Prowess-shock trial: a protocol overview and perspectives

Protein C Pathway in Paediatric and Neonatal Sepsis

Protein C plays a major role in the physiological regulation of coagulation pathways through inactivation of factor Va, factor VIIIa, and plasminogen activator inhibitor. Protein C is involved in the control of inflammation during sepsis, by inhibiting release of pro-inflammatory cytokines, thereby controlling neutrophil, and monocyte effects on injured tissue. Recombinant human activated protein C (rhAPC) reduced mortality in adult sepsis in earlier studies but had no significant benefit in more recent trials. Protein C levels are reduced during paediatric and neonatal sepsis, which may play a major role in the development of disseminated intravascular thrombosis, purpura fulminans, and multiorgan dysfunction. The role of protein C in paediatric sepsis requires further clinical and immunological evaluation to define the patient subgroups who may benefit from this therapy. Newer versions of rhAPC are under development with less risk of haemorrhage potentially broadening the scope of this intervention.

Epigenetic biomarkers for human sepsis and septic shock: insights from immunosuppression

Sepsis is a life-threatening condition that occurs when the body responds to an infection damaging its own tissues. Sepsis survivors sometimes suffer from immunosuppression increasing the risk of death. To our best knowledge, there is no 'gold standard' for defining immunosuppression except for a composite clinical end point. As the immune system is exposed to epigenetic changes during and after sepsis, research that focuses on identifying new biomarkers to detect septic patients with immunoparalysis could offer new epigenetic-based strategies to predict short- and long-term pathological events related to this life-threatening state. This review describes the most relevant epigenetic mechanisms underlying alterations in the innate and adaptive immune responses described in sepsis and septic shock, and their consequences for immunosuppression states, providing several candidates to become epigenetic biomarkers that could improve sepsis management and help predict immunosuppression in postseptic patients.

Endogenous thrombin potential as marker of procoagulant response that can be useful in early stage of sepsis

: Sepsis is associated with complex procoagulant and anticoagulant changes that modify inflammatory response. Identification of coagulation markers that can differentiate useful procoagulant response from adverse alteration of clotting mechanism in patient with sepsis. In total, 150 patients who fulfilled criteria for diagnosis of sepsis were included in this study. Patients were categorized in two groups according to sepsis severity in the first 24 h from intensive care unit admission: sepsis and septic shock. In total, 28-day mortality was assessed. Platelet count, activated partial thromboplastin time, prothrombin time, D-dimer, fibrinogen, protein C, protein S, antithrombin levels, and endogenous thrombin potential were determined within first 24 h from ICU admission. Differences between groups of septic patients were assessed by Mann-Whitney U test. Categorical variables were compared using χ test. Receiver operating characteristic curves were plotted to determine predictive values of variables for sepsis severity prediction. Activated partial thromboplastin time and prothrombin time were significantly prolonged with higher D-dimer, lower fibrinogen, and natural anticoagulant levels (protein C, protein S, and antithrombin) in patients with more severe form of the disease and worse outcome (P < 0.05). Endogenous thrombin potential [area under the curve (AUC) %] was significantly decreased in patients with more severe form of sepsis (66.01 ± 41.51 vs. 83.21 ± 28.83; AUC 0.76) and in patients with worse outcome (67.66 ± 37.79 vs. 81.79 ± 32.15; AUC 0.68; P < 0.05). Evaluation of initial thrombin generation is useful to distinguish between beneficial coagulation activation and hazardous haemostatic alteration, and to predict multiorgan dysfunction development and poor outcome in septic patients.

The Levels of Tissue Factor Pathway Inhibitor in Sepsis Patients Receiving Prophylactic Enoxaparin

OBJECTIVE

Sepsis syndrome is usually accompanied by activation of blood coagulation mechanisms. Earlier studies found deficiencies of the 3 main natural anticoagulants, antithrombin, protein C, and protein S. However, none of these inhibitors block tissue factor, the prime trigger of coagulation during sepsis that is controlled specifically by the tissue factor pathway inhibitor (TFPI). The aim of this study was to characterize the fluctuations in the levels of natural anticoagulants, particularly TFPI, in the course of sepsis and to find out their association with the anticoagulant action of the low-molecular-weight heparin enoxaparin.

MATERIALS AND METHODS

We studied 51 consecutive patients with sepsis. Blood samples were collected from patients at baseline (0 h) and at 4, 12, and 24 h after enoxaparin administration. The following assays were undertaken using commercial kits: activated partial thromboplastin time, prothrombin time, thrombin time, total and free TFPI, protein C and protein S, antithrombin, fibrinogen, and anti-factor Xa.

