Sepsis Subclasses: A Framework for Development and Interpretation

Clinical phenotyping of septic shock with latent profile analysis: A retrospective multicenter study

BACKGROUND

Septic shock (SS) is a highly fatal and heterogeneous syndrome. Identifying distinct clinical phenotypes provides valuable insights into the underlying pathophysiological mechanisms and may help to propose precise clinical management strategies.

METHODS

Latent profile analysis (LPA), a model-based unsupervised method, was used for phenotyping in the MIMIC cohort, and the model was externally independently validated in the eICU and AUMC cohorts.

RESULTS

Three phenotypes, labeled phenotype I, II, and III, were derived. These phenotypes varied in demographics, clinical features, comorbidities, patterns of organ dysfunction, organ support, and prognosis. Phenotype I, characterized by the most severe organ dysfunction (especially liver), the youngest age, and the highest BMI, had the highest mortality (p < 0.001). Phenotype II, with moderate mortality, was characterized by severe renal injury. In contrast, phenotype III, associated with the oldest age and the fewest comorbidities, exhibited significantly lower mortality. Phenotype I patients had the steepest survival curves and demonstrated an ultra-high risk of death, particularly within the first few days after SS onset.

CONCLUSIONS

The individualized identification of phenotypes is well suited to clinical practice. The three SS phenotypes differed significantly in pathophysiological and clinical outcomes, which are crucial for informing management decisions and prognosis.

Aiming for precision: personalized medicine through sepsis subtyping

According to the latest definition, sepsis is characterized by life-threatening organ dysfunction caused by a dysregulated host response to an infection. However, this definition fails to grasp the heterogeneous nature and the underlying dynamic pathophysiology of the syndrome. In response to this heterogeneity, efforts have been made to stratify sepsis patients into subtypes, either based on their clinical presentation or pathophysiological characteristics. Subtyping introduces the possibility of the implementation of personalized medicine, whereby each patient receives treatment tailored to their individual disease manifestation. This review explores the currently known subtypes, categorized by subphenotypes and endotypes, as well as the treatments that have been researched thus far in the context of sepsis subtypes and personalized medicine.

MiRNAs and Neutrophil-Related Membrane Proteins from Plasma-Derived Extracellular Vesicles for Early Prediction of Organ Dysfunction and Prognosis in Septic Patients

Purpose

The pathogenesis of sepsis-induced organ dysfunction remains elusive, and the mortality remains alarmingly high. We sought to investigate the profile of extracellular vesicles (EVs)-mediated communication between plasma and polymorphonuclear neutrophils (PMNs) in sepsis, and to elucidate whether miRNAs and PMN-related membrane proteins from plasma-derived EVs (plasma-EVs) are associated with sepsis-induced organ dysfunction and prognosis.

Methods

PMN-derived EVs (PMN-EVs) were isolated from the blood samples of healthy controls (N=3) and patients with septic shock (N=3) after ICU admission. We performed miRNA sequencing of the isolated EVs, followed by bioinformatic analysis. A miRNA model for comparing PMN-EVs and plasma-EVs was successfully established in the training cohort. Furthermore, miRNAs and PMN-related membrane proteins from the plasma-EV model were confirmed in the validation cohort. A logistic regression model, receiver operating characteristic (ROC) curves, and Kaplan-Meier analyses were performed to evaluate the efficiency of diagnostic and/or prognostic performance. Further, in vivo and in vitro experiments were conducted to explore the involvement of plasma-EVs in PMNs autophagy.

Results

Fifty-five miRNAs from PMN-EVs differed significantly between the healthy controls and patients with septic shock. Furthermore, the plasma-EV model (six miRNAs and eight PMN-related membrane proteins) was confirmed in the validation cohort, demonstrating that miR-34a-5p, miR-503-5p, miR-4772-3p, ITGAM, MPO, and MMP9 serve as sepsis biomarkers for distinguishing lung, liver, and kidney dysfunction. Kaplan-Meier survival analysis showed that miR-34a-5p, miR-4772-3p, ITGAM, and MMP9 were potential prognostic predictors. Finally, we found that plasma-EVs from sepsis patients exert an inhibitory effect on PMNs autophagy, which can be reversed by EV inhibitors such as GW4869 and enoxaparin.

Conclusion

These findings suggest that miRNAs and PMN-related membrane proteins from plasma-EVs could be valuable diagnostic tools for identifying sepsis-induced organ dysfunction and predicting prognosis, enabling proactive management of sepsis by physicians and improving the prognosis of sepsis patients.

Causal inference can lead us to modifiable mechanisms and informative archetypes in sepsis

Medical progress is reflected in the advance from broad clinical syndromes to mechanistically coherent diagnoses. By this metric, research in sepsis is far behind other areas of medicine-the word itself conflates multiple different disease mechanisms, whilst excluding noninfectious syndromes (e.g., trauma, pancreatitis) with similar pathogenesis. New technologies, both for deep phenotyping and data analysis, offer the capability to define biological states with extreme depth. Progress is limited by a fundamental problem: observed groupings of patients lacking shared causal mechanisms are very poor predictors of response to treatment. Here, we discuss concrete steps to identify groups of patients reflecting archetypes of disease with shared underlying mechanisms of pathogenesis. Recent evidence demonstrates the role of causal inference from host genetics and randomised clinical trials to inform stratification analyses. Genetic studies can directly illuminate drug targets, but in addition they create a reservoir of statistical power that can be divided many times among potential patient subgroups to test for mechanistic coherence, accelerating discovery of modifiable mechanisms for testing in trials. Novel approaches, such as subgroup identification in-flight in clinical trials, will improve efficiency. Within the next decade, we expect ongoing large-scale collaborative projects to discover and test therapeutically relevant sepsis archetypes.

Tanshinone IIA, a component of Salvia miltiorrhiza Bunge, attenuated sepsis-induced liver injury via the SIRT1/Sestrin2/HO-1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

As a traditional Chinese medicine, Salvia miltiorrhiza Bunge has been widely used to treat ischemic and inflammation-related diseases for more than 2000 years. S. miltiorrhiza Bunge has hepatoprotective effects, but the underlying mechanism is not fully understood.

OBJECTIVE

To verify the effect of tanshinone IIA (Tan IIA), the main fat-soluble component of S. miltiorrhiza Bunge, on liver damage induced by sepsis/LPS-induced inflammation and further explore the underlying mechanisms.

MATERIALS AND METHODS

Mice were administered Tan IIA 2 h before cecal ligation and puncture (CLP). Liver damage was evaluated by hematoxylin-eosin staining and changes in related serum factor levels. The expression of silent information regulator sirtuin 1 (SIRT1), Sestrin2, HO-1 and inflammatory cytokines was examined by immunohistochemistry or western blotting. LPS was used to induce the inflammatory response in vitro, and the activity of the related signaling pathway in response to Tan IIA was detected by western blotting. The SIRT1 inhibitor EX-527 and small interfering RNAs (siRNAs) were employed to determine the key roles of SIRT1 and Sestrin2 in Tan IIA's function.

RESULTS

We found that Tan IIA significantly improved the pathological changes and function of the liver, and alleviated liver damage in CLP mice. Additionally, SIRT1, Sestrin2, and HO-1 expression was significantly elevated after Tan IIA treatment compared with that in the CLP group both in vivo and in vitro, and Tan IIA treatment additionally suppressed pro-inflammatory cytokine release. However, inhibition of either SIRT1 or Sestrin2 remarkably abrogated the protective effects of Tan IIA. Most importantly, Sestrin2 appeared to function downstream of SIRT1 based on their expression changes after EX-527 or siRNA treatment.

CONCLUSION

Tan IIA inhibited sepsis/LPS-induced inflammation through the SIRT1/Sestrin2/HO-1 pathway, thereby protecting against sepsis-induced liver injury (SLI). This study suggests that Tan IIA has therapeutic potential against SLI and that the SIRT1/Sestrin2/HO-1 signaling pathway might be a viable target for SLI treatment.

Sepsis pathogenesis and outcome are shaped by the balance between the transcriptional states of systemic inflammation and antimicrobial response

Patients with sepsis differ in their clinical presentations and immune dysregulation in response to infection, but the fundamental processes that determine this heterogeneity remain elusive. Here, we aim to understand which types of immune dysregulation characterize patients with sepsis. To that end, we investigate sepsis pathogenesis in the context of two transcriptional states: one represents the immune response to eliminate pathogens (resistance, R) and the other is associated with systemic inflammation (SI). We find that patients with sepsis share a molecular fingerprint of a low R-to-SI balance-i.e., a low R relative to the level of SI. Differences between patients with sepsis are explained by the wide diversity of R and SI states that fall under this fingerprint, such as patients with high SI, patients with low R, or both. We show how this R/SI framework can be used to guide patient stratification that is relevant to disease prognosis and management, outperforming existing classifications of sepsis.

