Validation of SeptiCyte RAPID to Discriminate Sepsis from Non-Infectious Systemic Inflammation

(1) Background: SeptiCyte RAPID is a molecular test for discriminating sepsis from non-infectious systemic inflammation, and for estimating sepsis probabilities. The objective of this study was the clinical validation of SeptiCyte RAPID, based on testing retrospectively banked and prospectively collected patient samples. (2) Methods: The cartridge-based SeptiCyte RAPID test accepts a PAXgene blood RNA sample and provides sample-to-answer processing in ~1 h. The test output (SeptiScore, range 0-15) falls into four interpretation bands, with higher scores indicating higher probabilities of sepsis. Retrospective (N = 356) and prospective (N = 63) samples were tested from adult patients in ICU who either had the systemic inflammatory response syndrome (SIRS), or were suspected of having/diagnosed with sepsis. Patients were clinically evaluated by a panel of three expert physicians blinded to the SeptiCyte test results. Results were interpreted under either the Sepsis-2 or Sepsis-3 framework. (3) Results: Under the Sepsis-2 framework, SeptiCyte RAPID performance for the combined retrospective and prospective cohorts had Areas Under the ROC Curve (AUCs) ranging from 0.82 to 0.85, a negative predictive value of 0.91 (sensitivity 0.94) for SeptiScore Band 1 (score range 0.1-5.0; lowest risk of sepsis), and a positive predictive value of 0.81 (specificity 0.90) for SeptiScore Band 4 (score range 7.4-15; highest risk of sepsis). Performance estimates for the prospective cohort ranged from AUC 0.86-0.95. For physician-adjudicated sepsis cases that were blood culture (+) or blood, urine culture (+)(+), 43/48 (90%) of SeptiCyte scores fell in Bands 3 or 4. In multivariable analysis with up to 14 additional clinical variables, SeptiScore was the most important variable for sepsis diagnosis. A comparable performance was obtained for the majority of patients reanalyzed under the Sepsis-3 definition, although a subgroup of 16 patients was identified that was called septic under Sepsis-2 but not under Sepsis-3. (4) Conclusions: This study validates SeptiCyte RAPID for estimating sepsis probability, under both the Sepsis-2 and Sepsis-3 frameworks, for hospitalized patients on their first day of ICU admission.

Association between age and the host response in critically ill patients with sepsis

BACKGROUND

The association of ageing with increased sepsis mortality is well established. Nonetheless, current investigations on the influence of age on host response aberrations are largely limited to plasma cytokine levels while neglecting other pathophysiological sepsis domains like endothelial cell activation and function, and coagulation activation. The primary objective of this study was to gain insight into the association of ageing with aberrations in key host response pathways and blood transcriptomes in sepsis.

METHODS

We analysed the clinical outcome (n = 1952), 16 plasma biomarkers providing insight in deregulation of specific pathophysiological domains (n = 899), and blood leukocyte transcriptomes (n = 488) of sepsis patients stratified according to age decades. Blood transcriptome results were validated in an independent sepsis cohort and compared with healthy individuals.

RESULTS

Older age was associated with increased mortality independent of comorbidities and disease severity. Ageing was associated with lower endothelial cell activation and dysfunction, and similar inflammation and coagulation activation, despite higher disease severity scores. Blood leukocytes of patients ≥ 70 years, compared to patients < 50 years, showed decreased expression of genes involved in cytokine signaling, and innate and adaptive immunity, and increased expression of genes involved in hemostasis and endothelial cell activation. The diminished expression of gene pathways related to innate immunity and cytokine signaling in subjects ≥ 70 years was sepsis-induced, as healthy subjects ≥ 70 years showed enhanced expression of these pathways compared to healthy individuals < 50 years.

CONCLUSIONS

This study provides novel evidence that older age is associated with relatively mitigated sepsis-induced endothelial cell activation and dysfunction, and a blood leukocyte transcriptome signature indicating impaired innate immune and cytokine signaling. These data suggest that age should be considered in patient selection in future sepsis trials targeting the immune system and/or the endothelial cell response.

