Time course of hemostatic abnormalities in sepsis and its relation to outcome

Bench-to-bedside review: functional relationships between coagulation and the innate immune response and their respective roles in the pathogenesis of sepsis

The innate immune response system is designed to alert the host rapidly to the presence of an invasive microbial pathogen that has breached the integument of multicellular eukaryotic organisms. Microbial invasion poses an immediate threat to survival, and a vigorous defense response ensues in an effort to clear the pathogen from the internal milieu of the host. The innate immune system is able to eradicate many microbial pathogens directly, or innate immunity may indirectly facilitate the removal of pathogens by activation of specific elements of the adaptive immune response (cell-mediated and humoral immunity by T cells and B cells). The coagulation system has traditionally been viewed as an entirely separate system that has arisen to prevent or limit loss of blood volume and blood components following mechanical injury to the circulatory system. It is becoming increasingly clear that coagulation and innate immunity have coevolved from a common ancestral substrate early in eukaryotic development, and that these systems continue to function as a highly integrated unit for survival defense following tissue injury. The mechanisms by which these highly complex and coregulated defense strategies are linked together are the focus of the present review.

Drotrecogin alfa (recombinant human activated protein C) for the treatment of severe sepsis

BACKGROUND

The search for a life-preserving drug to treat sepsis has increased understanding of the pathogenesis of the process but produced little in the way of successful treatments. The prospective, randomized, double-blind, placebo-controlled, Phase III, multicenter Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) trial suggested that drotrecogin alfa--recombinant human activated protein C--significantly improved 28-day mortality rates in acute sepsis (P = 0.005).

OBJECTIVES

The goals of this drug review were to summarize the recent findings regarding the pathogenesis of sepsis and septic shock, as well as the results of select immunomodulator drug trials, and to offer a comprehensive review of the mechanism of action, pharmacokinetic profile, efficacy and safety profile, and pharmacoeconomics of drotrecogin alfa.

METHODS

The English-language literature was searched using the EMBASE and MEDLINE databases. In EMBASE, the subject headings drotrecogin, activated protein C, and sepsis were used to search publications from 1980 through September 2002. In MEDLINE, the MeSH heading protein C and subject heading sepsis were used to search publications from 1966 through September 2002. Published abstracts of recent meetings and proceedings of the US Food and Drug Administration were also reviewed.

RESULTS

Drotrecogin alfa mimics the endogenous protein depleted during acute sepsis. Its activity as an antithrombotic, anti-inflammatory, and profibrinolytic agent appears to diminish the negative outcomes of acute sepsis, notably mortality at 28 days. The results of the PROWESS trial support this finding. A bleeding risk was noted during Phase II and III trials despite efforts to exclude those patients at high risk of bleeding.

CONCLUSIONS

Drotrecogin alfa is the first adjunctive agent for the treatment of sepsis to display clinically and statistically significant effects on mortality rates at 28 days. Many questions remain regarding which patients are ideal candidates for treatment. New research and treatment guidelines are necessary to address these questions.

Cost-effectiveness of drotrecogin alfa (activated) in the treatment of severe sepsis

OBJECTIVE

To assess the cost-effectiveness of drotrecogin alfa (activated) therapy, which was recently shown to reduce mortality in severe sepsis.

DESIGN

Estimates of effectiveness and resource use were based on data collected prospectively as part of a multicenter international trial. Estimates of hospital costs were based on a subset of the patients treated in the United States (33% of all enrolled patients). Lifetime projections were modeled from published sources and tested in sensitivity analyses. Analyses were conducted from the United States societal perspective, limited to healthcare costs, and using a 3% annual discount rate.

SETTING

A total of 164 medical institutions in 11 countries.

PATIENTS

Adults > or = 18 yrs of age with severe sepsis

INTERVENTIONS

Eligible patients were randomly assigned to receive a 96-hr intravenous infusion of drotrecogin alfa (activated) at 24 microg/kg/hr (n = 850) or placebo (n = 840).

MEASUREMENTS AND MAIN RESULTS

Base Case: incremental short-term (days 1-28) healthcare costs per day-28 survivor; Panel on Cost-Effectiveness in Health and Medicine Reference Case: incremental lifetime healthcare costs per quality-adjusted life-year. Over the first 28 days (short-term Base Case), drotrecogin alfa (activated) increased the costs of care by $9,800 and survival by 0.061 lives saved per treated patient. Thus, drotrecogin alfa (activated) cost $160,000 per life saved (with 84.7% probability that ratio is <$250,000 per life saved). Projected to lifetime (lifetime Reference Case), drotrecogin alfa (activated) increased the costs of care by $16,000 and quality-adjusted survival by 0.33 quality-adjusted life-years per treated patient. Thus, drotrecogin alfa (activated) cost $48,800 per quality-adjusted life-year (with 82% probability that ratio is <$100,000 per quality-adjusted life-year). Estimates were generally robust to sensitivity analyses, although cost-effectiveness deteriorated to >$100,000 per quality-adjusted life-year if survivors lived <4.6 yrs on average. Drotrecogin alfa (activated) cost $27,400 per quality-adjusted life-year when limited to patients with an Acute Physiology and Chronic Health Evaluation II score > or = 25 and was cost-ineffective when limited to patients with a score <25.

CONCLUSIONS

Drotrecogin alfa has a cost-effectiveness profile similar to that of many well-accepted healthcare strategies and below commonly quoted thresholds.

New thoughts on sepsis: the unifier of critical care

In the United States, more than $16 billion annually is spent managing patients with severe sepsis and its sequelae. Insight into the inflammatory response, endothelial tissue, and the coagulation cascade suggest promising new treatment regimens that limit morbidity and mortality due to sepsis and multisystem organ failure. This article will discuss new information regarding the pathophysiology of the inflammatory response and sepsis. Current thoughts on clinical management and a promising new agent, Activated Protein C, will be presented.

Drotrecogin alfa (activated): a novel therapeutic strategy for severe sepsis

Recent studies have highlighted the close link between activation of the coagulation system and the inflammatory response in the pathophysiology of severe sepsis. The protein C anticoagulant pathway plays an integral part in modulating the coagulation and inflammatory responses to infection. In patients with sepsis, endogenous protein C levels are decreased, shifting the balance toward greater systemic inflammation, coagulation, and cell death. On the basis of a single large randomised phase 3 trial, drotrecogin alfa (activated), a recombinant form of human activated protein C, was recently approved for the treatment of adult patients with severe sepsis and a high risk of death. Since its approval, several questions have been raised regarding the appropriate use of this agent. Given the increased risk of serious bleeding and the high cost of treatment, drotrecogin alfa (activated) should be reserved at this time for the most acutely ill patients with severe sepsis who meet the criteria that were used in the phase 3 trial.

