Identification of candidate serum biomarkers for severe septic shock-associated kidney injury via microarray

Serum renin and prorenin concentrations predict severe persistent acute kidney injury and mortality in pediatric septic shock

BACKGROUND

Studies in critically ill adults demonstrate associations between serum renin concentrations (a proposed surrogate for renin-angiotensin-aldosterone system dysregulation) and poor outcomes, but data in critically ill children are lacking. We assessed serum renin + prorenin concentrations in children with septic shock to determine their predictive ability for acute kidney injury (AKI) and mortality.

METHODS

We conducted a secondary analysis of a multicenter observational study of children aged 1 week to 18 years admitted to 14 pediatric intensive care units (PICUs) with septic shock and residual serum available for renin + prorenin measurement. Primary outcomes were development of severe persistent AKI (≥ KDIGO stage 2 for ≥ 48 h) in the first week and 28-day mortality.

RESULTS

Among 233 patients, day 1 median renin + prorenin concentration was 3436 pg/ml (IQR 1452-6567). Forty-two (18%) developed severe persistent AKI and 32 (14%) died. Day 1 serum renin + prorenin predicted severe persistent AKI with an AUROC of 0.75 (95% CI 0.66-0.84, p < 0.0001; optimal cutoff 6769 pg/ml) and mortality with an AUROC of 0.79 (95% CI 0.69-0.89, p < 0.0001; optimal cutoff 6521 pg/ml). Day 3/day 1 (D3:D1) renin + prorenin ratio had an AUROC of 0.73 (95% CI 0.63-0.84, p < 0.001) for mortality. On multivariable regression, day 1 renin + prorenin > optimal cutoff retained associations with severe persistent AKI (aOR 6.8, 95% CI 3.0-15.8, p < 0.001) and mortality (aOR 6.9, 95% CI 2.2-20.9, p < 0.001). Similarly, D3:D1 renin + prorenin > optimal cutoff was associated with mortality (aOR 7.6, 95% CI 2.5-23.4, p < 0.001).

CONCLUSIONS

Children with septic shock have very elevated serum renin + prorenin concentrations on PICU admission, and these concentrations, as well as their trend over the first 72 h, predict severe persistent AKI and mortality. A higher resolution version of the Graphical abstract is available as Supplementary information.

Immunomodulatory therapy using a pediatric dialysis system ameliorates septic shock in miniature pigs

BACKGROUND

Application of the immunomodulatory selective cytopheretic device (SCD) to enhance renal replacement therapy and improve outcomes of acute kidney injury in pediatric patients is impeded by safety concerns. Therapy using a pediatric hemodialysis system could overcome these limitations.

METHODS

Yucatan minipigs (8-15 kg) with induced septic shock underwent continuous hemodiafiltration with the CARPEDIEM™ pediatric hemodialysis system using regional citrate anticoagulation (RCA) with or without SCD (n = 5 per group). Circuit function plus hemodynamic and hematologic parameters were assessed for 6 h.

RESULTS

SCD was readily integrated into the CARPEDIEM™ system and treatment delivered for 6 h without interference with pump operation. SCD-treated pigs maintained higher blood pressure (p = 0.009) commensurate with lesser degree of lactic acidosis (p = 0.008) compared to pigs only receiving hemodiafiltration. Renal failure occurred in untreated pigs while urine output was sustained with SCD therapy. Neutrophil activation levels and ss-SOFA scores at 6 h trended lower in the SCD-treated cohort.

CONCLUSIONS

SCD therapy under RCA was safely administered using the CARPEDIEM™ pediatric hemodialysis system for up to 6 h and no circuit compatibility issues were identified. Sepsis progression and organ dysfunction was diminished with SCD treatment in this model supportive of therapeutic benefit of this immunomodulatory therapy.

IMPACT

SCD therapy with regional citrate anticoagulation has the potential to be administered safely to patients weighing <20 kg using the Carpediem renal replacement therapy platform. Use of a renal replacement therapy platform designed specifically for neonates/infants overcomes safety concerns for delivery of SCD treatment in this population. SCD therapy using the Carpediem renal replacement therapy platform retained the suggestive efficacy seen in larger children and adults to reduce organ injury and dysfunction from sepsis.

FGF13-Sensitive Alteration of Parkin Safeguards Mitochondrial Homeostasis in Endothelium of Diabetic Nephropathy

Studies of diabetic glomerular injury have raised the possibility of developing useful early biomarkers and therapeutic approaches for the treatment of type 2 diabetic nephropathy (T2DN). In this study, we found that FGF13 expression is induced in glomerular endothelial cells (GECs) during T2DN progression. Endothelial-specific deletion of Fgf13 potentially alleviates T2DN damage, while Fgf13 overexpression has the opposite effect. Mechanistically, Fgf13 deficiency results in improved mitochondrial homeostasis and endothelial barrier integrity in T2DN. Moreover, FGF13-sensitive alteration of Parkin safeguards mitochondrial homeostasis in endothelium of T2DN through promotion of mitophagy and inhibition of apoptosis. Additionally, it is confirmed that the beneficial effects of Fgf13 deficiency on T2DN are abolished by endothelial-specific double deletion of Fgf13 and Prkn. The effects of Fgf13 deficiency on mitophagy and apoptosis through Parkin-dependent regulation may be distinct and separable events under diabetic conditions. These data show that the bifunctional role of Fgf13 deficiency in promoting mitophagy and inhibiting apoptosis through Parkin can shape mitochondrial homeostasis regulation in GECs and T2DN progression. As a potential therapeutic target for prevention and control of T2DN, a mechanistic understanding of the biofunction of FGF13 may also be relevant to the pathogenesis of other FGF13- and Parkin-associated diseases.

The complement system in pediatric acute kidney injury

The complement cascade is an important part of the innate immune system. In addition to helping the body to eliminate pathogens, however, complement activation also contributes to the pathogenesis of a wide range of kidney diseases. Recent work has revealed that uncontrolled complement activation is the key driver of several rare kidney diseases in children, including atypical hemolytic uremic syndrome and C3 glomerulopathy. In addition, a growing body of literature has implicated complement in the pathogenesis of more common kidney diseases, including acute kidney injury (AKI). Complement-targeted therapeutics are in use for a variety of diseases, and an increasing number of therapeutic agents are under development. With the implication of complement in the pathogenesis of AKI, complement-targeted therapeutics could be trialed to prevent or treat this condition. In this review, we discuss the evidence that the complement system is activated in pediatric patients with AKI, and we review the role of complement proteins as biomarkers and therapeutic targets in patients with AKI.

Multi-Omics Techniques Make it Possible to Analyze Sepsis-Associated Acute Kidney Injury Comprehensively

Sepsis-associated acute kidney injury (SA-AKI) is a common complication in critically ill patients with high morbidity and mortality. SA-AKI varies considerably in disease presentation, progression, and response to treatment, highlighting the heterogeneity of the underlying biological mechanisms. In this review, we briefly describe the pathophysiology of SA-AKI, biomarkers, reference databases, and available omics techniques. Advances in omics technology allow for comprehensive analysis of SA-AKI, and the integration of multiple omics provides an opportunity to understand the information flow behind the disease. These approaches will drive a shift in current paradigms for the prevention, diagnosis, and staging and provide the renal community with significant advances in precision medicine in SA-AKI analysis.

Multimerin-1 and cancer: a review

Multimerin-1 (MMRN1) is a platelet protein with a role in haemostasis and coagulation. It is also present in endothelial cells (ECs) and the extracellular matrix (ECM), where it may be involved in cell adhesion, but its molecular functions and protein–protein interactions in these cellular locations have not been studied in detail yet. In recent years, MMRN1 has been identified as a differentially expressed gene (DEG) in various cancers and it has been proposed as a possible cancer biomarker. Some evidence suggest that MMRN1 expression is regulated by methylation, protein interactions, and non-coding RNAs (ncRNAs) in different cancers. This raises the questions if a functional role of MMRN1 is being targeted during cancer development, and if MMRN1’s differential expression pattern correlates with cancer progression. As a result, it is timely to review the current state of what is known about MMRN1 to help inform future research into MMRN1’s molecular mechanisms in cancer.

