What is the approach to evaluating and managing a patient with a fever?

Approach to Evaluating and Managing Fever in Patients

The evaluation of a new fever in a patient should begin with a careful clinical assessment rather than automatic orders for laboratory and radiologic tests, followed by a directed, cost-conscious approach to obtaining cultures and imaging studies if indicated by the initial evaluation. 1

Initial Assessment

Temperature Measurement

• Preferred methods:
  • Central temperature monitoring (when available): pulmonary artery catheter thermistors, bladder catheter thermistors, or esophageal balloon thermistors 1
  • For patients without central monitoring devices: oral or rectal temperatures 1
• Avoid less reliable methods: axillary, tympanic membrane, temporal artery, or chemical dot thermometers 1

Definition of Fever

• Generally defined as temperature >38°C (100.9°F) 1
• In elderly patients (>65 years): single oral temperature >37.8°C or repeated measurements >37.2°C (oral) or >37.5°C (rectal) 1

Clinical Evaluation

• History: Recent procedures, antibiotic exposure, presence of indwelling devices, immunosuppression status, travel history
• Physical examination: Focus on:
  • Skin/soft tissue (wounds, catheters, rashes)
  • Respiratory system (cough, sputum, respiratory distress)
  • Abdomen (tenderness, distension)
  • Neurological status (altered mental status, focal deficits)

Diagnostic Workup

Initial Laboratory Studies

• Complete blood count (CBC) with differential 2
• Basic metabolic panel
• Liver function tests if abdominal symptoms or abnormal exam

Microbiological Studies

Blood Cultures

• Obtain at least two sets of blood cultures (ideally 60 mL total) from different anatomical sites 1
• For patients with central venous catheters:
  • Draw simultaneous cultures from the catheter and peripherally to calculate differential time to positivity 1
  • Sample at least two lumens if central line cultures are indicated 1

Respiratory Evaluation

• Chest radiograph for all patients with suspected respiratory infection 1
• For patients with abnormal chest radiograph:
  • Consider thoracic bedside ultrasound when expertise is available 1
  • Obtain respiratory secretions for culture before initiating or changing antibiotics 1
• For patients with suspected pneumonia or respiratory symptoms:
  • Consider viral pathogen testing using nucleic acid amplification panels 1

Urinary Tract Evaluation

• For patients with urinary catheters and suspected UTI:
  • Replace the catheter and obtain cultures from the newly placed catheter 1

Gastrointestinal Evaluation

• Test for C. difficile in patients with diarrhea who received antibiotics or chemotherapy within 60 days 1

Imaging Studies

Chest Imaging

• Chest radiograph for all patients with new fever 1
• Consider CT scan for:
  • Recent thoracic, abdominal, or pelvic surgery 1
  • Immunocompromised patients with suspected pulmonary infection 1
  • When higher resolution is needed for diagnosis 1

Abdominal Imaging

• Avoid routine abdominal ultrasound in patients without abdominal symptoms or abnormal liver function tests 1
• Perform formal bedside ultrasound for patients with:
  • Recent abdominal surgery
  • Abdominal symptoms
  • Abnormal physical exam
  • Elevated liver enzymes or bilirubin 1

Advanced Imaging

• Consider 18F-FDG PET/CT if other diagnostic tests have failed to establish etiology and transport risk is acceptable 1

Special Considerations

Central Nervous System Evaluation

• Consider lumbar puncture for patients with:
  • Altered consciousness
  • Unexplained focal neurologic signs 1
• Obtain imaging study before lumbar puncture if focal neurologic findings suggest disease above foramen magnum 1

Biomarkers

• For patients with low to intermediate probability of bacterial infection and no clear focus:
  • Consider measuring procalcitonin (PCT) or C-reactive protein (CRP) 1
• Do not use biomarkers to rule out bacterial infection when probability is high 1

Management Approach

Antipyretic Therapy

• Avoid routine use of antipyretics solely for temperature reduction 1
• For patients who value comfort, antipyretics are preferred over nonpharmacologic methods 1

Antimicrobial Therapy

• Base empiric therapy on most likely source of infection identified during evaluation
• Consider local antimicrobial resistance patterns
• Reassess need for continued antimicrobial therapy as diagnostic results return

Common Pitfalls and Caveats

1. Overreliance on automatic fever workups: Avoid reflexive ordering of multiple tests without clinical assessment 1

2. Inadequate blood culture technique: Ensure proper volume (20-30 mL per culture set) and collection from separate sites 1

3. Failure to consider non-infectious causes: Remember that fever can have many non-infectious etiologies including:

   • Medication reactions
   • Thromboembolism
   • Malignancy
   • Post-operative inflammation
   • Autoimmune conditions 1

4. Delayed imaging in appropriate cases: Recognize when advanced imaging is needed despite the challenges of patient transport 1

5. Overlooking device-related infections: Always consider indwelling devices as potential sources of fever 1