Serum electrolytes and glucose if dehydration or lethargy
Venous blood gas if respiratory distress
Lactate if shock concern
Liver enzymes if HSV concern
Stool studies if bloody diarrhea
Imaging
Scoring Systems
Clinical decision tools for IBI risk
PECARN febrile infant rule
Low risk criteria
Urinalysis negative
ANC at or below 4090 per microliter
Procalcitonin at or below 1.71 ng per mL
Not for ill appearing infants
Hemodynamic instability
Focal CNS signs
Step by Step approach
Low risk criteria
Well appearing
Age over 21 days
Urinalysis negative
Procalcitonin below 0.5 ng per mL
CRP at or below 20 mg per L
ANC at or below 10000 per microliter
Pitfalls
Early infection may have normal CRP
Antibiotics before sampling invalidates culture interpretation
MRI
Indications in febrile infant
Suspected spinal epidural infection
Suspected osteomyelitis when radiographs nondiagnostic
Constraints and safety
Need for sedation in young infants
Limited ED availability local protocol dependent
CT
Indications in febrile infant
Head CT if concern for intracranial pathology with abnormal neuro exam
CT abdomen pelvis only for specific surgical concern
Radiation and contrast cautions
Avoid routine CT for isolated fever
Contrast risk assessment in dehydration
Ultrasound
Renal and bladder ultrasound
After first febrile UTI based on local protocol
Hydronephrosis or anatomic abnormality assessment
Lung ultrasound and CXR alternatives
Focal respiratory findings
Hypoxia or significant work of breathing
Special Tests
Urine acquisition and interpretation
Collection method
Catheterized specimen preferred for culture
Bag specimen acceptable only for screening urinalysis
Urinalysis interpretation pearls
Leukocyte esterase or nitrite supports UTI
Pyuria on microscopy supports UTI
Negative urinalysis lowers likelihood of UTI
Viral testing and focused diagnostics
Respiratory viral testing local protocol dependent
Influenza and RSV during season
SARS CoV 2 testing based on local policy
Focused infection testing
HSV PCR if vesicles or seizure
Chest radiograph if focal lung findings
ECG
When ECG is relevant
Indications
Unexplained persistent tachycardia after antipyresis
Suspected myocarditis
Poor perfusion with disproportionate tachycardia
High risk patterns prompting escalation
Concerning findings
Supraventricular tachycardia
Heart block
ST segment changes with myocarditis concern
Assessment
Problem representation and risk category
Working assessment framing
Well appearing febrile infant 29 to 60 days
Source identified versus no source
Low risk versus high risk for invasive bacterial infection
Low risk profile elements
Urinalysis negative
Inflammatory markers not elevated
No focal bacterial source on exam
Higher risk profile elements
Urinalysis positive
Elevated inflammatory markers
Concern for meningitis
Inability to ensure reliable follow up
Diagnostic uncertainty and alternatives
Uncertain source considerations
Early bacterial infection with normal markers
Viral illness with coincident UTI
Must not miss alternatives
HSV disease features
Osteoarticular infection signs
Plan
First 5 minutes workflow
Stabilization and monitoring
Continuous pulse oximetry if any respiratory concern
Cardiac monitor if poor perfusion or persistent tachycardia
IV or IO access if ill appearing or dehydration
Point of care glucose if lethargy or seizure
Early targets
Cultures before antibiotics when feasible
Antipyresis and reassessment of appearance
Diagnostic pathway for well appearing 29 to 60 days
Baseline testing sequence
Urinalysis and urine culture
Blood culture
CBC and inflammatory markers
LP decision based on risk
If inflammatory markers elevated then lumbar puncture
If inflammatory markers normal and urinalysis negative then lumbar puncture optional
If urinalysis positive and inflammatory markers normal then lumbar puncture usually not required local protocol dependent
Empiric antimicrobials and dosing
If meningitis suspected or CSF abnormal
Ceftriaxone 50 mg per kg IV or IM every 24 hours
Vancomycin 15 mg per kg IV every 6 hours local protocol dependent
