Anesthesiology and cognitive impairment: a narrative review of current clinical literature

Metformin activates the PI3K/AKT/BDNF axis to attenuate postoperative cognitive dysfunction

Postoperative cognitive dysfunction (POCD) is a prevalent neurocognitive complication of anesthesia and surgery. Metformin, a widely used antidiabetic drug, has neuroprotective properties and improves cognitive impairment and memory deficits. However, the mechanisms underlying its action in improving cognitive dysfunction after anesthesia and surgery remain unclear. This study aimed to explore the effects of metformin on POCD and the underlying mechanisms at play. We established an in vivo POCD model using isoflurane inhalation anesthesia with exploratory laparotomy. We found that pretreatment with metformin significantly improved cognitive function and anxiety-like behaviors in mice. Additionally, metformin attenuated the impairment of synaptic plasticity induced by POCD and restored levels of synaptic proteins and dendritic density in the hippocampus. Furthermore, metformin attenuated neuroinflammation by downregulating the expression of interleukin (IL)-6, IL-1β, and tumor necrosis factor-α, and reducing neuronal apoptosis. It also activates the PI3K/AKT signaling pathway, resulting in increased expression of brain-derived neurotrophic factor (BDNF). Finally, the PI3K inhibitor, LY294002, reversed the effects of metformin on the levels of PI3K, AKT phosphorylation, and BDNF in vitro cultured HT-22 cells. Additionally, in an in vivo model of POCD, it was observed that cognitive function in mice was significantly suppressed by treatment with the PI3K inhibitor LY294002. These results reveal that metformin may alleviate POCD by modulating the PI3K/AKT/BDNF axis. Our study may provide a novel strategy for preventing and treating POCD with this medication.

Current Progress on Postoperative Cognitive Dysfunction: An Update

Postoperative cognitive dysfunction (POCD) represents a significant clinical concern, particularly among elderly surgical patients. It is characterized by a decline in cognitive performance, affecting memory, attention, coordination, orientation, verbal fluency, and executive function. This decline in cognitive abilities leads to longer hospital stays and increased mortality. This review provides a comprehensive overview of the current progress in understanding the relevant pathogenic factors, possible pathogenic mechanisms, diagnosing, prevention and treatment of POCD, as well as suggesting future research directions. It discusses neuronal damage, susceptible genes, central cholinergic system, central nervous system (CNS) inflammation, stress response and glucocorticoids, and oxidative stress in the development of POCD, aiming to uncover the pathological mechanism and develop effective treatment strategies for POCD.

Mechanistic insights into sevoflurane-induced hippocampal neuronal damage and cognitive dysfunction through the NEAT1/Nrf2 signaling axis in aged rats

The use of anesthetics during surgery can cause severe neurological damage and cognitive dysfunction in elderly patients. However, this health issue currently lacks corresponding therapeutic strategies. This research involved the utilization of single-cell RNA sequencing (scRNA-seq) and transcriptomic assessment to pinpoint crucial cell classifications and molecular pathways, as well as the lncRNA expression profiles, that undergo substantial alterations in aged rats experiencing sevoflurane-induced cognitive impairment. The results of our investigation pointed towards the enrichment of differentially expressed genes in neurons within the Nrf2/ARE signaling pathway, alongside an elevated expression of lncRNA NEAT1. Subsequently, by constructing a rat model to induce neuronal dysfunction with sevoflurane and performing experiments both in vivo and in vitro (including TUNEL staining, H&E staining, immunohistochemistry, immunofluorescence, and flow cytometry to assess apoptosis levels), we confirmed that NEAT1 inhibits the Nrf2/ARE/HO-1 pathway-related factors. Sevoflurane promotes oxidative stress and apoptosis in primary hippocampal neurons through the NEAT1/Nrf2/ARE/HO-1 axis. This study elucidates the molecular mechanism by which sevoflurane induces hippocampal neuronal damage and cognitive decline in elderly rats via the regulation of the lncRNA NEAT1/Nrf2 signaling axis. We discovered that upregulation of NEAT1 suppresses the Nrf2 signaling pathway, further inducing neuronal damage and cognitive dysfunction, furnishing an essential citation to grasp the molecular pathways involved in neuronal harm and devising corresponding treatment methodologies.

Novel Perspective on Sevoflurane-Induced Cognitive Dysfunction: Implications of Neuronal SIRPα and Microglial Synaptic Remodeling

This study aims to investigate the role of neuronal SIRPα and microglial synaptic remodeling in sevoflurane-induced cognitive dysfunction in newborn mice. Newborn mice were exposed to sevoflurane, followed by behavioral assessments and single-cell transcriptome sequencing of cortical cells. Lentivirus-mediated overexpression of neuronal SIRPα and assessment of the microglial morphology and synaptic function were conducted. Sevoflurane exposure resulted in social cognitive impairments without affecting motor coordination. Transcriptomic analysis revealed no significant changes in cortical microglial cells or neurons. However, sevoflurane inhibited nonsynaptic synapse modification by microglia. Overexpression of neuronal SIRPα enhanced microglial function, promoted neuron development, and ameliorated cognitive impairments. SCENIC analysis identified a correlation between IRF8 and SIRPα expression. This study sheds light on the involvement of neuronal SIRPα and microglial synaptic remodeling in sevoflurane-induced cognitive dysfunction. Understanding these mechanisms offers new avenues for exploring cognitive impairment pathways and potential therapeutic targets.

Sevoflurane exposure accelerates the onset of cognitive impairment via promoting p-Drp1S616-mediated mitochondrial fission in a mouse model of Alzheimer's disease

Sevoflurane is an inhalational anesthetic widely used in clinical settings. Accumulating evidence has shown that sevoflurane exposure may impair cognitive function, potentially contributing to Alzheimer's disease (AD)-related changes. However, the underlying mechanism remains poorly understood. In the present study, 4-month-old 5xFAD mice were used to investigate the effect of sevoflurane exposure on cognitive decline by Y-maze test and novel object recognition test. We found that sevoflurane exposure promoted the appearance of cognitive impairment of 5xFAD mice, accompanied with the deterioration of Aβ accumulation, synaptic defects, and neuroinflammation. Additionally, sevoflurane was also found to aggravate mitochondrial fission of 5xFAD mice, as indicated by the further upregulated expression of p-Drp1S616. Moreover, sevoflurane significantly increased mitochondrial damage and dysfunction of AD models both in vitro and in vivo experiments. Seahorse XF analysis further indicated that sevoflurane exposure facilitated a metabolic shift from oxidative phosphorylation to glycolysis. Further rescue experiments revealed that a key mechanism underlying sevoflurane-induced cognitive impairment was the excessive mitochondrial fission, as supported by the result that the mitochondrial fission inhibitor Mdivi-1 counteracted the sevoflurane-mediated deteriorative effects in 5xFAD mice. These findings provided evidence for a new mechanism of sevoflurane exposure accelerating AD-related cognitive decline.

Sevoflurane exposure in early life: mitochondrial dysfunction and neurotoxicity in immature rat brains without long-term memory loss

Neurotoxic effects of general anesthetics, particularly sevoflurane, on pediatric neurodevelopment are a global concern. This study investigated the molecular and metabolic impacts of repeated short exposures to sevoflurane in neonatal rats. Metabolomics analysis revealed significant changes in fatty acid and mitochondrial energy metabolism. Transcriptomic analysis identified altered gene expression related to neurodevelopment and mitochondrial function. Various analyses emphasized upregulation in oxidative phosphorylation and DNA repair pathways. Weighted gene co-expression network analysis (WGCNA) identified key gene modules associated with sevoflurane exposure. Despite these acute changes, no significant long-term memory impairments were detected. These findings highlight the impact of sevoflurane on mitochondrial energy metabolism, oxidative stress, and neuroinflammation, emphasizing its relevance to pediatric neurodevelopment. The absence of substantial long-term memory impairments provides insights into the safety and implications of sevoflurane use in pediatric anesthesia, calling for further research.

Unraveling the role and mechanism of mitochondria in postoperative cognitive dysfunction: a narrative review

Postoperative cognitive dysfunction (POCD) is a frequent neurological complication encountered during the perioperative period with unclear mechanisms and no effective treatments. Recent research into the pathogenesis of POCD has primarily focused on neuroinflammation, oxidative stress, changes in neural synaptic plasticity and neurotransmitter imbalances. Given the high-energy metabolism of neurons and their critical dependency on mitochondria, mitochondrial dysfunction directly affects neuronal function. Additionally, as the primary organelles generating reactive oxygen species, mitochondria are closely linked to the pathological processes of neuroinflammation. Surgery and anesthesia can induce mitochondrial dysfunction, increase mitochondrial oxidative stress, and disrupt mitochondrial quality-control mechanisms via various pathways, hence serving as key initiators of the POCD pathological process. We conducted a review on the role and potential mechanisms of mitochondria in postoperative cognitive dysfunction by consulting relevant literature from the PubMed and EMBASE databases spanning the past 25 years. Our findings indicate that surgery and anesthesia can inhibit mitochondrial respiration, thereby reducing ATP production, decreasing mitochondrial membrane potential, promoting mitochondrial fission, inducing mitochondrial calcium buffering abnormalities and iron accumulation, inhibiting mitophagy, and increasing mitochondrial oxidative stress. Mitochondrial dysfunction and damage can ultimately lead to impaired neuronal function, abnormal synaptic transmission, impaired synthesis and release of neurotransmitters, and even neuronal death, resulting in cognitive dysfunction. Targeted mitochondrial therapies have shown positive outcomes, holding promise as a novel treatment for POCD.

