Febrile Infants 8 to 28 Days Old! Pediatric Fever Update

Knowledge and Science evolve. Sure this can lead to confusion and frustration; however, those of us who wish to continue to use evidence to help us in our practice of the art of medicine know that the best information we have today will be different than that which we had in the past. This does not mean the past was maliciously moronic or today is provocatively disrespectful of prior knowledge. It is evolution, not revolution. It is this evolution that continues to push bright physician scientists to ask the important questions about management of febrile infants. Last week we discussed the new AAP Guidelines for the Febrile Infants 29 to 60 days old. [Pantell, 2021PMID 34281996]. So this week, let’s round out our understanding of the guideline updates for the evaluation and management of those Febrile Infants 8 to 28 Days Old:

Febrile Infants 8 to 28 days old: Some Basics to Keep in Mind

  • As was mentioned last week, the evaluation of febrile infants is evolving because of several factors: [Pantell, 2021, PMID 34281996]
    • Bacteriology is changing (ex, E. Coli is now the most common cause of invasive bacterial infections in this age group)
    • Testing is changing (ex, WBC is no longer recommended as a discriminator risk stratification)
    • Specific Pathogen Identification is improving and more timely (some results within 1 hr)
  • Risk Stratification is not an all or nothing proclamation. [Pantell, 2021, PMID 34281996]
    • Risk for invasive bacterial infection alters with age.
    • Performing Lumbar Punctures, giving empiric antibiotics, and admitting everyone is also not without its risks.
    • Involving parents/guardians in decision making can be appropriate when your risk : benefit ratio is equivalent.
  • Febrile Infants < 8 days old are NOT included in this Guideline.
    • This does not mean you get to ignore these febrile infants… in fact these ones are the neonates that you should trust the least.
    • Highest risk and should be evaluated and managed the most conservatively.
  • Febrile infants 8 – 28 days of age do NOT all have the same risk. [Pantell, 2021, PMID 34281996]
    • Today’s research shows that the risk for invasive bacterial infections decreases substantially after the 1st week of life.
    • This risk continues to decreased in the population of febrile infants over the next 8 weeks.
    • For instance, PECARN evidence shows that the rate of bacteremia decreases from 5.3% in week 2 to 3.3% in week 3 and 1.6% in week 4 of life with no difference between week 4 and weeks 5 and 6.
    • This allows there to be another risk stratum – the febrile infants 21 to 28 days of age!

Febrile Infants 8 to 28 days old: What is the same?

  • All still need Urine specimen and Blood Culture to be obtained. [Pantell, 2021, PMID 34281996]
  • For the febrile infants 8 – 21 days old, the management will be similar to what you have always done for the febrile neonate. [Pantell, 2021, PMID 34281996]
    • Obtain CSF for analysis and Culture.
    • All will be admitted for antibiotics.
    • Since they will be admitted, inflammatory markers are less necessary.

Febrile Infants 8 to 28 days old: What has changed?

  • Most obviously is the development of another age risk stratum. [Pantell, 2021, PMID 34281996]
    • Infants < 8 days old (not even a part of the guideline due to high risk)
    • Infants 8 to 21 days old
    • Infants 22 to 28 days old
    • Infants 29 to 60 days old
  • Urine assessment is a stepwise process. [Pantell, 2021, PMID 34281996]
    • Since the definition of UTI is dependent upon both an abnormal Urinalysis and Urine Culture, recommendations are to send Cultures on urine samples that have abnormal Urinalysis results.
    • Urine sample in the febrile infants 8 – 21 days old should be obtained by catheter or suprapubic aspiration.
    • Urine sample in the febrile infants 21 – 28 days old may be obtained from bag… and if that is abnormal then catheter / suprapubic aspiration is needed for culture (or you can just start with the catheter / suprapubic aspiration).
  • Infants 21 to 28 days old can be managed more like the slightly older febrile infants.
    • Based on provider and parent/guardian risk tolerance.
    • Based on Inflammatory Markers (IM) (abnormal values)
      • Procalcitonin (> 0.5 ng/mL)
      • CRP (> 20mg/L)
      • ANC (>4000, 5200 /mm^3)
      • Procalcitonin is favored, but if not available, then obtain both CRP and ANC and then a Temperature > 38.5C is also considered an abnormal IM.
      • NO one cares about the WBC count!
    • IMs can risk stratify this group.
      • ANY IM Abnormal = Obtain CSF
        • If CSF is normal, these patients may be appropriate for observation at Home!
        • Antibiotics should be given whether admitted or discharged home.
      • ALL IMs Normal = “May perform LP”
        • If no LP performed (or No CSF obtained from an attempted LP), then admit for observation in the hospital. You may still elect to give antibiotics per the guideline… but
        • If CSF is obtained, then manage based on CSF results (abnormal = admit for antibiotics; normal = choice of observing at home or in the hospital, with or without antibiotics.)

Moral of the Morsel

  • Neonates are not all created equal! The febrile infant who is in her/his 4th week of life does not have the same risk of invasive bacterial infections that the one in the 2nd week of life does.
  • It’s not as cookie cutter as it once was… which is good… provided that you know what cookies you are baking. (see what I did there?? Com’on! These are Morsels!)
  • Risk Tolerance is variable between all of us. Realize that there are options that these guidelines allow, but how you choose to select the options is dependent not just on the patient, but also on your own risk tolerance.


Sean M. Fox
Sean M. Fox

I enjoy taking care of patients and I finding it endlessly rewarding to help train others to do the same. I trained at the Combined Emergency Medicine and Pediatrics residency program at University of Maryland, where I had the tremendous fortune of learning from world renowned educators and clinicians. Now I have the unbelievable honor of working with an unbelievably gifted group of practitioners at Carolinas Medical Center. I strive every day to inspire my residents as much as they inspire me.

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