Heparin blunts endotoxin-induced coagulation activation

Fucoidan extracted from Fucus evanescens brown algae corrects immunity and hemostasis disorders in experimental endotoxemia

Fucoidan extracted from brown algae (Fucus evanescens) was used for correction of immunity and hemostasis disorders in experimental endotoxemia induced by injection of LPS. Fucoidan reduced the elevated levels of proinflammatory cytokines (TNF-alpha, IL-1, IL-6) and partially arrested hypercoagulation phenomena, thus improving animal resistance to LPS.

Early intravenous unfractionated heparin and mortality in septic shock

BACKGROUND

Sepsis and septic shock represent a systemic inflammatory state with substantial pro-coagulant elements. Unfractionated heparin is a known anticoagulant, which also possesses anti-inflammatory properties. Unfractionated heparin has been shown to increase survival in experimental models of septic shock.

OBJECTIVE

To evaluate the impact of intravenous therapeutic dose unfractionated heparin in a cohort of patients diagnosed with septic shock.

DESIGN

Retrospective, propensity matched, multicenter, cohort study.

SETTING

Regional intensive care units in Winnipeg, Canada between 1989 and 2005.

PATIENTS

Two thousand three hundred fifty-six patients diagnosed with septic shock, of which 722 received intravenous therapeutic dose heparin.

MEASUREMENTS AND MAIN RESULTS

The primary outcome of study was 28-day mortality, and mortality stratified by severity of illness (Acute Physiologic and Chronic Health Evaluation II quartile). Safety was assessed by comparing rates of gastrointestinal hemorrhage, intracranial hemorrhage, and the need for transfusion. By using a Cox proportional hazards model, systemic heparin therapy was associated with decreased 28-day mortality (307 of 695 [44.2%] vs. 279 of 695 [40.1%]; hazard ratio 0.85 [confidence interval (CI) 95% 0.73-1.00]; p = 0.05). In the highest quartile of severity of illness (Acute Physiologic and Chronic Health Evaluation II score 29-53), heparin administration was associated with a clinically and statistically significant reduction in 28-day mortality [127 of 184 (69.0%) vs. 94 of 168 (56.0%); hazard ratio 0.70 (CI 95% 0.54-0.92); p = 0.01]. The use of intravenous unfractionated heparin was associated with successful liberation from mechanical ventilation [odds ratio of 1.42 (CI 95% 1.13-1.80); p = 0.003], and successful discontinuation of vasopressor/inotropic support [odds ratio of 1.34 (CI 95% 1.06-1.71); p = 0.01]. No significant differences in the rates of major hemorrhage or need for transfusion were identified.

CONCLUSION

Early administration of intravenous therapeutic dose unfractionated heparin may be associated with decreased mortality when administered to patients diagnosed with septic shock, especially in patients with higher severity of illness. Prospective randomized trials are needed to further define the role of this agent in sepsis and septic shock.

Danaparoid sodium attenuates the increase in inflammatory cytokines and preserves organ function in endotoxemic rats

Introduction

Anticoagulant therapy attracts much attention for the treatment of severe sepsis since recent studies have revealed that some anticoagulants have the ability to regulate the inflammatory response. The purpose of this study was to examine whether danaparoid sodium (DA) is effective for the treatment of organ dysfunction in sepsis.

Methods

Sixty-four Wistar rats were intravenously injected with 5.0 mg/kg of lipopolysaccharide (LPS) and then divided into two groups: the DA group and the control group (n = 32 each). The DA group was injected intravenously with 400 U/kg of DA immediately after LPS injection, whereas the control group received saline. Blood samples were drawn at 1, 6, 12, and 24 hours after LPS injection, and organ damage markers and coagulation markers were measured. In the other series, 10 rats treated with LPS were divided into DA and control groups (n = 5 each). Blood samples were collected at 1, 3, and 6 hours after LPS injection and served for the cytokine measurements.

Results

The elevation of the organ damage markers, such as alanine aminotransferase and lactate dehydrogenase, was significantly suppressed in the DA group. Coagulation markers, such as AT activity and fibrinogen levels, were maintained better in the DA group at 6 hours. The elevation of proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin (IL)-1, and IL-6 was significantly suppressed in the DA group. On the other hand, there was no significant difference in anti-inflammatory cytokines such as IL-4 and IL-10.

Conclusion

DA preserves the organ dysfunction in LPS-challenged rats. Although the mechanism is not fully elucidated, not only the improvement of coagulation disorder but also the regulation of circulating levels of proinflammatory cytokines may play a role in the mechanism.

Disseminated intravascular coagulation

OBJECTIVE

To review the current knowledge on the clinical manifestation, pathogenesis, diagnosis, and management of disseminated intravascular coagulation (DIC).

DATA SOURCE

Selected articles from the MEDLINE database.

DATA SYNTHESIS

DIC may complicate a variety of disorders and can cause significant morbidity (in particular related to organ dysfunction and bleeding) and may contribute to mortality. The pathogenesis of DIC is based on tissue factor-mediated initiation of systemic coagulation activation that is insufficiently contained by physiologic anticoagulant pathways and amplified by impaired endogenous fibrinolysis. The diagnosis of DIC can be made using routinely available laboratory tests and scoring algorithms. Supportive treatment of DIC may be aimed at replacement of platelets and coagulation factors, anticoagulant treatment, and restoration of anticoagulant pathways.

CONCLUSIONS

Insight into the pathogenesis of DIC has resulted in better strategies for clinical management, including straightforward diagnostic criteria and potentially beneficial supportive treatment options.

Endotoxin-induced effects on platelets and monocytes in an in vivo model of inflammation

AIMS

Chronic inflammation is a major contributing factor to atherosclerosis and various markers of inflammation, fibrinolysis and coagulation are upregulated in patients with established atherosclerotic disease. The aim of this study was to investigate the direct and short-term effects of inflammation on platelet and monocyte activation with an in vivo model of endotoxemia in healthy volunteers.