Liver in sepsis and systemic inflammatory response syndrome

In patients with sepsis and SIRS, the liver has two opposing roles: a source of inflammatory mediators and a target organ for the effects of the inflammatory mediators. The liver is pivotal in modulating the systemic response to severe infection, because it contains the largest mass of macrophages (Kupffer cells) in the body; these macrophages can clear the endotoxin and bacteria that initiate the systemic inflammatory response. This article summarizes the functional changes that take place in the liver during sepsis and systemic inflammatory response syndrome and discusses the cellular and molecular mechanisms that underlie clinical outcomes.

Thrombogenic activity of doxorubicin in myeloma patients receiving thalidomide: implications for therapy

Ten percent of newly diagnosed myeloma patients treated with any type of chemotherapy develop deep venous thrombosis (DVT). Thalidomide has proven activity in refractory multiple myeloma (MM), and although single-agent thalidomide has minimal prothrombogenic activity, its combination with cytotoxic chemotherapy is associated with a significantly increased risk of DVT. We analyzed the incidence of DVT in 232 MM patients who received a combination of chemotherapy and thalidomide on 2 protocols that differed only by the inclusion of doxorubicin in one. DT-PACE (dexamethasone/thalidomide/cisplatin/doxorubicin/cyclophosphamide/etoposide) was offered to patients with preceding standard dose therapy, but no prior autotransplantation, while DCEP-T (dexamethasone/cyclophosphamide/etoposide/cisplatin/thalidomide) was administered for relapse after transplantation. If there were signs or symptoms suggestive of DVT, patients received additional investigations, including Doppler ultrasonography, followed by venography if indicated. Only patients on DT-PACE but not DCEP-T experienced an increased incidence of DVT. A statistical association between the incidence of DVT and combination chemotherapy including doxorubicin (P =.02) was observed; this association was confirmed on multivariate analysis. MM patients treated with thalidomide and doxorubicin have a high risk of developing DVT.

Drotrecogin alfa: a new approach in the treatment of severe sepsis

Severe sepsis is a common and frequently fatal condition. Evidence showing a link between the coagulation system and the inflammatory response to sepsis led to the development of drotrecogin alfa (activated) as an agent in the treatment of sepsis. This recombinant form of the natural protein, activated protein C (Xigris, Eli Lilly Co.), has been shown to significantly reduce mortality in a large randomised, controlled Phase III study involving 1690 patients. The exact mode of action of drotrecogin alfa (activated) remains uncertain, although it clearly combines anticoagulant and anti-inflammatory properties. Although associated with an increased risk of bleeding, this is usually procedure-related rather than spontaneous. Although costly, this is a drug that effectively reduces mortality rates in patients with severe sepsis.

Enzymatic activation of endothelial protease-activated receptors is dependent on artery diameter in human and porcine isolated coronary arteries

Protease-activated receptor (PAR)-mediated vascular relaxations have been compared in coronary arteries of different diameters isolated from both humans and pigs. Thrombin, trypsin, and the PAR1-activating peptide, TFLLR, all caused concentration-dependent relaxation of both large (epicardial; approximately 2 mm internal diameter) and small (intramyocardial; approximately 200 microm internal diameter) human coronary arteries. EC(50) values for thrombin (0.006 u ml(-1) in epicardial, 1.69 u ml(-1) in intramyocardial) and trypsin (0.02 u ml(-1) in epicardial, 1.05 u ml(-1) in intramyocardial) were significantly (P<0.01) greater in intramyocardial arteries. By contrast, EC(50) values for TFLLR were not different between epicardial (0.35 microM) and intramyocardial (0.43 microM) arteries. In porcine coronary arteries, EC(50) values for relaxations to thrombin (0.03 u ml(-1) in epicardial 0.17 u ml(-1) in intramyocardial) were also significantly (P<0.01) greater in the smaller arteries. EC(50) values for both TFLLR and the PAR2-activating peptide, SLIGKV, were not different between the two different-sized pig coronary arteries. PAR1-immunoreactivity was localized to the endothelium of human epicardial and intramyocardial arteries and both PAR1- and PAR2-immunoreactivity was observed in endothelial cells of equivalent porcine arteries. These findings indicate that enzymatic activation of endothelial cell PARs in human (PAR1) and porcine (PAR1 and PAR2) coronary arteries is markedly reduced in intramyocardial arteries when compared with epicardial arteries, suggesting increased regulation of PAR-mediated vascular responses in resistance-type arteries.

Venous thromboembolism and its prevention in critical care

BACKGROUND

Evidence-based guidelines for the prevention of venous thromboembolism (VTE) are available for most major surgical and medical patient groups. Such guidelines have not been established for critically ill patients.

OBJECTIVE

To perform a systematic review of the prevalence of deep vein thrombosis (DVT), the efficacy of thromboprophylaxis, and the rates of thromboprophylaxis use in critically ill patients.

METHODS

Computerized literature search for relevant studies meeting prespecified criteria.

RESULTS

The rates of objectively confirmed DVT in 4 prospective studies ranged from 13% to 31%. We identified only 3 randomized trials (1 in abstract form) of thromboprophylaxis in critical care unit patients. These studies show the efficacy of low-dose heparin and low molecular weight heparin compared with no prophylaxis; however, we found no trials comparing these 2 interventions. Eleven compliance studies reported that some form of thromboprophylaxis was used in 33% to 100% of critically ill patients, although only 1 study addressed the issue of appropriate prophylaxis use.

CONCLUSIONS

Data on the epidemiology of VTE and its prevention in critically ill patients are very limited. Further research is needed to better define patient risk factors for VTE, optimal methods of thromboprophylaxis, and strategies to improve compliance with prophylaxis recommendations. In the meantime, prevention strategies, shown to be effective in other related patient groups, and general principles of individual pharmacotherapy should guide the routine use of prophylaxis during critical illness.

Markers of endothelial damage in organ dysfunction and sepsis

OBJECTIVES

To review the literature on direct and indirect markers of endothelial activation and damage in patients with sepsis and systemic inflammation and to assess their clinical usefulness for diagnosis and outcome. Various markers derived from or activated by endothelial cells are described, such as adhesion molecules, thrombomodulin, von Willebrand factor, parameters of the coagulation system, and interleukin-6. Furthermore, the association of these markers with the severity of sepsis, systemic inflammation, and outcome is evaluated.

DATA EXTRACTION AND SYNTHESIS

Published research and review articles related to these parameters, with special emphasis on clinical studies.

CONCLUSIONS

Endothelial activation and damage occur early during sepsis and play a major role in the pathophysiology of systemic inflammation. Various markers of endothelial activation are increased during sepsis and systemic inflammation, and in most studies, the level of markers such as soluble intercellular adhesion molecule, vascular cell adhesion molecule, and E selectin correlate well with the severity of inflammation and the course of the disease. However, to date, it remains unclear whether adhesion molecules and coagulation parameters are superior in this respect to interleukin-6 and procalcitonin, as direct comparisons are lacking. In addition, it is evident that markers of endothelial activation and coagulation parameters lack specificity for infection-induced endothelial damage and organ dysfunction.

