Anesthetics and sedatives: toxic or protective for the developing brain?

Bexarotene drives the self-renewing proliferation of adult neural stem cells, promotes neuron-glial fate shift, and regulates late neuronal differentiation

Treatment with bexarotene, a selective retinoid X receptor (RXR) agonist, significantly improves behavioral dysfunctions in various neurodegenerative animal models. Additionally, it activates neurodevelopmental and plasticity pathways in the brains of adult mice. Our objective was to investigate the impact of RXR activation by bexarotene on adult neural stem cells (aNSC) and their cell lineages. To achieve this, we treated NSCs isolated from the subventricular zone (SVZ) of adult rat brains from the proliferative stage to the differentiated status. The results showed that bexarotene-treated aNSC exhibited increased BrdU incorporation, SOX2+ dividing cell pairs, and cell migration from neurospheres, revealing that the treatment promotes self-renewing proliferation and cell motility in SVZ-aNCS. Furthermore, bexarotene induced a cell fate shift characterized by a significant increase in GFAP+/S100B+ differentiated astrocytes, which uncovers the participation of activated-RXR in astrogenesis. In the neuronal lineage, the fate shift was counteracted by bexarotene-induced enhancement of NeuN+ nuclei together with neurite network outgrowth, indicating that the RXR agonist stimulates SVZ-aNCS neuronal differentiation at later stages. These findings establish new connections between RXR activation, astro- and neurogenesis in the adult brain, and contribute to the development of therapeutic strategies targeting nuclear receptors for neural repair.

The miR-182-5p/GPX4 Pathway Contributes to Sevoflurane-Induced Ototoxicity via Ferroptosis

Our study aimed to investigate the role of ferroptosis in sevoflurane-induced hearing impairment and explore the mechanism of the microRNA-182-5p (miR-182-5p)/Glutathione Peroxidase 4 (GPX4) pathway in sevoflurane-induced ototoxicity. Immunofluorescence staining was performed using myosin 7a and CtBP2. Cell viability was assessed using the CCK-8 kit. Fe2+ concentration was measured using FerroOrange and Mi-to-FerroGreen fluorescent probes. The lipid peroxide level was assessed using BODIPY 581/591 C11 and MitoSOX fluorescent probes. The auditory brainstem response (ABR) test was conducted to evaluate the hearing status. Bioinformatics tools and dual luciferase gene reporter analysis were used to confirm the direct targeting of miR-182-5p on GPX4 mRNA. GPX4 and miR-182-5p expression in cells was assessed by qRT-PCR and Western blot. Ferrostatin-1 (Fer-1) pretreatment significantly improved hearing impairment and damage to ribbon synapses in mice caused by sevoflurane exposure. Immunofluorescence staining revealed that Fer-1 pretreatment reduced intracellular and mitochondrial iron overload, as well as lipid peroxide accumulation. Our findings indicated that miR-182-5p was upregulated in sevoflurane-exposed HEI-OC1 cells, and miR-182-5p regulated GPX4 expression by binding to the 3'UTR of GPX4 mRNA. The inhibition of miR-182-5p attenuated sevoflurane-induced iron overload and lipid peroxide accumulation. Our study elucidated that the miR-182-5p/GPX4 pathway was implicated in sevoflurane-induced ototoxicity by promoting ferroptosis.

General anesthetic agents induce neurotoxicity through astrocytes

ABSTRACT

Neuroscientists have recognized the importance of astrocytes in regulating neurological function and their influence on the release of glial transmitters. Few studies, however, have focused on the effects of general anesthetic agents on neuroglia or astrocytes. Astrocytes can also be an important target of general anesthetic agents as they exert not only sedative, analgesic, and amnesic effects but also mediate general anesthetic-induced neurotoxicity and postoperative cognitive dysfunction. Here, we analyzed recent advances in understanding the mechanism of general anesthetic agents on astrocytes, and found that exposure to general anesthetic agents will destroy the morphology and proliferation of astrocytes, in addition to acting on the receptors on their surface, which not only affect Ca2+ signaling, inhibit the release of brain-derived neurotrophic factor and lactate from astrocytes, but are even involved in the regulation of the pro- and anti-inflammatory processes of astrocytes. These would obviously affect the communication between astrocytes as well as between astrocytes and neighboring neurons, other neuroglia, and vascular cells. In this review, we summarize how general anesthetic agents act on neurons via astrocytes, and explore potential mechanisms of action of general anesthetic agents on the nervous system. We hope that this review will provide a new direction for mitigating the neurotoxicity of general anesthetic agents.