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in kidney disease

Matrix metalloproteinases (MMPs) are a group of zinc and calcium endopeptidases which cleave extracellular matrix (ECM) proteins. They are also involved in the degradation of cell surface components and regulate multiple cellular processes, cell to cell interactions, cell proliferation, and cell signaling pathways. MMPs function in close interaction with the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), both of which regulate cell turnover, modulate various growth factors, and participate in the progression of tissue fibrosis and apoptosis. The multiple roles of MMPs and TIMPs are continuously elucidated in kidney development and repair, as well as in a number of kidney diseases. This chapter focuses on the current findings of the significance of MMPs and TIMPs in a wide range of kidney diseases, whether they result from kidney tissue changes, hemodynamic alterations, tubular epithelial cell apoptosis, inflammation, or fibrosis. In addition, the potential use of these endopeptidases as biomarkers of renal dysfunction and as targets for therapeutic interventions to attenuate kidney disease are also explored in this review.

Sepsis-Pathophysiology and Therapeutic Concepts

Sepsis is a life-threatening condition and a global disease burden. Today, the heterogeneous syndrome is defined as severe organ dysfunction caused by a dysregulated host response to infection, with renewed emphasis on immune pathophysiology. Despite all efforts of experimental and clinical research during the last three decades, the ability to positively influence course and outcome of the syndrome remains limited. Evidence-based therapy still consists of basic causal and supportive measures, while adjuvant interventions such as blood purification or targeted immunotherapy largely remain without proof of effectiveness so far. With this review, we aim to provide an overview of sepsis immune pathophysiology, to update the choice of therapeutic approaches targeting different immunological mechanisms in the course of sepsis and septic shock, and to call for a paradigm shift from the pathogen to the host response as a potentially more promising angle.

Recalibration of the Renal Angina Index for Pediatric Septic Shock

Introduction

Sepsis-associated acute kidney injury (AKI) is a common diagnosis in children that is associated with poor outcomes. The lack of therapeutic options once present makes early identification of at-risk patients essential. The renal angina index (RAI) has been previously validated to predict severe AKI in heterogeneous populations of critically ill children. The performance of this score specifically in children with septic shock is unknown.

Methods

A secondary analysis of a multicenter, prospective, observational study of 379 children with septic shock to determine the ability of the RAI to predict severe AKI at day 3, and to assess for the potential need for recalibration of the RAI in this unique subset of patients.

Results

At the original cutoff of ≥8, the RAI predicted day 3 severe AKI with an area under the receiving operating characteristic (AUROC) curve 0.90 (95% confidence interval [CI]: 0.86 to 93), 95% sensitivity, and 54% specificity. A Youden's index identified a higher optimal cutoff of ≥20 (sensitivity 83%, specificity 80%), and day 1 platelet count <150 × 10³/μl was an independent predictor of severe AKI (adjusted odds ratio: 3.2; 95% CI: 1.7 to 6.3; P < 0.001). Recalibration of the RAI to include platelet count and this new threshold restored the sensitivity of the original ≥8 threshold (95%), while improving its specificity (69%).

Conclusions

The RAI appears to be a sensitive and reliable tool for prediction of severe AKI in children with septic shock, although the use of a recalibrated sepsis-specific RAI using a higher cutoff and platelet count may be beneficial.

The application of omic technologies to research in sepsis-associated acute kidney injury

Acute kidney injury (AKI) is common in critically ill children and adults, and sepsis-associated AKI (SA-AKI) is the most frequent cause of AKI in the ICU. To date, no mechanistically targeted therapeutic interventions have been identified. High-throughput "omic" technologies (e.g., genomics, proteomics, metabolomics, etc.) offer a new angle of approach to achieve this end. In this review, we provide an update on the current understanding of SA-AKI pathophysiology. Omic technologies themselves are briefly discussed to facilitate interpretation of studies using them. We next summarize the body of SA-AKI research to date that has employed omic technologies. Importantly, omic studies are helping to elucidate a pathophysiology of SA-AKI centered around cellular stress responses, metabolic changes, and dysregulation of energy production that underlie its clinical features. Finally, we propose opportunities for future research using clinically relevant animal models, integrating multiple omic technologies and ultimately progressing to translational human studies focusing therapeutic strategies on targeted disease mechanisms.

Bioinformatic analysis identifies potential biomarkers and therapeutic targets of septic-shock-associated acute kidney injury

Background

Sepsis and septic shock are life-threatening diseases with high mortality rate in intensive care unit (ICU). Acute kidney injury (AKI) is a common complication of sepsis, and its occurrence is a poor prognostic sign to septic patients. We analyzed co-differentially expressed genes (co-DEGs) to explore relationships between septic shock and AKI and reveal potential biomarkers and therapeutic targets of septic-shock-associated AKI (SSAKI).

Methods

Two gene expression datasets (GSE30718 and GSE57065) were downloaded from the Gene Expression Omnibus (GEO). The GSE57065 dataset included 28 septic shock patients and 25 healthy volunteers and blood samples were collected within 0.5, 24 and 48 h after shock. Specimens of GSE30718 were collected from 26 patients with AKI and 11 control patents. AKI-DEGs and septic-shock-DEGs were identified using the two datasets. Subsequently, Gene Ontology (GO) functional analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and protein-protein interaction (PPI) network analysis were performed to elucidate molecular mechanisms of DEGs. We also evaluated co-DEGs and corresponding predicted miRNAs involved in septic shock and AKI.

Results

We identified 62 DEGs in AKI specimens and 888, 870, and 717 DEGs in septic shock blood samples within 0.5, 24 and 48 h, respectively. The hub genes of EGF and OLFM4 may be involved in AKI and QPCT, CKAP4, PRKCQ, PLAC8, PRC1, BCL9L, ATP11B, KLHL2, LDLRAP1, NDUFAF1, IFIT2, CSF1R, HGF, NRN1, GZMB, and STAT4 may be associated with septic shock. Besides, co-DEGs of VMP1, SLPI, PTX3, TIMP1, OLFM4, LCN2, and S100A9 coupled with corresponding predicted miRNAs, especially miR-29b-3p, miR-152-3p, and miR-223-3p may be regarded as promising targets for the diagnosis and treatment of SSAKI in the future.

Conclusions

Septic shock and AKI are related and VMP1, SLPI, PTX3, TIMP1, OLFM4, LCN2, and S100A9 genes are significantly associated with novel biomarkers involved in the occurrence and development of SSAKI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-021-00176-y.

Machine Learning Identifies Complicated Sepsis Course and Subsequent Mortality Based on 20 Genes in Peripheral Blood Immune Cells at 24 H Post-ICU Admission

A complicated clinical course for critically ill patients admitted to the intensive care unit (ICU) usually includes multiorgan dysfunction and subsequent death. Owing to the heterogeneity, complexity, and unpredictability of the disease progression, ICU patient care is challenging. Identifying the predictors of complicated courses and subsequent mortality at the early stages of the disease and recognizing the trajectory of the disease from the vast array of longitudinal quantitative clinical data is difficult. Therefore, we attempted to perform a meta-analysis of previously published gene expression datasets to identify novel early biomarkers and train the artificial intelligence systems to recognize the disease trajectories and subsequent clinical outcomes. Using the gene expression profile of peripheral blood cells obtained within 24 h of pediatric ICU (PICU) admission and numerous clinical data from 228 septic patients from pediatric ICU, we identified 20 differentially expressed genes predictive of complicated course outcomes and developed a new machine learning model. After 5-fold cross-validation with 10 iterations, the overall mean area under the curve reached 0.82. Using a subset of the same set of genes, we further achieved an overall area under the curve of 0.72, 0.96, 0.83, and 0.82, respectively, on four independent external validation sets. This model was highly effective in identifying the clinical trajectories of the patients and mortality. Artificial intelligence systems identified eight out of twenty novel genetic markers (SDC4, CLEC5A, TCN1, MS4A3, HCAR3, OLAH, PLCB1, and NLRP1) that help predict sepsis severity or mortality. While these genes have been previously associated with sepsis mortality, in this work, we show that these genes are also implicated in complex disease courses, even among survivors. The discovery of eight novel genetic biomarkers related to the overactive innate immune system, including neutrophil function, and a new predictive machine learning method provides options to effectively recognize sepsis trajectories, modify real-time treatment options, improve prognosis, and patient survival.

