Effect of beta-blocker therapy on the risk of infections and death after acute stroke--a historical cohort study

The Association between Statins Intake and Risk of Post Stroke Pneumonia: A Systematic Review and Meta-Analysis

AIM

This research aimed to examine the relationship between the intake of statins and the risk of post-stroke pneumonia in a systematic review and meta-analysis study.

METHODS

An extensive search of published articles on March 21st, 2023, was done in several databases, like Web of Science (ISI), PubMed, Cochrane Library, Embase, Scopus, and Google Scholar. The Newcastle Ottawa Scale (NOS) checklist was employed to evaluate the quality of observational studies. Statistical tests (Chi-square test and I2) and graphical techniques (Forest plot) were used to determine whether heterogeneity existed in the meta-analysis studies. Funnel plots and Begg and Egger's tests were used to assess the publication bias.

RESULTS

Seven studies (5 cohort and 2 case-control studies) were retrieved to examine the association between statins and post-stroke pneumonia. The sample size of the studies compiled in the meta- analysis was obtained to be 68,966 participants. Meta-analysis demonstrated that the overall odds of post-stroke pneumonia in the statin group was equal to 0.87 (95% CI: 0.67 - 1.13; p-value 0.458). Subgroup analysis indicated that the odds of post-stroke pneumonia in the statin group was equal to 0.93 (95% CI: 0.73-1.18; p-value = 0.558) in the cohort studies, and equal to 0.92 (95% CI: 0.37-2.26; p-value = 0.857) in the case-control studies. The examination of the association between the intake of statins and post-stroke pneumonia showed no evidence of publication bias (Begg's test, p-value = 0.368; Eggers test, p-value = 0.282).

CONCLUSION

In this study, no relationship has been observed between receiving statins and the risk of post-stroke pneumonia.

A study of the correlation between stroke and gut microbiota over the last 20years: a bibliometric analysis

Purpose

This study intends to uncover a more thorough knowledge structure, research hotspots, and future trends in the field by presenting an overview of the relationship between stroke and gut microbiota in the past two decades.

Method

Studies on stroke and gut microbiota correlations published between 1st January 2002 and 31st December 2021 were retrieved from the Web of Science Core Collection and then visualized and scientometrically analyzed using CiteSpace V.

Results

A total of 660 papers were included in the study, among which the United States, the United Kingdom, and Germany were the leading research centers. Cleveland Clinic, Southern Medical University, and Chinese Academy of Science were the top three institutions. The NATURE was the most frequently co-cited journal. STANLEY L HAZEN was the most published author, and Tang WHW was the most cited one. The co-occurrence analysis revealed eight clusters (i.e., brain-gut microbiota axis, fecal microbiome transplantation, gut microbiota, hypertension, TMAO, ischemic stroke, neuroinflammation, atopobiosis). "gut microbiota," "Escherichia coli," "cardiovascular disease," "risk," "disease," "ischemic stroke," "stroke," "metabolism," "inflammation," and "phosphatidylcholine" were the most recent keyword explosions.

Conclusion

Findings suggest that in the next 10 years, the number of publications produced annually may increase significantly. Future research trends tend to concentrate on the mechanisms of stroke and gut microbiota, with the inflammation and immunological mechanisms, TMAO, and fecal transplantation as hotspots. And the relationship between these mechanisms and a particular cardiovascular illness may also be a future research trend.

The gastrointestinal-brain-microbiota axis: a promising therapeutic target for ischemic stroke

Ischemic stroke is a highly complex systemic disease characterized by intricate interactions between the brain and gastrointestinal tract. While our current understanding of these interactions primarily stems from experimental models, their relevance to human stroke outcomes is of considerable interest. After stroke, bidirectional communication between the brain and gastrointestinal tract initiates changes in the gastrointestinal microenvironment. These changes involve the activation of gastrointestinal immunity, disruption of the gastrointestinal barrier, and alterations in gastrointestinal microbiota. Importantly, experimental evidence suggests that these alterations facilitate the migration of gastrointestinal immune cells and cytokines across the damaged blood-brain barrier, ultimately infiltrating the ischemic brain. Although the characterization of these phenomena in humans is still limited, recognizing the significance of the brain-gastrointestinal crosstalk after stroke offers potential avenues for therapeutic intervention. By targeting the mutually reinforcing processes between the brain and gastrointestinal tract, it may be possible to improve the prognosis of ischemic stroke. Further investigation is warranted to elucidate the clinical relevance and translational potential of these findings.

Premorbid use of selective beta-blockers improves sepsis incidence and course: Human cohort and animal model studies

Introduction

Beta-blockers are widely prescribed to manage hypertension and cardiovascular diseases and have been suggested as an attractive therapy to improve the prognosis of sepsis. Herein, we investigated the potential benefits of premorbid selective beta-blocker use in sepsis with a real-world database and explored the underlying mechanism by in vivo and in vitro experiments.

Methods

A total of 64,070 sepsis patients and 64,070 matched controls who were prescribed at least one anti-hypertensive drug for more than 300 days within 1 year were selected for the nested case-control study. Female C57BL/6 J mice and THP-1 cells stimulated with lipopolysaccharide (LPS) were used for studying systemic responses during sepsis to validate our clinical findings.

Results

The risk of sepsis was lower in current selective beta-blocker users than in non-users (adjusted OR (aOR), 0.842; 95% CI, 0.755-0.939), and in recent users than in non-users (aOR, 0.773; 95% CI, 0.737-0.810). A mean daily dose of ≥0.5 DDD was associated with a lower risk of sepsis (aOR, 0.7; 95% CI, 0.676-0.725). Metoprolol, atenolol, and bisoprolol users had lower risk of sepsis than non-users. In a LPS-induced sepsis mouse model, mice pre-fed with atenolol had significantly reduced mortality. While atenolol had some mild effects on LPS-induced release of inflammatory cytokines in septic mice, it significantly reduced serum soluble PD-L1 levels. Notably, atenolol treatment reversed the negative correlation of sPD-L1 with inflammatory cytokines in septic mice. Moreover, atenolol markedly downregulated the PD-L1 expression on LPS-stimulated THP-1 monocytes/macrophages via targeting ROS-induced NF-κB and STAT3 activation.

