Normal body temperature

The following levels may vary slightly in different textbooks, but the following is intended to offer a simple, useful guide.

Normal range = 36–37ºC
Pyrexia = 38–40ºC
Hyperpyrexia = 40.1ºC and above
Heat stroke = Usually occurs around 41–42ºC
Death = 43ºC and above
Hypothermia = 35ºC and below
Death = 20ºC

The range of normal through to abnormal body temperature is shown in Figure 9.2.

Figure 9.2 Range of body temperatures

The sites that can be used to monitor temperature are:
• the axilla (axillary)
• the mouth (orally)
• the tympanic membrane (inner ear, aural)
• the rectum (rectally)
• the skin.

Great care should be taken when selecting the site. Whilst the rectal route is considered the most accurate because of its proximity to the core of the body it is obviously the least convenient, the most invasive and carries a number of risks not least the potential to perforate the rectum. It is therefore the least-used site but the best option when a very accurate measurement is required, for example in cases of hypothermia.

For many years the mouth has been the most commonly used site in adults, but care must be taken to ensure that the thermometer is placed firmly in the pocket to the side of the frenulum below the tongue and that the client is fully orientated and co-operative; confused or disorientated clients may bite or try to swallow it. This site is therefore not recommended in children unless they are fully compliant, nor should it be used for measuring the temperature of breathless patients or patients who suffer from epilepsy. When using this site it is also important to check that the client has not just had a hot or cold drink as this can significantly affect the measurement.

The axilla and groin are useful and less dangerous but are less efficient, particularly in clients who are obese or very thin, as good skin contact is essential for accurate measurement.

The tympanic membrane has become by far the most common site for taking temperatures, as it is easily accessible, least invasive and most speedy. Accuracy does, however, rely on the operator fully occluding the aural canal.

Whichever route is selected, continuity is important, as the measurement can vary by between 0.5 and 4.0ºC depending on the site used.