What is the complete algorithm for managing fever?

Fever Management Algorithm

Initial Assessment and Risk Stratification

For any patient presenting with fever (≥38°C), immediately assess hemodynamic stability, oxygen saturation, mental status, and presence of organ dysfunction to determine if this is simple fever versus sepsis/septic shock requiring immediate resuscitation. 1

Critical First Steps (Within First Hour)

• Obtain vital signs including core temperature (oral temperatures have poor sensitivity; use rectal, bladder, or esophageal routes for accurate core measurement) 2
• Assess for hypotension: In children aged 1-10 years, hypotension is SBP <(70 + (2 × age in years)) mmHg; in patients >10 years, SBP <90 mmHg 1
• Evaluate oxygen saturation: SpO2 <90% on room air indicates significant respiratory compromise 1
• Check mental status: Altered mental status lasting ≥24 hours with fever suggests encephalitis and requires urgent neurologic evaluation 1

Immediate Blood Cultures and Diagnostic Testing

• Obtain blood cultures before antibiotics in any patient with suspected sepsis, hemodynamic instability, or when results will change management 1, 2
• Complete blood count with differential, complete metabolic panel, lactate, and inflammatory markers (CRP, procalcitonin if available) 1, 3
• Chest radiography only if respiratory symptoms present (cough, dyspnea, hypoxia) 1, 3
• Urinalysis and urine culture if urinary symptoms present or no other source identified 3

Empiric Antibiotic Decision Algorithm

For Hemodynamically Stable Patients WITHOUT Neutropenia

Do NOT start empiric antibiotics immediately in well-appearing, hemodynamically stable patients without neutropenia or immunosuppression. 3, 4

• Observe for 24-48 hours with close monitoring if patient meets low-risk criteria: normal vital signs, no dehydration, well-appearing, no respiratory distress 3, 4
• Reassess every 4-6 hours for clinical deterioration 1
• Start antibiotics only if: blood cultures become positive, patient develops hemodynamic instability, or clinical deterioration occurs 3, 4

For Hemodynamically Unstable Patients OR Neutropenic Patients (ANC <500 cells/mm³)

Immediately initiate broad-spectrum antibiotics after obtaining blood cultures. 1, 5

First-Line Antibiotic Choice:

• Ceftriaxone 2g IV every 24 hours is the optimal empiric choice for undifferentiated fever, as it requires no dose adjustment in renal impairment, provides broad Gram-negative and Gram-positive coverage, and has convenient once-daily dosing 5
• Alternative: Piperacillin-tazobactam 4.5g IV every 6 hours for broader coverage including Pseudomonas (requires dose adjustment if CrCl <20 mL/min to every 8 hours) 5

Critical Dosing Principle:

Always administer the full loading dose regardless of renal function—this is the most critical error to avoid, as delays in achieving therapeutic levels increase mortality in septic patients. 5

Antibiotics to Avoid:

• Never use aminoglycosides (gentamicin, tobramycin, amikacin) in patients with renal impairment due to direct nephrotoxicity 5
• Avoid nitrofurantoin in renal patients (produces toxic metabolites causing peripheral neuritis) 5
• Do not empirically add vancomycin for persistent fever alone without documented Gram-positive infection, as this increases nephrotoxicity without proven benefit 5

Fever Symptomatic Management

Antipyretic Therapy

Use paracetamol (acetaminophen) 1000mg as first-line antipyretic therapy; do not use antipyretics with the sole aim of reducing temperature, only when fever causes patient discomfort or other symptoms requiring relief. 1, 6

• Paracetamol 1000mg orally/IV is preferred over NSAIDs, particularly in COVID-19 or viral infections 1
• Paracetamol/Ibuprofen combination (500mg/150mg) may be more effective for bacterial fever at 1 hour, though both are equivalent at 2 hours 6
• Continue antipyretics only while symptoms persist, not routinely 1

Hydration

• Advise regular fluid intake (no more than 2 liters per day to avoid overhydration) 1
• Monitor urine output: oliguria is <0.5 mL/kg/hour for 8 hours in children 1

Persistent Fever Management (48-72 Hours)

If Patient Remains Febrile at 48 Hours

For clinically stable patients on appropriate antibiotics, continue the same regimen and do not switch based solely on persistent fever—median time to defervescence is 2-5 days. 1, 5

• Reassess for infectious source: repeat physical examination, review imaging, consider CT chest/abdomen if CRP rising 1
• Blood cultures should be negative at 48 hours before considering antibiotic discontinuation 5

If Patient Deteriorating at 48 Hours

• Seek infectious disease consultation immediately 1
• Consider antifungal therapy if fever persists >4-6 days with rising inflammatory markers, particularly in neutropenic patients 1
• High-resolution chest CT if invasive aspergillosis suspected (look for nodules with halos or ground-glass changes) 1
• Consider voriconazole or liposomal amphotericin B for presumed aspergillosis 1

Special Populations

Neurogenic Fever (Post-Traumatic Brain Injury)

Neurogenic fever (core temperature >37.5°C without sepsis) should be promptly treated with controlled normothermia targeting 36.0-37.5°C using automated feedback-controlled temperature management devices, as uncontrolled fever precipitates secondary brain injury. 1

Febrile Neutropenia

• Continue antibiotics until ANC >500 cells/mm³ AND patient afebrile for 48 hours 1
• In high-risk acute leukemia patients, continue antibiotics for up to 10 days or until neutrophil recovery 1

Pediatric Patients

• Children <3 years with fever ≥39°C and WBC ≥15,000/mm³ have higher risk of occult bacteremia and require closer monitoring 3
• Hypotension definition varies by age: use SBP <(70 + (2 × age)) mmHg for ages 1-10 years 1

Antibiotic Discontinuation Criteria

Discontinue antibiotics when ALL of the following are met: 1, 5

• Blood cultures negative at 48-72 hours 5
• Patient afebrile for ≥24 hours (≥48 hours in neutropenic patients) 1, 5
• Neutrophil count ≥0.5 × 10⁹/L (if applicable) 1
• Clinical stability maintained 5

Exception:

In neutropenic patients with persistent fever despite neutrophil recovery, obtain infectious disease consultation before discontinuing antibiotics. 1

Critical Pitfalls to Avoid

• Never reduce the initial loading dose of antibiotics based on renal function—this delays therapeutic levels and increases mortality 5
• Do not obtain chest X-ray routinely—only if respiratory symptoms present 1, 3
• Do not diagnose "viral syndrome" prematurely in children with persistent fever without appropriate evaluation 4
• Do not switch antibiotics at 48 hours based solely on persistent fever if patient is clinically stable 1, 5
• Do not use oral temperatures alone—they have poor sensitivity; obtain core temperature if fever suspected 2