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Anticipated patient outcomes

To determine the patient’s temperature on admission as a baseline for comparison with future measurements and to monitor fluctuations in temperature.

Preprocedural considerations

Temperature can be measured at a number of different sites, using different tools for measurement. When assessing the body temperature it is important to consider the methods and tools used for measurement (Docherty 2006).

The critical issue to consider when using any thermometer is whether you are controlling the factors that affect the accuracy and precision of the measurement. These factors must be addressed when educating staff on the use of different temperature measurement methods. It is therefore important to recall that therapeutic decisions should not be made on the basis of a single vital sign (Bridges 2009).

Equipment

A variety of thermometers are now available, from clinical glass thermometers with oral or rectal bulbs to the electronic sensor thermometer to the tympanic thermometer. Until recently, mercury in glass thermometers continued to be used, even though it had been shown that they were unable to detect temperatures lower than 34.5°C (94°F) or higher than 40.5°C (105°F) (Khorshid et al. 2005). The MHRA (2005) advises that, for safety, equipment with mercury should be replaced where possible. Mercury thermometers respond slowly to temperature changes, making use of an electronic device preferable when recording temperature extremes and rapid fluctuations (Marini and Wheeler 2010). Other types of thermometer include those listed by Docherty (2000).

Singleuse plasticcoated strips with heatsensitive recorders (dots) which change colour to indicate the temperature (record from 35.5 to 40.4°C).

Digital analogue probe thermometers with plastic disposable sheets (record from 32 to 42°C).

Invasive thermometers attached to a pulmonary artery catheter (record from 0 to 50°C) (Braun et al. 1998, O’Toole 1997).

Tympanic membrane thermometer

Tympanic thermometers are small handheld devices that have a disposable probe cover that is inserted into the patient’s ear canal. The sensor at the end of the probe records the infrared radiation (IRR) that is emitted by the tympanic membrane, as a result of its warmth, and converts this into a temperature reading presented on a digital screen (Jevon and Jevon 2001). The probe is protected by a disposable cover, which is changed between patients to prevent crossinfection (Gallimore 2004). Van Staaij et al. (2003) suggest that tympanic thermometers give a more accurate representation of actual body temperature because the tympanic membrane lies close to the temperature regulation centre in the hypothalamus and shares the same artery.

A common problem with using tympanic thermometers is poor technique leading to inaccurate temperature measurements (Gilbert et al. 2002). The placement of the probe to fit snugly within the ear canal (see Figure 12.21) is crucial as differences between the opening of the ear canal and the tympanic membrane can be as much as 2.8°C (Hudek et al. 1998). Jevon and Jevon (2001) highlight other causes of false readings, which include dirty or cracked probe lens, incorrect installation of the probe cover and short time intervals between measurements (less than 2–3 minutes).

Figure 12.21 Tympanic membrane thermometer.

Specific patient preparations

Asking the patient when they last ate, smoked and had a drink as these may have influences on their temperature.

Procedure guideline 12.6 Temperature measurement

Essential equipment

Tympanic membrane thermometer

Disposable probe covers

Alcohol handrub

Preprocedure

Action Rationale

1 Explain and discuss procedure with the patient. To ensure that the patient understands the procedure and gives their valid consent (NMC 2008b, C).

2 Wash and dry hands. To minimize the risks of crossinfection and contamination (Fraise and Bradley 2009, E).

Procedure

3 Document which ear is used to ensure consecutive