IMPORTANCE: There is a paucity of data assessing the effect of increased surgical duration on the incidence ofvenous thromboembolism (VTE). OBJECTIVE: To examine the association between surgical duration and the incidence of VTE. DESIGN, SETTINGS, AND PARTICIPANTS: Retrospective cohort of 1 432 855 patients undergoing surgery under general anesthesia at 315 US hospitals participating in the American College of Surgeons National Surgical Quality Improvement Program from 2005 to 2011. EXPOSURE: Duration of surgery. MAINOUTCOMES AND MEASURES: The ratesofdeep vein thrombosis (DVT), pulmonary embolism (PE), and VTE within 30 days of the index operation. Surgical duration was standardized across Current Procedural Terminology codes using a z score. Outcomes were compared across quintiles of the z score. Multiple logistic regression models were developed to examine the association while adjusting for patient demographics, clinical characteristics, and comorbidities. RESULTS: The overall VTE rate was 0.96% (n = 13 809); the rates of DVT and PE were 0.71% (n = 10 198) and 0.33% (n = 4772), respectively. The association between surgical duration and VTE increased in a stepwise fashion. Compared with a procedure of average duration, patients undergoing the longest procedures experienced a 1.27-fold (95% CI, 1.21-1.34; adjusted risk difference [ARD], 0.23%) increase in the odds of developing a VTE; the shortest procedures demonstrated an odds ratio of0.86 (95% CI, 0.83-0.88; ARD, -0.12%). The robustness of these results was substantiated with several sensitivity analyses attempting to minimize the effect of outliers, concurrent complications, procedural differences, and unmeasured confounding variables. CONCLUSIONS AND RELEVANCE: Among patients undergoing surgery, an increase in surgical duration was directly associated with an increase in the risk for VTE. These findings may help inform preoperative and postoperative decision making related to surgery.
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