Prevention of Postoperative Cognitive Dysfunction by Minocycline in Elderly Patients after Total Knee Arthroplasty: A Randomized, Double-blind, Placebo-controlled Clinical Trial

Comparative effectiveness of non-pharmacological therapies for postoperative cognitive dysfunction: Protocol for a systematic review and network meta-analysis

INTRODUCTION

Postoperative cognitive dysfunction (POCD) is a common complication following surgery. Electroacupuncture (EA), manual acupuncture (MA), transcutaneous electrical acupoint stimulation (TEAS), and cognitive training (CT) can effectively maintain or improve the postoperative cognitive function of patients. However, it remains unclear which therapy is the most effective. Therefore, this network meta-analysis aims to compare and rank the efficacy of these non-pharmacological therapies for POCD to identify the optimal therapy.

METHODS AND ANALYSIS

A systematic search will be conducted across seven databases (PubMed, Cochrane Library, EMBASE, Web of Science, CINAHL, AMED, and PsycINFO) for articles published between January 2000 and November 2023. Two reviewers will independently conduct study selection and data extraction. The primary outcome will be the changes in the overall cognitive function before and after the intervention. The secondary outcome will be the incidence of POCD. The risk of bias will be assessed using the revised Risk of Bias Assessment Tool. Pairwise and Bayesian network meta-analyses will be performed using RevMan, STATA, and Aggregate Data Drug Information System statistical software. Additionally, the quality of evidence will be assessed using the Grading of Recommendations Assessment, Development, and Evaluation guidelines. Ethics and dissemination: The results will be disseminated to peer-reviewed journals or conferences.

TRIAL REGISTRATION

PROSPERO registration number: CRD42023454028.

Role of glia in delirium: proposed mechanisms and translational implications

Delirium is a common acute onset neurological syndrome characterised by transient fluctuations in cognition. It affects over 20% of medical inpatients and 50% of those critically ill. Delirium is associated with morbidity and mortality, causes distress to patients and carers, and has significant socioeconomic costs in ageing populations. Despite its clinical significance, the pathophysiology of delirium is understudied, and many underlying cellular mechanisms remain unknown. There are currently no effective pharmacological treatments which directly target underlying disease processes. Although many studies focus on neuronal dysfunction in delirium, glial cells, primarily astrocytes, microglia, and oligodendrocytes, and their associated systems, are increasingly implicated in delirium pathophysiology. In this review, we discuss current evidence which implicates glial cells in delirium, including biomarker studies, post-mortem tissue analyses and pre-clinical models. In particular, we focus on how astrocyte pathology, including aberrant brain energy metabolism and glymphatic dysfunction, reactive microglia, blood-brain barrier impairment, and white matter changes may contribute to the pathogenesis of delirium. We also outline limitations in this body of work and the unique challenges faced in identifying causative mechanisms in delirium. Finally, we discuss how established neuroimaging and single-cell techniques may provide further mechanistic insight at pre-clinical and clinical levels.

Chronic Pain-Related Cognitive Deficits: Preclinical Insights into Molecular, Cellular, and Circuit Mechanisms

Cognitive impairment is a common comorbidity of chronic pain, significantly disrupting patients' quality of life. Despite this comorbidity being clinically recognized, the underlying neuropathological mechanisms remain unclear. Recent preclinical studies have focused on the fundamental mechanisms underlying the coexistence of chronic pain and cognitive decline. Pain chronification is accompanied by structural and functional changes in the neural substrate of cognition. Based on the developments in electrophysiology and optogenetics/chemogenetics, we summarized the relevant neural circuits involved in pain-induced cognitive impairment, as well as changes in connectivity and function in brain regions. We then present the cellular and molecular alternations related to pain-induced cognitive impairment in preclinical studies, mainly including modifications in neuronal excitability and structure, synaptic plasticity, glial cells and cytokines, neurotransmitters and other neurochemicals, and the gut-brain axis. Finally, we also discussed the potential treatment strategies and future research directions.