Functionally important binding site for a volatile anesthetic in a voltage-gated sodium channel identified by X-ray crystallography

Volatile general anesthetics are used for inhalational anesthesia in hundreds of millions of surgical procedures annually, yet their mechanisms of action remain unclear. Membrane proteins involved in cell signaling are major targets for anesthetics, and voltage-gated ion channels that mediate neurotransmission, movement, and cognition are sensitive to volatile anesthetics (VAs). In many cases, the effects produced by VAs on mammalian ion channels are reproduced in prokaryotic orthologues, providing an opportunity to investigate VA interactions at high resolution using these structurally simpler prokaryotic proteins. We utilized the bacterial voltage-gated sodium channel (VGSC) NavMs from Magnetococcus marinus to investigate its interaction with the widely used VA sevoflurane. Sevoflurane interacted directly with NavMs, producing effects consistent with multisite binding models for VA actions on their targets. We report the identification of one of these interactions at atomic detail providing the first high-resolution structure of a VA bound to a voltage-gated ion channel. The X-ray crystal structure shows sevoflurane binding to NavMs within an intramembrane hydrophobic pocket formed by residues from the voltage sensor and channel pore, domains essential for channel gating. Mutation of the dominant sevoflurane binding-site residue within this pocket, and analogous residues found in similar sites in human VGSCs, profoundly affected channel properties, supporting a critical role for this site in VGSC function. These findings provide the basis for future work to understand the role of VA interactions with VGSCs in both the anesthetic and toxic effects associated with general anesthesia.

Postoperative Electroacupuncture Boosts Cognitive Function Recovery after Laparotomy in Mice

Postoperative cognitive dysfunction (POCD) is a common complication that affects memory, executive function, and processing speed postoperatively. The pathogenesis of POCD is linked to excessive neuroinflammation and pre-existing Alzheimer's disease (AD) pathology. Previous studies have shown that acupuncture improves cognition in the early phase of POCD. However, POCD can last for longer periods (up to weeks and years). The long-term effects of acupuncture are unknown. In this study, we hypothesized that electroacupuncture (EA) could reduce inflammation and cognitive dysfunction induced by laparotomy over a longer period. We characterized the effects of postoperative EA on cognitive changes and investigated the underlying molecular mechanisms in mice. Laparotomy was performed in 3-month-old mice followed by daily EA treatment for 2 weeks. Our data indicated that laparotomy induced prolonged impairment in memory and executive functions, which were mitigated by postoperative EA. EA also reduced tau phosphorylation and suppressed the activation of tau-related kinases and glia, with effects comparable to ibuprofen. These findings demonstrate the beneficial effects of EA in a mouse model of POCD, suggesting that EA's ability to suppress neuroinflammation may contribute to its protective effects. In conclusion, EA may be a viable non-pharmacological intervention for managing POCD in different phases of the medical condition.

Optimizing post-craniotomy recovery: insights from symptom network analysis in primary brain tumor patients

BACKGROUND

Craniotomy to remove brain tumors is an intricate procedure with multiple postoperative symptoms. However, there has been limited research on the symptom networks of these patients. To this end, this study aims to explore these symptom networks, revealing their interplay to inform better symptom control, hasten the discovery of postoperative issues, and tailor Enhanced Recovery After Surgery (ERAS) protocols, all to enhance recovery and enhance patient care.

METHODS

From September 2023 to March 2024, 211 patients with primary brain tumors who underwent craniotomy at Shanghai Tongji Hospital were recruited. Their symptoms were assessed using the MDASI-BT (M.D. Anderson Symptom Inventory Brain Tumor Module) one day post-craniotomy. The symptom network of 22 symptoms was visualized using R, with central and bridge symptoms identified.

RESULTS

Sadness (rs=2.482) and difficulty in understanding (rs=1.138) have the highest strength of all symptoms, indicating they are the central symptoms. Sadness (rb=2.155) and loss of appetite (rb=1.828) have the highest value of betweenness, indicating they are the bridge symptoms. Strong correlations were found between difficulty in understanding and difficulty in speaking (r = 0.701), distress and sadness (r = 0.666), fatigue and lethargy (r = 0.632), and nausea and vomiting (r = 0.601). Subgroup analysis revealed that noninvasive tumor patients exhibited similar symptom networks to the overall cohort, whereas invasive tumor patients showed weak symptom connections, resulting in no discernible network.

CONCLUSION

This study underscores the importance of understanding symptom networks in brain tumor patients post-craniotomy, highlighting key symptom interrelationships. These insights can guide more effective symptom management, early complication detection, and optimization of ERAS protocols, ultimately enhancing recovery and patient care.

Expression of microRNA induced by postoperative delirium-like behavior is associated with long-term default mode network disruption: Sequencing and a secondary analysis of resting-state fMRI data

AIMS

Resting state functional magnetic resonance imaging (rs-fMRI) has been widely used in studying default mode network (DMN) changes in postoperative delirium (POD). Reproducibility and interpretability of the analyzing results remain insufficiently studied.

METHODS

Delirium-like behavior was induced by tibial fixation surgery under isoflurane anesthesia. Firstly, we evaluated delirium-like behavior and inflammatory responses in hippocampus and systemic level. Then the expressions of microRNA (miRNA) and target gene were sequenced and validated. Afterwards the functional connectivity (FC) in DMN was analyzed. Finally, results were correlated with DMN changes.

RESULTS

POD-like behavior caused significant changes of miR-34b-5p, miR-328-5p, and miR-3505 in miRNA level and Nos1, Tubb3, and Gys1 in the gene level. The FC in left and right hippocampus (L-Hip and R-Hip) and right auditory cortex (R-AC) was found significantly changed. Significant correlations were found in FCL-Hip/R-AC and FCR-Hip/R-AC for miR-34b-5p and miR-3505, as well as Nos1 and Tubb3. For miR-328-5p, no significant correlations were found.

CONCLUSION

Our study demonstrates that POD-like behavior induced significant miRNA and gene expression changes were associated with hippocampus related long-term FC disruption in DMN. The results increased reproducibility and interpretability for standardized rs-fMRI data analysis, as well as providing potential targets for postoperative delirium treatment.

No negative effects of intra-abdominal bio-logger implantation under general anaesthesia on spatial cognition learning in a hibernator the edible dormouse

The effect of hibernation on cognitive capacities of individuals is not fully understood, as studies provide conflicting results. Most studies focus on behavioural observations without taking the physiological state of individuals to account. To mechanistically understand the effect of hibernation on the brain, physiological parameters need to be included. The implantation of bio-loggers can provide insights on i.e. body temperature without further manipulation of the animals. Surgeries and anaesthesia, however, can harm animals' health and cause cognitive dysfunction, potentially biasing data collected through bio-loggers. We investigated the effects of bio-logger implantation surgery on cognitive performance and learning, controlling for animal and study design characteristics. First, juvenile dormice successfully learned to solve a spatial cognition task using a vertical maze. Distance, transitions, velocity, and duration were measured as indicators for performance. After training, bio-loggers were implanted intra-abdominally under general anaesthesia. Animals were re-tested in the maze two weeks after. We found no effect of bio-logger implantation and surgery on performance. This study is the first to show spatial cognition learning in edible dormice and provides a full description of the peri-anaesthetic management and a protocol for bio-logger implantation surgery in dormice. Importantly, measures were taken to mitigate common anaesthetic complications that could lead to post-operative cognitive dysfunction and influence animal behaviour. By pairing physiological measurements through bio-logger implantation with behaviour and cognition measurements, future research will significantly advance the understanding on mechanisms of learning and behaviour.

Cataract Surgery and Cognitive Benefits in the Older Person: A Systematic Review and Meta-analysis

TOPIC

This systematic review and meta-analysis aims to clarify the association of cataract surgery with cognitive impairment and dementia.

CLINICAL RELEVANCE

The association between vision impairment and cognitive decline is well-established. However, the cognitive benefits of cataract surgery are less clear. Given the lack of cure for dementia, identifying modifiable risk factors is key in caring for patients with cognitive deficits.

METHODS

The study was conducted following Preferred Reporting Items for Systematic Review and Meta-analyses guidelines. PubMed, Embase, and Cochrane Library were searched from inception through October 11, 2022, for studies reporting the effect of cataract surgery on cognitive impairment and dementia. We pooled maximally adjusted hazard ratios (HRs) for dichotomous outcomes and ratio of means (RoM) for continuous outcomes using a random-effects model. Heterogeneity was examined using sensitivity and subgroup analyses. The quality of evidence was evaluated using the Newcastle-Ottawa scale, Cochrane risk-of-bias tool for randomized trials, and Grading of Recommendations, Assessment, Development and Evaluations (GRADE) guidelines.

RESULTS

This review included 24 articles comprising 558 276 participants, of which 19 articles were analyzed qualitatively. The bias of studies ranged from low to moderate, and GRADE extended from very low to low. Cataract surgery was associated with a 25% reduced risk of long-term cognitive decline compared with those with uncorrected cataracts (HR, 0.75; 95% confidence interval [CI], 0.72-0.78). This cognitive benefit was seen across various cognitive outcomes and remained robust to sensitivity analyses. Participants who underwent cataract surgery showed a similar risk of long-term cognitive decline as healthy controls without cataracts (HR, 0.84; 95% CI, 0.66-1.06). Additionally, cataract surgery was associated with a 4% improvement in short-term cognitive test scores among participants with normal cognition (RoM, 0.96; 95% CI, 0.94-0.99), but no significant association was observed among participants with preexisting cognitive impairment.

DISCUSSION

Cataract surgery may be associated with a lower risk of cognitive impairment and dementia, and cataract-associated vision impairment may be a modifiable risk factor for cognitive decline. Physicians should be aware of the cognitive sequelae of cataracts and the possible benefits of surgery. The cognitive benefits of cataract surgery should be investigated further in randomized trials.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Cognitive dysfunction in older patients undergoing non-neurosurgery in the immediate postoperative period: A systematic review

AIM

To explore the risk factors associated with postoperative cognitive dysfunction in older patients within the first 7 days after non-neurosurgical surgery and anaesthesia.

DESIGN

A systematic review.

METHODS

Following, PRISMA 2020 (Preferred Reporting Items for Systematic Reviews and Meta-analyses). Checklist, a systematic review of studies published from January 2018 to January 2024. The literature search was conducted across six electronic online databases, including PubMed, EMBASE, Scopus, Ovid, MEDLINE and Science Direct, and the Johns Hopkins Nursing Evidence-Based Practice Evidence Rating Scale was used for study appraisal.

RESULTS

The initial search yielded 1750 studies. The review included 19 studies which comprised prospective observational, case-control and retrospective studies. The prevalence of postoperative cognitive dysfunction ranged from 19% to 64% among older adults undergoing non-neurosurgery. The identified risk factors were classified into three phases including preoperative, intraoperative and postoperative. Preoperative risk factors were found in age, educational attainment, malnutrition, preoperative biomarkers and co-morbidities. Intraoperative risk factors were the duration of the operation, blood loss during the operation and anaesthesia used. Postoperative risk factors consisted of postoperative biomarkers and postoperative pain.

PATIENT OR PUBLIC CONTRIBUTION

The result from this review may assist researchers and healthcare providers in assessing the underlying causes and risk factors of postoperative cognitive dysfunction, and in formulating suitable preventative and therapeutic strategies for older adults with non-neurosurgery during the short-term postoperative period.

Knowledge, attitudes, and practices regarding Post-anesthesia cognitive dysfunction in patients undergoing gastrointestinal endoscopy

BACKGROUND

The administration of anesthesia during gastrointestinal endoscopy potentially contributes to post-anesthesia cognitive dysfunction (PACD), with detrimental impacts for cognitive function. This study aimed to assess the knowledge, attitudes, and practices (KAP) towards PACD among patients undergoing gastrointestinal endoscopy in Wenzhou region.

METHODS

This cross-sectional study was conducted between June and August 2023, and recruited individuals undergoing gastrointestinal endoscopy. Demographic data and KAP scores were collected through questionnaires. Pearson correlation analysis was applied to evaluate correlations between KAP scores, and logistic regression was utilized to identify influential factors.

RESULTS

We collected 405 valid questionnaires, with 54.57% being male and 29.88% aged 31-40 years. Mean KAP scores were 13.99 ± 4.80, 16.19 ± 2.35, and 15.61 ± 2.86, respectively (possible range: 0-16, 0-25, and 0-25). Pearson correlation analysis demonstrated significant positive correlations between knowledge and practice (r = 0.209, P < 0.001), attitude and practice (r = 0.233, P < 0.001), and knowledge and attitude (r = 0.328, P < 0.001). Multivariate logistic regression revealed negative associations of opting for standard gastrointestinal endoscopy (without anesthesia) with knowledge (OR = 0.227, 95%CI: 0.088-0.582, P = 0.002) and practice scores (OR = 0.336, 95%CI: 0.154-0.731, P = 0.006). Additionally, the presence of cognitive-related diseases or symptoms before undergoing gastrointestinal endoscopy was negatively associated with knowledge scores (OR = 0.429, 95%CI: 0.225-0.818, P = 0.010).

CONCLUSION

Patients undergoing gastrointestinal endoscopy demonstrated good knowledge, neutral attitudes, and moderate practices regarding PACD. Educational interventions and behavior modification are recommended, particularly for individuals with lower monthly income, undergoing standard gastrointestinal endoscopy, or experiencing cognitive-related conditions.

Short-term inhalation of xenon during anesthesia for prevention of postoperative delirium in elderly patients undergoing laparoscopic radical colectomy: study protocol for a randomized controlled clinical trial

BACKGROUND

Postoperative delirium (POD) is a common complication that is characterized by acute onset of impaired cognitive function and is associated with an increased mortality, a prolonged duration of hospital stay, and additional healthcare expenditures. The incidence of POD in elderly patients undergoing laparoscopic radical colectomy ranges from 8 to 54%. Xenon has been shown to provide neuroprotection in various neural injury models, but the clinical researches assessing the preventive effect of xenon inhalation on the occurrence of POD obtained controversial findings. This study aims to investigate the effects of a short xenon inhalation on the occurrence of POD in elderly patients undergoing laparoscopic radical colectomy.

METHODS/DESIGN

This is a prospective, randomized, controlled trial and 132 patients aged 65-80 years and scheduled for laparoscopic radical colectomy will be enrolled. The participants will be randomly assigned to either the control group or the xenon group (n = 66 in each group). The primary outcome will be the incidence of POD in the first 5 days after surgery. Secondary outcomes will include the subtype, severity, and duration of POD, postoperative pain score, Pittsburgh Sleep Quality Index (PQSI), perioperative non-delirium complications, and economic parameters. Additionally, the study will investigate the activation of microglial cells, expression of inflammatory factors in colon tissues, plasma inflammatory factors, and neurochemical markers.

DISCUSSION

Elderly patients undergoing laparoscopic radical colectomy are at a high risk of POD, with delayed postoperative recovery and increased healthcare costs. The primary objective of this study is to determine the preventive effect of a short xenon inhalation on the occurrence of POD in these patients.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2300076666. Registered on October 16, 2023, http://www.chictr.org.cn .

Astrocytic GDNF ameliorates anesthesia and surgery-induced cognitive impairment by promoting hippocampal synaptic plasticity in aged mice

BACKGROUND

Perioperative neurocognitive disorders (PND) are common complications after surgery in older patients. However, the specific mechanism of this condition remains unclear. Glial cell line-derived neurotrophic factor (GDNF) is an important neurotrophin that abundantly expressed throughout the brain. It can enhance synaptic plasticity and alleviate learning and memory impairments. Thus, the purpose of this study was to investigate the role of GDNF in PND and the mechanisms involved.

METHODS

The PND animal model was established by performing left tibial fracture surgery on 18-month-old C57BL/6 mice under sevoflurane anesthesia. Recombinant adeno-associated virus (rAAV)-GDNF or empty vectors were injected bilaterally into the hippocampal CA1 region of aged mice 3 weeks before anesthesia/surgery. The open field and fear conditioning test were used to assess the behavior changes. Golgi staining and electrophysiology were utilized to evaluate the morphological and functional alterations of neuronal synaptic plasticity. Western blot analysis was carried out to measure the proteins expression levels and immunofluorescence staining was performed to probe the cellular localization of GDNF.

RESULTS

Mice with surgery and anesthesia showed a significant decrease in hippocampus-dependent learning and memory, accompanied by a decline in hippocampal synaptic plasticity. Anesthesia/surgery induced a reduction of GDNF, which was colocalized with astrocytes. Overexpression of GDNF in astrocytes could ameliorate the decline in cognitive function by improving hippocampal synaptic plasticity, meanwhile astrocytic GDNF rescued the anesthesia/surgery-induced decrease in GFRα1 and NCAM.

CONCLUSION

The study concludes that astrocytic GDNF may improve anesthesia/surgery-induced cognitive impairment by promoting hippocampal synaptic plasticity in aged mice via the GFRα1/NCAM pathway.

Postoperative cognitive dysfunction: a concept analysis

BACKGROUND

Post-operative cognitive dysfunction (POCD) is a concern for clinicians that often presents post-surgery where generalized anesthesia has been used. Its prevalence ranges from 36.6% in young adults to 42.4% in older individuals. Conceptual clarity for POCD is lacking in the currently body literature. Our two-fold purpose of this concept analysis was to (1) critically appraise the various definitions, while also providing the best definition, of POCD and (2) narratively synthesize the attributes, surrogate or related terms, antecedents (risk factors), and consequences of the concept.

METHOD

The reporting of our review was guided by the PRISMA statement and the 6-step evolutionary approach to concept analysis developed by Rodgers. Three databases, including Medline, CINAHL, and Web of Science, were searched to retrieve relevant literature on the concept of POCD. Two independent reviewers conducted abstract and full-text screening, data extraction, and appraisal. The review process yielded a final set of 86 eligible articles.

RESULT

POCD was defined with varying severities ranging from subtle-to-extensive cognitive changes (1) affecting single or multiple cognitive domains that manifest following major surgery (2), is transient and reversible, and (3) may last for several weeks to years. The consequences of POCD may include impaired quality of life, resulting from withdrawal from the labor force, increased patients' dependencies, cognitive decline, an elevated risk of dementia, rising healthcare costs, and eventual mortality.

CONCLUSION

This review resulted in a refined definition and comprehensive analysis of POCD that can be useful to both researchers and clinicians. Future research is needed to refine the operational definitions of POCD so that they better represent the defining attributes of the concept.

The influence of dexmedetomidine added to ropivacaine for transversus abdominis plane block on perioperative neurocognitive disorders after radical colorectal cancer surgery: randomized, double-blind, controlled trial

OBJECTIVE

Perioperative Neurocognitive Disorders (PND) is a common neurological complication after radical colorectal cancer surgery, which increases adverse outcomes. So, our objective is to explore the influence of dexmedetomidine added to ropivacaine for transversus abdominis plane block (TAPB) on perioperative neurocognitive disorders, and to provide a new way to reduce the incidence of PND.

