Sepsis Phenotypes Research Articles

Thiamine (vitamin B1) in septic shock: a targeted therapy.

Thiamine (vitamin B1) is a water-soluble vitamin essential for human health. Thiamine deficiency is causal and/or contributory in a number of debilitating diseases including beri-beri, the Wernicke-Korsakoff syndrome, optic neuropathy, and others. While thiamine deficiency is relatively rare in developed nations as a result of dietary supplementation, thiamine deficiency is more common in nutritionally compromised populations. Thiamine pyrophosphate, a thiamine derivative, is essential to the citric acid cycle and thiamine deficiency can result in impaired aerobic respiration and cellular energy production. Thiamine also plays an important role in the pentose phosphate pathway and other key metabolic processes. Although thiamine deficiency is a known cause of lactic acidosis, it has been recently evaluated as a potential contributor to refractory lactic acidosis and organ injury in septic shock and other shock states. In this article, we review the epidemiology of thiamine deficiency in septic shock and the existing evidence base supporting thiamine supplementation. We conclude that specific sepsis phenotypes may stand to benefit the most from thiamine supplementation, and efforts might be made to identify and supplement these patients early in their hospital course.

Murine sepsis phenotypes and differential treatment effects in a randomized trial of prompt antibiotics and fluids

BackgroundClinical and biologic phenotypes of sepsis are proposed in human studies, yet it is unknown whether prognostic or drug response phenotypes are present in animal models of sepsis. Using a biotelemetry-enhanced, murine cecal ligation and puncture (CLP) model, we determined phenotypes of polymicrobial sepsis prior to physiologic deterioration, and the association between phenotypes and outcome in a randomized trial of prompt or delayed antibiotics and fluids.MethodsWe performed a secondary analysis of male C57BL/6J mice in two observational cohorts and two randomized, laboratory animal experimental trials. In cohort 1, mice (n = 118) underwent biotelemetry-enhanced CLP, and we applied latent class mixed models to determine optimal number of phenotypes using clinical data collected between injury and physiologic deterioration. In cohort 2 (N = 73 mice), inflammatory cytokines measured at 24 h after deterioration were explored by phenotype. In a subset of 46 mice enrolled in two trials from cohort 1, we tested the association of phenotypes with the response to immediate (0 h) vs. delayed (2 to 4 h) antibiotics or fluids initiated after physiologic deterioration.ResultsLatent class mixture modeling derived a two-class model in cohort 1. Class 2 (N = 97) demonstrated a shorter time to deterioration (mean SD 7.3 (0.9) vs. 9.7 (3.2) h, p < 0.001) and lower heart rate at 7 h after injury (mean (SD) 564 (55) vs. 626 (35) beats per minute, p < 0.001). Overall mortality was similar between phenotypes (p = 0.75). In cohort 2 used for biomarker measurement, class 2 mice had greater plasma concentrations of IL6 and IL10 at 24 h after CLP (p = 0.05). In pilot randomized trials, the effects of sepsis treatment (immediate vs. delayed antibiotics) differed by phenotype (p = 0.03), with immediate treatment associated with greater survival in class 2 mice only. Similar differential treatment effect by class was observed in the trial of immediate vs. delayed fluids (p = 0.02).ConclusionsWe identified two sepsis phenotypes in a murine cecal ligation and puncture model, one of which is characterized by faster deterioration and more severe inflammation. Response to treatment in a randomized trial of immediate versus delayed antibiotics and fluids differed on the basis of phenotype.

Mitochondrial Dysfunction is Associated With an Immune Paralysis Phenotype in Pediatric Sepsis.

