Background: The PeriOperative ISchemia Evaluation-2 (POISE-2) trial compared aspirin with placebo after noncardiac surgery. Methods: The authors randomly assigned 10,010 patients undergoing noncardiac surgery to receive 200 mg aspirin or placebo 2 to 4 h before surgery and then 100 mg aspirin daily or placebo daily for up to 30 days after surgery. Herein, the authors report the effect of aspirin on venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism, as well as an updated pooled analysis of randomized trials of antiplatelet therapy for VTE prevention in noncardiac surgery patients. Results: Six thousand five hundred forty-eight patients (65.4percent-flag-change) received anticoagulant prophylaxis. VTE occurred in 53 patients (1.1percent-flag-change) allocated to aspirin and in 60 patients (1.2percent-flag-change) allocated to placebo (hazard ratio, 0.89; 95percent-flag-change CI, 0.61 to 1.28). Major or life-threatening bleeding occurred in 312 patients (6.3percent-flag-change) allocated to aspirin and in 256 patients (5.1percent-flag-change) allocated to placebo (hazard ratio, 1.22; 95percent-flag-change CI, 1.04 to 1.44). Concomitant use of anticoagulant prophylaxis did not modify the effect of aspirin on VTE or bleeding. Pooled analysis of the POISE-2 and Pulmonary Embolism Prevention trials demonstrated that symptomatic VTE occurred in 173 (1.3percent-flag-change) of 13,724 patients allocated to aspirin and in 246 (1.8percent-flag-change) of 13,730 patients allocated to placebo (odds ratio, 0.71; 95percent-flag-change CI, 0.56 to 0.89; heterogeneity P = 0.27; I2 = 17percent-flag-change); the impact of aspirin was very similar in those who did and did not receive pharmacologic prophylaxis. Pooled estimates for symptomatic VTE were similar to the pooled estimates for any deep vein thrombosis and pulmonary embolism from the POISE-2 trial, Pulmonary Embolism Prevention trial, and the Antiplatelet Trialists' Collaboration meta-analysis. Conclusions: Aspirin in the POISE-2 trial did not reduce VTE, but two thirds of patients received anticoagulant prophylaxis, there were few VTE events, and results were consistent with a wide range of aspirin effects. A pooled analysis of the randomized trials demonstrates evidence for the efficacy of aspirin for VTE prevention in hospitalized surgical patients.
