Also found in: Dictionary, Thesaurus, Legal, Acronyms, Idioms, Encyclopedia, Wikipedia.
Causes and symptoms
- newborn (three months or younger) with a fever over 100.5 °F (38 °C)
- infant or child with a fever over 103 °F (39.4 °C)
- fever accompanied by severe headache, neck stiffness, mental confusion, or severe swelling of the throat
Normal body temperature when the body is at rest is 37°C (98.6°F). This is an average or mean body temperature that varies from person to person and from hour to hour in an individual. The route by which a body temperature is measured affects the reading. The normal oral temperature ranges from 36° to 37.5°C (96.8° to 99.5°F). If the temperature is measured rectally, the norm would be 0.5°C (1°F) higher. An axillary temperature would be 0.5°C (1°F) lower. Because of these differences, the number should always be followed by the route by which the temperature was taken when the reading is recorded.
Factors that can cause a temporary elevation in body temperature include age, physical activity, emotional stress, and ovulation. If a person has a consistently elevated temperature, fever is said to exist. A low-grade fever is marked by temperatures between 37.5° and 38.2°C (99.5° and 101°F) when taken orally. A high-grade fever is present when the oral temperature is above 38.2°C (101°F).
Types of fever include continued or continuous fever, one lasting more than 24 hours without significant variation or any return to normal body temperature; intermittent fever, in which at least once during a 24-hour period the fever spikes are separated by a return to normal body temperature; remittent fever, in which elevated body temperature shows fluctuations each day but never returns to normal; and recurrent (or relapsing) fever, in which periods of fever and normal body temperature alternate and last about 5 to 7 days each.
The regulation of body temperature is under the control of the hypothalamus. Thermolysis, or dissipation of body heat, is regulated by the anterior hypothalamus in conjunction with the parasympathetic nervous system. The overall effect of heat loss is accomplished by vasodilation of the peripheral blood vessels, increased sweating, and decreased metabolic and muscular activities. The production and conservation of body heat, or thermogenesis, is regulated by the posterior hypothalamus in conjunction with the sympathetic nervous system. The mechanisms by which body heat is produced and conserved are in opposition to those that increase heat loss; that is, by constriction of cutaneous blood vessels, decreased sweat gland activity, and increased metabolic and muscular activities.
Fever develops when there is some disturbance in the homeostatic mechanisms by which the hypothalamus maintains a balance between heat production and peripheral heat loss. Although dehydration, cerebral hemorrhage, heat stroke, thyroxine, and certain other drugs can cause an elevated body temperature or hyperthermia, fever, in the precise sense of the term, occurs as a result of inflammation or infection, or both. During the infectious and inflammatory processes certain substances called pyrogens are produced within the body. These endogenous pyrogens are the result of inflammatory reactions, such as those that occur in tissue damage, cell necrosis, rejection of transplanted tissues, malignancy, and antigen-antibody reactions. Exogenous pyrogens are introduced into the body when it is invaded by bacteria, viruses, fungi, and other kinds of infectious organisms.
Endogenous pyrogens act directly on the hypothalamus, affecting its thermostatic functions by “resetting” it to a higher temperature. When this happens, all of the physiologic activities concerned with heat production and conservation operate to maintain body temperature at a higher setpoint. The symptoms of chill and shivering are the result of increased muscular activity, which is an attempt by the body to raise its temperature to the higher setting. This increased muscular activity is accompanied by an elevation of the metabolic rate, which in turn increases the demand for nutrients and oxygen. Outward signs of these internal activities include a higher pulse rate, increased respirations, and thirst caused by the loss of extracellular water via the lungs. The pulse rate increases at the rate of about eight to ten beats per minute for each degree of temperature rise.
Once the body temperature reaches the setpoint of the hypothalamic thermostat, the mechanisms of heat production and heat loss keep it at a fairly constant level and the fever persists. This is sometimes called the second stage of fever. If it continues, fluid and electrolyte losses become more severe and there is evidence of cellular dehydration. During this stage delirium in older persons and convulsions in infants and children can occur. Febrile convulsions in children are believed to be closely related to cerebral damage that becomes evident as afebrile convulsions later in life.
Prolonged fever eventually brings about tissue destruction owing to the catabolism of body proteins. Because of this the patient experiences muscle aches and weakness, malaise, and the excretion of albumin in the urine. Anorexia also is present. If the body does not receive a sufficient supply of energy from dietary intake to meet its metabolic needs, it catabolizes its own fat and protein. The patient then rapidly loses weight and can develop ketosis and metabolic acidosis.
The period during which a fever abates is called the period of defervescence. It may occur rapidly and dramatically, as the temperature falls from peak to normal in a matter of hours. This is called the crisis, that is, the critical point at which the fever is broken. A more gradual resetting of the thermostat and slow decline of the fever is called resolution of the fever by lysis.