METHODS AND RESULTS

In this study, 13 healthy male subjects with a mean age of 29.5+/-5.4 years received intravenous administration of lipopolysaccharide (LPS; 20 IU/kg IV). The kinetics of CD40-ligand and CD62P expression on platelets, tissue-factor binding on monocytes and platelet-monocyte aggregates were measured by whole blood flow cytometry at baseline and at 1, 2, 4, 6 and 24 hours after LPS administration. Plasma levels of soluble CD40-ligand were measured with an ELISA over the same time course. Platelet-monocyte aggregates, tissue-factor binding on monocytes and surface expression of platelet CD40L significantly increased in experimental endotoxemia in vivo, reaching peak values 1 hour after LPS administration. All values returned to baseline after 24 hours. Surface expression of CD62P on platelets and plasma levels of sCD40L did not change significantly in response to LPS.

CONCLUSIONS

In vivo administration of endotoxin leads to an activation of platelets and monocytes with an upregulation of proatherogenic CD40L on platelets. These findings underpin the role of inflammation in early atherogenesis through platelet and monocyte activation in an in vivo model.

Prophylactic heparin in patients with severe sepsis treated with drotrecogin alfa (activated)

RATIONALE

Patients with severe sepsis frequently receive prophylactic heparin during drotrecogin alfa (activated) (DrotAA) treatment due to risk of venous thromboembolic events (VTEs). Biological plausibility exists for heparin to reduce DrotAA efficacy and/or increase bleeding.

OBJECTIVES

Primary: demonstrate in adult patients with severe sepsis receiving DrotAA treatment that 28-day mortality was equivalent for patients treated with concomitant prophylactic heparin compared with placebo; secondary: safety and VTE incidence.

METHODS

International, randomized, double-blind, phase 4, equivalence-design trial (n = 1994). Patients were eligible if indicated for and receiving DrotAA treatment under the country's approved label. Study drug (low molecular weight/unfractionated heparin) or placebo (saline) was administered every 12 hours during DrotAA infusion (24 ug/kg/hr for 96 hr). In patients on baseline heparin and randomized to placebo, heparin was stopped.

MEASUREMENTS AND MAIN RESULTS

Twenty-eight-day mortality was not equivalent between treatment groups. Heparin mortality was numerically lower (28.3 vs. 31.9%; p = 0.08). In the prospectively defined subgroup of patients exposed to heparin at baseline, patients receiving placebo experienced higher mortality (35.6 vs. 26.9%; p = 0.005). For safety, significant differences were observed during Days 0-6 for any bleeding event (placebo, n = 78; heparin, n = 105; p = 0.049) and ischemic stroke during Days 0-6 (placebo, n = 12; heparin, n = 3; p = 0.02) and Days 0-28 (placebo, n = 17; heparin, n = 5; p = 0.009). The VTE rate was low, with no statistical difference between groups (0-6 d, p = 0.60; 0-28 d, p = 0.26).

CONCLUSIONS

Compared with placebo, concomitant prophylactic heparin was not equivalent, did not increase 28-day mortality, and had an acceptable safety profile in patients with severe sepsis receiving DrotAA. Heparin discontinuation should be carefully weighed in patients considered for DrotAA treatment. XPRESS clinical trial registered with www.clinicaltrials.gov (NCT 00049777). The study ID numbers are 6743; F1K-MC-EVBR.

Pharmacokinetics and Pharmacodynamics of the Dual FII/FX Inhibitor BIBT 986 in Endotoxin-induced Coagulation

BIBT986 is a dual inhibitor of factors Xa and IIa. The aim of this study was to compare with placebo the effect of three doses of BIBT986 on coagulation, platelet activation, and inflammation. This was a prospective, randomized, double-blind, placebo-controlled, parallel-group dose escalation trial in 48 healthy male volunteers. Participants received one of three doses of BIBT986 or placebo intravenously together with a bolus infusion of 2 ng/kg lipopolysaccharide (LPS). BIBT986 dose-dependently changed global coagulation parameters and in vivo markers of thrombin generation and action: BIBT986 doses, which prolonged activated partial thromboplastin time by 100%, completely suppressed the LPS-induced increases in prothrombin fragment, thrombin-antithrombin complexes, and D-dimer, which were 6.1-, 14.5, and 3.5-fold in the placebo group, respectively. BIBT986 did not influence inflammation, fibrinolysis, or platelet activation. Therefore, BIBT986 is a potent anticoagulant in the human endotoxemia model.

A coagulation factor VII deficiency protects against acute inflammatory responses in mice

Upregulation of the activated Factor VII (FVIIa)/Tissue Factor complex, downregulation of natural anticoagulation pathways, and inhibition of fibrinolysis, are major contributors to coagulopathies associated with acute inflammation. Provision of FVIIa, and consequent downstream coagulation-related proteases, also stimulates further inflammatory changes, which can result in disseminated intravascular coagulation. Thus, the potential protective effects in vivo of a genetic-based reduction in FVII levels have been investigated in a murine model of acute inflammation, namely lipopolysaccharide (LPS)-induced lethal endotoxaemia. Mice with a total FVII deficiency do not survive the neonatal period. Therefore mice expressing low levels of FVII (FVII(tTA/tTA)), producing sufficient amounts of FVII for survival (approximately 5% of wild-type (WT) FVII), were employed to investigate in vivo pathways involved in the crosstalk between coagulation, inflammation, and survival, consequent to administration of a lethal dose of LPS. The FVII(tTA/tTA) mice presented with reduced mortality, coagulation, and inflammatory responses in comparison with similarly treated WT mice after administration of LPS. The attenuated inflammatory responses in FVII(tTA/tTA) mice were associated with downregulation of Egr-1 signalling. Administration, in vivo, of specific inhibitors of FXa and thrombin demonstrated that the inflammatory responses were unaltered in WT mice, but further reduced in FVII(tTA/tTA) mice. Therefore, a FVII deficiency enhances survival from lethal endotoxaemia both through attenuation of inflammatory responses that result directly from reduced FVIIa levels, and, indirectly, from downregulation of coagulation proteases downstream of the FVII-dependent cascade.

Activated protein C increases sensitivity to vasoconstriction in rabbit Escherichia coli endotoxin-induced shock

Introduction

The aim of this study was to investigate the effects of activated protein C (aPC) on vascular function, endothelial injury, and haemostasis in a rabbit endotoxin-induced shock model.