Current perspectives on postoperative cognitive dysfunction in geriatric patients: insights from clinical practice

Postoperative cognitive dysfunction (POCD) is a common and serious postoperative complication in elderly patients, affecting cognitive function and quality of life. Its pathophysiology is complex, involving age-related cognitive decline, surgical and anesthetic factors, systemic and neuroinflammation, as well as genetic and environmental contributors. Comprehensive preoperative assessment and optimization, the selection of appropriate anesthetic agents, minimally invasive surgical techniques, and early postoperative rehabilitation and cognitive training are effective strategies to reduce the incidence of POCD. Recent research suggests that anti-inflammatory drugs and neuroprotective agents may be promising in preventing POCD. Additionally, non-pharmacological interventions, including cognitive and physical training, have shown positive effects. Future research directions should include large-scale clinical trials and mechanistic studies to further understand and manage POCD, along with integrating new findings into clinical practice. Continuous education and training for healthcare professionals are essential to ensure the effective application of the latest research findings in patient care. Through multidisciplinary collaboration and ongoing improvements, these efforts can significantly enhance the cognitive function and quality of life of elderly surgical patients.

Prophylactic Minocycline for Delirium in Critically Ill Patients: A Randomized Controlled Trial

BACKGROUND

Delirium is a potentially severe form of acute encephalopathy. Minocycline has neuroprotective effects in animal models of neurologic diseases; however, data from human studies remain scarce.

RESEARCH QUESTION

Does the neuroprotective effect of minocycline prevent delirium occurrence in critically ill patients?

STUDY DESIGN AND METHODS

This study was a randomized, placebo-controlled, double-anonymized trial conducted in four ICUs. Patients aged 18 years or older were eligible and randomized to receive minocycline (100 mg, twice daily) or placebo. The primary outcome was delirium incidence within 28 days or before ICU discharge. Secondary outcomes included days in delirium during ICU stay, delirium/coma-free days, length of mechanical ventilation, ICU length of stay, ICU mortality, and hospital mortality. The kinetics of various inflammatory (IL-1β, IL-6, IL-10, and C-reactive protein) and brain-related biomarkers (brain-derived neurotrophic factor and S100B) were used as exploratory outcomes.

RESULTS

A total of 160 patients were randomized, but one patient in the placebo group died before treatment; thus the data from 159 patients were analyzed (minocycline, n = 84; placebo, n = 75). After the COVID-19 pandemic it was decided to stop patient inclusion early. There was a small but significant decrease in delirium incidence: 17 patients (20%) in the minocycline arm compared with 26 patients (35%) in the placebo arm (P = .043). No other delirium-related outcomes were modified by minocycline treatment. Unexpectedly, there was a significant decrease in hospital mortality (39% vs. 23%; P = .029). Among all analyzed biomarkers, only plasma levels of C-reactive protein decreased significantly after minocycline treatment (F = 0.75, P = .78, within time; F = 4.09, P = .045, group × time).

INTERPRETATION

Our findings in this rather small study signal a possible positive effect of minocycline on delirium incidence. Further studies are needed to confirm the benefits of this drug as a preventive measure in critically ill patients.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov; No.: NCT04219735; URL: www.

CLINICALTRIALS

gov.

Itaconate alleviates anesthesia/surgery-induced cognitive impairment by activating a Nrf2-dependent anti-neuroinflammation and neurogenesis via gut-brain axis

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a common neurological complication of anesthesia and surgery in aging individuals. Neuroinflammation has been identified as a hallmark of POCD. However, safe and effective treatments of POCD are still lacking. Itaconate is an immunoregulatory metabolite derived from the tricarboxylic acid cycle that exerts anti-inflammatory effects by activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. In this study, we investigated the effects and underlying mechanism of 4-octyl itaconate (OI), a cell-permeable itaconate derivative, on POCD in aged mice.

METHODS

A POCD animal model was established by performing aseptic laparotomy in 18-month-old male C57BL/6 mice under isoflurane anesthesia while maintaining spontaneous ventilation. OI was intraperitoneally injected into the mice after surgery. Primary microglia and neurons were isolated and treated to lipopolysaccharide (LPS), isoflurane, and OI. Cognitive function, neuroinflammatory responses, as well as levels of gut microbiota and their metabolites were evaluated. To determine the mechanisms underlying the therapeutic effects of OI in POCD, ML385, an antagonist of Nrf2, was administered intraperitoneally. Cognitive function, neuroinflammatory responses, endogenous neurogenesis, neuronal apoptosis, and Nrf2/extracellular signal-related kinases (ERK) signaling pathway were evaluated.

