Baseline Body Temperature Research Articles

Care Bundles to Improve Hemoperfusion Performance in Patients with Severe COVID-19: A Retrospective Study.

Background/Objectives: Hemoperfusion (HP) is employed to modulate cytokine storms in severe coronavirus disease 2019 (COVID-19) patients, requiring careful attention for success and safety. Therefore, we investigated whether our care bundles could enhance HP performance. Methods: We conducted a retrospective cohort study on adult patients (≥20 years old) with severe COVID-19 pneumonia. In the first wave (Phase I), we identified HP-related issues and addressed them with care bundles in the second wave (Phase II). The care bundles included early temperature control, precise hemodynamic monitoring, and clot prevention measures for the HP membrane. The HP success rate and associated adverse events (AEs) were assessed between the two phases. Results: The study included 60 HP (HA330) sessions from 27 cases (Phase I: 21 sessions from 9 cases; Phase II: 39 sessions from 18 cases). Patient characteristics and treatments for COVID-19 were similar, except for baseline body temperature (BT) and heart rate (HR). Phase II showed a higher success rate (67% vs. 89%, p = 0.19), although it did not reach statistical significance. Phase I recorded a significantly higher frequency of AEs (3 [IQR 1, 4] events/case vs. 1 [IQR 0, 2] events/case, p = 0.014). After implementing the care bundles, hypothermia significantly decreased (78% vs. 33%, p = 0.037), with an adjusted odds ratio of 0.15; 95% CI 0.02-0.95, p = 0.044 for baseline BT. Conclusions: Further exploration with a larger sample size is required to establish the advantages of care bundles. However, the bundles' implementation has significantly improved hypothermia prevention.

Validation of a Novel Noninvasive Technology to Estimate Blood Oxygen Saturation Using Green Light: Observational Study

Background Pulse oximeters work within the red-infrared wavelengths. Therefore, these oximeters produce erratic results in dark-skinned subjects and in subjects with cold extremities. Pulse oximetry is routinely performed in patients with fever; however, an elevation in body temperature decreases the affinity of hemoglobin for oxygen, causing a drop in oxygen saturation or oxyhemoglobin concentrations. Objective We aimed to determine whether our new investigational device, the Shani device or SH1 (US Patent 11191460), detects a drop in oxygen saturation or a decrease in oxyhemoglobin concentrations. Methods An observational study (phase 1) was performed in two separate groups to validate measurements of hemoglobin and oxygen concentrations, including 39 participants recruited among current university students and staff aged 20-40 years. All volunteers completed baseline readings using the SH1 device and the commercially available Food and Drug Administration–approved pulse oximeter Masimo. SH1 uses two light-emitting diodes in which the emitted wavelengths match with absorption peaks of oxyhemoglobin (hemoglobin combined with oxygen) and deoxyhemoglobin (hemoglobin without oxygen or reduced hemoglobin). Total hemoglobin was calculated as the sum of oxyhemoglobin and deoxyhemoglobin. Subsequently, 16 subjects completed the “heat jacket study” and the others completed the “blood donation study.” Masimo was consistently used on the finger for comparison. The melanin level was accounted for using the von Luschan skin color scale (VLS) and a specifically designed algorithm. We here focus on the results of the heat jacket study, in which the subject wore a double-layered heated jacket and pair of trousers including a network of polythene tubules along with an inlet and outlet. Warm water was circulated to increase the body temperature by 0.5-0.8 °C above the baseline body temperature. We expected a slight drop in oxyhemoglobin concentrations in the heating phase at the tissue level. Results The mean age of the participants was 24.1 (SD 0.8) years. The skin tone varied from 12 to 36 on the VLS, representing a uniform distribution with one-third of the participants having fair skin, brown skin, and dark skin, respectively. Using a specific algorithm and software, the reflection ratio for oxyhemoglobin was displayed on the screen of the device along with direct hemoglobin values. The SH1 device picked up more minor changes in oxyhemoglobin levels after a change in body temperature compared to the pulse oximeter, with a maximum drop in oxyhemoglobin concentration detected of 6.5% and 2.54%, respectively. Conclusions Our new investigational device SH1 measures oxygen saturation at the tissue level by reflectance spectroscopy using green wavelengths. This device fared well regardless of skin color. This device can thus eliminate racial disparity in these key biomarker assessments. Moreover, since the light is shone on the wrist, SH1 can be readily miniaturized into a wearable device.

