What is a suitable alternative for Deep Vein Thrombosis (DVT) prophylaxis in an 88-year-old patient with a hip fracture and an allergy to aspirin (acetylsalicylic acid)?

DVT Prophylaxis in an 88-Year-Old with Hip Fracture and Aspirin Allergy

Low-molecular-weight heparin (LMWH), specifically enoxaparin 30 mg subcutaneously every 12 hours, is the first-line agent for DVT prophylaxis in this patient, as it demonstrates superior efficacy compared to unfractionated heparin with lower rates of DVT, PE, bleeding complications, and mortality in elderly trauma patients. 1

Primary Pharmacological Agent and Dosing

• LMWH (enoxaparin) is the drug of choice for elderly hip fracture patients, with the 2023 WSES guidelines specifically recommending it over unfractionated heparin (UFH) based on a large propensity-matched study of 40,000 elderly trauma patients showing LMWH was associated with lower incidence of DVT (P = 0.007), PE (P < 0.001), fewer bleeding complications and transfusions (P < 0.001), and lower mortality (P < 0.001). 1

• Standard dosing for patients over 65 years is enoxaparin 30 mg subcutaneously every 12 hours. 1

• If the patient has renal failure (creatinine clearance <30 mL/min), switch to UFH 5000 units subcutaneously every 8 hours, as LMWH is contraindicated in severe renal impairment. 1

Timing and Duration

• Initiate LMWH postoperatively once hemostasis is established, ideally 6-8 hours after surgery. 2, 3

• Minimum duration is 7-10 days, but extended prophylaxis up to 32 days total is strongly recommended for hip fracture patients, as the 2023 WSES guidelines cite a Norwegian study of 45,000 elderly hip fracture patients showing post-operative prophylaxis decreased intraoperative bleeding complications. 1, 2

• The FDA label for fondaparinux specifically states that hip fracture surgery patients should receive extended prophylaxis for up to 24 additional days beyond the initial perioperative period. 3

Alternative Agents When LMWH Cannot Be Used

If LMWH is contraindicated or unavailable:

• Fondaparinux 2.5 mg subcutaneously once daily is FDA-approved for hip fracture surgery prophylaxis and is specifically indicated when heparins cannot be used. 1, 3

• Critical caution: Fondaparinux should be used with extreme caution in this 88-year-old patient, as the FDA label and NCCN guidelines recommend against its use in elderly patients >75 years, particularly those weighing <50 kg or with renal dysfunction (CrCl 30-50 mL/min). 1, 3

• Unfractionated heparin 5000 units subcutaneously every 8 hours is the preferred alternative when LMWH is contraindicated, though it is less effective than LMWH. 1, 2

Why Aspirin Is NOT Appropriate

• Aspirin is explicitly NOT recommended as sole prophylaxis for hip fracture patients, as the 2025 Praxis Medical Insights summary states aspirin is not considered effective VTE prophylaxis in general settings, and the ACCP guidelines advise against aspirin as the sole method of thromboprophylaxis in surgical patients due to inferior efficacy compared to anticoagulants. 4

• While one 2019 study showed aspirin 100 mg daily was equivalent to rivaroxaban after an initial 5-day course of enoxaparin in hip fracture patients (VTE rate 6.6% vs 5.7%, P = 0.83), this was only as extended prophylaxis following initial LMWH treatment, not as primary prophylaxis. 5

• The aspirin allergy in this patient is irrelevant to the decision-making, as aspirin should not be used regardless of allergy status. 4

Adjunctive Mechanical Prophylaxis

• Combine pharmacological prophylaxis with intermittent pneumatic compression (IPC) devices for 18 hours daily, as the 2023 WSES guidelines cite a Cochrane review showing combined mechanical and pharmacological prophylaxis further decreases DVT risk (RR 0.34). 1, 2

• Mechanical prophylaxis alone (IPC or elastic stockings) should be used if pharmacological prophylaxis must be delayed due to active bleeding, coagulopathy, or hemodynamic instability. 1

Critical Contraindications and Monitoring

Delay pharmacological prophylaxis if:

• Active bleeding, coagulopathy, or hemodynamic instability is present. 1
• Traumatic brain injury or spinal trauma requiring neuraxial anesthesia exists. 1, 2

For this 88-year-old patient specifically:

• Dose adjustment according to anti-Xa levels may be warranted given advanced age. 1
• Monitor for bleeding complications, which occur in approximately 1.0-1.4% of patients on LMWH. 2
• Assess renal function, as fondaparinux clearance is approximately 55% lower in severe renal impairment and 25% lower in patients >75 years. 3

Risk Stratification Context

• This 88-year-old patient with hip fracture scores at least 4 points on the TESS score (2 points for age ≥65,2 points for lower extremity fracture), placing them in the moderate-to-high risk category requiring pharmacological prophylaxis. 1

• Age >75 years and lower extremity injury are independent risk factors for DVT in elderly trauma patients. 1