Continuing Warfarin May Be OK During Invasive Procedures

By Doug Brunk

It is possible to perform major surgery in patients receiving moderate doses of warfarin, targeting the preoperative dose to achieve an INR of 1.5-2.0, results from a long-term prospective study suggest.

"Close cooperation between treating physicians is essential for this approach to be successful," wrote the investigators, led by Bradley J.G. Larson, M.D., of the division of hematology and oncology in the department of medicine at the University of Florida, Gainesville.

Dr. Larson and his associates prospectively studied 100 consecutive patients who were receiving long-term anticoagulation therapy and required an invasive or surgical procedure between 1993 and 2003 (Chest 2005;127:922-7). All patients were considered to be at high risk for thromboembolism.

The investigators adjusted the preoperative dose of warfarin to achieve an INR goal of 1.5-2.0, performed standard coagulation tests, and used published instruments to gauge the risk of thromboembolism as well as overall surgical risk.

Of the 100 patients, 62% had experienced deep-vein thrombosis (DVT) or pulmonary embolism (PE) within the past 6 months, and 11% had experienced at least one prior postoperative DVT or PE. In addition, 58% of the surgical procedures ranked as Johns Hopkins category 3-5 (moderate to critical).

Mean INR levels were 2.1 the day before surgery, 1.8 the day of surgery, and 1.8 the first day after surgery. Two patients experienced major bleeding, four had minor bleeding, and one had a symptomatic DVT. "Another patient with a mechanical aortic valve died from an embolic stroke following 13 days of subtherapeutic INRs," the authors wrote. "Heparin-induced thrombocytopenia and warfarin skin necrosis were not observed."

Two key limitations of the study include its prospective design and the fact that it followed a heterogeneous patient population.

"The present study was neither randomized nor controlled," the investigators wrote. "Further investigation will be required before this strategy can be advocated for routine clinical practice."

Even so, the work is "a very good step" toward examining this approach in further detail, Thomas W. Wakefield, M.D., said in an interview.

"There should be separate studies [of this approach] based on procedure or discipline to confirm these findings," said Dr. Wakefield, professor of vascular surgery at the University of Michigan Medical Center, Ann Arbor. "This study allows me to have some feeling that 'Yes, it's OK to operate on people when their Coumadin [INR] is 1.5-2.0.' It gives me the backing to say to somebody, 'It can be done. You probably can get away with it.' But it doesn't give me any sense of the idea that I can go to somebody and say 'I have scientific proof that it's OK to do this.' It's certainly a good first step, which should spur some additional studies."

FURTHER INVESTIGATION WILL BE REQUIRED BEFORE THIS STRATEGY CAN BE ADVOCATED FOR ROUTINE CLINICAL PRACTICE.