Elevation of body temperature above the set point is called hyperthermia, fever or pyrexia.
Classification of Fever-
Fever is classified into three categories:-
- Low-grade fever: When the body temperature rises to 38°C to 39°C, (100.4°F to 102.2°F)
- Moderate-grade fever: When the temperature rises to 39°C to 40°C (102.2°F to 104°F)
- High-grade fever: When the temperature rises above 40°C to 42°C (104°F to 107.6°F).
Hyperpyrexia is the rise in body temperature beyond 42°C (107.6°F). Hyperpyrexia results in damage of body tissues. Further increase in temperature becomes life threatening.
Causes of Fever-
- Infection: Certain substances (pyrogens) released from bacteria or parasites affect the heatregulating system in hypothalamus, resulting in the production of excess heat and fever.
- Hyperthyroidism: Increased basal metabolic rate during hyperthyroidism causes fever
- Brain lesions: When lesion involves temperatureregulating centers, fever occurs.
- Diabetes insipidus: In this condition, fever occurs without any apparent cause.
Signs and Symptoms-
Signs and symptoms depend upon the cause of fever:-
- Muscle pain
- Loss of appetite
- General weakness.
Hyperpyrexia may result in: