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

The Potential Role of Angiotensin-Converting Enzyme Inhibitors and Beta-Blockers in Reducing Pneumonia Severity in Older Adults

Background Understanding the impact of pharmacological therapy on pneumonia severity is crucial for effective clinical management. The impact of angiotensin-converting enzyme inhibitors (ACEis) and beta-blockers (BBs) on pneumonia severity remains unknown, warranting further investigation. Methodology This retrospective study examined the hospital records of inpatients (≥75 years) admitted with community-acquired pneumonia in 2021. Pneumonia severity associated with the use of pre-established ACEi and BB therapy was documented using CURB-65 (confusion, uraemia, respiratory rate, blood pressure, age ≥65 years) and pneumonia severity index (PSI) scores. Descriptive statistics and multivariable linear regression were used to analyse differences across BB therapy, ACEi therapy, their combination, or neither (control group). Results A total of 803 patient records were examined, of whom 382 (47.6%) were male and 421 (52.4%) were female. Sample sizes for each group were as follows: control (n = 492), BB only (n = 185), ACEi only (n = 68), and BB + ACEi (n = 58). Distribution of aspiration pneumonia (AP) versus non-AP for each group, respectively, was control (21.1% vs. 78.9%), BB only (9.7% vs. 90.3%), ACEi only (7.3% vs. 92.7%), and ACEi + BB (12.1% vs. 87.9%). No significant differences in PSI and CURB-65 scores were found between intervention groups even after controlling for patient characteristics and irrespective of AP or non-AP aetiology. Patients with AP had significantly higher CURB-65 (p = 0.026) and PSI scores (p = 0.044) compared to those with non-AP. Conclusions Pre-prescribed ACEi or BB therapy did not appear to be associated with differences in pneumonia severity. There were no differences in pneumonia severity scores with ACEi and BB monotherapy or combined ACEi and BB therapy.

Premorbid Use of Beta-Blockers or Angiotensin-Converting Enzyme Inhibitors/Angiotensin Receptor Blockers in Patients with Acute Ischemic Stroke

This study was designed to investigate the impact of the preexisting use of beta-blockers, angiotensin-converting enzyme inhibitors (ACEIs), or angiotensin receptor blockers (ARBs) on the cellular immune response in peripheral blood and the clinical outcomes of patients with acute ischemic stroke. We retrospectively collected clinical data from a cohort of 69 patients with premorbid beta-blockers and 56 patients with premorbid ACEIs/ARBs. Additionally, we selected a cohort of 107 patients with acute ischemic stroke to be the control of the same age and sex. We analyzed cellular immune parameters in peripheral blood 1 day after the appearance of symptoms, including the frequencies of circulating white blood cell subpopulations, the neutrophil-to-lymphocyte ratio (NLR), and the lymphocyte-to-monocyte ratio (LMR). We found that the count of lymphocytes and the lymphocyte-to-monocyte ratio were significantly higher in the peripheral blood of patients treated with beta-blockers before stroke than in matched controls. However, the premorbid use of ACEIs/ARBs did not considerably impact the circulating immune parameters listed above in patients with acute ischemic stroke. Furthermore, we found that premorbid use of beta-blockers or ACEIs/ARBs did not significantly change functional outcomes in patients 3 months after the onset of stroke. These results suggest that premorbid use of beta-blockers, but not ACEIs/ARBs, reversed lymphopenia associated with acute ischemic stroke. As cellular immune changes in peripheral blood could be an independent predictor of stroke prognosis, more large-scale studies are warranted to further verify the impact of premorbid use of beta-blockers or ACEIs/ARBs on the prognosis of patients with ischemic stroke. Our research is beneficial to understanding the mechanism of the systemic immune response induced by stroke and has the potential for a therapeutic strategy in stroke interventions and treatment.

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.

Association between Antihypertensive Therapy and Risk of Acute Lower Respiratory Infections (ALRI): A Retrospective Cohort Study

Purpose: The aim of this study was to analyze the association between antihypertensive drugs and the incidence of acute lower respiratory infections in patients treated in general practices in Germany. Methods: After propensity score matching of five antihypertensive drug classes, a total of 377,470 patients aged ≥18 years were available for analysis. The association between each antihypertensive drug class and ALRI incidence as compared to all other antihypertensive drug classes (as a group) was studied using conditional Cox regression analyses. Because of multiple comparisons and large patient samples, findings were clinically considered relevant when the hazard ratio was <0.85 or >1.15. Results: The regression analyses applied found no clinically relevant associations between antihypertensive drugs and the incidence of acute lower respiratory infections, as all hazard ratios were between 0.85 and 1.15. Conclusion: In the present study, only slight and not clinically relevant increases or decreases in the ALRI incidence were observed. Additional studies are necessary to further explore the risks associated with antihypertensive agents that are widely embedded in today’s clinical practice.

