Therapeutic use of antithrombin concentrate in sepsis

Role of complement in multiorgan failure

Multiorgan failure (MOF) represents the leading cause of death in patients with sepsis and systemic inflammatory response syndrome (SIRS) following severe trauma. The underlying immune response is highly complex and involves activation of the complement system as a crucial entity of innate immunity. Uncontrolled activation of the complement system during sepsis and SIRS with in excessive generation of complement activation products contributes to an ensuing dysfunction of various organ systems. In the present review, mechanisms of the inflammatory response in the development of MOF in sepsis and SIRS with particular focus on the complement system are discussed.

Antithrombin deficiency and its relationship to severe burns

Antithrombin (AT) is an important endogenous anticoagulant and exhibits marked anti-inflammatory properties. To evaluate the incidence of AT deficiency in severe burn and its correlation to the variables of the abbreviated burn severity index (ABSI), length of hospital stay (LOS) and mortality we collected data on the substitution of human plasma-derived AT concentrate in 201 consecutive patients suffering from severe burn. One hundred and eight patients (54%) developed AT deficiency during their hospitalisation and, according to our institutional practice, received substitution therapy by continuous infusion to maintain physiological plasma activity (70-120%). The mean administered dose served as a measure of AT deficiency. The percentage of patients in an AT deficient state was highest within the first 5 days after injury. It was 26% on day 1 and between 38% and 41% on days 2-5 and thereafter decreased constantly over time. A multiple regression analysis between the dependent variable mean administered dose of AT concentrate and the independent variables age, total body surface area burned (TBSA), gender, inhalation injury (INHAL), full thickness burn (FTB), LOS and mortality was performed. Age, gender and FTB showed no significant influence on the development of AT deficiency. Increasing TBSA and INHAL clearly increase the risk of developing AT deficiency (p-values 0.0001 and 0.037). The analysis also identified AT deficiency as an independent predictor of LOS and mortality (p-values 0.036 and 0.003). Development of AT deficiency is a frequent event after burn with significant correlation to TBSA and INHAL, increased mortality rates and longer hospital stays.

Heparin nebulization attenuates acute lung injury in sepsis following smoke inhalation in sheep

Pseudomonas pneumonia is a common complication of smoke inhalation injury. Airway casts formed from clotted mucous occur frequently in this condition. A recent report shows that intravenous heparin improves oxygenation and reduces lung damage in a sheep model of smoke inhalation. We hypothesized that nebulized heparin could be an effective means of reducing cast formation. Female sheep (n = 19) were surgically prepared for a study of acute lung injury (ALI). After a tracheotomy, 48 breaths of cotton smoke (<40 degrees C) were inflated into the airway. Afterwards, live Pseudomonas aeruginosa (5 x 10(11) CFU) was instilled into the lung. All sheep were mechanically ventilated with 100% O2 and were divided into four groups: a heparin-nebulized group (n = 5; animals received aerosolized heparin [10,000 I.U.] 1 h after the bacterial instillation and subsequently every 4 h thereafter), an intravenous heparin group (n = 5,300 U/kg/23 h, infusion was started 1 h after the injury), a saline-nebulization group (n = 5; animals received inhaled nebulized saline), and a sham injury group (n = 4, treated in the same fashion, but no injury). The animals were sacrificed after 24 h of mechanical ventilation, and lung samples were harvested. Sheep exposed to lung injury presented with typical hyperdynamic cardiovascular changes and a corresponding drop in PaO2. These changes were significantly attenuated in the heparin groups. Histological changes consisting of cellular infiltrates, lung edema, congestion, and cast formation were reduced by heparin. These data suggest that nebulized inhaled heparin is a beneficial therapy for sepsis-induced ALI.

Activated protein C in normal human pregnancy and pregnancies complicated by severe preeclampsia: a therapeutic opportunity?

OBJECTIVES

Given the efficacy and safety of recombinant human activated protein C (rhAPC) in the systemic inflammatory response syndrome, this study was designed to review the evidence for a role for APC in the pathogenesis of preeclampsia. Preeclampsia is a proinflammatory and procoagulant state, and it is a pregnancy-specific condition that mimics the systemic inflammatory response syndrome. rhAPC reduces mortality in patients with systemic inflammatory response syndrome and could potentially have a role as disease-modifying therapy in preeclampsia. To determine which patients would be offered rhAPC, the literature pertaining to fetal/neonatal outcomes for preeclampsia remote from term, transplacental transport of protein C, and pregnancy experience with the compound were reviewed.

DATA SOURCES

MEDLINE, review papers, hand searches of relevant nonindexed journals, and the bibliographies of relevant textbooks and articles reviewed.

STUDY SELECTION

Randomized controlled trials were considered to provide the best quality of clinical data. Case-control series were considered over uncontrolled data. Some data were not available in the published literature (e.g., neonatal outcomes at various gestational ages and birthweights after a hypertensive pregnancy; and transplacental transfer of protein C), and these data were determined by us.

DATA EXTRACTION

Data were extracted by systematic review onto data collection sheets. Because of the quality of the data, this review is primarily qualitative.

