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Blood Clots

By Brian McGrory, Maine Joint Replacement Institute

Arteries are blood vessels that carry blood away from the heart to body tissues and organs. Veins are blood vessels through which blood travels from all parts of the body back to the heart.

A blood clot is a jelly-like mass of thickened blood. The body normally forms a blood clot to stop bleeding. After hip surgery there will be a blood clot near the new hip joint. This is normal, and not dangerous.

If a blood clot develops inside a vein, however, it can block the normal flow of blood and cause temporary and long-term problems. This can result in pain, tenderness and swelling of the leg. When a blood clot occurs in one of the main veins of the body (usually a leg or pelvic vein after hip surgery) it is called a deep vein thrombosis or DVT. These clots become life threatening if they move to the heart, lungs or brain. If a clot breaks loose from a vein, it may travel through the heart and can block lung arteries. This is called a pulmonary embolism or PE. A PE can cause sharp chest pain, shortness of breath, coughing up blood or passing out. If the clot is severe enough, it can be life threatening or fatal.

Methods to prevent blood clot after surgery may include early mobilization and activity, elevation of the feet, ankle exercises, elastic stockings, compression devices that passively help blood flow in the legs, and anti-coagulation medicines.



What Are The Issues?

The medical term for a blood clot in the blood vessel is a thrombus. Deep vein thrombosis (DVT) is a formation of a blood clot in one of the deep veins of the body, particularly in the leg or pelvis. It is a problem that can be asymptomatic (silent), or in the worse case scenario, fatal. Death can occur if a blood clot which forms in the deep veins of the body breaks off and travels to the lungs, heart or brain and causes severe overload of the capacity to breath or pump blood. Some doctors think that even a silent blood clot can cause chronic swelling or skin ulcerations, a difficulty called post-phlebitic syndrome.

The risk of DVT is increased in a number of circumstances. Lower extremity surgery, and specifically total hip replacement surgery, increases the risk of deep vein thrombosis. The surgery heightens the body’s tendency for coagulation or clotting. In addition, when the leg is manipulated during surgery there may be irritation to the walls of the major blood vessels in the leg. Finally, during and after surgery the lower extremity is not used as much and, therefore, the normal blood flow rate is decreased. The leg muscles usually help venous blood return to the heart when they are used.

Further factors heighten the risk of blood clotting. These include history of previous DVT or PE, cancer, obesity, and conditions that predispose to abnormal clotting (for example, a family history of DVT/PE or known medical condition associated with increased clotting).

Patients contemplating hip replacement surgery therefore need to understand the issues regarding what methods should be used to minimize the chance of deep vein thrombosis.

Why Is There Controversy?

1. There appears to be no known way to absolutely prevent deep vein thrombosis after total hip replacement surgery.

2. Some prevention strategies actually cause complications that can be worse than DVT. An example of this would be a bleeding complication near the spinal cord because the patient was on a blood thinner medicine.

3. Each of the methods used to diminish risk of DVT has an associated set of risks and benefits. Issues include the expense of the intervention, the convenience, and the ability of a given patient to utilize or comply with their use.

4. There are multiple treatments to minimize the risk of DVT and fatal PE.

5. Medical doctors and surgeons often disagree on what is a more serious complication for the patient and, therefore, disagree on the exact method to prevent blood clots at the time of surgery.

6. There appears to be significant marketing by some companies that may overstate the benefits of a given intervention and may gloss over some of the problems associated with that intervention.

7. There are conflicting data as to what is and what is not helpful in preventing blood clots. Most of the studies available look at several different factors at once; it is therefore difficult to understand if a specific intervention has made a large difference. Examples of this are:

  • The NIH has said that aspirin does not help prevent blood clots after total hip replacement surgery, but there is evidence that when taken with a global program of prophylaxis interventions, aspirin is helpful in preventing blood clots. More than one study has suggested that low dose aspirin reduced the risks of PE and DVT in high-risk surgical patients. This was confirmed in a recent clinical trial in which 160 mg of aspirin was given for 35 days after surgery.
  • Research studying DVT and PE is a “moving target.” As we change the specifics of a given type of surgery (including the type of anesthesia and the activity after the surgery), research data from surgeries done as recently as 5-10 years ago may not be applicable to surgery done today.
  • One of the blood thinners that is commonly given, sodium warfarin (Coumadin), can be given at many different dosages. Depending on the specific amount given and the response of individual patients to that dose (monitored by a blood test called the INR), the protection from DVT and PE may be different for different patients.
  • Some of the newer injectable anti-coagulant medicines were originally approved (and are argued to be as good or better than Coumadin) if given at the time of surgery or slightly before. Some of the companies have decided that these medicines should be given slightly later, however, because of a significant rate of bleeding complications. This, however, makes it unclear if they are helpful to the same degree that was noted when they were given at the time of surgery. One of these bleeding problems may occur when giving spinal anesthetics in patients that have been taking these medications (when spinal anesthesia is used with low molecular weight heparin drugs or heparinoids, bleeding next to the spine can occur and can result in long term or permanent paralysis).
  • The actual rate of deep vein thrombosis is difficult to assess, as most physicians do not obtain venograms or other invasive or non-invasive tests to screen for blood clots on all patients.
  • The type of anesthesia, operative time and blood loss are also important in determining the risk of deep vein thrombosis and, therefore, must be entered into the equation discussing these issues.

