Differences In Core Body Temperature Research Articles

Feeding behavior modifies the circadian variation in RR and QT intervals by distinct mechanisms in mice.

Rhythmic feeding behavior is critical for regulating phase and amplitude in the ≈24-h variation of heart rate (RR intervals), ventricular repolarization (QT intervals), and core body temperature in mice. We hypothesized changes in cardiac electrophysiology associated with feeding behavior were secondary to changes in core body temperature. Telemetry was used to record electrocardiograms and core body temperature in mice during ad libitum-fed conditions and after inverting normal feeding behavior by restricting food access to the light cycle. Light cycle-restricted feeding modified the phase and amplitude of 24-h rhythms in RR and QT intervals, and core body temperature to realign with the new feeding time. Changes in core body temperature alone could not account for changes in phase and amplitude in the ≈24-h variation of the RR intervals. Heart rate variability analysis and inhibiting β-adrenergic and muscarinic receptors suggested that changes in the phase and amplitude of 24-h rhythms in RR intervals were secondary to changes in autonomic signaling. In contrast, changes in QT intervals closely mirrored changes in core body temperature. Studies at thermoneutrality confirmed that the daily variation in QT interval, but not RR interval, primarily reflected daily changes in core body temperature (even in ad libitum-fed conditions). Correcting the QT interval for differences in core body temperature helped unmask QT interval prolongation after starting light cycle-restricted feeding and in a mouse model of long QT syndrome. We conclude feeding behavior alters autonomic signaling and core body temperature to regulate phase and amplitude in RR and QT intervals, respectively.NEW & NOTEWORTHY We used time-restricted feeding and thermoneutrality to demonstrate that different mechanisms regulate the 24-h rhythms in heart rate and ventricular repolarization. The daily rhythm in heart rate reflects changes in autonomic input, whereas daily rhythms in ventricular repolarization reflect changes in core body temperature. This novel finding has major implications for understanding 24-h rhythms in mouse cardiac electrophysiology, arrhythmia susceptibility in transgenic mouse models, and interpretability of cardiac electrophysiological data acquired in thermoneutrality.

Investigating the relationship between heat load and shade seeking behaviour in dairy buffaloes.

The study presented in this Research Communication aimed to investigate the relationship between physiological responses, body surface temperature and shade-seeking behaviour in Nili Ravi dairy buffaloes during summer months. We enrolled 60 buffaloes, and each animal was observed for three consecutive days starting before sunrise until they moved towards the shade structures. A repeated measures ANOVA was employed to assess the changes in physiological parameters and body surface temperature between the early morning and the occurrence of shade-seeking behaviour. The average temperature humidity index and heat load index during the behavioural monitoring period (0400 to 1200 h) were 81.3 ± 6.5 and 92.9 ± 17, respectively (mean ± sd). There was no significant difference in core body temperature between sunrise and the time of shade-seeking event. However, the buffaloes had a slightly higher respiration rate at the time of shade-seeking (19.2 vs. 22.4 breaths/min). In addition, body surface temperature, measured at the flank region, shoulder, base of the ear and forehead was significantly higher at the occurrence of shade-seeking behaviour compared to the early morning. On average, the buffaloes sought shade when the surface temperature was 2°C higher than the temperature recorded before sunrise. Overall, the current findings suggest that body surface temperature, rather than core body temperature was strongly associated with shade-seeking behaviour in dairy buffaloes. These findings could be useful in developing strategies to mitigate the effects of heat stress in dairy buffalo herds and thereby improve animal welfare.

Moderate-intensity exercise performed in the evening does not impair sleep in healthy males

The aim of this study was to examine the effect of single bouts of moderate-intensity aerobic exercise and moderate-intensity resistance exercise performed in the evening on the sleep of healthy young males. The study employed a repeated-measures, counterbalanced, crossover design with three conditions (control, evening aerobic exercise, evening resistance exercise). Twelve male participants (mean ± SD; age: 21.9 ± 2.7 yr) attended the laboratory on three occasions separated by one day between each visit. Between 20:45 h and 21:30 h, participants completed either no exercise, 30 min of aerobic exercise at 75%HRmax, or 30 min of resistance exercise corresponding to 75% of 10-repetition maximum. A 9-h sleep opportunity was provided between 23:00 h and 08:00 h. Core body temperature was measured using ingestible temperature capsules and sleep was measured using polysomnography. Core body temperature was higher during the aerobic exercise and resistance exercise compared to control (p = 0.001). There was no difference in core body temperature at bedtime between the conditions. Sleep onset latency, total sleep time, slow-wave sleep duration, REM sleep duration, wake after sleep onset and sleep efficiency were similar in each condition (p > 0.05). Single bouts of moderate-intensity aerobic exercise or moderate-intensity resistance exercise performed in the evening did not impact subsequent night-time sleep. Core body temperature increased during both forms of exercise, but returned to pre-exercise levels in the 90 min prior to bedtime. Healthy young males can engage in a single bout of moderate-intensity aerobic exercise or moderate-intensity resistance exercise ceasing 90 min before bed without compromising their subsequent sleep.

