Lepirudin blunts endotoxin-induced coagulation activation

Disseminated intravascular coagulation: epidemiology, biomarkers, and management

Disseminated intravascular coagulation (DIC) is a systemic activation of the coagulation system, which results in microvascular thrombosis and, simultaneously, potentially life-threatening haemorrhage attributed to consumption of platelets and coagulation factors. Underlying conditions, e.g. infection, cancer, or obstetrical complications are responsible for the initiation and propagation of the DIC process. This review provides insights into the epidemiology of DIC and the current understanding of its pathophysiology. It details the use of diagnostic biomarkers, current diagnostic recommendations from international medical societies, and it provides an overview of emerging diagnostic and prognostic biomarkers. Last, it provides guidance on management. It is concluded that timely and accurate diagnosis of DIC and its underlying condition is essential for the prognosis. Treatment should primarily focus on the underlying cause of DIC and supportive treatment should be individualised according to the underlying aetiology, patient's symptoms and laboratory records.

Human lipopolysaccharide models provide mechanistic and therapeutic insights into systemic and pulmonary inflammation

Inflammation is a key feature in the pathogenesis of sepsis and acute respiratory distress syndrome (ARDS). Sepsis and ARDS continue to be associated with high mortality. A key contributory factor is the rudimentary understanding of the early events in pulmonary and systemic inflammation in humans, which are difficult to study in clinical practice, as they precede the patient's presentation to medical services. Lipopolysaccharide (LPS), a constituent of the outer membrane of Gram-negative bacteria, is a trigger of inflammation and the dysregulated host response in sepsis. Human LPS models deliver a small quantity of LPS to healthy volunteers, triggering an inflammatory response and providing a window to study early inflammation in humans. This allows biological/mechanistic insights to be made and new therapeutic strategies to be tested in a controlled, reproducible environment from a defined point in time. We review the use of human LPS models, focussing on the underlying mechanistic insights that have been gained by studying the response to intravenous and pulmonary LPS challenge. We discuss variables that may influence the response to LPS before considering factors that should be considered when designing future human LPS studies.

Management of acute ischemic stroke in patients with COVID-19 infection: Report of an international panel

Background and purpose

On 11 March 2020, World Health Organization (WHO) declared the COVID-19 infection a pandemic. The risk of ischemic stroke may be higher in patients with COVID-19 infection similar to those with other respiratory tract infections. We present a comprehensive set of practice implications in a single document for clinicians caring for adult patients with acute ischemic stroke with confirmed or suspected COVID-19 infection.

Methods

The practice implications were prepared after review of data to reach the consensus among stroke experts from 18 countries. The writers used systematic literature reviews, reference to previously published stroke guidelines, personal files, and expert opinion to summarize existing evidence, indicate gaps in current knowledge, and when appropriate, formulate practice implications. All members of the writing group had opportunities to comment in writing on the practice implications and approved the final version of this document.

Results

This document with consensus is divided into 18 sections. A total of 41 conclusions and practice implications have been developed. The document includes practice implications for evaluation of stroke patients with caution for stroke team members to avoid COVID-19 exposure, during clinical evaluation and performance of imaging and laboratory procedures with special considerations of intravenous thrombolysis and mechanical thrombectomy in stroke patients with suspected or confirmed COVID-19 infection.

Conclusions

These practice implications with consensus based on the currently available evidence aim to guide clinicians caring for adult patients with acute ischemic stroke who are suspected of, or confirmed, with COVID-19 infection. Under certain circumstances, however, only limited evidence is available to support these practice implications, suggesting an urgent need for establishing procedures for the management of stroke patients with suspected or confirmed COVID-19 infection.

Defibrotide enhances fibrinolysis in human endotoxemia - a randomized, double blind, crossover trial in healthy volunteers

Defibrotide is approved for the treatment of sinusoidal obstruction syndrome after allogeneic stem cell transplantation. The exact mode of action of defibrotide is unclear and human in vivo data are scarce. In this randomized, double blind, crossover trial we included 20 healthy volunteers. Four were randomized to receive placebo, while 16 received a 2 ng/kg bodyweight bolus of lipopolysaccharide (LPS). Infusion of 6.25 mg/kg defibrotide or placebo was started one hour before the injection of the LPS bolus. Plasma levels of prothrombin fragments F1 + 2, thrombin-antithrombin complexes, von Willebrand factor, E-selectin, tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), plasmin-antiplasmin complexes (PAP), tumor necrosis factor-α, interleukin 6, and C-reactive protein were measured. Thromboelastometry was performed. Infusion of defibrotide did not reduce the LPS-induced activation of coagulation, the endothelium or the release of pro-inflammatory cytokines. However, defibrotide increased t-PA antigen levels by 31% (Quartiles: 2–49%, p = 0.026) and PAP concentrations by 13% (−4–41%, p = 0.039), while PAI-1 levels remained unaffected. Moreover, defibrotide reduced C-reactive protein levels by 13% (0–17%, p = 0.002). A transient increase in the clotting time in thromboelastometry and a decrease in F1 + 2 prothrombin fragments suggests modest anticoagulant properties. In conclusion, defibrotide infusion enhanced fibrinolysis and reduced C-reactive protein levels during experimental endotoxemia.