RESULTS

Our findings revealed that OI treatment significantly alleviated anesthesia/surgery-induced cognitive impairment, concomitant with reduced levels of the neuroinflammatory cytokines IL-1β and IL-6, as well as suppressed activation of microglia and astrocytes in the hippocampus. Similarly, OI treatment inhibited the expression of IL-1β and IL-6 in LPS and isoflurane-induced primary microglia in vitro. Intraperitoneal administration of OI led to alterations in the gut microbiota and promoted the production of microbiota-derived metabolites associated with neurogenesis. We further confirmed that OI promoted endogenous neurogenesis and inhibited neuronal apoptosis in the hippocampal dentate gyrus of aged mice. Mechanistically, we observed a decrease in Nrf2 expression in hippocampal neurons both in vitro and in vivo, which was reversed by OI treatment. We found that Nrf2 was required for OI treatment to inhibit neuroinflammation in POCD. The enhanced POCD recovery and promotion of neurogenesis triggered by OI exposure were, at least partially, mediated by the activation of the Nrf2/ERK signaling pathway.

CONCLUSIONS

Our findings demonstrate that OI can attenuate anesthesia/surgery-induced cognitive impairment by stabilizing the gut microbiota and activating Nrf2 signaling to restrict neuroinflammation and promote neurogenesis. Boosting endogenous itaconate or supplementation with exogenous itaconate derivatives may represent novel strategies for the treatment of POCD.

Association Between Preoperative Sleep Disturbance and Postoperative Delirium in Elderly: A Retrospective Cohort Study

Purpose

Postoperative sleep disturbance, characterized by diminished postoperative sleep quality, is a risk factor for postoperative delirium (POD); however, the association between pre-existing sleep disturbance and POD remains unclear. This study aimed to evaluate the association between preoperative sleep disturbance and POD in elderly patients after non-cardiac surgery.

Patients and methods

This retrospective cohort study was conducted at a single center and enrolled 489 elderly patients who underwent surgery between May 1, 2020, and March 31, 2021. Patients were divided into the sleep disorder (SD) and non-sleep disorder (NSD) groups according to the occurrence of one or more symptoms of insomnia within one month or sleep- Numerical Rating Scale (NRS)≥6 before surgery. The primary outcome was the incidence of POD. Propensity score matching analysis was performed between the two groups. Multiple logistic regression analysis was performed to identify the risk factors for POD.

Results

In both the unmatched cohort (16.0% vs 6.7%, P=0.003) and the matched cohort (17.0% vs 6.2%, P=0.023), the incidence of POD was higher in the SD group than in the NSD group. In addition, the postoperative sleep quality and the VAS score at postoperative 24 h were significantly lower in the SD group than in the NSD group. Multivariate logistic regression analysis indicated that age (Odds Ratio, 1.13 [95% CI: 1.04-1.23], P=0.003) and preoperative sleep disturbance (Odds Ratio, 3.03 [95% CI: 1.09-9.52], P=0.034) were independent risk factors for the development of POD.

Conclusion

The incidence of POD was higher in patients with pre-existing sleep disturbance than those without it. Whether improving sleep quality for preoperative sleep disturbance may help prevent POD remains to be determined.

IL-1β, the first piece to the puzzle of sepsis-related cognitive impairment?

Sepsis is a leading cause of death resulting from an uncontrolled inflammatory response to an infectious agent. Multiple organ injuries, including brain injuries, are common in sepsis. The underlying mechanism of sepsis-associated encephalopathy (SAE), which is associated with neuroinflammation, is not yet fully understood. Recent studies suggest that the release of interleukin-1β (IL-1β) following activation of microglial cells plays a crucial role in the development of long-lasting neuroinflammation after the initial sepsis episode. This review provides a comprehensive analysis of the recent literature on the molecular signaling pathways involved in microglial cell activation and interleukin-1β release. It also explores the physiological and pathophysiological role of IL-1β in cognitive function, with a particular focus on its contribution to long-lasting neuroinflammation after sepsis. The findings from this review may assist healthcare providers in developing novel interventions against SAE.