Effects of Perioperative Hypothermia on Extubation, Recovery Time, and Postoperative Shivering in Breast Surgery.

Women undergoing breast surgery seem to be under the risk for hypothermia (central body temperature <36°) due to the uncertainty caused by the preoperative preparation time and the variety of operations, leading to neglect of warming precautions. The study examines the perioperative hypothermia (PH) in breast surgery and the relationships between the depth of decrease in body temperature and individual or clinical variables. This prospective, cross-sectional, observational study includes 120 female patients 18-65 years of age who were given general anesthesia for breast surgery. The incidence of hypothermia was 68.1%. The given patients were discriminated as body temperature <36°, hypothermia was significantly related with lower weight, body mass index, American Society of Anesthesiology (ASA) score, baseline body temperatures, higher extubation, and recovery times. When patients' temperature decreases by >1 or 1.5°, lower age and longer durations of operation and anesthesia were also significant variables. The incidence of shivering is quite high at temperatures below 36°C or at 1 and 1.5°C reductions from baseline (72.7%, 84%, 94.1%, respectively). Body temperature changes of the patients had no effect on nausea-vomiting and pain scores. It turned out that the incidence of PH and shivering is high in women who underwent breast surgery. We think that the depth of decrease in body temperature should be taken into account when evaluating the predictors or clinical consequences of hypothermia, except for the 36°C limit for body temperature.

The Effects of Fever on Macrophage Metabolism and Function in Young and Aged Cells

Abstract Fever is an adaptive immune response to infections. With aging comes a rise in background inflammation that does not protect against infection. Here, we investigate the metabolism and function of macrophages at fever temperatures in a mouse cell line, in young and aged peritoneal resident macrophages, and bone marrow derived macrophages. Fever temperatures generally enhance macrophage functions although the effects are complex and dynamic. We show in the RAW264.7 murine cell line, that a raise in the baseline body temperature of 37°C to a fever temperature of 39°C increased the speed in which macrophages shift from mitochondrial oxidative phosphorylation to glycolysis. Driving this metabolic reprogramming, is the production of nitric oxide. There is also an increase in global protein synthesis and an increase in the mRNA for iNOS, the enzyme that produces NO and inflammatory cytokine production. The metabolic shift was measured via the oxygen consumption and the proton efflux rate over time. Cells were stimulated with lipopolysaccharide and/or interferon-gamma (IFNg). Our data also shows that tissue resident PRMs from aged mice exhibit a much stronger response to fever than those of young mice, while bone marrow derived microphages (BMDM) appeared to show a similar response to that of RAW264.7 cell line. However, with the addition of a cyclooxygenase2 inhibitor to block the production of prostaglandin E2, BMDMs of aged mice show an exaggerated increase in their response to LPS+IFNg activation. This work uncovers differences in fever responses between young and aged individuals that may explain the overall outcomes of the aged to infection. Arkansas Immunology Foundation

The Acute Effect of Chlorpromazine on Body Temperature in Intensive Care Unit Patients

Aim: Hypothermia is a rare complication of antipsychotic drugs but serious outcomes including death may result. In this study, we aimed to investigate body temperature alterations in acute phase of chlorpromazine treatment, the relationship of inflammatory indicators and risk factors for hypothermic effect in intensive care unit (ICU) patients.&#x0D; Materials and methods: 63 intensive care patients who needed sedative treatment due to agitation were divided into two groups as Group 1 (n = 30) with temperatures ≤ 38°C, and Group 2 (n = 33) with temperatures &gt; 38°C according to baseline body temperatures. Also, recurrent measurements for 12 hours were made at specific intervals following 25 mg intravenous chlorpromazine. &#x0D; Results: In Group 1, decrease in body temperatures was significant from 4th to 12th hours (p &lt; 0.01), while in Group 2, significant decreases in body temperatures at all measurement hours were observed (p &lt; 0.01). Temperature changes (delta temperature) observed at specific measurement intervals were significantly higher in Group 2 compared to Group 1. That difference was statistically significant at all intervals except for ΔTemperature B-6 (p &lt; 0.05). The odds of hypothermic effects by chlorpromazine were 16%, 46%, 3%, and 18% for Acute Physiology and Chronic Health Evaluation II, procalcitonin, C-reactive protein, and white blood cells, respectively. &#x0D; Conclusion: Chlorpromazine treatment applied for agitation in ICU patients was associated with acute hypothermic effect. Severity of disease and comorbidities might increase risk of hypothermia, and inflammatory biomarkers might be predictors of adverse drug reaction.

