Fiebre

• Fever is a common symptom associated with a range of infectious and noninfectious etiologies
• Two-thirds of all children visit a physician for fever before they reach the age of 2 years
• The appropriate evaluation for fever depends on age, duration of illness, comorbidities, and associated signs and symptoms
• The etiology of fever is often revealed with careful history and physical examination
• Fever without source (FWS) is when a child has fever with no obvious explanation, most commonly due to self-limited viral illnesses
• Bacterial pathogens account for a small but clinically significant number of Fever without source (FWS) cases
• Fever of unknown origin (FUO) refers to prolonged fevers with no initial etiology found, with varying specific definitions
• The thermoregulatory center in the hypothalamus controls body temperature, with fever resulting from an elevated set point
• The febrile response not only elevates body temperature but also enhances the body's ability to eliminate infection through physiologic changes
• Fever has both positive and negative effects, impacting microorganism survival and immunologic responses
• Elevated body temperature without infectious or inflammatory stimuli is termed hyperthermia
• Hyperthermia can result from excessive heat production, inadequate heat dissipation, or hypothalamic dysfunction
• A detailed history for Fever without source (FWS) should address duration and pattern of fever, height of fever, associated symptoms, and more
• Rectal temperature measurement is the gold standard for children 3 years of age or younger to define fever
• Oral temperature measurement is reliable for cooperative patients older than 4–5 years of age
• Axillary temperature measurement is less precise than rectal temperatures, usually 0.5–0.85°C lower
• Tympanic membrane thermometers are often inaccurate in children
• Temporal artery temperature measurement correlates well with rectal temperature in some studies
• Physical examination is vital to classify the febrile child
• Rectal temperatures should be used in children 3 years of age and younger when detection of fever is critical for diagnosis and management
• The physical examination is crucial to classify febrile children as ill- or well-appearing, informing the need for laboratory and radiographic evaluation and subsequent management
• Ill-appearing children may show signs of shock, including weak peripheral pulses, tachycardia, poor perfusion, respiratory distress, mottling, cyanosis, or decreased mental status
• Observational scales like the Acute Illness Observation Scale (AIOS) can be used to assess serious illness in young febrile children, aiding in determining the severity of illness
• Most children with fever without a source (FWS) have self-limited benign viral infections, with common pathogens being adenovirus, human herpesvirus 6, enterovirus, or parechovirus
• Bacterial infections, especially in younger children, can manifest as FWS without localizing symptoms, with notable causes being urinary tract infections, bacteremia, and meningitis
• Noninfectious conditions causing FWS are rare, with historical clues or systemic signs indicating malignancy, rheumatic disorders, hyperthermia-related conditions, or recent immunizations as potential causes
• Higher rates of UTIs are found in females, especially those younger than 12 months of age
• For febrile males younger than 3 months of age, 20.1% of uncircumcised have a UTI; for circumcised males, the rate is 2.4%
• UTI rates are higher among children with abnormal genitourinary tract anatomy or neurogenic bladder
• Urine specimens should be obtained from children with FWS who have a history of UTI, urinary tract anomalies, vesicoureteral reflux, females younger than 12–24 months, uncircumcised males younger than 12 months, and circumcised males younger than 6 months
• Prompt evaluation of urine in all febrile infants younger than 2 months is mandatory
• Age-associated risk of bacteremia with UTIs, particularly in infants; incidence of bacteremia in patients with UTI younger than 2 months ranges from 4% to 15% depending on the setting
• Opinions differ on when to obtain blood cultures in infants with UTI, but a reasonable approach is to obtain blood cultures in children younger than 2–6 months with suspected UTI and in older ill-appearing infants with UTI
• Occult bacteremia is defined by the presence of a positive blood culture for pathogenic bacteria in a febrile patient who does not appear extremely ill and who has no focus of infection, excluding otitis media
• Prior to the introduction of conjugate pneumococcal vaccines, Streptococcus pneumoniae was a common cause of occult bacteremia in young children
• With the introduction of the 7-valent conjugate pneumococcal vaccine in 2000, rates of pneumococcal bacteremia decreased from 74.5 to 10 cases per 100,000 per year
• In immunized febrile children 3–36 months of age, the likelihood of detecting a contaminant on blood culture may be double the incidence of true occult bacteremia in the post–PCV-13 era
• Risk factors for recurrent occult bacteremia include functional or anatomic asplenia, defects in the innate immune system, and abnormalities in the toll-like receptor signaling pathway
• Most cases of bacteremia in children are not occult; Escherichia coli is the most common cause of bacteremia in children aged younger than 12 months, often associated with UTI
• N. meningitidis bacteremia is frequently associated with serious sequelae, including shock and meningitis