Clinical trial results with antithrombin III in sepsis

Thromboinflammation: challenges of therapeutically targeting coagulation and other host defense mechanisms

Thrombosis with associated inflammation (thromboinflammation) occurs commonly in a broad range of human disorders. It is well recognized clinically in the context of superficial thrombophlebitis (thrombosis and inflammation of superficial veins); however, it is more dangerous when it develops in the microvasculature of injured tissues and organs. Microvascular thrombosis with associated inflammation is well recognized in the context of sepsis and ischemia-reperfusion injury; however, it also occurs in organ transplant rejection, major trauma, severe burns, the antiphospholipid syndrome, preeclampsia, sickle cell disease, and biomaterial-induced thromboinflammation. Central to thromboinflammation is the loss of the normal antithrombotic and anti-inflammatory functions of endothelial cells, leading to dysregulation of coagulation, complement, platelet activation, and leukocyte recruitment in the microvasculature. α-Thrombin plays a critical role in coordinating thrombotic and inflammatory responses and has long been considered an attractive therapeutic target to reduce thromboinflammatory complications. This review focuses on the role of basic aspects of coagulation and α-thrombin in promoting thromboinflammatory responses and discusses insights gained from clinical trials on the effects of various inhibitors of coagulation on thromboinflammatory disorders. Studies in sepsis patients have been particularly informative because, despite using anticoagulant approaches with different pharmacological profiles, which act at distinct points in the coagulation cascade, bleeding complications continue to undermine clinical benefit. Future advances may require the development of therapeutics with primary anti-inflammatory and cytoprotective properties, which have less impact on hemostasis. This may be possible with the growing recognition that components of blood coagulation and platelets have prothrombotic and proinflammatory functions independent of their hemostatic effects.

Auxiliary activation of the complement system and its importance for the pathophysiology of clinical conditions

Activation and regulation of the cascade systems of the blood (the complement system, the coagulation/contact activation/kallikrein system, and the fibrinolytic system) occurs via activation of zymogen molecules to specific active proteolytic enzymes. Despite the fact that the generated proteases are all present together in the blood, under physiological conditions, the activity of the generated proteases is controlled by endogenous protease inhibitors. Consequently, there is remarkable little crosstalk between the different systems in the fluid phase. This concept review article aims at identifying and describing conditions where the strict system-related control is circumvented. These include clinical settings where massive amounts of proteolytic enzymes are released from tissues, e.g., during pancreatitis or post-traumatic tissue damage, resulting in consumption of the natural substrates of the specific proteases and the available protease inhibitor. Another example of cascade system dysregulation is disseminated intravascular coagulation, with canonical activation of all cascade systems of the blood, also leading to specific substrate and protease inhibitor elimination. The present review explains basic concepts in protease biochemistry of importance to understand clinical conditions with extensive protease activation.

To What Extent Are the Terminal Stages of Sepsis, Septic Shock, Systemic Inflammatory Response Syndrome, and Multiple Organ Dysfunction Syndrome Actually Driven by a Prion/Amyloid Form of Fibrin?

A well-established development of increasing disease severity leads from sepsis through systemic inflammatory response syndrome, septic shock, multiple organ dysfunction syndrome, and cellular and organismal death. Less commonly discussed are the equally well-established coagulopathies that accompany this. We argue that a lipopolysaccharide-initiated (often disseminated intravascular) coagulation is accompanied by a proteolysis of fibrinogen such that formed fibrin is both inflammatory and resistant to fibrinolysis. In particular, we argue that the form of fibrin generated is amyloid in nature because much of its normal α-helical content is transformed to β-sheets, as occurs with other proteins in established amyloidogenic and prion diseases. We hypothesize that these processes of amyloidogenic clotting and the attendant coagulopathies play a role in the passage along the aforementioned pathways to organismal death, and that their inhibition would be of significant therapeutic value, a claim for which there is considerable emerging evidence.

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.

Antithrombin III for critically ill patients

BACKGROUND

Critical illness is associated with uncontrolled inflammation and vascular damage which can result in multiple organ failure and death. Antithrombin III (AT III) is an anticoagulant with anti-inflammatory properties but the efficacy and any harmful effects of AT III supplementation in critically ill patients are unknown. This review was published in 2008 and updated in 2015.

OBJECTIVES

To examine:1. The effect of AT III on mortality in critically ill participants.2. The benefits and harms of AT III.We investigated complications specific and not specific to the trial intervention, bleeding events, the effect on sepsis and disseminated intravascular coagulation (DIC) and the length of stay in the intensive care unit (ICU) and in hospital in general.

SEARCH METHODS

We searched the following databases from inception to 27 August 2015: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid SP), EMBASE (Ovid SP,), CAB, BIOSIS and CINAHL. We contacted the main authors of trials to ask for any missed, unreported or ongoing trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) irrespective of publication status, date of publication, blinding status, outcomes published, or language. We contacted the investigators and the trial authors in order to retrieve missing data. In this updated review we include trials only published as abstracts.

DATA COLLECTION AND ANALYSIS

Our primary outcome measure was mortality. Two authors each independently abstracted data and resolved any disagreements by discussion. We presented pooled estimates of the intervention effects on dichotomous outcomes as risk ratios (RR) with 95% confidence intervals (CI). We performed subgroup analyses to assess risk of bias, the effect of AT III in different populations (sepsis, trauma, obstetrics, and paediatrics), and the effect of AT III in patients with or without the use of concomitant heparin. We assessed the adequacy of the available number of participants and performed trial sequential analysis (TSA) to establish the implications for further research.