Recombinant human activated protein C attenuates the inflammatory response in endothelium and monocytes by modulating nuclear factor-kappaB

OBJECTIVE

To review the anti-inflammatory and anti-apoptotic properties of drotrecogin alfa (activated) (recombinant human activated protein C), emphasizing its modulatory effects on endothelial nuclear factor-kappaB. We propose a broad anti-inflammatory effect of drotrecogin alfa (activated), acting on both endothelium and monocytes.

DATA SOURCES

A selected review of the published literature on nuclear factor-kappaB, severe sepsis, and the use of drotrecogin alfa (activated) in clinical and preclinical models, together with data derived from preclinical gene profiling of model systems.

DATA EXTRACTION AND SYNTHESIS

Data from the PROWESS trial support the preclinical evidence of an antithrombotic effect of drotrecogin alfa (activated). Anti-inflammatory effects through reduction of thrombin generation and through thrombin-independent mechanisms in mononuclear and endothelial cells are reviewed. Inhibition of apoptosis is used as an example of the protective effect of drotrecogin alfa (activated) on endothelial and mononuclear cell dysfunction.

CONCLUSIONS

Drotrecogin alfa (activated) acts as a modulator of nuclear factor-kappaB to aid in the host immune response in endothelium and monocytes. Extrapolation of gene array findings to explain apoptosis in endothelium and monocytes, coupled with emerging preclinical reports, provides evidence to support the role of drotrecogin alfa (activated) in modulating nuclear factor-kappaB.

Endothelial cell dynamics and complexity theory

OBJECTIVE

To apply complexity theory to understanding endothelial cell function in health and disease.

DATA SOURCES AND STUDY SELECTION

Published research and review articles in the English language related to complexity theory and endothelial cell biology.

DATA EXTRACTION AND SYNTHESIS

The results of published studies have been used to generate a hypothesis of nonlinear dynamics in endothelial cell biology.

CONCLUSIONS

The endothelium displays nonlinear complexity. I propose a model in which healthy endothelium retains a broad range of responses and is therefore highly active, whereas dysfunctional endothelium becomes locked into a narrow range of responses, approaching a single steady state and eventual quiescence. These concepts lay a foundation for understanding the pathophysiology of endothelial cell dysfunction in the multiple organ dysfunction syndrome.

Soluble thrombomodulin, plasma-derived unactivated protein C, and recombinant human activated protein C in sepsis

OBJECTIVE

To review the physiologic and biochemical mechanisms and the rationale for the use of soluble thrombomodulin, plasma-derived protein C, and recombinant human activated protein C in sepsis.

DATA SOURCES AND STUDY SELECTION

Research and review articles related to the protein C pathway published in English from 1960 to present.

DATA EXTRACTION AND SYNTHESIS

The protein C anticoagulant pathway plays a major role in controlling microvascular coagulation and inflammation. Protein C is the zymogen of the vitamin K-dependent serine protease activated protein C. Protein C is converted to activated protein C when thrombin complexes with thrombomodulin, an endothelial surface transmembrane glycoprotein. Activated protein C inactivates factors Va and VIIIa and effectively limits further thrombin generation. This protein also enhances endogenous fibrinolytic activity and modulates the inflammatory response. A rapid depletion of protein C occurs in sepsis, which contributes to sepsis-induced coagulopathy and correlates with a poor prognosis. The decrease in tissue levels of thrombomodulin in patients with meningococcemia suggests that the ability to convert protein C to activated protein C may also be compromised. The ability of soluble thrombomodulin to block fibrinogen clotting and cell activation, to activate protein C, and to promote thrombin inhibition in different animal models suggests that soluble thrombomodulin could be a useful therapeutic agent in sepsis. However, soluble thrombomodulin is less effective in blocking fibrinogen and platelet activation and in promoting thrombin inhibition than endothelial surface membrane-bound thrombomodulin. Only activated protein C, and not protein C, has clearly shown a reduction in mortality in experimental animal models of sepsis and in humans.

CONCLUSIONS

The multipotent pharmacodynamic effects (antithrombotic, profibrinolytic, and anti-inflammatory) of activated protein C may explain why recombinantly derived human activated protein C is the first experimental agent to demonstrate a significant survival benefit in patients with severe sepsis.

Antithrombin, heparin, and heparan sulfate

OBJECTIVES

To review the experimental and clinical evidence that antithrombin has multiple mechanisms for both its anticoagulant and anti-inflammatory properties. The interaction between antithrombin and specific polysulfated, acidic oligosaccharide moieties found on heparin and related proteoglycan molecules within the circulation and on endothelial surfaces will also be examined.

DATA SOURCES

Review of the literature relating to antithrombin published during the past 25 yrs.

DATA SUMMARY

Antithrombin is the most abundant endogenous anticoagulant circulating in human plasma. This serine protease inhibitor participates in the regulation of clotting in both physiologic and pathologic states. Reduced antithrombin activity in the early phases of sepsis contributes to a procoagulant state with excess activation of the innate immune response. Antithrombin binds to specific pentasaccharides expressed on heparin, glycosaminoglycans, and related proteoglycans within the circulation and along endothelial surfaces. The functions of neutrophils, monocytes, and endothelial cells are altered as a result of their interaction with antithrombin. These effects are mediated by the enzyme inhibitory action of antithrombin and its ability to function as a ligand for antithrombin receptors on cell surfaces. In addition, antithrombin exerts anti-inflammatory properties by both prostacyclin-dependent and prostacyclin-independent actions; heparin interferes with these anti-inflammatory properties. The role of antithrombin in sepsis, its therapeutic utility in severe sepsis, and its combination with heparin remain the subject of considerable debate. The results of a recent phase 3 clinical trials with high-dose antithrombin in sepsis suggested a beneficial effect in patients who did not concomitantly receive heparin, thereby generating new challenges in the understanding of interactions between antithrombin and heparin or heparin-like proteoglycans.

CONCLUSIONS

Antithrombin has complex interactions with host coagulopathic and systemic inflammatory responses under physiologic conditions and in sepsis. The impact of these interactions in critically ill patients and the therapeutic implications of administration of antithrombin, and various doses and types of heparin in such patients, need further clarification.

New and emerging therapies for sepsis

OBJECTIVE

To review the recent advances related to the pathophysiology of sepsis and the rationale for recombinant human-activated protein C (drotrecogin alfa) and other antisepsis agents currently in Phase III trials.

DATA SOURCES

A MEDLINE (1990-December 2001) search was performed to identify pertinent literature on the pathophysiology of sepsis and treatment strategies. The search was supplemented with AdisInsight (Adis International) using the search terms sepsis, severe sepsis, or septic shock combined with agents in Phase II or higher clinical development. Abstracts presented at infectious diseases and critical care meetings were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

Clinical efficacy studies were selected for drotrecogin alfa and other Phase III investigational agents.

