Prevention of stroke-associated pneumonia: where next?

Does stroke-associated pneumonia play an important role on risk of in-hospital mortality associated with severe stroke? A four-way decomposition analysis of a national cohort of stroke patients

BACKGROUND

Severe strokes and stroke-associated pneumonia (SAP) have long been associated with poorer patient health outcomes, for example, in-hospital mortality. However, it is unclear what role SAP plays in the risk of in-hospital mortality associated with a severe stroke at admission.

METHODS

Using the Sentinel Stroke National Audit Program data on stroke admissions (2013-2018) in England and Wales, we modeled the "total" effect for severe stroke on risk of in-hospital mortality. Through four-way decomposition methodology, we broke down the "total" observed risk into four components. The direct "severity on outcome only" effect, the pure indirect effect of severity mediated via SAP only, the interaction between severity and SAP when mediation is not present, and when mediation via SAP is present.

RESULTS

Of 339,139 stroke patients included, 9.4% had SAP and 15.6% died in hospital. Of SAP patients, 45% died versus 12% of non-SAP patients. The risk ratio for in-hospital mortality associated with severe versus mild/moderate stroke (i.e. total effect) was 4.72 (95% confidence interval: 4.60-4.85). Of this, 43%-increased risk was due to additive SAP interaction, this increased to 50% for "very severe" stroke. The remaining excess relative risk was due to the direct severity on outcome effect only, that is, there was no evidence here for a mediation effect via SAP.

CONCLUSION

SAP was associated with a higher mortality in severe stroke patients. Prioritizing SAP prevention in severe stroke patients may improve in-hospital survival. Our results suggest that in severe stroke patients avoiding SAP might result in an up to 43% reduction in mortality.

Reversal of the detrimental effects of social isolation on ischemic cerebral injury and stroke-associated pneumonia by inhibiting small intestinal T-cell migration into the brain and lung

Social isolation (ISO) is associated with an increased risk and poor outcomes of ischemic stroke. However, the roles and mechanisms of ISO in stroke-associated pneumonia (SAP) remain unclear. Adult male mice were single- or pair-housed with an ovariectomized female mouse and then subjected to transient middle cerebral artery occlusion. Isolated mice were treated with the natriuretic peptide receptor A antagonist A71915 or anti-gamma-delta (γδ) TCR monoclonal antibody, whereas pair-housed mice were treated with recombinant human atrial natriuretic peptide (rhANP). Subdiaphragmatic vagotomy (SDV) was performed 14 days before single- or pair-housed conditions. We found that ISO significantly worsened brain and lung injuries relative to pair housing, which was partially mediated by elevated interleukin (IL)-17A levels and the migration of small intestine-derived inflammatory γδ T-cells into the brain and lung. However, rhANP treatment or SDV could ameliorate ISO-exacerbated post-stroke brain and lung damage by reducing IL-17A levels and inhibiting the migration of inflammatory γδ T-cells into the brain and lung. Our results suggest that rhANP mitigated ISO-induced exacerbation of SAP and ischemic cerebral injury by inhibiting small intestine-derived γδ T-cell migration into the lung and brain, which could be mediated by the subdiaphragmatic vagus nerve.

Aberrant branched-chain amino acid accumulation along the microbiota-gut-brain axis: Crucial targets affecting the occurrence and treatment of ischaemic stroke

BACKGROUND AND PURPOSE

Although increasing evidence illustrated that the bidirectional communication between the brain and the gut is closely related to the occurrence of various complex diseases. Limited effort has been made to explore the influence of intestinal flora on the risk of ischaemic stroke. The present study aims to identify microbiota and specialized microbiota metabolites related to the occurrence and treatment of ischaemic stroke.

EXPERIMENTAL APPROACH

The role of microbiota in the occurrence and the treatment of ischaemic stroke was evaluated on ischaemia/reperfusion (I/R), pseudo-germ-free and faecal transplantation animals. The target microbiota and specialized metabolites were identified by comparing their distribution in flora and metabolomic profiles in ischaemic stroke patients and animals with compared with healthy controls. The effects and mechanisms involved of the targeted metabolites in ischaemic stroke were explored in ischaemia/reperfusion rats, hypoxia/reoxygenation PC12 cells and LPS-induced inflammatory BV2 cells.

