Clinical anesthesia causes permanent damage to the fetal guinea pig brain

Mode of delivery and child and adolescent psychological well-being: Evidence from Hong Kong's "Children of 1997" birth cohort

Mode of delivery (vaginal or cesarean section) is thought to affect gut microbiota, which in turn may affect psychological well-being. As such, mode of delivery is potentially a modifiable factor for psychological well-being. Here we examined the association of mode of delivery with child and adolescent psychological well-being. We used multivariable linear regression in a population-representative Hong Kong Chinese birth cohort, “Children of 1997,” to examine the adjusted associations of mode of delivery with behavioral problems assessed from parent-reported Rutter score at ~7 (n = 6294) and ~11 years (n = 5598), self-esteem assessed from self-reported Culture-Free Self-Esteem Inventory score at ~11 years (n = 6937) and depressive symptoms assessed from self-reported Patient Health Questionnaire-9 score at ~13 years (n = 5797). Cesarean Section (CS) was associated with children born in private hospitals, boys, and firstborns, higher maternal body mass index, higher maternal age, preeclampsia, higher socioeconomic position (SEP) and maternal birth in Hong Kong. CS was unrelated to behavior, self-esteem and depressive symptoms adjusted for infant characteristics (sex, gestational age, birthweight, parity and breast feeding), maternal characteristics (mother’s age and place of birth) and SEP. In a developed non-Western setting, mode of delivery was not clearly associated with childhood or early adolescent psychological well-being.

The neuroprotective effects of remifentanil on isoflurane-induced apoptosis in the neonatal rat brain

Remifentanil is one of the most frequently prescribed opioids used in combination with inhalation anesthetics in clinical practice, but the effects of such combinations on the developing rat brain are unknown. In our study, we investigated first the potential neurotoxic effects of remifentanil on the developing brain and then the effects of remifentanil on isoflurane-induced apoptosis in the neonatal rat brain following exposure to a nociceptive stimulus. In the first experiment, postnatal day (P) 7 rats were randomly exposed to 30% oxygen, 1.5% isoflurane alone, 1.5% isoflurane and a plantar incision, normal saline, or remifentanil at a low (5 µg·kg^-1·h^-1), moderate (20 µg·kg^-1·h^-1) or high (80 µg·kg^-1·h^-1) dose for 4 h. In the second 4-h experiment, P7 rats were randomly exposed to 1.5% isoflurane, infused with different doses of remifentanil (5, 10, and 20 µg·kg^-1·h^-1), and subjected to a plantar incision. In both experiments, the number of apoptotic neurons in the cortex, hippocampus, and thalamus was assessed after two hours by cleaved caspase-3 or TUNEL staining. Our data showed that unlike 1.5% isoflurane, remifentanil at any dose did not cause significant neuronal apoptosis in any brain section. In addition, in response to a nociceptive stimulus, the infusion of 10 µg·kg^-1·h^-1 remifentanil reduced isoflurane-induced apoptosis in the hippocampus (P = 0.003 in CA1, P = 0.002 in CA3) but not in the cortex or thalamus. Our findings suggest that remifentanil does not induce apoptosis and reduces isoflurane-induced apoptosis in the developing brain.

Molecular Mechanisms of Anesthetic Neurotoxicity: A Review of the Current Literature

Data from epidemiologic studies and animal models have raised a concern that exposure to anesthetic agents during early postnatal life may cause lasting impairments in cognitive function. It is hypothesized that this is due to disruptions in brain development, but the mechanism underlying this toxic effect remains unknown. Ongoing research, particularly in rodents, has begun to address this question. In this review we examine currently postulated molecular mechanisms of anesthetic toxicity in the developing brain, including effects on cell death pathways, growth factor signaling systems, NMDA and GABA receptors, mitochondria, and epigenetic factors. The level of evidence for each putative mechanism is critically evaluated, and we attempt to draw connections between them where it is possible to do so. Although there are many promising avenues of research, at this time no consensus can be reached as to a definitive mechanism of injury.

General Anesthetics and Neurotoxicity: How Much Do We Know?

Over a decade ago, alarming findings were reported that exposure of the very young and very old animals to clinically used general anesthetics could be detrimental to their brains. The evidence presented suggested that the exposure to commonly used gaseous and intravenous general anesthetics induces the biochemical and morphologic changes in the immature and aging neurons ultimately resulting in their demise. More alarming was the demonstration of significant cognitive and behavioral impairments noted long after the initial anesthesia exposure. This article provides an overview of anesthesia-induced developmental neurotoxicity and commentary on the effects of general anesthesia on the aging brain.

General Anesthesia During the Third Trimester: Any Link to Neurocognitive Outcomes?

Rodent studies on the effect of general anesthesia during the third trimester on neurocognitive outcomes are mixed, but primate studies suggest that a clinically relevant exposure to anesthetic agents during the third trimester can trigger neuronal and glial cell death. Human studies are conflicting and the evidence is weak. This is an up-to-date review of the literature on the neurodevelopmental effects of anesthetic agents administered during the third trimester. Early brain development and critical periods of neurodevelopment as it relates to neurotoxicity are highlighted. Rodent, nonhuman primate, and population studies are discussed and placed in the context of clinical practice.

A holistic approach to anesthesia-induced neurotoxicity and its implications for future mechanistic studies

The year 2016 marked the 15th anniversary since anesthesia-induced developmental neurotoxicity and its resulting cognitive dysfunction were first described. Since that time, multiple scientific studies have supported these original findings and investigated possible mechanisms behind anesthesia-induced neurotoxicity. This paper reviews the existing mechanistic literature on anesthesia-induced neurotoxicity in the context of a holistic approach that emphasizes the importance of both neuronal and non-neuronal cells during early postnatal development. Sections are divided into key stages in early neural development; apoptosis, neurogenesis, migration, differentiation, synaptogenesis, gliogenesis, myelination and blood brain barrier/cerebrovasculature. In addition, the authors combine the established literature in the field of anesthesia-induced neurotoxicity with literature from other related scientific fields to speculate on the potential role of non-neuronal cells and to generate new future hypotheses for understanding anesthetic toxicity and its application to the practice of pediatric anesthesia.

Emerging Roles for MicroRNAs in Perioperative Medicine

MicroRNAs (miRNAs) are small, non-protein-coding, single-stranded RNAs. They function as posttranscriptional regulators of gene expression by interacting with target mRNAs. This process prevents translation of target mRNAs into a functional protein. miRNAs are considered to be functionally involved in virtually all physiologic processes, including differentiation and proliferation, metabolism, hemostasis, apoptosis, and inflammation. Many of these functions have important implications for anesthesiology and critical care medicine. Studies indicate that miRNA expression levels can be used to predict the risk for eminent organ injury or sepsis. Pharmacologic approaches targeting miRNAs for the treatment of human diseases are currently being tested in clinical trials. The present review highlights the important biological functions of miRNAs and their usefulness as perioperative biomarkers and discusses the pharmacologic approaches that modulate miRNA functions for disease treatment. In addition, the authors discuss the pharmacologic interactions of miRNAs with currently used anesthetics and their potential to impact anesthetic toxicity and side effects.