Method

This study included 22 male New Zealand rabbits weighing 2.5 to 3 kg each. In vitro vascular reactivity, endothelium CD31-PECAM1 immunohistochemistry, plasma coagulation factors and monocyte tissue factor (TF) expression were performed 5 days (D5) after onset of endotoxic shock (initiated by 0.5 mg/kg intravenous bolus of Escherichia coli lipopolysaccharide (LPS)) with or without treatment with aPC injected as an intravenous 2 mg/kg bolus 1 hour after LPS (LPS+aPC group and LPS group, respectively).

Results

LPS decreased the sensitivity to phenylephrine (PE) in aortic rings without endothelium (E-) when compared to E- rings from the control group (p < 0.05). This was abolished by N^G-nitro-L-arginine methyl ester and not observed in E- rings from aPC-treated rabbits. Although aPC failed to decrease monocyte TF expression in endotoxinic animals at D5, aPC treatment restored the endothelium-dependent sensitivity in response to PE (2.0 ± 0.2 μM in rings with endothelium (E+) versus 1.0 ± 0.2 μM in E- rings (p < 0.05) in the LPS+aPC group versus 2.4 ± 0.3 μM in E+ rings versus 2.2 ± 0.2 μM in E- rings (p value not significant), in the LPS group). Endotoxin-induced de-endothelialisation was reduced by aPC at D5 (28.5 ± 2.3% in the LPS+aPC group versus 40.4 ± 2.4% in the LPS group, p < 0.05).

Conclusion

These data indicate that aPC increased the sensitivity to a vasoconstrictor agent (PE) associated with restoration of endothelial modulation, and protected against endothelial histological injury in endotoxin-induced shock. It failed to inhibit TF expression at D5 after LPS injection.

Coagulation interventions in experimental human endotoxemia

Recognition of the link between coagulation activation and inflammation has led to the hypothesis that anticoagulants may be effective in the treatment of septic patients by altering the inflammatory response. However, only limited methodologies exist that can be used in human volunteers to mimic the physiologic alterations observed in critically ill patients. The human endotoxemia model represents a model of inflammation-induced tissue factor triggered coagulation activation. As it permits elucidation of a key player in this proinflammatory and procoagulant response, it serves as a useful tool to investigate novel therapeutics in a standardized setting. The aim of this review is to focus on coagulation interventions in the human endotoxemia model.

A randomized clinical trial of unfractioned heparin for treatment of sepsis (the HETRASE study): design and rationale [NCT00100308]

INTRODUCTION

Infection promotes coagulation via a large number of molecular and cellular mechanisms, and this procoagulant activity has boosted basic and clinical research using anticoagulant molecules as therapeutic tools in sepsis. Heparin, which is a naturally occurring proteoglycan that acts by reducing thrombin generation and fibrin formation, has not been rigorously tested in a randomized clinical trial.

METHODS

Randomized, double-masked, placebo-controlled, single-center clinical trial. Patients are recruited through the emergency room at Hospital Universitario San Vicente de Paul. This is a 650-bed University Hospital in Medellín, Colombia and is a referral center for a region with approximately 3 million habitants. The recruitment process started on July 2005 and will finish on June 2007. Patients aged 18 years or older, males or females, hospitalized with clinically or microbiological confirmed sepsis, have been included. The interventions are unfractioned heparin in low dose continuous infusion (500 units per hour for 7 days) or placebo, additionally to the standard of care for sepsis patients in Colombia.

RESULTS

Our primary aims are to estimate the effects of heparin on hospital length of stay and change from baseline Multiple Organ Dysfunction (MOD) score. Secondary objectives are to estimate the effects of heparin on 28-day all-cause mortality, and to estimate the possible effect modification on 28-day all-cause mortality, in subgroups defined by source and site of infection, and baseline values of APACHE II score, MOD score and D-dimer.

CONCLUSION

The available literature in animal and human research, and the understanding of the molecular biology regarding inflammation and coagulation, supports a randomized clinical trial for the use of heparin in sepsis. Our study will provide appropriate power to detect differences in valid surrogate outcomes, and it will explore important preliminary data for efficacy regarding the clinical end-point of mortality.

Tissue factor upregulation drives a thrombosis-inflammation circuit in relation to cardiovascular complications

The extrinsic coagulation is recognized as an 'inducible' signalling cascade resulting from tissue factor (TF) upregulation by exposure to clotting zymogen FVII upon inflammation or tissue injury. Following the substantial initiation, an array of proteolytic activation generates mediating signals (active serine proteases: FVIIa, FXa and FIIa) that lead to hypercoagulation with fibrin overproduction manifesting thrombosis. In addition, TF upregulation plays a central role in driving a thrombosis-inflammation circuit. Coagulant mediators (FVIIa, FXa and FIIa) and endproduct (fibrin) are proinflammatory, eliciting tissue necrosis factor, interleukins, adhesion molecules and many other intracellular signals in different cell types. Such resulting inflammation could ensure 'fibrin' thrombosis via feedback upregulation of TF. Alternatively, the resulting inflammation triggers platelet/leukocyte/polymononuclear cell activation thus contributing to 'cellular' thrombosis. TF is very vulnerable to upregulation resulting in hypercoagulability and subsequent thrombosis and inflammation, either of which presents cardiovascular risks. The prevention and intervention of TF hypercoagulability are of importance in cardioprotection. Blockade of inflammation reception and its intracellular signalling prevents TF expression from upregulation. Natural (activated protein C, tissue factor pathway inhibitor, or antithrombin III) or pharmacological anticoagulants readily offset the extrinsic hypercoagulation mainly through FVIIa, FXa or FIIa inhibition. Therefore, anticoagulants turn off the thrombosis-inflammation circuit, offering not only antithrombotic but anti-inflammatory significance in the prevention of cardiovascular complications.