Immune dysregulation is a defining feature of sepsis, but the role for mitochondria in the development of immunoparalysis in pediatric sepsis is not known. We sought to determine if mitochondrial dysfunction measured in peripheral blood mononuclear cells (PBMCs) is associated with immunoparalysis and systemic inflammation in children with sepsis. Prospective observational study. Single-academic pediatric intensive care unit (PICU). One hundred sixty-one children with sepsis/septic shock and 18 noninfected PICU controls. Mitochondrial respiration in PBMCs, markers of immune function, and plasma cytokines were measured on days 1 to 2 (T1), 3 to 5 (T2), and 8 to 14 (T3) after sepsis recognition, and once for controls. Immunoparalysis was defined as whole-blood ex vivo lipopolysaccharide-induced tumor necrosis factor-alpha (TNF-α) ≤200 pg/mL or monocyte human leukocyte antigen-DR ≤30%. Mitochondrial respiration was lower in children with versus without immunoparalysis measured at the same timepoint. Mitochondrial respiration measured early (at T1 and T2) was also lower in those with immunoparalysis at T2 and T3, respectively. Although most patients with immunoparalysis exhibited low mitochondrial respiration, this metabolic finding was not specific to the immunoparalysis phenotype. Plasma cytokines, including IL-8, IL-10, TNF-α, and MCP-1, were highest in the subset of sepsis patients with immune paralysis or low mitochondrial respiration at T1. Children with sepsis had lower PBMC mitochondrial respiration when immunoparalysis was present compared with those without immunoparalysis. The subsets with immune paralysis and low mitochondrial respiration exhibited the highest levels of systemic inflammation.

2 Sepsis Watch: A Successful Deployment of a Deep Learning Sepsis Detection and Treatment Platform

Sepsis is a leading cause of hospital mortality. Despite evidence that early initiation of treatment improves outcomes, rapid detection is challenging. Compliance with the CMS SEP-1 sepsis bundle is a nationally reported metric and will impact hospital reimbursements. Performance overall is poor with some reporting compliance at 33%. While the translational pathway for prognostic models has been well characterized, few machine learning models have been externally validated. This study aims to be the first deep learning model that is integrated into an operational workflow to successfully detect sepsis in real-time. The primary outcome is SEP-1 bundle compliance and secondary outcomes include inpatient mortality, hospital and emergency department (ED) length of stay, as well as process measures such as time from ED arrival identification of “time zero” (as defined by SEP-1) and time to bundle completion. March, 2016, an interdisciplinary team consisting of clinicians, data scientists and machine learning experts at a large academic medical center embarked on an innovation pilot to develop a novel machine learning model to detect sepsis, named Sepsis Watch (SW). A computable sepsis definition and deep learning model were developed using a curated dataset capturing over 43,000 inpatient admissions between 10/1/2014 – 12/31/2015. Ten sepsis definitions were compared and clinicians agreed on the following: >= 2 SIRS criteria, blood culture order, and end organ damage. A deep learning model was built to predict which patients would meet that phenotype of sepsis. The model incorporates 121 clinical variables that are continually collected and assessed in real time on every patient that presents to the ED and the first 6 hours of inpatient admission if applicable. Patient status is updated as being “low risk,” “medium risk,” “high risk,” or “septic.” If Sepsis Watch predicts a patient to be “High risk” or “septic” that information is communicated to the ED team. Data collected for operational feedback includes total volume of patients who are deemed “High Risk” or “septic”, time of day when the model made these predictions, compliance with antibiotic administration, collection of repeat lactate and obtaining cultures all within 3 hours both individually and as a bundle. Sepsis Watch operated in the pilot phase 11/06/18 – 05/05/19 and analyzed over 39,000 ED patients for their risk of sepsis. It predicted that 1,318 patients were “high risk.” Of those, 948 progressed to “septic” either in the ED or within 6 hours of admission. Bundle compliance within 3 hours was tracked. For those who were “High Risk” but never “septic,” 77% had antibiotics administered, 75% had a repeat lactate collected and 72% had cultures collected in 3 hours. For those deemed “septic”, 79% had antibiotics administered within 3 hours, 90% had a repeat lactate collected in 3 hours and 88% had cultures collected in 3 hours. Overall bundle compliance was 55.7% for “High Risk” patients and 67.1% for “Septic” patients. Sepsis Watch is the first deep learning model deployed to successfully detect sepsis in real time with operational workflows developed provide support directly to emergency physicians. Preliminary data suggests that Sepsis Watch has improved compliance with SEP-1. Validation of these internal results with the external nationally reportable metrics is forthcoming.