Increasing cumulative exposure to volatile anesthetic agents is associated with poorer neurodevelopmental outcomes in children with hypoplastic left heart syndrome

OBJECTIVES

Despite improved survival in children with hypoplastic left heart syndrome (HLHS), significant concern persists regarding their neurodevelopmental (ND) outcomes. Previous studies have identified patient factors, such as prematurity and genetic syndromes, to be associated with worse ND outcomes. However, no consistent relationships have been identified among modifiable management factors, including cardiopulmonary bypass strategies, and ND outcomes after cardiac surgery in infancy. Studies in immature animals, including primates, have demonstrated neurodegeneration and apoptosis in the brain after certain levels and extended durations of anesthetic exposure. Retrospective human studies have also suggested relationships between adverse ND effects and anesthetic exposure.

METHODS

Cumulative minimum alveolar concentration hours (MAC-hrs) of exposure to volatile anesthetic agents (VAA) (desflurane, halothane, isoflurane, and sevoflurane) were collected from an anesthetic database and medical record review for 96 patients with HLHS or variants. ND testing was performed between ages 4 and 5 years, including full-scale IQ, verbal IQ, performance IQ, and processing speed. Four generalized linear modes were hypothesized a priori and tested using a Gaussian (normal) distribution with an identity link.

RESULTS

Cumulative VAA exposure ranged from 0 to 35.3 MAC-hrs (median 7.5 hours). Using specified covariates identified previously as significant predictors of ND outcomes, statistically significant relationships were identified between total MAC-hrs exposure and worse full-scale IQ and verbal IQ scores (P's < .05) alone and after adjusting for relevant covariates.

CONCLUSIONS

Increased cumulative MAC-hrs exposure to VAA is associated with worse ND outcomes in certain domains in children with HLHS and variants.

Repeated isoflurane exposure and neuroapoptosis in the midgestation fetal sheep brain

BACKGROUND

Advances in surgery and technology have resulted in increased in-utero procedures. However, the effect of anesthesia on the fetal brain is not fully known. The inhalational anesthetic agent, isoflurane, other gamma amino butyric acid agonists (benzodiazepines, barbiturates, propofol, other inhalation anesthetics), and N-methyl D aspartate antagonists, eg, ketamine, have been shown to induce neuroapoptosis. The ovine model has been used extensively to study maternal-fetal physiologic interactions and to investigate different surgical interventions on the fetus.

OBJECTIVE

The purpose of this study was to determine effects of different doses and duration of isoflurane on neuroapoptosis in midgestation fetal sheep. We hypothesized that repeated anesthetic exposure and high concentrations of isoflurane would result in increased neuroapoptosis.

STUDY DESIGN

Time-dated, pregnant sheep at 70 days gestation (term 145 days) received either isoflurane 2% × 1 hour, 4% × 3 hours, or 2% × 1 hour every other day for 3 exposures (repeated exposure group). Euthanasia occurred following anesthetic exposure and fetal brains were processed. Neuroapoptosis was detected by immunohistochemistry using anticaspase-3 antibodies. Fetuses unexposed to anesthesia served as controls. Another midgestation group with repeated 2% isoflurane exposure was examined at day 130 (long-term group) and neuronal cell density compared to age-matched controls. Representative sections of the brain were analyzed using Aperio Digital imaging (Leica Microsystems Inc, Buffalo Grove, IL). Data, reported by number of neurons per cubic millimeter of brain tissue are presented as means and SEM. Data were analyzed using the Mann-Whitney U and Kruskal-Wallis tests as appropriate.

RESULTS

A total of 34 fetuses were studied. There was no significant difference in neuroapoptosis observed in fetuses exposed to 2% isoflurane for 1 hour or 4% isoflurane for 3 hours. Increased neuroapoptosis was observed in the frontal cortex following repeated 2% isoflurane exposure compared to controls (1.57 ± 0.22 × 10(6)/mm(3) vs 1.01 ± 0.44 × 10(6)/mm(3), P = .02). Fetuses at 70 days gestation with repeated exposure demonstrated decreased frontal cortex neurons at day 130 when compared to age-matched controls (2.42 ± 0.3 × 10(5)/mm(3) vs 7.32 ± 0.4 × 10(5)/mm(3), P = .02). No significant difference in neuroapoptosis was observed between the repeated exposure group and controls in the hippocampus, cerebellum, or basal ganglia.

CONCLUSION

Repeated isoflurane exposure in midgestation sheep resulted in increased frontal cortex neuroapoptosis. This persisted into late gestation as decreased neuronal cell density. While animal studies should be extrapolated to human beings with caution, our findings suggest that the number of anesthetic/sedative exposures should be considered when contemplating the risks and benefits of fetal intervention as certain fetal therapies may need to be repeated.

Anaesthesia in early childhood - is the development of the immature brain in danger?

Experimental studies performed on immature animal brains had demonstrated a neurotoxic effect following sedation and general anaesthetics administration. The same magnitude of neurotoxicity has been suggested but not been proven to neonates, infants and small children who have undergone anaesthesia. There is a justified and increasing inquiry regarding the administration of general anaesthesia to paediatric patients.

A Neonatal Mouse Spinal Cord Compression Injury Model

Spinal cord injury (SCI) typically causes devastating neurological deficits, particularly through damage to fibers descending from the brain to the spinal cord. A major current area of research is focused on the mechanisms of adaptive plasticity that underlie spontaneous or induced functional recovery following SCI. Spontaneous functional recovery is reported to be greater early in life, raising interesting questions about how adaptive plasticity changes as the spinal cord develops. To facilitate investigation of this dynamic, we have developed a SCI model in the neonatal mouse. The model has relevance for pediatric SCI, which is too little studied. Because neural plasticity in the adult involves some of the same mechanisms as neural plasticity in early life¹, this model may potentially have some relevance also for adult SCI. Here we describe the entire procedure for generating a reproducible spinal cord compression (SCC) injury in the neonatal mouse as early as postnatal (P) day 1. SCC is achieved by performing a laminectomy at a given spinal level (here described at thoracic levels 9-11) and then using a modified Yasargil aneurysm mini-clip to rapidly compress and decompress the spinal cord. As previously described, the injured neonatal mice can be tested for behavioral deficits or sacrificed for ex vivo physiological analysis of synaptic connectivity using electrophysiological and high-throughput optical recording techniques¹. Earlier and ongoing studies using behavioral and physiological assessment have demonstrated a dramatic, acute impairment of hindlimb motility followed by a complete functional recovery within 2 weeks, and the first evidence of changes in functional circuitry at the level of identified descending synaptic connections¹.

Dexmedetomidine protects spatial learning and memory ability in rats

BACKGROUND

The authors tested the hypothesis that combined use of dexmedetomidine on fetal rats during isoflurane exposure in maternal anesthesia can attenuate the abnormal spatial learning and memory abilities in adults via the renin-angiotensin-aldosterone system.

