Patients with hypothermic sepsis have a unique gene expression profile compared to patients with fever and sepsis.

The pathophysiology of hypothermia during sepsis is unclear. Using genomic profiling of blood leukocytes, we aimed to determine if hypothermia is associated with a different gene expression profile compared to fever during sepsis. Patients with sepsis and either hypothermia or fever within 24 hours after ICU admission were included in the study (n = 168). Hypothermia was defined as body temperature below 36 °C. Fever was defined as body temperature equal to or above 38.3°C. We compared blood gene expression (whole-genome transcriptome in leukocytes) in hypothermic septic compared to febrile septic patients in an unmatched analysis and matched for APACHE IV score and the presence of shock. In total, 67 septic patients were hypothermic and 101 patients were febrile. Hypothermia was associated with a distinct gene expression profile in both unmatched and matched analyses. There were significant differences related to the up- and downregulation of canonical signalling pathways. In the matched analysis, the top upregulated gene was cold-inducible mRNA binding protein (CIRBP) which plays a role in cold-induced suppression of cell proliferation. In addition, we found three signalling pathways significantly upregulated in hypothermic patients compared to febrile patients; tryptophan degradation X, phenylalanine degradation IV and putrescine degradation III. In conclusion, there are distinct signalling pathways and genes associated with hypothermia, including tryptophan degradation and CIRBP expression, providing a possible link to the modulation of body temperature and early immunosuppression. Future studies may focus on the canonical signalling pathways presented in this paper to further investigate spontaneous hypothermia in sepsis.

Intracellular expression of granzymes A, B, K and M in blood lymphocyte subsets of critically ill patients with or without sepsis.

Sepsis is a complex syndrome related to an infection-induced exaggerated inflammatory response, which is associated with a high mortality. Granzymes (Gzm) are proteases mainly found in cytotoxic lymphocytes that not only have a role in target cell death, but also as mediators of infection and inflammation. In this study we sought to analyse the intracellular expression of GzmA, B, M and K by flow cytometry in diverse blood lymphocyte populations from 22 sepsis patients, 12 non-infected intensive care unit (ICU) patients and 32 healthy controls. Additionally, we measured GzmA and B plasma levels. Both groups of patients presented decreased percentage of natural killer (NK) cells expressing GzmA, B and M relative to healthy controls, while sepsis patients showed an increased proportion of CD8+ T cells expressing GzmB compared to controls. Expression of GzmK remained relatively unaltered between groups. Extracellular levels of GzmB were increased in non-infected ICU patients relative to sepsis patients and healthy controls. Our results show differential alterations in intracellular expression of Gzm in sepsis patients and non-infected critically ill patients compared to healthy individuals depending on the lymphocyte population and on the Gzm.

Thrombocytopenia is associated with a dysregulated host response in critically ill sepsis patients.

Preclinical studies have suggested that platelets influence the host response during sepsis. We sought to assess the association of admission thrombocytopenia with the presentation, outcome, and host response in patients with sepsis. Nine hundred thirty-one consecutive sepsis patients were stratified according to platelet counts (very low <50 × 10(9)/L, intermediate-low 50 × 10(9) to 99 × 10(9)/L, low 100 × 10(9) to 149 × 10(9)/L, or normal 150 × 10(9) to 399 × 10(9)/L) on admission to the intensive care unit. Sepsis patients with platelet counts <50 × 10(9)/L and 50 × 10(9) to 99 × 10(9)/L presented with higher Acute Physiology and Chronic Health Evaluation scores and more shock. Both levels of thrombocytopenia were independently associated with increased 30-day mortality (hazard ratios with 95% confidence intervals 2.00 [1.32-3.05] and 1.72 [1.22-2.44], respectively). To account for baseline differences besides platelet counts, propensity matching was performed, after which the association between thrombocytopenia and the host response was tested, as evaluated by measuring 17 plasma biomarkers indicative of activation and/or dysregulation of pathways implicated in sepsis pathogenesis and by whole genome blood leukocyte expression profiling. In the propensity matched cohort, platelet counts < 50 × 10(9)/L were associated with increased cytokine levels and enhanced endothelial cell activation. All thrombocytopenic groups showed evidence of impaired vascular integrity, whereas coagulation activation was similar between groups. Blood microarray analysis revealed a distinct gene expression pattern in sepsis patients with <50 × 10(9)/L platelets, showing reduced signaling in leukocyte adhesion and diapedesis and increased complement signaling. These data show that admission thrombocytopenia is associated with enhanced mortality and a more disturbed host response during sepsis independent of disease severity, thereby providing clinical validity to animal studies on the role of platelets in severe infection.

