🌡️ Chapter 39: Fever

Nelson's Pediatric Symptom-Based Diagnosis | Fever without source · Neonatal fever · Bacteremia · UTI · Meningitis · Low-risk criteria · FUO · Age-based management

🔍 Fever in Children: Key Concepts

📊 Definitions
Fever: rectal temp ≥38°C (100.4°F). Fever without source (FWS): fever <7d with no apparent source. FUO: >8-14d daily fever, undiagnosed after initial evaluation.
🧪 Neonatal fever (<28d)
High risk for serious bacterial infection (GBS, E. coli, Listeria). Full sepsis evaluation (CBC, blood, urine, CSF cultures), hospitalization, empiric antibiotics (ampicillin + gentamicin/cefotaxime).
👶 Infants 29-60d
Low-risk criteria (Rochester/Boston/Philadelphia) identify well-appearing infants with normal labs who may be managed as outpatients with close follow-up. WBC 5-15k, bands <1500, normal UA/CSF.
🧒 3-36 months
UTI most common serious bacterial infection. Routine PCV13/Hib vaccination dramatically reduced occult bacteremia (now <0.5%). Screen for UTI in girls <24m, uncircumcised boys <12m.
🧫 Diagnostic tests
Urinalysis & culture (catheterized specimen). CBC, blood culture if high risk. Procalcitonin and CRP improve sensitivity. Chest X-ray if respiratory signs. LP if suspected meningitis.
🦠 FUO causes
Infections (UTI, EBV, CMV, TB, cat-scratch, brucellosis) >50%. Collagen vascular (JIA, SLE) ~10%. Malignancy ~5%. Many self-limited or undiagnosed.

💡 Key takeaway: Age-based protocols guide fever management. Infants <28d require full sepsis workup and admission. Low-risk 29-60 day olds may be observed without antibiotics. After 3 months, UTI screening is key; occult bacteremia is rare in vaccinated children.

🩺 Clinical Approach to Fever in Children (Age-Based Algorithm)

🔹 Step 1: Assess for toxicity and stability
• Ill-appearing, toxic, unstable vital signs → hospitalize, full sepsis evaluation, empiric antibiotics.
• Petechiae/purpura, altered mental status, respiratory distress → immediate evaluation.
🔹 Step 2: Age stratification
• <28 days: Full sepsis workup (CBC, blood culture, urine catheterization, CSF studies). Admit, IV ampicillin + gentamicin or cefotaxime. HSV PCR if risk factors.
• 29-60 days: Use low-risk criteria (Rochester, Philadelphia, Boston). If well-appearing, normal CBC, UA, CSF (if obtained) → may manage as outpatient with 24h follow-up. Otherwise admit.
• 3-36 months: Urinalysis for all girls <24m, uncircumcised boys <12m. Blood culture only if high risk (fever >39°C, no vaccines). CSF if meningitis suspected.
• >36 months: Clinical evaluation; testing only if ill-appearing or risk factors.
🔹 Step 3: Identify focus of infection
• Otitis media, pharyngitis, pneumonia, UTI, osteomyelitis, abscess.
• Always consider urinary tract infection in young children — sterile pyuria can be a clue.
🔹 Step 4: Diagnostic testing guided by age and risk
• Urinalysis + culture (catheter specimen for infants).
• CBC with differential, blood culture if high risk (younger than 3 months, unvaccinated, toxic).
• Lumbar puncture: all <28d, 29-60d if not meeting low-risk criteria, any age with meningeal signs or altered mental status.
• Chest X-ray: respiratory symptoms or tachypnea without wheezing.
🔹 Step 5: Outpatient management and follow-up
• Well-appearing, low-risk: supportive care, antipyretics, return precautions.
• Empiric antibiotics not recommended for 3-36 months without a focus.
• UTI treatment: oral or IV antibiotics based on age and severity.
• Re-evaluate in 24-48h if fever persists or worsens.