Conclusion

Atenolol pretreatment can reduce sepsis mortality in mice, and in vivo and in vitro studies of PD-L1 expression suggest a role for atenolol in the modulation of immune homeostasis. These findings may contribute to the reduced incidence of sepsis in hypertensive patients with premorbid treatment with selective beta-blockers, especially atenolol.

Definitions of Urinary Tract Infection Used in Interventional Studies Involving Neurourological Patients-A Systematic Review

CONTEXT

Neurourological patients often encounter bacteriuria without any symptoms or may experience symptoms suspicious of urinary tract infections (UTIs). However, there is a lack of guidelines that unequivocally state the definition of UTIs in this specific patient group.

OBJECTIVE

To present all used definitions of UTIs in neurourological patients.

EVIDENCE ACQUISITION

This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Studies were identified by electronic search of Medline, Embase, Cochrane controlled trials databases, and clinicaltrial.gov without a time limitation (last search September 2020) and by screening of reference lists and reviews. The occurrences of the various UTI definitions were counted and the frequencies calculated.

EVIDENCE SYNTHESIS

After screening 7164 abstracts, we included 32 studies enrolling a total of 8488 patients with a neurourological disorder who took part in an interventional clinical study. UTI definitions were heterogeneous. The concordance to predefined definitions was low.

CONCLUSIONS

Interventional clinical studies rarely report specific definitions for UTIs, and both clinical and laboratory criteria used are heterogeneous. A generally accepted UTI definition for neurourological patients is urgently needed.

PATIENT SUMMARY

Patients suffering from neurological disorders often experience symptoms in their lower urinary tract that resemble urinary tract infections. Furthermore, they can have positive urine cultures without symptoms (the so-called asymptomatic bacteriuria). However, clinical studies rarely report specific definitions for urinary tract infections, and when it is done, they are heterogeneous. A generally accepted urinary tract infection definition for neurourological patients is urgently needed. TAKE  HOME MESSAGE: Interventional clinical studies on neurourological patients rarely report specific definitions for urinary tract infections (UTIs), and both clinical and laboratory criteria used are heterogeneous. A generally accepted UTI definition for neurourological patients is urgently needed.

Systemic inflammation after stroke: implications for post-stroke comorbidities

Immunological mechanisms have come into the focus of current translational stroke research, and the modulation of neuroinflammatory pathways has been identified as a promising therapeutic approach to protect the ischemic brain. However, stroke not only induces a local neuroinflammatory response but also has a profound impact on systemic immunity. In this review, we will summarize the consequences of ischemic stroke on systemic immunity at all stages of the disease, from onset to long‐term outcome, and discuss underlying mechanisms of systemic brain‐immune communication. Furthermore, since stroke commonly occurs in patients with multiple comorbidities, we will also overview the current understanding of the potential role of systemic immunity in common stroke‐related comorbidities, such as cardiac dysfunction, atherosclerosis, diabetes, and infections. Finally, we will highlight how targeting systemic immunity after stroke could improve long‐term outcomes and alleviate comorbidities of stroke patients.

Hospital-acquired infections after acute ischaemic stroke and its association with healthcare-related costs and functional outcome

INTRODUCTION

Acute ischaemic stroke is associated with important mortality, morbidity, and healthcare-related costs. Age, pre-stroke functionality and stroke severity are important contributors to functional outcome. Stroke patients also risk developing infections during hospitalization. We sought to explore possible predictors of post-stroke infections and the relationship of post-stroke infection with healthcare-related costs and functional outcome.

METHODS

This single-centre retrospective study included 530 patients treated for ischaemic stroke between January 2017 and February 2019. Antibiotics' administration was used as a proxy for post-stroke infection. Functional outcome at 90 days was assessed by the modified Rankin Scale (mRS). Total healthcare-related costs were recorded for the index hospital stay. Multivariable analysis for post-stroke infection was done with the independent factors sex, age, pre-stroke mRS, National Institutes of Health Stroke Scale (NIHSS) and diabetes mellitus.

RESULTS

Twenty percent of patients had a post-stroke infection. NIHSS (OR 1.10, 95%CI 1.06-1.13, p < 0.0001) and diabetes mellitus (OR 2.18, 95%CI 1.28-3.71, p = 0.0042) were independent predictors for post-stroke infection. Mean total healthcare-related costs were 15,374 euro (SD 19,968; IQR 3,380-18,165), with a mean of 31,061 euro (SD 29,995; IQR 12,584-42,843) in patients with infection, compared to 11,406 euro (SD 13,987; IQR 3,083-12,726) in patients without (p < 0.0001). Median 90-days mRS was 5 (IQR 3-6) in patients with infection versus 1 (IQR 0-3.5) in patients without (p < 0.0001).

CONCLUSIONS

In patients, admitted for acute ischaemic stroke, stroke severity and diabetes mellitus were identified as the main predictors for post-stroke infection. Hospital-acquired infections were associated with increased costs and worse functional outcome.

Recent Advances in the Impact of Infection and Inflammation on Stroke Risk and Outcomes

PURPOSE OF THE REVIEW

Inflammation is a key component in the pathogenesis of cerebrovascular diseases. In the past few years, the role of systemic infection and gut dysbiosis in modulating inflammation and stroke risk has been increasingly acknowledged. In this review, we synthesize contemporary literature on the effects of infection and inflammation on stroke risk and outcomes, with a focus on periodontal disease, COVID-19 infection, and gut dysbiosis.

RECENT FINDINGS

Chronic and acute infections such as periodontitis and COVID-19 induce systemic inflammation that cause atherogenesis and increase cardiac injury and arrhythmias. These infections also directly injure the endothelium leading to worsened secondary inflammation after stroke. Gut dysbiosis engenders a pro-inflammatory state by modulating intestinal lymphocyte populations that can traffic directly to the brain. Additionally, post-stroke immune dysregulation creates a compounding feedback loop of further infections and gut dysbiosis that worsen outcomes. Recent advances in understanding the pathophysiology of how infection and dysbiosis affect the progression of stroke, as well as long-term recovery, have revealed tantalizing glimpses at potential therapeutic targets. We discuss the multidirectional relationship between stroke, infection, and gut dysbiosis, and identify areas for future research to further explore therapeutic opportunities.