Effect of General Anesthetic Agents on Microglia

The effects of general anesthetic agents (GAAs) on microglia and their potential neurotoxicity have attracted the attention of neuroscientists. Microglia play important roles in the inflammatory process and in neuromodulation of the central nervous system. Microglia-mediated neuroinflammation is a key mechanism of neurocognitive dysfunction during the perioperative period. Microglial activation by GAAs induces anti-inflammatory and pro-inflammatory effects in microglia, suggesting that GAAs play a dual role in the mechanism of postoperative cognitive dysfunction. Understanding of the mechanisms by which GAAs regulate microglia may help to reduce the incidence of postoperative adverse effects. Here, we review the actions of GAAs on microglia and the consequent changes in microglial function. We summarize clinical and animal studies associating microglia with general anesthesia and describe how GAAs interact with neurons via microglia to further explore the mechanisms of action of GAAs in the nervous system.

Editorial Commentary: The Pediatric Knee: Ultrasound Could Replace Magnetic Resonance Imaging for Evaluating a Discoid Lateral Meniscus

Magnetic resonance imaging has been referred to as the gold standard diagnostic modality for meniscal pathology in the adult knee. However, there are multiple issues with reliance on magnetic resonance imaging for evaluating the meniscus in children. Diagnostic accuracy for meniscus pathology in children is not as high as with adults. Additionally, young children often cannot tolerate lying still for the study and require sedation, with a small but non-zero risk of anesthetic complication and risk motion artifact even with sedation. Ultrasound can be used to reliably diagnose a discoid lateral meniscus in a testing environment that is well tolerated by young children.

Morphine use in the neonatal period and later neuropsychological development: a systematic review

AIM

To identify and evaluate the evidence documenting the association between neonatal morphine and later childhood neuropsychological development.

METHOD

We conducted a systematic literature search of eight electronic databases from inception until June 2019. We included all randomized controlled trials (RCTs) and cohort studies recruiting neonates who received morphine treatment, and measuring neuropsychological development outcomes with a minimum follow-up of 6 months.

RESULTS

Twelve separate reports from three RCTs and five cohort studies met our inclusion criteria. Owing to the small number of the included trials and the variable study designs, a meta-analysis was not performed. The findings from this review indicated that neonatal morphine use had no adverse effects on behaviour, cognition, motor, and executive function development at 8 to 9 years and earlier; except for the inconsistent conclusions on internalizing behavioural problems at 5 to 7 years and cognitive and motor developments at 18 months.

INTERPRETATION

Why a child needs morphine may have a more profound impact on later neuropsychological development than morphine itself. The small number, high heterogeneity, and limitations of the included studies limit confidence in the result of this systematic review.

Comparison of total cost and outcomes between single-stage open reduction and Pemberton periacetabular osteotomy operation and two separate consecutive operations in treatment of bilateral developmental hip dysplasia in children at walking age

Open reduction and Pemberton periacetabular osteotomy (PPO) is one of the most preferred techniques for the treatment of developmental hip dyslaplasia (DDH) after the walking age. Performing the surgery as a one-stage operation or two separate consecutive operations is a controversial issue. In this study, we aimed to compare the outcomes, length of hospitalization and total cost between the patients whom had single-stage open reduction and PPO or two consecutive operations due to bilateral DDH in the walking age children. One hundred thirty patients with bilateral DDH had undergone open reduction and PPO for both hips. Seventy-five patients had one-stage open reduction and PPO for both of the hips, whereas 55 patients have two separate consecutive operations. Total time of exposure to anesthetics, blood loss and duration of operation were noted. Hospitalization period and total treatment costs were also noted for each patient. There was no statistically significant difference between the groups regarding the preoperative and postoperative AIs (P > 0.05). Comparing the total cost, length of hospitalization, exposure to anesthetics, perioperative blood loss, there was statistically significant difference between the groups (P < 0.005). Single-stage surgery had favorable outcomes. Major benefits of single-stage surgery for treatment of bilateral DDH are the reduced costs, anesthesia duration, intraoperative blood loss and hospitalization period. Also it can be presumed that prolonged immobilization can lead to loss of bone strength and resulting in fragility fractures. So single-stage open reduction and PPO for bilateral DDH can be preferred in experienced clinics.

