Body temperature is a key vital sign in intensive care unit (ICU) practice due to its clinical implications. 1Moreover, body temperature abnormalities are frequent in the ICU, 2trigger interventions (eg, antibiotics), and allow prognostication. 3, 4, 5, 6, 7Finally, targeting of specific body temperature levels has been a key feature of multiple studies in patients after cardiac arrest, 8, 9, 10brain injury, 11, 12, 13, 14and infection 15, 16, 17(Online Appendix, 1).
Young P, Bellomo R, Bernard G, et al. Fever control in critically ill adults. An individual patient data meta-analysis of randomised controlled trials. Intensive Care Med 2019; 45: 468-76.
Peres Bota D, Lopes Ferreira F, Mélot C, Vincent J. Body temperature alterations in the critically ill. Intensive Care Med 2004; 30: 811-6.
Bhavani S, Carey K, Gilbert E, Afshar M, et al. Identifying novel sepsis subphenotypes using temperature trajectories. Am J Respir Crit Care Med 2019; 200: 327-35.
Laupland K, Zahar J, Adrie C, et al. Determinants of temperature abnormalities and influence on outcome of critical illness. Crit Care Med 2012; 40: 145-51.
Young P, Saxena M, Beasley R, et al. Early peak temperature and mortality in critically ill patients with or without infection. Intensive Care Med 2012; 38: 437-44
Saxena M, Young P, Pilcher D, et al. Early temperature and mortality in critically ill patients with acute neurological diseases: trauma and stroke differ from infection. Intensive Care Med 2015; 41: 823-32.
Hassager C, Nagao K, Hildick-Smith D. Out-of-hospital cardiac arrest: in-hospital intervention strategies. Lancet 2018; 391: 989-98.
Bernard S, Gray T, Buist M, et al. Treatment of comatose survivors of out-of-hospital cardiac arrest with induced hypothermia. N Engl J Med 2002; 346: 557-63.
Nielsen N, Wetterslev J, Cronberg T, et al. Targeted temperature management at 33°C versus 36°C after cardiac arrest. N Engl J Med 2013; 369: 2197-206.
Lascarrou J, Merdji H, Gouge AL, et al. Targeted temperature management for cardiac arrest with nonshockable rhythm. N Engl J Med 2019; 381: 2327-37.
Cooper D, Nichol A, Bailey M, et al. effect of early sustained prophylactic hypothermia on neurologic outcomes among patients with severe traumatic brain injury: the POLAR randomized clinical trial. JAMA 2018; 320: 2211-20.
Hypothermia after Cardiac Arrest Study Group. Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. N Engl J Med 2002; 346: 549-56.
Clifton G, Valadka A, Zygun D, et al. Very early hypothermia induction in patients with severe brain injury (the National Acute Brain Injury Study: Hypothermia II): a randomised trial. Lancet Neurol 2011; 10: 131-9.
Andrews P, Sinclair H, Rodriguez A, et al. Hypothermia for intracranial hypertension after traumatic brain injury. N Engl J Med 2015; 373: 2403-12.
Young P, Saxena M, Bellomo R, et al. Acetaminophen for fever in critically ill patients with suspected infection. N Engl J Med 2015; 373: 2215-24.
Mourvillier B, Tubach F, Van de Beek D, et al. Induced hypothermia in severe bacterial meningitis: a randomized clinical trial. JAMA 2013; 310: 2174-83.
Young P, Bailey M, Bass F, et al. Randomised evaluation of active control of temperature versus ordinary temperature management (REACTOR) trial. Intensive Care Med 2019; 45: 1382-91.
Body temperature is classified as “core”, which refers to the temperature of organs, measured by invasive methods (eg, oesophageal probes), and “peripheral”, which refers to the temperature of external body surfaces, measurable by non-invasive tools (eg, cutaneous) 18(Online Appendix, 2). Intravascular thermometers are considered to be the gold standard for core body temperature measurement, although pulmonary artery catheter (PAC) 19use is decreasing over time. 20, 21Other tools have been proposed for clinical use or trials. 22, 23Although invasive tools have been advised in severely ill patients, 24, 25, 26peripheral thermometers are widely used in the ICU. 27However, concerns about their low accuracy 28, 29and the impact of such possible inaccuracy on clinical management remain. Despite such concerns and the importance of accurate temperature measurement in ICU patients, the available evidence for these patients has never been systematically reviewed and analysed.
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Pandey A, Khera R, Kumar N, et al. Use of pulmonary artery catheterization in US patients with heart failure, 2001–2012. JAMA Intern Med 2016; 176: 129-32.
