What is the management approach for a patient with a native Arteriovenous Fistula (AVF) presenting with fever of unknown origin?

Management of Fever of Unknown Origin in a Patient with Native Arteriovenous Fistula

For a patient with a native arteriovenous fistula (AVF) presenting with fever of unknown origin, the management approach should include obtaining blood cultures from both the AVF and a peripheral vein, followed by targeted antimicrobial therapy based on culture results, with AVF removal only if there are signs of severe infection or failed antimicrobial treatment.

Initial Diagnostic Approach

• Obtain two sets of blood cultures: one from the AVF and one from a peripheral vein to allow calculation of differential time to positivity 1
• Collect at least 60 mL of blood total from different anatomical sites without time intervals between collections 2
• Examine the AVF site thoroughly for signs of infection including erythema, tenderness, purulence, or drainage 2, 1
• Assess for severity of illness (presence of hypotension, organ dysfunction) to guide management decisions 1
• Consider culture of samples obtained from the insertion site if available 2

Diagnostic Workup for Fever of Unknown Origin

• Perform chest radiography as part of the initial evaluation 2, 3
• Evaluate inflammatory markers, including C-reactive protein and erythrocyte sedimentation rate 3
• If the patient has pyuria, replace the urinary catheter (if present) and obtain urine cultures 2
• For patients with respiratory symptoms, consider testing for viral pathogens using nucleic acid amplification test panels 2
• If initial evaluation is unrevealing, consider 18F-fluorodeoxyglucose positron emission tomography/CT if transport risk is acceptable 2, 3

Management Algorithm Based on Severity

For Mild to Moderate Illness (no hypotension or organ failure):

• Consider empiric antimicrobial therapy while awaiting culture results 1
• If blood cultures are positive:
  • For uncomplicated infections without exit site or tunnel infection, attempt treatment with systemic antibiotics without AVF removal 2
  • Use both systemic and antimicrobial lock therapy if the patient has limited vascular access options 2
• If fever persists with no other source identified, consider removal and culture of the vascular access 1

For Severe Illness (hypotension, signs of organ failure):

• Remove the vascular access, culture the tip, and insert a new access at a different site 1
• Initiate broad-spectrum antimicrobial therapy immediately 1
• The AVF should be removed if the patient has unexplained sepsis or erythema overlying the insertion site or purulence at the insertion site 2

Pathogen-Specific Considerations

• Staphylococcus species (both S. aureus and coagulase-negative staphylococci) are the most common pathogens in vascular access infections 2, 1
• If a single blood culture grows coagulase-negative Staphylococcus, obtain additional cultures before initiating antimicrobial therapy to confirm true bloodstream infection 2
• For S. aureus infections, consider nasal culture and treatment of carriers with mupirocin ointment 1
• Treat AVF infections with antibiotics for a total of 6 weeks, analogous to subacute bacterial endocarditis 2

Important Caveats and Pitfalls

• Avoid unnecessary removal of vascular access as most suspected infections are sterile (71% in one series) 1
• Thrombolytic agents (e.g., urokinase) should not be used as adjunctive therapy for vascular access infections 2, 1
• Avoid empiric antibiotics or steroids in patients with fever of unknown origin without clear evidence of infection 4, 5
• Be aware that AVF infections, though rare, are potentially lethal due to the impaired immunologic status of long-term dialysis patients 2
• Infections at the AV anastomosis require immediate surgery with resection of the infected tissue 2

Follow-up and Monitoring

• For patients with positive blood cultures, repeat blood cultures should be obtained 72 hours after initiation of appropriate therapy 2
• If blood cultures remain positive after 72 hours of appropriate therapy, the AVF should be removed 2
• Monitor for metastatic complications of access-related bacteremia, which can be serious 2
• For infections at cannulation sites, cease cannulation at that site and rest the arm 2