Delirium after Cardiac Surgery-A Narrative Review

Postoperative delirium (POD) after cardiac surgery is a well-known phenomenon which carries a higher risk of morbidity and mortality. Multiple patient-specific risk factors and pathophysiologic mechanisms have been identified and therapies have been proposed to mitigate risk of delirium development postoperatively. Notably, cardiac surgery frequently involves the use of an intraoperative cardiopulmonary bypass (CPB), which may contribute to the mechanisms responsible for POD. Despite our greater understanding of these causative factors, a substantial reduction in the incidence of POD remains high among cardiac surgical patients. Multiple therapeutic interventions have been implemented intraoperatively and postoperatively, many with conflicting results. This review article will highlight the incidence and impact of POD in cardiac surgical patients. It will describe some of the primary risk factors associated with POD, as well as anesthetic management and therapies postoperatively that may help to reduce delirium.

Minocycline Attenuates Sevoflurane-Induced Postoperative Cognitive Dysfunction in Aged Mice by Suppressing Hippocampal Apoptosis and the Notch Signaling Pathway-Mediated Neuroinflammation

Postoperative cognitive dysfunction (POCD), an important postoperative neurological complication, is very common and has an elevated incidence in elderly patients. Sevoflurane, an inhaled anesthetic, has been demonstrated to be associated with POCD in both clinical and animal studies. However, how to prevent POCD remains unclear. Minocycline, a commonly used antibiotic can cross the blood-brain barrier and exert an inhibitory effect on inflammation in the central nervous system. The present work aimed to examine the protective effect and mechanism of minocycline on sevoflurane-induced POCD in aged mice. We found that 3% sevoflurane administered 2 h a day for 3 consecutive days led to cognitive impairment in aged animals. Further investigation revealed that sevoflurane impaired synapse plasticity by causing apoptosis and neuroinflammation and thus induced cognitive dysfunction. However, minocycline pretreatment (50 mg/kg, i.p, 1 h prior to sevoflurane exposure) significantly attenuated learning and memory impairments associated with sevoflurane in aged animals by suppressing apoptosis and neuroinflammation. Moreover, a mechanistic analysis showed that minocycline suppressed sevoflurane-triggered neuroinflammation by inhibiting Notch signaling. Similar results were also obtained in vitro. Collectively, these findings suggested minocycline may be an effective drug for the prevention of sevoflurane-induced POCD in elderly patients.

Caffeic Acid Phenethyl Ester Suppresses Oxidative Stress and Regulates M1/M2 Microglia Polarization via Sirt6/Nrf2 Pathway to Mitigate Cognitive Impairment in Aged Mice following Anesthesia and Surgery

Postoperative cognitive dysfunction (POCD) is a severe neurological complication after anesthesia and surgery. However, there is still a lack of effective clinical pharmacotherapy due to its unclear pathogenesis. Caffeic acid phenethyl ester (CAPE), which is obtained from honeybee propolis and medicinal plants, shows powerful antioxidant, anti-inflammatory, and immunomodulating properties. In this study, we aimed to evaluate whether CAPE mitigated cognitive impairment following anesthesia and surgery and its potential underlying mechanisms in aged mice. Here, isoflurane anesthesia and tibial fracture surgery were used as the POCD model, and H2O2-induced BV2 cells were established as the microglial oxidative stress model. We revealed that CAPE pretreatment suppressed oxidative stress and promoted the switch of microglia from the M1 to the M2 type in the hippocampus, thereby ameliorating cognitive impairment caused by anesthesia and surgery. Further investigation indicated that CAPE pretreatment upregulated hippocampal Sirt6/Nrf2 expression after anesthesia and surgery. Moreover, mechanistic studies in BV2 cells demonstrated that the potent effects of CAPE pretreatment on reducing ROS generation and promoting protective polarization were attenuated by a specific Sirt6 inhibitor, OSS_128167. In summary, our findings opened a promising avenue for POCD prevention through CAPE pretreatment that enhanced the Sirt6/Nrf2 pathway to suppress oxidative stress as well as favor microglia protective polarization.