DATA SYNTHESIS

APC levels fall during normal gestation, returning to normal values by 6 wks postpartum. Limited data suggest that early onset preeclampsia is a state of further, and inappropriate, reduction in APC. Preeclampsia resembles systemic inflammatory response syndrome in this regard. After hypertensive pregnancies, neonates have a 50% chance of intact survival if delivered after 27 + 0 wks of gestation with a birthweight of >600 g. It would seem ethical to offer women with preeclampsia with <50% chance of intact perinatal survival novel and potentially disease-modifying therapy such as rhAPC, especially as there is no transplacental transfer of protein C. Limited evidence would support the use of rhAPC in women with severe postpartum preeclampsia.

CONCLUSIONS

Sufficient data exist to support the use of rhAPC in phase II clinical studies for women with either early onset preeclampsia or severe or deteriorating postpartum disease.

Pharmacology of acute lung injury

The acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a clinical syndrome that affects both medical and surgical patients. To date, despite improved understanding of the pathogenesis of ALI/ARDS, pharmacological modalities have been unsuccessful in decreasing mortality. However, several pharmacological agents for ARDS are in development and have shown great promise. In addition to the anti-inflammatory category including late corticosteroids, inhaled nitric oxide, alveolar surfactant, and vasodilators are being evaluated. Replacements of anticoagulation mediators have also suggested beneficial effects on the patient outcome. This article provides an overview of pharmacological treatments of ALI/ARDS.

Predictive value of antithrombin III and serum C-reactive protein concentration in critically ill patients with suspected sepsis

OBJECTIVE

To evaluate at admission the performance of serum antithrombin III, serum C-reactive protein, white blood cell and platelet counts, and thromboplastin time values in prediction of hospital mortality rates in critically ill patients with suspected sepsis.

DESIGN

Prospective, cohort study.

SETTING

University hospital medical-surgical intensive care unit.

PATIENTS

One hundred eight consecutive critically ill patients with suspected sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The outcome measure was hospital mortality rate. Hospital survivors (n = 66) and nonsurvivors (n = 42) differed statistically significantly in admission antithrombin III activity (percentage of normal): survivors' median 66% (interquartile range, 48% to 82%) vs. nonsurvivors' median 46% (37% to 65%, p =.0002 by Mann-Whitney test). Analysis revealed similarly statistically significant differences between survivors and nonsurvivors in admission platelet count, admission thromboplastin time, day 1 Logistic Organ Dysfunction score, and Acute Physiology and Chronic Health Evaluation III score, but not in serum C-reactive protein concentrations or in white blood cells. However, the areas under the receiver operating curves (AUC) showed significantly worse discriminative power for admission antithrombin III concentration (AUC, 0.71; SE, 0.05), platelet count (AUC, 0.67; SE, 0.05), thromboplastin time (AUC, 0.65; SE, 0.05), C-reactive protein concentration (AUC, 0.60; SE, 0.05), and white blood cell count (AUC, 0.53; SE, 0.06) than did the day 1 Logistic Organ Dysfunction score (AUC, 0.82; SE, 0.04) and the Acute Physiology and Chronic Health Evaluation III score (AUC, 0.84; SE, 0.04). Multivariate logistic regression analysis revealed that only the Acute Physiology and Chronic Health Evaluation III score was independently associated with hospital mortality rate.

CONCLUSIONS

Admission antithrombin III concentrations, but not C-reactive protein concentrations, differ significantly between hospital survivors and nonsurvivors among critically ill patients with septic infection. However, in prediction of hospital mortality rate, the discriminative power of admission antithrombin III concentration is poor, as judged by analysis of areas under the receiver operating curves, and is not independently associated with hospital mortality rate.

Antithrombin effects on endotoxin-induced microcirculatory disorders are mediated mainly by its interaction with microvascular endothelium

OBJECTIVE

To investigate whether the protective effect of antithrombin III, which has been shown to exert beneficial effects during septic disorders, including reduction of endotoxin-associated leukocyte/endothelial cell interaction and capillary perfusion failure, is mainly based on its anticoagulant capacity or direct effects on the microvascular endothelium.

DESIGN

Animal study with three treatment groups.

SETTING

Animal research facility.

SUBJECTS

Syrian golden hamsters, 6-8 wks old with a body weight of 60-80 g.

INTERVENTIONS

In skinfold preparations of hamsters, normotensive endotoxemia was induced by intravenous administration of 2 mg/kg endotoxin (lipopolysaccharide, 2 mg/kg). Antithrombin III (n = 7 animals; 250 units/kg) or tryptophan49-blocked antithrombin III (n = 6; 250 units/kg) was substituted intravenously 5 mins before lipopolysaccharide administration. Saline-treated animals (n = 11), receiving only lipopolysaccharide, served as controls. Tryptophan49-blocked antithrombin III binds to glycosaminoglycans at the endothelial surface to a significantly lower extent while retaining its progressive anticoagulant effects.