Disseminated Intravascular Coagulation: An Update on Pathogenesis, Diagnosis, and Therapeutic Strategies

Disseminated intravascular coagulation (DIC) is an acquired clinicobiological syndrome characterized by widespread activation of coagulation leading to fibrin deposition in the vasculature, organ dysfunction, consumption of clotting factors and platelets, and life-threatening hemorrhage. Disseminated intravascular coagulation is provoked by several underlying disorders (sepsis, cancer, trauma, and pregnancy complicated with eclampsia or other calamities). Treatment of the underlying disease and elimination of the trigger mechanism are the cornerstone therapeutic approaches. Therapeutic strategies specific for DIC aim to control activation of blood coagulation and bleeding risk. The clinical trials using DIC as entry criterion are limited. Large randomized, phase III clinical trials have investigated the efficacy of antithrombin (AT), activated protein C (APC), tissue factor pathway inhibitor (TFPI), and thrombomodulin (TM) in patients with sepsis, but the diagnosis of DIC was not part of the inclusion criteria. Treatment with APC reduced 28-day mortality of patients with severe sepsis, including patients retrospectively assigned to a subgroup with sepsis-associated DIC. Treatment with APC did not have any positive effects in other patient groups. The APC treatment increased the bleeding risk in patients with sepsis, which led to the withdrawal of this drug from the market. Treatment with AT failed to reduce 28-day mortality in patients with severe sepsis, but a retrospective subgroup analysis suggested possible efficacy in patients with DIC. Clinical studies with recombinant TFPI or TM have been carried out showing promising results. The efficacy and safety of other anticoagulants (ie, unfractionated heparin, low-molecular-weight heparin) or transfusion of platelet concentrates or clotting factor concentrates have not been objectively assessed.

Dual inhibition of thrombin and activated factor X attenuates disseminated intravascular coagulation and protects organ function in a baboon model of severe Gram-negative sepsis

Background

Inhibition of procoagulant pathways may improve outcome in sepsis. We examined whether a dual short-acting thrombin (factor II) and factor X (FX)a inhibitor (SATI) ameliorates sepsis-induced disseminated intravascular coagulation (DIC) and is organ-protective.

Methods

Escherichia coli were infused for 2 h in 22 anesthetized baboons. The control (CO) group (n = 8) received sterile isotonic solution only. In the treatment groups, SATI was administered starting 15 minutes after the end of the bacterial exposure. In the low-dose group (LD-SATI, n = 8), SATI was infused with 75 μg/kg/h for the first hour, followed by 23 μg/kg/h until the end of the study. In the high-dose SATI group (HD-SATI, n = 6), 225 μg/kg/h was administered for the first hour followed by continuous infusion of 69 μg/kg/h until termination of the study.

Results

Sepsis-induced DIC was attenuated, as reflected by lower peak thrombin-antithrombin complexes (threefold) and D-dimer levels (twofold) in both SATI groups compared to the CO. This coincided with strongly improved cell/organ protection assessed by decreased levels of lactate dehydrogenase (threefold), creatinine (twofold), aspartate aminotransferase (threefold), and amylase (twofold) compared to the CO group. Anuria, which started at 8 h in the CO group, was prevented in both SATI groups. Peak interleukin-6 release at 12 h was prevented in the treatment groups. In both SATI groups, fewer catecholamines were necessary and no bleeding complications were observed.

Conclusions

Dual inhibition of thrombin and FXa preserved activation of coagulation, protected organ function and ameliorated inflammation in severe Gram-negative sepsis in baboons. SATI could be a novel therapeutic agent against sepsis-induced DIC.

Obesity and Sepsis

Obesity has reached epidemic proportions over the last few decades. Obesity is associated with increased morbidity and mortality in hypertension, cardiovascular diseases, stroke, and cancer and is feared to decrease overall life expectancy over the next few decades. There is a growing body of evidence suggesting that obesity is a chronic inflammatory disease. Obesity is becoming a cause of concern in critically ill patients as well. Sepsis is the number one cause of morbidity and mortality in noncoronary artery disease critical care units all over the world and is associated with a high cost of care. An increase in morbidity in obese septic patients compared with lean people is a cause of growing concern. Laboratory evidence suggests that there is exaggeration in the inflammatory and prothrombogenic phenotype assumed by obese compared with lean septic animals. The exact mechanisms underlying this phenomenon are unknown. This article reviews some of the pathophysiological processes responsible for the underlying inflammation in obesity and sepsis and reviews the literature for the association of the two.

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

Establishment of a low dose canine endotoxemia model to test anti-inflammatory drugs: effects of prednisolone

Infusion of low doses of lipopolysaccharide (LPS) in human volunteers provides a standardised model to study novel anti-inflammatory drugs. However, low dose endotoxemia is not well characterised in animals larger than rodents and trials with immunomodulating substances are scarce. We conducted a dose-finding study to establish a canine endotoxemia model combining optimal cytokine response with minimal burden for the animals. We thereafter evaluated the pharmacodynamics and pharmacokinetics (PK) of prednisolone. For dose-finding, dogs randomly received a single bolus of 0.03, 0.1 or 1.0 microg/kg BW LPS i.v. The second part was a randomised, placebo controlled trial with 4 parallel groups. Either 0.25, 0.5 or 5mg/kgBW prednisolone or placebo were given for 3 days. On day 3, all animals received 0.1microg/kg BW LPS i.v. Blood was sampled to measure interleukin 6 (IL-6) and tumor necrosis factor-alpha, C-reactive protein, prednisolone and cortisol concentrations. In accordance with human endotoxemia, LPS substantially and dose-dependently increased IL-6 and TNF-alpha several 1000-fold. Prednisolone significantly attenuated the LPS-induced IL-6 and TNF-alpha responses by a maximum of 96 percent (p less than 0.03 for all treatment groups) and significantly reduced peak cortisol concentrations in a dose-dependent way (p less than 0.004 for all treatment groups). PK showed a non-linear kinetic. In conclusion, this dog model could provide a reliable setting to test experimental drugs for canine or human use.