METHODS

One hundred and eighty patients submitted to radical laparoscopic colorectal cancer surgery were randomly divided into Control group and Dex group. Ultrasound guided TAPB was performed after anesthesia induction: 0.5% ropivacaine 20 ml was injected into each transversus abdominis plane in Control group, 0.5% ropivacaine + 1 μg/kg dexmedetomidine (amounting to 20 ml) in Dex group. We observed the incidence of PND within 30 days after surgery.

RESULTS

One hundred and sixty-nine cases were finally analyzed, including 84 cases in Control group and 85 cases in Dex group. Compared with Control group, there was no significant difference in terms of the incidence of PND on the 3rd day and the 7th day (P > 0.05), but the incidence significantly decreased at the 6th hour, at the 24th hour and on the 30th day after surgery (P < 0.05) in Dex group.

CONCLUSION

Dexmedetomidine added to ropivacaine for TAPB can reduce the incidence of PND in the first 24 h after surgery and on the 30th postoperative day, which may be related to reduce the consumption of general anesthetics and provide satisfactory postoperative analgesia.

TRIAL REGISTRATION

29 /05/ 2021, ChiCTR2100046876.

Intravenous infusion of dexmedetomidine during the surgery to prevent postoperative delirium and postoperative cognitive dysfunction undergoing non-cardiac surgery: a meta-analysis of randomized controlled trials

BACKGROUND

Dexmedetomidine plays a pivotal role in mitigating postoperative delirium and cognitive dysfunction while enhancing the overall quality of life among surgical patients. Nevertheless, the influence of dexmedetomidine on such complications in various anaesthesia techniques remains inadequately explored. As such, in the present study, a meta-analysis was conducted to comprehensively evaluate its effects on postoperative delirium and cognitive dysfunction.

METHODS

A number of databases were searched for randomised controlled trials comparing intravenous dexmedetomidine to other interventions in preventing postoperative delirium and cognitive dysfunction in non-cardiac and non-neurosurgical patients. These databases included PubMed, Embase, and Cochrane Library. Statistical analysis and graphing were performed using Review Manager, STATA, the second version of the Cochrane risk-of-bias tool for randomised controlled trials, and GRADE profiler.

MAIN RESULTS

This meta-analysis comprised a total of 24 randomised controlled trials, including 20 trials assessing postoperative delirium and 6 trials assessing postoperative cognitive dysfunction. Across these 24 studies, a statistically significant positive association was observed between intravenous administration of dexmedetomidine and a reduced incidence of postoperative delirium (RR: 0.55; 95% CI 0.47 to 0.64, p < 0.00001, I2 = 2%) and postoperative cognitive dysfunction (RR: 0.60; 95% CI 0.38 to 0.96, p = 0.03, I2 = 60%). Subgroup analysis did not reveal a significant difference in the incidence of postoperative delirium between the general anaesthesia and non-general anaesthesia groups, but a significant difference was observed in the incidence of postoperative cognitive dysfunction. Nonetheless, when the data were pooled, it was evident that the utilisation of dexmedetomidine was associated with an increased incidence of hypotension (RR: 1.42; 95% CI 1.08 to 1.86, p = 0.01, I2 = 0%) and bradycardia (RR: 1.66; 95% CI 1.23 to 2.26, p = 0.001, I2 = 0%) compared with other interventions. However, there was no significantly higher occurrence of hypertension in the DEX groups (RR = 1.35, 95% CI 0.81-2.24, p = 0.25, I2 = 0%).

CONCLUSION

Compared with other interventions, intravenous dexmedetomidine infusion during non-cardiac and non-neurosurgical procedures may significantly reduce the risk of postoperative delirium and cognitive dysfunction. The results of subgroup analysis reveal a consistent preventive effect on postoperative delirium in both general and non-general anaesthesia groups. Meanwhile, continuous infusion during general anaesthesia was more effective in reducing the risk of cognitive dysfunction. Despite such findings, hypotension and bradycardia were more frequent in patients who received dexmedetomidine during surgery.

Knowledge, attitudes, and practice toward postoperative cognitive dysfunction among anesthesiologists in China: a cross-sectional study

BACKGROUND

To investigate the knowledge, attitudes, and practice (KAP) toward postoperative cognitive dysfunction (POCD) among anesthesiologists in China.

METHODS

This cross-sectional study was conducted nationwide among Chinese anesthesiologists between December 2022 and January 2023. The demographic information and KAP scores of the respondents were collected using a web-based questionnaire. The mean KAP dimension scores ≥ 60% were considered good.

RESULTS

This study enrolled 1032 anesthesiologists (51.2% male). The mean total scores of knowledge, positive attitude, and positive practice were 9.3 ± 1.2 (max 12), 34.8 ± 3.3 (max 40), and 30.6 ± 6.7 (max 40), respectively. The knowledge items with correctness scores < 60% were "the anesthetic drugs that tend to cause POCD" (23.3%) and "Treatment of POCD" (40.3%). Multivariable analysis showed that ≥ 40 years old, master's degree or above, intermediate professional title (i.e., attending physician), senior professional title (i.e., chief physician), and working in tertiary hospitals were independently associated with adequate knowledge. Multivariable analysis showed that the attitude scores, middle professional title, and ≥ 16 years of experience were independently associated with good practice.

CONCLUSIONS

These results suggest that Chinese anesthesiologists have good knowledge, favorable attitudes, and good practice toward POCD. Still, some points remain to be improved (e.g., the drugs causing POCD and managing POCD) and should be emphasized in training and continuing education.

TRIAL REGISTRATION

ChiCTR2200066749.

HSP90 Inhibition Attenuated Isoflurane-Induced Neurotoxicity in Mice and Human Neuroglioma Cells

Isoflurane, a widely used inhalation anesthetic in clinical practice, is associated with an increased risk of neuronal injury. Heat shock protein 90 (HSP90) plays a crucial role in maintaining neuronal homeostasis under stress conditions; however, its role during isoflurane exposure remains poorly understood. In this study, we aimed to investigate the protective effects of HSP90 inhibition and explore the regulatory mechanisms underlying these effects during isoflurane exposure. We found that the HSP90 inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17 AAG) has great protective effects in mitigating isoflurane-induced ferroptosis of mouse hippocampus and cultured neuronal cells. We focused on the activity of the crucial protein GPX4 in ferroptosis and found that 17 AAG exerted protective effects, preserving the physiological GPX4 activity under isoflurane exposure; further, 17 AAG restored the protein level of GPX4. Further, we observed that the chaperone-mediated autophagy (CMA) pathway was activated; 17 AAG also mediated GPX4 degradation under isoflurane exposure. Additionally, it interfered with the formation of complexes between HSP90 and Lamp-2a, inhibiting CMA activity, followed by the blockade of GPX4 degradation, further affecting the isoflurane-induced ferroptosis. Based on these findings, we proposed HSP90 inhibition as a protective mechanism against isoflurane-induced ferroptosis in neurons.

Anesthesia and dementia: An up-to-date review of the existing literature

Concerns around the impact of anesthesia on cognitive decline and dementia, including Alzheimer's Disease (AD), have been increasing and recently attracting considerable attention in the research community. One unanswered question is whether anesthesia is a risk factor of dementia, specifically AD type dementia. A large body of evidence, coming from in vivo and in vitro models, suggests that exposure to anesthetic agents may increase the risk of AD through mechanisms of action similar to AD's neuropathology. In terms of clinical studies, our knowledge of the relationship between anesthesia and dementia is based on limited data, with most studies suggesting that there is no association. The aim of this paper was therefore to outline recent clinical studies exploring this controversial relationship and discuss future directions in terms of study design and potential areas of study. As the aging population and the prevalence of dementia and AD increases, we need a better understanding of anesthesia as a risk factor for neurodegeneration through well-designed studies. Despite the controversy, there seems to be little evidence to support that anesthesia itself or other surgical and patient factors can cause or accelerate AD.

Assessment of seizure duration and utility of using SedLine® EEG tracing in veterans undergoing electroconvulsive therapy: a retrospective analysis

BACKGROUND

Electroconvulsive therapy (ECT) endures as a definitive treatment for refractory depression and catatonia and is also considered an effective treatment for a number of other severe psychiatric disorders (Lisanby, N Engl J Med 357:1939-1945, 2007)(Weiner and Prudic, Biol Psychiatry 73:105-106, 2013). GA is an essential component of the ECT procedure for various reasons (Lee, Jenkins and Sparkle, Life 11, 2021). Monitoring anesthetic effects on the brain is desirable as anesthetic agents affect seizure duration and recovery (Rasulo, Hopkins, Lobo, et al,  Neurocrit Care 38:296-311, 2023) (Jones , Nittur , Fleming and Applegate,  BMC Anesthesiol 21:105, 2021) (Soehle , Kayser , Ellerkmann and Schlaepfer,  BJA 112:695-702, 2013). Perioperative anesthetic effects on consciousness can be assessed with brain function monitoring using raw electroencephalogram (EEG) traces and processed EEG indices.

OBJECTIVE

We examined the usefulness and utility of the SedLine® anesthetic effect monitor during ECT procedures. We hypothesized that the seizure duration as measured by the EEG tracing of the ECT machine is equivalent to the duration assessed by the SedLine® EEG tracing. A secondary objective was to describe the SedLine® patient state indices (PSI) at different phases of treatment.

METHODS

Following IRB approval, we analyzed the data of the electronic medical records of 45 ECT treatments of 23 patients in an urban VA medical center between July 01, 2021, and March 30, 2022. We compared the seizure duration in minutes and seconds as measured either by the ECT machine EEG tracing or the SedLine® EEG tracing. We then collected SedLine® processed EEG indices at four different stages during the treatment. Appropriate comparative and observational statistical analyses were applied.