A Pilot Randomized Controlled Trial of Outcomes Associated with Parent-Nurse Controlled Analgesia vs. Continuous Opioid Infusion in the Neonatal Intensive Care Unit

PURPOSE

Prospectively compare parent/nurse controlled analgesia (PNCA) to continuous opioid infusion (COI) in the post-operative neonatal intensive care unit (NICU) population.

DESIGN/METHODS

A randomized controlled trial compared neonates treated with morphine PNCA to those treated with morphine COI. The primary outcome was average opioid consumption up to 3 post-operative days. Secondary outcomes included 1) pain intensity, 2) adverse events that may be directly related to opioid consumption, and 3) parent and nurse satisfaction.

RESULTS

The sample consisted of 25 post-operative neonates and young infants randomized to either morphine PNCA (n = 16) or COI (n = 9). Groups differed significantly on daily opioid consumption, with the PNCA group receiving significantly less opioid (P = .02). Groups did not differ on average pain score or frequency of adverse events (P values > .05). Parents in both groups were satisfied with their infant's pain management and parents in the PNCA group were slightly more satisfied with their level of involvement (P = .03). Groups did not differ in nursing satisfaction.

CONCLUSIONS

PNCA may be an effective alternative to COI for pain management in the NICU population. This method may also substantially reduce opioid consumption, provide more individualized care, and improve parent satisfaction with their level of participation.

CLINICAL IMPLICATIONS

Patients in the NICU represent one of our most vulnerable patient populations. As nurses strive to provide safe and effective pain management, results of this study suggest PNCA may allow nurses to maintain their patients' comfort while providing less opioid and potentially improving parental perception of involvement.

STUDY TYPE

Treatment study.

LEVEL OF EVIDENCE

I.

Neurodevelopmental outcomes following necrotizing enterocolitis

Necrotizing enterocolitis (NEC), a gastrointestinal emergency predominantly affecting premature infants, is associated with increased risk for poor neurodevelopmental outcomes. NEC often strikes during a period of rapid and dynamic neurologic development when the brain is particularly vulnerable to insults and nutrient deficits. The pathogenesis of neurodevelopmental impairment following NEC is likely multifactorial, with both nutritional and non-nutritional factors at play. Follow-up testing that ensures early detection and intervention for impairments is crucial to optimize neurodevelopmental outcomes following NEC. A multifaceted approach to follow-up after NEC is necessary, with close monitoring of growth, serial developmental assessments, neurologic examinations, hearing and vision testing and neuroimaging. Further research is needed to understand the pathogenesis of neurodevelopmental impairment following NEC, to identify more targeted follow-up tests, and to discover interventions aimed at optimizing neurodevelopmental outcomes following NEC.

A survey of the dose of inhalational agents used to maintain anaesthesia in infants

BACKGROUND

Various animal studies suggest that currently used anaesthetics are toxic to the developing brain. Many reviews advise that the total anaesthetic drug exposure should be reduced but the dose usually used in clinical practice has not been clearly elucidated.

OBJECTIVES

To provide an overview of the dose ranges currently used in clinical practice during the maintenance phase of anaesthesia in infants undergoing anaesthesia for noncardiac surgery and diagnostic procedures.

DESIGN

A two-centre mixed prospective (London) and retrospective (Utrecht) observational cohort study.

SETTING

Two independent tertiary paediatric referral centres in March and November 2013; Great Ormond Street Hospital (GOSH), London, United Kingdom and Wilhelmina Children's Hospital, University Medical Center Utrecht (UMCU), The Netherlands.

PATIENTS

A total of 76 infants were included in the analysis, 38 infants from each hospital.

METHODS

Patients from GOSH were matched by procedure, age and weight with patients from the UMCU. The end-tidal concentrations of the inhalational agents were investigated from anaesthetic charts during the maintenance phase and corrected for the age-specific minimal alveolar concentration (MAC), expressed as a percentage from the MAC (%MAC).

