Anticoagulatory and antiadhesive effects of heparin during systemic inflammation in humans

Sepsis is associated with excessive activation of a variety of host mediator systems, including the cytokine network, the hemostatic system, and leukocytes, each of which contribute to the development of tissue injury, which may eventually lead to multiple organ failure. Animal models have convincingly shown that blockade of even single adhesion molecules considerably improves survival, and that inhibition of the tissue factor (TF)- dependent activation of factor VII/VIIa completely prevents LPS induced coagulation. Experimental studies suggest adhesion and coagulation cascades to be interdependent. Blockade of either pathway alone or simultaneously may provide a useful future therapeutic approach in humans. The LPS-infusion to healthy volunteers provides a powerful tool to safely study the influence of endotoxemia on the activation of the inflammatory, coagulatory and adhesive cascades in humans. Heparin is well known for its anticoagulatory properties, and recent reports indicate that heparin may block the expression of TF and plasminogen activator inhibitor, which are key mediators in endotoxemia induced coagulation. Less well known is that heparin can also modulate the immune system: particularly unfractionated heparin is a powerful inhibitor of selectin/ligand interactions and can block adhesion events in-vitro and in-vivo. Finally, animal models have shown that heparin can decrease mortality of LPS-induced shock. Thus, it seems warranted to study the anticoagulatory, and antiadhesive properties of heparin in the human endotoxin model. To compare the effect of an iv. bolus of 2 ng/kg endotoxin with and without co-administration of unfractionated or low molecular weight heparin on systemic coagulatory, immunologic, and hemodynamic responses to reveal a possible prophylactic role for heparin in preventing endotoxin induced coagulation. Randomized, placebo- controlled trial in parallel groups A, B & C 3x5 healthy men aged 19 to 45 years and calculation of a final sample size after an interim analysis (max. number 3 x 10). Study medication: LPS:2 ng/kg bolus infusion in 10 mL NaCl over 1-2 min (groups A. B & C) generic name: National Reference Endotoxin, E coli, manufacturer: United States Pharmacopeial Convention Inc., Rockville, MD, 20852. paracetamol:(groups A, B & C) 500 mg Paracetamol Genericon, Genericon AG glucose 5%:(groups A. B & C): 3 mL/kg/h over 8.5 hours: Glucose 5% Laevosan Gesellschaft Infusionsflasche heparin: group A:unfractionated heparin 80 I.U./kg bolus, followed by a continuous infusion of 18 IU/kg/h over 6 hours, dose adjustments according to aPTT; brand name: Heparin "Immuno" 1000 IE Durchstichflasche; group B:low molecular weight heparin 40 I.U./kg bolus followed by a continuous infusion of 15 IE/kg/h; brandname: Fragmin 10.000 IE/4mL "Kabi" Stechampullen placebo:group C (approx. 30-50 mL NaCl 0.9%) Outcome variables and methods: A. Generation of prothrombin fragment F1+2 (as an activation marker of coagulation; primary aim) B. Maximal % decrease in neutrophils (primary aim). Secondary aims: Various activation markers of the inflammation (soluble cytokines), coagulation (such as fibrinogen, platelet count, TF & FVIIa) and adhesion cascade (soluble adhesion molecules and platelet leukocyte aggregates) all parameters will be measured by enzyme immuno assay and flowcytometry, C. Subjective symptoms, systemic cardiovascular, and febrile response will be recorded by automated cardiovascular monitoring Risk/benefit assessment: Approval by the Ethics Committee of the Vienna University Medical School has already been obtained. Published experience from more than 800 subjects and our own unpublished data from 30 subjects suggest that low-dose endotoxemia in human volunteers may serve as a powerful model to study new therapeutic approaches for the treatment of an activated coagulation system during the conditions of sepsis and generalized inflammation.