Anesthesia and surgery induce age-dependent changes in behaviors and microbiota

Microbiota-gut-brain axis in perioperative neurocognitive and depressive disorders: Pathogenesis to treatment

An increasing number of people undergo anesthesia and surgery. Perioperative neurocognitive and depressive disorders are common central nervous system complications with similar pathogeneses. These conditions pose a deleterious threat to human health and a significant societal burden. In recent years, numerous studies have focused on the role of the gut microbiota and its metabolites in the central nervous system via the gut-brain axis. Its involvement in perioperative neurocognitive and depressive disorders has attracted considerable attention. This review aimed to elucidate the role of the gut microbiota and its metabolites in the pathogenesis of perioperative neurocognitive and depressive disorders, as well as the value of targeted interventions and treatments.

Gut Microbiota-Metabolite-Brain Axis Reconstitution Reverses Sevoflurane-Induced Social and Synaptic Deficits in Neonatal Mice

Background: The mechanisms underlying social dysfunction caused by repeated sevoflurane in early life remain unclear. Whether the gut microbiota-metabolite-brain axis is involved in the mechanism of sevoflurane developmental neurotoxicity still lacks report. Methods: Mice received 3% sevoflurane at postnatal day (PND) 6, 7, and 8 for 2 h per day. Metagenomic sequencing and untargeted metabolomic analysis were applied to investigate the effects of sevoflurane on gut microbiota and metabolism. The animal social behavior and the synaptic development were analyzed during PND 35. Subsequently, fecal microbiota transplantation (FMT) from the control group and bile acid administration were performed to see the expected rescuing effect on socially related behaviors that were impaired by repeated sevoflurane exposure in the mice. Results: In the 3-chamber test, sevoflurane-exposed mice spent less time with stranger mice compared with the control group. The density of both the apical and basal spine decreased in mice exposed to sevoflurane. In addition, repeated sevoflurane exposure led to a notable alteration in the gut microbiota and metabolite synthesis, particularly bile acid. FMT reduced the production of intestinal bile acid and attenuated the effect of sevoflurane exposure on social function and synaptic development. Cholestyramine treatment mimics the protective effects of FMT. Conclusions: The gut microbiota-metabolite-brain axis underlies social dysfunction caused by sevoflurane exposure in early age, and bile acid regulation may be a promising intervention to this impairment.

Recent developments in delirium after oral and maxillofacial free-flap reconstruction

Postoperative delirium (POD), a common complication following surgery and anesthesia, is particularly prone to occur after reconstruction surgery in the oral and maxillofacial region. The occurrence of POD seriously affects the incidence of postoperative complications, the survival of free flaps, the length of hospital stays, and brings great pain to patients and their families, and even increases perioperative mortality. Currently, a large number of studies have reported on the risk factors for POD after oral and maxillofacial free-flap reconstruction. Multiple independent risk factors have been identified, including age, history of excessive alcohol consumption, and perioperative nutritional status. This review summarizes the relevant literature and hopes to provide insights for the prevention of POD in high-risk patients.

Electroacupuncture remodels gut microbiota and metabolites in mice with perioperative neurocognitive impairment

Gut microbiota and metabolites are considered key factors in the pathogenesis of perioperative neurocognitive disorders (PND), and the brain-gut axis may be a promising target for PND treatment. Electroacupuncture has been shown to improve a wide range of neurological disorders and to restore function to the gastrointestinal tract. Thus, we hypothesized whether electroacupuncture could remodel gut microbiota and neuroinflammation induced by anesthesia/surgery. First, we observed electroacupuncture at acupoints GV20, LI4 and PC6 significantly improved memory in behavioral tests. Next, we found electroacupuncture decreased the levels of inflammatory factors (NSE, S-100β, IL-6, etc.) in the hippocampus, indicating that nerve inflammation was blocked by electroacupuncture. Furthermore, via 16S rRNA sequence analysis and LC-MS analysis, the gut microbiota and its metabolites were appropriately restored after electroacupuncture treatment. Additionally, we further confirmed the restorative effect of electroacupuncture on PND by fecal transplantation. In conclusion, the role of electroacupuncture in improving cognitive function and protecting neurons may be related to the modulation of gut microbiota and their metabolite dysregulation, thereby inhibiting neuroinflammation in PND mice.

Gut Microbiota and Probiotics in Perioperative Management: A Narrative Review

The human gut is the abode of several complex and diverse microbes. It is a fact that the human brain is interconnected with the spinal cord and sense organs; however, there is also a possibility of a connection between the brain and the gut microbiome. The human gut can be altered in various ways, the principal method being the intake of prebiotics, probiotics and synbiotics. Can this alteration in the gut microbiome be clinically utilised in the perioperative period? We conducted a literature search related to this topic using databases and search engines (Medical Literature Analysis and Retrieval System Online {MEDLINE}, Embase, Scopus, PubMed and Google Scholar). The search revealed some preclinical and clinical studies in animals and humans that demonstrate the alteration of the gut microbiome with the use of anxiolysis, probiotics/prebiotics and other perioperative factors including opioids, anaesthetics and perioperative stress. The significant effects of this alteration have been seen on preoperative anxiety and postoperative delirium/cognitive dysfunction/pain. These effects are described in this narrative review, which opens up newer vistas for high-quality research related to the gut microbiome, gut-brain axis, the related signaling pathways and their clinical application in the perioperative period.

Incidence and related risk factors for postoperative delirium following revision total knee arthroplasty: a retrospective nationwide inpatient sample database study

BACKGROUND

Postoperative delirium (POD) is a common surgical complication. However, the incidence and risk factors associated with postoperative delirium after revision total knee arthroplasty (rTKA) have not been comprehensively explored through extensive national databases.

METHODS

Utilizing the National Inpatient Sample (NIS), the largest comprehensive U.S. hospital healthcare database, we undertook a retrospective investigation involving 127,400 patients who underwent rTKA between 2010 and 2019. We assessed various aspects, including patient demographics, hospital characteristics, pre-existing medical conditions, and perioperative complications.

RESULTS

The overall incidence of postoperative delirium (POD) in patients undergoing rTKA between 2010 and 2019 was 0.97%. The highest incidence rate of 1.31% was recorded in 2013. Notably, this patient cohort demonstrated advanced age, increased burden of co-morbidities, prolonged hospital stays, increased hospitalization costs, and elevated in-hospital mortality rates (P < 0.001). Moreover, non-elective admissions, non-private insurance payments, and a preference for teaching hospitals were commonly observed among these patients. During their hospitalization, individuals who developed delirium subsequent to rTKA were more prone to experiencing certain perioperative complications. These complications encompassed medical issues like acute myocardial infarction, continuous invasive mechanical ventilation, postoperative shock, sepsis, stroke and other medical problems. Additionally, surgical complications including hemorrhage / seroma / hematoma, irrigation and debridement, prosthetic joint infection, periprosthetic fracture, and wound dehiscence / nonunion were noted. Several risk factors were found to be linked with the development of POD. These included advanced age (≥ 75 years), alcohol abuse, coagulation disorders, congestive heart failure, depression, fluid and electrolyte imbalances, and more. Conversely, female sex, having private insurance, and undergoing elective hospitalization emerged as protective factors against POD.

CONCLUSION

Our findings suggest that the general prevalence of POD in rTKA is relatively low according to NIS. There was a significant connection between the POD of rTKA and advanced age, prolonged length of stay (LOS), more in-patients' costs, higher in-hospital mortality rate, increased comorbidities, postoperative medical complications and postoperative surgical complications. This study helps to understand the risk factors associated with POD to improve poor outcomes.

Role of the circRNA_34414/miR-6960a-5p/SIRT3 axis in postoperative delirium via CA1 Vglut1+ neurons in older mice

AIMS

Postoperative delirium (POD) is a common neurological complication in elderly patients after anesthesia/surgery. The main purpose of this study is to explore the effect of circRNA-targeted miRNA regulating SIRT3 on mitochondrial function through ceRNA mechanism under the surgical model of tibial fracture and to further explore the potential mechanism of postoperative delirium mediated by circRNA, so as to provide new ideas for clinical diagnosis and prevention of POD.

METHODS

The surgical model of tibial fracture under sevoflurane anesthesia caused acute delirium-like behavior in elderly mice. We observed that the decrease of SIRT3 and mitochondrial dysfunction was related to POD, and miRNA and circRNA (circRNA_34414) related to SIRT3 were further studied. Through luciferase and RAP, we observed that circRNA_34414, as a miRNA sponge, was involved in the regulation of SIRT3 expression.