If bacteremia risk without meningitis and cultures obtained
Ceftriaxone 50 mg per kg IV or IM every 24 hours
Observation versus admission based on risk and follow up
If UTI likely and well appearing
Ceftriaxone 50 mg per kg IV or IM once then oral step down local protocol dependent
Cephalexin 25 mg per kg per dose PO every 8 hours
Cefixime 4 mg per kg per dose PO every 12 hours local protocol dependent
Avoid trimethoprim sulfamethoxazole in infants under 2 months
Antiviral coverage when HSV concern
Acyclovir 20 mg per kg IV every 8 hours
Add liver enzymes and HSV PCR testing
Reassessment loop
Repeat clinical checks
Appearance after antipyresis
Perfusion and hydration after fluids if given
Respiratory status trend
Escalation triggers during observation
Worsening mental status
New respiratory distress
Persistent poor feeding
New rash petechiae or vesicles
Disposition
ICU and high acuity indications
ICU level care criteria
Shock or need for vasoactive support
Apnea or need for ventilatory support
Seizure with persistent altered mental status
Suspected meningitis with instability
Admission and observation indications
Inpatient admission criteria
CSF obtained and abnormal or pending with antibiotics started
High risk inflammatory markers
Inability to ensure reliable 24 hour follow up
Social concerns or transportation barriers
Observation pathway candidates
Well appearing with pending cultures
Borderline risk markers with shared decision making
Discharge eligibility criteria
Home observation candidates
Well appearing
Urinalysis negative
Inflammatory markers not elevated
No CSF needed or CSF reassuring if obtained
Reliable caregiver and access to care
Clear plan for follow up within 24 hours
If UTI treated as outpatient
Tolerating feeds
First dose given and prescription filled plan
Follow up within 24 hours
Discharge Instructions
Copy discharge instructions
Your baby has a fever and was checked for serious infections
Blood and urine tests were done
A blood culture and urine culture were sent and results take 1 to 2 days
Medications
Use acetaminophen only as directed for age and weight
Do not use ibuprofen unless you were told it is safe
If antibiotics were prescribed take every dose as directed
Feeding and hydration
Encourage regular feeds
Watch wet diapers and hydration
Follow up
Follow up appointment within 24 hours
Return for a recheck sooner if symptoms worsen
Return to the ED now for any of these
Trouble breathing
Blue color or pauses in breathing
Very sleepy or hard to wake
Weak cry or not feeding
Fewer wet diapers than usual
New rash with spots that do not blanch
Seizure
Vomiting that prevents keeping feeds down
Fever that persists or any new concern
References
Guidelines and decision tools
American Academy of Pediatrics Clinical Practice Guideline Evaluation and Management of Well Appearing Febrile Infants 8 to 60 Days Old 2021
Risk stratified approach using urinalysis blood culture and inflammatory markers
LP and antibiotics selective in 29 to 60 days based on risk
Canadian Paediatric Society Position Statement Management of Well Appearing Febrile Young Infants Aged 90 Days or Younger 2024
Provides 29 to 60 day pathway and estimated invasive bacterial infection rates
Endorses risk stratification with inflammatory markers and urinalysis
Kuppermann et al PECARN clinical prediction rule for febrile infants 60 days and younger JAMA Pediatrics 2019
Uses urinalysis ANC and procalcitonin to identify low risk infants
Supports reduced LP and antibiotics in low risk profiles
Gomez et al Step by Step approach for febrile infants 90 days or younger 2016
Uses appearance age urinalysis procalcitonin CRP and ANC
Focuses on identifying low risk invasive bacterial infection
American Academy of Pediatrics Urinary Tract Infection guideline for 2 to 24 months 2011
Urine collection and interpretation principles applicable to infant evaluation
Imaging considerations after febrile UTI local protocol dependent
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.