METHODS

Fifty timed-pregnancy rats were randomly assigned to five groups (Dex+Iso, Sal+Iso, Sal+Oxy, Dex+Oxy, and a control group ) on embryonic day 14 to receive five different dispositions, i.e. combined injection of dexmedetomidine (Dex) or saline (Sal) and inhalation of isoflurane (Iso), oxygen (Oxy), or normal air for 4 h (n = 10).

RESULTS

The latency time(s) from day 1 to day 4 all showed a decreasing tendency in all four groups. The synaptic count of the Sal+Iso group was significantly lower than the Control group (p < 0.05), suggesting that severe neurodegeneration occurred under the influence of fetal isoflurane exposure. In contrast, the synapse count of the Dex+Iso group was near to that of Control group. The rats are protected in neurodevelopmental, normal development.

CONCLUSION

Combine use of dexmedetomidine during exposure to isoflurane in utero during middle-pregnancy can attenuate the impairment of spatial learning and memory abilities for the rats in adulthood.

Perioperative care of infants with pyloric stenosis

Pyloric stenosis (PS) is one of the most common surgical conditions affecting neonates and young infants. The definitive treatment for PS is surgical pyloromyotomy, either open or laparoscopic. However, surgical intervention should never be considered urgent or emergent. More importantly, emergent medical intervention may be required to correct intravascular volume depletion and electrolyte disturbances. Given advancements in surgical and perioperative care, morbidity and mortality from PS should be limited. However, either may occur related to poor preoperative resuscitation, anesthetic management difficulties, or postoperative complications. The following manuscript reviews the current evidence-based medicine regarding the perioperative care of infants with PS with focus on the preoperative assessment and correction of metabolic abnormalities, intraoperative care including airway management (particularly debate related to rapid sequence intubation), maintenance anesthetic techniques, and techniques for postoperative pain management. Additionally, reports of applications of regional anesthesia for either postoperative pain control or as an alternative to general anesthesia are discussed. Management recommendations are provided whenever possible.

Intravitreal anti-vascular endothelial growth factor treatment for retinopathy of prematurity: comparison between Ranibizumab and Bevacizumab

PURPOSE

To compare the effect and the treatment outcomes of bevacizumab and ranibizumab in the treatment of Type 1 retinopathy of prematurity (ROP).

METHODS

This was a bicentered retrospective case series performed at institutional referral centers. Seventy-two eyes of 37 patients who had intravitreal injections of either bevacizumab or ranibizumab as the primary treatment for Type 1 ROP were included. Outcomes' measures included regression and recurrence of ROP, the surgical complications, and refractive errors at a corrected age of 1 year.

RESULTS

All but one eye in the bevacizumab group had retinal neovascularization and plus disease regression after anti-vascular endothelium growth factor treatment. Neither recurrence of ROP nor major ocular complications, including cataract, retinal detachment, and endophthalmitis occurred in any of the treated eyes. There were no significant differences in mean refractive errors between the patients treated with intravitreal injections of bevacizumab or ranibizumab at the corrected age of 1 year. A significantly higher chance of high myopia was noted in the bevacizumab group (P = 0.03).

CONCLUSION

Both bevacizumab and ranibizumab showed similar efficacy in the regression of ROP with minor mean refractive errors at 1 year of corrected age. However, high myopia was more prevalent in the bevacizumab-treated eyes.

Potential of the ovine brain as a model for anesthesia-induced neuroapoptosis

PURPOSE

This study aimed to determine the feasibility of the fetal ovine model for anesthesia-induced neuroapoptosis detection and effect of dexmedetomidine on neuroapoptosis.

METHODS

Brains of fetal lambs that underwent tracheal occlusion for congenital diaphragmatic hernia were studied following anesthetic exposure. The brains of nine fetuses from six pregnant sheep were studied. Seven of these fetuses underwent surgery for tracheal balloon insertion at 118-120 days gestational age (GA) under 1.5-2.0% isoflurane for 2-3 h. Two weeks afterward, at balloon retrieval, a repeat anesthetic: 1.5-2% isoflurane for 6 h was administered. Five of these fetuses were also exposed to dexmedetomidine concurrently. Immunohistochemistry of fetal brains for apoptotic neurons using activated caspase-3 antibodies was compared to that of an unexposed control group at GA 109 and 122 days.

RESULTS

Neuroapoptosis was detected in the ovine fetus with GA- dependent variation observed in the hippocampus. Increased neuroapoptosis occurred in the isoflurane-only group. Fetuses with isoflurane-dexmedetomidine exposure exhibited decreased neuroapoptosis compared to isoflurane-only group.

CONCLUSION

The fetal ovine model is a suitable option for neuroapoptosis analysis. Isoflurane use appears to be associated with additional neuroapoptosis in ovine fetuses undergoing surgical stimulation. Possible amelioration of isoflurane-induced neuroapoptosis by dexmedetomidine deserves further study. Further studies of the effect of gestational age, dose, duration of anesthesia and surgical stimulation on neuroapoptosis are needed.

Early Exposure to General Anesthesia Disrupts Spatial Organization of Presynaptic Vesicles in Nerve Terminals of the Developing Rat Subiculum

Exposure to general anesthesia (GA) during critical stages of brain development induces widespread neuronal apoptosis and causes long-lasting behavioral deficits in numerous animal species. Although several studies have focused on the morphological fate of neurons dying acutely by GA-induced developmental neuroapoptosis, the effects of an early exposure to GA on the surviving synapses remain unclear. The aim of this study is to study whether exposure to GA disrupts the fine regulation of the dynamic spatial organization and trafficking of synaptic vesicles in presynaptic terminals. We exposed postnatal day 7 (PND7) rat pups to a clinically relevant anesthetic combination of midazolam, nitrous oxide, and isoflurane and performed a detailed ultrastructural analysis of the synaptic vesicle architecture at presynaptic terminals in the subiculum of rats at PND 12. In addition to a significant decrease in the density of presynaptic vesicles, we observed a reduction of docked vesicles, as well as a reduction of vesicles located within 100 nm from the active zone, in animals 5 days after an initial exposure to GA. We also found that the synaptic vesicles of animals exposed to GA are located more distally with respect to the plasma membrane than those of sham control animals and that the distance between presynaptic vesicles is increased in GA-exposed animals compared to sham controls. We report that exposure of immature rats to GA during critical stages of brain development causes significant disruption of the strategic topography of presynaptic vesicles within the nerve terminals of the subiculum.

Review: effects of anesthetics on brain circuit formation

The results of several retrospective clinical studies suggest that exposure to anesthetic agents early in life is correlated with subsequent learning and behavioral disorders. Although ongoing prospective clinical trials may help to clarify this association, they remain confounded by numerous factors. Thus, some of the most compelling data supporting the hypothesis that a relatively short anesthetic exposure can lead to a long-lasting change in brain function are derived from animal models. The mechanism by which such changes could occur remains incompletely understood. Early studies identified anesthetic-induced neuronal apoptosis as a possible mechanism of injury, and more recent work suggests that anesthetics may interfere with several critical processes in brain development. The function of the mature brain requires the presence of circuits, established during development, which perform the computations underlying learning and cognition. In this review, we examine the mechanisms by which anesthetics could disrupt brain circuit formation, including effects on neuronal survival and neurogenesis, neurite growth and guidance, formation of synapses, and function of supporting cells. There is evidence that anesthetics can disrupt aspects of all of these processes, and further research is required to elucidate which are most relevant to pediatric anesthetic neurotoxicity.

