1.2 Temperature changes Listen

In nursing terms fever is referred to as pyrexia. Pyrexia is rarely dangerous but persistent pyrexia may be fatal.

Pyrexia is not a disease in itself but the body’s own defenses against infections by stimulating the immune system. The immune system works better at 39 ° C because there is an increased antibody production in the body. Additionally fever increases blood circulation and thus gives a better opportunity to eliminate pathogens and to influence the living conditions of the microorganisms. 

Substances that evoke fevers are called pyrogens. Pyrogens affect the temperature regulation centre, namely the hypothalamus, so that the centre is set at a higher temperature level. Bacteria, viruses, and toxins from certain infectious agents supply the body from the outside and release exogenous pyrogens.

Certain chemical reactions and tissue damage in the body can also release pyrogens and is then called endogenous pyrogens.

The chills in fevers are known as rigors and happen because the”thermostat” in the hypothalamus is suddenly put on a higher level. The temperature of the circulating blood does not match the higher level in the thermostat and other reactions are automatically initiated as the body temperature should be in accordance with the thermostat level.

A person with pyrexia can therefore feel cold but the body tries to produce heat by the person shivering and they may curl up and put on warm clothes. When the body temperature reaches the level of the thermostat, the muscle activity to create heat production reduces and the shivering subsides.

The chills/rigor is an unpleasant experience for both patient and caregiver. Temperature measurement must be done during the episode and afterwards and the nature and duration of the rigor must be carefully observed.  The nurse should liaise with the medical team regarding treatment.


Febrile seizures
Febrile seizures can occur when a person has a temperature of 40° C or over. Most frequently febrile seizures occur in young children, but generally decrease from age 3 onwards. A seizure can be frightening and presents in the same manner as an epileptic seizure but generally febrile seizures are harmless. In all cases of febrile seizures the medical team should be consulted in order to rule out any other underlying causes.


Heat stroke occurs when there is a total failure of heat regulation. The body is supplied with more heat than it is able to get rid of. If the temperature rises above 41° C the hypothalamus stops regulating the temperature and the effects can be fatal.



The opposite of hyperthermia is hypothermia. Hypothermia is a general cooling of the body to below 35°. In hypothermia the cell functions are reduced. The nervous system can be affected quickly and it can lead to cognitive impairment, fatigue and confusion; older people  are particularly vulnerable to rapid decline due to hypothermia.