RESULTS

Three different types of inhalational anaesthetics were used: sevoflurane, desflurane, isoflurane. The mean %MAC was 0.85. No significant differences in %MAC were found between GOSH and the UMCU (P = 0.329); the mean %MAC in GOSH was 0.87 and in the UMCU was 0.82. There was a significant increase in the %MAC in relation to age (slope = 0.036 MAC month, P < 0.001). Of all patients, 75% had an end-tidal concentration lower than 1 MAC. There was no significant effect of the use of analgesia on the end-tidal concentration of inhalational anaesthetics (P = 0.366).

CONCLUSION

The concentration of inhalational anaesthetics in %MAC increased with age and was lowest in neonates. Most young infants received inhalational anaesthetics at a concentration below 1 MAC, which accords with current guidance to minimise anaesthetic drug exposure but may have unintended consequences.

Neurocognitive Adverse Effects of Anesthesia in Adults and Children: Gaps in Knowledge

Numerous preclinical and clinical studies investigating the neurodevelopmental and neurocognitive effects of exposure to anesthesia and the combination of anesthesia and surgery have demonstrated histopathological and both temporary and long-term cognitive and behavioral effects at the extremes of the human age spectrum. Increasing coverage in the lay press for both our youngest and oldest patient populations has led to heightened concerns regarding the potential harmful side effects of almost all commonly used anesthetic drug regimens. Although the majority of information regarding anesthetic risks in the developing brain derives from preclinical work in rodents, research involving the aged brain has identified a well-defined postoperative cognitive phenotype in humans. While preclinical and clinical data appear to support some association between anesthesia and surgery and the development of detrimental cognitive changes in both the developing and the aged brain, correlation between anesthesia and surgery and poor neurological outcomes does not imply causation. Given this information, no single anesthetic or group of anesthetics can be recommended over any other in terms of causing or preventing negative neurocognitive outcomes in either population. This review summarizes the growing body of preclinical and clinical literature dedicated to the detrimental effects of anesthesia on both the developing and the aging brain.

Pediatric brain MRI part 1: basic techniques

Pediatric neuroimaging is a complex and specialized field that uses magnetic resonance (MR) imaging as the workhorse for diagnosis. Standard MR techniques used in adult neuroimaging are suboptimal for imaging in pediatrics because there are significant differences in the child's developing brain. These differences include size, myelination and sulcation. MR protocols need to be tailored to the specific indication and reviewed by the supervising radiologist in real time, and the specialized needs of this population require careful consideration of issues such as scan timing, sequence order, sedation, anesthesia and gadolinium administration. In part 1 of this review, we focus on basic protocol development and anatomical characterization. We provide multiple imaging examples optimized for evaluation of supratentorial and infratentorial brain, midline structures, head and neck, and intracranial vasculature.

Pain assessment and management in paediatric oncology: a cross-sectional audit

AIMS AND OBJECTIVES

To describe the pain assessment and management practices documented by health professionals within a tertiary-level Children's Cancer Centre and to evaluate how these practices were compared with international recommendations.

BACKGROUND

Children with cancer are vulnerable to pain due to the intensity of antineoplastic therapy. Therefore, it is imperative to ensure that current pain management practices provided to paediatric oncology inpatients are of a high quality.

DESIGN

A single-site cross-sectional audit.

METHODS

A 24-hour period of documented pain-related care in randomly selected inpatients of an Australian tertiary-level Children's Cancer Centre was examined. The current pain management practices were audited over a two-month period resulting in 258 episodes of pain-related care being reviewed.

RESULTS

Pain related to medical treatment for cancer was common (n = 146/258, 57%) and persistent. The presence of pain was not consistently recorded by health professionals (n = 75/146, 51%). Pain was mild (n = 26/75, 35%) and opioids were the mainstay of pain management interventions (n = 63/112, 56%). Adjuvants were an important component of pain management (n = 47/112, 42%), and nonpharmacological methods of managing pain were under-represented in this audit (n = 38/146, 26%). According to the Pain Management Index, pain was appropriately managed for the majority of children (n = 65/76, 87%).

CONCLUSIONS

Pain management practices did not fully reflect the recommendations of contemporary paediatric pain management. Due to limitations in the documentation of children's pain, it was difficult to determine the effectiveness of pain management interventions.