Consumptive coagulopathy is associated with a disturbed host response in patients with sepsis

BACKGROUND

A prolonged prothrombin time (PT) is a common feature in sepsis indicating consumptive coagulopathy.

OBJECTIVES

To determine the association between a prolonged PT and aberrations in other host response mechanisms in sepsis.

METHODS

Patients admitted to the intensive care unit with sepsis were divided in quartiles according to the highest PT value measured within 24 h after admission. The host response was evaluated by measuring 19 plasma biomarkers reflecting pathways implicated in sepsis pathogenesis and by blood leukocyte gene expression profiling.

MEASUREMENTS AND MAIN RESULTS

Of 1524 admissions for sepsis, 386 (25.3%) involved patients with a normal PT (≤12.7 s); the remaining quartiles entailed 379 (24.9%) patients with a slightly prolonged PT (12.8 ≤ PT ≤ 15.0 s), 383 (25.1%) with an intermediately prolonged PT (15.1 ≤ PT ≤ 17.2 s), and 376 (24.7%) with an extremely prolonged PT (≥17.3 s). While patients with an extremely prolonged PT showed an increased crude mortality up to 1 year after admission, none of the prolonged PT groups was independently associated with 30-day adjusted mortality. Comparison of the host response between patients with a normal PT or an extremely prolonged PT matched for baseline characteristics including severity of disease showed that an extremely prolonged PT was associated with impaired anticoagulant mechanisms, a more disturbed endothelial barrier integrity and increased systemic inflammation, and blood leukocyte transcriptomes indicating more prominent metabolic reprogramming and protein catabolism.

CONCLUSION

A prolonged PT is associated with stronger anomalies in pathways implicated in the pathogenesis of sepsis, suggesting that activation of coagulation impacts other host response mechanisms.

Predicting the clinical trajectory in critically ill patients with sepsis: a cohort study

Background

To develop a mathematical model to estimate daily evolution of disease severity using routinely available parameters in patients admitted to the intensive care unit (ICU).

Methods

Over a 3-year period, we prospectively enrolled consecutive adults with sepsis and categorized patients as (1) being at risk for developing (more severe) organ dysfunction, (2) having (potentially still reversible) limited organ failure, or (3) having multiple-organ failure. Daily probabilities for transitions between these disease states, and to death or discharge, during the first 2 weeks in ICU were calculated using a multi-state model that was updated every 2 days using both baseline and time-varying information. The model was validated in independent patients.

Results

We studied 1371 sepsis admissions in 1251 patients. Upon presentation, 53 (4%) were classed at risk, 1151 (84%) had limited organ failure, and 167 (12%) had multiple-organ failure. Among patients with limited organ failure, 197 (17%) evolved to multiple-organ failure or died and 809 (70%) improved or were discharged alive within 14 days. Among patients with multiple-organ failure, 67 (40%) died and 91 (54%) improved or were discharged. Treatment response could be predicted with reasonable accuracy (c-statistic ranging from 0.55 to 0.81 for individual disease states, and 0.67 overall). Model performance in the validation cohort was similar.

Conclusions

This prediction model that estimates daily evolution of disease severity during sepsis may eventually support clinicians in making better informed treatment decisions and could be used to evaluate prognostic biomarkers or perform in silico modeling of novel sepsis therapies during trial design.

Clinical trial registration

ClinicalTrials.gov NCT01905033

Robustness of sepsis-3 criteria in critically ill patients

Background

Early recognition of sepsis is challenging, and diagnostic criteria have changed repeatedly. We assessed the robustness of sepsis-3 criteria in intensive care unit (ICU) patients.

Methods

We studied the apparent incidence and associated mortality of sepsis-3 among patients who were prospectively enrolled in the Molecular Diagnosis and Risk Stratification of Sepsis (MARS) cohort in the Netherlands, and explored the effects of minor variations in the precise definition and timing of diagnostic criteria for organ failure.

