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peds.febrile-infant.core.v1PRODUCTION
peds.febrile-infant.core.v1

Febrile infant (0-90 days)

pediatricsacutepediatric
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Encounter flow

12/12 authored

Canonical 12-phase frame with authored status for this dossier.

Current phase

Frame

Detailed

Confirm febrile infant criteria: age 0-90 days + temperature ≥38°C rectal; assign age tier (0-28d / 29-60d / 61-90d) per AAP 2021 Pantell

Inputs
2
Actions
0
Advance rule
Set
Advance when

Age tier assigned + fever confirmed

Patient inputs (8)

Age tier drives entire workup algorithm: 0-28d vs 29-60d vs 61-90d (AAP 2021 Pantell)

Fever ≥38°C rectal defines inclusion; degree of fever factors into risk (AAP 2021 Pantell)

WBC abnormality (<5000 or >15000) raises SBI probability; used in Rochester criteria (Jaskiewicz 1994; AAP 2021 Pantell)

UTI is most common SBI in febrile infants; pyuria ≥10 WBC/hpf or positive LE (AAP 2021 Pantell; PECARN Kuppermann 2019)

LP mandatory in 0-28d and ill-appearing any age; CSF pleocytosis, protein, glucose, culture, HSV PCR (AAP 2021 Pantell)

Ill-appearing infant bypasses risk stratification → immediate full sepsis workup + empiric therapy (AAP 2021 Pantell)

PCT ≥0.5 ng/mL high-risk marker for invasive bacterial infection (Step-by-Step Kuppermann JAMA Pediatr 2019; AAP 2021 Pantell)

CRP ≥20 mg/L supports inflammatory marker-based risk stratification (Step-by-Step Kuppermann JAMA Pediatr 2019; AAP 2021 Pantell)

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (7)

7 need judgement
  • informationallife_threateningill_appearing_febrile_neonate (AAP 2021 Pantell)
    Ill-appearing infant at any age 0-90d: lethargy, poor perfusion, mottled skin, weak cry, bulging fontanelle (AAP 2021 Pantell)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateninghsv_concern_neonate (Kimberlin 2013)
    HSV clinical features: vesicular lesions, seizures, CSF pleocytosis without bacteria, elevated AST/ALT, maternal HSV history, age ≤21d (Kimberlin Pediatrics 2013; AAP 2021 Pantell)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningbacterial_meningitis_confirmed (AAP 2021 Pantell)
    CSF culture positive or CSF gram stain positive with compatible CSF profile (pleocytosis, elevated protein, low glucose) (AAP 2021 Pantell)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateninghemodynamic_instability_febrile_infant (PALS 2020)
    Hypotension for age, tachycardia with poor perfusion, delayed capillary refill >3 seconds in febrile infant (PALS 2020; AAP 2021 Pantell)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningage_0_to_7_days_any_fever
    Any rectal temperature ≥ 38.0 °C (100.4 °F) in an infant aged 0-7 days (AAP 2021 Pantell + neonatal-sepsis convention; below the 8-60 d AAP CPG window — defer to convention)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevereneutropenia_febrile_infant (AAP 2021 Pantell)
    ANC <1000/mcL in febrile infant 0-90d (AAP 2021 Pantell)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevereabnormal_inflammatory_markers
    Any of: procalcitonin > 0.5 ng/mL OR CRP > 20 mg/L OR WBC < 5 000 or > 15 000 /μL OR ANC ≥ 4 090 /μL (Step-by-Step Gomez Pediatrics 2016 PMID 27382134; AAP 2021 Pantell Section 6 + Table 4 cutoffs)
    Trigger could not be auto-evaluated — needs clinician judgement.

Workflow calculators

This dossier does not reference any calculators.

