What is the role of aspirin (acetylsalicylic acid) in preventing major vascular events in patients undergoing noncardiac surgery, according to the Perioperative Ischemic Evaluation-2 (POISE 2) trial?

POISE-2 Trial: Aspirin Does Not Prevent Major Vascular Events in Noncardiac Surgery

The POISE-2 trial definitively demonstrated that aspirin (200 mg preoperatively, then 100 mg daily) does not reduce death or myocardial infarction in patients undergoing noncardiac surgery, but significantly increases major bleeding risk. 1

Key Trial Findings

The POISE-2 trial randomized 10,010 patients at risk for vascular complications undergoing noncardiac surgery to aspirin versus placebo in two strata 1:

• Initiation stratum: 5,628 patients not previously taking aspirin
• Continuation stratum: 4,382 patients already on aspirin therapy

Primary Outcome: No Cardiovascular Benefit

The composite of death or nonfatal myocardial infarction at 30 days occurred in:

• 7.0% in the aspirin group (351 of 4,998 patients)
• 7.1% in the placebo group (355 of 5,012 patients)
• Hazard ratio: 0.99 (95% CI: 0.86-1.15; P=0.92) 1

This finding was consistent across both the initiation and continuation strata, meaning aspirin provided no protection whether patients were starting it new or continuing chronic therapy. 1

Harm: Increased Bleeding Risk

Major bleeding occurred significantly more often with aspirin:

• 4.6% in the aspirin group (230 patients)
• 3.8% in the placebo group (188 patients)
• Hazard ratio: 1.23 (95% CI: 1.01-1.49; P=0.04) 1

The bleeding increase was particularly pronounced in the initiation stratum (4.6% vs 3.5%; HR 1.34,95% CI: 1.03-1.74), though not statistically significant in the continuation stratum (4.6% vs 4.1%; HR 1.11,95% CI: 0.84-1.48). 2

Clinical Implications Based on Current Guidelines

For Patients WITHOUT Coronary Stents

The ACC/AHA guidelines now classify aspirin initiation or continuation as Class III: No Benefit in patients undergoing elective noncardiac noncarotid surgery who have not had previous coronary stenting, unless the risk of ischemic events outweighs the risk of surgical bleeding. 2

This represents a fundamental shift: aspirin should not be routinely used for perioperative cardiovascular protection in nonstented patients. 2

Important Exceptions Where Continuation May Be Reasonable

The ACC/AHA acknowledges that continuation may still be reasonable in specific high-risk populations excluded or underrepresented in POISE-2 2:

• High-risk coronary artery disease patients where cardiovascular event risk clearly outweighs bleeding risk
• Cerebrovascular disease patients (carotid endarterectomy patients were excluded from POISE-2)
• Patients with recent acute coronary syndrome (only 23% of POISE-2 patients had known prior CAD)

For these patients, the decision to continue aspirin should involve consensus between surgeon, anesthesiologist, cardiologist, and patient, weighing individual bleeding versus thrombotic risk. 2

For Patients WITH Coronary Stents

POISE-2 specifically excluded patients within 6 weeks of bare-metal stent (BMS) placement or within 1 year of drug-eluting stent (DES) placement, and had too few stented patients outside these intervals to draw firm conclusions. 2

In stented patients, aspirin management follows different principles 2:

• Class I recommendation: Continue dual antiplatelet therapy (DAPT) if urgent surgery occurs within 4-6 weeks of BMS or DES implantation, unless bleeding risk outweighs stent thrombosis prevention benefit
• Class I recommendation: If P2Y12 inhibitor must be stopped, continue aspirin if possible and restart P2Y12 inhibitor as soon as possible postoperatively
• Elective surgery should be delayed until 30 days after BMS and 365 days after DES when possible

Vascular Surgery Subgroup Analysis

A dedicated POISE-2 substudy examined 603 patients undergoing vascular surgery (319 continuation stratum, 284 initiation stratum) 3:

• Aneurysm repair: Primary outcome occurred in 13.7% with aspirin vs 9.0% with placebo (HR 1.48,95% CI: 0.71-3.09)
• Occlusive vascular disease surgery: Primary outcome occurred in 15.8% with aspirin vs 13.6% with placebo (HR 1.16,95% CI: 0.62-2.17)
• No significant interaction for type of surgery (P=0.294) or aspirin stratum (P=0.623)

These results suggest the overall POISE-2 findings apply equally to vascular surgery—perioperative aspirin withdrawal did not increase cardiovascular or vascular occlusive complications. 3

Venous Thromboembolism Findings

POISE-2 also evaluated aspirin's effect on VTE prevention 4:

• VTE occurred in 1.1% with aspirin vs 1.2% with placebo (HR 0.89,95% CI: 0.61-1.28)
• 65.4% of patients received concomitant anticoagulant prophylaxis
• Pooled analysis with other trials showed aspirin reduced symptomatic VTE (OR 0.71,95% CI: 0.56-0.89), but this benefit must be weighed against bleeding risk

Current ACCP Guidelines Recommendations

The 2022 American College of Chest Physicians guidelines, incorporating POISE-2 data, provide specific management recommendations 2:

For patients on aspirin requiring elective noncardiac surgery:

• If aspirin interruption is chosen, stop ≤7 days (not 7-10 days) before surgery (Conditional Recommendation)
• This shorter interruption window minimizes thrombotic risk while allowing platelet function recovery

Critical Methodological Considerations

Several POISE-2 design features limit generalizability 2:

• Postoperative NSAID use occurred in 37% of patients, potentially impairing aspirin's cardioprotective effects
• Aspirin was stopped 3-7 days preoperatively in the continuation stratum, not truly testing "continuation"
• Low prevalence of high-risk CAD (only 23% had known prior CAD)
• Exclusion of carotid endarterectomy patients
• Exclusion of recent stent patients (within 6 weeks BMS, 1 year DES)

Common Pitfalls to Avoid

Do not routinely stop aspirin in patients with coronary stents placed within the past year without cardiology consultation—stent thrombosis risk is highest in the first 4-6 weeks and remains elevated up to 6-12 months, particularly for DES. 2

Do not assume POISE-2 results apply to patients with very high-risk coronary disease or recent cerebrovascular events—these populations were underrepresented or excluded, and individualized assessment remains necessary. 2

Do not initiate aspirin perioperatively for cardiovascular protection in previously aspirin-naive patients—POISE-2 showed no benefit and increased bleeding in the initiation stratum. 1

Do not bridge with heparin when stopping aspirin—there is no evidence this reduces thrombotic risk and it increases bleeding complications. 5