1022. The Role of Baseline Body Temperature in Neutropenic Fever

Abstract Background The management of neutropenic fever patients is challenging – from identification to diagnosis to treatment. We hypothesize that patients’ individual baseline body temperature provides diagnostic and prognostic value. Methods This is an analysis of 92 adult patients admitted for neutropenic fever to a tertiary medical center over 1 year period. We modelled the length of stay and the ability to find a definitive diagnosis using the change in body temperature from each patient’s outpatient baseline, the neutropenia level and overall patient acuity on admission, persistence of fever over 48-72 hours, and age. All temperatures were standardized to oral. Refer to Table 1 for the inclusion and exclusion criteria and statistical methods. Table 1.Inclusion and exclusion criteria and statistical methods. Results Refer to Tables 2 and 3 for demographics and descriptive statistics of temperature readings, to Table 4 for advanced statistical analyses. Importantly, the average baseline body temperature was at 36.7C; the average fever on admission was at 38.1C; based on the ≥ 38C cutoff, only 24% of patients had persistent fever over 48-72 hours but based on personalized cutoffs at &amp;gt; 2 standard deviations (SDs) or &amp;gt; 3 SDs above their outpatient baseline, 54% and 34% had persistent fever, respectively; the etiology of fever was identified in 48% of patients, all of which constituted infections; our multiple regression model demonstrated that a longer length of stay (LOS) of ≥ 4 days was predicted by larger deviation from baseline body temperature at admission and independently by fever persistence, after correcting for age, neutropenia level, and need for ICU level of care on admission. A similar model could not predict the ability to identify a fever-explaining diagnosis. Conclusion Given the average outpatient baseline body temperature of 36.7 +/- 0.3C, at 2 standard deviations (SDs) above this baseline, only 3% of patients would be at the 38C cutoff for fever, at 3 SDs, it would be 20%, thus rendering the standard 38C cutoff too high to be useful in identifying many neutropenic fever cases and supporting the use of personalized cutoffs based on patient’s baseline temperature. Further, consideration of the specific deviation from patients’ baseline body temperature could serve as a predictor for hospital LOS in patients admitted with neutropenic fever. Disclosures All Authors: No reported disclosures.

Body temperature and activity patterns modulate glucocorticoid levels across lizard species: A macrophysiological approach

Environmental and intrinsic factors interact to determine energy requirements in vertebrates. Glucocorticoid hormones (GCs) are key mediators of this interaction, as they fluctuate with energetic demands and regulate physiological and behavioral responses to environmental challenges. While a great body of research has focused on GC variation among individuals, the mechanisms driving GC variation across species and at broad spatial scales remain largely unexplored. Here, we adopted a macrophysiological approach to investigate the environmental factors and life-history traits driving variation in baseline GCs across lizard species. We tested three hypotheses: (1) If GCs increase with body temperature to meet higher metabolic demand, we expect an association between average baseline GCs and the mean species’ body temperature in the field (GC-temperature dependence hypothesis); (2) If GCs mediate behavioral responses to avoid thermal extremes, we expect that individuals frequently exposed to extreme conditions exhibit higher baseline GC levels (Behavioral thermoregulation hypothesis); (3) If GCs increase to support higher energy demands in active foragers during their period of activity, we expect that active foraging species have higher baseline GCs than sit-and-wait foragers, and that GC levels increase in relation to the duration of daily activity windows (Activity hypothesis). We used biophysical models to calculate operative temperatures and the activity patterns of lizards in sun-exposed and shaded microenvironments. Then, we tested the association between baseline GCs, body temperature, operative temperatures, foraging mode, and activity windows across 37 lizard species, using data from HormoneBase. Our comparative analyses showed that variation in baseline GCs was primarily related to the mean field body temperature and foraging mode, with higher baseline GCs in active foragers with higher body temperatures. Our results suggest that body temperature and foraging mode drive GC variation through their effects on energy requirements across lizard species.

Tumor Temperature: Friend or Foe of Virus-Based Cancer Immunotherapy.

