Low-molecular-weight heparin prophylaxis: preoperative versus postoperative initiation in patients undergoing elective hip surgery.

Administration of low-molecular-weight heparin prophylaxis in elective hip implant patients commonly begins 12 h preoperatively in European practices to optimize effectiveness, and 12 to 24 h postoperatively in North American practices to optimize safety. A meta-analysis comparing these two treatment regimes revealed that preoperative initiation demonstrated greater efficacy and superior safety for patients (10.0% rate of total deep-vein thrombosis vs. 15.3%, P = .023). In addition to the pre/postsurgical debate, proximity of initiation of low-molecular-weight heparin in relation to surgery is an issue of critical importance. Recent studies revealed that beginning therapy immediately within 2 h preoperatively or 6 h postoperatively dramatically decreased the risk of venous thrombosis. An investigation of low-molecular-weight heparin prophylaxis initiated 2 h before elective hip surgery or approximately 6 h after surgery compared with warfarin sodium revealed that total and proximal deep-vein thrombosis rates were reduced in patients receiving low-molecular-weight heparin compared with warfarin. The frequencies of deep-vein thrombosis for patients receiving preoperative and postoperative dalteparin vs. warfarin for all deep-vein thrombosis were 36 of 337 (10.7%, P < .001) and 44 of 336 (13.1%, P < .001) vs. 81 of 338 (24.0%); and for proximal deep-vein thrombosis were 3 of 354 (0.8%, P = .035) and 3 of 358 (0.8%, P = .033) vs. 11 of 363 (3.0%). Relative risk reductions for the dalteparin groups vs. warfarin ranged from 45% to 72%. In this case, low-molecular-weight heparin administered in close proximity to surgery provided superior efficacy over warfarin. Major bleeding was significantly increased with the preoperative regimen but not the postoperative regimen.