KEY RESULTS

Both ischaemic stroke patients and I/R rats had significant accumulation of branched-chain amino acids, which were closely associated with gut microflora dysbiosis and the development of ischaemic stroke. Lactobacillus helveticus (L.hel) and Lactobacillus brevis (L.bre) are identified as the microbiota most affected by ischaemia/reperfusion modelling and treatment. L.hel and L.bre colonization exhibited significant neuroprotective activity and could greatly alleviate the accumulation of branched-chain amino acids. In addition, branched-chain amino acid (BCAA) accumulation was shown to exacerbate microglia-induced neuroinflammation by activating AKT/STAT3/NF-κB signalling.

CONCLUSION AND IMPLICATIONS

Our findings demonstrated the crucial role of intestinal flora and microbiota metabolites in the occurrence and treatment of ischaemic stroke.

Interventional strategies for ischemic stroke based on the modulation of the gut microbiota

The microbiota-gut-brain axis connects the brain and the gut in a bidirectional manner. The organism's homeostasis is disrupted during an ischemic stroke (IS). Cerebral ischemia affects the intestinal flora and microbiota metabolites. Microbiome dysbiosis, on the other hand, exacerbates the severity of IS outcomes by inducing systemic inflammation. Some studies have recently provided novel insights into the pathogenesis, efficacy, prognosis, and treatment-related adverse events of the gut microbiome in IS. In this review, we discussed the view that the gut microbiome is of clinical value in personalized therapeutic regimens for IS. Based on recent non-clinical and clinical studies on stroke, we discussed new therapeutic strategies that might be developed by modulating gut bacterial flora. These strategies include dietary intervention, fecal microbiota transplantation, probiotics, antibiotics, traditional Chinese medication, and gut-derived stem cell transplantation. Although the gut microbiota-targeted intervention is optimistic, some issues need to be addressed before clinical translation. These issues include a deeper understanding of the potential underlying mechanisms, conducting larger longitudinal cohort studies on the gut microbiome and host responses with multiple layers of data, developing standardized protocols for conducting and reporting clinical analyses, and performing a clinical assessment of multiple large-scale IS cohorts. In this review, we presented certain opportunities and challenges that might be considered for developing effective strategies by manipulating the gut microbiome to improve the treatment and prevention of ischemic stroke.

Gut microbiota composition reflects disease progression, severity and outcome, and dysfunctional immune responses in patients with hypertensive intracerebral hemorrhage

OBJECTIVE

In this study, we aimed to explore the alterations in gut microbiota composition and cytokine responses related to disease progression, severity, and outcomes in patients with hypertensive intracerebral hemorrhage (ICH).

METHODS

Fecal microbiota communities of 64 patients with ICH, 46 coronary heart disease controls, and 23 healthy controls were measured by sequencing the V3-V4 region of the 16S ribosomal RNA (16S rRNA) gene. Serum concentrations of a broad spectrum of cytokines were examined by liquid chips and ELISA. Relationships between clinical phenotypes, microbiotas, and cytokine responses were analyzed in the group with ICH and stroke-associated pneumonia (SAP), the major complication of ICH.