Systemic physiology and neuroapoptotic profiles in young and adult rats exposed to surgery: A randomized controlled study comprising four different anaesthetic techniques

BACKGROUND

Experimental evidence indicates that general anaesthetics can induce apoptotic neurodegeneration in the developing brain. The majority of these studies have been performed in the absence of surgery and it currently remains unclear how the presence of surgical stimuli would influence neuroapoptosis as well as systemic homeostasis. Here we explored this possibility by performing dorsal skin flap surgery in young and adult rats under four distinct currently used anaesthesia regimens.

METHODS

Young (21-days) and adult (2 months) male Sprague-Dawley rats were randomized to 150 min exposure to one of four anaesthetics regimens: (i) sevoflurane/dexmedetomidine, (ii) sevoflurane/fentanyl; (iii) propofol/dexmedetomidine, and (iv) propofol/fentanyl. Animals underwent a dorsal skin flap procedure while physiologic, metabolic and biochemical parameters were closely monitored. Neuroapoptotic profiles were evaluated in the cortex, thalamus and hippocampus (CA1 and CA3) at the end of the procedure in each experimental group.

RESULTS

Significant perturbations of systemic homeostasis were found under all anaesthetic regimens. Hyperglycemia and decreased heart rate were particularly relevant in experimental groups receiving dexmedetomidine, while propofol administration was associated with increased systemic lactate levels and metabolic acidosis. A substantial difference in anaesthesia/surgery-induced neuroapoptosis was found between young and adult rats in several brain regions. Combination of sevoflurane and dexmedetomidine resulted in the highest number of caspase-3 positive cells, although the extent of cell death remained relatively low in all experimental groups.

CONCLUSION

Combination of anaesthesia and surgery induces significant perturbations of physiological parameters in both young and adult spontaneously breathing rats undergoing surgery. These observations further enlighten the need for detailed physiological monitoring under these experimental conditions. Although some statistically significant differences in activated caspase-3 profiles were detected between experimental groups, the overall extent of neuronal cell death remained very low under all conditions questioning, thereby, the physiological significance of apoptotic neurodegeneration in the context of anaesthesia and surgery.

Transient activation of microglia following acute alcohol exposure in developing mouse neocortex is primarily driven by BAX-dependent neurodegeneration

Fetal alcohol exposure is the most common known cause of preventable mental retardation, yet we know little about how microglia respond to, or are affected by, alcohol in the developing brain in vivo. Using an acute (single day) model of moderate (3 g/kg) to severe (5 g/kg) alcohol exposure in postnatal day (P) 7 or P8 mice, we found that alcohol-induced neuroapoptosis in the neocortex is closely correlated in space and time with the appearance of activated microglia near dead cells. The timing and molecular pattern of microglial activation varied with the level of cell death. Although microglia rapidly mobilized to contact and engulf late-stage apoptotic neurons, apoptotic bodies temporarily accumulated in neocortex, suggesting that in severe cases of alcohol toxicity the neurodegeneration rate exceeds the clearance capacity of endogenous microglia. Nevertheless, most dead cells were cleared and microglia began to deactivate within 1-2 days of the initial insult. Coincident with microglial activation and deactivation, there was a transient increase in expression of pro-inflammatory factors, TNFα and IL-1β, after severe (5 g/kg) but not moderate (3 g/kg) EtOH levels. Alcohol-induced microglial activation and pro-inflammatory factor expression were largely abolished in BAX null mice lacking neuroapoptosis, indicating that microglial activation is primarily triggered by apoptosis rather than the alcohol. Therefore, acute alcohol exposure in the developing neocortex causes transient microglial activation and mobilization, promoting clearance of dead cells and tissue recovery. Moreover, cortical microglia show a remarkable capacity to rapidly deactivate following even severe neurodegenerative insults in the developing brain.

Neurodevelopmental implications of the general anesthesia in neonate and infants

Each year, about six million children, including 1.5 million infants, in the United States undergo surgery with general anesthesia, often requiring repeated exposures. However, a crucial question remains of whether neonatal anesthetics are safe for the developing central nervous system (CNS). General anesthesia encompasses the administration of agents that induce analgesic, sedative, and muscle relaxant effects. Although the mechanisms of action of general anesthetics are still not completely understood, recent data have suggested that anesthetics primarily modulate two major neurotransmitter receptor groups, either by inhibiting N-methyl-D-aspartate (NMDA) receptors, or conversely by activating γ-aminobutyric acid (GABA) receptors. Both of these mechanisms result in the same effect of inhibiting excitatory activity of neurons. In developing brains, which are more sensitive to disruptions in activity-dependent plasticity, this transient inhibition may have longterm neurodevelopmental consequences. Accumulating reports from preclinical studies show that anesthetics in neonates cause cellular toxicity including apoptosis and neurodegeneration in the developing brain. Importantly, animal and clinical studies indicate that exposure to general anesthetics may affect CNS development, resulting in long-lasting cognitive and behavioral deficiencies, such as learning and memory deficits, as well as abnormalities in social memory and social activity. While the casual relationship between cellular toxicity and neurological impairments is still not clear, recent reports in animal experiments showed that anesthetics in neonates can affect neurogenesis, which could be a possible mechanism underlying the chronic effect of anesthetics. Understanding the cellular and molecular mechanisms of anesthetic effects will help to define the scope of the problem in humans and may lead to preventive and therapeutic strategies. Therefore, in this review, we summarize the current evidence on neonatal anesthetic effects in the developmental CNS and discuss how factors influencing these processes can be translated into new therapeutic strategies.

Hyperexcitability of rat thalamocortical networks after exposure to general anesthesia during brain development

Prevailing literature supports the idea that common general anesthetics (GAs) cause long-term cognitive changes and neurodegeneration in the developing mammalian brain, especially in the thalamus. However, the possible role of GAs in modifying ion channels that control neuronal excitability has not been taken into consideration. Here we show that rats exposed to GAs at postnatal day 7 display a lasting reduction in inhibitory synaptic transmission, an increase in excitatory synaptic transmission, and concomitant increase in the amplitude of T-type calcium currents (T-currents) in neurons of the nucleus reticularis thalami (nRT). Collectively, this plasticity of ionic currents leads to increased action potential firing in vitro and increased strength of pharmacologically induced spike and wave discharges in vivo. Selective blockade of T-currents reversed neuronal hyperexcitability in vitro and in vivo. We conclude that drugs that regulate thalamic excitability may improve the safety of GAs used during early brain development.

