Review: Low-molecular-weight heparin reduces risk for venous thromboembolism in adults with leg immobilization

In adults with leg immobilization, does low-molecular-weight heparin (LMWH) prevent venous thromboembolism (VTE)?

Studies selected compared LMWH with placebo or no thromboprophylaxis in adults with a leg injury requiring immobilization in a plaster cast or brace in an ambulatory setting. Outcomes were symptomatic or asymptomatic VTE (deep venous thrombosis [DVT] or pulmonary embolism) and bleeding events.

Cochrane Peripheral Vascular Diseases Group Specialized Register, PubMed, and EMBASE/Excerpta Medica (May 2008); Cochrane Central Register of Controlled Trials (Issue 2, 2008); and reference lists were searched for randomized controlled trials (RCTs) and controlled clinical trials. Pharmaceutical companies were consulted. 6 RCTs (n = 1490, mean age 34 to 49 y, 46% to 79% men) met the selection criteria. DVT was diagnosed by venography or by compression ultrasonography and/or duplex scanning confirmed by phlebography or venography. 4 trials reported adequate allocation concealment, 3 placebo-controlled trials were double-blind, and the outcome assessor was blinded in 1 trial.

Risk for VTE was 18% in the control group. LMWH reduced risk for VTE (symptomatic or identified by screening) and symptomatic VTE (Table). Treatment effect was similar in patients with a below-knee cast, in operated or nonoperated patients, in patients with fracture or soft-tissue injury, and in patients with distal or proximal segment DVT. Pulmonary embolism was reported in 2 patients (0.4%), both receiving placebo. Major bleeding events were rare, and groups did not differ for minor bleeding events.

In adults with leg immobilization, thromboprophylaxis with low-molecular-weight heparin reduces risk for venous thromboembolism by about half, and risk for bleeding events is low.