Fever

CHAPTER 16 Fever


Fever is an elevation of temperature above the normal daily variation and is a symptom of an underlying process. The major common cause of fever is infection; however, noninfectious processes may present with fever. Fever of unknown origin (FUO) occurs in a small percentage of cases. These fevers are usually caused by an infection that has not yet been identified. A meticulous history and physical examination supported by laboratory investigation are necessary to find the origin of the fever.


There are three types of fevers, each caused by a specific pathophysiological process. The first involves the raising of the hypothalamic set point. The receptors in the area of the hypothalamus regulating body temperature are triggered to reset at a higher core body temperature. This results in an elevation of the helper T-cell production and an elevation in the effectiveness of interferon. Infection, collagen disease, vascular disease, and malignancy are commonly responsible for these fevers.


A second type of fever is a result of heat production exceeding heat loss. Here the set point is normal, and heat loss mechanisms are active. Fever occurs either because the body raises its metabolic heat production or because the environmental heat load exceeds normal heat loss mechanisms. Aspirin overdose, malignant hyperthermia, hyperthyroidism, or hypernatremia may cause this type of fever.


A third type of fever is caused by a defective heat loss mechanism that cannot cope with normal heat load. Heat stroke, poisoning with anticholinergic drugs, ectodermal dysplasia, and burns are causes of this kind of fever.


For the first type of fever, antipyretics are given to lower the hypothalamic set point. Antipyretics are ineffective for the second and third types of fever.



Diagnostic reasoning: focused history














Genitourinary tract


Upper urinary tract infection (UTI) in adults commonly produces systemic symptoms with flank pain and fever (see Chapters 17, 31, and 32). Fever with cystitis is uncommon in adults, but children with UTIs present with systemic rather than localized signs and symptoms. UTI is the most common infection in girls younger than 2 years who present with a high fever and in all infants younger than 90 days with fever. Pelvic inflammatory disease in women may cause fever as well as an increased amount of vaginal discharge and bleeding after intercourse. Men who have an acute UTI often present with chills, high fever, urinary frequency and urgency, perineal pain, and low back pain. They may also have penile discharge.



Ear, nose, and throat symptoms


Viral infections of the upper respiratory tract are common and usually produce fever (see Chapters 14, 22, and 29). Otitis media is common in children. Fever may accompany both viral and bacterial pharyngitis. Pharyngitis is frequently manifested only by fever, with the infection localizing 1 or 2 days later. Acute sinusitis can produce a fever. Aphthous ulcers with pharyngitis and cervical lymphadenopathy are seen in children with periodic fevers.



Respiratory or gastrointestinal symptoms


Most febrile illnesses are caused by viral upper respiratory infection (URI), lower respiratory infection (LRI) (see Chapters 10 and 13), or gastrointestinal (GI) tract infection (see Chapter 2). Localized symptoms can help pinpoint the cause of the fever. Vomiting occasionally signals pneumonia.











Travel


Patients can be exposed to an emerging infectious disease based on their travel activities. A history of travel out of the country presents the possibility of infection with amebiasis, malaria, schistosomiasis, typhoid fever, or hepatitis A and B. Dengue is the most common vector-borne disease worldwide and is a differential diagnosis for acute febrile illnesses in patients who live or have recently traveled to the tropics or subtropical areas of the United States. Epidemiological surveillance data continually provide updates on patterns of occurrence of infections such as severe acute respiratory syndrome (SARS), avian influenza or “bird flu,” and West Nile virus (see Box 16-1).



Box 16-1 Emerging Infectious Diseases Associated with Fever



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Apr 10, 2017 | Posted by in NURSING | Comments Off on Fever

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