1. FEVER
FEVER
TREASA JAMES
2015 batch

2. Pyrexia ( Greek  Fire ) FEVER - Also known as Pyrexia DEFINITION:-
Fever is an elevated core body temperature more than 38oC
Fever is in response to cytokines and acute phase proteins and occurs in infectious and noninfectious conditions.
Measured using thermometer.

3. Temp. > 37.1oC  the rate of heat loss > heat gain
CONCEPT OF SETPOINT FOR TEMPERATURE CONTROL
Any Variation in normal body temperature 37.1oC cause drastic changes to occur in body for regulating heat loss & heat production.
Temp. > 37.1oC  the rate of heat loss > heat gain
Temp. < 37.1oC  the rate of heat production > heat loss
Brings body to normal temp
And this crucial temperature level is called Setpoint .

4. During Fever, Max oral temperature-diurnal variation
At 6 AM oF (37.2 oC)
At 4 PM oF (37.7oC) -
due to increasing Basal Metabolic Rate & increasing muscle activity
Idealy core temperature-lower end of esophagus
Rectal 0.6oC > Oral 0.6oC > axillary
During Fever,
Morning oral temp >98.9oF
Evening oral temp. >99.9oF
Rectal temp. > 38.3oC
Axillary temp > 37 oC

5. CAUSES OF FEVER
Viral/Bacterial/ Parasitic infection including Cold, UTI, Meningitis, Malaria, appendicitis etc..
Non infectious : Vasculitis, Deep vein thrombosis, side effects of medication, cancer etc.

6. SIGNS & SYMPTOMS Lethargy Depression Anorexia Sleepiness Hyperalgesia
Inability to Concentrate etc.

7. PYROGENS
Any substance that can raise hypothalamic thermostat setpoint.
Pyrogens
Endogenous Pyrogenic cytokines

8. Exogenous: Pyrogenic cytokines: Derived outside the patient
Microbial product,or its toxin or whole organism
Eg: Lipopolysaccharide (gram –ve bac)
Pyrogenic cytokines:
Formerly refered as endogenous pyrogens
Cytokines are small proteins that regulate immune,inflammatory & haematopoietic processes.
Includes IL-1,IL-6,TNF,CNTF & interferons.
Ciliary neurotropic factor

9. Exogenous factor causes release of endogenous factor.
Exogenous Pyrogens Lipopolysaccharide (LPS) binds to LPS binding protein forms complex.
Attaches to CD14 receptor over Macrophages
Release endogenous pyrogens like cytokines

11. Pyrogens in tissue/blood
MECHANISM
Pyrogens in tissue/blood
Phagocytized by the blood leukocytes/tissue macrophage/ large granular killer lymphocyte.
Gets digested and release cytokines like IL-1, IL-6 to general circulation

12. Cytokines through Circulation Circum ventricular vascular organs
Cytokines through Circulation Circum ventricular vascular organs. Due to large absorption by BBB Release of PGE2 from the brain side of hypothalamic endothelium. Triggers PGE2 receptor on glial cell. Release of cyclic AMP from glial cell. Increased cyclic AMP elevates hypothalamic setpoint

13. Distinct receptors for microbial products on hypothalamic endothelium
Toll like receptors
Direct activation of receptors
PGE2 production

14. Once Hypothalamic setpoint is raised Neurons in Vasomotor center is activated Vasoconstriction Shunts blood from periphery to internal organ Person feels cold Starts shivering, Temp. increases 1oC to 2oC

15. Process continues till the temp
Process continues till the temp. of blood bathing the hypothalamic neurons matches the new thermostat setting. When setpoint temp. returns to normal Heat loss through vasodilation, muscle contraction & sweating Person feels hot