RESULTS

Postoperative delirium in elderly mice showed decreased expression of hippocampal circRNA_34414, increased expression of miR-6960-5p, decreased expression of SIRT3, and impaired mitochondrial membrane potential. Overexpression of circRNA_34414, or knockdown of miR-6960-5p, or overexpression of SIRT3 in hippocampal CA1 glutamatergic neurons significantly upregulated hippocampal SIRT3 expression, increased mitochondrial membrane potential levels, and significantly ameliorated postoperative delirium in aged mice; CircRNA_34414 ameliorates postoperative delirium in mice, possibly by targeting miR-6960-5p to upregulate SIRT3.

CONCLUSIONS

CircRNA_34414 is involved in the improvement of postoperative delirium induced by anesthesia/surgery by upregulating SIRT3 via sponging miR-6960-5p.

Postoperative Delirium and the Older Adult: Untangling the Confusion

Postoperative delirium is one of the most prevalent postoperative complications, affecting mostly older adults. Its incidence is expected to rise because of surgical advances, shifting demographics, and increased life expectancy. Although an acute alteration in brain function, postoperative delirium is associated with adverse outcomes, including progressive cognitive decline and dementia, that place significant burdens on patients' lives and healthcare systems. This has prompted efforts to understand the mechanisms of postoperative delirium to provide effective prevention and treatment. There are multiple mechanisms involved in the etiology of postoperative delirium that share similarities with the physiological changes associated with the aging brain. In addition, older patients often have multiple comorbidities including increased cognitive impairment that is also implicated in the genesis of delirium. These tangled connections pinpointed a shift toward creation of a holistic model of the pathophysiology of postoperative delirium. Scientific advancements integrating clinical risk factors, possible postoperative delirium biomarkers, genetic features, digital platforms, and other biotechnical and information technological innovations, will become available in the near future. Advances in artificial intelligence, for example, will aggregate cognitive testing platforms with patient-specific postoperative delirium risk stratification studies, panels of serum and cerebrospinal fluid molecules, electroencephalogram signatures, and gut microbiome features, along with the integration of novel polygenetic variants of sleep and cognition. These advances will allow for the enrollment of high-risk patients into prevention programs and help uncover new pharmacologic targets.

The Effects of Appropriate Perioperative Exercise on Perioperative Neurocognitive Disorders: a Narrative Review

Perioperative neurocognitive disorders (PNDs) are now considered the most common neurological complication in older adult patients undergoing surgical procedures. A significant increase exists in the incidence of post-operative disability and mortality in patients with PNDs. However, no specific treatment is still available for PNDs. Recent studies have shown that exercise may improve cognitive dysfunction-related disorders, including PNDs. Neuroinflammation is a key mechanism underlying exercise-induced neuroprotection in PNDs; others include the regulation of gut microbiota and mitochondrial and synaptic function. Maintaining optimal skeletal muscle mass through preoperative exercise is important to prevent the occurrence of PNDs. This review summarizes current clinical and preclinical evidence and proposes potential molecular mechanisms by which perioperative exercise improves PNDs, providing a new direction for exploring exercise-mediated neuroprotective effects on PNDs. In addition, it intends to provide new strategies for the prevention and treatment of PNDs.

Emerging Insights into Postoperative Neurocognitive Disorders: The Role of Signaling Across the Gut-Brain Axis

The pathophysiological regulatory mechanisms in postoperative neurocognitive disorders (PNCDs) are intricately complex. Currently, the pathogenesis of PNCDs has not been fully elucidated. The mechanism involved may include a variety of factors, such as neuroinflammation, oxidative stress, and neuroendocrine dysregulation. Research into the gut microbiota-induced regulations on brain functions is increasingly becoming a focal point of exploration. Emerging evidence has shown that intestinal bacteria may play an essential role in maintaining the homeostasis of various physiological systems and regulating disease occurrence. Recent studies have confirmed the association of the gut-brain axis with central nervous system diseases. However, the regulatory effects of this axis in the pathogenesis of PNCDs remain unclear. Therefore, this paper intends to review the bidirectional signaling and mechanism of the gut-brain axis in PNCDs, summarize the latest research progress, and discuss the possible mechanism of intestinal bacteria affecting nervous system diseases. This review is aimed at providing a scientific reference for predicting the clinical risk of PNCD patients and identifying early diagnostic markers and prevention targets.

Survival and cancer recurrence after short-course perioperative probiotics in a randomized trial

BACKGROUND & AIMS

The long-term impact of perioperative probiotics remains understudied while mounting evidence links microbiome and oncogenesis. Therefore, we analyzed overall survival and cancer recurrence among patients enrolled in a randomized trial of perioperative probiotics.

METHODS

6-year follow-up of surgical patients participating in a randomized trial evaluating short-course perioperative oral probiotic VSL#3 (n = 57) or placebo (n = 63).

RESULTS

Study groups did not differ in age, preoperative hemoglobin, ASA status, and Charlson comorbidity index. There was a significant difference in preoperative serum albumin (placebo group 4.0 ± 0.1 vs. 3.7 ± 0.1 g/dL in the probiotic group, p = 0.030). Thirty-seven deaths (30.8 %) have occurred during a median follow-up of 6.2 years. Overall survival stratified on preoperative serum albumin and surgical specialty was similar between groups (p = 0.691). Age (aHR = 1.081, p = 0.001), serum albumin (aHR = 0.162, p = 0.001), and surgical specialty (aHR = 0.304, p < 0.001) were the only predictors of overall survival in the multivariate model, while the placebo/probiotic group (aHR = 0.808, p = 0.726) was not predictive. The progression rate among cancer patients was similar in the probiotic group (30.3 %, 10/33) compared to the placebo group (21.2 %, 7/33; p = 0.398). The progression-free survival was not significantly different (unstratified p = 0.270, stratified p = 0.317).

CONCLUSIONS

Perioperative short-course use of VSL#3 probiotics does not influence overall or progression-free survival after complex surgery for visceral malignancy.

Electroencephalographic monitoring of anesthesia during surgical procedures in mice using a modified clinical monitoring system

Monitoring brain activity and associated physiology during the administration of general anesthesia (GA) in mice is pivotal to guarantee postanesthetic health. Clinically, electroencephalogram (EEG) monitoring is a well-established method to guide GA. There are no established methods available for monitoring EEG in mice (Mus musculus) during surgery. In this study, a minimally invasive rodent intraoperative EEG monitoring system was implemented using subdermal needle electrodes and a modified EEG-based commercial patient monitor. EEG recordings were acquired at three different isoflurane concentrations revealing that surgical concentrations of isoflurane anesthesia predominantly contained burst suppression patterns in mice. EEG suppression ratios and suppression durations showed strong positive correlations with the isoflurane concentrations. The electroencephalographic indices provided by the monitor did not support online monitoring of the anesthetic status. The online available suppression duration in the raw EEG signals during isoflurane anesthesia is a straight forward and reliable marker to assure safe, adequate and reproducible anesthesia protocols.

Prolonged oral intake of green tea polyphenols attenuates delirium-like behaviors in mice induced by anesthesia/surgery

Postoperative delirium (POD) is a severe postoperative complication characterized by delirium-like symptoms. So far, no effective preventable strategy for POD prevention has been identified. Reports show that the consumption of green tea polyphenols (GTP) is associated with better cognitive function by modulating the composition of gut microbiota. Whether GTP also play a role in alleviating POD through gut microbiota is unknown. Herein, we studied the effect of prolonged (eight weeks) GTP intake on postoperative delirium in C57BL/6 mice with laparotomies under isoflurane anesthesia (anesthesia/surgery). We subsequently investigated anesthesia/surgery caused behavioral changes and increased the expression of malondialdehyde (MAD), an oxidative stress marker, and the activities of superoxide dismutase (SOD), an antioxidant marker, in the mice at 6 h after anesthesia/surgery. However, GTP administration reversed these changes and alleviated anesthesia/surgery-induced decrease in the abundance of gut bacterial genera, Roseburia. Further, fecal microbiota transplant demonstrated that compared with mice in the control group, treatment of C57BL/6 mice with feces from GTP-treated mice had a slight effect on the behavioral changes of mice. These data suggest that daily consumption of GTP could protect against anesthesia/surgery-induced behavioral changes, which is closely associated with gut microbiota modification by GTP.

Melatonin regulates the circadian rhythm to ameliorate postoperative sleep disorder and neurobehavioral abnormalities in aged mice

BACKGROUND

Postoperative sleep disorder (PSD) and delirium, which may be associated with surgery and inhalational anesthetics, induce adverse effects in old adults. Emerging evidence indicates that circadian rhythm contributes to various neuropathological diseases, including Alzheimer's disease. Thus, we analyzed the potential role of circadian rhythm in PSD and delirium-like behavior in aged mice and determined whether exogenous melatonin could facilitate entrainment of the circadian rhythm after laparotomy under sevoflurane anesthesia.

