Prevention and treatment of a deep vein thrombosis (DVT)
Long distance flights are thought to cause deep vein thrombosis (DVT) because of restriction of movement (hence the term “economy class syndrome”) and dehydration, although more recent research has suggested that the lower levels of oxygen in the on-board air (which is usually pressurised at between 7,000 and 12,000 feet) has an adverse effect on the lining of the vein wall. This can predispose to clots forming on the vein wall, extending into fully fledged deep vein thrombosis (DVT).
Prevention of deep vein thrombosis (DVT) on long-distance flights is therefore encouraging passengers to exercise their legs, move around the cabin, as well as to drink water and fruit juice. In addition, properly fitted below knee graduated pressure stockings or “flight socks” have been shown to reduce swelling of the ankle and deep vein thrombosis (DVT).
Surgical operations that have high risks of deep vein thrombosis (DVT) are generally those that are performed under a general anaesthetic, take longer than an hour and often include operations to pelvis or legs.
A general anaesthetic is risky because the patient has to starve before the operation, meaning that they are often dehydrated at the time of surgery, making the blood more likely to clot, and during the procedure they do not move meaning the blood in the veins flows very slowly. By changing both the concentration of the blood by dehydration and the flow of blood by lack of movement, there are two separate risks of clotting from Virchow’s triad.
Prevention of deep vein thrombosis (DVT) around the time of surgery includes wearing specialised compression stockings before and after the surgery (thromboembolic disease stockings or TEDS), having an intravenous drip going before, during and after surgery preventing dehydration, and subcutaneous heparin injected around the time of surgery to reduce the risk of thrombosis.
In people who have a familial risk of deep vein thrombosis (DVT) called a thrombophilia, other precautions may be needed including the injection of heparin during flights or, if severe enough, anticoagulation for the whole of their life. This is a very specialised area and for patients who have got thrombophilia, specialists called haematologists control medication to try keep risks to a minimum.
Q1 Treatment of a deep vein thrombosis (DVT)
Anticoagulation therapy, initially heparin which is injectable followed by an oral anticoagulant (either warfarin or coumarin), stops any more blood clotting and so stops the deep vein thrombosis (DVT) from extending. However anticoagulation does not actually break any clot down. What anticoagulants do is to allow the body’s own immune system to start breaking the deep vein thrombosis (DVT) down by stopping the body from replacing it.
The human body is always in a dynamic state of forming clots and breaking them down. If this is not the case, we would always be bleeding from our bowel, gums and elsewhere in our body. Hence we are always forming little clots to stop bleeding and then breaking them down so blood vessels don’t become completely blocked. When we use anticoagulation to stop clots from forming, we alter this balance allowing the body to break down any thrombus or clots without any more forming.
There are other drugs that can actually break down the thrombus or clots. These are called “fibrinolytic agents” – the original one was streptokinase which was superceeded by tissue plasminogen activator (TPA), and now different versions are becoming available. Fibrinolytic agents are very powerful drugs that are often used in the treatment of heart attacks. However, as they break down all clots, there is a risk if too much is given in the wrong area, the patient may start bleeding internally which will put the patient at risk. Therefore the risks of giving fibrinolytic agents are often more than the benefits that might be achieved. Hence these very powerful fibrinolytic agents are rarely used in treating deep vein thrombosis (DVT).
The position and size of the deep vein thrombosis (DVT) affects how aggressively the anticoagulation is given.
If there is only a small deep vein thrombosis in one of the tiny veins in the calf, then many doctors will treat it only with a graduated pressure stocking, exercise and sometimes aspirin or other antiplatelet drug, asking the patient to return within a few days to check that the deep vein thrombosis (DVT) hasn’t got any bigger. Other doctors will treat these as any other deep vein thrombosis (DVT) with heparin injections followed by anticoagulation with warfarin or coumarin, usually for a period of three months.
When the deep vein thrombosis (DVT) is in the larger thigh veins or behind the knee, it is clearly bigger and therefore has more symptoms. The potential damage to the vein is also more and so heparin is given immediately on diagnosis and full anticoagulation with warfarin or coumarin for 3 to 6 months is usually recommended.
A deep vein thrombosis (DVT) in the groin or in the pelvic veins is clearly a much larger clot again and is often treated by admission to hospital and immediate intravenous heparin and full anticoagulation.
At this point it is worth noting one of the differences that are starting to appear in the treatment of deep vein thrombosis (DVTs).