The Host Response in Patients with Sepsis Developing Intensive Care Unit-acquired Secondary Infections.

RATIONALE: Sepsis can be complicated by secondary infections. We explored the possibility that patients with sepsis developing a secondary infection while in the intensive care unit (ICU) display sustained inflammatory, vascular, and procoagulant responses. OBJECTIVES: To compare systemic proinflammatory host responses in patients with sepsis who acquire a new infection with those who do not. METHODS: Consecutive patients with sepsis with a length of ICU stay greater than 48 hours were prospectively analyzed for the development of ICU-acquired infections. Twenty host response biomarkers reflective of key pathways implicated in sepsis pathogenesis were measured during the first 4 days after ICU admission and at the day of an ICU-acquired infection or noninfectious complication. MEASUREMENTS AND MAIN RESULTS: Of 1,237 admissions for sepsis (1,089 patients), 178 (14.4%) admissions were complicated by ICU-acquired infections (at Day 10 [6-13], median with interquartile range). Patients who developed a secondary infection showed higher disease severity scores and higher mortality up to 1 year than those who did not. Analyses of biomarkers in patients who later went on to develop secondary infections revealed a more dysregulated host response during the first 4 days after admission, as reflected by enhanced inflammation, stronger endothelial cell activation, a more disturbed vascular integrity, and evidence for enhanced coagulation activation. Host response reactions were similar at the time of ICU-acquired infectious or noninfectious complications. CONCLUSIONS: Patients with sepsis who developed an ICU-acquired infection showed a more dysregulated proinflammatory and vascular host response during the first 4 days of ICU admission than those who did not develop a secondary infection.

Prior Use of Calcium Channel Blockers Is Associated With Decreased Mortality in Critically Ill Patients With Sepsis: A Prospective Observational Study.

OBJECTIVES: Experimental studies suggest that calcium channel blockers can improve sepsis outcome. The aim of this study was to determine the association between prior use of calcium channel blockers and the outcome of patients admitted to the ICU with sepsis. DESIGN: A prospective observational study. SETTING: The ICUs of two tertiary care hospitals in the Netherlands. PATIENTS: In total, 1,060 consecutive patients admitted with sepsis were analyzed, 18.6% of whom used calcium channel blockers. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Considering large baseline differences between calcium channel blocker users and nonusers, a propensity score matched cohort was constructed to account for differential likelihoods of receiving calcium channel blockers. Fifteen plasma biomarkers providing insight in key host responses implicated in sepsis pathogenesis were measured during the first 4 days after admission. Severity of illness over the first 24 hours, sites of infection and causative pathogens were similar in both groups. Prior use of calcium channel blockers was associated with improved 30-day survival in the propensity-matched cohort (20.2% vs 32.9% in non-calcium channel blockers users; p = 0.009) and in multivariate analysis (odds ratio, 0.48; 95% CI, 0.31-0.74; p = 0.0007). Prior calcium channel blocker use was not associated with changes in the plasma levels of host biomarkers indicative of activation of the cytokine network, the vascular endothelium and the coagulation system, with the exception of antithrombin levels, which were less decreased in calcium channel blocker users. CONCLUSIONS: Prior calcium channel blocker use is associated with reduced mortality in patients following ICU admission with sepsis.

Sepsis Patients Display a Reduced Capacity to Activate Nuclear Factor-κB in Multiple Cell Types.

