heparin for DVT prophylaxis

I wondering if you guys know what studies show about the usefullness of heparin for DVT prophylaxis. At my hospitals we give 5000 units SQ to many patients. Just wondering how commonly patient's develop DVT's while in the hospital, and how effective heparin is for preventing them.
here are some articlesheparin dvt - Google Scholar

I don't know, but I swear every pt at my hospital gets heparin, so whoever manufactures it is sure making a huge profit.

The research articles are not difficult to find, there is over twenty years of research to support prophylactic anticoagulant therapy. I am surprised that it is not part of core nursing education.