Chapter 119: Fever and Serious Bacterial Illness in Infants and Children

INTRODUCTION AND EPIDEMIOLOGY

Fever is the most common chief complaint of children presenting to the ED, accounting for approximately 30% of pediatric outpatient visits. It is critical to differentiate mildly ill from seriously ill children with fever, especially in the neonate and infant. This challenge is compounded by the nonspecific symptoms and lack of a focus of infection in most children with fever. Many factors influence evaluation and management, including clinical assessment, physical examination findings, patient age, immunization status, and height of the fever.

This chapter focuses on the management of a neonate, infant, or child with acute fever at risk for serious bacterial illness, because morbidity and mortality are high if serious bacterial illness is missed or not properly treated. Neonates, defined as infants <1 month old, are at highest risk. Infants between 1 and 2 months of age are also at risk due to relative immunosuppression. The significance of age groups is discussed in the subsequent sections.

FEVER

Any elevation in temperature above normal is commonly considered a fever. A cutoff temperature formally defining fever is not universally accepted. In infants, the threshold for relative concern has traditionally been 38°C (100.4°F). In the neonate or infant <2 to 3 months of age, temperature <36°C (96.8°F) is equally concerning. Historically, occult bacteremia criteria used 39°C (102.2°F) in those 3 to 36 months in age, and a temperature >41°C (105.8°F) was considered to confer increased risk for serious bacterial infection.

In children >36 months old, sources of serious bacterial infection can be reliably ascertained by specific signs or symptoms. In infants and younger children, or children with developmental delay, who have limited ability to demonstrate specific signs and symptoms, the cause of fever may be difficult to determine, and more testing is often necessary.

Axillary temperatures are 0.6°C (1°F) lower than oral temperatures, which are 0.6°C (1°F) lower than rectal temperatures. Temperatures taken with infrared thermometers are of variable reliability and reproducibility.^1,2

Fever is treated with acetaminophen or ibuprofen. The dosage of acetaminophen is 15 milligrams/kg/dose PO or PR (maximum daily dose, 80 milligrams/kg) every 4 to 6 hours, up to five times per day. Acetaminophen may also be given IV with dosages, intervals, and maximum daily dose differing by age. The dosage of ibuprofen is 10 milligrams/kg/dose (maximum daily dose, 40 milligrams/kg) every 6 to 8 hours. Ibuprofen can be given to children older than 6 months of age.

SERIOUS BACTERIAL ILLNESS

Infants ≤3 months of age, and especially neonates, are relatively immunodeficient. Neonates and young infants demonstrate decreased opsonin activity, decreased ...