MAIN RESULTS

We included 30 RCTs with a total of 3933 participants (3882 in the primary outcome analyses).Combining all trials, regardless of bias, showed no statistically significant effect of AT III on mortality with a RR of 0.95 (95% CI 0.88 to 1.03), I² statistic = 0%, fixed-effect model, 29 trials, 3882 participants, moderate quality of evidence). For trials with low risk of bias the RR was 0.96 (95% Cl 0.88 to 1.04, I² statistic = 0%, fixed-effect model, 9 trials, 2915 participants) and for high risk of bias RR 0.94 (95% Cl 0.77 to 1.14, I² statistic = 0%, fixed-effect model, 20 trials, 967 participants).For participants with severe sepsis and DIC the RR for mortality was non-significant, 0.95 (95% Cl 0.88 to 1.03, I² statistic = 0%, fixed-effect model, 12 trials, 2858 participants, moderate quality of evidence).We conducted 14 subgroup and sensitivity analyses with respect to the different domains of risk of bias, but detected no statistically significant benefit in any subgroup analyses.Our secondary objective was to assess the benefits and harms of AT III. For complications specific to the trial intervention the RR was 1.26 (95% Cl 0.83 to 1.92, I² statistic = 0%, random-effect model, 3 trials, 2454 participants, very low quality of evidence). For complications not specific to the trial intervention, the RR was 0.71 (95% Cl 0.08 to 6.11, I² statistic = 28%, random-effects model, 2 trials, 65 participants, very low quality of evidence). For complications other than bleeding, the RR was 0.72 ( 95% Cl 0.42 to 1.25, I² statistic = 0%, fixed-effect model, 3 trials, 187 participants, very low quality of evidence). Eleven trials investigated bleeding events and we found a statistically significant increase, RR 1.58 (95% CI 1.35 to 1.84, I² statistic = 0%, fixed-effect model, 11 trials, 3019 participants, moderate quality of evidence) in the AT III group. The amount of red blood cells administered had a mean difference (MD) of 138.49 (95% Cl -391.35 to 668.34, I² statistic = 84%, random-effect model, 4 trials, 137 participants, very low quality of evidence). The effect of AT III in patients with multiple organ failure (MOF) was a MD of -1.24 (95% Cl -2.18 to -0.29, I² statistic = 48%, random-effects model, 3 trials, 156 participants, very low quality of evidence) and for patients with an Acute Physiology and Chronic Health Evaluation score (APACHE) at II and III the MD was -2.18 (95% Cl -4.36 to -0.00, I² statistic = 0%, fixed-effect model, 3 trials, 102 participants, very low quality of evidence). The incidence of respiratory failure had a RR of 0.93 (95% Cl 0.76 to 1.14, I² statistic = 32%, random-effects model, 6 trials, 2591 participants, moderate quality of evidence). AT III had no statistically significant impact on the duration of mechanical ventilation (MD 2.20 days, 95% Cl -1.21 to 5.60, I² statistic = 0%, fixed-effect model, 3 trials, 190 participants, very low quality of evidence); on the length of stay in the ICU (MD 0.24, 95% Cl -1.34 to 1.83, I² statistic = 0%, fixed-effect model, 7 trials, 376 participants, very low quality of evidence) or on the length of stay in hospital in general (MD 1.10, 95% Cl -7.16 to 9.36), I² statistic = 74%, 4 trials, 202 participants, very low quality of evidence).

AUTHORS' CONCLUSIONS

There is insufficient evidence to support AT III substitution in any category of critically ill participants including the subset of patients with sepsis and DIC. We did not find a statistically significant effect of AT III on mortality, but AT III increased the risk of bleeding events. Subgroup analyses performed according to duration of intervention, length of follow-up, different patient groups, and use of adjuvant heparin did not show differences in the estimates of intervention effects. The majority of included trials were at high risk of bias (GRADE; very low quality of evidence for most of the analyses). Hence a large RCT of AT III is needed, without adjuvant heparin among critically ill patients such as those with severe sepsis and DIC, with prespecified inclusion criteria and good bias protection.

[Sepsis-associated Purpura Fulminans International Registry--Europe (SAPFIRE)]

BACKGROUND

Purpura fulminans is a rare life-threatening condition which is characterized by disseminated thrombosis in dermal and systemic microcirculation, cutaneous hemorrhages with progressing necrosis and multiple organ failure. The underlying pathogenesis is based on the disruption of the intrinsic anticoagulation cascade, with protein C deficiency being considered the leading factor in this process. In the majority of cases, the condition emerges as consumptive coagulopathy associated with severe sepsis.

OBJECTIVES

Epidemiological data on sepsis-associated purpura fulminans (SAPF) are scarce and evidence-based treatment guidelines have not been established yet. While restoration of the balance in the coagulation cascade is a declared therapeutic goal, evaluations of the efficacy of different therapeutic approaches in randomized clinical trials are still lacking. The causal role of individual microbial pathogens also requires comprehensive evaluation.

METHODS

A prospective multicenter Sepsis-Associated Purpura Fulminans International Registry-Europe (SAPFIRE) will be established in the first quarter of 2015. For the first time, participating centers will systematically collect information on etiology, clinical course, biomarkers, treatment, morbidity, and mortality of SAPF.

RESULTS

The SAPFIRE data will be periodically evaluated and disseminated. Retrospective analysis of each center's data and regular access to aggregated information collected by other centers will enable the participants to monitor and update care quality standards.

Systemic inhibition and liver-specific over-expression of PAI-1 failed to improve survival in all-inclusive populations or homogenous cohorts of CLP mice

BACKGROUND

The role of plasminogen activator inhibitor type-1 (PAI-1) in abdominal sepsis remains elusive.

OBJECTIVES

To study the influence of inhibition and over-expression of PAI-1 upon survival in cecal ligation and puncture (CLP) sepsis.

METHODS

(i) Mice underwent moderate CLP and received 10 mg kg(-1) of either monoclonal anti-PAI-1 (MA-MP6H6) or control (MA-Control) antibody intravenously at 0, 18 or 30 h post-CLP. The 30-h treatment group was additionally stratified into mice predicted to survive (P-SUR) or die (P-DIE) based on IL 6 measured at 24 h post-CLP. (ii) PAI-1 expression was induced with pLIVE.PAI-1 plasmid administered 72 h pre-CLP. Blood was sampled for 5 days and survival was monitored for 28 days.

RESULTS

MA-MP6H6 effectively neutralized active PAI-1 and fully restored fibrinolysis while PAI-1 over-expression was liver-specific and correlated with PAI-1 increase in the blood. Without stratification, MA-MP6H6 co-/post-treatment conferred no survival benefit. Prospective stratification (IL-6 cut-off: 14 ng mL(-1) ) suggested increased mortality by MA-MP6H6 treatment in P-SUR that reached 30% difference (vs. MA-Control; P < 0.05) after a retrospective cut-off readjustment to 3.3 ng mL(-1) for better P-SUR homogeneity. Subsequent prospective anti-PAI-1 treatment in P-SUR mice with 3.3 ng mL(-1) cut-off demonstrated a negative but statistically insignificant effect: mortality was higher by 17% after MA-MP6H6 vs. MA-Control. Over-expression of PAI 1 did not alter post-CLP survival. Neither PAI-1 inhibition nor over-expression meaningfully modified inflammatory response and/or organ function.

CONCLUSIONS

Restoration of fibrinolysis in early abdominal sepsis was not beneficial and it may prove detrimental in subjects with the lowest risk of death, while preemptive PAI-1 up-regulation at the current magnitude was not protective.

A randomized, controlled, multicenter trial of the effects of antithrombin on disseminated intravascular coagulation in patients with sepsis

INTRODUCTION

To test the hypothesis that the administration of antithrombin concentrate improves disseminated intravascular coagulation (DIC), resulting in recovery from DIC and better outcomes in patients with sepsis, we conducted a prospective, randomized controlled multicenter trial at 13 critical care centers in tertiary care hospitals.

