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Stopping clots in their tracks

Tips on when and how to use prophylaxis

By Stacey Butterfield

From the June ACP Hospitalist, copyright © 2008 by the American College of Physicians

Although his lecture was titled "Clot Controversies," Timothy A. Morris, ACP Member, professor of critical care and pulmonary medicine at the University of California, San Diego, sees nothing controversial about thromboembolism prophylaxis.

"Just do it," Dr. Morris advised attendees at the Society of Hospital Medicine's annual meeting, held this April in San Diego. "Over half a million people in this country alone have clinically recognized thromboembolism. Since clinicians often miss the diagnosis of thromboembolism, the real incidence may be a lot higher than that," he warned.

To help hospitalists improve those statistics, Dr. Morris offered advice on determining patients' clot risk, selecting appropriate prophylaxis and making sure that the proper precautions are taken for every patient.

"The fallacy that I want [dispelled] immediately is that pulmonary embolism (PE) is the old man's friend, that these people are at the end of life," he said. He presented data showing that fatal PEs are actually more common among people in their 50s and 60s than in elderly patients.

The belief that clots are a surgical problem is also a common misconception, Dr. Morris said. "It happens just as frequently in the medical population," he noted. He cited studies finding that 10% to 26% of general medical cases and 25% to 42% of medical intensive care patients have venous thromboembolisms (VTEs).

A 1997 autopsy study of 200 consecutive medical admissions, published in the Journal of Clinical Pathology, found that 5.5% of the patients died of PE. "If you extrapolate, about 6% of folks in consecutive medical admissions are going to end up dying from PE, so it becomes one of the major problems of hospitalized patients," said Dr. Morris.

Efforts to screen people for the condition have been proven ineffective, but it's fairly simple to determine a given patient's risk, according to Dr. Morris. The risk factors fall into three categories: venous stasis (immobility, surgery, congestive heart failure, venous obstruction, obesity), endothelial damage (previous deep venous thrombosis, trauma, hip or knee replacement) and hypercoagulability (estrogen in pharmacologic doses, factor V Leiden, protein C or S deficiency, lupus, cancer).

Low-risk patients are those unusual patients who are under age 40 and have no risk factors for clots. They may not need prophylaxis. "If they're pretty young and they don't have any big risk factors for DVT (deep venous thrombosis), they're not immobilized, you probably don't need to do anything except walk [them] around," Dr. Morris said.

Patients who are between age 40 and 60 or have a risk factor are at moderate risk, and anyone who meets both those criteria or is over age 60 is at high risk. The highest-risk patients are those with major surgery and multiple risk factors, hip or knee arthroplasty, hip fracture surgery, major trauma or spinal cord injury.

"You do have to treat those people a little bit differently. They have a higher risk of everything from calf DVT to mortality," said Dr. Morris.

Some very high-risk patients may require a filter, but in most cases pharmacological prophylaxis with or without mechanical prophylaxis is in order. "Filters are usually reserved for people who are very high risk and other therapy is contraindicated. Of course, it does nothing about DVTs, but it can help prevent them from having a fatal PE at least in the short term," said Dr. Morris.

For other patients, venous compression, by either custom-fitted stockings or intermittent pneumatic compression stockings, can be an effective prophylaxis with very few adverse events, according to Dr. Morris. "There's been great evidence for them being effective every time they've been looked at. They've not really been compared to each other yet," he said.

The pharmacological options, which are for the most part variants of heparin, do carry a risk of bleeding. Dr. Morris noted that there has been some debate about low-molecular-weight heparin versus unfractionated heparin, but he believes either will work in most cases.

"Most people don’t notice the problem until something bad happens." —Timothy A. Morris, ACP Member

"If you're doing small doses, the pharmacology looks very similar. There really hasn't been that much of a difference in efficacy, much of a difference in safety," he said. If a patient's high risk for bleeding makes heparin unfeasible, that's when a filter should be considered as prophylaxis.

Despite these varied options, some patients are still not receiving prophylaxis, and Dr. Morris offered both an explanation and a solution. "Frankly, it has a little more to do with psychology than medicine. Everybody knows a doctor who says, 'I don't prophylax. I've never had a problem with it.' But the same thing can be said about seat belts or smoking. Most people don’t notice the problem until something bad happens," said Dr. Morris.

To encourage physicians to use clot prophylaxis, a simple form can be effective. Dr. Morris described the use of such a form at his hospital: "When you admitted a patient, you had to declare whether you thought he or she was a low-risk, moderate-risk or high-risk patient. After you finished evaluating the risk factors, you evaluated any possible contraindications and then you had to say, 'I'm going to prophylax' or 'I'm not going to prophylax.'"

It sounds basic, but it worked, he said. "It caused a tremendous reduction in our DVT and PE rates."

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ACP Hospitalist provides news and information for internists about the practice of medicine and reports on the policies, products and activities of ACP. All published material, which is covered by copyright, represents the views of the contributor and does not reflect the opinion of the American College of Physicians or any other institution unless clearly stated