Of all surgery's risks, developing blood clots of deep vein thrombosis (DVT) is one of the most dangerous — and one of the deadliest. It's also one of the most sinister. It's impossible to detect DVT about half of the time because there are no symptoms when a blood clot forms inside a vein, deep within the body very often in the thigh or lower leg. And when there are telltale signs of DVT, like shortness of breath, lung pain and chest pain, they often don't show up in patients until after you've discharged them. Of course, blood clots can break off and travel to another part of the body, such as the lungs. This is called a pulmonary embolism, or PE, and it can be fatal. PE claims the lives of up to 300,000 Americans every year.

The good news is that DVT is completely treatable if caught in time. It's also a largely preventable complication, as long as you identify which patients are most likely to develop it ahead of time. Once you have that information, you can decide on what prophylaxis — mechanical or anticoagulant or both — to administer and what precautions to take during surgery to cut down on the risk.

Precision medicine

My colleagues and I created a point-based scoring model to help facilities determine which surgical patients are most at risk of developing DVT and exactly what in their medical history leads them to be particularly vulnerable. The Caprini Risk Assessment includes 20 variables and is derived from a prospective study of 538 general surgery patients. The higher the Caprini score, the greater the risk of DVT.

Ask patients to compute their Caprini score 1-2 weeks before their procedure and instruct them to take their time filling out each question. That means sitting down with family members to ask about any family history of thrombosis, which is the most commonly missed question and, along with your patient's personal history of thrombosis, is one of the biggest causes of DVT. Don't try to give the assessment the day of surgery. There's a risk that patients will miss a question or answer it incorrectly because they haven't had the time to fully look it over. It's not reasonable to expect patients to know off the top of their head if their BMI is over 25, if they've had past obstetrical complications or if they had a venous thromboembolism (VTE) in the past but thought it not important — perhaps because it was caused by oral contraceptives that they're no longer taking.

Your patient's answers to those questions will give you an overall "Caprini score," which you can use on the day of surgery to stratify each patient's risk of DVT and, subsequently, what measures of prophylaxis you should provide. Patients with a score of under 5, who are classified as low-risk of developing DVT, may not need anticoagulant prophylaxis, whereas you should instruct patients with a score of 5-8, who are deemed at-risk of developing DVT, to take anticoagulants for 7-10 days following the surgery, even after they're discharged, or if they are outpatients. Classify patients who score a 9 or above as very high-risk and tell them to take a full 30 days of anticoagulant medication.

Precision medicine

Obtaining the score and understanding your patient's risk is only one part of preventing DVT. The key to cutting down on the rate of thrombosis cases is using that score to determine when and how you should administer thromboprophylaxis to your patient.

Anticoagulants, such as low molecular weight or unfractionated heparin, can cost up to $500 for 30-day preventative doses, but studies have shown that they can reduce the risk of VTE in higher risk patients. One such study, published in the Current Opinion on Pulmonary Medicine, found the risk of a fatal pulmonary embolism reduced by 62% in patients who underwent prophylaxis with low-dose anticoagulants. The same study found the risk for symptomatic DVT reduced by 53%. However, there's still some debate surrounding the use of anticoagulant prophylaxis, due largely to concerns about patient bleeding. While it's true that anticoagulants can lead to bleeding, no one dies from receiving preventative doses of anticoagulants.

Risks of overtreatment

On the other hand, beware of the risk of overtreating. Three-fourths of surgical patients might be receiving anti-clotting medications they don't need, according to research my colleagues and I published in the Annals of Surgery. We concluded that the benefit of perioperative venous thromboembolism chemoprophylaxis was only found among surgical patients with Caprini scores ???7. Precision medicine using individualized VTE risk stratification helps ensure that chemoprophylaxis is used only in appropriate surgical patients and may minimize bleeding complications.

You should avoid using the popular practice of stopping anticoagulation when the patient is discharged because it's not evidence-based and could do more harm than good. Your patients might have some concerns of their own — namely the fear of administering the blood thinner through injection. If this is the case, you can look into several approved direct oral anticoagulants (DOACs), which have been shown to be safe and effective at reducing bleeding. They can be taken in pill form, rather than an injection, but they tend to be more expensive.

Periop prevention

Apart from deciding which anticoagulant prophylaxis to use, you should also take other measures to prevent DVT during and immediately following surgery on at-risk or high-risk patients.

Muscle relaxants that are used as part of general anesthesia can increase the size of your patient's leg veins during anesthesia — causing cracks in the vein lining — and they can slow blood flow out of the legs, both of which can result in DVT. During surgery on at-risk patients, use intermittent pneumatic compression (IPC) devices, which are wrapped around the lower leg or foot and inflate, applying varying pressure on the leg to help increase blood flow and prevent a clot during a procedure.

It also helps to keep operations as short as possible. General anesthesia that lasts more than 45 minutes can increase the risk of your patient developing a blood clot by 66% if they have a past history of DVT.

For patients you've determined to be at risk, take additional post-operative measures to ensure they don't develop a clot in the weeks following their surgery. Fit patients for anti-embolism stockings before surgery and instruct your patient to use the stockings until they are fully mobile after discharge. Be sure the stockings fit properly. You can keep the stockings on during surgery and fit an IPC device over the stocking to increase the degree of protection. Compression stockings — also known as anti-embolism hose — work by applying pressure to the ankle and lower leg in order to reduce the risk of swelling and prevent blood pooling, or venous stasis. While compression stockings are popular in post-op prevention, they're less effective than IPC devices and may be a challenge to some patients due to leg size.

Follow-up after discharge

Should you find a patient gets a clot after their discharge, recheck his Caprini score and ensure he received the proper type and duration of prophylaxis. If he had a score of 5-8 and did not get prophylaxis for 1 week, or if he had a score of 9 or above and did not get extended prophylaxis, that could explain the clot, even after a minor surgical procedure.

Send your patients home with specific verbal and written instructions to seek medical attention immediately for the signs of VTE, including:

• leg pain, cramps or discomfort;
• shortness of breath at rest or after minor exertion;
• leg swelling;
• anxiety or rapid heart rate;
• fainting episodes; and
• chest pain.

Follow up with a phone call to patients 30 — or, if possible, 90 — days after surgery and ask if they've experienced any of the symptoms of VTE. Make sure to reach out to all of your patients; even the patients who were classified as average or low risk of developing DVT are at risk once they stop taking anticoagulants. Studies have shown that 77% of people get blood clots after they're discharged, while 55% get them after anticoagulation shots are stopped. Once you identify which of your patients have experienced VTE symptoms following their discharge from your facility, examine their treatment. Did they undergo prophylaxis? How many days did they take anticoagulants for, if at all? Did they take low molecular weight heparin or a DOAC? Record the answers you get from those calls — if a person had a risk score of 5 and did not receive anticoagulant prophylaxis, for instance — in order to track what type of prophylaxis to administer in the future. OSM