Circulating Inflammatory Biomarkers in Early Prediction of Stroke-Associated Infections

(1) Background: Patients with acute ischaemic stroke (AIS) are at high risk for stroke-associated infections (SAIs). We hypothesised that increased concentrations of systemic inflammation markers predict SAIs and unfavourable outcomes; (2) Methods: In 223 patients with AIS, blood samples were taken at ≤24 h, 3 d and 7d after a stroke, to determine IL-6, IL-10, CRP and LBP. The outcome was assessed using the modified Rankin Scale at 90 d. Patients were thoroughly examined regarding the development of SAIs; (3) Results: 47 patients developed SAIs, including 15 lower respiratory tract infections (LRTIs). IL-6 and LBP at 24 h differed, between patients with and without SAIs (IL-6: p < 0.001; LBP: p = 0.042). However, these associations could not be confirmed after adjustment for age, white blood cell count, reduced consciousness and NIHSS. When considering the subgroup of LRTIs, in patients who presented early (≤12 h after stroke, n = 139), IL-6 was independently associated with LRTIs (OR: 1.073, 95% CI: 1.002−1.148). The ROC-analysis for prediction of LRTIs showed an AUC of 0.918 for the combination of IL-6 and clinical factors; (4) Conclusions: Blood biomarkers were not predictive for total SAIs. At early stages, IL-6 was independently associated with outcome-relevant LRTIs. Further studies need to clarify the use of biochemical markers to identify patients prone to SAIs.

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.

An Unexplored Role for MMP-7 (Matrix Metalloproteinase-7) in Promoting Gut Permeability After Ischemic Stroke

Poststroke infections are common complications of stroke and are highly associated with poor outcomes for patients. Stroke induces profound immunodepression coupled with alterations to autonomic signaling, which together render the body more susceptible to infection from without (nosocomial/community-acquired infection) and from within (commensal bacterial infection). Critical to the hypothesis of commensal infection is the phenomenon of poststroke gut permeability and gut dysbiosis. Few studies have provided adequate explanations for the mechanisms underlying the molecular alterations that produce a more permeable gut and perturbed gut microbiota after stroke. A dysregulation in the production of matrix MMP-7 (metalloproteinase-7) may play a critical role in the progression of gut permeability after stroke. By cleaving junctional and extracellular matrix proteins, MMP-7 is capable of compromising gut barrier integrity. Because of MMP-7's unique abundance in the small intestine and its capacity to be induced in states of bacterial invasion and inflammation, along with its unique degradative capability, MMP-7 may be crucially important to the progression of gut permeability after ischemic stroke.

Interactions between the Autonomic Nervous System and the Immune System after Stroke

Acute stroke is one of the leading causes of morbidity and mortality worldwide. Stroke-induced immune-inflammatory response occurs in the perilesion areas and the periphery. Although stroke-induced immunosuppression may alleviate brain injury, it hinders brain repair as the immune-inflammatory response plays a bidirectional role after acute stroke. Furthermore, suppression of the systemic immune-inflammatory response increases the risk of life-threatening systemic bacterial infections after acute stroke. Therefore, it is essential to explore the mechanisms that underlie the stroke-induced immune-inflammatory response. Autonomic nervous system (ANS) activation is critical for regulating the local and systemic immune-inflammatory responses and may influence the prognosis of acute stroke. We review the changes in the sympathetic and parasympathetic nervous systems and their influence on the immune-inflammatory response after stroke. Importantly, this article summarizes the mechanisms on how ANS regulates the immune-inflammatory response through neurotransmitters and their receptors in immunocytes and immune organs after stroke. To facilitate translational research, we also discuss the promising therapeutic approaches modulating the activation of the ANS or the immune-inflammatory response to promote neurologic recovery after stroke. © 2022 American Physiological Society. Compr Physiol 12:3665-3704, 2022.