Derivation, Validation, and Potential Treatment Implications of Novel Clinical Phenotypes for Sepsis

Sepsis is a heterogeneous syndrome. Identification of distinct clinical phenotypes may allow more precise therapy and improve care. To derive sepsis phenotypes from clinical data, determine their reproducibility and correlation with host-response biomarkers and clinical outcomes, and assess the potential causal relationship with results from randomized clinical trials (RCTs). Retrospective analysis of data sets using statistical, machine learning, and simulation tools. Phenotypes were derived among 20 189 total patients (16 552 unique patients) who met Sepsis-3 criteria within 6 hours of hospital presentation at 12 Pennsylvania hospitals (2010-2012) using consensus k means clustering applied to 29 variables. Reproducibility and correlation with biological parameters and clinical outcomes were assessed in a second database (2013-2014; n = 43 086 total patients and n = 31 160 unique patients), in a prospective cohort study of sepsis due to pneumonia (n = 583), and in 3 sepsis RCTs (n = 4737). All clinical and laboratory variables in the electronic health record. Derived phenotype (α, β, γ, and δ) frequency, host-response biomarkers, 28-day and 365-day mortality, and RCT simulation outputs. The derivation cohort included 20 189 patients with sepsis (mean age, 64 [SD, 17] years; 10 022 [50%] male; mean maximum 24-hour Sequential Organ Failure Assessment [SOFA] score, 3.9 [SD, 2.4]). The validation cohort included 43 086 patients (mean age, 67 [SD, 17] years; 21 993 [51%] male; mean maximum 24-hour SOFA score, 3.6 [SD, 2.0]). Of the 4 derived phenotypes, the α phenotype was the most common (n = 6625; 33%) and included patients with the lowest administration of a vasopressor; in the β phenotype (n = 5512; 27%), patients were older and had more chronic illness and renal dysfunction; in the γ phenotype (n = 5385; 27%), patients had more inflammation and pulmonary dysfunction; and in the δ phenotype (n = 2667; 13%), patients had more liver dysfunction and septic shock. Phenotype distributions were similar in the validation cohort. There were consistent differences in biomarker patterns by phenotype. In the derivation cohort, cumulative 28-day mortality was 287 deaths of 5691 unique patients (5%) for the α phenotype; 561 of 4420 (13%) for the β phenotype; 1031 of 4318 (24%) for the γ phenotype; and 897 of 2223 (40%) for the δ phenotype. Across all cohorts and trials, 28-day and 365-day mortality were highest among the δ phenotype vs the other 3 phenotypes (P < .001). In simulation models, the proportion of RCTs reporting benefit, harm, or no effect changed considerably (eg, varying the phenotype frequencies within an RCT of early goal-directed therapy changed the results from >33% chance of benefit to >60% chance of harm). In this retrospective analysis of data sets from patients with sepsis, 4 clinical phenotypes were identified that correlated with host-response patterns and clinical outcomes, and simulations suggested these phenotypes may help in understanding heterogeneity of treatment effects. Further research is needed to determine the utility of these phenotypes in clinical care and for informing trial design and interpretation.

The use of light to potentiate antidepressant medication: Preclinical evidence

Experimental animal models are indispensable components of preclinical sepsis research. Reproducible results highly rely on defined and invariant baseline conditions. Our hypothesis was that the murine gut microbiota varies among different distributors of laboratory animals and that these variations influence the phenotype of abdominal sepsis derived from a bacterial inoculum model (intraperitoneal stool injection).Male C57BL/6 mice (8-wk old) purchased from Charles River (CR), Janvier (J), and Harlan (H) were sacrificed, and the bacterial composition of feces was analyzed using CHROMagar orientation medium. Stool was injected intraperitoneally into CR mice, followed by clinical observation and gene expression analysis. Experiments were repeated 16 mo later under the same conditions.Stool analysis revealed profound intervendor differences in bacterial composition, mainly regarding Staphylococcus aureus and Bacillus licheniformis. Mice challenged with CR as well as H feces developed significantly higher severity of disease and died within the observation period, whereas stool from J mice did not induce any of these symptoms. Real-time polymerase chain reaction revealed corresponding results with significant upregulation of proinflammatory cytokines and vascular leakage-related mediators in CR and H injected animals. Sixteen months later, the bacterial fecal composition had significantly shifted. The differences in clinical phenotype of sepsis after intraperitoneal stool injection had vanished.We are the first to demonstrate vendor and time effects on the murine fecal microbiota influencing sepsis models of intraabdominal stool contamination. The intestinal microbiota must be defined and standardized when designing and interpreting past and future studies using murine abdominal sepsis models.