Bacterial endotoxin as inhibitor of the enzymatic activity of human thrombin

Endotoxemia caused by bacterial lipopolysaccharides (LPS) deleteriously affects many aspects of hemostasis. Much of this effect is well characterized as being secondary to the LPS-mediated inflammatory response, but direct effects of LPS on coagulation factors may also contribute to disregulation of the hemostatic process. Spectrophotometric assays were used to investigate the effects of LPS from different bacteria on thrombin and plasmin activities. We found that enzymatic activity of purified thrombin, but not plasmin, decreases in the presence of endotoxin. LPS-mediated inhibition of thrombin activity can be reversed by plasma gelsolin and recombinant endotoxin-neutralizing protein. Preincubation of thrombin with LPS before platelet activation results in inhibition of aggregation and secretion. Additionally, a decrease of elastic shear moduli of fibrin gels was observed when their formation was induced with thrombin preincubated with LPS or when LPS was present in fibrinogen solutions during fibrin gel formation. When added to platelet-rich plasma, after activation with collagen, LPS-inhibited thrombin activity. LPS-mediated inhibition of thrombin activity may contribute to the hemostasis dysfunctions observed during endotoxemia.

Recent acquisitions in the pathophysiology, diagnosis and treatment of disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is a disorder characterized by both acute generalized, widespread activation of coagulation, which results in thrombotic complications due to the intravascular formation of fibrin, and diffuse hemorrhages, due to the consumption of platelets and coagulation factors. Systemic activation of coagulation may occur in a variety of disorders, including sepsis, severe infections, malignancies, obstetric or vascular disorders, and severe toxic or immunological reactions.

In this review, we briefly report the present knowledge about the pathophysiology and diagnosis of DIC. Particular attention is also given to the current standard and experimental therapies of overt DIC.

Effects of recombinant human activated protein C in human models of endotoxin administration

Alterations in the generation of activated protein C (APC) as well as in the interactions of APC with the endothelial protein C receptor are present in severe sepsis and acute lung injury. Administration of recombinant human activated protein C (rhAPC) improves the survival of critically ill patients with sepsis, but the mechanisms by which rhAPC produces benefit are not well defined. Human models of systemic and pulmonary endotoxin exposure may provide important insights into the mechanisms of action of rhAPC in critical illness. In volunteers given systemic endotoxin, rhAPC had minimal effects on physiologic parameters, including blood pressure, markers of inflammation, and measures of sepsis-induced coagulopathy. In contrast, in the setting of pulmonary endotoxin exposure, rhAPC decreased neutrophil migration into the airspaces and also diminished neutrophil chemotaxis. Administration of rhAPC did not affect other parameters of neutrophil function, including kinase activation, production of proinflammatory cytokines, or apoptosis. Such results indicate that the effects of rhAPC in inhibiting the infiltration of neutrophils into the lungs and other inflammatory sites may contribute to its beneficial effects in sepsis.

Tissue factor-dependent coagulation is preferentially up-regulated within arterial branching areas in a baboon model of Escherichia coli sepsis

Endothelium plays a critical role in the pathobiology of sepsis by integrating systemic host responses and local rheological stimuli. We studied the differential expression and activation of tissue factor (TF)-dependent coagulation on linear versus branched arterial segments in a baboon sepsis model. Animals were injected intravenously with lethal doses of Escherichia coli or saline and sacrificed after 2 to 8 hours. Whole-mount arterial segments were stained for TF, TF-pathway inhibitor (TFPI), factor VII (FVII), and markers for endothelial cells (ECs), leukocytes, and platelets, followed by confocal microscopy and image analysis. In septic animals, TF localized preferentially at branches, EC surface, leukocytes, and platelet aggregates and accumulated in large amounts in the subendothelial space. FVII strongly co-localized with TF on ECs and leukocytes but less so with subendothelial TF. TFPI co-localized with TF and FVII on endothelium and leukocytes but not in the subendothelial space. Focal TF increases correlated with fibrin deposition and increased endothelial permeability to plasma proteins. Biochemical analysis confirmed that aortas of septic baboons expressed more TF mRNA and protein than controls. Branched segments contained higher TF protein levels and coagulant activity than equivalent linear areas. These data suggest that site-dependent endothelial heterogeneity and rheological factors contribute to focal procoagulant responses to E. coli.

Tetrahydrobiopterin corrects Escherichia coli endotoxin-induced endothelial dysfunction

Acute inflammation causes endothelial dysfunction, which is partly mediated by oxidant stress and inactivation of nitric oxide. The contribution of depletion of tetrahydrobiopterin (BH(4)), the cofactor required for nitric oxide generation, is unclear. In this randomized, double-blind, three-way crossover study, forearm blood flow (FBF) responses to ACh and glyceryltrinitrate (GTN) were measured before and 3.5 h after infusion of Escherichia coli endotoxin (LPS, 20 IU/kg iv) in eight healthy men. The effect of intra-arterial BH(4) (500 microg/min), placebo, or vitamin C (24 mg/min) was studied on separate days 3.5 h after LPS infusion. In addition, human umbilical vein endothelial cells were incubated for 24 h with vitamin C and LPS. ACh and GTN caused dose-dependent forearm vasodilation. The FBF response to ACh, which was decreased by 23 +/- 17% (P < 0.05) by LPS infusion, was restored to baseline reactivity by BH(4) and vitamin C. FBF responses to GTN were not affected by BH(4) or vitamin C. LPS increased leukocyte count, high-sensitivity C-reactive protein, IL-6, IL-1beta, IFN-gamma, monocyte chemoattractant protein-1, pulse rate, and body temperature and decreased platelet count and vitamin C concentration. Vitamin C increased forearm plasma concentration of BH(4) by 32% (P < 0.02). Incubation with LPS and vitamin C, but not LPS alone, increased intracellular BH(4) concentration in human umbilical vein endothelial cells. Impaired endothelial function during acute inflammation can be restored by BH(4) or vitamin C. Vitamin C may exert some of its salutary effects by increasing BH(4) concentration.

