Blood Clots and Surgery
Sunday, January 3, 2010
Blood Clots and Surgery
Clotting Risk Higher, Persists Longer Than Anyone Knew
It's no surprise to anyone that blood clots form more commonly following surgery, and plenty of strategies are in place to make sure they don't. Medicalese for this is venous thromboembolism or VTE, with two forms, DVT or deep vein thrombosis, and PE or pulmonary embolism, the usual suspects. But now a huge study in the British Medical Journal has shown that the risk of blood clot formation is much higher and lasts longer than was previously suspected: Duration and Magnitude of the Postoperative Risk of Venous Thromboembolism in Middle Aged Women: Prospective Cohort Study.
First of all, this study is astonishing because it is part of the 'Million Women Study,' an effort by the British national health service to collect health data on just about a million women with an average of of 55. Clearly, such a gigantic collection of statistics has a lot of power to discern trends, and that's just what happened here.
Researchers examined records of women having surgery and then looked at whether VTE occurred and when. What they found is that women were almost 70 times more likely to require hospitalization for VTE following inpatient surgery, and even outpatient surgery increased risk by a factor of 10. Risks were further stratified based on what type of surgery took place. Women who had hip or knee replacements were almost 220 times more likely to suffer a clot than women who hadn't had surgery, and this risk was highest during the three weeks following surgery but was still increased 12 weeks postoperatively.
This is huge for many reasons. Most methods for decreasing the risk of blood clots, such as use of compression stockings and medications, are used while people are still in the hospital, but this study shows the risk remains high when discharge is almost certain to have taken place. As Rick points out, these observations argue for longer use of anticlotting medications, but that comes with risk, too.
What's needed are more studies to determine what the best duration of anticlotting medications and other strategies is, and whether newer drugs such as clopidogrel and dabigatran would be helpful. For now, people who've had surgery, and especially those who've had knee or hip replacements, need to be aware of symptoms they may develop that would point to the formation of a blood clot.
Symptoms of clot formation would depend on where the clot formed but could include excessive swelling of the legs, especially one or the other, excessive fatigue, or pain in the legs or chest. If you've had surgery recently and develop such problems seek immediate medical attention.
Other topics this week include transmission of the flu among those who live in the same house in NEJM, more autism than we thought in Morbidity and Mortality Weekly Report, and a lack of benefit to telemedicine in the ICU in JAMA. Until next week, y'all live well.