METHODS

We enrolled 60 DIC patients with sepsis and antithrombin levels of 50 to 80% in this study. The participating patients were randomly assigned to an antithrombin arm receiving antithrombin at a dose of 30 IU/kg per day for three days or a control arm treated with no intervention. The primary efficacy end point was recovery from DIC on day 3. The analysis was conducted with an intention-to-treat approach. DIC was diagnosed according to the Japanese Association for Acute Medicine (JAAM) scoring system. The systemic inflammatory response syndrome (SIRS) score, platelet count and global markers of coagulation and fibrinolysis were measured on day 0 and day 3.

RESULTS

Antithrombin treatment resulted in significantly decreased DIC scores and better recovery rates from DIC compared with those observed in the control group on day 3. The incidence of minor bleeding complications did not increase, and no major bleeding related to antithrombin treatment was observed. The platelet count significantly increased; however, antithrombin did not influence the sequential organ failure assessment (SOFA) score or markers of coagulation and fibrinolysis on day 3.

CONCLUSIONS

Moderate doses of antithrombin improve DIC scores, thereby increasing the recovery rate from DIC without any risk of bleeding in DIC patients with sepsis.

TRIAL REGISTRATION

UMIN Clinical Trials Registry (UMIN-CTR) UMIN000000882.

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.

Assessment of the usefulness of antithrombin-III in the management of disseminated intravascular coagulation in obstetrically Ill patients

OBJECTIVE

The aim of this study was to analyze the antithrombin-III (AT-III) activity in the serum in relation to other laboratory findings, including the serum albumin, total protein (TP), and uric acid (UA), and to assess the recovery of the AT-III activity in the serum after its administration in obstetrically ill patients.

PATIENTS AND METHODS

The medical records of 27 patients who were diagnosed to have disseminated intravascular coagulation (DIC) based on the obstetric DIC scores were reviewed and the relationships between the activity of AT-III in the serum and other laboratory findings were evaluated. The effect of administration of AT-III on the recovery of AT-III activity in the serum was also evaluated.

RESULTS

All the patients survived without any sequelae. The mean obstetric DIC score was 11.1 ± 3.1 (range 8-19) and the mean blood loss during the first 24 hours was 3798 ± 3,435 mL (range 480-16 208 mL). There was a significant correlation between the serum AT-III activity before the treatment and the serum albumin (r = .67, P = .001) and TP (r = .59, P = .021), but not serum UA. Seven patients required over 3000 IU of AT-III concentrate to obtain an increase in the serum AT-III activity to over 70%. The UA level in this group was significantly higher than that in the remaining patients.

CONCLUSION

The serum AT-III activity was correlated with the serum albumin level before the start of treatment. Therefore, measurement of the serum albumin level before and during treatment is helpful.

Effects of antithrombin III in patients with disseminated intravascular coagulation diagnosed by newly developed diagnostic criteria for critical illness

A study was conducted to test the hypotheses that antithrombin III (antithrombin) improves disseminated intravascular coagulation (DIC) when applied to DIC patients diagnosed by sensitive criteria and that the administration of high-dose antithrombin is a beneficial treatment for DIC. Twenty-three DIC patients diagnosed based on the Japanese Association for Acute Medicine (JAAM) DIC diagnostic criteria were treated with either high-dose (60 IU/kg/day) or low-dose (30 IU/kg/day) antithrombin concentrates for 3 days. The clinical conditions that cause DIC were restricted to systemic inflammatory response syndrome (SIRS) and sepsis. Data of antithrombin activity, platelet counts, coagulation and fibrinolytic markers, and DIC scores before antithrombin administration (day 0), on days 1 to 3, and on day 7 were retrospectively collected from computer-based records. Patients who met the JAAM DIC criteria were administered either high-dose (12 patients) or low-dose (11 patients) antithrombin. The patients' backgrounds and antithrombin activity (high dose, 51.5 +/- 14.5%; low dose, 62.6 +/- 19.3%; P = .153) on day 0 were identical in the 2 groups. The JAAM DIC score and prothrombin time ratio on day 7 significantly improved when compared with those on day 0. However, mortality at 28 days as well as interaction within the antithrombin doses administered showed no difference. There were also no differences in the time course of the platelet counts, coagulation and fibrinolytic markers, and DIC scores in the 2 groups. The authors conclude that the effects of antithrombin on prognosis and coagulation and fibrinolytic parameters are independent of the doses administered in patients with SIRS/sepsis-associated DIC.

Antithrombin III for critically ill patients

BACKGROUND

Critical illness is associated with uncontrolled inflammation and vascular damage which can result in multiple organ failure and death. Antithrombin III (AT III) is an anticoagulant with anti-inflammatory properties but the efficacy and any harmful effects of AT III supplementation in critically ill patients are unknown.

OBJECTIVES

To assess the benefits and harms of AT III in critically ill patients.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); MEDLINE; EMBASE; Science Citation Index Expanded; International Web of Science; CINAHL; LILACS; and the Chinese Biomedical Literature Database (up to November 2006). We contacted authors and manufacturers in the field.

SELECTION CRITERIA

We included all randomized clinical trials, irrespective of blinding or language, that compared AT III with no intervention or placebo in critically ill patients.

DATA COLLECTION AND ANALYSIS

Our primary outcome measure was mortality. We each independently abstracted data and resolved any disagreements by discussion. We presented pooled estimates of the intervention effects on dichotomous outcomes as relative risks (RR) with 95% confidence intervals (CI). We performed subgroup analyses to assess risk of bias, the effect of AT III in different populations (sepsis, trauma, obstetric, and paediatric patients), and the effect of AT III in patients with or without the use of concomitant heparin. We assessed the adequacy of the available number of participants and performed a trial sequential analysis to establish the implications for further research.

MAIN RESULTS

We included 20 randomized trials with a total of 3458 participants; 13 of these trials had high risk of bias. When we combined all trials, AT III did not statistically significantly reduce overall mortality compared with the control group (RR 0.96, 95% CI 0.89 to 1.03; no heterogeneity between trials). A total of 32 subgroup and sensitivity analyses were carried out. Analyses based on risk of bias, different populations, and the role of adjuvant heparin gave insignificant differences. AT III reduced the multiorgan failure score among survivors in an analysis involving very few patients. AT III increased bleeding events (RR 1.52, 95% CI 1.30 to 1.78).

AUTHORS' CONCLUSIONS

AT III cannot be recommended for critically ill patients based on the available evidence. A randomized controlled trial of AT III, without adjuvant heparin, with prespecified inclusion criteria and good bias protection is needed.