The role of β2 adrenergic receptor on infection development after ischaemic stroke

Mechanisms underlying post-stroke immune impairments and subsequent development of fatal lung infection have been suggested to involve multiple pathways, including hyperactivation of the sympathetic nervous system (SNS), which results in the excessive release of catecholamines and activation of β-adrenergic receptors (βARs). Indeed, previous reports from experimental studies demonstrated that post-stroke infection can be inhibited with treatment of β-blockers. However, the effectiveness of β-blockers in reducing post-stroke infection has yielded mixed results in retrospective clinical trials and its use remain controversial. In this study, we performed mid-cerebral artery occlusion in mice either genetically deficient in β₂-adrenergic receptor (β₂AR) or treated with non-selective and selective βAR antagonists to explore the contributions of the SNS in the development of post-stroke lung infection. Stroke induced a systemic activation of the SNS as indicated by elevated levels of plasma catecholamines and UCP-1 activity. However, β₂AR deficient mice showed similar degrees of post-stroke immune impairment and infection rate compared to wildtype counterparts, potentially due to compensatory mechanisms common in transgenic animals. To overcome this, we treated post-stroke wildtype mice with pharmacological inhibitors of the βARs, including the non-selective antagonist propranolol (PPL) and selective β₂AR antagonist ICI-118551. Both pharmacological strategies to block the action of SNS signalling were unable to reduce infection in mice that underwent ischaemic stroke. Overall, our data suggests that other mechanisms independent or in combination with β₂AR activation contribute to the development of post-stroke infection.

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Ischaemic stroke induced a systemic activation of the sympathetic nervous system.

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Mice deficient of β₂ adrenergic receptor showed similar post-stroke infection and signs of immune impairment compared to wildtype counterparts.

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Pharmacological blockade of sympathetic signalling was unable to reduce infection in mice after stroke.

Dynamic Process of Secondary Pulmonary Infection in Mice With Intracerebral Hemorrhage

Stroke is a common central nervous system disease in clinical practice. Stroke patients often have infectious complications, such as pneumonia and infections of the urinary tract and gastrointestinal tract. Although it has been shown that translocation of the host gut microbiota to the lungs and immune dysfunction plays a vital role in the development of infection after ischemic stroke, the occurrence and mechanism of pulmonary infection at different time points after hemorrhagic cerebral remain unclear. In this study, the changes in the immune system and intestinal barrier function in mice during disease development were investigated at 1 day (M 1 d), 3 days (M 3 d) and 7 days (M 7 d) following hemorrhagic stroke to clarify the mechanism of secondary pulmonary infection. The experimental results revealed that after hemorrhagic stroke, model mice showed increased brain damage from day 1 to 3, followed by a trend of brain recovery from day 3 to 7 . After hemorrhagic stroke, the immune system was disturbed in model mice. Significant immunosuppression of the peripheral immune system was observed in the M 3 d group but improved in the M 7 d group. Staining of lung tissues with hematoxylin and eosin (H&E) and for inflammatory factors revealed considerable disease and immune disorders in the M 7 d group. Stroke seriously impaired intestinal barrier function in mice and significantly changed the small intestine structure. From 1 to 7 d after stroke, intestinal permeability was increased, whereas the levels of markers for intestinal tight junctions, mucus and immunoglobulin A were decreased. Analysis based on 16S rRNA suggested that the microflora in the lung and ileum was significantly altered after stroke. The composition of microflora in lung and ileum tissue was similar in the M 7d group, suggesting that intestinal bacteria had migrated to lung tissue and caused lung infection at this time point after hemorrhagic stroke. In stroke mice, the aggravation of intestinal barrier dysfunction and immune disorders after intracerebral hemorrhage, promoted the migration of enteric bacteria, and increased the risk of pneumonia poststroke. Our findings reveal the dynamic process of infection after hemorrhagic stroke and provide clues for the optimal timing of intervention for secondary pulmonary infection in stroke patients.

Brain to periphery in acute ischemic stroke: Mechanisms and clinical significance

The social and public health burdens of ischemic stroke have been increasing worldwide. In addition to focal brain damage, acute ischemic stroke (AIS) provokes systemic abnormalities across peripheral organs. AIS profoundly alters the autonomic nervous system, hypothalamic-pituitary-adrenal axis, and immune system, which further yield deleterious organ-specific consequences. Poststroke systemic pathological alterations in turn considerably contribute to the progression of ischemic brain injury, which accounts for the substantial impact of systemic complications on stroke outcomes. This review provides a comprehensive and updated pathophysiological model elucidating the systemic effects of AIS. To address their clinical significance and inform stroke management, we also outline the resulting systemic complications at particular stages of AIS and highlight the mechanisms. Future therapeutic strategies should attempt to integrate the treatment of primary brain lesions with interventions for secondary systemic complications, and should be tailored to patient individualized characteristics to optimize stroke outcomes.

Ischemic stroke and infection: A brief update on mechanisms and potential therapies

Ischemic stroke triggers a multifaceted inflammatory response in the brain that contributes to secondary brain injury and infarct expansion. In parallel with brain inflammation, ischemic stroke also leads to post-stroke immunosuppression. Stroke-induced leukopenia then predisposes patients to opportunistic infections potentially leading to pneumonia or unrinary tract infections and a worsened stroke outcome. There is evidence that the hypothalamic-pituitaryadrenal axis plays an important role in the etiology of post-stroke immunosuppression, by which prolonged glucocorticoid signalling leads to changes in immune responses. While opportunistic microbes in hospitals have been thought to be the source of infection, recent studies have reported that gut flora may also be a cause of post-stroke infection as a consequence of compromised integrity of the gut barrier after stroke. While antimicrobial drugs would appear to be a rational form of treatment for bacterial infections in stroke patients, the rise in drug-resistant bacteria and possible adverse effects of disrupting beneficial gut flora represent major challenges with these drugs. Considering the prominent role of gut microbiota in modulating immune responses, protecting and restoring the post-stroke gut bacteriome may provide significant benefit in the context of post-stroke infection. With such broad aspects of post-stroke infection occurring together with an extensive inflammatory response in the brain, a carefully considered administration of therapies for ischemic stroke is warranted.

