Preoperative Platelet and International Normalized Ratio Thresholds and Risk of Complications After Primary Hip Fracture Surgery

Background: A paucity of data exists on safe platelet and international normalized ratio (INR) thresholds for hip fracture surgery. Recent work has called into question the safety of preoperative INRs < 1.5 for total knee arthroplasty, and optimal platelet thresholds are unknown. The purpose of this study was to identify the risk of 30-day postoperative morbidity and mortality in patients with thrombocytopenia or elevated INRs undergoing hip fracture surgery. Methods: The National Surgical Quality Improvement Program database was queried for patients undergoing surgical treatment of a native hip fracture from 2012 to 2017 (N = 86,850). Patient demographic, laboratory, and complication data were collected. Patients with preoperative platelet counts or INRs within one day of surgery were included for analysis. Preoperative platelet counts and INRs were divided into four groups (<50 k/μL, ≥50 k to 100 k/μL, ≥100 k to 150 k/μL, ≥150 k/μL, and ≤1.0, >1.0 to 1.5, >1.5 to 2.0, and >2.0, respectively). Multivariable logistic regressions were used to assess the independent association between platelet count and INR on bleeding complications requiring transfusion, wound complications, reoperations, readmissions, and deaths. Results: A total of 72,306 and 56,027 patients were included for analysis of preoperative platelet and INR levels, respectively. In reference to platelet levels ≥150 k/μL, a notably increased risk of bleeding events was observed for patients with platelet counts ≥100 k to 150 k/μL (odds ratio [OR] 1.21, 95% confidence interval 1.15 to 1.27), ≥50 to 100 k/μL (OR 1.85, 1.69 to 2.03), and <50 k/μL (OR 1.60, 1.25 to 2.04). Decreasing platelet counts were associated with a stepwise increased risk of mortality from OR 1.12 (1.02 to 1.22) for platelet counts ≥100 k to 150 k/μL to OR 1.63 (1.41 to 1.90) and OR 1.59 (1.06 to 2.39) for platelet counts ≥50 k to 100 k/μL and <50 k/μL, respectively. Elevated INR was associated with an increased risk of reoperations, readmissions, and death ( P < 0.001 for all), with largest effect sizes observed starting at INRs >1.5. Discussion: The results of this study suggest that preoperative platelet thresholds of <100,000/μL and INR thresholds of 1.5 serve as an important risk factor for complications after hip fracture surgery. Future work is warranted to determine whether preoperative platelet transfusions and/or INR reversal will improve outcomes for these patients. Level of Evidence: Prognostic Level III