a blood clot blocking a blood vessel
|Other names||Thrombosis prophylaxis|
|ICD-9-CM||437.6, 453, 671.5, 671.9|
Thrombosis prevention or thromboprophylaxis is medical treatment to prevent the development of thrombosis (blood clots inside blood vessels) in those considered at risk for developing thrombosis.Some people are at a higher risk for the formation of blood clots than others. Prevention measures or interventions are usually begun after surgery as people are at higher risk due to immobility.
People undergoing surgery with cancer are at an increased risk of blood clots. Blood thinners are used to prevent clots , these blood thinners have different effectiveness and safety profiles. Researchfound 20 studies that included 9771 people with cancer. The evidence did not identify any difference between the effects of different blood thinners on death, developing a clot, or bleeding. Less bruising following surgery occurred with some while others may have reduced the risk of getting a blood clot but the reliability of evidence varied from low to moderate.
Data from five studies with 422 participantssuggested the effect of low molecular weight heparin (LMWH) on death compared with unfractionated heparin was uncertain.
There are medication-based interventions and non-medication-based interventions.The risk of developing blood clots can be modified by life style modifications, the discontinuation of oral contraceptives, and weight loss. In those at high risk both interventions are often used. The treatments to prevent the formation of blood clots is balanced against the risk of bleeding.
One of the goals of blood clot prevention is to limit venous stasis as this is a significant risk factor for forming blood clots in the deep veins of the legs.Venous stasis can occur during the long periods of not moving. Thrombosis prevention is also recommended during air travel. Thrombosis prophylaxis is effective in preventing the formation of blood clots, their lodging in the veins, and their developing into thromboemboli that can travel through the circulatory system to cause blockage and subsequent tissue death in other organs. Clarence Crafoord is credited with the first use of thrombosis prophylaxis in the 1930s.
The development of blood clots can be interrupted and prevented by the use of medication, changing risk factors and other interventions. Some risk factors can be modified. These would be losing weight, increasing exercise and the cessation of oral contraceptives. Moving during periods of travel is a modifiable behavior. Preventing blood clots includes the use of medications that interrupt the complex clotting cascade and changing the proteins that are needed for clotting. Antiplatelet drugs also have an effect in preventing the formation of clots.[ citation needed ]
If a blood clot has already formed in a blood vessel, treatment will differ significantly from clot prevention. Hemolytic medications are used. These are medications that will help dissolve the clot. Physical interventions then become contraindicated due to the risk of the clot migrating to distant locations like the heart, brain, and lungs. Once a clot has formed, a person will be prescribed bed rest and remain relatively immobile until it the clot is undetectable.[ citation needed ]
Thrombosis prophylaxis is not only used for the prevention of deep vein thrombosis, but can be initiated for the prevention of the formation of blood clots in other organs and circumstances unrelated to deep vein thrombosis:
The risk of developing deep vein thrombosis, or pulmonary embolism is different than the total risk of the formation of blood clots. This is due to the observation that not all blood clots form in the lower legs. Most hospitalized medical patients have at least 1 risk factor for thrombosis that progresses to thromboembolism and this risk persists weeks after discharge. Those who remain undiagnosed and not treated prophylactically have a 26% chance of suffering a fatal embolism. Another 26% develop another embolism. Between 5% and 10% of all in hospital deaths are due to pulmonary embolism (as a consequence of thrombosis). Estimates of the incidence of pulmonary embolism in the US is 0.1% persons/year. Hospital admissions in the US for pulmonary embolism are 200,000 to 300,000 yearly.Thrombosis that develops into DVT will affect 900,000 people and kill up to 100,000 in the US. On average 28,726 hospitalized adults aged 18 and older with a VTE blood clot diagnosis die each year. Risk of thrombosis is related to hospitalization. In 2005 the UK the Parliamentary Health Select Committee determined the annual rate of death due to thrombosis was 25,000 with at least 50% being hospital-acquired.
