Neuroinflammation in delirium: a postmortem case-control study

Calorie restriction increases the sensitivity of progeroid Ercc1Δ/- mice to acute (neuro)inflammation

Hospitalized elderly patients frequently suffer from delirium, especially in the context of sepsis-associated encephalopathy. Current treatments of delirium are merely symptomatic. Calorie restriction (CR) is both a promising strategy to protect against sepsis and has beneficial effects on aging-induced neurodegeneration. In this study, we investigated whether six weeks of 30% CR had protective effects on lipopolysaccharide (LPS) induced (neuro)inflammation in wild-type (WT) and progeroid mice deficient in the DNA excision-repair gene Ercc1 (Ercc1Δ/-). While CR did not affect the LPS-induced inflammatory response in WT mice, CR exaggerated the peripheral inflammatory response in Ercc1Δ/- mice, as evidenced by an increase of pro-inflammatory serum cytokines (TNF-α, IL-1β, and IFN-γ) and kidney injury marker Ngal. Neuroinflammatory effects were assessed by RNA-sequencing of isolated microglia. Similarly, CR did not affect microglia gene expression in WT mice, but increased neuroinflammation-associated gene expression in Ercc1Δ/- mice. In conclusion, CR increases the peripheral and brain inflammatory response of Ercc1Δ/- mice to a systemic inflammatory stimulus.

A transient brain endothelial translatome response to endotoxin is associated with mild cognitive changes post-shock in young mice

Sepsis-associated encephalopathy (SAE) is associated with increased risk of long-term cognitive impairment. SAE is driven, at least in part, by brain endothelial dysfunction in response to systemic cytokine signaling. However, the mechanisms driving SAE and its consequences remain largely unknown. Here, we performed translating ribosome affinity purification and RNA-sequencing (TRAP-seq) from the brain endothelium to determine the transcriptional changes after an acute endotoxemic (LPS) challenge. LPS induced a strong acute transcriptional response in the brain endothelium that partially correlates with the whole brain transcriptional response and suggested an endothelial-specific hypoxia response. Consistent with a crucial role for IL-6, loss of the main regulator of this pathway, SOCS3, leads to a broadening of the population of genes responsive to LPS, suggesting that an overactivation of the IL-6/JAK/STAT3 pathway leads to an increased transcriptional response that could explain our prior findings of severe brain injury in these mice. To identify any potential sequelae of this acute response, we performed brain TRAP-seq following a battery of behavioral tests in mice after apparent recovery. We found that the transcriptional response returns to baseline within days post-challenge, but reductions in gene expression regulating protein translation and respiratory electron transport remained. We observed that mice that recovered from the endotoxemic shock showed mild, sex-dependent cognitive impairment, suggesting that the acute brain injury led to sustained effects. A better understanding of the transcriptional and non-transcriptional changes in response to shock is needed in order to prevent and/or revert the devastating consequences of septic shock.

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.

Common molecular and pathophysiological underpinnings of delirium and Alzheimer's disease: molecular signatures and therapeutic indications

BACKGROUND

Delirium and Alzheimer's disease (AD) are common causes of cognitive dysfunction among older adults. These neurodegenerative diseases share a common and complex relationship, and can occur individually or concurrently, increasing the chance of permanent mental dysfunction. However, the common molecular pathophysiology, key proteomic biomarkers, and functional pathways are largely unknown, whereby delirium is superimposed on AD and dementia.

METHODS

We employed an integrated bioinformatics and system biology analysis approach to decipher such common key proteomic signatures, pathophysiological links between delirium and AD by analyzing the gene expression data of AD-affected human brain samples and comparing them with delirium-associated proteins. The present study identified the common drug target hub-proteins examining the protein-protein interaction (PPI) and gene regulatory network analysis. The functional enrichment and pathway analysis was conducted to reveal the common pathophysiological relationship. Finally, the molecular docking and dynamic simulation was used to computationally identify and validate the potential drug target and repurposable drugs for delirium and AD.

RESULTS

We detected 99 shared differentially expressed genes (sDEGs) associated with AD and delirium. The sDEGs-set enrichment analysis detected the transmission across chemical synapses, neurodegeneration pathways, neuroinflammation and glutamatergic signaling pathway, oxidative stress, and BDNF signaling pathway as the most significant signaling pathways shared by delirium and AD. The disease-sDEGs interaction analysis highlighted the other disease risk factors with delirium and AD development and progression. Among the sDEGs of delirium and AD, the top 10 hub-proteins including ALB, APP, BDNF, CREB1, DLG4, GAD1, GAD2, GFAP, GRIN2B and GRIN2A were found by the PPI network analysis. Based on the maximum molecular docking binding affinities and molecular dynamic simulation (100 ns) results, the ALB and GAD2 were found as prominent drug target proteins when tacrine and donepezil were identified as potential drug candidates for delirium and AD.

CONCLUSION

The study outlined the common key biomolecules and biological pathways shared by delirium and AD. The computationally reported potential drug molecules need a deeper investigation including clinical trials to validate their effectiveness. The outcomes from this study will help to understand the typical pathophysiological relationship between delirium and AD and flag future therapeutic development research for delirium.

Discovery of Delirium Biomarkers through Minimally Invasive Serum Molecular Fingerprinting

Delirium presents a significant clinical challenge, primarily due to its profound impact on patient outcomes and the limitations of the current diagnostic methods, which are largely subjective. During the COVID-19 pandemic, this challenge was intensified as the frequency of delirium assessments decreased in Intensive Care Units (ICUs), even as the prevalence of delirium among critically ill patients increased. The present study evaluated how the serum molecular fingerprint, as acquired by Fourier-Transform InfraRed (FTIR) spectroscopy, can enable the development of predictive models for delirium. A preliminary univariate analysis of serum FTIR spectra indicated significantly different bands between 26 ICU patients with delirium and 26 patients without, all of whom were admitted with COVID-19. However, these bands resulted in a poorly performing Naïve-Bayes predictive model. Considering the use of a Fast-Correlation-Based Filter for feature selection, it was possible to define a new set of spectral bands with a wider coverage of molecular functional groups. These bands ensured an excellent Naïve-Bayes predictive model, with an AUC, a sensitivity, and a specificity all exceeding 0.92. These spectral bands, acquired through a minimally invasive analysis and obtained rapidly, economically, and in a high-throughput mode, therefore offer significant potential for managing delirium in critically ill patients.

A transient brain endothelial translatome response to endotoxin is associated with mild cognitive changes post-shock in young mice

Sepsis-associated encephalopathy (SAE) is a common manifestation in septic patients that is associated with increased risk of long-term cognitive impairment. SAE is driven, at least in part, by brain endothelial dysfunction in response to systemic cytokine signaling. However, the mechanisms driving SAE and its consequences remain largely unknown. Here, we performed translating ribosome affinity purification and RNA-sequencing (TRAP-seq) from the brain endothelium to determine the transcriptional changes after an acute endotoxemic (LPS) challenge. LPS induced a strong acute transcriptional response in the brain endothelium that partially correlates with the whole brain transcriptional response and suggested an endothelial-specific hypoxia response. Consistent with a crucial role for IL-6, loss of the main regulator of this pathway, SOCS3, leads to a broadening of the population of genes responsive to LPS, suggesting that an overactivation of the IL-6/JAK/STAT3 pathway leads to an increased transcriptional response that could explain our prior findings of severe brain injury in these mice. To identify any potential sequelae of this acute response, we performed brain TRAP-seq following a battery of behavioral tests in mice after apparent recovery. We found that the transcriptional response returns to baseline within days post-challenge. Despite the transient nature of the response, we observed that mice that recovered from the endotoxemic shock showed mild, sex-dependent cognitive impairment, suggesting that the acute brain injury led to sustained, non-transcriptional effects. A better understanding of the transcriptional and non-transcriptional changes in response to shock is needed in order to prevent and/or revert the devastating consequences of septic shock.