Circadian Rhythms Influence the Severity of Sepsis in Mice via a TLR2-Dependent, Leukocyte-Intrinsic Mechanism.

Circadian rhythms coordinate an organism's activities and biological processes to the optimal time in the 24-h daylight cycle. We previously demonstrated that male C57BL/6 mice develop sepsis more rapidly when the disease is induced in the nighttime versus the daytime. In this report, we elucidate the mechanism of this diurnal difference. Sepsis was induced via cecal ligation and puncture (CLP) at zeitgeber time (ZT)-19 (2 am) or ZT-7 (2 pm). Like the males used in our prior study, female C57BL/6 mice had a worse outcome when CLP was induced at ZT-19 versus ZT-7, and these effects persisted when we pooled the data from both sexes. In contrast, mice with a mutated Period 2 (Per2) gene had a similar outcome when CLP was induced at ZT-19 versus ZT-7. Bone marrow chimeras reconstituted with C57BL/6 immune cells exhibited a worse outcome when sepsis was induced at ZT-19 versus ZT-7, whereas chimeras with Per2-mutated immune cells did not. Next, murine macrophages were subjected to serum shock to synchronize circadian rhythms and exposed to bacteria cultured from the mouse cecum at 4-h intervals for 48 h. We observed that IL-6 production oscillated with a 24-h period in C57BL/6 cells exposed to cecal bacteria. Interestingly, we observed a similar pattern when cells were exposed to the TLR2 agonist lipoteichoic acid. Furthermore, TLR2-knockout mice exhibited a similar sepsis phenotype when CLP was induced at ZT-19 versus ZT-7. Together, these data suggest that circadian rhythms in immune cells mediate diurnal variations in murine sepsis severity via a TLR2-dependent mechanism.

Hypofibrinogenemia Is Associated With Poor Outcome and Secondary Hemophagocytic Lymphohistiocytosis/Macrophage Activation Syndrome in Pediatric Severe Sepsis.

Some children with sepsis exhibit a sustained hyperinflammatory response that can trigger secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome. Although hypofibrinogenemia is a shared feature of sepsis and hemophagocytic lymphohistiocytosis, there are no data about fibrinogen as a biomarker to identify children with sepsis/secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome overlap. We hypothesized that hypofibrinogenemia is associated with poor outcomes and secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome and has utility as a screening biomarker for this sepsis phenotype. A retrospective cohort study of patients less than or equal to 21 years treated for severe sepsis from January 2012 to December 2014. Emergency department and PICU at a single academic children's hospital. Consecutive patients with greater than or equal to one episode of hypofibrinogenemia (serum fibrinogen < 150 mg/dL) within 7 days of sepsis were compared with a random sample of patients without hypofibrinogenemia using an a priori sample size target of 190. Thirty-eight patients with hypofibrinogenemia were compared with 154 without hypofibrinogenemia. None. The primary outcome was "complicated course" (composite of 28-d mortality or ≥ two organ failures at 7 d). Secondary outcomes were 28-day mortality and fulfillment of diagnostic criteria for secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome. We used Wilcoxon rank-sum, Fisher exact test, and multivariable logistic regression to compare patients with versus without hypofibrinogenemia. Patients with hypofibrinogenemia were more likely to have a complicated course (73.7% vs 29.2%; p < 0.001), 28-day mortality (26.3% vs 7.1%, p = 0.002), and meet diagnostic criteria for secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome (21.1% vs 1.3%; p < 0.001). After controlling for confounders, hypofibrinogenemia remained associated with complicated course (adjusted odds ratio, 8.8; 95% CI, 3.5-22.4), mortality (adjusted odds ratio, 6.0; 95% CI, 2.0-18.1), and secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome (adjusted odds ratio, 27.6; 95% CI, 4.4-173). Hypofibrinogenemia was independently associated with poor outcome and secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome in pediatric sepsis. Measurement of fibrinogen may provide a pragmatic biomarker to identify children with possible sepsis/secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome overlap for whom further diagnostic testing and consideration of adjunctive immunomodulatory therapies should be considered.