RESULTS

There was no significant difference in measured seizure duration between the two methods examined (p < 0.05). We observed a lag of the SedLine PSI value at the time before stimulus delivery and limited PSI utility during the course of ECT.

CONCLUSION

The SedLine® EEG tracing can be an alternative to the machine EEG tracing for the determination of seizure duration. The SedLine® processed EEG indices are not consistently useful before and after ECT delivery. Anesthetic effect monitoring during ECT is feasible.

Sub-dose anesthetics combined with chloride regulators protect the brain against chronic ischemia-hypoxia injury

BACKGROUND

Cerebral ischemia-hypoxia leads to excitotoxicity-mediated neuronal damage and cognitive dysfunction, especially in the elderly. Excessive intracellular [Cl- ]i accumulation weakens γ-aminobutyric acid (GABA) compensatory effects. Sub-anesthetic dose of propofol protected the brain against ischemia-hypoxia, which was abolished by blocking Cl- efflux transporter K+ /Cl- cotransporter 2 (KCC2). We aimed to determine whether low-dose anesthetic combined with [Cl- ]i regulators could restore the compensatory GABAergic system and improve cognitive function.

METHODS

Chronic cerebral hypoxia (CCH) model was established by bilateral carotid artery ligation in aged rats. Sub-dose of anesthetics (propofol and sevoflurane) with or without KCC2 agonist N-ethylmaleimide (NEM) or Na+ /K+ /Cl- cotransporter 1 (NKCC1) antagonist bumetanide (BTN) was administered systemically 30 days post-surgery. Primary rat hippocampal neuronal cultures were subjected to hypoxic injury with or without drug treatment. Memory function, hippocampal neuronal survival, GABAergic system functioning, and brain-derived neurotrophic factor (BDNF) expressions were evaluated.

RESULTS

Sub-anesthetic dose of combined propofol (1.2 μg mL-1 ) and sevoflurane [0.7 MAC (minimum alveolar concentration)] did not aggravate the hypoxic brain injury in rats or cell damage in neuronal cultures. Adding either BTN or NEM protected against hypoxic injury, associated with improved cognitive function in vivo, less intracellular accumulation of [Cl- ]i , reduced cell death, restored GABAergic compensation, and increased BDNF expression both in vivo and in vitro.

CONCLUSION

Sub-anesthetic dose of propofol and sevoflurane is a recommended anesthesia regimen in at-risk patients. Restoration of [Cl- ]i homeostasis and GABAergic could further reduce the brain damage caused by ischemia-hypoxia.

Post-Anesthesia Cognitive Dysfunction in Mice Is Associated with an Age-Related Increase in Neuronal Intracellular [Ca2+]-Neuroprotective Effect of Reducing Intracellular [Ca2+]: In Vivo and In Vitro Studies

Background: Postoperative cognitive dysfunction (POCD) is a common disorder after general anesthesia in elderly patients, the precise mechanisms of which remain unclear. Methods: We investigated the effect of isoflurane with or without dantrolene pretreatment on intracellular calcium concentration ([Ca2+]i), reactive oxygen species (ROS) production, cellular lactate dehydrogenase (LDH) leak, calpain activity, and cognitive function using the Morris water maze test of young (3 months), middle-aged (12-13 months), and aged (24-25 months) C57BL6/J mice. Results: Aged cortical and hippocampal neurons showed chronically elevated [Ca2+]i compared to young neurons. Furthermore, aged hippocampal neurons exhibited higher ROS production, increased LDH leak, and elevated calpain activity. Exposure to isoflurane exacerbated these markers in aged neurons, contributing to increased cognitive deficits in aged mice. Dantrolene pretreatment reduced [Ca2+]i for all age groups and prevented or significantly mitigated the effects of isoflurane on [Ca2+]i, ROS production, LDH leak, and calpain activity in aged neurons. Dantrolene also normalized or improved age-associated cognitive deficits and mitigated the cognitive deficits caused by isoflurane. Conclusions: These findings suggest that isoflurane-induced cytotoxicity and cognitive decline in aging are linked to disruptions in neuronal intracellular processes, highlighting the reduction of [Ca2+]i as a potential therapeutic intervention.

Postoperative cognitive dysfunction-current research progress

Postoperative cognitive dysfunction (POCD) commonly occurs after surgery, particularly in elderly individuals. It is characterized by a notable decline in cognitive performance, encompassing memory, attention, coordination, orientation, verbal fluency, and executive function. This reduction in cognitive abilities contributes to extended hospital stays and heightened mortality. The prevalence of POCD can reach 40% within 1 week following cardiovascular surgery and remains as high as 17% 3 months post-surgery. Furthermore, POCD exacerbates the long-term risk of Alzheimer's disease (AD). As a result, numerous studies have been conducted to investigate the molecular mechanisms underlying POCD and potential preventive strategies. This article provides a review of the research progress on POCD.

Impact of propofol and sevoflurane anesthesia on cognition and emotion in gastric cancer patients undergoing radical resection

BACKGROUND

Propofol and sevoflurane are commonly used anesthetic agents for maintenance anesthesia during radical resection of gastric cancer. However, there is a debate concerning their differential effects on cognitive function, anxiety, and depression in patients undergoing this procedure.

AIM

To compare the effects of propofol and sevoflurane anesthesia on postoperative cognitive function, anxiety, depression, and organ function in patients undergoing radical resection of gastric cancer.

METHODS

A total of 80 patients were involved in this research. The subjects were divided into two groups: Propofol group and sevoflurane group. The evaluation scale for cognitive function was the Loewenstein occupational therapy cognitive assessment (LOTCA), and anxiety and depression were assessed with the aid of the self-rating anxiety scale (SAS) and self-rating depression scale (SDS). Hemodynamic indicators, oxidative stress levels, and pulmonary function were also measured.

RESULTS

The LOTCA score at 1 d after surgery was significantly lower in the propofol group than in the sevoflurane group. Additionally, the SAS and SDS scores of the sevoflurane group were significantly lower than those of the propofol group. The sevoflurane group showed greater stability in heart rate as well as the mean arterial pressure compared to the propofol group. Moreover, the sevoflurane group displayed better pulmonary function and less lung injury than the propofol group.

CONCLUSION

Both propofol and sevoflurane could be utilized as maintenance anesthesia during radical resection of gastric cancer. Propofol anesthesia has a minimal effect on patients' pulmonary function, consequently enhancing their postoperative recovery. Sevoflurane anesthesia causes less impairment on patients' cognitive function and mitigates negative emotions, leading to an improved postoperative mental state. Therefore, the selection of anesthetic agents should be based on the individual patient's specific circumstances.

Dexmedetomidine alleviates hippocampal neuronal loss and cognitive decline in rats undergoing open surgery under sevoflurane anaesthesia by suppressing CCAAT/enhancer-binding protein beta

Dexmedetomidine (Dex) may exert neuroprotective effects by attenuating inflammatory responses. However, whether Dex specifically improves postoperative cognitive dysfunction (POCD) by inhibiting microglial inflammation through what pathway remains unclear. In this study, the POCD model was constructed by performing open surgery after 3 h of continuous inhalation of 3% sevoflurane to rats, which were intraperitoneally injected with 25 μg/kg Dex .5 h before anaesthesia. The results displayed that Dex intervention decreased rat escape latency, maintained swimming speed and increased the number of times rats crossed the platform and the time spent in the target quadrant. Furthermore, the rat neuronal injury was restored, alleviated POCD modelling-induced rat hippocampal microglial activation and inhibited microglial M1 type polarization. Besides, we administered Dex injection and/or CCAAT/enhancer-binding protein beta (CEBPB) knockdown on the basis of sevoflurane exposure and open surgery and found that CEBPB was knocked down, resulting in the inability of Dex to function, which confirmed CEBPB as a target for Dex treatment. To sum up, Dex improved POCD by considering CEBPB as a drug target to activate the c-Jun N-terminal kinase (JNK)/p-38 signaling pathway, inhibiting microglial M1 polarization-mediated inflammation in the central nervous system.

The Role of Vitamin K in the Development of Neurodegenerative Diseases

Neurodegenerative diseases are a growing global health problem with enormous consequences for individuals and society. The most common neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases, can be caused by both genetic factors (mutations) and epigenetic changes caused by the environment, in particular, oxidative stress. One of the factors contributing to the development of oxidative stress that has an important effect on the nervous system is vitamin K, which is involved in redox processes. However, its role in cells is ambiguous: accumulation of high concentrations of vitamin K increases the content of reactive oxygen species increases, while small amounts of vitamin K have a protective effect and activate the antioxidant defense systems. The main function of vitamin K is its involvement in the gamma carboxylation of the so-called Gla proteins. Some Gla proteins are expressed in the nervous system and participate in its development. Vitamin K deficiency can lead to a decrease or loss of function of Gla proteins in the nervous system. It is assumed that the level of vitamin K in the body is associated with specific changes involved in the development of dementia and cognitive abilities. Vitamin K also influences the sphingolipid profile in the brain, which also affects cognitive function. The role of vitamin K in the regulation of biochemical processes at the cellular and whole-organism levels has been studied insufficiently. Further research can lead to the discovery of new targets for vitamin K and development of personalized diets and therapies.

Ultrasound-guided serratus anterior plane block to prevent neurocognitive impairment in elderly patients after thoracoscopic lobectomy: protocol for a single-centre, double-blind, randomised controlled trial

INTRODUCTION

Postoperative neurocognitive dysfunction (PND), including postoperative delirium (POD), is a common complication in elderly patients after major surgeries, often leading to poor postoperative recovery. Although the pathological mechanism underlying PND is still unclear, postoperative pain is strongly associated with the development of PND. The ultrasound-guided serratus anterior plane block (SAPB) has been reported to relieve postoperative pain in thoracic surgery. Therefore, this prospective trial hypothesises that SAPB may reduce the incidence of PND in the elderly undergoing thoracoscopic lobectomy.