New insights into the protein C pathway: potential implications for the biological activities of drotrecogin alfa (activated)

It has been hypothesized that the protein C pathway is a pivotal link between the inflammation and coagulation cascades. The demonstration that a survival benefit is associated with administration of drotrecogin alfa (activated) (recombinant human activated protein C [APC]) in severe sepsis patients has provided new insights into the protein C pathway. APC was originally identified based on its antithrombotic properties, which result from the inhibition of activated Factors V and VIII. In the early 1990s, any potential anti-inflammatory properties of APC were thought to relate primarily to its inhibition of thrombin generation. However, the mid-1990s saw the identification of the endothelial protein C receptor (EPCR), which has subsequently been shown to be neither endothelial specific nor protein C specific, but has a primary function as a cofactor for enhancing the generation of APC or behaving as an APC receptor. Thus, the potential biologic activities of APC can be classed into two categories related either to the limiting of thrombin generation or to cellular effects initiated by binding to the EPCR. Intracellular signaling initiated by binding of APC to its receptor appears to be mediated by interaction with an adjacent protease-activated receptor (PAR), or by indirect activation of the sphingosine 1-phosphate pathway. Based mostly on in vitro studies, binding of APC to its receptor on endothelial cells leads to a decrease in thrombin-induced endothelial permeability injury, while such binding on blood cells, epithelial cells, and neurons has been shown to inhibit chemotaxis, be anti-apoptotic, and be neuroprotective, respectively. In the Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) study, drotrecogin alfa (activated) was associated with improved cardiovascular function, respiratory function, and a prevention of hematologic dysfunction. This article discusses the way in which the interactions of APC may alter the microcirculation.

Tissue factor mediates inflammation

The role of tissue factor (TF) in inflammation is mediated by blood coagulation. TF initiates the extrinsic blood coagulation that proceeds as an extracellular signaling cascade by a series of active serine proteases: FVIIa, FXa, and thrombin (FIIa) for fibrin clot production in the presence of phospholipids and Ca2+. TF upregulation resulting from its enhanced exposure to clotting factor FVII/FVIIa often manifests not only hypercoagulable but also inflammatory state. Coagulant mediators (FVIIa, FXa, and FIIa) are proinflammatory, which are largely transmitted by protease-activated receptors (PAR) to elicit inflammation including the expression of tissue necrosis factor, interleukins, adhesion molecules (MCP-1, ICAM-1, VCAM-1, selectins, etc.), and growth factors (VEGF, PDGF, bFGF, etc.). In addition, fibrin, and its fragments are also able to promote inflammation. In the event of TF hypercoagulability accompanied by the elevations in clotting signals including fibrin overproduction, the inflammatory consequence could be enormous. Antagonism to coagulation-dependent inflammation includes (1) TF downregulation, (2) anti-coagulation, and (3) PAR blockade. TF downregulation and anti-coagulation prevent and limit the proceeding of coagulation cascade in the generation of proinflammatory coagulant signals, while PAR antagonists block the transmission of such signals. These approaches are of significance in interrupting the coagulation-inflammation cycle in contribution to not only anti-inflammation but also anti-thrombosis for cardioprotection.

The role of microvascular thrombosis in sepsis

The acute inflammatory response to sepsis gives rise to significant morbidity and mortality. The mechanisms underlying this form of tissue injury are poorly understood. This review examines the evidence that tissue ischaemia due, to generalized microvascular thrombosis may play an important role. Microvascular thrombosis is probably an adaptive response that prevents bacteria in the tissues reaching the systemic circulation via the capillaries. In time, a definitive response by leucocytes removes the bacteria and repairs the damaged tissues. There is however evidence that if microvascular thrombosis becomes generalized, then extensive tissue ischaemia may precipitate organ failure and death. Post-mortem studies of patients with sepsis demonstrate microvascular thrombi in many organs including the kidney, liver, lung, gut, adrenals and brain, and the degree of organ injury is related to the quantity of thrombi. Furthermore studies in human and animal models of sepsis demonstrate therapies that inhibit coagulation or promote fibrinolysis reduce organ failure and mortality. In view of the personal and economic burdens that tissue injury associated with the acute inflammatory response places on the community, further studies to establish the role of microvascular thrombosis are clearly required. Such studies may lead to new therapies to limit or prevent this form of injury.

Effects of drotrecogin alfa (activated) in human endotoxemia

In a phase III clinical trial, drotrecogin alfa (activated) was shown to improve survival and promote faster improvement of cardiovascular and respiratory dysfunction in patients with severe sepsis. To further examine mechanisms involved in the action of this drug, a healthy human endotoxin model was used. Healthy volunteers (eight per group) received drotrecogin alfa (activated) or placebo intravenously for 8 h in a randomized, double-blind, controlled manner. After 2 h of study drug infusion, endotoxin (2 ng/kg) was infused and measurement of physiologic responses and biomarkers continued for 24 h. Consistent with results from severe sepsis clinical trials, drotrecogin alfa (activated) improved mean arterial pressure during the period of infusion after endotoxin exposure. In contrast to severe sepsis clinical trials using drotrecogin alfa (activated) but similar to another human endotoxin study, no significant antithrombotic, profibrinolytic, or anti-inflammatory effects were observed. These results suggest a novel role for drotrecogin alfa (activated) in the human endotoxin model.

Steady plasma concentration of unfractionated heparin reduces infarct volume and prevents inflammatory damage after transient focal cerebral ischemia in the rat

Unfractionated heparin (UH) decreases the extent of infarction after transient focal brain ischemia in the rat and abridges neuroinflammatory damage in patients with acute stroke. This study was aimed at assessing whether controlled and steady heparinemia in plasma can reduce infarct volume and exert neuroprotective effects after ischemia. Infarct volume was measured at 24 and 7 days following a 1-hr intraluminal middle cerebral artery (MCA) occlusion in rats treated with UH or with vehicle. After testing several UH administration protocols, we choose to give a bolus of 200 U/kg, which was started 3 hr after the occlusion, followed by a 24-hr intraperitoneal perfusion of 70 U/kg/hr, which maintained a 24-hr steady plasma heparinemia (0.3-0.6 U/ml) and caused no CNS or systemic bleeding. In addition, plasma IL-10 concentration was measured by ELISA, endothelial VCAM-1 expression was evaluated by i.v. injection of a (125)I-labeled monoclonal antibody against VCAM-1, and brain hemeoxygenase-1 (HO-1) expression was determined by Western blot. UH-treated rats showed smaller infarctions than rats treated with vehicle, as well as higher IL-10 plasma levels and HO-1 brain expression and lower endothelial VCAM-1 induction. The study shows that a stable plasma concentration of UH given at nonhemorrhagic doses reduces infarct volume after ischemia-reperfusion in the rat. It also shows that UH prevented the induction of cell adhesion molecules in the cerebral vasculature and increased the expression of molecules with antiinflammatory and prosurvival properties. These findings support further testing of the clinical value of parenteral, adjusted, high-dose UH in patients with acute stroke.