OBJECTIVES: Sepsis is a complex clinical condition associated with high morbidity and mortality. A distinctive feature of sepsis is the reduced capacity of leukocytes to release proinflammatory cytokines in response to ex vivo stimulation. Cellular signaling events leading to immunosuppression in sepsis are not well defined. We investigated cell-specific signaling events underlying the immunosuppressed phenotype in sepsis. DESIGN: Ex vivo study. SETTING: ICU of an academic hospital. PATIENTS: Nineteen patients with sepsis and 19 age-matched healthy controls. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The phosphorylation state of p38 mitogen activated protein kinase and nuclear factor kappa-light-chain-enhancer of activated B cells were determined in ex vivo stimulated CD4 T cells, CD8 T cells, B cells, monocytes, and neutrophils. Messenger RNA expression levels of p38 mitogen activated protein kinase and nuclear factor kappa-light-chain-enhancer of activated B cells and negative regulators tumor necrosis factor-α-induced protein 3 (A20) and mitogen activated protein kinase phosphatase-1 were determined in neutrophils and peripheral blood mononuclear cells. Upon ex vivo stimulation, monocytes of sepsis patients were less capable in phosphorylating nuclear factor kappa-light-chain-enhancer of activated B cells. Sepsis was also associated with reduced phosphorylation of nuclear factor kappa-light-chain-enhancer of activated B cells in stimulated B cells, CD4 and CD8 T cells. Messenger RNA expression levels of nuclear factor kappa-light-chain-enhancer of activated B cells and A20 were diminished in peripheral blood mononuclear cells of sepsis patients, whereas p38 mitogen activated protein kinase messenger RNA was up-regulated. In neutrophils of sepsis patients, mitogen activated protein kinase phosphatase-1 messenger RNA levels were down-regulated. CONCLUSIONS: Sepsis-induced immunosuppression associates with a defect in the capacity to phosphorylate nuclear factor kappa-light-chain-enhancer of activated B cells in lymphoid cells and monocytes.

Association of Gender With Outcome and Host Response in Critically Ill Sepsis Patients.

OBJECTIVE: To determine the association of gender with the presentation, outcome, and host response in critically ill patients with sepsis. DESIGN AND SETTING: A prospective observational cohort study in the ICU of two tertiary hospitals between January 2011 and January 2014. PATIENTS: All consecutive critically ill patients admitted with sepsis, involving 1,815 admissions (1,533 patients). INTERVENTIONS: The host response was evaluated on ICU admission by measuring 19 plasma biomarkers reflecting organ systems implicated in sepsis pathogenesis (1,205 admissions) and by applying genome-wide blood gene expression profiling (582 admissions). MEASUREMENTS AND MAIN RESULTS: Sepsis patients admitted to the ICU were more frequently males (61.0%; p < 0.0001 vs females). Baseline characteristics were not different between genders. Urosepsis was more common in females; endocarditis and mediastinitis in men. Disease severity was similar throughout ICU stay. Mortality was similar up to 1 year after ICU admission, and gender was not associated with 90-day mortality in multivariate analyses in a variety of subgroups. Although plasma proteome analyses (including systemic inflammatory and cytokine responses, and activation of coagulation) were largely similar between genders, females showed enhanced endothelial cell activation; this difference was virtually absent in patients more than 55 years old. More than 80% of the leukocyte blood gene expression response was similar in male and female patients. CONCLUSIONS: The host response and outcome in male and female sepsis patients requiring ICU admission are largely similar.

Quantifying the Effects of Prior Acetyl-Salicylic Acid on Sepsis-Related Deaths: An Individual Patient Data Meta-Analysis Using Propensity Matching.

