Little research has been done on the current cut-off international normalized ratio (INR) value of 1.5 for patients undergoing surgery. The objectives of this study are to assess the association between INR and postoperative major bleeding and mortality in patients undergoing surgery and to identify an ideal pre-operative INR for surgical patients. We analyzed data from the American College of Surgeons' National Surgical Quality Improvement Program database between 2008 and 2011 (636,231 patients). The primary outcomes were major bleeding and mortality at 30 days postoperatively. Multivariate logistic regression analyses were carried out to assess these associations. Compared to an INR of <1, the adjusted odds ratio (aOR) for major bleeding was 1.22 (95 % CI 1.18-1.25) for INR 1-1.49, 1.48 (95 % CI 1.40-1.56) for INR 1.5-1.9, and 1.49 (95 % CI 1.39-1.60) for INR ≥2. The aOR for mortality at 30 days post-operation compared to INR of <1 was 1.51 (95 % CI 1.41-1.62), 2.31 (95 % CI 2.12-2.52), and 2.81 (95 % CI 2.56-3.10) for INR 1-1.49, 1.5-1.9, and ≥2, respectively. The ideal pre-operative INR value to predict an increased risk for major bleeding was 1.10 and 1.13 for mortality. In conclusion, preoperative INR is significantly and independently associated with postoperative major bleeding and mortality.
Keywords: ACS NSQIP; Hemostasis; INR; Outcomes; Prothrombin time; Surgery.