Anesthesia for the young child undergoing ambulatory procedures: current concerns regarding harm to the developing brain

PURPOSE OF REVIEW

Sedation and anesthesia are often necessary for children at any age, and are frequently provided in ambulatory settings. Concerns have mounted, based on both laboratory studies including various mammalian species and retrospective human clinical studies, that the very drugs that induce sedation and anesthesia may trigger an injury in the developing brain, resulting in long-lasting neurobehavioral consequences.

RECENT FINDINGS

New retrospective studies further augment these concerns. Specifically, recent studies support that a single anesthesia exposure before age 3 may increase the risk for long-term disabilities in language acquisition and abstract reasoning, and that exposure to two or more anesthetics before age 2 nearly doubles the risk for an attention-deficit hyperactivity disorder diagnosis by age 19. However, methodological limitations preclude final conclusions or change in practice based on these reports, as retrospective studies cannot prove causation. Ongoing prospective clinical studies such as 'General Anesthesia and Apoptosis Study', 'Pediatric Anesthesia NeuroDevelopment Assessment', and 'Mayo Safety in Kids' trials will offer more answers in the future. Meanwhile, laboratory experiments continue to describe differential morphologic injury to individual structures in the neuropil, and have identified mitochondrial dysfunction and neuroinflammation as potential links in the injury process. Additionally, concepts for protection against anesthesia-induced neurotoxicity continue to be tested in the laboratory.

SUMMARY

Results from ongoing prospective clinical trials and translational research will help clarify whether anesthesia-associated neurotoxicity affects the developing human brain, including whether it causes long-term disability, and may further identify the injury mechanisms and potential strategies for protection. Currently, the available evidence does not support a change in practice.

Hippocampal granule cell pathology in epilepsy - a possible structural basis for comorbidities of epilepsy?

Temporal lobe epilepsy in both animals and humans is characterized by abnormally integrated hippocampal dentate granule cells. Among other abnormalities, these cells make axonal connections with inappropriate targets, grow dendrites in the wrong direction, and migrate to ectopic locations. These changes promote the formation of recurrent excitatory circuits, leading to the appealing hypothesis that these abnormal cells may by epileptogenic. While this hypothesis has been the subject of intense study, less attention has been paid to the possibility that abnormal granule cells in the epileptic brain may also contribute to comorbidities associated with the disease. Epilepsy is associated with a variety of general findings, such as memory disturbances and cognitive dysfunction, and is often comorbid with a number of other conditions, including schizophrenia and autism. Interestingly, recent studies implicate disruption of common genes and gene pathways in all three diseases. Moreover, while neuropsychiatric conditions are associated with changes in a variety of brain regions, granule cell abnormalities in temporal lobe epilepsy appear to be phenocopies of granule cell deficits produced by genetic mouse models of autism and schizophrenia, suggesting that granule cell dysmorphogenesis may be a common factor uniting these seemingly diverse diseases. Disruption of common signaling pathways regulating granule cell neurogenesis may begin to provide mechanistic insight into the cooccurrence of temporal lobe epilepsy and cognitive and behavioral disorders.

Morphological features of the neonatal brain following exposure to regional anesthesia during labor and delivery

INTRODUCTION

Recent animal and human epidemiological studies suggest that early childhood exposure to anesthesia may have adverse effects on brain development. As more than 50% of pregnant women in the United States and one-third in the United Kingdom receive regional anesthesia during labor and delivery, understanding the effects of perinatal anesthesia on postnatal brain development has important public health relevance.

METHODS

We used high-resolution magnetic resonance imaging (MRI) to assess the effects of regional anesthesia during labor and delivery as part of a larger study of perinatal exposures on the morphological features of the neonatal brain. We mapped morphological features of the cortical surface in 37 healthy infants, 24 exposed and 13 unexposed to regional anesthesia at delivery, who were scanned within the first 6 weeks of life.

RESULTS

Infants exposed to maternal anesthesia compared with unexposed infants had greater local volumes in portions of the frontal and occipital lobes bilaterally and right posterior portion of the cingulate gyrus. Longer durations of exposure to anesthesia correlated positively with local volumes in the occipital lobe.

CONCLUSIONS

Anesthesia exposure during labor and delivery was associated with larger volumes in portions of the frontal and occipital lobes and cingulate gyrus in neonates. Longitudinal MRI studies are needed to determine whether these morphological effects of anesthesia persist and what their consequences on cognition and behavior may be.

Developmental neurotoxicity of alcohol and anesthetic drugs is augmented by co-exposure to caffeine

Anesthetic and anti-epileptic drugs used in pediatric and obstetric medicine and several drugs, including alcohol, that are abused by pregnant women, trigger widespread neuroapoptosis in the developing brain of several animal species, including non-human primates. Caffeine (CAF) is often administered to premature infants to stimulate respiration, and these infants are also exposed simultaneously to anesthetic drugs for procedural sedation and/or surgical procedures. Pregnant women who abuse alcohol or other apoptogenic drugs also may heavily consume CAF. We administered CAF to infant mice alone or in combination with alcohol, phencyclidine, diazepam, midazolam, ketamine, or isoflurane, which are drugs of abuse and/or drugs frequently used in pediatric medicine, and found that CAF weakly triggers neuroapoptosis by itself and markedly potentiates the neuroapoptogenic action of each of these other drugs. Exposure of infant mice to CAF + phencyclidine resulted in long-term impairment in behavioral domains relevant to attention deficit/hyperactivity disorder, whereas exposure to CAF + diazepam resulted in long-term learning/memory impairment. At doses used in these experiments, these behavioral impairments either did not occur or were substantially less pronounced in mice exposed to CAF alone or to phencyclidine or diazepam alone. CAF currently enjoys the reputation of being highly beneficial and safe for use in neonatal medicine. Our data suggest the need to consider whether CAF may have harmful as well as beneficial effects on the developing brain, and the need for research aimed at understanding the full advantage of its beneficial effects while avoiding its potentially harmful effects.

Dexmedetomidine reduces isoflurane-induced neuroapoptosis partly by preserving PI3K/Akt pathway in the hippocampus of neonatal rats

