Abnormal deviation of central body temperature leading to manifestations In inflammatory diseases-Increased Basal Metabolic Rate (BMR) and increased temperature Heat regulating centre in Hypothalamus In fever: increased pulse rate, anorexia, nausea, vomiting, constipation, scanty urine, increased thirst and dehydration Hyperthermia is increased body temperature without systemic effects. Causes of fever: Pyrogenic substances derived from microbes 1. Endotoxins – Gram negative bacteria produces Lipopolysaccharide (LPS) or lipoglycans. Ram positive bacteria do not have LPS. Gram negative bacteria are potent fever producers 2. Virus 3. Fungi, protozoa, rickettsia 4. Hypersensitivity: Antigen-Antibody complexPyrogen. Pyrogen is released from damaged tissues 5. Mechanical injuries 6. Vascular disorders 7. Neoplasms Pathogenesis of fever Endogenous pyrogens act on hypothalamus to produce fever Most important pyrogen producing cells are Neutrophils, Monocytes and Macrophages T lymphocyte produces lymphokines which stimulate Monocytes, Neutrophils to release endogenous pyrogens Changes in fever Circulation: Increased pulse rate and lowered Blood Pressure (BP) Respiration: Increased respiration due to action of Carbon Dioxide (CO2) on respiratory centre. Increased CO2 produced due to increased metabolism in fever Decreased bile, decreased saliva and decreased urine, decreased vitamin absorption and Vitamin deficiency occur Circulatory, renal failure due to excess fluid loss BMR increased to 10% for each degree of rise in temperature Course of fever Three stages in fever 1. Cold stage or stage of rising temperature or stage increment 2. Hot stage or fastigium or flush 3. Sweating phase or stage of decrement Of fever i. Increased phagocytosis ii. Increased neutrophil production iii. Increased production of antibodies iv. Increased bacteriostatic action v. Increased antigen-antibody reaction
