Jos F. Frencken

Classification of patients with sepsis according to blood genomic endotype: a prospective cohort study

BACKGROUND Host responses during sepsis are highly heterogeneous, which hampers the identification of patients at high risk of mortality and their selection for targeted therapies. In this study, we aimed to identify biologically relevant molecular endotypes in patients with sepsis. METHODS This was a prospective observational cohort study that included consecutive patients admitted for sepsis to two intensive care units (ICUs) in the Netherlands between Jan 1, 2011, and July 20, 2012 (discovery and first validation cohorts) and patients admitted with sepsis due to community-acquired pneumonia to 29 ICUs in the UK (second validation cohort). We generated genome-wide blood gene expression profiles from admission samples and analysed them by unsupervised consensus clustering and machine learning. The primary objective of this study was to establish endotypes for patients with sepsis, and assess the association of these endotypes with clinical traits and survival outcomes. We also established candidate biomarkers for the endotypes to allow identification of patient endotypes in clinical practice. FINDINGS The discovery cohort had 306 patients, the first validation cohort had 216, and the second validation cohort had 265 patients. Four molecular endotypes for sepsis, designated Mars1-4, were identified in the discovery cohort, and were associated with 28-day mortality (log-rank p=0·022). In the discovery cohort, the worst outcome was found for patients classified as having a Mars1 endotype, and at 28 days, 35 (39%) of 90 people with a Mars1 endotype had died (hazard ratio [HR] vs all other endotypes 1·86 [95% CI 1·21-2·86]; p=0·0045), compared with 23 (22%) of 105 people with a Mars2 endotype (HR 0·64 [0·40-1·04]; p=0·061), 16 (23%) of 71 people with a Mars3 endotype (HR 0·71 [0·41-1·22]; p=0·19), and 13 (33%) of 40 patients with a Mars4 endotype (HR 1·13 [0·63-2·04]; p=0·69). Analysis of the net reclassification improvement using a combined clinical and endotype model significantly improved risk prediction to 0·33 (0·09-0·58; p=0·008). A 140-gene expression signature reliably stratified patients with sepsis to the four endotypes in both the first and second validation cohorts. Only Mars1 was consistently significantly associated with 28-day mortality across the cohorts. To facilitate possible clinical use, a biomarker was derived for each endotype; BPGM and TAP2 reliably identified patients with a Mars1 endotype. INTERPRETATION This study provides a method for the molecular classification of patients with sepsis to four different endotypes upon ICU admission. Detection of sepsis endotypes might assist in providing personalised patient management and in selection for trials. FUNDING Center for Translational Molecular Medicine, Netherlands.

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

IntroductionA 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.MethodsWe 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.ResultsAmong 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).ConclusionsThis 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 registrationClinicalTrials.gov NCT01905033. Registered 11 July 2013.

Incidence, Predictors, and Outcomes of New-Onset Atrial Fibrillation in Critically Ill Patients with Sepsis. A Cohort Study

Rationale: Patients admitted to intensive care units with sepsis are prone to developing cardiac dysrhythmias, most commonly atrial fibrillation. Objectives: To determine the incidence, risk factors, and outcomes of atrial fibrillation in a cohort of critically ill patients with sepsis. Methods: We assessed the association between atrial fibrillation and mortality using time‐dependent competing risks survival analysis. Subsequently, for development of a risk score estimating the probability of a first occurrence of atrial fibrillation within the following 24 hours, we performed logistic regression analysis. Measurements and Main Results: Among 1,782 patients with sepsis admitted to two tertiary intensive care units in the Netherlands between January 2011 and June 2013, a total of 1,087 episodes of atrial fibrillation occurred in 418 (23%) individuals. The cumulative risk of new‐onset atrial fibrillation was 10% (95% confidence interval [CI], 8‐12), 22% (95% CI, 18‐25), and 40% (95% CI, 36‐44) in patients with sepsis, severe sepsis, and septic shock, respectively. New‐onset atrial fibrillation was associated with a longer stay (hazard ratio [HR], 0.55; 95% CI, 0.48‐0.64), an increased death rate (HR, 1.52; 95% CI, 1.16‐2.00), and an overall increased mortality risk (subdistribution HR, 2.10; 95% CI, 1.61‐2.73) when considering discharge as a competing event. A simple risk score for daily prediction of atrial fibrillation occurrence yielded good discrimination (C statistic, 0.81; 95% CI, 0.79‐0.84) and calibration (chi‐square, 9.38; P = 0.31), with similar performance in an independent validation cohort (C statistic, 0.80; 95% CI, 0.76‐0.85). Conclusions: Atrial fibrillation is a common complication of sepsis and independently associated with excess mortality. A simple risk score may identify patients at high risk of this complication. Clinical trial registered with www.clinicaltrials.gov (NCT 01905033).

