Low molecular weight heparin for the prevention of venous thromboembolism after abdominal surgery

BACKGROUND: Abdominal surgery carries a significant risk of venous thrombosis, a risk further increased in patients with cancer. METHODS: Embase and Pubmed searches between 1980 and 2003, using the key words 'heparin,' 'surgery,' 'abdominal or rectal or colorectal or rectum or colon' and 'clinical trial', were conducted to identify studies of thromboprophylaxis in patients having abdominal surgery. RESULTS: A total of 16 comparative studies were identified. These show that low molecular weight heparin (LMWH) is as effective as unfractionated heparin (UFH) in reducing venous thromboembolism after abdominal surgery and, at appropriate doses, can reduce bleeding complications. In very high-risk patients, a higher dose of LMWH may offer increased efficacy without increasing bleeding risk. Extending the standard 7-10-day period of prophylaxis may benefit certain high-risk groups; recent data show a significant benefit of 4-week enoxaparin thromboprophylaxis compared with a standard regimen, at no cost to safety. CONCLUSION: Patients undergoing abdominal surgery should be stratified according to thromboembolism risk and managed accordingly. LMWH is a recommended alternative to UFH in moderate- or high-risk patients. In patients with cancer, high doses of LMWH may offer increased efficacy without increasing the bleeding risk and an extended 4-week period of prophylaxis appears beneficial.