Fucoidan extracted from Fucus evanescens prevents endotoxin-induced damage in a mouse model of endotoxemia

An important problem of treating patients with endotoxemia is to find drugs to reduce the negative effects of endotoxin on the organism. We tested fucoidan (sulfated polysaccharide) from the brown alga Fucus evanescens as a potential drug in a mouse model of endotoxemia inducted by lipopolysaccharide (LPS). The survival time of mice injected with LPS increased under fucoidan treatment compared with the group of mice injected with LPS only. The preventive administration of fucoidan to mice with endotoxemia resulted in inhibition of increased levels of proinflammatory cytokines (TNFα and IL-6), as well as decreasing of the processes of hypercoagulability. The parenteral or per os administration of fucoidan resulted in decreasing the degree of microcirculatory disorders and secondary dystrophic-destructive changes in parenchymal organs of mice with endotoxemia. Taken together, these results demonstrate that fucoidan prevents endotoxin-induced damage in a mouse model of endotoxemia and increases the mice's resistance to LPS.

Update on the Treatment of Disseminated Intravascular Coagulation

Disseminated intravascular coagulation (DIC) is characterized by an acute generalized, widespread activation of coagulation, which results in thrombotic complications, due to the intravascular formation of fibrin, as well as diffuse hemorrhages, due to the consumption of platelets and coagulation factors. In this review, we briefly report the present knowledge about the treatment of DIC. We focus on the current standard treatment of overt DIC in clinical practice. Moreover, particular attention is made to novel therapeutic strategies, who reflect the important progresses in the understanding of the pathogenesis of this syndrome in the last few years.

Differential ability of tissue factor antibody clones on detection of tissue factor in blood cells and microparticles

INTRODUCTION

Tissue factor (TF), the primary initiator of coagulation in vivo, plays a major role in both thrombosis and hemostasis. The expression of TF in monocytes is well documented, but its presence in other blood cells has been disputed, possibly due to methodological variations among different studies.

MATERIALS AND METHODS

We studied TF expression on platelets, monocytes, lymphocytes and microparticles (MPs) by flow cytometry (FCM) with five commercially available mouse anti-human TF antibodies (HTF-1, TF9-10H10, CLB/TF-5, VIC7 and VD8). The ability of different TF antibodies to inhibit cell surface TF activity was explored by incubating LPS-stimulated monocytes and MPs derived from LPS-stimulated monocytes (MMPs) with TF antibodies followed by measuring TF activity.

RESULTS

HTF-1 detected TF only on LPS-stimulated monocytes, whereas, TF9-10H10 and VD8 detected TF associated with MPs and MMPs in addition to LPS stimulated monocytes. Surprisingly, CLB/TF-5 and VIC7 detected TF on platelets, monocytes even under unstimulated conditions, in addition to MPs and MMPs. CLB/TF-5 also detected TF on unstimulated lymphocytes. Inhibitory studies showed that at a final concentration of 10 μg/mL, HTF-1, CLB/TF-5 and VD8 inhibited monocyte TF activity by 81-84% and MMP TF activity by 92-96%; whereas TF9-10H10 had no inhibitory effect on TF activity in monocytes and MMPs.

CONCLUSIONS

Our results suggest non-specific binding by the CLB/TF-5 and VIC7 antibodies in a FCM test system and explain at least some of the reports on TF presence in blood cells, particularly TF associated with platelets and MPs. TF9-10H10 and VD8 are more suitable to detect TF on MPs by FCM.

Thrombin as a multi-functional enzyme. Focus on in vitro and in vivo effects

Thrombin is the central protease in the coagulation cascade and one of the most extensively studied of all enzymes. In addition to its recognised role in the coagulation cascade and haemostasis, thrombin is known to have multiple pleiotropic effects, which mostly have been shown only in in vitro studies: it plays a role in inflammation and cellular proliferation and displays a mitogen activity on smooth muscle cells and endothelial cells, predominantly by activation of angiogenesis. In vivo , thrombin effects were examined in animal models of intravenous or intraarterial thrombin infusion. An extensive literature search regarding in vivo data showed that i) thrombin administered as a bolus causes microembolism, ii) thrombin infused slowly at steady-state conditions (up to 1.6 U/kg/min) leads to bleeds but not to intravascular clotting, iii) large quantity of thrombin infused at low rates (0.05 U/kg/min) does not have any measurable effect, and iv) thrombin increases vascular permeability leading to tissue damage. Although several decades of research on thrombin functions have provided a framework for understanding the biology of thrombin, animal and human studies with use of newer laboratory techniques are still needed to confirm the pleiotropic thrombin functions shown in in vitro studies.

Heparin protects against septic mortality via apoE-antagonism

BACKGROUND

Apolipoprotein E (apoE), a component of plasma lipoproteins, increases septic mortality in a rodent model of sepsis, presumably by enhancing lipid antigen presentation to antigen-presenting cells via the low-density lipoprotein receptor (LDLR). Downstream, this culminates in natural killer T (NKT) cell activation and cytokine secretion. To determine whether apoE antagonism would protect against septic mortality in mice, apoE-LDLR binding was antagonized using heparin, which can inhibit apoE's LDLR-binding site.

METHODS

C57BL/6 mice underwent cecal ligation and puncture (CLP) and heparin infusion. Serum partial thromboplastin time and alanine aminotransferase were measured at 24 hours, and survival was monitored for 7 days after CLP. LDLR+/+ and LDLR-/- fibroblasts were incubated with apoE and heparin to measure apoE internalization. Hepatic NKT cells and cytokine levels were quantified via fluorescence-activated cell sorting.

