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Dec 27, 2011

One of the most important factors driving the medical workup on a well appearing, febrile infant is the prevalence of serious bacterial infection (SBI) . This number changes depending on age and immunization status (pneumococcus vaccine having the most impact in North America.) The higher the likelihood of disease, the more aggressive the workup and treatment.

Prevalence of serious bacterial infection/meningitis by age

  • 0-14 days    (pre-vaccine)                             1/10
  • 14-28 days                                                       1/20
  • 28-60 days (pre-vaccine)                              1/100
  • 28-60 days (post-vaccine)                            1/1,000
  • 60-90 days                                                       1/1,000-1/10,000
  • >90 days                                                           1/>10,000
How do we make sense of these numbers and apply them to our evaluation of febrile infants? In this podcast, an interview with Dr. Andy Sloas of the PEM ED podcast goes through the method and madness of figuring out what to do when and why we do it at all. The above statistics and age related fever workups later in the blog post are adapted from Dr. Sloas' algorithm on fever without a source.

Pediatric Fever Trivia

Many parents will bring their febrile infant to the emergency department because the fever is not responding to antipyretics. Does response to antipyretics make SBI less likely?

No. This has been extensively studied and no relationship has been found between response to antipyretics and severity of illness or presence of bacteremia.

Yamamoto LT, Wigder HN, Fligner DJ, et al. Relationship of bacteremia to antipyretic therapy in febrile children. Pediatr Emerg Care. 1987;3:223-227. 

Should a chest X-ray be ordered on a febrile child < 3 months of age without respiratory symptoms?

The data to date would suggest no. The likelihood of finding an infiltrate on CXR is extremely low in the absence of ANY of the following exam findings:

  • tachypnea > 50 bpm
  • cough
  • nasal flaring
  • stridor
  • grunting
  • wheezing
  • ronchi
  • rales
  • hypoxia
  • coryza (runny nose)

If you see even one of these criteria in a febrile infant or neonate, it's a mandatory CXR, although I still find runny nose a bit of a hard sell indicating a lower respiratory tract infection. Caveat: a child >3 months with a WBC >20,000 should get a CXR to evaluate for occult pneumonia (even if asymptomatic)

ACEP Policy on Pediatric Fever PDF

Bachur R,Perry H,Harper MB.Occult pneumonias: empiric chest radiographs in febrile children with leukocytosis. Ann Emerg Med. 1999;33:166-173. [II]

What age groups of children are at higher risk for urinary tract infection?

0-6 months circumcised males

0-12 months uncircumcised males

0-24 months females

The term fever without a source implies that a child looks well yet still has a fever. When we want to say that a fever is caused by something we can identify on clinical presentation, what are the recognized/acceptable sources?

  1. HSV/Gingivostomatits
  2. Herpangina/Ulcerative Stomatits
  3. RSV
  4. Croup
  5. Influenza
  6. Varicella
  7. Viral Exanthum (rash)
  8. Enterovirus, coxsackie HFM dz, echovirus, rhinovirus, enterovirus
In the emergency department, it's virtually impossible to identify the exact type of virus causing an upper respiratory infection or gastroenteritis.  A little sniffle or drop of mucous from one nostril doesn't stop the workup, but a copious river of rhinorrhea and a hacking cough in a febrile 3 month old seal the deal.

 The Workup

It all comes down to what tests to order and what treatment to give for the different age groups. The following age based guidelines are based on Dr. Sloas’ approach to the febrile infant as laid out in the podcast. If you disagree with any of this, send us a note or leave a comment on our google voice line. There's nothing like a feud over pediatric fever.

Reference ABNORMAL values in the febrile infant

  • WBC<5 or >15, Band/neutrophil >0.2, Bandemia >1,500 mm3, absolute neutrophil count of >10,000
  • CSF > 8 WBC or positive gram stain
  • UA  > 10 WBC or positive gram stain
  • Stool WBCs or heme
  • Infiltrate on CXR

Age 0-28 days

Temp > 100.4  or 38C


CBC, blood cx, cath UA, CXR (I still do it), lumbar puncture, stool studies if needed

Disposition: Automatic admission and antibiotics


Ampicillin 50mg/kg plus

Gentamicin - Dose varies by age. Give if child is under 9 days old or

Cefotaxime - 50mg/kg. Give if child is 9-28 days.

Possible add ons

Vancomycin  15-20mg/kg

Acyclovir 60mg/kg/day divided q8hrs

The below presume that the child is well appearing, is on the recommended vaccination schedule and does not have an identifiable source of infection

 Age 29-60 days

temp >100.4 F or 38C


cbc, blood cx, cath UA, possible CXR, spinal tap, stool studies if needed


Admit for anything positive in workup, unable to get follow-up


50mg/kg ceftriaxone or

If Workup completely negative, no antibiotics and next day follow-up

 Age 60-90 days

If the temp is <39C, no testing and followup the next day

Temp >102.2F or 39C


Start with CBC and UA

If both CBC and UA are normal, no antibiotics. Have patient follow-up next day.

 Option 1

If either the CBC or UA are abnormal then proceed with LP and blood culture. And then...

If just the CBC is abnormal, give 50mg/kg ceftriaxone and follow-up next day

If UA is abnormal, give 50mg/kg ceftriaxone, and prior to discharge, initiate oral antibiotics for urinary pathogens (E. coli is the main player) cefixime orTMP/Sulfa. There are many other antibiotic choices for oral agents. The best choice often depends on resistance patterns in your region.

Option 2

There is wide variability in philosophy regarding LP with an abnormal CBC or UA in the 60-90 day age group. Many community ED docs and pediatricians will send blood culture after an abnormal CBC/UA but do not subscribe to the idea that all patients in this cohort need a spinal tap.

Age 3-6 months

Temp >102.2F or 39C


Cath UA

Treat if positive

Key Links

The PEM ED Podcast

Andy Sloas' algorithm for pediatric fever

EM BASIC Podcast

Emergency Ultrasound Podcast

Castlefest 2012