RELEVANCE TO CLINICAL PRACTICE

This study highlights the ongoing problem of pain for children receiving antineoplastic therapy. It is recommended that health professionals routinely screen for the presence of pain during hospitalisation and assess the efficacy of pain-related care.

Pediatric Neurocritical Care: A Short Survey of Current Perceptions and Practices

BACKGROUND

Although attention to neurologic injuries and illnesses in pediatric critical care is not new, a sub-specialized field of pediatric neurocritical care has only recently been recognized. Pediatric neurocritical care is an emerging area of clinical and investigative focus. Little is known about the prevalence of specialized pediatric neurocritical care services nor about perceptions regarding how it is impacting medical practice. This survey sought to capture perceptions about an emerging area of specialized pediatric neurocritical care among practitioners in intersecting disciplines, including pediatric intensivists, pediatric neurologits and pediatric neurosurgeons.

METHODS

A web-based survey was distributed via email to members of relevant professional societies and groups. Survey responses were analyzed using descriptive statistics. Differences in responses between groups of respondents were analyzed using Chi-squared analysis where appropriate.

MAIN RESULTS

Specialized clinical PNCC programs were not uncommon among the survey respondents with 20% currently having a PNCC service at their institution. Despite familiarity with this area of sub-specialization among the survey respondents, the survey did not find consensus regarding its value. Overall, 46% of respondents believed that a specialized clinical PNCC service improves the quality of care of critically ill children. Support for PNCC sub-specialization was more common among pediatric neurologists and pediatric neurosurgeons than pediatric intensivists. This survey found support across specialties for creating PNCC training pathways for both pediatric intensivists and pediatric neurologists with an interest in this specialized field.

CONCLUSIONS

PNCC programs are not uncommon; however, there is not clear agreement on the optimal role or benefit of this area of practice sub-specialization. A broader dialog should be undertaken regarding the emerging practice of pediatric neurocritical care, the potential benefits and drawbacks of this partitioning of neurology and critical care medicine practice, economic and other practical factors, the organization of clinical support services, and the formalization of training and certification pathways for sub-specialization.

Neurotoxicity, general anesthesia in young children, and a survey of current pediatric anesthesia practice at US teaching institutions

BACKGROUND

Recent articles in both scholarly journals and the lay press about the topic of anesthetic related neurotoxicity have increased the awareness and discussion of this topic with parents and other pediatric medical specialties (i.e., surgeons, radiologists, and pediatricians).

AIM

The purpose of the present study was to survey how a subset of pediatric anesthesia departments in the US have responded to the issue of anesthetic related neurotoxicity in terms of clinical practice, training and communication with other medical specialties, and the frequency and timing of discussions with families.

METHODS

A survey consisting of 22 questions was sent to PALC (Pediatric Anesthesia Leadership Council) & PAPDA (Pediatric Anesthesia Program Directors Association) via SurveyMonkey. The survey was divided into sections on Anesthesia Faculty/Trainees, Parents and Non-Anesthesia Providers. Responses to the survey were solicited via email to PALC and PAPDA, and then followed up with reminders to individual emails using the mailing lists of both organizations.

RESULTS

The results of this survey demonstrate that pediatric anesthesia programs around the US do not have a consistent approach in managing the topic of anesthesia-related neurotoxicity with pediatric anesthesiologists, anesthesiology residents, pediatric anesthesiology fellows and their non-anesthesia medical and surgical colleagues, as well as the discussion of this topic with parents.

CONCLUSION

A significant need exists to provide information to other pediatric professionals and parents. A consistent message from all providers that includes what is known, and indeed more importantly what is not known may be a useful approach.

Evidence and consensus based guideline for the management of delirium, analgesia, and sedation in intensive care medicine. Revision 2015 (DAS-Guideline 2015) - short version