Innate Immunity in the Persistent Inflammation, Immunosuppression, and Catabolism Syndrome and Its Implications for Therapy

Clinical and technological advances promoting early hemorrhage control and physiologic resuscitation as well as early diagnosis and optimal treatment of sepsis have significantly decreased in-hospital mortality for many critically ill patient populations. However, a substantial proportion of severe trauma and sepsis survivors will develop protracted organ dysfunction termed chronic critical illness (CCI), defined as ≥14 days requiring intensive care unit (ICU) resources with ongoing organ dysfunction. A subset of CCI patients will develop the persistent inflammation, immunosuppression, and catabolism syndrome (PICS), and these individuals are predisposed to a poor quality of life and indolent death. We propose that CCI and PICS after trauma or sepsis are the result of an inappropriate bone marrow response characterized by the generation of dysfunctional myeloid populations at the expense of lympho- and erythropoiesis. This review describes similarities among CCI/PICS phenotypes in sepsis, cancer, and aging and reviews the role of aberrant myelopoiesis in the pathophysiology of CCI and PICS. In addition, we characterize pathogen recognition, the interface between innate and adaptive immune systems, and therapeutic approaches including immune modulators, gut microbiota support, and nutritional and exercise therapy. Finally, we discuss the future of diagnostic and prognostic approaches guided by machine and deep-learning models trained and validated on big data to identify patients for whom these approaches will yield the greatest benefits. A deeper understanding of the pathophysiology of CCI and PICS and continued investigation into novel therapies harbor the potential to improve the current dismal long-term outcomes for critically ill post-injury and post-infection patients.

Program Cell Death Receptor-1-Mediated Invariant Natural Killer T-Cell Control of Peritoneal Macrophage Modulates Survival in Neonatal Sepsis.

We have shown that invariant natural killer T (iNKT) cells mediate sepsis-induced end-organ changes and immune responses, including macrophage bacterial phagocytosis, a finding regulated by the check point protein program cell death receptor-1 (PD-1). Furthermore, PD-1 mediates mortality in both adult and neonatal murine sepsis as well as in surgical patients. Given our previous findings, we hypothesize that iNKT cells will also modulate neonatal sepsis survival, and that this effect is regulated in part through PD-1. We utilized a polymicrobial intra-peritoneal cecal slurry (CS) sepsis model in wild type (WT), iNKT−/− or PD-1−/− 5–7 day old neonatal pups. Typically, tissues were harvested at 24 h for various bioassays/histology and, in some cases, survival was assessed for up to 7 days. Interestingly, similar to what we recently reported for PD-1−/− mice following CS, iNKT−/−-deficient animals exhibit a markedly improved survival vs. WT. Histologically, minor alterations in liver architectural, which were noted in WT pups, were attenuated in both iNKT−/− and PD-1−/− pups. Following CS, PECAM-1 expression was unchanged in the WT pups but increased in both iNKT−/− and PD-1−/− pups. In WT, following CS the emergence of a Ly6Clow subpopulation was noted among the influxed peritoneal macrophage population. Conversely, within iNKT−/− pups, there were fewer peritoneal macrophages and a greater percentage of Ly6Chigh macrophages. We show not only a key role for iNKT cells in affecting end-organ damage as well as alterations in phagocytes phenotypes in neonatal sepsis but that this iNKT cell mediated effect is driven by the central checkpoint protein PD-1.

