Pulmonary embolism may be the most common preventable cause of hospital death. It's often the result of deep vein thrombosis, which is a very real risk for anyone undergoing surgery. But DVT, as it's more commonly known, can be prevented. What's more, there's more than one way to prevent it.

Partly because of that, our physicians' orders for DVT prevention lacked consistency. So we at Maine Medical Center undertook a literature search to determine a holistic protocol based on best practices. Here's what we learned, and the guidelines we've since instituted as a result.

Getting the facts
Many factors put patients at risk for DVT, most of them related to the procedure or to patients' physical well-being (see "Out of Your Control"). When such risk factors exist - such as long procedures, advanced age, obesity and co-morbid conditions - you must take steps to prevent Virchow's triad of venous stasis, venous injury and hypercoaguability.

There are several ways to target the pathophysiological components that cause DVT, though not all are appropriate in all situations. They include light exercises as well as mechanical and pharmacologic measures.

• Mobilization. Simply getting the patient up and about or having him perform ambulatory leg exercises as soon as possible after surgery gets the blood flowing, and strong blood flow is key to helping prevent DVT.
• Medication. Several types of pharmacologic agents can prevent DVT by inhibiting or preventing altogether thrombosis formation: antiplatelets, anticoagulants and antithrombotics. There is another class of drugs called thrombolytics, which break up thrombi after they've formed. The most commonly administered drugs with regard to DVT are aspirin, warfarin, low-dose unfractionated heparin and low molecular weight heparin. There are recommendations regarding the use of each, but before you institute a pharmacologic DVT prevention protocol, discuss these options with the surgeon or attending physician, who should collaborate with your facility's pharmacist to understand the indications and potential drug interactions for each (see "Pharmacologic Prevention at a Glance" on page 68).
• Graduated compression. This method calls for using elastic stockings or graduated compression stockings - much like non-medical support hose - that encourage circulation. They come in either knee- or thigh-high lengths. The U.S. government's Agency for Healthcare Research and Quality notes in its recommendation for DVT preventions that "fitted hose are more efficacious than non-fitted."1 Further, thigh-high GCS can actually injure patients because they can cause a tourniquet effect around the thigh, impeding rather than encouraging blood flow.
• Pneumatic compression devices. These devices are wrapped around the thigh, calf or feet (depending on which type you have) and attached with a hose to a machine that sequentially inflates and deflates the bladders within the stockings or booties. At regular intervals, the bladders squeeze the leg muscles, increasing blood flow by as much as 500 percent. Known in the literature as intermittent pneumatic compression or IPC, it is recommended you apply the devices before anesthesia and leave them on until the patient is fully ambulatory.

A question of compression
While leg compression has been established as a safe method of DVT prophylaxis in surgical patients, it's where the majority of confusion lay in our hospital. As a result, we had unclear policy guidelines directing the practice of mechanical compression.

There's no shortage of literature on the efficacy of compression devices. Here's some of what we found:

• One meta-analysis demonstrates that pneumatic compression devices are more effective at preventing DVT than placebo, GCS or mini-dose heparin.2
• Another showed that patients who received prophylactic pneumatic compression had the lowest incidence of DVT by far when assessing DVT by venography.3
• A retrospective study by a single institution with 7,520 patients treated with prophylaxis found that pneumatic compression had the lowest incidence of failure for prophylaxis measures at 2.2 percent.4

We were also able to determine that knee-high pneumatic compression was just as effective at preventing DVT as whole-leg pneumatic compression; there is also little difference between graduated and single-pulse pneumatic compression. Whole-leg compression is difficult to fit properly, soils easily and may cause a tourniquet effect. Calf-only compression is preferred by nurses and patients, and as a result sees better compliance.

Even better, knee-high compression is a money-saver: A study in the Journal of Urological Surgery that looked at 3,960 patients found that facilities could save about $126,000 a year by switching to knee-high from whole-leg pneumatic compression - without compromising prophylaxis efficacy.5 We therefore decided our facility would use only knee-high pneumatic compression for moderate- to high-risk patients.

Step by step
Using the information we'd gathered, we developed a standardized policy for compression and other prophylaxis, and educated nurses so they are able to identify patients who are at risk for DVT. Nurses go through the list of risk factors (see "Out of Your Control" on page 67) to determine the risk levels patients present. The criteria we now use:

• Low risk. Patients younger than 40 having minor surgery with no additional risk factors have a DVT risk of about 2 percent. Treatment: Aggressive mobilization post-op.
• Moderate risk. Patients 40 to 60 years old having minor surgery with additional risk factors have a DVT risk of 10 to 20 percent. Treatment: GCS, IPC or meds.
• High risk. Patients older than 60 having minor surgery; patients older than 40 having major surgery; and patients younger than 40 having major surgery with additional risk factors have a DVT risk of 20 to 40 percent. Treatment: IPC or meds.
• Highest risk. Patients with major trauma or a spinal cord injury; patients undergoing hip or knee arthroplasty or hip fracture repair; or patients with a history of DVT, cancer or hypercoagulable state have a DVT risk between 40 and 80 percent. Treatment: IPC, GCS and meds; inferior vena cava filters; and duplex ultrasonography screening.

Toward better practices
Thanks to collaboration with nurses and physicians, we've successfully implemented evidence-based practices, but we're not stopping there. We'll continue searching the literature for DVT prophylaxis guidelines as we work to establish an incidence rate here at MMC. We're also considering undertaking an outcome study.