The type of surgery performed prior to the formation of blood clots influences the risk. Without prophylactic interventions, the calculated incidence of clot formation in the lower leg veins after surgery is:
As the population of the US ages, the development of blood clots is becoming more common.
Some risk factors for developing blood clots are considered higher that others. One scoring system analyzes the probability for clot formation by assigning a point value system to significant risk factors.The benefit of treating those who are at low risk of developing blood clots may not outweigh the higher risks of significant bleeding.
Risk factors for developing blood clots that are assessed prior to treatments
|Major risk (=1 point)||Minor risk (=2 points)|
|Cancer||Family history of |
deep vein thrombosis
the past 6 months
|Calf swelling||superficial vein dilation|
|Recent major surgery||redness of area|
|Edema or swelling of only leg||Recent trauma|
the calf and/or thigh
|Probability determination and scoring|
|High probability scoring (12–7 points|
|3 major points OR |
2 major points AND >2 minor points
|Low probability scoring (3–5 points)|
|0 major points AND > 2 minor points|
1 major point AND >2 minor points
0 major points and >3 minor point
1 major point and more than one minor point
|Moderate probability scoring (varies)|
|all other risk combinations|
Developing blood clots is more probable after the first episode. Risk assessment and intervention for those with one or more episodes of deep vein thrombosis or blood clots in the veins utilizes the Well's test. It has been inconsistently modified by a number of publishers with the results listed below:
|D-dimer abonormal one month after stopping anticoagulants||2|
|Age > or = to 50||1|
|use of hormone at DVT onset||1|
|Age > or = to 50||1|
|cast on lower leg/Paralysis/paresis/||1|
|Recent surgery or immobility||1|
|tenderness over deep vein||1|
|entire leg swollen||1|
|difference of 3 cm between legs||1|
|pitting edema of affected leg||1|
|Collateral superficial veins||1|
|another diagnosis more probable than DVT||-2|
The Centers for Disease Control and Prevention have issued general guidelines describing the interventions that can be taken to reduce the risk of the formation of blood clots:
Seat-edge pressure from the seat on an airplane on the popliteal area may contribute to vessel wall damage as well as venous stasis. Coagulation activation may result from an interaction between cabin conditions (such as hypobaric hypoxia) and individual risk factors for the formation of blood clots. Studies of the pathophysiologic mechanisms for the increased risk of Venous thrombosis embolism or VTE after long-distance travel have not produced consistent results, but venous stasis appears to play a major role; other factors specific to air travel may increase coagulation activation, particularly in passengers with individual risk factors for VTE.
The use of fitted intermittent pneumatic compression devices before, during and after procedures is another way to It consists of an air pump and inflatable auxiliary compartments that sequentially inflates and deflated to provide an external 'pump' that returns venous blood toward the heart.The use of intermittent pneumatic compression is common. These devices are also placed on a surgical patient in the operating room (the intra-surgical period) and remain on the person while recovering from the surgery.
The application of antiembolism stockings (TED stockings) can be used to prevent thrombosis. The correct use and properly fitted graded compression stockings can reduce the rate of thrombosis by 50%. 745–46 Contraindications for the use of antiembolism stockings include the presence of advanced peripheral and obstructive arterial disease, septic phlebitis, heart failure, open wounds, dermatitis and peripheral neuropathy. Differences between the use of thigh-high compression stockings and shorter types to prevent blood clots exist, but remain inconsistent.:
There has been some success in preventing blood clots by an early risk assessment upon admission to the hospital, which is a strategy recognized by the Centers for Disease Control and Prevention. Hospitals that have participated in this effort to reduce the incidence of thrombosis found that rates of DVT decreased in some instances.Some of the hospitals developed a mandatory assessment quantifying the risk for developing blood clots and a plan of care developed from the assessment. The person's risk for developing blood clots is entered into their record, ‘following’ them through their treatment regime. If the hospital stay exceeded three days, the person was reassessed for risk. Clinicians were then able to apply protocols for prevention based upon best clinical practices.
