Amidolytic heparin activity and values for several hemostatic variables after repeated subcutaneous administration of high doses of a low molecular weight heparin in healthy dogs

Objective—To determine effects of SC administration of repeated doses of a low molecular weight heparin (LMWH) in dogs. Animals—5 healthy dogs. Procedure—Each dog received 6 injections (each injection, 150 U of anti-factor-Xa [anti-FXa]/kg of body weight, SC) at 8-hour intervals. Blood samples were collected before and 2 hours after the first, second, third, and sixth injections to measure heparin activity, thrombin time, activated partial thromboplastin time (APTT), antithrombin activity, Hct, and platelet count. Results—Heparin activity varied between 0.36 ± 0.10 and 0.77 ± 0.08 U of anti-FXa/ml (before and 2 hours after the third injection) and between 0.46 ± 0.11 and 0.82 ± 0.15 U of anti-FXa/ml (before and 2 hours after the sixth injection). Thrombin time and APTT were influenced only slightly. Platelet count, Hct, and antithrombin activity started to decrease significantly 2 hours after the second LMWH injection. Because of the increased consumption of antithrombin, antithrombin activity continuousl...