RESULTS

In comparison with the control groups, the gut microbiota of the patients with ICH had increased microbial richness and diversity, an expanded spectrum of facultative anaerobes and opportunistic pathogens, and depletion of anaerobes. Enterococcus enrichment and Prevotella depletion were more significant in the ICH group and were associated with the severity and functional outcome of ICH. Furthermore, Enterococcus enrichment and Prevotella depletion were also noted in the SAP group in contrast to the non-SAP group. Enterococci were also promising factors in the prognosis of ICH. The onset of ICH induced massive, rapid activation of the peripheral immune system. There were 12 cytokines (Eotaxin, GM-CSF, IL-8, IL-9, IL-10, IL-12p70, IL-15, IL-23, IL-1RA, IP-10, RANTES, and TNF-α) changed significantly with prolongation of ICH, and the Th2 responses correlated with the 90-day outcomes. Cytokines TNF-α, IP-10, IL-1RA, IL-8, IL-18, and MIP-1β in SAP group significantly differed from non-SAP group. Among these cytokines, only IP-10 levels decreased in the SAP group. Enterococcus was positively associated with IL-1RA and negatively associated with IP-10, while Prevotella was inversely associated in both the ICH and SAP groups.

CONCLUSION

This study revealed that gut dysbiosis with enriched Enterococcus and depleted Prevotella increased the risk of ICH and subsequently SAP. The altered gut microbiota composition and serum cytokine profiles are potential biomarkers that reflect the inciting physiologic insult/stress involved with ICH.

Microbiology and Outcomes of Institutionalized Patients With Stroke-Associated Pneumonia: An Observational Cohort Study

Background: The attributable mortality and microbial etiology of stroke-associated pneumonia (SAP) vary among different studies and were inconsistent. Purpose: To determine the microbiology and outcomes of SAP in the lower respiratory tract (LRT) for patients with invasive mechanical ventilation (MV). Methods: In this observational study, included patients were divided into SAP and non-SAP based on a comprehensive analysis of symptom, imaging, and laboratory results. Baseline characteristics, clinical characteristics, microbiology, and outcomes were recorded and evaluated. Results: Of 200 patients, 42.5% developed SAP after the onset of stroke, and they had a lower proportion of non-smokers (p = 0.002), lower GCS score (p < 0.001), higher serum CRP (p < 0.001) at ICU admission, and a higher proportion of males (p < 0.001) and hypertension (p = 0.039) than patients with non-SAP. Gram-negative aerobic bacilli were the predominant organisms isolated (78.8%), followed by Gram-positive aerobic cocci (29.4%). The main pathogens included K. pneumoniae, S. aureus, H. influenzae, A. baumannii, P. aeruginosa, E. aerogenes, Serratia marcescens, and Burkholderia cepacia. SAP prolonged length of MV (p < 0.001), duration of ICU stay (p < 0.001) and hospital stay (p = 0.027), shortened MV-free days by 28 (p < 0.001), and caused elevated vasopressor application (p = 0.001) and 60-day mortality (p = 0.001). Logistic regression analysis suggested that patients with coma (p < 0.001) have a higher risk of developing SAP. Conclusion: The microbiology of SAP is similar to early phase of HAP and VAP. SAP prolongs the duration of MV and length of ICU and hospital stays, but also markedly increases 60-day mortality.

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.

Individualized Prediction Of Stroke-Associated Pneumonia For Patients With Acute Ischemic Stroke

Background

Stroke-associated pneumonia (SAP) is a serious and common complication in stroke patients.

Purpose

We aimed to develop and validate an easy-to-use model for predicting the risk of SAP in acute ischemic stroke (AIS) patients.

Patients and methods

The nomogram was established by univariate and multivariate binary logistic analyses in a training cohort of 643 AIS patients. The prediction performance was determined based on the receiver operating characteristic curve (ROC) and calibration plots in a validation cohort (N=340). Individualized clinical decision-making was conducted by weighing the net benefit in each AIS patient by decision curve analysis (DCA).

Results

Seven predictors, including age, NIHSS score on admission, atrial fibrillation, nasogastric tube intervention, mechanical ventilation, fibrinogen, and leukocyte count were incorporated to construct the nomogram model. The nomogram showed good predictive performance in ROC analysis [AUROC of 0.845 (95% CI: 0.814-0.872) in training cohort, and 0.897 (95% CI: 0.860-0.927) in validation cohort], and was superior to the A²DS², ISAN, and PANTHERIS scores. Furthermore, the calibration plots showed good agreement between actual and nomogram-predicted SAP probabilities, in both training and validation cohorts. The DCA confirmed that the SAP nomogram was clinically useful.

