JULY 2008


Exhaustive blood clot guidelines unleashed

Spotlight on pregnancy issues. Plus new info on bridging for surgery

The 8th edition of guidelines on antithrombotic and thrombolytic therapy from the American College of Chest Physicians (ACCP) is out. The 900-page document boasts more than 700 recommendations for the prophylaxis, treatment and followup of blood clot disorders. The full guidelines, along with a 40-page executive summary, were published as a supplement to the June issue of Chest.

Highlights include new advice on anticoagulation during pregnancy and a full chapter on how to manage patients on longterm antithrombotic therapy undergoing surgery.

The old guidelines recommended that thrombosis-prone patients who become pregnant should be taken off vitamin K antagonists (VKAs) such as warfarin as soon as possible because the drugs increase the risk of birth defects and miscarriage. This advice remains, but the new version makes allowances for women at high risk for blood clots, such as those with certain types of mechanical heart valves, recommending that they continue on VKAs and switch to low-molecular weight heparin (LWMH) or unfractionated heparin (UFH) closer to the birth. This brings the guidelines in line with what's currently being done in Europe, explains guideline author Dr Shannon Bates, a thromboembolism specialist at McMaster University.

If a woman is a candidate for discontinuation of VKAs, it's recommended to put her on LWMH or UFH. You can either follow your patient closely with frequent pregnancy tests and initiate the new drug once conception is confirmed, or you can start her on LMWH or UFH before she tries to get pregnant, advise the guidelines.

The chapter on following patients on longterm antithrombotic therapy is good news for physicians. These individuals need special attention when they go under the knife, as the anticoagulants they're on boost the risk of bleeding. Until now, the recommendations on how to bridge these patients were based on a very thin evidence base, but the section on perioperative management addresses many of the pressing issues.

For people taking warfarin, there are a number of options. If they're undergoing a small procedure such as cataract surgery, it may be possible to simply lower the dose. You can also stop warfarin five days before the operation and substitute with LMWH. In special cases, you may even choose to continue warfarin therapy until 48 hours before the procedure and then give a low dose of vitamin K.

Traditionally, the guidelines issued by the ACCP had a tendency to be "very North American-based," Dr Bates told NRM. It's a concern the new edition has tried to address by increasing the number of international experts on the panels — a change Dr Bates welcomes. "It makes more sense to have guidelines that are applicable to everyone," she says.

To make the heavy document more user-friendly, the authors have also altered the set-up of the chapters. They now begin with the recommendations, followed by tables outlining the evidence from clinical trials. To further help physicians find the information that applies to their practice, the chapters are organized according to specific patient populations and their concerns, rather than divvying them up by treatment approaches.



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