When to restart enoxaparin (low molecular weight heparin) in a patient with a femoral shaft fracture?

When to Restart Enoxaparin After Femoral Shaft Fracture

For patients with femoral shaft fracture, enoxaparin should be initiated 12-24 hours after surgery once adequate hemostasis has been established, or within 36 hours of injury in non-operative cases. 1

Timing of Initiation

Post-Surgical Patients

• Start enoxaparin 12-24 hours after surgery once hemostasis is confirmed 1
• For high bleeding risk procedures (which includes major orthopedic trauma surgery), consider waiting 48-72 hours before resuming full therapeutic doses if the patient was previously anticoagulated 2
• The standard prophylactic dose is 40 mg subcutaneously once daily 1

Multiple Trauma Patients

• Initiate within 36 hours of injury to effectively reduce venous thromboembolism risk 1
• Earlier initiation (preoperative start) is associated with lower mortality compared to postoperative start in hip fracture patients (RR 1.13 for death with postoperative start, p<0.001) 3

Special Considerations for Neuraxial Anesthesia

Critical timing restrictions apply if epidural or spinal anesthesia was used:

• Do not administer enoxaparin within 10-12 hours before epidural catheter removal 1
• Wait at least 2 hours after catheter removal before giving the first prophylactic dose 1
• Failure to follow these guidelines significantly increases the risk of spinal hematoma 1

Duration of Prophylaxis

Extended prophylaxis is essential and should not be discontinued prematurely:

• Minimum duration: 7-10 days for all lower extremity fractures 2, 1
• Optimal duration: 28-35 days (4 weeks) for hip fractures and major lower extremity trauma due to persistently elevated VTE risk 1
• Discontinuing prophylaxis before 10-14 days significantly increases venous thromboembolism risk 1

Dosing Adjustments

Renal Impairment

• For creatinine clearance <30 mL/min: Switch to unfractionated heparin rather than enoxaparin 1
• Enoxaparin has delayed clearance in renal dysfunction due to its longer half-life 4

Initial Dosing Strategy

• Full prophylactic dose (40 mg) can be given from the start once the appropriate timing window is met 3
• Half-dose initiation followed by full dose the next day is an alternative, though evidence shows no difference in bleeding or reoperation rates between full and half initial dosing 3

Common Pitfalls to Avoid

Critical errors that increase morbidity and mortality:

• Starting too late: Postoperative initiation beyond 24 hours increases mortality (RR 1.13) and reoperation risk (RR 1.19) compared to earlier initiation 3
• Stopping too early: Discontinuing before 10-14 days dramatically increases VTE risk, and failure to extend beyond hospital discharge is a frequent error 1
• Ignoring neuraxial anesthesia timing: Administering enoxaparin too close to epidural catheter manipulation risks catastrophic spinal hematoma 1
• Not adjusting for renal function: Using enoxaparin in severe renal impairment (CrCl <30 mL/min) leads to drug accumulation and bleeding risk 1

Monitoring Requirements

• Check complete blood count and platelet count every 2-3 days from day 4 to day 14 in high-risk orthopedic patients to detect heparin-induced thrombocytopenia 5, 4
• Monitor for signs of bleeding complications, which occur in 2.6-3.3% of patients 4
• Assess hemoglobin and hematocrit regularly during the prophylaxis period 4

Alternative Approaches

• Mechanical prophylaxis (intermittent pneumatic compression) should be used in combination with pharmacological prophylaxis when possible 1
• For patients who cannot receive enoxaparin immediately due to bleeding concerns, mechanical prophylaxis alone is acceptable until pharmacological agents can be safely initiated 2