Levels of protein C activity and clinical factors in early phase of pediatric septic shock may be associated with the risk of death

Severe sepsis and septic shock are major causes of morbidity and mortality among children in pediatric intensive care units (PICUs) worldwide. Activated protein C (PC) is a critical endogenous regulator of coagulation and inflammation in patients with sepsis. However, the role of PC in pediatric sepsis is still obscure. We prospectively recruited infants and children aged between 1 month and 15 years old who were admitted to PICU with a clinical diagnosis of systemic inflammatory response syndrome, sepsis, or septic shock. Clinical data were recorded and blood samples kept for further analysis. We then measured the levels of PC activity. Of the approximately 1,100 pediatric patients admitted to PICU from January 1, 2004 to December 31, 2005, 75 were diagnosed with septic shock (6.8%), and 67 samples were available for analysis. Out of these, 41 (61%) were survivors, and 26 (39%) were nonsurvivors. The average plasma PC activity (%) was at 37.8 +/- 4.4. Plasma PC activity (%) was significantly lower in the nonsurvivors compared with the survivors at 23.6 +/- 4.3 and 46.8 +/- 6.3 (P = 0.002), respectively. D-Dimer levels were not significantly different between the survivors (1,461 +/- 266 ng/mL) and the nonsurvivors (1,989 +/- 489 ng/mL) (P = 0.68). Also, there was no correlation between plasma PC activity and D-dimer levels (r = -0.07; P = 0.6). Importantly, the odds of dying were significantly higher in patients whose level of PC activity was less than 25% (odds ratio = 5.6; P = 0.02). Pediatric patients with septic shock demonstrate very low levels of PC activity, and this may be associated with an increased risk of death.

Presentation and outcome of purpura fulminans associated with peripheral gangrene in 12 patients at Mayo Clinic

BACKGROUND

Dermatologists may be called to assist in the diagnosis and management of purpura fulminans.

METHODS

This retrospective case series details the clinical presentation and outcomes of patients presenting with purpura fulminans associated with peripheral gangrene between 1989 and 2004.

RESULTS

All 12 patients presented with sudden onset of purpuric patches and evolving gangrene of the extremities in association with a shock syndrome (hypotension, oliguria). Eleven patients had disseminated intravascular coagulation. The cause of purpura fulminans was infectious in 9 patients, surgical in two, and cancer in one. Three patients died (25%) within a week of onset of purpura fulminans. Of the 9 surviving patients, 8 required amputation of at least one limb. Four patients required amputation of all 4 limbs.

LIMITATIONS

Retrospective study design, varying clinical descriptions, and potential referral bias are limitations.

CONCLUSION

Purpura fulminans in association with symmetric peripheral gangrene is an ominous clinical presentation.

[Hemostasis disorders in severe infections: State of the art]

The haemostatic system is greatly modified during severe infections. The early activation of coagulation is triggered by tissue factor expression and secondary fibrinolysis impaired by the upregulation of fibrinolysis inhibitors. This imbalance is a major cause of subsequent organ dysfunction. Natural anticoagulants (Tissue factor pathway inhibitor (TFPI), Antithrombin (AT), and Protein C (PC) are consumed or inhibited in this pathological process justifying a therapeutic supplementation with these inhibitors to improve sepsis-induced organ failure and mortality. No effect on the mortality rate could be documented in controlled studies using recombinant TFPI or AT concentrates but a biological interaction with heparin therapy could have biased the results. Treatment with recombinant activated PC was associated with a significant reduction in the mortality rate of severely ill patients. An increase in the rate of hemorrhagic adverse effects was observed with these compounds, justifying a strict observance of contraindications and of patient selection.

Antithrombin supplementation for anticoagulation during continuous hemofiltration in critically ill patients with septic shock: a case-control study

Introduction

Acquired antithrombin III (AT) deficiency may induce heparin resistance and premature membrane clotting during continuous renal replacement therapy (CRRT). The purpose of this study was to evaluate the effect of AT supplementation on filter lifespan in critically ill patients with septic shock requiring CRRT.

Methods

We conducted a retrospective case-control analysis based on a 4-year observational study with prospectively collected data in two medical intensive care units in a university hospital. In all, 106 patients with septic shock underwent CRRT during the study period (55 during 2001 to 2002 and 51 during 2003 to 2004). Of these, 78 had acquired AT deficiency (plasma level below 70%) at onset of renal supportive therapy, 40 in the first 2-year period and 38 in the last 2-year period. In the latter intervention period, patients received AT supplementation (50 IU/kg) during CRRT each time that plasma AT activity, measured once daily, fell below 70%.

Results

In a case-control analysis of the 78 patients with acquired AT deficiency, groups were similar for baseline characteristics, except in severity of illness as assessed by a higher Simplified Acute Physiology Score (SAPS) II after 2002. In comparison with controls, cases had a significantly greater AT level after AT supplementation, but not at baseline, and a smaller number of episodes of clots, without excess bleeding risk. The median hemofilter survival time was longer in the AT group than in the heparin group (44.5 versus 33.4 hours; p = 0.0045). The hemofiltration dose, assessed by the ratio of delivered to prescribed ultrafiltration, increased during intervention. AT supplementation was independently associated with a decrease in clotting rate, whereas femoral angioaccess and higher SAPS II were independent predictors of filter failure. However, mortality did not differ between periods, in the control period the observed mortality was significantly higher than predicted by the SAPS II score, unlike in the treatment period.

Conclusion

In sepsis patients requiring CRRT and with acquired AT deficiency, anticoagulation with unfractionated heparin plus AT supplementation prevent premature filter clotting and may contribute to improving outcome, but the cost-effectiveness of AT remains to be determined.

[Hemostasis disorders in severe infections: state of the art]

The haemostatic system is greatly modified during severe infections. The early activation of coagulation is triggered by tissue factor expression and secondary fibrinolysis impaired by the upregulation of fibrinolysis inhibitors. This imbalance is a major cause of subsequent organ dysfunction. Natural anticoagulants (Tissue factor pathway inhibitor (TFPI), Antithrombin (AT), and Protein C (PC) are consumed or inhibited in this pathological process justifying a therapeutic supplementation with these inhibitors to improve sepsis-induced organ failure and mortality. No effect on the mortality rate could be documented in controlled studies using recombinant TFPI or AT concentrates but a biological interaction with heparin therapy could have biased the results. Treatment with recombinant activated PC was associated with a significant reduction in the mortality rate of severely ill patients. An increase in the rate of hemorrhagic adverse effects was observed with these compounds, justifying a strict observance of contraindications and of patient selection.

Clinical use of plasma and plasma fractions

The use of plasma and plasma-derived products has always involved a careful balance of anticipated benefit versus risk. Risk reduction through pathogen-inactivated products has been successful, but the expense of manufacture does not warrant widespread use. Although plasma has always had limited indications for use, these are often misunderstood or ignored in favor of received knowledge and tradition. Solid evidence from multiple trials support the limited indications for FFP described here and support products that target specific coagulation defects.

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.