Conclusion

Our nomogram may provide clinicians with a simple and reliable tool for predicting SAP based on routinely available data. It may also assist clinicians with respect to individualized treatment decision-making for patients differing in risk level.

Brain-gut axis after stroke

Stroke leads to inflammatory and immune response in the brain and immune organs. The gut or gastrointestinal tract is a major immune organ equipped with the largest pool of immune cells representing more than 70% of the entire immune system and the largest population of macrophages in the human body. The bidirectional communication between the brain and the gut is commonly known as brain–gut or gut–brain axis. Stroke often leads to gut dysmotility, gut microbiota dysbiosis, “leaky” gut, gut hemorrhage, and even gut-origin sepsis, which is often associated with poor prognosis. Emerging evidence suggests that gut inflammatory and immune response plays a key role in the pathophysiology of stroke and may become a key therapeutic target for its treatment. Ischemic brain tissue produces damage-associated molecular patterns to initiate innate and adaptive immune response both locally and systemically through the specialized pattern-recognition receptors (e.g., toll-like receptors). After stroke, innate immune cells including neutrophils, microglia or macrophages, mast cells, innate lymphocytes (IL-17 secreting γδ T-cell), and natural killer T-cell respond within hours, followed by the adaptive immune response through activation of T and B lymphocytes. Subpopulations of T-cells can help or worsen ischemic brain injury. Pro-inflammatory Th1, Th17, and γδ T-cells are often associated with increased inflammatory damage, whereas regulatory T-cells are known to suppress postischemic inflammation by increasing the secretion of anti-inflammatory cytokine IL-10. Although known to play a key role, research in the gut inflammatory and immune response after stroke is still in its initial stage. A better understanding of the gut inflammatory and immune response after stroke may be important for the development of effective stroke therapies. The present review will discuss recent advances in the studies of the brain–gut axis after stroke, the key issues to be solved, and the future directions.

Elevated C-reactive protein increases diagnostic accuracy of algorithm-defined stroke-associated pneumonia in afebrile patients

BACKGROUND AND AIM

Pyrexia-dependent clinical algorithms may under or overdiagnose stroke-associated pneumonia. This study investigates whether inclusion of elevated C-reactive protein as a criterion improves diagnosis.

METHODS

The contribution of C-reactive protein  ≥30 mg/l as an additional criterion to a Centers for Disease Control and Prevention-based algorithm incorporating pyrexia with chest signs and leukocytosis and/or chest infiltrates to diagnose stroke-associated pneumonia was assessed in 1088 acute stroke patients from 37 UK stroke units. The sensitivity, specificity, and positive predictive value of different approaches were assessed using adjudicated stroke-associated pneumonia as the reference standard.

RESULTS

Adding elevated C-reactive protein to all algorithm criteria did not increase diagnostic accuracy compared with the algorithm alone against adjudicated stroke-associated pneumonia (sensitivity 0.74 (95% CI 0.65-0.81) versus 0.72 (95% CI 0.64-0.80), specificity 0.97 (95% CI 0.96-0.98) for both; kappa 0.70 (95% CI 0.63-0.77) for both). In afebrile patients (n = 965), elevated C-reactive protein with chest and laboratory findings had sensitivity of 0.84 (95% CI 0.67-0.93), specificity of 0.99 (95% CI 0.98-1.00), and kappa 0.80 (95% CI 0.70-0.90). The modified algorithm of pyrexia or elevated C-reactive protein and chest signs with infiltrates or leukocytosis had sensitivity of 0.94 (95% CI 0.87-0.97), specificity of 0.96 (95% CI 0.94-0.97), and kappa of 0.88 (95% CI 0.84-0.93) against adjudicated stroke-associated pneumonia.

CONCLUSIONS

An algorithm consisting of pyrexia or C-reactive protein ≥30 mg/l, positive chest signs, leukocytosis, and/or chest infiltrates has high accuracy and can be used to standardize stroke-associated pneumonia diagnosis in clinical or research settings.

