The quality of evidence is downgraded by study limitations (unclear allocation concealment), and by imprecise results (few outcome events).
A Cochrane review included 16 studies with a total of 3 005 subjects. Thromboprophylaxis did not reduce the primary outcome mortality or the secondary outcome pulmonary embolism (PE) but prophylaxis reduced the risk of deep vein thrombosis (DVT) in people with major trauma. Pharmacological prophylaxis was more effective than mechanical methods. Pharmacological prophylaxis increased the risk of bleeding (RR 2.04, 95% CI 1.08 to 3.86; 5 studies, n=953) compared to mechanical methods. People who received both mechanical and pharmacological prophylaxis had a lower risk of DVT than those receiving only pharmacological prophylaxis. LMWH appeared to reduce the risk of DVT compared to unfractionated heparin (UH) (RR 0.68, 95% CI 0.50 to 0.94; 2 studies, n=331). There was no statistically significant difference in the risk of bleeding between LMWH and UH. Comparison between pharmacological prophylaxis against placebo was not possible due to lack of studies.
| Comparison/Outcome | Participants (studies) | RR (95% CI) |
|---|---|---|
| Any type (mechanical and/or pharmacological) prophylaxis vs. no prophylaxis | ||
| DVT | 997 (4) | 0.52 (0.32 to 0.84) |
| PE | 997 (4) | 0.65 (0.29 to 1.43) |
| Mortality | 997 (4) | 0.59 (0.20 to 1.70) |
| Mechanical prophylaxis vs. no prophylaxis | ||
| DVT | 907 (5) | 0.55 (0.34 to 0.90) |
| PE | 907 (5) | 0.77 (0.36 to 1.66) |
| Mortality | 907 (5) | 0.74 (0.27 to 2.04) |
| Pharmacological prophylaxis vs. mechanical prophylaxis | ||
| DVT | 1033 (6) | 0.48 (0.25 to 0.95) |
| PE | 1033 (6) | 0.94 (0.36 to 2.42) |
| Mortality | 1033 (6) | 1.50 (0.44 to 5.16) |
| Mechanical + pharmacological prophylaxis vs. pharmacological | ||
| DVT | 507 (3) | 0.34 (0.19 to 0.60) |
| PE | 507 (3) | 0.32 (0.05 to 2.01) |
| Mortality | 507 (3) | 0.50 (0.05 to 5.30) |
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