Results

Among 1081 patients with suspected infection upon ICU admission, 648 (60%) were considered to have sepsis according to prospective adjudication in the MARS study, whereas 976 (90%) met sepsis-3 criteria, yielding only 64% agreement at the individual patient level. Among 501 subjects developing ICU-acquired infection, these rates were 270 (54%) and 260 (52%), respectively (yielding 58% agreement). Hospital mortality was 234 (36%) vs 277 (28%) for those meeting MARS-sepsis or sepsis-3 criteria upon presentation (p < 0.001), and 121 (45%) vs 103 (40%) for those having sepsis onset in the ICU (p < 0.001). Minor variations in timing and interpretation of organ failure criteria had a considerable effect on the apparent prevalence of sepsis-3, which ranged from 68 to 96% among those with infection at admission, and from 22 to 99% among ICU-acquired cases.

Conclusion

The sepsis-3 definition lacks robustness as well as discriminatory ability, since nearly all patients presenting to ICU with suspected infection fulfill its criteria. These should therefore be specified in greater detail, and applied more consistently, during future sepsis studies.

Trial registration

The MARS study is registered at ClinicalTrials.gov (identifier NCT 01905033).

Electronic supplementary material

The online version of this article (10.1186/s40560-019-0400-6) contains supplementary material, which is available to authorized users.

Effect of cytomegalovirus reactivation on the time course of systemic host response biomarkers in previously immunocompetent critically ill patients with sepsis: a matched cohort study

BACKGROUND

Cytomegalovirus (CMV) reactivation in previously immunocompetent critically ill patients is associated with increased mortality, which has been hypothesized to result from virus-induced immunomodulation. Therefore, we studied the effects of CMV reactivation on the temporal course of host response biomarkers in patients with sepsis.

METHODS

In this matched cohort study, each sepsis patient developing CMV reactivation between day 3 and 17 (CMV+) was compared with one CMV seropositive patient without reactivation (CMVs+) and one CMV seronegative patient (CMVs-). CMV serostatus and plasma loads were determined by enzyme-linked immunoassays and real-time polymerase chain reaction, respectively. Systemic interleukin-6 (IL-6), IL-8, IL-18, interferon-gamma-induced protein-10 (IP-10), neutrophilic elastase, IL-1 receptor antagonist (RA), and IL-10 were measured at five time points by multiplex immunoassay. The effects of CMV reactivation on sequential concentrations of these biomarkers were assessed in multivariable mixed models.

RESULTS

Among 64 CMV+ patients, 45 could be matched to CMVs+ or CMVs- controls or both. The two baseline characteristics and host response biomarker levels at viremia onset were similar between groups. CMV+ patients had increased IP-10 on day 7 after viremia onset (symmetric percentage difference +44% versus -15% when compared with CMVs+ and +37% versus +4% when compared with CMVs-) and decreased IL-1RA (-41% versus 0% and -49% versus +10%, respectively). However, multivariable analyses did not show an independent association between CMV reactivation and time trends of IL-6, IP-10, IL-10, or IL-1RA.

CONCLUSION

CMV reactivation was not independently associated with changes in the temporal trends of host response biomarkers in comparison with non-reactivating patients. Therefore, these markers should not be used as surrogate clinical endpoints for interventional studies evaluating anti-CMV therapy.

Short-Course Adjunctive Gentamicin as Empirical Therapy in Patients With Severe Sepsis and Septic Shock: A Prospective Observational Cohort Study

Background.

Metaanalyses failed to demonstrate clinical benefits of beta lactam plus aminoglycoside combination therapy compared to beta lactam monotherapy in patients with sepsis. However, few data exist on the effects of short-course adjunctive aminoglycoside therapy in sepsis patients with organ failure or shock.

Methods.

We prospectively enrolled consecutive patients with severe sepsis or septic shock in 2 intensive care units in the Netherlands from 2011 to 2015. Local antibiotic protocols recommended empirical gentamicin add-on therapy in only 1 of the units. We used logistic regression analyses to determine the association between gentamicin use and the number of days alive and free of renal failure, shock, and death, all on day 14.

Results.