Recommended regimen

Febrile infant 0-28d — full empiric coverage (AAP 2021 Pantell + Kimberlin 2013)
axis: febrile_infant_0_28d_empiric
Selected axis "Febrile infant 0-28d — full empiric coverage (AAP 2021 Pantell + Kimberlin 2013)" by default fallback (first axis)
  • ampicillin
    first line
    aminopenicillin
    50 mg/kg IV q8h (meningitis dose: 75-100 mg/kg IV q6h) • IV • q8h (q6h meningitis dosing)
    triggers: age_0_28d_febrile
    Covers Listeria monocytogenes + enterococcus + GBS (AAP 2021 Pantell)
    rxcui 733
  • gentamicin
    first line
    aminoglycoside
    4-5 mg/kg IV q24h (term neonates) • IV • q24h
    triggers: age_0_28d_febrile
    Synergistic gram-negative and GBS coverage (AAP 2021 Pantell; Neofax 2024)
    rxcui 1596450
  • acyclovir
    first line
    antiviral_nucleoside_analog
    20 mg/kg IV q8h • IV • q8h
    triggers: age_le_21d_or_hsv_risk_factors
    HSV coverage mandatory when age ≤21d or clinical concern for neonatal HSV (Kimberlin Pediatrics 2013; AAP 2021 Pantell)
    rxcui 281

ed playbook — drug actions (5)

  1. 1. ampicillin 50 mg/kg IV + gentamicin 4-5 mg/kg IV (0-28d)
    ampicillin 50 mg/kg; gentamicin 4-5 mg/kg • IV • ampicillin q8h; gentamicin q24h
    trigger: Age 0-28d with fever ≥38°C
    Full empiric neonatal sepsis coverage (AAP 2021 Pantell)
  2. 2. acyclovir 20 mg/kg IV (if ≤21d or HSV concern)
    20 mg/kg • IV • q8h
    trigger: Age ≤21d OR vesicles, seizures, CSF pleocytosis without organism, maternal HSV, elevated AST/ALT
    Neonatal HSV mortality 30% untreated; empiric coverage essential (Kimberlin 2013)
  3. 3. ceftriaxone 50 mg/kg IV/IM (29-60d high-risk)
    50 mg/kg • IV/IM • once daily
    trigger: Age 29-60d + ill-appearing OR elevated inflammatory markers OR positive UA
    Empiric gram-negative + GBS coverage (AAP 2021 Pantell)
  4. 4. ceftriaxone 50 mg/kg IM (61-90d high-risk)
    50 mg/kg • IM • single dose
    trigger: Age 61-90d + high-risk by Rochester/Step-by-Step criteria
    Empiric coverage pending cultures; IM allows ED observation pathway (AAP 2021 Pantell)
  5. 5. observation without antibiotics (61-90d low-risk)
    N/A — clinical observation • N/A • 24h follow-up
    trigger: Age 61-90d + low-risk by Rochester criteria + reliable caregiver
    SBI risk <1% in low-risk 61-90d infants; safe to observe with follow-up (Jaskiewicz 1994; AAP 2021 Pantell)

Auto-drafted A&P note

ed

Subjective

- Possible entry pathways: Fever ≥38°C (100.4°F) rectal in infant 0-90 days (AAP 2021 Pantell); Ill-appearing neonate requiring immediate stabilization (AAP 2021 Pantell); Maternal GBS colonization or chorioamnionitis with neonatal fever (AAP 2021 Pantell; CDC 2020 GBS).

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**Febrile infant (0-90 days)** (peds.febrile-infant.core.v1).
Phenotype framing: Viral fever (RSV, enterovirus, influenza, parechovirus per PECARN 2019) vs UTI (most common SBI; PECARN Kuppermann 2019) vs bacteremia vs meningitis (bacterial or HSV per Kimberlin 2013) vs late-onset GBS (CDC 2020)
Scope: Confirm febrile infant criteria: age 0-90 days + temperature ≥38°C rectal; assign age tier (0-28d / 29-60d / 61-90d) per AAP 2021 Pantell

No severity triggers fired against current inputs.