METHODS

We selected old C57BL/6J mice which receiving laparotomy/sevoflurane anesthesia as model animals. We employed buried food, open field, and Y maze test to assess delirium-like behavior, and electroencephalography/electromyography (EEG/EMG) were used to investigate sleep changes. We analyzed the transcription rhythm of clock genes in superchiasmatic nucleus (SCN) to explore the effects of surgery and melatonin pretreatment on the circadian rhythm. Then, we measured melatonin receptor levels in SCN and ERK/CREB pathway-related proteins in hippocampus and prefrontal cortex to assess their role in PSDs and delirium-like behavior.

RESULTS

Laparotomy under sevoflurane anesthesia had a greater influence than sevoflurane alone, leading to sleep disorder, a shift in sleep-wake rhythm, and delirium-like behavior. Bmal1, Clock, and Cry1 mRNA expression showed a peak shift, MT1 melatonin receptor expression level was increased in the SCN, and p-ERK/ERK and p-CREB/CREB were decreased in hippocampus and prefrontal cortex of aged mice 1 day after laparotomy. Melatonin showed significant efficacy in ameliorating PSD and delirium-like behavior and restoring the circadian rhythm, reversing melatonin receptor and ERK/CREB pathway expression abnormalities. In addition, most of the beneficial effect of melatonin was antagonized by luzindole, a melatonin receptor antagonist.

CONCLUSIONS

Melatonin receptors in SCN, circadian rhythm, and ERK/CREB signaling pathway participate in the pathophysiological processes of PSD and delirium-like behavior. Melatonin intervention could be a potential preventative approach for PSD and delirium.

The activation impact of lactobacillus-derived extracellular vesicles on lipopolysaccharide-induced microglial cell

Perioperative neurocognitive dysfunction (PND) emerges as a common postoperative complication among elderly patients. Currently, the mechanism of PND remains unclear, but there exists a tendency to believe that inflammation plays a significant role in PND. Alterations in the abundance of intestinal microbiota can increase the permeability of the intestinal mucosal barrier and incite extraintestinal inflammatory responses. Metabolites from these microbiota can be absorbed by the intestinal mucosa into the bloodstream, exerting influence upon the central nervous system (CNS). Lactobacillus (Lac), serving as an intestinal probiotic bacterium, possesses the capacity to modulate emotional behavior and cognitive functions. Extracellular vesicles (EVs) are recognized as novel therapeutic carriers for targeted delivery to regulate physiology and pathogenesis. While the mechanism governing the primary function of Lac-EVs in the CNS remains uncertain. Therefore, we established an in vitro neuroinflammation model to induce PND and then treated the mice with Lac-EVs to observe the effect of these EVs on neuroinflammation, particularly on microglial (MG) polarization. Our research unveils that Lac-EVs reduced inflammation induced by LPS in microglia and the activation of related proteins, including the mRNA expression of M1 labeled protein (iNOS). Moreover, the mRNA expression of M2-labeled protein (Arg1) increased. In addition, flow cytometry revealed that the ratio of M1/M2 microglia also changed significantly. Therefore, Lac-EVs promoted the differentiation of M2 microglia by inducing the preferential expression of specific markers related to M2 macrophages and inflammation. In terms of inflammatory cytokine expression, Lac-EVs decreased the secretion of proinflammatory cytokines (IL-1β and IL-6) and increased IL-10 production after lipopolysaccharide (LPS) stimulation. Therefore, Lac-EVs induce the activation of M2 microglial cells without inducing cellular harm in vitro, and they demonstrate anti-inflammatory effects against lipopolysaccharide-induced neuroinflammation. This finding suggested that it is an effective anti-inflammatory strategy for alleviating inflammation-driven PNDs.

Indole-3-Propionic Acid, a Gut Microbiota Metabolite, Protects Against the Development of Postoperative Delirium

OBJECTIVE

The aim was to determine preoperative gut microbiota metabolites that may be associated with postoperative delirium (POD) development in patients and further study in rodents.

SUMMARY BACKGROUND DATA

POD occurs in 9% to 50% of older patients undergoing anesthesia/surgery but lacks effective treatments or prevention. High-throughput metabolomics using liquid chromatography with tandem mass spectrometry has accelerated disease-related biomarkers discovery. We performed metabolomic studies in humans to identify potential metabolite biomarkers linked to POD and examined potential mechanisms in rodents.

METHODS

We performed a prospective observational cohort study to examine the metabolomic changes that were associated with the development of POD. Then the gut microbiota-related metabolomic changes were recapitulated by gut microbiota perturbation in rodents. POD was assessed in mice using a battery of behavioral tests including novel objective test, Y-maze test, open-field test, and buried food test. The mechanisms through which gut microbiota-related metabolomic changes influenced POD were examined using chemogenetics.

RESULTS

Indole-3-propionic acid (IPA) is a gut microbiota metabolite that belongs to the indole family. Baseline plasma levels of IPA were significantly inversely correlated with the onset of POD in 103 (17 cases) human individuals. This relationship was validated in preclinical mouse models for POD: reducing IPA levels through gut microbiota perturbation promoted POD-like behavior. More importantly, IPA administration deterred POD-like behavior. Colonization of germ-free mice with mutant Clostridium sporogenes that did not produce IPA-promoted POD-like behavior. Chemogenetic studies revealed that the protective effect of IPA in mice was mediated, in part, by peroxisome proliferator-activated receptor gamma coactivator 1-alpha in hippocampal interneurons.

CONCLUSIONS

Gut microbiota-derived IPA is an important molecule implicated in the pathogenesis of POD, which could potentially be harnessed for POD prevention.

Probiotics in Postoperative Pain Management

Postoperative pain is the unpleasant sensory and emotional experience after surgery, its origin being both the inflammatory reaction induced by the surgical trauma on the abdominal wall and the splanchnic pain induced by the activation of nociceptors of the viscera, which are highly sensitive to distension, ischemia, and inflammation. Nowadays, it is well recognized that there is a close relationship between the gut microbiome and pain perception, and that microbiome is highly affected by both anesthesia and surgical manipulation. Thus, efforts to restore the disturbed microbiome via supplementation with beneficial bacteria, namely probiotics, seem to be effective. In this article, the knowledge gained mainly from experimental research on this topic is analyzed, the concluding message being that each probiotic strain works in its own way towards pain relief.

Transmission of Alzheimer's disease-associated microbiota dysbiosis and its impact on cognitive function: evidence from mice and patients

Spouses of Alzheimer's disease (AD) patients are at a higher risk of developing incidental dementia. However, the causes and underlying mechanism of this clinical observation remain largely unknown. One possible explanation is linked to microbiota dysbiosis, a condition that has been associated with AD. However, it remains unclear whether gut microbiota dysbiosis can be transmitted from AD individuals to non-AD individuals and contribute to the development of AD pathogenesis and cognitive impairment. We, therefore, set out to perform both animal studies and clinical investigation by co-housing wild-type mice and AD transgenic mice, analyzing microbiota via 16S rRNA gene sequencing, measuring short-chain fatty acid amounts, and employing behavioral test, mass spectrometry, site-mutations and other methods. The present study revealed that co-housing between wild-type mice and AD transgenic mice or administrating feces of AD transgenic mice to wild-type mice resulted in AD-associated gut microbiota dysbiosis, Tau phosphorylation, and cognitive impairment in the wild-type mice. Gavage with Lactobacillus and Bifidobacterium restored these changes in the wild-type mice. The oral and gut microbiota of AD patient partners resembled that of AD patients but differed from healthy controls, indicating the transmission of microbiota. The underlying mechanism of these findings includes that the butyric acid-mediated acetylation of GSK3β at lysine 15 regulated its phosphorylation at serine 9, consequently impacting Tau phosphorylation. Pending confirmative studies, these results provide insight into a potential link between the transmission of AD-associated microbiota dysbiosis and development of cognitive impairment, which underscore the need for further research in this area.

General anesthesia alters the diversity and composition of the lung microbiota in rat

BACKGROUND

The lung microbiome plays a crucial role in human health and disease. Extensive studies have demonstrated that the disturbance of the lung microbiome influences immune response, cognition, and behavior. The goal of this study was to investigate the effect of general anesthetics on lung microbiome.

METHODS

Eight-week-old male SD rats received a continuous intravenous infusion of propofol or inhalation of isoflurane for 4 h. 16S rRNA gene amplification from BALF samples was used to investigate the changes in the lung microbiome after interventions. We further performed neurobehavioral assessments to find the differential strains' association with behavior disorder after isoflurane anesthesia.

RESULTS

The absolute and relative quantitation of 16S rRNA sequencing data showed that isoflurane altered the diversity and abundance of the lung microbiome in rats more than propofol. Elusimicrobia increased significantly in the isoflurane group. Both EPM and OFT results showed that rats exhibited depression-like behaviors after inhalation of isoflurane. In addition, significant differences were found in the COG/KO/MetaCyc/KEGG pathway enrichment analyses among the groups.

CONCLUSION

Continuous inhalation of isoflurane changed the diversity and composition of the lung microbiota in rats, resulting in post-anesthesia depression.

