Sepsis and septic shock: pathophysiological and cardiovascular background as basis for therapy

Fibroblast growth factor 23 during septic shock and myocardial injury in ICU patients

Objective

Fibroblast growth factor 23 (FGF23) has been recognized as an important biomarker of cardiovascular disease and is closely related to inflammation over the past decade. This study aimed to assess the relationship between FGF23 and myocardial injury in patients with sepsis.

Methods

We sequentially measured serum FGF23, Klotho, biomarkers of inflammation (CRP, IL-6 and WBC), myocardial injury (cTnI and N-terminal B-type natriuretic peptide) and sepsis (procalcitonin) at peak of intercurrent septic shock and after complete resolution or before death in a series of 29 patients with septic shock. 29 healthy adults without infections were used as controls.

Results

There was a difference in serum FGF23 level between patients with septic shock and healthy adults (p < 0.0001), and the peak level of FGF23 in septic shock in the survivor group was higher than that after complete remission (p < 0.0001). No statistical difference was found in the level of FGF23 before and after treatment in the death group (p = 0.0947). At the peak of septic shock, FGF23 was significantly correlated with inflammatory markers, CRP (r = 0.8063, p < 0.0001), PCT (r = 0.6091, p = 0.0005) and WBC (r = 0.8312, p < 0.0001), while the correlation with IL-6 was not statistically significant (r = 0.0098, p = 0.9598). At the same time, it was found that FGF23 was significantly correlated with myocardial injury markers, cTNI (r = 0.8475, p < 0.0001) and NTproBNP (r = 0.8505, p < 0.0001). Nevertheless, FGF23 and klotho are not correlated (r = 0.2609, p = 0.1717).

Conclusion

In conclusion, in patients with septic shock and myocardial injury, the exacerbation of inflammation in the septic process was accompanied by a abnormal increase of circulating FGF23 level. FGF23 also subsided after the improvement of inflammation, and the opposite was true for patients who did not survive. The up-regulation of FGF23 may be involved in the response of patients to septic shocks, and it is also speculated that FGF23 is involved in the myocardial injury of septic shock.

Comparative analysis of peripheral blood immunoinflammatory landscapes in patients with acute cholangitis and its secondary septic shock using single-cell RNA sequencing

BACKGROUND

Acute cholangitis (AC) is a key pathogeny of septic shock, which has a high mortality rate. AC has significant clinical heterogeneity, but no study has analyzed the discrepancies in immunoresponsiveness between AC and its secondary septic shock. The immune inflammatory responses play a critical role in the development of septic shock.

METHODS

We performed single-cell RNA sequencing (scRNA-seq) to analyze the differences of immunocytes in immunoresponse and inflammation between the early stages of AC (A1, A2, and A3) and its secondary septic shock (B1, B2, and B3).

RESULTS

This study has identified seven cell types, including T cells, B cells, plasma cells, neutrophils, monocytes, platelets and erythrocytes. We mainly focused on neutrophils, monocytes, and T cells. Neutrophil subpopulation analysis indicated that neutrophil progenitors (proNeus) were identified in neutrophil subsets. Compared with patients suffering from AC, the gene phenotypes of proNeus (ELANE, AZU1, MPO, and PRTN3) were significantly upregulated in septic shock. The differentiation direction of neutrophil subsets in peripheral blood mononuclear cells (PBMCs) was determined; Moreover, the proNeus in septic shock presented a state of "expansion", with upregulation of neutrophil degranulation and downregulation of monocyte and T cell proliferation. Neutrophils-7 (CCL5, RPL23A, RPL13, RPS19 and RPS18) were mainly involved in the regulation of cellular functions. The neutrophils-7 subpopulation in septic shock were in a state of "exhaustion", and its biological functions showed the characteristics of weakening neutrophil migration and phagocytosis, etc., which maked infection difficult to control and aggravated the development of septic shock. Analysis of monocyte and T cell subpopulations showed that the expression genes and biological functions of subpopulations were closely related to immunoinflammatory regulation. In addition, CCL3 - CCR1, CXCL1 - CXCR2 and other ligand-receptors were highly expressed in neutrophils and monocytes, enhancing interactions between immune cells.

