The quality of evidence is downgraded by study limitations (unclear allocation concealment and high loss to follow-up).
A Cochrane review [Abstract] 1 included 7 studies with a total of 1 728 subjects to evaluate the efficacy and safety of prolonged thromboprophylaxis with LMWH for at least 14 days after abdominal or pelvic surgery compared with thromboprophylaxis administered during the in-hospital period only in preventing late onset venous thromboembolism (VTE). Prolonged thromboprophylaxis with LMWH was compared to control or placebo. Five studies included only cancer patients and 2 studies included patients undergoing surgery for both benign and malignant diseases. One study performed minimally invasive (laparoscopic) abdominal surgery, and the remaining studies open surgery.
The incidence of overall venous thromboembolism (VTE), all deep venous thrombosis (DVT), and proximal DVT was reduced in the prolonged thromboprophylaxis group (table T1).The observed reduction in the incidence of symptomatic VTE was not statistically significant.No difference in the incidence of bleeding and in mortality was found.
| Outcome | Relative effect (95% CI) | Risk with control | Risk with prolonged LMWH (95% CI) | Participants (studies) |
|---|---|---|---|---|
| All VTE* | OR 0.38 (0.26 to 0.54) | 132 per 1000 | 50 per 1000(34 to 71) | 1 728(7 studies) |
| All DVT* | OR 0.39 (0.27 to 0.55) | 129 per 1000 | 50 per 1000(35 to 71) | 1 728(7 studies) |
| Proximal DVT* | OR 0.22 (0.10 to 0.47) | 39 per 1000 | 9 per 1000(4 to 18) | 1 728(7 studies) |
| Symptomatic VTE* | OR 0.30 (0.08 to 1.11) | 10 per 1000 | 3 per 1000(1 to 11) | 1 728(7 studies) |
| Mortality** | OR 1.15 (0.72 to 1.84) | 38 per 1000 | 43 per 1000(28 to 68) | 1 881(7 studies) |
| Bleeding complications** | OR 1.10 (0.67 to 1.81) | 28 per 1000 | 31 per 1000(19 to 51) | 2 239 (7 studies) |
| VTE = venous thromboembolism; DVT = deep venous thrombosis; * follow-up 30 days postoperatively; **follow-up 3 months postoperatively | ||||
| References | ||||
| Felder S, Rasmussen MS, King R et al. Prolonged thromboprophylaxis with low molecular weight heparin for abdominal or pelvic surgery. Cochrane Database Syst Rev 2019;(8):CD004318. [PubMed].
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