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Venous thromboembolism (VTE) is a prevalent and avoidable complication of hospitalization. Patients hospitalized with trauma, traumatic brain injury, burns, or liver disease; patients on antiplatelet therapy; obese or underweight patients; those having obesity surgery; or with acute or chronic renal failure have unequal risks for bleeding and thrombosis and may benefit differently from prophylactic therapy medication.
To systematically review the comparative effectiveness and safety of pharmacological and mechanical methods of prophylaxis of VTE in these special populations.
We searched MEDLINE®, Embase®, SCOPUS, CINAHL®, www.clinicaltrials.gov, International Pharmaceutical Abstracts (IPA), and the Cochrane Library in July 2012. This was complemented by hand searches from the reference lists and unpublished studies provided by sponsors.
We included randomized controlled trials on these special populations. Since these populations may be excluded from trials, we also included controlled observational studies of pharmacologic agents, and uncontrolled observational studies and case series of inferior vena cava (IVC) filter use. Two reviewers evaluated studies for eligibility, serially abstracted data using standardized forms, and independently evaluated the risk of bias in the studies and strength of evidence for major outcomes and comparisons. We qualitatively synthesized the evidence and also pooled the relative risks from the controlled studies.
After a review of 30,902 unique citations, we included 101 studies of which just 6 were trials. The majority of observational studies had a high risk of bias. The strength of evidence is low that IVC filter placement is associated with a lower incidence of pulmonary embolism and fatal pulmonary embolism in hospitalized patients with trauma compared with no IVC filter placement. The strength of evidence is low that enoxaparin reduces deep vein thrombosis and that unfractionated heparin reduces mortality in patients with traumatic brain injury when compared with patients without anticoagulation. Low-grade evidence supports the idea that IVC filters with usual care are associated with increased mortality and do not decrease the risk of pulmonary embolism in patients undergoing bariatric surgery compared with usual care alone. All other comparisons, for all of the Key Questions, had insufficient evidence to permit conclusions.
Our systematic review demonstrates that there is a paucity of high-quality evidence to inform treatment of these special populations. Future research using robust observational studies that control for confounding by indication and disease severity are needed as randomized controlled trials typically exclude or do not report on these populations.