What are the recommended regimens for Deep Vein Thrombosis (DVT) prophylaxis after hip surgery?

DVT Prophylaxis After Hip Surgery

Low-molecular-weight heparin (LMWH), specifically enoxaparin 40 mg subcutaneously once daily or 30 mg twice daily, is the first-line pharmacological agent for DVT prophylaxis after hip surgery, initiated 12 hours before or after surgery and continued for a minimum of 10-14 days, with strong consideration for extended prophylaxis up to 35 days. 1, 2

Primary Pharmacological Regimens

LMWH (Enoxaparin) - First-Line Agent

• Standard dosing: Enoxaparin 40 mg subcutaneously once daily OR 30 mg twice daily 1, 2
• Timing of initiation: Start 12 hours before or after surgery once hemostasis is established 1, 2
• Duration: Minimum 10-14 days for all patients 1, 2
• Extended prophylaxis: Continue up to 35 days, particularly for hip fracture patients who have exceptionally high VTE risk 1, 2
• Evidence base: LMWH demonstrates superior efficacy compared to unfractionated heparin, reducing proximal DVT from 18.5% to 7.5% (p=0.014) and total DVT from 25% to 12.5% (p=0.03) 3

Alternative Pharmacological Options

Fondaparinux - Highly Effective Alternative

• Dosing: 2.5 mg subcutaneously once daily 1, 4
• Timing: Initiate 6-8 hours after surgery once hemostasis is established 1
• Efficacy data: In hip fracture surgery, fondaparinux reduced VTE from 19.1% to 8.3% compared to enoxaparin (56% relative risk reduction, p<0.001) 4
• Extended prophylaxis efficacy: When continued for 3 weeks post-operatively, fondaparinux reduced VTE from 35.0% to 1.4% compared to placebo (95.9% relative risk reduction, p<0.0001) 4
• Renal dosing: Reduce to 1.5 mg daily for creatinine clearance 30-50 mL/min 1, 2

Unfractionated Heparin - When LMWH Contraindicated

• Dosing: 5,000 units subcutaneously every 8-12 hours 5, 2
• Indication: Use when LMWH is contraindicated or in severe renal failure (CrCl <30 mL/min) 1, 2
• Timing: Start after surgery once hemostasis is confirmed 5

Warfarin - Less Preferred Option

• Target INR: 2.0-3.0 1
• Note: Not preferred over LMWH or fondaparinux due to delayed onset and monitoring requirements 1

Special Dosing Considerations

Renal Impairment

• CrCl <30 mL/min: Reduce enoxaparin to 30 mg subcutaneously once daily 5, 1
• CrCl 30-50 mL/min: Reduce fondaparinux to 1.5 mg daily 1, 2
• Severe renal failure: Avoid LMWH and fondaparinux; use unfractionated heparin or warfarin 1, 2

Obesity

• Body weight >150 kg: Increase enoxaparin prophylaxis dose to 40 mg subcutaneously every 12 hours 5, 1

Neuraxial Anesthesia - Critical Safety Consideration

• Before catheter manipulation: Hold enoxaparin for 24 hours 5, 1
• After catheter removal: Resume enoxaparin no earlier than 2 hours following manipulation 5, 1
• LMWH timing: Do not administer within 10-12 hours before epidural catheter removal 2
• Rationale: Prevents catastrophic spinal/epidural hematoma 6

History of Heparin-Induced Thrombocytopenia

• Action required: Special testing indicated before using enoxaparin 5, 1
• Alternative: Consider fondaparinux if HIT confirmed 1

Mechanical Prophylaxis - Essential Adjunct

Intermittent Pneumatic Compression (IPC)

• Target duration: 18 hours daily in addition to pharmacological prophylaxis 1, 2
• High bleeding risk patients: Use IPC alone until bleeding risk diminishes, then add pharmacological prophylaxis 1, 2
• Mechanism: Provides additional VTE protection through enhanced venous return 1

Early Ambulation

• Recommendation: Encourage as part of multimodal prophylaxis approach 5, 1

Duration of Prophylaxis - Critical for Efficacy

Standard Duration

• Minimum: 10-14 days for all hip surgery patients 1, 2

Extended Duration - Strongly Recommended

• Hip arthroplasty: Extend up to 35 days 1
• Hip fracture surgery: 28-35 days strongly recommended due to exceptionally high VTE risk 2
• Evidence: Extended prophylaxis reduces VTE from 35% to 1.4% in hip fracture patients 4
• Selected very high-risk patients: Consider post-discharge enoxaparin or warfarin 5, 1

Common Pitfalls and How to Avoid Them

Premature Discontinuation

• Problem: 42-58% of at-risk patients do not receive appropriate VTE prophylaxis despite clear guidelines 1, 2
• Solution: Ensure prophylaxis continues for minimum 10-14 days, with strong consideration for 28-35 days 1, 2
• Risk: Discontinuing prophylaxis too early significantly increases VTE risk 2

Timing Errors with Neuraxial Anesthesia

• Problem: Starting anticoagulation too early after epidural/spinal anesthesia increases spinal hematoma risk 2
• Solution: Strict adherence to 24-hour hold before catheter manipulation and 2-hour delay after removal 5, 1

Inadequate Bleeding Risk Assessment

• Problem: Starting pharmacological prophylaxis before adequate hemostasis 1
• Solution: Confirm hemostasis before initiating anticoagulation; use mechanical prophylaxis alone initially if bleeding risk is high 1, 2

Failure to Adjust for Renal Function

• Problem: Standard LMWH dosing in severe renal impairment causes drug accumulation and bleeding 1
• Solution: Check creatinine clearance and adjust doses accordingly or switch to unfractionated heparin 5, 1, 2

Algorithm for Drug Selection

1. First-line for most patients: Enoxaparin 40 mg SC once daily (or 30 mg twice daily) starting 12 hours before/after surgery 1, 2

2. If renal impairment (CrCl <30 mL/min): Switch to unfractionated heparin 5,000 units SC every 8-12 hours 5, 2

3. If HIT history: Consider fondaparinux 2.5 mg SC once daily 1

4. If high bleeding risk: Use IPC alone initially, add pharmacological prophylaxis when bleeding risk decreases 1, 2

5. Duration decision: Minimum 10-14 days for all patients; extend to 28-35 days for hip fracture or high VTE risk 1, 2

6. Add mechanical prophylaxis: IPC devices for 18 hours daily regardless of pharmacological choice 1, 2