RESULTS

Before enoxaparin administration, there was significant prolongation of the prothrombin time and activated partial thromboplastin time, and this remained the case in the 3 subsequent samples. There was marked reduction in the levels of antithrombin, protein C, and total and free protein S to below control values throughout the study. In contrast, plasma levels of both total and free TFPI were markedly elevated and increased after enoxaparin therapy. Anti-factor Xa levels were within the therapeutic range throughout. There was no difference in TFPI levels between those patients who died and those who survived.

CONCLUSION

Sepsis triggered marked release of TFPI from endothelial cells. This persisted and was increased further following the administration of enoxaparin. In contrast, there was marked consumption of the natural coagulation inhibitors antithrombin, protein C, and protein S. These results go some way towards explaining why the therapeutic use of recombinant TFPI fails to correct sepsis-associated coagulopathy.

Functional role of protease activated receptors in vascular biology

Protease activated receptors (PARs) are a small family of G protein-coupled receptors (GPCR) mediating the cellular effects of some proteases of the coagulation system, such as thrombin, or other proteases, such as trypsin or metalloproteinase 1. As the prototype of PARs, PAR1 is a seven transmembrane GPCR that, upon cleavage by thrombin, unmasks a new amino-terminus able to bind intramolecularly to PAR1 itself thus inducing signaling. In the vascular system, thrombin and other proteases of the coagulation-fibrinolysis system, such as plasmin, factor VIIa and factor Xa, activated protein C, are considered physiologically relevant agonists, and PARs appear to largely account for the cellular effects of these enzymes. In the vasculature, PARs are expressed on platelets, endothelial cells (ECs) and vascular smooth muscle cells (VSMCs). In the vessel wall, under physiological conditions, PARs are mainly expressed in ECs and participate in the regulation of vascular tone, by inducing endothelium-dependent relaxation. PAR activation on ECs promotes conversion of these cells into a proinflammatory phenotype, causes increase of vascular permeability, and the exposure/secretion of proteins and cytokines mediating the local accumulation of platelets and leukocytes. These effects contribute to the vascular consequences of sepsis and of diseases such as acute lung injury and acute respiratory distress syndrome. In normal arteries PARs are to a much lesser amount expressed on VSMCs. However, in conditions associated with endothelial dysfunction, PARs mediate contraction, proliferation, migration, hypertrophy of VSMCs and their production of extracellular matrix, thereby contributing to the pathophysiology of atherosclerosis and hypertension. Inhibition of protease-PAR interaction might thus become a potential therapeutic target in various vascular diseases.

Studies on therapeutic effects and pathological features of an antithrombin preparation in septic disseminated intravascular coagulation patients

PURPOSE

Few reports have been made on the therapeutic effects as well as pathological features of an antithrombin preparation in patients diagnosed with septic disseminated intravascular coagulation (DIC) by the diagnostic criteria for acute DIC.

MATERIALS AND METHODS

A total of 88 sepsis patients who had received inpatient hospital care during the period from January 2000 through December 2008 were divided into two groups, an antithrombin group and a non-antithrombin group, to study the outcomes. Furthermore, the relationship between sepsis-related factors and DIC in 44 patients was studied.

RESULTS

The antithrombin group contained 34 patients, and the non-antithrombin group contained 54 patients. The outcomes were significantly better in the antithrombin group. The levels of protein C were low in DIC patients.

CONCLUSION

Our results suggest that early administration of antithrombin might improve outcomes of septic DIC patients in the diagnostic criteria for Japanese Association for Acute Medicine acute DIC.

Angiopoietin-2 may contribute to multiple organ dysfunction and death in sepsis*

OBJECTIVE

: In sepsis, quiescent blood vessels become leaky and inflamed by mechanisms that are incompletely understood. We hypothesized that angiopoietin-2, a partial antagonist of the endothelium-stabilizing receptor Tie-2 secreted by endothelium, contributes to adverse outcomes in this disease.

DESIGN

: Laboratory and animal research.

SETTINGS

: Research laboratories and Emergency Department of Beth Israel Deaconess Medical Center, Boston, MA.

SUBJECTS

: Angiopoietin-2 heterozygous mice, emergency department patients.

MEASUREMENTS AND MAIN RESULTS

: Mice with one functional angiopoietin-2 allele developed milder kidney and lung injury, less tissue inflammation, and less vascular leakage compared to wild-type counterparts. Heterozygotes experienced >40% absolute survival advantage following two different models of sepsis (p = .004 and .018). In human subjects presenting to our emergency department with suspected infection (n = 270 combined), circulating angiopoietin-2 was markedly elevated within the first hour of clinical care. First-hour angiopoietin-2 concentrations were proportional to current disease severity (p < .0001), rose further over time in eventual nonsurvivors (p < .0001), and predicted the future occurrence of shock (p < .0001) or death (p < .0001) in the original cohort and an independent validation group. Finally, septic human serum disrupted the barrier function of microvascular endothelial cells, an effect fully neutralized by an angiopoietin-2 monoclonal antibody.

