Preaching DVT Prophylaxis Gospel Reduces Emboli

GRENOBLE, France, Oct. 23 -- The risk of deep venous thromboembolism (DVT) in older patients could be significantly reduced if clinicians in post-acute care settings regularly followed evidence-based guidelines, according to French researchers.

The rate of venous thromboembolic events in the post-acute care phase in older patients decreased significantly after clinicians were taught about and implemented venous thromboembolism prophylaxis guidelines reported Jose Labarere, M.D., of University Hospital here, and colleagues at other French centers.

The prophylaxis approaches involved a combination of pharmacologic management and mechanical techniques.

"In this prospective multicenter study, a multifaceted intervention designed to implement an evidence-based guideline addressing venous thromboembolism prophylaxis after acute care was followed by a reduction in DVT without compromising patient safety," the investigators wrote in the Oct. 23 issue of the Archives of Internal Medicine.

But getting physicians, hospitals, and post-acute care facilities to embrace and adopt the guidelines may be the biggest barrier to reducing DVT rates, the authors suggested. In an earlier study, published in the Archives in 2003, they found that 16% of older patients in a post-acute care setting had DVT detected on ultrasound screening.

In that study "the rate of anticoagulant-based prophylaxis ranged from 20% to 87% across departments, reflecting a high degree of uncertainty in the decision to use prophylaxis," they wrote.

To remove at least some of that uncertainty, the authors developed evidence-based guidelines to help clinicians determine the proper course of prevention for older patients at risk for DVT.

The authors then conducted a before-and-after prospective study in 33 hospital-based post-acute care centers in France, including 17 in teaching hospitals, 25 in skilled nursing facilities, and eight in rehabilitation facilities.

Eligible patients included all who were 65-years-old or older and were hospitalized in the participating post-acute care departments. Patients were excluded from the study if they had a positive diagnosis of DVT or pulmonary embolism at admission, or if they required long-term anticoagulant therapy with heparin or an oral anticoagulant agent for any reason other than prophylaxis (for example, atrial fibrillation or prosthetic heart valve).

Physicians and nurses from every department involved were given on-site training in the guidelines and were provided with pocket-sized cards containing the guidelines, as well as posters that could be placed in various departments.

The guidelines recommend pharmacologic prophylaxis for up to six weeks after hip or knee replacement or other major surgical procedure; until discharge in patients with pulmonary embolism or proximal DVT within the previous two years, and for one week or longer (depending on the persistence of the risk factors), in patients with two or more risk factors such as recent immobility, venous thromboembolism at other sites, hemiplegia, cancer, acute infectious disease, acute heart failure, acute respiratory failure, and myocardial infarction.

The recommended drug intervention was either with low-molecular-weight heparin at the usual high-risk dose, an adjusted-dose vitamin K antagonist, or unfractionated heparin.

For patients with creatinine clearance of 30 mL/min (0.50 mL/s) or less, the guidelines recommend prophylaxis with unfractionated heparin, 5000 U per 12 hours, rather than low molecular-weight heparin.

The guidelines also discuss mechanical prophylaxis including the use of graduated compression stockings, early ambulation, and physical therapy.

The investigators compared outcomes in 709 patients treated before the intervention was put into place, and in 664 who were treated after the intervention was implemented.

The main outcome measure was any DVT diagnosed at routine comprehensive ultrasonography performed by registered angiologists.

They found that 12.8% of all patients in the pre-intervention group were found to have a DVT, compared with 7.8% in the post-intervention phase (P=0.002).

The rate of DVT in the calf was cut in half, from 7.1% before to 3.6%; after (P=0.005). A small change was seen in proximal venous segments, which decreased in frequency from 5.8% before to 4.2% after (P=0.18)

The overall differences remained significant after adjusting for risk factors with the adjusted odds ratio of any DVT after vs. before the intervention being 0.58 (95% confidence interval, 0.39-0.86).

"Pharmacologic prophylaxis with either low-molecular-weight heparin at the high-risk dose, unfractionated heparin, and vitamin K antagonist was similar in the two study groups, whereas patients in the post-intervention group were more likely to use graduated compression stockings (27.4% vs. 34.6%; P=0.004) and less likely to receive low-molecular-weight heparin at the low-risk dose (24.7% vs 18.5%; P=0.006), which was not recommended by our guideline," the authors wrote.

They noted that there were no episodes of major bleeding either before or after the guidelines were put into place, and there were no between group differences either before or after in the rates of minor bleeding or thrombocytopenia.

"This finding confirms safety results from previous studies that included large numbers of elderly patients, and supports the idea that physicians may often overestimate the risk for bleeding in their patients and inappropriately withhold pharmacologic prophylaxis," the investigators wrote.

They acknowledged that the study results were limited by the uncontrolled design, and by the fact that much of the decrease in DVTs occurred with distal rather than proximal clots; compression ultransonography is less accurate at diagnosing emboli occurring distally, they noted.