Keywords: Temperature/Vital signs/ Nursing Practice Monitoring Practice educator ●This article has been double-blind Body temperature peer reviewed Body temperature is a vital sign and it is important to measure it accurately. This article reviews and compares the various methods available to nurses Measuring body temperature
In this article... 5 key The physiological processes that regulate body temperature points Body The clinical indications for measuring temperature 1temperature is A review of various methods of temperature measurement one of the four main vital signs that must be Authors Louise McCallum is a lecturer at body temperature is not evenly distributed monitored in a the University of the West of Scotland, Ayr; across the body (Childs, 2011). patient Dan Higgins is a freelance educator, Core body temperature is found in the Wide variations resuscitation and critical care, and senior blood supplying organs such as the brain 2in practice exist charge nurse, critical care, at University and those in the abdominal and thoracic across the Hospitals Birmingham Foundation Trust. cavities. Core temperature may be affected healthcare system Abstract McCallum L, Higgins D (2012) by intrinsic factors and, to a lesser degree, for measuring Measuring body temperature. Nursing extrinsic (environmental) factors. body temperature Times; 108: 45, 20-22. Peripheral temperature is recorded in Body tempera- Body temperature is one of the four tissues such as the skin, where environ- 3ture should be main vital signs that must be monitored mental factors and a lack of insulating con- measured and to ensure safe and effective care. nective tissue influence temperature. recorded regularly Temperature measurement is Box 1 sets out some intrinsic factors that with precision, recommended by the National Institute of influence temperature. consistency and Clinical Excellence a part of the initial A healthy body maintains its tempera- diligence assessment in acute illness in adults (NICE, ture within a narrow range using homeo- It is vital to 2007) and by the Scottish Intercollegiate static thermoregulation mechanisms 4measure Guidelines Network guidelines for (Pocock and Richards, 2009). The normal temperature post-operative management in adults range for core temperature in the litera- accurately as it has (SIGN, 2004). Despite applying in all ture varies, although 36°C-37.5°C is accept- an impact on healthcare environments, wide variations able in clinical practice (Childs, 2011). diagnosis and exist on the methods and techniques used Extremes of temperature are easier to treatment to measure body temperature. interpret (Box 2). It is estimated that accom- Inaccurate It is essential to use the most appropri- panying every 1°C rise in body temperature 5temperature ate technique to ensure that temperature is is a 10% rise in the rate of enzyme-con- measurement may measured accurately. Inaccurate results trolled chemical reactions (Marieb and compromise may influence diagnosis and treatment, Hoehn, 2010). At 43°C and above, cells are patient safety lead to a failure to identify patient deterio- irreparably damaged and enzymes dena- ration and compromise patient safety. tured, rendering death a certainty (Marieb This article explains the importance of and Hoehn, 2010). Conversely, as tempera- temperature regulation and compares ture drops, cellular processes become slug- methods of its measurement. gish and the metabolic rate falls. Pocock and Richards (2009) suggest that con- ody temperature represents the sciousness is lost 33°C. The body is gener- balance between heat produc- ally more tolerant of lower than higher tion and heat loss (Marieb and temperatures (Marieb and Hoehn, 2010). BHoehn, 2010). If the rate of heat generated equates to the rate of heat lost, Maintenance of body temperature the core body temperature will be stable The thermoregulatory centre is located in (Tortora and Derrickson, 2011). the hypothalamus in the brain. It consists All metabolising body cells manufac- of the heat-loss centre, the heat-promoting ture heat in varying amounts. Therefore, centre and the pre-optic region, which
20 Nursing Times 06.11.12 / Vol 108 No 45 / www.nursingtimes.net Nursing For more articles on critical care, go to Times.net nursingtimes.net/criticalcare analyse and coordinate responses to main- tain body temperature within the homeo- FIG 1. AUTONOMIC PHYSIOLOGICAL MECHANISMS static range (Marieb and Hoehn, 2010). Signals arrive at the thermoregulatory Dilation of cutaneous centre via afferent pathways from the sen- blood vessels (radiation) sory receptors in the skin and organs. The centre's response is propagated along Hypothalamic Activation of efferent neural pathways to the target heat loss centre sweat glands organ or blood vessel to elicit a response to activated (evaporation) Body temperature ▼ gain or lose heat (Childs, 2011). to normal range Behavioural mechanisms, such as removing or adding layers of clothing, also play an important role. Trigger ▲ body Fig 1 outlines the autonomic physiolog- temperature (due to hot ical mechanisms that are activated through environment) Normal range body the thermoregulatory centre to keep body temperature o o temperature within the normal range. 35.6 C-38.2 C Trigger ▼ body temperature Indications for measurement (due to cool climate) There are many clinical indications for measuring body temperature (Dougherty Vasoconstriction and Lister, 2011; Pocock and Richards, of cutaneous 2009). They include: Body temperature blood vessels ▲ to normal range causing blood to » To obtain a the baseline temperature to Hypothalamic be shunted to heat promotion enable comparisons to be made with deeper-lying centre activated future recordings; organs to ▼ heat » To enable close observation in resolving loss to the environment hypothermia/hyperthermia; » To observe and monitor patients for changes indicating an infection; » To monitor the effect of treatment for Additional heat produced by skeletal muscles antimicrobial therapy for infection; twiching (shivering) » Before and during a blood transfusion to monitor for signs of a reaction. Adapted from: Marieb and Hoehn (2010)
