Stress Mediators and Immune Dysfunction in Patients with Acute Cerebrovascular Diseases

<div><p>Background</p><p>Post-stroke immune depression contributes to the development of infections which are major complications after stroke. Previous experimental and clinical studies suggested that humoral stress mediators induce immune dysfunction. However, prospective clinical studies testing this concept are missing and no data exists for other cerebrovascular diseases including intracerebral hemorrhage (ICH) and TIA.</p><p>Methods</p><p>We performed a prospective clinical study investigating 166 patients with TIA, ischemic and hemorrhagic stroke. We measured a broad panel of stress mediators, leukocyte subpopulations, cytokines and infection markers from hospital admission to day 7 and on follow-up after 2–3 months. Multivariate regression analyses detected independent predictors of immune dysfunction and bacterial infections. ROC curves were used to test the diagnostic value of these parameters.</p><p>Results</p><p>Only severe ischemic strokes and ICH increased some catecholamine metabolites, ACTH and cortisol levels. Immunodysfunction was eminent already on hospital admission after large brain lesions with lymphocytopenia as a key feature. None of the stress mediators was an independent predictor of lymphocytopenia or infections. However, lymphocytopenia on hospital admission was detected as an independent explanatory variable of later infections. NIHSSS and lymphocytopenia on admission were excellent predictors of infection.</p><p>Conclusions</p><p>Our results question the present pathophysiological concept of stress-hormone mediated immunodysfunction after stroke. Early lymphocytopenia was identified as an early independent predictor of post-stroke infections. Absence of lymphocytopenia may serve as a negative predictive marker for stratification for early antibiotic treatment.</p></div

Results of univariate binary logistic regression analysis for lymphocytes <13% on day 1.

<p>B: regression coefficient; OR: odds ratio; CI: confidence interval; Std. OR: odds ratio standardized for standard deviation of continuous predictors (e^B*SD). Total patients n = 136 (control patients excluded); patients without catecholamine treatment (w/o Norepi.) n = 109 (on day 1).</p

Results of multivariate binary logistic regression analyses for independent predictors of lymphocytes <13% on day 1.

<p>Variables in the model: Age, NIHSSS, volume, smoking, catecholamine treatment d1, noradrenalin, cortisol; method: forward (likelihood ratio), p(in) = 0.05, p(out) = 0.10.</p

Humoral stress response in patients with acute cerebrovascular diseases.

<p>Blood plasma concentrations of indicated catecholamines and metanephrines were analyzed in (<b>A</b>) all patients (n = 166) or (<b>B</b>) only in patients not receiving catecholamine treatment (n = 134). Urin excretion of noradrenalin, metanephrines and vanillylmandelic acid (VMA) within the first 24 h after admission was investigated (<b>C</b>) in all patients with cerebrovascular events (left) or after exclusion of patients receiving catecholamine treatment during the urine collection period (right). (<b>D</b>) To investigate the HPA-axis, blood plasma concentrations of ACTH and cortisol were measured at the indicated time points after cerebrovascular events and in control patients. Group differences for all parameters were analyzed by Kruskal-Wallis H-test and Dunn’s post hoc test. Data is presented as median and interquartile range. * indicates significant (p<0.05) difference of the indicated group compared to the control group; horizontal bars indicate significant differences among groups at the respective time point.</p

Results of univariate binary logistic regression analysis for bacterial infection d2–d7.

<p>B: regression coefficient; OR: odds ratio; CI: confidence interval; Std. OR: odds ratio standardized for standard deviation for continuous predictors (e^B*SD). Total patients n = 136 (control patients excluded); patients without catecholamine treatment (w/o Norepi.) n = 104 (during first week).</p

Infection markers and microbiological culture results.

<p>(<b>A</b>) The proportion of the positive infection markers febrile body temperature (>38°C), CRP>5 mg/l and hsPCT >0.1 ng/ml within the study cohorts is presented as percentage of the respective group. (<b>B</b>) The proportion of patients receiving antibiotic treatment is depicted for the first week after symptom onset (d2–d7, left panel) or for a new antibiotic treatment after hospital discharge until follow-up (FU) after 60–90d (right panel). (<b>C</b>) Bars depict the percentage of patients of the respective group with at least one pathological bacterial culture result during the first week after symptom onset (d2–d7) (cp. methods for definition). Data was tested using chi-squared tests and is presented as proportions per group. Horizontal lines indicate significant (p<0.05) group differences (chi-squared test).</p

Clinical characteristics of patients used for analysis in the control, transient ischemic attack (TIA), ischemic stroke (stroke) and intracerebral hemorrhage (ICH) group.

1<p>previous TIA, stroke or myocardial infarction;</p>2<p>phenprocoumon, rivaroxaban;</p>3<p>aspirin, aspirin+dipyridamole, clopidogrel;</p>4<p>clonidin, oxybutinin, inhalable β2-AR agonists, doxazosin, terazosin.</p><p>Metric data is shown as mean±SD, non-metric values as absolute numbers and percentage.</p>#<p>U test for stroke and ICH;</p>†<p>chi square test for TIA, stroke and ICH;</p>‡<p>chi square test for stroke and ICH.</p

Results of multivariate binary logistic regression analyses for independent predictors of bacterial infections during d2–d7 excluding obvious infection markers.

<p>Variables in the model: NIHSSS, volume, catecholamine treatment, noradrenalin, normetanephrin, lymphocytes <13%, mechan. ventilation; method: forward (likelihood ration), p(in) = 0.05, p(out) = 0.10.</p

Alterations of the immune system after cerebrovascular events.

<p>(<b>A</b>) Changes of the cellular immune system were measured by the relative lymphocyte fraction, absolute lymphocyte counts, total leukocyte number and the absolute monocyte cell counts in control patients and at the indicated time points after cerebrovascular events. (<b>B</b>) Blood plasma concentrations of IL-10, IL-6 and IL-1β were determined to analyze humoral mediators of immune function. Blood cell counts and cytokines were analyzed by analysis of variance (ANOVA) after testing for normal distribution. Data are presented as mean+/− standard deviation. * indicates a significant (p<0.05) difference of the indicated group compared to control; horizontal bars indicate significant group differences at the respective time point.</p

ROC curve analysis of independent predictors for lymphocytopenia and bacterial infections.

<p>(<b>A</b>) ROC curve performance of the independent variables age and NIHSSS for relative lymphocytopenia on admission (day1). (<b>B</b>) ROC curves of the independent predictors of bacterial infections as detected by multivariate regression analysis. NIHSSS and lymphocytes on admission (day 1) and mechanical ventilation and PCT during the first week. Lymphocytes were plotted as probabilities to avoid curve inversion by the negative correlation. (<b>C</b>) Analysis of ROC performance for the combined predictive variables available on admission. AUC: area under the curve.</p