A Precision Medicine Approach to Biomarker Utilization in Pediatric Sepsis-Associated Acute Kidney Injury

Sepsis is a leading cause of morbidity and mortality in critically ill children, and acute kidney injury (AKI) is a frequent complication that confers an increased risk for poor outcomes. Despite the documented consequences of sepsis-associated AKI (SA-AKI), no effective disease-modifying therapies have been identified to date. As such, the only treatment options for these patients remain prevention and supportive care, both of which rely on the ability to promptly and accurately identify at risk and affected individuals. To achieve these goals, a variety of biomarkers have been investigated to help augment our currently limited predictive and diagnostic strategies for SA-AKI, however, these have had variable success in pediatric sepsis. In this mini-review, we will briefly outline the current use of biomarkers for SA-AKI, and propose a new framework for biomarker discovery and utilization that considers the individual patient's sepsis inflammatory response. Now recognized to be a key driver in the complex pathophysiology of SA-AKI, understanding the dysregulated host immune response to sepsis is a growing area of research that can and should be leveraged to improve the prediction and diagnosis of SA-AKI, while also potentially identifying novel therapeutic targets. Reframing SA-AKI in this manner - as a direct consequence of the individual patient's sepsis inflammatory response - will facilitate a precision medicine approach to its management, something that is required to move the care of this consequential disorder forward.

Clinical phenotypes of acute kidney injury are associated with unique outcomes in critically ill septic children

BACKGROUND

Assessment of acute kidney injury (AKI) in septic patients remains imprecise. In adults, the classification of septic patients by clinical AKI phenotypes (severity and timing) demonstrates unique associations with patient outcome vs. broadly defined AKI.

METHODS

In a multinational prospective observational study, AKI diagnosis in critically ill septic children was stratified by duration (transient vs. persistent) and severity (mild vs. severe by creatinine change and urine output). The outcomes of interest were mortality and intensive care unit resource complexity at 28 days.

RESULTS

Seven hundred and fifty-seven septic children were studied (male 52.7%, age 4.6 years (1.5-11.9)). Mortality (overall 12.1%) was different between severe AKI and mild AKI (18.3 vs. 4.4%, p < 0.001) as well as intensive care unit (ICU) complexity (overall 34.5%, 45 vs. 21.7%, p < 0.001). Patients with Persistent AKI had fewer ICU-free days (17 (7, 21) vs. 24 (17, 26), p < 0.001) and higher ICU complexity (52.8 vs. 22.9%, p = 0.002) than transient AKI, even after exclusion of patients with early mortality. AKI phenotypes incorporating temporal and severity data correlate with unique survival (range 4.4-21.6%) and ICU-free days (range of 15-25 days) CONCLUSIONS: The outcome of septic children with AKI changes by clinical phenotype. Our findings underscore the importance of prognostic enrichment in sepsis and AKI for the purpose of trial design and patient management.

IMPACT

Although AKI occurs commonly in patients with sepsis (S-AKI), outcomes for children with S-AKI varies based on the severity and timing of the AKI. Existing S-AKI pediatric data utilize a broad singular definition of kidney injury. Increasing the precision of AKI classification results in a new understanding of how S-AKI associates with patient outcome. A refined classification of S-AKI identifies subgroups of children, making possible a targeted and a personalized medicine approach to S-AKI study and management.

Use of the Selective Cytopheretic Device in Critically Ill Children

Introduction

Critically ill children with acute kidney injury (AKI) requiring continuous kidney replacement therapy (CKRT) are at increased risk of death. The selective cytopheretic device (SCD) promotes an immunomodulatory effect when circuit ionized calcium (iCa²⁺) is maintained at <0.40 mmol/l with regional citrate anticoagulation (RCA). In a randomized trial of adult patients on CRRT, those treated with the SCD maintaining an iCa²⁺ <0.40 mmol/l had improved survival/dialysis independence. We conducted a US Food and Drug Administration (FDA)–sponsored study to evaluate safety and feasibility of the SCD in 16 critically ill children.

Methods

Four pediatric intensive care units (ICUs) enrolled children with AKI and multiorgan dysfunction receiving CKRT to receive the SCD integrated post-CKRT membrane. RCA was used to achieve a circuit iCa²⁺ level <0.40 mmol/l. Subjects received SCD treatment for 7 days or CKRT discontinuation, whichever came first.

Results

The FDA target enrollment of 16 subjects completed the study from December 2016 to February 2020. Mean age was 12.3 ± 5.1 years, weight was 53.8 ± 28.9 kg, and median Pediatric Risk of Mortality II was 7 (range 2–19). Circuit iCa²⁺ levels were maintained at <0.40 mmol/l for 90.2% of the SCD therapy time. Median SCD duration was 6 days. Fifteen subjects survived SCD therapy; 12 survived to ICU discharge. All ICU survivors were dialysis independent at 60 days. No SCD-related adverse events (AEs) were reported.

Conclusion

Our data demonstrate that SCD therapy is feasible and safe in children who require CKRT. Although we cannot make efficacy claims, the 75% survival rate and 100% renal recovery rate observed suggest a possible favorable benefit-to-risk ratio.

Biomarkers in pediatric sepsis: a review of recent literature

Sepsis remains the leading cause of death in infants and children worldwide. Prompt diagnosis and monitoring of infection is pivotal to guide therapy and optimize outcomes. No single biomarker has so far been identified to accurately diagnose sepsis, monitor response and predict severity. We aimed to assess existing evidence of available sepsis biomarkers, and their utility in pediatric population. C-reactive protein and procalcitonin remain the most extensively evaluated and used biomarkers. However, biomarkers related to endothelial damage, vasodilation, oxidative stress, cytokines/chemokines and cell bioproducts have also been identified, often with regard to the site of infection and etiologic pathogen; still, with controversial utility. A multi-biomarker model driven by genomic tools could establish a personalized approach in future disease management.

Two subphenotypes of septic acute kidney injury are associated with different 90-day mortality and renal recovery

BACKGROUND

The pathophysiology of septic acute kidney injury is inadequately understood. Recently, subphenotypes for sepsis and AKI have been derived. The objective of this study was to assess whether a combination of comorbidities, baseline clinical data, and biomarkers could classify meaningful subphenotypes in septic AKI with different outcomes.

METHODS

We performed a post hoc analysis of the prospective Finnish Acute Kidney Injury (FINNAKI) study cohort. We included patients admitted with sepsis and acute kidney injury during the first 48 h from admission to intensive care (according to Kidney Disease Improving Global Outcome criteria). Primary outcomes were 90-day mortality and renal recovery on day 5. We performed latent class analysis using 30 variables obtained on admission to classify subphenotypes. Second, we used logistic regression to assess the association of derived subphenotypes with 90-day mortality and renal recovery on day 5.

RESULTS

In total, 301 patients with septic acute kidney injury were included. Based on the latent class analysis, a two-class model was chosen. Subphenotype 1 was assigned to 133 patients (44%) and subphenotype 2 to 168 patients (56%). Increased levels of inflammatory and endothelial injury markers characterized subphenotype 2. At 90 days, 29% of patients in subphenotype 1 and 41% of patients in subphenotype 2 had died. Subphenotype 2 was associated with a lower probability of short-term renal recovery and increased 90-day mortality.

CONCLUSIONS

In this post hoc analysis, we identified two subphenotypes of septic acute kidney injury with different clinical outcomes. Future studies are warranted to validate the suggested subphenotypes of septic acute kidney injury.