Immobility is a significant risk factor in the development of thrombosis.Immediate post-surgical interventions, such as out of bed orders (OOB), are typically ordered by the physician to prevent thrombosis. These orders, typically delegated to a nurse, but may include the participation of a physical therapist and others trained to perform the intervention, are to perform range of motion (ROM) activities that include: muscle contractions of the lower legs for those who are very weak, moving the feet, wiggling the toes, bending the knees, raise and lower the legs. In addition, changes in positioning prevents immobility and shifts areas of venous stasis. If the person is too weak to perform these preventative activities, hospital personnel will perform these movements independently. Exercise of the lower extremities is a post-operative method of prophylaxis. Nursing personnel will often perform range of motion exercises and encourage frequent moving of the legs, feet, and ankles. Frequent positioning changes and adequate fluid intake. After a surgical procedure, ambulation as soon as possible is prophylactic in preventing the formation of blood clots.
Early ambulation also prevents venous stasis and physicians order OOB activities on the same day of surgery. This is accomplished in increments. The progression of increasing mobility proceeds by: raising the head of the bed, sitting up in bed, moving to the edge of the bed, dangling the legs off the bed and then ambulating to a close chair.
Patient education and compliance reduces the risk of developing blood clots. These exercises and use of equipment and follow up by clinicians reduces the risk of developing blood clots.
Note that if a blood clot has already formed in the deep veins of the leg, bedrest is usually prescribed and the treatment to prevent bloods with physical intervention is contraindicated.
Thromboprophylaxis, such as anticoagulants or pre-operative low-molecular weight heparin, is effective for hospitalized patients at risk for VTE.Additional risk factors such as obesity, disease, malignancies, long surgeries, and immobility may influence the prescribed dosage. Anticoagulant medications prevent the formation of blood clots in people who are at high risk for their development. Treating blood clots that have already formed is managed by the use of anti-hemolytic ("clot busters"). Despite its effectiveness, the use of thromboprophylaxis remains under-utilized, though alerts (computer or human) in hospitals are associated with increased prescription and reductions in symptomatic VTE. The list below describes some of the more common medications used to prevent blood clots. Note that generally that since blood clotting is inhibited, a side effect typically is bleeding, though it can be reversed by administering a medication that stops the bleeding or by discontinuation of the medication itself. Anti-coagulant administration is often given before the start of the operation. There are concerns with the potential of increased risk of bleeding and so many surgeons start giving anti-coagulants the first 6 hours after surgery. Medications that inhibit blood clot formation include:
Medications used to prevent blood clots
The discontinuation of contraceptives also prevents blood clots.
The therapeutic effects of warfarin may be decreased by valerian. Anticoagulants can be affected by chamomile. Dong quai, garlic, ginger, Ginkgo biloba, bilberry and feverfew can increase bleeding time. These same herbal supplements taken with warfarin increased prothrombin time.
By containing significant content of vitamin K, some foods act as antagonists to antiplatelet and anticoagulant medications; these include green leafy vegetables, like spinach, legumes, and broccoli.
Preventing blood clots with medication is not considered safe in the following circumstances:
Adding heparin to the use of compression stockings may prevent thrombosis.
An international registry and risk assessment calculator is being used to centralize data on post-surgical venous thrombosis and its prevention.Hospitals are implementing a multi-disciplinary approach to prevent of blood clots. This includes adequate assessment of the risks, follow up on missed doses of medication and instituting a 'patient-centered' approach endorsed by the Joint Commission. Recommendations regarding the prevention of blood clots vary widely between clinicians and treatment facilities. Research continues to clarify these discrepancies. The metabolic state of hypercoagulability (the tendency to form blood clots) tests are being developed. These include the evaluation of the thrombin–antithrombin complexes (TAT), low levels of the anticoagulants ATIII and protein C, but these tests are not yet widely available.
Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where they help keep the bite area unclotted long enough for the animal to obtain some blood. As a class of medications, anticoagulants are used in therapy for thrombotic disorders. Oral anticoagulants (OACs) are taken by many people in pill or tablet form, and various intravenous anticoagulant dosage forms are used in hospitals. Some anticoagulants are used in medical equipment, such as sample tubes, blood transfusion bags, heart-lung machines, and dialysis equipment. One of the first anticoagulants, warfarin, was initially approved as a rodenticide.
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets (thrombocytes) and fibrin to form a blood clot to prevent blood loss. Even when a blood vessel is not injured, blood clots may form in the body under certain conditions. A clot, or a piece of the clot, that breaks free and begins to travel around the body is known as an embolus.
A venous thrombosis is a thrombosis in a vein, caused by a thrombus. A common type of venous thrombosis is a deep vein thrombosis (DVT), which is a blood clot usually found in the deep veins of the leg. It is increasingly found in the deep veins of the arm, accounting for more than 10% of all deep vein thromboses. If the thrombus breaks off (embolizes) and flows towards the lungs, it can become a pulmonary embolism (PE), a blood clot in the lungs. This combination is called venous thromboembolism. Various other forms of venous thrombosis also exist; some of these can also lead to pulmonary embolism.
Factor V Leiden is a variant of human factor V, which causes an increase in blood clotting (hypercoagulability). Due to this mutation, Protein C, an anticoagulant protein which normally inhibits the pro-clotting activity of factor V, is not able to bind normally to Factor V, leading to a hypercoagulable state, i.e., an increased tendency for the patient to form abnormal and potentially harmful blood clots. Factor V Leiden is the most common hereditary hypercoagulability disorder amongst ethnic Europeans. It is named after the Dutch city Leiden, where it was first identified in 1994 by Prof R. Bertina under the direction of Prof P. Reitsma. Despite the increased risk of VTE, people with one copy of this gene have not been found to have shorter lives than the general population.
Deep vein thrombosis (DVT) is the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. Symptoms can include pain, swelling, redness, and enlarged veins in the affected area, but some DVTs have no symptoms. The most life-threatening concern with DVT is the potential for a clot to detach, travel through the right side of the heart, and become stuck in arteries that supply blood to the lungs. This is called pulmonary embolism (PE). Both DVT and PE are considered as part of the same overall disease process, which is called venous thromboembolism (VTE). VTE can occur as an isolated DVT or as PE with or without DVT. The most frequent long-term complication is post-thrombotic syndrome, which can cause pain, swelling, a sensation of heaviness, itching, and in severe cases, ulcers. Also, recurrent VTE occurs in about 30% of those in the ten years following an initial VTE.
Low-molecular-weight heparin (LMWH) is a class of anticoagulant medications. They are used in the prevention of blood clots and treatment of venous thromboembolism and in the treatment of myocardial infarction.
Renal vein thrombosis (RVT) is the formation of a clot in the vein that drains blood from the kidneys, ultimately leading to a reduction in the drainage of one or both kidneys and the possible migration of the clot to other parts of the body. First described by German pathologist Friedrich Daniel von Recklinghausen in 1861, RVT most commonly affects two subpopulations: newly born infants with blood clotting abnormalities or dehydration and adults with nephrotic syndrome.
Rivaroxaban, sold under the brand name Xarelto among others, is an anticoagulant medication used to treat and prevent blood clots. Specifically it is used to treat deep vein thrombosis and pulmonary emboli and prevent blood clots in atrial fibrillation and following hip or knee surgery. It is taken by mouth.
Dalteparin is a low molecular weight heparin. It is marketed as Fragmin. Like other low molecular weight heparins, dalteparin is used for prophylaxis or treatment of deep vein thrombosis and pulmonary embolism to reduce the risk of a stroke or heart attack. Dalteparin acts by potentiating the activity of antithrombin III, inhibiting formation of both Factor Xa and thrombin. It is normally administered by self-injection.
