Fever in pediatrics
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Fever in Pediatrics
Fever is the most common complaint among pediatric patients presenting to the emergency department. Viruses cause the vast majority of childhood febrile illnesses and are generally self-limited. However, identifying the subset of children with serious bacterial infection (SBI) is the central clinical challenge.
Source: Rosen's Emergency Medicine - Concepts and Clinical Practice
Definition
- Fever = rectal temperature ≥ 38°C (100.4°F); some guidelines use ≥ 38.3°C
- High fever = ≥ 39°C (102.2°F)
- Rectal measurement is the standard in infants and young children
- Defervescence after acetaminophen does not reliably exclude bacteremia
Serious Bacterial Infection (SBI)
SBI = growth of pathogenic bacteria in a previously sterile site. Includes:
- UTI (most common cause of SBI at all pediatric ages)
- Bacteremia / sepsis
- Bacterial meningitis
- Pneumonia
- Osteomyelitis / septic arthritis
- Bacterial gastroenteritis
- Cellulitis
Age-Stratified Approach
1. Neonates (0-28 days)
- Highest risk group - immature immune system, incomplete vaccination, exposure to birthing-process pathogens (Group B Streptococcus, Chlamydia trachomatis, N. gonorrhoeae)
- Rate of SBI: 6-10% in febrile infants < 3 months
- Bacterial meningitis: ~3/1000 febrile infants < 3 months
- All febrile neonates require full septic workup and empirical antibiotics
Workup:
- CBC with differential
- Blood culture
- Urinalysis + urine culture (catheterization - not bag specimen)
- Lumbar puncture (CSF culture, cell count, glucose, protein)
- CXR if respiratory symptoms
Empirical antibiotic therapy:
- Ampicillin + gentamicin OR ampicillin + cefotaxime
- Covers Group B Strep, Listeria, gram-negatives
HSV empirical therapy (IV acyclovir) is indicated if:
- Maternal history of genital herpes
- Ill appearance with fever + seizure
- Cutaneous vesicles on exam
- Transaminitis or coagulopathy
Note: RSV and influenza do not reduce SBI risk in neonates < 28 days - a positive viral test does not change the workup in this age group.
2. Infants 1-3 Months (29-90 days)
- Immune function is improving but still immature
- Primary vaccination series begins at 2 months
- Risk stratification tools help guide management:
Rochester/Philadelphia/Boston Criteria are used to identify "low-risk" infants who may be managed as outpatients without antibiotics. Low-risk features include:
- Previously healthy, term infant
- Non-toxic appearance
- No focal bacterial infection on exam
- WBC 5,000-15,000/mm³
- Normal urinalysis
- Stool: WBC < 5/hpf if diarrhea present
- CSF: WBC < 10 cells/mm³
Management:
- Low-risk infants: may be discharged with close follow-up (24 hours) after blood culture and urinalysis; LP may be deferred
- High-risk or ill-appearing infants: full septic workup + admission + empirical antibiotics
3. Infants 3-36 Months
The post-vaccine era has dramatically changed this age group. Since introduction of PCV7 and PCV13:
- Invasive pneumococcal infections decreased >75% in children < 24 months
- Routine blood cultures for all febrile children in this age group are no longer recommended
Management algorithm for 3-36 month old febrile infants:
- T < 102.2°F: antipyresis + further labs per clinical judgment
- T ≥ 102.2°F + low clinical risk for occult bacteremia: UA + urine culture ± CXR ± stool culture
- T ≥ 102.2°F + higher risk: CBC + blood culture + UA + urine culture ± CXR; antibiotics if WBC > 15,000
Urine screening indications:
- Females < 24 months
- Circumcised males < 6 months
- Uncircumcised males < 12 months
- Bladder catheterization is the preferred method for non-toilet-trained infants (bag specimen has high false-positive rate but if negative, rules out UTI)
4. Children ≥ 3 Years to Adulthood
- Occult bacteremia risk decreases markedly
- Focal infections predominate: strep pharyngitis, pneumonia, otitis media, cellulitis, peritonsillar abscess (adolescents), septic arthritis
- Consider Mycoplasma pneumoniae in community-acquired pneumonia
- Community-acquired MRSA is increasing - consider in skin abscesses/pyogenic infections
- Management: incision and drainage + antibiotics (especially abscesses > 5 cm, cellulitis, or fever)
- Viral causes: EBV (infectious mononucleosis), influenza, RSV
Clinical Evaluation
History
- Duration of fever, localizing symptoms (headache/neck stiffness, ear pain, cough)
- Sick contacts, travel history
- Immunization status
- Prior antibiotic use (may mask meningitis findings)
- Birth history in young infants (gestational age, maternal infections)
- Rash history (roseola vs. meningococcemia, RMSF, toxic shock syndrome)
Physical Examination - "Traffic Light" Approach
Assess for toxicity: lethargy, poor perfusion, hypo/hyperventilation, cyanosis, petechiae/purpura
| Feature | Low Concern | High Concern |
|---|---|---|
| Color | Normal | Pale, mottled, ashen, cyanotic |
| Activity | Normal | Decreased, inconsolable |
| Hydration | Normal skin/eyes/mucosa | Dry mucosa, sunken eyes, poor turgor |
| Respirations | Normal | Tachypneic, grunting, retractions |
| Rash | None / viral exanthem | Petechiae, purpura (meningococcemia) |
Purpuric/petechial rash in a febrile child = meningococcemia until proven otherwise - immediate management required.