In 2010, under the guidance of the DGAI (German Society of Anaesthesiology and Intensive Care Medicine) and DIVI (German Interdisciplinary Association for Intensive Care and Emergency Medicine), twelve German medical societies published the “Evidence- and Consensus-based Guidelines on the Management of Analgesia, Sedation and Delirium in Intensive Care”. Since then, several new studies and publications have considerably increased the body of evidence, including the new recommendations from the American College of Critical Care Medicine (ACCM) in conjunction with Society of Critical Care Medicine (SCCM) and American Society of Health-System Pharmacists (ASHP) from 2013. For this update, a major restructuring and extension of the guidelines were needed in order to cover new aspects of treatment, such as sleep and anxiety management. The literature was systematically searched and evaluated using the criteria of the Oxford Center of Evidence Based Medicine. The body of evidence used to formulate these recommendations was reviewed and approved by representatives of 17 national societies. Three grades of recommendation were used as follows: Grade “A” (strong recommendation), Grade “B” (recommendation) and Grade “0” (open recommendation). The result is a comprehensive, interdisciplinary, evidence and consensus-based set of level 3 guidelines. This publication was designed for all ICU professionals, and takes into account all critically ill patient populations. It represents a guide to symptom-oriented prevention, diagnosis, and treatment of delirium, anxiety, stress, and protocol-based analgesia, sedation, and sleep-management in intensive care medicine.

Positron Emission Tomography with [(18)F]FLT Revealed Sevoflurane-Induced Inhibition of Neural Progenitor Cell Expansion in vivo

Neural progenitor cell expansion is critical for normal brain development and an appropriate response to injury. During the brain growth spurt, exposures to general anesthetics, which either block the N-methyl-d-aspartate receptor or enhance the γ-aminobutyric acid receptor type A can disturb neuronal transduction. This effect can be detrimental to brain development. Until now, the effects of anesthetic exposure on neural progenitor cell expansion in vivo had seldom been reported. Here, minimally invasive micro positron emission tomography (microPET) coupled with 3'-deoxy-3' [(18)F] fluoro-l-thymidine ([(18)F]FLT) was utilized to assess the effects of sevoflurane exposure on neural progenitor cell proliferation. FLT, a thymidine analog, is taken up by proliferating cells and phosphorylated in the cytoplasm, leading to its intracellular trapping. Intracellular retention of [(18)F]FLT, thus, represents an observable in vivo marker of cell proliferation. Here, postnatal day 7 rats (n = 11/group) were exposed to 2.5% sevoflurane or room air for 9 h. For up to 2 weeks following the exposure, standard uptake values (SUVs) for [(18)F]-FLT in the hippocampal formation were significantly attenuated in the sevoflurane-exposed rats (p < 0.0001), suggesting decreased uptake and retention of [(18)F]FLT (decreased proliferation) in these regions. Four weeks following exposure, SUVs for [(18)F]FLT were comparable in the sevoflurane-exposed rats and in controls. Co-administration of 7-nitroindazole (30 mg/kg, n = 5), a selective inhibitor of neuronal nitric oxide synthase, significantly attenuated the SUVs for [(18)F]FLT in both the air-exposed (p = 0.00006) and sevoflurane-exposed rats (p = 0.0427) in the first week following the exposure. These findings suggested that microPET in couple with [(18)F]FLT as cell proliferation marker could be used as a non-invasive modality to monitor the sevoflurane-induced inhibition of neural progenitor cell proliferation in vivo.

[Implementation of a specific premedication protocol for tracheal intubation in the delivery room. Practice in two level-III hospitals]

Tracheal intubation in neonates is a painful procedure performed daily in the delivery room despite the widespread development of noninvasive ventilation. Specific analgesia is not commonly performed. The objective of this observational study was to compare practices between two level-III centers: one with a specific protocol for premedication before tracheal intubation of newborns in the delivery room, the other without.

RESULTS

One hundred and fifteen neonates were intubated in the delivery room and included over a 4-month period: 25% of them received specific premedication before intubation, exclusively in the center with the protocol. None of the extreme premature neonates (age≤28 gestational weeks) received analgosedation before the procedure. Nalbuphine, midazolam, and sufentanil were mainly used, via the intravenous or intrarectal route. Infants receiving a premedication were significantly heavier and had a greater gestational age than the others (1500 g [range, 1180-2260 g] vs. 1170 [range, 860-1680 g] P=0.003, and 31 GW [range, 29-34 GW] vs. 29 [range, 27-32 GW] P=0.014, respectively). Most pediatricians (85-100%) favored a specific protocol for sedation before tracheal intubation. Implementation of a specific protocol allows specific analgesia to be implemented for newborns undergoing tracheal intubation. Further studies should be conducted to determine the best strategies for pain management during tracheal intubation of neonates, especially in the delivery room.

