When are anticoagulants (blood thinners) typically started after hip replacement surgery?

Timing of Anticoagulant Initiation After Hip Replacement Surgery

Anticoagulants are typically started 6-10 hours after hip replacement surgery once hemostasis has been established, and should be continued for 5 weeks (35 days) for optimal prevention of venous thromboembolism. 1, 2

Standard Timing for Anticoagulant Initiation

• For injectable anticoagulants like low-molecular-weight heparin (LMWH), administration typically begins 12-24 hours after surgery once adequate hemostasis has been achieved 3
• For oral direct anticoagulants (DOACs) like rivaroxaban, the first dose is typically given 6-10 hours after surgery once hemostasis has been established 1
• Dabigatran regimens are commonly started 1-4 hours after surgery when compared with once-daily enoxaparin regimens 3
• If an epidural catheter is used, special timing considerations apply, and anticoagulants should be administered at least six hours after the end of the invasive procedure 3

Duration of Anticoagulation

• For total hip replacement (THR), anticoagulation should be continued for 5 weeks (35 days) 2, 1
• Extended-duration prophylaxis (5-7 weeks) has been shown to be more effective than short-duration prophylaxis (7-14 days) in preventing venous thromboembolism after hip replacement 4
• The risk of venous thromboembolism after hip surgery can last up to three months, with most events occurring within the first month after discharge 5

Specific Anticoagulant Regimens

• Rivaroxaban: 10 mg once daily for 35 days, starting 6-10 hours after surgery once hemostasis has been established 1
• Apixaban: 2.5 mg twice daily for 5 weeks, starting 12-24 hours after surgery 2, 3
• Dabigatran: 220 mg once daily (or 150 mg once daily for patients with specific risk factors) for 28-35 days 3
• Enoxaparin: 40 mg once daily starting the evening before surgery or 30 mg twice daily starting 12-24 hours after surgery 3

Clinical Considerations and Potential Pitfalls

• Despite hospital-based thromboprophylaxis, approximately 70% of venous thromboembolic events occur after discharge, highlighting the importance of extended prophylaxis 5
• Delaying the start of anticoagulation may contribute to inferior results in preventing venous thromboembolism 3
• Patients present with deep venous thrombosis at a median of 21 days and pulmonary embolism at 34 days after total hip replacement 5
• Renal function should be monitored postoperatively as surgical procedures may affect kidney function and potentially impact anticoagulant dosing 2
• Avoid overlapping anticoagulants when transitioning between different agents to prevent excessive anticoagulation 2

Special Considerations

• For patients with epidural catheters, therapeutic anticoagulation must be administered with heparin to safely withdraw the catheter 3
• In patients with high bleeding risk, consider delaying the first dose or using mechanical prophylaxis initially 3
• For patients already on anticoagulants requiring hip surgery, interruption times up to five days may be needed for DOACs if neuraxial anesthesia is planned 2

The evidence strongly supports initiating anticoagulation shortly after surgery (6-24 hours) once hemostasis is established, with continuation for a full 5 weeks after hip replacement to effectively reduce the risk of venous thromboembolism while maintaining an acceptable bleeding risk profile.