Of 648 patients enrolled, 245 received gentamicin (222 of 309 [72%] in hospital A and 23 of 339 [7%] in hospital B) for a median duration of 2 days (interquartile range, 1-3). The adjusted odds ratios associated with gentamicin use were 1.39 (95% confidence interval [CI], 1.00-1.94) for renal failure, 1.34 (95% CI, 0.96-1.86) for shock duration, and 1.41 (95% CI, 0.94-2.12) for day-14 mortality. Based on in vitro susceptibilities, inappropriate (initial) gram-negative coverage was given in 9 of 245 (4%) and 18 of 403 (4%) patients treated and not treated with gentamicin, respectively (P = .62).

Conclusions.

Short-course empirical gentamicin use in patients with sepsis was associated with an increased incidence of renal failure but not with faster reversal of shock or improved survival in a setting with low prevalence of antimicrobial resistance.

Epidemiology of Multiple Herpes Viremia in Previously Immunocompetent Patients With Septic Shock

Background

Systemic reactivations of herpesviruses may occur in intensive care unit (ICU) patients, even in those without prior immune deficiency. However, the clinical relevance of these events is uncertain.

Methods

In this study we selected patients admitted with septic shock and treated for more than 4 days from a prospectively enrolled cohort of consecutive adults in the mixed ICUs of 2 tertiary care hospitals in the Netherlands. We excluded patients who had received antiviral treatment in the week before ICU admission and those with known immunodeficiency. We studied viremia episodes with cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), and varicella zoster virus (VZV) by weekly polymerase chain reaction in plasma.

Results

Among 329 patients, we observed 399 viremia episodes in 223 (68%) patients. Viremia with CMV, EBV, HHV-6, HSV-1, HSV-2, and VZV was detected in 60 (18%), 157 (48%), 80 (24%), 87 (26%), 13 (4%), and 2 (0.6%) patients, respectively; 112 (34%) patients had multiple concurrent viremia events. Crude mortality in the ICU was 36% in this latter group compared to 19% in remaining patients (P < .01). After adjustment for potential confounders, time-dependent bias, and competing risks, only concurrent CMV and EBV reactivations remained independently associated with increased mortality (adjusted subdistribution hazard ratio, 3.17; 95% confidence interval, 1.41-7.13).

Conclusions

Herpesvirus reactivations were documented in 68% of septic shock patients without prior immunodeficiency and frequently occurred simultaneously. Concurrent reactivations could be independently associated with mortality.

Clinical Trials Registration

NCT01905033.

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.

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.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1429-8) contains supplementary material, which is available to authorized users.

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.

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).

Chronic antiplatelet therapy is not associated with alterations in the presentation, outcome, or host response biomarkers during sepsis: a propensity-matched analysis

Purpose

Sepsis is a major health burden worldwide. Preclinical investigations in animals and retrospective studies in patients have suggested that inhibition of platelets may improve the outcome of sepsis. In this study we investigated whether chronic antiplatelet therapy impacts on the presentation and outcome of sepsis, and the host response.

Methods

We performed a prospective observational study in 972 patients admitted with sepsis to the mixed intensive care units (ICUs) of two hospitals in the Netherlands between January 2011 and July 2013. Of them, 267 patients (27.5 %) were on antiplatelet therapy (95.9 % acetylsalicylic acid) before admission. To account for differential likelihoods of receiving antiplatelet therapy, a propensity score was constructed, including variables associated with use of antiplatelet therapy. Cox proportional hazards regression was used to estimate the association of antiplatelet therapy with mortality.

Results

Antiplatelet therapy was not associated with sepsis severity at presentation, the primary source of infection, causative pathogens, the development of organ failure or shock during ICU stay, or mortality up to 90 days after admission, in either unmatched or propensity-matched analyses. Antiplatelet therapy did not modify the values of 19 biomarkers providing insight into hallmark host responses to sepsis, including activation of the coagulation system, the vascular endothelium, the cytokine network, and renal function, during the first 4 days after ICU admission.

Conclusions

Pre-existing antiplatelet therapy is not associated with alterations in the presentation or outcome of sepsis, or the host response.

Electronic supplementary material

The online version of this article (doi:10.1007/s00134-015-4171-9) contains supplementary material, which is available to authorized users.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1125-0) contains supplementary material, which is available to authorized users.

