From the Guidelines
Arthrocentesis with a high white blood cell (WBC) count typically requires prompt antibiotic therapy for suspected septic arthritis, with empiric antibiotics started immediately after obtaining synovial fluid cultures. The management of such cases involves a comprehensive approach to diagnose and treat the underlying infection. According to the guidelines by the Infectious Diseases Society of America 1, a diagnostic arthrocentesis should be performed in all patients with suspected acute prosthetic joint infection (PJI) unless the diagnosis is evident clinically and surgery is planned, and antimicrobials can be safely withheld prior to surgery.
Key considerations in the management include:
- Starting empiric antibiotics immediately after obtaining synovial fluid cultures, with a regimen such as vancomycin 15-20 mg/kg IV every 12 hours plus either ceftriaxone 1-2 g IV daily or cefepime 2 g IV every 8-12 hours, as suggested by clinical practice 1.
- Ensuring joint drainage, either through repeated needle aspiration or surgical intervention, depending on the joint involved and clinical severity.
- Obtaining orthopedic consultation urgently.
- Implementing pain management with analgesics and joint rest as important supportive measures.
- Adjusting the antibiotic regimen based on culture results, with typical treatment duration of 2-4 weeks for uncomplicated cases and 4-6 weeks for more complex infections.
It's crucial to note that a high synovial WBC count (>50,000 cells/mm³) strongly suggests infection, though crystal arthropathies can sometimes present with elevated counts 1. Serial joint aspirations may be necessary to monitor treatment response, with decreasing WBC counts indicating improvement. The guidelines emphasize the importance of synovial fluid analysis, including a total cell count and differential leukocyte count, as well as culture for aerobic and anaerobic organisms 1.
From the Research
Arthrocentesis with High WBC Count Management
- The management of arthrocentesis with a high White Blood Cell (WBC) count involves prompt diagnosis and treatment to prevent permanent morbidity and mortality 2.
- Risk factors for septic arthritis, which can cause a high WBC count, include age older than 80 years, diabetes mellitus, rheumatoid arthritis, recent joint surgery, hip or knee prosthesis, skin infection, and immunosuppressive medication use 2.
- Synovial fluid studies are required to confirm the diagnosis of septic arthritis, and history and Gram stain aid in determining initial antibiotic selection 2.
- Empiric antibiotic therapy should be initiated if there is clinical concern for septic arthritis, and oral antibiotics can be given in most cases because they are not inferior to intravenous therapy 2.
- The total duration of therapy ranges from two to six weeks; however, certain infections require longer courses 2.
Diagnostic Considerations
- Physical examination findings and serum markers, including erythrocyte sedimentation rate and C-reactive protein, are helpful in the diagnosis but are nonspecific 2.
- Imaging modalities can be used to guide patient selection for percutaneous aspiration and to safely perform arthrocentesis to assess for infection in both native and prosthetic joints 3.
- Consideration for microorganisms such as Neisseria gonorrhoeae, Borrelia burgdorferi, and fungal infections should be based on history findings and laboratory results 2.
Treatment Approach
- Septic arthritis is an emergency that can lead to rapidly progressive, irreversible joint damage, and prompt treatment is essential 3.
- Despite the urgency associated with this diagnosis, there remains a lack of consensus regarding many aspects of the management of native and periprosthetic joint infections 3.
- Staphylococcus aureus is the most common pathogen isolated in septic arthritis; however, other bacteria, viruses, fungi, and mycobacterium can cause the disease 2.