Abstract Figure

Serum NFL and tau, but not serum UCHL-1 and GFAP or CSF SNAP-25, NPTX2, or sTREM2, correlate with delirium in a 3-year retrospective analysis

Delirium represents a common terminal pathway of heterogeneous neurological conditions characterized by disturbances in consciousness and attention. Contemporary theories highlight the acute impairment of synaptic function and network connectivity, driven by neuroinflammation, oxidative stress, and neurotransmitter imbalances. However, established biomarkers are still missing. Innovative diagnostic techniques, such as single-molecule array analysis, enable the detection of biomarkers in blood at picomolar concentrations. This approach paves the way for deeper insights into delirium and potentially therapeutic targets for tailored medical treatments. In a retrospective 3-year study, we investigated seven biomarkers indicative of neuroaxonal damage [neurofilament light chain (NFL), ubiquitin carboxyl-terminal hydrolase (UCHL-1), and tau protein], microglial activation [glial fibrillary acidic protein (GFAP) and soluble triggering receptor expressed on myeloid cells 2 (sTREM2)], and synaptic dysfunction [synaptosomal-associated protein 25 (SNAP-25) and neuronal pentraxin 2 (NPTX2)]. The analysis of 71 patients with delirium, Alzheimer's disease (AD), and non-AD controls revealed that serum NFL levels are higher in delirium cases compared to both AD and non-AD. This suggests that elevated NFL levels in delirium are not exclusively the result of dementia-related damage. Serum tau levels were also elevated in delirium cases compared to controls. Conversely, cerebrospinal fluid (CSF) SNAP-25 showed higher levels in AD patients compared to controls only. These findings add to the increasing body of evidence suggesting that serum NFL could be a valuable biomarker of neuroaxonal damage in delirium research. Although SNAP-25 and NPTX2 did not exhibit significant differences in delirium, the exploration of synaptic biomarkers remains promising for enhancing our understanding of this condition.

Biomarkers of neurodegeneration and neural injury as potential predictors for delirium

OBJECTIVES

Determine if biomarkers of Alzheimer's disease and neural injury may play a role in the prediction of delirium risk.

METHODS

In a cohort of older adults who underwent elective surgery, delirium case-no delirium control pairs (N = 70, or 35 matched pairs) were matched by age, sex and vascular comorbidities. Biomarkers from CSF and plasma samples collected prior to surgery, including amyloid beta (Aβ)42 , Aβ40 , total (t)-Tau, phosphorylated (p)-Tau181 , neurofilament-light (NfL), and glial fibrillary acid protein (GFAP) were measured in cerebrospinal fluid (CSF) and plasma using sandwich enzyme-linked immunosorbent assays (ELISAs) or ultrasensitive single molecule array (Simoa) immunoassays.

RESULTS

Plasma GFAP correlated significantly with CSF GFAP and both plasma and CSF GFAP values were nearly two-fold higher in delirium cases. The median paired difference between delirium case and control without delirium for plasma GFAP was not significant (p = 0.074) but higher levels were associated with a greater risk for delirium (odds ratio 1.52, 95% confidence interval 0.85, 2.72 per standard deviation increase in plasma GFAP concentration) in this small study. No matched pair differences or associations with delirium were observed for NfL, p-Tau 181, Aβ40 and Aβ42 .

CONCLUSIONS

These preliminary findings suggest that plasma GFAP, a marker of astroglial activation, may be worth further investigation as a predictive risk marker for delirium.

Phrenic Nerve Stimulation for Acute Respiratory Failure

Diaphragm inactivity during invasive mechanical ventilation leads to diaphragm atrophy and weakness, hemodynamic instability, and ventilatory heterogeneity. Absent respiratory drive and effort can, therefore, worsen injury to both lung and diaphragm and is a major cause of failure to wean. Phrenic nerve stimulation (PNS) can maintain controlled levels of diaphragm activity independent of intrinsic drive and as such may offer a promising approach to achieving lung and diaphragm protective ventilatory targets. Whereas PNS has an established role in the management of chronic respiratory failure, there is emerging interest in how its multisystem putative benefits may be temporarily harnessed in the management of invasively ventilated patients with acute respiratory failure.

A Prospective Randomized Study of the Herbal Medicine Yokukansan for Preventing Delirium After Gastrointestinal Cancer Surgery

Background

Yokukansan, the Chinese Herbal Medicine, may be effective for treating postoperative delirium. However, there is no sufficient evidence supporting this notion. This study aimed to investigate whether yokukansan was effective for preventing delirium after gastrointestinal cancer surgery by the prospective randomized study.

Methods

This was a double-blind, randomized, controlled trial. Patients aged 75 years or older who underwent surgery between May 2017 and December 2019 were randomized to the yokukansan or anchusan (another Herbal Medicine) group. They received treatments with oral intake of assigned medicine from the day before surgery until postoperative day 3. Then, the incidence of postoperative delirium was compared. A psychiatrist diagnosed patients with postoperative delirium.

Results

Seventy-seven patients were enrolled in this study, and the full analysis set comprised 68 patients. In total, 25 of 68 (36.8%) patients presented with postoperative delirium. Specifically, 13 (37.1%) patients in the control group and 12 (36.4%) in the yokukansan group were diagnosed with postoperative delirium. However, the results did not differ significantly in both groups. Moreover, there was no remarkable difference in terms of delirium severity, and adverse events correlated with the medications were not observed.

Conclusion

Yokukansan was ineffective in preventing delirium after gastrointestinal cancer surgery.

Microglial Activation: Key Players in Sepsis-Associated Encephalopathy

Sepsis-associated encephalopathy (SAE) is a common brain dysfunction, which results in severe cognitive and neurological sequelae and an increased mortality rate in patients with sepsis. Depending on the stimulus, microglia (resident macrophages in the brain that are involved in SAE pathology and physiology) can adopt two polarization states (M1/M2), corresponding to altered microglial morphology, gene expression, and function. We systematically described the pathogenesis, morphology, function, and phenotype of microglial activation in SAE and demonstrated that microglia are closely related to SAE occurrence and development, and concomitant cognitive impairment. Finally, some potential therapeutic approaches that can prime microglia and neuroinflammation toward the beneficial restorative microglial phenotype in SAE were outlined.

Grip Strength is a Predictor for Subsyndromal Delirium Among Older Adults Following Joint Replacement

Background

Delirium is common in older patients during the postoperative period, increasing the number of adverse events, and grip strength is associated with delirium. Subsyndromal delirium (SSD) is a prostate of clinical delirium; nevertheless, the relationship between grip strength and SSD has not been elucidated. This study aimed to examine the association between grip strength and SSD in the elderly after arthroplasty.

Methods

A total of 181 patients were recruited from two Chinese hospitals. SSD and delirium were evaluated before the surgery and the first week after surgery using the confusion assessment method. The Mini-mental State Examination was used to assess patients' cognitive function, and their grip strength was evaluated with an electronic hand dynamometer before surgery. Logistic regression and ROC curve analysis were conducted to determine the odds ratio and predictive value of grip strength for SSD.

Results

The incidence of SSD and postoperative delirium (POD) was 41.44% and 14.36% for the elderly following arthroplasty respectively, and approximately 1/3 of SSD progressed into POD. Older age, declined cognitive function, fall history, and lower grip strength were risk factors for SSD (P<0.05). The area under the ROC curve of grip strength was 0.863 and 0.900 for males and females respectively, and the cut-off point of it was determined to be 22.050 kg for men and 18.050 kg for women.

Conclusion

SSD and POD are common among older people. Decreased grip strength, advanced age, lower cognitive function, and fall history were independent risk factors for SSD, and grip strength was a significant predictor for SSD in aged patients after the arthroplasty.

Potential Neuroprotective Role of Melatonin in Sepsis-Associated Encephalopathy Due to Its Scavenging and Anti-Oxidative Properties

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. The brain is one of the organs involved in sepsis, and sepsis-induced brain injury manifests as sepsis-associated encephalopathy (SAE). SAE may be present in up to 70% of septic patients. SAE has a very wide spectrum of clinical symptoms, ranging from mild behavioral changes through cognitive disorders to disorders of consciousness and coma. The presence of SAE increases mortality in the population of septic patients and may lead to chronic cognitive dysfunction in sepsis survivors. Therefore, therapeutic interventions with neuroprotective effects in sepsis are needed. Melatonin, a neurohormone responsible for the control of circadian rhythms, exerts many beneficial physiological effects. Its anti-inflammatory and antioxidant properties are well described. It is considered a potential therapeutic factor in sepsis, with positive results from studies on animal models and with encouraging results from the first human clinical trials. With its antioxidant and anti-inflammatory potential, it may also exert a neuroprotective effect in sepsis-associated encephalopathy. The review presents data on melatonin as a potential drug in SAE in the wider context of the pathophysiology of SAE and the specific actions of the pineal neurohormone.