Anaesthetics-induced neurotoxicity in developing brain: an update on preclinical evidence

Every year millions of young people are treated with anaesthetic agents for surgery and sedation in a seemingly safe manner. However, growing and convincing preclinical evidence in rodents and nonhuman primates, together with recent epidemiological observations, suggest that exposure to anaesthetics in common clinical use can be neurotoxic to the developing brain and lead to long-term neurological sequelae. These findings have seriously questioned the safe use of general anaesthetics in obstetric and paediatric patients. The mechanisms and human applicability of anaesthetic neurotoxicity and neuroprotection have remained under intense investigation over the past decade. Ongoing pre-clinical investigation may have significant impact on clinical practice in the near future. This review represents recent developments in this rapidly emerging field. The aim is to summarise recently available laboratory data, especially those being published after 2010, in the field of anaesthetics-induced neurotoxicity and its impact on cognitive function. In addition, we will discuss recent findings in mechanisms of early-life anaesthetics-induced neurotoxicity, the role of human stem cell-derived models in detecting such toxicity, and new potential alleviating strategies.

Xenon Neurotoxicity in Rat Hippocampal Slice Cultures Is Similar to Isoflurane and Sevoflurane

Background:

Anesthetic neurotoxicity in the developing brain of rodents and primates has raised concern. Xenon may be a nonneurotoxic alternative to halogenated anesthetics, but its toxicity has only been studied at low concentrations, where neuroprotective effects predominate in animal models. An equipotent comparison of xenon and halogenated anesthetics with respect to neurotoxicity in developing neurons has not been made.

Methods:

Organotypic hippocampal cultures from 7-day-old rats were exposed to 0.75, 1, and 2 minimum alveolar concentrations (MAC) partial pressures (60% xenon at 1.2, 2.67, and 3.67 atm; isoflurane at 1.4, 1.9, and 3.8%; and sevoflurane at 3.4 and 6.8%) for 6 h, at atmospheric pressure or in a pressure chamber. Cell death was assessed 24 h later with fluorojade and fluorescent dye exclusion techniques.

Results:

Xenon caused death of hippocampal neurons in CA1, CA3, and dentate regions after 1 and 2 MAC exposures, but not at 0.75 MAC. At 1 MAC, xenon increased cell death 40% above baseline (P &lt; 0.01; ANOVA with Dunnett test). Both isoflurane and sevoflurane increased neuron death at 1 but not 2 MAC. At 1 MAC, the increase in cell death compared with controls was 63% with isoflurane and 90% with sevoflurane (both P &lt; 0.001). Pretreatment of cultures with isoflurane (0.75 MAC) reduced neuron death after 1 MAC xenon, isoflurane, and sevoflurane.

Conclusion:

Xenon causes neuronal cell death in an in vitro model of the developing rodent brain at 1 MAC, as does isoflurane and sevoflurane at similarly potent concentrations. Preconditioning with a subtoxic dose of isoflurane eliminates this toxicity.

Effect of propofol in the immature rat brain on short- and long-term neurodevelopmental outcome

Background

Propofol is commonly used as sedative in newborns and children. Recent experimental studies led to contradictory results, revealing neurodegenerative or neuroprotective properties of propofol on the developing brain. We investigated neurodevelopmental short- and long-term effects of neonatal propofol treatment.

Methods

6-day-old Wistar rats (P6), randomised in two groups, received repeated intraperitoneal injections (0, 90, 180 min) of 30 mg/kg propofol or normal saline and sacrificed 6, 12 and 24 hrs following the first injection. Cortical and thalamic areas were analysed by Western blot and quantitative real-time PCR (qRT-PCR) for expression of apoptotic and neurotrophin-dependent signalling pathways. Long-term effects were assessed by Open-field and Novel-Object-Recognition at P30 and P120.

Results

Western blot analyses revealed a transient increase of activated caspase-3 in cortical, and a reduction of active mitogen-activated protein kinases (ERK1/2, AKT) in cortical and thalamic areas. qRT-PCR analyses showed a down-regulation of neurotrophic factors (BDNF, NGF, NT-3) in cortical and thalamic regions. Minor impairment in locomotive activity was observed in propofol treated adolescent animals at P30. Memory or anxiety were not impaired at any time point.