CONCLUSION

ScRNA-seq revealed significant differences in immune cells between AC and its secondary septic shock, which were primarily manifested in the cellular numbers, differentially expressed genes, functions of cellular subsets, differentiation trajectories, cell-cell interactions and so on. We identified many subsets of neutrophil, T cell and monocyte were associated with inflammation and immunosuppression induced by septic shock. These provided a reference for accurately evaluating the pathological severity of patients with AC and discovering the targets for therapy.

Oxidative stress and DNA damage in critically ill patients with sepsis

The aim of our study was to assess the oxidative stress and inflammatory status in critically ill patients with sepsis as well as their relationship with the level of DNA damage. The study also evaluated the influence of all analyzed parameters on the outcome of the patients. The study included 27 critically ill patients with sepsis and 20 healthy subjects. Comet Assay was used for the measurement of the level of DNA damage, expressed as genetic damage index (GDI). Both oxidative stress parameters and the antioxidant parameters were obtained spectrophotometrically. The standard laboratory methods and the appropriate autoanalyzers were performed for determination the parameters of inflammation. A higher level of oxidative stress and more pronounced inflammation were found in the patients with sepsis compared to healthy subjects. The activity of the antioxidant enzymes was statistically declined in patients with sepsis, so that the most notable differences between two groups of participants were found for the activity of superoxide dismutase (SOD) (p = 0.004). Comet assay indicated that patients with sepsis had significantly higher GDI compared to healthy subjects (p < 0.001), which positively correlated with the concentration of superoxide anion radical (О₂^-) (r = 0.497, p = 0.010), and nitrites (NО₂^-) (r = 0.473, p = 0.015), as well with the concentration of C reactive protein (CRP) (r = 0.460, p = 0.041). Regression analysis confirmed that patients' age (p = 0.033), the level of О₂^- (p = 0.007), CRP concentration (p = 0.029) and GDI (p = 0.001) increased the risk of lethal outcome in critically ill patients with sepsis. In conclusion, critically ill patients with sepsis have a higher degree of oxidative stress and inflammation which contribute to a higher level of DNA damage. Consequently, above mentioned parameters, including patients' age, adversely affect the outcome of critically ill patients with sepsis.

Research Progress on the Mechanism of Sepsis Induced Myocardial Injury

Sepsis is an abnormal condition with multiple organ dysfunctions caused by the uncontrolled infection response and one of the major diseases that seriously hang over global human health. Besides, sepsis is characterized by high morbidity and mortality, especially in intensive care unit (ICU). Among the numerous subsequent organ injuries of sepsis, myocardial injury is one of the most common complications and the main cause of death in septic patients. To better manage septic inpatients, it is necessary to understand the specific mechanisms of sepsis induced myocardial injury (SIMI). Therefore, this review will elucidate the pathophysiology of SIMI from the following certain mechanisms: apoptosis, mitochondrial damage, autophagy, excessive inflammatory response, oxidative stress and pyroptosis, and outline current therapeutic strategies and potential approaches in SIMI.

Inhibition of miR‑101‑3p protects against sepsis‑induced myocardial injury by inhibiting MAPK and NF‑κB pathway activation via the upregulation of DUSP1