Measuring body temperature consistently and recorded on the chart Electronic or disposable chemical ther- The measurement of core body tempera- with the reading (Davie and Amoore, 2010). mometers may be used. Chemical ther- ture may seem simple, but several issues mometers should be avoided if the patient affect the accuracy of the reading. These Oral cavity is hypothermic (<35°C) because their range include the measurement site, the relia- The oral cavity temperature is considered of operation is 35.5°C-40.4°C (Fulbrook, bility of the instrument and user technique to be reliable when the thermometer is 1997). Low-reading thermometers may be of (Pusnik and Miklavec, 2009). Practitioners placed posteriorly into the sublingual some use. Mercury-in-glass thermometers must understand the advantages and dis- pocket (Hamilton and Price, 2007). This can no longer be bought because of Euro- advantages associated with the chosen landmark is close to the sublingual artery, pean Council rules (Medicines and Health- method so they can explain the procedure so this site tracks changes in core body care products Regulatory Agency, 2011). to patients and obtain valid consent temperature (Dougherty and Lister, 2011). Care must be taken to avoid the anterior (Nursing and Midwifery Council, 2008). region immediately posterior to the lower True core temperature readings can BOX 1. INTRINSIC FACTORS THAT incisors because the temperature here only be measured by invasive means, such INFLUENCE TEMPERATURE is substantially lower (Dougherty and as placing a temperature probe into the Factor Effect Lister, 2011). oesophagus, pulmonary artery or urinary Factors affecting accuracy include ▲ bladder (Childs, 2011). It is not practical, Ovulation Body temperature recent ingestion of food or fluid, having a nor indeed necessary, to use such sites and Circadian ▲ In evening respiratory rate >18 per minute and smoking methods in all cases; they tend to be rhythm ▼ In early hours of (Dougherty and Lister, 2011). Oxygen reserved for patients who are critically ill. morning therapy, particularly with high-flow rates, Non-invasive sites such as the rectum, Age Young and older may influence temperature but this claim oral cavity, axilla, temporal artery (fore- inability to maintain has been refuted by Stanhope (2006). head) and external auditory canal are equilibrium accessible and are believed to provide the Exercise ▲ Body temperature Tympanic temperature best estimation of the core temperature The tympanic thermometer senses reflected ▲ (Pusnik and Miklavec, 2009). The tempera- Thyroid Metabolic rate infrared emissions from the tympanic hormones therefore... ture measured between these sites can vary membrane through a probe placed in the ▲ Body temperature greatly, so the same site ought to be used external auditory canal (Davie and Amoore,
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2010). This method is quick (<1 minute), BOX 2. TEMPERATURE INTERPRETATIONS minimally invasive and easy to perform. It has been reported to estimate rapid fluctu- Term Definition ations in core temperature accurately Hypothermia Core temperature <35°C because the tympanic membrane is close Metabolic rate falls to the hypothalamus (Stanhope, 2006). Subcategories: Mild: 32°C-35°C Although its accuracy and reliability Moderate: 28°C-32°C have been questioned in many studies in Severe: <28°C the past decade, with differing outcomes. Fever Fever is a rise in temperature >38°C and is a normal response to Tympanic thermometry continues to be infection, inflammation or drug therapy. used. Operator error and poor technique Hypothalamus is functioning normally but the set point is raised are frequently cited problems (Farnell et al, beyond the normal level by pyrogens. 2005), so training is recommended. Ear wax Hyperthermia Core temperature >40°C and body temperature is out of control. is known to reduce the accuracy of read- Associated with injury/damage to the head resulting in ings, so it is recommended that the ear is hypothalamic failure. inspected before measurement (Farnell et al, 2005). because of the low flow of blood to the area, Journal of Oncology Nursing; 13, 250-254. Advantages of this site are that the so core temperature may be under- or over- Farnell S et al (2005) Temperature measurement: comparison of non-invasive methods in critical measurement does not appear to be influ- estimated at times of rapid flux. care. Journal of Clinical Nursing; 14: 632-639. enced by oral fluids or diet, environmental Fulbrook P (1997) Core body temperature temperature or other extraneous variables Temporal artery temperature measurement: a comparison of axilla, tympanic membrane and pulmonary artery blood (Robb and Shahab, 2001). If patients have The temporal artery thermometer is quick temperature. Intensive and Critical Care Nursing; been lying with their ear on a pillow, allow to use. It is held over the forehead and 13: 266-272. 