Application of Multiple Omics to Understand Postoperative Delirium Pathophysiology in Humans

Delirium, an acute change in cognition, is common, morbid, and costly, particularly among hospitalized older adults. Despite growing knowledge of its epidemiology, far less is known about delirium pathophysiology. Initial work understanding delirium pathogenesis has focused on assaying single or a limited subset of molecules or genetic loci. Recent technological advances at the forefront of biomarker and drug target discovery have facilitated application of multiple "omics" approaches aimed to provide a more complete understanding of complex disease processes such as delirium. At its basic level, "omics" involves comparison of genes (genomics, epigenomics), transcripts (transcriptomics), proteins (proteomics), metabolites (metabolomics), or lipids (lipidomics) in biological fluids or tissues obtained from patients who have a certain condition (i.e., delirium) and those who do not. Multi-omics analyses of these various types of molecules combined with machine learning and systems biology enable the discovery of biomarkers, biological pathways, and predictors of delirium, thus elucidating its pathophysiology. This review provides an overview of the most recent omics techniques, their current impact on identifying delirium biomarkers, and future potential in enhancing our understanding of delirium pathogenesis. We summarize challenges in identification of specific biomarkers of delirium and, more importantly, in discovering the mechanisms underlying delirium pathophysiology. Based on mounting evidence, we highlight a heightened inflammatory response as one common pathway in delirium risk and progression, and we suggest other promising biological mechanisms that have recently emerged. Advanced multiple omics approaches coupled with bioinformatics methodologies have great promise to yield important discoveries that will advance delirium research.

Meta-analysis of serological biomarkers at hospital admission for the likelihood of developing delirium during hospitalization

Importance

Identifying biomarkers that, at hospital admission, predict subsequent delirium will help to focus our clinical efforts on prevention and management.

Objective

The study aimed to investigate biomarkers at hospital admission that may be associated with delirium during hospitalization.

Data sources

A librarian at the Fraser Health Authority Health Sciences Library performed searches from 28 June 2021 to 9 July 2021, using the following sources: Medline, EMBASE, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Cochrane Methodology Register, and the Database of Abstracts of Reviews and Effects.

Study selection

The inclusion criteria were articles in English that investigated the link between serum concentration of biomarkers at hospital admission and delirium during hospitalization. Exclusion criteria were single case reports, case series, comments, editorials, letters to the editor, articles that were not relevant to the review objective, and articles concerning pediatrics. After excluding duplicates, 55 studies were included.

Data extraction and synthesis

This meta-analysis followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) protocol. Independent extraction, with the consensus of multiple reviewers, was used to determine the final studies included. The weight and heterogeneity of the manuscripts were calculated using inverse covariance with a random-effects model.

Main outcomes and measures

Differences in mean serum concentration of biomarkers at hospital admission between patients who did and did not develop delirium during hospitalization.

Results

Our search found evidence that patients who developed delirium during hospitalization had, at hospital admission, significantly greater concentrations of certain inflammatory biomarkers and one blood-brain barrier leakage marker than patients who did not develop delirium during hospitalization (differences in the mean: cortisol: 3.36 ng/ml, p < 0.0001; CRP: 41.39 mg/L, p < 0.00001; IL-6: 24.05 pg/ml, p < 0.00001; S100β 0.07 ng/ml, p < 0.00001). These differences were independent of other confounding variables such as the patient's severity of illness. A significantly lower serum concentration, at hospital admission, of acetylcholinesterase (difference in the means -0.86 U/ml, p = 0.004) was also associated with an increased vulnerability to developing delirium during hospitalization.

Conclusion and relevance

Our meta-analysis supports the hypothesis that patients with hypothalamic-pituitary axis dysfunction, increased blood-brain barrier permeability, and chronic overload of the cholinergic system, at hospital admission, are more vulnerable to developing delirium during hospitalization.

Phrenic nerve stimulation mitigates hippocampal and brainstem inflammation in an ARDS model

Rationale: In porcine healthy-lung and moderate acute respiratory distress syndrome (ARDS) models, groups that received phrenic nerve stimulation (PNS) with mechanical ventilation (MV) showed lower hippocampal apoptosis, and microglia and astrocyte percentages than MV alone. Objectives: Explore whether PNS in combination with MV for 12 h leads to differences in hippocampal and brainstem tissue concentrations of inflammatory and synaptic markers compared to MV-only animals. Methods: Compare tissue concentrations of inflammatory markers (IL-1α, IL-1β, IL-6, IL-8, IL-10, IFN-γ, TNFα and GM-CSF), pre-synaptic markers (synapsin and synaptophysin) and post-synaptic markers (disc-large-homolog 4, N-methyl-D-aspartate receptors 2A and 2B) in the hippocampus and brainstem in three groups of mechanically ventilated pigs with injured lungs: MV only (MV), MV plus PNS every other breath (MV + PNS50%), and MV plus PNS every breath (MV + PNS100%). MV settings in volume control were tidal volume 8 ml/kg, and positive end-expiratory pressure 5 cmH₂O. Moderate ARDS was achieved by infusing oleic acid into the pulmonary artery. Measurements and Main Results: Hippocampal concentrations of GM-CSF, N-methyl-D-aspartate receptor 2B, and synaptophysin were greater in the MV + PNS100% group compared to the MV group, p = 0.0199, p = 0.0175, and p = 0.0479, respectively. The MV + PNS100% group had lower brainstem concentrations of IL-1β, and IL-8 than the MV group, p = 0.0194, and p = 0.0319, respectively; and greater brainstem concentrations of IFN-γ and N-methyl-D-aspartate receptor 2A than the MV group, p = 0.0329, and p = 0.0125, respectively. Conclusion: In a moderate-ARDS porcine model, MV is associated with hippocampal and brainstem inflammation, and phrenic nerve stimulation on every breath mitigates that inflammation.

Altered Tryptophan-Kynurenine Pathway in Delirium: A Review of the Current Literature

Delirium, a common form of acute brain dysfunction, is associated with increased morbidity and mortality, especially in older patients. The underlying pathophysiology of delirium is not clearly understood, but acute systemic inflammation is known to drive delirium in cases of acute illnesses, such as sepsis, trauma, and surgery. Based on psychomotor presentations, delirium has three main subtypes, such as hypoactive, hyperactive, and mixed subtype. There are similarities in the initial presentation of delirium with depression and dementia, especially in the hypoactive subtype. Hence, patients with hypoactive delirium are frequently misdiagnosed. The altered kynurenine pathway (KP) is a promising molecular pathway implicated in the pathogenesis of delirium. The KP is highly regulated in the immune system and influences neurological functions. The activation of indoleamine 2,3-dioxygenase, and specific KP neuroactive metabolites, such as quinolinic acid and kynurenic acid, could play a role in the event of delirium. Here, we collectively describe the roles of the KP and speculate on its relevance in delirium.

Neutrophil to lymphocyte ratio and platelet to lymphocyte ratio as prognostic predictors for delirium in critically ill patients: a systematic review and meta-analysis

INTRODUCTION

In this systematic review and meta-analysis, we aim to analyze the current literature to evaluate neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) values among critically ill patients who develop delirium as compared to those who do not.

METHODS

PubMed, Web of Science, and Scopus were used to conduct a systematic search for relevant publications published before June 12, 2022. The Newcastle-Ottawa scale was used for quality assessment. Because a significant level of heterogeneity was found, we used the random-effects model to generate pooled effects.

