Low molecular weight heparin prevents activation of coagulation in a hypobaric environment

It is commonly thought that people are at increased risk of venous thrombos is during air flights, but the magnitude of the risk is unknown. Suggested risk factors are hypobaric hypoxia, stasis, and dehydration. In a previous experimental study, we found immediate activation of coagulation as determi ned by the levels of prothrombin fragments 1 + 2 (F1+2) and thrombin-antith rombin complex (TAT) after rapid exposure to a hypobaric and hypoxic enviro nment (76 kPa). The aim of the present study was to examine the ability of low molecular weight heparin (LMWH) to prevent such activation. Twelve heal thy male volunteers were given 40 mg enoxaparin as a single subcutaneous in jection 1 h prior to exposure from 96.3 to 76 kPa. We found no activation o f coagulation as judged by F1+2 or TAT. Anti-activated factor X activity le vels and release of tissue factor pathway inhibitor was normal. We conclude that high prophylactic doses of a LMWH most probably prevent activation of coagulation in a hypobaric environment. (C) 2001 Lippincott Williams & Wil kins.