What is the definition and management of fever according to Harrison's textbook?

From the Guidelines

Fever is defined as a measured temperature of greater than 38°C, according to the United States Centers for Disease Control and Prevention, and the Infectious Diseases Society of America defines fever in individuals greater than 65 years old as a single oral temperature greater than 37.8°C. The definition of fever can vary depending on the population and context, with different thresholds used for different age groups and clinical settings 1.

Key Considerations

• The normal body temperature range is subject to various factors such as age, gender, diurnal variation, and sampling site, and has been decreasing in the human population over the last 157 years 1.
• Fever management should focus on identifying and treating the underlying cause rather than simply normalizing temperature, with antipyretic medications recommended primarily for patient comfort 1.
• The use of antipyretic medications such as acetaminophen or ibuprofen may be beneficial in reducing fever and alleviating symptoms, but physical cooling measures like tepid sponging may be used for hyperpyrexia (temperature >41°C or 105.8°F) 1.

Clinical Guidelines

• The Society of Critical Care Medicine and the Infectious Diseases Society of America have defined fever in ICU patients as the presence of a single temperature measurement greater than or equal to 38.3°C 1.
• The Infectious Diseases Society of America has defined fever in individuals greater than 65 years old as a single oral temperature greater than 37.8°C, repeated temperature measurements greater than 37.2°C (oral) or greater than 37.5°C (rectal), or an increase from baseline greater than 1.1°C 1.
• The American College of Critical Care Medicine and the Infectious Diseases Society of America have recommended guidelines for evaluating new fever in critically ill adult patients, including the use of a thorough history, physical examination, and appropriate laboratory tests to identify infectious or non-infectious etiologies 1.

Patient Populations

• Fever in pediatric patients is a common presenting complaint, and the management of febrile infants and children can be challenging due to the risk of serious bacterial infections 1.
• The definition of fever in pediatric patients can vary, but a rectal temperature of greater than or equal to 38.0°C (100.4°F) is commonly used 1.
• The risk of serious bacterial infections in febrile infants and children varies by age, with neonates and young infants at higher risk 1.

Treatment Approach

• The treatment approach for fever should prioritize identifying and treating the underlying cause, rather than simply normalizing temperature, and should take into account the patient's age, clinical context, and underlying health status. Antipyretic medications and physical cooling measures may be used to alleviate symptoms and reduce fever, but the primary focus should be on addressing the underlying cause of the fever 1.

From the Research

Definition of Fever

• Fever is a complex physiological response involving the innate immune system and should not be characterized merely as a temperature above a certain threshold 2.
• The term "fever" is rarely defined in terms of the minimum temperature used to qualify as a fever, the type of thermometer employed in measuring patients' temperatures, or the site at which temperatures are taken 3.
• Historically, a temperature of 37.0°C (98.6°F) has been regarded as normal body temperature, but this definition may not be accurate for all individuals 4.

Management of Fever

• The management of fever depends on the underlying cause, and treatment should be tailored to the specific etiology 5.
• Paracetamol 1,000 mg is often used as the first-line treatment for fever, followed by a combination of paracetamol and ibuprofen 5.
• In cases of fever of unknown origin, a comprehensive history and physical examination should be performed to help narrow potential etiologies, and initial testing should include an evaluation for infectious etiologies, malignancies, inflammatory diseases, and miscellaneous causes 6.
• Empiric antimicrobial therapy is not recommended for the treatment of fever of unknown origin, except in patients who are neutropenic, immunocompromised, or critically ill 6.

Fever of Unknown Origin

• Fever of unknown origin is defined as a clinically documented temperature of 101°F or higher on several occasions, coupled with an unrevealing diagnostic workup 6.
• The differential diagnosis for fever of unknown origin is broad and includes infection, malignancy, noninfectious inflammatory disease, and miscellaneous causes 6.
• Up to 75% of cases of fever of unknown origin will resolve spontaneously without reaching a definitive diagnosis 6.