Guidelines for Aspirin Doses in Post-Operative Patients
For post-operative patients, aspirin should be dosed at 75-162 mg daily for most indications, with specific dosing regimens for certain surgical scenarios such as coronary artery bypass grafting (CABG) where 100-325 mg daily is recommended. 1
General Post-Operative Aspirin Dosing
Coronary Artery Disease Patients
- Standard maintenance dose: 75-162 mg daily 1
- Continue indefinitely in all patients unless contraindicated 1
- For patients intolerant or allergic to aspirin, clopidogrel 75 mg daily is a reasonable alternative 1, 2
Post-CABG Specific Recommendations
- Aspirin 100-325 mg daily should be initiated within 6 hours after CABG surgery 1, 2
- Early postoperative aspirin (within 48 hours) improves saphenous vein graft patency rates 2, 3
- Aspirin 81 mg daily is widely used and considered acceptable by ACC/AHA 1, 2
- For long-term maintenance after CABG, 75-162 mg daily is recommended 1, 2
- Delaying aspirin initiation beyond 48 hours results in lost benefit for graft patency 2, 3
Post-PCI with Stent Placement
- Higher-dose aspirin (325 mg daily) is recommended initially: 1
- 1 month for bare metal stent
- 3 months for sirolimus-eluting stent
- 6 months for paclitaxel-eluting stent
- After this initial period, return to maintenance dose of 75-162 mg daily 1
Special Considerations
Dual Antiplatelet Therapy (DAPT)
- For patients after acute coronary syndrome (ACS) or PCI with stent placement: 1
- Continue aspirin 75-162 mg daily plus P2Y12 inhibitor for at least 12 months
- For bare-metal stent: DAPT for at least 1 month
- For drug-eluting stent: DAPT for 3-12 months depending on stent type
Orthopedic Surgery
- Low-dose aspirin (81 mg twice daily) appears as effective as standard-dose (325 mg twice daily) for VTE prophylaxis after total hip arthroplasty 4
- Continuing low-dose aspirin (100 mg/day) perioperatively is safe as part of multimodal VTE prophylaxis 5
Bleeding Risk Considerations
- Lower doses (75-100 mg) have fewer gastrointestinal adverse effects while maintaining efficacy 6
- Use of warfarin in conjunction with aspirin increases bleeding risk and should be monitored closely 1
Perioperative Management
- For patients already on aspirin therapy before CABG, continue aspirin through the perioperative period 2
- For patients undergoing elective CABG who are not already taking aspirin, initiation in the immediate preoperative period (<24 hours before surgery) is not recommended 1
- If CABG is performed within 12 months of PCI, continue single antiplatelet therapy (preferably aspirin) until 1 year post-PCI 2
Evidence Quality and Caveats
- The recommendation for aspirin 75-162 mg daily for most post-operative patients is supported by Level A evidence 1
- Early studies demonstrated that immediate postoperative administration of aspirin (324 mg) improves early graft patency without significantly increasing blood loss 3
- More recent evidence suggests that lower doses (81-100 mg) may provide similar efficacy with potentially fewer side effects 1, 2, 4
Remember that aspirin therapy should be continued indefinitely in patients with coronary artery disease unless contraindicated, and the timing of initiation post-operatively is critical, particularly after CABG where early administration (within 6 hours) is associated with improved outcomes.