Immunonutrients and intestinal microbiota: a gap in the literature

The human intestinal microbiota is composed of a wide variety of microorganisms that play an important role in intestinal permeability, digestion, and especially, in the maturation of host's immune system. At the same time, effectiveness of immunomodulatory nutrients is known, especially in situations of stress and in strengthening body's defenses. However, the influence of the use of immunonutrients on microbiota's composition and variability is still poorly investigated. Studies indicate that the use of immunomodulators such as omega 3, glutamine, and arginine, can play a role in its modulation, through the immunological enhancement of the hosts. Therefore, this article sought to concentrate the latest evidence on the influence of the use of the main immunonutrients used in clinical practice on human gut microbiota, and their potential benefits.

Towards experimental models of delirium utilizing zebrafish

Delirium is an acute neuropsychiatric condition characterized by impaired behavior and cognition. Although the syndrome has been known for millennia, its CNS mechanisms and risk factors remain poorly understood. Experimental animal models, especially rodent-based, are commonly used to probe various pathogenetic aspects of delirium. Complementing rodents, the zebrafish (Danio rerio) emerges as a promising novel model organism to study delirium. Zebrafish demonstrate high genetic and physiological homology to mammals, easy maintenance, robust behaviors in various sensitive behavioral tests, and the potential to screen for pharmacological agents relevant to delirium. Here, we critically discuss recent developments in the field, and emphasize the developing utility of zebrafish models for translational studies of delirium and deliriant drugs. Overall, the zebrafish represents a valuable and promising aquatic model species whose use may help understand delirium etiology, as well as develop novel therapies for this severely debilitating disorder.

Blood tau-PT217 contributes to the anesthesia/surgery-induced delirium-like behavior in aged mice

INTRODUCTION

Blood phosphorylated tau at threonine 217 (tau-PT217) is a newly established biomarker for Alzheimer's disease and postoperative delirium in patients. However, the mechanisms and consequences of acute changes in blood tau-PT217 remain largely unknown.

METHODS

We investigated the effects of anesthesia/surgery on blood tau-PT217 in aged mice, and evaluated the associated changes in B cell populations, neuronal excitability in anterior cingulate cortex, and delirium-like behavior using positron emission tomography imaging, nanoneedle technology, flow cytometry, electrophysiology, and behavioral tests.

RESULTS

Anesthesia/surgery induced acute increases in blood tau-PT217 via enhanced generation in the lungs and release from B cells. Tau-PT217 might cross the blood-brain barrier, increasing neuronal excitability and inducing delirium-like behavior. B cell transfer and WS635, a mitochondrial function enhancer, mitigated the anesthesia/surgery-induced changes.

DISCUSSION

Acute increases in blood tau-PT217 may contribute to brain dysfunction and postoperative delirium. Targeting B cells or mitochondrial function may have therapeutic potential for preventing or treating these conditions.

Automated phenotyping of postoperative delirium-like behaviour in mice reveals the therapeutic efficacy of dexmedetomidine

Postoperative delirium (POD) is a complicated and harmful clinical syndrome. Traditional behaviour analysis mostly focuses on static parameters. However, animal behaviour is a bottom-up and hierarchical organizational structure composed of time-varying posture dynamics. Spontaneous and task-driven behaviours are used to conduct comprehensive profiling of behavioural data of various aspects of model animals. A machine-learning based method is used to assess the effect of dexmedetomidine. Fourteen statistically different spontaneous behaviours are used to distinguish the non-POD group from the POD group. In the task-driven behaviour, the non-POD group has greater deep versus shallow investigation preference, with no significant preference in the POD group. Hyperactive and hypoactive subtypes can be distinguished through pose evaluation. Dexmedetomidine at a dose of 25 μg kg-1 reduces the severity and incidence of POD. Here we propose a multi-scaled clustering analysis framework that includes pose, behaviour and action sequence evaluation. This may represent the hierarchical dynamics of delirium-like behaviours.

Odor Enrichment Attenuates the Anesthesia/Surgery-induced Cognitive Impairment

OBJECTIVE

To determine the association between olfactory function and cognition in patients and rodents.

BACKGROUND

Perioperative neurocognitive disorders include delayed neurocognitive recovery (dNCR). The contribution of olfactory function to dNCR remains undetermined. It is unknown whether odor enrichment could mitigate dNCR.

METHODS

We performed a prospective observational cohort study to determine potential association between olfactory impairment and dNCR in patients. We assessed the effects of anesthesia/surgery on olfactory and cognitive function in mice using the block test and Barnes maze. We measured interleukin-6 (IL-6), olfactory mature protein, growth-associated protein 43, mature and premature olfactory neurons, postsynaptic density 95, and synaptophysin in blood, nasal epithelium, and hippocampus of mice. Odor enrichment, IL-6 antibody, and knockout of IL-6 were used in the interaction experiments.

RESULTS

Patients with dNCR had worse odor identification than the patients without dNCR [preoperative: 7 (1.25, 9) vs 10 (8, 11), median (interquartile range), P <0.001; postoperative: 8 (2.25, 10) vs 10 (8, 11), P <0.001]. Olfactory impairment associated with dNCR in patients before and after adjusting age, sex, education, preoperative mini-mental state examination score, and days of the neuropsychological tests. Anesthesia/surgery induced olfactory and cognitive impairment, increased levels of IL-6 in blood and nasal epithelium, decreased amounts of olfactory receptor neurons and their markers in the nasal epithelium, and reduced amounts of synapse markers in the hippocampus of mice. These changes were attenuated by odor enrichment and IL-6 antibody.

CONCLUSION

The anesthesia/surgery-induced olfactory impairment may contribute to dNCR in patients and postoperative cognitive impairment in mice. Odor enrichment could be a potential intervention.

Effect of the gut microbiota and their metabolites on postoperative intestinal motility and its underlying mechanisms

Gut microbiota is closely related to human health and disease because, together with their metabolites, gut microbiota maintain normal intestinal peristalsis. The use of antibiotics or opioid anesthetics, or both, during surgical procedures can lead to dysbiosis and affect intestinal motility; however, the underlying mechanisms are not fully known. This review aims to discuss the effect of gut microbiota and their metabolites on postoperative intestinal motility, focusing on regulating the enteric nervous system, 5-hydroxytryptamine neurotransmitter, and aryl hydrocarbon receptor.

The possible role of gut microbiota dysbiosis in the pathophysiology of delirium in older persons

Delirium is a clinical syndrome characterized by an acute change in attention, awareness and cognition with fluctuating course, frequently observed in older patients during hospitalization for acute medical illness or after surgery. Its pathogenesis is multifactorial and still not completely understood, but there is general consensus on the fact that it results from the interaction between an underlying predisposition, such as neurodegenerative diseases, and an acute stressor acting as a trigger, such as infection or anesthesia. Alterations in brain insulin sensitivity and metabolic function, increased blood-brain barrier permeability, neurotransmitter imbalances, abnormal microglial activation and neuroinflammation have all been involved in the pathophysiology of delirium. Interestingly, all these mechanisms can be regulated by the gut microbiota, as demonstrated in experimental studies investigating the microbiota-gut-brain axis in dementia. Aging is also associated with profound changes in gut microbiota composition and functions, which can influence several aspects of disease pathophysiology in the host. This review provides an overview of the emerging evidence linking age-related gut microbiota dysbiosis with delirium, opening new perspectives for the microbiota as a possible target of interventions aimed at delirium prevention and treatment.

Impact of Repeated Infantile Exposure to Surgery and Anesthesia on Gut Microbiota and Anxiety Behaviors at Age 6-9

(1) Background: Preclinical as well as population studies have connected general anesthesia and surgery with a higher risk of abnormal cognitive development, including emotional development. Gut microbiota dysbiosis in neonatal rodents during the perioperative period has been reported, however, the relevance of this to human children who undergo multiple anesthesia for surgeries is unknown. Given the emerging role of altered gut microbes in propagating anxiety and depression, we sought to study whether repeated infantile exposures to surgery and anesthesia affect gut microbiota and anxiety behaviors later in life. (2) Methods: This is a retrospectively matched cohort study comparing 22 pediatric patients of less than 3 years of age with multiple exposures (≥3) to anesthesia for surgeries and 22 healthy controls with no history of exposure to anesthesia. The parent report version of the Spence Children's Anxiety Scale (SCAS-P) was applied to evaluate anxiety in children aged between 6 and 9 years old. Additionally, the gut microbiota profiles of the two groups were compared using 16S rRNA gene sequencing. (3) Results: In behavioral tests, the p-SCAS score of obsessive compulsive disorder and social phobia were significantly higher in children with repeated anesthesia exposure relative to the controls. There were no significant differences between the two groups with respect to panic attacks and agoraphobia, separation anxiety disorder, physical injury fears, generalized anxiety disorder, and the total SCAS-P scores. In the control group, 3 children out of 22 were found to have moderately elevated scores, but none of them had abnormally elevated scores. In the multiple-exposure group, 5 children out of 22 obtained moderately elevated scores, while 2 scored as abnormally elevated. However, no statistically significant differences were detected in the number of children with elevated and abnormally elevated scores. The data show that repeated anesthesia and surgical exposures in children led to long-lasting severe gut microbiota dysbiosis. (4) Conclusions: In this preliminary study, our findings demonstrated that early repeated exposures to anesthesia and surgical predisposes children to anxiety as well as long-term gut microbiota dysbiosis. We should confirm these findings in a larger data population size and with detailed analysis. However, the authors cannot confirm an association between the dysbiosis and anxiety.