Progress in understanding of adrenal insufficiency in septic patients

Background Sepsis is one of the critical complications following serious injuries or major surgeries. It is a leading cause of death. The mortality of septic shock exceeds 40%. Accumulating studies have demonstrated that the severity of adrenal cortex dysfunction has a vital impact on the phenotype and prognosis of sepsis, while glucocorticoid(GC) may be an effective intervention. However, the mechanisms underlying adrenocortical dysfunction remain unclear. Objective To review strategies for assessment of adrenocortical function, and timely supplement of GC, aiming to appropriately compensate the impaired adrenal function, finally, to improve prognosis and to reduce mortality of sepsis. Content At the early stage of sepsis, hypothalamus-pituitary-adrenal axis(H-P-A) is activated, and is followed by release of GC and mobilization of inflammation cascades, especially mitogen-activated protein kinase(MAPK) and nuclear regulatory factor-κB pathways. GC counteracts the inflammation cascades. At the late stage of sepsis or during sepsis shock, damages of adrenocortical cells and vascular epithelia cells occur in adrenal gland, resulting in adrenocortical dysfunction, including low levels of GC and low affinity of GC receptors. The measurement of serum GC and adrenocorticotrophic hormone are combined to assess adrenocortical function: adrenal insufficiency(AI) or relative adrenal insufficiency(RAI). Low doses of GC help to reverse septic shock, improve adrenal function, and maintain normal hemodynamics in septic patients. Trend Further investigation in understanding the mechanisms underlying AI and RAI are highly demanded to optimize therapeutic application of GC in sepsis. Key words: Sepsis; Septic shock; Adrenal insufficiency; Relative adrenal insufficiency

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

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

Searching for a Pediatric Severe Sepsis Phenotype: We Might Indeed Be There

Searching for a Pediatric Severe Sepsis Phenotype: We Might Indeed Be There

Vendor effects on murine gut microbiota influence experimental abdominal sepsis

BackgroundExperimental animal models are indispensable components of preclinical sepsis research. Reproducible results highly rely on defined and invariant baseline conditions. Our hypothesis was that the murine gut microbiota varies among different distributors of laboratory animals and that these variations influence the phenotype of abdominal sepsis derived from a bacterial inoculum model (intraperitoneal stool injection). Materials and methodsMale C57BL/6 mice (8-wk old) purchased from Charles River (CR), Janvier (J), and Harlan (H) were sacrificed, and the bacterial composition of feces was analyzed using CHROMagar orientation medium. Stool was injected intraperitoneally into CR mice, followed by clinical observation and gene expression analysis. Experiments were repeated 16 mo later under the same conditions. ResultsStool analysis revealed profound intervendor differences in bacterial composition, mainly regarding Staphylococcus aureus and Bacillus licheniformis. Mice challenged with CR as well as H feces developed significantly higher severity of disease and died within the observation period, whereas stool from J mice did not induce any of these symptoms. Real-time polymerase chain reaction revealed corresponding results with significant upregulation of proinflammatory cytokines and vascular leakage-related mediators in CR and H injected animals. Sixteen months later, the bacterial fecal composition had significantly shifted. The differences in clinical phenotype of sepsis after intraperitoneal stool injection had vanished. ConclusionsWe are the first to demonstrate vendor and time effects on the murine fecal microbiota influencing sepsis models of intraabdominal stool contamination. The intestinal microbiota must be defined and standardized when designing and interpreting past and future studies using murine abdominal sepsis models.

Modulating sphingosine 1‐phosphate signaling with DOP or FTY720 alleviates vascular and immune defects in mouse sepsis