A host immune-related LncRNA and mRNA signature as a discriminant classifier for bacterial from non-bacterial sepsis in children

Background

The variations in non-coding RNA alterations and the host immune response between patients with bacterial and non-bacterial sepsis, along with their clinical characteristics, are largely unknown.

Methods

The landscape of long non-coding RNA (lncRNA) and mRNA in whole blood cells from pediatric patients with bacterial sepsis or non-bacterial sepsis were characterized using an Arraystar human LncRNA microarray. Weighted correlation network analysis (WGCNA) were conducted to identify immune-related LncRNA-mRNA signatures. Least absolute shrinkage and selection operator (Lasso) regression and Ridge regression analysis were employed to develop a specific LncRNA-mRNA signature, serving as a discriminant classifier for bacterial and non-bacterial sepsis in children.

Results

A total of 33 differentially expressed lncRNAs and 52 mRNAs were identified in pediatric patients with either bacterial sepsis or non-bacterial sepsis. Among these, 69 lncRNAs and mRNAs were pinpointed using WGCNA and found to be significantly correlated with clinical parameters. Further intersection analysis identified 12 lncRNAs and 16 mRNAs as immune-related signature for discerning bacterial infections in children with sepsis. Additionaly, the lncRNA-mRNA co-expression network highlighted the key lncRNAs (AC090159.1 and AC080129.2) and mRNAs (S100A8 and TCF7L2) as an infection score model. Lasso regression analysis revealed that this infection score model achieved an area under the received operating curve (AUROC) of 0.96 in the training set and 0.86 in the validation set. Ultimately, the expression levels of these 4 key lncRNAs and mRNAs showed significant correlation with CRP or PCT levels.

Conclusion

The machine learning model, developed utilizing key lncRNAs (AC090159.1 and AC080129.2) and mRNAs (S100A8 and TCF7L2), demonstrates robust discrimination and calibration capabilities for distinguishing between bacterial and non-bacterial sepsis in children.

Transcriptional pathways of terminal differentiation in high- and low-density blood granulocytes in sepsis

BACKGROUND

Trauma and infection induce emergency granulopoiesis. Counts of immature granulocytes and transcriptional pathways of terminal granulocytic differentiation in blood are elevated in sepsis but correlate with disease severity. This limits their performance as sepsis biomarkers in critically ill patients. We hypothesized that activation of these pathways in sepsis is attributable to immature low-density (LD) rather than mature high-density (HD) granulocytes.

METHODS

We included patients with sepsis and systemic inflammatory response syndrome (SIRS) of comparable disease severity, and additionally septic shock, on intensive or intermediate care unit admission. Blood granulocyte isolation by CD15 MicroBeads was followed by density-gradient centrifugation. Flow cytometry was used to determine counts of developmental stages (precursors) and their relative abundancies in total, HD, and LD granulocytes. Five degranulation markers were quantified in plasma by multiplex immunoassays. A set of 135 genes mapping granulocyte differentiation was assayed by QuantiGene™ Plex. CEACAM4, PLAC8, and CD63 were analyzed by qRT-PCR. Nonparametric statistical tests were applied.

RESULTS

Precursor counts appeared higher in sepsis than SIRS but did not correlate with disease severity for early immature and mature granulocytes. Precursor subpopulations were enriched at least ten-fold in LD over HD granulocytes without sepsis-SIRS differences. Degranulation markers in blood were comparable in sepsis and SIRS. Higher expression of early developmental genes in sepsis than SIRS was more pronounced in LD and less in HD than total granulocytes. Only the cell membrane protein encoding genes CXCR2 and CEACAM4 were more highly expressed in SIRS than sepsis. By qRT-PCR, the azurophilic granule genes CD63 and PLAC8 showed higher sepsis than SIRS levels in LD granulocytes and PLAC8 also in total granulocytes where its discriminatory performance resembled C-reactive protein (CRP).

CONCLUSIONS

Transcriptional programs of early terminal granulocytic differentiation distinguish sepsis from SIRS due to both higher counts of immature granulocytes and elevated expression of early developmental genes in sepsis. The sustained expression of PLAC8 in mature granulocytes likely accounts for its selection in the whole blood SeptiCyte™ LAB test. Total granulocyte PLAC8 rivals CRP as sepsis biomarker. However, infection-specific transcriptional pathways, that differentiate sepsis from sterile stress-induced granulocytosis more reliably than CRP, remain to be identified.

Rapid and Robust Identification of Sepsis Using SeptiCyte RAPID in a Heterogeneous Patient Population

Background/Objective: SeptiCyte RAPID is a transcriptional host response assay that discriminates between sepsis and non-infectious systemic inflammation (SIRS) with a one-hour turnaround time. The overall performance of this test in a cohort of 419 patients has recently been described [Balk et al., J Clin Med 2024, 13, 1194]. In this study, we present the results from a detailed stratification analysis in which SeptiCyte RAPID performance was evaluated in the same cohort across patient groups and subgroups encompassing different demographics, comorbidities and disease, sources and types of pathogens, interventional treatments, and clinically defined phenotypes. The aims were to identify variables that might affect the ability of SeptiCyte RAPID to discriminate between sepsis and SIRS and to determine if any patient subgroups appeared to present a diagnostic challenge for the test. Methods: (1) Subgroup analysis, with subgroups defined by individual demographic or clinical variables, using conventional statistical comparison tests. (2) Principal component analysis and k-means clustering analysis to investigate phenotypic subgroups defined by unique combinations of demographic and clinical variables. Results: No significant differences in SeptiCyte RAPID performance were observed between most groups and subgroups. One notable exception involved an enhanced SeptiCyte RAPID performance for a phenotypic subgroup defined by a combination of clinical variables suggesting a septic shock response. Conclusions: We conclude that for this patient cohort, SeptiCyte RAPID performance was largely unaffected by key variables associated with heterogeneity in patients suspected of sepsis.

Early Mortality Stratification with Serum Albumin and the Sequential Organ Failure Assessment Score at Emergency Department Admission in Septic Shock Patients

Background: Early risk stratification is crucial due to septic patients' heterogeneity. Serum albumin level may reflect the severity of sepsis and host status. This study aimed to evaluate the prognostic ability of the initial sequential organ failure assessment (SOFA) score alone and combined with serum albumin levels for predicting 28-day mortality in patients with septic shock. Methods: We conducted an observational study using a prospective, multicenter registry of septic shock patients between October 2015 and May 2022 from 12 emergency departments in the Korean Shock Society and the results were validated by examining those from the septic shock cohort in Asan Medical Center. The primary outcome was 28-day mortality. The area under the receiver operating characteristic (ROC) curve was used to compare the predictive values of SOFA score alone and SOFA score combined with serum albumin level. Results: Among 5805 septic shock patients, 1529 (26.3%) died within 28 days. Mortality increased stepwise with decreasing serum albumin levels (13.6% in albumin ≥3.5, 20.7% in 3.5-3.0, 29.7% in 3.0-2.5, 44.0% in 2.5-2.0, 56.4% in <2.0). The albumin SOFA score was calculated by adding the initial SOFA score to the 4 points assigned for albumin levels. ROC analysis for predicting 28-day mortality showed that the area under the curve for the albumin SOFA score was 0.71 (95% CI 0.70-0.73), which was significantly higher than that of the initial SOFA score alone (0.68, 95% CI: 0.67-0.69). Conclusions: The combination of the initial SOFA score with albumin can improve prognostic accuracy for patients with septic shock, suggesting the albumin SOFA score may be used as an early mortality stratification tool.

Shared neutrophil and T cell dysfunction is accompanied by a distinct interferon signature during severe febrile illnesses in children

Severe febrile illnesses in children encompass life-threatening organ dysfunction caused by diverse pathogens and other severe inflammatory syndromes. A comparative approach to these illnesses may identify shared and distinct features of host immune dysfunction amenable to immunomodulation. Here, using immunophenotyping with mass cytometry and cell stimulation experiments, we illustrate trajectories of immune dysfunction in 74 children with multi-system inflammatory syndrome in children (MIS-C) associated with SARS-CoV-2, 30 with bacterial infection, 16 with viral infection, 8 with Kawasaki disease, and 42 controls. We explore these findings in a secondary cohort of 500 children with these illnesses and 134 controls. We show that neutrophil activation and apoptosis are prominent in multi-system inflammatory syndrome, and that this is partially shared with bacterial infection. We show that memory T cells from patients with multi-system inflammatory syndrome and bacterial infection are exhausted. In contrast, we show viral infection to be characterized by a distinct signature of decreased interferon signaling and lower interferon receptor gene expression. Improved understanding of immune dysfunction may improve approaches to immunomodulator therapy in severe febrile illnesses in children.

