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FEVER AND SERIOUS BACTERIAL ILLNESS (SBI)

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Fever is the most common pediatric chief complaint presenting to an emergency department (ED) and accounts for 30% of outpatient visits. Infants and children are at relatively high risk for serious bacterial illness (SBI), which includes urinary tract infection (UTI), pneumonia, bacteremia or sepsis, and meningitis—in decreasing prevalence. Neonates are at the highest risk due to their immature immune response, while infants from 1 to 3 months of age gradually transition to the lower risk profile of older infants and children. The incidence of UTI is 5% overall in children 2 months to 2 years, with a prevalence of 3% to 8% in all febrile children visiting an ED. Widespread vaccination has dropped the incidence of occult bacteremia for children 3 to 36 months of age to 0.5% to 0.7%, with further decreases expected with the 13-valent pneumococcal conjugate vaccine. Meningitis risk decreases from about 1% in the first month of life to <0.1% later in infancy and childhood.

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Clinical Features

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In the neonate or infant <3 months of age, the threshold for concerning fever is 38°C (100.4°F); in infants and children 3 to 36 months old, the threshold is 39°C (102.2°F). In general, higher temperatures are associated with a higher incidence of SBI. Immature development may make reliable examination of younger infants difficult. Persistent crying, inability to console, poor feeding, or temperature instability may be the only findings suggestive of an SBI. In the neonate, there may not be any findings other than fever.

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Diagnosis and Differential

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Infants <3 months
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An ill-appearing infant should be managed aggressively for SBI, with full sepsis evaluation, parenteral antibiotics, and admission, but a well-appearing febrile infant less than 3 months of age presents a challenge because history and physical examination are rarely helpful in diagnosing or excluding SBI in this age group. Meningismus is rarely present; rales may not be appreciated without strong negative inspiratory forces; and bacteremia occurs even in the well-appearing infant. A history of cough, tachypnea, or hypoxemia (by pulse oximetry), however, should alert the examiner to a possible lower respiratory tract infection and consideration of the diagnosis of pneumonia.

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All febrile infants 0 to 28 days of age should receive full SBI evaluations, admission, and empiric antibiotic treatment. Antibiotic coverage in this age group includes ampicillin 50 mg/kg IV for Listeria monocytogenes and either gentamicin 2.5 mg/kg IV or cefotaxime 50 mg/kg IV for other common organisms. Avoid using ceftriaxone in this age group. Sepsis testing includes complete blood count (CBC), blood culture, urinalysis and urine culture, and lumbar puncture for CSF indices and culture. Obtain a chest radiograph if any respiratory signs described above are present, and order stool studies if the infant has diarrhea.

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Febrile infants 29 to 90 days old without a focal source may be stratified to low or high risk of SBI using one of three classic criteria: Rochester Criteria, Boston Criteria, or Philadelphia Protocol. To meet low-risk SBI status, the infant must be well-appearing with a normal urinalysis and normal White Blood Cell (WBC) count, between 5,000/mm3 and 15,000/mm3 for the Rochester and Philadelphia, and 5,000/mm3 and 20,000/mm3 for Boston. A negative CSF (WBC < 10 per hpf in Boston and WBC < 8 per hpf in Philadelphia) is also required for Boston and Philadelphia, and each criteria set has other parameters to complete a low-risk status (Table 66-1). Obtain a chest radiograph for infants with a suggestion of lower respiratory tract disease. Although there is evidence to support the use ...

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