Febrile Infants: What to do?

3 groups of infants:

  1. Neonates <30 days (i.e < 1month)
  2. Young infants 30-90 days (i.e < 3months)
  3. Old infants 3 months-1 year
  4. Young children 1 year-3 years

Let’s classify the infants into low and high risk:

  • The most widely used is Rochester criteria (applied to <2 months infants)
  • Toxic looking infants is a no brainer for us.
  • What about well appearing infants? Which criteria should we be using?

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Risk of SBI (serious bacterial infection) in well appearing group according to ages:

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ummary is excpet in neonates, the risk of occult SBIs in infants (>1 month) is ~2-4% if focal infections (including otitis media) have been excluded and low risk lab criteria (i.e no leucocytosis, UFEME is clean and stool WBC is negative).

1. Neonates

  • Low risk criteria is controversial in them. In view of the 7% risk of occult SBI, a full septic workup should be done in every febrile infant, including getting a LP.

2. Young infants (not vaccinated yet)

  • Apply Rochester criteria + UFEME.
  • Routine LP is (maybe) not indicated.
    – However, this is controversial. Some other criteria eg Philadelphia use LP to stratify infants into low risk category while some others eg Rochester do not use.
    – In five studies of the risk of SBIs in infants < 3 months of age in which examination of CSF was not performed,
    872 of 1,713 febrile young infants with FWS were classified as low risk. Ten had an SBI; none had occult meningitis.
  • CXR should be done if the febrile infant has leucocytosis, fever>1 days, cough/other resp.signs or abnormal auscultatory findings. Use of pulse oximetry may also help in deciding whether a CXR should be done, although a normal pulse oximetry does not exclude occult pneumonias.
  • If the infant has diarrhea, make sure no blood (not dysenteric) and stool WBC should be done. Stool culture should be done if stool WBC is positive.

3. Older infants (vaccinated)

  • Rochester criteria is NOT validated in this group of infants.
  • Vaccination reduces the risk of pneumonia and meningitis, but it is not to risk = 0.
  • Occult bacteremia in this group is usually due to Salmonella (most have diarrhea) or N.meningitidis.
    – If patient has diarrhea, stool WBC should be done.
    – Unfortunately, no way to detect occult meningococcemia unless if there are physical signs.
    – Compared to occult pneumococcal infections, occult Salmonella bacteremia and meningococcemia often have NORMAL WBC count.
  • Routine UFEME (by urethral catherization) should be done in febrile infants (>39 celcius):
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    – In all circumsized males < 6 months
    – In all females and uncircumsized males <24 months
    – In infants with prior history of UTI (possibility of urinary tract anatomic anomalies)
  • Pyuria is falsely negative in 20%, use of leucocyte esterase and/or nitrite together will increase sens & spec.
  • Occult pneumonias are most probably(and mostly) due to viral infections.
    – bacterial pneumonia is often secondary to viral infections. However, CXR and lab cannot differentiate viral vs bacterial
    – Need to identify those who need CXR:
    i) Febrile + resp.signs or abnormal ausc.findings
    ii) Leucocytosis (WBC >20,000: more likely to be bacterial)

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Reference:

Larry J. Baraff, MD. Management of Infants and Young Children with Fever without Source. PEDIATRIC ANNALS 2009:37(10);673-79

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