Analysis of the diagnostic value of coagulation markers and coagulation function indices on the occurrence of DIC in sepsis and its prognosis

Sepsis is a life-threatening condition that has the potential to multiple organ dysfunction and mortality. One of its frequent complications is disseminated intravascular coagulation (DIC), characterized by hyperactive clotting mechanisms that cause widespread clot formation and tissue damage. This study aimed to investigate early diagnostic markers of sepsis-associated DIC by comparing inflammatory factor levels, 28-day survival rates, coagulation function, and markers between patients with sepsis (non-DIC group) and those with sepsis-induced DIC (DIC group). The study analyzed the diagnostic efficacy of coagulation function and markers in predicting the occurrence and prognosis of sepsis-associated DIC, presenting survival curves. Results indicated significantly increased levels of APTT, TAT, tPAIC, PIC, and sTM in the DIC group compared to the non-DIC group. Sequential Organ Failure Assessment (SOFA) scores on days 1, 3, and 7 were notably lower in the non-DIC group. Correlation analysis revealed positive associations between PT, APTT, TAT, tPAIC, PIC, sTM levels, and SOFA scores, as well as negative associations with Fib and SOFA scores. Survival curves showed substantially lower mortality rates in the non-DIC group, highlighting significant survival disparities between groups. Combining all four coagulation indicators (TAT+ tPAIC + PIC + sTM) showed promising diagnostic value in evaluating disease severity, early DIC diagnosis, and sepsis prognosis.

Digital solutions in paediatric sepsis: current state, challenges, and opportunities to improve care around the world

The digitisation of health care is offering the promise of transforming the management of paediatric sepsis, which is a major source of morbidity and mortality in children worldwide. Digital technology is already making an impact in paediatric sepsis, but is almost exclusively benefiting patients in high-resource health-care settings. However, digital tools can be highly scalable and cost-effective, and-with the right planning-have the potential to reduce global health disparities. Novel digital solutions, from wearable devices and mobile apps, to electronic health record-embedded decision support tools, have an unprecedented opportunity to transform paediatric sepsis research and care. In this Series paper, we describe the current state of digital solutions in paediatric sepsis around the world, the advances in digital technology that are enabling the development of novel applications, and the potential effect of advances in artificial intelligence in paediatric sepsis research and clinical care.

Susceptibility to childhood sepsis, contemporary management, and future directions

Sepsis disproportionally affects children across all health-care settings and is one of the leading causes of morbidity and mortality in neonatal and paediatric age groups. As shown in the first paper in this Series, the age-specific incidence of sepsis is highest during the first years of life, before approaching adult incidence rates during adolescence. In the second paper in this Series, we focus on the unique susceptibility of paediatric patients to sepsis and how the underlying dysregulated host response relates to developmental aspects of children's immune system, genetic, perinatal, and environmental factors, and comorbidities and socioeconomic determinants of health, which often differ between children and adults. State-of-the-art clinical management of paediatric sepsis is organised around three treatment pillars-diagnosis, early resuscitation, and titration of advanced care-and we examine available treatment guidelines and the limitations of their supporting evidence. Serious evidence gaps remain in key areas of paediatric sepsis care, especially surrounding recognition, common interventions, and survivor support, and to this end we offer a research roadmap for the next decade that could accelerate targeted diagnostics and personalised use of immunomodulation. However, improving outcomes for children with sepsis relies fundamentally on systematic quality improvement in both recognition and treatment, which is the theme of the third paper in this Series. Digital health, as shown in the fourth and final paper of this Series, holds promising potential in breaking down the barriers that hinder progress in paediatric sepsis care and, ultimately, global child health.

From Traditional Typing to Intelligent Insights: A Narrative Review of Directions Toward Targeted Therapies in Delirium

Delirium is a heterogeneous syndrome characterized by an acute change in level of consciousness that is associated with inattention and disorganized thinking. Delirium affects most critically ill patients and is associated with poor patient-oriented outcomes such as increased mortality, longer ICU and hospital length of stay, and worse long-term cognitive outcomes. The concept of delirium and its subtypes has existed since nearly the beginning of recorded medical literature, yet robust therapies have yet to be identified. Analogous to other critical illness syndromes, we suspect the lack of identified therapies stems from patient heterogeneity and prior subtyping efforts that do not capture the underlying etiology of delirium. The time has come to leverage machine learning approaches, such as supervised and unsupervised clustering, to identify clinical and pathophysiological distinct clusters of delirium that will likely respond differently to various interventions. We use sedation in the ICU as an example of how precision therapies can be applied to critically ill patients, highlighting the fact that while for some patients a sedative drug may cause delirium, in another cohort sedation is the specific treatment. Finally, we conclude with a proposition to move away from the term delirium, and rather focus on the treatable traits that may allow precision therapies to be tested.

Informative Subtyping of Patients with Sepsis

Sepsis pathobiology is complex. Heterogeneity refers to the clinical and biological variation within sepsis cohorts. Sepsis subtypes refer to subpopulations within sepsis cohorts derived based on these observable variations and latent features. The overarching goal of such endeavors is to enable precision immunomodulation. However, we are yet to identify immune endotypes of sepsis to achieve this goal. The sepsis subtyping field is just starting to take shape. The current subtypes in the literature do not have a core set of shared features between studies. Thus, in this narrative review, we reason that there is a need to a priori state the purpose of sepsis subtyping and minimum set of features that would be required to achieve the goal of precision immunomodulation for future sepsis.

Clinical phenotypes of sepsis: a narrative review

Background and Objective

Sepsis, characterized by an aberrant immune response to infection leading to acute organ dysfunction, impacts millions of individuals each year and carries a substantial risk of mortality, even with prompt care. Despite notable medical advancements, managing sepsis remains a formidable challenge for clinicians and researchers, with treatment options limited to antibiotics, fluid therapy, and organ-supportive measures. Given the heterogeneous nature of sepsis, the identification of distinct clinical phenotypes holds the promise of more precise therapy and enhanced patient care. In this review, we explore various phenotyping schemes applied to sepsis.

Methods

We searched PubMed with the terms "Clinical phenotypes AND sepsis" for any type of article published in English up to September 2023. Only reports in English were included, editorials or articles lacking full text were excluded. A review of clinical phenotypes of sepsis is provided.

Key Content and Findings

While discerning clinical phenotypes may seem daunting, the application of artificial intelligence and machine learning techniques provides a viable approach to quantifying similarities among individuals within a sepsis population. These methods enable the differentiation of individuals into distinct phenotypes based on not only factors such as infectious diseases, infection sites, pathogens, body temperature changes and hemodynamics, but also conventional clinical data and molecular omics.

Conclusions

The classification of sepsis holds immense significance in improving clinical cure rates, reducing mortality, and alleviating the economic burden associated with this condition.

Enhancing sepsis biomarker development: key considerations from public and private perspectives

Implementation of biomarkers in sepsis and septic shock in emergency situations, remains highly challenging. This viewpoint arose from a public-private 3-day workshop aiming to facilitate the transition of sepsis biomarkers into clinical practice. The authors consist of international academic researchers and clinician-scientists and industry experts who gathered (i) to identify current obstacles impeding biomarker research in sepsis, (ii) to outline the important milestones of the critical path of biomarker development and (iii) to discuss novel avenues in biomarker discovery and implementation. To define more appropriately the potential place of biomarkers in sepsis, a better understanding of sepsis pathophysiology is mandatory, in particular the sepsis patient's trajectory from the early inflammatory onset to the late persisting immunosuppression phase. This time-varying host response urges to develop time-resolved test to characterize persistence of immunological dysfunctions. Furthermore, age-related difference has to be considered between adult and paediatric septic patients. In this context, numerous barriers to biomarker adoption in practice, such as lack of consensus about diagnostic performances, the absence of strict recommendations for sepsis biomarker development, cost and resources implications, methodological validation challenges or limited awareness and education have been identified. Biomarker-guided interventions for sepsis to identify patients that would benefit more from therapy, such as sTREM-1-guided Nangibotide treatment or Adrenomedullin-guided Enibarcimab treatment, appear promising but require further evaluation. Artificial intelligence also has great potential in the sepsis biomarker discovery field through capability to analyse high volume complex data and identify complex multiparametric patient endotypes or trajectories. To conclude, biomarker development in sepsis requires (i) a comprehensive and multidisciplinary approach employing the most advanced analytical tools, (ii) the creation of a platform that collaboratively merges scientific and commercial needs and (iii) the support of an expedited regulatory approval process.

SS-31 inhibits the inflammatory response by increasing ATG5 and promoting autophagy in lipopolysaccharide-stimulated HepG2 cells

SS-31 is a mitochondria-targeting short peptide. Recent studies have indicated its hepatoprotective effects. In our study, we investigated the impact of SS-31 on LPS-induced autophagy in HepG2 cells. The results obtained from a dual-fluorescence autophagy detection system revealed that SS-31 promotes the formation of autolysosomes and autophagosomes, thereby facilitating autophagic flux to a certain degree. Additionally, both ELISA and qPCR analyses provided further evidence that SS-31 safeguards HepG2 cells against inflammatory responses triggered by LPS through ATG5-dependent autophagy. In summary, our study demonstrates that SS-31 inhibits LPS-stimulated inflammation in HepG2 cells by upregulating ATG5-dependent autophagy.

