Primary prophylaxis for venous thromboembolism in people undergoing major amputation of the lower extremity.
People undergoing major amputation of the lower limb are at increased risk of venous thromboembolism (VTE). Risk factors for VTE in amputees include advanced age, sedentary lifestyle, longstanding arterial disease and an identifiable hypercoagulable condition. Evidence suggests that pharmacological prophylaxis (e.g. heparin, factor Xa inhibitors, vitamin K antagonists, direct thrombin inhibitors, antiplatelets) is effective in preventing deep vein thrombosis (DVT), but is associated with an increased risk of bleeding. Mechanical prophylaxis (e.g. antiembolism stockings, intermittent pneumatic compression and foot impulse devices), on the other hand, is non-invasive and has minimal side effects. However, mechanical prophylaxis is not always appropriate for people with contraindications such as peripheral arterial disease (PAD), arteriosclerosis or bilateral lower limb amputations. It is important to determine the most effective thromboprophylaxis for people undergoing major amputation and whether this is one treatment alone or in combination with another. This is an update of the review first published in 2013.
To determine the effectiveness of thromboprophylaxis in preventing VTE in people undergoing major amputation of the lower extremity.
The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, Cochrane Central Register of Controlled Trials, MEDLINE, Embase and Cumulative Index to Nursing and Allied Health Literature databases, the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 5 November 2019. We planned to undertake reference checking of identified trials to identify additional studies. We did not apply any language restrictions.
We included randomised controlled trials and quasi-randomised controlled trials which allocated people undergoing a major unilateral or bilateral amputation (e.g. hip disarticulation, transfemoral, knee disarticulation and transtibial) of the lower extremity to different types or regimens of thromboprophylaxis (including pharmacological or mechanical prophylaxis) or placebo.
Two review authors independently selected studies, extracted data and assessed risk of bias. We resolved any disagreements by discussion. Outcomes of interest were VTE (DVT and pulmonary embolism (PE)), mortality, adverse events and bleeding. We used GRADE criteria to assess the certainty of the evidence. The two included studies compared different treatments, so we could not pool the data in a meta-analysis.
We did not identify any eligible new studies for this update. Two studies with a combined total of 288 participants met the inclusion criteria for this review. Unfractionated heparin compared to low molecular weight heparin One study compared unfractionated heparin with low molecular weight heparin and found no evidence of a difference between the treatments in the prevention of DVT (odds ratio (OR) 1.23, 95% confidence interval (CI) 0.28 to 5.35; 75 participants; very low-certainty evidence). No bleeding events occurred in either group. Deaths and adverse events were not reported. This study was open-label and therefore at a high risk of performance bias. Additionally, the study did not report the method of randomisation, so the risk of selection bias was unclear. Heparin compared to placebo In the second study, there was no evidence of a benefit from heparin use in preventing PE when compared to placebo (OR 0.84, 95% CI 0.35 to 2.01; 134 participants; low-certainty evidence). Similarly, no evidence of improvement was detected when the level of amputation was considered, with a similar incidence of PE between the two treatment groups: above knee amputation (OR 0.79, 95% CI 0.31 to 1.97; 94 participants; low-certainty evidence); and below knee amputation (OR 1.53, 95% CI 0.09 to 26.43; 40 participants; low-certainty evidence). Ten participants died during the study; five underwent a post-mortem and three were found to have had a recent PE, all of whom had been on placebo (low-certainty evidence). Bleeding events were reported in less than 10% of participants in both treatment groups, but the study did not present specific data (low-certainty evidence). There were no reports of other adverse events. This study did not report the methods used to conceal allocation of treatment, so it was unclear whether selection bias occurred. However, this study appeared to be free from all other sources of bias. No study looked at mechanical prophylaxis.
We did not identify any eligible new studies for this update. As we only included two studies in this review, each comparing different interventions, there is insufficient evidence to make any conclusions regarding the most effective thromboprophylaxis regimen in people undergoing lower limb amputation. Further large-scale studies of good quality are required.
Herlihy DR
，Thomas M
，Tran QH
，Puttaswamy V
... -
《Cochrane Database of Systematic Reviews》
Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy.
Venous thromboembolism (VTE) often complicates the clinical course of cancer. The risk is further increased by chemotherapy, but the trade-off between safety and efficacy of primary thromboprophylaxis in cancer patients treated with chemotherapy is uncertain. This is the third update of a review first published in February 2012.
