Determining a preoperative international normalised ratio threshold safe for hip fracture surgery

Introduction: The purpose of this study was first, to assess the relationship between preoperative INR (international normalised ratio) and postoperative complication rates in patients with a hip fracture, and second, to establish a threshold for INR below which the risk of complications is comparable to those in patients with a normal INR. Methods: We retrospectively reviewed the American College of Surgeons National Surgical Quality Improvement Program and found 35,910 cases who had undergone surgery for a hip fracture between 2012 and 2018. Cases were stratified into 4 groups based on their preoperative INR levels: <1.4; > 1.4 and <1.6; > 1.6 and <1.8 and > 1.8. These cohorts were assessed for differences in preoperative factors, intraoperative factors, and postoperative course. Multivariate logistic regression was used to assess the risk of transfusion, 30-day mortality, cardiac complications, and wound complications adjusting for all preoperative and intraoperative factors. Results: Of the 35,910 cases, 33,484 (93.2%) had a preoperative INR < 1.4; 867 (2.4%) an INR > 1.4 and <1.6; 865 (2.4%) an INR > 1.6 and <1.8 and 692 (1.9%) an INR > 1.8. A preoperative INR > 1.8 was independently associated with an increased risk of bleeding requiring transfusion. A preoperative INR > 1.6 was associated with an increased risk of mortality. Conclusions: We found that an INR of <1.6 is a safe value for patients who are to undergo surgery for a hip fracture. Below this value, patients avoid an increased risk of both transfusion and 30-day mortality seen with higher INR values. These findings may allow adjustment of preoperative protocols and improve the outcome of hip fracture surgery in this group of patients.