Authors:

Based on Nicol: Essential Nursing Skills 4E
Adapted by: John Larkin BSc (Hons) MSc GradCertNursEd RGN RCN RNT
Updated by: Marsh Gelbart MA BA(Hons) RN PGCert
Last updated: August 2020

Figure 1

Heat pockets in the oral cavity. (Adapted from Jamieson E M, Whyte L A, McCall J M (eds) 2007 Clinical Nursing Practices, 5th edn. Churchill Livingstone, Edinburgh.)

Figure 2

Thermometer reading (Adapted from Nicol M, Bavin C, Cronin P, et al. 2012 Essential Nursing Skills, 4th edn. Mosby Elsevier, Edinburgh)

Introduction

Body temperature is one of the four main vital signs that must be monitored to ensure safe and effective patient care (McCallum & Higgins 2012). The National Institute for Health and Clinical Excellence (NICE) recommends temperature measurement as part of the initial assessment in acute illness in adults (NICE 2020). The Royal College of Nursing has collaborated with the Royal College of Physicians (RCP) to produce National Early Warning Scores for acute illness in the NHS and temperature measurement is a key component of this assessment (RCP 2015).

Body temperature can be considered as the balance of heat lost from the body and gained by the body (Walsh 2019).  A healthy body maintains its temperature within a narrow range using homeostatic thermoregulation mechanisms (Waugh & Grant 2014). Walsh (2019) describes the normal range of body temperature as 36–37.5°C, but says that this may vary by as much as 0.6°C according to the site used for measurement and from individual to individual. Fluctuations in body temperature occur naturally as a result of circadian rhythms, extremes of age (the young or elderly are unable to maintain an efficient equilibrium in thermoregulation), exertion or exercise, food intake, hormonal balance (e.g. ovulation), medication or alcohol, smoking, or deteriorating physiological function (e.g. shock, infection) (Dougherty et al. 2015, Evans 2009, Geneva et al. 2019, Walsh 2019).

The following terms are used to describe abnormal temperature ranges:

• Mild hypothermia (32–35°C).
• Moderate hypothermia (28–32°C).
• Severe hypothermia (below 28°C).
• Mild pyrexia (depending on the patient’s normal baseline temperature, 37.5–38.9°C).
• Hyperpyrexia (defined as above 40.0°C)

(Smith et al. 2019).

According to Sund-Levander and Grodzinsky (2010), assessment and evaluation of body temperature is one of the oldest known diagnostic methods and still has a huge influence on decisions about medical diagnosis, nursing care, treatment, and requesting laboratory results.  Body temperature is useful in monitoring health and illness as it reflects the ability of the body to manage heat loss and gain (McCallum & Higgins 2012).

There are many clinical indications for measuring body temperature, including:

• To ascertain a baseline temperature on admission to enable comparisons in the future.
• To enable close observation in resolving hypothermia or hyperpyrexia.
• To observe and monitor the patient for changes indicating an infection.
• To monitor the effect of treatment for antimicrobial therapy for infection.
• Before and during a blood transfusion for signs of a reaction.

The frequency of measurement will depend upon the patient’s condition and recorded temperature (Walsh 2019). Frequency of recording may also be identified in local hospital policy (e.g. frequency of recording while receiving a blood transfusion). Nurses should also ensure that both the method of taking the temperature and the site used are consistent, and documented to accurately reflect fluctuations, while also taking into account any other factors that may cause a fluctuation. Note: chemical disposable thermometers should be avoided in suspected cases of hypothermia, as under those circumstances, they lack sufficient clinical accuracy (McCallum & Higgins 2012). 

Any changes above or below the normal limits should prompt appropriate reporting and responses as set out in line with an early warning scoring system (McCallum & Higgins 2012, Royal College of Nursing First Steps 2017). Most clinical areas in the UK use the National Early Warning Score (NEWS) system, as designed by the Royal College of Physicians (RCP 2017).

It is important that the procedure is carried out in accordance with the manufacturer’s instructions and local policies and procedures.

To accurately measure the oral temperature the thermometer is placed in the posterior sublingual pocket of tissue at the base of the tongue (Figure 1). It is vital that the thermometer is placed in this region and not in the area in front of the tongue, as there may be a temperature difference of up to 1.7°C between these sites. Neff and colleagues' 1989 research (cited by Dougherty et al. 2015) found that this variance in temperature is due to sublingual pockets being protected from the air currents that cool the frontal areas.

