Lactante Febril

The Febrile Infant: What’s New?
M. Douglas Baker, MD, FAAP, ⁎ Jeffrey R. Avner, MD, FAAP†
Fever in young infants often accompanies bacterial disease. Approximately 10% of febrile infants younger than 2 months will have associated bacteriuria, bacteremia, or other bacterial disease. In spite of assertions to the contrary, well physical appearance does not reliably rule out the presence ofbacterial disease in this population. Accordingly, the presence of fever in infants younger than 2 months demands immediate and comprehensive management. The manuscript reviews current management controversies in the evaluation and management of febrile young infants. We describe the use and applicability of various clinical predictor sets for determining which infants are at low risk for seriousbacterial illness and, in particular, whether a minimum workup is required, and if so, what constitutes those necessary laboratory tests. We also discuss whether the management should vary by the age of the infant (younger than 1 month vs 1-2 months old), the practice setting (office vs the emergency department), and the presence of concurrent viral infections. Clin Ped Emerg Med 9:213-220 © 2008Elsevier Inc. All rights reserved. KEYWORDS fever, infant, neonate, management, infection, emergency

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he management of the febrile illnesses in young infants has been a topic of debate for decades. In a large part, the concerns of the practitioner lie in the knowledge that not only is the risk of serious bacterial illness higher in young infants, but also the clinical clues that are often used todetect serious illness are not reliable. During the first 2 months of life, the infant's immune system is relatively immature. Chemotactic responses such as opsonin activity, macrophage function, and neutrophil activity are decreased, making the infant more susceptible to bacterial illness. In addition, although recent vaccination for Haemophilus influenzae type b and Streptococcus pneumoniae hasled to a decline in invasive illness from those organisms, the newborn is still exposed to maternally transmitted organisms. In particular, gram-negative bacilli, Listeria, Enterococcous, and group B Streptococcus remain frequent etiologies of disease at this age. These bacterial

⁎University of Texas Southwestern Medical Center, Children's Medical Center, Dallas, TX. †Albert Einstein Collegeof Medicine, Children's Hospital at Montefiore, Bronx, NY. Reprint requests and correspondence: M. Douglas Baker, MD, Children's Medical Center, 1935 Medical District Drive, Dallas, TX 75235. (E-mail: douglas.baker@utsouthwestern.edu) 1522-8401/$ - see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.cpem.2008.09.005

diseases constitute about 10% of discharge diagnoses forinfants younger than 2 months [1-5]. Although urinary tract infection is the most common serious bacterial illness identified, 1% to 3% of febrile infants have bacteremia and/ or bacterial meningitis. Furthermore, clinical illness indicators such as state variation and reaction to parent stimulation are not reliable predictors of serious bacterial illness at this age [2,3,6]. As many as 65% offebrile infants with serious bacterial illness appear well on initial examination [6]. These concerns led to a conservative management strategy that was extrapolated from the experience with febrile infants in the newborn nursery. Thus, in the 1980s, the “rules” for management of febrile infants younger than 2 months generally included an evaluation for sepsis (including urine, blood and spinal fluidexamination), inpatient admission, and empirical antibiotic therapy pending culture results [1,7,8]. By the 1990s, several investigators developed a combination of clinical and laboratory criteria to be used as a way of stratifying these febrile infants by their risk of serious illness [2-4]. Most of these studies showed high sensitivities and negative predictive values. Although the data sets...