The association between gut microbiota and postoperative delirium in patients

Postoperative delirium is a common postoperative complication in older patients, and its pathogenesis and biomarkers remain largely undetermined. The gut microbiota has been shown to regulate brain function, and therefore, it is vital to explore the association between gut microbiota and postoperative delirium. Of 220 patients (65 years old or older) who had a knee replacement, hip replacement, or laminectomy under general or spinal anesthesia, 86 participants were included in the data analysis. The incidence (primary outcome) and severity of postoperative delirium were assessed for two days. Fecal swabs were collected from participants immediately after surgery. The 16S rRNA gene sequencing was used to assess gut microbiota. Principal component analyses along with a literature review were used to identify plausible gut microbiota, and three gut bacteria were further studied for their associations with postoperative delirium. Of the 86 participants [age 71.0 (69.0-76.0, 25-75% percentile of quartile), 53% female], 10 (12%) developed postoperative delirium. Postoperative gut bacteria Parabacteroides distasonis was associated with postoperative delirium after adjusting for age and sex (Odds Ratio [OR] 2.13, 95% Confidence Interval (CI): 1.09-4.17, P = 0.026). The association between delirium and both Prevotella (OR: 0.59, 95% CI: 0.33-1.04, P = 0.067) and Collinsella (OR: 0.57, 95% CI: 0.27-1.24, P = 0.158) did not meet statistical significance. These findings suggest that there may be an association between postoperative gut microbiota, specifically Parabacteroides distasonis, and postoperative delirium. However, further research is needed to confirm these findings and better understand the gut-brain axis's role in postoperative outcomes.

Preclinical and translational models for delirium: Recommendations for future research from the NIDUS delirium network

Delirium is a common, morbid, and costly syndrome that is closely linked to Alzheimer's disease (AD) and AD-related dementias (ADRD) as a risk factor and outcome. Human studies of delirium have advanced our knowledge of delirium incidence and prevalence, risk factors, biomarkers, outcomes, prevention, and management. However, understanding of delirium neurobiology remains limited. Preclinical and translational models for delirium, while challenging to develop, could advance our knowledge of delirium neurobiology and inform the development of new prevention and treatment approaches. We discuss the use of preclinical and translational animal models in delirium, focusing on (1) a review of current animal models, (2) challenges and strategies for replicating elements of human delirium in animals, and (3) the utility of biofluid, neurophysiology, and neuroimaging translational markers in animals. We conclude with recommendations for the development and validation of preclinical and translational models for delirium, with the goal of advancing awareness in this important field.

The contribution of probiotics for the double-edge effect of cefazolin on postoperative neurocognitive disorders by rebalancing the gut microbiota

Introduction

Emerging data suggest that perioperative gut dysbiosis is prevalent and may be associated with postoperative neurocognitive disorders (PND). Antibiotics and probiotics are key factors influencing the microbiota. Many antibiotics have anti-microorganisms and direct anti-inflammatory properties, which may have cognitive repercussions. NLRP3 inflammasome activation has been reported to be involved with cognitive deficits. This study aimed to determine the effect and mechanism of probiotics on neurocognitive problems associated with perioperative gut dysbiosis by the NLRP3 pathway.

Methods

In a randomized, controlled trial, adult male Kunming mice undergoing surgery were administered cefazolin, FOS + probiotics, CY-09, or a placebo in four distinct experimental cohorts. Fear conditioning (FC) tests evaluate learning and memory. Following FC tests to evaluate inflammatory response (IR) and the permeability of barrier systems, the hippocampus and colon were extracted, and feces were collected for 16 s rRNA.

Results

One week after surgery, surgery/anesthesia decreased the frozen behavior. Cefazolin attenuated this declination but aggravated postoperative freezing behavior 3 weeks after surgery. Probiotics ameliorated surgery/anesthesia-induced memory deficits and perioperative cefazolin-induced postoperative memory deficits 3 weeks after surgery. NLRP3, caspase-1, Interleukin-1β (IL-1β), and Interleukin-18 (IL-18) levels were increased 1 week after the hippocampus and colon surgery, which were attenuated by CY-09 and probiotics, respectively.

Discussion

Probiotics could correct dysbacteria and IR caused by surgery/anesthesia stress and cefazolin alone. These findings imply that probiotics are an efficient and effective way of maintaining the balance of gut microbiota, which may reduce NLRP3-related inflammation and alleviate PND.

Ketamine Induces Delirium-Like Behavior and Interferes With Endosomal Tau Trafficking

BACKGROUND

Ketamine is an intravenous anesthetic. However, whether ketamine can induce neurotoxicity and neurobehavioral deficits remains largely unknown. Delirium is a syndrome of acute brain dysfunction associated with anesthesia and surgery in patients, and tau protein may contribute to postoperative delirium. Finally, ketamine may affect the function of the endosome, the key organelle for tau release from neurons. Therefore, we set out to determine the effects of ketamine on delirium-like behavior in mice and on tau trafficking in cultured cells.

METHODS

We used the buried-food test, open-field test, and Y-maze test in adult mice to assess the presence of delirium-like behavior in mice. We quantified tau amounts in the serum of mice. We used cell fraction methods to determine the effects of ketamine on tau intracellular trafficking, extracellular release, and endosome trafficking in cultured cells.

RESULTS

Ketamine induced delirium-like behavior in mice and increased tau amounts in serum of mice. The ketamine treatments also led to increased accumulation of endosomes, as evidenced by increased endosomal markers Rab5 and Rab7. Moreover, ketamine inhibited endosome maturation, demonstrated by decreased membrane-bound but increased cytoplasm amounts of Rab5 and Rab7. Consequently, ketamine increased tau in the endosomes of cultured cells and the cell culture medium.

CONCLUSIONS

These data suggest that ketamine may interfere with intracellular tau trafficking and induce delirium-like behavior, promoting future research regarding the potential neurotoxicity of anesthetics.

Dexmedetomidine alleviates host ADHD-like behaviors by reshaping the gut microbiota and reducing gut-brain inflammation

Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent psychiatric disorders that affects children and even continues into adulthood. Dexmedetomidine (DEX), a short-term sedative, can selectively activate the α2-adrenoceptor. Treatment with α2-adrenergic agonists in patients with ADHD is becoming increasingly common. However, the therapeutic potential of DEX for the treatment of ADHD is unknown. Here, we evaluated the effect of DEX on ADHD-like behavior in spontaneously hypertensive rats (SHRs), a widely used animal model of ADHD. DEX treatment ameliorated hyperactivity and spatial working memory deficits and normalized θ electroencephalogram (EEG) rhythms in SHRs. We also found that DEX treatment altered the gut microbiota composition and promoted the enrichment of beneficial gut bacterial genera associated with anti-inflammatory effects in SHRs. The gut pathological scores and permeability and the level of inflammation observed in the gut and brain were remarkably improved after DEX administration. Moreover, transplantation of fecal microbiota from DEX-treated SHRs produced effects that mimicked the therapeutic effects of DEX administration. Therefore, DEX is a promising treatment for ADHD that functions by reshaping the composition of the gut microbiota and reducing inflammation in the gut and brain.

The effects of microbiome-targeted therapy on cognitive impairment and postoperative cognitive dysfunction-A systematic review

BACKGROUND

The gut-brain axis involves bidirectional communication between the gut-microbiota and central nervous system. This study aimed to investigate whether probiotics and/or prebiotics, known as Microbiome-targeted Therapies (MTTs), improve cognition and prevent postoperative cognitive dysfunction (POCD).

METHODS

Relevant animal and human studies were identified using a systematic database search (PubMed, EMBASE, Cochrane Library, and Web of Science), focusing on the effects of MTTs on inflammation, perioperative and non-perioperative cognitive impairment. Screening and data extraction were conducted by two independent reviewers. The Risk of bias was assessed using the SYRCLE's risk of bias tool for animal studies. The revised Cochrane risk of bias tool (RoB 2) was used for human studies.