Association between septic shock and tracheal injury score in intensive care unit patients with invasive ventilation: a prospective single-centre cohort study in China

OBJECTIVES

There was no evidence regarding the relationship between septic shock and tracheal injury scores. Investigate whether septic shock was independently associated with tracheal injury scores in intensive care unit (ICU) patients with invasive ventilation.

DESIGN

Prospective observational cohort study.

SETTING

Our study was conducted in a Class III hospital in Hebei province, China.

PARTICIPANTS

Patients over 18 years of age admitted to the ICU between 31 May 2020 and 3 May 2022 with a tracheal tube and expected to be on the tube for more than 24 hours.

PRIMARY AND SECONDARY OUTCOME MEASURES

Tracheal injuries were evaluated by examining hyperaemia, ischaemia, ulcers and tracheal perforation by fiberoptic bronchoscope. Depending on the number of lesions, the lesions were further classified as moderate, severe or confluent.

RESULTS

Among the 97 selected participants, the average age was 56.6±16.5 years, with approximately 64.9% being men. The results of adjusted linear regression showed that septic shock was associated with tracheal injury scores (β: 2.99; 95% CI 0.70 to 5.29). Subgroup analysis revealed a stronger association with a duration of intubation ≥8 days (p=0.013).

CONCLUSION

Patients with septic shock exhibit significantly higher tracheal injury scores compared with those without septic shock, suggesting that septic shock may serve as an independent risk factor for tracheal injury.

TRIAL REGISTRATION NUMBER

ChiCTR2000037842, registered 03 September 2020. Retrospectively registered, https://www.chictr.org.cn/edit.aspx?pid=57011&htm=4.

Can Machine Learning Personalize Cardiovascular Therapy in Sepsis?

Large randomized trials in sepsis have generally failed to find effective novel treatments. This is increasingly attributed to patient heterogeneity, including heterogeneous cardiovascular changes in septic shock. We discuss the potential for machine learning systems to personalize cardiovascular resuscitation in sepsis. While the literature is replete with proofs of concept, the technological readiness of current systems is low, with a paucity of clinical trials and proven patient benefit. Systems may be vulnerable to confounding and poor generalization to new patient populations or contemporary patterns of care. Typical electronic health records do not capture rich enough data, at sufficient temporal resolution, to produce systems that make actionable treatment suggestions. To resolve these issues, we recommend a simultaneous focus on technical challenges and removing barriers to translation. This will involve improving data quality, adopting causally grounded models, prioritizing safety assessment and integration into healthcare workflows, conducting randomized clinical trials and aligning with regulatory requirements.

Profiling the dysregulated immune response in sepsis: overcoming challenges to achieve the goal of precision medicine

Sepsis is characterised by a dysregulated host immune response to infection. Despite recognition of its significance, immune status monitoring is not implemented in clinical practice due in part to the current absence of direct therapeutic implications. Technological advances in immunological profiling could enhance our understanding of immune dysregulation and facilitate integration into clinical practice. In this Review, we provide an overview of the current state of immune profiling in sepsis, including its use, current challenges, and opportunities for progress. We highlight the important role of immunological biomarkers in facilitating predictive enrichment in current and future treatment scenarios. We propose that multiple immune and non-immune-related parameters, including clinical and microbiological data, be integrated into diagnostic and predictive combitypes, with the aid of machine learning and artificial intelligence techniques. These combitypes could form the basis of workable algorithms to guide clinical decisions that make precision medicine in sepsis a reality and improve patient outcomes.

Soft phenotyping for sepsis via EHR time-aware soft clustering

OBJECTIVE

Sepsis is one of the most serious hospital conditions associated with high mortality. Sepsis is the result of a dysregulated immune response to infection that can lead to multiple organ dysfunction and death. Due to the wide variability in the causes of sepsis, clinical presentation, and the recovery trajectories, identifying sepsis sub-phenotypes is crucial to advance our understanding of sepsis characterization, to choose targeted treatments and optimal timing of interventions, and to improve prognostication. Prior studies have described different sub-phenotypes of sepsis using organ-specific characteristics. These studies applied clustering algorithms to electronic health records (EHRs) to identify disease sub-phenotypes. However, prior approaches did not capture temporal information and made uncertain assumptions about the relationships among the sub-phenotypes for clustering procedures.

METHODS

We developed a time-aware soft clustering algorithm guided by clinical variables to identify sepsis sub-phenotypes using data available in the EHR.

RESULTS

We identified six novel sepsis hybrid sub-phenotypes and evaluated them for medical plausibility. In addition, we built an early-warning sepsis prediction model using logistic regression.

CONCLUSION

Our results suggest that these novel sepsis hybrid sub-phenotypes are promising to provide more accurate information on sepsis-related organ dysfunction and sepsis recovery trajectories which can be important to inform management decisions and sepsis prognosis.

Sepsis-associated acute kidney injury: recent advances in enrichment strategies, sub-phenotyping and clinical trials

Acute kidney injury (AKI) often complicates sepsis and is associated with high morbidity and mortality. In recent years, several important clinical trials have improved our understanding of sepsis-associated AKI (SA-AKI) and impacted clinical care. Advances in sub-phenotyping of sepsis and AKI and clinical trial design offer unprecedented opportunities to fill gaps in knowledge and generate better evidence for improving the outcome of critically ill patients with SA-AKI. In this manuscript, we review the recent literature of clinical trials in sepsis with focus on studies that explore SA-AKI as a primary or secondary outcome. We discuss lessons learned and potential opportunities to improve the design of clinical trials and generate actionable evidence in future research. We specifically discuss the role of enrichment strategies to target populations that are most likely to derive benefit and the importance of patient-centered clinical trial endpoints and appropriate trial designs with the aim to provide guidance in designing future trials.

Sivelestat ameliorates sepsis-induced myocardial dysfunction by activating the PI3K/AKT/mTOR signaling pathway

The cardioprotective role of sivelestat, a neutrophil elastase inhibitor, has already been demonstrated, but the underlying molecular mechanism remains unclear. This study aimed to explore the mechanism underlying the role of sivelestat in sepsis-induced myocardial dysfunction (SIMD). We found that sivelestat treatment remarkably improved the viability and suppressed the apoptosis of lipopolysaccharide (LPS)-stimulated H9c2 cells. In vivo, sivelestat treatment was associated with an improved survival rate; reduced serum cTnT, TNF-α, IL-1β levels and myocardial TNF-α and IL-1β levels; ameliorated cardiac function and structure; and reduced cardiomyocyte apoptosis. Moreover, sivelestat treatment substantially increased Bcl-2 expression and suppressed caspase-3 and Bax expression in LPS-induced H9c2 cells and in the heart tissues of septic rats. Furthermore, the phosphatidylinositol 3-kinase/protein kinase B/mechanistic target of rapamycin (PI3K/AKT/mTOR) signaling pathway was activated both in vitro and in vivo. The protective effect of sivelestat against SIMD was reversed by the PI3K inhibitor LY294002. In summary, sivelestat can protect against SIMD by activating the PI3K/AKT/mTOR signaling pathway.

A novel model of urosepsis in mice developed by ureteral ligation and injection of Escherichia coli into the renal pelvis

Despite extensive investigations, urosepsis remains a life-threatening and high-mortality illness. The absence of widely acknowledged animal models for urosepsis prompted this investigation with the objective of formulating a replicable murine model. Eighty-four adult male C57BL/6J mice were arbitrarily distributed into three cohorts based on the concentration of the Escherichia coli (E. coli) solution administered into the renal pelvis: Sham, Low-grade sepsis (1.0 × 108 cfu/mL), and High-grade sepsis (1.0 × 109 cfu/mL). By fabricating a glass needle with a 100 μm outer diameter, bacterial leakage during renal pelvic injection was minimized. After the ureteral ligation, the mice were injected with this needle into the right renal pelvis (normal saline or E. coli solution, 1 ml/kg). Ten days post after E. coli injection, the mortality rates for the Low-grade sepsis and High-grade sepsis groups stood at 30 % and 100 %, respectively. Post-successful modeling, mice in the urosepsis cohort exhibited a noteworthy reduction in activity, body temperature, and white blood cell count within a 2-h timeframe. At the 24-h mark post-modeling, mice afflicted with urosepsis displayed compromised coagulation functionality. Concurrently, multiple organ dysfunction was confirmed as evidenced by markedly elevated levels of inflammatory factors (IL-6 and TNF-α) in four distinct organs (heart, lung, liver, and kidney). This study confirmed the feasibility of establishing a standardized mouse model of urosepsis by ureteral ligation and E. coli injection into the renal pelvis. A primary drawback of this model resides in the mice's diminished blood volume, rendering continuous blood extraction at multiple intervals challenging.