Are beta blockers effective in preventing stroke associated infections? - a systematic review and meta-analysis

BACKGROUND

Excessive sympathoexcitation could lead to stroke associated infection. Inhibiting sympathetic excitation may reduce the infection risk after stroke. Thus, the present study aimed to determine the protective effect of beta blockers on stroke associated infection through systematic review and meta-analysis.

METHODS

A systematic search of multiple databases were performed up to February 2022. The included studies required beta blockers therapy in stroke patients and assessed the incidence of stroke-associated infections. Outcomes of interest included infections, pneumonia, urinary tract infection and sepsis. Random-effects model was used for analysis. Heterogeneity was evaluated using I2 statistics and publication bias was evaluated by the funnel plot.

RESULT

A total of 83 potentially relevant publications was identified in the initial search. Six studies met the inclusion criteria for meta-analysis. The risk of bias in the included articles satisfies the quality requirement of meta-analysis. No significant associations between beta blockers therapy and the prevention of stroke associated infection, stroke associated pneumonia and septicemia were found, However, subgroup analyses revealed an association between beta blockers treatment and the increased risk of post-stroke urinary tract infection or stroke associated pneumonia in some stroke patients (OR = 1.69 [1.33, 2.14], P < 0.0001; OR = 1.85 [1.51, 2.26], P < 0.0001).

CONCLUSION

Due to the lack of robust evidence, this meta-analysis may not support the preventive effect of beta blockers on stroke associated infection. But beta blockers treatment may be associated with development of post-stroke urinary tract infection and stroke associated pneumonia in some stroke patients.

Immune Pathways in Etiology, Acute Phase, and Chronic Sequelae of Ischemic Stroke

Inflammation and immune mechanisms are crucially involved in the pathophysiology of the development, acute damage cascades, and chronic course after ischemic stroke. Atherosclerosis is an inflammatory disease, and, in addition to classical risk factors, maladaptive immune mechanisms lead to an increased risk of stroke. Accordingly, individuals with signs of inflammation or corresponding biomarkers have an increased risk of stroke. Anti-inflammatory drugs, such as IL (interleukin)-1β blockers, methotrexate, or colchicine, represent attractive treatment strategies to prevent vascular events and stroke. Lately, the COVID-19 pandemic shows a clear association between SARS-CoV2 infections and increased risk of cerebrovascular events. Furthermore, mechanisms of both innate and adaptive immune systems influence cerebral damage cascades after ischemic stroke. Neutrophils, monocytes, and microglia, as well as T and B lymphocytes each play complex interdependent roles that synergize to remove dead tissue but also can cause bystander injury to intact brain cells and generate maladaptive chronic inflammation. Chronic systemic inflammation and comorbid infections may unfavorably influence both outcome after stroke and recurrence risk for further stroke. In addition, stroke triggers specific immune depression, which in turn can promote infections. Recent research is now increasingly addressing the question of the extent to which immune mechanisms may influence long-term outcome after stroke and, in particular, cause specific complications such as poststroke dementia or even poststroke depression.

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.

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.

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.

Prophylactic Antibiotics, the Mediator of Post-Stroke Infections: A Systematic Review

Infections frequently complicate an acute stroke and have been associated with an unfavorable prognosis among patients. The use of prophylactic antibiotics seems rational, however, its efficacy has remained obscure. This systematic review aims to offer more clarity to this established dilemma. PubMed and Google Scholar were explored to gain access to studies on post-stroke infection. A systematic review was carried out to analyze how profitable it would be to offer preventive antibiotics immediately after an acute stroke. Five randomized control trials were obtained and analyzed the efficacy of antibiotics in acute stroke according to their intrinsic effects on the infection rate, functionality, and mortality benefits. Based on our findings, we discovered that antibiotics reduce the onset of early infections, especially urinary tract infections, but have absolutely no effect on the functionality and offer no mortality benefit. These results were emphatically shown in two large, open-labeled randomized controlled trials involved in this systematic review. Prophylactic antibiotics provide no additional benefits to the standard of care and should not be used following an acute stroke. They may decrease the incidence of acute infections, especially urinary tract infections, but have no effects on functional outcome and mortality.

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.