20 minutes to elapse so the temperature senses infrared emissions radiating from Giantin V et al (2008) Reliability of body can normalise (Bridges and Thomas, 2009). the skin (Davie and Amoore, 2010). How- temperature measurements in hospitalised older patients. Journal of Clinical Nursing; 17: 1518-1525. ever, its reliability and validity have not Hamilton P, Price T (2007) The nursing process, Axillary temperature been widely tested. A single-centre study holistic assessment and baseline observations. In: Temperature is measured at the axilla by comparing it with other methods found Brooker C, Waugh A (eds) Foundations of Nursing Practice Fundamentals of Holistic Care. London: placing the thermometer in the central that, despite the infection control advan- Mosby Elsevier. position and adducting the arm close to tages of this non-touch method, it under- Lefrant J et al (2003) Temperature measurement the chest wall. estimated body temperature compared in intensive care patients: comparison of urinary The literature suggests that this is an with the control (Duncan et al, 2008). bladder, oesophageal, rectal, axillary, inguinal methods versus pulmonary artery core method. unreliable site for estimating core body Intensive Care Medicine; 29: 3, 414-418. temperature because there are no main Conclusion Marieb E, Hoehn K (2010) Human Anatomy and blood vessels around this area (Sund- Body temperature should be measured and Physiology with Interactive Physiology 10-System Suite. New York, NY: Pearson Publishing. Levander and Grodzinsky, 2009). These recorded regularly with precision, consist- Medicines and Healthcare products Regulatory authors also argue that the axillary tem- ency and diligence. Practitioners should be Agency (2011) Mercury in Medical Devices. London: perature can be affected by the environ- acutely aware of patients’ temperature MHRA. tinyurl.com/mhraMercurymedical National Institute for Health and Clinical mental temperature and perspiration. because it serves as a useful indicator of Excellence (2007) Acutely Ill Patients in Hospital: Fulbrook (1997) produced convincing change in their clinical condition. Recognition of and Response to Acute Illness in evidence indicating that chemical ther- A review has illustrated that none of the Adults in Hospital. London: NICE. www.nice.org.uk/ mometers are clinically unreliable for methods for measuring temperature at the CG50 Nursing and Midwifery Council (2008) The Code: measuring axillary temperature. Giantin et bedside is perfect (Davie and Amoore, Standards of Conduct, Performance and Ethics for al (2008) suggested that electronic digital 2010). Once a site and a method have been Nurses and Midwives. London: NMC. ww.nmc-uk. thermometers can be used at this site as a selected, they must be used consistently to org/code Pocock G, Richards C (2009) The Human Body: an reliable alternative in older people. ensure accuracy and patient safety. NT Introduction for the Biomedical and Health Sciences. New York, NY: Oxford University Press. Rectal temperature Pusnik I, Miklavec A (2009) Dilemmas in References measurement of human body temperature. Rectal temperature is said to be the most Bridges E, Thomas K (2009) Noninvasive Instrument Science Technology; 37: 516-530. measurement of body temperature in critically ill accurate method for measuring the core Robb P, Shahab R (2001) Infrared transtympanic patients. Critical Care Nurse; 29, 94-97. temperature (Lefrant et al, 2003). However, temperature measurement and otitis media with Childs C (2011) Maintaining body temperature. In: effusion.International Journal of Pediatric obtaining this is more time consuming Brooker C, Nicol M (eds) Alexander’s Nursing Otorhinolaryngology; 59: 3, 195–200. Practice. Oxford: Elesvier. than other methods and might be consid- Scottish Intercollegiate Guidelines Network (2004) Davie A, Amoore J (2010) Best practice in the ered unfavourable for some patients (Dzarr Postoperative Management in Adults: a Practical measurement of body temperature. Nursing Guide to Postoperative Care for Clinical Staff. et al, 2009). Practitioners should pay par- Standard; 24: 42, 42-49. Edinburgh: SIGN. www.sign.ac.uk/pdf/sign77.pdf ticular attention to issues of privacy. Dougherty L, Lister S (2011) The Royal Marsden Stanhope N (2006) Temperature measurement in The presence of faeces prevents the ther- Hospital Manual of Clinical Nursing Procedures. Oxford: Blackwell Publishing. the phase I PACU. Journal of PeriAnesthesia mometer from touching the wall of the Duncan A et al (2008) Can a non-contact infrared Nursing; 21: 1, 27-36. bowel and may generate inaccurate read- thermometer be used interchangeably with other Sund-Levander M, Grodzinsky E (2009) Time for a ings (Sund-Levander and Grodzinsky, thermometers in an adult emergency department? change to assess and evaluate body temperature in clinical practice. International Journal of Nursing 2009). Sund-Levander and Grodzinsky Australasian Emergency Nursing Journal; 11: 130-134. Dzarr A et al (2009) A comparison between Practice; 15: 4, 241-249. (2009) suggested this method does not track infrared tympanic thermometry, oral and axilla with Tortora G, Derrickson B (2011) Principles of Anatomy immediate changes to core temperature rectal thermometry in neutropenic adults. European and Physiology. New York, NY: John Wiley & Sons.
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