CONCLUSIONS

: We conclude that angiopoietin-2 induction precedes and contributes to the adverse outcomes in sepsis, opening a new avenue for therapeutic investigation.

Critical care clinical trials: getting off the roller coaster

Optimizing care in the ICU is an important goal. The heightened severity of illness in patients who are critically ill combined with the tremendous costs of critical care make the ICU an ideal target for improvement in outcomes and efficiency. Incorporation of evidence-based medicine into everyday practice is one method to optimize care; however, intensivists have struggled to define optimal practices because clinical trials in the ICU have yielded conflicting results. This article reviews examples where such conflicts have occurred and explores possible causes of these discrepant data as well as strategies to better use critical care clinical trials in the future.

Immune-modulating interventions in critically ill septic patients: pharmacological options

Critically ill patients with severe sepsis and septic shock are characterized by a systemic inflammatory response consisting of pro- and anti-inflammatory mediators. Owing to the high mortality of severe sepsis, great efforts have been undertaken within the last 30 years to develop an immune-modulating therapy to improve survival. Relatively few pharmacological immune-modulating interventions have demonstrated a beneficial impact on survival, while other studies have shown a detrimental effect of such interventions. Among the immune-modulating interventions tested, activated protein C and intensive insulin therapy have been shown to improve survival in septic patients. However, in later studies, it has been difficult to reproduce these beneficial effects. There appears to be a discrepancy between the promising effects of immune-modulating interventions in animal studies and the effects seen in the clinical setting. In the future, the onset of the proinflammatory versus the anti-inflammatory response must be better defined and the timing of treatment with immune-modulating agents should be better managed.

Clinical review: Clinical imaging of the sublingual microcirculation in the critically ill--where do we stand?

A growing body of evidence exists associating depressed microcirculatory function and morbidity and mortality in a wide array of clinical scenarios. It has been suggested that volume replacement therapy using fluids and/or blood in combination with vasoactive agents to modulate macro- and microvascular perfusion might be essential for resuscitation of severely septic patients. Even after interventions effectively optimizing macrocirculatory hemodynamics, however, high mortality rates still persist in critically ill and especially in septic patients. Therefore, rather than limiting therapy to macrocirculatory targets alone, microcirculatory targets could be incorporated to potentially reduce mortality rates in these critically ill patients. In the present review we first provide a brief history of clinical imaging of the microcirculation and describe how microcirculatory imaging has been of prognostic value in intensive care patients. We then give an overview of therapies potentially improving the microcirculation in critically ill patients and propose a clinical trial aimed at demonstrating that therapy targeting improvement of the microcirculation results in improved organ function in patients with severe sepsis and septic shock. We end with some recent technological advances in clinical microcirculatory image acquisition and analysis.

Methods for estimating subgroup effects in cost-effectiveness analyses that use observational data

Decision makers require cost-effectiveness estimates for patient subgroups. In nonrandomized studies, propensity score (PS) matching and inverse probability of treatment weighting (IPTW) can address overt selection bias, but only if they balance observed covariates between treatment groups. Genetic matching (GM) matches on the PS and individual covariates using an automated search algorithm to directly balance baseline covariates. This article compares these methods for estimating subgroup effects in cost-effectiveness analyses (CEA). The motivating case study is a CEA of a pharmaceutical intervention, drotrecogin alfa (DrotAA), for patient subgroups with severe sepsis (n = 2726). Here, GM reported better covariate balance than PS matching and IPTW. For the subgroup at a high level of baseline risk, the probability that DrotAA was cost-effective ranged from 30% (IPTW) to 90% (PS matching and GM), at a threshold of £20 000 per quality-adjusted life-year. We then compared the methods in a simulation study, in which initially the PS was correctly specified and then misspecified, for example, by ignoring the subgroup-specific treatment assignment. Relative performance was assessed as bias and root mean squared error (RMSE) in the estimated incremental net benefits. When the PS was correctly specified and inverse probability weights were stable, each method performed well; IPTW reported the lowest RMSE. When the subgroup-specific treatment assignment was ignored, PS matching and IPTW reported covariate imbalance and bias; GM reported better balance, less bias, and more precise estimates. We conclude that if the PS is correctly specified and the weights for IPTW are stable, each method can provide unbiased cost-effectiveness estimates. However, unlike IPTW and PS matching, GM is relatively robust to PS misspecification.