Benzodiazepine-associated delirium in critically ill adults

PURPOSE

The association between benzodiazepine use and delirium risk in the ICU remains unclear. Prior investigations have failed to account for disease severity prior to delirium onset, competing events that may preclude delirium detection, other important delirium risk factors, and an adequate number of patients receiving continuous midazolam. The aim of this study was to address these limitations and evaluate the association between benzodiazepine exposure and ICU delirium occurrence.

METHODS

In a cohort of consecutive critically ill adults, daily mental status was classified as either awake without delirium, delirium, or coma. In a first-order Markov model, multinomial logistic regression analysis was used, which considered five possible outcomes the next day (i.e., awake without delirium, delirium, coma, ICU discharge, and death) and 16 delirium-related covariables, to quantify the association between benzodiazepine use and delirium occurrence the following day.

RESULTS

Among 1112 patients, 9867 daily transitions occurred. Benzodiazepine administration in an awake patient without delirium was associated with increased risk of delirium the next day [OR 1.04 (per 5 mg of midazolam equivalent administered) 95 % CI 1.02-1.05). When the method of benzodiazepine administration was incorporated in the model, the odds of transitioning to delirium was higher with benzodiazepines given continuously (OR 1.04, 95 % CI 1.03-1.06) compared to benzodiazepines given intermittently (OR 0.97, 95 % CI 0.88-1.05).

CONCLUSIONS

After addressing potential methodological limitations of prior studies, we confirm that benzodiazepine administration increases the risk for delirium in critically ill adults but this association seems to be limited to continuous infusion use only.

Likelihood of infection in patients with presumed sepsis at the time of intensive care unit admission: a cohort study

Introduction

A clinical suspicion of infection is mandatory for diagnosing sepsis in patients with a systemic inflammatory response syndrome. Yet, the accuracy of categorizing critically ill patients presenting to the intensive care unit (ICU) as being infected or not is unknown. We therefore assessed the likelihood of infection in patients who were treated for sepsis upon admission to the ICU, and quantified the association between plausibility of infection and mortality.

Methods

We studied a cohort of critically ill patients admitted with clinically suspected sepsis to two tertiary ICUs in the Netherlands between January 2011 and December 2013. The likelihood of infection was categorized as none, possible, probable or definite by post-hoc assessment. We used multivariable competing risks survival analyses to determine the association of the plausibility of infection with mortality.

Results

Among 2579 patients treated for sepsis, 13% had a post-hoc infection likelihood of “none”, and an additional 30% of only “possible”. These percentages were largely similar for different suspected sites of infection. In crude analyses, the likelihood of infection was associated with increased length of stay and complications. In multivariable analysis, patients with an unlikely infection had a higher mortality rate compared to patients with a definite infection (subdistribution hazard ratio 1.23; 95% confidence interval 1.03-1.49).

Conclusions

This study is the first prospective analysis to show that the clinical diagnosis of sepsis upon ICU admission corresponds poorly with the presence of infection on post-hoc assessment. A higher likelihood of infection does not adversely influence outcome in this population.

Trial registration

ClinicalTrials.gov NCT01905033. Registered 11 July 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1035-1) contains supplementary material, which is available to authorized users.

Epidemiology, Management, and Risk-Adjusted Mortality of ICU-Acquired Enterococcal Bacteremia

BACKGROUND

Enterococcal bacteremia has been associated with high case fatality, but it remains unknown to what extent death is caused by these infections. We therefore quantified attributable mortality of intensive care unit (ICU)-acquired bacteremia caused by enterococci.

METHODS

From 2011 to 2013 we studied consecutive patients who stayed >48 hours in 2 tertiary ICUs in the Netherlands, using competing risk survival regression and marginal structural modeling to estimate ICU mortality caused by enterococcal bacteremia.