Sepsis is a systemic inflammatory response to pathogens and a leading cause of hospital related mortality worldwide. Sphingosine 1-phosphate (S1P) regulates multiple cellular processes potentially involved in the pathogenesis of sepsis, including antigen presentation, lymphocyte egress, and maintenance of vascular integrity. We thus explored the impact of manipulating S1P signaling in experimental polymicrobial sepsis in mice. Administration of 4-deoxypyridoxine (DOP), an inhibitor of the S1P-degrading enzyme S1P-lyase, or of the sphingosine analog FTY720 that serves as an S1P receptor agonist after phosphorylation ameliorated morbidity, improved recovery from sepsis in surviving mice, and reduced sepsis-elicited hypothermia and body weight loss. Treated mice developed lymphopenia, leading to an accumulation of lymphocytes in peripheral lymph nodes, and reduced bacterial burden in liver, but not in blood. Sepsis-induced upregulation of mRNA expression of cytokines in spleen remained unchanged, but reduction of IL-6, TNF-α, MCP-1, and IL-10 in plasma was evident. DOP and FTY720 treatment significantly reduced levels of Evans blue leakage from blood into liver and lung, decreased hematocrit values, and lowered plasma levels of VEGF-A in septic mice. Collectively, our results indicate that modulation of S1P signaling showed a protective phenotype in experimental sepsis by modulating vascular and immune functions.

Measurement of functional and morphodynamic neutrophil phenotypes in systemic inflammation and sepsis

We read with great interest the review by Leliefeld et al. [1] published in Critical Care on the role of neutrophils in immune paralysis during systemic inflammation (SI). This is of high clinical importance since immune paralysis potentially increases susceptibility to new infections or may cause inability to clear existing infections, leading to detrimental outcome. One mechanism proposed for immune paralysis is the release of neutrophil populations with decreased microbicidal properties [1]. During SI, heterogeneous subsets of neutrophils exist with different priming states and functions [2]. In particular, large numbers of immature neutrophils appear in the circulation with diminished expression of receptors, important for pathogen killing [3]. We recently reviewed the literature on morphodynamic changes in neutrophils during sepsis [4]. Sepsis increases neutrophil circulating numbers (and percentages of immature neutrophils) and their cell size and stiffness, and decreases migration/chemotaxis, compared with nondiseased conditions or mild infection. Septic neutrophils are also prone to produce neutrophil extracellular traps (NETs).

Intra‐renal and Urinary Oxygenation during Resuscitation with Norepinephrine and Angiotensin II in Ovine Acute Kidney Injury

Background and AimsAcute kidney Injury (AKI) is a common phenotype of sepsis leading to high mortality rates. Norepinephrine (NE) is the first choice vasopressor used clinically to restore blood pressure and renal function, whilst there is emerging interest in angiotensin II (Ang II) as an effective adjunctive therapy in patients with septic shock. Increasing evidence suggests that hypoxia in the renal medulla may play a critical role in the pathogenesis of AKI. We therefore measured renal cortical and medullary tissue oxygen tension (PO2) in conscious sheep during development of septic AKI and following resuscitation with NE and Ang II. In addition, since the renal medullary vasa recta run close and parallel to the collecting ducts, we examined whether urinary PO2 and medullary tissue PO2 changed in a similar manner during development of septic AKI and treatment with NE and Ang II.MethodsSheep were surgically instrumented with a renal artery flow probe and fibre‐optic probes in the cortex and medulla to measure tissue perfusion and oxygenation. An oxygen probe was inserted into the tip of the bladder catheter for measurement of urinary oxygenation. Conscious sheep received a continuous infusion of live Escherichia coli (2.8 × 109 bolus + 1.26 × 109 colony forming units i.v) for 32 h. NE (0.4–0.8 μg/kg/h, n=8) or Ang II (0.5–33μg/kg/min, n=8) or saline‐vehicle (n=8) were infused from 24–30 h of sepsis.ResultsPrior to treatment, septic AKI was characterized by hypotension (~14 mmHg), renal hyperperfusion (~70%) and reduced glomerular filtration rate (~65%). Medullary perfusion (1289±95 to 628±113 blood perfusion units (BPU)), medullary oxygenation (32±3 to 16±4 mmHg) and urinary oxygenation (36±2 to 24±2 mmHg) were all significantly reduced. Restoring blood pressure with NE further reduced medullary perfusion (331±64 BPU), medullary PO2 (8±2 mmHg) and urinary PO2 (18±4 mmHg). In contrast, Ang II reversed the sepsis‐induced hypotension without further exacerbating medullary perfusion (553±58 BPU), medullary PO2 (26±2 mmHg) or urinary PO2 (24±1 mmHg). Cortical perfusion and oxygenation were preserved during development of septic AKI and resuscitation with NE and Ang II.ConclusionsRenal medullary hypoxia due to intra‐renal blood flow redistribution may contribute to the development of septic AKI. Resuscitation with NE reversed sepsis‐induced hypotension, but exacerbated the medullary hypoxia, which may have long‐term effects to worsen kidney injury. Interestingly, Ang II restored blood pressure without worsening medullary hypoxia, suggesting that Ang II has less adverse effects than NE on kidney oxygenation during treatment of septic AKI. The parallel changes in medullary tissue and urinary PO2 during development of sepsis and vasopressor treatment suggest that urinary PO2 may be a useful real‐time biomarker to monitor patients at risk of developing AKI.Support or Funding InformatioThis work was supported by grants from the National Health and Medical Research Council of Australia (NHMRC, 454615, 1009280, 1050672), and by funding from the Victorian Government Operational Infrastructure Support Grant.