Exploring the Impact of Model-Informed Precision Dosing on Procalcitonin Concentrations in Critically Ill Patients: A Secondary Analysis of the DOLPHIN Trial

Model-informed precision dosing (MIPD) might be used to optimize antibiotic treatment. Procalcitonin (PCT) is a biomarker for severity of infection and response to antibiotic treatment. The aim of this study was to assess the impact of MIPD on the course of PCT and to investigate the association of PCT with pharmacodynamic target (PDT) attainment in critically ill patients. This is a secondary analysis of the DOLPHIN trial, a multicentre, open-label, randomised controlled trial. Patients with a PCT value available at day 1 (T1), day 3 (T3), or day 5 (T5) after randomisation were included. The primary outcome was the absolute difference in PCT concentration at T1, T3, and T5 between the MIPD and the standard dosing group. In total, 662 PCT concentrations from 351 critically ill patients were analysed. There was no statistically significant difference in PCT concentration between the trial arms at T1, T3, or T5. The median PCT concentration was highest in patients who exceeded 10× PDT at T1 [13.15 ng/mL (IQR 5.43-22.75)]. In 28-day non-survivors and in patients that exceeded PDT at T1, PCT decreased significantly between T1 and T3, but plateaued between T3 and T5. PCT concentrations were not significantly different between patients receiving antibiotic treatment with or without MIPD guidance. The potential of PCT to guide antibiotic dosing merits further investigation.

miR-129-2-3p mediates LPS-induced macrophage polarization and ferroptosis by targeting the SMAD3-GPX4 axis

Macrophages has become a promising target of sepsis treatment because macrophages dysfunction contributes to the progress of sepsis. The targeted therapy of sepsis based on macrophages ferroptosis is drawing more and more attention, but the molecular mechanism involved is poorly understood. In this study, Mus musculus-derived macrophages were used for in-vitro experiments. We found that LPS could induce ferroptosis in macrophages via the detection of apoptosis, GSH, lipid peroxide and GPX4 levels. Meanwhile, miR-129-2-3p was up-regulated in macrophages exposure to LPS. Next, we confirmed that miR-129-2-3p promoted the LPS-induced polarization of M1 phenotype in macrophages via the detection of Arg-1 and iNOS levels; miR-129-2-3p promoted the LPS-induced ferroptosis in macrophages. Further, luciferase assay showed that SMAD3 was identified as a target gene of miR-129-2-3p and its expression was negatively regulated by miR-129-2-3p and LPS. SMAD3 could inhibit the LPS-induced polarization of M1 phenotype and ferroptosis in macrophages by targeting GPX4. Collectively, we demonstrated the target gene and molecular mechanism of miR-129-2-3p mediating LPS-induced polarization and ferroptosis in macrophages by targeting the SMAD3-GPX4 axis, which would provide a novel strategy for sepsis targeted therapy based on macrophages polarization and ferroptosis.

Monotropein induces autophagy through activation of the NRF2/PINK axis, thereby alleviating sepsis-induced colonic injury

Sepsis is a systemic inflammatory disease that is caused by a dysregulated host response to infection and is a life-threatening organ dysfunction that affects many organs, which includes the colon. Mounting evidence suggests that sepsis-induced colonic damage is a major contributor to organ failure and cellular dysfunction. Monotropein (MON) is the major natural compound in the iris glycoside that is extracted from Morendae officinalis radix, which possesses the potent pharmacological activities of anti-inflammatory and antioxidant properties. This research evaluated whether MON is able to alleviate septic colonic injury in mice by cecal ligation and puncture. Colonic tissues were analyzed using histopathology, immunofluorescence, quantitative real-time polymerase chain reaction, and Western blot methods. It was initially discovered that MON reduced colonic damage in infected mice, in addition to inflammation, apoptosis, and oxidative stress in colonic tissues, while it activated autophagy, with the NRF2/keap1 and PINK1/Parkin pathways also being activated. Through the stimulation of NCM460 cells with lipopolysaccharides, an in vitro model of sepsis was created as a means of further elucidating the potential mechanisms of MON. In the in vitro model, it was found that MON could still activate the NRF2/keap1, PINK1/Parkin, and autophagy pathways. However, when MON was paired with the NRF2 inhibitor ML385, it counteracted MON-induced activation of PINK1/Parkin and autophagy, while also promoting inflammatory response and apoptosis in NCM460 cells. Therefore, the data implies that MON could play a therapeutic role through the activation of the NFR2/PINK pathway as a means of inducing autophagy to alleviate the oxidative stress in colonic tissues that is induced by sepsis, which will improve inflammation and apoptosis in colonic tissues.

EMERGENCE OF A TECHNOLOGY-DEPENDENT PHENOTYPE OF PEDIATRIC SEPSIS IN A LARGE CHILDREN'S HOSPITAL

ABSTRACT

Objective: To investigate whether pediatric sepsis phenotypes are stable in time. Methods: Retrospective cohort study examining children with suspected sepsis admitted to a Pediatric Intensive Care Unit at a large freestanding children's hospital during two distinct periods: 2010-2014 (early cohort) and 2018-2020 (late cohort). K-means consensus clustering was used to derive types separately in the cohorts. Variables included ensured representation of all organ systems. Results: One thousand ninety-one subjects were in the early cohort and 737 subjects in the late cohort. Clustering analysis yielded four phenotypes in the early cohort and five in the late cohort. Four types were in both: type A (34% of early cohort, 25% of late cohort), mild sepsis, with minimal organ dysfunction and low mortality; type B (25%, 22%), primary respiratory failure; type C (25%, 18%), liver dysfunction, coagulopathy, and higher measures of systemic inflammation; type D (16%, 17%), severe multiorgan dysfunction, with high degrees of cardiorespiratory support, renal dysfunction, and highest mortality. Type E was only detected in the late cohort (19%) and was notable for respiratory failure less severe than B or D, mild hypothermia, and high proportion of diagnoses and technological dependence associated with medical complexity. Despite low mortality, this type had the longest PICU length of stay. Conclusions: This single center study identified four pediatric sepsis phenotypes in an earlier epoch but five in a later epoch, with the new type having a large proportion of characteristics associated with medical complexity, particularly technology dependence. Personalized sepsis therapies need to account for this expanding patient population.

The pathophysiology of sepsis and precision-medicine-based immunotherapy

Sepsis remains a major cause of morbidity and mortality in both low- and high-income countries. Antibiotic therapy and supportive care have significantly improved survival following sepsis in the twentieth century, but further progress has been challenging. Immunotherapy trials for sepsis, mainly aimed at suppressing the immune response, from the 1990s and 2000s, have largely failed, in part owing to unresolved patient heterogeneity in the underlying immune disbalance. The past decade has brought the promise to break this blockade through technological developments based on omics-based technologies and systems medicine that can provide a much larger data space to describe in greater detail the immune endotypes in sepsis. Patient stratification opens new avenues towards precision medicine approaches that aim to apply immunotherapies to sepsis, on the basis of precise biomarkers and molecular mechanisms defining specific immune endotypes. This approach has the potential to lead to the establishment of immunotherapy as a successful pillar in the treatment of sepsis for future generations.

Whole blood transcriptomics identifies subclasses of pediatric septic shock

BACKGROUND

Sepsis is a highly heterogeneous syndrome, which has hindered the development of effective therapies. This has prompted investigators to develop a precision medicine approach aimed at identifying biologically homogenous subgroups of patients with septic shock and critical illnesses. Transcriptomic analysis can identify subclasses derived from differences in underlying pathophysiological processes that may provide the basis for new targeted therapies. The goal of this study was to elucidate pathophysiological pathways and identify pediatric septic shock subclasses based on whole blood RNA expression profiles.

METHODS

The subjects were critically ill children with cardiopulmonary failure who were a part of a prospective randomized insulin titration trial to treat hyperglycemia. Genome-wide expression profiling was conducted using RNA sequencing from whole blood samples obtained from 46 children with septic shock and 52 mechanically ventilated noninfected controls without shock. Patients with septic shock were allocated to subclasses based on hierarchical clustering of gene expression profiles, and we then compared clinical characteristics, plasma inflammatory markers, cell compositions using GEDIT, and immune repertoires using Imrep between the two subclasses.

RESULTS

Patients with septic shock depicted alterations in innate and adaptive immune pathways. Among patients with septic shock, we identified two subtypes based on gene expression patterns. Compared with Subclass 2, Subclass 1 was characterized by upregulation of innate immunity pathways and downregulation of adaptive immunity pathways. Subclass 1 had significantly worse clinical outcomes despite the two classes having similar illness severity on initial clinical presentation. Subclass 1 had elevated levels of plasma inflammatory cytokines and endothelial injury biomarkers and demonstrated decreased percentages of CD4 T cells and B cells and less diverse T cell receptor repertoires.

