What is the appropriate management for a full-term infant presenting with fever?

Management of a Febrile Full-Term Infant

This infant requires immediate hospitalization with full septic workup (blood culture, catheterized urine culture, and lumbar puncture) followed by empiric intravenous antibiotics before any culture results return. 1, 2

Age-Specific Risk Assessment

The critical first step is determining the infant's exact age in days, as management differs dramatically across age thresholds:

• 0-28 days (neonates): Highest risk group with mandatory full evaluation and hospitalization 2, 3
• 29-60 days: High risk requiring full evaluation and hospitalization 1
• 61-90 days: May potentially use risk stratification if well-appearing 4, 5

Since the question states "[AGE]-day-old," and the infant is described as "full-term," this infant falls into one of these high-risk categories requiring aggressive management. Neonates under 2 weeks have the highest rates of bacteremia (4.8%) and bacterial meningitis, with serious bacterial illness occurring in 25% of cases. 6

Mandatory Diagnostic Evaluation

Complete the following tests immediately, before initiating antibiotics: 1, 2

• Blood culture: Mandatory for all febrile infants 0-60 days 1
• Urine culture via catheterization: Never use bag collection (catheterization has 95% sensitivity and 99% specificity) 1, 2
• Lumbar puncture with CSF analysis: Essential for all infants 0-60 days, as clinical examination cannot reliably exclude meningitis even in well-appearing infants 1, 2
• Rectal temperature documentation: Confirm fever ≥38.0°C (100.4°F) 1, 2

The American College of Emergency Physicians guidelines acknowledge that while there are no predictors that adequately identify which febrile infants aged 29-90 days require lumbar puncture, the procedure should still be strongly considered. 4 However, the American Academy of Pediatrics is more definitive, stating lumbar puncture is essential for all infants 0-60 days. 1, 2

Empiric Antibiotic Therapy

Initiate antibiotics immediately after obtaining cultures: 1, 2

Standard regimen (no meningitis confirmed):

• Ampicillin IV 150 mg/kg/day divided every 8 hours
• PLUS either:
  • Ceftazidime IV 150 mg/kg/day divided every 8 hours, OR
  • Gentamicin IV 4 mg/kg/dose every 24 hours 1, 2

If meningitis confirmed by CSF analysis:

• Ampicillin IV 300 mg/kg/day divided every 6 hours (doubled dose)
• Ceftazidime IV 150 mg/kg/day divided every 8 hours (same dose) 1, 2

Hospitalization Requirements

All febrile infants 0-60 days require hospitalization in a unit with nurses and staff experienced in caring for young infants. 1, 2 This is non-negotiable regardless of clinical appearance, as well-appearing infants can harbor serious bacterial infections. 1

Historical data from 1990 suggested some febrile infants could be managed outpatient with close follow-up 6, but current American Academy of Pediatrics guidelines supersede this older approach for infants under 60 days. 1, 2

Criteria for Discontinuing Antibiotics

Antibiotics may be stopped only if ALL of the following are met at 48 hours: 1

• CSF analysis is normal or enterovirus-positive
• Urinalysis is negative
• All inflammatory markers obtained are normal
• Blood and CSF cultures remain negative at 48 hours

Critical Pitfalls to Avoid

• Never rely on clinical appearance alone: Well-appearing infants can have serious bacterial infections including meningitis 1, 2
• Never delay antibiotics: Do not wait for imaging or subspecialty consultation 1
• Never use bag collection for urine: Only catheterization or suprapubic aspiration is acceptable 1, 2
• Never defer lumbar puncture based solely on viral symptoms: Even if viral illness is suspected, the 29-90 day age group may have concurrent bacterial meningitis 4

Monitoring During Hospitalization

Watch for signs of clinical deterioration: 1

• Altered mental status or decreased consciousness
• Poor perfusion or abnormal vital signs
• Petechial rash
• Respiratory distress
• Refusal to feed or persistent vomiting

Special Consideration for 29-90 Day Age Group

If this infant is specifically 29-90 days old AND a clear viral illness is diagnosed (such as bronchiolitis with wheezing), the American College of Emergency Physicians suggests deferment of lumbar puncture is a reasonable option given lower meningitis risk. However, if lumbar puncture is deferred, antibiotics must be withheld unless another bacterial source is identified, and admission with close follow-up remains mandatory. 4 This represents a Level C recommendation with lower evidence quality compared to the American Academy of Pediatrics' more aggressive approach. 1

Given the mortality and morbidity risks of missed meningitis in this age group, the safest approach is full evaluation including lumbar puncture for all infants 0-90 days with fever. 1, 2