When can aspirin (acetylsalicylic acid) be resumed after a subdural hematoma?

When to Resume Aspirin After Subdural Hematoma

Aspirin should be restarted 1-2 weeks after subdural hematoma in standard-risk patients, with earlier resumption at 7-10 days for very high thrombotic risk conditions (mechanical heart valves, recent stent placement), and delayed resumption at 3-4 weeks or longer for high hemorrhagic risk features (lobar location, multiple microbleeds). 1

Immediate Management

• Discontinue aspirin immediately upon diagnosis of subdural hematoma to prevent hematoma expansion 2, 1
• The acute period of highest risk for expansion is the first 1-2 weeks after hemorrhage 2, 1
• Obtain baseline CT or MRI to document hemorrhage extent before making any decisions about resumption 1

Risk Stratification Framework

Very High Thrombotic Risk (Restart at 7-10 Days)

• Mechanical heart valves - highest thrombotic risk condition 1
• Atrial fibrillation with CHADS₂ score ≥4 1
• Recent acute coronary syndrome or coronary stent placement (especially within 6 months) 2, 1
• History of prior stroke or TIA while off antiplatelet therapy 1

For these patients, obtain repeat brain imaging at 7-10 days to confirm hemorrhage stability before restarting 1

Standard Risk (Restart at 1-2 Weeks)

• Wait at least 1-2 weeks for patients without very high thrombotic risk or high hemorrhagic risk features 2, 1
• Confirm hemorrhage stability with repeat CT or MRI before restarting 1
• Resume with low-dose aspirin 81 mg daily - do not use higher doses 3

High Hemorrhagic Risk (Restart at 3-4 Weeks or Avoid)

• Lobar location of subdural hematoma suggests possible cerebral amyloid angiopathy with higher rebleeding risk 1
• Multiple microbleeds on MRI indicate underlying microangiopathy 1
• Elderly patients with lobar hemorrhage are at particularly high risk for amyloid angiopathy 1

For these patients, delay restart to 3-4 weeks minimum or consider avoiding aspirin altogether if thrombotic risk is not prohibitive 1

Practical Resumption Algorithm

Step 1: Timing Decision

• Very high thrombotic risk → 7-10 days 1
• Standard risk → 1-2 weeks 2, 1
• High hemorrhagic risk → 3-4 weeks or longer 1

Step 2: Mandatory Pre-Restart Imaging

• Never restart without repeat imaging - clinical assessment alone is insufficient 1
• Confirm hemorrhage stability or resolution on CT or MRI 1

Step 3: Dosing Strategy

• Use low-dose aspirin 81 mg daily for maintenance 3
• Do not use loading doses when restarting after hemorrhage 3
• If patient was on dual antiplatelet therapy, restart aspirin alone initially - do not resume both agents simultaneously 1

Special Considerations

Hemorrhagic Transformation of Ischemic Stroke

• This represents a different pathophysiology than primary subdural hematoma 1
• Aspirin may be continued if the hemorrhagic transformation is asymptomatic and minimal, depending on the underlying indication 2, 1

Chronic Subdural Hematoma

• Research shows that early aspirin resumption might be safe in chronic subdural hematoma, though most neurosurgeons discontinue for at least 7 days perioperatively 4
• The median restart time in clinical practice is approximately 2-4 weeks after trauma for aspirin 5

Anticoagulation vs. Antiplatelet Considerations

• If patient requires both anticoagulation and antiplatelet therapy, the thrombotic risk can be managed with aspirin alone initially rather than resuming both simultaneously 1
• Patients requiring anticoagulation face higher thromboembolic risk (5.8% for anticoagulation alone, 16% for dual therapy) compared to antiplatelet therapy alone (1.9%) 5

Critical Pitfalls to Avoid

• Never delay obtaining repeat imaging before restart - this is mandatory to confirm hemorrhage stability 1
• Do not restart both antiplatelet agents simultaneously if patient was on dual therapy - start with aspirin alone 1
• Do not use higher aspirin doses - standard low-dose 81 mg is appropriate when restarting 3
• Do not ignore lobar location or microbleeds - these features mandate delayed or avoided resumption 1
• Do not restart while residual subdural hematoma is large - one study showed 62.5% rebleeding risk with large residual hematomas 6

Evidence Quality Considerations

The strongest evidence comes from the American Heart Association/American Stroke Association guidelines, which recommend waiting 1-2 weeks for the acute period after cerebral hemorrhage before considering antiplatelet resumption 2. The Praxis Medical Insights synthesis provides the most comprehensive algorithm, stratifying by both thrombotic and hemorrhagic risk 1. Research data confirm that aspirin increases subdural hematoma risk by 1.5-fold (95% CI 1.1-2.0), but the absolute risk is low at approximately 1 per 6,500 patients annually 7. Clinical studies show that restarting anticoagulation with residual subdural hematoma carries a 41.2% rebleeding risk, climbing to 62.5% if the remnant is large 6.