Current trends in the use of heparins in thromboprophylaxis.

Unfractionated heparin (UH), administered subcutaneously in low doses of 5000 U every 12 h, is safe and effective in preventing thrombosis in most patients. However, in persons with neurological disease, surgical replacement of joints, or operations for cancer, low-dose UH is often inadequate or unsafe, and dose-adjusted UH, warfarin, or low molecular weight heparins (LMWH) may be needed. In trauma patients, LMWH is significantly more effective than UH in reducing the frequency of DVT with a minimal increase in bleeding risk. LMWH also significantly decreases thromboembolism in patients with acute spinal cord injury and complete motor paralysis, and with less bleeding as compared to UH. In acute stroke, a heparinoid was more effective than either placebo or UH (5000 U every 12 h) in preventing deep-vein thrombosis in acute thrombotic stroke, and the risk of bleeding was low. Following total hip or knee replacement, LMWH is more efficacious than warfarin but may be associated with perioperative bleeding. The duration of thrombo-prophylaxis following arthroplasty is controversial; venography demonstrates thrombi in approximately 29% of patients after hospital discharge, but only 3% have clinical symptoms. Lastly, perioperative thrombosis in cancer patients having abdominal surgery has been decreased by LMWH, and experience with outpatient treatment in the long-term management of Trousseau's syndrome has been positive.