RESULTS

Twenty-four studies including 11,579 critically ill patients, of whom 2439 were diagnosed with delirium, were included in our meta-analysis. Compared with the non-delirious group, the delirious group's NLR levels were significantly higher (WMD = 2.14; CI 95% = 1.48-2.80, p < 0.01). In the subgroup analysis according to the type of critical condition, the NLR levels in patients of delirious group were significantly more than those of non-delirious group in studies on POD, PSD and PCD (WMD = 1.14, CI 95% = 0.38-1.91, p < 0.01, WMD = 1.38, CI 95% = 1.04-1.72, p < 0.001, and WMD = 4.22, CI 95% = 3.47-4.98, p < 0.001, respectively). However, compared with the non-delirious group, the delirious group's PLR levels were not significantly different (WMD = 1.74; CI 95% = -12.39-15.86, p = 0.80).

CONCLUSION

Our findings support NLR to be a promising biomarker that can be readily integrated into clinical settings to aid in the prediction and prevention of delirium.

Protective effects of omega-3 fatty acids in a blood-brain barrier-on-chip model and on postoperative delirium-like behaviour in mice

BACKGROUND

Peripheral surgical trauma can trigger neuroinflammation and ensuing neurological complications, such as delirium. The mechanisms whereby surgery contributes to postoperative neuroinflammation remain unclear and without effective therapies. Here, we developed a microfluidic-assisted blood-brain barrier (BBB) device and tested the effects of omega-3 fatty acids on neuroimmune interactions after orthopaedic surgery.

METHODS

A microfluidic-assisted BBB device was established using primary human cells. Tight junction proteins, vascular cell adhesion molecule 1 (VCAM-1), BBB permeability, and astrocytic networks were assessed after stimulation with interleukin (IL)-1β and in the presence or absence of a clinically available omega-3 fatty acid emulsion (Omegaven®; Fresenius Kabi, Bad Homburg, Germany). Mice were treated 1 h before orthopaedic surgery with 10 μl g-1 body weight of omega-3 fatty acid emulsion i.v. or equal volumes of saline. Changes in pericytes, perivascular macrophages, BBB opening, microglial activation, and inattention were evaluated.

RESULTS

Omega-3 fatty acids protected barrier permeability, endothelial tight junctions, and VCAM-1 after exposure to IL-1β in the BBB model. In vivo studies confirmed that omega-3 fatty acid treatment inhibited surgery-induced BBB impairment, microglial activation, and delirium-like behaviour. We identified a novel role for pericyte loss and perivascular macrophage activation in mice after surgery, which were rescued by prophylaxis with i.v. omega-3 fatty acids.

CONCLUSIONS

We present a new approach to study neuroimmune interactions relevant to perioperative recovery using a microphysiological BBB platform. Changes in barrier function, including dysregulation of pericytes and perivascular macrophages, provide new targets to reduce postoperative delirium.

Diaphragm Neurostimulation Mitigates Ventilation-Associated Brain Injury in a Preclinical Acute Respiratory Distress Syndrome Model

In a porcine healthy lung model, temporary transvenous diaphragm neurostimulation (TTDN) for 50 hours mitigated hippocampal apoptosis and inflammation associated with mechanical ventilation (MV).

HYPOTHESIS

Explore whether TTDN in combination with MV for 12 hours mitigates hippocampal apoptosis and inflammation in an acute respiratory distress syndrome (ARDS) preclinical model.

METHODS AND MODELS

Compare hippocampal apoptosis, inflammatory markers, and serum markers of neurologic injury between never ventilated subjects and three groups of mechanically ventilated subjects with injured lungs: MV only (LI-MV), MV plus TTDN every other breath, and MV plus TTDN every breath. MV settings in volume control were tidal volume 8 mL/kg and positive end-expiratory pressure 5 cm H₂O. Lung injury, equivalent to moderate ARDS, was achieved by infusing oleic acid into the pulmonary artery.

RESULTS

Hippocampal apoptosis, microglia, and reactive-astrocyte percentages were similar between the TTDN-every-breath and never ventilated groups. The LI-MV group had a higher percentage of these measures than all other groups (p < 0.05). Transpulmonary driving pressure at study end was lower in the TTDN-every-breath group than in the LI-MV group; systemic inflammation and lung injury scores were not significantly different. The TTDN-every-breath group had considerably lower serum concentration of homovanillic acid (cerebral dopamine production surrogate) at study end than the LI-MV group (p < 0.05). Heart rate variability declined in the LI-MV group and increased in both TTDN groups (p < 0.05).

INTERPRETATIONS AND CONCLUSIONS

In a moderate-ARDS porcine model, MV is associated with hippocampal apoptosis and inflammation, and TTDN mitigates that hippocampal apoptosis and inflammation.

Peripheral interleukin-6-associated microglial QUIN elevation in basolateral amygdala contributed to cognitive dysfunction in a mouse model of postoperative delirium

Background

Developing effective approaches for postoperative delirium has been hampered due to the lack of a pathophysiologically similar animal model to offer insights into the pathogenesis. The study, therefore, aimed to develop a delirium-like mouse model and explore the underlying mechanism.

Methods

The three cycles of 10-min clamp following 5-min reopening of the superior mesenteric artery (SMA) were performed in adult male C57BL/6 mice to induce a delirium-like phenotype. Composite Z score calculated based on the results of Open Field, Y Maze and Buried Food Tests was employed to assess the delirium phenotype in mice. Microglia activities were monitored by immunofluorescence staining and comprehensive morphological analysis. Systemic administration of minocycline (MINO), IL-6 antibody or IL-6 neutralizing antibody, was applied to manipulate microglia. The expressions of Indoleamine 2,3-dioxygenase-1 (IDO-1) and quinolinic acid (QUIN) were examined by RT-PCR and High-Performance Liquid Chromatography/Mass Spectrometry, respectively. Cytokines were measured using fluorescence activated cell sorting method.

Results

The repeated ischemia/reperfusion (I/R) surgery caused significant anxiety (P < 0.05) and cognition decline in working memory and orientation (P < 0.05) in mice at postoperative 24 h. The composite Z score, indicating an overall disturbance of brain function, fluctuated over 24 h after I/R surgery (P < 0.001). Immunofluorescent staining showed that the percentage of microglia in the basolateral amygdala (BLA) (P < 0.05) was reactivated after I/R surgery and was negatively correlated with dwell time at Y maze (R = −0.759, P = 0.035). Inhibiting microglia activities by MINO reduced QUIN productions (P < 0.01) that improved cognitive deficits (P < 0.05). The peripheral IL-6 might cause IL-6 elevation in the BLA. Systemic administration of IL-6 antibodies suppressed I/R-induced IL-6 elevations (P < 0.05), microglial reactivations (P < 0.05), IDO-1 expressions (P < 0.01), and neuroactive metabolite QUIN productions (P < 0.05) in the BLA, resulting in a recovery of cognitive deficits (P < 0.05). Injection of IL-6 exerted opposite effects.

Conclusion

The repeated intestinal I/R surgery-induced mouse model is a simple and reproducible one of postoperative delirium. Peripheral IL-6-associated microglial QUIN elevations in the BLA contributed to cognitive dysfunction in the model of postoperative delirium.

Sepsis and the brain: a review for acute and general physicians

Sepsis-associated encephalopathy (SAE) describes acute cognitive dysfunction secondary to systemic or peripheral infection occurring outside of the central nervous system (CNS). Symptoms can range from mild confusion to coma and may precede the clinical signs of sepsis. Recognition that SAE is a potential differential diagnosis in patients presenting with delirium is important, as SAE is a diagnosis of exclusion. Physicians should also be aware that severe SAE is associated with a high mortality. Although mortality is often secondary to multiorgan failure rather than neurological sequelae, long-term cognitive and psychological morbidities have been reported in sepsis survivors. Early treatment (which can include prompt identification and source control of the infection) and good supportive care might improve cognitive outcomes. Future work should aim to improve understanding of both acute and chronic SAE with a focus on therapeutic interventions and improving patient outcomes.

Pharmacologic Management of Delirium in the Intensive Care Unit

Delirium, often underdiagnosed in the intensive care unit, is a common complication of critical illness that contributes to significant morbidity and mortality. Clinicians should be aware of common risk factors and triggers and should work to mitigate these as much as possible to reduce the occurrence of delirium. This review first provides an overview of the epidemiology, pathophysiology, evaluation, and consequences of delirium in critically ill patients. Presented next is the current evidence for the pharmacologic management of delirium, focusing on prevention and treatment of delirium in the intensive care unit. It concludes by outlining some emerging treatments of delirium.

