One size does not fit all: Assuming the same normal body temperature for everyone is not justified

Personalized Cutoffs for the Diagnosis of Neutropenic Fever Based on Patients' Baseline Body Temperature: A Retrospective Pilot Study

Background The management of neutropenic fever patients remains challenging. Patients' individual baseline body temperature may provide diagnostic and prognostic value. Methods This study is a retrospective analysis of 92 adults admitted for neutropenic fever to model the length of stay (LOS) and the ability to find a definitive diagnosis using the deviation of patients' temperature on admission from their outpatient baseline, acuity on admission, neutropenia level and persistence, fever persistence, and patients' age. Results Patients' average baseline body temperature was 36.7°C+/-0.3°C - the body temperature had to be over four standard deviations above the baseline to reach the gold standard fever threshold of 38.0°C. Their average fever on admission was 38.1°C. Fever etiologies were identified in 48%, and all constituted infections. Multiple regression modelling demonstrated that a longer LOS of >3 days was predicted by larger deviation from baseline body temperature at admission and by fever persistence at 72 hours post-admission, after correcting for the persistence of severe neutropenia (absolute neutrophil count <500) at 72 hours, age, neutropenia level, and need for intensive care unit admission. A similar model could not predict the ability to identify a fever-explaining diagnosis. Conclusions This pilot project provides support for the use of patients' individual baseline body temperature rather than a pre-established universal fever cutoff in the diagnosis of neutropenic fever. Using a personalized cutoff is expected to avoid missing cases. Further, deviation from patients' baseline body temperature at admission could serve as a predictor for the hospital LOS, which can serve as a potential tool for hospital bed management.

Advances in the multimodal management of perioperative hypothermia: approaches from traditional Chinese and Western medicine

PURPOSE

Maintaining normothermia during the perioperative period is crucial for preventing complications, such as surgical site infections, prolonged hospital stays, and adverse cardiovascular events. This study aimed to elucidate methods of perioperative temperature management by integrating Western and traditional Chinese medicine (TCM) approaches. By combining advanced techniques of Western medicine with holistic and preventative practices of TCM, we aimed to provide a comprehensive strategy for effective perioperative thermal regulation.

METHODS

And a comprehensive literature review was conducted to analyze the causes of perioperative hypothermia and methods of perioperative temperature management from both Western and traditional Chinese medicine (TCM) perspectives. Special emphasis was placed on evaluating the underlying factors contributing to perioperative hypothermia, as well as the effectiveness, selection criteria, indications, contraindications, adverse reactions, and potential complications associated with various temperature management techniques.

RESULTS

Effective prevention and management strategies include preoperative risk assessment, physical warming measures, environmental temperature control, pharmacological interventions, perioperative temperature monitoring, comprehensive warming protocols, and postoperative warming and monitoring. Integrating traditional Chinese medicine provides additional methods to enhance overall effectiveness and patient outcomes. By combining these approaches, healthcare providers can significantly reduce the incidence of inadvertent perioperative hypothermia (IPH) and its associated complications, improving patient safety and recovery.

CONCLUSION

For IPH, a complex and challenging medical condition, both traditional Chinese medicine and Western medicine have established their own theoretical bases and developed corresponding prevention and treatment methods. However, it is important to note that although each of these methods has unique value and potential, they also have specific indications and unavoidable limitations. Therefore, by integrating and combining the complementary strengths and resources of traditional Chinese medicine and Western medicine, we can achieve a more comprehensive and effective prevention of IPH, ultimately improving the health and well-being of those affected.

Temperature Measurement Timings and the Fever Detection Rate After Gastrointestinal Surgery: Retrospective Cross-Sectional Study

BACKGROUND

Postoperative fever frequently indicates surgical complications and is commonly used to evaluate the efficacy of interventions against surgical stress. However, the presence of circadian rhythms in body temperature may compromise the accurate detection of fever.

OBJECTIVE

This study aimed to investigate the detection rate of fever under intermittent measurement.

METHODS

We retrospectively reviewed the clinical records of patients who underwent nonemergency gastrointestinal surgery between November 2020 and April 2021. Patients' temperature data were continuously collected every 4 seconds using a wireless axillary thermometer, and fever was defined as a temperature exceeding 38 °C within a day. To simulate intermittent measurement in clinical practice, the body temperature at each hour was selected from the continuously collected temperature dataset. Considering that temperatures are measured multiple times per day, all possible measurement plans using intermittent measurement were composed by combining 1-24 time points from the 24-hour daily cycle. Fever was clinically diagnosed based on the temperature readings at the selected time points per day. The fever detection rates for each plan, with varying measurement times, were listed and ranked.

