Lawson Researcher Aims to Find the Best Postoperative Management of Anticoagulation

London, ON – Patients who are at risk of developing blood clots deep in the arteries take anticoagulants to prevent the clots. When these patients face surgery, however, anticoagulation could cause excessive bleeding. A London scientist and his team are trying to determine the best balance between preventing bleeding during surgery and preventing clotting complications.

Dr. Michael Kovacs – scientist at Lawson Health Research Institute, Hematologist at London Health Sciences Centre and Professor of Medicine at Schulich School of Medicine & Dentistry at The University of Western Ontario – is dedicating five years to a randomized controlled trial of the best postoperative treatment for patients whose anticoagulation medicine is interrupted to allow for surgery. The $2.3-million trial is being funded by the Canadian Institutes for Health Research.

A popular treatment for patients who are at risk of developing blood clots deep in the arteries – arterial thrombembolism – is the oral blood thinning drug warfarin. This drug is effective in preventing blood clots from developing within blood vessels (a process called thrombosis), and in patients with prosthetic (artificial) heart valves or atrial fibrillation. It is important to reduce the risk of clots forming that could cause serious complications such as stroke or death.

Performing surgery when a patient is taking anticoagulation medication, however, presents an interesting challenge as the drugs interfere with the body’s natural ability to clot blood. The patient’s blood needs to clot to allow for healing, yet the risk of clotting in the blood vessels must still be managed. Dr. Kovacs and his colleagues, including co-principal investigator Dr. Marc Rodger at Ottawa Health Research Institute and eight other researchers, hope to discover a definitive way to overcome this. This project will look at patients with the prosthetic heart valves or atrial fibrillation who are at high risk for aterial thrombembolism. The controlled trial - titled PERIOP 2 - involves 12 centres and 1,773 patients.

“Our controlled trial will determine the best way to manage treatment for patients with a high risk for arterial thrombembolism who have their warfarin dosage interrupted for surgery,” says Dr. Kovacs. In the controlled trial, researchers at several sites across Canada will identify whether the use of an alternative anticoagulant – Low Molecular Weight Heparin (LMWH) – as a post-operative bridging treatment is effective at allowing sufficient blood clotting during and after the surgery, while still minimizing the risk of clotting complications.

Warfarin takes several days to wear off and then several days to work when dosage is started again after surgery. The randomized control trial will allow the research team to compare the LMWH bridging therapy against placebo treatment to prove a reduction in post-operative bleeding, lower risk of stroke and other complications in the placebo arm of the controlled trial.

“Most clinicians recommend bridging therapy such as LMWH; however, the use is not standardized and has not been assessed by adequate randomized studies,” says Dr. Kovacs. “This is why we are conducting the first multi-centre double-blind randomized control trial. A pilot study, done by this team in 2002 with 220 patients suggested that postoperative LMWH caused increased bleeding and ultimately increased thrombotic events. With our current study, we hope to arrive at a standardized way to treat these patients with this risk.”

Lawson Health Research Institute (Lawson) in London, Ontario, Canada is the research institute of London Health Sciences Centre, and St. Joseph’s Health Care London. It is one of the largest hospital-based research institutes in Canada and is dedicated to helping people live healthier lives by advancing knowledge of how to prevent, diagnose and treat disease.


For more information please contact:

Andrew Kaszowski, Communications Consultant
Lawson Health Research Institute
519-646-6100 ext. 65516, andrew.kaszowski@sjhc.london.on.ca