Confusion Still Surrounds Prophylaxis for Venous Thromboembolism

Caroline Helwick

March 2012, Vol 3, No 2 - ASH Annual Meeting


San Diego, CA—Venous thromboembolism (VTE) occurs in 1% of hematologic malignancies and can lead to fatal pulmonary emboli, postthrombotic syndromes, bleeding as a result of anticoagulant treatment, and recurrent VTE. VTEs are potentially preventable with appropriate thromboprophylaxis, and numerous quality measures have been developed to enhance this practice. The "curve ball" is that there is "much confusion" regarding VTE prophylaxis, said Richard H. White, MD, of the University of California Davis School of Medicine, who spoke at a special symposium on quality indicators in hematology. In its most recent assessment (Ann Intern Med. 2011;155:625-632), the American College of Physicians (ACP) issued guidelines for VTE prophylaxis in hospitalized patients, noting that risk of VTE should be carefully assessed because there is no net benefit in lowrisk patients. The group also advised using pharmacologic prophylaxis rather than mechanical means. The ACP does not support universal VTE prophylaxis, stating the lack of evidence that it reduces deep-vein thrombosis (although it does protect against pulmonary embolism) and the lack of an accurate means of assessing risks versus benefits. "But VTE quality and safety measures are here to stay, and preventing VTE in hospitalized patients is a major goal," Dr White said. "The Centers for Medicare & Medicaid Services, The Joint Commission, and nongovernmental agencies all endorse prevention. Quality-of-care measures for VTE will evolve."

Table 1
Hierarchy of Successsful VTE Prevention Programs.
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Prevention Measures "Will Take Work"
"Setting up a VTE prevention program will take a lot of work and effort," added Dr White. To institute optimal prophylaxis, there needs to be a hospital-wide policy to provide VTE prophylaxis to all appropriate patients. This requires "buy in" from all departments and the education of all caregivers. Simple order sets need to be created on paper or in the electronic health record. All must include VTE prophylaxis orders coupled with a risk assessment tool, or an "opt out" tool stating which patients can be appropriately excluded. A designated thrombosis expert (eg, hematologist) must "monitor the process," he said. There are many barriers to useful protocols, for example, the risk tool is overly complicated; practical guidance is lacking (ie, a prompt does not link to a protocol); there is failure to update and streamline old order sets; there are too many risk categories; mechanical prophylaxis is allowed over medical prophylaxis; there is failure to pilot, revise, and monitor; and there is too much separation (in time or space) between risk assessment and prophylaxis choices. Not all programs are successful, he noted, citing the ways to "get to 95%" (Table 1). Dr White said that patients lacking anticoagulation should be readily identified, nurses should be empowered to place pneumatic compression, physicians should be contacted if no anticoagulant is in place and there is no obvious contraindication, and program directors should have the "political will" to back up these interventions after risk assessment.

Table 2
Hierarchy of Successsful VTE Prevention Programs.
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Simple Risk Assessment Model
Investigators from the University of Vermont in Burlington described a simple risk assessment model for use with hospitalized patients. "The score is simple, relies only on information easily known at the time of admission, and could be incorporated into an electronic medical record," said Neil Zakai, MD, MSc. "It will allow clinicians to assess VTE risk at admission for medical inpatients and weight the risks and benefits of pharmacologic prophylaxis." Dr Zakai and colleagues evaluated 299 cases of VTE and 601 matched controls, and found the rate of VTE per 1000 admissions to be 4.6. They identified factors that placed patients at greatest risk (Table 2) and generated a Medical Inpatients and Thrombosis Study Score. Using a cutoff of ≥2 as indicative of high risk, they determined that the probability of VTE in the absence of prophylaxis for a score <2 was only 1.5 per 1000 admissions but was 8.8 for a score ≥2; in their population, 74% of cases and 39% of controls were considered at high risk. Dr Zakai suggested that this model could be applied to studies to determine the optimal VTE prevention strategies in medical inpatients, including patients with cancer.