Cytomegalovirus seroprevalence as a risk factor for poor outcome in acute respiratory distress syndrome

Objective:Cytomegalovirus reactivation may complicate critical illness in latent carriers of the virus, even in patients who were previously immunocompetent. Patients with acute respiratory distress syndrome are considered to be prone for reactivation. Prophylactic antiviral therapy in immunocompetent cytomegalovirus seropositive patients admitted to the ICU with acute respiratory distress syndrome has therefore been proposed. We assessed cytomegalovirus seroprevalence as a risk factor for morbidity and mortality in patients with acute respiratory distress syndrome. Design:Prospective observational cohort study. We used the number of days alive and free of mechanical ventilation on day 28 as a composite outcome measure and used multivariable ordinal logistic regression analyses to adjust for potential confounders. Setting:ICUs of two tertiary care hospitals in The Netherlands. Patients:We included all newly admitted patients with acute respiratory distress syndrome who received mechanical ventilation for at least 4 days. Patients with known immunocompromise and those receiving antiviral treatment prior to ICU admission were excluded. Interventions:None. Measurements and Main Results:Over a 2-year period, 306 patients were included, 209 (68%) of whom were cytomegalovirus seropositive. Cytomegalovirus reactivation occurred in 53 of these cases (26%). One hundred patients (33%) died or continued to be mechanically ventilated by day 28. After adjustment for confounding, cytomegalovirus seroprevalence was not associated with the primary outcome (crude odds ratio, 1.09; 95% CI, 0.70–1.70; adjusted odds ratio, 1.01; 95% CI, 0.64–1.59). Seroprevalence was also not associated with poor outcome in any of the prespecified subgroup analyses. However, a significant association was found in a post hoc subgroup of patients who had developed acute respiratory distress syndrome in a setting of septic shock (adjusted odds ratio, 2.86; 95% CI, 1.32–6.23). The time course of pulmonary markers in survivors was comparable between the two serogroups. Conclusions:Cytomegalovirus seroprevalence is not associated with prolonged mechanical ventilation or increased mortality in critically ill patients with acute respiratory distress syndrome, with possible exception of patients presenting with septic shock. Therefore, a prevention strategy targeting an unselected cohort of seropositive patients with acute respiratory distress syndrome is unlikely to show any meaningful benefit.

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.

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.

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.

Handling time dependent variables: antibiotics and antibiotic resistance

Elucidating quantitative associations between antibiotic exposure and antibiotic resistance development is important. In the absence of randomized trials, observational studies are the next best alternative to derive such estimates. Yet, as antibiotics are prescribed for varying time periods, antibiotics constitute time-dependent exposures. Cox regression models are suited for determining such associations. After explaining the concepts of hazard, hazard ratio, and proportional hazards, the effects of treating antibiotic exposure as fixed or time-dependent variables are illustrated and discussed. Wider acceptance of these techniques will improve quantification of the effects of antibiotics on antibiotic resistance development and provide better evidence for guideline recommendations.

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.

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.