What is the best approach for venous thromboembolism (VTE) prophylaxis in a patient with a femoral neck fracture and delayed surgery due to immobility and underlying hypertension and hypothyroidism?

VTE Prophylaxis in Femoral Neck Fracture with Delayed Surgery

Start enoxaparin 40 mg subcutaneously once daily now, and discontinue 12 hours before surgery (Option A).

Rationale for Immediate Pharmacologic Prophylaxis

A patient with a hip/femoral neck fracture represents one of the highest-risk scenarios for VTE, scoring 5 points on risk stratification systems, placing them in the "highest risk" category with a 40-80% risk of DVT and 4-10% risk of PE without prophylaxis 1. The combination of advanced age, fracture, and prolonged immobility (48-hour surgical delay) creates a critical window where VTE risk accumulates rapidly 2.

Why Pharmacologic Prophylaxis Should Start Immediately

• Hip and pelvic fractures are explicitly categorized as 5-point risk factors (highest tier) requiring immediate pharmacologic intervention 1
• The American College of Chest Physicians guidelines specifically recommend LMWH for orthopedic trauma patients at high VTE risk, with prophylaxis initiated as soon as bleeding is controlled 1
• VTE risk is directly related to continued immobility and may persist for up to 2 months following injury, making the 48-hour preoperative period particularly dangerous 2
• Up to 40% of VTE events in surgical patients occur within 21 days of surgery, and VTE is responsible for 46% of deaths within 30 days, emphasizing the importance of early prophylaxis 1

Enoxaparin Dosing and Timing

• Enoxaparin 40 mg subcutaneously once daily is the preferred LMWH regimen for orthopedic fracture patients 1, 2
• Begin pharmacological prophylaxis within 24 hours after ensuring bleeding has been controlled 2
• Discontinue enoxaparin 12 hours before surgery to minimize bleeding risk while maintaining VTE protection 1
• Resume prophylaxis postoperatively and continue for a minimum of 10-14 days, with consideration for extended prophylaxis up to 35 days given the high-risk features 1, 2

Why Other Options Are Inadequate

Option B (Hold Until After Surgery) Is Dangerous

Waiting 48 hours without any prophylaxis in a highest-risk patient contradicts all major guidelines 1, 2. The immobility period before surgery is when VTE risk is actively accumulating, and delaying prophylaxis increases the likelihood of preoperative thrombosis that could embolize perioperatively 1, 2.

Option C (Mechanical Prophylaxis Alone) Is Insufficient

While mechanical prophylaxis (pneumatic compression devices) reduces DVT by 66%, it achieves only a modest 31% reduction in PE and should not be used as monotherapy when pharmacologic methods are feasible 1. Mechanical methods should be added to pharmacologic prophylaxis in highest-risk patients, not substituted for it 1. The guidelines are explicit: mechanical prophylaxis alone is reserved only for patients with active bleeding or contraindications to anticoagulation 1.

Option D (Apixaban) Is Not Recommended

Apixaban is not appropriate for this scenario for multiple reasons:

• Apixaban was not superior to enoxaparin in preventing VTE in acutely ill medical patients and was associated with increased major bleeding 1
• The half-life of apixaban is approximately 12 hours, so holding it for 48 hours before surgery provides no advantage over enoxaparin (which only requires 12-hour discontinuation) 1
• Apixaban lacks robust evidence in the orthopedic trauma population, whereas LMWH has extensive validation 1

Practical Implementation

Initiate enoxaparin 40 mg subcutaneously once daily immediately (assuming no active bleeding, platelet count >50 × 10⁹/L, and controlled hypertension) 2. Adjust to 30 mg daily if creatinine clearance is <30 mL/min 3.

Combine with mechanical prophylaxis: Apply intermittent pneumatic compression devices as soon as possible and maintain for 18 hours daily 1, 2.

Perioperative management: Stop enoxaparin 12 hours before the scheduled surgery time 1. Resume 6-8 hours postoperatively once hemostasis is confirmed 3, 2.

Duration: Continue prophylaxis for at least 10-14 days postoperatively, with strong consideration for extending to 35 days given the patient's age, fracture type, and anticipated mobility limitations 1, 2.

Critical Monitoring

Monitor platelet counts regularly as heparin-induced thrombocytopenia risk increases with trauma severity 2. Watch for signs of bleeding complications, which may be more common in elderly patients 2.