Cohort and Period Effects as Explanations for Declining Dementia Trends and Cognitive Aging

Studies have reported that the age-adjusted incidence of cognitive impairment and dementia may have decreased over the past two decades. Aging is the predominant risk factor for Alzheimer's disease and related dementias and for neurocognitive decline. However, aging cannot explain changes in overall age-adjusted incidence of dementia. The objective of this position paper was to describe the potential for cohort and period effects in cognitive decline and incidence of dementia. Cohort effects have long been reported in demographic literature, but starting in the early 1980s, researchers began reporting cohort trends in cognitive function. At the same time, period effects have emerged in economic factors and stressors in early and midlife that may result in reduced cognitive dysfunction. Recognizing that aging individuals today were once children and adolescents, and that research has clearly noted that childhood cognitive performance is a primary determinant of old-age cognitive performance, this is the first study that proposes the need to connect known cohort effects in childhood cognition with differences in late-life functioning.

Stroke-induced immunosuppression: implications for the prevention and prediction of post-stroke infections

Stroke produces a powerful inflammatory cascade in the brain, but also a suppression of the peripheral immune system, which is also called stroke-induced immunosuppression (SIIS). The main processes that lead to SIIS are a shift from a lymphocyte phenotype T-helper (Th) 1 to a Th2 phenotype, a decrease of the lymphocyte counts and NK cells in the blood and spleen, and an impairment of the defense mechanisms of neutrophils and monocytes. The direct clinical consequence of SIIS in stroke patients is an increased susceptibility to stroke-associated infections, which is enhanced by clinical factors like dysphagia. Among these infections, stroke-associated pneumonia (SAP) is the one that accounts for the highest impact on stroke outcome, so research is focused on its early diagnosis and prevention. Biomarkers indicating modifications in SIIS pathways could have an important role in the early prediction of SAP, but currently, there are no individual biomarkers or panels of biomarkers that are accurate enough to be translated to clinical practice. Similarly, there is still no efficient therapy to prevent the onset of SAP, and clinical trials testing prophylactic antibiotic treatment and β-blockers have failed. However, local immunomodulation could open up a new research opportunity to find a preventive therapy for SAP. Recent studies have focused on the pulmonary immune changes that could be caused by stroke similarly to other acquired brain injuries. Some of the traits observed in animal models of stroke include lung edema and inflammation, as well as inflammation of the bronchoalveolar lavage fluid.

Non-Selective Beta-Blockers Decrease Infection, Acute Kidney Injury Episodes, and Ameliorate Sarcopenic Changes in Patients with Cirrhosis: A Propensity-Score Matching Tertiary-Center Cohort Study

Background: Cirrhotic complications resulting from portal hypertension can be considerably reduced by non-selective beta-blockers (NSBBs); however, scarce studies have investigated therapeutic agents for other complications. We aimed to investigate the effects of NSBBs on common cirrhotic complications of infection, acute kidney injury (AKI), chronic renal function declination, and sarcopenic changes. Methods: Medical records of hospitalization for cirrhosis with at least a 4-year follow-up were analyzed and selected using propensity-score matching (PSM). Generalized estimating equation (GEE) was applied to assess the association of NSBBs with infection requiring hospitalization and AKI. Chronic renal function declination was evaluated by slope of regression lines derived from reciprocal of the serum creatinine level. The covariates of CT-measured skeletal muscle index (SMI) alterations were analyzed by generalized linear mixed model. Results: Among the 4946 reviewed individuals, 166 (83 NSBB group, 83 non-NSBB group) were eligible. Using GEE, Charlson comorbidity index, Child-Pugh score and non-NSBB were risk factors for infection; non-NSBB group revealed a robust trend toward AKI, showed no significant difference with chronic renal function declination of NSBB group, and was negatively associated with SMI alteration. Conclusion: Chronic NSBB use lowered the episodes of infection requiring hospitalization and AKIs, whereas non-NSBB was associated with sarcopenic changes.

Usefulness of the Neutrophil-to-Lymphocyte Ratio as a Predictor of Pneumonia and Urinary Tract Infection Within the First Week After Acute Ischemic Stroke

Background: A high Neutrophil-to-Lymphocyte ratio (NLR) in patients with acute ischemic stroke (AIS) has been associated with post-stroke infections, but it's role as an early predictive biomarker for post-stroke pneumonia (PSP) and urinary tract infection (UTI) is not clear.

Aim: To investigate the usefulness of NLR obtained within 24 h after AIS for predicting PSP and UTI in the first week.

Methods: Clinical and laboratory data were retrieved from the University Hospital Brussels stroke database/electronic record system. Patients were divided into those who developed PSP or UTI within the first week after stroke onset and those who didn't. Receiver operating characteristics (ROC) curves and logistic regression analysis were used to identify independent predictors.

Results: Five hundred and fourteen patients were included, of which 15.4% (n = 79) developed PSP and 22% (n = 115) UTI. In univariate analysis, NLR was significantly higher in patients who developed PSP (4.1 vs. 2.8, p < 0.001) but not in those who developed UTI (3.3 vs. 2.9, p = 0.074). Multiple logistic regression analysis for PSP showed that NLR, male gender, dysphagia, and stroke severity measured by the National Institutes of Health Stroke Scale (NIHSS), were independent predictors of PSP. For NLR alone, the area under the curve (AUC) in the ROC curve was 0.66 (95% CI = 0.59–0.73). When combining NLR ≥ 4.7 with age >75 years, male gender, NIHSS > 7, and dysphagia, the AUC increased to 0.84 (95% CI = 0.79–0.89).

Conclusion: The NLR within 24 h after AIS appears to have no predictive value for post-stroke UTI, and is only a weak predictor for identifying patients at high risk for PSP. Its predictive value for PSP appears to be much stronger when incorporated in a prediction model including age, gender, NIHSS score, and dysphagia.

Effect of Beta-Blockers on Stroke Outcome: A Meta-Analysis

Introduction

Cardiovascular events and infections are common in the acute phase after stroke. It has been suggested that these complications may be associated with excessive sympathetic activation due to the stroke, and that beta-adrenergic antagonists (beta-blockers) therefore may be beneficial.

Aim

The aim of the current meta-analysis was to investigate the association between beta-blocker treatment in acute stroke and the three outcomes: mortality, functional outcome and post-stroke infections.

Methods

A literature search was performed using the keywords stroke, cerebrovascular disorders, adrenergic beta-antagonists, treatment outcome and mortality. Randomized clinical trials and observational studies were eligible for data extraction. Heterogeneity was investigated using I² statistics. Random effect model was used when heterogeneity presented among studies; otherwise, a fixed-effect model was used. Publication bias was assessed using Egger’s test and by visually inspecting funnel plots.