Conclusion

Exposing the neonatal rat brain to propofol induces acute neurotrophic imbalance and neuroapoptosis in a region- and time-specific manner and minor behavioural changes in adolescent animals.

Risk factors for adverse neurocognitive outcomes in school-aged patients after the Fontan operation

OBJECTIVES

As the surgical results for Fontan candidates improve, much attention has been given to the long-term cognitive outcomes. This study aimed to assess the neurocognitive outcomes after Fontan completion, and to determine the factors associated with an extremely low intelligence quotient (IQ <70).

METHODS

A total of 70 local eligible school-aged patients were enrolled in the study (hypoplastic left heart syndrome, 17; right atrial isomerism, 15 and others, 38). Fontan operations were performed at a median age of 1.8 (range, 0.5-8.9) years (primary Fontan, 4 of 70 [6%]). The Wechsler Intelligence Test was taken at a median age of 9 (range, 5.1-14.4) years for the purpose of neurocognitive evaluation. Patients' data were collected from medical records, and a retrospective analysis of potential predictors for an IQ <70 was performed.

RESULTS

The median full-scale IQ (FSIQ) for the entire cohort was 85 (range, 43-118). Of the lower order composites, the perceptual reasoning index and the working memory index were significantly lower in low-FSIQ patients (P < 0.05). Overall, 15 of 70 (21%) of the cohort had an IQ <70. Univariate analysis identified three significant risk factors for FSIQ <70 (15 of 70, 21%): body weight <2.5 kg at initial palliative surgery (P < 0.05), low 5-min Apgar score <4 (P < 0.05) and inter-stage events requiring cardiopulmonary resuscitation (CPR) (P < 0.05). No other patient-specific factors (e.g. cardiac morphology) or modifiable surgical factors (e.g. the use of hypothermic cardiac arrest) were associated with FSIQ <70.

CONCLUSIONS

Low body weight (<2.5 kg) at initial operation, low 5-min Apgar score (<4) and inter-stage CPR were significant risk factors for impaired neurocognitive outcomes. An evolving strategy for preventing inter-stage CPR may improve cognitive outcomes.

Newly postulated neurodevelopmental risks of pediatric anesthesia: theories that could rock our world

PURPOSE

General anesthetics can induce apoptotic neurodegeneration and subsequent maladaptive behaviors in animals. Retrospective human studies suggest associations between early anesthetic exposure and subsequent adverse neurodevelopmental outcomes. The relevance of animal data to clinical practice is unclear and to our knowledge the causality underlying observed associations in humans is unknown. We reviewed newly postulated neurodevelopmental risks of pediatric anesthesia and discuss implications for the surgical care of children.

MATERIALS AND METHODS

We queried the MEDLINE®/PubMed® and EMBASE® databases for citations in English on pediatric anesthetic neurotoxicity with the focus on references from the last decade.

RESULTS

Animal studies in rodents and primates demonstrate apoptotic neuropathology and subsequent maladaptive behaviors after exposure to all currently available general anesthetics with the possible exception of α2-adrenergic agonists. Similar adverse pathological and clinical effects occur after untreated pain. Anesthetic neurotoxicity in animals develops only after exposure above threshold doses and durations during a critical neurodevelopmental window of maximal synaptogenesis in the absence of concomitant painful stimuli. Anesthetic exposure outside this window or below threshold doses and durations shows no apparent neurotoxicity, while exposure in the context of concomitant painful stimuli is neuroprotective. Retrospective human studies suggest associations between early anesthetic exposure and subsequent adverse neurodevelopmental outcomes, particularly after multiple exposures. The causality underlying the associations is unknown. Ongoing investigations may clarify the risks associated with current practice.

CONCLUSIONS

Surgical care of all patients mandates appropriate anesthesia. Neurotoxic doses and the duration of anesthetic exposure in animals may have little relevance to clinical practice, particularly surgical anesthesia for perioperative pain. The causality underlying the observed associations between early anesthetic exposure and subsequent adverse neurodevelopmental outcomes is unknown. Anesthetic exposure may be a marker of increased risk. Especially in young children, procedures requiring general anesthesia should be performed only as necessary and general anesthesia duration should be minimized. Alternatives to general anesthesia and the deferral of elective procedures beyond the first few years of life should be considered, as appropriate. Participation in ongoing efforts should be encouraged to generate further data.