Thrombosis Prophylaxis

Preventing blood clots before they form is one of the most important safety measures in hospitals today, yet only about half of at-risk patients receive the protective treatments they need. Understanding who needs protection and what methods work best can save lives and prevent serious complications.

Table of contents

• What Is Thrombosis Prophylaxis?
• Why Thrombosis Prophylaxis Is Needed
• Who Needs Protection Against Blood Clots
• How Blood Clots Form
• Types of Prevention Methods
• Mechanical Methods
• Medication-Based Prevention
• Prevention in Specific Situations
• How Well Prevention Works

What Is Thrombosis Prophylaxis?

Thrombosis prophylaxis, also called thromboprophylaxis, is medical treatment designed to prevent the development of blood clots (also called thrombi) inside blood vessels before they can form. The term “prophylaxis” simply means prevention. This type of care is given to people who are considered at higher risk for developing dangerous blood clots, even though they don’t have clots yet.^[1][3]

These preventive measures consist of both medications and physical methods that work to diminish the risk of deep vein thrombosis (DVT) and pulmonary embolism (PE). DVT happens when a blood clot develops in one of the major deep veins in the leg or thigh, which leads to reduced blood flow and usually causes leg swelling and pain. PE occurs when a blood clot, or part of one, travels to the lungs and blocks blood vessels there, which can be life-threatening.^[4]

Why Thrombosis Prophylaxis Is Needed

Blood clots in the veins are serious medical problems that can often be prevented. Together, DVT and PE are called venous thromboembolism (VTE), and they represent a major preventable cause of death and illness around the world. In the United States alone, DVT and PE account for 60,000 to 100,000 deaths every year.^[1]

The most likely source of clots in the lungs is when pieces break off from deep veins in the legs and travel through the bloodstream. This happens in about one out of every three patients with DVT. Preventing DVT therefore decreases the chance of PE, which is a serious and potentially fatal condition.^[1]

Thromboprophylaxis is considered the most important patient safety strategy in hospitals. PE remains the leading cause of preventable death among hospitalized patients. Even though national and international guidelines have repeatedly recommended prevention for patients admitted to hospitals, only 40 to 50 percent of medical patients and 60 to 75 percent of surgical patients receive adequate protection.^[4]

Who Needs Protection Against Blood Clots

Not everyone needs thrombosis prophylaxis. People at low risk include those undergoing minor surgery with no other risk factors for blood clots, or those who need to stay still temporarily, such as during a long airplane flight. For these individuals, simply moving the legs periodically is usually enough.^[7]

People at higher risk who need additional preventive treatment include those undergoing minor surgery if they have risk factors for DVT, those having major surgery (especially bone and joint operations), and bedridden patients with serious medical conditions such as heart failure, chronic lung disease, or stroke.^[7]

Hospitalized patients face increased risk of developing DVT—approximately 50 percent may develop clots without prevention. This increases their risk of PE, which is one of the most common but preventable causes of death in hospitals. Only about 50 percent of hospitalized patients currently receive DVT prophylaxis, even though prevention significantly decreases the risk of both DVT and PE, reducing deaths and complications.^[1]

How Blood Clots Form

Normally, the body maintains a careful balance of substances in the blood that prevent clots from forming inside blood vessels when they shouldn’t. However, one or more factors described in what doctors call “Virchow’s triad” can disrupt this balance and lead to DVT formation.^[1]

The three factors in Virchow’s triad are:

• Venous stasis: This means blood doesn’t flow as well as it should. It can happen when someone doesn’t move much, such as during bed rest, or when someone has heart failure that weakens blood circulation.
• Endothelial injury: This is damage to the inner lining of blood vessels, which can occur during surgery or after an accident.
• Hypercoagulability: This means the blood has an increased tendency to clot. It can be caused by birth control pills, cancer, or inherited conditions that make blood clot more easily.^[1]

Venous stasis is considered the most important factor. Hospitalized patients are particularly at risk for venous stasis because they often can’t move around normally. When this is combined with other risk factors, their chances of developing DVT increase significantly compared to people in the community.^[1]

Types of Prevention Methods

DVT prophylaxis can be primary or secondary. Primary prophylaxis is the preferred approach and uses medications and mechanical methods to prevent DVT before it starts. Secondary prophylaxis is less commonly used and involves early detection through screening and treating DVT that has already begun but isn’t causing symptoms yet.^[1]

The treatments used to prevent blood clots must be carefully balanced against the risk of bleeding. One of the main goals is to limit venous stasis, which is a significant risk factor for forming blood clots in the deep veins of the legs.^[3][4]

DVT prophylaxis targets either venous stasis through mechanical methods or hypercoagulability through medications.^[1]

Mechanical Methods

Mechanical methods help prevent blood clots by keeping blood moving through the legs. These approaches don’t involve medications, so they don’t carry a risk of bleeding complications.

