In an 82-year-old woman with ischemic dilated cardiomyopathy who has undergone surgery for a femoral fracture, when should low-molecular-weight heparin and antiplatelet therapy be initiated?

Timing of Heparin and Antiplatelet Therapy After Femoral Fracture Surgery

In this 82-year-old woman with ischemic dilated cardiomyopathy who underwent femoral fracture surgery, initiate low-molecular-weight heparin (enoxaparin 30 mg subcutaneously twice daily) within 12-24 hours postoperatively, and resume antiplatelet therapy (aspirin) within 24 hours if hemostasis is secure.

VTE Prophylaxis Timing After Orthopedic Surgery

Optimal Initiation Window

• Start LMWH 12-24 hours after surgery for optimal balance between thromboprophylaxis efficacy and bleeding risk 1
• Initiating LMWH in close proximity to surgery (within 12-24 hours postoperatively) provides absolute risk reductions of 11-13% for deep vein thrombosis compared to delayed initiation 2
• Delayed initiation beyond 24 hours results in suboptimal antithrombotic effectiveness without substantive safety advantage 2

Specific Dosing for This Patient

• Enoxaparin 30 mg subcutaneously every 12 hours is the appropriate prophylactic dose for major orthopedic surgery 3
• This dosing regimen reduced deep vein thrombosis by 30% and proximal vein thrombosis by 58% compared to unfractionated heparin in trauma patients with fractures 3
• Continue prophylaxis for the duration of immobilization or until the patient is fully ambulatory 1

Critical Considerations for This High-Risk Patient

Multiple Thrombotic Risk Factors

• Age >75 years, major orthopedic surgery, ischemic cardiomyopathy, and expected immobilization place this patient at very high risk for venous thromboembolism 1, 3
• Orthopedic surgery patients have particularly high rates of heparin-induced thrombocytopenia (HIT) with unfractionated heparin, making LMWH the preferred agent 1
• LMWH carries approximately 10-fold lower HIT risk compared to unfractionated heparin in surgical settings 4

Renal Function Assessment

• Check creatinine clearance before initiating enoxaparin - if CrCl <30 mL/min, use caution as LMWH accumulation occurs 1
• In severe renal impairment (CrCl <30 mL/min), consider unfractionated heparin with monitoring or dose-adjusted LMWH 1

Antiplatelet Therapy Resumption

Timing for Aspirin

• Resume aspirin 75-100 mg daily within 24 hours postoperatively if there is no active bleeding and hemostasis is secure 1
• For patients with ischemic cardiomyopathy, aspirin provides critical secondary prevention of cardiovascular events 1
• The combination of aspirin plus LMWH is more effective than either agent alone for preventing both arterial and venous thrombotic events 1, 5

Bleeding Risk Management

• Assess surgical site for hemostasis before initiating dual therapy - ensure no active bleeding, stable hemoglobin, and secure wound closure 1
• The combination of enoxaparin plus aspirin increases minor bleeding (primarily injection site ecchymoses) but not major bleeding in most studies 5
• Monitor platelet count every 2-3 days from day 4 to day 14 to screen for HIT, given the orthopedic surgery context 1

Monitoring Protocol

Essential Laboratory Surveillance

• Baseline platelet count, hemoglobin, and creatinine before initiating therapy 1
• Platelet monitoring every 2-3 days from day 4-14 due to intermediate HIT risk (0.1-1%) in orthopedic surgery patients 4
• A platelet decline >50% from baseline warrants immediate HIT evaluation, even if absolute count remains >150,000/μL 4
• No routine aPTT monitoring needed with LMWH 1

Signs Requiring Immediate Intervention

• Severe thrombocytopenia (<50,000/μL), new thrombosis despite anticoagulation, or major bleeding require immediate reassessment 4
• If HIT suspected, switch to fondaparinux, argatroban, or bivalirudin - never use warfarin alone initially 4

Duration of Prophylaxis

Extended Prophylaxis Indications

• Continue LMWH prophylaxis for minimum 10-14 days or until patient is fully ambulatory 1
• For patients with limited mobility or additional risk factors (age >75, heart failure), consider extended prophylaxis up to 35 days 1
• The combination of advanced age, cardiac disease, and major orthopedic surgery justifies extended duration prophylaxis 1, 3

Common Pitfalls to Avoid

• Do not delay LMWH beyond 24 hours postoperatively - this eliminates the efficacy advantage over oral anticoagulants 2
• Do not use fixed prophylactic dosing in obese patients - consider weight-adjusted dosing (enoxaparin 0.5 mg/kg twice daily) if BMI >30 6
• Do not withhold aspirin indefinitely - the cardiovascular risk from aspirin cessation in ischemic cardiomyopathy outweighs bleeding risk after the first 24 hours 1
• Do not use unfractionated heparin as first-line in this orthopedic patient due to 10-fold higher HIT risk 1, 4
• Do not add unfractionated heparin to LMWH - switching between anticoagulants increases bleeding risk without benefit 7