N, B Vollmar, M Laschke, D Inthorn, FW Schildberg, MD Menger Klinikum Grosshadern Ludwig Maximilians University of Munich, Marchioninistr. 15, 81377 Munich, Germany Objective: A recent prospective randomized clinical sepsis trial ((??)-Monastro biological activity Kybersept study) shows a reduction in 90-day mortality by antithrombin (ATIII) only in the prospectively defined subgroup of patients without simultaneous heparin treatment. To investigate whether this clinically observed heparin-ATIII antagonism is caused by a heparin-related reversal of ATIII effects on the microcirculation during endotoxemia, experimental ATIII administration was combined with administration of different heparins at a clinically relevant dose. Methods: In skin fold preparations of the Syrian hamster, normotensive endotoxemia was induced by i.v. administration of 2 mg/kg endotoxin (LPS, E. coli, 2 mg/kg), whereby intravital video fluorescence microscopy allowed determination of venular adherent leukocyte count (VALC) and functional capillary density (FCD), which served as a measure of capillary perfusion. ATIII (ATIII group, n = 6, Kybernin, 250 IU/kg i.v.) was substituted 5 min before LPS administration. Another group simultaneously received intravenous unfractionated heparin (ATIII + Hep, n = 5, sodium heparin, 100 IE/24 hours, i.v.), whereas additional animals received low molecular weight heparin (ATIII PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/20724077 + LMWH, n = 5, fraxiparin, 5 /kg, 2 hours before LPS, s.c.). Controls: Saline-treated animals receiving only LPS. Results: LPS induced a massive increase in VALC with a maximum at 8 hours and a decrease in FCD (P < 0.01 vs baseline). Both LPS effects were effectively prevented by ATIII (P < 0.01), whereas ATIII + Hep and ATIII + LMWH animals showed microcirculatory disturbances comparable to that observed in endotoxemic controls. In accordance with the clinical finding that beneficial AT III effects during sepsis are antagonized by concomitant heparin administration, our study indicates a relevant in-vivo adverse effect of heparins on microcirculatory AT III effects.P123 Evaluation of anti-inflammatory and anti-adhesive effects of heparins in human endotoxemiaU Derhaschnig*, T Pernerstorfer, B Jilma *Department of Emergency Medicine, and Department of Clinical Pharmacology, University of Vienna, Austria Introduction: Sepsis results from a generalized inflammatory and pro-coagulant response to an infectious agent. Adhesion molecules and cytokines are of utmost importance for the development of early symptoms as well as the late sequela of endotoxemia. Heparin is widely known as an antithrombotic agent. But beyond its well-understood anticoagulant activity heparin is able to influence immunologic responses. In addition, in vitro experiments and animal studies have shown that heparin inhibits P-selectin and L-selectin mediated adhesion. Intravenous infusion of LPS into human volunteers provides a standardized model to study activation of inflammatory, pro-coagulant and adhesive cascades in humans. It was recently demonstrated that heparin blunts endotoxininduced coagulation activation in a human LPS-model. As procoagulant and inflammatory processes are intricately linked in sepsis, we used this LPS-model to elucidate whether clinically applied doses of unfractionated (UFH) or low-molecular weight heparin (LMWH) are able to affect early inflammatory responses in low grade human endotoxemia. Methods: The trial was a randomized, double-blind, placebocontrolled study in three parallel groups of.