DATA SYNTHESIS

Our current understanding of the pathophysiology of sepsis underscores the contribution of increased coagulation and diminished fibrinolytic activity working in conjunction with an excessive and dysregulated inflammatory response. The loss of homeostatic balance among these systems results in a systemic inflammatory response with generalized coagulopathy, microvascular thrombosis, and, ultimately, acute organ failure and death. As a result of these advances, several compounds are now in various phases of development. A recombinant human form of endogenous activated protein C (drotrecogin alfa) was recently approved by the Food and Drug Administration for severe sepsis in adults who have a high risk of death. It possesses anticoagulant, profibrinolytic, and antiinflammatory properties. Other compounds currently in Phase III trials include tissue-factor pathway inhibitor, tumor-necrosis factor antibody fragment, platelet-activating factor acetylhydrolase, antithrombin III, and pyridoxylated hemoglobin polyoxyethylene.

CONCLUSIONS

With the recent approval of drotrecogin alfa, there is renewed optimism that we can effectively reduce sepsis-associated mortality.

Drotrecogin alfa (activated)

Drotrecogin alfa (activated), recombinant human activated protein C, inhibits coagulation and inflammation and promotes fibrinolysis in patients with severe sepsis. 850 patients with severe sepsis treated with intravenous drotrecogin alfa (activated) 24 microg/kg/h for 96 hours had a significantly greater reduction in 28-day all-cause mortality (24.7%) than 840 placebo recipients (30.8%) in a randomised, double-blind, placebo-controlled study. The drug was associated with a 19.4% reduction in the relative risk of death at 28 days compared with placebo. Baseline characteristics of and pre-existing conditions in patients with sepsis appeared to have no effect on the efficacy of drotrecogin alfa (activated). A significantly greater reduction in median percentage change from baseline plasma D-dimer levels (a coagulation marker) was seen with drotrecogin alfa (activated) treatment than with placebo on study days 1 to 7 in patients with severe sepsis. On study days 1, 4, 5, 6 and 7, a significantly greater median reduction in interleukin-6 levels (an inflammation marker) from baseline was seen with drotrecogin alfa (activated) treatment than placebo. Drotrecogin alfa (activated) was associated with an increased incidence of serious bleeding events during the infusion period [2.4% vs 1.0% with placebo; p = 0.024] and the 28-day study period (3.5 vs 2.0%; p = 0.06) of the efficacy trial. This increase was primarily related to procedure-related events; there were no significant differences between the treatment groups in nonprocedure-related serious bleeding events. The most frequent site of bleeding was the gastrointestinal tract. With the exception of bleeding events, there were no clinically significant differences between treatment groups in the efficacy trial in the incidence of adverse events. Of the 210 deaths in patients with severe sepsis treated with drotrecogin alfa (activated) 24 microg/kg/h in the efficacy trial, four deaths due to haemorrhage and one due to cerebral oedema were possibly related to the study drug.

Coagulation inhibitors in the treatment of sepsis

Despite advances in supportive care, sepsis and septic shock continue to be major causes of morbidity and mortality in critically ill patients. The lack of efficacy of anti-inflammatory drugs in patients with sepsis has shifted interest toward developing alternative treatments. The observation that clotting system activation may in part underlie the physiological derangements of sepsis has resulted in efforts to target the clotting cascade as a therapeutic strategy. Anticoagulants have been shown to ameliorate physiological derangements and improve survival in animal sepsis models. Three agents have undergone extensive study in humans: recombinant human activated protein C (rhAPC, drotrecogin-alpha), antithrombin III (ATIII) and tissue factor pathway inhibitor (TFPI). While a recent Phase III study of rhAPC suggests a survival benefit in patients with sepsis, major concerns about this trial include the manner in which the study was conducted, the potential toxicity of rhAPC and the questionable efficacy of this agent in patients with low mortality risk. Further clinical testing of rhAPC appears to be necessary to better define the target population most appropriate for its use. In contrast, a large Phase III study of high dose ATIII in patients with sepsis failed to show a treatment benefit with this agent. Finally, while TFPI has undergone extensive preclinical and Phase II testing, the results of Phase III studies have not been published. In summary, while coagulation inhibitors may ultimately have a therapeutic role in selected subgroups of patients with sepsis, the efficacy and safety of this class of agents remain to be proven.

Recombinant human activated protein C, drotrecogin alfa (activated): a novel therapy for severe sepsis

Sepsis remains a major cause of death in hospitalized patients. Despite a massive research effort over the past 2 decades to identify innovative therapies for sepsis, current treatment strategies consist primarily of antiinfective agents and a variety of supportive measures. Activated protein C, an endogenous protein that inhibits thrombosis and inflammation while promoting fibrinolysis, plays an important role in the pathogenesis of sepsis. Recombinant human activated protein C, drotrecogin alfa (activated), when compared with placebo in a randomized, double-blind study of 1690 patients with severe sepsis (Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis [PROWESS] trial), decreased the relative risk of death at 28 days by 19.4% (95% confidence interval 6.6-30.5%, p=0.005), although there was a trend for more serious bleeding (3.5% vs 2.0%, p=0.06) with its use. Drotrecogin alfa is the first antisepsis drug found to have a mortality benefit. It should be administered only to patients with severe sepsis who meet the PROWESS study inclusion criteria and should be avoided when risk factors for bleeding are present. Ongoing research will help determine the cost-effectiveness of drotrecogin alfa, as well as its role in critically ill populations not studied in the PROWESS trial.

Safety and dose relationship of recombinant human activated protein C for coagulopathy in severe sepsis

OBJECTIVES

To assess the safety and effect on coagulopathy of a range of doses of recombinant human activated protein C (rhAPC). To determine an effective dose and duration of rhAPC for use in future clinical trials.

DESIGN

Double-blind, randomized, placebo-controlled, multicenter, dose-ranging (sequential), phase II clinical trial.

SETTING

Forty community or academic medical institutions in United States and Canada.

PATIENTS

One hundred thirty-one adult patients with severe sepsis.

INTERVENTIONS

Intravenous infusion of rhAPC (12, 18, 24, or 30 microg/kg/hr) or placebo for 48 or 96 hrs.

MEASUREMENTS AND MAIN RESULTS

No significant differences in incidence of serious bleeding events (4% rhAPC, 5% placebo, p >.999) or incidence of serious adverse events (39% rhAPC, 46% placebo, p = 0.422) between rhAPC- and placebo-treated patients were observed. One of 53 rhAPC-treated patients with suitable immunogenicity samples had a low level, transient, non-neutralizing anti-APC antibody response not associated with any clinical adverse event. Significant dose-dependent decreases in both D-dimer (p <0.001) and end of infusion interleukin 6 levels (p =.021) were demonstrated. No statistically significant effects on fibrinogen or platelet counts were observed. A nonstatistically significant 15% relative risk reduction in 28-day all-cause mortality was observed between rhAPC- and placebo-treated patients.

CONCLUSIONS

rhAPC was safe and well-tolerated and demonstrated a dose-dependent reduction in D-dimer and interleukin 6 levels relative to placebo. The dose of 24 microg/kg/hr for 96 hrs was selected for use in future clinical studies.

Low levels of protein C are associated with poor outcome in severe sepsis

STUDY OBJECTIVE

To investigate whether protein C levels predict 30-day mortality rate, shock status, duration of ICU stay, and ventilator dependence in patients with sepsis.

