What is the recommended duration of Acetylsalicylic Acid (ASA) therapy after hip surgery?

Duration of ASA Therapy After Hip Surgery

For patients undergoing hip replacement surgery, continue aspirin for 35 days postoperatively when used for VTE prophylaxis, or continue indefinitely when used for cardiovascular indications. 1

ASA Duration Based on Indication

For VTE Prophylaxis (De Novo Use)

• Continue aspirin for 35 days after hip replacement surgery when initiated specifically for thromboprophylaxis 1
• This duration is based on the Pulmonary Embolism Prevention trial of 19,000 patients undergoing hip fracture repair or joint replacement, which demonstrated that 35 days of aspirin reduced VTE risk (RR 0.71,95% CI 0.54-0.94) with only a modest increase in major bleeding (2.9% vs 2.4%, P=0.04) 1
• Extended prophylaxis up to 6 weeks (42 days) is cost-effective and reduces recurrent DVT from 1,172 to 493 cases per 10,000 patients, and symptomatic PE from 234 to 99 cases 2

For Cardiovascular Indications (Secondary Prevention)

• Continue aspirin indefinitely throughout the perioperative period for patients taking it for secondary prevention of cardiovascular disease 1, 3
• This includes patients with prior myocardial infarction, prior stroke, coronary stents, ischemic heart disease, compensated or prior congestive heart failure, diabetes mellitus, renal insufficiency, or cerebrovascular disease 1
• Do not stop aspirin 7-10 days before surgery in moderate-to-high cardiovascular risk patients 1, 4

Resumption Timing After Surgery

• Resume aspirin within 24 hours postoperatively once adequate hemostasis is achieved 3, 4
• Maximal antiplatelet effect occurs within minutes of taking aspirin, providing immediate cardiovascular and VTE protection 3
• For patients with coronary stents or high cardiovascular risk, restart aspirin as soon as possible postoperatively, ideally within the first 24 hours 3

Evidence Supporting Extended Duration

• A Cochrane review of extended-duration anticoagulants (5-7 weeks) versus short-duration (7-14 days) found moderate quality evidence supporting extended prophylaxis for hip replacement to prevent VTE 5
• The benefit must be weighed against increased risk of minor bleeding (OR 2.01,95% CI 1.43-2.81) 1
• Recent multicenter analysis of 3,000 revision THAs demonstrated aspirin is safe and effective regardless of weight-bearing status, with VTE incidence of only 1.2% in the aspirin cohort versus 3.5% in non-aspirin cohort (P<0.001) 6

Common Pitfalls to Avoid

• Do not use the outdated 7-10 day interruption window for patients on aspirin for cardiovascular indications, as this unnecessarily increases thrombotic risk without additional bleeding benefit 3, 4
• Do not stop aspirin at hospital discharge (typically 7-14 days) when used for VTE prophylaxis, as this leaves patients unprotected during the high-risk period extending to 35 days postoperatively 1
• Do not assume all patients need aspirin held preoperatively; hip replacement is not a closed-space surgery where minor bleeding causes catastrophic complications 3
• Ensure thorough medication reconciliation, as patients may not report over-the-counter NSAIDs that compound antiplatelet effects 3, 7

Special Considerations for Dual Antiplatelet Therapy

• For patients on aspirin plus clopidogrel, continue aspirin but stop clopidogrel 5 days before surgery 1, 4
• Resume both agents within 24 hours postoperatively when adequate hemostasis is achieved 4
• Consider a 300 mg loading dose of clopidogrel when resuming therapy in patients with drug-eluting stents 4