TRIAL REGISTRATION

http://www.isrctn.com/ISRCTN37118456.

Effectiveness and Safety of Antibiotics for Preventing Pneumonia and Improving Outcome after Acute Stroke: Systematic Review and Meta-analysis

BACKGROUND

Pneumonia is a common complication after stroke which increases morbidity and mortality. This systematic review was conducted to evaluate the efficacy and safety of antibiotics for the prevention of pneumonia after acute stroke.

METHODS

Medline, EMBASE, and Cochrane databases were searched for randomized controlled trials comparing preventive antibiotics to placebo or no antibiotics after acute stroke. The primary outcome was poststroke pneumonia. Secondary outcomes were all infections, urinary tract infections, death, dependency, length of hospital stay, and adverse events. Treatment effects were summarized using random effects metaanalysis.

RESULTS

Six trials (4111 patients) were eligible for inclusion. The median National Institute of Health Stroke Scale score in included trials ranged from 5 to 16.5. The proportion of dysphagia ranged from 26% to 100%. Preventive antibiotics were commenced within 48hours after acute stroke. Compared to control, preventive antibiotics reduced the risk of poststroke pneumonia (RR .75, 95%CI ·.57-.99), and all infections (RR .58, 95%CI .48-.69). There was no significant difference in the risks of dependency (RR 0.99, 95%CI 0·80-1·11), or mortality (RR .96, 95%CI .78-1.19) between the preventive antibiotics and control groups. Preventive antibiotics did not increase the risk of elevated liver enzymes (RR 1.20, 95% CI .97-1.49). Preventive antibiotics had uncertain effects on the risks of other adverse events.

CONCLUSION

Preventive antibiotics reduced the risk of post-stroke pneumonia. However, there is insufficient evidence to currently recommend routine use of preventive antibiotics after acute stroke.

Stroke-induced immunodepression and dysphagia independently predict stroke-associated pneumonia - The PREDICT study

Stroke-associated pneumonia is a frequent complication after stroke associated with poor outcome. Dysphagia is a known risk factor for stroke-associated pneumonia but accumulating evidence suggests that stroke induces an immunodepressive state increasing susceptibility for stroke-associated pneumonia. We aimed to confirm that stroke-induced immunodepression syndrome is associated with stroke-associated pneumonia independently from dysphagia by investigating the predictive properties of monocytic HLA-DR expression as a marker of immunodepression as well as biomarkers for inflammation (interleukin-6) and infection (lipopolysaccharide-binding protein). This was a prospective, multicenter study with 11 study sites in Germany and Spain, including 486 patients with acute ischemic stroke. Daily screening for stroke-associated pneumonia, dysphagia and biomarkers was performed. Frequency of stroke-associated pneumonia was 5.2%. Dysphagia and decreased monocytic HLA-DR were independent predictors for stroke-associated pneumonia in multivariable regression analysis. Proportion of pneumonia ranged between 0.9% in the higher monocytic HLA-DR quartile (≥21,876 mAb/cell) and 8.5% in the lower quartile (≤12,369 mAb/cell). In the presence of dysphagia, proportion of pneumonia increased to 5.9% and 18.8%, respectively. Patients without dysphagia and normal monocytic HLA-DR expression had no stroke-associated pneumonia risk. We demonstrate that dysphagia and stroke-induced immunodepression syndrome are independent risk factors for stroke-associated pneumonia. Screening for immunodepression and dysphagia might be useful for identifying patients at high risk for stroke-associated pneumonia.