RESULTS

Based on the temperature data continuously collected by the thermometer, fever occurred in 60 (40.8%) of the 147 included patients within 3 days after surgery. Of the measurement plans that included 1-24 measurements daily, the fever detection rates ranged from 3.3% (2/60) to 85% (51/60). The highest detection rates and corresponding timings for measurement plans with 1, 2, 3, and 4 measurements daily were 38.3% (23/60; at 8 PM), 56.7% (34/60; at 3 AM and 7 or 8 PM), 65% (39/60; at 3 AM, 8 PM, and 10 or 11 PM), and 70% (42/60; at 12 AM, 3 AM, 8 PM, and 11 PM), respectively; and the lowest detection rates were 3.3% (2/60), 6.7% (4/60), 6.7% (4/60), and 8.3% (5/60), respectively. Although fever within 3 days after surgery was not correlated with an increased incidence of postoperative complications (5/60, 8.3% vs 6/87, 6.9%; P=.76), it was correlated with a longer hospital stay (median 7, IQR 6-9 days vs median 6, IQR 5-7 days; P<.001).

CONCLUSIONS

The fever detection rate of the intermittent approach is determined by the timing and frequency of measurement. Measuring at randomly selected time points can miss many fever events after gastrointestinal surgery. However, we can improve the fever detection rate by optimizing the timing and frequency of measurement.

Association of body temperature and mortality in critically ill patients: an observational study using two large databases

BACKGROUND

Body temperature (BT) is routinely measured and can be controlled in critical care settings. BT can impact patient outcome, but the relationship between BT and mortality has not been well-established.

METHODS

A retrospective cohort study was conducted based on the MIMIC-IV (N = 43,537) and eICU (N = 75,184) datasets. The primary outcome and exposure variables were hospital mortality and first 48-h median BT, respectively. Generalized additive models were used to model the associations between exposures and outcomes, while adjusting for patient age, sex, APS-III, SOFA, and Charlson comorbidity scores, temperature gap, as well as ventilation, vasopressor, steroids, and dialysis usage. We conducted subgroup analysis according to ICU setting, diagnoses, and demographics.

RESULTS

Optimal BT was 37 °C for the general ICU and subgroup populations. A 10% increase in the proportion of time that BT was within the 36-38 °C range was associated with reduced hospital mortality risk in both MIMIC-IV (OR 0.91; 95% CI 0.90-0.93) and eICU (OR 0.86; 95% CI 0.85-0.87). On the other hand, a 10% increase in the proportion of time when BT < 36 °C was associated with increased mortality risk in both MIMIC-IV (OR 1.08; 95% CI 1.06-1.10) and eICU (OR 1.18; 95% CI 1.16-1.19). Similarly, a 10% increase in the proportion of time when BT > 38 °C was associated with increased mortality risk in both MIMIC-IV (OR 1.09; 95% CI 1.07-1.12) and eICU (OR 1.09; 95% CI 1.08-1.11). All patient subgroups tested consistently showed an optimal temperature within the 36-38 °C range.

CONCLUSIONS

A BT of 37 °C is associated with the lowest mortality risk among ICU patients. Further studies to explore the causal relationship between the optimal BT and mortality should be conducted and may help with establishing guidelines for active BT management in critical care settings.

Defining Usual Oral Temperature Ranges in Outpatients Using an Unsupervised Learning Algorithm

Importance

Although oral temperature is commonly assessed in medical examinations, the range of usual or "normal" temperature is poorly defined.

Objective

To determine normal oral temperature ranges by age, sex, height, weight, and time of day.

Design, Setting, and Participants

This cross-sectional study used clinical visit information from the divisions of Internal Medicine and Family Medicine in a single large medical care system. All adult outpatient encounters that included temperature measurements from April 28, 2008, through June 4, 2017, were eligible for inclusion. The LIMIT (Laboratory Information Mining for Individualized Thresholds) filtering algorithm was applied to iteratively remove encounters with primary diagnoses overrepresented in the tails of the temperature distribution, leaving only those diagnoses unrelated to temperature. Mixed-effects modeling was applied to the remaining temperature measurements to identify independent factors associated with normal oral temperature and to generate individualized normal temperature ranges. Data were analyzed from July 5, 2017, to June 23, 2023.

