Patients who've been injured are at increased risk for venous thromboembolism (VT), including both deep venous thrombosis and pulmonary embolism. Pulmonary embolism is fatal in one-third of trauma patients, yet there are no consistent recommendations for VT prophylaxis after injury.

To identify the best methods for preventing VT, the Agency for Healthcare Research and Quality (AHRQ) analyzed 73 published studies of trauma patients. The pooled rates of deep venous thrombosis and pulmonary embolism across all studies were 11.8% and 1.5%, respectively.

How prophylactic methods stack up. There was no significant difference in the rates of VT between patients who received either low-dose heparin or mechanical prophylaxis and those who received no prophylaxis. And neither low-dose heparin nor mechanical prophylaxis was better at preventing VT.

Three studies showed that low-molecular-weight heparin was superior to low-dose heparin or sequential compression devices in preventing VT, but three other studies showed no difference between low-molecular-weight heparin and low-dose heparin. In observational studies, vena cava filter placement was shown to reduce the risk of pulmonary embolism, but the lack of randomized, controlled studies prevents conclusions from being drawn.

Who's at risk. The risk of deep venous thrombosis after trauma is highest in older and more severely injured patients. The risk also increases in patients with spinal fractures and spinal-cord injury. Several commonly reported risk factors, such as head injury, pelvic fracture, or long-bone fracture, weren't found to increase risk.

Large-scale, multicenter, randomized controlled trials are needed to better assess the prophylactic methods available, including vena cava filter placement. Meanwhile, severely injured patients should be screened carefully using duplex ultrasonography.

For more information, visit http://www.ahrq.gov/clinic/vtsumm.htm.