Numerous studies have found that microRNAs (miRNAs or miRs) are aberrantly expressed when sepsis occurs. The present study aimed to investigate the role of miR-101-3p in sepsis-induced myocardial injury and to elucidate the underlying mechanisms. Models of myocardial injury were established both in vivo and in vitro. The results revealed that miR-101-3p was upregulated in the serum of patients with sepsis-induced cardiomyopathy (SIC) and positively correlated with the levels of pro-inflammatory cytokines (including IL-1β, IL-6 and TNF-α). Subsequently, rats were treated with miR-101-3p inhibitor to suppress miR-101-3p and were then exposed to lipopolysaccharide (LPS). The results revealed that LPS induced marked cardiac dysfunction, apoptosis and inflammation. The inhibition of miR-101-3p markedly attenuated sepsis-induced myocardial injury by attenuating apoptosis and the expression of pro-inflammatory cytokines. Mechanistically, dual specificity phosphatase-1 (DUSP1) was found to be a functional target of miR-101-3p. The downregulation of miR-101-3p led to the overexpression of DUSP1, and the inactivation of the MAPK p38 and NF-κB pathways. Moreover, blocking DUSP1 by short hairpin RNA against DUSP1 (sh-DUSP1) significantly reduced the myocardial protective effects mediated by the inhibition of miR-101-3p. Collectively, the findings of the present study demonstrate that the inhibition of miR-101-3p exerts cardioprotective effects by suppressing MAPK p38 and NF-κB pathway activation, and thus attenuating inflammation and apoptosis dependently by enhancing DUSP1 expression.

Shenfu injection attenuates lipopolysaccharide-induced myocardial inflammation and apoptosis in rats

Shenfu injection (SFI), a Chinese medicinal product, shows potent efficacy in treating sepsis. The aim of the present study was to clarify the protective effects of SFI against lipopolysaccharide (LPS)-induced myocardial inflammation and apoptosis. Experiments were carried out in Sprague-Dawley (SD) rats treated with LPS or LPS + SFI, and in H9C2 cardiomyocytes. The sepsis-associated myocardial inflammation and apoptosis was induced by the intraperitoneal injection of LPS (20 mg·kg^-1). SFI attenuated the increased expression of tumor necrosis factor (TNF)-α and interleukin (IL)-1β induced by LPS both in serum and heart. In LPS group, cell viability was reduced, and reversed after SFI administration. LPS treatment increased the expression levels of cleaved-caspase 3 and Bax, and those of Bcl2 and Bcl2/Bax. These two trends were reversed by SFI administration. The expression levels of phosphorylated mitogen-activated protein kinase kinase (p-MEK) and phosphorylated extracellular regulated protein kinases (p-ERK) were increased by LPS, and reversed by SFI. MEK inhibitor U0126 attenuated the apoptosis induced by LPS. These results indicate that SFI could treat LPS-induced cardiac dysfunction. In conclusion, SFI attenuates the inflammation and apoptosis induced by LPS via downregulating the MEK and ERK signaling pathways.

Role of Mitochondrial Oxidative Stress in Sepsis

Mitochondria are considered the power house of the cell and are an essential part of the cellular infrastructure, serving as the primary site for adenosine triphosphate production via oxidative phosphorylation. These organelles also release reactive oxygen species (ROS), which are normal byproducts of metabolism at physiological levels; however, overproduction of ROS under pathophysiological conditions is considered part of a disease process, as in sepsis. The inflammatory response inherent in sepsis initiates changes in normal mitochondrial functions that may result in organ damage. There is a complex system of interacting antioxidant defenses that normally function to combat oxidative stress and prevent damage to the mitochondria. It is widely accepted that oxidative stress-mediated injury plays an important role in the development of organ failure; however, conclusive evidence of any beneficial effect of systemic antioxidant supplementation in patients with sepsis and organ dysfunction is lacking. Nevertheless, it has been suggested that antioxidant therapy delivered specifically to the mitochondria may be useful.