OBJECTIVE: The primary objective was to conduct a meta-analysis on published observational cohort data describing the association between acetyl-salicylic acid (aspirin) use prior to the onset of sepsis and mortality in hospitalized patients. STUDY SELECTION: Studies that reported mortality in patients on aspirin with sepsis with a comparison group of patients with sepsis not on prior aspirin therapy were included. DATA SOURCES: Fifteen studies described hospital-based cohorts (n = 17,065), whereas one was a large insurance-based database (n = 683,421). Individual-level patient data were incorporated from all selected studies. DATA EXTRACTION: Propensity analyses with 1:1 propensity score matching at the study level were performed, using the most consistently available covariates judged to be associated with aspirin. Meta-analyses were performed to estimate the pooled average treatment effect of aspirin on sepsis-related mortality. DATA SYNTHESIS: Use of aspirin was associated with a 7% (95% CI, 2-12%; p = 0.005) reduction in the risk of death as shown by meta-analysis with considerable statistical heterogeneity (I = 61.6%). CONCLUSIONS: These results are consistent with effects ranging from a 2% to 12% reduction in mortality risk in patients taking aspirin prior to sepsis onset. This association anticipates results of definitive studies of the use of low-dose aspirin as a strategy for reduction of deaths in patients with sepsis.

Comparative Analysis of the Host Response to Community-acquired and Hospital-acquired Pneumonia in Critically Ill Patients.

RATIONALE: Preclinical studies suggest that hospitalized patients are susceptible to infections caused by nosocomial respiratory pathogens at least in part because of immune suppression caused by the condition for which they were admitted. OBJECTIVES: We aimed to characterize the systemic host response in hospital-acquired pneumonia (HAP) when compared with community-acquired pneumonia (CAP). METHODS: We performed a prospective study in two intensive care units (ICUs) in 453 patients with HAP (n = 222) or CAP (n = 231). Immune responses were determined on ICU admission by measuring 19 plasma biomarkers reflecting organ systems implicated in infection pathogenesis (in 192 patients with HAP and 183 patients with CAP) and by applying genome-wide blood gene expression profiling (in 111 patients with HAP and 110 patients with CAP). MEASUREMENTS AND MAIN RESULTS: Patients with HAP and CAP presented with similar disease severities and mortality rates did not differ up to 1 year after admission. Plasma proteome analysis revealed largely similar responses, including systemic inflammatory and cytokine responses, and activation of coagulation and the vascular endothelium. The blood leukocyte genomic response was greater than 75% common in patients with HAP and CAP, comprising proinflammatory, antiinflammatory, T-cell signaling, and metabolic pathway gene sets. Patients with HAP showed overexpression of genes involved in cell-cell junction remodeling, adhesion, and diapedesis, which corresponded with lower plasma levels of matrix metalloproteinase-8 and soluble E-selectin. In addition, patients with HAP demonstrated underexpression of a type-I interferon signaling gene signature. CONCLUSIONS: Patients with HAP and CAP present with a largely similar host response at ICU admission.

Admission Hyperglycemia in Critically Ill Sepsis Patients: Association With Outcome and Host Response.

OBJECTIVES: To investigate whether admission hyperglycemia is associated with the presentation and/or outcome of sepsis, what the influence of hyperglycemia is on key host responses to sepsis, and whether hyperglycemia differentially affects patients with diabetes mellitus. DESIGN AND SETTING: A substudy of a prospective observational cohort study was conducted in the intensive care of two tertiary hospitals between January 2011 and July 2013. PATIENTS: Of all consecutive critically ill sepsis patients, admission glucose was used to stratify patients in euglycemia (71-140 mg/dL), mild hyperglycemia (141-199 mg/dL), and severe hyperglycemia (≥ 200 mg/dL), and patients with hypoglycemia were excluded. Fifteen plasma biomarkers providing insight in key host responses implicated in sepsis pathogenesis were measured on admission. MEASUREMENTS AND MAIN RESULTS: Of 987 sepsis patients with admission glucose levels greater than 70 mg/dL, 519 (52.6%) had normal glucose levels, 267 (27.1%) had mild, and 201 (20.4%) severe hyperglycemia. Admission hyperglycemia was accompanied by mitigated alterations in plasma host response biomarker levels indicative of activation of the cytokine network, the vascular endothelium, and the coagulation system in patients without a history of diabetes. Severe, but not mild, admission hyperglycemia was associated with increased 30-day mortality (adjusted hazard ratio, 1.66 [95% CI, 1.24-2.23]), in both patients without diabetes (adjusted hazard ratio, 1.65 [95% CI, 1.12-2.42]) and with diabetes (adjusted hazard ratio, 1.91 [95% CI, 1.01-3.62]). CONCLUSION: Admission hyperglycemia is associated with adverse outcome of sepsis irrespective of the presence or absence of preexisting diabetes by a mechanism unrelated to exaggerated inflammation or coagulation.

