Overview of Deep Venous Thrombosis Prophylaxis
Deep vein thrombosis (DVT) is the medical term for a blood clot that forms in the deeper veins of your body, mostly in the legs. Sometimes, clots can also happen in the upper body, but this is less common. Pulmonary embolism (PE) happens when one of these blood clots, or sometimes fat or air, gets lodged in the lungs. Often, these clots in the lungs come from DVT in the leg. One in every three patients with DVT will have this happen. Preventing DVT is important because it can stop PE, which can be very severe and even lethal.
These two conditions (DVT and PE) are grouped together under the label of venous thromboembolism (VTE). DVT is a major cause of illness and death that can be avoided globally. In the United States, DVT and PE cause between 60,000 and 100,000 deaths every year.
In a healthy body, there’s a balance in your blood that stops these dangerous clots from forming in your veins. If there is a disruption in this balance, you can get DVT. This disruption can come from one or more of what doctors call the “Triad of Virchow”:
1. Venous stasis: This is when your blood doesn’t flow as well as it should because you’re not moving much, or because you have a condition like congestive heart failure.
2. Endothelial injury: This can happen during medical procedures or accidents that injure your veins.
3. Hypercoagulability: This means your blood is more likely to clot than normal due to things like certain medications, cancer, or inherited conditions.
Patients in the hospital are at higher risk of getting DVT as they often have to stay still for long periods, and for other reasons. That’s why doctors often provide these patients with DVT prophylaxis – treatments to help prevent DVT.
There are two main ways to do this: mechanical methods that help blood flow better, and drugs that make your blood less prone to clotting. Even though about half of all patients in the hospital could get DVT, which increases their risk of getting PE, only half of them get these preventative treatments. Providing these treatments to patients in the hospital can significantly reduce the chances of DVT and PE, leading to better patient outcomes overall.
This prevention can either be primary (preferred), which uses medications and mechanical methods to avoid DVT from happening, or secondary, which is less common and involves early detection and treatment when DVT has already begun, but is not yet causing symptoms.
Anatomy and Physiology of Deep Venous Thrombosis Prophylaxis
The veins in our body act like a road system for our blood. They transport blood from our body back to our heart. Let’s talk about the main veins in our legs and arms.
In our lower body, we have the following important veins:
– Common femoral vein: This is a large vein located in the thigh.
– Deep femoral vein: This vein runs deep inside the thigh to help move blood towards the heart.
– Superficial femoral vein: This vein is found just below the skin is also located in the thigh.
– Popliteal vein: This vein is located behind the knee.
– Anterior tibial vein: This vein runs along the front part of the lower leg or calf.
– Posterior tibial vein: This vein is at the back of the lower leg or calf.
– Peroneal vein: This vein is located in the leg, mainly serving the calf and foot.
In our upper body, we have:
– Paired radial vein: These veins are in the forearm part of the arm and are paired on either side of the radius bone.
– Paired ulnar vein: These veins are also in the forearm and are paired alongside the ulna bone.
– Interosseous vein: This vein runs between the bones of the forearm.
– Brachial vein: This vein is located in the upper arm area.
– Axillary vein: This vein is found in the armpit area and helps move blood from the arm to the heart.
– Subclavian vein: This vein is located just under your collarbone and drains blood from the upper body.
Why do People Need Deep Venous Thrombosis Prophylaxis
Patients who are hospitalized are more likely to develop blood clots in their veins, something known as venous thromboembolism (VTE). Proactive measures to prevent these clots, or deep vein thrombosis (DVT) prophylaxis, should be considered for every patient staying in a hospital. Doctors determine the risk of clot formation and bleeding by examining a patient’s history and current health condition.
Several factors can increase the risk of blood clots, such as being older than 70, having a history of DVT or pulmonary embolism (PE, a clot in the lungs), being critically ill, being immobile, having a stroke with paralysis, advanced heart failure, active cancer, acute respiratory failure, certain genetic clotting disorders (thrombophilia), recent surgery or trauma, obesity, and the use of hormonal therapy.
To decide the best preventive measures, patients at risk of developing clots (thrombosis) are categorized into three groups:
- Low-risk patients: Young individuals without any risk factors for clot formation. They usually don’t need preventive measures.
- Moderate-risk patients: Patients with at least one risk factor. Regular medication, sometimes combined with mechanical preventive measures, is often recommended to prevent clot formation.