Alamandine attenuates sepsis-associated cardiac dysfunction via inhibiting MAPKs signaling pathways

Sepsis-induced myocardial dysfunction represents a major cause of death. Alamandine is an important biologically active peptide. The present study evaluated whether alamandine improves cardiac dysfunction, inflammation, and apoptosis, and affects the signaling pathways involved in these events. Experiments were carried out in mice treated with lipopolysaccharide (LPS) or alamandine, and in neonatal rat cardiomyocytes. Alamandine increased the ejection fraction and fractional shortening, both of which were decreased upon LPS infusion in mice. LPS and alamandine reduced blood pressure, and increased the expression of inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) in the heart in mice. The LPS-induced decrease in α-myosin heavy chain (MHC) and β-MHC, and increase in S100 calcium binding protein A8 (S100A8) and S100A9, were reversed by alamandine pre-treatment. Alamandine pre-treatment prevented LPS-induced myocardial inflammation, apoptosis and autophagy. LPS increased p-ERK, p-JNK, and p-p38 levels, which were inhibited by alamandine. Dibutyryl cyclic AMP (db-cAMP) increased p-ERK, p-JNK, and p-p38 levels, and reversed the inhibitory effects of alamandine on the LPS-induced increase in p-ERK, p-JNK, and p-p38. Moreover, db-cAMP reduced the expression of α-MHC and β-MHC in cardiomyocytes, and reversed the almandine-induced attenuation of the LPS-induced decrease in α-MHC and β-MHC. These results indicate that alamandine attenuates LPS-induced cardiac dysfunction, resulting in increased cardiac contractility, and reduced inflammation, autophagy, and apoptosis. Furthermore, alamandine attenuates sepsis induced by LPS via inhibiting the mitogen-activated protein kinases (MAPKs) signaling pathways.

Short-term hypoxia upregulated Mas receptor expression to repress the AT1 R signaling pathway and attenuate Ang II-induced cardiomyocyte apoptosis

Hypertension-stimulated cardiac hypertrophy and apoptosis play critical roles in the progression of heart failure. Our previous study suggested that hypertensive angiotensin II (Ang II) enhanced insulin-like growth factor receptor II (IGF-IIR) expression and cardiomyocyte apoptosis, which are involved JNK activation, sirtuin1 (SIRT1) degradation, and heat-shock transcription factor 1 (HSF1) acetylation. Moreover, previous studies have implied that short-term hypoxia (STH) might exert cardioprotective effects. However, the effects of STH on Ang II-induced cardiomyocyte apoptosis remain unknown. In this study, we found that STH reduced myocardial apoptosis caused by Ang II via upregulation of the Mas receptor (MasR) to inhibit the AT₁ R signaling pathway. STH activates MasR to counteract the Ang II pro-apoptotic signaling cascade by inhibiting IGF-IIR expression via downregulation of JNK activation and reduction of SIRT1 degradation. Hence, HSF could remain deacetylated, and repress IGF-IIR expression. These effects decrease the activation of downstream pro-apoptotic and hypertrophic cascades and protect cardiomyocytes from Ang II-induced injury. In addition, we also found that silencing MasR expression enhanced Ang II-induced cardiac hypertrophy and the apoptosis signaling pathway. These findings suggest a critical role for MasR in cardiomyocyte survival. Altogether, our findings indicate that STH protects cardiomyocytes from Ang II-stimulated apoptosis. The protective effects of STH are associated with the upregulation of MasR to inhibit AT₁ R signaling. STH could be a potential therapeutic strategy for cardiac diseases in hypertensive patients.

Involvement of Mitochondrial Disorders in Septic Cardiomyopathy

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. It remains a leading cause of death worldwide, despite the development of various therapeutic strategies. Cardiac dysfunction, also referred to as septic cardiomyopathy, is a frequent and well-described complication of sepsis and associated with worse clinical outcomes. Recent research has increased our understanding of the role of mitochondrial dysfunction in the pathophysiology of septic cardiomyopathy. The purpose of this review is to present this evidence as a coherent whole and to highlight future research directions.