RESULTS

Heparin decreased CLP-induced mortality by 50% versus saline-treated controls, independent of anticoagulation. LDLR+/+ fibroblasts displayed decreased uptake of apoE when treated concurrently with heparin for 12 hours. In septic mice, hepatic alanine aminotransferase levels, hepatic NKT cells, and plasma cytokine levels decreased after heparin treatment.

CONCLUSIONS

This study demonstrates that heparin protects against septic mortality independent of its anticoagulant effect. This protective effect is associated with the inhibition of apoE-LDLR binding, diminished NKT proliferation and cytokine production, and hepatic dysfunction. These findings indicate a potential clinical role for apoE antagonism in the treatment of sepsis.

Factor V Leiden mutation enhances fibrin formation and dissolution in vivo in a human endotoxemia model

Disseminated intravascular coagulation in sepsis is associated with microvascular thrombosis and organ dysfunction. It was expected that prothrombotic disposition such as factor V Leiden (FVL) mutation would worsen clinical outcome. Astonishingly, clinical trial and animal experimental data indicate that FVL can be associated with improved survival. This study investigated the effect of FVL on the response to endotoxin of the coagulation and fibrinolytic system in humans. Fourteen healthy male subjects without FVL and 15 healthy males with heterozygous FVL received an intravenous bolus dose of endotoxin, 2 ng/kg of body weight. Blood samples were drawn before and 1, 2, 4, 6, and 24 hours after administration of the endotoxin. Injection of endotoxin led to a more pronounced increase in soluble fibrin in patients with FVL than in controls. Patients with FVL displayed a more sustained increase in plasmin-plasmin inhibitor complex after 4, 6, and 24 hours. Patients with FVL mutation also displayed higher levels of D-dimer and fibrinogen-fibrin degradation products in plasma after 24 hours. Patients with FVL generate higher levels of soluble fibrin, which may serve as cofactor in tissue plasminogen activator-induced plasminogen activation, leading to a more sustained activation of fibrinolysis with production of more fibrinogen- and fibrin-degradation products.

Racial differences in endotoxin-induced tissue factor-triggered coagulation

BACKGROUND

Racial differences in coagulation are poorly understood. While some studies suggest a 'prothrombotic' coagulation profile in blacks compared with whites, others report an increased bleeding risk for blacks in various clinical settings. Moreover, preclinical data suggest a link between the Duffy antigen (=DARC, Duffy antigen receptor of chemokines) and coagulation.

OBJECTIVES

Based on our previous research in Duffy antigen negative Africans, we hypothesized that Africans have an attenuated procoagulant response compared with Caucasians in a model of lipopolysaccharide (LPS)-induced, tissue factor (TF)-triggered coagulation activation.

PATIENTS/METHODS

Healthy male volunteers (16 Duffy-negative Africans, 16 Duffy-positive Caucasians) received 2 ng kg(-1) LPS, and outcome parameters were measured using enzyme immunoassays and real-time polymerase chain reaction (RT-PCR, Taqman).

RESULTS

LPS increased microparticle (MP)-associated TF procoagulant activity (PCA) less in Africans than Caucasians. Africans had reduced in vivo thrombin formation compared with Caucasians: they generated less thrombin-antithrombin (TAT) complexes (10.4 pg mL(-1) vs. 23.0 pg mL(-1), P<0.0001) and less prothrombin fragments (F1+2) (337 pmol mL(-1) vs. 819 pmol mL(-1), P<0.0001). Consistently, Africans also had decreased fibrin formation (D-dimer: 0.3 pg mL(-1) vs. 0.5 pg mL(-1), P=0.02).

CONCLUSION

Duffy-negative subjects of African descent have a markedly reduced procoagulant response in a model of LPS-induced, TF-triggered coagulation activation compared with Duffy-positive healthy Caucasians.

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.

Effects of low dose endotoxemia on endothelial progenitor cells in humans

BACKGROUND

Endothelial progenitor cells (EPCs) are a specific subtype of hematopoietic stem cells that migrate from the bone marrow to the peripheral circulation where they contribute to the repair of injured endothelium and to the formation of new blood vessels. Levels of circulating EPCs have been investigated in different inflammatory disease states. However, data on circulating EPC levels and systemic inflammation remain scarce and contradictory.

OBJECTIVE

We investigated a putative relationship of low grade experimental endotoxemia to changes in circulating EPC levels.

METHODS

Randomized, double-blind, placebo-controlled parallel group trial in 36 healthy male volunteers. Thirty-two volunteers received 2 ng/kg LPS intravenously, the remaining four an equal volume of physiologic saline solution as placebo.

RESULTS

Endothelial progenitor cells showed a significant decrease over the observation period among the 32 subjects challenged with LPS (P<0.0001) and reached their nadir at 6 h, with a median decrease of 62% (interquartile range: 48-81%) compared with baseline levels. Circulating EPCs returned to values comparable to baseline 24 h after LPS challenge.

CONCLUSION

Infusion of 2 ng/kg LPS led to a significant decrease in peripheral EPCs. These results suggest that the early phase of acute inflammation is associated with a decrease in peripheral EPCs.

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.

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.

