This Medical Monday series is about risk factors for venous thromboembolism, VTE (pulmonary embolism and DVT). The post ‘Are you on the red or blue team?‘ outlines the difference between arterial and venous clots.
We are going to cover
Strong risk factors; being in hospital, having surgery and immobility
Moderate risk factors; age (60+), a previous blood clot, family history of blood clots, thrombophilia, cancer, contraceptive pill and hormone replacement therapy
Other risk factors; obesity, pregnancy, smoking and alcohol
Doctors have known for a long while that patients undergoing surgery have an increased risk of venous thrombosis and pulmonary embolus. Data from the 1960s reported that fatal PEs occurred in between 0.1 and 0.8% of all patients having surgery and the incidence was as high as 7% in patients undergoing surgery for hip fractures. Fortunately things have improved with changes in surgical technique, early mobilisation after surgery and anticoagulant prophylaxis. However we should not be too complacent as a study from 2009 showed higher rates of blood clots after surgery than expected. This was in a long-term study of 1.3 million women followed over an average 6 years; approximately 240,000 women had surgery during the follow-up period, 5,419 were admitted with blood clots and 270 died of a PE. From this the researchers were able to calculate the risk of various types of surgery.
- 1 in 45 had a clot after hip or knee surgery
- 1 in 85 after cancer surgery
- 1 in 815 after day surgery
- 1 in 6200 in people who did not have surgery
- The overall 1 in 140 middle-aged women in the UK who had surgery in hospital would have a blood clot.
The highest risk of a blood clot is approximately 3 weeks after surgery, but the risk is increased for up to 3 months after surgery and there is still a slight risk even 12 months after.
Can the risk be reduced?
Early mobilisation. The doctors, nurses and physiotherapist will discuss with you the importance of getting moving after surgery. You may be encouraged to get out of bed as early as the day after surgery.
Calf compression. For some types of surgery you may be given compression stockings to wear while in bed. These compress the superficial veins in your legs and improve blood flow in the deep vessels. For some operations the surgical team may use devices in theatre that increase blood flow in your feet or calves and you may still be wearing these in the recovery room after surgery.
Anticoagulants. Your doctors should discuss the use of anticoagulants with you if you are having major abdominal surgery or orthopaedic surgery, such as a joint replacements. There are several different types of anticoagulant therapy used. Low molecular weight heparin (Clexane or Fragmin) is commonly given for major abdominal surgery, gynaecological surgery and high risk orthopaedic surgery. This usually starts soon after surgery and is continued until you are mobile; in some high risk cases it can be continued at home. It is given as an injection under the skin once a day. Another option is to be given aspirin, which is used for people at low risk of clots after some orthopaedic surgery and should be continued after leaving hospital. Some of the newer anticoagulants such as dabigatran and rivaroxaban are used in some hospitals after orthopaedic surgery. Remember that different treatment is used for different operations and the same treatment is not suitable for everybody.
Remember to discuss anticoagulant prophylaxis with your surgeon. It is a good idea to bring this up when you see your surgeon in the outpatient clinic or with the anaesthetist during your preoperative assessment.
IMPORTANT: If you have previously had a blood clot tell your surgeon well before your surgery as you may need additional treatment to prevent blood clots. Also if you are on anticoagulants let your surgeon know well in advance as treatment may need to be stopped or reduced.