Effect of continuous renal replacement therapy on kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin in patients with septic acute kidney injury

Kidney injury molecule-1 (Kim-1) and neutrophil gelatinase-associated lipocalin (NGAL) have been investigated as biomarkers for acute kidney injury (AKI). However, they are seldom investigated in patients with septic AKI treated with continuous renal replacement therapy (CRRT). The aim of the present study was to investigate the therapeutic effectiveness and possible mechanisms of CRRT in septic AKI by observing the changes in Kim-1 and NGAL levels. A group of 38 patients with septic AKI was randomly divided into the conventional drug treatment group (group A) and the CRRT group (group B). All patients were treated with standard antisepsis agents, and group B was additionally submitted to CRRT for 24 h. The levels of Kim-1 and NGAL in serum, urine and the ultrafiltrate of CRRT were measured prior to and at 12, 24, and 48 h after treatment. In group A, urinary Kim-1 (uKim-1) levels at 12, 24 and 48 h were lower than prior to treatment (P<0.05), whereas urinary NGAL (uNGAL) showed no difference among the various time points (P>0.05). In group B, uKim-1 was decreased at 24 and 48 h compared with before treatment (all P<0.05), whereas uNGAL was decreased at 48 h (P<0.05). Serum Kim-1 did not change with time in groups A and B (P>0.05), whereas serum NGAL was increased after treatment in group A (P<0.05) but did not change in group B (P>0.05). Kim-1 and NGAL were not detected in the ultrafiltrate of CRRT. uKim-1 and uNGAL decreased significantly after CRRT, and therefore may be used to reflect the change of renal function during CRRT and to evaluate the therapeutic effectiveness of the method.

Inhibition of miR-155 Protects Against LPS-induced Cardiac Dysfunction and Apoptosis in Mice

Sepsis-induced myocardial dysfunction represents a major cause of death in intensive care units. Dysregulated microRNAs (miR)-155 has been implicated in multiple cardiovascular diseases and miR-155 can be induced by lipopolysaccharide (LPS). However, the role of miR-155 in LPS-induced cardiac dysfunction is unclear. Septic cardiac dysfunction in mice was induced by intraperitoneal injection of LPS (5 mg/kg) and miR-155 was found to be significantly increased in heart challenged with LPS. Pharmacological inhibition of miR-155 using antagomiR improved cardiac function and suppressed cardiac apoptosis induced by LPS in mice as determined by echocardiography, terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) assay, and Western blot for Bax and Bcl-2, while overexpression of miR-155 using agomiR had inverse effects. Pea15a was identified as a target gene of miR-155, mediating its effects in controlling apoptosis of cardiomyocytes as evidenced by luciferase reporter assays, quantitative real time-polymerase chain reaction, Western blot, and TUNEL staining. Noteworthy, miR-155 was also found to be upregulated in the plasma of patients with septic cardiac dysfunction compared to sepsis patients without cardiac dysfunction, indicating a potential clinical relevance of miR-155. The receiver-operator characteristic curve indicated that plasma miR-155 might be a biomarker for sepsis patients developing cardiac dysfunction. Therefore, inhibition of miR-155 represents a novel therapy for septic myocardial dysfunction.

The holistic view on perfusion monitoring in septic shock

PURPOSE OF REVIEW

To review recent evidence concerning the interactions between hemodynamic and perfusion parameters during septic shock resuscitation, and to propose some basic foundations for a more comprehensive perfusion assessment.

RECENT FINDINGS

Several recent studies have expanded our knowledge about the physiologic determinants and limitations of currently used perfusion parameters such as central venous oxygen saturation and lactate. Macrohemodynamic, metabolic, peripheral and microcirculatory parameters tend to change in parallel in response to fluid loading during initial resuscitation. In contrast, perfusion markers are poorly correlated in patients who evolve with a persistent circulatory dysfunction. Therefore, assessment of perfusion status based solely on a single parameter can lead to inaccurate or misleading conclusions.

SUMMARY

All individual perfusion parameters have extensive limitations to adequately reflect tissue perfusion during persistent sepsis-related circulatory dysfunction. A multimodal approach integrating macrohemodynamic, metabolic, peripheral and eventually microcirculatory perfusion parameters may overcome those limitations. This approach may also provide a thorough understanding on the predominant driving forces of hypoperfusion, and lead to physiologically oriented interventions.