Results

A total of 20 studies were eligible for at least one of the three outcomes. Two of the included studies were randomized controlled trials and 18 were observational studies. Quality assessments indicated that the risk of bias was moderate. The meta-analysis found no significant association between treatment with beta-blockers and any of the three outcomes. The studies analyzed for the outcomes mortality and infection were heterogeneous, while studies analyzed for functional outcome were homogeneous. The articles analyzed for mortality showed signs of publication bias.

Conclusion

The lack of significant effects in the current meta-analysis, comprising more than 100,000 patients, does not support the proposed beneficial effects of beta-blockers in the acute phase of stroke.

Ischemic stroke alters immune cell niche and chemokine profile in mice independent of spontaneous bacterial infection

Introduction

Stroke‐associated pneumonia (SAP) is a major cause of mortality in patients who have suffered from severe ischemic stroke. Although multifactorial in nature, stroke‐induced immunosuppression plays a key role in the development of SAP. Previous studies using a murine model of transient middle cerebral artery occlusion (tMCAO) have shown that focal ischemic stroke induction results in functional defects of lymphocytes in the spleen, thymus, and peripheral blood, leading to spontaneous bacterial infection in the lungs without inoculation. However, how ischemic stroke alters immune cell niche and the expression of cytokines and chemokines in the lungs has not been fully characterized.

Methods

Ischemic stroke was induced in mice by tMCAO. Immune cell profiles in the brain and the lungs at 24‐ and 72‐hour time points were compared by flow cytometric analysis. Cytokine and chemokine expression in the lungs were determined by multiplex bead arrays. Tissue damage and bacterial burden in the lungs following tMCAO were evaluated.

Results

Ischemic stroke increases the percentage of alveolar macrophages, neutrophils, and CD11b⁺ dendritic cells, but reduces the percentage of CD4⁺ T cells, CD8⁺ T cells, B cells, natural killer cells, and eosinophils in the lungs. The alteration of immune cell niche in the lungs coincides with a significant reduction in the levels of multiple chemokines in the lungs, including CCL3, CCL4, CCL5, CCL17, CCL20, CCL22, CXCL5, CXCL9, and CXCL10. Spontaneous bacterial infection and tissue damage following tMCAO, however, were not observed.

Conclusion

This is the first report to demonstrate a significant reduction of lymphocytes and multiple proinflammatory chemokines in the lungs following ischemic stroke in mice. These findings suggest that ischemic stroke directly impacts pulmonary immunity.

Neuroimmune crosstalk in central nervous system injury-induced infection and pharmacological intervention

Infection (such as pneumonia and urinary tract infection) is one of the leading causes of death in patients with acute central nervous system (CNS) injury, which also greatly affects the patients' prognosis and quality of life. Antibiotics are commonly used for the treatment of various infections, however, available evidence demonstrate that prophylactic antibiotic treatments for CNS injury-induced infection have been unsuccessful. Effective approaches for prevention of CNS injury induced-infection remain scarce, therefore, better understanding the molecular and cellular mechanisms of infection post-CNS injury may aid in the development of efficacious therapeutic options. CNS injury-induced infection is confirmed affected by the sympathetic/parasympathetic nervous system, hypothalamic-pituitary-adrenal axis, and even brain-gut axis. In this review, we summarized the mechanisms of CNS injury- induced infection, crosstalk between the CNS and the immune system and current pharmacological intervention to provide ideas for the development of new anti- infective therapeutic strategies.

Inhibition of CD147 Attenuates Stroke-Associated Pneumonia Through Modulating Lung Immune Response in Mice

Background and Purpose: Acute ischemic stroke triggers a profound systemic and local immunodysfunction that increased the susceptibility to infections, especially stroke-associated pneumonia (SAP). Our previous study has shown that inhibition of CD147 ameliorates acute ischemic stroke, however, the role of CD147 in post-stroke lung infection has not been investigated.

Methods: C57BL/6 mice were subjected to transient (60 min) middle cerebral artery occlusion, and treated with anti-CD147 antibody (αCD147). Lung histological changes, vascular permeability, and pulmonary edema were determined. Bacterial burden in the lung tissue and Broncho alveolar lavage fluid (BALF) were measured. Lung leukocyte infiltration, circulating platelet-leukocyte aggregates, cell type-specific IL-17A, and IFN-γ expression in the lung were detected by flow cytometry.

Results: CD147 expression was markedly upregulated in the lung after stroke. αCD147 treatment significantly decreased the stroke-associated lung histological damages, bacterial load, vascular permeability and pulmonary edema. The protective effects by αCD147 treatment were associated with deceased lung inflammatory cell infiltration by reducing IL-17A expression in lung γδ T cells and attenuated bacterial load by enhancing IFN-γ expression in the lung NK1.1⁺ cells and CD4⁺ T cells. In addition, CD147 expression was also increased in the circulating platelets and leukocytes. Enhanced platelet-leukocyte aggregates following stroke was inhibited by αCD147 treatment.

Conclusions: Inhibition of CD147 ameliorates aberrant lung inflammatory and immune response and reduces bacterial infection after stroke. CD147 might represent a novel and promising therapeutic target for post-stroke lung infection.

Old Dog New Tricks; Revisiting How Stroke Modulates the Systemic Immune Landscape

Infections in the post-acute phase of cerebral ischaemia impede optimal recovery by exacerbating morbidity and mortality. Our review aims to reconcile the increased infection susceptibility of patients post-stroke by consolidating our understanding of compartmentalised alterations to systemic immunity. Mounting evidence has catalogued alterations to numerous immune cell populations but an understanding of the mechanisms of long-range communication between the immune system, nervous system and other organs beyond the involvement of autonomic signalling is lacking. By taking our cues from established and emerging concepts of neuro-immune interactions, immune-mediated inter-organ cross-talk, innate immune training and the role of microbiota-derived signals in central nervous system (CNS) function we will explore mechanisms of how cerebral ischaemia could shape systemic immune function. In this context, we will also discuss a key question: how are immune requirements critical for mediating repair of the ischaemic insult balanced by the need for anti-microbial immunity post-stroke, given that they are mediated by mutually exclusive immune networks? Our reformed understanding of the immune landscape post-stroke and novel mechanisms at play could guide targeted therapeutic interventions and initiate a step-change in the clinical management of these infectious complications post-stroke.