The temperature of a solid tumor is often dissimilar to baseline body temperature and, compared to healthy tissues, may be elevated, reduced, or a mix of both. The temperature of a tumor is dependent on metabolic activity and vascularization and can change due to tumor progression, treatment, or cancer type. Despite the need to function optimally within temperature-variable tumors, oncolytic viruses (OVs) are primarily tested at 37 °C in vitro. Furthermore, animal species utilized to test oncolytic viruses, such as mice, dogs, cats, and non-human primates, poorly recapitulate the temperature profile of humans. In this review, we discuss the importance of temperature as a variable for OV immunotherapy of solid tumors. Accumulating evidence supports that the temperature sensitivity of OVs lies on a spectrum, with some OVs likely hindered but others enhanced by elevated temperatures. We suggest that in vitro temperature sensitivity screening be performed for all OVs destined for the clinic to identify potential hinderances or benefits with regard to elevated temperature. Furthermore, we provide recommendations for the clinical use of temperature and OVs.

Risk Factors for Postoperative Hypothermia in Patients Undergoing Robot-Assisted Gynecological Surgery: A Retrospective Cohort Study.

Since postoperative hypothermia increases the morbidity and mortality rates of surgery, identifying its risk factors is an important part of perioperative management. Considering the increasing demand for robot-assisted surgery and other characteristics of conventional laparoscopic surgery, identifying the risk factors for hypothermia in robot-assisted surgery is necessary. However, this has not yet been clearly established. This study aimed to identify the risk factors and incidence rate of postoperative hypothermia in patients undergoing robot-assisted gynecological surgery. In total, 516 patients aged ≥ 19 years undergoing robot-assisted gynecological surgery at a single university hospital between January 2018 and November 2020 were retrospectively analyzed. Postoperative hypothermia was defined as 36.0°C or lower body temperature at the end of the surgery, and multivariate logistic regression analysis was performed to identify the risk factors for postoperative hypothermia. Among the 516 patients, the incidence rate of postoperative hypothermia was 28.1% in 145 patients. The independent risk factors for postoperative hypothermia included body mass index ≤ 22.9 kg/m2, baseline heart rate ≤ 73 rate/min, baseline body temperature ≤ 36.8°C, use of intraoperative nicardipine, and amount of administered intravenous fluid larger than 800 mL. Therefore, to prevent hypothermia in patients undergoing robot-assisted gynecological surgery, these risk factors must be considered.

Full title: The prevalence of and predictors for perioperative hypothermia in postanaesthesia care unit.

Hypothermia is a common clinical issue during the perioperative period. The patients with perioperative inadvertent hypothermia are associated with higher risk of postoperative complications and higher hospitalisation costs. The aim of this study is to explore the prevalence of and predictors for hypothermia in patients entering postanaesthesia care unit. Retrospective cohort study. A rigorous retrospective cohort study was conducted according to the STROBE reporting checklist. A total of 7216 patients were enrolled in this study. The perioperative variables potentially related to hypothermia were collected. Univariate analysis and multivariate logistic regression analysis were performed to investigate the contributing factors. The overall prevalence of inadvertent hypothermia in postanaesthesia care unit was 21.3% (n=1505). The multivariate logistic regression analysis showed that age >65 (OR=1.561, 95% CI 1.371-1.778, p<.001), non-supine position [lateral decubitus position (OR=1.341, 95% CI 1.133-1.586, p=.001), lithotomy position (OR=1.639, 95% CI 1.295-2.075, p<.001)], non-superficial surgery (OR=2.195, 95% CI 1.566-3.077, p<.001), non-open surgery [laparoscopic surgery (OR=1.205, 95% CI 1.020-1.423, p=.029), endoscopic surgery (OR=1.430, 95%CI 1.084-1.887, p=.011)], the volume of intravenous infusion fluid >1000ml (OR=1.814, 95% CI 1.500-2.194, p<.001), blood transfusion (OR=1.552, 95% CI 1.159-2.078, p=.003), operation performed in the summer or fall (OR=1.874, 95%CI 1.656-2.122, p<.001) and use of dexmedetomidine (OR=1.147, 95%CI 1.015-1.296, p=.028) were associated with increased risk of hypothermia. In contrast, our finding showed that body mass index ≥25kg/m2 (OR=0.556, 95%CI 0.491-0.630, p<.001), higher baseline body temperature (OR=0.641, 95%CI 0.541-0.761, p<.001) and duration of fasting ≥18h (OR=0.487, 95%CI 0.345-0.689, p<.001) were associated with decreased risk of hypothermia. Compared with non-hypothermic patients, patients with hypothermia were associated with prolonged length of hospital days (5 vs. 4days, p<.001). For patients admitted to postanaesthesia care unit after elective procedures, old age, non-supine position, non-open surgery, non-superficial surgery, large volume of intravenous infusion fluid, dexmedetomidine, blood transfusion and Summer or Fall operative season were associated with increased risk of hypothermia, whereas high body mass index, high baseline body temperature and long fasting duration were associated with decreased risk of hypothermia. The outcomes of this study will raise the concerns of perioperative care team on hypothermia in surgical patients. Measures should be taken to improve perioperative hypothermia and clinical outcome.