Physicians and haematologists have traditionally decided to either treat deep vein thrombosis (DVT) with anticoagulation for three months if small, or six months if larger. Since phlebologists and interested vascular surgeons have been performing more duplex ultrasound scans and have been seeing not only the deep vein thrombosis but the damage they cause if not completely cleared, there has been a push to start tailoring treatment to the patient.
Research from Prof CV Ruckley from Edinburgh (Scotland) has shown that if a deep vein thrombosis (DVT) forms and it is completely cleared very quickly with full anticoagulation, then the long-term damage to the deep vein and the deep venous valves is minimal or non-existent. However those patients who have damage to the deep veins and deep vein valves have usually had either recurrent deep vein thrombosis’ (DVTs) or have had a long-term deep vein thrombosis (DVT) that has not been adequately cleared.
Thus it seems a far more sensible and logical way to treat patients by re-scanning them every three months and only advising the anticoagulation to stop when the veins are found to be completely clear. Being on anticoagulation is not risk-free and there are estimates that being fully anticoagulated causes a risk of a major bleed in 1% of people per year. Therefore the balance between clearing the veins completely but not having the risk of bleeding is best served by re-scanning every three months and stopping anticoagulation when the veins are clear.
Unfortunately this does not fit with most deep vein thrombosis (DVT) treatment guidelines that are currently around, but over the years it is likely that this logical treatment plan will become the norm.
Finally, as you can see from the discussion above, the treatment depends upon knowing how big the deep vein thrombosis (DVT) is and in which veins it is in. This is one of the reasons why although a blood test may be acceptable for screening, it is never acceptable for full planning of treatment. The optimal way of diagnosing people and planning treatment is to have a full duplex ultrasound scan immediately as soon as possible and treatment recommended by an experienced phlebologist who can then take advice from a haematologist if there turns out to be thrombophilia present in the family.
Q2 What you should do if you have a deep vein thrombosis (DVT)
Different countries and areas have different ways of providing this emergency service. Sometimes this will be through an emergency room in a local hospital, sometimes there will be an emergency clinic. In some countries, more progressive vein clinics will run emergency deep vein thrombosis (DVT) services, providing expert scans immediately.
The very best service available would be to have a venous duplex ultrasound scan performed by a specialist vein clinic who scans nothing but veins. Such a scan should look at all of the veins, from the pelvic veins down to the ankle veins. A second best service will perform a brief scan, looking at three or more points on the legs, just to check there isn’t a deep vein thrombosis (DVT) at certain areas (usually groin, midthigh and behind the knee). Unfortunately these “three-point” scans can miss deep vein thrombosis in the calf veins but are much simpler and quicker to perform.
Many hospitals are unable to provide expert scanning and therefore use a variety of tests, the most popular and probably the most useful screening test being a blood test measuring D-dimers. These are proteins which are present if clot has been formed. Unfortunately this is less accurate than an expert venous duplex ultrasound scan, but as the expertise and equipment needed for such scans is not widespread, it is certainly better than nothing and it helps guide correct treatment in the majority of patients.
If you have never had a deep vein thrombosis (DVT) before, but they do run in your family, you should follow the above route but you should tell every doctor and nurse that treats you that deep vein thrombosis (DVT) runs in your family so that once you have treatment started, you can then be investigated for thrombophilia. It is possible that you will be given further advice on anticoagulation and other ways to reduce your risks of getting one in the future such as taking heparin for long flights etc. Such advice is individually tailored depending on what your thrombophilia tests will show.
If you have a history of deep vein thrombosis (DVT) previously, then you are likely to know what it feels like. You will probably also have a doctor, hospital or clinic that already looks after you, and you should notify them as soon as possible so they can continue your care.
Q3 Long-term prognosis after a deep vein thrombosis (DVT)
Fortunately, this is shown not to be the case. As noted before, Prof CV Ruckley from Edinburgh (Scotland) has shown that provided the deep vein thrombosis (DVT) is diagnosed quickly and treated efficiently and quickly, then deterioration to postphlebitic limb is highly unlikely.
Furthermore, considerable research into leg ulcers and the other chronic damage that is seen in the legs that was previously diagnosed as “postphlebitic limb” has shown that in a great many cases, the cause of such changes is actually just severe varicose veins that have not been treated. Treatment of these, including incompetent perforating veins, using endovenous techniques can usually cure ulcers and reverse the swelling and skin damage.
As such, a deep vein thrombosis (DVT) needs to be investigated and treated quickly and efficiently, and most patients can expect a very good outcome provided they get expert care quickly.