Acute inflammation is exacerbated in mice genetically predisposed to a severe protein C deficiency

The anticoagulant, activated protein C (aPC), possesses antithrombotic, profibrinolytic, anti-inflammatory, and antiapoptotic properties, and the level of this protein is an important marker of acute inflammatory responses. Although infusion of aPC improves survival in a subset of patients with severe sepsis, evidence as to how aPC decreases mortality in these cases is limited. Because a total deficiency of PC shows complete neonatal lethality, no animal model currently exists to address the mechanistic relationships between very low endogenous aPC levels and inflammatory diseases. Here, we show for the first time that novel genetic dosing of PC strongly correlates with survival outcomes following endotoxin (LPS) challenge in mice. The data provide evidence that very low endogenous levels of PC predispose mice to early-onset disseminated intravascular coagulation, thrombocytopenia, hypotension, organ damage, and reduced survival after LPS challenge. Furthermore, evidence of an exacerbated inflammatory response is observed in very low PC mice but is greatly reduced in wild-type cohorts. Reconstitution of low-PC mice with recombinant human aPC improves hypotension and extends survival after LPS challenge. This study directly links host endogenous levels of PC with various coagulation, inflammation, and hemodynamic end points following a severe acute inflammatory challenge.

Validation of rotation thrombelastography in a model of systemic activation of fibrinolysis and coagulation in humans

BACKGROUND

Thrombelastography (TEG) is a whole blood assay to evaluate the viscoelastic properties during blood clot formation and clot lysis. Rotation thrombelastography (e.g. ROTEM) has overcome some of the limitations of classical TEG and is used as a point-of-care device in several clinical settings of coagulation disorders. Endotoxemia leads to systemic activation of the coagulation system and fibrinolysis in humans.

OBJECTIVES

We validated whether ROTEM is sensitive to endotoxin induced, tissue factor-triggered coagulation and fibrinolysis and if its measures correlate with biohumoral markers of coagulation and fibrinolysis.

PATIENTS AND METHODS

Twenty healthy male volunteers participated in this randomized placebo-controlled trial. Volunteers received either 2 ng kg(-1) National Reference Endotoxin or saline.

RESULTS

Endotoxemia significantly shortened ROTEM clotting time (CT) by 36% (CI 0.26-0.46; P < 0.05) with a strong inverse correlation with the peak plasma levels of prothrombin fragments (F(1 + 2)) (r = -0.83, P < 0.05). Additionally, endotoxin infusion enhanced maximal lysis (ML) 3.9-fold (CI: 2.5-5.2) compared with placebo or baseline after 2 h (P < 0.05). Peak ML and peak tissue plasminogen activator (t-PA) values correlated excellently (r = 0.82, P < 0.05). ROTEM parameters clot formation time and maximal clot firmness were not affected by LPS infusion, whereas platelet function analyzer (PFA-100) closure times decreased.

CONCLUSIONS

Rotation thrombelastography (ROTEM) detects systemic changes of in vivo coagulation activation, and importantly it is a point of care device, which is sensitive to changes in fibrinolysis in humans. The ex vivo measures CT and ML correlate very well with established in vivo markers of coagulation activation (F(1 + 2)) and fibrinolysis (t-PA), respectively.

Direct thrombin inhibitors: pharmacology and clinical relevance

Although heparin has been a cornerstone of treatment for the prevention of thrombosis, it is limited by its adverse effects and unpredictable bioavailability. Direct thrombin inhibitors are a novel class of drugs that have been developed as an effective alternative mode of anticoagulation in patients who suffer from heparin-induced thrombocytopaenia, and for the management of thromboembolic disorders and acute coronary syndromes. The main disadvantages of the direct thrombin inhibitors are the lack of an antidote or readily available clinical monitoring. The mechanism of action, the properties of direct thrombin inhibitors and their potential to replace currently available anticoagulants are reviewed.

Endotoxemia enhances expression of the signaling receptor (GP130) on protein and molecular level

Interleukin 6 (IL-6) performs a prominent role during sepsis. To examine the molecular regulation of IL-6, IL-6 receptor, and signaling receptor gp130 during endotoxemia, nine healthy young volunteers received a bolus injection of lipopolysaccharide (LPS) on day 1 and saline on day 2 in a double blind, randomized, placebo-controlled trial. LPS enhanced IL-6 release 300-fold. IL-6 mRNA expression was not significantly altered in blood samples at any time after LPS infusion in vivo, while incubation of whole blood with 50 pg/ml LPS up-regulated IL-6 mRNA levels 8000- to 50,000-fold in vitro. LPS infusion increased synthesis of gp130 mRNA 5.5-fold compared to baseline at 4 h (P < 0.05), while no significant change was observed in the placebo period (P = 0.001 between groups). LPS increased the percentage of gp130 positive neutrophils gp130 700% over baseline at 8 h (P < 0.01 versus baseline and placebo). IL-6 receptor levels were not significantly altered by low-grade endotoxemia. In conclusion, endotoxemia up-regulates gp130 expression in vivo and in vitro. Quantification of IL-6 mRNA expression in circulating leukocytes is unlikely a suitable marker for monitoring of endotoxemia.

The single nucleotide polymorphism Ser128Arg in the E-selectin gene is associated with enhanced coagulation during human endotoxemia

The single nucleotide polymorphism (SNP) Ser128Arg in the E-selectin gene is overrepresented in certain patient groups with atherosclerosis or restenosis. We hypothesized and tested whether it may affect cytokine-induced levels of soluble (s) E-selectin, or be associated with proinflammatory or procoagulant properties in a well-standardized inflammation model. Healthy male volunteers (n = 157) received a lipopolysaccharide (LPS) infusion and were genotyped for the S128R SNP, and outcome parameters were measured by enzyme immunoassays and real-time polymerase chain reaction (RT-PCR, Taqman). The S128R SNP had no pronounced effects on basal or inducible sE-selectin levels, or levels of tumor necrosis factor or interleukin-6. However, carriers of the S128R SNP had 20% higher monocyte counts at 24 hours after LPS infusion. Importantly, the S128R allele enhanced thrombin generation by 50% to 80%, as measured by prothrombin fragment F1+2 (P &lt; .01), and hence fibrin formation (D-dimer) 2-fold (P = .01 to P = .002). However, tissue factor (TF) mRNA levels were not affected. The S128R E-selectin genotype is associated with procoagulant effects in a human model of endotoxin-induced, TF-triggered coagulation. This could contribute to its linkage with various thrombotic cardiovascular disorders.