RESULTS

Among 3080 admissions, 266 events of ICU-acquired bacteremia occurred in 218 (7.1%) patients, of which 76 were caused by enterococci (incidence rate, 3.0 per 1000 patient-days at risk; 95% confidence interval [CI], 2.3-3.7). A catheter-related bloodstream infection (CRBSI) was suspected in 44 (58%) of these, prompting removal of 68% of indwelling catheters and initiation of antibiotic treatment for a median duration of 3 (interquartile range 1-7) days. Enterococcal bacteremia was independently associated with an increased case fatality rate (adjusted subdistribution hazard ratio [SHR], 2.68; 95% CI, 1.44-4.98). However, for patients with CRBSI, case fatality was similar for infections caused by enterococci and coagulase-negative staphylococci (CoNS; adjusted SHR, 0.91; 95% CI, .50-1.67). Population-attributable fraction of mortality was 4.9% (95% CI, 2.9%-6.9%) by day 90, reflecting a population-attributable risk of 0.8% (95% CI, .4%-1.1%).

CONCLUSIONS

ICU-acquired enterococcal bacteremia is associated with increased case fatality; however, the mortality attributable to these infections is low from a population perspective. The virulence of enterococci and CoNS in a setting of CRBSI seems comparable.

Incidence, risk factors and outcomes of new-onset atrial fibrillation in patients with sepsis: a systematic review

Introduction

Critically ill patients with sepsis are prone to develop cardiac dysrhythmias, most commonly atrial fibrillation (AF). Systemic inflammation, circulating stress hormones, autonomic dysfunction, and volume shifts are all possible triggers for AF in this setting. We conducted a systematic review to describe the incidence, risk factors and outcomes of new-onset AF in patients with sepsis.

Methods

MEDLINE, EMBASE and Web Of Science were searched for studies reporting the incidence of new-onset AF, atrial flutter or supraventricular tachycardia in patients with sepsis admitted to an intensive care unit, excluding studies that primarily focused on postcardiotomy patients. Studies were assessed for methodological quality using the GRADE system. Risk factors were considered to have a high level of evidence if they were reported in ≥2 studies using multivariable analyses at a P value <0.05. Subsequently, the strength of association was classified as strong, moderate or weak, based on the reported odds ratios.

Results

Eleven studies were included. Overall quality was low to moderate. The weighted mean incidence of new-onset AF was 8% (range 0 to 14%), 10% (4 to 23%) and 23% (6 to 46%) in critically ill patients with sepsis, severe sepsis and septic shock, respectively. Independent risk factors with a high level of evidence included advanced age (weak strength of association), white race (moderate association), presence of a respiratory tract infection (weak association), organ failure (moderate association), and pulmonary artery catheter use (moderate association). Protective factors were a history of diabetes mellitus (weak association) and the presence of a urinary tract infection (weak association). New-onset AF was associated with increased short-term mortality in five studies (crude relative effect estimates ranging from 1.96 to 3.32; adjusted effects 1.07 to 3.28). Three studies reported a significantly increased length of stay in the ICU (weighted mean difference 9 days, range 5 to 13 days), whereas an increased risk of ischemic stroke was reported in the single study that looked at this outcome.

Conclusions

New-onset AF is a common consequence of sepsis and is independently associated with poor outcome. Early risk stratification of patients may allow for pharmacological interventions to prevent this complication.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0688-5) contains supplementary material, which is available to authorized users.

The attributable mortality of delirium in critically ill patients: prospective cohort study

OBJECTIVE

To determine the attributable mortality caused by delirium in critically ill patients.

DESIGN

Prospective cohort study.

SETTING

32 mixed bed intensive care unit in the Netherlands, January 2011 to July 2013.

PARTICIPANTS

1112 consecutive adults admitted to an intensive care unit for a minimum of 24 hours.

EXPOSURES

Trained observers evaluated delirium daily using a validated protocol. Logistic regression and competing risks survival analyses were used to adjust for baseline variables and a marginal structural model analysis to adjust for confounding by evolution of disease severity before the onset of delirium.

MAIN OUTCOME MEASURE

Mortality during admission to an intensive care unit.