METHODS AND ANALYSIS

This study is designed as a single-centre, double-blind, randomised controlled clinical trial. A total of 256 elderly patients scheduled to undergo thoracoscopic lobectomy at Shanghai Pulmonary Hospital will be randomly assigned to general anaesthesia group or SAPB group. The primary outcome is the incidence of PND 7 days postoperatively or before discharge from hospital. The secondary outcomes include the occurrence of POD, the postoperative pain scores, Quality of Recovery at 1-2 days postoperatively and incidence of PND at 3 months postoperatively. The levels of fasting blood glucose in peripheral blood will be examined before and 1-2 days postoperatively.

ETHICS AND DISSEMINATION

The trial has been approved by the Clinical Research Ethics Committee of Shanghai Pulmonary Hospital (identifier: K20-290). All participants will be required to provide written informed consent before any protocol-specific procedures. Findings will be disseminated in a peer-reviewed journal and in national and/or international meetings to guide future practice.

TRIAL REGISTRATION NUMBER

ChiCTR2100052633.

Brief isoflurane administration as an adjunct treatment to control organophosphate-induced convulsions and neuropathology

Organophosphate-based chemical agents (OP), including nerve agents and certain pesticides such as paraoxon, are potent acetylcholinesterase inhibitors that cause severe convulsions and seizures, leading to permanent central nervous system (CNS) damage if not treated promptly. The current treatment regimen for OP poisoning is intramuscular injection of atropine sulfate with an oxime such as pralidoxime (2-PAM) to mitigate cholinergic over-activation of the somatic musculature and autonomic nervous system. This treatment does not provide protection against CNS cholinergic overactivation and therefore convulsions require additional medication. Benzodiazepines are the currently accepted treatment for OP-induced convulsions, but the convulsions become refractory to these GABAA agonists and repeated dosing has diminishing effectiveness. As such, adjunct anticonvulsant treatments are needed to provide improved protection against recurrent and prolonged convulsions and the associated excitotoxic CNS damage that results from them. Previously we have shown that brief, 4-min administration of 3%-5% isoflurane in 100% oxygen has profound anticonvulsant and CNS protective effects when administered 30 min after a lethal dose of paraoxon. In this report we provide an extended time course of the effectiveness of 5% isoflurane delivered for 5 min, ranging from 60 to 180 min after a lethal dose of paraoxon in rats. We observed substantial effectiveness in preventing neuronal loss as shown by Fluoro-Jade B staining when isoflurane was administered 1 h after paraoxon, with diminishing effectiveness at 90, 120 and 180 min. In vivo magnetic resonance imaging (MRI) derived T2 and mean diffusivity (MD) values showed that 5-min isoflurane administration at a concentration of 5% prevents brain edema and tissue damage when administered 1 h after a lethal dose of paraoxon. We also observed reduced astrogliosis as shown by GFAP immunohistochemistry. Studies with continuous EEG monitoring are ongoing to demonstrate effectiveness in animal models of soman poisoning.

Phoenixin-20 ameliorates Sevoflurane inhalation-induced post-operative cognitive dysfunction in rats via activation of the PKA/CREB signaling

Post-operative cognitive dysfunction (POCD) is a common complication after surgery due to the usage of anesthetics, such as Sevoflurane, which severely impacts the life quality of patients. Currently, the pathogenesis of Sevoflurane-induced POCD has not been fully elucidated but is reportedly involved with oxidative stress (OS) injury and aggravated inflammation. Phoenixin-20 (PNX-20) is a PNX peptide consisting of 20 amino acids with promising inhibitory effects on OS and inflammation. Herein, we proposed to explore the potential protective function of PNX-20 on Sevoflurane inhalation-induced POCD in rats. Sprague-Dawley (SD) rats were treated with 100 ng/g PNX-20 for 7 days with or without pre-inhalation with 2.2% Sevoflurane. Markedly increased escape latency and decreased time in the target quadrant in the Morris water maze (MWM) test, and aggravated pathological changes and apoptosis in the hippocampus tissue were observed in Sevoflurane-treated rats, which were markedly attenuated by PNX-20. Furthermore, the aggravated inflammation and OS in the hippocampus observed in Sevoflurane-treated rats were notably abolished by PNX-20. Moreover, the brain-derived neurotrophic factor (BDNF), protein kinase A (PKA), and phospho-cAMP response element binding protein/cAMP response element binding protein (p-CREB/CREB) levels were markedly decreased in Sevoflurane-treated rats, which were memorably increased by PNX-20. Our results indicated that PNX-20 ameliorated Sevoflurane inhalation-induced POCD in rats via the activation of PKA/CREB signaling, which might supply a new treatment approach for POCD.

Scientific rationale for the use of α2A-adrenoceptor agonists in treating neuroinflammatory cognitive disorders

Neuroinflammatory disorders preferentially impair the higher cognitive and executive functions of the prefrontal cortex (PFC). This includes such challenging disorders as delirium, perioperative neurocognitive disorder, and the sustained cognitive deficits from "long-COVID" or traumatic brain injury. There are no FDA-approved treatments for these symptoms; thus, understanding their etiology is important for generating therapeutic strategies. The current review describes the molecular rationale for why PFC circuits are especially vulnerable to inflammation, and how α2A-adrenoceptor (α2A-AR) actions throughout the nervous and immune systems can benefit the circuits in PFC needed for higher cognition. The layer III circuits in the dorsolateral PFC (dlPFC) that generate and sustain the mental representations needed for higher cognition have unusual neurotransmission and neuromodulation. They are wholly dependent on NMDAR neurotransmission, with little AMPAR contribution, and thus are especially vulnerable to kynurenic acid inflammatory signaling which blocks NMDAR. Layer III dlPFC spines also have unusual neuromodulation, with cAMP magnification of calcium signaling in spines, which opens nearby potassium channels to rapidly weaken connectivity and reduce neuronal firing. This process must be tightly regulated, e.g. by mGluR3 or α2A-AR on spines, to prevent loss of firing. However, the production of GCPII inflammatory signaling reduces mGluR3 actions and markedly diminishes dlPFC network firing. Both basic and clinical studies show that α2A-AR agonists such as guanfacine can restore dlPFC network firing and cognitive function, through direct actions in the dlPFC, but also by reducing the activity of stress-related circuits, e.g. in the locus coeruleus and amygdala, and by having anti-inflammatory actions in the immune system. This information is particularly timely, as guanfacine is currently the focus of large clinical trials for the treatment of delirium, and in open label studies for the treatment of cognitive deficits from long-COVID.

High Variability Periods in the EEG Distinguish Cognitive Brain States

OBJECTIVE

To describe a novel measure of EEG signal variability that distinguishes cognitive brain states.

METHOD

We describe a novel characterization of amplitude variability in the EEG signal termed "High Variability Periods" or "HVPs", defined as segments when the standard deviation of a moving window is continuously higher than the quartile cutoff. We characterize the parameter space of the metric in terms of window size, overlap, and threshold to suggest ideal parameter choice and compare its performance as a discriminator of brain state to alternate single channel measures of variability such as entropy, complexity, harmonic regression fit, and spectral measures.

RESULTS

We show that the average HVP duration provides a substantially distinct view of the signal relative to alternate metrics of variability and, when used in combination with these metrics, significantly enhances the ability to predict whether an individual has their eyes open or closed and is performing a working memory and Raven's pattern completion task. In addition, HVPs disappear under anesthesia and do not reappear in early periods of recovery.

CONCLUSIONS

HVP metrics enhance the discrimination of various brain states and are fast to estimate.

SIGNIFICANCE

HVP metrics can provide an additional view of signal variability that has potential clinical application in the rapid discrimination of brain states.

Sevoflurane suppresses ALG13 transcription in a CREBBP-dependent manner to induce hippocampal damage and cognitive impairment

BACKGROUND

Sevoflurane (Sev) is a common clinical anesthetic but may lead to cognitive impairment. This study aims to deconstruct the underpinning molecular mechanism involved in Sev-induced neurological damage.

METHODS

Bioinformatics analyses was conducted to investigate candidate cognitive impairment-related physiological substrates of Sev. C57BL/6 mice and SH-SY5Y cells were exposed to Sev to generate animal and cellular models, respectively. Neurological impairment in mice was evaluated by Morris water maze test, modified Longa scoring, and pathological changes and cell apoptosis in the hippocampal tissues. In vitro, viability, apoptosis, and inflammatory cytokine concentration in SH-SY5Y cells were measured. Gain- or loss-of-function studies of CREB binding protein (CREBBP) and its predicted target asparagine-linked glycosylation 13 (ALG13) were performed in mice and in SH-SY5Y cells to investigate their roles in neural damage.

RESULTS

Sev treatment induced neurological deficit in mice and damage on SH-SY5Y cells, and reduced protein level of CREBBP protein in both models. CREBBP overexpression restored learning and memory ability of mice, reduced neurological deficit score, and reduced cell apoptosis while enhancing neuronal viability in the hippocampus. In vitro, the CREBBP overexpression increased viability while suppressing apoptosis and inflammation in SH-SY5Y cells. CREBBP bound to the ALG13 promoter to increase its transcription. Further knockdown of ALG13 negated the neuro-protective functions of CREBBP in vivo and in vitro.

CONCLUSION

This study demonstrates that Sev targets CREBBP to inhibit ALG13 transcription to induce hippocampal damage and cognitive impairment.