Human models of endotoxemia and recombinant human activated protein C

OBJECTIVES

To review human models of endotoxemia with an emphasis on the inflammatory and coagulopathic effects of lipopolysaccharide to describe the possible mechanisms of clinical benefit of recombinant human activated protein C (drotrecogin alfa [activated]) in severe sepsis.

DATA SOURCE

A selected review of published literature in English on human endotoxemia models with special attention to studies using drotrecogin alfa (activated) in concert with endotoxemia.

DATA EXTRACTION AND SYNTHESIS

After intravenous administration of purified lipopolysaccharide, subjects report constitutional influenza-like symptoms associated with an increase in temperature. Within 1 hr of lipopolysaccharide infusion, total leukocyte counts decline. Sustained leukocytosis, due to an increase in neutrophils counts, follows. An increase in markers of neutrophil activation (e.g., serum elastase) accompanies this leukocytosis. Production of tumor necrosis factor-alpha, interleukin-6, and interleukin-8 is also increased. In association with an inflammatory response, lipopolysaccharide administration also activates the coagulation system. Lipopolysaccharide infusion generates thrombin and initially activates fibrinolysis but subsequently generates inhibitors of the fibrinolytic system. Serum levels of endogenous inhibitors of coagulation (e.g., antithrombin, protein C, tissue factor pathway inhibitor) are not affected. Data are available for 40 subjects who have participated in placebo-controlled studies of drotrecogin alfa (activated) infusion before an intravenous dose of lipopolysaccharide. In these subjects, drotrecogin alfa (activated) has minimal effects on measured variables, including physiologic variables, markers of inflammation, and measures of sepsis-induced coagulopathy.

CONCLUSION

Human endotoxemia is, at best, an incomplete model of human sepsis. In two studies using recombinant human activated protein C in the setting of human endotoxemia, there were minimal effects on hemodynamics, inflammation, thrombin generation, fibrinolysis, and markers of cellular activation. Other putative mechanisms of recombinant human activated protein C, such as inhibition of apoptosis and leukocyte recruitment, remain to be studied.

Inflammation-induced vasoconstrictor hyporeactivity is caused by oxidative stress

OBJECTIVES

We sought to determine the role of oxidative stress in the development of vascular dysfunction in inflammation.

BACKGROUND

Hyporeactivity to catecholamines and other vasoconstrictors is present in acute inflammation. Because oxidative stress plays a significant role in inflammation, impaired responsiveness may be overcome by anti-oxidants.

METHODS

In randomized, double-blind, cross-over studies, forearm blood flow (FBF) responses to norepinephrine (NE), angiotensin II (ANG II), and vasopressin (VP) were assessed before and 4 h after induction of systemic inflammation by low doses of Escherichia coli endotoxin (lipopolysaccharide [LPS], 20 IU/kg intravenously) or after placebo in healthy volunteers. Furthermore, the effect of intra-arterial vitamin C (24 mg/min) or placebo on NE-induced or ANG II-induced vasoconstriction was studied after LPS.

RESULTS

Administration of LPS caused systemic and forearm vasodilation, increased white blood cell count, elevated body temperature, and reduced vitamin C plasma concentrations. Lipopolysaccharide decreased the responses of FBF to NE by 59%, to ANG II by 25%, and to VP by 51% (n = 9, p < 0.05, all effects). Co-administration of vitamin C completely restored the response to NE and to ANG II, which was comparable to that observed under baseline conditions (n = 8).

CONCLUSIONS

E. coli-endotoxemia reduces FBF responsiveness to vasoconstrictors. The hyporeactivity can be corrected by high doses of vitamin C, suggesting that oxidative stress may represent an important target for inflammation-induced impaired vascular function.

Recombinant human activated protein C (rhAPC; drotrecogin alfa [activated]) has minimal effect on markers of coagulation, fibrinolysis, and inflammation in acute human endotoxemia

Inflammatory and procoagulant host responses are closely related in sepsis. The protein C pathway serves as a regulatory pathway with anti-inflammatory and anticoagulant properties. Recently, recombinant human activated protein C (rhAPC) was shown to reduce mortality in severe sepsis. Nevertheless, the effects of rhAPC in humans are still ill defined. The infusion of low endotoxin doses into humans provides a standardized model to study inflammatory and hemostatic mechanisms. Thus, we investigated whether rhAPC acts as an anticoagulant or anti-inflammatory drug in human endotoxemia. There were 24 volunteers randomized to receive either 24 microg/kg per hour rhAPC or placebo intravenously for 8 hours. Lipopolysaccharide (LPS, 2 ng/kg) was administered 2 hours after starting the infusions. rhAPC decreased basal tissue factor (TF)-mRNA expression, and thrombin formation and action. In contrast, rhAPC did not significantly blunt LPS-induced thrombin generation. Consistently, rhAPC did not reduce LPS-induced levels of TF-mRNA or D-dimer and had no effect on fibrinolytic activity or inflammation. Finally, endogenous APC formation was enhanced during endotoxemia and appeared to be associated with inflammation rather than thrombin formation. In conclusion, even low-grade endotoxemia induces significant protein C activation. Infusion of rhAPC decreases "spontaneous" activation of coagulation but does not blunt LPS-induced, TF-mediated coagulation in healthy volunteers, which is in contrast to a number of anticoagulants.