If it is decided that treatment is necessary, there are two major goals: to identify the cause and to provide symptomatic relief. Antipyretic drugs such as aspirin and acetaminophen (Tylenol) are generally safe and effective. However, acetaminophen is preferred in children and when the patient has gastrointestinal sensitivity, allergy to aspirin, or a clotting disorder or is suspected of having Reye's syndrome.
Fluids and electrolytes are replaced orally or intravenously as indicated by laboratory tests and signs of dehydration. Frequent, small feedings of high-calorie, high-protein foods are recommended to combat fatigue and debility caused by the increased metabolic rate. The selection of oral liquids and foods should be based on the patient's preferences. Vitamin supplements may be prescribed in prolonged, low-grade fevers.
Chills are uncomfortable and sometimes frightening to the patient. When the patient complains of feeling chilled or cold, some form of external warmth should be provided. An extra blanket is helpful as is a hot water bottle filled with warm, not hot, water. As the body temperature declines the difference between body temperature and environmental temperature will decrease and the patient will begin to feel warmer. During the second stage of fever the patient may complain of feeling hot; the skin feels warm to the touch and the face is flushed. These symptoms are the result of vasodilation of surface blood vessels, an attempt by the body to prevent further escalation of the body temperature.
Classic fever of unknown origin, as defined by the preceding criteria, is distinguished from neutropenic and nosocomial FUO, as well as that associated with human immunodeficiency virus infection. In the neutropenic form, fever is accompanied by a neutrophil level that is lower than 500/mm3 or is expected to fall below that level within one or two days. The nosocomial form is a fever that occurs on several occasions in a hospitalized patient in whom neither fever nor infection was present on admission. In HIV-associated FUO, fever occurs in a person with human immunodeficiency virus infection on several occasions over a period of four weeks of outpatient care or three days of hospitalization. In all three of these forms of FUO, the cause of the fever cannot be determined after three days of investigation, including two days of incubation of cultures.
feverInternal medicine A body temperature of ≥ 37.2ºC/99.0ºF in early morning or ≥ 37.8ºC/100.0ºF in the evening that is a complex and coordinated adaptive response, which is part of the reaction to an immune challenge; this response is stereotyped, and largely independent of a causitive agent; as with other integrated responses–eg, regulation of energy metabolism, BP and volume, and reproduction, fever depends on humoral cues and is orchestrated by the hypothalamus, which coordinates autonomic, behavioral, endocrine, and metabolic responses– when corporal temperature is raised by endogenous pyrogen, T cell production ↑ 20-fold; endogenous pyrogen also shifts iron–needed by bacteria away from plasma; hyperthermia–up to 40ºC may trigger CA regression. See 'Animal House fever' Argentine hemorrhagic fever, Blackwater fever, Blue fever, Breakbone fever, Bolivian hemorrhagic fever, Bullis fever, Cabin fever, Cat-bite fever, Coley's toxin, Colorado tick fever, Congo-Crimean hemorrhagic fever, Cotton fever, Dehydration fever, Dengue hemorrhagic fever, Epidemic louse-borne typhus fever, Familial hibernian fever, Familial Mediterranean fever, Filarial fever, Fort Bragg fever, Haverhill fever, Hay fever, Hectic-septic fever, Hypothalamic fever, Izumi fever, Korean hemorrhagic fever, Lassa fever, Malta fever, Mediterranean fever, Metal fume fever, Omsk hemorrhagic fever, O'nyong-nyong fever, Polymer fume fever, Pontiac fever, Potamic fever, Q fever, Quartan fever, Quintan fever, Rat-bite fever, Relapsing fever, Rheumatic fever, Rift Valley fever, Rocky Mountain spotted fever, Sandfly fever, Scarlet fever, Seven-day fever, Simian hemorrhagic fever, Spring fever, Swamp fever, Tertian fever, Thirteen day fever, Three day fever, Trench fever, Valley fever, West Nile fever, Yellow fever.
feverElevation of body temperature above about 37 C, taken in the mouth. Fever is due to a resetting of the body's thermostat at a higher level so that heat production, mainly by shivering, is induced. The resetting is caused by the CYTOKINE interleukin-1 produced by white cells under the influence of bacteria, cancer, CORONARY THROMBOSIS, STROKE, crushing injury and other conditions. Fever inhibits the growth of bacteria and causes an increase in antibody production. The recognition of these advantages has led to a general abandonment of the former practice of routinely trying to reduce moderate fever.
Patient discussion about fever
Q. High Fever - is it dangerous? high fever over a long period can be dangerous. on the other hand it shows also that your body is working like Superman...
Q. What Causes Cough With Fever? Often during winter I become sick with fever and on going cough. What causes it?
Q. What Treats Cough With Fever? I have the flu and so my entire body hurts, and I can't stop coughing. What type of medications can I buy over-the-counter to help me feel better?