Physical activity compensates for isoflurane-induced selective impairment of neuronal progenitor cell proliferation in the young adult hippocampus

General anesthesia is considered a risk factor for postoperative cognitive dysfunction. However, it is unclear what the neuronal and cognitive consequences of general anesthesia are and whether they can be treated. One possible pathomechanism is hippocampal neurogenesis. We investigated how the anesthetic isoflurane affects adult hippocampal neurogenesis and associated cognitive functions and whether the neurogenic stimulus of physical activity reverses isoflurane-induced changes. We exposed young adult mice to isoflurane (ISO) - half had access to a running wheel (ISO-RW). Both groups were compared with a control condition (CTR; CTR-RW). Cell proliferation and survival in the dentate gyrus of the hippocampus were quantified histologically 48 h and 3 weeks after anesthesia by bromodeoxyuridine incorporation. Cell phenotype was determined by expression of neuronal markers, and the extent of continuous endogenous neuronal proliferation was estimated from the number of doublecortin-positive cells. The Morris water maze was used to test hippocampus-dependent functions. We found that isoflurane decreased proliferation of neuronal progenitor cells, whereas survival of mature neurons remained intact. Consistent with intact neuronal survival, spatial memory associated with neurogenesis also proved intact in the Morris water maze despite isoflurane exposure. Physical activity attenuated the observed neuronal changes by preventing the decrease in newborn neuronal progenitor cells and the decline in continuous endogenous neuronal proliferation in isoflurane-treated animals. In conclusion, isoflurane selectively impairs neuronal proliferation but not survival or neurogenesis-linked cognition in adult mice. The observed adverse effects can be attenuated by physical activity, a cost-effective means of preventing the neurogenic consequences of general anesthesia.

Index of consciousness monitoring during general anesthesia may effectively enhance rehabilitation in elderly patients undergoing laparoscopic urological surgery: a randomized controlled clinical trial

BACKGROUND

Based on electroencephalogram (EEG) analysis, index of consciousness (IoC) monitoring is a new technique for monitoring anesthesia depth. IoC is divided into IoC1 (depth of sedation) and IoC2 (depth of analgesia). The potential for concurrent monitoring of IoC1 and IoC2 to expedite postoperative convalescence remains to be elucidated. We investigated whether combined monitoring of IoC1 and IoC2 can effectively enhances postoperative recovery compared with bispectral index (BIS) in elderly patients undergoing laparoscopic urological surgery under general anesthesia.

METHODS

In this prospective, controlled, double-blinded trail, 120 patients aged 65 years or older were arbitrarily assigned to either the IoC group or the control group (BIS monitoring). All patients underwent blood gas analysis at T1 (before anesthesia induction) and T2 (the end of operation). The Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were administered to all patients at T0 (1 day before surgery) and T4 (7 days after surgery). Serum concentrations of C-reactive protein (CRP) and glial fibrillary acid protein (GFAP) were assessed at T1, T2, and T3 (24 h after surgery). Postoperative complications and the duration of hospitalization were subjected to comparative evaluation.

RESULTS

The incidence of postoperative cognitive dysfunction (POCD) was notably lower in the IoC group (10%) than in the control group (31.7%) (P = 0.003). Postoperative serum CRP and GFAP concentrations exhibited significant differences at time points T2 (CRP: P = 0.000; GFAP: P = 0.000) and T3 (CRP: P = 0.003; GFAP: P = 0.008). Postoperative blood glucose levels (P = 0.000) and the overall rate of complications (P = 0.037) were significantly lower in Group IoC than in Group control.

CONCLUSION

The employment of IoC monitoring for the management of elderly surgical patients can accelerate postoperative convalescence by mitigating intraoperative stress and reducing peripheral and central inflammatory injury.

TRIAL REGISTRATION

Chinese Clinical Trial Registry Identifier: ChiCTR1900025241 (17/08/2019).

Predicting Death or Disability after Surgery in the Older Adult

BACKGROUND

Older patients are vulnerable to developing new or worsening disability after surgery. Despite this, patient or surgical characteristics predisposing to postoperative disability are poorly defined. The aim of the study was to develop and validate a model, subsequently transformed to point-score form, to predict 6-month death or disability in older patients after surgery.

METHODS

The authors built a prospective, single-center registry to develop and validate the prediction model. The registry included patients 70 yr of age or older undergoing elective and nonelective, cardiac and noncardiac surgery between May 25, 2017, and February 11, 2021, and combined clinical data from the electronic medical record, hospital administrative data (International Classification of Diseases, Tenth Revision, Australian Modification codes) and World Health Organization (Geneva, Switzerland) Disability Assessment Schedule data collected directly from the patients. Death or disability was defined as being dead or having a World Health Organization Disability Assessment Schedule score 16% or greater. Included patients were randomly divided into model development (70%) and internal validation (30%) cohorts. Once constructed, the logistic regression and point-score models were assessed using the internal validation cohort and an external validation cohort comprising data from a separate randomized trial.

RESULTS

Of 2,176 patients who completed the World Health Organization Disability Assessment Schedule immediately before surgery, 927 (43%) patients were disabled, and 413 (19%) had significant disability. By 6 months after surgery, 1,640 patients (75%) had data available for the primary outcome analysis. Of these patients, 195 (12%) patients had died, and 691 (42%) were dead or disabled. The developed point-score model included the preoperative World Health Organization Disability Assessment Schedule score, patient age, dementia, and chronic kidney disease. The point score model retained good discrimination in the internal (area under the curve, 0.74; 95% CI, 0.69 to 0.79) and external (area under the curve, 0.77; 95% CI, 0.74 to 0.80) validation data sets.

CONCLUSIONS

The authors developed and validated a point score model to predict death or disability in older patients after surgery.

EDITOR’S PERSPECTIVE

Apamin, an SK2 Inhibitor, Attenuated Neonatal Sevoflurane Exposures Caused Cognitive Deficits in Mice through the Regulation of Hippocampal Neuroinflammation

Cognitive dysfunction induced by anesthesia in the infant is a crucial clinical issue that is still being debated and the focus of concern for the parents. However, the mechanism of cognitive decline caused by anesthesia and the corresponding treatment methods remain unclear. Postnatal day 7 (PND7) C57BL/6 mice included in the study were randomly divided into a control group (Control), a group with repeated exposure to sevoflurane (Sevo), and an Apamin intervention group (Sevo + Apamin). Apamin (0.5 μL at the concentration of 100 nmol/L) was injected into the bilateral hippocampus of mice. qRT-PCR, enzyme-linked immunosorbent assay (ELISA), and western blotting assay were used to evaluate the protein levels in the hippocampus. Object location memory (OLM) and novel object recognition (NOR) tasks, as well as elevated plus maze and contextual and cued fear conditioning tasks were used to evaluate the cognitive function of mice. Apamin mitigated sevoflurane-induced cognitive impairment of mice, sevoflurane-induced neuronal injury, and sevoflurane-induced activation of microglial in the hippocampus of the mice. Apamin inhibited M1-type polarization but promoted M2-type polarization of microglia after neonatal sevoflurane exposures in the hippocampus. In conclusion, Apamin attenuates neonatal sevoflurane exposures that cause cognitive deficits in mice through regulating hippocampal neuroinflammation.

General anesthesia versus regional anesthesia in patients undergoing obliterative vaginal procedures for pelvic organ prolapse

INTRODUCTION AND HYPOTHESIS

The objective was to compare outcomes in patients receiving general versus regional anesthesia when undergoing obliterative vaginal surgery for pelvic organ prolapse.

METHODS

Obliterative vaginal procedures performed from 2010 to 2020 were identified in the American College of Surgeons National Surgical Quality Improvement Program database using Current Procedural Terminology codes. Surgeries were categorized into general anesthesia (GA) or regional anesthesia (RA). Rates of reoperation, readmission, operative time, and length of stay were determined. A composite adverse outcome was calculated including any of the following: nonserious or serious adverse events, 30-day readmission, or reoperation. Propensity score-weighted analysis of perioperative outcomes was performed.

RESULTS

The cohort included 6,951 patients, of whom 6,537 (94%) underwent obliterative vaginal surgery under GA and 414 (6%) received RA. When comparing outcomes under the propensity score-weighted analysis, operative times were shorter (median 96 vs 104 min, p<0.01) in the RA group versus GA. There were no significant differences between composite adverse outcomes (10% vs 12%, p=0.06), or readmission (5% vs 5%, p=0.83) and reoperation rates (1% vs 2%, p=0.12) between the RA and GA groups. Length of stay was shorter in patients receiving GA than in those receiving RA, especially when undergoing concomitant hysterectomy (67% discharged within 1 day in GA vs 45% in RA, p<0.01).

CONCLUSIONS

Composite adverse outcomes, reoperation rates, and readmission rates were similar in patients who received RA for obliterative vaginal procedures compared with GA. Operative times were shorter in patients receiving RA than in those receiving GA, and length of stay was shorter in patients receiving GA than in those receiving RA.