Exposures

Primary diagnoses and medications, age, sex, height, weight, time of day, and month, abstracted from each outpatient encounter.

Main Outcomes and Measures

Normal temperature ranges by age, sex, height, weight, and time of day.

Results

Of 618 306 patient encounters, 35.92% were removed by LIMIT because they included diagnoses or medications that fell disproportionately in the tails of the temperature distribution. The encounters removed due to overrepresentation in the upper tail were primarily linked to infectious diseases (76.81% of all removed encounters); type 2 diabetes was the only diagnosis removed for overrepresentation in the lower tail (15.71% of all removed encounters). The 396 195 encounters included in the analysis set consisted of 126 705 patients (57.35% women; mean [SD] age, 52.7 [15.9] years). Prior to running LIMIT, the mean (SD) overall oral temperature was 36.71 °C (0.43 °C); following LIMIT, the mean (SD) temperature was 36.64 °C (0.35 °C). Using mixed-effects modeling, age, sex, height, weight, and time of day accounted for 6.86% (overall) and up to 25.52% (per patient) of the observed variability in temperature. Mean normal oral temperature did not reach 37 °C for any subgroup; the upper 99th percentile ranged from 36.81 °C (a tall man with underweight aged 80 years at 8:00 am) to 37.88 °C (a short woman with obesity aged 20 years at 2:00 pm).

Conclusions and Relevance

The findings of this cross-sectional study suggest that normal oral temperature varies in an expected manner based on sex, age, height, weight, and time of day, allowing individualized normal temperature ranges to be established. The clinical significance of a value outside of the usual range is an area for future study.

Interdependence of Tissue Temperature, Cavitation, and Displacement Imaging During Focused Ultrasound Nerve Sonication

Focused ultrasound (FUS) peripheral neuromodulation has been linked to nerve displacement caused by the acoustic radiation force; however, the roles of cavitation and temperature accumulation on nerve modulation are less clear, as are the relationships between these three mechanisms of action. Temperature directly changes tissue stiffness and viscosity. Viscoelastic properties have been shown to affect cavitation thresholds in both theoretical and ex vivo models, but the direct effect of temperature on cavitation has not been investigated in vivo. Here, cavitation and tissue displacement were simultaneously mapped in response to baseline tissue temperatures of either 30 °C or 38 °C during sciatic nerve sonication in mice. In each mouse, the sciatic nerve was repeatedly sonicated at 1.1-MHz, 4-MPa peak-negative pressure, 5-ms pulse duration, and either 15- or 30-Hz pulse repetition frequency (PRF) for 10 s at each tissue temperature. Cavitation increased by 1.8-4.5 dB at a tissue temperature of 38 °C compared to 30 °C, as measured both by passive cavitation images and cavitation doses. Tissue displacement also increased by 1.3- [Formula: see text] at baseline temperatures of 38 °C compared to 30 °C. Histological findings indicated small increases in red blood cell extravasation in the 38 °C baseline temperature condition compared to 30 °C at both PRFs. A strong positive correlation was found between the inertial cavitation dose and displacement imaging noise, indicating the potential ability of displacement imaging to simultaneously detect inertial cavitation in vivo. Overall, tissue temperature was found to modulate both in vivo cavitation and tissue displacement, and thus, both tissue temperature and cavitation can be monitored during FUS to ensure both safety and efficiency.

A Novel Non-Invasive Thermometer for Continuous Core Body Temperature: Comparison with Tympanic Temperature in an Acute Stroke Clinical Setting

There is a growing research interest in wireless non-invasive solutions for core temperature estimation and their application in clinical settings. This study aimed to investigate the use of a novel wireless non-invasive heat flux-based thermometer in acute stroke patients admitted to a stroke unit and compare the measurements with the currently used infrared (IR) tympanic temperature readings. The study encompassed 30 acute ischemic stroke patients who underwent continuous measurement (Tcore) with the novel wearable non-invasive CORE device. Paired measurements of Tcore and tympanic temperature (Ttym) by using a standard IR-device were performed 3−5 times/day, yielding a total of 305 measurements. The predicted core temperatures (Tcore) were significantly correlated with Ttym (r = 0.89, p < 0.001). The comparison of the Tcore and Ttym measurements by Bland−Altman analysis showed a good agreement between them, with a low mean difference of 0.11 ± 0.34 °C, and no proportional bias was observed (B = −0.003, p = 0.923). The Tcore measurements correctly predicted the presence or absence of Ttym hyperthermia or fever in 94.1% and 97.4% of cases, respectively. Temperature monitoring with a novel wireless non-invasive heat flux-based thermometer could be a reliable alternative to the Ttym method for assessing core temperature in acute ischemic stroke patients.

Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis

BACKGROUND

Heat is associated with physiological strain and endurance performance (EP) impairments. Studies have investigated the impact of caffeine intake upon EP and core temperature (C_T) in the heat, but results are conflicting. There is a need to systematically determine the impact of pre-exercise caffeine intake in the heat.

OBJECTIVE

To use a meta-analytical approach to determine the effect of pre-exercise caffeine intake on EP and C_T in the heat.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

Four databases and cross-referencing.

DATA ANALYSIS

Weighted mean effect summaries using robust variance random-effects models for EP and C_T, as well as robust variance meta-regressions to explore confounders.

STUDY SELECTION

Placebo-controlled, randomized studies in adults (≥ 18 years old) with caffeine intake at least 30 min before endurance exercise ≥ 30 min, performed in ambient conditions ≥ 27 °C.

RESULTS

Respectively six and 12 studies examined caffeine's impact on EP and C_T, representing 52 and 205 endurance-trained individuals. On average, 6 mg/kg body mass of caffeine were taken 1 h before exercises of ~ 70 min conducted at 34 °C and 47% relative humidity. Caffeine supplementation non-significantly improved EP by 2.1 ± 0.8% (95% CI - 0.7 to 4.8) and significantly increased the rate of change in C_T by 0.10 ± 0.03 °C/h (95% CI 0.02 to 0.19), compared with the ingestion of a placebo.

CONCLUSION

Caffeine ingestion of 6 mg/kg body mass ~ 1 h before exercise in the heat may provide a worthwhile improvement in EP, is unlikely to be deleterious to EP, and trivially increases the rate of change in C_T.

The Possible Role of Body Temperature in Modulating Brain and Body Sizes in Hominin Evolution

Many models have posited that the concomitant evolution of large brains and body sizes in hominins was constrained by metabolic costs. In such studies, the impact of body temperature has arguably not been sufficiently addressed despite the well-established fact that the rates of most physiological processes are manifestly temperature-dependent. Hence, the potential role of body temperature in regulating the number of neurons and body size is investigated by means of a heuristic quantitative model. It is suggested that modest deviations in body temperature (i.e., by a couple of degrees Celsius) might allow for substantive changes in brain and body parameters. In particular, a higher body temperature may prove amenable to an increased number of neurons, a higher brain-to-body mass ratio and fewer hours expended on feeding activities, while the converse could apply when the temperature is lowered. Future studies should, therefore, endeavor to explore and incorporate the effects of body temperature in metabolic theories of hominin evolution, while also integrating other factors such as foraging efficiency, diet, and fire control in tandem.

Is body temperature mass screening a reliable and safe option for preventing COVID-19 spread?

With the ongoing coronavirus disease 2019 (COVID-19) pandemic continuing worldwide, mass screening of severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) infection is a cornerstone of strategies for limiting viral spread within communities. Although mass screening of body temperature with handheld, non-contact infrared thermometers and thermal imagine scanners is now widespread in a kaleidoscope of social and healthcare settings for the purpose of detecting febrile individuals bearing SARS-CoV-2 infection, this strategy carries some drawbacks, which will be highlighted and discussed in this article. These caveats basically include high rate of asymptomatic SARS-CoV-2 infections, the challenging definition of "normal" body temperature, variation of measured values according to the body district, false negative cases due to antipyretics, device inaccuracy, impact of environmental temperature, along with the low specificity of this symptom for screening COVID-19 in patients with other febrile conditions. Some pragmatic suggestions will also be endorsed for increasing accuracy and precision of mass screening of body temperature. These encompass the regular assessment of body temperature (possibly twice) with validated devices, which shall be constantly monitored over time and used following manufacturer's instructions, the definition of a range of "normal" body temperatures in the local population, patients interrogation on usual body temperature, measurement standardization of one body district, allowance of sufficient environmental acclimatization before temperature check, integration with contact history and other clinical information, along with exclusion of other causes of increased body temperature. We also endorse the importance of individual and primary care physician's regular and repeated check of personal body temperature.