Exposure to general anesthesia and the risk of dementia

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.

Differential Susceptibility to Propofol and Ketamine in Primary Cultures of Young and Senesced Astrocytes

The adverse effects of general anesthesia on the long-term cognition of young children and senior adults have become of concern in recent years. Previously, mechanistic and pathogenic investigations focused on neurons, and little is known about the effect of commonly used intravenous anesthetics such as propofol and ketamine on astrocytes. Recently, astrocyte dysfunction has been implicated in a wide range of age-related brain diseases. In this study, we examined the survival and viability of both young and senescent astrocytes in culture after adding propofol and ketamine to the media at varying strengths. Oxidative stimulus was applied to commercially available fetal cell lines of human astrocytes in vitro to induce morphological changes in cellular senescence. Our results indicate that propofol reduces the survival of young astrocytes as compared to controls, as well as to ketamine. These effects were seen in comparisons of total cell count and at both high and low dose concentrations. High doses of propofol also significantly reduced cell viability compared to those exposed to baseline controls and ketamine. Senescent astrocytes, on the other hand, demonstrated cell count reductions as compared to baseline controls and ketamine when exposed to either DMSO or propofol. The data show differential susceptibility of young astrocytes to propofol than to ketamine. The observed cell count reduction may be related to the adverse effects of propofol on mitochondrial function and free radical production, as described in previous studies. We speculate that ketamine may have a more favorable safety profile in infants and young children.

COVID-19 and cognitive impairment: A cross-sectional clinic-based study

BACKGROUND

Patients with dementia are more prone to acquire COVID-19 infection. Patients with COVID-19 showed a tendency to develop cognitive impairment.

OBJECTIVES

We aimed to study the clinical manifestations of COVID-19 infection among adult Sudanese demented patients and the prevalence of cognitive impairment among adult Sudanese nondemented patients.

METHODOLOGY

This is a descriptive cross-sectional study that took place in Sudan, Khartoum state in the period (September to December 2021) in a private neurology/psychiatry clinic. A total of 135 adult Sudanese patients were included in this study and were divided into two groups. The first group consists of 100 patients with a known history of dementia that got infected recently with COVID-19, while the second group consists of 35 patients who developed some sort of cognitive impairment after recovering from COVID-19 infection. Regarding the second group, cognitive functions were assessed by senior consultant neurologist and senior consultant psychiatrist using a well validated neuropsychological measure.

RESULTS

Out of 100 patients in the first group, females were 60 and males were 40. Age distribution is between 63 and 98. The common presenting symptoms of COVID-19 among this group were cough and fever (90 patients), diarrhea and vomiting (5 patients), breathlessness (4 patients), coughing of blood (5 patients), convulsions (1 patient), paraplegia (1 patient), and hemiplegia (1 patient). Regarding the second group, age distribution varied from 30 to 80 years. Cognitive functions impairment was noticed as follows: memory recall (22%), memory recognition (23%), memory encoding (24%), processing speed (16%), executive functioning (19%), phonemic fluency (17%), and category fluency (17%).

CONCLUSION

Patients with dementia are more susceptible to develop COVID-19 infection. Patients with COVID-19 Infection are at risk of developing some sort of cognitive impairment after recovery.

Roflumilast Ameliorates Isoflurane-Induced Inflammation in Astrocytes via the CREB/BDNF Signaling Pathway

Background and purpose: Astrocyte-mediated neuroinflammation plays an important role in anesthetic isoflurane-induced cognitive impairment. Roflumilast, a selective inhibitor of phosphodiesterase-4 (PDE-4) used for the treatment of chronic obstructive pulmonary disease (COPD), has displayed a wide range of anti-inflammatory capacity in different types of cells and tissues. In the current study, we aimed to investigate whether roflumilast possesses a protective effect against isoflurane-induced insults in mouse primary astrocytes. Methods: Primary astrocytes were isolated from the cerebral cortices of immature rats. The production of NO was determined using DAF-FM DA staining assay. QRT-PCR and western blot were used to evaluate the expression levels of iNOS, COX-2, and BDNF in the astrocytes treated with different therapies. The gene expressions and concentrations of IL-6 and MCP-1 released by the astrocytes were detected using qRT-PCR and ELISA, respectively. The expression levels of phosphorylated CREB and PGE₂ were determined using western blot and ELISA, respectively. H89 was introduced to evaluate the function of CREB. Recombinant human BDNF and ANA-12 were used to verify the role of BDNF. Results: The upregulated iNOS, excessive production of NO, IL-6, and MCP-1, and activated COX-2/PGE₂ signaling pathways in the astrocytes induced by isoflurane were significantly reversed by the introduction of roflumilast, in a dose-dependent manner. Subsequently, we found that BDNF could be upregulated by roflumilast, which was verified to be related to the activation of CREB and blocked by H89 (a CREB inhibitor). In addition, the COX-2/PGE₂ signaling pathway activated by isoflurane can be inactivated by recombinant human BDNF. Finally, the regulatory effect of roflumilast against the isoflurane-activated COX-2/PGE₂ signaling pathway was significantly blocked by ANA-12, which is a BDNF inhibitor. Conclusion: Roflumilast might ameliorate isoflurane-induced inflammation in astrocytes via the CREB/BDNF signaling pathway.