Biomarker Panels in Critical Care

Biomarker panels have the potential to advance the field of critical care medicine by stratifying patients according to prognosis and/or underlying pathophysiology. This article discusses the discovery and validation of biomarker panels, along with their translation to the clinical setting. The current literature on the use of biomarker panels in sepsis, acute respiratory distress syndrome, and acute kidney injury is reviewed.

PERSEVERE Biomarkers Predict Severe Acute Kidney Injury and Renal Recovery in Pediatric Septic Shock

Rationale: Acute kidney injury (AKI), a common complication of sepsis, is associated with substantial morbidity and mortality and lacks definitive disease-modifying therapy. Early, reliable identification of at-risk patients is important for targeted implementation of renal protective measures. The updated Pediatric Sepsis Biomarker Risk Model (PERSEVERE-II) is a validated, multibiomarker prognostic enrichment strategy to estimate baseline mortality risk in pediatric septic shock.Objectives: To assess the association between PERSEVERE-II mortality probability and the development of severe, sepsis-associated AKI on Day 3 (D3 SA-AKI) in pediatric septic shock.Methods: We performed secondary analysis of a prospective observational study of children with septic shock in whom the PERSEVERE biomarkers were measured to assign a PERSEVERE-II baseline mortality risk.Measurements and Main Results: Among 379 patients, 65 (17%) developed severe D3 SA-AKI. The proportion of patients developing severe D3 SA-AKI increased directly with increasing PERSEVERE-II risk category, and increasing PERSEVERE-II mortality probability was independently associated with increased odds of severe D3 SA-AKI after adjustment for age and illness severity (odds ratio, 1.4; 95% confidence interval, 1.2-1.7; P < 0.001). Similar associations were found between increasing PERSEVERE-II mortality probability and the need for renal replacement therapy. Lower PERSEVERE-II mortality probability was independently associated with increased odds of renal recovery among patients with early AKI. A newly derived model incorporating the PERSEVERE biomarkers and Day 1 AKI status predicted severe D3 SA-AKI with an area under the received operating characteristic curve of 0.95 (95% confidence interval, 0.92-0.98).Conclusions: Among children with septic shock, the PERSEVERE biomarkers predict severe D3 SA-AKI and identify patients with early AKI who are likely to recover.

Juvenile OLFM4-null mice are protected from sepsis

Pediatric sepsis is a leading cause of morbidity and mortality in children. One of the most common and devastating morbidities is sepsis-related acute kidney injury (AKI). AKI was traditionally thought to be related to low perfusion and acute tubular necrosis. However, little acute tubular necrosis can be found following septic AKI, and little is known about the mechanism of septic AKI. Olfactomedin-4 (OLFM4) is a secreted glycoprotein that marks a subset of neutrophils. Increased expression of OLFM4 in the blood is associated with worse outcomes in sepsis. Here, we investigated a pediatric model of murine sepsis using murine pups to investigate the mechanisms of OLFM4 in sepsis. When sepsis was induced in murine pups, survival was significantly increased in OLFM4-null pups. Immunohistochemistry at 24 h after the induction of sepsis demonstrated increased expression of OLFM4 in the kidney, which was localized to the loop of Henle. Renal cell apoptosis and plasma creatinine were significantly increased in wild-type versus OLFM4-null pups. Finally, bone marrow transplant suggested that increased OLFM4 in the kidney reflects local production rather than filtered from the plasma. These results demonstrate renal expression of OLFM4 for the first time and suggest that a kidney-specific mechanism may contribute to survival differences in OLFM4-null animals.

Quantification of Immune Dysregulation by Next-generation Polymerase Chain Reaction to Improve Sepsis Diagnosis in Surgical Patients

OBJECTIVES

To quantify immunological dysfunction in surgical patients with presence/absence of sepsis using a droplet digital polymerase chain reaction (ddPCR) transcriptomic analysis. The study also aims to evaluate this approach for improving identification of sepsis in these patients.

BACKGROUND

Immune dysregulation is a central event in sepsis. Quantification of the expression of immunological genes participating in the pathogenesis of sepsis could represent a new avenue to improve its diagnosis.

METHODS

Expression of 6 neutrophil protease genes (MMP8, OLFM4, LCN2/NGAL, LTF, PRTN3, MPO) and also of 5 genes involved in the immunological synapse (HLA-DRA, CD40LG, CD3E, CD28, ICOS) was quantified in blood from 101 surgical patients with sepsis, 53 uninfected surgical patients, and 16 blood donors by using ddPCR. Areas under receiver operating characteristic curves (AUROC) and multivariate regression analysis were employed to test individual genes and gene ratios to identify sepsis, in comparison with procalcitonin.

RESULTS

Sepsis-induced overexpression of neutrophil protease genes and depressed expression of immunological synapse genes. MMP8/HLA-DRA, LCN2/HLA-DRA outperformed procalcitonin in differentiating between patients with sepsis and surgical controls in the AUROC analysis: LCN2/HLA-DRA: 0.90 (0.85-0.96), MMP8/HLA-DRA: 0.89 (0.84-0.95), procalcitonin: 0.80 (0.73-0.88) (AUROC, confidence interval 95%), and also in the multivariate analysis: LCN2/HLA-DRA: 8.57 (2.25-32.62); MMP8/HLA-DRA: 8.03 (2.10-30.76), procalcitonin: 4.20 (1.15-15.43) [odds ratio (confidence interval 95%)]. Gene expression levels of HLA-DRA were an independent marker of hospital mortality.

CONCLUSIONS

Quantifying the transcriptomic ratios MMP8/HLA-DRA, LCN2/HLA-DRA by ddPCR is a promising approach to improve sepsis diagnosis in surgical patients.

Prognostic and predictive enrichment in sepsis

Sepsis is a heterogeneous disease state that is both common and consequential in critically ill patients. Unfortunately, the heterogeneity of sepsis at the individual patient level has hindered advances in the field beyond the current therapeutic standards, which consist of supportive care and antibiotics. This complexity has prompted attempts to develop a precision medicine approach, with research aimed towards stratifying patients into more homogeneous cohorts with shared biological features, potentially facilitating the identification of new therapies. Several investigators have successfully utilized leukocyte-derived mRNA and discovery-based approaches to subgroup patients on the basis of biological similarities defined by transcriptomic signatures. A critical next step is to develop a consensus sepsis subclassification system, which includes transcriptomic signatures as well as other biological and clinical data. This goal will require collaboration among various investigative groups, and validation in both existing data sets and prospective studies. Such studies are required to bring precision medicine to the bedside of critically ill patients with sepsis.

PPARα contributes to protection against metabolic and inflammatory derangements associated with acute kidney injury in experimental sepsis

Sepsis-associated acute kidney injury (AKI) is a significant problem in critically ill children and adults resulting in increased morbidity and mortality. Fundamental mechanisms contributing to sepsis-associated AKI are poorly understood. Previous research has demonstrated that peroxisome proliferator-activated receptor α (PPARα) expression is associated with reduced organ system failure in sepsis. Using an experimental model of polymicrobial sepsis, we demonstrate that mice deficient in PPARα have worse kidney function, which is likely related to reduced fatty acid oxidation and increased inflammation. Ultrastructural evaluation with electron microscopy reveals that the proximal convoluted tubule is specifically injured in septic PPARα deficient mice. In this experimental group, serum metabolomic analysis reveals unanticipated metabolic derangements in tryptophan-kynurenine-NAD+ and pantothenate pathways. We also show that a subgroup of children with sepsis whose genome-wide expression profiles are characterized by repression of the PPARα signaling pathway has increased incidence of severe AKI. These findings point toward interesting associations between sepsis-associated AKI and PPARα-driven fatty acid metabolism that merit further investigation.

