Assess before anticoagulating


Prophylaxis against venous thromboembolism (VTE) for medical inpatients seems like it should be straightforward. There are checklists, and even performance measures, to remind physicians of the need, and getting it done is as simple as writing, or keying in, an order.

But three new evidence-based recommendations (see sidebar) from ACP point out that VTE prophylaxis is not quite as simple as some might think. After a thorough review of the evidence, College experts drew conclusions about the importance of assessing individual patients' risk for VTE before ordering prophylaxis, and the differences in effectiveness between pharmacological and mechanical methods.

Courtesy of Amir Qaseem
Courtesy of Amir Qaseem.

The evidence review and guidelines were published in the Nov. 1 Annals of Internal Medicine. Lead author Amir Qaseem, MD, PhD, FACP, director of clinical policy for the College, recently spoke to ACP Hospitalist about the guidelines' development and their likely impact on physician practice, patient safety and health care policy.

Q: What motivated the development of these guidelines?

A: VTE is a really major clinical issue. Evidence shows that almost 5% to 10% of all in-hospital deaths are a direct result of pulmonary embolism (PE). There's a big percentage of patients with undiagnosed and untreated PE who will eventually develop a fatal embolic event. The mortality associated with VTE is so high that there is a major need to address appropriate management of VTE prophylaxis in hospitalized patients.

Q: Are there any aspects of this guideline that may surprise physicians?

A: The main surprise—[given that] routine prophylaxis in medical patients is current practice—is that the current evidence does not support this practice. We found that there is no reduction in mortality or symptomatic DVT events; there is an increased risk of bleeding events. However, the major benefit of VTE prophylaxis was a significant reduction in PE events in medical patients. And hence, we say not to start VTE prophylaxis in every patient who is hospitalized, but start out with an assessment of risks of thromboembolism and bleeding in medical and stroke patients, prior to initiation of prophylaxis. The decision to initiate VTE prophylaxis should be based on an individualized assessment of risk factors. The benefit and harms need to be evaluated.

Q: Is there a preferred way for physicians to do that evaluation?

A: There are many instruments that are available, but none of these risk assessment tools have been tested in terms of their reliability and validity. So we don't actually recommend any specific tools, but there are certain risk factors for thromboembolism that are evidence-based and can be utilized. They are listed [in the guideline].

Q: What does the guideline advise as a next step after the risk assessment?

A: Once you're done with the risk assessment, then we recommend that the pharmacological prophylaxis should be with heparin or related drugs in medical, including stroke, patients, unless the assessed risk outweighs the likely benefit. We found evidence that showed prophylaxis with heparin was associated with a statistically significant reduction in PE events and an increase in bleeding events. In most cases, what we found was that the clinical benefit in reduction of PE events outweighs the harm of increased risk of bleeding events.

In this guideline, we also evaluated the evidence from the International Stroke Trial and we found that the current evidence is limited in its ability to help us differentiate the risks and benefits of VTE prophylaxis between the non-stroke medical and stroke patients.

Q: What type and what duration of prophylaxis should patients get?

A: The optimal duration we are actually uncertain about, because most of the trials that have been evaluated only did it during the hospitalized period. So we don't really understand what might be the effect of extended therapy on the balance of benefit and harms.

In terms of what to use, unfractionated heparin versus low-molecular-weight heparin, we did not find any difference in clinical benefits and harms between these two. Decide on an individual basis based on ease of use, adverse effect profile, and costs.

ACP also recommends against use of mechanical prophylaxis with graduated compression stockings. What we found was that compression stockings were not effective in preventing VTE or reducing mortality. Actually, they resulted in clinically significant increases in lower-extremity skin damage. We are asking physicians to select heparin or related drugs rather than compression stockings for patients in whom heparin can be used. For patients who might have high risk of bleeding and in whom heparin might be contraindicated, intermittent pneumatic compression may be a reasonable option, because it has been studied in surgical patients and shown benefits. We don't have studies in medical patients, so we don't have enough evidence to know that we can reliably estimate the benefits and harms.

Q: What are the policy implications of these new guidelines?

A: What we are saying is that ACP does not support the application of performance measures, including in stroke patients, that promote universal VTE prophylaxis in hospitalized patients. The evidence that we reviewed in this guideline does not support routine VTE prophylaxis in all medical patients. In some clinical settings, performance measures have been based on VTE prophylaxis rates in all patients regardless of their risk factors. It's actually being done without looking at the benefit and harms. We are saying that it is important to do the risk assessment because in certain cases VTE prophylaxis may not be justified or beneficial.

There's an editorial [accompanying the guidelines] as well. In there, we talk about the performance measures. We exactly address why we shouldn't have measures that aren't evidence-based. When the performance measures are being constructed, I think it needs to be taken into account whether the risk assessment was done or not rather than implicitly encouraging prophylaxis for all patients. There is a disconnect with some of the existing performance measures and evidence-based guidelines on VTE.

Q: What response do you expect the guidelines will receive?

A: I think people will be very receptive. When you look at the evidence, people will find that the evidence supports what we are recommending. Some assessment of risks and benefits must be done by physicians prior to making the decision regarding initiation of prophylaxis.