15 Fever

This chapter emphasizes fever as the presenting problem rather than fever of unknown origin (FUO). Classically, FUO is a temperature greater than 101° F that occurs on several occasions during a 3-week period in an ambulatory patient or during a 1-week period in a hospitalized patient. Some suggest that the fever must persist for only 10 to 14 days in an outpatient. The cause of the fever should not be apparent, even after a complete history, physical examination, complete blood count (CBC) with differential, urinalysis, 27-item blood chemistry analysis (SMA-27), cardiogram, chest radiograph, monospot test, and intermediate-strength purified protein derivative (tuberculin [PPD]) test.

In most febrile patients, a diagnosis is readily apparent or becomes evident within a few days. FUO is usually caused by a common disorder that displays atypical manifestations or is a benign, self-limiting illness for which no specific cause is found. Nevertheless, it is still important for the physician to search for occult sources of infection, especially if a response to antibiotics is possible.

Normal oral temperature is 98.6° F (37° C) plus or minus about 1° F. Body temperature shows normal diurnal variation; the lowest point is registered in the early-morning hours, and the highest is reached in the late afternoon.

Acute fevers are caused most often by upper respiratory infections (URIs), tonsillitis, viral syndromes (e.g., influenza, gastroenteritis), drug reactions, and genitourinary (GU) tract infections (e.g., cystitis, pyelonephritis, prostatitis). Less often, acute fevers accompany meningitis, intra-abdominal abscess, and other forms of sepsis.

Chronic low-grade fevers are caused most often by hepatitis, tuberculosis (TB), infectious mononucleosis (especially in children and young adults), lymphomas, and occult neoplasms (especially in elderly patients). If the source of a fever is not readily apparent on the basis of history, symptoms, or physical examination, the possibility of drug fever (particularly from penicillins, cephalosporins, antituberculosis agents, sulfonamides, macrolides, aminoglycosides, methyldopa, procainamide, and phenytoin), sinusitis, dental abscess, prostatitis, TB, infectious mononucleosis (especially with associated fatigue), and hepatitis (both anicteric and icteric) should be considered. Cocaine, Ecstasy, and amphetamine abuse may also cause hyperpyrexia.

When recurrent fever occurs at regular intervals (21-28 days) in a child, the most likely cause is PFAPA syndrome (periodic fever, aphthous ulcers, pharyngitis, and adenopathy). When recurrent fever occurs at irregular intervals in a child, the most common causes include repeated viral infections; repeated bacterial or occult bacterial infections, especially urinary tract infections; and inflammatory bowel disease, especially Crohn’s disease.

Less common causes of fever without a readily apparent cause from presenting symptomatology include neoplasms, abdominal abscess, multiple pulmonary emboli, diverticulitis, subacute bacterial endocarditis (SBE), osteomyelitis, and thrombophlebitis.

Nature of Patient

The most common cause of fever in children is a viral URI. Young children usually have signs or symptoms of a respiratory infection but may show only fever. Other viral causes of fever in children are chickenpox (varicella), “slapped cheek disease” (erythema infectiosum,) roseola infantum, papulovesicular acro-located syndrome (PALS), and enteroviral infections. Common causes of fever in children who have no localizing signs or symptoms at the time of examination include URIs, gastroenteritis, tonsillitis, otitis media, urinary tract infections (UTIs), measles, and roseola. A true FUO in a child has serious implications. In one study, 41% of children with true FUO were found to have a chronic or fatal disease. Fever in children younger than 3 months may be the only indication of a serious disease. Unexplained fever in adolescents may be a manifestation of drug abuse or endocarditis. Severe, acute respiratory disease (SARS) seems to occur more frequently in young adults, for whom the average age is 40 years.

A history of UTI, sinusitis, prostatitis, and recurrent pneumonia on the same side increases the likelihood that the current febrile episode may be similar to those in the past.

In the absence of physical signs or symptoms suggesting the cause of fever, the physician should question the patient specifically about occupational history, exposure or contact with animals (e.g., bird flu, Lyme disease), chemicals, drug ingestion, travel away from the patient’s usual residence (SARS, malaria, typhoid, and rickettsial infections). Fever from unusual infections is more common in immunocompromised patients and in those with human immunodeficiency virus (HIV) infection. In febrile, elderly patients who lack signs or symptoms that suggest a cause, TB, occult neoplasm, temporal arteritis, and recurrent pulmonary emboli must be considered. Febrile response to infections is often diminished or absent in elderly patients,

In the postoperative patient, fever may be caused by infection, atelectasis, or a reaction to anesthesia or medications.

Nature of Symptoms

Contrary to common belief, studies have shown that the fever pattern is not likely to be helpful diagnostically, although the magnitude may. Temperatures above 105° F (40.5° C) suggest intracranial pathology, factitious fever, pancreatitis, or UTI, especially with shaking chills. When severe hyperthermia is associated with muscle rigidity, the following causes should be suspected: Ecstasy, cocaine, or other sympathomimetic agents, serotonin syndrome, antipsychotic drugs, drugs with strong anticholinergic properties, and inhalational anesthetics. Other causes are thyrotoxicosis, tetanus, strychnine poisoning, and central nervous system (CNS) infections. A mild fever suggests URI or a flulike syndrome. Low-grade fever (especially when associated with fatigue) may be the initial manifestation of tuberculosis, infectious mononucleosis, or hepatitis. The fever range may also be helpful. A narrow range of fever, without spikes or chills, may be seen in lymphomas such as Hodgkin’s disease, lymphatic leukemia, and hypernephroma.

A fever in an emotionally disturbed patient who is otherwise in good health and is employed in a health care–related position, has no weight loss, and demonstrates no related or proportional increase in pulse rate should make the physician suspect a factitious cause. Some investigators report that this situation is more likely in female patients. If a factitious cause is suspected, a simultaneous measurement of urine and rectal temperature should be obtained. The temperature of the urine normally approximates rectal temperature, and a factitious cause should be suspected if the rectal temperature is significantly (usually more than 2.7° C) higher than the urine temperature. Other clues to a factitious cause include failure of temperature to follow a diurnal pattern, rapid defervescence without sweating, high temperature without prostration, and high temperature without weight loss or night sweats.

Drug fevers usually occur about 7 to 10 days after initial administration but reappear rapidly with subsequent administration.

Mar 21, 2018 | Posted by in BIOCHEMISTRY | Comments Off on Fever
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