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Childs C. Body temperature and clinical thermometry. Handb Clin Neurol 2018; 157: 467-82.
Bridges E, Thomas K. Noninvasive measurement of body temperature in critically ill patients. Crit Care Nurse 2009; 29: 94-7.
Carney N, Totten A, O’Reilly C, et al. Guidelines for the management of severe traumatic brain injury, fourth edition. Neurosurgery 2017; 80: 6-15.
Nolan J, Soar J, Cariou A, et al. European Resuscitation Council and European Society of Intensive Care Medicine guidelines for post-resuscitation care 2015: section 5 of the European Resuscitation Council Guidelines for Resuscitation 2015. Resuscitation 2015; 95: 202-22.
O’Grady N, Barie P, Bartlett J, et al. Guidelines for evaluation of new fever in critically ill adult patients: 2008 update from the American College of Critical Care Medicine and the Infectious Diseases Society of America. Crit Care Med 2008; 36: 1330-49.
Cutuli S, Osawa E, Glassford N, et al. Body temperature measurement methods and targets in Australian and New Zealand intensive care units. Crit Care Resusc 2018; 20: 241-4.
Niven D, Gaudet J, Laupland K, et al. Accuracy of peripheral thermometers for estimating temperature. a systematic review and meta-analysis. Ann Intern Med 2015; 163: 768-77.
Jefferies S, Weatherall M, Young P, Beasley R. A systematic review of the accuracy of peripheral thermometry in estimating core temperatures among febrile critically ill patients. Crit Care Resusc 2011; 13: 194-9.
Accordingly, we aimed to survey the literature with the intention to systematically assess the accuracy and precision of both peripheral and invasive thermometers in the ICU.
The protocol for this systematic review and meta-analysis was published 30before commencement and was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. 31
Cutuli S, Ancona P, Osawa E, et al. Accuracy of non-invasive body temperature measurement methods in adult patients admitted to the intensive care unit: a systematic review: PROSPERO; 2017 http://www.crd.york.ac.uk/PROSPERO/display_record.php?ID=CRD42017077838 (viewed Jan 2021).
Liberati A, Altman D, Tetzlaff J, et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration. BMJ 2009; 21: b2700.
MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials were searched to identify relevant studies published from 1966 to 2017 (Online Appendix, 3). Electronic database searches were supplemented by hand-searching of reference lists of retrieved articles, previous reviews and international guidelines.
Study inclusion and exclusion criteria
We included observational studies and randomised controlled trials published in English in peer-reviewed journals. These studies were performed in adult (aged ≥ 18 years) ICU patients and investigated accuracy and precision of non-invasive peripheral and invasive body temperature methods, using intravascular measurements as the comparator. We excluded unpublished articles and commentaries. Furthermore, we excluded animal studies and articles that did not use the Bland–Altman approach to investigate accuracy of different body temperature measurement methods.
The primary outcome was the assessment of accuracy and precision of non-invasive peripheral thermometers compared with intravascular methods.
Assessment of accuracy and precision
Accuracy was assessed by the Bland–Altman approach. 32The mean difference (reference test minus index test) between measures is the bias. The 95% confidence interval (CI) of the differences between measures is the limits of agreement (LoA), a measure of the variance between body temperature measurements. Precision was assessed by the Lin concordance correlation coefficient. 33
Bland J, Altman D. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1: 307-10.
Moran J, Peter J, Solomon P, et al. Tympanic temperature measurements: are they reliable in the critically ill? A clinical study of measures of agreement. Crit Care Med 2007; 35: 155-64.
Study selection and data extraction
Two reviewers (SLC and DM) independently performed the initial search and the study selection by title, abstract and full text. All disagreements were managed through discussion. In the case of consensus not being reached, a third reviewer (NJG) was consulted.
Study design and setting, authors, study population, device, and body temperature measurements were independently extracted by four reviewers (SLC, EAO, DM and PA) using a standardised online spreadsheet (Covidence systematic review software, Veritas Health Innovation, Melbourne, Australia). One additional reviewer (EJS) checked all data abstractions.
Invasive extravascular measurement methods included urinary bladder, oesophageal, rectal, nasopharyngeal and tracheal body temperature-sensing probes. Non-invasive peripheral measurement methods included axillary, tympanic infrared, temporal scanner, oral, inguinal and zero heat flux (ZHF) thermometers. ZHF is a dot-shaped electronic thermometer that measures body temperature about 1–2 cm below the skin surface.