Nitric Oxide Synthase Neurons in the Preoptic Hypothalamus Are NREM and REM Sleep-Active and Lower Body Temperature.

When mice are exposed to external warmth, nitric oxide synthase (NOS1) neurons in the median and medial preoptic (MnPO/MPO) hypothalamus induce sleep and concomitant body cooling. However, how these neurons regulate baseline sleep and body temperature is unknown. Using calcium photometry, we show that NOS1 neurons in MnPO/MPO are predominantly NREM and REM active, especially at the boundary of wake to NREM transitions, and in the later parts of REM bouts, with lower activity during wakefulness. In addition to releasing nitric oxide, NOS1 neurons in MnPO/MPO can release GABA, glutamate and peptides. We expressed tetanus-toxin light-chain in MnPO/MPO NOS1 cells to reduce vesicular release of transmitters. This induced changes in sleep structure: over 24 h, mice had less NREM sleep in their dark (active) phase, and more NREM sleep in their light (sleep) phase. REM sleep episodes in the dark phase were longer, and there were fewer REM transitions between other vigilance states. REM sleep had less theta power. Mice with synaptically blocked MnPO/MPO NOS1 neurons were also warmer than control mice at the dark-light transition (ZT0), as well as during the dark phase siesta (ZT16-20), where there is usually a body temperature dip. Also, at this siesta point of cooled body temperature, mice usually have more NREM, but mice with synaptically blocked MnPO/MPO NOS1 cells showed reduced NREM sleep at this time. Overall, MnPO/MPO NOS1 neurons promote both NREM and REM sleep and contribute to chronically lowering body temperature, particularly at transitions where the mice normally enter NREM sleep.

Risk factors for inadvertent intraoperative hypothermia in patients undergoing laparoscopic surgery: A prospective cohort study.

BackgroundInadvertent intraoperative hypothermia is frequent during open surgeries; however, few studies on hypothermia during laparoscopic abdominal surgery have been reported. We aimed to investigate the incidence and risk factors for hypothermia in patients undergoing laparoscopic abdominal surgery.MethodsThis single-center prospective cohort observational study involved patients undergoing laparoscopic surgery between October 2018 and June 2019. Data on core body temperature and potential variables were collected. A multivariate logistic regression analysis was performed to identify the risk factors associated with hypothermia. A Cox regression analysis was used to verify the sensitivity of the results.ResultsIn total, 690 patients were included in the analysis, of whom 200 (29.0%, 95% CI: 26%−32%) had a core temperature < 36°C. The core temperature decreased over time, and the incident hypothermia increased gradually. In the multivariate logistic regression analysis, age (OR = 1.017, 95% CI: 1.000–1.034, P = 0.050), BMI (OR = 0.938, 95% CI: 0.880–1.000; P = 0.049), baseline body temperature (OR = 0.025, 95% CI: 0.010–0.060; P < 0.001), volume of irrigation fluids (OR = 1.001, 95% CI: 1.000–1.001, P = 0.001), volume of urine (OR = 1.001, 95% CI: 1.000–1.003, P = 0.070), and duration of surgery (OR = 1.010, 95% CI: 1.006–1.015, P < 0.001) were significantly associated with hypothermia. In the Cox analysis, variables in the final model were age, BMI, baseline body temperature, volume of irrigation fluids, blood loss, and duration of surgery.ConclusionsInadvertent intraoperative hypothermia is evident in patients undergoing laparoscopic surgeries. Age, BMI, baseline body temperature, volume of irrigation fluids, and duration of surgery are significantly associated with intraoperative hypothermia.