Vinpocetine Inhibits NF-κB-Dependent Inflammation in Acute Ischemic Stroke Patients

Immunity and inflammation play critical roles in the pathogenesis of acute ischemic stroke. Therefore, immune intervention, as a new therapeutic strategy, is worthy of exploration. Here, we tested the inflammation modulator, vinpocetine, for its effect on the outcomes of stroke. For this multi-center study, we recruited 60 patients with anterior cerebral circulation occlusion and onset of stroke that had exceeded 4.5 h but lasted less than 48 h. These patients, after random division into two groups, received either standard management alone (controls) or standard management plus vinpocetine (30 mg per day intravenously for 14 consecutive days, Gedeon Richter Plc., Hungary). Vinpocetine treatment did not change the lymphocyte count; however, nuclear factor kappa-light-chain-enhancer of activated B cell activation was inhibited as seen not only by the increased transcription of IκBα mRNA but also by the impeded phosphorylation and degradation of IκBα and subsequent induction of pro-inflammatory mediators. These effects led to significantly reduced secondary lesion enlargement and an attenuated inflammation reaction. Compared to controls, patients treated with vinpocetine had a better recovery of neurological function and improved clinical outcomes during the acute phase and at 3-month follow-up. These findings identify vinpocetine as an inflammation modulator that could improve clinical outcomes after acute ischemic stroke. This study also indicated the important role of immunity and inflammation in the pathogenesis of acute ischemic stroke and the significance of immunomodulatory treatment.

CLINICAL TRIAL REGISTRATION INFORMATION

www.clinicaltrials.gov . Identifier: NCT02878772.

Comparison of the diagnostic utility of physician-diagnosed with algorithm-defined stroke-associated pneumonia

OBJECTIVE

Diagnosing stroke-associated pneumonia (SAP) is challenging and may result in inappropriate antibiotic use or confound research outcomes. This study evaluates the diagnostic accuracy of algorithm-defined versus physician-diagnosed SAP in 1088 patients who had dysphagic acute stroke from 37 UK stroke units between 21 April 2008 and 17 May 2014.

METHODS

SAP in the first 14 days was diagnosed by a criteria-based algorithm applied to blinded patient data and independently by treating physicians. Patients in whom diagnoses differed were reassigned following blinded adjudication of individual patient records. The sensitivity, specificity, positive predictive value (PPV) and diagnostic OR of algorithmic and physician diagnosis of SAP were assessed using adjudicated SAP as the reference standard. Agreement was assessed using the κ statistic.

RESULTS

Physicians diagnosed SAP in 176/1088 (16%) and the algorithm in 123/1088 (11.3%) patients. Diagnosis agreed in 885/1088 (81.3%) patients (κ 0.22 (95% CI 0.14 to 0.29)). On a blinded review, 129/1088 (11.8%) patients were adjudicated as patients with SAP. The algorithm and the physicians had high specificity (97% (95% CI 96% to 98%) and 90% (95% CI 88% to 92%), respectively) but only moderate sensitivity (72% (95% CI 64% to 80%) and 65% (95% CI 56% to 73%), respectively) in diagnosing SAP. The algorithm showed better PPV (76% (95% CI 67% to 83%) vs 48% (95% CI 40% to 55%)), diagnostic OR (80 (95% CI 42 to 136) vs 18 (95% CI 12 to 27)) and agreement (κ 0.70 (95% CI 0.63 to 0.78) vs 0.48 (95% CI 0.41 to 0.54)) than physician diagnosis with adjudicated SAP.

CONCLUSIONS

Algorithm-based approaches can standardise SAP diagnosis for clinical practice and research.

TRIAL REGISTRATION NUMBER

ISRCTN37118456; Post-results.

The Gut Microbiome as Therapeutic Target in Central Nervous System Diseases: Implications for Stroke

Research on commensal microbiota and its contribution to health and disease is a new and very dynamically developing field of biology and medicine. Recent experimental and clinical investigations underscore the importance of gut microbiota in the pathogenesis and course of stroke. Importantly, microbiota may influence the outcome of cerebral ischemia by modulating central nervous system antigen-specific immune responses. In this review we summarize studies linking gut microbiota with physiological function and disorders of the central nervous system. Based on these insights we speculate about targeting the gut microbiome in order to treat stroke.

Association between nasogastric tubes, pneumonia, and clinical outcomes in acute stroke patients

OBJECTIVE

To investigate whether nasogastric tubes (NGTs) increase poststroke pneumonia (PSP), mortality, or poor outcomes in nil-by-mouth acute stroke patients.

