Fever

Fever describes an elevation in body temperature that results from a cytokine-induced increase in the set point of the thermostatic center in the hypothalamus.

Mechanism

Pyrogenic activator

microorganisms, their products and parasites (exogenous pyrogen)

viruses, bacteria, mycobacteria, fungi,

and parasites

non-microbial factors

antigen-antibody compound, alkaloids

Endogenous pyrogen (EP)

Fever activators induce host cells to produce fever-producing substances called endogenous pyrogens.

Cytokines: IL-1, IL-6, TNF-α, IFN

Monocytes, endothelial cells, lymphocytes, fibroblasts

Routes of peripheral pyrogenic signals into thermostatic center

Humoral mechanisms through OVLT

circulatory EP

local EP

activated monocytes

pyrogenic activators

Neural mechanism

peripheral nerve and vagal nerve

Increased set point of thermostatic center

PGE2

CRH

Na+/Ca2+

cAMP

Negative regulatory mediators

AVP(ADH), α-MSH, lipocortin-1

Stages

The fervescence period

shivering, oxidation of brown adipose tissue

vasoconstriction

The persistent febrile period

metabolic rate↑

vasodilation

The defervescence period

vasodilation, sweating

Alterations of metabolism and function

Metabolism

metabolic rate will increase 13% while

1 elevation in body T ℃

gulcose, adipose, protein

Central nervous system

headache, irritability, delirium, hallucination,

febrile convulsion (children)

Cardiovascular system (SN ↑, blood T ↑) every 1 rise in body T will lead to a ℃ 18 bpm increase in heart beats.

Respiratory system (blood T ↑→respiratory center)

hyperventilation

respiratory alkalosis

Digestive system be suppressed(SN↑,PG)

anorexia, abdominal distension,

constipation, vomiting

Immune system be activated

APP(complements), lymphocyte activation

Pathophysiological basis of prevention and treatment

Treatment of the primary disease

Anti-pyretic medications drugs (salicylate)

(>40 except children, pregnant ℃

women and patients with severe

heart disease)

Fluid and carbohydrates