Compression stockings are a specialized hosiery designed to help prevent the occurrence of, and guard against further progression of, venous disorders such as edema, phlebitis and thrombosis. Compression stockings are elastic compression garments worn around the leg, compressing the limb. This reduces the diameter of distended veins and increases venous blood flow velocity and valve effectiveness. Compression therapy helps decrease venous pressure, prevents venous stasis and impairments of venous walls, and relieves heavy and aching legs.
Post-thrombotic syndrome (PTS), also called postphlebitic syndrome and venous stress disorder is a medical condition that may occur as a long-term complication of deep vein thrombosis (DVT).
Bemiparin is an antithrombotic and belongs to the group of low molecular weight heparins (LMWH).
Venostasis, or venous stasis, is a condition of slow blood flow in the veins, usually of the legs.
Intermittent pneumatic compression is a therapeutic technique used in medical devices that include an air pump and inflatable auxiliary sleeves, gloves or boots in a system designed to improve venous circulation in the limbs of patients who suffer edema or the risk of deep vein thrombosis (DVT) or pulmonary embolism (PE).
Edoxaban, sold under the brand name Lixiana among others, is an anticoagulant medication and a direct factor Xa inhibitor. It is taken by mouth.
Betrixaban is an oral anticoagulant drug which acts as a direct factor Xa inhibitor. Betrixaban is FDA approved for venous thrombosis prevention in adults hospitalized for an acute medical illness who are at risk for thromboembolic complications due to restricted mobility and other risk factors. Compared to other DOACs betrixaban has relatively low renal excretion and is not metabolized by CYP3A4.
Apixaban, sold under the brand name Eliquis among others, is an anticoagulant medication used to treat and prevent blood clots and to prevent stroke in people with nonvalvular atrial fibrillation. Specifically it is used to prevent blood clots following hip or knee replacement and in those with a history of prior clots. It is used as an alternative to warfarin and does not require monitoring by blood tests. It is taken by mouth.
Prothrombin G20210A is a genetic condition that increases the risk of blood clots including deep vein thrombosis and pulmonary embolism. One copy of the mutation increases the risk of a blood clot from 1 in 1,000 per year to 2.5 in 1,000. Two copies increases the risk to up to 20 in 1,000 per year. Most people never develop a blood clot in their lifetimes.
Superficial vein thrombosis (SVT) is a type blood clot in a vein, which forms in a superficial vein near the surface of the body. Usually there is thrombophlebitis, which is an inflammatory reaction around a thrombosed vein, presenting as a painful induration with redness. SVT itself has limited significance when compared to a deep vein thrombosis (DVT), which occurs deeper in the body at the deep venous system level. However, SVT can lead to serious complications, and is therefore no longer regarded as a benign condition. If the blood clot is too near the saphenofemoral junction there is a higher risk of pulmonary embolism, a potentially life-threatening complication.
Direct thrombin inhibitors (DTIs) are a class of anticoagulant drugs that can be used to prevent and treat embolisms and blood clots caused by various diseases. They inhibit thrombin, a serine protease which affects the coagulation cascade in many ways. DTIs have undergone rapid development since the 90's. With technological advances in genetic engineering the production of recombinant hirudin was made possible which opened the door to this new group of drugs. Before the use of DTIs the therapy and prophylaxis for anticoagulation had stayed the same for over 50 years with the use of heparin derivatives and warfarin which have some well known disadvantages. DTIs are still under development, but the research focus has shifted towards factor Xa inhibitors, or even dual thrombin and fXa inhibitors that have a broader mechanism of action by both inhibiting factor IIa (thrombin) and Xa. A recent review of patents and literature on thrombin inhibitors has demonstrated that the development of allosteric and multi-mechanism inhibitors might lead the way to a safer anticoagulant.