METHODS

This study analyzed prespecified outcomes of PSP at 14 days and mortality and function measured by the modified Rankin Scale at 90 days in 1,217 nil-by-mouth stroke patients at ≤48 hours of symptom onset in a multicenter randomized controlled trial of preventive antibiotics between April 21, 2008, and May 17, 2014. Generalized mixed models adjusted for age, comorbidities, stroke type and severity, and quality of care were used. No patients were lost to follow-up at 14 days, and 36 (3%) were lost at 90 days.

RESULTS

Patients with NGT (298 of 1,217 [24.4%]) had more severe strokes (median NIH Stroke Scale score 17 vs 14, p = 0.0001) and impaired consciousness (39% vs 28%, p = 0.001). NGT did not increase PSP (43 of 298 [14.4%] vs 80 of 790 [10.1%], adjusted odds ratio [OR] 1.26 [95% confidence interval (CI) 0.78-2.03], p = 0.35) or 14- and 90-day mortality (33 of 298 [11.1%] vs 78 of 790 [9.9%], adjusted OR 1.10 [95% CI 0.67-1.78], p = 0.71; and 79 of 298 [26.5%] vs 152 of 790 [19.2%], adjusted OR 0.95 [95% CI 0.67-1.33], p = 0.75, respectively). Ninety-day modified Rankin Scale score distribution was comparable between groups (adjusted OR 1.14 [95% CI 0.87-1.56], p = 0.08). PSP independently increased 90-day mortality (40 of 123 [32.5%] vs 191 of 965 [19.8%], adjusted OR 1.71 [95% CI 1.11-2.65], p = 0.015) and was not prevented by antibiotics in patients with NGT (adjusted OR 1.1 [95% CI 0.89-1.54], p = 0.16).

CONCLUSIONS

Early NGT does not increase PSP incidence, mortality, or poor functional outcomes and can be used safely in acute stroke patients.

The reciprocal interaction of sympathetic nervous system and cAMP-PKA-NF-kB pathway in immune suppression after experimental stroke

BACKGROUND

Sympathetic nervous system(SNS) is involved in the mechanism of immune suppression after stroke. Furthermore, as the pro-inflammatory effect of nuclear factor kappa B(NF-kB) is inhibited after stroke, which is regulated by cyclic adenosine monophosphate(cAMP) and proteinkinase A(PKA). The cAMP-PKA-NF-kB pathway might play an important role in noradrenergic-mediated immune dysfunction.

AIM

The purpose of our research is to analyze how SNS interfere with the immune system after acute stroke and the underlying mechanism of cAMP-PKA-NF-kB pathway in regulating the inflammation.

METHODS

32 healthy male Sprague-Dawley rats were divided into 4 groups equally and randomly (1) Sham operation group; (2) middle cerebral artery occlusion; (MCAO) control group; (3) propranolol MCAO group; (4) isopropylarterenol sham group. 72h later after MCAO or sham operation, tumor necrosis factor-α(TNF-α)and interleukine-10(IL-10) in serum as well as cAMP, PKA and NF-kB in spleen cells were tested.

RESULTS

TNF-α decreased while IL-10 increased in serum after acute ischemia stroke (p<0.05). Meanwhile, the levels of cAMP and PKA in spleen both increased in MCAO model while the expression of NF-kB was inhibited (p<0.05). When propranolol was used to inhibit SNS, all of the results reversed (p<0.05). But the reversed results were still significantly different from the sham operation group (p<0.05). Isopropylarterenol administrated rats appeared the same trend as MCAO group when compared to the sham operation group (p<0.05). However, the differences still existed (p<0.05).

CONCLUSION

On account of the SNS activation after stroke, epinephrine activates the expression of cAMP, which further increases the level of PKA. Therefore, the level of nuclear factor NF-kB is down-regulated. Since the pro-inflammatory effect of NF-kB slacked, the immune system may be inhibited after stroke.