Effects of carbon monoxide inhalation during experimental endotoxemia in humans

Data show that carbon monoxide (CO) exerts direct antiinflammatory effects in vitro and in vivo after LPS challenge in a mouse model. We hypothesized that CO may act as an antiinflammatory agent in human endotoxemia. The aim of this trial was to study the effects of CO inhalation on cytokine production during experimental human endotoxemia. The main study was a randomized, double-blinded, placebo-controlled, two-way cross-over trial in healthy volunteers. Each volunteer inhaled synthetic air (as placebo) and 500 ppm CO for 1 hour in random order with a washout period of 6 weeks and received a 2-ng/kg intravenous bolus of LPS after inhalation. Carboxyhemoglobin levels were assessed as a safety parameter. CO inhalation increased carboxyhemoglobin levels from 1.2% (95% confidence interval, 1.0 to 1.4%) to peak values of 7.0% (95% confidence interval, 6.5 to 7.7%). LPS infusion transiently increased plasma concentrations of tumor necrosis factor-alpha, interleukin (IL)-6 (approximately 150-fold increases), and IL-8, as well as IL-1alpha and IL-1beta mRNA levels (an approximately 200-fold increase). These LPS-induced changes were not influenced by CO inhalation. Inhalation of 500 ppm CO for 1 hour had no antiinflammatory effects in a systemic inflammation model in humans, as 250 ppm for 1 hour did in rodents.

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.

Validation of a novel tissue factor assay in experimental human endotoxemia

BACKGROUND

Nuclear factor kappa B (NF-kappa B) activation and tissue factor (TF) expression may contribute to lethality in sepsis. Inappropriate in vivo expression of TF is likely responsible for fibrin deposition in sepsis-associated disseminated intravascular coagulation (DIC). Clinical assessment of TF expression has remained a major challenge. No point-of-care assays are currently available to measure the level of TF activity in whole blood. The current study examined the suitability of the TiFaCT assay as a point-of-care assay to detect TF expression.

METHODS

30 healthy male volunteers received 2 ng/kg of LPS. Tissue factor-dependent coagulation was quantified with a novel assay called tissue factor clotting time (TiFaCT), and by measurement of activation markers of downstream coagulation.

RESULTS

Ex vivo addition of anti-TF antibodies to blood slightly increased clotting times at 0-24 h (p<0.01) indicating that some tissue factor activity was present in whole blood at any time. LPS bolus infusion decreased TiFaCT clotting time by -23% compared to baseline (p<0.01), when in vivo clotting increased, as demonstrated by a 10-fold increase in prothrombin fragment levels (F1+2). Ex vivo incubation with LPS considerably shortened TiFaCT (from 1000s to 400s as compared to control incubation; p<0.01). This effect was blunted at 2-4 h after LPS infusion (i.e. the time of monocytopenia), but twofold enhanced 24 h after LPS challenge (p<0.01).

CONCLUSIONS

In summary, the TiFaCT assay was validated in our in vivo model of LPS-induced coagulation. It detected minute quantities of circulating TF even at baseline. TiFaCT is shortened at times of in vivo thrombin generation.

Recombinant hirudin enhances cardiac output and decreases systemic vascular resistance during reperfusion after cardiopulmonary bypass in a porcine model

OBJECTIVE

Cardiopulmonary bypass and surgical stress are accompanied by a systemic inflammatory response and activation of coagulation. Thrombin forms fibrin and activates platelets and neutrophils. Consequently, disseminated microthrombosis might increase capillary vascular resistance and thus impair reperfusion. We hypothesized that recombinant hirudin, a direct inhibitor of thrombin, could attenuate coagulation and enhance microvascular flow during reperfusion.

METHODS

Twenty pigs undergoing 60 minutes of aortic clamping and 75 minutes of normothermic perfusion were randomized in a blinded setting to receive an intravenous bolus of recombinant hirudin (10 mg, 0.4 mg/kg; n = 10) or placebo (n = 10) 15 minutes before aortic declamping and then continued with an intravenous 135-minute infusion of recombinant hirudin (3.75 mg/h, 0.15 mg/kg) or placebo. Thrombin-antithrombin complexes, activated clotting times, and several hemodynamic parameters were measured before cardiopulmonary bypass, after weaning from cardiopulmonary bypass, and at 30, 60, 90, and 120 minutes after aortic declamping. Intramucosal pH and Pco(2) were measured from the luminal surface of ileum simultaneously with arterial gas analysis at 30-minute intervals.

RESULTS

Recombinant hirudin inhibited thrombin formation after aortic declamping; at 120 minutes, thrombin-antithrombin complexes levels (microg/L, mean +/- SD) were 75 +/- 21 and 29 +/- 44 (P <.001) for placebo and pigs receiving recombinant hirudin, respectively. When compared with the placebo group, pigs receiving recombinant hirudin showed significantly higher stroke volume, cardiac output, and lower systemic vascular resistance at 60 and 90 minutes after aortic declamping (P <.05). Based on arteriomucosal Pco(2) and pH differences, progressive worsening of intestinal microcirculatory perfusion occurred in the placebo group but not in the recombinant hirudin group.