Plan

Regimen axis: **Febrile infant 0-28d — full empiric coverage (AAP 2021 Pantell + Kimberlin 2013)**.
1. ampicillin 50 mg/kg IV q8h (meningitis dose: 75-100 mg/kg IV q6h) IV q8h (q6h meningitis dosing) (aminopenicillin, first line) — Covers Listeria monocytogenes + enterococcus + GBS (AAP 2021 Pantell)
2. gentamicin 4-5 mg/kg IV q24h (term neonates) IV q24h (aminoglycoside, first line) — Synergistic gram-negative and GBS coverage (AAP 2021 Pantell; Neofax 2024)
3. acyclovir 20 mg/kg IV q8h IV q8h (antiviral_nucleoside_analog, first line) — HSV coverage mandatory when age ≤21d or clinical concern for neonatal HSV (Kimberlin Pediatrics 2013; AAP 2021 Pantell)

Setting playbook (ed) — Age-stratify febrile infant, complete sepsis evaluation per AAP 2021 tier, initiate empiric antibiotics or classify as low-risk for observation
4. ampicillin 50 mg/kg IV + gentamicin 4-5 mg/kg IV (0-28d) ampicillin 50 mg/kg; gentamicin 4-5 mg/kg IV ampicillin q8h; gentamicin q24h — Age 0-28d with fever ≥38°C (Full empiric neonatal sepsis coverage (AAP 2021 Pantell))
5. acyclovir 20 mg/kg IV (if ≤21d or HSV concern) 20 mg/kg IV q8h — Age ≤21d OR vesicles, seizures, CSF pleocytosis without organism, maternal HSV, elevated AST/ALT (Neonatal HSV mortality 30% untreated; empiric coverage essential (Kimberlin 2013))
6. ceftriaxone 50 mg/kg IV/IM (29-60d high-risk) 50 mg/kg IV/IM once daily — Age 29-60d + ill-appearing OR elevated inflammatory markers OR positive UA (Empiric gram-negative + GBS coverage (AAP 2021 Pantell))
7. ceftriaxone 50 mg/kg IM (61-90d high-risk) 50 mg/kg IM single dose — Age 61-90d + high-risk by Rochester/Step-by-Step criteria (Empiric coverage pending cultures; IM allows ED observation pathway (AAP 2021 Pantell))
8. observation without antibiotics (61-90d low-risk) N/A — clinical observation N/A 24h follow-up — Age 61-90d + low-risk by Rochester criteria + reliable caregiver (SBI risk <1% in low-risk 61-90d infants; safe to observe with follow-up (Jaskiewicz 1994; AAP 2021 Pantell))

Non-pharmacologic actions:
- IV access with fluid bolus 20 mL/kg NS if ill-appearing or poor perfusion (AAP 2021 Pantell)
- Continuous pulse oximetry if ill-appearing (AAP 2021 Pantell)
- Contact isolation pending viral respiratory panel (AAP 2021 Pantell)
- Social work consult if non-accidental trauma concern (AAP 2021 Pantell)

AVOID / contraindication checks:
- Gentamicin trough monitoring required to avoid nephro/ototoxicity (Neofax 2024)
- Acyclovir requires adequate hydration to prevent crystalline nephropathy (Kimberlin 2013)
- Adjust gentamicin for prematurity and renal function (Neofax 2024)

Monitoring

Regimen monitoring:
- gentamicin trough before 3rd dose target <2 mcg/mL (Neofax 2024)
- BUN and creatinine q48h while on acyclovir (Kimberlin 2013)
- CBC q48h while on acyclovir for neutropenia monitoring (Kimberlin 2013)
- blood culture follow-up at 24h and 48h (AAP 2021 Pantell)

Setting (ed) monitoring:
- Vitals q4h during ED observation (AAP 2021 Pantell)
- Clinical reassessment before disposition (AAP 2021 Pantell)
- Culture status check at 24h and 48h (AAP 2021 Pantell)

Follow-up plan: Discharge with reliable caregiver + 24h PCP follow-up if sent home on observation (AAP 2021 Pantell); return precautions for fever recurrence, poor feeding, lethargy, irritability; final culture check at 48-72h for all blood/urine/CSF cultures (AAP 2021 Pantell)
- Close-out criterion: Follow-up appointment confirmed + return precautions given + culture tracking complete