Prolonged exposure to volatile anesthetics, such as isoflurane and sevoflurane, causes neurodegeneration in the developing animal brains. Recent studies showed that dexmedetomidine, a selective α2-adrenergic agonist, reduced isoflurane-induced cognitive impairment and neuroapoptosis. However, the mechanisms for the effect are not completely clear. Thus, we investigated whether exposure to isoflurane or sevoflurane at an equivalent dose for anesthesia during brain development causes different degrees of neuroapoptosis and whether this neuroapoptosis is reduced by dexmedetomidine via effects on PI3K/Akt pathway that can regulate cell survival. Seven-day-old (P7) neonatal Sprague-Dawley rats were randomly exposed to 0.75% isoflurane, 1.2% sevoflurane or air for 6 h. Activated caspase-3 was detected by immunohistochemistry and Western blotting. Phospho-Akt, phospho-Bad, Akt, Bad and Bcl-xL proteins were detected by Western blotting in the hippocampus at the end of exposure. Also, P7 rats were pretreated with various concentrations of dexmedetomidine alone or together with PI3K inhibitor LY294002, and then exposed to 0.75% isoflurane. Terminal deoxyribonucleotide transferase-mediated dUTP nick end labeling (TUNEL) and activated caspase-3 were used to detect neuronal apoptosis in their hippocampus. Isoflurane, not sevoflurane at the equivalent dose, induced significant neuroapoptosis, decreased the levels of phospho-Akt and phospho-Bad proteins, increased the expression of Bad protein and reduced the ratio of Bcl-xL/Bad in the hippocampus. Dexmedetomidine pretreatment dose-dependently inhibited isoflurane-induced neuroapoptosis and restored protein expression of phospho-Akt and Bad as well as the Bcl-xL/Bad ratio induced by isoflurane. Pretreatment with single dose of 75 µg/kg dexmedetomidine provided a protective effect similar to that with three doses of 25 µg/kg dexmedetomidine. Moreover, LY294002, partly inhibited neuroprotection of dexmedetomidine. Our results suggest that dexmedetomidine pretreatment provides neuroprotection against isoflurane-induced neuroapoptosis in the hippocampus of neonatal rats by preserving PI3K/Akt pathway activity.

Isoflurane-induced apoptosis of neurons and oligodendrocytes in the fetal rhesus macaque brain

BACKGROUND

The authors have previously shown that exposure of the neonatal nonhuman primate (NHP) brain to isoflurane for 5 h causes widespread acute apoptotic degeneration of neurons and oligodendrocyte. The current study explored the potential apoptogenic action of isoflurane in the fetal NHP brain.

METHODS

Fetal rhesus macaques at gestational age of 120 days (G120) were exposed in utero for 5 h to isoflurane anesthesia (n = 5) or to no anesthesia (control condition; n = 4), and all regions of the brain were systematically evaluated 3 h later for evidence of apoptotic degeneration of neurons or glia.

RESULTS

Exposure of the G120 fetal NHP brain to isoflurane caused a significant increase in apoptosis of neurons and of oligodendrocytes at a stage when oligodendrocytes were just beginning to myelinate axons. The neuroapoptosis response was most prominent in the cerebellum, caudate, putamen, amygdala, and several cerebrocortical regions. Oligodendrocyte apoptosis was diffusely distributed over many white matter regions. The total number of apoptotic profiles (neurons + oligodendrocytes) in the isoflurane-exposed brains was increased 4.1-fold, compared with the brains from drug-naive controls. The total number of oligodendrocytes deleted by isoflurane was higher than the number of neurons deleted.

CONCLUSIONS

Isoflurane anesthesia for 5 h causes death of neurons and oligodendrocytes in the G120 fetal NHP brain. In the fetal brain, as the authors previously found in the neonatal NHP brain, oligodendrocytes become vulnerable when they are just achieving myelination competence. The neurotoxic potential of isoflurane increases between the third trimester (G120) and the neonatal period in the NHP brain.

Adverse effect of inhalational anesthetics on the developing brain

We did a PubMed search and summarized studies on the potential adverse effect of anesthetics especially neurotoxicity in the developing brain, so named anesthesia-induced developmental neurotoxicity. Even though many experimental studies using animal models indicated some adverse effect of anesthetics, more evidence is needed before a recommendation can be made to change the way those anesthetics are used in the pediatric population. Two large clinical trials are underway and may provide insight to the potential human neurotoxic effect of anesthetics.

Neonatal pain

Effective management of procedural and postoperative pain in neonates is required to minimize acute physiological and behavioral distress and may also improve acute and long-term outcomes. Painful stimuli activate nociceptive pathways, from the periphery to the cortex, in neonates and behavioral responses form the basis for validated pain assessment tools. However, there is an increasing awareness of the need to not only reduce acute behavioral responses to pain in neonates, but also to protect the developing nervous system from persistent sensitization of pain pathways and potential damaging effects of altered neural activity on central nervous system development. Analgesic requirements are influenced by age-related changes in both pharmacokinetic and pharmacodynamic response, and increasing data are available to guide safe and effective dosing with opioids and paracetamol. Regional analgesic techniques provide effective perioperative analgesia, but higher complication rates in neonates emphasize the importance of monitoring and choice of the most appropriate drug and dose. There have been significant improvements in the understanding and management of neonatal pain, but additional research evidence will further reduce the need to extrapolate data from older age groups. Translation into improved clinical care will continue to depend on an integrated approach to implementation that encompasses assessment and titration against individual response, education and training, and audit and feedback.

Regional anesthesia in neonates and infants

Optimal pain management can significantly impact the surgical outcome and length of stay in the neonatal intensive care unit (NICU). Regional anesthesia is an effective alternative that can be used in both term and preterm neonates. A variety of neuraxial and peripheral nerve blocks have been used for specific surgical and NICU procedures. Ultrasound guidance has increased the feasibility of using these techniques in neonates. Education and training staff in the use of continuous epidural infusions are important prerequisites for successful implementation of regional anesthesia in NICU management protocols.

Drug-Induced Apoptosis: Mechanism by which Alcohol and Many Other Drugs Can Disrupt Brain Development

Maternal ingestion of alcohol during pregnancy can cause a disability syndrome termed Fetal Alcohol Spectrum Disorder (FASD), which may include craniofacial malformations, structural pathology in the brain, and a variety of long-term neuropsychiatric disturbances. There is compelling evidence that exposure to alcohol during early embryogenesis (4th week of gestation) can cause excessive death of cell populations that are essential for normal development of the face and brain. While this can explain craniofacial malformations and certain structural brain anomalies that sometimes accompany FASD, in many cases these features are absent, and the FASD syndrome manifests primarily as neurobehavioral disorders. It is not clear from the literature how alcohol causes these latter manifestations. In this review we will describe a growing body of evidence documenting that alcohol triggers widespread apoptotic death of neurons and oligodendroglia (OLs) in the developing brain when administered to animals, including non-human primates, during a period equivalent to the human third trimester of gestation. This cell death reaction is associated with brain changes, including overall or regional reductions in brain mass, and long-term neurobehavioral disturbances. We will also review evidence that many drugs used in pediatric and obstetric medicine, including general anesthetics (GAs) and anti-epileptics (AEDs), mimic alcohol in triggering widespread apoptotic death of neurons and OLs in the third trimester-equivalent animal brain, and that human children exposed to GAs during early infancy, or to AEDs during the third trimester of gestation, have a significantly increased incidence of FASD-like neurobehavioral disturbances. These findings provide evidence that exposure of the developing human brain to GAs in early infancy, or to alcohol or AEDs in late gestation, can cause FASD-like neurodevelopmental disability syndromes. We propose that the mechanism by which alcohol, GAs and AEDs produce neurobehavioral deficit syndromes is by triggering apoptotic death and deletion of neurons and OLs (or their precursors) from the developing brain. Therefore, there is a need for research aimed at deciphering mechanisms by which these agents trip the apoptosis trigger, the ultimate goal being to learn how to prevent these agents from causing neurodevelopmental disabilities.