Enalapril does not alter adhesion molecule levels in human endotoxemia

The angiotensin-converting enzyme inhibitor (ACE-I) enalapril has been shown to lower elevated levels of circulating adhesion molecules (cAM) in critically ill patients. To delineate the mechanisms of this possibly beneficial effect of enalapril, we studied the acute effects of enalapril in a well-defined model of endotoxin-triggered, cytokine-mediated cAM up-regulation. In a randomized, controlled trial, 30 healthy male volunteers received 2 ng/kg lipopolysaccharide (LPS) after pretreatment with placebo or 20 mg/day enalapril for 5 days or with a single dose of 20 mg of enalapril 2 h before LPS infusion. LPS infusion increased TNF levels 300-fold above normal, circulating (c) E-selectin levels by 425% (CI, 359%-492%), and P-selectin, VCAM-1, ICAM-1, and von Willebrand factor levels by 47%-74%. LPS infusion also enhanced ICAM-1 and CD11b expression 2- to 3-fold on monocytes. However, no differences were seen between treatment groups (P > 0.05), despite 95% inhibition of ACE activity by enalapril. Inhibition of ACE activity by enalapril does not influence plasma indices of endothelial activation after endotoxin infusion in healthy individuals. Our results do not support the concept of a beneficial clinical effect of enalaprilat in septicemia.

Evaluation of antiinflammatory and antiadhesive effects of heparins in human endotoxemia

OBJECTIVE

Cytokines and adhesion molecules have a decisive role in the development of early inflammatory response as well as the late sequelae of sepsis. Because L-selectin-deficient mice are protected from lethal endotoxemia, blockade of L-selectin may provide a useful therapeutic option in human sepsis. Heparin has immunomodulatory properties and effectively inhibits L- and P-selectin binding in vitro. We therefore investigated whether clinically applied doses of unfractionated or low-molecular-weight heparin affect early inflammatory response in human endotoxemia.

DESIGN

The study was randomized, double-blinded, placebo-controlled, in three parallel groups consisting of 30 healthy male volunteers.

SETTING

University medical center.

INTERVENTIONS

All subjects received a 2-ng/kg intravenous bolus of lipopolysaccharide and 10 mins later unfractionated heparin, low-molecular-weight heparin, or placebo as bolus primed continuous infusion for 6 hrs.

MEASUREMENTS AND MAIN RESULTS

Lipopolysaccharide infusion induced similar increases of tumor necrosis factor-alpha, interleukin-6, interleukin-8, C-reactive protein, and soluble E-selectin levels in all treatment groups. CD11b expression increased by approximately 400%, but L-selectin decreased by 41% in the placebo arm 6 hrs after lipopolysaccharide infusion. Interestingly, both heparins (in particular unfractionated heparin) decreased L-selectin down-regulation as compared with placebo. Similarly, the decrease in lymphocyte counts was significantly less in the unfractionated heparin group during the first 24 hrs (p <.05 vs. placebo)

CONCLUSIONS

Heparins displayed little effects on cytokine production and endothelial cell activation in endotoxemia. Of note, however, unfractionated heparin reduced L-selectin down-regulation and lymphocytopenia. These could present novel mechanisms of action of unfractionated heparin.

Evaluation of Coagulation Markers for Early Diagnosis of Acute Coronary Syndromes in the Emergency Room

Background: Diagnosis of acute coronary syndromes (ACS) is a major challenge for emergency physicians. Because soluble fibrin (sF) has been suggested as a potential early marker of impending myocardial ischemia, we were interested whether a sF bedside test could help in early identification of patients with ACS in the emergency department.

Methods: We evaluated plasma coagulation markers, including a newly developed sF bedside test, prothrombin fragment (F1+2), sF, and D-dimer, in a cross-sectional trial with 184 patients suggestive of ACS.

Results: Whereas 76% (13 of 17) of patients with unstable angina pectoris (UAP) had a positive sF bedside test, only 10 of 33 patients (30%) with non-ST-segment-elevation myocardial infarction and 10 of 44 patients (23%) with ST-elevation myocardial infarction tested positive. Three percent of controls (1 of 33) and 11% of patients (6 of 57) with preexisting stable angina had a positive sF bedside test (P &lt;0.001 for noncardiac chest pain vs ACS), yielding an overall specificity of 92% and a sensitivity of 35%. The sensitivity of the established coagulation markers was significantly less to detect ACS (11% for F1+2, 20% for thrombus precursor protein, and 18% for D-dimer; P &lt;0.02 vs sF bedside test). The sF bedside test presented the earliest objective indicator of impending myocardial damage in the majority (10 of 13) of ACS patients with a normal or nondiagnostic electrocardiogram (ECG).

Conclusions: A sF bedside test offers a specific tool for early identification of patients with ACS in an emergency department setting, although its sensitivity seems sufficient only for the early identification of patients with UAP. A sF bedside test could be useful, particularly in UAP patients with a nondiagnostic ECG.

Point of care measurement of lepirudin and heparin anticoagulation during systemic inflammation

BACKGROUND

The number of indications for recombinant human hirudin lepirudin therapy has increased in recent years, and now includes acute coronary syndromes and heparin-induced thrombocytopenia. Hence, point of care monitoring appears desirable for therapy with lepirudin. As CoaguChek Plus (CCP) provides a rapid bedside test to monitor therapy with other anticoagulants, we aimed to determine its suitability for lepirudin therapy.

METHODS

Forty-four healthy volunteers received a 2 ng/kg endotoxin infusion (to induce coagulation) together with clinically relevant doses of lepirudin or heparin in a prospective, placebo-controlled, randomised fashion. Measurements of CCP-partial thromboplastin time (aPTT) were compared to laboratory STA-aPTT.

RESULTS

As expected, baseline values of CCP-aPTT were shorter than STA-aPTT. Lepirudin increased CCP-aPTT 3-fold, and STA-aPTT 2-fold 1 h after bolus infusion. During lepirudin infusion, the correlation between CCP-aPTT and STA-aPTT was excellent (r=0.86-0.92). Both methods were equally sensitive to over-anticoagulation with heparin. Acute systemic inflammation had little effects on CCP-aPTT.

CONCLUSION

CCP-aPTT is suitable for longitudinal point of care monitoring of lepirudin therapy. As baseline values of CCP-aPTT are shorter than STA-aPTT, it is recommended not to indiscriminately change between methods in the follow-up of individual patients.