Comparison of intravenous sedation using midazolam during dental treatment in elderly patients with/without dementia: a prospective, controlled clinical trial

The effects of intravenous sedation with midazolam on the cerebral function of elderly patients with severe dementia are unclear. This study aimed to evaluate its effects on parameters such as brainwaves and cerebral blood flow (CBF) and compare them between elderly individuals with dementia and without cognitive impairment. Ten patients with severe dementia and 10 without cognitive impairment were registered. The bispectral index (BIS) and normalized tissue hemoglobin index (nTHI), which reflects CBF using near-infrared spectroscopy, were measured. Midazolam was administered until a Modified Observer’s Assessment of Alertness/Sedation score of 2 was reached. The chi-squared, Mann–Whitney U, Wilcoxon signed-rank, and Friedman tests and multiple regression analysis were used for comparisons. Whereas a similar decline in BIS values was observed in both groups after midazolam administration (P < 0.018), there was a significant decrease by 9% in the nTHI of the dementia-positive group (P < 0.013). However, there was no significant difference in the nTHI between the dementia-positive and dementia-negative group according to the multiple regression analysis (P = 0.058). In the dementia-negative group, none of the measured values differed from the baseline values. In the dementia-positive group, sedation with midazolam resulted in a 9% decrease in the CBF.

Do Complexity Measures of Frontal EEG Distinguish Loss of Consciousness in Geriatric Patients Under Anesthesia?

While geriatric patients have a high likelihood of requiring anesthesia, they carry an increased risk for adverse cognitive outcomes from its use. Previous work suggests this could be mitigated by better intraoperative monitoring using indexes defined by several processed electroencephalogram (EEG) measures. Unfortunately, inconsistencies between patients and anesthetic agents in current analysis techniques have limited the adoption of EEG as standard of care. In attempts to identify new analyses that discriminate clinically-relevant anesthesia timepoints, we tested 1/f frequency scaling as well as measures of complexity from nonlinear dynamics. Specifically, we tested whether analyses that characterize time-delayed embeddings, correlation dimension (CD), phase-space geometric analysis, and multiscale entropy (MSE) capture loss-of-consciousness changes in EEG activity. We performed these analyses on EEG activity collected from a traditionally hard-to-monitor patient population: geriatric patients on beta-adrenergic blockade who were anesthetized using a combination of fentanyl and propofol. We compared these analyses to traditional frequency-derived measures to test how well they discriminated EEG states before and after loss of response to verbal stimuli. We found spectral changes similar to those reported previously during loss of response. We also found significant changes in 1/f frequency scaling. Additionally, we found that our phase-space geometric characterization of time-delayed embeddings showed significant differences before and after loss of response, as did measures of MSE. Our results suggest that our new spectral and complexity measures are capable of capturing subtle differences in EEG activity with anesthesia administration-differences which future work may reveal to improve geriatric patient monitoring.

The role of general anesthetics and the mechanisms of hippocampal and extra-hippocampal dysfunctions in the genesis of postoperative cognitive dysfunction

Postoperative cognitive dysfunction (POCD) is a multifactorial process with a huge number of predisposing, causal, and precipitating factors. In this scenario, the neuroinflammation and the microglial activation play a pivotal role by triggering and amplifying a complex cascade involving the immuno-hormonal activation, the micro circle alterations, the hippocampal oxidative stress activation and, finally, an increased blood-brain barrier's permeability. While the role of anesthetics in the POCD's genesis in humans is debated, a huge number of preclinical studies have been conducted on the topic and many mechanisms have been proposed to explain the potential neurodegenerative effects of general anesthetics. Probably, the problem concerns on what we are searching for and how we are searching and, surprisingly, preclinical studies showed that anesthetics may also manifest neuroprotective properties. The aim of this paper is to offer an overview on the potential impact of general anesthetics on POCD. Mechanisms of hippocampal and extra-hippocampal dysfunction due to neuroinflammation are discussed, whereas further research perspectives are also given.

Intranasal Insulin Prevents Anesthesia-Induced Cognitive Impairment and Chronic Neurobehavioral Changes

General anesthesia increases the risk for cognitive impairment post operation, especially in the elderly and vulnerable individuals. Recent animal studies on the impact of anesthesia on postoperative cognitive impairment have provided some valuable insights, but much remains to be understood. Here, by using mice of various ages and conditions, we found that anesthesia with propofol and sevoflurane caused significant deficits in spatial learning and memory, as tested using Morris Water Maze (MWM) 2–6 days after anesthesia exposure, in aged (17–18 months old) wild-type (WT) mice and in adult (7–8 months old) 3xTg-AD mice (a triple transgenic mouse model of Alzheimer’s disease (AD)), but not in adult WT mice. Anesthesia resulted in long-term neurobehavioral changes in the fear conditioning task carried out 65 days after exposure to anesthesia in 3xTg-AD mice. Importantly, daily intranasal administration of insulin (1.75 U/mouse/day) for only 3 days prior to anesthesia completely prevented the anesthesia-induced deficits in spatial learning and memory and the long-term neurobehavioral changes tested 65 days after exposure to anesthesia in 3xTg-AD mice. These results indicate that aging and AD-like brain pathology increase the vulnerability to cognitive impairment after anesthesia and that intranasal treatment with insulin can prevent anesthesia-induced cognitive impairment.