Risk factors, host response and outcome of hypothermic sepsis.

BACKGROUND: Hypothermia is associated with adverse outcome in patients with sepsis. The objective of this study was to characterize the host immune response in patients with hypothermic sepsis in order to determine if an excessive anti-inflammatory response could explain immunosuppression and adverse outcome. Markers of endothelial activation and integrity were also measured to explore potential alternative mechanisms of hypothermia. Finally we studied risk factors for hypothermia in an attempt to find new clues to the etiology of hypothermia in sepsis. METHODS: Consecutive patients diagnosed with sepsis within 24 hours after admission to ICUs in two tertiary hospitals in the Netherlands were included in the study (n = 525). Hypothermia was defined as body temperature below 36 °C in the first 24 h of ICU admission. RESULTS: Hypothermia was identified in 186 patients and was independently associated with mortality. Levels of proinflammatory and anti-inflammatory cytokines were not different between groups. Hypothermia was also not associated with an altered response to ex vivo stimulation with lipopolysaccharide in a subset of 15 patients. Risk factors for hypothermia included low body mass index, hypertension and chronic cardiovascular insufficiency. Levels of the endothelial activation marker fractalkine were increased during the first 4 days of ICU stay. CONCLUSIONS: Hypothermia during sepsis is independently associated with mortality, which cannot be attributed to alterations in the host immune responses that were measured in this study. Given that risk factors for hypothermic sepsis are mainly cardiovascular and that the endothelial activation marker fractalkine increased in hypothermia, these findings may suggest that vascular dysfunction plays a role in hypothermic sepsis.

Impact of HIV infection on the presentation, outcome and host response in patients admitted to the intensive care unit with sepsis; a case control study.

BACKGROUND: Sepsis is a prominent reason for intensive care unit (ICU) admission in patients with HIV. We aimed to investigate the impact of HIV infection on presentation, outcome and host response in sepsis. METHODS: We performed a prospective observational study in the ICUs of two tertiary hospitals. For the current analyses, we selected all patients diagnosed with sepsis within 24 hours after admission. Host response biomarkers were analyzed in a more homogeneous subgroup of admissions involving HIV-positive patients with pneumosepsis, matched to admissions of HIV-negative patients for age, gender and race. Matching was done by nearest neighbor matching with R package "MatchIt". RESULTS: We analyzed 2251 sepsis admissions including 41 (1.8 %) with HIV infection (32 unique patients). HIV-positive patients were younger and admission of HIV-positive patients more frequently involved pneumonia (73.2 % versus 48.8 % of admissions of HIV-negative patients, P = 0.004). Disease severity and mortality up to one year after admission did not differ according to HIV status. Furthermore, sequential plasma levels of host response biomarkers, providing insight into activation of the cytokine network, the vascular endothelium and the coagulation system, were largely similar in matched admissions of HIV-positive and HIV-negative patients with pneumosepsis. CONCLUSIONS: Sepsis is more often caused by pneumonia in HIV-positive patients. HIV infection has little impact on the disease severity, mortality and host response during sepsis.

Association of diabetes and diabetes treatment with the host response in critically ill sepsis patients.