Thermal effects of thulium: YAG laser treatment of the prostate\u2014an in vitro study

PurposeTo objectively determine whether there is potential thermal tissue damage during Tm:YAG laser-based LUTS treatment.MethodsOur experimental model was comprised of a prostatic resection trainer placed in a 37 °C water bath. In a hollowed-out central area simulating the urethral lumen, we placed a RigiFib 800 fibre, irrigation inflow regulated with a digital pump, and a type K thermocouple. A second thermocouple was inserted 0.5/1 cm adjacently and protected with an aluminum barrier to prevent it from urethral fluid. We investigated continuous and intermittent 120 W and 80 W laser application with various irrigation rates in eight measurement sessions lasting up to 14 min. Thermal measurements were recorded continuously and in real-time using MatLab. All experiments were repeated five times to balance out variations.ResultsContinuous laser application at 120 W and 125 ml/min caused a urethral ∆T of ~ 15 K and a parenchymal temperature increase of up to 7 K. With 50 ml/min irrigation, a urethral and parenchymal ∆T of 30 K and 15 K were reached, respectively. Subsequently and in absence of laser application, prostatic parenchyma needed over 16 min to reach baseline body temperature. At 80 W lower temperature increases were reached compared to similar irrigation but higher power.ConclusionsWe showed that potentially harming temperatures can be reached, especially during high laser power and low irrigation. The heat generation can also be conveyed to the prostate parenchyma and deeper structures, potentially affecting the neurovascular bundles. Further clinical studies with intracorporal temperature measurement are necessary to further investigate this potentially harming surgical adverse effect.

The Effect of Medium-Term Sauna-Based Heat Acclimation (MPHA) on Thermophysiological and Plasma Volume Responses to Exercise Performed under Temperate Conditions in Elite Cross-Country Skiers.

The influence of a series of ten sauna baths (MPHA) on thermophysiological and selected hematological responses in 14 elite cross-country skiers to a submaximal endurance exercise test performed under thermoneutral environmental conditions was studied. Thermal and physiological variables were measured before and after the exercise test, whereas selected hematological indices were studied before, immediately after, and during recovery after a run, before (T1) and after sauna baths (T2). MPHA did not influence the baseline internal, body, and skin temperatures. There was a decrease in the resting heart rate (HR: p = 0.001) and physiological strain (PSI: p = 0.052) after MPHA and a significant effect of MPHA on systolic blood pressure (p = 0.03), hematological indices, and an exercise effect but no combined effect of treatments and exercise on the tested variables. A positive correlation was reported between PSI and total protein (%ΔTP) in T2 and a negative between plasma volume (%ΔPV) and mean red cellular volume (%ΔMCV) in T1 and T2 in response to exercise and a positive one during recovery. This may suggest that MPHA has a weak influence on body temperatures but causes a moderate decrease in PSI and modifications of plasma volume restoration in response to exercise under temperate conditions in elite athletes.

Correlation between the Perfusion Index and Intraoperative Hypothermia: A Prospective Observational Pilot Study.

Background and Objectives: We examined the association between the baseline perfusion index (PI) and changes in intraoperative body temperature during general anesthesia. The PI reflects the peripheral perfusion state. The PI may be associated with changes in body temperature during general anesthesia because the degree of redistribution of body heat from the central to the peripheral compartment varies depending on the peripheral perfusion state. Materials and Methods: Thirty-eight patients who underwent brain surgery were enrolled in this study. The baseline PI and body temperature of the patients were measured on entering the operating room. Body temperature was recorded every 15 min after induction of anesthesia using an esophageal temperature probe. Univariate and multivariate logistic regression analyses were performed to identify the risk factors for intraoperative hypothermia. Results: Eighteen patients (47 %) developed hypothermia intraoperatively. The baseline PI was significantly lower among patients in the hypothermia group (1.8 ± 0.7) than among those in the normothermia group (3.0 ± 1.2) (P < 0.001). The baseline PI and body temperature were independently associated with intraoperative hypothermia (PI: odds ratio [OR], 0.270; 95% confidence interval [CI], 0.105–0.697; P = 0.007, baseline body temperature: OR, 0.061; 95% CI, 0.005–0.743; P = 0.028). Conclusions: This study showed that low baseline PI was the factor most related to the development of intraoperative hypothermia. Future studies should consider the PI as a predictor of intraoperative hypothermia.

