Dr. Nigel Sharrock and a team of colleagues at the Hospital for Special Surgery in New York reviewed 20 studies involving a total of more than 28,000 patients and found patients receiving powerful anti-coagulants were 60 percent to 70 percent more likely to have a non-fatal embolism. The findings indicate pulmonary embolism occurs despite the use of anti-coagulants, Sharrock says.

"The American College of Chest Physicians should reconsider its guidelines to reflect the fact that pulmonary embolism occurs despite the use of potent anti-coagulants and may, in fact, expose patients to increased mortality after surgery," the study authors say in a statement.

The researchers say following current guidelines to prescribe anti-coagulants -- perhaps to avoid potential litigation -- could be doing more harm than good.

The researchers found those having joint surgery and treated with either a potent anti-coagulant like low molecular heparin or a slow-acting anti-coagulant like warfarin were more than twice as likely to have died than those having joint surgery with local spinal or epidural anesthesia, pneumatic compression and aspirin.

The paper was published in the journal Clinical Orthopaedics and Related Research.