MEASUREMENTS AND MAIN RESULTS

Compared with controls, antithrombin III significantly reduced lipopolysaccharide-induced arteriolar and venular leukocyte adherence (p < .01) and prevented depression of functional capillary density (p < .01), whereas tryptophan49-blocked antithrombin III failed to significantly improve both variables. As measured in vivo by a monoclonal fluorescein isothiocyanate-labeled anti-antithrombin III antibody and intravital microscopy, the lack of effect of tryptophan49-blocked antithrombin III was associated with significantly lower antithrombin III/endothelium binding coefficients after 1 hr, 3 hrs, and 24 hrs of endotoxemia (p < .01).

CONCLUSIONS

We conclude that specific antithrombin III interactions with cell-surface glycosaminoglycans on the endothelium rather than anticoagulant properties are the mechanism of antithrombin III-mediated attenuation of leukocyte/endothelial cell interaction and capillary perfusion failure.

Coagulation inhibitor replacement in sepsis is a potentially useful clinical approach

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

Antithrombin concentrate with plasma exchange in purpura fulminans

OBJECTIVE: To report successful treatment of three patients admitted with purpura fulminans. DESIGN: Three cases with purpura fulminans: clinical presentation, laboratory findings, treatment, and outcome. SETTING: A seven-bed medical and general surgical Intensive therapy unit in a district general hospital. PATIENTS: Three young patients with clinical and laboratory findings of severe meningococcal sepsis and purpura. INTERVENTIONS: Early replacement therapy with antithrombin concentrate after a single initial plasma exchange, together with conventional antibiotic and supportive treatment. MEASUREMENTS AND MAIN RESULTS: All three cases had abnormal coagulation profile consistent with disseminated intravascular coagulation, adult respiratory distress syndrome, impaired renal function, and severe hemodynamic instability requiring inotropic support. Plasma antithrombin levels were measured in all cases. All patients survived and made a good recovery. CONCLUSIONS: We consider that correction of antithrombin to supranormal levels may have a beneficial effect on survival and outcome in purpura fulminans despite sustained low levels of protein C.

Disseminated intravascular coagulation and purpura fulminans secondary to infection

Infection is one of the commonest causes of disseminated intravascular coagulation (DIC). DIC is a complex disorder that results from an imbalance of the pro- and anticoagulant regulatory pathways. This chapter will explain the cellular and molecular basis of the disorder and consider the rationale behind current and experimental treatment strategies.

Selective thrombolysis in acute deep vein thrombosis: evaluation of adjuvant therapy in vivo

PURPOSE

To evaluate in a porcine model of acute deep vein thrombosis (DVT) the efficacy of dalteparin and antithrombin with respect to heparin for local adjuvant therapy during selective thrombolysis, and the utility of nitroglycerin and iloprost as heparin supplements.

METHODS

DVT was induced in both hind limbs using a previously described technique (n = 20). Thirty minutes later, the animal was heparinized (2500 IU IV), and bilateral sequestrated thrombolysis was performed using 8 mg alteplase: both external iliac veins were endoluminally occluded with Swan-Ganz catheters, and a multi-sideport infusion wire coaxially introduced through each catheter and advanced into the ipsilateral popliteal vein. In the control limbs, tissue plasminogen activator (tPA) 8 mg was injected as 0.8-ml boluses at 3-min intervals for 2 hr as a 0. 25-mg/ml solution containing heparin 50 IU/ml (n = 20). On the contralateral side, heparin was substituted with either dalteparin 50 IU/ml (n = 5) or antithrombin 12.5 IU/ml (n = 5), or supplemented with either nitroglycerin 0.075 mg/ml (n = 5) or iloprost (150 ng/ml) (n = 5). Blood samples were taken at predetermined intervals to measure the activated partial thromboplastin time (aPTT), prothrombin time (PT), and fibrinogen concentration. At autopsy, the thrombus mass in the iliofemoral veins was measured, and the extent of residual thrombosis in the venous tributaries graded at four sites.

RESULTS

Bilateral thrombolysis was successfully completed in all animals. The median thrombus mass in the iliofemoral veins after thrombolysis was 0.48 g (range 0.06-1.58 g), 0.95 g (0.59-1.29 g), 0. 74 g (0.52-0.96 g), and 0.29 g (0.0-0.77 g) for dalteparin, antithrombin, iloprost, and nitroglycerin respectively, as compared with 0.53 g (0.18-0.88 g) (p = 0.69), 0.97 g (0.46-1.15 g) (p = 0. 69), 0.53 g (0.48-1.10 g) (p = 0.69), and 0.18 g (0.13-1.04 g) (p = 0.5) for the respective controls. Likewise, the severity of residual thrombosis in the venous tributaries was not affected by the constituents of adjuvant therapy. Nitroglycerin induced a small drop in blood pressure, which was transient. The temporal change in aPTT was similar in all four groups. Invariably PT progressively shortened during thrombolysis (p = 0.0001); this effect was somewhat blunted with antithrombin. Fibrinogen levels demonstrated a time-dependent increase (p = 0.004) that was not influenced by the adjuvant therapy used.

CONCLUSIONS

Dalteparin or antithrombin demonstrated no appreciable advantage over heparin as local adjuvant therapy for selective venous thrombolysis. Supplementation of heparin with iloprost or nitroglycerin also had virtually no effect on thrombolytic efficacy.