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Surgery confers risk for subsequent venous thromboembolism (VTE), but the time course and magnitude of risk elevation are not well defined. British investigators linked National Health Service data on hospital admissions and deaths with survey information from participants in the prospective population-based Million Women Study. Women with multiple surgeries or previous VTE were excluded; adjustments were made for BMI and use of hormone therapy.
Compared with the background incidence of VTE in the general population, inpatient surgery was associated with substantial risk for VTE within 1 week (relative risk, 40.3); risk peaked at 3 weeks (RR, 112.5) then declined but was still higher than that in unoperated women during the next 12 months (RR at 4–6 months, 9.4; RR at 10–12 months, 3.7). Hip or knee replacement conferred markedly higher VTE risk within 6 weeks (RR, 220.6) than did inpatient gynecologic surgery (RR, 22.7).
Sweetland S et al. Duration and magnitude of the postoperative risk of venous thromboembolism in middle aged women: Prospective cohort study. BMJ 2009 Dec 3; 339:b4583. (http://dx.doi.org/10.1136/bmj.b4583)
Cohen AT. Prevention of postoperative venous thromboembolism. BMJ 2009 Dec 3; 339:b4477. (http://dx.doi.org/10.1136/bmj.b4477)
Comment
This study shows that risk for postoperative VTE is substantial and is longer lasting than previously suspected. An editorialist notes that, because VTE also is treated on an outpatient basis, these data might underestimate the true prevalence of the condition. Prophylaxis for VTE has become standard after many surgeries but often only during hospitalization or for 30 days after surgery. These findings highlight the importance of continued vigilance for VTE as long as 12 months after surgery, as well as the necessity of studying the risks and benefits associated with prolonged postoperative thromboprophylaxis.