DESIGN

Retrospective analysis of a subset of a previously published, prospective, randomized, double-blind, placebo-controlled trial ("Effects of Ibuprofen on the Physiology and Survival of Patients With Sepsis" [ISS]).

SETTING

A multicenter study performed in the United States and Canada (seven sites).

PATIENTS

Seventy hospitalized patients with acute severe sepsis and failure in one or more organs at entry into the ISS trial.

MEASUREMENTS AND MAIN RESULTS

Blood samples were obtained from all patients at baseline and at 20, 44, 72, and 120 h after the initiation of study drug (ibuprofen or placebo) infusion. Data obtained at these times included platelet count, prothrombin time, and partial thromboplastin time. The results described in this article are based on a subset of the total ISS population for whom additional coagulation assays were performed on the blood samples obtained at baseline and 44 h. These assays included protein C antigen, D-dimer, and fibrinogen levels. A total of 63 of the 70 patients (90%) studied in this report had acquired protein C deficiency at entry to the ISS trial (baseline). The presence and severity of acquired protein C deficiency were associated with poor clinical outcome, including lower survival rate, higher incidence of shock, and fewer ICU-free and ventilator-free days.

CONCLUSIONS

Acquired protein C deficiency may be useful in predicting clinical outcome in patients with sepsis. Clinical studies are warranted to determine whether the replacement of protein C in sepsis patients may improve outcome.

Dysfunction of endothelial protein C activation in severe meningococcal sepsis

BACKGROUND

Impairment of the protein C anticoagulation pathway is critical to the thrombosis associated with sepsis and to the development of purpura fulminans in meningococcemia. We studied the expression of thrombomodulin and the endothelial protein C receptor in the dermal microvasculature of children with severe meningococcemia and purpuric or petechial lesions.

METHODS

We assessed the integrity of the endothelium and the expression of thrombomodulin and the endothelial protein C receptor in biopsy specimens of purpuric lesions from 21 children with meningococcal sepsis (median age, 41 months), as compared with control skin-biopsy specimens.

RESULTS

The expression of endothelial thrombomodulin and of the endothelial protein C receptor was lower in the patients with meningococcal sepsis than in the controls, both in vessels with thrombosis and in vessels without thrombosis. On electron microscopical examination, the endothelial cells were generally intact in both thrombosed and nonthrombosed vessels. Plasma thrombomodulin levels in the children with meningococcal sepsis (median, 6.4 ng per liter) were higher than those in the controls (median, 3.6 ng per liter; P=0.002). Plasma levels, protein C antigen, protein S antigen, and antithrombin antigen were lower than those in the controls. In two patients treated with unactivated protein C concentrate, activated protein C was undetectable at the time of admission, and plasma levels remained low.

CONCLUSIONS

In severe meningococcal sepsis, protein C activation is impaired, a finding consistent with down-regulation of the endothelial thrombomodulin-endothelial protein C receptor pathway.

Experimental and emerging therapies for sepsis and septic shock

The underlying principles of sepsis therapy have remained unchanged for decades. These include: prompt institution of antimicrobial agents aimed at the inciting pathogen, source control directed at removal of the infection nidus whenever possible, and support of organ dysfunction. Despite advances in antibiotics, surgical techniques and organ support technology, the morbidity and mortality from sepsis-related diseases have remained substantially unchanged (30 - 50%). Immunomodulation of the inflammatory cascade has been suggested as a crucial but inadequately addressed element in the treatment of sepsis. The list of potential therapeutic targets has been growing as more and more mediators are identified in the pathogenesis of sepsis. To date, numerous anti-inflammatory agents, found to have favourable effects in animal models of septic shock, have been tested in a number of clinical trials on thousands of patients. In this first of a three part series, we go through some of the background and current strategies in sepsis therapy. In this review, we include the two novel therapies that have shown clear survival benefit in large, randomised, placebo-controlled, multi-centre trials, low-dose steroids and recombinant activated protein C. Also included in this review are studies on antithrombin III, platelet-activating factor antagonists, complement modulators, nitric oxide synthase inhibitors and caspase inhibitors (apoptosis inhibitors).

Activated protein C versus protein C in severe sepsis

OBJECTIVE

To delineate critical differences between activated protein C (APC) and its precursor, protein C, with regard to plasma levels in health and in severe sepsis, and to discuss the implications of these differences as they relate to treatment strategies in patients with severe sepsis. DATA SOURCE/STUDY SELECTION: Published literature including abstracts, manuscripts, and review articles reporting studies in both experimental animal models and humans that provide an understanding of the relationship and the critical differences between circulating levels of APC and protein C.

DATA EXTRACTION AND SYNTHESIS

The protein C pathway represents one of the major regulatory systems of hemostasis, exhibiting antithrombotic, profibrinolytic and anti-inflammatory properties. This pathway also plays a critical role in the pathophysiology of severe sepsis. Central to this pathway is the vitamin K-dependent serine protease, APC, and its precursor, protein C. The conversion of protein C to APC is dependent on the complex of thrombin and thrombomodulin, an integral endothelial surface receptor. The conversion of protein C to APC is further augmented by another endothelial surface protein, the endothelial protein C receptor. There are limited published data on APC levels in health and disease, probably due to the complexity of the assay methodology for measuring APC and the absence of commercially available diagnostic kits. In animals and humans with normal functioning endothelium, circulating levels of APC (1-3 ng/mL) are positively correlated with protein C (4000-5000 ng/mL) concentration and the amount of thrombin generated. In patients with severe sepsis, there is a generalized endothelial dysfunction, contributing to multiple organ failure with increased morbidity and mortality. Persistently low protein C levels are related to poor prognosis. Key to understanding the treatment strategy with APC or protein C is knowledge of the functional status of the endothelium and, specifically, whether the microvasculature in patients with severe sepsis can support the conversion of protein C to APC. To date, only APC (drotrecogin alfa [activated]) has been shown to reduce mortality in severe sepsis in a large, phase 3, placebo-controlled, double-blind international trial. In contrast, no data, other than open-label case studies, are available for evaluation of the effects of protein C in the treatment of severe sepsis.

CONCLUSION

The limited data available indicate that lower levels of protein C in sepsis occur in the absence of appreciable conversion to APC. These observations indicate that treatment with APC may be more efficacious than protein C in severe sepsis, where generalized endothelial dysfunction may impair conversion of protein C to APC. Additional research is required to confirm these observations.

Recombinant human activated protein C: a system modulator of vascular function for treatment of severe sepsis

OBJECTIVE

To review the mechanisms of action and rationale for the use of recombinant human activated protein C in the treatment of severe sepsis. Specifically, we focus on the mechanisms of action in the protein C pathway that converge to modulate the pathophysiology of severe inflammatory disease and sepsis. This analysis includes a discussion of the role of activated protein C in directly modulating cell system biology, independent of antithrombotic activity.

