Influence of a high single subcutan dose of unfractionated heparin on platelet function in dogs

The influence of heparin on different tests of platelet function was invest igated in 5 healthy dogs receiving subcutaneously 1000 I.E./kg BW of a comm ercial unfractionated Sodium heparin preparation. Blood samples were collec ted before and 4 hours after heparin injection. Besides plasma activity of heparin platelet count, capillary bleeding time with two different methods, platelet aggregation according to Breddin and to Born with the inductors A DP, collagen, and thrombin as well as in vitro bleeding time were measured. The activity of heparin four hours after the subcutaneous heparin applicati on was 1.20 +/- 0.11 I.E./ml. Compared to the starting values no significan t influence of this heparin level could be demonstrated on platelet count, platelet aggregation according to Born with the inductors ADP and collagen, platelet aggregation according to the Breddin method as well as in vitro b leeding time (p > 0.05). Only one of the two methods used for measuring the capillary bleeding time showed a slight prolongation compared to the start ing value (mean = 77 sec) to 88 sec (p < 0.05). The most significant influe nce was seen on the platelet aggregation induced by I I.U./ml thrombin, whe reby the aggregation maximum decreased from 92.0 % (mean) to 12.2 % (p < 0. 001). Whereas the latter result has to be interpreted primarily as a conseq uence of the anti-thrombin effect of heparin, the results of the other test s in summary illustrate the clinical unimportant influence of heparin on pl atelet function in dogs.