- High-risk patients: Patients with several risk factors. Medication in combination with mechanical measures is the preferred preventive option.
Various drugs are commonly used to prevent clots in hospitalized patients and include low-molecular-weight heparins (LMWH), unfractionated heparin (UFH), and fondaparinux. LMWH is often the preferred option due to its easier administration and lower chance of clot formation. LMWH can be given once a day, whereas UFH often needs to be given two to three times a day.
However, in patients with poor kidney function, UFH may be used. For obese patients, the dosage may be increased. While the cost of UFH is usually lower than LMWH, it is not suitable for people with a condition known as heparin-induced thrombocytopenia (HIT), a decrease in platelets caused by heparin. Thus, any patient on UFH needs regular monitoring of their platelet counts.
Direct oral anticoagulants, a new type of blood thinner, have also been shown to reduce death rates among hospitalized patients, with betrixaban and rivaroxaban being approved for use in the hospital setting.
Patient’s deemed at risk for developing clots yet also at high risk for bleeding may require mechanical measures, which include the use of devices like intermittent pneumatic compression, graduated compression stockings, and venous foot pump.
Cancer patients admitted to the hospital who have no other risk factors are typically not given DVT preventive measures when outside the hospital. But if cancer patients have additional risk factors, LMWH or UFH may be prescribed.
Outpatient cancer patients generally are not advised to take routine DVT preventive measures, unless they have a very high risk for DVT, such as multiple myeloma patients undergoing certain chemotherapies. In these cases, medications to prevent clot formation might be used.
Long-distance travelers who have a risk of VTE are recommended to wear properly fitted, below-knee compression stockings that apply 15-30 mm Hg of pressure. They are also advised to regularly stand and move around during the trip.
When a Person Should Avoid Deep Venous Thrombosis Prophylaxis
There might be reasons why a person can’t get treatment to prevent deep vein thrombosis (DVT), a blood clot in a deep vein, usually in the leg. The reasons a person should avoid these treatments are:
If they are currently bleeding, have recently been bleeding, or if they are highly likely to bleed (like if they have active PUD, which is stomach or intestinal ulcers).
If their blood does not clot properly (a condition called coagulopathy) – this is measured with a test called INR, and an INR greater than 1.5 suggests that their blood is thinner than normal.
If they are scheduled to have a surgical procedure in the next 6 to 12 hours. What medications people take can affect surgery, so doctors are careful about treatment timing.
If they have thrombocytopenia, which is a condition where they have low blood platelets. Platelets are the parts of the blood that help in clotting, so if they have less than 50,000 or 100,000 platelets, they might not respond to this treatment well.
If they have a disorder that affects the ability of their body to stop bleeding.
Additionally, there might be reasons why a person can’t use mechanical methods to prevent DVT. A mechanical method might be something like wearing special socks that squeeze the legs to help blood flow better.
These reasons could include ischemia (lack of blood supply) to the limbs because of peripheral vascular disease, which is a circulatory condition where narrowed blood vessels reduce blood flow to your limbs.
Another reason could be if the skin is broken down and not healable. In such conditions, these treatments might not be safe or effective.
Possible Complications of Deep Venous Thrombosis Prophylaxis
Taking preventative medicines can sometimes lead to side effects, including:
- Disturbed kidney function: This means the kidneys aren’t working as well as they should.
- Bleeding: This could involve blood in urine or stools, nosebleeds, or other unusual bleeding.
- Heparin-induced thrombocytopenia (HIT): This is a reaction to a blood-thinning drug called heparin, leading to a low platelet count in the blood. Platelets help your blood clot, so a low count can increase risk of bleeding.
What Else Should I Know About Deep Venous Thrombosis Prophylaxis?
DVT, or deep vein thrombosis, is a condition where a blood clot forms in one of your deep veins, typically in your leg. This condition can lead to serious health complications. It can increase the risk of a pulmonary embolism, a blockage in one of the arteries in your lungs, by 50%. It can also lead to something called post-thrombotic syndrome, which includes long-term issues such as painful swelling in the legs.
There are measures in place for hospitalized patients called DVT prophylaxis – these are steps to prevent DVT. They can decrease the chances of getting DVT by 10 to 80%. This prevention method is beneficial for both hospitalized patients who are there for medical and surgical reasons. However, studies show that while these preventative measures can decrease the possibility of death in surgical patients, they have not been shown to have the same effect in medical patients.