CONCLUSION

Infusion of thrombin inhibitor recombinant hirudin during reperfusion was associated with attenuated postischemia left ventricular dysfunction and decreased vascular resistance. Consequently microvascular flow was improved during ischemia-reperfusion injury. Control of thrombin formation during reperfusion may be a feasible approach to improve oxygen delivery to reperfused vascular beds.

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.

Induction of microparticle- and cell-associated intravascular tissue factor in human endotoxemia

The precise role of intravascular tissue factor (TF) remains poorly defined, due to the limited availability of assays capable of measuring circulating TF procoagulant activity (PCA). As a model of inflammation-associated intravascular thrombin generation, we studied 18 volunteers receiving an infusion of endotoxin. A novel assay that measures microparticle (MP)-associated TF PCA from a number of cellular sources (but not platelets) demonstrated an 8-fold increase in activity at 3 to 4 hours after endotoxin administration (P <.001), with a return to baseline by 8 hours. TF antigen-positive MPs isolated from plasma were visualized by electron microscopy. Interindividual MP-associated TF response to lipopolysaccharide (LPS) was highly variable. In contrast, a previously described assay that measures total (cell and MP-borne) whole-blood TF PCA demonstrated a more modest increase, with a peak in activity (1.3-fold over baseline; P <.000 01) at 3 to 4 hours, and persistence for more than 24 hours. This surprisingly modest increase in whole-blood TF activity is likely explained by a profound although transient LPS-induced monocytopenia. MP-associated TF PCA was highly correlated with whole-blood TF PCA and total number of circulating MPs, and whole-blood TF PCA was highly correlated with TF mRNA levels.

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.

Marked increase in vascular endothelial growth factor concentrations during Escherichia coli endotoxin-induced acute inflammation in humans

BACKGROUND

Bacterial endotoxins can induce the synthesis and release of vascular endothelial growth factor (VEGF), which may alter vascular permeability and cause vascular leakage.

MATERIALS AND METHODS

The effect of acute systemic inflammation on VEGF concentration was measured in healthy males after an intravenous bolus infusion of Escherichia coli endotoxin (lipopolysaccharide, LPS, 20 IU kg-1) in a double-blind, placebo-controlled parallel group study. LPS administration was followed by an infusion of lepirudin (bolus 0.1 mg kg-1, continuous infusion of 0.1 mg kg-1 h-1, n = 12) or saline (n = 12).

RESULTS

Plasma VEGF increased from a mean of 15.1 pg mL-1 to 74.6 pg mL-1 5 h after LPS (P < 0.003). Body temperature, pulse rate, leukcytes, prothrombin fragment 1 + 2 (F1 + 2) and lactoferrin increased and platelets decreased after LPS (P < 0.05). The LPS-induced increase in VEGF was paralleled by the neutrophil cell degranulation marker lactoferrin but not by F1 + 2, and was not affected by lepirudin, which blunted F1 + 2 formation (P < 0.05).

CONCLUSIONS

Inflammation-induced activation of leukcytes rather than platelets plays a role in the marked increase in VEGF, which cannot be abrogated by antithrombotic therapy.

The role of the endothelium in severe sepsis and multiple organ dysfunction syndrome

Severe sepsis, defined as sepsis with acute organ dysfunction, is associated with high morbidity and mortality rates. The development of novel therapies for sepsis is critically dependent on an understanding of the basic mechanisms of the disease. The pathophysiology of severe sepsis involves a highly complex, integrated response that includes the activation of a number of cell types, inflammatory mediators, and the hemostatic system. Central to this process is an alteration of endothelial cell function. The goals of this article are to (1) provide an overview of sepsis and its complications, (2) discuss the role of the endothelium in orchestrating the host response in sepsis, and (3) emphasize the potential value of the endothelium as a target for sepsis therapy.

Recent developments in the treatment of sepsis

Despite advances in supportive care, septic shock remains a major cause of morbidity and mortality. With the identification of the systemic inflammatory response as a major component in the pathogenesis of the septic shock syndrome, much of the recent work has focused on modulating this response. This includes antiendotoxin therapies in patients with Gram-negative sepsis, and therapies to modulate the pro-inflammatory mediators produced in response to infection, such as TNF-alpha, platelet-activating factor and complement. High-flow haemofiltration has the potential advantage of clearing both endotoxin and pro-inflammatory mediators. Antithrombotic strategies have been investigated and have yielded the first major success in the treatment of sepsis with activated protein C. Nitric oxide produces the cardiovascular features of sepsis and investigators have looked at both reducing its production and mopping up the excess. Attempts to reduce apoptosis have been a new focus in the treatment of sepsis. There have also been recent developments in supportive care suggesting a role for vasopressin and replacement corticosteroid therapy.

Evaluation of unfractionated heparin and recombinant hirudin on survival in a sustained ovine endotoxin shock model

OBJECTIVE

To compare and evaluate the potential benefit of two different anticoagulation regimens during endotoxemia in an ovine model.

DESIGN

Animal prospective randomized and controlled study following preliminary dose-range study conforming with the Guide for the Care and Use of Laboratory Animals as promulgated by the Council of the American Physiologic Society and reviewed by the Ethical Committee for Animal Research of our institution.

SETTING

Laboratories of anesthesiological investigations and hemostasis, primary care university medical center.

SUBJECTS

Twenty-two adult sheep of either sex, weighing 29-42 kg (mean 35.8 kg), surgically instrumented for chronic studies and randomly allocated to receive three different treatment groups: unfractionated heparin (40 units.kg.hr; n = 7), recombinant hirudin (500 units.kg.hr; n = 7), or saline (nonanticoagulated controls; n = 8).