Cytokine profiles in intensive care unit delirium

Background

Neuroinflammation causing disruption of the blood-brain barrier and immune cell extravasation into the brain parenchyma may cause delirium; however, knowledge of the exact pathophysiologic mechanism remains incomplete. The purpose of our study was to determine whether cytokine profiles differ depending on whether delirium occurs in the setting of sepsis, coronavirus disease 2019 (COVID-19), or recent surgery.

Methods

This prospective observational cohort study involved 119 critically ill patients admitted to a multidisciplinary intensive care unit (ICU) during 2019 and 2020. Delirium was identified using the validated confusion assessment method for the ICU. Multiple delirium risk factors were collected daily including clinical characteristics, hospital course, lab values, vital signs, surgical exposure, drug exposure, and COVID-19 characteristics. Serums samples were collected within 12 hours of ICU admission and cytokine levels were measured.

Results:

The following proinflammatory cytokines were elevated in our delirium population: tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-18, C-C motif ligand (CCL) 2, CCL3, C-X-C motif chemokine ligand (CXCL)1, CXCL10, IL-8, IL-1 receptor antagonist, and IL-10. Analysis of relative cytokine levels in those patients that developed delirium in the setting of sepsis, COVID-19, and recent surgery showed elevations of CCL2, CXCL10, and TNF-α in both the sepsis and COVID-19 group in comparison to the postsurgical population. In the postsurgical group, granulocyte colony-stimulating factor was elevated and CXCL10 was decreased relative to the opposing groups.

Conclusions

We identify several cytokines and precipitating factors known to be associated with delirium. However, our study suggests that the cytokine profile associated with delirium is variable and contingent upon delirium precipitating factors.

The inter-relationship between delirium and dementia: the importance of delirium prevention

Delirium and dementia are two frequent causes of cognitive impairment among older adults and have a distinct, complex and interconnected relationship. Delirium is an acute confusional state characterized by inattention, cognitive dysfunction and an altered level of consciousness, whereas dementia is an insidious, chronic and progressive loss of a previously acquired cognitive ability. People with dementia have a higher risk of developing delirium than the general population, and the occurrence of delirium is an independent risk factor for subsequent development of dementia. Furthermore, delirium in individuals with dementia can accelerate the trajectory of the underlying cognitive decline. Delirium prevention strategies can reduce the incidence of delirium and associated adverse outcomes, including falls and functional decline. Therefore, delirium might represent a modifiable risk factor for dementia, and interventions that prevent or minimize delirium might also reduce or prevent long-term cognitive impairment. Additionally, understanding the pathophysiology of delirium and the connection between delirium and dementia might ultimately lead to additional treatments for both conditions. In this Review, we explore mechanisms that might be common to both delirium and dementia by reviewing evidence on shared biomarkers, and we discuss the importance of delirium recognition and prevention in people with dementia.

In this Review, Fong and Inouye explore mechanisms that might be common to both delirium and dementia. They present delirium as a possible modifiable risk factor for dementia and discuss the importance of delirium prevention strategies in reducing this risk.

Delirium and dementia are frequent causes of cognitive impairment among older adults and have a distinct, complex and interconnected relationship.

Delirium prevention strategies have been shown to reduce not only the incidence of delirium but also the incidence of adverse outcomes associated with delirium such as falls and functional decline.

Adverse outcomes associated with delirium, such as the onset of dementia symptoms in individuals with preclinical dementia, and/or the acceleration of cognitive decline in individuals with dementia might also be delayed by the implementation of delirium prevention strategies.

Evidence regarding the association of systemic inflammatory and neuroinflammatory biomarkers with delirium is variable, possibly as a result of co-occurring dementia pathology or disruption of the blood–brain barrier.

Alzheimer disease pathology, even prior to the onset of symptoms, might have an effect on delirium risk, with potential mechanisms including neuroinflammation and gene–protein interactions with the APOE ε4 allele.

Novel strategies, including proteomics, multi-omics, neuroimaging, transcranial magnetic stimulation and EEG, are beginning to reveal how changes in cerebral blood flow, spectral power and connectivity can be associated with delirium; further work is needed to expand these findings to patients with delirium superimposed upon dementia.

Breaking barriers in postoperative delirium

Systemic perturbations such as peripheral surgical trauma induce neurovascular, inflammatory, and cognitive changes. The blood-brain barrier is a key interface between the periphery and the central nervous system, and is critically involved in regulating neuroimmune interactions to maintain overall homeostasis. Mounting evidence suggests that blood-brain barrier dysfunction is a hallmark of ageing and multiple neurological conditions including Alzheimer's disease. We discuss a recent study published in the British Journal of Anaesthesia that describes blood-brain barrier changes and neuroinflammation in patients with postoperative delirium after non-intracranial surgery.

Central role of microglia in sepsis-associated encephalopathy: From mechanism to therapy

Sepsis-associated encephalopathy (SAE) is a cognitive impairment associated with sepsis that occurs in the absence of direct infection in the central nervous system or structural brain damage. Microglia are thought to be macrophages of the central nervous system, devouring bits of neuronal cells and dead cells in the brain. They are activated in various ways, and microglia-mediated neuroinflammation is characteristic of central nervous system diseases, including SAE. Here, we systematically described the pathogenesis of SAE and demonstrated that microglia are closely related to the occurrence and development of SAE. Furthermore, we comprehensively discussed the function and phenotype of microglia and summarized their activation mechanism and role in SAE pathogenesis. Finally, this review summarizes recent studies on treating cognitive impairment in SAE by blocking microglial activation and toxic factors produced after activation. We suggest that targeting microglial activation may be a putative treatment for SAE.

Sepsis-Associated Encephalopathy: A Mini-Review of Inflammation in the Brain and Body

Sepsis is defined as a life-threatening multi-organ dysfunction triggered by an uncontrolled host response to infectious disease. Systemic inflammation elicited by sepsis can cause acute cerebral dysfunction, characterized by delirium, coma, and cognitive dysfunction, known as septic encephalopathy. Recent evidence has reported the underlying mechanisms of sepsis. However, the reasons for the development of inflammation and degeneration in some brain regions and the persistence of neuroinflammation remain unclear. This mini-review describes the pathophysiology of region-specific inflammation after sepsis-associated encephalopathy (SAE), clinical features, and future prospects for SAE treatment. The hippocampus is highly susceptible to inflammation, and studies that perform treatments with antibodies to cytokine receptors, such as interleukin-1β, are in progress. Future development of clinically applicable therapies is expected.

Albumin/fibrinogen ratio, an independent risk factor for postoperative delirium after total joint arthroplasty

AIM

Postoperative delirium (POD) is a very common and serious complication after total joint arthroplasty (TJA), which is closely associated with many adverse consequences and a poor prognosis. This study aimed to establish the potential risk factors for POD.

METHODS

In total, 336 patients who underwent elective TJA under general anesthesia between 2018 and 2021 were included and deemed eligible for inclusion. POD was diagnosed based on the criteria by the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM V). The receiver operating characteristic curve was drawn to evaluate the predictive and cut-off values of continuous variables for POD. Potential risk factors for POD were evaluated by binary univariate and multivariate analysis with the "Enter" method.

RESULTS

According to the criteria by DSM V, 43 patients were categorized into the POD group, with an incidence of 12.8% (43 of 336). The receiver operating characteristic curve showed that albumin/fibrinogen ratio (AFR) was a good predictor for POD with an area under the curve of 0.754, cut-off value of 9.65, sensitivity of 57.00% and specificity of 83.72% (P <0.001). A low preoperative AFR level (<9.65) was determined as the only independent risk factor for POD by the univariate and multivariate logistic regression analyses (OR: 2.45, 95% CI: 2.01-2.94, P = 0.008).

CONCLUSIONS

Our results indicate that a low AFR is an independent risk factor for POD in elderly subjects after TJA. Geriatr Gerontol Int 2022; 22: 412-417.

