Can medication prevent thrombosis in immobilized legs?
If you cannot move your leg for days, because of a broken bone for example, then some anticoagulant drugs can reduce the risk of developing deep vein thrombosis. However, the most important preventive measure is to start moving around again as soon as possible.
Sometimes a leg has to be kept still (immobilized) because of an injury or a leg operation. This could be because the leg is in a cast or splint after a bone fracture or torn ligament. This means that the person cannot move it or put any strain on it, or only a little bit.
DVT can be dangerous if the clot dislodges from the vein and travels through the blood system into the lungs. If it reaches the lungs and lodges in a blood vessel there, it can cause a pulmonary embolism (PE). This can block the flow of blood from the heart to the lungs, which overstrains the heart and can even cause heart failure. As well as this, the lung tissue does not get enough blood and nutrients, which causes problems with oxygen uptake in the lungs. Signs of PE may include sudden breathlessness, chest pain when breathing, coughing up blood, dizziness, anxiety and a racing pulse.
Options for preventing thrombosis
There are several ways to lower the risk of DVT. The most important is to get moving again as soon as possible: immobility increases the risk of a blood clot. However, it is also important not to over-exert the leg too soon as this could slow down recovery. When people have to stay in bed for days after an operation or due to injury, they often wear compression socks or stockings. These put the leg under light pressure, which helps the blood flow back to the heart a little faster.
Various medications are also used to reduce the blood’s clotting ability and lower the risk of DVT. These drugs are called anticoagulants. Heparins are among the most established anticoagulant medications. They are injected subcutaneously (under the skin). There are two types of heparin: “low molecular weight” heparin (LMWH) and “unfractionated” heparin. They work in similar ways but they differ, for example, in how long their effect lasts. LMWH only needs to be injected once a day, whereas unfractionated heparin needs to be injected two to three times a day. People who have an immobilized leg usually use LMWH. Many people can recover at home instead of in hospital and inject themselves.
Some medications from the group of drugs called coumarins are another option. These are taken as tablets. They tend to be used for long-term prevention in people who have a permanently higher risk of thrombosis.
Research on preventive medication
Researchers from the Cochrane Collaboration – an international network of researchers – wanted to know how effective low molecular weight heparin is at preventing DVT and pulmonary embolism in patients who have a leg in a cast or splint following an injury.
The researchers found six high-quality trials (randomized controlled trials, or RCTs) involving a total of 1,490 participants who had a leg in a cast or splint. Of these participants, 750 received heparin and the 740 people in the control groups had a placebo treatment.
A different group of researchers from the Isala Clinics in Zwolle, the Netherlands, analyzed trials on all the medications that are used to prevent DVT in people with immobilized legs. They found the same randomized controlled trials that the Cochrane researchers did on LMWH, and they did not find any trials on unfractionated heparin or coumarin.
Low molecular weight heparin can prevent deep vein thrombosis
Both groups of researchers found that people who have immobilized legs are less likely to develop DVT if they take LMWH. However, these drugs do not always prevent DVT. In the group of people who took heparin, 10 out of 100 people had DVT. By comparison, of the people who did not take these medications, 18 out of 100 developed DVT. In other words: for every 100 people with immobilized legs who take low molecular weight heparin, DVT is prevented in 8 people.
But thrombosis is not always a problem. It sometimes goes unnoticed and does not have any health consequences. Some types of DVT lead to a higher risk of pulmonary embolism, particularly those that cause symptoms and those occurring higher in the leg and pelvis.
Pulmonary embolism was very rare in the trials. None of the people who took heparin had one, compared to 2 of the 740 people who did not take heparin.
Hardly any differences in side effects, between patient groups or products
The possible adverse effects of heparins include allergic reactions and more frequent bleeding because these drugs reduce the ability of the blood to clot. However, both of these adverse effects were equally seldom in the treatment and control groups. More serious bleeding occurred in 2 out of 750 people in the treatment group, compared with 1 out of 740 people in the control group. The injections sometimes caused minor bleeding and bruising at the site of injection.
There is an ongoing debate among experts about whether DVT prevention is especially effective for some groups of people. The researchers also looked into whether particular groups benefited more from treatment than others, but found no differences. Everyone benefited equally from low molecular weight heparins, regardless of whether they had bone fractures or ligament injuries, wore a cast or a splint, had surgery or other treatment.
There was no difference between the various medications made by different manufacturers either. Although they did not have enough data to be certain, the Cochrane researchers concluded that if there are any differences, they are probably very small. There was also not enough data to be able to say how long people should take the medication to get the best effect. In the trials that were analyzed, the patients took LMWH for as long as their leg was immobilized.
Taking medication can reduce the likelihood of DVT developing, but does not always prevent it. The most important thing is to do something about the main thing that increases the risk and get back on your feet and move around again as soon as your condition allows you to.
In August 2012 we checked for new research results on using medication to prevent deep vein thrombosis in immobilized legs but found no new systematic reviews. Other sources also do not indicate that any new research results are available. We therefore believe that this information reflects the current state of scientific knowledge on this topic.
Published by the Institute for Quality and Efficiency in Health Care (IQWiG)
Next planned update: January 2016. You can find out more about how our health information is updated in our text "Informed Health Online: How our information is produced."
- January 17th 2013 10:52
- July 15th 2009 14:28
- Show list
IQWiG health information is based on research in the international literature. We identify the most scientifically reliable knowledge currently available, particularly what are known as “systematic reviews.” These summarize and analyze the results of scientific research on the benefits and harms of treatments and other health care interventions. This helps medical professionals and people who are affected by the medical condition to weigh up the pros and cons. You can read more about systematic reviews and why these can provide the most trustworthy evidence about the state of knowledge in our information “Evidence-based medicine.” We also have our health information reviewed to ensure medical and scientific accuracy.
Ettema HB, Kollen BJ, Verheyen CC, Büller HR. Prevention of venous thromboembolism in patients with immobilization of the lower extremities: a meta-analysis of randomized controlled trials. J Thromb Haemost 2008; 6: 1093-1098. [PubMed summary]
Testroote M, Stigter W, de Visser DC, Janzing H. Low molecular weight heparin for prevention of venous thromboembolism in patients with lower-leg immobilization. Cochrane Database of Syst Rev 2008; (4): CD006681. [Cochrane summary]