Chemical Sympathectomy, but not Adrenergic Blockade, Improves Stroke Outcome

BACKGROUND

A robust adrenergic response following stroke impairs lymphocyte function, which may prevent the development of autoimmune responses to brain antigens. We tested whether inhibition of the sympathetic response after stroke would increase the propensity for developing autoimmune responses to brain antigens.

METHODS

Male Lewis rats were treated with 6-hydroxydopamine (OHDA) prior to middle cerebral artery occlusion (MCAO), labetalol after MCAO, or appropriate controls. Behavior was assessed weekly and animals survived to 1 month at which time ELISPOT assays were done on lymphocytes from spleen and brain to determine the Th1 and Th17 responses to myelin basic protein (MBP), ovalbumin (OVA), and concanavalin A. A subset of animals was sacrificed 72 hours after MCAO for evaluation of infarct volume and lymphocyte responsiveness. Plasma C-reactive protein (CRP) was measured as a biomarker of systemic inflammation.

RESULTS

Despite similar initial stroke severity and infarct volumes, 6-OHDA-treated animals lost less weight and experienced less hyperthermia after stroke. 6-OHDA-treated animals also had decreased CRP in circulation early after stroke and experienced better neurological outcomes at 1 month. The Th1 and Th17 responses to MBP did not differ among treatment groups at 1 month, but the Th1 response to OVA in spleen was more robust in labetalol and less robust in 6-OHDA-treated animals.

CONCLUSIONS

Chemical sympathectomy with 6-OHDA, but not treatment with labetalol, decreased systemic markers of inflammation early after stroke and improved long-term outcome. An increase in Th1 and Th17 responses to MBP was not seen with inhibition of the sympathetic response.

Complex interplay of multiple biological systems that contribute to post-stroke infections

Stroke is a leading contributor of death and disability around the world. Despite its recognised debilitating neurological deficits, a devastating clinical complication of surviving stroke patients that needs more attention is infection. Up to half of the patients develop infections after stroke, and a high proportion of them will die as a direct consequence. Major clinical trials that examined preventive antibiotic therapy in stroke patients have demonstrated this method of prevention is not effective as it does not reduce incidence of post-stroke pneumonia or improve patient outcome. Additionally, retrospective studies evaluating the use of β-blockers for the modulation of the sympathetic nervous system to prevent post-stroke infections have given mixed results. Therefore, there is an urgent need for more effective therapeutic options that target the underlying mechanisms of post-stroke infections. The understanding that infections are largely attributable to the "stroke-induced systemic immunosuppression" phenomenon has begun to emerge, and thus, exploring the pathways that trigger post-stroke immunosuppression is expected to reveal potential new therapeutics. As such, we will outline the impacts that stroke has on several biological systems in this review, and discuss how these contribute to host susceptibility to infection after stroke. Furthermore, the emerging role of the gut and its microbiota has recently come to surface and intensifies the complex pathways to post-stroke infection. Finally, we identify potential avenues to combat infection that target the pathways of stroke-induced systemic immunosuppression to ultimately improve stroke patient outcome.

Influence of beta-blocker therapy on the risk of infections and death in patients at high risk for stroke induced immunodepression

Background

Stroke-induced immunodepression is a well characterized complication of acute ischemic stroke. In experimental studies beta-blocker therapy reversed stroke-induced immunodepression, reduced infection rates and mortality. Recent, heterogeneous studies in stroke patients could not provide evidence of a protective effect of beta-blocker therapy. Aim of this study is to investigate the potential preventive effect of beta-blockers in subgroups of patients at high risk for stroke-induced immunodepression.

Methods

Data from a prospectively derived registry of major stroke patients receiving endovascular therapy between 2011–2017 in a tertiary stroke center (University Medical Center Göttingen. Germany) was used. The effect of beta-blocker therapy on pneumonia, urinary tract infection, sepsis and mortality was assessed using multivariate logistic regression analysis.

Results

Three hundred six patients with a mean age of 72 ± 13 years and a median NIHSS of 16 (IQR 10.75–20) were included. 158 patients (51.6%) had pre-stroke- and continued beta-blocker therapy. Beta-blocker therapy did not reduce the incidence of pneumonia (OR 0.78, 95% CI 0.31–1.92, p = 0.584), urinary tract infections (OR 1.51, 0.88–2.60, p = 0.135), sepsis (OR 0.57, 0.18–1.80, p = 0.334) or mortality (OR 0.59, 0.16–2.17, p = 0.429). Strokes involving the insula and anterio-medial cortex increased the risk for pneumonia (OR 4.55, 2.41–8.56, p<0.001) and sepsis (OR 4.13, 1.81–9.43, p = 0.001), while right hemispheric strokes increased the risk for pneumonia (OR 1.60, 0.92–2.77, p = 0.096). There was a non-significantly increased risk for urinary tract infections in patients with beta-blocker therapy and insula/anterio-medial cortex strokes (OR 3.12, 95% CI 0.88–11.05, p = 0.077) with no effect of beta-blocker therapy on pneumonia, sepsis or mortality in both subgroups.

Conclusions

In major ischemic stroke patients, beta-blocker therapy did not lower post-stroke infection rates and was associated with urinary tract infections in a subgroup with insula/anterio-medial strokes.

Stroke-induced immunosuppression and poststroke infection

Infections occur commonly after stroke and are strongly associated with an unfavourable functional outcome of these patients. Approaches for effective management of poststroke infection remain scarce, presenting an urgent need for preventive anti-infection strategies for patients who have suffered a stroke. Emerging evidence indicates that stroke impairs systemic immune responses and increases the susceptibility to infections, suggesting that the modification of impaired immune defence could be beneficial. In this review, we summarised previous attempts to prevent poststroke infections using prophylactic antibiotics and the current understanding of stroke-induced immunosuppression. Further elucidation of the immune mechanisms of stroke will pave the way to tailored design of new treatment to combat poststroke infection via modifying the immune system.

