerebral blood flow was lower than the prehypoxia value in the animals with a mean arterial pressure of 75 mmHg or less. In the nicardipine group, the mean arterial pressure was lower, but the cerebral blood flow was higher than the prehypoxia value and cerebral ischemia was not induced. The mean arterial pressure 120 min after the resuscitation was 72.0 +/- 8.2 mmHg in the control group, while it was 56.7 +/- 7.5 mmHg in the nicardipine group. It was significantly lower in the latter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal models of perinatal asphyxia: contributions, contradictions, clinical relevance

Animal models have contributed immensely to our understanding of hypoxic ischemic encephalopathy in the newborn. A number of animal models have been used, including both primate and subprimate species. Although the Rhesus monkey model has a dramatically similar pathological distribution of brain injury when compared with the human, other pathologic processes secondary to asphyxia may be more appropriately assessed in other species. The maxim that because primates are closer on the phylogenetic tree to humans than are subprimates all observations in the primate are applicable to the human is simply not true. Understanding of the neurochemical consequences of asphyxia in the past decade have arisen from experiments primarily in the neonatal rat. We have come to understand that not only is the hypoxic event of major significance, but that, once reperfused, reoxygenation causes further injury. Free-radical generation following reperfusion may be massive and may further contribute to cell membrane injury. These observations have lead to rational theoretic approaches to the treatment of hypoxic ischemic brain injury. On the other hand, previously used treatments such as osmotic agents and glucocorticoids would appear to be not only inefficacious but hazardous in the treatment of hypoxic ischemic brain injury. The role of nitric oxide (NO) in the pathogenesis of brain injury is yet uncertain, but there is little doubt that it plays a significant role. Although survival of the immature animal subjected to hypoxic environment is longer than in the mature animal, the central nervous system of the immature animal is more sensitive to glutamate and N-Methyl-D-aspartate (NMDA) receptor-mediated injury.

Predictive value of early continuous amplitude integrated EEG recordings on outcome after severe birth asphyxia in full term infants

The background pattern in single channel amplitude integrated EEG recordings (aEEG) was recorded in 47 infants within the first six hours after birth to see if this could predict outcome after birth asphyxia. The aEEG background pattern during the first six hours of life was continuous and of normal voltage in 26 infants. All these infants survived; 25 were healthy, one had delayed psychomotor development. A continuous but extremely low voltage pattern was present in two infants, both of whom survived with severe handicap. Five infants had flat (mainly isoelectric) tracings during the first six hours of life; four died in the neonatal period, and one survived with severe neurological handicap. Burst-suppression pattern was identified in 14 infants, of whom five died, six survived with severe handicap, and three were healthy at follow up. The type of background pattern recorded within the first six postnatal hours in the aEEG tracings predicted outcome correctly in 43 of 47 (91.5%) infants. Use of aEEG monitoring can predict outcome, with a high degree of accuracy, after birth asphyxia, within the first six hours after birth. The predictive value of a suppression-burst pattern was, however, somewhat lower than the other background patterns. The aEEG seems to be a feasible technique for identifying infants at high risk of subsequent brain damage who might benefit from interventionist treatment after asphyxia.

Monosialoganglioside GM1 treatment after a hypoxic-ischemic episode reduces the vulnerability of the fetal sheep brain to subsequent injuries

OBJECTIVE

A transient hypoxic-ischemic episode can markedly sensitize regions of the fetal brain, particularly the striatum, to further insults occurring in close succession. The purpose of this study was to determine whether ganglioside GM1 given to the fetus after a hypoxic-ischemic episode can counteract this sensitization and protect against subsequent insults.

STUDY DESIGN

Chronically instrumented near-term fetal sheep (119 to 133 days) were subjected to three 10-minute episodes of reversible cerebral ischemia at 1-hour intervals. Six were given 30 mg/kg ganglioside GM1 through the umbilical vein, commencing immediately after the release of the occluder, over the next 2 hours, followed by a continuous infusion of 30 mg/kg/day over 60 hours after ischemia; these were compared with seven vehicle-treated controls. The time course of electrocorticographic activity and cytotoxic edema within the parasagittal cortex were determined with real-time spectral analysis and continuous impedance measurements, respectively. The degree and distribution of neuronal death was assessed histologically 72 hours later.

RESULTS

Ganglioside GM1 improved recovery of primary edema and markedly reduced histologic damage (p < 0.001), particularly in the striatum, hippocampus, and cortex. At 72 hours after ischemia electrocorticographic activity had returned to normal in the ganglioside GM1-treated group but was still depressed (p < 0.001) in the control group.

CONCLUSION

These results showed that ganglioside GM1 treatment initiated immediately after a transient hypoxic-ischemic episode stabilized membrane function and markedly improved neuronal outcome after subsequent insults, suggesting its potential therapeutic value in acute situations of repeated hypoxia-ischemia in the perinatal period.

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

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

Perinatal hypoxic-ischaemic brain injury: prediction of outcome

Twenty-six term babies with hypoxic-ischaemic brain injury were studied during the neonatal period to evaluate the prediction of outcome to at least one year of age by means of ultrasonography, CT scanning and Doppler ultrasound assessment of cerebral palsy blood flow velocity (CBFV). Adverse outcome was defined as the occurrence of cerebral palsy, developmental delay or death. At follow-up, 17 infants had an adverse outcome (seven died, 10 had disability); the remainder had no detectable impairment. Abnormalities on cranial ultrasound were not, but generalised decreased tissue density on CT scan was, associated with adverse outcome. Abnormal mean CBFV in the middle cerebral artery had no association with outcome, but abnormal mean CBFV in the anterior cerebral artery and a low resistance index in both arteries were significantly associated with adverse outcome. Such information may be used for appropriate counselling of parents of asphyxiated infants.