The protein C pathway and sepsis

After the discovery of the key components of the protein C (PC) pathway a beneficial effect on survival of the infusion of activated protein C (APC) in animal models of sepsis was demonstrated, leading to the development of recombinant human activated protein C (rh-APC) as a therapeutic agent. It soon became clear that rather than the anticoagulant and profibrinolytic activities of APC, its anti-inflammatory and cytoprotective properties played a major role in the treatment of patients with severe sepsis. Such properties affect the response to inflammation of endothelial cells and leukocytes and are exerted through binding of APC to at least five receptors with intracellular signaling. The main APC protective mechanism involves binding of the Gla-domain to the endothelial protein C receptor (EPCR) and cleavage of protease activated receptor 1 (PAR-1), eliciting suppression of proinflammatory cytokines synthesis and of intracellular proapoptotic pathways and activation of endothelial barrier properties. However, thrombin cleaves PAR-1 with much higher catalytic efficiency, followed by pro-inflammatory, pro-apoptotic and barrier disruptive intracellular signaling, and it is unclear how APC can exert a protective activity through the cleavage of PAR-1 when thrombin is also present in the same environment. Interestingly, in endothelial cell cultures, PAR-1 cleavage by thrombin results in anti-inflammatory and barrier protective signaling provided occupation of EPCR by the PC gla-domain, raising the possibility that the beneficial effects of rh-APC might be recapitulated in vivo by administration of h-PC zymogen to patients with severe sepsis. Recent reports of h-PC infusion in animal models of sepsis support this hypothesis.

Systemic inflammation in the elderly

Inflammation is an adaptive response to surgery. When the pro-inflammatory responses are unregulated and become over reactive, systemic inflammatory response syndrome may occur. Postoperative systemic inflammation is more common than is generally acknowledged and is observed in about 10-15% of elderly patients undergoing major surgery. Although the vast majority of systemic inflammation is related to infections, other important predisposing risk factors, such as extent of trauma and haemorrhage, should not be overlooked. Increased awareness, modification of risk factors and early recognition are the key elements in the management of systemic inflammation. Prompt resuscitation aiming to correct hypotension, hypovolaemia and tissue hypoxia may improve outcome. Future large prospective observational studies are needed to define the incidence, risk factors and impact of systemic inflammatory syndrome in the elderly surgical patients. A better understanding of the molecular events during the systemic inflammatory response syndrome is required for future development of specific immunotherapy.

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.

The coagulopathy in sepsis: significance and implications for treatment

Sepsis related coagulopathy ranges from mild laboratory alterations up to severe disseminated intravascular coagulation (DIC). There is evidence that DIC is involved in the pathogenesis of microvascular dysfunction contributing to organ failure. Additionally, the systemic activation of coagulation, by consuming platelets and coagulation factors, may cause bleeding. Thrombin generation via the tissue factor/factor VIIa route, contemporary depression of antithrombin and protein C anticoagulant systems, as well as impaired fibrin degradation, due to high circulating levels of PAI-1, contribute to enhanced intravascular fibrin deposition. This deranged coagulopathy is an independent predictor of clinical outcome in patients with severe sepsis. Innovative supportive strategies aiming at the inhibition of coagulation activation should comprise inhibition of tissue factor-mediated activation or restoration of physiological anticoagulant pathways, as the administration of recombinant human activated protein C or concentrate. In spite of some promising initial studies, additional trials are needed to define their clinical effectiveness in adults and children with severe sepsis.

Biomarkers in acute lung injury: insights into the pathogenesis of acute lung injury

Studies of potential biomarkers of acute lung injury (ALI) have provided information relating to the pathophysiology of the mechanisms of lung injury and repair. The utility of biomarkers remains solely among research tools to investigate lung injury and repair mechanisms. Because of lack of sensitivity and specificity, they cannot be used in decision making in patients with ALI or acute respiratory distress syndrome. The authors reviewed known biomarkers in context of their major biologic activity. The continued interest in identifying and studying biomarkers is relevant, as it provides information regarding the mechanisms involved in lung injury and repair and how this may be helpful in identifying and designing future therapeutic targets and strategies and possibly identifying a sensitive and specific biomarker.

Immunomodulation in sepsis: state of the art and future perspective

Despite advances in supportive care of critically ill patients, sepsis remains an important cause of death worldwide. More than 750,000 individuals develop severe sepsis in North America annually, with a mortality rate varying between 35 and 50%. Over recent years, numerous efforts have been committed to understanding the pathophysiology of septic syndrome, as well as attempts to intervene in the inflammatory cascade with the aim of altering the outcome of the syndrome and to improve survival. Not all of these attempts have been successful. Issued guidelines by the International Sepsis Forum have incorporated only the use of corticosteroids, tight glycemic control and the use of recombinant activated protein C as recommendations for the management of the septic patient along with the initial resuscitation and infection-site control measures. These strategies along, with novel attempts of immunomodulation, are thoroughly reviewed in this article.