A hyperacute immune map of ischaemic stroke patients reveals alterations to circulating innate and adaptive cells

Systemic immune changes following ischaemic stroke are associated with increased susceptibility to infection and poor patient outcome due to their role in exacerbating the ischaemic injury and long-term disability. Alterations to the abundance or function of almost all components of the immune system post-stroke have been identified, including lymphocytes, monocytes and granulocytes. However, subsequent infections have often confounded the identification of stroke-specific effects. Global understanding of very early changes to systemic immunity is critical to identify immune targets to improve clinical outcome. To this end, we performed a small, prospective, observational study in stroke patients with immunophenotyping at a hyperacute time point (< 3 h) to explore early changes to circulating immune cells. We report, for the first time, decreased frequencies of type 1 conventional dendritic cells (cDC1), haematopoietic stem and progenitor cells (HSPCs), unswitched memory B cells and terminally differentiated effector memory T cells re-expressing CD45RA (TEMRA). We also observed concomitant alterations to human leucocyte antigen D-related (HLA-DR), CD64 and CD14 expression in distinct myeloid subsets and a rapid activation of CD4+ T cells based on CD69 expression. The CD69+ CD4+ T cell phenotype inversely correlated with stroke severity and was associated with naive and central memory T (TCM) cells. Our findings highlight early changes in both the innate and adaptive immune compartments for further investigation as they could have implications the development of post-stroke infection and poorer patient outcomes.

Autonomic nervous system activity and the risk of nosocomial infection in critically ill patients with brain injury

PURPOSE

Nosocomial infection contributes to adverse outcome after brain injury. This study investigates whether autonomic nervous system activity is associated with a decreased host immune response in patients following stroke or traumatic brain injury (TBI).

METHODS

A prospective study was performed in adult patients with TBI or stroke who were admitted to the Intensive Care Unit of our tertiary university hospital between 2013 and 2016. Heart rate variability (HRV) was recorded daily and assessed for autonomic nervous system activity. Outcomes were nosocomial infections and immunosuppression, which was assessed ex vivo using whole blood stimulations with plasma of patients with infections, matched non-infected patients and healthy controls.

RESULTS

Out of 64 brain injured patients, 23 (36%) developed an infection during their hospital stay. The ability of brain injured patients to generate a host response to the bacterial endotoxin lipopolysaccharides (LPS) was diminished compared to healthy controls (p < 0.001). Patients who developed an infection yielded significantly lower TNF-α values (86 vs 192 pg/mL, p = 0.030) and a trend towards higher IL-10 values (122 vs 84 pg/mL, p = 0.071) following ex vivo whole blood stimulations when compared to patients not developing an infection. This decreased host immune response was associated with altered admission HRV values. Brain injured patients who developed an infection showed increased normalized high-frequency power compared to patients not developing an infection (0.54 vs 0.36, p = 0.033), whereas normalized low-frequency power was lower in infected patients (0.46 vs 0.64, p = 0.033).

CONCLUSION

Brain injured patients developing a nosocomial infection show parasympathetic predominance in the acute phase following brain injury, reflected by alterations in HRV, which parallels a decreased ability to generate an immune response to stimulation with LPS.

[Pulmonary insufficiency in acute stroke: risk factors and mechanisms of development]

Various degrees of pulmonary insufficiency (PI) (PaO₂ ≤60 mm Hg, SaO₂ ≤90%) are diagnosed in most of patients with severe acute stroke (AS). Frequency and severity of PI positively correlates with the severity of AS. PI worsens patient's condition, prolongs the hospitalization period, and increases the probability of fatal outcome. Early clinical signs of PI may be undiagnosed due to the severity of stroke and thus not treated. The initiating pathogenic mechanism of PI is stress-related activation of sympathetic nervous system (SNS) and systemic immunosuppression. In severe stroke with mass effect, the rapid and significant increase in intracranial pressure may additionally activate the SNS. Risk factors of PI include older age, previous pulmonary disease, prolonged supine position, respiratory muscle dysfunction, apnea, and concomitant somatic diseases. Decompensation of somatic diseases leads to multiple stage reactions with facilitation of functional and morphologic changes in the pulmonary system, hypoxemia and hypoxia, promotes infectious complications and multiple organ failure and worsens neurological outcome. Diagnosis and treatment of PI in AS decreases mortality and improves rehabilitation prognosis.