When sepsis affects the heart: A case report and literature review

A 59-year-old nursing home patient with Down syndrome was brought to the internal medicine department of our hospital due to fever, cough without expectorate, and dyspnea. A thoracic computed tomography revealed the presence of bilateral basal parenchymal opacities. Her condition deteriorated after admission and troponin reached a peak serum concentration of 16.9 ng/mL. The patient was in cardiogenic shock. In addition to fluid resuscitation, vaso-active amine infusion was administered to achieve hemodynamic stabilization. The differential diagnosis investigated possible pulmonary embolism, myocardial infarction, and myocarditis. Furthermore, a second transthoracic echocardiogram suggested Tako-Tsubo syndrome. This is a septic patient. The purpose of this manuscript is to review studies which formerly examined the possible association between high levels of troponin and mortality to see if it can be considered a positive predictive factor of fatal prognosis as the case of thrombocytopenia, already a positive independent predictive factor of multiple organ failure syndrome, and generally to characterize risk profile in a septic patient.

The role of complement system in septic shock

Septic shock is a critical clinical condition with a high mortality rate. A better understanding of the underlying mechanisms is important to develop effective therapies. Basic and clinical studies suggest that activation of complements in the common cascade, for example, complement component 3 (C3) and C5, is involved in the development of septic shock. The involvement of three upstream complement pathways in septic shock is more complicated. Both the classical and alternative pathways appear to be activated in septic shock, but the alternative pathway may be activated earlier than the classical pathway. Activation of these two pathways is essential to clear endotoxin. Recent investigations have shed light on the role of lectin complement pathway in septic shock. Published reports suggest a protective role of mannose-binding lectin (MBL) against sepsis. Our preliminary study of MBL-associated serine protease-2 (MASP-2) in septic shock patients indicated that acute decrease of MASP-2 in the early phase of septic shock might correlate with in-hospital mortality. It is unknown whether excessive activation of these three upstream complement pathways may contribute to the detrimental effects in septic shock. This paper also discusses additional complement-related pathogenic mechanisms and intervention strategies for septic shock.

Design of clinical trials in AKI: a report from an NIDDK workshop. Trials of patients with sepsis and in selected hospital settings

AKI remains an important clinical problem, with a high mortality rate, increasing incidence, and no Food and Drug Administration-approved therapeutics. Advances in addressing this clinical need require approaches for rapid diagnosis and stratification of injury, development of therapeutic agents based on precise understanding of key pathophysiological events, and implementation of well designed clinical trials. In the near future, AKI biomarkers may facilitate trial design. To address these issues, the National Institute of Diabetes and Digestive and Kidney Diseases sponsored a meeting, "Clinical Trials in Acute Kidney Injury: Current Opportunities and Barriers," in December of 2010 that brought together academic investigators, industry partners, and representatives from the National Institutes of Health and the Food and Drug Administration. Important issues in the design of clinical trials for interventions in AKI in patients with sepsis or AKI in the setting of critical illness after surgery or trauma were discussed. The sepsis working group discussed use of severity of illness scores and focus on patients with specific etiologies to enhance homogeneity of trial participants. The group also discussed endpoints congruent with those endpoints used in critical care studies. The second workgroup emphasized difficulties in obtaining consent before admission and collaboration among interdisciplinary healthcare groups. Despite the difficult trial design issues, these clinical situations represent a clinical opportunity because of the high event rates, severity of AKI, and poor outcomes. The groups considered trial design issues and discussed advantages and disadvantages of several short- and long-term primary endpoints in these patients.

The effects of sepsis on mitochondria

BACKGROUND

Sepsis is associated with mitochondrial dysfunction and impaired oxygen consumption, which may condition clinical outcome independent of tissue oxygenation. However, mitochondrial role in sepsis severity remains unknown. We aimed to characterize mitochondrial function in sepsis, establish its origin and cellular consequences, and determine its correlation with clinical symptoms and outcome.