Neither Xenon nor Fentanyl Induces Neuroapoptosis in the Newborn Pig Brain

Background:

Some inhalation anesthetics increase apoptotic cell death in the developing brain. Xenon, an inhalation anesthetic, increases neuroprotection when combined with therapeutic hypothermia after hypoxic-ischemic brain injury in newborn animals. The authors, therefore, examined whether there was any neuroapoptotic effect of breathing 50% xenon with continuous fentanyl sedation for 24 h at normothermia or hypothermia on newborn pigs.

Methods:

Twenty-six healthy pigs (&lt;24-h old) were randomized into four groups: (1) 24 h of 50% inhaled xenon with fentanyl at hypothermia (Trec = 33.5°C), (2) 24 h of 50% inhaled xenon with fentanyl at normothermia (Trec = 38.5°C), (3) 24 h of fentanyl at normothermia, or (4) nonventilated juvenile controls at normothermia. Five additional nonrandomized pigs inhaled 2% isoflurane at normothermia for 24 h to verify any proapoptotic effect of inhalation anesthetics in our model. Pathological cells were morphologically assessed in cortex, putamen, hippocampus, thalamus, and white matter. To quantify the findings, immunostained cells (caspase-3 and terminal deoxynucleotidyl transferase–mediated deoxyuridine-triphosphate nick-end labeling) were counted in the same brain regions.

Results:

For groups (1) to (4), the total number of apoptotic cells was less than 5 per brain region, representing normal developmental neuroapoptosis. After immunostaining and cell counting, regression analysis showed that neither 50% xenon with fentanyl nor fentanyl alone increased neuroapoptosis. Isoflurane caused on average a 5- to 10-fold increase of immunostained cells.

Conclusion:

At normothermia or hypothermia, neither 24 h of inhaled 50% xenon with fentanyl sedation nor fentanyl alone induces neuroapoptosis in the neonatal pig brain. Breathing 2% isoflurane increases neuroapoptosis in neonatal pigs.

Propofol-induced apoptosis of neurones and oligodendrocytes in fetal and neonatal rhesus macaque brain

BACKGROUND

Exposure of the fetal or neonatal non-human primate (NHP) brain to isoflurane or ketamine for 5 h causes widespread apoptotic degeneration of neurones, and exposure to isoflurane also causes apoptotic degeneration of oligodendrocytes (OLs). The present study explored the apoptogenic potential of propofol in the fetal and neonatal NHP brain.

METHOD

Fetal rhesus macaques at gestational age 120 days were exposed in utero, or postnatal day 6 rhesus neonates were exposed directly for 5 h to propofol anaesthesia (n=4 fetuses; and n=4 neonates) or to no anaesthesia (n=4 fetuses; n=5 neonates), and the brains were systematically evaluated 3 h later for evidence of apoptotic degeneration of neurones or glia.

RESULTS

Exposure of fetal or neonatal NHP brain to propofol caused a significant increase in apoptosis of neurones, and of OLs at a stage when OLs were just beginning to myelinate axons. Apoptotic degeneration affected similar brain regions but to a lesser extent than we previously described after isoflurane. The number of OLs affected by propofol was approximately equal to the number of neurones affected at both developmental ages. In the fetus, neuroapoptosis affected particularly subcortical and caudal regions, while in the neonate injury involved neocortical regions in a distinct laminar pattern and caudal brain regions were less affected.

CONCLUSIONS

Propofol anaesthesia for 5 h caused death of neurones and OLs in both the fetal and neonatal NHP brain. OLs become vulnerable to the apoptogenic action of propofol when they are beginning to achieve myelination competence.

Modeling anesthetic developmental neurotoxicity using human stem cells

Mounting preclinical evidence in rodents and nonhuman primates has demonstrated that prolonged exposure of developing animals to general anesthetics can induce widespread neuronal cell death followed by long-term memory and learning disabilities. In vitro experimental evidence from cultured neonatal animal neurons confirmed the in vivo findings. However, there is no direct clinical evidence of the detrimental effects of anesthetics in human fetuses, infants, or children. Development of an in vitro neurogenesis system using human stem cells has opened up avenues of research for advancing our understanding of human brain development and the issues relevant to anesthetic-induced developmental toxicity in human neuronal lineages. Recent studies from our group, as well as other groups, showed that isoflurane influences human neural stem cell proliferation and neurogenesis, whereas ketamine induces neuroapoptosis. Application of this high throughput in vitro stem cell neurogenesis approach is a major stride toward ensuring the safety of anesthetic agents in young children. This in vitro human model allows us to (1) screen the toxic effects of various anesthetics under controlled conditions during intense neuronal growth, (2) find the trigger for the anesthetic-induced catastrophic chain of toxic events, and (3) develop prevention strategies to avoid this toxic effect. In this article, we reviewed the current findings in anesthetic-induced neurotoxicity studies, specifically focusing on the in vitro human stem cell model.

Long-term effects of neonatal single or multiple isoflurane exposures on spatial memory in rats

General anesthetics are neurotoxic to neonatal rodents and non-human primates. Neonatal exposure to general anesthetics has been associated with long-term cognitive deficits in animal models. Some data from humans are consistent with long-term deleterious effects of anesthetic exposure early in life on cognitive development, with multiple exposures to general anesthetics being particularly damaging. We sought to determine whether repeated exposure of neonatal rats to anesthesia was associated with long-term cognitive impairments and whether the magnitude of impairments was greater than that resulting from a single exposure. Male or female Long–Evans rat pups were exposed to 1.8% isoflurane for 2 h on postnatal day (P) 7, or for 2 h each on P7, P10, and P13. Testing in a spatial working memory task began on P91. Rats that were repeatedly exposed to isoflurane were impaired relative to controls in the spatial working memory task. Male rats that received a single exposure to isoflurane showed an unexpected facilitation in spatial memory performance. These results support the hypothesis that multiple neonatal exposures to general anesthesia are associated with greater long-term cognitive impairment than a single exposure. The findings are congruent with human epidemiological studies reporting long-term cognitive impairments following multiple but not single general anesthetics early in life.

Functional implications of an early exposure to general anesthesia: are we changing the behavior of our children?

There is a rapidly growing body of animal and clinical evidence suggesting that the exposure to anesthetics and sedatives during the critical stages of brain development results in long-lasting (perhaps permanent) impairment in cognitive development in a variety of mammalian species. With improved understanding of the mechanisms responsible for behavioral outcomes of anesthesia-induced developmental neurotoxicity, there is hope for development of protective strategies that will enable safe use of anesthesia in the youngest members of our society. Here, I review presently available evidence regarding anesthesia-induced neurocognitive and social behavioral impairments and possible strategies for preventing them. I also review limited and somewhat controversial evidence that examines the effects of nociception and surgical stimulation on anesthesia--induced developmental neurotoxicity.

Diagnostic yield of EGD in children: a retrospective single-center study of 1000 cases

BACKGROUND

Pediatric EGD is increasingly being used, but few studies have recently evaluated the diagnostic yield.