Sepsis Biomarkers

Sepsis-related biomarkers have a variety of potential applications. The most well-known application is to differentiate patients with signs of systemic inflammation caused by infection, from those with systemic inflammation due to a non-infectious cause. This application is important for timely and judicious prescription of antibiotics. Apart from diagnostic applications, biomarkers can also be used to identify patients with sepsis who are at risk for poor outcome and to subgroup patients with sepsis based on biological commonalities. The latter two applications embody the concepts of prognostic and predictive enrichment, which are fundamental to precision medicine. This review will elaborate on these concepts, provide relevant examples, and discuss important considerations in the process of biomarkers discovery and development.

Hyperchloremia Is Associated With Complicated Course and Mortality in Pediatric Patients With Septic Shock

OBJECTIVE

Hyperchloremia is associated with poor outcome among critically ill adults, but it is unknown if a similar association exists among critically ill children. We determined if hyperchloremia is associated with poor outcomes in children with septic shock.

DESIGN

Retrospective analysis of a pediatric septic shock database.

SETTING

Twenty-nine PICUs in the United States.

PATIENTS

Eight hundred ninety children 10 years and younger with septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We considered the minimum, maximum, and mean chloride values during the initial 7 days of septic shock for each study subject as separate hyperchloremia variables. Within each category, we considered hyperchloremia as a dichotomous variable defined as a serum concentration greater than or equal to 110 mmol/L. We used multivariable logistic regression to determine the association between the hyperchloremia variables and outcome, adjusted for illness severity. We considered all cause 28-day mortality and complicated course as the primary outcome variables. Complicated course was defined as mortality by 28 days or persistence of greater than or equal to two organ failures at day 7 of septic shock. Secondarily, we conducted a stratified analysis using a biomarker-based mortality risk stratification tool. There were 226 patients (25%) with a complicated course and 93 mortalities (10%). Seventy patients had a minimum chloride greater than or equal to 110 mmol/L, 179 had a mean chloride greater than or equal to 110 mmol/L, and 514 had a maximum chloride greater than or equal to 110 mmol/L. A minimum chloride greater than or equal to 110 mmol/L was associated with increased odds of complicated course (odds ratio, 1.9; 95% CI, 1.1-3.2; p = 0.023) and mortality (odds ratio, 3.7; 95% CI, 2.0-6.8; p < 0.001). A mean chloride greater than or equal to 110 mmol/L was also associated with increased odds of mortality (odds ratio, 2.1; 95% CI, 1.3-3.5; p = 0.002). The secondary analysis yielded similar results.

CONCLUSION

Hyperchloremia is independently associated with poor outcomes among children with septic shock.

A path to precision in the ICU

Precision medicine is increasingly touted as a groundbreaking new paradigm in biomedicine. In the ICU, the complexity and ambiguity of critical illness syndromes have been identified as fundamental justifications for the adoption of a precision approach to research and practice. Inherently protean diseases states such as sepsis and acute respiratory distress syndrome have manifestations that are physiologically and anatomically diffuse, and that fluctuate over short periods of time. This leads to considerable heterogeneity among patients, and conditions in which a “one size fits all” approach to therapy can lead to widely divergent results. Current ICU therapy can thus be seen as imprecise, with the potential to realize substantial gains from the adoption of precision medicine approaches. A number of challenges still face the development and adoption of precision critical care, a transition that may occur incrementally rather than wholesale. This article describes a few concrete approaches to addressing these challenges.

First, novel clinical trial designs, including registry randomized controlled trials and platform trials, suggest ways in which conventional trials can be adapted to better accommodate the physiologic heterogeneity of critical illness. Second, beyond the “omics” technologies already synonymous with precision medicine, the data-rich environment of the ICU can generate complex physiologic signatures that could fuel precision-minded research and practice. Third, the role of computing infrastructure and modern informatics methods will be central to the pursuit of precision medicine in the ICU, necessitating close collaboration with data scientists. As work toward precision critical care continues, small proof-of-concept studies may prove useful in highlighting the potential of this approach.

Monitoring Severity of Multiple Organ Dysfunction Syndrome: New Technologies

OBJECTIVE

To describe new technologies (biomarkers and tests) used to assess and monitor the severity and progression of multiple organ dysfunction syndrome in children as discussed as part of the Eunice Kennedy Shriver National Institute of Child Health and Human Development MODS Workshop (March 26-27, 2015).

DATA SOURCES

Literature review, research data, and expert opinion.

STUDY SELECTION

Not applicable.

DATA EXTRACTION

Moderated by an experienced expert from the field, investigators developing and assessing new technologies to improve the care and understanding of critical illness presented their research and the relevant literature.

DATA SYNTHESIS

Summary of presentations and discussion supported and supplemented by relevant literature.

CONCLUSIONS

There are many innovative tools and techniques with the potential application for the assessment and monitoring of severity of multiple organ dysfunction syndrome. If the reliability and added value of these candidate technologies can be established, they hold promise to enhance the understanding, monitoring, and perhaps, treatment of multiple organ dysfunction syndrome in children.

Association of Matrix Metalloproteinases -7, -8 and -9 and TIMP -1 with Disease Severity in Acute Pancreatitis. A Cohort Study

Objectives

Several biomarkers for early detection of severe acute pancreatitis (SAP) have been presented. Matrix metalloproteinases (MMP) and their tissue inhibitors (TIMP) are released early in inflammation. We aimed to assess levels of MMP-7, -8, -9 and TIMP-1 in acute pancreatitis (AP) and explore their ability to detect disease severity. Our second aim was to find an association between MMPs, TIMP and creatinine.

Methods

We collected plasma samples for MMP-7, -8, -9 and TIMP-1 analyses from 176 patients presenting within 96 h from onset of acute pancreatitis (AP) symptoms. We used samples from 32 control subjects as comparison. The revised Atlanta Classification was utilised to assess severity of disease. Receiver operating characteristic curve analysis and Spearman´s Rho-test were utilised for statistical calculations.

Results

Compared with controls, patients showed higher levels of all studied markers. MMP-8 was higher in moderately severe AP than in mild AP (p = 0.005) and MMP-8, -9 and TIMP-1 were higher in severe than in mild AP (p<0.001, p = 0.005 and p = 0.019). MMP-8 detected SAP with an AUC of 0.939 [95% CI 0.894–0.984], LR+ 9.03 [5.30–15.39]. MMP-8, -9 and TIMP-1 failed to discern moderately severe AP from SAP. MMP-7 was not different between patient groups. MMP-7 and TIMP-1 correlated weakly with creatinine (Rho = 0.221 and 0.243). MMP-8 might be a useful biomarker in early detection of SAP.

Cross-species validation of cell cycle arrest markers for acute kidney injury in the rat during sepsis

Background

The recent discovery of cell cycle arrest biomarkers, tissue inhibitor of metalloproteinases (TIMP)-2 and insulin-like growth factor binding protein 7 (IGFBP7), has led to a newly available clinical test for acute kidney injury. The performance of these markers in preclinical studies has not been established. Therefore, we sought to evaluate the performance of TIMP-2 and IGFBP7 in rats undergoing cecal ligation and puncture.

Methods

In this secondary analysis, we analyzed banked urine samples from 60 Sprague-Dawley rats undergoing cecal ligation and puncture (CLP). Samples were obtained from baseline, 18 h after CLP, at the end of fluid resuscitation (22 h after CLP), and again 24 h later. We measured TIMP-2 and IGFBP7 and compared the results to acute kidney injury by RIFLE criteria for creatinine using area under the receiver operating characteristic curve (AUC). The primary endpoint was moderate-to-severe acute kidney injury (AKI) (I or F criteria), and the primary time point was immediately after fluid resuscitation. Secondary outcomes included mortality and comparisons with other biomarkers: cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) in both urine and plasma.

Results

After fluid resuscitation, urine [TIMP-2] and [IGFBP7] were significantly higher in animals developing moderate-to-severe AKI (p = 0.002 and p = 0.01). AUC of [TIMP-2]·[IGFBP7] for AKI was 0.89 (95 % CI 0.80–0.98). By contrast, the next best AUC was seen with plasma cystatin C (0.78; 95 % CI 0.65–0.90). [TIMP-2]·[IGFBP7] also predicted mortality (AUC 0.69; 95 % CI 0.53–0.85).

