What is the recommended acute management of a high‑grade fever (≥39 °C) in an otherwise healthy adult and in children, including appropriate antipyretic selection, dosing, contraindications, and indications for urgent evaluation?

Acute Management of High-Grade Fever (≥39°C)

For high-grade fever (≥39°C) in otherwise healthy adults and children, use acetaminophen (paracetamol) as first-line therapy at weight-appropriate doses every 4-6 hours (maximum 4g/day in adults), with ibuprofen as an alternative or adjunct in children; the primary goal is symptomatic relief and patient comfort rather than normalization of temperature. 1

Antipyretic Selection and Dosing

Adults

• Acetaminophen (paracetamol) 1000 mg orally every 4-6 hours is the first-line agent, with a maximum daily dose of 4 grams 1
• Oral route is preferred for all patients capable of oral intake 1
• Acetaminophen has superior cardiovascular safety compared to NSAIDs and no increased gastrointestinal complications versus placebo 1
• Reduce maximum dose to 2 g/day in patients with hepatic insufficiency, active alcohol use, malnutrition, or fasting 1
• Avoid acetaminophen entirely in acute liver failure 1

Children

• Acetaminophen and ibuprofen are both acceptable for fever management in children 2
• Alternating acetaminophen and ibuprofen every 3-4 hours is appropriate when fever recurs rapidly (within 3 hours despite treatment), which may indicate severe viral response or bacterial superinfection 2
• Never use aspirin in children due to risk of Reye's syndrome 2
• The goal is symptom relief and comfort, not achieving normal temperature 1

Physical Cooling Methods

• Do not use physical cooling methods (tepid sponging, fanning) as they cause patient discomfort without improving outcomes and are not recommended 1
• Cooling devices should only be considered for refractory fevers unresponsive to antipyretics 1
• Simple environmental measures (uncovering the patient, lowering ambient temperature) are acceptable during hot weather 1

Indications for Urgent Evaluation

Infants and Young Children (Age-Specific Thresholds)

Infants < 3 months with fever ≥38°C:

• Require immediate hospitalization and comprehensive evaluation including urinalysis with culture, blood culture, and lumbar puncture 3
• Risk of invasive bacterial infection is 8-13% in this age group 3
• Start empirical parenteral antibiotics (ampicillin plus gentamicin) immediately after cultures are obtained 3
• Clinical appearance is unreliable—only 58% of infants with bacteremia or meningitis appear clinically ill 3

Infants 1-3 months with fever:

• Mandatory evaluation includes urinalysis, blood culture, and inflammatory markers 3
• Lumbar puncture is highly recommended 3
• Urinary tract infections account for >90% of serious bacterial infections in this population 3

Children 2 months to 2 years with fever ≥39°C:

• Obtain white blood cell count to guide management decisions 3
• If WBC ≥15,000/mm³, consider empiric antibiotic therapy to reduce meningitis risk 3
• If WBC >20,000/mm³, obtain chest radiograph due to 26-40% risk of occult pneumonia 3
• Urinary tract infection prevalence is 3-7% in febrile children without apparent source 4

Red-Flag Signs Requiring Emergency Evaluation (All Ages)

• Respiratory distress: rapid breathing, grunting, chest retractions, difficulty breathing 2
• Cyanosis: bluish discoloration of lips or skin 2
• Severe dehydration: no urine output >8 hours, absence of tears, sunken eyes 2
• Altered consciousness: excessive drowsiness, confusion, difficulty waking 2
• Toxic appearance or signs of sepsis 3
• Fever persisting >48 hours on antibiotics or overall clinical deterioration 2

Adults

• Temperature >39°C (102.2°F) warrants investigation for infectious causes, particularly pneumonia, urinary tract infection, line infections, and intra-abdominal infections 5
• Temperatures <38.9°C (102°F) or >41.1°C (106°F) are more likely non-infectious (DVT, drug fever, aspiration) 5
• Obtain chest radiograph for any critically ill patient with new fever, as pneumonia is the most common infection causing fever 1

Special Clinical Scenarios

Suspected Influenza in Children

• If fever >38.5°C with influenza-like illness and symptoms ≤2 days, consider oseltamivir 2
• Fever recurring within 3 hours despite alternating antipyretics indicates either severe viral response or bacterial superinfection (most commonly pneumonia) 2
• Add co-amoxiclav (amoxicillin-clavulanate) for children <12 years at risk of bacterial superinfection, covering S. pneumoniae, S. aureus, and H. influenzae 2
• Treatment duration: 7 days for uncomplicated infection, 10 days for severe disease 2

Critically Ill Patients

• Use antipyretics primarily for symptomatic relief and patient comfort, not routinely to reduce temperature 1
• In septic shock, maintaining normothermia with antipyretics is reasonable, though it does not improve mortality or ICU length of stay 4
• Meta-analysis of 13 RCTs (n=1,963) showed fever management did not improve 28-day mortality (RR 1.03; 95% CI 0.79-1.35) 1

Bacterial Meningitis

• In comatose patients without intracranial hypertension, consider normothermia to improve survival and neurological outcome 4
• In comatose patients with intracranial hypertension, consider targeted temperature management at 34-36°C 4

Common Pitfalls to Avoid

• Do not rely solely on clinical appearance: many children with serious bacterial infections appear well initially 3
• Recent antipyretic use can mask fever severity: recorded temperature may not reflect actual disease severity 3
• Viral infection does not exclude bacterial co-infection: both can occur simultaneously 3
• Antipyretics do not prevent febrile seizure recurrence in children with history of febrile seizures 1
• Avoid intramuscular acetaminophen due to injection site pain, tissue trauma, and risk of hematoma (especially in anticoagulated patients) 1

Monitoring and Follow-Up

• Maintain adequate hydration to counteract dehydration risk 2
• Re-evaluate if fever persists >48 hours despite appropriate therapy for possible imaging or antimicrobial modification 2
• With appropriate treatment, fever typically resolves within 24-48 hours 2
• Most previously healthy children do not require formal follow-up after uncomplicated fever, but primary care follow-up is appropriate if illness has been prolonged 2