Review: VTE prophylaxis guidelines
Background: Pharmacologic interventions with heparin or related drugs and mechanical interventions have become the standard of care in the prevention of venous thromboembolism (VTE) in hospitalized patients. The studies evaluating the efficacy of these therapies in relation to each other have become more robust over the last decade. Despite these advances, however, there remains controversy over meaningful outcomes and how the results should be applied to different patient populations.
Many studies address the issue of VTE prophylaxis using surrogate outcomes, such as asymptomatic deep venous thromboembolism (DVT), given the low incidence of significant clinical outcomes, e.g., symptomatic DVT, pulmonary embolus (PE), or mortality. There have been few large, prospective, randomized trials that show a statistically significant benefit of pharmacologic or mechanical VTE prophylaxis in a purely medical population when looking for these meaningful outcomes.
Significant bleeding and thrombocytopenia are the most common risks identified in pharmacologic intervention studies against which the benefits have to be weighed. Stroke patients are one medical population in which bleeding risk has been of particular concern.
Guideline update: In November 2011, the American College of Physicians (ACP) published new guidelines for medical patients regarding VTE prophylaxis.1 These evidence-based guidelines were not based on new trial data, but rather a review of previous studies looking at only medical patients; they did not consider asymptomatic DVT as a significant outcome.
The new guidelines recommend that all hospitalized medical patients, including stroke patients, be evaluated for risk of VTE and bleeding, which is not a change from any previous standard. Routine use of VTE prophylaxis is not recommended, and prophylactic pharmacologic therapy with heparin or related drugs should only be instituted if the benefit in a decreased incidence of VTE outweighs the risk of bleeding in an individual patient. The use of mechanical prophylaxis with graduated compression stockings is not recommended, given the risk of lower extremity skin damage and a lack of clear benefit.
Last month, the American College of Chest Physicians (ACCP) followed suit in their 9th edition of clinical practice guidelines regarding VTE prevention in non-surgical patients.2 The ACC recommends the use of heparin or related drugs for VTE prophylaxis for medical patients at increased risk of thrombosis, but recommends against pharmacologic VTE prophylaxis in patients at low risk. Patients at high risk of bleeding with a concomitant high risk of VTE are recommended to use mechanical prophylaxis until the bleeding risk diminishes. These guidelines go a step further and provide parameters defining both high risk of VTE and high risk of bleeding, making them a very clinically useful tool. Neither guideline indicates a prefererence for pharmacologic prophylaxis.
Analysis: The most comprehensive and broadly accepted guidelines for VTE prevention before these updates were put forth by ACCP and published in the June 2008 issue of Chest.3
This review-based guideline, which included asymptomatic DVT as an appropriate outcome, recommended the routine use of heparin or related drugs for prophylaxis of VTE in medical patients confined to bed who have at least one risk factor for VTE. For patients with a contraindication to anticoagulant prophylaxis, they recommend mechanical thromboprophylaxis.
Most national organizations have established their standards and measures based on these clinical practice guidelines. The Joint Commission’s VTE-1 Core Measure evaluates the percentage of inpatients who received VTE prophylaxis or who had documentation as to why no prophylaxis was given.4 The measure states that “appropriately used thromboprophylaxis has a desirable risk-benefit ratio and is cost-effective,” but it does not define appropriate use and lists limited exclusion criteria. The Joint Commission has responded in a statement to the new ACP guidelines, but it has not changed its guidelines based on the 2008 Chest guidelines.5
The Centers for Medicare & Medicaid Services (CMS), through the Inpatient Prospective Payment System 2009, determined that VTE during a hospitalization for total knee or hip replacement was a hospital-acquired condition that will not be reimbursable.6 This is not the case in general medical inpatients. Also of interest, observational studies suggest that 50% of patients who develop a VTE in hospital will do so despite appropriate prophylaxis.
Surgical patient populations are not addressed in the ACP update but are covered in the 2012 Chest updated guidelines. The recommendations for surgical patients have no major changes since 2008 except for choice of anticoagulant for specific patient populations and new categories of intermediate and high risk, the specifics of which are beyond the scope of this review.
Surgical patients with risk factors for VTE undergoing major procedures should receive pharmacologic prophylaxis with the addition of mechanical prophylaxis. For patients with a high risk of bleeding, mechanical prophylaxis can be used alone until bleeding risk diminishes.
Caution is recommended for any patient undergoing neuraxial analgesia or anesthesia when considering pharmacologic prophylaxis. Routine use of pharmacologic prophylaxis is recommended in patients undergoing bariatric surgery, elective hip replacement, hip fracture surgery, major thoracic surgery, or major open urologic procedures regardless of VTE risk factors, and should be extended in patients with additional VTE risks. All other surgical populations should be evaluated for bleeding risk and VTE risk factors prior to decision for pharmacologic and/or mechanical prophylaxis.
HM takeaways: In medical populations including stroke, routine use of VTE prophylaxis is not recommended, and should only be instituted if they are at high risk of VTE and the benefit in a decreased incidence of VTE outweighs the risk of bleeding.
Dr. Pell is a hospitalist and assistant professor of medicine at the University of Colorado Denver School of Medicine.