Effect of antithrombin III on neutrophil deformability

As the spherical diameter of pulmonary capillaries is smaller than that of neutrophils, increased neutrophil stiffness or conversely, decreased neutrophil deformability is a key step in the initial sequestration of neutrophils within the lungs during inflammatory processes. Antithrombin III (AT) is known to exert a therapeutic effect against disseminated intravascular coagulation, and accumulating evidence suggests that AT also has anti-inflammatory properties. The mechanisms of its anti-inflammatory effects remain unclear, but in a rat endotoxin model, AT apparently inhibited neutrophil sequestration in the lung. In the present in vitro study, therefore, we examined the effect of AT on the deformability of human neutrophils and correlated those findings with their F-actin content. Isolated human neutrophils were stimulated with formyl-Met-Leu-Phe (1 muM, 2 min) in the presence or absence of the alpha, beta, or low heparin-affinity isoforms of AT (1 IU/ml, 20 min), and deformability was evaluated using a filter assay system. Neutrophils were also stained with fluorescein isothiocyanate-phalloidin and subjected to a fluorescein-activated cell sorter scan to assess F-actin content. The results showed that pretreatment with any of the three AT isoforms similarly inhibited the decreased neutrophil deformability and increased F-actin content of stimulated cells. Notably, heparinase had no effect on deformability or F-actin content in the presence or absence of AT, which was somewhat unexpected, as heparin sulfate proteoglycans likely function as AT receptors. These findings suggested that AT inhibits the increase in neutrophil stiffness seen during inflammatory processes by inhibiting actin polymerization via a heparin-independent pathway.

Use of blood products in sepsis: An evidence-based review

OBJECTIVE

In 2003, critical care and infectious disease experts representing 11 international organizations developed management guidelines for the use of blood products in sepsis that would be of practical use for the bedside clinician, under the auspices of the Surviving Sepsis Campaign, an international effort to increase awareness and to improve outcome in severe sepsis.

DESIGN

The process included a modified Delphi method, a consensus conference, several subsequent smaller meetings of subgroups and key individuals, teleconferences, and electronic-based discussion among subgroups and among the entire committee.

METHODS

The modified Delphi methodology used for grading recommendations built on a 2001 publication sponsored by the International Sepsis Forum. We undertook a systematic review of the literature graded along five levels to create recommendation grades from A to E, with A being the highest grade. Pediatric considerations to contrast adult and pediatric management are in the article by Parker et al. on p. S591.

CONCLUSION

In the absence of extenuating circumstances and following resolution of tissue hypoperfusion, red blood cell transfusion should be targeted to maintain hemoglobin at 7.0 g/dL or greater. Erythropoietin is not recommended as a specific treatment for sepsis-associated anemia. Fresh-frozen plasma should be given for documented deficiency of coagulation factors and in the presence of active bleeding or before surgical or invasive procedures. Antithrombin administration is not recommended. Specific platelet transfusion thresholds are based on the presence or absence of bleeding, significant risk for bleeding, plans for surgery or invasive procedures, and platelet count </=5,000/mm.

Massive alveolar thrombin activation in Pseudomonas aeruginosa-induced acute lung injury

In acute lung injury (ALI), a coagulation/fibrinolysis imbalance leads to fibrin deposition, persistence of which contributes to fibrotic evolution. Our study evaluated the effects of early inhibition of coagulation in Pseudomonas aeruginosa (Pa)-induced ALI through the use of recombinant human antithrombin (rhAT). The study was conducted in vivo on a murine model of Pa-induced ALI. Intravenous rhAT was administered simultaneously with intratracheal Pa. Four experimental groups were compared: CTR, intratracheal saline (0.5 mL/kg)/intravenous saline (1 mL); PNP, intratracheal Pa (0.5 mL/kg of 2 x 10(9) cfu)/intravenous saline; AT, intratracheal saline/intravenous rhAT (500 IU/kg); ATPNP, intratracheal Pa/intravenous rhAT. Epithelial and endothelial permeabilities were evaluated with radiolabeled albumin flux across the alveolar barrier (125I- and 131I-labeled albumin). Thrombin-antithrombin (TAT) complexes levels were used as markers of coagulation activation in blood samples and in BAL fluid. Epithelial and endothelial protein permeability were increased in Pa-induced ALI versus control. Intravenous rhAT administration led to further permeability disorders. Administration of rhAT in Pa ALI led to a rise in TAT complexes in ATPNP blood serum and BAL fluids compared with the other groups. In Pa-induced ALI the administration intravenous rhAT leads to major histologic damage, alveolar capillary barrier injury, and permeability increase. Such effects of the inhibition of thrombin activation by rhAT lead to the hypothesis of a probable beneficial role of early coagulation activation in ALI as a factor limiting both the extent of injury and permeability disorders. Our study suggests that inhibition of this initial procoagulative imbalance is potentially dangerous.

Coagulation in Sepsis

Activation of the coagulation cascade during invasive infection can result in purpura fulminans, with rapid progression of tissue ischemia, or may manifest as abnormal clotting indices alone. Although severe derangements in coagulation are associated with organ dysfunction and increased mortality, the contribution of coagulopathy to the pathophysiology of sepsis remains incompletely understood. Over the past decade, investigators have evaluated several therapeutic anticoagulant strategies in sepsis, and manipulation of the coagulation system has emerged as a key concept in the current management of this disease. Clinical observations during treatment of septic patients with the endogenous anticoagulant activated protein C have stimulated additional study of interactions between endothelial injury, coagulation, and inflammation. This review describes clotting abnormalities during sepsis and discusses the clinical experience with therapeutic strategies intended to oppose excessive coagulation.

Antithrombin administration during experimental cardiopulmonary resuscitation

OBJECTIVE

To determine whether antithrombin (AT) administration during cardiopulmonary resuscitation (CPR) increased cerebral circulation and reduced reperfusion injury.

METHODS

Ventricular fibrillation was induced in 24 anaesthetised pigs. After a 5-min non-intervention interval, CPR was started. The animals were randomised into two groups. The treatment group received AT (250 U/kg) and the control group received placebo, after 7 min of CPR. Defibrillation was attempted after 9 min of CPR. If restoration of spontaneous circulation (ROSC) was achieved, the animals were observed for 4 h. Cortical cerebral blood flow was measured using laser-Doppler flowmetry. Cerebral oxygen extraction was calculated to reflect the relation between global cerebral circulation and oxygen demand. Measurements of eicosanoids (8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha)), AT, thrombin-antithrombin complex (TAT) and soluble fibrin in jugular bulb plasma were performed to detect any signs of cerebral oxidative injury, inflammation and coagulation.

RESULTS

There was no difference between the groups in cortical cerebral blood flow, cerebral oxygen extraction, or levels of eicosanoids, TAT or soluble fibrin in jugular bulb plasma after ROSC. In the control group reduction of AT began 15 min after ROSC and continued throughout the entire observation period (P < 0.05). Eicosanoids and TAT were increased compared to baseline in all animals (P < 0.01).

