What anticoagulant to use for patients with fractures?

Anticoagulant Selection for Fracture Patients

For venous thromboembolism (VTE) prophylaxis in fracture patients, low-molecular-weight heparin (LMWH) is the preferred first-line anticoagulant, with fondaparinux as an effective alternative. 1, 2

Primary Recommendation by Fracture Type

Hip Fracture Surgery

• LMWH is the recommended prophylactic agent (enoxaparin 30 mg subcutaneously every 12 hours or 40 mg once daily), started postoperatively once hemostasis is established 1, 2
• Fondaparinux 2.5 mg subcutaneously once daily is an equally effective alternative, initiated 6-8 hours after surgery 1, 3
• Duration: minimum 7-10 days, with extended prophylaxis recommended for 28-35 days due to persistent VTE risk 1, 4
• Adjusted-dose warfarin (INR 2.0-3.0) is an alternative but more complex to manage 1

Hip Replacement Surgery

• LMWH is preferred over adjusted-dose warfarin due to superior efficacy in preventing asymptomatic VTE 1, 2
• The bleeding risk at the surgical site may be slightly higher with LMWH compared to warfarin, but efficacy benefits outweigh this concern 1
• Extended prophylaxis up to 35 days is strongly recommended 2

Knee Replacement Surgery

• LMWH or adjusted-dose warfarin are both acceptable options 1
• LMWH demonstrates superior effectiveness compared to warfarin, aspirin, or dextran 1

Multiple Trauma with Fractures

• LMWH (enoxaparin 30 mg subcutaneously every 12 hours) is superior to unfractionated heparin 1
• In the landmark trauma study, LMWH reduced venous thrombosis from 44% to 31% compared to low-dose heparin (p=0.014) 1
• Initiate pharmacological thromboprophylaxis within 36 hours after trauma once hemorrhage control is achieved 1

Pelvic and Acetabular Fractures

• LMWH is the standard prophylactic agent 5
• Recent evidence suggests aspirin 81 mg twice daily may be noninferior to LMWH for mortality prevention, though LMWH showed lower deep-vein thrombosis rates (1.71% vs 2.51%) 5

Dosing Protocols

LMWH (Enoxaparin)

• Standard dose: 30 mg subcutaneously every 12 hours OR 40 mg once daily 1, 2
• Renal impairment (CrCl <30 mL/min): reduce to 30 mg once daily 2
• Body weight >150 kg: increase to 40 mg every 12 hours 2
• Timing: initiate 12-24 hours postoperatively to reduce spinal hematoma risk with neuraxial anesthesia 1

Fondaparinux

• Standard dose: 2.5 mg subcutaneously once daily 3
• Renal impairment (CrCl 30-50 mL/min): reduce to 1.5 mg daily 2
• Contraindicated if CrCl <30 mL/min 3
• Contraindicated if body weight <50 kg 3
• Timing: initiate 6-8 hours after surgery once hemostasis is established 2, 3

Unfractionated Heparin

• Dose: 5,000 units subcutaneously every 8 hours for high-risk patients including hip fractures 4
• Use when LMWH is contraindicated (severe renal impairment) 1, 2

Critical Timing Considerations

Never initiate anticoagulation before emergency fracture surgery due to significantly increased bleeding risk at the surgical site and wound hematoma formation 6

Postoperative Initiation Windows

• LMWH: 12-24 hours after surgery 1, 2
• Fondaparinux: 6-8 hours after surgery 2, 3
• For spinal/epidural anesthesia: delay first LMWH dose until after catheter removal, or remove catheter ≥8 hours after last LMWH dose 1

Duration of Prophylaxis

• Hip fracture: 28-35 days (4-5 weeks) 1, 4
• Hip replacement: 28-35 days 1, 2
• Knee replacement: 10-14 days minimum 1, 2
• Multiple trauma: continue while immobility persists, typically 2-4 weeks 1

Adjunctive Mechanical Prophylaxis

• Intermittent pneumatic compression (IPC) devices should be used in addition to pharmacological prophylaxis for 18 hours daily 2
• For patients at high bleeding risk, use mechanical prophylaxis alone until bleeding risk diminishes 2

Special Populations

Elderly and Frail Patients

• Carefully monitor renal function as elderly patients are more likely to have reduced creatinine clearance 3
• Use unfractionated heparin if CrCl <30 mL/min 1

Patients on Chronic Anticoagulation

• For patients on warfarin with life-threatening bleeding: administer four-factor prothrombin complex concentrates (4F-PCCs) plus 5 mg intravenous vitamin K to achieve INR <1.5 1
• For patients on DOACs: use specific reversal agents only if dosable plasma levels are present and patient has hemorrhagic shock unresponsive to resuscitation 1
• Fresh frozen plasma should only be used if no other reversal treatment is available 1

Common Pitfalls to Avoid

• Discontinuing prophylaxis at hospital discharge when patients transfer to rehabilitation facilities—the VTE risk persists for weeks 1
• Initiating anticoagulation too early postoperatively (<6 hours) significantly increases major bleeding risk (4.8% at <4 hours vs 1.9% at 6-8 hours) 3
• Using LMWH or fondaparinux in severe renal impairment (CrCl <30 mL/min)—switch to unfractionated heparin 1, 3
• Failing to hold LMWH before neuraxial catheter manipulation—must wait ≥8 hours after last dose 2
• Using fondaparinux in patients <50 kg—absolute contraindication due to bleeding risk 3

Monitoring Requirements

• Periodic complete blood counts including platelet counts to detect thrombocytopenia 3
• Serum creatinine monitoring especially in elderly patients 3
• Routine coagulation tests (PT/aPTT) are relatively insensitive to fondaparinux activity and should not guide dosing 3