Conclusions

In this experimental model of sepsis in the rat, cell cycle arrest biomarkers TIMP-2 and IGFBP7 are valid predictors of acute kidney injury.

Risk Stratification and Prognosis in Sepsis: What Have We Learned from Microarrays?

Sepsis mortality rates have decreased in recent years but remain unacceptably high. Risk stratification and prognostication is of particular importance because high-risk patients may benefit from earlier clinical interventions, whereas low-risk patients may benefit from not undergoing unnecessary procedures. Prognostication is currently done mostly via clinical criteria and blood lactate levels. This article summarizes the literature on the complexity of changes at the molecular level for the casual reader.

Could Biomarkers Direct Therapy for the Septic Patient?

Sepsis is a serious medical condition caused by a severe systemic inflammatory response to a bacterial, fungal, or viral infection that most commonly affects neonates and the elderly. Advances in understanding the pathophysiology of sepsis have resulted in guidelines for care that have helped reduce the risk of dying from sepsis for both children and older adults. Still, over the past three decades, a large number of clinical trials have been undertaken to evaluate pharmacological agents for sepsis. Unfortunately, all of these trials have failed, with the use of some agents even shown to be harmful. One key issue in these trials was the heterogeneity of the patient population that participated. What has emerged is the need to target therapeutic interventions to the specific patient's underlying pathophysiological processes, rather than looking for a universal therapy that would be effective in a "typical" septic patient, who does not exist. This review supports the concept that identification of the right biomarkers that can direct therapy and provide timely feedback on its effectiveness will enable critical care physicians to decrease mortality of patients with sepsis and improve the quality of life of survivors.

A Multibiomarker-Based Model for Estimating the Risk of Septic Acute Kidney Injury

OBJECTIVE

The development of acute kidney injury in patients with sepsis is associated with worse outcomes. Identifying those at risk for septic acute kidney injury could help to inform clinical decision making. We derived and tested a multibiomarker-based model to estimate the risk of septic acute kidney injury in children with septic shock.

DESIGN

Candidate serum protein septic acute kidney injury biomarkers were identified from previous transcriptomic studies. Model derivation involved measuring these biomarkers in serum samples from 241 subjects with septic shock obtained during the first 24 hours of admission and then using a Classification and Regression Tree approach to estimate the probability of septic acute kidney injury 3 days after the onset of septic shock, defined as at least two-fold increase from baseline serum creatinine. The model was then tested in a separate cohort of 200 subjects.

SETTING

Multiple PICUs in the United States.

INTERVENTIONS

None other than standard care.

MEASUREMENTS AND MAIN RESULTS

The decision tree included a first-level decision node based on day 1 septic acute kidney injury status and five subsequent biomarker-based decision nodes. The area under the curve for the tree was 0.95 (CI95, 0.91-0.99), with a sensitivity of 93% and a specificity of 88%. The tree was superior to day 1 septic acute kidney injury status alone for estimating day 3 septic acute kidney injury risk. In the test cohort, the tree had an area under the curve of 0.83 (0.72-0.95), with a sensitivity of 85% and a specificity of 77% and was also superior to day 1 septic acute kidney injury status alone for estimating day 3 septic acute kidney injury risk.

CONCLUSIONS

We have derived and tested a model to estimate the risk of septic acute kidney injury on day 3 of septic shock using a novel panel of biomarkers. The model had very good performance in a test cohort and has test characteristics supporting clinical utility and further prospective evaluation.

Host response biomarkers in the diagnosis of sepsis: a general overview

Critically ill patients who display a systemic inflammatory response syndrome (SIRS) are prone to develop nosocomial infections. The challenge remains to distinguish as early as possible among SIRS patients those who are developing sepsis. Following a sterile insult, damage-associated molecular patterns (DAMPs) released by damaged tissues and necrotic cells initiate an inflammatory response close to that observed during sepsis. During sepsis, pathogen-associated molecular patterns (PAMPs) trigger the release of host mediators involved in innate immunity and inflammation through identical receptors as DAMPs. In both clinical settings, a compensatory anti-inflammatory response syndrome (CARS) is concomitantly initiated. The exacerbated production of pro- or anti-inflammatory mediators allows their detection in biological fluids and particularly within the bloodstream. Some of these mediators can be used as biomarkers to decipher among the patients those who developed sepsis, and eventually they can be used as prognosis markers. In addition to plasma biomarkers, the analysis of some surface markers on circulating leukocytes or the study of mRNA and miRNA can be helpful. While there is no magic marker, a combination of few biomarkers might offer a high accuracy for diagnosis.

Cerium oxide nanoparticle aggregates affect stress response and function in Caenorhabditis elegans

OBJECTIVE

The continual increase in production and disposal of nanomaterials raises concerns regarding the safety of nanoparticles on the environmental and human health. Recent studies suggest that cerium oxide (CeO2) nanoparticles may possess both harmful and beneficial effects on biological processes. The primary objective of this study is to evaluate how exposure to different concentrations (0.17-17.21 µg/mL) of aggregated CeO2 nanoparticles affects indices of whole animal stress and survivability in Caenorhabditis elegans.

METHODS

Caenorhabditis elegans were exposed to different concentrations of CeO2 nanoparticles and evaluated.

RESULTS

Our findings demonstrate that chronic exposure of CeO2 nanoparticle aggregates is associated with increased levels of reactive oxygen species and heat shock stress response (HSP-4) in Caenorhabditis elegans, but not mortality. Conversely, CeO2 aggregates promoted strain-dependent decreases in animal fertility, a decline in stress resistance as measured by thermotolerance, and shortened worm length.

CONCLUSION

The data obtained from this study reveal the sublethal toxic effects of CeO2 nanoparticle aggregates in Caenorhabditis elegans and contribute to our understanding of how exposure to CeO2 may affect the environment.

Loss of matrix metalloproteinase-8 is associated with worsened recovery after ischemic kidney injury

Acute kidney injury (AKI) leads to chronic kidney disease. The mechanisms involved with recovery from AKI are poorly understood and molecular mediators responsible for healing and restoration of kidney function are understudied. We previously discovered differential expression of matrix metalloproteinase-8 (MMP-8) mRNA and protein in patients with severe sepsis associated AKI versus sepsis without AKI. Here, we demonstrate the involvement of MMP-8 in purely ischemic AKI. Mice subjected to 30 min of bilateral renal ischemia developed increased plasma creatinine and MMP-8 expression within 24 h versus sham controls. After an initial surge and subsequent return toward baseline, both kidney MMP-8 expression and activity exhibited a late increase (Days 5-7 post-ischemia reperfusion) in mice subjected to AKI. Neutrophil infiltration of the kidney was significantly higher after AKI in wild-type mice than in MMP-8 null mice, starting at 4 days. Additionally, MMP-8 null mice subjected to AKI demonstrated a persistent histopathologic and functional injury and worsened health (greater overall weight loss) versus wild-type cohorts after seven days. Taken together, our findings suggest that MMP-8 is involved with restoration of baseline kidney health after ischemic kidney injury and that a potential mechanism involves the interaction of MMP-8 and neutrophil recruitment to the site of injury.

Differential expression of the nuclear-encoded mitochondrial transcriptome in pediatric septic shock

Introduction

Increasing evidence supports a role for mitochondrial dysfunction in organ injury and immune dysregulation in sepsis. Although differential expression of mitochondrial genes in blood cells has been reported for several diseases in which bioenergetic failure is a postulated mechanism, there are no data about the blood cell mitochondrial transcriptome in pediatric sepsis.

Methods

We conducted a focused analysis using a multicenter genome-wide expression database of 180 children ≤10 years of age with septic shock and 53 healthy controls. Using total RNA isolated from whole blood within 24 hours of PICU admission for septic shock, we evaluated 296 nuclear-encoded mitochondrial genes using a false discovery rate of 1%. A series of bioinformatic approaches were applied to compare differentially expressed genes across previously validated gene expression-based subclasses (groups A, B, and C) of pediatric septic shock.