RESULTS

Among 1112 evaluated patients, 558 (50.2%) developed at least one episode of delirium, with a median duration of 3 days (interquartile range 2-7 days). Crude mortality was 94/558 (17%) in patients with delirium compared with 40/554 (7%) in patients without delirium (P<0.001). Delirium was significantly associated with mortality in the multivariable logistic regression analysis (odds ratio 1.77, 95% confidence interval 1.15 to 2.72) and survival analysis (subdistribution hazard ratio 2.08, 95% confidence interval 1.40 to 3.09). However, the association disappeared after adjustment for time varying confounders in the marginal structural model (subdistribution hazard ratio 1.19, 95% confidence interval 0.75 to 1.89). Using this approach, only 7.2% (95% confidence interval -7.5% to 19.5%) of deaths in the intensive care unit were attributable to delirium, with an absolute mortality excess in patients with delirium of 0.9% (95% confidence interval -0.9% to 2.3%) by day 30. In post hoc analyses, however, delirium that persisted for two days or more remained associated with a 2.0% (95% confidence interval 1.2% to 2.8%) absolute mortality increase. Furthermore, competing risk analysis showed that delirium of any duration was associated with a significantly reduced rate of discharge from the intensive care unit (cause specific hazard ratio 0.65, 95% confidence interval 0.55 to 0.76).

CONCLUSIONS

Overall, delirium prolongs admission in the intensive care unit but does not cause death in critically ill patients. Future studies should focus on episodes of persistent delirium and its long term sequelae rather than on acute mortality.Trial registration Clinicaltrials.gov NCT01905033.

Electronic implementation of a novel surveillance paradigm for ventilator-associated events. Feasibility and validation

RATIONALE

Accurate surveillance of ventilator-associated pneumonia (VAP) is hampered by subjective diagnostic criteria. A novel surveillance paradigm for ventilator-associated events (VAEs) was introduced.

OBJECTIVES

To determine the validity of surveillance using the new VAE algorithm.

METHODS

Prospective cohort study in two Dutch academic medical centers (2011-2012). VAE surveillance was electronically implemented and included assessment of (infection-related) ventilator-associated conditions (VAC, IVAC) and VAP. Concordance with ongoing prospective VAP surveillance was assessed, along with clinical diagnoses underlying VAEs and associated mortality of all conditions. Consequences of minor differences in electronic VAE implementation were evaluated.

MEASUREMENTS AND MAIN RESULTS

The study included 2,080 patients with 2,296 admissions. Incidences of VAC, IVAC, VAE-VAP, and VAP according to prospective surveillance were 10.0, 4.2, 3.2, and 8.0 per 1000 ventilation days, respectively. The VAE algorithm detected at most 32% of the patients with VAP identified by prospective surveillance. VAC signals were most often caused by volume overload and infections, but not necessarily VAP. Subdistribution hazards for mortality were 3.9 (95% confidence interval, 2.9-5.3) for VAC, 2.5 (1.5-4.1) for IVAC, 2.0 (1.1-3.6) for VAE-VAP, and 7.2 (5.1-10.3) for VAP identified by prospective surveillance. In sensitivity analyses, mortality estimates varied considerably after minor differences in electronic algorithm implementation.

CONCLUSIONS

Concordance between the novel VAE algorithm and VAP was poor. Incidence and associated mortality of VAE were susceptible to small differences in electronic implementation. More studies are needed to characterize the clinical entities underlying VAE and to ensure comparability of rates from different institutions.

Interobserver agreement of Centers for Disease Control and Prevention criteria for classifying infections in critically ill patients

OBJECTIVES

Correct classification of the source of infection is important in observational and interventional studies of sepsis. Centers for Disease Control and Prevention criteria are most commonly used for this purpose, but the robustness of these definitions in critically ill patients is not known. We hypothesized that in a mixed ICU population, the performance of these criteria would be generally reduced and would vary among diagnostic subgroups.

DESIGN

Prospective cohort.

SETTING

Data were collected as part of a cohort of 1,214 critically ill patients admitted to two hospitals in The Netherlands between January 2011 and June 2011.