RESULTS

A total of 24 articles were selected; 16 of these involved animal studies, and 8 described studies in humans. In these papers, the use of MTTs consistently resulted in decreased inflammation in perioperative and non-perioperative settings. Out of 16 animal studies, 5 studies (2 associated with delirium and 3 studies related to POCD) were conducted in a perioperative setting. MTTs improved perioperative cognitive behavior and reduced inflammation in all 5 animal studies. Eleven animal studies were conducted in a non-perioperative setting. In all of these studies, MTTs showed improvement in learning and memory function. MTTs showed a positive effect on levels of pro-inflammatory cytokines and biomarkers related to cognitive function. Among the 8 human studies, only one study examined the effects of perioperative MTTs on cognitive function. This study showed a reduced incidence of POCD along with improved cognitive function. Of the remaining 7 studies, 6 suggested that MTTs improved behavioral test results and cognition in non-perioperative environments. One study failed to show any significant differences in memory, biomarkers of inflammation, or oxidative factors.

CONCLUSION

In the studies we examined, most showed that MTTs decrease inflammation by down-regulating inflammatory cytokines and oxidative stress in both perioperative and non-perioperative settings. In general, MTTs also seem to have a positive effect on cognition through neural, immune, endocrine, and metabolic pathways. However, these effects have not yet resulted in a consensus regarding preventative strategies or treatments. Based on these current research results, MTTs could be a potential new preventative strategy for cognitive impairment after surgery.

The association between gut microbiota and postoperative delirium in patients

Postoperative delirium is one of the most common postoperative complications in older patients. Its pathogenesis and biomarkers, however, remain largely undetermined. Majority of human microbiota is gut microbiota and gut microbiota has been shown to regulate brain function. Therefore, this study aimed to determine the association between gut microbiota and postoperative delirium in patients. Of 220 patients (65 years old or older) who had a knee replacement, hip replacement, or laminectomy under general or spinal anesthesia, 86 participants were included in the data analysis. The incidence (primary outcome) and severity of postoperative delirium was assessed for two days. Fecal swabs were collected from participants immediately after surgery. The 16S rRNA gene sequencing was used to assess gut microbiota. Using principal component analyses along with a literature review to identify biologically plausible mechanisms, and three bacterials were studied for their associations with postoperative delirium. Of the 86 participants [age 71.0 (69.0-76.0, 25%-75% percentile of quartile), 53% female], ten (12%) developed postoperative delirium. Postoperative gut bacteria Parabacteroides distasonis (Odds Ratio [OR] 2.13, 95% Confidence Interval (CI): 1.09-4.17, P = 0.026) was associated with postoperative delirium after adjusting for age and sex. The association between delirium and both Prevotella (OR: 0.59, 95% CI: 0.33-1.04, P = 0.067) and Collinsella (OR: 0.57, 95% CI: 0.27-1.24, P = 0.158) did not meet statistical significance. These findings suggest that postoperative gut microbiota (e.g., Parabacteroides distasonis ) may serve as biomarkers in the pathogenesis of postoperative delirium, pending confirmative studies.

Postoperative Delirium in Neurosurgical Patients: Recent Insights into the Pathogenesis

Postoperative delirium (POD) is a complication characterized by disturbances in attention, awareness, and cognitive function that occur shortly after surgery or emergence from anesthesia. Since it occurs prevalently in neurosurgical patients and poses great threats to the well-being of patients, much emphasis is placed on POD in neurosurgical units. However, there are intricate theories about its pathogenesis and limited pharmacological interventions for POD. In this study, we review the recent insights into its pathogenesis, mainly based on studies within five years, and the five dominant pathological theories that account for the development of POD, with the intention of furthering our understanding and boosting its clinical management.

The hotspots and publication trends in postoperative delirium: A bibliometric analysis from 2000 to 2020

Background

Postoperative delirium (POD) is a common aging-associated postoperative complication that has received increasing attention in the context of the aging global population and the number of articles published on POD is gradually increasing. This study aimed to quantify the basic information of scholarly publications on POD and identify the most impactful literature, trends, and hotspots in POD research.

Materials and methods

We searched articles on POD through the Science Citation Index Expanded databases published from 2000 to 2020. Bibliographic information, including year, country, authorship, type, journal, funding, affiliations, subject areas, and hotspots, was collected for further analysis.

Results

A total of 2,114 articles on POD from 2000 to 2020 were identified. The highest number of studies (n = 748) were published in the United States, comprising the most total citations (13,928), followed by China (n = 278), and Germany (n = 209). Inouye, Sharon K. was the most productive author, with 66 publications on POD. The Journal of the American Geriatrics Society published the highest number of articles (n = 80), with the most total citations (4,561) and average (57.01), followed by Anesthesia and Analgesia (n = 52), and the British Journal of Anaesthesia (n = 43). Harvard University was the most productive institute, with the highest H-index (n = 46) and highest degree centrality (n = 191). The top hotspots in the field of POD during this period were "elderly," "cardiac surgery," "cognitive impairment," "hip fracture," and "intensive care unit."

Conclusion

This study provides an overview of developments in the field of POD over the past 20 years using bibliometric analysis. Overall, research on POD has flourished worldwide. The United States (US) has a relatively high academic impact owing to its productive expertise and institutions in this field. Despite much research illustrating the diagnosis and management of POD in clinical practice, more basic research is needed.

Urinary Catheterization Induces Delirium-Like Behavior Through Glucose Metabolism Impairment in Mice

BACKGROUND

Delirium, an acute confusion status, is associated with adverse effects, including the development of Alzheimer's disease. However, the etiology and underlying mechanisms of delirium remain largely to be determined. Many patients have urinary catheterization (UC), and UC is associated with delirium. However, the cause effects of UC-associated delirium and the underlying mechanisms remain largely unknown. We, therefore, established an animal model of UC, without urinary tract infection, in mice and determined whether UC could induce delirium-like behavior in the mice and the underlying mechanism of these effects.

METHODS

Adult female mice (16 weeks old) had UC placement under brief isoflurane anesthesia. The delirium-like behavior was determined using our established mice model at 3, 6, 9, and 24 hours after UC placement. We measured the amounts of glucose in both blood and brain interstitial fluid, adenosine triphosphate (ATP) concentration in the cortex, and glucose transporter 1 in the cortex of mice using western blot, immunohistochemistry imaging, reverse transcriptase-polymerase chain reaction (RT-PCR), and fluorescence at 6 hours after the UC placement. Finally, we used vascular endothelial growth factor (VEGF) in the interaction studies.

RESULTS

We found that UC induced delirium-like behavior in mice at 3, 6, 9, but not 24 hours after the UC placement. UC decreased glucose amounts in brain interstitial fluid (86.38% ± 4.99% vs 100% ± 6.26%, P = .003), but not blood of mice and reduced ATP amounts (84.49% ± 8.85% vs 100% ± 10.64%, P = .031) in the cortex of mice. Finally, UC reduced both protein amount (85.49% ± 6.83% vs 100% ± 11.93%, P = .040) and messenger ribonucleic acid (mRNA) expression (41.95% ± 6.48% vs 100% ± 19.80%, P = .017) of glucose transporter 1 in the cortex of mice. VEGF attenuated these UC-induced changes.

CONCLUSIONS

These data demonstrated that UC decreased brain glucose and energy amounts via impairing the glucose transport from blood to brain, leading to delirium-like behavior in mice. These findings will promote more research to identify the etiologies and underlying mechanisms of delirium.

Electroacupuncture attenuates surgical pain-induced delirium-like behavior in mice via remodeling gut microbiota and dendritic spine

Surgical pain is associated with delirium in patients, and acupuncture can treat pain. However, whether electroacupuncture can attenuate the surgical pain-associated delirium via the gut-brain axis remains unknown. Leveraging a mouse model of foot incision-induced surgical pain and delirium-like behavior, we found that electroacupuncture stimulation at specific acupoints (e.g., DU20+KI1) attenuated both surgical pain and delirium-like behavior in mice. Mechanistically, mice with incision-induced surgical pain and delirium-like behavior showed gut microbiota imbalance, microglia activation in the spinal cord, somatosensory cortex, and hippocampus, as well as an enhanced dendritic spine elimination in cortex revealed by two-photon imaging. The electroacupuncture regimen that alleviated surgical pain and delirium-like behavior in mice also effectively restored the gut microbiota balance, prevented the microglia activation, and reversed the dendritic spine elimination. These data demonstrated a potentially important gut-brain interactive mechanism underlying the surgical pain-induced delirium in mice. Pending further studies, these findings revealed a possible therapeutic approach in preventing and/or treating postoperative delirium by using perioperative electroacupuncture stimulation in patients.