What Do Most Surgeons Do

Eighty-six members of the hip and knee societies in North America were surveyed to determine what they do after total hip replacement to minimize the chance of blood clots.

All surgeons responding used some type of prophylaxis. Sixty-four percent of the time warfarin was used, fifteen percent of the time low molecular weight heparin was used, and twenty-one percent of the time aspirin was used. Ten percent of surgeons gave intra-operative heparin during their surgeries in addition to one of these other regimens.

Mechanical DVT prophylaxis, such as compression stockings, were used in 76% of cases in addition to one of the medicines.

Medicines were continued less than two weeks in 38% of those responding, between two and four weeks in 29% of those responding, and greater than four weeks in 33% of those responding. Perioperative testing with a method such as an ultrasound was performed routinely 22% of the time, only in symptomatic patients in 71% of the time, and never used in 7% of the time.

What I Do

Because there is no absolute way to prevent deep vein thrombosis in a small amount of patients after hip replacement surgery, my philosophy is to minimize the chance of blood clot while also minimizing the inconvenience and expense to the patient.

I think that it is important to differentiate between patients at standard risk of DVT after hip replacement surgery and those at very high risk of blood clot, as I treat them differently.

In those patients at standard risk, I initiate blood thinner medicine the day of surgery by having the hospital staff give the patient warfarin on the morning of surgery. During the surgery I use a hypotensive spinal anesthetic if possible, and minimize blood loss and operative time. The patient is wearing a thigh-high TED stocking on the contralateral leg during the surgery, and a thigh-high TED stocking is placed on the operative leg immediately after surgery.

In the recovery room the patient is instructed to do ankle pumps as soon as the spinal anesthetic wears off, and this is encouraged throughout the hospital stay. The morning after surgery the patient stands by the bedside and does toe pumping exercises. Physical and occupational therapy are initiated with the goal of maximizing muscle use (even if the patient is not bearing full weight on the operative leg).

INR is monitored throughout the hospitalization, and each day the patient is given a dose of warfarin to try to obtain an INR between 1.7 and 2.0. Once this is achieved, this level of anti-coagulation is continued for between 7 and 10 days. The patient continues to wear the thigh-high TED stockings during this period, and continues leg elevation and ankle pumping when appropriate. The patient takes 160 mg of aspirin per day after the warfarin treatment is completed and this is continued for a minimum of 35 days.

Aspirin and warfarin are usually not given together because an increase in bleeding episodes can be seen when combination therapy is given. Discontinuation of the thigh-high TED stockings depends on the swelling any given patient experiences, but are usually worn for 2 –6 weeks.

We are vigilant throughout the perioperative periodto monitor for the signs and symptoms of deep vein thrombosis and pulmonary embolus. If any of these signs are present, consideration of an ultrasound test or, if necessary, a lung scan may be the next appropriate step.

In patients with very high risk of blood clot, warfarin therapy is continued for 6 to 12 weeks after surgery.

A higher INR (between 2 and 2.5) is usually achieved, and aspirin is not routinely given. Once or twice a week the INR is measured with a blood test. All other aspects of the program are similar in this group.

Discharge Instructions to Prevent DVT

  • Take several short walks each day
  • Do ankle pump exercises every hour while awake
  • Wear the TED stockings while sitting and standing. You may (with help) take them off when in bed, but your legs should be elevated on one or two pillows. At the 2 week follow-up you will get further instructions on how long to wear the stockings.

If you go to the rehabilitation hospital or nursing home:

  • You will be given blood thinner by your nurses.
  • You should take 160 mg aspirin each day for 35 days after you are discharged.

If you are discharged to home:

  • You will be given a prescription for warfarin, also known as Coumadin, which you should take until empty (there are no refills).
  • You should take 160 mg aspirin each day for 35 days after you have finished your warfarin.
  • If we know that you are at very high risk of blood clot, the team will tell you and give you special medicine instructions
  • If you have leg swelling that gets worse during the day, but that is minimal in the morning, take 3 twenty minute rests during the day. During the rests you should lay completely flat with 2 to 3 pillows under both of the feet.
  • Call the office immediately if you think that you have signs or symptoms of DVT, PE, or excessive bleeding.
  • Deep Vein Thrombosis
    Pulmonary Embolism
    Excessive Bleeding
  • Increasing leg pain
    Shortness of breath
    Excessive bleeding after shaving
  • Swelling that does not decrease with leg elevation
    Chest pain that may be worse with deep breaths
    Bleeding from the gums
  • Enlargement of the veins near the skin surface
    Coughing up blood
    Black or red stool
  • Reddish skin color
    Rapid heart beat
  • Skin that is warm to the touch
    Feeling faint

What You Should Ask

It is important for the patient considering hip replacement surgery to understand:

1. That there is a risk of deep vein thrombosis.

2. Some patients are at an even higher risk and may need to be treated differently than patients under the standard risk.

It is important to discuss with your surgeon what he or she suggests to minimize the chance of deep vein thrombosis and pulmonary embolus after your hip surgery. In my opinion, all patients undergoing hip replacement surgery should understand the pros and cons of the different treatments to prevent these complications, and the surgeon should have a well thought out plan for minimizing the risk of deep vein thrombosis.