Delayed Initiation of Low-Molecular-Weight Heparin Chemoprophylaxis Is Associated with Higher Risk of In-Hospital Screen-Detected Distal Deep Vein Thrombosis Following Hip Fracture Arthroplasty.

Abstract

This study aimed to determine the impact of the time from admission to initiation of low-molecular-weight heparin (LMWH) chemoprophylaxis on postoperative in-hospital venous thromboembolism (VTE) in patients who underwent hip fracture arthroplasty. This retrospective cohort study included 2,639 patients who a mean age of 72 years (range, 55 to 99) who underwent arthroplasty for hip fracture and received perioperative LMWH chemoprophylaxis. The primary exposure was door-to-prophylaxis (DTP) time. The primary outcome was screen-detected postoperative in-hospital VTE. The key secondary endpoint was postoperative in-hospital proximal deep vein thrombosis (DVT) and/or pulmonary embolism (PE). Patients were categorized as early or delayed DTP based on median values (18.9 hours; interquartile range, 13.6 to 43.7). Restricted cubic splines and Cox proportional hazards regressions were used to analyze the relationship between DTP time and VTE risk. A significant linear correlation was identified between DTP time and postoperative in-hospital VTE. On multivariable Cox analyses, delayed DTP (≥ 19 hours) was independently associated with increased VTE risk by 22.8% versus early DTP (less than 19 hours) (adjusted hazard ratio [HR], 1.228; 95% confidence interval [CI], 1.036 to 1.456; P = 0.018). This association persisted across types and dosing regimens of LMWH (adjusted HR, 1.248; 95% CI, 1.041 to 1.497; P = 0.017). Similarly, for every 1-hour delay in DTP, the likelihood of VTE increased by 0.3% (adjusted HR, 1.003; 95% CI, 1.000 to 1.006; P = 0.030). There was no association detected between DTP and proximal DVT and/or PE, with imprecise estimates (all P > 0.05). The DTP time was linearly associated with the occurrence of screen-detected postoperative in-hospital VTE in hip fracture arthroplasty. Notably, DTP delayed to 19 hours or later was associated with a higher risk of screen-detected distal DVT, whereas no robust association was observed for proximal DVT and/or PE.