CONCLUSIONS

In this experimental model of CPR, AT administration did not increase cerebral circulation or reduce reperfusion injury after ROSC.

Hemostatic markers and the sepsis-related organ failure assessment score in patients with disseminated intravascular coagulation in an intensive care unit

We investigated the correlation between disseminated intravascular coagulation (DIC) score and hemostatic parameters and sepsis-related organ failure assessment (SOFA) score with clinical outcome of patients with DIC in an intensive care unit (ICU). The SOFA score was markedly elevated in patients with DIC relative to patients without DIC and significantly higher in non-survivors than in survivors. Abnormalities in almost all hemostatic parameters were significant in patients with DIC, but there was no significant difference in almost all hemostatic parameters between survivors and non-survivors. However, plasma antithrombin (AT) levels were significantly lower in non-survivors than in survivors. Soluble fibrin (SF) and tissue type plasminogen activator (tPA)-plasminogen activator inhibitor-I (PAI-I) complex correlated significantly with the SOFA score, whereas AT levels correlated significantly and negatively with the SOFA score. We conclude that the SOFA score is useful for predicting outcome in DIC patients in the ICU, and that hemostatic parameters, especially plasma AT levels, are also useful markers for organ failure and clinical outcome.

Anti-thrombin III in the management of hematopoietic stem-cell transplantation-associated toxicity

OBJECTIVE

To describe the evidence assessing the use of anti-thrombin III (AT-III) in the management of toxicity associated with hematopoietic stem-cell transplantation (HSCT)-conditioning regimens.

DATA SOURCES

Clinical literature was accessed through conference proceedings, EMBASE, the Cochrane database, and MEDLINE (1966-December 2003).

STUDY SELECTION AND DATA EXTRACTION

Case reports, small case series, case-control and cohort studies, and randomized controlled trials of AT-III in HSCT were evaluated. Publications examining AT-III use in the non-HSCT setting were also explored. Key search terms included AT-III, transplantation, and veno-occlusive disease (VOD).

DATA SYNTHESIS

Severe VOD and ensuing multiple organ dysfunction is associated with high mortality in HSCT. A low AT-III level has been shown to correlate with the development of organ dysfunction. Phase II trials, case series, and one small, randomized, placebo-controlled study suggest a benefit when AT-III therapy is instituted early in the course of VOD/multiple organ dysfunction syndrome. In all of these reports, AT-III use was devoid of adverse events.

CONCLUSIONS

Although further studies are needed to ascertain the optimal target level, method, and duration of administration, AT-III is still a viable alternative for the treatment of severe VOD and ensuing multiple organ dysfunction.

Antithrombin III Diminishes Production of Oxygen Radical in Endotoxin-Infused Rat Lung

The interaction of antithrombin III (AT) with cell surface glycosaminoglycans is known to have an inhibitory effect on inflammatory processes. We evaluated the effect of AT on endotoxin-induced production of oxygen radical in the pulmonary circulation using a fluorescent imaging technique. Also measured was the myeloperoxidase content of the lung, which served as an index of neutrophil accumulation, and neutrophil F-actin levels. Four groups of rats were infused for 2 h with endotoxin at 4.5 mg/kg/h (Et group), physiological saline (CT group), 100 U/kg of AT + endotoxin (AT group), or 100 U/kg of low-heparin-affinity latent-AT + endotoxin (L-AT group), respectively. Production of oxygen radical, neutrophil accumulation, and neutrophil F-actin levels were all significantly higher in the ET and L-AT groups than in the CT or AT group. Moreover; the levels of myeloperoxidase within the lung were well correlated with levels of oxygen radical production, which was consistent with the electron microscopic finding that cerium was deposited almost exclusively around neutrophils. Thus, it appears that AT most likely reduces F-actin formation in neutrophil by binding to glycosaminoglycans (e.g., syndecan-4) on the neutrophil, thereby reducing neutrophil accumulation in the lung, which would in turn inhibit oxygen radical production in the lung.

Antithrombin reduction after experimental cardiopulmonary resuscitation

OBJECTIVE

To determine whether activation of coagulation and inflammation during cardiac arrest results in a reduction of antithrombin (AT) and an increase in thrombin-antithrombin (TAT) complex during reperfusion.

METHODS

Ventricular fibrillation (VF) was induced in ten anaesthetized pigs. After a 5-min non-intervention interval, closed-chest cardiopulmonary resuscitation (CPR) was performed for 9 min before defibrillation was attempted. If restoration of spontaneous circulation (ROSC) was achieved, the animals were observed for 4 h and repeated blood samples were taken for assay of AT, TAT and eicosanoids (8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha)).

RESULTS

AT began to decrease 15 min after ROSC and the reduction continued throughout the observation period (P<0.05). The lowest mean value (79%) occurred 60 min after ROSC. The TAT level was increased during the first 3 h after ROSC (P<0.05), indicating thrombin generation. The eicosanoids were increased throughout the observation period (P<0.05).

CONCLUSIONS

AT is reduced and TAT and eicosanoids are increased after cardiac arrest, indicating activation of coagulation and inflammation.

Coagulation dysfunction in sepsis and multiple organ system failure

In patients diagnosed with sepsis, severe sepsis or septic shock, cytokine-mediated endothelial injury, and TF activation initiate a cascade of events that culminate in the development of coagulation dysfunction characterized as procoagulant and antifibrinolytic. This abnormal state predisposes the patient to develop microvascular thrombosis, tissue ischemia, and organ hypoperfusion. Multiple organ dysfunction syndrome may be a product of this pertubation in coagulation regulation. Treatments aimed at correcting this coagulation dysfunction have met with mixed success. Current data suggest that AT III replacement therapy has limited efficacy in adults with severe sepsis. In contrast, adult patients diagnosed with severe sepsis and organ failure and treated with aPC (drotrecogin alfa activate) have a significantly reduced risk of death when compared with placebo-treated patients. A phase III trial examining the efficacy of protein C replacement therapy in pediatric patients with severe sepsis and organ failure is underway.

[Coagulation inhibitors in severe sepsis: state of the art]

OBJECTIVE

To present and discuss the rationale and the results of clinical trials using supplementation with physiologic anticoagulants (Tissue Factor Pathway Inhibitor (TFPI), AntiThrombin (AT), and Protein C (PC) in patients with severe sepsis.

RATIONALE

An early activation of the coagulation cascade occurs in severe sepsis. TFPI, AT, and PC are major inhibitors of the coagulation cascade, and additionally modulate inflammatory and vascular reactions. They are consumed or inhibited in the sepsis pathologic process. Therapeutic supplementation with these inhibitors could improve the sepsis-induced organ failures and mortality.

