How do I manage a new onset fever?

Management of New Onset Fever

For a patient with new onset fever, do not routinely use antipyretic medications solely to reduce temperature, as this does not improve mortality or clinical outcomes; instead, focus on identifying and treating the underlying cause through systematic evaluation. 1, 2

Initial Assessment and Temperature Measurement

Accurate temperature measurement is critical for diagnosis and management:

• Use oral or rectal thermometry when central monitoring (pulmonary artery catheter, bladder catheter, or esophageal thermistor) is unavailable 1, 2
• Avoid tympanic membrane, temporal artery, or axillary measurements as they are unreliable and show poor agreement with core temperature 1
• Fever is defined as a single temperature measurement ≥38.3°C 2

Diagnostic Workup

The priority is identifying the fever source, not treating the number on the thermometer:

• Obtain a chest radiograph, as pneumonia is the most common cause of fever in hospitalized patients 1, 2
• Collect blood cultures (at least two sets, 60 mL total) before initiating antimicrobials 2, 3
• Perform complete blood count, liver function tests, urinalysis, and urine culture 3
• Consider serum procalcitonin and endotoxin activity assay to distinguish infectious from non-infectious causes 1, 3

For specific clinical scenarios:

• Recent abdominal/thoracic/pelvic surgery without obvious source: Obtain CT imaging in collaboration with surgical service 1, 2
• Abdominal symptoms or liver function abnormalities: Perform formal bedside diagnostic ultrasound 1, 2
• Recent travel to tropical regions: Consider malaria testing with blood smear 1, 3

Antipyretic Use: When and Why

The evidence is clear that routine antipyretic use does not improve outcomes:

• A meta-analysis of 13 RCTs (1,963 patients) showed fever management reduced temperature but did not improve 28-day mortality (RR 1.03; 95% CI 0.79-1.35), hospital mortality (RR 0.97; 95% CI 0.73-1.30), or shock reversal 1
• Antipyretics should be avoided for the sole purpose of temperature reduction 1, 2

Use antipyretics only for symptomatic relief:

• If the patient desires comfort from fever-related symptoms (headache, myalgias, malaise), use paracetamol (acetaminophen) as first-line 1, 2
• Paracetamol is preferred over NSAIDs, particularly in COVID-19 or when gastrointestinal tolerance is a concern 1
• When using antipyretics for symptom relief, use pharmacologic agents rather than physical cooling methods (cooling blankets), as medications are more effective and better tolerated 1, 2

Important caveat: Stop antipyretics and seek medical attention if fever worsens or lasts more than 3 days, or if new symptoms develop 4

Antimicrobial Therapy Considerations

If infection is suspected based on clinical presentation:

• Initiate empirical antimicrobial therapy as soon as possible after obtaining cultures, ideally within 1 hour if sepsis is suspected 3
• Tailor antibiotics to the suspected source, local resistance patterns, and patient risk factors for multidrug-resistant organisms 3
• Do not use empiric antimicrobials for fever of unknown origin without evidence of infection, as this has not been shown to be effective and may obscure diagnosis 5

Special Populations Requiring Different Approaches

Neutropenic patients with fever:

• Require immediate hospitalization and empiric therapy with vancomycin plus antipseudomonal antibiotics 2, 3
• Consider fungal infections if fever persists despite antibacterial therapy 3

Critically ill patients:

• Require more aggressive evaluation including consideration of "silent" sources and invasive diagnostic procedures if non-invasive tests are unrevealing 3
• May have blunted fever responses if elderly or immunosuppressed, so monitor for other signs of infection 6

Common Pitfalls to Avoid

• Treating the thermometer reading rather than the patient: Focus on identifying and treating the underlying cause, not the fever itself 2
• Delaying antimicrobial therapy when infection is likely: This increases mortality risk 2, 3
• Using unreliable temperature measurement methods (tympanic, temporal, axillary) for clinical decision-making 1, 2
• Overlooking non-infectious causes: Drug-induced fever, malignant hyperthermia, neuroleptic malignant syndrome, and venous thromboembolism can all present with fever 1, 5
• Failing to consider travel history: Malaria can be fatal if diagnosis is delayed in returning travelers 1, 3

When to Escalate Care

Seek immediate emergency evaluation if fever is accompanied by:

• Signs of sepsis (hypotension, altered mental status, tachypnea, elevated lactate) 3
• Severe muscle rigidity suggesting malignant hyperthermia or neuroleptic malignant syndrome 1, 3
• Confusion or neurological changes, particularly after recent travel to malaria-endemic areas 1