Differential Diagnosis
| Category | Examples |
|---|---|
| Viral | RSV, influenza, rhinovirus, adenovirus, EBV, roseola (HHV-6), parainfluenza |
| Bacterial | UTI, bacteremia, meningitis, pneumonia, otitis media, strep pharyngitis, GBS (neonates) |
| HSV | Neonatal HSV (encephalitis, disseminated) |
| Autoimmune | Kawasaki disease, juvenile idiopathic arthritis, SLE |
| Other | Malignancy, CNS tumors (rare), drug fever, heat stroke |
Antipyretic Management
Goals: Improve patient comfort; does not alter disease course or prevent febrile seizures.
| Drug | Dose | Route | Notes |
|---|---|---|---|
| Acetaminophen | 15 mg/kg q4-6h | PO/PR | First-line; safe from birth |
| Ibuprofen | 10 mg/kg q6-8h | PO | Use ≥ 6 months; avoid in renal disease, dehydration |
- Aspirin is contraindicated in children with viral illness (Reye syndrome risk)
- Alternating acetaminophen and ibuprofen: A 2024 network meta-analysis (PMID: 39318339) showed short-term dual therapy has modest superiority for fever reduction vs. monotherapy, but clinical guidelines traditionally favor monotherapy for simplicity
- Tepid sponging may provide temporary comfort but does not substitute for antipyretics
Febrile Seizures
- Simple febrile seizure: generalized, < 15 minutes, occurs once in 24 hours in a child 6 months - 5 years with fever, no neurological deficits
- Complex febrile seizure: focal onset, > 15 minutes, recurs within 24 hours, or child has a neurological abnormality
- LP is indicated in complex febrile seizures or if meningitis is suspected
- Antipyretics do not prevent febrile seizures
Red Flags - Do Not Miss
| Finding | Concern |
|---|---|
| Petechiae / purpura | Meningococcemia, DIC |
| Bulging fontanelle | Meningitis (infants) |
| Nuchal rigidity / Kernig's / Brudzinski's | Bacterial meningitis |
| Strawberry tongue, conjunctivitis, rash, lip cracking | Kawasaki disease |
| Ill appearance / toxic-looking child | SBI, sepsis |
| Neonatal fever (< 28 days) | Always high-risk - treat empirically |
| Fever in immunocompromised child | Broad workup + urgent empirical antibiotics |
Disposition Summary
| Age | Action |
|---|---|
| < 28 days | Full septic workup + admission + empirical antibiotics |
| 29-90 days, low-risk | Blood culture + UA; may discharge with 24-hr follow-up |
| 29-90 days, high-risk | Full workup + admission |
| 3-36 months, non-toxic, vaccinated | UA/urine culture; selective blood work |
| 3-36 months, toxic or high WBC | Blood culture + antibiotics |
| > 3 years, non-toxic, focal source | Treat source; outpatient |
Sources:
- Rosen's Emergency Medicine - Pediatric Fever chapter (Nathan W. Mick), pp. 3151-3160
- 2024 Network Meta-Analysis on dual vs. mono antipyretic therapy - PMID 39318339 (Pediatrics, Oct 2024)
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