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Fever is the most common chief complaint of children presenting to the ED, and accounts for approximately 30% of pediatric outpatient visits. Emergency providers evaluating febrile children must differentiate mildly ill from seriously ill children, a challenge that may be compounded when nonspecific symptoms or no focus of infection are apparent, especially in the neonate and infant. The extent of the diagnostic workup and the initiation of appropriate management must be determined. Many factors, such as clinical assessment, physical examination findings, age of the patient, immunization status, and height of the fever, influence evaluation and management decisions.

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Fever is a symptom of underlying disease, which may be due to acute processes secondary to infection, or more chronic processes, such as rheumatologic or oncologic diseases. The focus of this chapter is the management of a neonate, infant, or child (Table 113-1) with acute fever who is at risk for serious bacterial illness (SBI). SBI is bacterial infection in neonates, infants, and young children with high morbidity and mortality if not properly treated.

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Table 113-1 Pediatric Age Definitions 
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Pathophysiology

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Fever is defined as a rise in core body temperature associated with a resetting of the body’s thermostat. This thermostat is located in the preoptic region of the anterior hypothalamus. Exogenous fever-producing substances (pyrogens), such as bacteria, bacterial endotoxin, antigen-antibody complexes, yeast, viruses, and etiocholanolone, may stimulate the formation and release of endogenous pyrogens. Endogenous pyrogens are produced by neutrophils, monocytes, hepatic Kupffer cells, splenic sinusoidal cells, alveolar macrophages, and peritoneal lining cells, and are believed to induce the synthesis of prostaglandins in the hypothalamus. Endogenous pyrogens include interleukin-1, interleukin-6, and tumor necrosis factor.1 The body’s thermostat is then reset at a higher setting, and the patient, whose own temperature is below that of the body’s thermostat, experiences chills. Peripheral vasoconstriction, shivering, central pooling, and behavioral activity (e.g., putting on a sweater or drinking hot tea) lead to an increase in body temperature.

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Clinical Features

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Any elevation in temperature above normal is considered a fever, but the threshold for concerning fever varies with the age group and is related to the ability of signs and symptoms to identify the underlying cause of fever. Acute fever is fever for <7 days. In the neonate or infant <2 to 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 children >36 months old, the definition of significant fever is not fixed because most children >36 months old should demonstrate signs or symptoms of the underlying cause. In children with developmental delay or mental retardation, with limited ability to demonstrate specific signs and symptoms, the cause of fever may be difficult ...

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