Should stroke patients on 300mg Aspirin (acetylsalicylic acid) receive Venous Thromboembolism (VTE) prophylaxis?

VTE Prophylaxis in Stroke Patients on 300mg Aspirin

Stroke patients on 300mg aspirin should still receive pharmacologic VTE prophylaxis with heparin or LMWH unless their bleeding risk outweighs the benefits. 1

Risk Assessment and Decision Making

Stroke patients are at high risk for venous thromboembolism (VTE), with up to 75% developing VTE without prophylaxis and a 20% chance of pulmonary embolism (PE) in hemiplegic patients 1. The decision to initiate VTE prophylaxis should be based on:

1. Individual VTE risk factors:

   • Immobility
   • Hemiparesis
   • Advanced age
   • Inherited conditions (factor V Leiden, prothrombin gene mutation, etc.)
   • Acquired risk factors (cancer, central venous catheter, etc.)

2. Bleeding risk factors:

   • Concomitant use of aspirin (already present in these patients)
   • Prior stroke or intracerebral hemorrhage
   • Older age
   • Hypertension
   • Liver disease
   • Severe chronic kidney disease
   • Bleeding disorders

Evidence-Based Recommendations

The American College of Physicians guidelines strongly recommend pharmacologic prophylaxis with heparin or related drugs for VTE in medical patients, including stroke patients, unless bleeding risk outweighs benefits 1. This recommendation is based on moderate-quality evidence.

For stroke patients specifically:

• Prophylactic heparin reduces PE risk (absolute decrease of 3 events per 1000 persons)
• However, it increases major bleeding risk (absolute increase of 6 events per 1000 persons) 1

The American College of Chest Physicians guidelines similarly recommend prophylactic-dose heparin for stroke patients with restricted mobility 1. The evidence shows:

• LMWH is superior to UFH in reducing symptomatic DVT (7 fewer per 1000) and PE (8 fewer per 1000)
• Bleeding risks are comparable between LMWH and UFH

Aspirin's Role in VTE Prophylaxis

Aspirin alone is not considered adequate VTE prophylaxis for stroke patients:

1. The Women's Health Study showed aspirin (100mg) provided no significant benefit for VTE prevention in healthy women 2
2. In orthopedic patients, aspirin was found to be ineffective for VTE prophylaxis in Achilles tendon injuries (6.4% VTE rate with aspirin vs. 6.3% without) 3
3. While aspirin is effective for preventing recurrent ischemic stroke 4, it does not provide adequate protection against VTE

Practical Approach

1. For ischemic stroke patients on 300mg aspirin:

   • Add prophylactic-dose LMWH (preferred) or UFH unless contraindicated
   • Initiate within 48 hours of stroke onset
   • Continue throughout hospitalization or until fully mobile
   • LMWH dose: 3,000-6,000 IU daily
   • UFH dose: 10,000-15,000 units daily

2. For hemorrhagic stroke patients on 300mg aspirin:

   • Consider mechanical prophylaxis initially
   • Reassess for pharmacologic prophylaxis when bleeding risk stabilizes

3. Combination approach:

   • Dual pharmacological (aspirin + heparin) and mechanical therapy is recommended
   • Early mobilization when clinically appropriate

Important Caveats

• The 300mg aspirin dose being used for stroke treatment does not replace the need for dedicated VTE prophylaxis
• Concomitant use of aspirin increases bleeding risk but does not eliminate the need for heparin prophylaxis
• Delay prophylactic heparin for at least 24 hours after thrombolytic therapy 1
• LMWH is preferred over UFH due to better efficacy profile and similar bleeding risk 1
• Consider mechanical prophylaxis with intermittent pneumatic compression devices in patients with high bleeding risk 1

Monitoring

• Regular assessment of bleeding risk
• Monitor for signs and symptoms of DVT/PE
• Adjust prophylaxis strategy if bleeding complications occur

The benefits of VTE prophylaxis generally outweigh the risks in stroke patients, even those already on aspirin therapy, unless specific contraindications exist.