Effects of Perioperative Fascia Iliaca Compartment Block on Postoperative Pain and Hip Function in Elderly Patients With Hip Fracture

Purpose

Pain management is a challenging issue in elderly patients with hip fracture. Despite the accepted clinical outcomes following hip surgery, pain and prolonged recovery time are the most difficult consequences associated with the rehabilitation process. The purpose of this study was to evaluate pain relief and functional improvement associated with the Fascia Iliaca Compartment Block (FICB) during the perioperative period of elderly patients with hip fracture.

Patients and methods

This study included 120 elderly patients with hip fracture, who were admitted to our institution between January 2019 and December 2020. The participants were subsequently randomly divided into the routine analgesia (RA) and fascia iliaca compartment block (FICB) groups. Inter-group differences were compared via VAS scores at rest and during movement, Harris hip scores (HHS), presence of complications, adverse events after surgery, and length of hospital stay.

Results

The FICB group VAS scores at rest at 6 hour, 1 and 3 days, and 1 week after surgery were significantly lower than the RA group (P < .05). Moreover, the FICB group VAS scores with movement were markedly lower at 6 hour, 1 and 3 days, as well as 1 and 2 weeks after surgery (P < .05). The HHS of the FICB and RA groups were (53.41±8.63) and (40.02±9.61), respectively, on the seventh day after surgery, and the difference was statistically significant (P < .05). The incidence of postoperative complications and adverse events in the FICB group were not statistically different from the RA group. The average hospital stay of the FICB group was 2.12 days shorter than the RA group, but the difference did not reach statistical significance (P = .13).

Conclusion

FICB provides superior analgesic effect both at rest and with movement, along with rapid short-term recovery of hip function following surgery in elderly patients with hip fracture, without increasing postoperative complications or adverse events.

Dexmedetomidine after Cardiac Surgery for Prevention of Delirium (EXACTUM) trial protocol: a multicentre randomised, double-blind, placebo-controlled trial

INTRODUCTION

Incidence of delirium after cardiac surgery remains high and delirium has a significant burden on short-term and long-term outcomes. Multiple causes can trigger delirium occurence, and it has been hypothesised that sleep disturbances can be one of them. Preserving the circadian rhythm with overnight infusion of low-dose dexmedetomidine has been shown to lower the occurrence of delirium in older patients after non-cardiac surgery. However, these results remain controversial. The aim of this study was to demonstrate the usefulness of sleep induction by overnight infusion of dexmedetomidine to prevent delirium after cardiac surgery.

METHODS AND ANALYSIS

Dexmedetomidine after Cardiac Surgery for Prevention of Delirium is an investigator-initiated, randomised, placebo-controlled, parallel, multicentre, double-blinded trial. Nine centres in France will participate in the study. Patients aged 65 years or older and undergoing cardiac surgery will be enrolled in the study. The intervention starts on day 0 (the day of surgery) until intensive care unit (ICU) discharge; the treatment is administered from 20:00 to 08:00 on the next day. Infusion rate is modified by the treating nurse or the clinician with an objective of Richmond Agitation and Sedation Scale score from -1 to +1. The primary outcome is delirium occurrence evaluated with confusion assessment method for the ICU two times per day during 7 days following surgery. Secondary outcomes include incidence of agitation related events, self-evaluated quality of sleep, cognitive evaluation 3 months after surgery and quality of life 3 months after surgery. The sample size is 348.

ETHICS AND DISSEMINATION

The study was approved for all participating centers by the French Central Ethics Committee (Comité de Protection des Personnes Ile de France VI, registration number 2018-000850-22). The results will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03477344.

Potential of nobiletin against Alzheimer's disease through inhibiting neuroinflammation

OBJECTIVE

This study aimed to explore the mechanism of Nobiletin attenuating Alzheimer's disease (AD) by inhibiting neuroinflammation.

METHODS

The expression of inflammatory cytokines and HMGB-1 in serum of AD patients were examined. Microglia (MGs) were treated with different doses of Nobiletin before LPS and Nigericin induction. Cell viability and apoptosis were determined by CCK-8 and TUNEL assays, respectively. APP/PS1 mice were gavaged with Nobiletin, and Morris water maze (MWM) was established to record swimming speed, escape latency, the number of platform crossings, and time spent in the platform quadrant. MGs activation in brain tissues was evaluated by immunofluorescence. The expression of pyroptosis-related proteins, inflammatory cytokines, and HMGB-1 was determined in the hippocampus and MGs.

RESULTS

The levels of inflammatory cytokines and HMGB-1 were high in serum of AD patients. Treatment with different concentrations of Nobiletin prominently enhanced cell viability and reduced apoptosis and the expression of inflammatory cytokine and pyroptosis-related proteins in LPS + Nigericin-induced MGs. Gavage of different doses of Nobiletin into APP/PS1 mice shortened the escape latency in mice, diminished MGs activation in brain tissues, and remarkably elevated the number of platform crossings and the time spent in the platform quadrant without obvious change in swimming speed, suggesting that Nobiletin improved the spatial learning and memory abilities in APP/PS1 mice. The expression of pyroptosis-related proteins, HMGB-1, and inflammatory cytokines was decreased dramatically by Nobiletin in the hippocampus of APP/PS1 mice.

CONCLUSIONS

Nobiletin can inhibit neuroinflammation by inhibiting HMGB-1, pyroptosis-related proteins, and inflammatory cytokines, thus mitigating AD.

Serum Biomarkers in Postoperative Delirium After Esophagectomy

BACKGROUND

Esophagectomy is associated with postoperative delirium, but its pathophysiology is not well defined. We conducted this study to measure the relationship among serum biomarkers of inflammation and neuronal injury and delirium incidence and severity in a cohort of esophagectomy patients.

METHODS

Blood samples were obtained from patients preoperatively and on postoperative days 1 and 3 and were analyzed for S100 calcium-binding protein B, C-reactive protein (CRP), interleukin (IL) 8 and IL-10, tumor necrosis factor-α, and insulin-like growth factor 1. Delirium was assessed twice daily using the Richmond Agitation Sedation Scale and Confusion Assessment Method for Intensive Care Unit. Delirium severity was assessed once daily with the Delirium Rating Scale-Revised-98.

RESULTS

Samples from 71 patients were included. Preoperative biomarker concentrations were not associated with postoperative delirium. Significant differences in change in concentrations from preoperatively to postoperative day 1 were seen in IL-8 (delirium, 38.6; interquartile range [IQR], 29.3-69.8; no delirium, 24.8; IQR, 16.0-41.7, P = .022), and IL-10 (delirium, 26.1; IQR, 13.9-36.7; no delirium, 12.4; IQR, 7.7-25.7; P = .025). Greater postoperative increase in S100 calcium-binding protein B (Spearman r = 0.289, P = .020) and lower levels of insulin-like growth factor 1 were correlated with greater delirium severity (Spearman r = -0.27, P = .040). Greater CRP change quartiles were associated with higher delirium incidence adjusting for severity of illness (odds ratio, 1.68; 95% confidence interval, 1.03-2.75; P = .037) or comorbidities (odds ratio, 1.70; 95% confidence interval, 1.05-2.76, P = .030).

CONCLUSIONS

Differences in change in serum CRP, IL-8, and IL-10 concentrations were associated with postoperative delirium, suggesting biomarker measurement early in the postoperative course is associated with delirium.

Cytokines in the Brain and Neuroinflammation: We Didn’t Starve the Fire!

In spite of the brain-protecting tissues of the skull, meninges, and blood-brain barrier, some forms of injury to or infection of the CNS can give rise to cerebral cytokine production and action and result in drastic changes in brain function and behavior. Interestingly, peripheral infection-induced systemic inflammation can also be accompanied by increased cerebral cytokine production. Furthermore, it has been recently proposed that some forms of psychological stress may have similar CNS effects. Different conditions of cerebral cytokine production and action will be reviewed here against the background of neuroinflammation. Within this context, it is important to both deepen our understanding along already taken paths as well as to explore new ways in which neural functioning can be modified by cytokines. This, in turn, should enable us to put forward different modes of cerebral cytokine production and action in relation to distinct forms of neuroinflammation.

