Hypoxia exposure results in hypercoagulation. Rats were exposed to simulated hypoxic conditions as described in Materials and methods; tail vein bleeding assay, PT, and activated partial thromboplastin time (aPTT) assays were performed. (A) Rat tail was transected 4 mm from the tip and immersed in warm normal saline (37°C), and the time taken for complete cessation of blood flow was noted (it was significantly lower in hypoxia-exposed rats than in controls). (B) In the filter paper method, the tail tip was blotted gently onto Whatman paper at 1-minute intervals. The diameter of blood spots and the duration of bleeding were significantly lower in exposed rats compared with control rats. (C-D) PT (C) and aPTT (D) were measured in citrated plasma and reflected a similar trend as bleeding time. Data are presented as mean ± SEM (n = 10). *P < .05 vs control.