BACKGROUND: Diabetes is associated with chronic inflammation and activation of the vascular endothelium and the coagulation system, which in a more acute manner are also observed in sepsis. Insulin and metformin exert immune modulatory effects. In this study, we aimed to determine the association of diabetes and preadmission insulin and metformin use with sepsis outcome and host response. METHODS: We evaluated 1104 patients with sepsis, admitted to the intensive care unit and stratified according to the presence or absence of diabetes mellitus. The host response was examined by a targeted approach (by measuring 15 plasma biomarkers reflective of pathways implicated in sepsis pathogenesis) and an unbiased approach (by analyzing whole genome expression profiles in blood leukocytes). RESULTS: Diabetes mellitus was not associated with differences in sepsis presentation or mortality up to 90 days after admission. Plasma biomarker measurements revealed signs of systemic inflammation, and strong endothelial and coagulation activation in patients with sepsis, none of which were altered in those with diabetes. Patients with and without diabetes mellitus, who had sepsis demonstrated similar transcriptional alterations, comprising 74 % of the expressed gene content and involving over-expression of genes associated with pro-inflammatory, anti-inflammatory, Toll-like receptor and metabolic signaling pathways and under-expression of genes associated with T cell signaling pathways. Amongst patients with diabetes mellitus and sepsis, preadmission treatment with insulin or metformin was not associated with an altered sepsis outcome or host response. CONCLUSIONS: Neither diabetes mellitus nor preadmission insulin or metformin use are associated with altered disease presentation, outcome or host response in patients with sepsis requiring intensive care.

A molecular biomarker to diagnose community-acquired pneumonia on intensive care unit admission.

RATIONALE: Community-acquired pneumonia (CAP) accounts for a major proportion of intensive care unit (ICU) admissions for respiratory failure and sepsis. Diagnostic uncertainty complicates case management, which may delay appropriate cause-specific treatment. OBJECTIVES: To characterize the blood genomic response in patients with suspected CAP and identify a candidate biomarker for the rapid diagnosis of CAP on ICU admission. METHODS: The study comprised two cohorts of consecutively enrolled patients treated for suspected CAP on ICU admission. Patients were designated CAP (cases) and no-CAP patients (control subjects) by post hoc assessment. The first (discovery) cohort (101 CAP and 33 no-CAP patients) was enrolled between January 2011 and July 2012; the second (validation) cohort (70 CAP and 30 no-CAP patients) between July 2012 and June 2013. Blood was collected within 24 hours of ICU admission. MEASUREMENTS AND MAIN RESULTS: Blood microarray analysis of CAP and no-CAP patients revealed shared and distinct gene expression patterns. A 78-gene signature was defined for CAP, from which a FAIM3:PLAC8 gene expression ratio was derived with area under curve of 0.845 (95% confidence interval, 0.764-0.917) and positive and negative predictive values of 83% and 81%, respectively. Robustness of the FAIM3:PLAC8 ratio was ascertained by quantitative polymerase chain reaction in the validation cohort. The FAIM3:PLAC8 ratio outperformed plasma procalcitonin and IL-8 and IL-6 in discriminating between CAP and no-CAP patients. CONCLUSIONS: CAP and no-CAP patients presented shared and distinct blood genomic responses. We propose the FAIM3:PLAC8 ratio as a candidate biomarker to assist in the rapid diagnosis of CAP on ICU admission. Clinical trial registered with www.clinicaltrials.gov (NCT 01905033).

Incidence, Risk Factors, and Attributable Mortality of Secondary Infections in the Intensive Care Unit After Admission for Sepsis.