Animal-Assisted Interventions in Intensive Care Delirium: A Literature Review

Critical illness has lasting consequences on the mind and the body. Acute sequelae include a decline in cognitive function known as delirium. Increased interest in improving outcomes for intensive care unit survivors without a high incidence of delirium has initiated a focus on an array of nonpharmacologic interventions in many countries. One such intervention is animalassisted intervention. As the role of animals in human healing is being recognized by clinicians, need is increasing for formal and professionally directed therapies. This review ascertains the effect of interaction with animals on critically ill patients. Emerging evidence indicates that animal-assisted intervention improves the efficacy of critical care regarding primary symptoms and secondary factors of delirium.

A geroscience motivated approach to treat Alzheimer's disease: Senolytics move to clinical trials

The pathogenic processes driving Alzheimer's disease (AD) are complex. An incomplete understanding of underlying disease mechanisms has presented insurmountable obstacles for developing effective disease-modifying therapies. Advanced chronological age is the greatest risk factor for developing AD. Intervening on biological aging may alter disease progression and represents a novel, complementary approach to current strategies. Toward this end, cellular senescence has emerged as a promising target. This complex stress response harbors damaged cells in a cell cycle arrested, apoptosis-resistant cell state. Senescent cells accumulate with age where they notoriously secrete molecules that contribute to chronic tissue dysfunction and disease. Thus, benefits of cell survival in a senescent fate are countered by their toxic secretome. The removal of senescent cells improves brain structure and function in rodent models at risk of developing AD, and in those with advanced Aβ and tau pathology. The present review describes the path to translating this promising treatment strategy to AD clinical trials. We review evidence for senescent cell accumulation in the human brain, considerations and strategies for senescence-targeting trials specific to AD, approaches to detect senescent brain cells in biofluids, and summarize the goals of the first senolytic trials for the treatment of AD (NCT04063124 and NCT04685590). This article is part of the Special Issue - Senolytics - Edited by Joao Passos and Diana Jurk.

Treatment of Delirium During Critical Illness

Delirium, an acute disturbance in mental status due to another medical condition, is common and morbid in the intensive care unit. Despite its clear association with multiple common risk factors and important outcomes, including mortality and long-term cognitive impairment, both the ultimate causes of and ideal treatments for delirium remain unclear. Studies suggest that neuroinflammation, hypoxia, alterations in energy metabolism, and imbalances in multiple neurotransmitter pathways contribute to delirium, but commonly used treatments (e.g., antipsychotic medications) target only one or a few of these potential mechanisms and are not supported by evidence of efficacy. At this time, the optimal treatment for delirium during critical illness remains avoidance of risk factors, though ongoing trials may expand on the promise shown by agents such as melatonin and dexmedetomidine. Expected final online publication date for the Annual Review of Medicine, Volume 73 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

COVID-19-related neuropathology and microglial activation in elderly with and without dementia

The actual role of SARS-CoV-2 in brain damage remains controversial due to lack of matched controls. We aim to highlight to what extent is neuropathology determined by SARS-CoV-2 or by pre-existing conditions. Findings of 9 Coronavirus disease 2019 (COVID-19) cases and 6 matched non-COVID controls (mean age 79 y/o) were compared. Brains were analyzed through immunohistochemistry to detect SARS-CoV-2, lymphocytes, astrocytes, endothelium, and microglia. A semi-quantitative scoring was applied to grade microglial activation. Thal-Braak stages and the presence of small vessel disease were determined in all cases. COVID-19 cases had a relatively short clinical course (0-32 days; mean: 10 days), and did not undergo mechanical ventilation. Five patients with neurocognitive disorder had delirium. All COVID-19 cases showed non-SARS-CoV-2-specific changes including hypoxic-agonal alterations, and a variable degree of neurodegeneration and/or pre-existent SVD. The neuroinflammatory picture was dominated by ameboid CD68 positive microglia, while only scant lymphocytic presence and very few traces of SARS-CoV-2 were detected. Microglial activation in the brainstem was significantly greater in COVID-19 cases (p = 0.046). Instead, microglial hyperactivation in the frontal cortex and hippocampus was clearly associated to AD pathology (p = 0.001), regardless of the SARS-CoV-2 infection. In COVID-19 cases complicated by delirium (all with neurocognitive disorders), there was a significant enhancement of microglia in the hippocampus (p = 0.048). Although higher in cases with both Alzheimer's pathology and COVID-19, cortical neuroinflammation is not related to COVID-19 per se but mostly to pre-existing neurodegeneration. COVID-19 brains seem to manifest a boosting of innate immunity with microglial reinforcement, and adaptive immunity suppression with low number of brain lymphocytes probably related to systemic lymphopenia. Thus, no neuropathological evidence of SARS-CoV-2-specific encephalitis is detectable. The microglial hyperactivation in the brainstem, and in the hippocampus of COVID-19 patients with delirium, appears as a specific topographical phenomenon, and probably represents the neuropathological basis of the "COVID-19 encephalopathic syndrome" in the elderly.

Preoperative inflammatory mediators and postoperative delirium: systematic review and meta-analysis

BACKGROUND

Postoperative delirium has eluded attempts to define its complex aetiology and describe specific risk factors. The role of neuroinflammation as a risk factor, determined by measuring blood levels of preoperative 'innate' inflammatory mediator levels, has been investigated. However, results have been conflicting. We conducted a systematic review and meta-analysis of the evidence on associations between preoperative blood levels of inflammatory mediators and postoperative delirium in the older person. Influence of type of surgery was also assessed.

METHODS

Original, low risk of bias studies, published in peer-reviewed journals, which fulfilled the eligibility criteria were included. Seventeen articles fulfilled study criteria. Data extraction, synthesis, and risk of bias analysis were guided by Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) and quality in prognostic studies guidelines. Meta-analyses used a random-effects model. Inflammatory mediators included C-reactive protein, interleukin-6, -8, and -10, tumour necrosis factor-α, insulin-like growth factor-1, cortisol, and neopterin. Surgical groups were cardiac, noncardiac, and hip fracture.

RESULTS

Higher preoperative interleukin-6 was associated with postoperative delirium with a standardised mean difference (95% confidence interval) of 0.33 (0.11-0.56) and P=0.003. Higher neopterin was also associated with postoperative delirium.

CONCLUSIONS

The association of preoperative blood levels of inflammatory mediators with postoperative delirium may be influenced by the type of surgery and the specific mediator. The potential modulating effect of type of surgery, intrinsic brain vulnerability, and the complex interactions between inflammatory mediators and binding proteins will need to be considered in future studies.

CLINICAL TRIAL REGISTRATION

CRD42019159471 (PROSPERO).

Development and Validation of a Postoperative Delirium Prediction Model for Elderly Orthopedic Patients in the Intensive Care Unit

We developed a prediction model for delirium in elderly patients in the intensive care unit who underwent orthopedic surgery and then temporally validated its predictive power in the same hospital. In the development stage, we designed a prospective cohort study, and 319 consecutive patients aged over 65 years from January 2018 to December 2019 were screened. Demographic characteristics and clinical variables were evaluated, and a final prediction model was developed using the multivariate logistic regression analysis. In the validation stage, 108 patients were included for temporal validation between January 2020 and June 2020. The effectiveness of the model was evaluated through discrimination and calibration. As a result, the prediction model contains seven risk factors (age, anesthesia method, score of mini-mental state examination, hypoxia, major hemorrhage, level of interleukin-6, and company of family members), which had an area under the receiver operating characteristics curve of 0.82 (95% confidence interval 0.76-0.88) and was stable after bootstrapping. The temporal validation resulted in an area under the curve of 0.80 (95% confidence interval 0.67-0.93). Our prediction model had excellent discrimination power in predicting postoperative delirium in elderly patients and could assist intensive care physicians with early prevention.

Why is delirium more frequent in the elderly?