Gut microbiota-mediated metabolic restructuring aggravates emotional deficits after anesthesia/surgery in rats with preoperative stress

Patients with preoperative stress are prone to postoperative emotional deficits. However, the underlying mechanisms are largely unknown. Here, we characterize the changes of microbial composition and specific metabolites after anesthesia/surgery in rats with preoperative stress based on 16S rRNA gene sequencing and non-targeted metabolomics technique. Consequently, we found that anesthesia/surgery aggravated anxiety-like and depression-like behaviors in rats under preoperative stress. Microglia were activated and pro-inflammatory cytokines, including interleukin 6 (IL-6) and tumor necrosis factor ɑ (TNF-α) were upregulated after anesthesia/surgery. The postoperative gut microbiota and metabolite composition of rats exposed to preoperative stress differed from those of control rats. Lastly, emotional impairments, metabolic alterations, and neuroinflammation returned normal in antibiotics-treated rats. Our findings provide further evidence that abnormalities in the gut microbiota contribute to postoperative metabolic restructuring, neuroinflammation, and psychiatric deficits in rats under preoperative stress.

Study of Correlation between Intestinal Microbiota and Traditional Chinese Medicine Syndrome of Patients with Colon Cancer

Objective

This research aims to study the material basis of the formation and specific bacteria of traditional Chinese medicine (TCM) syndrome from the characteristics of the intestinal microbiota of patients with colon cancer (CC) before and after the operation.

Methods

A cross-sectional study was conducted on 84 patients with CC and 24 healthy controls. A total of 168 and 24 stool samples were collected from CC patients before and after the operation and healthy controls. DNA was extracted from 192 stool samples and then amplified using PCR. The V3-V4 high variable areas were analyzed by 16s rDNA sequencing.

Results

The community diversity, in descending order, was the healthy control group and postoperative and preoperative groups of CC patients. The abundance of beneficial bacteria was postoperative group of CC patients > healthy control group > preoperative group of CC patients. Among the comparisons of the intestinal microbiota of preoperative groups of CC patients with different TCM syndromes, the community diversity in descending order was damp heat accumulation (DHA), spleen deficiency and dampness (SDD), spleen and kidney yang deficiency (SKYD), liver and kidney yin deficiency (LKYD), and deficiency of qi and blood (QBD), respectively. Specific microbiome analysis showed that the differences in the abundance of 42 taxons were statistically significant among the preoperative groups of CC patients with the five TCM syndromes and the healthy control group. While comparing the intestinal microbiota of postoperative groups with the five TCM syndromes, the community diversity in descending order is DHA, SDD, LKYD, SKYD, and QBD. Specific microbiome analysis showed that the differences in the abundance of 46 taxons were statistically significant among the postoperative groups of CC patients with the five TCM syndromes and the healthy control group. Streptococcus and Streptococcus mutans showed no statistical significance between the preoperative group and postoperative groups of CC with DHA syndrome (P > 0.05). Bacteroides at phylum and genus levels showed that there was no statistical significance between the preoperative group and the postoperative group of CC with SKYD syndrome (P > 0.05).

Conclusions

Before and after surgery, with the deterioration of TCM syndrome: DHA ⟶ SDD ⟶ SKYD ⟶ LKYD ⟶ QBD, the number of beneficial bacteria in CC patients' intestines decreased while the number of pathogenic bacteria increased, and the community structure of intestinal microbiota tends to be unitized, indicating a serious intestinal microbiological disorder. After radical surgery and perioperative intervention, the intestinal microbiota diversity and community structure of postoperative CC patients were closer to those of healthy people than preoperative. However, they were still imbalanced. The intestinal microbiota of CC patients with different TCM syndromes differs significantly, which is important for understanding the pathogenesis of CC in TCM. The DHA and SKYD syndromes in CC patients before and after surgery showed significant differences in the microbial structure. Streptococcus and Streptococcus mutans were the specific species with a significant difference in CC patients with DHA syndrome, while bacteroides were the specific species in CC patients with SKYD syndrome.

Orthopedic Surgery Causes Gut Microbiome Dysbiosis and Intestinal Barrier Dysfunction in Prodromal Alzheimer's Disease Patients: A Prospective Observational Cohort Study

Objective:

To investigate gut microbiota and intestinal barrier function changes after orthopedic surgery in elderly patients with either normal cognition (NC) or a prodromal Alzheimer disease phenotype (pAD) comprising either subjective cognitive decline (SCD) or amnestic mild cognitive impairment (aMCI).

Background:

Homeostatic disturbances induced by surgical trauma and/or stress can potentially alter the gut microbiota and intestinal barrier function in elderly patients before and after orthopedic surgery.

Methods:

In this prospective cohort study, 135 patients were subject to preoperative neuropsychological assessment and then classified into: NC (n=40), SCD (n=58), or aMCI (n=37). Their gut microbiota, bacterial endotoxin (lipopolysaccharide), tight junction (TJ) protein, and inflammatory cytokines in blood were measured before surgery and on postsurgical day 1, 3, and 7 (or before discharge).

Results:

The short-chain fatty acid (SCFA)-producing bacteria were lower while the gram-negative bacteria, lipopolysaccharide and TJ were higher preoperatively in both the SCD and aMCI (pAD) groups compared with the NC group. After surgery, a decrease in SCFA-producing bacteria, and an increase in both gram-negative bacteria and plasma claudin were significant in the pAD groups relative to the NC group. SCFA-producing bacteria were negatively correlated with TJ and cytokines in pAD patients on postsurgical day 7. Furthermore, surgery-induced perioperative metabolic stress and inflammatory responses were associated with gut microbiota alterations.

Conclusions:

Surgery exacerbates both preexisting microbiota dysbiosis and intestinal barrier dysfunction in pAD patients, all of which may be associated with systemic inflammation and, in turn, may lead to further cognitive deterioration.

The Role of Gut Microbiota—Gut—Brain Axis in Perioperative Neurocognitive Dysfunction

With the aging of the world population and advances in medical and health technology, more and more elderly patients are undergoing anesthesia and surgery, and perioperative neurocognitive dysfunction (PND) is receiving increasing attention. The latest definition of PND, published simultaneously in November 2018 in 6 leading journals in the field of anesthesiology, clarifies that PND includes preoperatively cognitive impairment, postoperative delirium, delayed neurocognitive recovery, and postoperative cognitive dysfunction and meets the diagnostic criteria for neurocognitive impairment in the Diagnostic and Statistical Manual of Mental Disorders -fifth edition (DSM-5). The time frame for PND includes preoperatively and within 12 months postoperatively. Recent studies have shown that gut microbiota regulates central nervous function and behavior through the gut microbiota - gut - brain axis, but the role of the axis in the pathogenesis of PND remains unclear. Therefore, this article reviews the mechanism of the role of gut microbiota-gut-brain axis in PND, so as to help explore reasonable early treatment strategies.

Gut Microbiome in Anesthesiology and Pain Medicine

The gut microbiome plays critical roles in human health and disease. Recent studies suggest it may also be associated with chronic pain and postoperative pain outcomes. In animal models, the composition of the gut microbiome changes after general anesthesia and affects the host response to medications, including anesthetics and opioids. In humans, the gut microbiome is associated with the development of postoperative pain and neurocognitive disorders. Additionally, the composition of the gut microbiome has been associated with pain conditions including visceral pain, nociplastic pain, complex regional pain syndrome, and headaches, partly through altered concentration of circulating bacterial-derived metabolites. Furthermore, animal studies demonstrate the critical role of the gut microbiome in neuropathic pain via immunomodulatory mechanisms. This article reviews basic concepts of the human gut microbiome and its interactions with the host and provide a comprehensive overview of the evidence linking the gut microbiome to anesthesiology, critical care, and pain medicine.

Inhibition of unfolded protein response prevents post-anesthesia neuronal hyperactivity and synapse loss in aged mice

Delirium is the most common postoperative complication in older patients after prolonged anesthesia and surgery and is associated with accelerated cognitive decline and dementia. The neuronal pathogenesis of postoperative delirium is largely unknown. The unfolded protein response (UPR) is an adaptive reaction of cells to perturbations in endoplasmic reticulum function. Dysregulation of UPR has been implicated in a variety of diseases including Alzheimer's disease and related dementias. However, whether UPR plays a role in anesthesia-induced cognitive impairment remains unexplored. By performing in vivo calcium imaging in the mouse frontal cortex, we showed that exposure of aged mice to the inhalational anesthetic sevoflurane for 2 hours resulted in a marked elevation of neuronal activity during recovery, which lasted for at least 24 hours after the end of exposure. Concomitantly, sevoflurane anesthesia caused a prolonged increase in phosphorylation of PERK and eIF2α, the markers of UPR activation. Genetic deletion or pharmacological inhibition of PERK prevented neuronal hyperactivity and memory impairment induced by sevoflurane. Moreover, we showed that PERK suppression also reversed various molecular and synaptic changes induced by sevoflurane anesthesia, including alterations of synaptic NMDA receptors, tau protein phosphorylation, and dendritic spine loss. Together, these findings suggest that sevoflurane anesthesia causes abnormal UPR in the aged brain, which contributes to neuronal hyperactivity, synapse loss and cognitive decline in aged mice.