Prognostic significance of early pyrexia in acute intracerebral haemorrhage: The INTERACT2 study

IntroductionUncertainty exists over the prognostic significance of pyrexia in acute intracerebral haemorrhage (ICH). We aimed to determine the association of elevated body temperature with clinical and imaging outcomes among participants of the main Intensive Blood Pressure Reduction in Acute Cerebral Haemorrhage Trial (INTERACT2). MethodsPost-hoc analyses of INTERACT2, an international open, blinded outcome assessed, randomised trial of 2839 patients with spontaneous ICH (<6 h of onset) and elevated systolic blood pressure (SBP, 150–220 mmHg) randomly assigned to intensive (SBP target <140 mmHg) or guideline-recommended (SBP target < 180 mmHg) BP management. Multivariable logistic regression was used to determine associations of elevated baseline body temperature (<37.5 vs. ≥37.5 °C) and 90-day clinical outcome defined on the modified Rankin scale (mRS). Analysis of covariance determined relations of body temperature and haematoma and perihaematomal oedema (PHE) volumes, at baseline and 24 h post-randomisation. ResultsOf 2792 participants with data available at admission, 39 (1.4%) patients had elevated body temperature ≥ 37.5 °C. Elevated body temperature was significantly associated with 90-day mortality (adjusted odds ratio 2.44; 95% confidence interval 1.02–5.82; P = .044) but not with major disability alone (mRS scores 3–5) and combination death or major disability (mRS scores 3–6). Elevated body temperature was also associated with larger PHE volume at baseline (10.89 vs. 3.14 cm3, P < .001;) and 24 h (12.43 vs 5.76 cm3, P = .018) but not with haematoma volumes at these time points. ConclusionEarly pyrexia in mild to moderate ICH is associated with greater mortality and larger PHE volume, suggesting an early inflammatory-mediated reaction. Clinical trial registrationwww.clinicaltrials.gov (NCT00716079).

Risk factors for hypothermia in patients undergoing general anesthesia in the postanesthesia care unit

Objective: To investigate the incidence of hypothermia and its risk factors in patients after general anesthesia in the post anesthesia recovery unit (PACU). Methods: A total of 10 341 patients after general anesthesia in the PACU of Peking University People's Hospital from January to December 2019 were retrospectively reviewed. According to whether hypothermia occurred in the PACU, the patients were divided into hypothermia group and non-hypothermia group. After propensity score matching based on age and gender, 336 cases in hypothermia group and 336 cases in non-hypothermia group were finally included. The clinical characteristics of the two groups were compared, and the potential risk factors of hypothermia in the PACU were analyzed by multivariate logistic regression model. Results: The incidence of hypothermia in PACU was 3.3% (339/10 341). The age of hypothermia group was (54.1±17.1) years, with 156 males and 180 females; the age of non-hypothermia group was (53.1±16.0) years, with 156 males and 180 females. There was no statistically significant difference in age, gender, American Society of Anesthesiologists (ASA) classification and operation type between the two groups (all P>0.05). Compared with the non-hypothermia group, the body mass index (BMI) [(22.8±3.5) kg/m2 vs (24.7±4.2) kg/m2] and baseline body temperature [(36.3±0.5)℃ vs (36.5±0.5)℃] were lower, and anesthesia time [(4.4±1.6) h vs (3.2±1.5) h] and operation time [(3.1±1.4) h vs (2.1±1.3) h] were longer in hypothermia group. The amount of intraoperative bleeding, blood transfusion and intravenous fluid was larger in hypothermia group (all P<0.001). Multivariate logistic regression analysis showed that larger amount of blood loss (L) (OR=5.361, 95%CI: 2.863-10.037, P<0.001), prone position operation (OR=3.653, 95%CI: 2.104-6.342, P<0.001), longer anesthesia time (h) (OR=1.421, 95%CI: 1.227-1.646, P<0.001), and general anesthesia combined with regional nerve block (OR=1.708, 95%CI: 1.026-2.843, P=0.039) were independent risk factors of hypothermia in the PACU, and higher BMI (OR=0.849, 95%CI: 0.801-0.900, P<0.001) was an independent protective factor. Conclusions: The incidence of hypothermia in patients after general anesthesia in the PACU remains relatively high. Therefore, more attention should be paid to identify high-risk patients, and active preventive measures should be taken for the risk factors of hypothermia.

Effect of Exercise Training on Body Temperature in the Elderly: A Retrospective Cohort Study.