An aging-related reduction in the brain's functional reserve may explain why delirium is more frequent in the elderly than in younger people insofar as the reserve becomes inadequate to cover the metabolic requirements that are critically increased by stressors. The aim of this paper is to review the normal aging-related changes that theoretically compromise complex mental activities, neuronal and synaptic densities, and the neurocomputational flexibility of the functional reserve. A pivotal factor is diminished connectivity, which is substantially due to the loss of synapses and should specifically affect association systems and cholinergic fibres in delirious patients. However, micro-angiopathy with impaired blood flow autoregulation, increased blood/brain barrier permeability, changes in cerebrospinal fluid dynamics, weakened mitochondrial performance, and a pro-inflammatory involution of the immune system may also jointly affect neurons and their synaptic assets, and even cause the progression of delirium to dementia regardless of the presence of co-existing plaques, tangles, or other pathological markers. On the other hand, the developmental growth in functional reserve during childhood and adolescence makes the brain increasingly resistant to delirium, and residual reserve can allow the elderly to recover. These data support the view that functional reserve is the variable that confronts stressors and governs the risk and intensity of and recovery from delirium. Although people of any age are at risk of delirium, the elderly are at greater risk because aging and age-dependent structural changes inevitably affect the brain's functional reserve.

Neuroinflammation in Sepsis: Molecular Pathways of Microglia Activation

Frequently underestimated, encephalopathy or delirium are common neurological manifestations associated with sepsis. Brain dysfunction occurs in up to 80% of cases and is directly associated with increased mortality and long-term neurocognitive consequences. Although the central nervous system (CNS) has been classically viewed as an immune-privileged system, neuroinflammation is emerging as a central mechanism of brain dysfunction in sepsis. Microglial cells are major players in this setting. Here, we aimed to discuss the current knowledge on how the brain is affected by peripheral immune activation in sepsis and the role of microglia in these processes. This review focused on the molecular pathways of microglial activity in sepsis, its regulatory mechanisms, and their interaction with other CNS cells, especially with neuronal cells and circuits.

Systematic review of cognitive impairment and brain insult after mechanical ventilation

We conducted a systematic review following the PRISMA protocol primarily to identify publications that assessed any links between mechanical ventilation (MV) and either cognitive impairment or brain insult, independent of underlying medical conditions. Secondary objectives were to identify possible gaps in the literature that can be used to inform future studies and move toward a better understanding of this complex problem. The preclinical literature suggests that MV is associated with neuroinflammation, cognitive impairment, and brain insult, reporting higher neuroinflammatory markers, greater evidence of brain injury markers, and lower cognitive scores in subjects that were ventilated longer, compared to those ventilated less, and to never-ventilated subjects. The clinical literature suggests an association between MV and delirium, and that delirium in mechanically ventilated patients may be associated with greater likelihood of long-term cognitive impairment; our systematic review found no clinical study that demonstrated a causal link between MV, cognitive dysfunction, and brain insult. More studies should be designed to investigate ventilation-induced brain injury pathways as well as any causative linkage between MV, cognitive impairment, and brain insult.

Brain injury after 50 h of lung-protective mechanical ventilation in a preclinical model

Mechanical ventilation is the cornerstone of the Intensive Care Unit. However, it has been associated with many negative consequences. Recently, ventilator-induced brain injury has been reported in rodents under injurious ventilation settings. Our group wanted to explore the extent of brain injury after 50 h of mechanical ventilation, sedation and physical immobility, quantifying hippocampal apoptosis and inflammation, in a normal-lung porcine study. After 50 h of lung-protective mechanical ventilation, sedation and immobility, greater levels of hippocampal apoptosis and neuroinflammation were clearly observed in the mechanically ventilated group, in comparison to a never-ventilated group. Markers in the serum for astrocyte damage and neuronal damage were also higher in the mechanically ventilated group. Therefore, our study demonstrated that considerable hippocampal insult can be observed after 50 h of lung-protective mechanical ventilation, sedation and physical immobility.

Delirium after Deep Brain Stimulation in Parkinson's Disease

Deep brain stimulation is a primary treatment method that improves motor and motor complications in patients with advanced Parkinson's disease. Delirium is a common and serious complication following deep brain stimulation. However, the clinical attention toward this complication remains insufficient. Advanced age, cognitive decline, and the severity of the disease may all be risk factors for delirium. The presence of delirium may also affect cognitive function and disease prognosis. Neurotransmitters such as acetylcholine and dopamine may be involved in the occurrence of delirium. Furthermore, inflammation, the effects of microlesioning of local nuclei, and brain atrophy may also play roles in the onset of delirium. Nonpharmacological therapy appears to be the primary treatment for postoperative delirium in Parkinson's disease. The current article reviews the pathogenesis, epidemiology, prognosis, and treatment of delirium following deep brain stimulation in Parkinson's disease to help clinicians better understand this common complication and to prevent, identify, and treat it as soon as possible, as well as to provide more accurate treatment for patients.

Targeted metabolomics analysis of postoperative delirium

Postoperative delirium is the most common complication among older adults undergoing major surgery. The pathophysiology of delirium is poorly understood, and no blood-based, predictive markers are available. We characterized the plasma metabolome of 52 delirium cases and 52 matched controls from the Successful Aging after Elective Surgery (SAGES) cohort (N = 560) of patients ≥ 70 years old without dementia undergoing scheduled major non-cardiac surgery. We applied targeted mass spectrometry with internal standards and pooled controls using a nested matched case-control study preoperatively (PREOP) and on postoperative day 2 (POD2) to identify potential delirium risk and disease markers. Univariate analyses identified 37 PREOP and 53 POD2 metabolites associated with delirium and multivariate analyses achieved significant separation between the two groups with an 11-metabolite prediction model at PREOP (AUC = 83.80%). Systems biology analysis using the metabolites with differential concentrations rendered "valine, leucine, and isoleucine biosynthesis" at PREOP and "citrate cycle" at POD2 as the most significantly enriched pathways (false discovery rate < 0.05). Perturbations in energy metabolism and amino acid synthesis pathways may be associated with postoperative delirium and suggest potential mechanisms for delirium pathogenesis. Our results could lead to the development of a metabolomic delirium predictor.

Delusion and Delirium in Neurodegenerative Disorders: An Overlooked Relationship?

Delusions are part of the neuropsychiatric symptoms that patients suffering from neurodegenerative conditions frequently develop at some point of the disease course and are associated with an increased risk of cognitive and functional decline. Delirium is a syndrome characterized by acute onset of deficits in attention, awareness, and cognition that fluctuate in severity over a short time period. Delusions and delirium are frequently observed in the context of neurodegeneration, and their presence can easily mislead clinicians toward a misdiagnosis of psychiatric disorder further delaying the proper treatment. Risk factors for developing delusion and delirium in neurodegenerative conditions have been investigated separately while the possible interplay between these two conditions has not been explored so far. With this study, we aim to achieve a more comprehensive picture of the relationship between delusions and delirium in neurodegeneration by analyzing prevalence and subtypes of delusions in different neurodegenerative disorders; providing an overview of clinical tools to assess delusions in neurodegenerative patients and how delusions are covered by delirium assessment tools and discussing the possible common pathophysiology mechanisms between delusion and delirium in neurodegenerative patients. A more extensive characterization of the relationship between delusions and delirium may help to understand whether delusions may constitute a risk factor for delirium and may ameliorate the management of both conditions in patients with neurodegenerative disorders.

Delirium

Delirium, a syndrome characterized by an acute change in attention, awareness and cognition, is caused by a medical condition that cannot be better explained by a pre-existing neurocognitive disorder. Multiple predisposing factors (for example, pre-existing cognitive impairment) and precipitating factors (for example, urinary tract infection) for delirium have been described, with most patients having both types. Because multiple factors are implicated in the aetiology of delirium, there are likely several neurobiological processes that contribute to delirium pathogenesis, including neuroinflammation, brain vascular dysfunction, altered brain metabolism, neurotransmitter imbalance and impaired neuronal network connectivity. The Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) is the most commonly used diagnostic system upon which a reference standard diagnosis is made, although many other delirium screening tools have been developed given the impracticality of using the DSM-5 in many settings. Pharmacological treatments for delirium (such as antipsychotic drugs) are not effective, reflecting substantial gaps in our understanding of its pathophysiology. Currently, the best management strategies are multidomain interventions that focus on treating precipitating conditions, medication review, managing distress, mitigating complications and maintaining engagement to environmental issues. The effective implementation of delirium detection, treatment and prevention strategies remains a major challenge for health-care organizations globally.