Fever without focus

Fever Without Localizing Signs in Children

• Fever is defined as an elevation of body temperature exceeding the normal daily variation, accompanied by an increase in hypothalamic set point.
• Another definition is a temperature of more than 37.2°C before noon or 37.7°C after noon.
• Fever without localizing signs refers to cases where the only sign is fever, and no other localized symptoms are present.
• Fever without localizing signs in children accounts for about 70% of consultations to pediatricians.
• The etiology, evaluation, and management of this condition depend on the child's age, as younger children are at higher risk of serious bacterial infection.

Objectives of Studying Fever in Children

• Defining fever.
• Evaluating and treating patients with fever.
• Determining appropriate laboratory tests based on age group.
• Identifying high-risk patients for sepsis.
• Determining appropriate hospitalization criteria.
• Establishing when empirical antibiotic therapy should be initiated.
• Recognizing patterns of fever (intermittent, remittent, continuous).
• Recognizing altered fever responses and situations where fever may not be present despite infection.
• Understanding the factors associated with neonatal sepsis.
• Identifying pathogens in neonates.

Definitions of Fever

• Fever is defined as an elevation in body temperature that exceeds the normal daily variation. This increase is typically accompanied by a change in the hypothalamic set point.

Classifications of Fever

• Normal body temperature ranges from 36.6°C to 37.2°C.
• Low-grade fever ranges from 37.2°C to 37.8°C.
• Moderate fever ranges from 37.8°C to 39.4°C.
• High-grade fever ranges from 39.4°C to 40.5°C.
• Hyperpyrexia is a temperature greater than 40.5°C.

Different Body Sites and Temperature Measurement

• Rectal temperature is considered the standard and is 0.5-0.6°C higher than oral temperature.
• Oral temperature is 0.8-1.0°C lower than rectal temperature.
• Axillary temperature is 0.5-0.6°C lower than rectal temperature.
• Tympanic temperature is 0.5-0.6°C lower than rectal temperature.

Physiology of Fever

• Fever is not a disease but a body response to pyrogens (exogenous or endogenous).
• Exogenous pyrogens include bacteria, viruses, fungi, and allergens.
• Endogenous pyrogens (EPs) include immune complexes and lymphokines.
• Major EPs include IL-1, IL-6, and TNF-α.

Pathogenesis of Fever

• Pyrogens & destroyed cells activate macrophages.
• Toxins trigger the release of IL-1β and cytokines, which affect the hypothalamus.
• Prostaglandin E2 is produced in response to these cytokines, increasing body temperature.
• Antipyretics like paracetamol and ibuprofen block the production of PGE2.

Benefits of Fever

• WBCs function best in the range of 38-40°C, effectively fighting bacteria.
• Fever boosts interferon activity, which hinders viral replication.
• Fever directly inhibits the replication of Coxsackie and polio viruses.

Disadvantages of Fever

• Hypercatabolism leads to nitrogen wastage, weight loss, and weakness.
• Excessive sweating can cause electrolyte imbalance.
• High fevers can lead to febrile convulsions and brain damage.
• Circulatory overload and arrhythmia are possible complications.

Patterns of Fever

• Intermittent fever: Fever that fluctuates, touching the baseline for periods during the day.
• Remittent fever: Fever fluctuations above a baseline but never reaching the baseline within a 24-hour period.
• Continuous fever: Fever that stays above the baseline without significant fluctuations within a 24-hour period.

Altered Fever Responses

• Newborns, elderly individuals, patients with uremia, severe malnutrition or those on corticosteroids may not demonstrate fever despite infection.

Fever with Focus vs. Fever without Focus

• Fever with focus: Fever associated with localized symptoms or signs (e.g., urinary tract infection, pneumonia, cough).
• Fever without focus: Fever as the only sign, unrelated to any localized symptoms or signs.

Fever of Unknown Origin (FUO)

• Characterized by persistent fever (≥ 38.3°C on multiple occasions) lasting for more than 3 weeks, with no identifiable cause after a week of extensive investigations.

Evaluation of Patients with Fever Without Localizing Signs/Symptoms

• Step 1: Detailed history and physical examination, including head-to-toe assessment
• Step 2: Specific lab tests and accessory studies, choosing appropriate tests
• Step 3: Decision on next steps, including hospitalization or outpatient care, and need for antibiotics according to age and risk factors.

Neonatal Fever (up to one month)

• Physical examination may not reliably detect serious infections.
• Meningitis should be a strong clinical consideration in neonates with fever.
• Common symptoms include hyperthermia or hypothermia, lethargy, poor feeding, vomiting, apnea, jaundice, dyspnea, hypotension, diarrhea, abdominal distension, bulging fontanelle, seizures, and bleeding.
• Risk factors for sepsis include premature rupture of membranes, maternal fever, and foul-smelling amniotic fluid.
• Common pathogens include Group B streptococcus, E. coli, Staphylococcus aureus, Klebsiellae, Listeria monocytogenes, fungi, and herpes simplex virus.
• Full sepsis workup including CBC, CRP, electrolytes, blood cultures, urine cultures (via catheter or suprapubic aspiration), CXR, and possibly lumbar puncture is needed for suspected sepsis.

Children (One to three months old)

• Majority of fevers are viral, but serious bacterial infections are possible.
• Common pathogens include Group B strep, Listeria monocytogenes, H influenzae, Staphylococcus aureus, Salmonella, Meningococcus, and E. coli.
• Low-risk criteria for children with fever but no other apparent symptoms: non-toxic appearance, no significant complications in medical history, normal physical examination, and normal lab tests.
• Hospitalization and broad-spectrum antibiotics with empirical therapy are crucial for high-risk cases.
• Reassurance and symptomatic care are appropriate for low-risk situations.

Children (Three to 36 months old)

• Fever in this age range is often viral, with a 30% chance of no localized infection symptoms.
• Common pathogens include Streptococcus pneumoniae, Meningococcus, Salmonella, and HiB.
• Low-risk cases might be managed with symptomatic treatment and outpatient follow-up.
• High-risk criteria include unwell or toxic appearance, WBC greater than 15,000 or less than 5,000, and any positive findings on various investigations.
• Hospitalization and parental antibiotics are necessary for potentially severe cases.

Antipyretics

• Acetaminophen is a first-line antipyretic for fever and is generally well-tolerated with minimal side effects.
• Pediatric dose is 10-15 mg/kg every 4-6 hours.
• Adult dose is 650 mg every 4 hours.
• Acetaminophen can be hepatotoxic in high doses and can upset the stomach.
• Other antipyretics include ibuprofen and mefenamic acid.

Important Considerations

• Avoid giving aspirin to children under 18 years old due to the risk of Reye's syndrome.
• Tepid sponge baths (27°C) can help reduce fever.
• Maintaining a comfortable room temperature is recommended.