The Association of Autonomic Nervous System Function With Ischemic Stroke, and Treatment Strategies

Acute ischemic stroke, especially minor stroke, and transient ischemic attack have high risks of recurrence and exacerbation into severe ischemic strokes. It remains challenging to perform risk stratification and screen high-risk groups for initiation of early treatment in these patients. Moreover, with the growing population of patients with chronic small vessel disease, the mechanisms and clinical implications require further investigation. Traditional tools such as the ABCD2 score (age, blood pressure, clinical features, duration of symptoms, diabetes) have only moderate predictive value in patients with transient ischemic attack or minor stroke. By contrast, measurement of changes in heart rate variability (HRV) is an important and novel tool for risk stratification and outcome prediction in patients with cardiovascular diseases, as it reflects the overall level of autonomic nervous system dysfunction. Thus, abnormal HRV may be useful for prognosis and improve stratification of stroke patients with diverse risks. HRV may also partially explain autonomic nervous dysfunction and other manifestations during the process of chronic cerebral small vessel disease. In summary, measurement of HRV may contribute to early initiation of interventions in acute or chronic stroke patients using novel treatments involving rebalancing of autonomic nervous system function.

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.

Healthcare-Associated Infections in the Neurocritical Care Unit

PURPOSE OF REVIEW

This article summarizes updated data and knowledge on healthcare-associated infections in the neurocritical care unit, with a focus on central nervous system infections and systemic infectious complications in patients with acute brain disease. It also reviews the concept of brain injury-induced immune modulation, an underlying mechanism to explain why the neuro-ICU population is particularly susceptible to infections.

RECENT FINDINGS

Healthcare-associated infections in the neuro-ICU are common: up to 40 % of meningitides in the developed world are now healthcare-associated. The number of gram-negative infections is rising. New diagnostic approaches attempt to aid in the diagnosis of healthcare-associated meningitis and ventriculitis. Healthcare-associated infections in the neurocritical care unit remain a challenge for diagnosis, treatment, and prevention. Gaining a better understanding of at-risk patients and development of preventative strategies will be the goal for future investigation.

Augmented β2-adrenergic signaling dampens the neuroinflammatory response following ischemic stroke and increases stroke size

Background

Ischemic stroke provokes a neuroinflammatory response and simultaneously promotes release of epinephrine and norepinephrine by the sympathetic nervous system. This increased sympathetic outflow can act on β2-adrenergic receptors expressed by immune cells such as brain-resident microglia and monocyte-derived macrophages (MDMs), but the effect on post-stroke neuroinflammation is unknown. Thus, we investigated how changes in β2-adrenergic signaling after stroke onset influence the microglia/MDM stroke response, and the specific importance of microglia/MDM β2-adrenergic receptors to post-stroke neuroinflammation.

Methods

To investigate the effects of β2-adrenergic receptor manipulation on post-stroke neuroinflammation, we administered the β2-adrenergic receptor agonist clenbuterol to mice 3 h after the onset of photothrombotic stroke. We immunostained to quantify microglia/MDM numbers and proliferation and to assess morphology and activation 3 days later. We assessed stroke outcomes by measuring infarct volume and functional motor recovery and analyzed gene expression levels of neuroinflammatory molecules. Finally, we evaluated changes in cytokine expression and microglia/MDM response in brains of mice with selective knockout of the β2-adrenergic receptor from microglia and monocyte-lineage cells.

Results

We report that clenbuterol treatment after stroke onset causes enlarged microglia/MDMs and impairs their proliferation, resulting in reduced numbers of these cells in the peri-infarct cortex by 1.7-fold at 3 days after stroke. These changes in microglia/MDMs were associated with increased infarct volume in clenbuterol-treated animals. In mice that had the β2-adrenergic receptor specifically knocked out of microglia/MDMs, there was no change in morphology or numbers of these cells after stroke. However, knockdown of β2-adrenergic receptors in microglia and MDMs resulted in increased expression of TNFα and IL-10 in peri-infarct tissue, while stimulation of β2-adrenergic receptors with clenbuterol had the opposite effect, suppressing TNFα and IL-10 expression.

Conclusions

We identified β2-adrenergic receptor signaling as an important regulator of the neuroimmune response after ischemic stroke. Increased β2-adrenergic signaling after stroke onset generally suppressed the microglia/MDM response, reducing upregulation of both pro- and anti-inflammatory cytokines, and increasing stroke size. In contrast, diminished β2-adrenergic signaling in microglia/MDMs augmented both pro- and anti-inflammatory cytokine expression after stroke. The β2-adrenergic receptor may therefore present a therapeutic target for improving the post-stroke neuroinflammatory and repair process.