Background: This study evaluated the effect of exercise training on body temperature and clarified the relationship between body temperature and body composition in the elderly. Methods: In this retrospective cohort study, a total of 91 elderly participants performed aerobic and anaerobic exercise training twice a week for 2 years. Non-contact infrared thermometer and bioelectrical impedance analysis were performed at baseline and at 2 years. Results: Mean age of study participants was 81.0 years. The participants were divided into two groups by baseline body temperature of 36.3 °C; lower body temperature group (n = 67) and normal body temperature group (n = 24). Body temperature rose significantly after exercise training in the lower body temperature group (36.04 ± 0.11 °C to 36.30 ± 0.13 °C, p < 0.0001), whereas there was no significant difference in the normal body temperature group (36.35 ± 0.07 °C to 36.36 ± 0.13 °C, p = 0.39). A positive correlation was observed between the amount of change in body temperature and baseline body temperature (r = −0.68, p < 0.0001). Increase in skeletal muscle mass was an independent variable related to the rise in body temperature by the multivariate logistic regression analysis (odds ratio: 4.77, 95% confidence interval: 1.29–17.70, p = 0.02). Conclusions: Exercise training raised body temperature in the elderly, especially those with lower baseline body temperature.

Selection on phenotypic plasticity favors thermal canalization

Climate change affects organisms worldwide with profound ecological and evolutionary consequences, often increasing population extinction risk. Climatic factors can increase the strength, variability, or direction of natural selection on phenotypic traits, potentially driving adaptive evolution. Phenotypic plasticity in relation to temperature can allow organisms to maintain fitness in response to increasing temperatures, thereby "buying time" for subsequent genetic adaptation and promoting evolutionary rescue. Although many studies have shown that organisms respond plastically to increasing temperatures, it is unclear if such thermal plasticity is adaptive. Moreover, we know little about how natural and sexual selection operate on thermal reaction norms, reflecting such plasticity. Here, we investigate how natural and sexual selection shape phenotypic plasticity in two congeneric and phenotypically similar sympatric insect species. We show that the thermal optima for longevity and mating success differ, suggesting temperature-dependent trade-offs between survival and reproduction in both sexes. Males in these species have similar thermal reaction norm slopes but have diverged in baseline body temperature (intercepts), being higher for the more northern species. Natural selection favored reduced thermal reaction norm slopes at high ambient temperatures, suggesting that the current level of thermal plasticity is maladaptive in the context of anthropogenic climate change and that selection now promotes thermal canalization and robustness. Our results show that ectothermic animals also at high latitudes can suffer from overheating and challenge the common view of phenotypic plasticity as being beneficial in harsh and novel environments.

Use of a Servo-Controlled Cooling Gel Pad System to Regulate Body Temperature in Critically Ill Children.

To assess the efficacy and safety of a servo-controlled cooling pad system for target temperature management in critically ill pediatric patients. A prospective, single-center, observational study. PICU of a tertiary hospital from September 2018 to September 2019. Children from 28 days to 16 years old subjected to servo-controlled body temperature control. The Arctic Sun 5000 system (Bard Medical, Covington, GA) and Arctic Gel Hydrogel pads were used for the purposes of the study. Data collected included demographics, indication of therapy, patient's body temperature, target temperature, time-to-target temperature, duration of therapy, and need to start or increase sedation and/or muscle relaxants. A total of 16 patients were included, of whom 68.8% were male; mean age was 4.7 years. The most frequent indication was fever associated with hemodynamic instability (62.5%). The target temperature was normothermia (36 or 36.5°C) in 81% of cases. Mean baseline body temperature was 37.6°C (± 1.2°C), and 50% of patients had fever (> 38°C). The mean speed of cooling was 1.2°C/hr (± 1°C/hr). Mean time to target temperature was 118 minutes (± 98.8 min). Mean duration of therapy was 68.7 hours (± 58.3 hr). Two patients had fever related to device disconnection during the treatment. At the start of the therapy, 15 patients were receiving sedative and analgesic drugs, and four received muscle relaxants. A patient required increased sedation, whereas another patient needed to start muscle relaxants. One of the patients developed a skin lesion in the axilla, no other adverse events were registered. Despite the small sample size, the results of the study showed that target temperature management by the servo-controlled gel pad system in critically ill pediatric patients was effective in achieving satisfactory temperature control and it was well-tolerated.