Chemical thermometers are contact thermometers consisting of a matrix of temperature-sensitive dots (Davie & Amoore 2010). Within each of these dots, a different combination of chemicals reacts and changes colour, for example, in the case of Tempadots from beige to blue, at intervals of 0.1°C.  The temperature is read by observing the number of dots that have changed colour and correlating them on the scale marked on the thermometer (Childs 2011; Figure 2). These thermometers are for single use only and the manufacturer’s instructions for use must be followed to ensure accurate recordings.

Preparation and safety

• Explain the procedure to the patient to gain consent and cooperation.
• Assess the patient regarding a suitable site for temperature recording. If the patient is unconscious, confused, prone to seizures, has mouth sores, or has undergone oral surgery, the oral site should not be used.
• Ensure that the patient has not recently had a hot or cold drink, had a hot bath, smoked a cigarette, or been engaged in strenuous exercise as this may temporarily raise the body temperature. An accurate reading cannot be expected if the patient has engaged in these activities within the previous 20 min.
• Hand hygiene must be performed and an apron should be worn.
• Ensure that all the necessary equipment is assembled: apron, thermometer, watch, and patient documentation.
• Additional personal protective clothing may be necessary if indicated by the patient’s condition.

Procedure

1. Perform hand hygiene and explain the procedure to the patient. Rationale – To prevent cross-infection and gain the patient’s consent
2. Check that the patient has not had a hot or cold drink, had a bath, smoked a cigarette, or been engaged in strenuous exercise within the previous 20 min. Rationale – This may affect the accuracy of the reading.
3. If the patient is very breathless with a respiratory rate of greater than 20, an alternative temperature recording method such as tympanic may be a more comfortable patient option. Rationale – Breathless patients usually breathe through an open mouth. Therefore by asking a breathless patient  to close their lips in order to hold a thermometer in situ for 1–2 minutes may be uncomfortable and cause distress. 
4. Check the expiry date of the thermometer and open the packaging taking care not to touch the end with the dots. Rationale – These dots are heat sensitive and accuracy may be affected.
5. Gently insert the thermometer under the patient’s tongue, next to the frenulum at the junction of the floor of the mouth and the base of the tongue, on either the right or left side. Rationale – This is adjacent to the sublingual artery and so the temperature will be close to core temperature.
6. Ask the patient to close their lips, but not their teeth, around the thermometer. Rationale – To prevent cool air circulating in the mouth.
7. It does not matter which way the dots are facing. The patient’s lips should close around the middle of the thermometer.
8. It is vital to leave the thermometer in position for the manufacturer’s recommended length of time. This is usually a minimum of 1 min and no longer than 2 min. Rationale – For accurate recording it is vital to follow the manufacturer’s instructions.
9. Remove the thermometer, taking care not to touch the part that has been in the patient’s mouth. Rationale – The dots are heat sensitive and also to prevent contact with saliva, which is a body fluid.
10. In accordance with the manufacturer’s instructions, wait a few seconds for the dots to stabilise and then read the temperature by noting the way that the dots have changed colour. Rationale – To ensure accuracy. Some dots may disappear before you read the thermometer; this is normal.
11. Discard the thermometer into the clinical waste bag. Rationale – The thermometer has been in contact with a body fluid and so must be discarded into the clinical waste. In hospital you can use the locker bag; this is later discarded into clinical waste.
12. Document the temperature according to local policy and report any abnormalities. Rationale – To ensure patient safety.
13. Perform hand hygiene. Rationale – To prevent cross-infection.

Ongoing care, monitoring and support

• Ensure patient comfort.
• Answer any questions regarding the recording.
• Record the temperature according to local policy. See the video for an example of charting.
• Report any abnormality. The normal range for adults is 36–37.5°C:
  • a temperature above 37.5°C is pyrexia
  • a temperature below 35°C is hypothermia.

Documentation and reporting

• According to the Nursing and Midwifery Council (NMC), good record-keeping is an integral part of nursing and midwifery practice, and is essential to the provision of safe and effective care (Childs 2011, NMC 2018).
• The Nursing and Midwifery Council states that the nurse must keep clear and accurate records of the discussions that have taken place, the assessments undertaken, the treatment and medicines given, and how effective these have been (NMC 2018).
• Accurate documentation and prompt reporting of any changes in temperature are vital for patient safety. The NEWS system of recording and tracking clinical observations is now widely used in most UK Trusts. NEWS gives guidance on the appropriate action to be taken if the temperature is above or below set clinical parameters (RCP 2017).
• Through documentation, registered nurses communicate to other nurses and members of the multidisciplinary team their assessment about the patient’s status. Documentation and reporting must be in line with local hospital policy.