Early movement is one of the simplest and most effective ways to prevent blood clots. Getting out of bed and walking as soon as doctors say it’s safe is one of the best preventive actions. Being active helps keep blood flowing normally through the veins.^[1]

Leg exercises are important when full movement isn’t possible. Even simple movements help. Pumping the feet up and down by pulling toes toward the knees and then pointing them down helps blood move through the legs. This exercise is particularly useful when sitting for long periods. Flexing the foot up and down about 10 times per hour is probably sufficient during extended periods of inactivity.^[7]

Compression stockings are specially fitted stockings that apply gentle pressure to the legs. They may prevent blood clots by keeping blood from pooling in the legs. These should only be used if a doctor prescribes them.^[1]

Intermittent pneumatic compression devices use inflatable sleeves placed around the legs that periodically inflate and deflate, squeezing the legs to promote blood flow. These are commonly used during and after surgery.^[7]

Medication-Based Prevention

Medication-based interventions for thrombosis prophylaxis work by making the blood less likely to form clots. Several types of medications can be used.

Low molecular weight heparin (LMWH) is one of the most commonly used medications for preventing blood clots. It is given as an injection under the skin, typically once or twice daily. Studies have shown that LMWH is effective for preventing DVT in hospitalized patients.^[2][3]

Unfractionated heparin is another type of blood thinner given by injection. It can be given in low doses at regular intervals to prevent clots.^[7]

Fondaparinux is a synthetic medication that works similarly to heparin. It is given as a once-daily injection under the skin and can be used in certain high-risk situations.^[7]

Direct oral anticoagulants (DOACs) are newer medications taken by mouth rather than by injection. They work by directly blocking certain clotting factors in the blood.^[7]

Warfarin is an older oral medication that has been used for decades. However, it requires regular blood tests to monitor its effects and adjust the dose.^[7]

Research comparing different blood thinners in people with cancer found that the evidence did not identify any major differences between the effects of different blood thinners on death, developing a clot, or bleeding. However, a 2021 review found that low molecular weight heparin was superior to unfractionated heparin for the initial treatment of venous thromboembolism in people with cancer.^[2][3]

Prevention in Specific Situations

For medical patients: People hospitalized with acute medical illnesses, long-term care residents, and those with minor injuries are at increased risk of VTE. Medical patients with severely restricted movement during acute illness may receive prevention medication for a median of 7 days, with most patients treated for 6 to 11 days. The usual duration can extend up to a maximum of 14 days.^[6]

In one study of medical patients with severely restricted mobility, those treated with medication had a 63 percent relative reduction in DVT and PE events compared to those who received no prevention treatment. The actual reduction in events was 7.5 percent—with 4.4 percent developing clots with prevention versus 11.9 percent without prevention.^[14]

For surgical patients: The risk of DVT in surgical patients varies depending on the type of surgery. Major surgery, especially orthopedic procedures like hip or knee replacement, carries very high risk. Prevention typically begins after surgery because the immobility associated with surgery increases risk significantly.^[4][7]

During travel: Long-distance travelers, particularly those on flights longer than 6 hours, have increased risk of blood clots. Thrombosis prophylaxis is recommended during air travel for those at risk. Simple measures like walking periodically during the flight and doing leg exercises while seated can help.^[3][6]

How Well Prevention Works

Thrombosis prophylaxis is effective in preventing the formation of blood clots, stopping them from lodging in the veins, and preventing them from developing into thromboemboli—clots that travel through the circulatory system and can cause blockage and tissue death in other organs.^[3]

The risk of developing blood clots can be lowered through lifestyle changes, stopping oral contraceptives, and losing weight. In people at high risk, both medication and non-medication interventions are often used together.^[3]

At about 3 months following hospital enrollment in prevention programs, the occurrence of venous blood clots remained lower in those who received prevention treatment compared to those who did not.^[14]

Computer-based decision systems and pre-printed orders have proven most effective in helping doctors follow thromboprophylaxis guidelines consistently. Regular reviews by pharmacists or other health professionals help reinforce the consistent use of venous thromboembolism prophylaxis.^[4]

It is preferable and safer to prevent DVT than to treat it after it has formed, particularly in patients at high risk. Prevention begins with assessing each person’s risk level, which allows healthcare providers to select the most appropriate preventive approach.^[7]