Fever
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I. Definition:
Fever is most accurately characterized as a temporary elevation in the body's thermoregulatory set-point, usually by about 1–2 °C.
In normal:
Oral temperature = 37 C
Rectal temperature = 37.2 C
Fever serves as one of the body's natural defenses against bacteria and viruses which cannot live at a higher temperature.
Body Temperature in fever:
• 100°Fahrenheit (37.8° C), taken orally, indicates a mild fever.
• 100° to 103°F (37.8° to 39.4°C) taken orally, indicates a moderate fever.
• 104°F (40°C) taken orally, indicates a high fever.
• 110°F. (43.3°C), this is the uppermost limit of the human body, this kind of fever is extremely rare.
II. Types of Fever
• Continued Fever
The temperature remains above normal for long period of time (usually 1.0 to 1.5oF).
• Intermittent Fever
Body temperature rises and falls in the contiguous days.
• Relapsing Fever
Type that recurs sometimes a number of times, several days after the temperature has returned to normal.
• Remittent Fever
A fever in which temperature varies during each 24 hour period, but never reaches normal.
• Pel-Epstein fever
- In Hodgkin disease.
III. Pathophysiology:
(1) Relase of endogenous pyrogens , activate arachidonic pathway.
- A pyrogen is a substance that induces fever.
These can be either endogenous or exogenous to the body.
Endogenous:
-Cytokines (IL-6, tumor necrosis factor-alpha, especially IL-1) which increase the thermoregulatory set-point in the hypothalamus are released into general circulation and to the circumventricular of the brain and bind with endothelial receptors on the vessel walls and then activate the arachidonic acid pathway.
Exogenous:
- A cell wall component of gram-negative bacteria, which has lipopolysaccharide (LPS).
- LPS is bound with lipopolysaccharide-binding protein (LBP).
- The LBP–LPS complex then binds to the CD14 receptor of a nearby macrophage.
- Finally, they release endogenous factors, which, in turn, activate the arachidonic acid pathway and then release PGE2.
(2) PGE2 is released by 3 enzymes:
+ Phospholipase A2 (PLA2)
+ Cyclooxygenase-2 (COX-2)
+ Prostaglandin E2 synthase.
PGE2 is the ultimate mediator of the febrile response. The set-point temperature of the body will remain elevated until PGE2 is no longer present.
IV. Stages of fever:
3 stages:
-1st stage (the invasion period):
• Chill( even rigors)
• Loss of appetite
• Headache.
-2nd stage:
• Hot and flushed
• The skin dry
• The pulse and respiration are rapid.
• Thirsty and restless.
Note:
In high fever, delirium and convulsions may occur.
-3rd stage :
• The temperature falls
• Breathing and pulse slow down
• The skin becomes moist
• Sweats.
V.Clinical occurrence:
Fever can be divided into 2 groups:
- Congenital
- Acquired:
(1) Bacteria:
• Inflammatory
• Infectious
(2) Non-bacteria
+ Systemic:
• Endocrine
• Metabolic/ Toxic
• Neoplastic
+ Organs:
• Neurologic
• Vascular
+ Others:
• Mechanical/traumatic
• Psychosocial
VI. Fever of unknown origin ( FUO)
1. How to give a diagnosis?
3 conditions:
(a) have a fever at least 3 weeks in duration.
(b) The temperature repeatedly >38.3 oC
(c) Couldn’t give any other diagnosis at least 1 weeks.
2. Causes:
The most common causes are:
• Noninfectious inflammatory diseases.
• Infection
• Malignancies (especially hematologic malignancies).
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