Lymphocyte-to-monocyte ratio on day 7 is associated with outcomes in acute ischemic stroke

The main features of stroke-induced immunosuppression are lymphopenia and deactivation of monocytes in peripheral blood. We hypothesized that lymphocyte-to-monocyte ratio (LMR) in peripheral blood may represent the degree of stroke-induced immunosuppression. To prove this hypothesis, we evaluated whether LMR is associated with risk of post-stroke infection and clinical outcome at 3 months in patients with acute ischemic stroke. We selected patients with stroke in anterior circulation within 24 h from onset. Peripheral blood sampling for differential blood count was performed on days 1 and 7. The LMRs on days 1 and 7 were analyzed to determine associations with excellent outcomes (modified Rankin Scale of score 0-1 at 3 months). One hundred and two patients were included. The initial National Institutes of Health Stroke Scale score (adjusted odd ratio [OR] 0.89; 95% confidence interval [CI], 0.83-0.95; P = 0.001) and LMR on day 7 (adjusted OR 1.49; 95% CI, 1.09-2.02; P = 0.011) were associated with excellent outcomes. LMRs on day 1 were significantly lower in stroke patients with pneumonia (P = 0.007) and pneumonia or urinary tract infection (P = 0.012) than those without infections. LMRs on day 7 were also significantly lower in stroke patients with infection (P = 0.005 in pneumonia, P = 0.003 in urinary tract infection, and P < 0.001 in pneumonia or urinary tract infection) than those without infections. Lower LMRs on day 7 are associated with worse outcomes at 3 months after stroke onset. LMR may be a useful marker for assessing the stroke-induced immunosuppression.

Monocyte-lymphocyte cross-communication via soluble CD163 directly links innate immune system activation and adaptive immune system suppression following ischemic stroke

CD163 is a scavenger receptor expressed on innate immune cell populations which can be shed from the plasma membrane via the metalloprotease ADAM17 to generate a soluble peptide with lympho-inhibitory properties. The purpose of this study was to investigate CD163 as a possible effector of stroke-induced adaptive immune system suppression. Liquid biopsies were collected from ischemic stroke patients (n = 39), neurologically asymptomatic controls (n = 20), and stroke mimics (n = 20) within 24 hours of symptom onset. Peripheral blood ADAM17 activity and soluble CD163 levels were elevated in stroke patients relative to non-stroke control groups, and negatively associated with post-stroke lymphocyte counts. Subsequent in vitro experiments suggested that this stroke-induced elevation in circulating soluble CD163 likely originates from activated monocytic cells, as serum from stroke patients stimulated ADAM17-dependant CD163 shedding from healthy donor-derived monocytes. Additional in vitro experiments demonstrated that stroke-induced elevations in circulating soluble CD163 can elicit direct suppressive effects on the adaptive immune system, as serum from stroke patients inhibited the proliferation of healthy donor-derived lymphocytes, an effect which was attenuated following serum CD163 depletion. Collectively, these observations provide novel evidence that the innate immune system employs protective mechanisms aimed at mitigating the risk of post-stroke autoimmune complications driven by adaptive immune system overactivation, and that CD163 is key mediator of this phenomenon.

Systemic antibiotics for preventing ventilator-associated pneumonia in comatose patients: a systematic review and meta-analysis

BACKGROUND

Early-onset ventilator-associated pneumonia (EO-VAP) is the leading cause of morbidity and mortality in comatose patients. However, VAP prevention bundles focus mainly on late-onset VAP and may be less effective in preventing EO-VAP in comatose patients. Systemic antibiotic administration at the time of intubation may have a role in preventing EO-VAP. Therefore, we evaluated the effectiveness of systemic antibiotic administration in VAP prevention in comatose patients through a systematic review and meta-analysis.

METHODS

We searched for studies published through December 2015 that evaluated systemic antibiotic prophylaxis in comatose patients. Two authors independently selected and evaluated full-length reports of randomized clinical trials or prospective cohorts in patients aged >16 years that evaluated the impact of systemic antibiotics at the time of intubation on EO-VAP compared to placebo or no prophylaxis. The outcome variables were the incidence of EO-VAP, the duration of mechanical ventilation, ICU length of stay, and ICU mortality.

RESULTS

We identified 10,988 citations, yielding 26 articles for further analysis; three studies with 267 patients were finally analyzed. Most patients (n = 135) were comatose due to head trauma. Systemic antibiotic administration was associated with decreased incidence of EO-VAP (RR 0.32; 95% CI 0.19-0.54) and shorter ICU LOS (standardized mean difference -0.32; 95% CI -0.56 to -0.08), but had no effect on mortality (RR 1.03; 95% CI 0.7-1.53) or duration of mechanical ventilation (standardized mean difference -0.16; 95% CI -0.41 to 0.08).

CONCLUSIONS

Antibiotic prophylaxis in comatose patients reduced the incidence of EO-VAP and decreased the ICU stay slightly. Future trials are needed to confirm these results.

Immunomodulation after ischemic stroke: potential mechanisms and implications for therapy

Brain injuries are often associated with intensive care admissions, and carry high morbidity and mortality rates. Ischemic stroke is one of the most frequent causes of injury to the central nervous system. It is now increasingly clear that human stroke causes multi-organ systemic disease. Brain inflammation may lead to opposing local and systemic effects. Suppression of systemic immunity by the nervous system could protect the brain from additional inflammatory damage; however, it may increase the susceptibility to infection. Pneumonia and urinary tract infection are the most common complications occurring in patients after stroke. The mechanisms involved in lung-brain interactions are still unknown, but some studies have suggested that inhibition of the cholinergic anti-inflammatory pathway and release of glucocorticoids, catecholamines, and damage-associated molecular patterns (DAMPs) are among the pathophysiological mechanisms involved in communication from the ischemic brain to the lungs after stroke. This review describes the modifications in local and systemic immunity that occur after stroke, outlines mechanisms of stroke-induced immunosuppression and their role in pneumonia, and highlights potential therapeutic targets to reduce post-stroke complications. Despite significant advances towards a better understanding of the pathophysiology of ischemic stroke-induced immunosuppression and stroke-associated pneumonia (SAP) in recent years, many unanswered questions remain. The true incidence and outcomes of SAP, especially in intensive care unit settings, have yet to be determined, as has the full extent of stroke-induced immunosuppression and its clinical implications.

Pre-Stroke Use of Beta-Blockers Does Not Lower Post-Stroke Infection Rate: An Exploratory Analysis of the Preventive Antibiotics in Stroke Study

BACKGROUND

Stroke-associated infections occur frequently and are associated with unfavorable outcome. Previous cohort studies suggest a protective effect of beta-blockers (BBs) against infections. A sympathetic drive may increase immune suppression and infections.

