Post-Op Blood Clot Risk High
Study Finds Postoperative Blood Clot Risk Greater, More Persistent Than Experts Thought
Dec. 4, 2009 -- The risk of getting a potentially deadly blood clot after
surgery is even higher than experts believed -- and it persists longer than
they thought, according to a new study that evaluated nearly a million women in
the U.K., including nearly 240,000 who had surgery.
''We already know there is a substantially increased risk of blood clots
after major surgery," says researcher Jane Green, MD, PhD, a clinical
epidemiologist at the University of Oxford, England. "What is striking about
our finding is the scale of the risk. Even more important is the fact that this
risk is raised for quite a long time."
"The bulk of the increased risk is up to three months after surgery," she
says. "The peak is at three weeks. Then the risk falls off." But some level of
risk remains for a year, the researchers say.
The study is published in BMJ Online First.
Blood Clot Risk After Surgery: Study Details
Green's team drew on questionnaire data from the Million Women Study, which
recruited 1.3 million women, average age 56, through the National Health
Service to quiz them about lifestyle and other characteristics for health
For this study, they looked at hospital admission and death records for
947,454 participants, tracking each for an average of 6.2 years.
They tracked women who were diagnosed with venous thromboembolism, an
umbrella term for both deep vein thrombosis (a clot in a vein deep within the
body) and a pulmonary embolism (blockage of the main artery of the lung). The
risk of blood clots is known to be higher after surgery, especially orthopedic
surgery, but less is known about long-term risk and about patterns with
Green and her colleagues compared the risk of blood clots for those who
didn't have surgery with those who did have surgery. Of the total, 239,614
women had surgery during the follow-up period; 5,419 of those were admitted to
the hospital for blood clots, and 270 died of a blood clot.
The researchers excluded from the analysis women who had been in the
hospital previously for blood clots or who had a history of blood clot
problems, as well as those who had a cancer history or who had surgery the year
before the follow-up started.
Blood Clot Risk After Surgery: Study Results
Compared to the risk of women who didn't have surgery, those who had surgery
in the hospital were nearly 70 times more likely to be admitted with blood
clots during the first six postoperative weeks. Women who had day surgery
(including arthroscopy and minor procedures such as biopsies) were nearly 10
times as likely to have a clot as those who had no surgery.
Overall, one in 140 middle-aged women in the U.K. who have surgery in a
hospital would be expected to be admitted with a blood clot during the 12 weeks
after the surgery.