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DVT Link to Knee and Hip Surgery

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DVT Link to Knee and Hip Surgery

DVT Link to Knee and Hip Surgery

November 26, 2002
(AP) - Mention deep vein thrombosis (DVT) and it brings to mind "economy- class syndrome", a potentially fatal condition linked to blood clots in the legs during long distance flights.

In reality, DVT is much more likely to be caused by a particular kind of surgery than by long-haul flights.

Dr Visalachy Purushothaman, who heads the haematology department at Hospital Kuala Lumpur, said patients are at very high risk of DVT following orthopaedic surgery, particularly hip and knee replacement surgery and that of hip fracture.

Dr Puru, as she is usually known, said DVT is a frequent medical complication that results in the formation of blood clots, most often in the legs.

"DVT often begins in the calf or thigh because blood moves relatively slowly in these areas, particularly if exercise is limited. As the blood begins to pool in an area, a clot develops and can attach itself to the wall of a vessel or in more severe cases, become wedged within a vessel, blocking blood flow.

"The major risk associated with DVT is development of pulmonary embolism (PE)," she continues.

"This occurs when a fragment of a blood clot breaks loose from the wall of the vein and migrates to the lungs, where it blocks a pulmonary artery or one of its branches. Blockage of the main pulmonary artery by one or more of these migrating clots (emboli) may be fatal."

In rarer cases, the clot could also be pumped towards the brain and block arteries that supply the brain. If this happens, a potentially fatal stroke may result.

She says the three main reasons for the increased risk of developing DVT after major orthopaedic surgery are: vessel damage can occur during surgery; post-surgical tissue debris can increase the tendency of the blood to clot; and an extended period of immobility can slow blood flow.

In 2000, a study done at the Singapore General Hospital showed that 14 per cent of the Asian patients who underwent knee replacement surgery suffered DVT.

Studies in Singapore also reported DVT occurrence rates of three to seven per cent after general surgery, and 9.7 per cent after hip surgery.

But specialists believe that a new anti-clotting drug, fondaparinux sodium, will help reduce the number of patients who end up with DVT after orthopaedic surgery.

International clinical trials involving over 7,300 patients found that it was a major improvement over conventional treatments. The studies revealed that injections with fondaparinux reduced the overall risk of patients developing DVT and PE in hip fracture surgery and hip and knee replacement surgery by 55 per cent, compared to the currently most widely prescribed anti-clotting agent, enoxaparin. Unlike enoxaparin, fondaparinux does not affect the blood platelets which help prevent bleeding.

"Fondaparinux blocks a blood enzyme called activated factor X, which stimulates blood clotting. And this activates the normal mechanisms in the body that defend us against blood clotting," says Dr Puru. "It is an indirect thrombin inhibitor, like the low molecular weight heparins."

Also, since the drug is made synthetically, there is no risk of problems related to pork or beef allergies, she adds.

Fondaparinux, as with all anti-clotting agents, carries a risk of increased bleeding. However, the trials showed positive results.

"It doesn't seem to increase the occurrence of significant bleeding."

Fondaparinux sodium will be made available to doctors in Malaysia by the end of this year or early next year. Before a knee or hip operation, doctors would give the drug to those who have a high risk of developing DVT. These include those who have a previous history of DVT, are overweight or are taking contraceptive pills.

Consultant haematologist Dr Jameela Sathar adds that the other major DVT risk factors are blood conditions that increase the propensity for blood to clot, pregnancy, childbirth, previous or current cancer, oestrogen hormone therapy, Smoking, trauma or prolonged periods of bed rest.

Dr Jameela calls DVT the "silent killer" because 80 per cent of sufferers do not know they have developed the condition.

"Fewer than half of those with DVT have symptoms such as swelling, discoloration and pain to the legs. Many times, it's actually silent and patients don't even know it's there. More than half have symptoms when it reaches the lungs, however, and the typical symptoms may be chest pain, shortness of breath, rapid pulse or a cough. Sometimes, a cough will produce bloody sputum. They may just black out," she says.

She says that the diagnostic Ultrasound is the best method to detect restrictions in blood flow, often in combination with blood tests.

But, as with many complications, prevention is often the best strategy.

"Almost 99 per cent of all blood clots are preventable," said Dr Puru. "If people are at risk, they should go for a check up and find out how high their risk is. Then they can be given a drug or a nonpharmacologic agent. Things like compression devices or compression stockings can be effective, but you need to be thinking about it and acting on it early."

Dr Puru advises patients to exercise and flex their leg muscles, especially if they are sitting in a cramped position for a long period of time.

"Nature sends out a lot of signals. If you have been sitting in one position that the body doesn't like, you will feel cramped. That's the body telling you to change position or get up and move about," she says.

In relation to air travel, she advises those more at risk of developing DVT to begin taking half an aspirin a day for 10 days prior to travel.

Medical professionals also recommend seeking medical advice before travel and during the flight, to wear special compression socks and drink lots of water. * The writer can be contacted at [email protected]

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