To assess the efficacy and safety of primary thromboprophylaxis for VTE in ambulatory cancer patients receiving chemotherapy compared with placebo or no thromboprophylaxis, or an active control intervention.
For this update, the Cochrane Vascular Information Specialist searched the Cochrane Vascular, CENTRAL, MEDLINE, Embase and CINAHL databases and World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 3 August 2020. We also searched the reference lists of identified studies and contacted content experts and trialists for relevant references.
Randomised controlled trials comparing any oral or parenteral anticoagulant or mechanical intervention to no thromboprophylaxis or placebo, or comparing two different anticoagulants.
We extracted data on risk of bias, participant characteristics, interventions, and outcomes including symptomatic VTE and major bleeding as the primary effectiveness and safety outcomes, respectively. We applied GRADE to assess the certainty of evidence.
We identified six additional randomised controlled trials (3326 participants) for this update, bringing the included study total to 32 (15,678 participants), all evaluating pharmacological interventions and performed mainly in people with locally advanced or metastatic cancer. The certainty of the evidence ranged from high to very low across the different outcomes and comparisons. The main limiting factors were imprecision and risk of bias. Thromboprophylaxis with direct oral anticoagulants (direct factor Xa inhibitors apixaban and rivaroxaban) may decrease the incidence of symptomatic VTE (risk ratio (RR) 0.43, 95% confidence interval (CI) 0.18 to 1.06; 3 studies, 1526 participants; low-certainty evidence); and probably increases the risk of major bleeding compared with placebo (RR 1.74, 95% CI 0.82 to 3.68; 3 studies, 1494 participants; moderate-certainty evidence). When compared with no thromboprophylaxis, low-molecular-weight heparin (LMWH) reduced the incidence of symptomatic VTE (RR 0.62, 95% CI 0.46 to 0.83; 11 studies, 3931 participants; high-certainty evidence); and probably increased the risk of major bleeding events (RR 1.63, 95% CI 1.12 to 2.35; 15 studies, 7282 participants; moderate-certainty evidence). In participants with multiple myeloma, LMWH resulted in lower symptomatic VTE compared with the vitamin K antagonist warfarin (RR 0.33, 95% CI 0.14 to 0.83; 1 study, 439 participants; high-certainty evidence), while LMWH probably lowers symptomatic VTE more than aspirin (RR 0.51, 95% CI 0.22 to 1.17; 2 studies, 781 participants; moderate-certainty evidence). Major bleeding was observed in none of the participants with multiple myeloma treated with LMWH or warfarin and in less than 1% of those treated with aspirin. Only one study evaluated unfractionated heparin against no thromboprophylaxis, but did not report on VTE or major bleeding. When compared with placebo or no thromboprophylaxis, warfarin may importantly reduce symptomatic VTE (RR 0.15, 95% CI 0.02 to 1.20; 1 study, 311 participants; low-certainty evidence) and may result in a large increase in major bleeding (RR 3.82, 95% CI 0.97 to 15.04; 4 studies, 994 participants; low-certainty evidence). One study evaluated antithrombin versus no antithrombin in children. This study did not report on symptomatic VTE but did report any VTE (symptomatic and incidental VTE). The effect of antithrombin on any VTE and major bleeding is uncertain (any VTE: RR 0.84, 95% CI 0.41 to 1.73; major bleeding: RR 0.78, 95% CI 0.03 to 18.57; 1 study, 85 participants; very low-certainty evidence).
In ambulatory cancer patients, primary thromboprophylaxis with direct factor Xa inhibitors may reduce the incidence of symptomatic VTE (low-certainty evidence) and probably increases the risk of major bleeding (moderate-certainty evidence) when compared with placebo. LMWH decreases the incidence of symptomatic VTE (high-certainty evidence), but increases the risk of major bleeding (moderate-certainty evidence) when compared with placebo or no thromboprophylaxis. Evidence for the use of thromboprophylaxis with anticoagulants other than direct factor Xa inhibitors and LMWH is limited. More studies are warranted to evaluate the efficacy and safety of primary prophylaxis in specific types of chemotherapeutic agents and types of cancer, such as gastrointestinal or genitourinary cancer.
Rutjes AW
，Porreca E
，Candeloro M
，Valeriani E
，Di Nisio M
... -
《Cochrane Database of Systematic Reviews》
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