CLINICAL RESULTS

Randomized controlled studies were recently completed. No effect on the mortality rate could be documented after treatment with recombinant TFPI. AT concentrates neither improve mortality, but a biological interaction with heparin therapy could have biased the study results. Treatment with recombinant activated PC (alpha-drotrecogin) was associated with a significant reduction in the mortality rate of severely ill patients and received recently the approval from FDA and EC authorities in this indication. An increase in the rate of hemorrhagic adverse effects has been observed with these compounds, justifying a strict observance of contraindications and of patients selection. PROSPECTIVE: Additional studies are needed to give confirmation of the positive effects of activated PC supplementation in less severely ill patients, children and specific clinical situations. The effects of new anticoagulant compounds are currently evaluated in preclinical studies.

Heat shock proteins and ventilator-induced lung injury

In this review, we discuss the heat shock response, a specific example of gene expression that has been studied over the past 25 years, and its relevance to acute lung injury and other critical conditions. The heat shock response has been observed in virtually all organisms and involves the rapid induction of a set of highly conserved genes that encode heat shock proteins (HSPs). The HSP70 family represents the most prominent eukaryotic group of HSPs. It has been suggested that members of the HSP70 family act in the protection of cellular damage by binding to denatured or abnormal proteins after heat shock, thereby preventing protein aggregation. The capacity of HSPs to subserve cytoprotection has produced considerable interest from the perspective of elucidating the pathophysiology of organ damage and dysfunction. Several studies support the hypothesis that HSPs are cytoprotective In addition, recent investigations have demonstrated that HSP70 is released into the systemic circulation and is involved in the activation of innate immunity.

Recombinant antithrombin attenuates pulmonary inflammation following smoke inhalation and pneumonia in sheep

OBJECTIVE

The interaction between coagulation and inflammation has become one of the major topics in critical care medicine. In the present study, we investigated the effect of posttreatment of sepsis with recombinant human antithrombin.

DESIGN

Experimental laboratory in a university hospital.

SETTING

University laboratory.

SUBJECTS

Female merino ewes (n = 16).

INTERVENTIONS

After 1 wk of recovery from the surgical preparation, a tracheotomy was performed followed by insufflation of 48 breaths of cotton smoke (<40 degrees C). Afterward, a stock solution of live (5 x 10(11) colony-forming units) was instilled in the both lung lobes through a bronchoscope. All sheep were mechanically ventilated employing 100% oxygen. An infusion of recombinant human antithrombin (100 units x kg(-1) x 24 hrs(-1), intravenously; n = 6) or saline (n = 6) was started 1 hr after injury. Sham control animals (n = 4) were surgically prepared but not insufflated with smoke and bacteria. Lung histologic changes were evaluated by a scoring system.

MEASUREMENTS AND MAIN RESULTS

The infusion of recombinant human antithrombin maintained the baseline antithrombin activity throughout the study; in the saline-treated group, antithrombin activity decreased significantly. The lung wet/dry weight ratio and the histology score (combined scores for congestion, edema, inflammation, and hemorrhage) were significantly increased by the insult, but recombinant human antithrombin attenuated these responses. More than 30% of both bronchi and bronchioles were obstructed by cast formation after smoke inhalation and pneumonia. The cast was composed of epithelial cells, neutrophils, mucus, and fibrin. The obstruction was significantly improved by recombinant human antithrombin infusion. Arterial pressure and urine output were also attenuated in recombinant human antithrombin-treated animals. The increases in plasma nitrate/nitrite concentrations and pulmonary shunt fraction after the injury were not attenuated by recombinant human antithrombin.

CONCLUSION

Posttreatment by recombinant human antithrombin was effective in treating acute lung injury after smoke inhalation and pneumonia in sheep. We hypothesize that the decrease in antithrombin activity during sepsis might induce severe airway obstruction and that supplementation with antithrombin inhibits this decrease.

Antithrombin: a new look at the actions of a serine protease inhibitor

Antithrombin (AT) is a plasma-derived, single-chain glycoprotein with a molecular weight of 58 kDa. It is a serine protease inhibitor (serpin), sharing about 30% homology in amino acid sequence with other serpins. AT is a complex molecule with multiple biologically important properties. It is a potent anticoagulant that has been demonstrated to provide benefit in animal models and small cohorts of patients with coagulation disorders. AT also has remarkable anti-inflammatory properties, several of which result from its actions in the coagulation cascade. Activated coagulation proteases like activated factor X and thrombin contribute to inflammation; for instance, by the release of pro-inflammatory mediators. Inhibition of these proteases by AT prevents their specific interaction with cells and subsequent reactions. Anti-inflammatory properties of AT independent of coagulation involve direct interactions with cells leading to the release of, for instance, prostacyclin. Binding of AT to a recently identified cellular receptor, syndecan-4, leads to the interference with the intracellular signal induced by mediators like lipopolysaccharides and, thereby, to a down-modulation of the inflammatory response. AT has been shown to be effective in prospective and well-controlled small-scale studies of patients with inflammatory conditions, including sepsis. Although AT did not decrease overall patient mortality in a double-blind, placebo-controlled, phase III trial of patients with sepsis, it is important to note that AT improved the survival of individuals in this study not receiving heparin as a prophylactic regimen, which can be explained by the impaired interaction of AT with its cellular receptor in the presence of heparin, resulting in the reduction of the anti-inflammatory properties. Accordingly, the supplementation of AT without concomitant heparin may be beneficial in disorders with inflammatory characteristics, which has to be demonstrated in further clinical studies. Finally, recent results suggest that latent AT can induce apoptosis of endothelial cells by disrupting cell-matrix interactions. Further investigations will have to demonstrate whether latent and/or cleaved AT are physiological means to control angiogenesis. A potential prophylactic or therapeutic use as an anti-angiogenic and antitumor agent merits further exploration, including whether the growth of vessels in tumor tissues or close to tumors can be controlled by latent AT without affecting the formation of blood vessels during wound healing processes.

Antithrombin prevents endotoxin-induced hypotension by inhibiting the induction of nitric oxide synthase in rats

Antithrombin (AT) prevents Escherichia coli-induced hypotension in animal models of sepsis, and it further reduces the mortality of patients with septic shock. In the present study, we examined whether AT may prevent the endotoxin (ET)-induced hypotension by promoting the endothelial release of prostacyclin (PGI(2)) in rats. Intravenous administration of AT (250 U/kg) prevented both hypotension and the increases in plasma levels of NO(2)(-)/NO(3)(-) in rats given ET. Lung expression of messenger RNA (mRNA) for tumor necrosis factor-alpha (TNF-alpha) was transiently increased after ET administration, followed by the increases in lung tissue levels of TNF-alpha. Both the lung activity of the inducible form of nitric oxide synthase (iNOS) and the lung expression of iNOS mRNA in animals administered ET were gradually increased after the TNF-alpha mRNA expression had peaked. Administration of AT significantly inhibited these increases. Neither DEGR-F.Xa, a selective inhibitor of thrombin generation, nor Trp(49)-modified AT, which is not capable of promoting the endothelial release of PGI(2), showed any effects on these changes induced by ET. Administration of antirat TNF-alpha antibody produced effects similar to those induced by AT. Indomethacin pretreatment abrogated the effects induced by AT. Iloprost, a stable derivative of PGI(2), produced effects similar to those of AT. These findings suggested that AT prevents the ET-induced hypotension by inhibiting the induction of iNOS through inhibiting TNF-alpha production. These effects of AT could be mediated by the promotion of endothelial release of PGI(2) and might at least partly explain the therapeutic effects for septic shock.