General anesthesia bullies the gut: a toxic relationship with dysbiosis and cognitive dysfunction

Perioperative neurocognitive disorder (PND) is a common surgery outcome affecting up to a third of the elderly patients, and it is associated with high morbidity and increased risk for Alzheimer's disease development. PND is characterized by cognitive impairment that can manifest acutely in the form of postoperative delirium (POD) or after hospital discharge as postoperative cognitive dysfunction (POCD). Although POD and POCD are clinically distinct, their development seems to be mediated by a systemic inflammatory reaction triggered by surgical trauma that leads to dysfunction of the blood-brain barrier and facilitates the occurrence of neuroinflammation. Recent studies have suggested that the gut microbiota composition may play a pivotal role in the PND development by modulating the risk of neuroinflammation establishment. In fact, modulation of gut microbiome composition with pre- and probiotics seems to be effective for the prevention and treatment of PND in animals. Interestingly, general anesthetics seem to have major responsibility on the gut microbiota composition changes following surgery and, consequently, can be an important element in the process of PND initiation. This concept represents an important milestone for the understanding of PND pathogenesis and may unveil new opportunities for the development of preventive or mitigatory strategies against the development of these conditions. The aim of this review is to discuss how anesthetics used in general anesthesia can interact and alter the gut microbiome composition and contribute to PND development by favoring the emergence of neuroinflammation.

The role of intracerebral dopamine D1 and D2 receptors in sleep-wake cycles and general anesthesia

Dopamine (DA), a monoamine neurotransmitter, is synthesized and released mainly by neurons in the ventral tegmental area and the substantia nigra (SN) pars compacta of the midbrain. DA and its receptors are essential for the regulation of arousal, movement, cognition, reward, and other neurobiological behaviors. Arousal, locomotion, cognition, reward, and other neurobiological functions are all regulated by dopamine and its receptors. Dopamine receptors can be divided into D1-like receptors (including D1 and D5) or D2-like receptors (containing D2, D3, and D4), with D1 and D2 receptors (D1Rs, and D2Rs) being the most important. Currently, studies indicated that D1Rs and D2Rs are tightly involved with the process of sleep-wake and general anesthesia, but the specific mechanism remains unclear. In this review, we compiled the most recent findings, mainly focusing on the structure, distribution, and signal pathway of D1Rs and D2Rs in the central nervous system, as well as the involvement of D1Rs and D2Rs in sleep-wake and general anesthesia. Thus, the investigations of the D1Rs and D2Rs will benefit not only better knowledge for how sleep-wake control works but also the mechanism of general anesthesia.

Mitochondrial DNA methylation drift and postoperative delirium in mice

BACKGROUND

Mitochondrial dysfunction is linked to the etiopathogenesis of postoperative delirium (POD), which severely affects the prognosis of elderly patients undergoing surgery. The methylation of mitochondrial DNA (mtDNA), a new and incompletely described phenomenon that regulates the structure and function of mitochondria, is associated with ageing. However, the relationship between mtDNA methylation and POD has not been established.

OBJECTIVE

To explore the potential roles of mitochondrial epigenetic regulation in POD.

DESIGN

A randomised animal study.

PARTICIPANTS

Eighty-eight 6-month-old and one hundred seventy-six 18-month-old male C57BL/6N mice.

INTERVENTIONS

POD was induced by abdominal surgery under 1.4% isoflurane for 2 h. Behavioural tests were performed at 24 h before surgery and at 6, 9 and 24 h after surgery.

MAIN OUTCOME MEASURES

5-methylcytosine (5-mC) at five CpG sites of the displacement loop (D-loop) and at 60 CpG sites of coding gene loci in the mitochondrial genome after surgery of the hippocampus, prefrontal cortex, amygdala and anterior cingulate cortex in 6 and 18-month-old mice were detected using bisulfite pyrosequencing. Mitochondrial structure, mitochondrial gene expression and mtDNA copy number were also examined using Electron microscopy and real time PCR to find the association with mtDNA methylation.

RESULTS

The mtDNA methylation drift manifested as a decrease in the methylation levels at the D-loop and an increase or decrease in the methylation levels at several coding gene loci, ultimately resulting in reduced mtDNA copy numbers, altered mitochondrial gene expression and damaged mitochondrial structures in the hippocampus and prefrontal cortex after surgery. The activation of Silent information regulator-1 (SIRT1) ameliorated anaesthesia-induced and surgery-induced mitochondrial dysfunction and delirium-like behaviours by regulating mtDNA methyltransferase-mediated mtDNA methylation.

CONCLUSION

These data support the existence of epigenetic mtDNA regulation in POD; however, further studies are required to explore the specific mechanisms.

TRIAL REGISTRATION

No 20181204 Drum tower hospital.

Gut-Brain Axis: Possible Role of Gut Microbiota in Perioperative Neurocognitive Disorders

Aging is becoming a severe social phenomenon globally, and the improvements in health care and increased health awareness among the elderly have led to a dramatic increase in the number of surgical procedures. Because of the degenerative changes in the brain structure and function in the elderly, the incidence of perioperative neurocognitive disorders (PND) is much higher in elderly patients than in young people following anesthesia/surgery. PND is attracting more and more attention, though the exact mechanisms remain unknown. A growing body of evidence has shown that the gut microbiota is likely involved. Recent studies have indicated that the gut microbiota may affect postoperative cognitive function via the gut-brain axis. Nonetheless, understanding of the mechanistic associations between the gut microbiota and the brain during PND progression remains very limited. In this review, we begin by providing an overview of the latest progress concerning the gut-brain axis and PND, and then we summarize the influence of perioperative factors on the gut microbiota. Next, we review the literature on the relationship between gut microbiota and PND and discuss how gut microbiota affects cognitive function during the perioperative period. Finally, we explore effective early interventions for PND to provide new ideas for related clinical research.

Postoperative delirium and neurocognitive disorders

PURPOSE OF REVIEW

Postoperative neurocognitive disorders (NCD) are significant causes of morbidity and mortality. In this paper, we will review our understanding and potential management of postoperative NCD.

RECENT FINDINGS

Postoperative delirium, delayed neurocognitive recovery and postoperative cognitive dysfunction (POCD) are recognized as a part of the continuous spectrum of postoperative NCD. Although the pathophysiology is still poorly understood, there is renewed focus on improving neurocognitive outcomes of aging surgical population. Novel methods of neurocognitive screening are developed and research in the prevention and management of NCD has gained traction.

SUMMARY

A spectrum of NCD exists in surgical patients ranging from postoperative delirium, delayed neurocognitive recovery, and POCD. Identification of patients at-risk for developing NCD can help target appropriate perioperative intervention. Also, specialized care teams and the implementation of standardized protocols are crucial for the successful management perioperative NCD. Finally, large, randomized, multicenter studies are needed to confirm benefits of preventive and treatment strategies.

Effect of Anesthesia/Surgery on Gut Microbiota and Fecal Metabolites and Their Relationship With Cognitive Dysfunction

Aims: Post-operative cognitive dysfunction (POCD) is the decline in cognitive function of the central nervous system (CNS) after anesthesia/surgery. The present study explored whether anesthesia/surgery altered gut microbiota and fecal metabolites, examining their associations with risk factors of cognitive dysfunction in aged mice.

Methods: Sixteen-month-old C57BL/6 mice underwent abdominal surgery under isoflurane anesthesia to establish an animal model of POCD. The Morris water maze test (MWMT) was used as an indicator of memory after surgery. The effects of anesthesia/surgical interventions on gut microbiota, fecal metabolites, hippocampus, and serum levels of inflammatory factors were examined.

Results: The anesthesia/surgery induced more serious POCD behavior, increasing brain interleukin (IL)-6, and IL-1β levels than sham control mice. The relative abundance of bacterial genera Bacteroidales_unclassified, Mucispirillum, and Clostridiales_unclassified declined, whereas that of Escherichia–Shigella, actinomyces, Ruminococcus_gnavus_group, and Lachnospiraceae_FCS020_group were enriched after anesthesia/surgery compared to the baseline controls. Liquid chromatography–mass spectrometry (LC–MS) showed that the metabolites differed between post-anesthesia+surgery (post_A + S) and baseline samples and were associated with the fecal metabolism of tryptophan, kynurenic acid, N-oleoyl γ-aminobutyric acid (GABA), 2-indolecarboxylic acid, and glutamic acid. Furthermore, the differential metabolites were associated with alterations in the abundance of specific bacteria. These results indicate that the POCD intervention may be achieved by targeting specific bacteria associated with neurotransmitter metabolism.

Conclusions: A transient cognitive disturbance induced by anesthesia/surgery may be associated with unfavorable alterations in gut microbiota and fecal metabolites, thereby contributing to the POCD development.