INTERVENTIONS

Ovine model of severe endotoxin shock induced by a continuous intravenous endotoxin infusion over 72 hrs (10 ng.kg.min ).

MEASUREMENTS AND MAIN RESULTS

Endotoxin infusion alone produced a progressive hypotensive, hyperdynamic shock state with right ventricle failure leading to the death of all animals of the control group within 44 hrs (median, 12 hrs). Heparin profoundly improved survival rate in this model, whereas effective anticoagulation with hirudin did not significantly increase the survival rate compared with controls. Animals in the control group died from disseminated intravascular coagulation, metabolic acidosis, and hemorrhagic pulmonary edema, whereas sheep treated with hirudin died from severe pulmonary edema (hypoxemia, increased alveoloarterial oxygen gradient associated with an increased wet/dry lung weight ratio) in the absence of disseminated intravascular coagulation.

CONCLUSIONS

We conclude that systemic anticoagulation with the thrombin inhibitor hirudin is without benefit in this sheep model of lethal endotoxemia, whereas anticoagulation with heparin affords not only effective prevention of endotoxin-induced coagulation disorders but also global protection with prevention of respiratory decompensation and thus markedly improves survival rate in this situation.

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.

Marked difference in pathophysiology between tissue factor- and lipopolysaccharide-induced disseminated intravascular coagulation models in rats

OBJECTIVE

Tissue factor and lipopolysaccharide frequently have been used to induce disseminated intravascular coagulation in experimental animal models. Although the pathophysiology of disseminated intravascular coagulation may differ according to the agents used to induce it, these previous models have not distinguished between the use of different disseminated intravascular coagulation-inducing agents. In this study, we attempted to evaluate the characteristic features of these agents in two types of disseminated intravascular coagulation models, with special reference to selected hemostatic parameters and pathologic findings in the kidney.

DESIGN

Prospective, comparative, experimental study.

SETTING

Laboratory at a university hospital.

SUBJECTS

Twenty-seven male Wistar rats, age 6-7 wks, weighing 160-170 g.

INTERVENTIONS

Three groups of animals were studied: a control group (n = 8) receiving physiologic saline, a tissue factor-treated group (n = 11) receiving tissue factor 3.75 units/kg, and a lipopolysaccharide-treated group (n = 8) receiving lipopolysaccharide 30 mg/kg; each group sustained infusion for 4 hrs via the tail vein.

MEASUREMENTS AND MAIN RESULTS

The degree of hemostatic activation in both types of experimental disseminated intravascular coagulation was identical, based on the results of thrombin-antithrombin III complex levels. Markedly elevated D-dimer concentrations were observed without organ dysfunction or fibrin deposition in the kidney on administration of tissue factor, whereas markedly elevated plasminogen activator inhibitor activity, decreased antithrombin III activity, severe organ failure, and marked fibrin deposition in the kidney were observed for lipopolysaccharide administration.

CONCLUSION

Because pathophysiology differed remarkably between the tissue factor- and lipopolysaccharide-induced disseminated intravascular coagulation models in rats, we recommend that they be assessed carefully as distinct entities to determine implications of their experimental and clinical use.

Vascular bed-specific hemostasis: role of endothelium in sepsis pathogenesis

OBJECTIVES

To examine the role of vascular bed-specific pathways in determining the hemostatic phenotype in sepsis.

DATA SOURCES/STUDY SELECTION

Published research and review articles related to hemostasis and endothelial cell biology.

DATA EXTRACTION AND SYNTHESIS

The results of published studies have been used to generate a hypothesis of vascular bed-specific hemostasis in sepsis.

CONCLUSIONS

In sepsis, coagulation is initiated by the extrinsic pathway and is amplified through the intrinsic pathway. In addition, the body's natural anticoagulant mechanisms are significantly dampened. Together, these changes result in a net imbalance of hemostasis. The nature of this imbalance varies from one vascular bed to the next according to the local set point of the endothelium. These concepts lay an important foundation for understanding the pathophysiology of sepsis.

All-trans retinoic acid is partially effective against lipopolysaccharide-induced but not against tissue-factor-induced disseminated intravascular coagulation in rat models

All-trans retinoic acid (ATRA) has been introduced to the management of acute promyelocytic leukemia (APL) as a differentiation treatment. This drug not only causes complete remission, but also improves disseminated intravascular coagulation (DIC) without adding anticoagulants in APL. We have attempted to determine whether ATRA is effective against DIC in rat models induced by tissue factor (TF) or lipopolysaccharide (LPS), because the anticoagulant effect of ATRA has been considered to induce thrombomodulin upregulation and TF downregulation on endothelial cells as well as on APL cells. In male Wistar rats, DIC was induced by a 4-h infusion of thromboplastin (3.75 U/kg) or lipopolysaccharide (30 mg/kg). The rats were given ATRA orally each day at a dose of 100 mg/kg per day for 1 week before the injection of TF or LPS in ATRA treatment groups, or given low molecular weight heparin (LMWH) 10 min before the injection of TF or LPS (200 U/kg, bolus intravenously) in LMWH treatment groups. No significant changes in hemostatic parameters or markers of organ dysfunction were caused by the ATRA administration, while DIC was significantly improved by LMWH in the TF-induced model. DIC was significantly improved by both ATRA and LMWH in the LPS-induced model. These findings suggested that ATRA was useful for treating DIC only in the LPS-induced model, and that drug efficacy should be carefully assessed because the agents used to induce DIC considerably influenced the outcome.

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.