Unfractionated heparin is associated with a lower rise of serum vascular cell adhesion molecule-1 in acute ischemic stroke patients

We sought to assess the anti-inflammatory properties of unfractionated heparin (UFH) in patients with ischemic stroke treated within 24 h from the onset of symptoms. We studied prospectively 167 patients that received 1000 IU/h intravenous UFH (n=70) or 300 mg oral aspirin (n=97) at a mean treatment delay of 6.7 h. Repeated plasma levels of interleukin (IL)-6, IL-10, IL-4, tumor necrosis factor (TNF)-alpha, soluble intercellular adhesion molecule-1 (sICAM-1), and soluble vascular cell adhesion molecule-1 (sVCAM-1) were compared in both groups using multivariate analyses. Whereas TNF-alpha and sICAM-1 decreased at 48 h, IL-6, IL-4, and sVCAM-1 increased compared with baseline values (P<0.01). The rise of sVCAM-1 levels at 48 h was significantly lower in patients treated with UFH (P=0.017) and a two-fold increase of baseline sVCAM-1 was an independent predictor of poor outcome (odds ratio, 2.19, 1.1-4.39). These results suggest that adjusted high-dose UFH has anti-inflammatory effects which might improve recovery if administered early after stroke onset.

Effects of anticoagulation on thrombopoietin release during endotoxemia

Several lines of evidence suggest that coagulation may induce the release of thrombopoietin (TPO) into plasma and that TPO levels are higher in disseminated intravascular coagulation. Therefore we set out to illuminate the mechanism of TPO release in the setting of experimental endotoxemia, which induces activation of coagulation and platelets. Endotoxin (lipopolysachharide [LPS], 2 ng/kg) was infused into a total of 54 healthy men in two subsequent studies. Volunteers received infusions of unfractionated heparin, low-molecular-weight heparin, lepirudin, or placebo in a randomized, placebo-controlled fashion after bolus injection of LPS. TPO levels increased on average by 27% to 38% in all groups at 6 hours (P <.05 vs baseline), although all active drugs effectively blocked coagulation. Platelet counts dropped by about 15% at 1 hour after LPS infusion, recovered after 2 days, and exceeded baseline values by 8% to 18% after 7 days (P <.001 vs baseline for all groups). Yet lepirudin blunted the LPS-induced increase in circulating P-selectin by one half (P <.005 vs placebo), whereas both heparins did not diminish the increase in this platelet or endothelial activation marker as compared with placebo. Endotoxemia enhances TPO plasma levels independent of the degree of coagulation induction, which eventually results in increased platelet numbers. Of potential clinical interest is the observation that the direct thrombin inhibitor lepirudin, in contrast to heparins, mitigated LPS-induced platelet activation.

Biocompatibility of a cuprophane charcoal-based detoxification device in cirrhotic patients with hepatic encephalopathy

Extracorporeal detoxification has been proposed to treat patients with hepatic encephalopathy (HE) not responding to standard therapy. To investigate the biocompatibility of a cuprophane charcoal-based detoxification device, a prospective, randomized, controlled study was performed. Of 41 consecutive patients with cirrhosis and HE grade II or III who did not improve with conventional treatment, 20 patients (median age, 56 years; range, 33 to 71 years; 13 men) were randomly assigned to either ongoing conventional treatment or one additional 6-hour treatment with a sorbent suspension dialysis system. Main outcome parameters were physiological function and blood parameters of biocompatibility. In the 10 patients undergoing combined conventional and sorbent suspension dialysis treatment, blood pressure remained unchanged and body temperature and heart rate increased (P: < 0.01). Platelet count decreased (medians, from 75 to 26 g/L; P: < 0.001) and international normalized ratio increased after combined treatment (2.0 to 2.2; P: < 0.001). Three patients developed bleeding complications during treatment or shortly after. Treated patients showed increases in levels of plasma elastase (104 to 586 microg/L; P: = 0.001), tumor necrosis factor-alpha (5.4 to 7.5 pg/mL; P: = 0.04), and interleukin-6 (118 to 139 pg/mL; P: = 0.04), but not interferon-gamma and E-selectin. No changes were observed in the 10 patients treated conventionally. In conclusion, despite technical refinements compared with charcoal hemoperfusion, biocompatibility of sorbent suspension dialysis is still very limited. Clinical complications were apparently caused by blood-membrane interactions and disseminated intravascular coagulation. We suggest further developments in design and appropriate strategies of anticoagulation to improve the biocompatibility of artificial liver support.

Lepirudin blunts endotoxin-induced coagulation activation

During sepsis, lipopolysaccharide (LPS) triggers the development of disseminated intravascular coagulation (DIC) via the tissue factor-dependent pathway of coagulation resulting in massive thrombin generation and fibrin polymerization. Recently, animal studies demonstrated that hirudin reduced fibrin deposition in liver and kidney and decreased mortality in LPS-induced DIC. Accordingly, the effects of recombinant hirudin (lepirudin) was compared with those caused by placebo on LPS-induced coagulation in humans. Twenty-four healthy male subjects participated in this randomized, double-blind, placebo-controlled, parallel group study. Volunteers received 2 ng/kg LPS intravenously, followed by a bolus-primed continuous infusion of placebo or lepirudin (Refludan, bolus: 0.1 mg/kg, infusion: 0.1 mg/kg/h for 5 hours) to achieve a 2-fold prolongation of the activated partial thromboplastin time (aPTT). LPS infusion enhanced thrombin activity as evidenced by a 20-fold increase of thrombin-antithrombin complexes (TAT), a 6-fold increase of polymerized soluble fibrin, termed thrombus precursor protein (TpP), and a 4-fold increase in D-dimer. In the lepirudin group, TAT increased only 5-fold, TpP increased by only 50%, and D-dimer only slightly exceeded baseline values (P &lt; .01 versus placebo). Concomitantly, lepirudin also blunted thrombin generation evidenced by an attenuated rise in prothrombin fragment levels (F1 + 2,P &lt; .01 versus placebo) and blunted the expression of tissue factor on circulating monocytes. This experimental model proved the anticoagulatory potency of lepirudin in LPS-induced coagulation activation. Results from this trial provide a rationale for a randomized clinical trial on the efficacy of lepirudin in DIC.