PATIENTS

Eight observers assessed a random sample of 168 of 554 patients who had experienced at least one infectious episode in the ICU. Each patient was assessed by two randomly selected observers who independently scored the source of infection (by affected organ system or site), the plausibility of infection (rated as none, possible, probable, or definite), and the most likely causative pathogen. Assessments were based on a post hoc review of all available clinical, radiological, and microbiological evidence. The observed diagnostic agreement for source of infection was classified as partial (i.e., matching on organ system or site) or complete (i.e., matching on specific diagnostic terms), for plausibility as partial (2-point scale) or complete (4-point scale), and for causative pathogens as an approximate or exact pathogen match. Interobserver agreement was expressed as a concordant percentage and as a kappa statistic.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 206 infectious episodes were observed. Agreement regarding the source of infection was 89% (183/206) and 69% (142/206) for a partial and complete diagnostic match, respectively. This resulted in a kappa of 0.85 (95% CI, 0.79-0.90). Agreement varied from 63% to 91% within major diagnostic categories and from 35% to 97% within specific diagnostic subgroups, with the lowest concordance observed in cases of ventilator-associated pneumonia. In the 142 episodes for which a complete match on source of infection was obtained, the interobserver agreement for plausibility of infection was 83% and 65% on a 2- and 4-point scale, respectively. For causative pathogen, agreement was 78% and 70% for an approximate and exact pathogen match, respectively.

CONCLUSIONS

Interobserver agreement for classifying sources of infection using Centers for Disease Control and Prevention criteria was excellent overall. However, full concordance on all aspects of the diagnosis between independent observers was rare for some types of infection, in particular for ventilator-associated pneumonia.

Nebulised amphotericin B to eradicate Candida colonisation from the respiratory tract in critically ill patients receiving selective digestive decontamination: a cohort study

Introduction

Colonisation of the lower respiratory tract with Candida species occurs in 25% of mechanically ventilated critically ill patients, and is associated with increased morbidity. Nebulised amphotericin B has been used to eradicate Candida as part of selective decontamination of the digestive tract (SDD) protocols, but its effectiveness is unknown. We aimed to determine the effectiveness of nebulised amphotericin B in eradicating Candida respiratory tract colonisation in patients receiving SDD.

Methods

We included consecutive mechanically ventilated patients during a four-year period. Microbiological screening was performed upon admission and twice weekly thereafter according to a standardised protocol. A colonisation episode was defined as the presence of Candida species in two consecutive sputum samples taken at least one day apart. To correct for time-varying bias and possible confounding, we used a multistate approach and performed time-varying Cox regression with adjustment for age, disease severity, Candida load at baseline and concurrent corticosteroid use.

Results

Among 1,819 patients, colonisation with Candida occurred 401 times in 363 patients; 333 of these events were included for analysis. Decolonisation occurred in 51 of 59 episodes (86%) and in 170 of 274 episodes (62%) in patients receiving and not receiving nebulised amphotericin B, respectively. Nebulised amphotericin B was associated with an increased rate of Candida eradication (crude HR 2.0; 95% CI 1.4 to 2.7, adjusted HR 2.2; 95% CI 1.6 to 3.0). Median times to decolonisation were six and nine days, respectively. The incidence rate of ventilator-associated pneumonia, length of stay and mortality did not differ between both groups.

Conclusions

Nebulised amphotericin B reduces the duration of Candida colonisation in the lower respiratory tracts of mechanically ventilated critically ill patients receiving SDD, but data remain lacking that this is associated with a meaningful improvement in clinical outcomes. Until more evidence becomes available, nebulised amphotericin B should not be used routinely as part of the SDD protocol.

Malaria and asymptomatic parasitaemia in Gabonese infants under the age of 3 months

We determined the incidence of both malaria and asymptomatic parasitaemia in infants under the age of 3 months within the framework of a longitudinal cohort study in Lambaréné, Gabon, between December 2002 and July 2004. Of 878 infants who were included at birth, we identified malaria in three infants and, additionally, asymptomatic parasitaemia in six infants. The malaria incidence density was 1.1/1000 person-months or 0.1% of observations. Our findings underpin the notion that the incidence of malaria and parasitaemia in infants below the age of 3 months is very low.