DATA SOURCES/STUDY SELECTION

Published research and review articles relating to the protein C pathway, recombinant human protein C, and the role of protein C in sepsis. Data were also derived from broad gene profiling in model systems of endothelial dysfunction.

DATA EXTRACTION AND SYNTHESIS

Relevant studies were included to support discussion of the unique mechanistic aspect of protein C and its role in the pathogenesis of severe sepsis. We discuss the potential of activated protein C as a unique system modulator for the treatment of severe sepsis and other systemic inflammatory responses that result in microvascular coagulopathy, endothelial dysfunction, and vascular bed failure.

CONCLUSIONS

The protein C pathway plays a unique role in modulating vascular function. As an antithrombotic/profibrinolytic agent, it plays a clear role in maintaining vascular patency. Moreover, it has anti-inflammatory properties and appears to play a unique role as an antiapoptotic and endothelial cell survival factor. In states of systemic inflammatory activation, loss of protein C due to consumptive processes results in a compromised ability to modulate coagulation as well as inflammatory and cell survival functions. This compromise leads to vascular dysfunction, end-organ failure, and death. Replacement with recombinant human activated protein C offers a system-modulating approach to improved outcome.

Efficacy and safety of recombinant human activated protein C for severe sepsis

BACKGROUND

Drotrecogin alfa (activated), or recombinant human activated protein C, has antithrombotic, antiinflammatory, and profibrinolytic properties. In a previous study, drotrecogin alfa activated produced dose-dependent reductions in the levels of markers of coagulation and inflammation in patients with severe sepsis. In this phase 3 trial, we assessed whether treatment with drotrecogin alfa activated reduced the rate of death from any cause among patients with severe sepsis.

METHODS

We conducted a randomized, double-blind, placebo-controlled, multicenter trial. Patients with systemic inflammation and organ failure due to acute infection were enrolled and assigned to receive an intravenous infusion of either placebo or drotrecogin alfa activated (24 microg per kilogram of body weight per hour) for a total duration of 96 hours. The prospectively defined primary end point was death from any cause and was assessed 28 days after the start of the infusion. Patients were monitored for adverse events; changes in vital signs, laboratory variables, and the results of microbiologic cultures; and the development of neutralizing antibodies against activated protein C.

RESULTS

A total of 1690 randomized patients were treated (840 in the placebo group and 850 in the drotrecogin alfa activated group). The mortality rate was 30.8 percent in the placebo group and 24.7 percent in the drotrecogin alfa activated group. On the basis of the prospectively defined primary analysis, treatment with drotrecogin alfa activated was associated with a reduction in the relative risk of death of 19.4 percent (95 percent confidence interval, 6.6 to 30.5) and an absolute reduction in the risk of death of 6.1 percent (P=0.005). The incidence of serious bleeding was higher in the drotrecogin alfa activated group than in the placebo group (3.5 percent vs. 2.0 percent, P=0.06).

CONCLUSIONS

Treatment with drotrecogin alfa activated significantly reduces mortality in patients with severe sepsis and may be associated with an increased risk of bleeding.

Endothelial cell activation, injury, damage and dysfunction: separate entities or mutual terms?

The loss of well-regulated endothelial cell functioning is followed by adverse changes in a variety of physiological systems, such as the expression of adhesion molecules, maintenance of adequate blood vessel tone and haemostasis. Therefore, a full understanding of endothelial cell biology is essential if the losses of normal function of these systems are to be avoided. The viewpoint presented in this paper suggests that a spectrum between endothelial cell health and disease can be drawn: midway between these two extremes is immunological activation (by, for example, cytokines), which is reversible. Endothelial cell damage or injury (which may be the result of chronic inflammatory activation, hypercholesterolaemia, and/or smoking) are invariably associated with clinical conditions such as hypertension and oedema (and, ultimately, thrombosis and infarction), and are more difficult to reverse. A better understanding of the events, including apoptosis, that lead to vascular dysfunction may be useful in developing our understanding of vascular biology.

Hemostatic disturbances in patients with systemic inflammatory response syndrome (SIRS) and associated acute renal failure (ARF)

Endothelial damage plays a central role in the development of an SIRS-related Multiple Organ Dysfunction Syndrome (MODS) as a consequence of the establishment of a hemostatic imbalance between coagulation and fibrinolysis systems. Until now, sepsis is the SIRS model that has been most studied. The aim of this study was to assess the endothelial damage and the hemostatic imbalance in early stages of an SIRS of different origins, and to study if there are any differences in these disturbances between infectious and noninfectious SIRS. The endothelial damage and hemostatic changes were studied in 40 patients with SIRS (with less than 12 h of evolution) and an acute renal failure. Infectious SIRS was diagnosed in 19 cases and noninfectious SIRS in the remaining 21 patients. Patients with SIRS presented significantly higher values (p<0.001) for factors related to endothelial damage [von Willebrand factor (vWF), thrombomodulin, tissue plasminogen activator (t-PA), and plasminogen activator inhibitor type 1 (PAI-1) antigen], hypercoagulability [prothrombin fragment 1+2 (F1+2) and thrombin-antithrombin complexes (TAT)], and fibrinolysis (D-dimer and PAI activity) with respect to the control group. However, although the group with infectious SIRS presented higher values for all the factors except for the t-PA and D-dimer with respect to SIRS of other origins, none of these differences reached statistical significance (p>0.05). Our data show that patients with SIRS and associated acute renal failure, irrespective of the origin (infectious or noninfectious), show signs of intense endothelial damage and hypercoagulability throughout the process.

Therapeutic rationale for antithrombin III in sepsis

OBJECTIVE

To review the preclinical evidence that provides the therapeutic rationale for antithrombin as a novel treatment for human sepsis.

DATA SOURCES

A summary of published medical literature from MEDLINE search files and other reviews published about antithrombin use in sepsis.

DATA SUMMARY

Antithrombin has a variety of antiinflammatory properties in addition to its functions as an endogenous anticoagulant that appear to have an important therapeutic role in the prevention of microvascular dysfunction and multiple organ injury in sepsis. Appropriate timing and dosing of antithrombin III is critical to realize its full therapeutic potential as an anti-sepsis therapy.

CONCLUSIONS

Antithrombin is a potent inhibitor of thrombin-mediated vascular injury in the microcirculation in severe sepsis. This endogenous anticoagulant is rapidly depleted in the early phases of sepsis as a result of decreased synthesis, increased destruction, and enhanced clearance by thrombin-antithrombin complex formation. The therapeutic efficacy of antithrombin in experimental sepsis is readily demonstrable in numerous animal systems. Appropriately defined patient populations with early onset severe sepsis and/or septic shock may benefit from antithrombin therapy if it is administered in adequate doses at the optimal time interval.

Protein C levels as a prognostic indicator of outcome in sepsis and related diseases

OBJECTIVE

To consider the appropriateness of protein C levels as a prognostic indicator for sepsis and related diseases.

DATA SOURCES/STUDY SELECTION

Published research and review articles related to protein C deficiency in patients with sepsis and related diseases.