IMPORTANCE: Sepsis is considered to induce immune suppression, leading to increased susceptibility to secondary infections with associated late mortality. OBJECTIVE: To determine the clinical and host genomic characteristics, incidence, and attributable mortality of intensive care unit (ICU)-acquired infections in patients admitted to the ICU with or without sepsis. DESIGN, SETTING, AND PARTICIPANTS: Prospective observational study comprising consecutive admissions of more than 48 hours in 2 ICUs in the Netherlands from January 2011 to July 2013 stratified according to admission diagnosis (sepsis or noninfectious). MAIN OUTCOMES AND MEASURES: The primary outcome was ICU-acquired infection (onset >48 hours). Attributable mortality risk (fraction of mortality that can be prevented by elimination of the risk factor, acquired infection) was determined using time-to-event models accounting for competing risk. In a subset of sepsis admissions (n = 461), blood gene expression (whole-genome transcriptome in leukocytes) was analyzed at baseline and at onset of ICU-acquired infectious (n = 19) and noninfectious (n = 9) events. RESULTS: The primary cohort included 1719 sepsis admissions (1504 patients; median age, 62 years; interquartile range [IQR], 51-71 years]; 924 men [61.4%]). A comparative cohort included 1921 admissions (1825 patients, median age, 62 years; IQR, 49-71 years; 1128 men [61.8%] in whom infection was not present in the first 48 hours. Intensive care unit-acquired infections occurred in 13.5% of sepsis ICU admissions (n = 232) and 15.1% of nonsepsis ICU admissions (n = 291). Patients with sepsis who developed an ICU-acquired infection had higher disease severity scores on admission than patients with sepsis who did not develop an ICU-acquired infection (Acute Physiology and Chronic Health Evaluation IV [APACHE IV] median score, 90 [IQR, 72-107] vs 79 [IQR, 62-98]; P < .001) and throughout their ICU stay but did not have differences in baseline gene expression. The population attributable mortality fraction of ICU-acquired infections in patients with sepsis was 10.9% (95% CI, 0.9%-20.6%) by day 60; the estimated difference between mortality in all patients with a sepsis admission diagnosis and mortality in those without ICU-acquired infection was 2.0% (95% CI, 0.2%-3.8%; P = .03) by day 60. Among nonsepsis ICU admissions, ICU-acquired infections had a population attributable mortality fraction of 21.1% (95% CI, 0.6%-41.7%) by day 60. Compared with baseline, blood gene expression at the onset of ICU-acquired infections showed reduced expression of genes involved in gluconeogenesis and glycolysis. CONCLUSIONS AND RELEVANCE: Intensive care unit-acquired infections occurred more commonly in patients with sepsis with higher disease severity, but such infections contributed only modestly to overall mortality. The genomic response of patients with sepsis was consistent with immune suppression at the onset of secondary infection.

Plasma fractalkine is a sustained marker of disease severity and outcome in sepsis patients.

INTRODUCTION: Fractalkine is a chemokine implicated as a mediator in a variety of inflammatory conditions. Knowledge of fractalkine release in patients presenting with infection to the Intensive Care Unit (ICU) is highly limited. The primary objective of this study was to establish whether plasma fractalkine levels are elevated in sepsis and associate with outcome. The secondary objective was to determine whether fractalkine can assist in the diagnosis of infection upon ICU admission. METHODS: Fractalkine was measured in 1103 consecutive sepsis patients (including 271 patients with community-acquired pneumonia (CAP)) upon ICU admission and at days 2 and 4 thereafter; in 73 ICU patients treated for suspected CAP in whom this diagnosis was refuted in retrospect; and in 5 healthy humans intravenously injected with endotoxin. RESULTS: Compared to healthy volunteers, sepsis patients had strongly elevated fractalkine levels. Fractalkine levels increased with the number of organs failing, were higher in patients presenting with shock, but did not vary by site of infection. Non-survivors had sustained elevated fractalkine levels when compared to survivors. Fractalkine was equally elevated in CAP patients and patients treated for CAP but in whom the diagnosis was retrospectively refuted. Fractalkine release induced by intravenous endotoxin followed highly similar kinetics as the endothelial cell marker E-selectin. CONCLUSIONS: Plasma fractalkine is an endothelial cell derived biomarker that, while not specific for infection, correlates with disease severity in sepsis patients admitted to the ICU.

Immune suppression is associated with enhanced systemic inflammatory, endothelial and procoagulant responses in critically ill patients.