Results

In total, 118 genes were differentially regulated in subjects with septic shock compared to healthy controls, including 48 genes that were upregulated and 70 that were downregulated. The top scoring canonical pathway was oxidative phosphorylation, with general downregulation of the 51 genes corresponding to the electron transport system (ETS). The top two gene networks were composed primarily of mitochondrial ribosomal proteins highly connected to ETS complex I, and genes encoding for ETS complexes I, II, and IV that were highly connected to the peroxisome proliferator activated receptor (PPAR) family. There were 162 mitochondrial genes differentially regulated between groups A, B, and C. Group A, which had the highest maximum number of organ failures and mortality, exhibited a greater downregulation of mitochondrial genes compared to groups B and C.

Conclusions

Based on a focused analysis of a pediatric septic shock transcriptomic database, nuclear-encoded mitochondrial genes were differentially regulated early in pediatric septic shock compared to healthy controls, as well as across genotypic and phenotypic distinct pediatric septic shock subclasses. The nuclear genome may be an important mechanism contributing to alterations in mitochondrial bioenergetic function and outcomes in pediatric sepsis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0623-9) contains supplementary material, which is available to authorized users.

Incorporation of biomarkers with the renal angina index for prediction of severe AKI in critically ill children

BACKGROUND AND OBJECTIVES

Novel AKI biomarkers carry variable performance for prediction of AKI in patients with heterogeneous illness. Until utility is demonstrated in critically ill patients outside of the cardiopulmonary bypass population, AKI biomarkers are unlikely to gain widespread implementation. Operationalization of an AKI risk stratification methodology, termed renal angina, was recently reported to enhance prediction at the time of intensive care unit admission for persistent severe AKI. The renal angina index (RAI) was developed to provide the clinical context to direct AKI biomarker testing. This study tested the hypothesis that incorporation of AKI biomarkers in patients fulfilling renal angina improves the prediction of persistent severe AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a multicenter study of 214 patients admitted to the pediatric intensive care unit with sepsis, the discrimination of plasma neutrophil gelatinase-associated lipocalin (NGAL), matrix metalloproteinase-8 (MMP-8), and neutrophil elastase-2 (Ela-2) were determined individually and in combination with the RAI for severe AKI. Net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were calculated.

RESULTS

Individual biomarkers demonstrated marginal discrimination for severe AKI (area under curve [AUC]: NGAL, 0.72; MMP-8, 0.68; Ela-2, 0.72), inferior to prediction by the clinical model of the RAI (AUC=0.80). Incorporation of each biomarker significantly added to the renal angina model AKI prediction (AUC=0.80, increased to 0.84-0.88; P<0.05 for each). The inclusion of each biomarker with the RAI demonstrated NRI (0.512, 0.428, and 0.545 for NGAL, MMP-8, and Ela-2, respectively; all P<0.03) and IDI (0.075 for Ela-2). The inclusion of both Ela-2 and NGAL with RAI demonstrated an NRI of 0.871 (P<0.001) and an IDI of 0.1 (P=0.01).

CONCLUSIONS

This study shows that incorporation of AKI biomarkers into the RAI improves discrimination for severe AKI. The RAI optimizes the utility of AKI biomarkers in a heterogeneous, critically ill patient population.

Post-ICU admission fluid balance and pediatric septic shock outcomes: a risk-stratified analysis

OBJECTIVE

Observed associations between fluid balance and septic shock outcomes are likely confounded by initial mortality risk. We conducted a risk-stratified analysis of the association between post-ICU admission fluid balance and pediatric septic shock outcomes.

DESIGN

Retrospective analysis of an ongoing multicenter pediatric septic shock clinical and biological database.

SETTING

Seventeen PICUs in the United States.

PATIENTS

Three hundred and seventeen children with septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We stratified subjects into three mortality risk categories (low, intermediate, and high) using a validated biomarker-based stratification tool. Within each category, we assessed three fluid balance variables: total fluid intake/kg/d during the first 24 hours, percent positive fluid balance during the first 24 hours, and cumulative percent positive fluid balance up to 7 days. We used logistic regression to estimate the effect of fluid balance on the odds of 28-day mortality, and on complicated course, which we defined as either death within 28 days or persistence of two or more organ failures at 7 days. There were 40 deaths, and 91 subjects had a complicated course. Increased cumulative percent positive fluid balance was associated with mortality in the low-risk cohort (n = 204; odds ratio, 1.035; 95% CI, 1.004-1.066) but not in the intermediate- and high-risk cohorts. No other associations with mortality were observed. Fluid intake, percent positive fluid balance in the first 24 hours, and cumulative percent positive fluid balance were all associated with increased odds of a complicated course in the low-risk cohort but not in the intermediate- and high-risk cohorts.

CONCLUSIONS

When stratified for mortality risk, increased fluid intake and positive fluid balance after ICU admission are associated with worse outcomes in pediatric septic shock patients with a low initial mortality risk but not in patients at moderate or high mortality risk.

The temporal version of the pediatric sepsis biomarker risk model

Background

PERSEVERE is a risk model for estimating mortality probability in pediatric septic shock, using five biomarkers measured within 24 hours of clinical presentation.

Objective

Here, we derive and test a temporal version of PERSEVERE (tPERSEVERE) that considers biomarker values at the first and third day following presentation to estimate the probability of a “complicated course”, defined as persistence of ≥2 organ failures at seven days after meeting criteria for septic shock, or death within 28 days.

Methods

Biomarkers were measured in the derivation cohort (n = 225) using serum samples obtained during days 1 and 3 of septic shock. Classification and Regression Tree (CART) analysis was used to derive a model to estimate the risk of a complicated course. The derived model was validated in the test cohort (n = 74), and subsequently updated using the combined derivation and test cohorts.

Results

A complicated course occurred in 23% of the derivation cohort subjects. The derived model had a sensitivity for a complicated course of 90% (95% CI 78–96), specificity was 70% (62–77), positive predictive value was 47% (37–58), and negative predictive value was 96% (91–99). The area under the receiver operating characteristic curve was 0.85 (0.79–0.90). Similar test characteristics were observed in the test cohort. The updated model had a sensitivity of 91% (81–96), a specificity of 70% (64–76), a positive predictive value of 47% (39–56), and a negative predictive value of 96% (92–99).

Conclusions

tPERSEVERE reasonably estimates the probability of a complicated course in children with septic shock. tPERSEVERE could potentially serve as an adjunct to physiological assessments for monitoring how risk for poor outcomes changes during early interventions in pediatric septic shock.

Testing the prognostic accuracy of the updated pediatric sepsis biomarker risk model

BACKGROUND

We previously derived and validated a risk model to estimate mortality probability in children with septic shock (PERSEVERE; PEdiatRic SEpsis biomarkEr Risk modEl). PERSEVERE uses five biomarkers and age to estimate mortality probability. After the initial derivation and validation of PERSEVERE, we combined the derivation and validation cohorts (n = 355) and updated PERSEVERE. An important step in the development of updated risk models is to test their accuracy using an independent test cohort.

OBJECTIVE

To test the prognostic accuracy of the updated version PERSEVERE in an independent test cohort.

METHODS

Study subjects were recruited from multiple pediatric intensive care units in the United States. Biomarkers were measured in 182 pediatric subjects with septic shock using serum samples obtained during the first 24 hours of presentation. The accuracy of PERSEVERE 28-day mortality risk estimate was tested using diagnostic test statistics, and the net reclassification improvement (NRI) was used to test whether PERSEVERE adds information to a physiology-based scoring system.

RESULTS

Mortality in the test cohort was 13.2%. Using a risk cut-off of 2.5%, the sensitivity of PERSEVERE for mortality was 83% (95% CI 62-95), specificity was 75% (68-82), positive predictive value was 34% (22-47), and negative predictive value was 97% (91-99). The area under the receiver operating characteristic curve was 0.81 (0.70-0.92). The false positive subjects had a greater degree of organ failure burden and longer intensive care unit length of stay, compared to the true negative subjects. When adding PERSEVERE to a physiology-based scoring system, the net reclassification improvement was 0.91 (0.47-1.35; p<0.001).