Monitoring phase: Inpatient: vitals q4h, clinical reassessment q8-12h, culture follow-up at 24h and 48h; if on acyclovir monitor renal function + CBC q48h (Kimberlin 2013); repeat LP if CSF initially abnormal and not improving at 48-72h (AAP 2021 Pantell)

Disposition

Current setting: ed — Age-stratify febrile infant, complete sepsis evaluation per AAP 2021 tier, initiate empiric antibiotics or classify as low-risk for observation

Disposition criteria:
- Admit: all 0-28d; 29-60d if ill-appearing or elevated inflammatory markers or positive UA; 61-90d if high-risk (AAP 2021 Pantell)
- Discharge with 24h follow-up: 61-90d low-risk by Rochester/Step-by-Step + reliable caregiver + culture tracking plan (AAP 2021 Pantell)
- Discharge with 24h follow-up: 29-60d well-appearing + all inflammatory markers normal + UA negative + reliable caregiver (AAP 2021 Pantell)

Escalation triggers (move to higher acuity):
- Ill-appearing at any age tier → immediate full workup + empiric antibiotics + admit (AAP 2021 Pantell)
- CSF pleocytosis → admit + broaden to meningitis dosing + add acyclovir if not already started (AAP 2021 Pantell)
- Hemodynamic instability → fluid resuscitation + vasopressors per PALS 2020 + PICU consult (AAP 2021 Pantell)
- Seizure → acyclovir immediately if not started + PICU consult (Kimberlin 2013)

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Ill-appearing infant at any age 0-90d: lethargy, poor perfusion, mottled skin, weak cry, bulging fontanelle (AAP 2021 Pantell)
- [LIFE_THREATENING] HSV clinical features: vesicular lesions, seizures, CSF pleocytosis without bacteria, elevated AST/ALT, maternal HSV history, age ≤21d (Kimberlin Pediatrics 2013; AAP 2021 Pantell)
- [LIFE_THREATENING] CSF culture positive or CSF gram stain positive with compatible CSF profile (pleocytosis, elevated protein, low glucose) (AAP 2021 Pantell)

Citations

- AAP 2021 Clinical Practice Guideline for Febrile Infants 8-60d (Pantell Pediatrics 2021) + PECARN derivation (Kuppermann JAMA Pediatr 2019) + Step-by-Step (Gomez Pediatrics 2016) + Rochester criteria (Jaskiewicz Pediatrics 1994) + Philadelphia criteria (Baker Pediatrics 1993) + Boston criteria (Baskin J Pediatr 1992) + neonatal HSV (Kimberlin Pediatrics 2013) [PMID:34281996](https://pubmed.ncbi.nlm.nih.gov/34281996/)
- Cited evidence (PMID 30776077) [PMID:30776077](https://pubmed.ncbi.nlm.nih.gov/30776077/)
- Cited evidence (PMID 27382134) [PMID:27382134](https://pubmed.ncbi.nlm.nih.gov/27382134/)
- Cited evidence (PMID 8065869) [PMID:8065869](https://pubmed.ncbi.nlm.nih.gov/8065869/)
- Cited evidence (PMID 23378604) [PMID:23378604](https://pubmed.ncbi.nlm.nih.gov/23378604/)

Last reconciled with current guidelines: 2026-05-14.
References
  • AAP 2021 Clinical Practice Guideline for Febrile Infants 8-60d (Pantell Pediatrics 2021) + PECARN derivation (Kuppermann JAMA Pediatr 2019) + Step-by-Step (Gomez Pediatrics 2016) + Rochester criteria (Jaskiewicz Pediatrics 1994) + Philadelphia criteria (Baker Pediatrics 1993) + Boston criteria (Baskin J Pediatr 1992) + neonatal HSV (Kimberlin Pediatrics 2013) — PMID:34281996
  • Cited evidence (PMID 30776077) — PMID:30776077
  • Cited evidence (PMID 27382134) — PMID:27382134
  • Cited evidence (PMID 8065869) — PMID:8065869
  • Cited evidence (PMID 23378604) — PMID:23378604