From the Guidelines
The approach to a patient with fever requires a systematic evaluation to identify the underlying cause and provide appropriate management, starting with a detailed clinical history and physical examination, as recommended by the Society of Critical Care Medicine and the Infectious Diseases Society of America guidelines 1.
Clinical History and Findings
Begin by taking a detailed clinical history, including the fever pattern (continuous, intermittent, remittent), duration, associated symptoms, recent travel, medication use, and past medical conditions. Physical examination should be comprehensive, focusing on potential sources of infection such as the respiratory system, urinary tract, skin, and abdomen. Vital signs including temperature, heart rate, blood pressure, and respiratory rate should be documented.
Investigations
Initial investigations typically include:
- Complete blood count
- C-reactive protein
- Blood cultures (before starting antibiotics) 1
- Urinalysis
- Chest X-ray
- Other tests guided by clinical suspicion, such as a chest radiograph for patients who develop fever during ICU stay 1
- CT scan (in collaboration with the surgical service) for patients who have recently undergone thoracic, abdominal, or pelvic surgery and an etiology is not readily identified by initial workup 1
Management
Management involves treating the underlying cause while providing supportive care.
- Antipyretics like acetaminophen or ibuprofen can provide symptomatic relief, but their use should be guided by the patient's clinical condition and the potential benefits and risks, as suggested by the guidelines 1.
- Adequate hydration is essential.
- Empiric antibiotics may be initiated in suspected bacterial infections based on the likely source, such as ceftriaxone for community-acquired pneumonia or piperacillin-tazobactam for intra-abdominal infections.
- The antibiotic regimen should be narrowed once culture results are available.
- Severe cases with signs of sepsis require aggressive fluid resuscitation, early antibiotics, and close monitoring.
Specific Considerations
- For critically ill patients with fever, avoiding routine use of antipyretic medications for the specific purpose of reducing the temperature is recommended, unless the patient values comfort by reducing temperature 1.
- For patients who develop fever during ICU stay, performing a chest radiograph is recommended 1.
- For patients who have recently undergone thoracic, abdominal, or pelvic surgery, performing CT (in collaboration with the surgical service) as part of a fever workup if an etiology is not readily identified by initial workup is recommended 1.
From the Research
Clinical History
- A comprehensive history is essential in evaluating a patient with fever, as it helps to narrow down potential etiologies 2, 3
- The history should include information about the patient's travel history, exposure to infectious agents, and any underlying medical conditions 3, 4
- A detailed medical history is crucial in identifying the cause of fever, especially in patients with fever and rash 4
Clinical Findings
- A thorough physical examination is necessary to identify any localizing signs or symptoms that may indicate the source of the fever 2, 3
- The physical examination should include a careful evaluation of the patient's vital signs, including temperature, blood pressure, and heart rate 5
- A focused physical examination can help to identify the source of infection in patients with neutropenia and fever 5
Investigations
- Initial testing should include an evaluation for infectious etiologies, malignancies, inflammatory diseases, and miscellaneous causes such as venous thromboembolism and thyroiditis 2
- Laboratory tests should be guided by the most likely diagnoses based on the presenting clinical syndrome 6
- Imaging studies such as computed tomography (CT) and magnetic resonance imaging (MRI) may be useful in evaluating patients with fever of unknown origin 3
- In some cases, invasive tests such as tissue biopsy may be necessary to reach a diagnosis 2
Approach and Management
- A focused diagnostic approach based on clinical clues from the history, physical examination, and laboratory tests is essential in evaluating patients with fever of unknown origin 6
- Empiric antimicrobial therapy should be avoided except in patients who are neutropenic, immunocompromised, or critically ill 2
- A thorough history, physical examination, and standard laboratory testing remain the basis of the initial evaluation of the patient with fever of unknown origin 3
- Meticulous evaluation of patients with neutropenia and fever may be sufficient to diagnose most sources of infection, but a significant number of patients without an identifiable focus may have bacteremia 5