CONCLUSIONS

Two subclasses of pediatric septic shock patients were discovered through genome-wide expression profiling based on whole blood RNA sequencing with major biological and clinical differences. Trial Registration This is a secondary analysis of data generated as part of the observational CAF-PINT ancillary of the HALF-PINT study (NCT01565941). Registered March 29, 2012.

Novel transdermal curcumin therapeutic preserves endothelial barrier function in a high-dose LPS rat model

Sepsis is a devastating complication of infection and injury that, through widespread endothelial dysfunction, can cause perfusion deficits and multi-organ failure. To address the recognised need for therapeutics targetting the endothelial barrier, a topical formulation (CUR; VASCEPTOR™; Vascarta Inc, Summit, NJ) was developed to transdermally deliver bio-active concentrations of curcumin-an anti-inflammatory and nitric oxide promoter. Male, Sprague Dawley rats were treated daily with lipopolysaccharide (LPS, 10 mg/kg, IP) to induce endotoxemia, and topical applications of Vehicle Control (LPS + VC; N = 7) or Curcumin (LPS + CUR; N = 7). A third group received neither LPS nor treatment (No-LPS; N = 8). After 72 h, animals were surgically prepared for measurements of physiology and endothelial dysfunction in the exteriorised spinotrapezius muscle through the extravasation of 67 kDa TRITC-BSA (albumin) and 500 kDa FITC-dextran (dextran). At 72 h, LPS + VC saw weight loss, and increases to pulse pressure, lactate, pCO₂, CXCL5 (vs No-LPS) and IL-6 (vs 0 h; p < 0.05). LPS + CUR was similar to No-LPS, but with hypotension. Phenylephrine response was increased in LPS + CUR. Regarding endothelial function, LPS + CUR albumin and dextran extravasation were significantly reduced versus LPS + VC suggesting that Curcumin mitigated endotoxemic endothelial dysfunction. The speculated mechanisms are nitric oxide modulation of the endothelium and/or an indirect anti-inflammatory effect.

Identification of Clinically Significant Cytokine Signature Clusters in Patients With Septic Shock

OBJECTIVES

To identify cytokine signature clusters in patients with septic shock.

DESIGN

Prospective observational cohort study.

SETTING

Single academic center in the United States.

PATIENTS

Adult (≥ 18 yr old) patients admitted to the medical ICU with septic shock requiring vasoactive medication support.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One hundred fourteen patients with septic shock completed cytokine measurement at time of enrollment (t 1 ) and 24 hours later (t 2 ). Unsupervised random forest analysis of the change in cytokines over time, defined as delta (t 2 -t 1 ), identified three clusters with distinct cytokine profiles. Patients in cluster 1 had the lowest initial levels of circulating cytokines that decreased over time. Patients in cluster 2 and cluster 3 had higher initial levels that decreased over time in cluster 2 and increased in cluster 3. Patients in clusters 2 and 3 had higher mortality compared with cluster 1 (clusters 1-3: 11% vs 31%; odds ratio [OR], 3.56 [1.10-14.23] vs 54% OR, 9.23 [2.89-37.22]). Cluster 3 was independently associated with in-hospital mortality (hazard ratio, 5.24; p = 0.005) in multivariable analysis. There were no significant differences in initial clinical severity scoring or steroid use between the clusters. Analysis of either t 1 or t 2 cytokine measurements alone or in combination did not reveal clusters with clear clinical significance.

CONCLUSIONS

Longitudinal measurement of cytokine profiles at initiation of vasoactive medications and 24 hours later revealed three distinct cytokine signature clusters that correlated with clinical outcomes.

N6-methyladenosine modification: Regulatory mechanisms and therapeutic potential in sepsis

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection and is characterized by multiple biological and clinical features. N6-methyladenosine (m6A) modification is the most common type of RNA modifications in eukaryotes and plays an important regulatory role in various biological processes. Recently, m6A modification has been found to be involved in the regulation of immune responses in sepsis. In addition, several studies have shown that m6A modification is involved in sepsis-induced multiple organ dysfunctions, including cardiovascular dysfunction, acute lung injury (ALI), acute kidney injury (AKI) and etc. Considering the complex pathogenesis of sepsis and the lack of specific therapeutic drugs, m6A modification may be the important bond in the pathophysiological process of sepsis and even therapeutic targets. This review systematically highlights the recent advances regarding the roles of m6A modification in sepsis and sheds light on their use as treatment targets for sepsis.

Maresin1 prevents sepsis-induced acute liver injury by suppressing NF-κB/Stat3/MAPK pathways, mitigating inflammation

Aims

The treatment of sepsis remains challenging and the liver is a non-neglectful target of sepsis-induced injury. Uncontrolled inflammatory responses exert a central role in the pathophysiological process of sepsis-induced acute liver injury (SI-ALI). Maresin1 (MaR1) is a derivative of omega-3 docosahexaenoic acid (DHA), which has been shown to have anti-inflammatory effects and is effective in a variety of sepsis-related diseases. This study aimed to determine the effect of MaR1 on cecal ligation and puncture (CLP)-caused SI-ALI and explore its possible mechanisms.

Main methods

Mice were subjected to CLP, and then intravenously injected via tail vein with low-dose MaR1 (0.5 ng, 200 μL) or high-dose MaR1 (1 ng, 200 μL) or sterile normal saline (NS) (200 μL) 1 h later. Then, the survival rate, body weight change, liver function, bacterial load, neutrophil infiltration, and inflammatory cytokines were detected.

Results

MaR1 significantly increased the 7-day survival rate and reduced the bacterial load in peritoneal lavage fluid and blood in a dose-dependent manner in mice with SI-ALI. Treatment with MaR1 could also restore the function of the liver in septic mice. Besides, MaR1 exerted anti-inflammatory effects by decreasing the expression of pro-inflammatory molecules (TNF-α, IL-6 and IL-1β), bacterial load, and neutrophil infiltration and increasing the expression of anti-inflammatory molecules (IL-10).

Significance

Our experimental results showed that MaR1 alleviated liver injury induced by sepsis. This work highlighted a potential clinic use of MaR1 in treating acute inflammation of SI-ALI, but also provided new insight into the underlying molecular mechanism.

Uncovering heterogeneity in sepsis: a comparative analysis of subphenotypes

PURPOSE

The heterogeneity in sepsis is held responsible, in part, for the lack of precision treatment. Many attempts to identify subtypes of sepsis patients identify those with shared underlying biology or outcomes. To date, though, there has been limited effort to determine overlap across these previously identified subtypes. We aimed to determine the concordance of critically ill patients with sepsis classified by four previously described subtype strategies.

METHODS

This secondary analysis of a multicenter prospective observational study included 522 critically ill patients with sepsis assigned to four previously established subtype strategies, primarily based on: (i) clinical data in the electronic health record (α, β, γ, and δ), (ii) biomarker data (hyper- and hypoinflammatory), and (iii-iv) transcriptomic data (Mars1-Mars4 and SRS1-SRS2). Concordance was studied between different subtype labels, clinical characteristics, biological host response aberrations, as well as combinations of subtypes by sepsis ensembles.

RESULTS

All four subtype labels could be adjudicated in this cohort, with the distribution of the clinical subtype varying most from the original cohort. The most common subtypes in each of the four strategies were γ (61%), which is higher compared to the original classification, hypoinflammatory (60%), Mars2 (35%), and SRS2 (54%). There was no clear relationship between any of the subtyping approaches (Cramer's V = 0.086-0.456). Mars2 and SRS1 were most alike in terms of host response biomarkers (p = 0.079-0.424), while other subtype strategies showed no clear relationship. Patients enriched for multiple subtypes revealed that characteristics and outcomes differ dependent on the combination of subtypes made.

CONCLUSION

Among critically ill patients with sepsis, subtype strategies using clinical, biomarker, and transcriptomic data do not identify comparable patient populations and are likely to reflect disparate clinical characteristics and underlying biology.

Sepsis and Adrenal Insufficiency

In sepsis, dysregulation of the hypothalamic-pituitary-adrenal axis, alterations in cortisol metabolism, and tissue resistance to glucocorticoids can all result in relative adrenal insufficiency or critical illness-related corticosteroid insufficiency (CIRCI). The symptoms and signs of CIRCI during sepsis are nonspecific, generally including decreased mental status, unexplained fever, or hypotension refractory to fluids, and the requirement of vasopressor therapy to maintain adequate blood pressure. While we have been aware of this syndrome for over a decade, it remains a poorly understood condition, challenging to diagnose, and associated with significantly diverging practices among clinicians, particularly regarding the optimal dosing and duration of corticosteroid therapy. The existing literature on corticosteroid use in patients with sepsis and septic shock is vast with dozens of randomized controlled trials conducted across the past 4 decades. These studies have universally demonstrated reduced duration of shock, though the effects of corticosteroids on mortality have been inconsistent, and their use has been associated with adverse effects including hyperglycemia, neuromuscular weakness, and an increased risk of infection. In this article, we aim to provide a thorough, evidence-based, and practical review of the current recommendations for the diagnosis and management of patients with sepsis who develop CIRCI, explore the controversies surrounding this topic, and highlight what lies on the horizon as new evidence continues to shape our practice.