ACUTE DIALYSIS QUALITY INITIATIVE (ADQI) XIV SEPSIS PHENOTYPES AND TARGETS FOR BLOOD PURIFICATION IN SEPSIS: THE BOGOTÁ CONSENSUS.

Despite widespread use, there is currently no consensus on how extracorporeal blood purification therapies should be applied or studied in patients with sepsis. One major obstacle has been the lack of clear descriptions of specific sepsis phenotypes tied to mechanisms that would permit the identification of molecular targets. Current evidence suggests that sepsis-related morbidity and mortality involve widely different clinical phenotypes that variably include mitochondrial dysfunction, abnormalities of vascular biology including endothelial dysfunction and coagulopathy, epithelial dysfunction, and immune suppression and dysregulation. While most cases of sepsis involve some element of all of these pathobiologic processes, the magnitude of each varies greatly from patient to patient in part as a result of the pathogen and in part related to host-specific factors. Thus, the purpose of the fourteenth international consensus conference of acute dialysis quality initiative was to develop consensus for a conceptual model of sepsis-induced organ failure that can be treated by extracorporeal blood purification and possibly also with drugs or other therapies. We assembled a group of experts from around the world and used a modified Delphi method to reach consensus. Specific findings and recommendations for future research are provided in the four accompanying papers.

IMMUNE CELL PHENOTYPE AND FUNCTION IN SEPSIS.

Cells of the innate and adaptive immune systems play a critical role in the host response to sepsis. Moreover, their accessibility for sampling and their capacity to respond dynamically to an acute threat increases the possibility that leukocytes might serve as a measure of a systemic state of altered responsiveness in sepsis.The working group of the 14th Acute Dialysis Quality Initiative (ADQI) conference sought to obtain consensus on the characteristic functional and phenotypic changes in cells of the innate and adaptive immune system in the setting of sepsis. Techniques for the study of circulating leukocytes were also reviewed and the impact on cellular phenotypes and leukocyte function of nonextracorporeal treatments and extracorporeal blood purification therapies proposed for sepsis was analyzed.A large number of alterations in the expression of distinct neutrophil and monocyte surface markers have been reported in septic patients. The most consistent alteration seen in septic neutrophils is their activation of a survival program that resists apoptotic death. Reduced expression of HLA-DR is a characteristic finding on septic monocytes, but monocyte antimicrobial function does not appear to be significantly altered in sepsis. Regarding adaptive immunity, sepsis-induced apoptosis leads to lymphopenia in patients with septic shock and it involves all types of T cells (CD4, CD8, and Natural Killer) except T regulatory cells, thus favoring immunosuppression. Finally, numerous promising therapies targeting the host immune response to sepsis are under investigation. These potential treatments can have an effect on the number of immune cells, the proportion of cell subtypes, and the cell function.

HIF-1α at the center of the sepsis Yin and Yang

Human monocytes up-regulate hypoxia-inducible factor-1α and acquire an immunosuppressive phenotype in sepsis.