OBJECTIVE: Patients admitted to the Intensive Care Unit (ICU) oftentimes show immunological signs of immune suppression. Consequently, immune stimulatory agents have been proposed as an adjunctive therapy approach in the ICU. The objective of this study was to determine the relationship between the degree of immune suppression and systemic inflammation in patients shortly after admission to the ICU. Design: An observational study in two ICUs in the Netherlands. METHODS: The capacity of blood leukocytes to produce cytokines upon stimulation with lipopolysaccharide (LPS) was measured in 77 patients on the first morning after ICU admission. Patients were divided in four groups based on quartiles of LPS stimulated tumor necrosis factor (TNF)-α release, reflecting increasing extents of immune suppression. 15 host response biomarkers indicative of aberrations in inflammatory pathways implicated in sepsis pathogenesis were measured in plasma. RESULTS: A diminished capacity of blood leukocytes to produce TNF-α upon stimulation with LPS was accompanied by a correspondingly reduced ability to release of IL-1ß and IL-6. Concurrently measured plasma concentrations of host response biomarkers demonstrated that the degree of reduction in TNF-α release by blood leukocytes was associated with increasing systemic inflammation, stronger endothelial cell activation, loss of endothelial barrier integrity and enhanced procoagulant responses. CONCLUSIONS: In patients admitted to the ICU the strongest immune suppression occurs in those who simultaneously display signs of stronger systemic inflammation. These findings may have relevance for the selection of patients eligible for administration of immune enhancing agents. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT01905033.

Impact of a Machine Learning-Based Decision Support System for Urinary Tract Infections: Prospective Observational Study in 36 Primary Care Practices.

BACKGROUND: There is increasing attention on machine learning (ML)-based clinical decision support systems (CDSS), but their added value and pitfalls are very rarely evaluated in clinical practice. We implemented a CDSS to aid general practitioners (GPs) in treating patients with urinary tract infections (UTIs), which are a significant health burden worldwide. OBJECTIVE: This study aims to prospectively assess the impact of this CDSS on treatment success and change in antibiotic prescription behavior of the physician. In doing so, we hope to identify drivers and obstacles that positively impact the quality of health care practice with ML. METHODS: The CDSS was developed by Pacmed, Nivel, and Leiden University Medical Center (LUMC). The CDSS presents the expected outcomes of treatments, using interpretable decision trees as ML classifiers. Treatment success was defined as a subsequent period of 28 days during which no new antibiotic treatment for UTI was needed. In this prospective observational study, 36 primary care practices used the software for 4 months. Furthermore, 29 control practices were identified using propensity score-matching. All analyses were performed using electronic health records from the Nivel Primary Care Database. Patients for whom the software was used were identified in the Nivel database by sequential matching using CDSS use data. We compared the proportion of successful treatments before and during the study within the treatment arm. The same analysis was performed for the control practices and the patient subgroup the software was definitely used for. All analyses, including that of physicians' prescription behavior, were statistically tested using 2-sided z tests with an α level of .05. RESULTS: In the treatment practices, 4998 observations were included before and 3422 observations (of 2423 unique patients) were included during the implementation period. In the control practices, 5044 observations were included before and 3360 observations were included during the implementation period. The proportion of successful treatments increased significantly from 75% to 80% in treatment practices (z=5.47, P<.001). No significant difference was detected in control practices (76% before and 76% during the pilot, z=0.02; P=.98). Of the 2423 patients, we identified 734 (30.29%) in the CDSS use database in the Nivel database. For these patients, the proportion of successful treatments during the study was 83%-a statistically significant difference, with 75% of successful treatments before the study in the treatment practices (z=4.95; P<.001). CONCLUSIONS: The introduction of the CDSS as an intervention in the 36 treatment practices was associated with a statistically significant improvement in treatment success. We excluded temporal effects and validated the results with the subgroup analysis in patients for whom we were certain that the software was used. This study shows important strengths and points of attention for the development and implementation of an ML-based CDSS in clinical practice. TRIAL REGISTRATION: ClinicalTrials.gov NCT04408976; https://clinicaltrials.gov/ct2/show/NCT04408976.