Rebastinib attenuates liver injury following cecal ligation and puncture in male mice

Sepsis remains a public health issue with high morbidity and mortality. Liver injury due to sepsis is associated with poor outcomes and an increased risk of death among septic patients. Rebastinib is a small molecule inhibiting the Tie2 receptor and vascular endothelial growth factor receptor-2 (VEGFR2). The current study aimed to reveal the potential protective impact of Rebastinib against sepsis-induced liver injury. Twenty-four adult male mice were allocated into four groups (six per group) as follows: Sham group was exposed to anesthesia and laparotomy with no cecal ligation and puncture procedure (CLP); CLP group was subjected CLP procedure; vehicle-treated group was pretreated with vehicle (oral route) one hour prior to CLP procedure; Rebastinib group was pretreated with oral Rebastinib one hour before induction of CLP. Collected blood was used to measure the serum levels of AST, ALT, and angiopoietin 2. Homogenized liver tissues were used to investigate IL-6, TNF-α, ICAM-1, MIF, VEGF, F2-isoprostanes, and caspase-11 levels. Histological examination was used to determine the severity of liver damage. Compared to the sham group, mice subjected to CLP had high levels of these biomarkers with a high degree of liver injury. In contrast, Rebastinib markedly reduced these levels and mitigated the liver damage. Rebastinib may be a hepatoprotective agent against sepsis-associated liver injury.

Derivation, Validation, and Clinical Relevance of a Pediatric Sepsis Phenotype With Persistent Hypoxemia, Encephalopathy, and Shock

OBJECTIVES

Untangling the heterogeneity of sepsis in children and identifying clinically relevant phenotypes could lead to the development of targeted therapies. Our aim was to analyze the organ dysfunction trajectories of children with sepsis-associated multiple organ dysfunction syndrome (MODS) to identify reproducible and clinically relevant sepsis phenotypes and determine if they are associated with heterogeneity of treatment effect (HTE) to common therapies.

DESIGN

Multicenter observational cohort study.

SETTING

Thirteen PICUs in the United States.

PATIENTS

Patients admitted with suspected infections to the PICU between 2012 and 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We used subgraph-augmented nonnegative matrix factorization to identify candidate trajectory-based phenotypes based on the type, severity, and progression of organ dysfunction in the first 72 hours. We analyzed the candidate phenotypes to determine reproducibility as well as prognostic, therapeutic, and biological relevance. Overall, 38,732 children had suspected infection, of which 15,246 (39.4%) had sepsis-associated MODS with an in-hospital mortality of 10.1%. We identified an organ dysfunction trajectory-based phenotype (which we termed persistent hypoxemia, encephalopathy, and shock) that was highly reproducible, had features of systemic inflammation and coagulopathy, and was independently associated with higher mortality. In a propensity score-matched analysis, patients with persistent hypoxemia, encephalopathy, and shock phenotype appeared to have HTE and benefit from adjuvant therapy with hydrocortisone and albumin. When compared with other high-risk clinical syndromes, the persistent hypoxemia, encephalopathy, and shock phenotype only overlapped with 50%-60% of patients with septic shock, moderate-to-severe pediatric acute respiratory distress syndrome, or those in the top tier of organ dysfunction burden, suggesting that it represents a nonsynonymous clinical phenotype of sepsis-associated MODS.

CONCLUSIONS

We derived and validated the persistent hypoxemia, encephalopathy, and shock phenotype, which is highly reproducible, clinically relevant, and associated with HTE to common adjuvant therapies in children with sepsis.

Leveraging Data Science and Novel Technologies to Develop and Implement Precision Medicine Strategies in Critical Care

Precision medicine aims to identify treatments that are most likely to result in favorable outcomes for subgroups of patients with similar clinical and biological characteristics. The gaps for the development and implementation of precision medicine strategies in the critical care setting are many, but the advent of data science and multi-omics approaches, combined with the rich data ecosystem in the intensive care unit, offer unprecedented opportunities to realize the promise of precision critical care. In this article, the authors review the data-driven and technology-based approaches being leveraged to discover and implement precision medicine strategies in the critical care setting.

Sepsis heterogeneity

BACKGROUND

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, with extremely high mortality. Notably, sepsis is a heterogeneous syndrome characterized by a vast, multidimensional array of clinical and biologic features, which has hindered advances in the therapeutic field beyond the current standards.

DATA SOURCES

We used PubMed to search the subject-related medical literature by searching for the following single and/or combination keywords: sepsis, heterogeneity, personalized treatment, host response, infection, epidemiology, mortality, incidence, age, children, sex, comorbidities, gene susceptibility, infection sites, bacteria, fungi, virus, host response, organ dysfunction and management.

RESULTS

We found that host factors (age, biological sex, comorbidities, and genetics), infection etiology, host response dysregulation and multiple organ dysfunctions can all result in different disease manifestations, progression, and response to treatment, which make it difficult to effectively treat and manage sepsis patients.

CONCLUSIONS

Herein, we have summarized contributing factors to sepsis heterogeneity, including host factors, infection etiology, host response dysregulation, and multiple organ dysfunctions, from the key elements of pathogenesis of sepsis. An in-depth understanding of the factors that contribute to the heterogeneity of sepsis will help clinicians understand the complexity of sepsis and enable researchers to conduct more personalized clinical studies for homogenous patients.

Whole Blood Transcriptomics Identifies Subclasses of Pediatric Septic Shock

Background

Sepsis is a highly heterogeneous syndrome, that has hindered the development of effective therapies. This has prompted investigators to develop a precision medicine approach aimed at identifying biologically homogenous subgroups of patients with septic shock and critical illnesses. Transcriptomic analysis can identify subclasses derived from differences in underlying pathophysiological processes that may provide the basis for new targeted therapies. The goal of this study was to elucidate pathophysiological pathways and identify pediatric septic shock subclasses based on whole blood RNA expression profiles.

Methods

The subjects were critically ill children with cardiopulmonary failure who were a part of a prospective randomized insulin titration trial to treat hyperglycemia. Genome-wide expression profiling was conducted using RNA-sequencing from whole blood samples obtained from 46 children with septic shock and 52 mechanically ventilated noninfected controls without shock. Patients with septic shock were allocated to subclasses based on hierarchical clustering of gene expression profiles, and we then compared clinical characteristics, plasma inflammatory markers, cell compositions using GEDIT, and immune repertoires using Imrep between the two subclasses.

Results

Patients with septic shock depicted alterations in innate and adaptive immune pathways. Among patients with septic shock, we identified two subtypes based on gene expression patterns. Compared with Subclass 2, Subclass 1 was characterized by upregulation of innate immunity pathways and downregulation of adaptive immunity pathways. Subclass 1 had significantly worse clinical outcomes despite the two classes having similar illness severity on initial clinical presentation. Subclass 1 had elevated levels of plasma inflammatory cytokines and endothelial injury biomarkers and demonstrated decreased percentages of CD4 T cells and B cells, and less diverse T-Cell receptor repertoires.

Conclusions

Two subclasses of pediatric septic shock patients were discovered through genome-wide expression profiling based on whole blood RNA sequencing with major biological and clinical differences.

Trial Registration

This is a secondary analysis of data generated as part of the observational CAF PINT ancillary of the HALF PINT study (NCT01565941). Registered 29 March 2012.

The role of macrophages polarization in sepsis-induced acute lung injury

Sepsis presents as a severe infectious disease frequently documented in clinical settings. Characterized by its systemic inflammatory response syndrome, sepsis has the potential to trigger multi-organ dysfunction and can escalate to becoming life-threatening. A common fallout from sepsis is acute lung injury (ALI), which often progresses to acute respiratory distress syndrome (ARDS). Macrophages, due to their significant role in the immune system, are receiving increased attention in clinical studies. Macrophage polarization is a process that hinges on an intricate regulatory network influenced by a myriad of signaling molecules, transcription factors, epigenetic modifications, and metabolic reprogramming. In this review, our primary focus is on the classically activated macrophages (M1-like) and alternatively activated macrophages (M2-like) as the two paramount phenotypes instrumental in sepsis' host immune response. An imbalance between M1-like and M2-like macrophages can precipitate the onset and exacerbate the progression of sepsis. This review provides a comprehensive understanding of the interplay between macrophage polarization and sepsis-induced acute lung injury (SALI) and elaborates on the intervention strategy that centers around the crucial process of macrophage polarization.