DATA EXTRACTION AND SYNTHESIS

All applicable data were extracted, and relevant literature was cited to support factual statements in the text. The protein C pathway represents one of the major regulatory systems of hemostasis, exhibiting antithrombotic, profibrinolytic, and anti-inflammatory properties. Numerous studies have shown that acquired protein C deficiency is prevalent in the majority of septic patients (>85%) and is associated with increased morbidity and mortality in patients with severe sepsis and septic shock. This deficiency in protein C is not simply a transient marker for sepsis, but parallels the progress of the disease. In addition, protein C deficiency occurs in the presence of a wide range of pathogens and develops early in the disease process.

CONCLUSIONS

A review of the relevant literature suggests that protein C levels may serve as a useful prognostic indicator of outcome in sepsis and related diseases.

Coagulation inhibitor replacement in sepsis is a potentially useful clinical approach

In sepsis, levels of the endogenous coagulation inhibitors antithrombin III and protein C are lowered as a result of complex formation with multiple activated clotting factors. In addition, their activity can further be curtailed by proteolytic inactivation. Loss of antithrombin III and protein C activity blocks the endogenous control mechanism for thrombin generation resulting in a state of systemic activation of coagulation and inflammatory processes. Levels of tissue factor pathway inhibitor, a third endogenous coagulation inhibitor, are increased in sepsis rather than decreased, probably reflecting a depletion of the endothelial cell bound tissue factor pathway inhibitor pool with loss of its endothelial protective function. Administration of any of these three inhibitors in various animal species and sepsis models reduces morbidity and mortality. In addition to their anticoagulant effects, these inhibitors also have various anti-inflammatory activities that may contribute to their protective effects. Phase II studies in patients with severe sepsis using coagulation inhibitors have indicated that this therapeutic approach may be useful. Large-scale phase III trials will ultimately decide whether adjunctive coagulation inhibitor replacement will have a place in the treatment of patients with severe sepsis.

Phylogenetic and functional relationships between coagulation and the innate immune response

Activation of the coagulation system frequently accompanies systemic inflammatory states and is an almost invariable consequence of septic shock. The simultaneous activation of the innate immune response and the coagulation system after injury is a phylogenetically ancient, adaptive response that can be traced back to the early stages of eukaryotic evolution. Most invertebrate species lack differentiated phagocytic cells and platelets. They possess a common cellular and humoral pathway of inflammation and clotting after a breach in their internal milieu by either trauma or infection. The close linkage between clotting and inflammation has been preserved throughout vertebrate evolution and is readily demonstrable in human physiologic responses to a variety of potentially injurious stimuli. The same proinflammatory stimuli that activate the human clotting cascade also activate the phagocytic effector cells (neutrophils, monocytes, and macrophages). The complex and highly integrated linkage between systemic inflammation and coagulation are reviewed in this article.

Prognostic value of protein C concentrations in neutropenic patients at high risk of severe septic complications

OBJECTIVE

To assess the prognostic value of protein C, endogenous activated protein C, and D-dimer concentrations in patients at high risk of developing severe septic complications secondary to cytostatic chemotherapy.

DESIGN

Prospective, comparative, single-center study.

SETTING

Specialized ward for treating patients with acute leukemia and associated intensive care unit at a university hospital.

SUBJECTS

Twenty-six consecutive patients who developed either severe sepsis (n = 13) or septic shock (n = 13) during chemotherapy-induced neutropenia (leukocytes <1,000/microL).

INTERVENTION

None, other than standard care.

MEASUREMENTS AND MAIN RESULTS

Baseline blood samples were obtained from 97 adult patients treated with intensive cytostatic chemotherapy. Serial blood sampling was performed in 62 of 97 patients who developed fever (>38.3 degrees C). Thirteen patients progressed to severe sepsis and 13 patients to septic shock. Protein C, endogenous activated protein C, and D-dimer were measured in these 26 patients. At fever onset, protein C concentrations decreased from normal baseline concentrations and were significantly lower in the group of patients who progressed to septic shock compared with those who developed severe sepsis (medians for protein C activity: 23.1% vs. 69.5%; p = .0003). The median elapsed time between detection of fever and the diagnosis of severe sepsis or septic shock was 16 hrs and 12 hrs, respectively. All septic shock patients died, whereas patients who progressed only to severe sepsis survived.

CONCLUSIONS

Septic shock in neutropenic patients is associated with increased protein C consumption. The data demonstrate that the coagulation cascade is activated and produces a hypercoagulable state before the onset of clinical symptoms of severe sepsis and septic shock. Low protein C concentrations at the onset of fever and before the onset of clinical symptoms of severe sepsis or septic shock may have prognostic value in predicting an unfavorable outcome. Protein C measurements may help identify patients at risk in an early phase of neutropenic sepsis. It is also attractive to speculate that because low protein C concentrations were seen in these patients, protein C replacement may be beneficial in sepsis.

Changes of the hemostatic network in critically ill patients--is there a difference between sepsis, trauma, and neurosurgery patients?

OBJECTIVE

To study the time course of coagulation data in intensive care patients.

DESIGN

Prospective, descriptive study.

SETTING

Clinical investigation on a surgical and neurosurgical intensive care unit of a university hospital.

PATIENTS

Fifteen patients with severe trauma (injury severity score, 15 to 25), 15 sepsis patients secondary to major surgery, and 15 neurosurgery patients (cancer surgery) were studied.

INTERVENTIONS

Standardized intensive care therapy.

MEASUREMENTS AND MAIN RESULTS

Standard coagulation data and molecular markers of coagulation activation and fibrinolytic activity (soluble thrombomodulin, protein C, free protein S, thrombin/antithrombin III complex, plasmin-alpha 2-antiplasmin complex, tissue plasminogen activator, platelet factor 4, beta-thromboglobulin were measured from arterial blood samples on the day of admission to the intensive care unit (trauma/neurosurgery patients) or on the day of diagnosis of sepsis (baseline value) and serially during the next 5 days. Antithrombin III, fibrinogen, and platelet counts were highest in neurosurgery patients but without significant differences between sepsis and trauma patients. Thrombin/antithrombin III complex increased in the sepsis patients (from 22.6+/-4.2 microg/L to 39.9+/-6.8 microg/L), but decreased in trauma (from 40.2+/-5.1 microg/L to 17.6+/-4.0 microg/L) and neurosurgery patients (from 28.2+/-4.2 microg/L to 16.2+/-3.8 microg/L). Tissue plasminogen activator increased in the sepsis patients (from 14.4+/-3.9 microg/L to 20.7+/-3.8 microg/mL) and remained almost unchanged in the other two groups. Soluble thrombomodulin plasma concentration increased significantly in the sepsis group (max, 131.8+/-22.5 ng/mL), while it remained elevated in the trauma (max, 75.5+/-5.9 ng/mL) and was almost normal in the neurosurgery patients. Protein C and free protein S remained decreased only in the sepsis group.

