What is the recommended suppressive treatment for an aortic aneurysm infection?

Suppressive Antibiotic Treatment for Aortic Aneurysm Infection

For aortic aneurysm infections, long-term suppressive antibiotic therapy for 6 weeks to 6 months is recommended, with lifelong suppression considered in selected cases where surgical intervention is not feasible or for patients with retained endovascular devices. 1

Treatment Approach

Primary Management Strategy

1. Team-based approach is essential:

   • Management should involve experts in vascular diseases/surgery, cardiology, interventional radiology, critical care, infectious diseases, and microbiology 1
   • Treatment decisions should be made at a facility with emergency access to these services

2. Surgical intervention remains first-line when feasible:

   • Antimicrobial therapy alone has a reported mortality rate of 60-100% 1
   • Antibiotic-only approach should be reserved for patients who:
     • Are unfit for surgery
     • Refuse surgical intervention
     • Require palliative care

Antimicrobial Therapy Protocol

Duration of Treatment:

• Initial phase: 6 weeks of parenteral antimicrobial therapy post-operatively 1
• Extended phase: Additional 3-6 months of oral antimicrobial therapy may be considered 1
• Lifelong suppression: Appropriate in selected cases, particularly:
  • Patients with retained endovascular devices
  • Patients with rifampin-bonded synthetic grafts
  • Cases involving MRSA, Pseudomonas, or multidrug-resistant organisms
  • Patients with extensive perigraft infection 1

Selection of Antimicrobial Agents:

• Base selection on identification and susceptibilities of the specific microorganism
• Bactericidal therapy should be administered when possible
• Empiric therapy is often necessary as blood cultures may be positive in only 40-50% of patients 1
• Consultation with infectious disease specialists is crucial for regimen selection

Special Considerations

Endovascular Device Infections

• After endovascular therapy (EVT), if there is a retained device, lifelong suppressive antimicrobial therapy should be considered 1
• Infection rates with endovascular abdominal repair are approximately 1%, while TEVAR (thoracic endovascular aortic repair) has higher rates up to 5% 1

Monitoring During Suppressive Therapy

• Regular monitoring of inflammatory markers (erythrocyte sedimentation rate, C-reactive protein)
• Decision to continue long-term suppression should be based on:
  • Microorganism identified
  • Persistence of elevated inflammatory markers
  • Patient's clinical response

Route of Administration

• Oral therapy is preferred for long-term suppression when:
  • Adequate gastrointestinal absorption is expected
  • Bioavailability of the agent is reasonable
• For cases where effective oral agents aren't available, consider intravenous administration 2-3 times weekly 1

Evidence from Clinical Experience

Early studies have shown promising results with antibiotic suppressive therapy in selected patients. In a small case series, patients with abdominal aortic graft infections who were poor surgical candidates survived with indefinite antibiotic suppressive therapy, with the longest survival being 6 years 2.

Pitfalls and Caveats

1. Antibiotic therapy alone is insufficient for most patients:

   • Higher mortality rates compared to surgical intervention (78% vs 0% in one study) 3
   • Cannot reliably stop aneurysm expansion before rupture occurs

2. Organism-specific considerations:

   • Gram-negative infections (particularly Salmonella) are associated with higher risk of early rupture and mortality 4
   • Response to suppressive therapy may vary by organism (potentially more favorable with Salmonella) 5

3. Drug selection challenges:

   • Long-term antibiotic use carries risks of resistance development
   • Some patients may not have safe, effective oral options available
   • Fluoroquinolones, while sometimes needed, should generally be discouraged in patients with aortic aneurysms 1

4. Monitoring requirements:

   • Regular imaging surveillance is essential alongside antibiotic therapy
   • Duplex ultrasound surveillance is recommended for abdominal aortic aneurysms 1
   • CT or MRI is necessary when ultrasound is inadequate 1

In conclusion, while surgical or endovascular intervention remains the standard of care for infected aortic aneurysms, long-term suppressive antibiotic therapy plays a crucial role in management, particularly for patients who cannot undergo definitive surgical treatment or as an adjunct to surgical/endovascular interventions.