Fucoxanthin Attenuates Inflammation via Interferon Regulatory Factor 3 (IRF3) to Improve Sepsis

Suppression of excessive inflammatory responses improves the survival of patients with sepsis. We previously illustrated the anti-inflammatory effects of fucoxanthin (FX), a natural carotenoid isolated from brown algae; nevertheless, the underlying mechanism remains unknown. In this study, we examine the mechanism of the action of FX by targeting interferon regulatory factor 3 (IRF3) to inhibit inflammatory response. We observed that FX regulated innate immunity by inhibiting IRF3 phosphorylation in vitro. The in silico approach demonstrated a good binding mode between FX and IRF3. To examine the in vivo effects of FX, a mouse model of sepsis induced by cecal ligation and puncture (CLP) was created using both wild-type (WT) and Irf3-/- mice. FX significantly reduced pro-inflammatory cytokine levels and reactive oxygen species production, changed the circulating immune cell composition, and increased the survival rate of the CLP-induced sepsis model. Overall, FX ameliorated sepsis by targeting IRF3 activation, providing novel insights into the therapeutic potential and molecular mechanism of action of FX in the treatment of sepsis and suggesting that it may be used clinically to improve the survival rate in mice undergoing sepsis.

Defining critical illness using immunological endotypes in patients with and without sepsis: a cohort study

BACKGROUND

Sepsis is a heterogenous syndrome with limited therapeutic options. Identifying immunological endotypes through gene expression patterns in septic patients may lead to targeted interventions. We investigated whether patients admitted to a surgical intensive care unit (ICU) with sepsis and with high risk of mortality express similar endotypes to non-septic, but still critically ill patients using two multiplex transcriptomic metrics obtained both on admission to a surgical ICU and at set intervals.

METHODS

We analyzed transcriptomic data from 522 patients in two single-site, prospective, observational cohorts admitted to surgical ICUs over a 5-year period ending in July 2020. Using an FDA-cleared analytical platform (nCounter FLEX^®, NanoString, Inc.), we assessed a previously validated 29-messenger RNA transcriptomic classifier for likelihood of 30-day mortality (IMX-SEV-3) and a 33-messenger RNA transcriptomic endotype classifier. Clinical outcomes included all-cause mortality, development of chronic critical illness, and secondary infections. Univariate and multivariate analyses were performed to assess for true effect and confounding.

RESULTS

Sepsis was associated with a significantly higher predicted and actual hospital mortality. At enrollment, the predominant endotype for both septic and non-septic patients was adaptive, though with significantly different distributions. Inflammopathic and coagulopathic septic patients, as well as inflammopathic non-septic patients, showed significantly higher frequencies of secondary infections compared to those with adaptive endotypes (p < 0.01). Endotypes changed during ICU hospitalization in 57.5% of patients. Patients who remained adaptive had overall better prognosis, while those who remained inflammopathic or coagulopathic had worse overall outcomes. For severity metrics, patients admitted with sepsis and a high predicted likelihood of mortality showed an inflammopathic (49.6%) endotype and had higher rates of cumulative adverse outcomes (67.4%). Patients at low mortality risk, whether septic or non-septic, almost uniformly presented with an adaptive endotype (100% and 93.4%, respectively).

CONCLUSION

Critically ill surgical patients express different and evolving immunological endotypes depending upon both their sepsis status and severity of their clinical course. Future studies will elucidate whether endotyping critically ill, septic patients can identify individuals for targeted therapeutic interventions to improve patient management and outcomes.

Broad-Spectrum Clearance of Lipopolysaccharides from Blood Based on a Hemocompatible Dihistidine Polymer

Blood infection can release toxic bacterial lipopolysaccharides (LPSs) into bloodstream, trigger a series of inflammatory reactions, and eventually lead to multiple organ dysfunction, irreversible shock, and even death, which seriously threatens human life and health. Herein, a functional block copolymer with excellent hemocompatibility is proposed to enable broad-spectrum clearance of LPSs from whole blood blindly before pathogen identification, facilitating timely rescue from sepsis. A dipeptide ligand of histidine-histidine (HH) was designed as the LPS binding unit, and poly[(trimethylamine N-oxide)-co-(histidine-histidine)], a functional block copolymer combining the LPS ligand of HH and a zwitterionic antifouling unit of trimethylamine N-oxide (TMAO), was then designed by reversible addition-fragmentation chain transfer (RAFT) polymerization. The functional polymer achieved effective clearance of LPSs from solutions and whole blood in a broad-spectrum manner and had good antifouling and anti-interference properties and hemocompatibility. The proposed functional dihistidine polymer provides a novel strategy for achieving broad-spectrum clearance of LPSs, with potential applications in clinical blood purification.

Representation Learning and Spectral Clustering for the Development and External Validation of Dynamic Sepsis Phenotypes: Observational Cohort Study

BACKGROUND

Recent attempts at clinical phenotyping for sepsis have shown promise in identifying groups of patients with distinct treatment responses. Nonetheless, the replicability and actionability of these phenotypes remain an issue because the patient trajectory is a function of both the patient's physiological state and the interventions they receive.

OBJECTIVE

We aimed to develop a novel approach for deriving clinical phenotypes using unsupervised learning and transition modeling.

METHODS

Forty commonly used clinical variables from the electronic health record were used as inputs to a feed-forward neural network trained to predict the onset of sepsis. Using spectral clustering on the representations from this network, we derived and validated consistent phenotypes across a diverse cohort of patients with sepsis. We modeled phenotype dynamics as a Markov decision process with transitions as a function of the patient's current state and the interventions they received.

RESULTS

Four consistent and distinct phenotypes were derived from over 11,500 adult patients who were admitted from the University of California, San Diego emergency department (ED) with sepsis between January 1, 2016, and January 31, 2020. Over 2000 adult patients admitted from the University of California, Irvine ED with sepsis between November 4, 2017, and August 4, 2022, were involved in the external validation. We demonstrate that sepsis phenotypes are not static and evolve in response to physiological factors and based on interventions. We show that roughly 45% of patients change phenotype membership within the first 6 hours of ED arrival. We observed consistent trends in patient dynamics as a function of interventions including early administration of antibiotics.

CONCLUSIONS

We derived and describe 4 sepsis phenotypes present within 6 hours of triage in the ED. We observe that the administration of a 30 mL/kg fluid bolus may be associated with worse outcomes in certain phenotypes, whereas prompt antimicrobial therapy is associated with improved outcomes.

Defining critical illness using immunological endotypes in patients with and without of sepsis: A cohort study

Background: Sepsis is a heterogenous syndrome with limited therapeutic options. Identifying characteristic gene expression patterns, or endotypes, in septic patients may lead to targeted interventions. We investigated whether patients admitted to a surgical ICU with sepsis and with high risk of mortality express similar endotypes to non-septic, but still critically ill patients using two multiplex transcriptomic metrics obtained both on admission to a surgical intensive care unit (ICU) and at set intervals. Methods: We analyzed transcriptomic data from 522 patients in two single-site, prospective, observational cohorts admitted to surgical ICUs over a 5-year period ending in July 2020 . Using an FDA-cleared analytical platform (nCounter FLEX ^® , NanoString, Inc.), we assessed a previously validated 29-messenger RNA transcriptomic classifier for likelihood of 30-day mortality (IMX-SEV-3) and a 33-messenger RNA transcriptomic endotype classifier. Clinical outcomes included all-cause (in-hospital, 30-, 90-day) mortality, development of chronic critical illness (CCI), and secondary infections. Univariate and multivariate analyses were performed to assess for true effect and confounding. Results: Sepsis was associated with a significantly higher predicted and actual hospital mortality. At enrollment, the predominant endotype for both septic and non-septic patients was adaptive , though with significantly different distributions. Inflammopathic and coagulopathic septic patients, as well as inflammopathic non-septic patients, showed significantly higher frequencies of secondary infections compared to those with adaptive endotypes (p<0.01). Endotypes changed during ICU hospitalization in 57.5% of patients. Patients who remained adaptive had overall better prognosis, while those who remained inflammopathic or coagulopathic had worse overall outcomes. For severity metrics, patients admitted with sepsis and a high predicted likelihood of mortality showed an inflammopathic (49.6%) endotype and had higher rates of cumulative adverse outcomes (67.4%). Patients at low mortality risk, whether septic or non-septic, almost uniformly presented with an adaptive endotype (100% and 93.4%, respectively). Conclusion : Critically ill surgical patients express different and evolving immunological endotypes depending upon both their sepsis status and severity of their clinical course. Future studies will elucidate whether endotyping critically ill, septic patients can identify individuals for targeted therapeutic interventions to improve patient management and outcomes.