OBJECTIVE

To assess the association between presenting clinical symptoms and the likelihood of significant endoscopic and histologic abnormalities for initial diagnostic endoscopy.

DESIGN

Retrospective cohort study.

SETTING

Large, tertiary care children's hospital.

PATIENTS

One thousand patients, ages 1 month to 18 years, who underwent initial diagnostic EGD in 2009 and 2010.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Endoscopic and histologic abnormalities.

RESULTS

The most common primary indications for endoscopy were generalized abdominal pain (28.7%), gastroesophageal reflux (11.7%), and failure to thrive (9.5%). The overall prevalence of an endoscopic abnormality was 34.7% and of a histologic abnormality, 40.4%. The highest rates of endoscopic abnormalities were found in patients with strictures on upper GI radiology (100%), foreign body (88%), and GI bleeding (57%). The highest rates of histologic abnormalities were in patients with positive celiac screening (91%), foreign body (88%), dysphagia (51%), and GI bleeding (49%), and the lowest rates of histologic abnormalities were miscellaneous indications (17%), strictures on radiology (25%), and reflux (26%). Females and patients < 1 year of age had lower rates of abnormal histologic abnormalities.

LIMITATIONS

Retrospective nature of the study, limitation to a single tertiary care center, and simplification of complex patient presentations to a single indication.

CONCLUSIONS

Rates of endoscopic and histologic abnormalities from EGD vary based on age and indication for endoscopy, and this should be factored into the decision to proceed with initial endoscopy along with consideration of adverse event rates and effects of anesthesia.

Early exposure to general anesthesia disturbs mitochondrial fission and fusion in the developing rat brain

BACKGROUND

General anesthetics induce apoptotic neurodegeneration in the developing mammalian brain. General anesthesia (GA) also causes significant disturbances in mitochondrial morphogenesis during intense synaptogenesis. Mitochondria are dynamic organelles that undergo remodeling via fusion and fission. The fine balance between these two opposing processes determines mitochondrial morphometric properties, allowing for their regeneration and enabling normal functioning. As mitochondria are exquisitely sensitive to anesthesia-induced damage, we examined how GA affects mitochondrial fusion/fission.

METHODS

Seven-day-old rat pups received anesthesia containing a sedative dose of midazolam followed by a combined nitrous oxide and isoflurane anesthesia for 6 h.

RESULTS

GA causes 30% upregulation of reactive oxygen species (n = 3-5 pups/group), accompanied by a 2-fold downregulation of an important scavenging enzyme, superoxide dismutase (n = 6 pups/group). Reactive oxygen species upregulation is associated with impaired mitochondrial fission/fusion balance, leading to excessive mitochondrial fission. The imbalance between fission and fusion is due to acute sequestration of the main fission protein, dynamin-related protein 1, from the cytoplasm to mitochondria, and its oligomerization on the outer mitochondrial membrane. These are necessary steps in the formation of the ring-like structures that are required for mitochondrial fission. The fission is further promoted by GA-induced 40% downregulation of cytosolic mitofusin-2, a protein necessary for maintaining the opposing process, mitochondrial fusion (n = 6 pups/group).

CONCLUSIONS

Early exposure to GA causes acute reactive oxygen species upregulation and disturbs the fine balance between mitochondrial fission and fusion, leading to excessive fission and disturbed mitochondrial morphogenesis. These effects may play a causal role in GA-induced developmental neuroapoptosis.

Alcohol-induced apoptosis of oligodendrocytes in the fetal macaque brain

Background

In utero exposure of the fetal non-human primate (NHP) brain to alcohol on a single occasion during early or late third-trimester gestation triggers widespread acute apoptotic death of cells in both gray and white matter (WM) regions of the fetal brain. In a prior publication, we documented that the dying gray matter cells are neurons, and described the regional distribution and magnitude of this cell death response. Here, we present new findings regarding the magnitude, identity and maturational status of the dying WM cells in these alcohol-exposed fetal NHP brains.

Results

Our findings document that the dying WM cells belong to the oligodendrocyte (OL) lineage. OLs become vulnerable when they are just beginning to generate myelin basic protein in preparation for myelinating axons, and they remain vulnerable throughout later stages of myelination. We found no evidence linking astrocytes, microglia or OL progenitors to this WM cell death response. The mean density (profiles per mm³) of dying WM cells in alcohol-exposed brains was 12.7 times higher than the mean density of WM cells dying by natural apoptosis in drug-naive control brains.

Conclusions

In utero exposure of the fetal NHP brain to alcohol on a single occasion triggers widespread acute apoptotic death of neurons (previous study) and of OLs (present study) throughout WM regions of the developing brain. The rate of OL apoptosis in alcohol-exposed brains was 12.7 times higher than the natural OL apoptosis rate. OLs become sensitive to the apoptogenic action of alcohol when they are just beginning to generate constituents of myelin in their cytoplasm, and they remain vulnerable throughout later stages of myelination. There is growing evidence for a similar apoptotic response of both neurons and OLs following exposure of the developing brain to anesthetic and anticonvulsant drugs. Collectively, this body of evidence raises important questions regarding the role that neuro and oligo apoptosis may play in the human condition known as fetal alcohol spectrum disorder (FASD), and also poses a question whether other apoptogenic drugs, although long considered safe for pediatric/obstetric use, may have the potential to cause iatrogenic FASD-like developmental disability syndromes.

Sevoflurane induces short-term changes in proteins in the cerebral cortices of developing rats

BACKGROUND

Exposure to intravenous or inhaled anesthetic agents has potential deleterious effects on the developing brain. However, the mechanisms are not clear. Herein, we investigated protein expression changes in neonatal rat brains after exposure to sevoflurane, an inhalational anesthetic commonly used for pediatric patients.

METHODS

Seven-day-old rats were treated with 1.8% sevoflurane or 30% oxygen for 4 h. Cerebral cortices were obtained at 3 h and 3 days after sevoflurane exposure for cell apoptosis detection, proteomic analysis and Western blotting.

RESULTS

There was a significant increase of cleaved caspase 3 at 3 h after sevoflurane exposure. Six proteins had 1.5-fold or higher changes in expression at 3 h after sevoflurane anesthesia as compared with sham-treated pups. No proteins had this degree of change at 3 days after sevoflurane anesthesia. Proteins whose expression was downregulated included collapsin response mediator protein-1 (CRMP-1), truncated CRMP-4, beta-tubulin IIc and neuron-specific class III beta-tubulin. These four proteins are important for neuronal migration and differentiation. Adenosine triphosphate synthase beta subunit, a protein associated with energy metabolism, was also downregulated. Guanine nucleotide-binding protein beta 1, a signaling protein, was upregulated. Sevoflurane also increased phosphorylation of glycogen synthase kinase 3β (GSK-3β) at 3 h after anesthesia and inhibited the normal increase of GSK-3β at 72 h after anesthesia.

CONCLUSION

These findings suggest that sevoflurane may cause short-term neuronal apoptosis and disturbances of neuronal migration, differentiation and energy metabolism in neonatal rat brains, and that these disturbances may contribute to its neurodegenerative effects.