AIM

This study is aimed at investigating the association between BB treatment at baseline and post-stroke infection in the Preventive Antibiotics in Stroke Study (PASS), a prospective clinical trial.

METHODS

We performed an exploratory analysis in PASS, 2,538 patients with acute phase of stroke (24 h after onset) were randomized to ceftriaxone (intravenous, 2 g per day for 4 days) in addition to stroke unit care, or standard stroke unit care without preventive antibiotic treatment. All clinical data, including use of BBs, was prospectively collected. Infection was diagnosed by the treating physician, and independently by an expert panel blinded for all other data. Multivariable analysis was performed to investigate the relation between BB treatment and infection rate.

RESULTS

Infection, as defined by the physician, occurred in 348 of 2,538 patients (14%). Multivariable analysis showed that the use of BBs at baseline was associated with the development of infection during clinical course (adjusted OR (aOR) 1.61, 95% CI 1.19-2.18; p < 0.01). BB use at baseline was also associated with the development of pneumonia (aOR 1.56, 95% CI 1.05-2.30; p = 0.03). Baseline BB use was not associated with mortality (aOR 1.14, 95% CI 0.84-1.53; p = 0.41) or unfavorable outcome at 3 months (aOR 1.10, 95% CI 0.89-1.35; p = 0.39).

CONCLUSIONS

Patients treated with BBs prior to stroke have a higher rate of infection and pneumonia.

Statin Medication Use and Nosocomial Infection Risk in the Acute Phase of Stroke

GOAL

Statins have immunomodulatory and peripheral anti-inflammatory properties that are independent of their lipid-lowering action. Whether these properties reduce the risk for developing poststroke infection is debated in clinical literature. We estimated the risk for developing nosocomial poststroke infection based on statin exposure in patients aged 18 or older hospitalized for ischemic stroke.

MATERIALS AND METHODS

A consecutive sample of acute care hospital electronic medical records was retrospectively analyzed. Patients were assigned to the exposed cohort either when statin use preceded infection or statin medication was used, but no infection developed. The unexposed cohort included patients not on statins or initiating statins after infection developed. The association of statin exposure with infection was examined with conditional logistic regression adjusted for poststroke infection risk factors. Cochran-Mantel-Haenszel analyses examined the association of statin exposure and infection status within strata of binary predictor variables that increased infection risk.

FINDINGS

Up to 1612 records were analyzed: 1151 in the exposed cohort and 461 in the unexposed cohort. Infection developed in 20% of the statin-exposed patients and in 41% of the statin-unexposed patients (P < .001). Exposure to statins reduced odds for developing nosocomial infection by 58% over no exposure (adjusted odds ratio = .418, P < .001). Statins lowered the infection risk for both sexes, patients with a nasogastric tube, and patients with dysphagia (P < .05). Statins did not change infection risk for patients with endotracheal intubation.

CONCLUSIONS

In patients with ischemic stroke and without endotracheal intubation, statin medications were associated with reduced risk of nosocomial infections.

Ischemia, Immunosuppression and Infection--Tackling the Predicaments of Post-Stroke Complications

The incidence of stroke has risen over the past decade and will continue to be one of the leading causes of death and disability worldwide. While a large portion of immediate death following stroke is due to cerebral infarction and neurological complications, the most common medical complication in stroke patients is infection. In fact, infections, such as pneumonia and urinary tract infections, greatly worsen the clinical outcome of stroke patients. Recent evidence suggests that the disrupted interplay between the central nervous system and immune system contributes to the development of infection after stroke. The suppression of systemic immunity by the nervous system is thought to protect the brain from further inflammatory insult, yet this comes at the cost of increased susceptibility to infection after stroke. To improve patient outcome, there have been attempts to lessen the stroke-associated bacterial burden through the prophylactic use of broad-spectrum antibiotics. However, preventative antibiotic treatments have been unsuccessful, and therefore have been discouraged. Additionally, with the ever-rising obstacle of antibiotic-resistance, future therapeutic options to reverse immune impairment after stroke by augmentation of host immunity may be a viable alternative option. However, cautionary steps are required to ensure that collateral ischemic damage caused by cerebral inflammation remains minimal.

Dynamics of T cell responses after stroke

T cells are integral to the pathophysiology of stroke. The initial inflammatory cascade leads to T cell migration, which results in deleterious and protective effects mediated through CD4(+), CD(8)+, γδ T cells and regulatory T cells, respectively. Cytokines are central to the T cell responses, with key roles established for TNF-α, IFN-γ, IL-17, IL-21 and IL-10. Through communication with the systemic immune system via neural and hormonal pathways, there is also transient immunosuppression after severe strokes. With time, the inflammatory process eventually transforms to one more conducive of repair and recovery, though some evidence also suggests ongoing chronic inflammation. The role of antigen-specific T cell responses requires further investigation. As our understanding develops, there is increasing scope to modulate the T cell response after stroke.

Preliminary Prospective Study to Assess the Effect of Early Blood Urea Nitrogen/Creatinine Ratio-Based Hydration Therapy on Poststroke Infection Rate and Length of Stay in Acute Ischemic Stroke

BACKGROUND

This study aimed to determine whether blood urea nitrogen (BUN)/creatinine (Cr)-based hydration therapy can decrease the rate of poststroke infection and length of stay (LOS) in the neurology ward.

METHODS

This was a nonblinded, phase II single-arm prospective study with a historical control group of patients with acute ischemic stroke and a BUN/Cr ratio of 15 or higher. The study group (n = 134) received an intravenous saline bolus (300-500 mL) followed by maintenance saline (40-80 mL/hour) for the first 72 hours. The control group (n = 103) received maintenance saline infusions (40-60 mL/hour for the first 24 hours and 0-60 mL/hour for the next 24-72 hours).

RESULTS

The hydration group had a significantly lower poststroke infection rate than did the control group (7.5% versus 17.5%, P = .018) and significantly shorter LOS in the neurology ward (13.5 ± 11.6 versus 19.6 ± 14.6 days, P < .01). With regard to adverse events, two patients in each group had cerebral edema.

CONCLUSIONS

The findings suggest that the BUN/Cr ratio needs to be corrected in a timely manner in patients with acute ischemic stroke. Providing prompt saline hydration therapy based on the daily BUN/Cr ratio might decrease the poststroke infection rate and shorten LOS.