Management of the patient with coagulation disorders

Understanding normal haemostasis and the pathophysiology of its disorders is essential for providing optimal care and ensuring judicious usage of blood products, as is keeping abreast of novel therapeutic modalities in a rapidly evolving field. The growing availability of synthetic coagulation factors has (at least in the western hemisphere) helped to reduce morbidity and therapeutic complications, while expanding the indications and usage of these agents. Promising advances in gene therapy may indeed introduce a sea change in the next decade or two.

Coagulation blockade prevents sepsis-induced respiratory and renal failure in baboons

Sepsis-induced tissue factor (TF) expression activates coagulation in the lung and leads to a procoagulant environment, which results in fibrin deposition and potentiates inflammation. We hypothesized that preventing initiation of coagulation at TF-Factor VIIa (FVIIa) complex would block fibrin deposition and control inflammation in sepsis, thereby limiting acute lung injury (ALI) and other organ damage in baboons. A model of ALI was used in which adult baboons were primed with killed Escherichia coli (1 x 10(9) CFU/kg), and bacteremic sepsis was induced 12 h later by infusion of live E. coli at 1 x 10(10) CFU/kg. Animals in the treatment group were given a competitive inhibitor of TF, site-inactivated FVIIa (FVIIai), intravenously at the time of the infusion of live bacteria and monitored physiologically for another 36 h. FVIIai dramatically protected gas exchange and lung compliance, prevented lung edema and pulmonary hypertension, and preserved renal function relative to vehicle (all p < 0.05). Treatment attenuated sepsis-induced fibrinogen depletion (p < 0.01) and decreased systemic proinflammatory cytokine responses, for example, interleukin 6 (p < 0.01). The protective effects of TF blockade in sepsis-induced ALI were confirmed by using tissue factor pathway inhibitor. The results show that TF-FVIIa complex contributes to organ injury in septic primates in part through selective stimulation of proinflammatory cytokine release and fibrin deposition.

The impact of molecular biology on the practice of pediatric critical care medicine

Molecular biology is increasingly affecting all areas of clinical medicine, including pediatric critical care medicine. Recent advances in genomics will allow for a more in-depth understanding of disease processes that are relevant to the pediatric intensivist, such as sepsis, the acute respiratory distress syndrome, and multiple organ dysfunction syndrome. In turn, understanding critical illness at the genomic level may allow for more effective stratification of patient subclasses and targeted, patient-specific therapy. The related fields of pharmacogenomics and pharmacogenetics hold the promise of improved drug development and the tailoring of drug therapy based on the individual's drug metabolism profile. Therapeutic strategies aimed at modulating host inflammatory responses remain viable but will need to take into account the inherent redundancy of the host inflammatory response and the heterogenous responses between individual patients. Thus, "immuno-phenotyping" of critically ill patients will allow for more rational immune-modulating therapies, either in the form of inhibiting or enhancing specific immune/inflammatory responses. The host also contains powerful, broad cytoprotective mechanisms that could potentially be harnessed as a strategy for organ and tissue protection in many forms of critical illness. Finally, prospects for gene therapy, although quite challenging at present, may be applicable to the intensive care unit in the near future. With these rapid advancements in molecular biology, it is imperative that all pediatric critical care practitioners become, at least, familiar with the field and its related technology. Hopefully, clinician-scientists involved in pediatric critical care will also shape the direction of these future prospects.

Clinical impact of novel anticoagulation strategies in sepsis

Derangements in coagulation and fibrinolysis are frequent complications of systemic infection, and septic shock is the most common recognized cause of disseminated intravascular coagulation. Anticoagulant therapy has been used as a treatment strategy for severe sepsis for several decades without compelling evidence of efficacy until the 2001 publication of the phase III trial with recombinant human activated protein C. Major phase III international trials with antithrombin and tissue factor pathway inhibitor also have been completed recently. The molecular mechanisms by which the clotting system interacts with the innate immune response have greatly facilitated the understanding of coagulation and the pathophysiology of septic shock. Anticoagulants such as recombinant human activated protein C and related agents may become the mainstay of adjuvant therapies for severe sepsis in the near future.

Pediatric sepsis and multiple organ dysfunction syndrome

Systemic inflammatory response syndrome may be viewed as the systemic expression of cytokine signals that normally function on an autocrine or paracrine level. Sepsis is defined as systemic inflammatory response syndrome caused by an infection. Multiple organ dysfunction syndrome may represent the end stage of severe systemic inflammatory response syndrome or sepsis. Many cells are involved, including endothelial cells and leukocytes and multiple proinflammatory and antiinflammatory mediators (cytokines, oxygen free radicals, coagulation factors, and so forth). Various pathophysiologic mechanisms have been postulated. The most popular theory is that the inflammatory process loses its autoregulatory capacity; however, microcirculatory dysregulation and apoptosis may also be important, and a new paradigm posits a complex nonlinear system. Many new treatments have been studied recently. The usefulness of immune modulating diets remains to be evaluated. Molecular immunomodulation is still of unclear value. The therapy of sepsis and multiple organ dysfunction syndrome remains mainly supportive.

Microvascular endothelial dysfunction: a renewed appreciation of sepsis pathophysiology

Severe sepsis, defined as sepsis associated with acute organ dysfunction, results from a generalized inflammatory and procoagulant host response to infection. Coagulopathy in severe sepsis is commonly associated with multiple organ dysfunction, and often results in death. The molecule that is central to these effects is thrombin, although it may also have anticoagulant and antithrombotic effects through the activation of Protein C and induction of prostacyclin. In recent years, it has been recognized that chemicals produced by endothelial cells play a key role in the pathogenesis of sepsis. Thrombomodulin on endothelial cells coverts Protein C to Activated Protein C, which has important antithrombotic, profibrinolytic and anti-inflammatory properties. A number of studies have shown that Protein C levels are reduced in patients with severe infection, or even in inflammatory states without infection. Because coagulopathy is associated with high mortality rates, and animal studies have indicated that therapeutic intervention may result in improved outcomes, it was rational to initiate clinical studies.