In a febrile neonate (≤28 days), what examinations and assessments are indicated?

Examination of Febrile Neonates (≤28 Days)

All febrile neonates ≤28 days old require a complete sepsis workup including blood culture, urinalysis with urine culture (via catheterization), and lumbar puncture for cerebrospinal fluid (CSF) analysis and culture, followed by empiric parenteral antibiotics and hospitalization 1, 2.

Critical Initial Assessment

Vital Signs and Appearance

• Temperature documentation: Confirm fever ≥38.0°C (100.4°F) measured rectally
• Assess clinical appearance: Well-appearing vs. ill-appearing (lethargy, poor perfusion, respiratory distress, irritability)
• Vital sign abnormalities: Tachycardia, tachypnea, hypotension, or hypothermia

Pertinent History Elements

• Age in days (critical for risk stratification: 8-21 days vs. 22-28 days)
• Gestational age at birth (guideline applies only to ≥37 weeks)
• Feeding patterns: Poor feeding, vomiting, decreased intake
• Urine output: Decreased wet diapers
• Perinatal history: Maternal GBS status, prolonged rupture of membranes, maternal fever
• Previous health status: Any prior hospitalizations or chronic conditions

Mandatory Laboratory Evaluation

Complete Sepsis Workup (All Neonates ≤28 Days)

Blood Studies:

• Blood culture (before antibiotics)
• Complete blood count with differential
• Consider inflammatory markers (procalcitonin, C-reactive protein) though not required by guideline

Urine Studies:

• Urinalysis (looking for pyuria, nitrites, leukocyte esterase)
• Urine culture via catheterization (never bag specimen for culture)

Cerebrospinal Fluid Studies:

• CSF cell count and differential
• CSF glucose and protein
• CSF Gram stain
• CSF bacterial culture
• Consider CSF enterovirus PCR (may influence management decisions) 1

Important Caveat for 22-28 Day Olds

For infants 22-28 days old specifically, if initial blood and urine studies are normal, shared decision-making with parents may guide whether to perform lumbar puncture, though this represents a nuanced exception requiring careful discussion 1.

Physical Examination Focus

Systematic Approach to Identify Focal Infection

Skin examination:

• Petechiae, purpura (meningococcemia)
• Cellulitis, abscess
• Umbilical erythema or discharge (omphalitis)

HEENT examination:

• Bulging fontanelle (meningitis)
• Otoscopic examination (otitis media, though rare cause of fever alone in neonates)
• Oral thrush or lesions

Respiratory examination:

• Work of breathing, retractions, grunting
• Auscultation for pneumonia (though chest radiography not routine unless respiratory symptoms)

Cardiovascular examination:

• Perfusion, capillary refill
• Heart murmur (endocarditis rare but possible)

Abdominal examination:

• Distension, tenderness (rare focal findings)

Musculoskeletal examination:

• Limited range of motion, swelling, erythema (osteomyelitis, septic arthritis)
• Pseudoparalysis of extremity

Neurological examination:

• Level of alertness and responsiveness
• Tone (hypotonia concerning)
• Seizure activity

Risk Stratification by Age

The 2021 AAP guideline stratifies management by specific age cutoffs 1:

8-21 Days Old (Highest Risk)

• Mandatory: Full sepsis workup including LP
• Mandatory: Empiric IV antibiotics (ampicillin + gentamicin or ceftazidime)
• Mandatory: Hospital admission
• No exceptions for observation without treatment in this age group

22-28 Days Old (Intermediate Risk)

• Mandatory: Blood and urine studies
• Conditional: LP may be deferred if blood/urine normal AND shared decision-making supports this
• Conditional: May observe without antibiotics if all labs normal and family agrees
• Requires: Close follow-up if managed as outpatient

Common Pitfalls to Avoid

1. Never rely on clinical appearance alone: Well-appearing neonates can have serious bacterial infections including meningitis 2

2. Never use bag urine specimens for culture: Only catheterized specimens are acceptable for culture in this age group

3. Never delay antibiotics while awaiting LP: If LP is delayed or traumatic, give antibiotics after blood culture obtained

4. Never discharge neonates ≤21 days without full workup and admission: This age group has highest risk of invasive bacterial infection (bacteremia 2.9%, meningitis 1.5%) 3

5. Never assume viral testing excludes bacterial infection: Positive viral studies do not reliably exclude serious bacterial infection in neonates 4

Immediate Management Algorithm

1. Obtain blood culture → Start IV access
2. Catheterize for urinalysis and culture
3. Perform lumbar puncture (unless 22-28 days with normal initial labs and family discussion supports deferral)
4. Administer empiric antibiotics immediately after cultures obtained:
   • 8-28 days: Ampicillin 150 mg/kg/day divided q8h + gentamicin 4 mg/kg q24h (or ceftazidime 150 mg/kg/day divided q8h) 1
   • If meningitis suspected/confirmed: Increase ampicillin to 300 mg/kg/day divided q6h + ceftazidime 150 mg/kg/day divided q8h 1
5. Admit to hospital for monitoring and culture results

This algorithmic approach prioritizes early detection and treatment of life-threatening infections while the immature neonatal immune system provides minimal margin for error 2, 5.