METHODS

Different markers of mitochondrial activity, nitrosative and oxidative stress, apoptosis, and inflammation were measured in peripheral blood mononuclear cells (PBMCs) and plasma of 19 septic patients and 20 controls. Plasma capacity to induce mitochondrial dysfunction was assessed in muscle mitochondria from 5 healthy individuals incubated with plasma of septic patients or controls.

RESULTS

Despite unaltered mitochondrial mass and protein synthesis, enzymatic mitochondrial complexes I, III, and IV and oxygen consumption were significantly inhibited in sepsis. Septic plasma tended to reduce oxygen consumption of healthy mitochondria and showed significantly increased amounts of extracellular mitochondrial DNA and inflammatory cytokines, especially in patients presenting adverse outcome. Active nuclear factor kappa-light-chain enhancer of activated B cells (NFKB) was also significantly increased, together with nitric oxide, oxidative stress and apoptosis. Additionally, sepsis severity significantly correlated with complex I inhibition, NFKB activation and intercellular adhesion molecule expression.

CONCLUSIONS

A plasmatic factor such as nitric oxide, increased in inflammation and able to induce mitochondrial dysfunction, oxidative stress and apoptosis, may be responsible for cell damage in sepsis. Together with bacterial infection, leakage of mitochondrial DNA from damaged cells into circulation could contribute to systemic inflammatory response syndrome. Mitochondrial dysfunction and inflammation correlate with sepsis severity and outcome, becoming targets for supporting therapies.

Sepsis: the inflammatory foundation of pathophysiology and therapy

Sepsis, defined as an infection accompanied by inflammation, is a complex disease process wherein the body's response to a pathogen is amplified far beyond the initial site of infection. The process begins when pathogen-associated molecular patterns on the bacteria or other pathogens induce an inflammatory cascade in the host. In the United States, it is estimated that every minute a patient with severe sepsis or septic shock presents to an emergency department and that > 751 000 cases of severe sepsis occur annually, resulting in an estimated 215 000 deaths. A rapid progression of illness severity from sepsis to severe sepsis to septic shock frequently occurs, driven by the body's inflammatory and anti-inflammatory responses to a pathogen, making sepsis a condition requiring timely intervention. The clinical management of severe sepsis and septic shock has evolved dramatically over the past decade and these new therapeutic approaches have been built on a deeper understanding of the natural evolution of sepsis. This article examines the underlying pathophysiological mechanisms of sepsis to help explain the clinical signs and symptoms manifested by severe sepsis patients. It also examines the significance of current proposed treatment strategies, including early goal-directed therapy, from a pathophysiological and inflammatory perspective.

Assessing mitochondrial dysfunction in cells

Assessing mitochondrial dysfunction requires definition of the dysfunction to be investigated. Usually, it is the ability of the mitochondria to make ATP appropriately in response to energy demands. Where other functions are of interest, tailored solutions are required. Dysfunction can be assessed in isolated mitochondria, in cells or in vivo, with different balances between precise experimental control and physiological relevance. There are many methods to measure mitochondrial function and dysfunction in these systems. Generally, measurements of fluxes give more information about the ability to make ATP than do measurements of intermediates and potentials. For isolated mitochondria, the best assay is mitochondrial respiratory control: the increase in respiration rate in response to ADP. For intact cells, the best assay is the equivalent measurement of cell respiratory control, which reports the rate of ATP production, the proton leak rate, the coupling efficiency, the maximum respiratory rate, the respiratory control ratio and the spare respiratory capacity. Measurements of membrane potential provide useful additional information. Measurement of both respiration and potential during appropriate titrations enables the identification of the primary sites of effectors and the distribution of control, allowing deeper quantitative analyses. Many other measurements in current use can be more problematic, as discussed in the present review.