Aspirin Therapy in Post-Operative Patients

Introduction to Aspirin Dosage

The American College of Cardiology recommends aspirin to be dosed at 75-162 mg daily for most post-operative indications, with specific dosing regimens for certain surgical scenarios such as coronary artery bypass grafting (CABG) where 100-325 mg daily is recommended 1, 2
The standard maintenance dose of aspirin is 75-162 mg daily, which should be continued indefinitely in all patients unless contraindicated, supported by Level A evidence 1, 2

For patients undergoing CABG, aspirin 100-325 mg daily should be initiated within 6 hours after surgery, and for long-term maintenance, 75-162 mg daily is recommended 1, 2
Higher-dose aspirin (325 mg daily) is recommended initially for certain periods depending on the type of stent used: 1 month for bare metal stent, 3 months for sirolimus-eluting stent, and 6 months for paclitaxel-eluting stent, after which the maintenance dose of 75-162 mg daily should be resumed 2
The following table summarizes the recommended aspirin doses:

Aspirin Dose	Recommendation
100-325 mg	American College of Cardiology recommends for perioperative period
81 mg	Commonly used in practice and considered acceptable by ACC/AHA
75-162 mg	Recommended for long-term maintenance

For patients after acute coronary syndrome (ACS) or PCI with stent placement, aspirin 75-162 mg daily plus a P2Y12 inhibitor should be continued for at least 12 months, and dual antiplatelet therapy (DAPT) should be continued for at least 1 month for bare-metal stent and 3-12 months for drug-eluting stent 1, 2
For patients with Acute Coronary Syndrome (ACS) within 12 months prior to CABG, the American College of Cardiology recommends continuing aspirin (81-100 mg daily) and considering continuing clopidogrel for up to 12 months after ACS 3

The use of warfarin in conjunction with aspirin increases bleeding risk and should be monitored closely 1, 2
Lower doses of aspirin (75-100 mg) have fewer gastrointestinal adverse effects while maintaining efficacy 4
Early postoperative aspirin (within 48 hours) improves saphenous vein graft patency rates, reduces rates of mortality, MI, stroke, renal failure, and bowel infarction, and provides continued protection against graft occlusion up to 1 year after CABG 5

For patients already on aspirin therapy before CABG, aspirin should be continued through the perioperative period, but for patients undergoing elective CABG who are not already taking aspirin, initiation in the immediate preoperative period (<24 hours before surgery) is not recommended 4, 5
The American College of Cardiology recommends that aspirin (100-325 mg daily) should be continued through the perioperative period for patients already on antiplatelet therapy before CABG, and clopidogrel and ticagrelor should be discontinued at least 5 days before elective CABG, while prasugrel should be discontinued at least 7 days before elective CABG 5
For patients intolerant or allergic to aspirin, clopidogrel 75 mg daily is a reasonable alternative, as recommended by the American College of Cardiology 5
Adding clopidogrel to aspirin may be reasonable to improve vein graft patency, particularly for radial artery grafts, but evidence for routine DAPT in stable CAD patients after CABG is insufficient for a strong recommendation 6