When can aspirin (acetylsalicylic acid) be started after a craniotomy in a patient at risk for venous thromboembolism (VTE) or arterial thrombosis?

When to Start Aspirin After Craniotomy

For patients requiring aspirin for secondary prevention (e.g., coronary stents, prior stroke), aspirin should be restarted within 24-72 hours after craniotomy once hemostasis is confirmed, with a target total cessation duration of less than 7-10 days to minimize thrombotic risk. 1, 2

Risk Stratification: Primary vs. Secondary Prevention

The timing of aspirin resumption critically depends on the indication:

• Secondary prevention patients (prior MI, stroke, coronary stents) face significantly elevated thrombotic risk when aspirin is discontinued, with a 2.6-fold increased risk of major cardio- and cerebrovascular events (MACCEs) compared to continuation 2
• Primary prevention patients have lower thrombotic risk and can tolerate longer aspirin cessation periods 3

Evidence-Based Timing Recommendations

For Secondary Prevention (High Thrombotic Risk)

• Resume aspirin within 24-72 hours postoperatively if no evidence of intracranial hemorrhage on imaging 1, 2
• Target total cessation duration <7-10 days to minimize MACCE risk 2
• Obtain brain imaging (CT or MRI) before resumption to confirm absence of residual bleeding 1
• Consider multidisciplinary evaluation involving neurosurgery, cardiology, and hematology for complex cases 1, 4

For Primary Prevention (Lower Thrombotic Risk)

• Can safely delay resumption to approximately 4 weeks post-craniotomy if no chronic alcohol abuse or substantial fall risk exists 1
• Earlier resumption (within days) remains reasonable if bleeding risk is low 3

Special Considerations for Coronary Stent Patients

Patients with recent coronary stents require particularly aggressive management:

• For stents placed <1 month ago, surgery should ideally be postponed or performed only at centers with 24/7 catheterization laboratory availability 4
• For drug-eluting stents <6 months post-implantation, maintain aspirin perioperatively when possible and resume P2Y12 inhibitor (clopidogrel) within 24-72 hours 4, 1
• Aspirin continuation during surgery may be considered for very high-risk stent patients, accepting slightly increased hemorrhagic risk 4, 1

Hemorrhagic Risk Assessment

Perioperative aspirin continuation does not significantly increase hemorrhagic complications in most craniotomy patients:

• Pooled analysis shows 3% hemorrhagic complication rate with aspirin continuation versus 3% with discontinuation (p=0.9) 3
• However, aspirin continuation increases intracranial hemorrhage specifically (10.6% vs 2.9%, p=0.001) in some cohorts 2
• Risk factors for hemorrhagic complications include: age >70 years (OR 2.9), multiple aneurysm operations (OR 2.2), large aneurysms >10mm (OR 4.5), and aspirin continuation (OR 2.6) 2

Thrombotic Risk Without Aspirin

Discontinuing aspirin carries substantial thrombotic consequences:

• Thromboembolic event rate: 3% with continuation vs 6% with discontinuation (p=0.1) 3
• In secondary prevention patients, discontinuation increases MACCE risk with adjusted hazard ratio of 2.58 2
• VTE prophylaxis alone (mechanical or pharmacologic heparin) does not substitute for aspirin's arterial protection 5, 6

Practical Algorithm

1. Preoperatively: Determine if aspirin is for primary or secondary prevention
2. Intraoperatively: Achieve meticulous hemostasis
3. Immediate postoperative period (0-24 hours): Obtain brain imaging to assess for hemorrhage
4. 24-72 hours postoperatively:
   • If secondary prevention + no hemorrhage on imaging → restart aspirin
   • If primary prevention → can delay 2-4 weeks
5. Consider lower dosing: 75-81 mg daily rather than 325 mg when restarting 1, 4

Concurrent VTE Prophylaxis

Aspirin does not replace standard VTE prophylaxis:

• Initiate mechanical prophylaxis (intermittent pneumatic compression) preoperatively or on admission 5
• Add low molecular weight heparin postoperatively when bleeding risk decreases (typically 24-48 hours) for high-risk patients 5
• Continue thromboprophylaxis until full mobilization 5
• Aspirin provides 32% reduction in VTE recurrence but is insufficient as sole prophylaxis in acute postoperative period 6

Critical Pitfalls to Avoid

• Do not empirically withhold aspirin for weeks in secondary prevention patients—this dramatically increases MACCE risk 2
• Do not restart aspirin without imaging confirmation of hemostasis 1
• Do not assume VTE prophylaxis substitutes for aspirin in patients with arterial disease 5, 6
• Do not use aspirin alone for VTE prophylaxis in the immediate postoperative period—mechanical and/or pharmacologic anticoagulation remains necessary 5