Prospective association of general anesthesia with risk of cognitive decline in a Chinese elderly community population

As life expectancy increases and the population grows, the number of surgeries performed each year is likely to continue to increase. We evaluated whether surgery with general anesthesia increases risk for cognitive impairment in a Chinese elderly community population. The current data was obtained from the China Longitudinal Aging Study (cohort 1) and Shanghai Brain Aging study (cohort 2). Cohort 1 included 1545 elderly people with normal cognitive function, who underwent a screening process that included physical examination, medical history, baseline and 1-year follow-up assessments of cognitive function by a face-to-face interview. Cohort 2 included an additional 194 elderly people with normal cognitive function, all of whom, unlike cohort 1, underwent T1-phase MR imaging scans. In cohort 1, 127 elderly people with normal cognitive function transformed into mild cognitive impairment, 27 into dementia, while 1391 still maintained normal cognitive function. By using Cox regression analysis, we found that surgery with general anesthesia was a risk factor for cognitive impairment (p = 0.013, HR = 1.506, 95% CI 1.091-2.078); In cohort 2, we found that elderly people with a history of surgery with general anesthesia had lower Montreal Cognitive Assessment (MoCA) scores and smaller right amygdala volume (p < 0.05). Through correlation analysis, we found that the volume of the right amygdala was significantly correlated (p = 0.003, r = 0.212) with MoCA. Then by using the linear regression analysis (mediation model), we found that surgery with general anesthesia directly affected the MoCA score by affecting the volume of the right amygdala (B = 1.315, p = 0.036 95% CI 0.088-2.542). We confirm surgery with general anesthesia as a risk factor for cognitive impairment, and its mechanism may be related to its effect on the volume of the right amygdala.

Plasma lipidomics reveals potential lipid markers for the prediction of delayed neurocognitive recovery after cardiac surgery with cardiopulmonary bypass

BACKGROUND

Delayed neurocognitive recovery (DNR) is a cognitive change that affects patients after anesthesia and surgery, with a high incidence, severely impairing their quality of life. We identified relevant metabolic pathways to determine predictive lipid markers and understand the pathogenesis of DNR.

METHODS

A non-targeted lipidomic strategy using Waters Acquity I Class UPLC-Xevo G2-S QTOF UPLC-MS was employed to identify different lipids in the 24 h postoperative plasma of patients whose cognitive function was assessed 7-14 days after surgery. Principal component analysis, orthogonal partial least squares discriminant analysis, and receiver operating characteristic (ROC) curves were used to identify potential biomarkers for predicting DNR. Metabolic pathway analysis was performed using the online platform MetaboAnalyst 5.0.

RESULTS

Pre-operative hemoglobin was identified as an independent risk factor for DNR. The individual areas under the ROC curves (AUC) of the 5 representative lipids were all > 0.6, and the AUC of the combined predictor was 0.912. Glycerophospholipid metabolic pathway was dysregulated in patients with subsequent DNR.

CONCLUSION

This study identified a series of potential predictive biomarkers for DNR. These data suggested that glycerophospholipid metabolism may be the mechanism underlying the occurrence and progression of DNR.

Sevoflurane inhibited reproductive function in male mice by reducing oxidative phosphorylation through inducing iron deficiency

Sevoflurane (Sev) is one of the commonly used inhalation anesthetic chemicals in clinics. It has great impact on spermatogenesis and fertilization in male animals. The underlying mechanism remains largely unexplored. Based on our previous research, we hypothesized that Sev induced iron metabolism disturbance in the testis and epididymis and inhibited the spermatogenesis. In this study, two-month-old C57BL/6 male mice were treated with 3% Sev for 6 h, and their fertility (including sperm concentration, sperm mobility, and the number of offspring) was evaluated. Mice testis, epididymis, and sperm were harvested and subjected to Western blot analysis and immunofluorescence analysis. Iron levels were reflected by the gene expression of iron metabolism-related proteins (including ferritin, TfR1, and FpN1) and ICP-MS and Perl's iron staining. Electron transport and oxidative phosphorylation levels were measured by Oxygraph-2k and ATP contents. The activity of ribonucleotide reductase was evaluated by assay kit. DNA synthesis status in testis and/or epididymis was marked with BrdU. Cell proliferation was evaluated by double immunofluorescence staining of specific protein marker expression. Our results revealed that the mice exposed to Sev showed damaged testicular and epididymis structure and significantly reduced the sperm concentration, sperm motility, and fertility. Sev decreases the iron levels through down-regulating the expression of H-ferritin, L-ferritin, and FpN1, and up-regulating the expression of TfR1 in the testis and epididymis. Iron levels also significantly reduced in germ cells which decrease the number of germ cells, including sperm, Sertoli cells, and primary spermatocyte. Iron deficiency not only decreases electron transport, oxidative phosphorylation level, and ATP production but also suppresses the activity of ribonucleotide reductase and the expression of Ki67, DDX4, GATA1, and SCP3, indicating that Sev affects the spermatogenesis and development. Meanwhile, Sev impaired the blood-testis barrier by decreasing the ZO1 expression in the testis and epididymis. The damage effect induced by Sev can be significantly ameliorated by iron supplementation. In conclusion, our study illustrates a new mechanism by which Sev inhibits spermatogenesis and fertility through an oxidative phosphorylation pathway due to iron deficiency of epididymis and testis or sperm. Furthermore, the damaging effects could be ameliorated by iron supplementation.

Neurodegenerative and Neurodevelopmental Diseases and the Gut-Brain Axis: The Potential of Therapeutic Targeting of the Microbiome

The human gut microbiome contains the largest number of bacteria in the body and has the potential to greatly influence metabolism, not only locally but also systemically. There is an established link between a healthy, balanced, and diverse microbiome and overall health. When the gut microbiome becomes unbalanced (dysbiosis) through dietary changes, medication use, lifestyle choices, environmental factors, and ageing, this has a profound effect on our health and is linked to many diseases, including lifestyle diseases, metabolic diseases, inflammatory diseases, and neurological diseases. While this link in humans is largely an association of dysbiosis with disease, in animal models, a causative link can be demonstrated. The link between the gut and the brain is particularly important in maintaining brain health, with a strong association between dysbiosis in the gut and neurodegenerative and neurodevelopmental diseases. This link suggests not only that the gut microbiota composition can be used to make an early diagnosis of neurodegenerative and neurodevelopmental diseases but also that modifying the gut microbiome to influence the microbiome-gut-brain axis might present a therapeutic target for diseases that have proved intractable, with the aim of altering the trajectory of neurodegenerative and neurodevelopmental diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, autism spectrum disorder, and attention-deficit hyperactivity disorder, among others. There is also a microbiome-gut-brain link to other potentially reversible neurological diseases, such as migraine, post-operative cognitive dysfunction, and long COVID, which might be considered models of therapy for neurodegenerative disease. The role of traditional methods in altering the microbiome, as well as newer, more novel treatments such as faecal microbiome transplants and photobiomodulation, are discussed.

P2X7 Receptor in microglia contributes to propofol-induced unconsciousness by regulating synaptic plasticity in mice

Propofol infusion is processed through the wake-sleep cycle in neural connections, and the ionotropic purine type 2X7 receptor (P2X7R) is a nonspecific cation channel implicated in sleep regulation and synaptic plasticity through its regulation of electric activity in the brain. Here, we explored the potential roles of P2X7R of microglia in propofol-induced unconsciousness. Propofol induced loss of the righting reflex in male C57BL/6 wild-type mice and increased spectral power of the slow wave and delta wave of the medial prefrontal cortex (mPFC), all of which were reversed with P2X7R antagonist A-740003 and strengthened with P2X7R agonist Bz-ATP. Propofol increased the P2X7R expression level and P2X7R immunoreactivity with microglia in the mPFC, induced mild synaptic injury and increased GABA release in the mPFC, and these changes were less severe when treated with A-740003 and were more obvious when treated with Bz-ATP. Electrophysiological approaches showed that propofol induced a decreased frequency of sEPSCs and an increased frequency of sIPSCs, A-740003 decrease frequency of sEPSCs and sIPSCs and Bz-ATP increase frequency of sEPSCs and sIPSCs under propofol anesthesia. These findings indicated that P2X7R in microglia regulates synaptic plasticity and may contribute to propofol-mediated unconsciousness.

Quantitative Evaluation of Oxygen Extraction Fraction Changes in the Monkey Brain during Acute Stroke by Using Quantitative Susceptibility Mapping

BACKGROUND

The oxygen extraction fraction (OEF) indicates the brain's oxygen consumption and can be estimated by using the quantitative susceptibility mapping (QSM) MRI technique. Recent studies have suggested that OEF alteration following stroke is associated with the viability of at-risk tissue. In the present study, the temporal evolution of OEF in the monkey brain during acute stroke was investigated using QSM.

METHODS

Ischemic stroke was induced in adult rhesus monkeys (n = 8) with permanent middle cerebral artery occlusion (pMCAO) by using an interventional approach. Diffusion-, T2-, and T2*-weighted images were conducted on day 0, day 2, and day 4 post-stroke using a clinical 3T scanner. Progressive changes in magnetic susceptibility and OEF, along with their correlations with the transverse relaxation rates and diffusion indices, were examined.

RESULTS

The magnetic susceptibility and OEF in injured gray matter of the brain significantly increased during the hyperacute phase, and then decreased significantly on day 2 and day 4. Moreover, the temporal changes of OEF in gray matter were moderately correlated with mean diffusivity (MD) (r = 0.52; p = 0.046) from day 0 to day 4. Magnetic susceptibility in white matter progressively increased (from negative values to near zero) during acute stroke, and significant increases were seen on day 2 (p = 0.08) and day 4 (p = 0.003) when white matter was significantly degenerated. However, significant reduction of OEF in white matter was not seen until day 4 post-stroke.

CONCLUSION

The preliminary results demonstrate that QSM-derived OEF is a robust approach to examine the progressive changes of gray matter in the ischemic brain from the hyperacute phase to the subacute phase of stroke. The changes of OEF in gray matter were more prominent than those in white matter following stroke insult. The findings suggest that QSM-derived OEF may provide complementary information for understanding the neuropathology of the brain tissue following stroke and predicting stroke outcomes.