CONCLUSIONS

Alterations of the hemostatic network were seen in all three groups of critically ill patients. Hemostasis normalized in the neurosurgery patients and posttraumatic hypercoagulability recovered within the study period. By contrast, monitoring of molecular markers of the coagulation process demonstrated abnormal hemostasis in the sepsis patients during the entire study period indicating ongoing coagulation disorders and abnormalities in fibrinolysis in these patients.

Time course and prognostic significance of hemostatic changes in sepsis: relation to tumor necrosis factor-alpha

OBJECTIVES

To describe the time course and prognostic significance of tumor necrosis factor-alpha (TNF-alpha) levels and hemostatic abnormalities in clinical sepsis.

DESIGN

Prospective, observational study with sequential measurements in an inception cohort.

SETTING

An emergency department in a university teaching hospital. Patients were followed up until they either left the hospital or died.

PATIENTS

During a 1-yr period, 43 adult patients were selected from all emergency department patients who met the established criteria for sepsis. Excluded were patients with either organ dysfunction or septic shock at the time of admission.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Blood samples were collected serially (day of admission and on days 3, 5, and 7) to determine TNF-alpha, platelet count, fibrinogen, factor VII, antithrombin III, tissue-type plasminogen activator activity, plasminogen activator inhibitor activity, plasminogen, and alpha2-antiplasmin. Fibrinopeptide A was measured only on the day of admission. Data were analyzed to determine whether admission values or serially obtained values within 7 days were useful in predicting outcome. Thirteen patients died and 30 survived. On admission, assay values indicated that platelet count and antithrombin III were significantly lower than normal (as observed in 50 healthy adults). Fibrinogen, plasminogen activator inhibitor type 1, tissue-type plasminogen activator, fibrinopeptide A, and TNF-alpha were higher than normal, whereas concentrations of factor VII, plasminogen, and alpha2-antiplasmin were in the normal range. No differences were detected in the admission values between survivors and nonsurvivors, except for antithrombin III. However, subsequent values of some variables demonstrated a difference between survivors and nonsurvivors. Survivors showed increasing platelet count and antithrombin III values compared with nonsurvivors, in whom the values remained low, with no significant changes during the study period. High TNF-alpha levels were found in both groups, but only survivors experienced progressive decrease during the observation period.

CONCLUSIONS

Early clinical sepsis is characterized by high plasma levels of TNF-alpha and by activation of the coagulation and fibrinolysis systems. Longitudinal analysis of some variables (antithrombin III, platelet count, and TNF-ea) showed some differences with time between the survivor and nonsurvivor groups, but we feel that such differences were not large enough to be predictive in individual patients.

The imbalance between coagulation and fibrinolysis is related to the severity of the illness and the prognosis in sepsis

OBJECTIVES

The coagulation and fibrinolytic system appears to be activated by the septic process independently, leading to the syndrome of disseminated intravascular coagulation (DIC). In this study, we investigated the changes within the hemostatic system related to the severity of the illness and the prognosis in patients with sepsis.

METHODS

Plasma thrombin-antithrombin III (TAT) and plasmin-alpha 2-antiplasmin (PAP) complexes were measured using ELISA methods in 32 patients with sepsis and 20 controls and were analyzed according to the APACHE III scores and survival of the patients.

RESULTS

Plasma TAT and PAP in patients with sepsis were significantly higher than controls. Nonsurvivors showed greater levels of TAT (21.7 +/- 22.3 ng/mL) and lower levels of PAP (628.4 +/- 378.1 ng/mL) than survivors (TAT: 11.1 +/- 11.2 ng/mL; PAP: 857.1 +/- 364.1 ng/mL). The imbalance between coagulation and fibrinolysis described as TAT/PAP ratio was closely related with APACHE III scores in patients with sepsis (r = 0.47) and the TAT/PAP ratio in nonsurvivors was significantly higher compared with survivors (34.4 +/- 21.4 vs. 14.4 +/- 13.8).

CONCLUSION

In sepsis, both coagulation and the fibrinolysis system are activated and the imbalance between coagulation and fibrinolysis predisposes to the hypercoagulation state and is closely related to the severity of the disease and the prognosis.

Activation of the tissue factor pathway occurs during continuous venovenous hemofiltration

BACKGROUND

Activation of the tissue factor pathway occurs during continuous venovenous hemofiltration (CVVH). Despite adequate exogenous anticoagulation, the occlusion of CVVH circuits can occur within minutes to a few hours of use and is associated with evidence of thrombin generation. Having found no evidence of activation of the contact factor (intrinsic coagulation) pathway during CVVH, we sought to examine the effect of the first episode of CVVH on the tissue factor (extrinsic) pathway of coagulation and thrombin generation.

METHODS

Twelve critically ill patients were studied prior to the commencement of hemofiltration and at regular intervals thereafter until the filter clotted.

RESULTS

Prior to hemofiltration, most patients had increased levels of plasma tissue factor, thrombin-antithrombin (TAT) complexes, and tissue factor pathway inhibitor (TFPI); during hemofiltration, further generation of TAT complexes occurred. Initially, levels of activated factor VII (FVIIa) fell and TFPI increased, but during the course of hemofiltration, the levels of TFPI fell and FVIIa increased. Levels of tissue factor increased during CVVH in some patients, but this was not related to the generation of FVIIa.

CONCLUSIONS

These data indicate that activation of FVII occurred during CVVH, which was related to levels of TFPI, but not tissue factor, and was coincidental to thrombin generation.

Activation of the extrinsic coagulation pathway in patients with severe sepsis and septic shock

OBJECTIVES

To obtain systematic information on the extrinsic coagulation pathway, as well as to investigate the time course of the coagulation abnormalities in sepsis.

DESIGN

Prospective observational study.

SETTING

General intensive care unit.

PATIENTS

Nineteen patients with the diagnosis of severe sepsis or septic shock and nine control patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Tissue factor antigen concentration (tissue factor antigen), prothrombin fragment F1+2, thrombin antithrombin III complex, fibrinopeptide A, D-dimer, and antithrombin III concentrations were measured on the day of diagnosis of severe sepsis and septic shock, and on days 1, 2, 3, and 4 after diagnosis. The concentrations of tissue factor antigen, prothrombin fragment F1+2, fibrinopeptide A, and D-dimer were significantly increased in patients with severe sepsis and septic shock compared with control subjects. However, the concentrations of thrombin antithrombin III complex showed no statistical differences between the septic patients and the control subjects. Significantly, low antithrombin III concentrations were observed in the septic patient groups compared with control subjects. With the exception of D-dimer, the concentrations of the hemostatic markers were similar between severe sepsis and septic shock patients. Significant correlations were noted between tissue factor antigen and the disseminated intravascular coagulation score (r2=.236, p< .0001) and the number of dysfunctioning organs (r2=.229, p=.035).

CONCLUSIONS

We systematically elucidated coagulation disorders in newly defined sepsis. The extrinsic coagulation pathway is activated in patients with severe sepsis and septic shock. In these patients, enhanced thrombin generation and activation, and fibrin formation were demonstrated when compared with the control subjects. Furthermore, the thrombin generated appears not to be fully neutralized by antithrombin III.