CONCLUSIONS

The updated version of PERSEVERE estimates mortality probability reliably in a heterogeneous test cohort of children with septic shock and provides information over and above a physiology-based scoring system.

Myocardial dysfunction in pediatric septic shock

OBJECTIVE

To evaluate the prevalence and significance of myocardial dysfunction in children with septic shock.

STUDY DESIGN

Thirty patients with septic shock were evaluated by transthoracic echocardiography within 24 hours of admission to a pediatric critical care unit. Transthoracic echocardiography evaluation included left ventricular (LV) size and function, mitral valve inflow velocities in early and late diastole, mitral valve annular velocities in systole and early and late diastole, and LV myocardial performance index. LV systolic dysfunction was defined as an ejection fraction or shortening fraction z-score <-2, and LV diastolic dysfunction was defined as a mitral valve inflow velocity/annular velocity in early diastole ratio z-score >2. Secondary outcomes included troponin I concentration, acute kidney injury, and 28-day mechanical ventilation-free duration.

RESULTS

Mortality for the 30 patients (mean age, 9.5 ± 7 years) was 7%. The prevalence of LV systolic and/or diastolic dysfunction was 53% (16 of 30). Eleven patients (37%) had systolic dysfunction, 10 (33%) had diastolic dysfunction, and 5 (17%) had both. Systolic and/or diastolic dysfunction was significantly associated with troponin I level (P = .007) and acute kidney injury (P = .02), but not with ventilation-free duration (P = .12). Kaplan-Meier analyses for pediatric critical care unit and hospital length of stay identified no differences between patients with and those without myocardial dysfunction.

CONCLUSION

Myocardial dysfunction occurs frequently in children with septic shock but might not affect hospital length of stay.

Renal complications and therapy in the PICU: hypertension, CKD, AKI, and RRT

This article provides the bedside clinician an overview of the unique renal complications that are seen commonly in the pediatric intensive care unit. These sections are purposely succinct to give a quick guide to the clinician for the care of these children. We have identified four major areas that should result in discussion and cooperative care between intensive care physicians and nephrologists for the care of these children: (1) hypertension, (2) chronic kidney failure, (3) acute kidney injury, and (4) renal replacement therapy.

Acute kidney injury in children: an update on diagnosis and treatment

The concept and definition of acute kidney injury (AKI) in adults and children has undergone significant change in recent years. Biomarker assessment is aiding in description, defining and understanding timing of AKI. AKI demonstrates unique characteristics in association with sepsis and septic shock, organ dysfunction, and fluid overload. Treatment remains problematic, but growing experience with pediatric continuous renal replacement therapies has improved the delivery of care in children. Increasingly, continuous renal replacement therapy is provided in combination with other extracorporeal technologies, and approaches are advancing to improve combined therapy use.

Genome-wide expression profiling in pediatric septic shock

For nearly a decade, our research group has had the privilege of developing and mining a multicenter, microarray-based, genome-wide expression database of critically ill children (≤10 y of age) with septic shock. Using bioinformatic and systems biology approaches, the expression data generated through this discovery-oriented, exploratory approach have been leveraged for a variety of objectives, which are reviewed here. Fundamental observations include widespread repression of gene programs corresponding to the adaptive immune system and biologically significant differential patterns of gene expression across developmental age groups. The data have also identified gene expression-based subclasses of pediatric septic shock having clinically relevant phenotypic differences. The data have also been leveraged for the discovery of novel therapeutic targets, as well as for the discovery and development of novel stratification and diagnostic biomarkers. Almost a decade of genome-wide expression profiling in pediatric septic shock is now demonstrating tangible results. The studies have progressed from an initial discovery-oriented and exploratory phase to a new phase in which the data are being translated and applied to address several areas of clinical need.

Interleukin-27 is a novel candidate diagnostic biomarker for bacterial infection in critically ill children

Introduction

Differentiating between sterile inflammation and bacterial infection in critically ill patients with fever and other signs of the systemic inflammatory response syndrome (SIRS) remains a clinical challenge. The objective of our study was to mine an existing genome-wide expression database for the discovery of candidate diagnostic biomarkers to predict the presence of bacterial infection in critically ill children.

Methods

Genome-wide expression data were compared between patients with SIRS having negative bacterial cultures (n = 21) and patients with sepsis having positive bacterial cultures (n = 60). Differentially expressed genes were subjected to a leave-one-out cross-validation (LOOCV) procedure to predict SIRS or sepsis classes. Serum concentrations of interleukin-27 (IL-27) and procalcitonin (PCT) were compared between 101 patients with SIRS and 130 patients with sepsis. All data represent the first 24 hours of meeting criteria for either SIRS or sepsis.

Results

Two hundred twenty one gene probes were differentially regulated between patients with SIRS and patients with sepsis. The LOOCV procedure correctly predicted 86% of the SIRS and sepsis classes, and Epstein-Barr virus-induced gene 3 (EBI3) had the highest predictive strength. Computer-assisted image analyses of gene-expression mosaics were able to predict infection with a specificity of 90% and a positive predictive value of 94%. Because EBI3 is a subunit of the heterodimeric cytokine, IL-27, we tested the ability of serum IL-27 protein concentrations to predict infection. At a cut-point value of ≥5 ng/ml, serum IL-27 protein concentrations predicted infection with a specificity and a positive predictive value of >90%, and the overall performance of IL-27 was generally better than that of PCT. A decision tree combining IL-27 and PCT improved overall predictive capacity compared with that of either biomarker alone.

Conclusions

Genome-wide expression analysis has provided the foundation for the identification of IL-27 as a novel candidate diagnostic biomarker for predicting bacterial infection in critically ill children. Additional studies will be required to test further the diagnostic performance of IL-27.

The microarray data reported in this article have been deposited in the Gene Expression Omnibus under accession number GSE4607.

The pediatric sepsis biomarker risk model

INTRODUCTION

The intrinsic heterogeneity of clinical septic shock is a major challenge. For clinical trials, individual patient management, and quality improvement efforts, it is unclear which patients are least likely to survive and thus benefit from alternative treatment approaches. A robust risk stratification tool would greatly aid decision-making. The objective of our study was to derive and test a multi-biomarker-based risk model to predict outcome in pediatric septic shock.

METHODS

Twelve candidate serum protein stratification biomarkers were identified from previous genome-wide expression profiling. To derive the risk stratification tool, biomarkers were measured in serum samples from 220 unselected children with septic shock, obtained during the first 24 hours of admission to the intensive care unit. Classification and Regression Tree (CART) analysis was used to generate a decision tree to predict 28-day all-cause mortality based on both biomarkers and clinical variables. The derived tree was subsequently tested in an independent cohort of 135 children with septic shock.

RESULTS

The derived decision tree included five biomarkers. In the derivation cohort, sensitivity for mortality was 91% (95% CI 70 - 98), specificity was 86% (80 - 90), positive predictive value was 43% (29 - 58), and negative predictive value was 99% (95 - 100). When applied to the test cohort, sensitivity was 89% (64 - 98) and specificity was 64% (55 - 73). In an updated model including all 355 subjects in the combined derivation and test cohorts, sensitivity for mortality was 93% (79 - 98), specificity was 74% (69 - 79), positive predictive value was 32% (24 - 41), and negative predictive value was 99% (96 - 100). False positive subjects in the updated model had greater illness severity compared to the true negative subjects, as measured by persistence of organ failure, length of stay, and intensive care unit free days.

CONCLUSIONS

The pediatric sepsis biomarker risk model (PERSEVERE; PEdiatRic SEpsis biomarkEr Risk modEl) reliably identifies children at risk of death and greater illness severity from pediatric septic shock. PERSEVERE has the potential to substantially enhance clinical decision making, to adjust for risk in clinical trials, and to serve as a septic shock-specific quality metric.