Effects of heating intravenous fluid infusion and blood transfusion based on guidelines in sever trauma patients with hypothermia

Objective To explore the effects of heating intravenous fluid infusion and blood transfusion based on guidelines in severe trauma patients with hypothermia. Methods A total of 40 severe trauma patients with hypothermia admitted from July 2014 to December 2015 were enrolled as the control group treated with routine measures to maintain the body temperature at normothermia by such as electrical heating blanket; other 40 severe casualties with hypothermia admitted from January 2016 to July 2017 were recruited as the warming up group treated with heating intravenous fluid infusion and blood transfusion by hot water bath in addition to the routine measures for keeping body temperature at normothermia. The differences in core body temperature, prothrombin time, activated partial thromboplastin time, incidence of shivering and mortality rate were compared between the two groups. Results There was statistically significant difference in core body temperature at 0.5 h, 1.0 h, 1.5 h, 3.0 h between the two groups (P<0.05). Though the prothrombin time and shivering were improved after warming up in both groups, and there were significant differences in prothrombin time at 3.0 h after warming up and the incidence of shivering between two groups(P<0.05).There was no significant difference in mean arterial pressure at all seven intervals between two groups. Conclusion The heating intravenous fluid infusion and blood transfusion had remarkable effects to prevent hypothermia, improves blood coagulation and reduced the incidence of shivering to provide more simple and convenient warming up intervention for clinical practice. Key words: Sever trauma patients; Hypothermia; Heating intravenous infusion and blood transfusion; Rewarming

Interventions to prevent hypothermia at birth in preterm and/or low birth weight infants.

Interventions to prevent hypothermia at birth in preterm and/or low birth weight infants.

A randomized field study comparing differences in core body temperature, health, and performance in crossbred beef heifers administered 2 antimicrobial products given upon arrival at a stocker facility

ABSTRACT Antimicrobial metaphylaxis is an important tool used for the prevention of bovine respiratory disease complex, an economically important disease that typically affects newly weaned beef calves that are marketed and transported a distance from their origin. An experiment was conducted to determine the effects of administering 2 different metaphylactic products [tulathromycin (TULA) and gamithromycin (GAMI)] on differences on core body temperature, health, and performance on 284 highly stressed stocker calves. Calves were procured and delivered (transient time = 13.5 h average) from a southeastern United States order buyer in 3 truckload lots during a 6-d period in October 2011. The core body temperatures in nonmorbid calves in the TULA calves were greater compared with the GAMI calves the first 2 h after administration and at multiple time points on d 4 through 6 of the experiment (P

Effects of Cooling During Exercise on Thermoregulatory Responses of Men With Paraplegia.

People with spinal cord injury (SCI) have an altered afferent input to the thermoregulatory center, resulting in a reduced efferent response (vasomotor control and sweating capacity) below the level of the lesion. Consequently, core body temperature rises more rapidly during exercise in individuals with SCI compared with people who are able-bodied. Cooling strategies may reduce the thermophysiological strain in SCI. The aim of this study was to examine the effects of a cooling vest on the core body temperature response of people with a thoracic SCI during submaximal exercise. Ten men (mean age=44 years, SD=11) with a thoracic lesion (T4-T5 or below) participated in this randomized crossover study. Participants performed two 45-minute exercise bouts at 50% maximal workload (ambient temperature 25°C), with participants randomized to a group wearing a cooling vest or a group wearing no vest (separate days). Core body temperature and skin temperature were continuously measured, and thermal sensation was assessed every 3 minutes. Exercise resulted in an increased core body temperature, skin temperature, and thermal sensation, whereas cooling did not affect core body temperature. The cooling vest effectively decreased skin temperature, increased the core-to-trunk skin temperature gradient, and tended to lower thermal sensation compared with the control condition. The lack of differences in core body temperature among conditions may be a result of the relative moderate ambient temperature in which the exercise was performed. Despite effectively lowering skin temperature and increasing the core-to-trunk skin temperature gradient, there was no impact of the cooling vest on the exercise-induced increase in core body temperature in men with low thoracic SCI.

Warming of intravenous and irrigation fluids for preventing inadvertent perioperative hypothermia.

Inadvertent perioperative hypothermia (a drop in core temperature to below 36°C) occurs because of interference with normal temperature regulation by anaesthetic drugs, exposure of skin for prolonged periods and receipt of large volumes of intravenous and irrigation fluids. If the temperature of these fluids is below core body temperature, they can cause significant heat loss. Warming intravenous and irrigation fluids to core body temperature or above might prevent some of this heat loss and subsequent hypothermia. To estimate the effectiveness of preoperative or intraoperative warming, or both, of intravenous and irrigation fluids in preventing perioperative hypothermia and its complications during surgery in adults. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 2), MEDLINE Ovid SP (1956 to 4 February 2014), EMBASE Ovid SP (1982 to 4 February 2014), the Institute for Scientific Information (ISI) Web of Science (1950 to 4 February 2014), Cumulative Index to Nursing and Allied Health Literature (CINAHL) EBSCOhost (1980 to 4 February 2014) and reference lists of identified articles. We also searched the Current Controlled Trials website and ClinicalTrials.gov. We included randomized controlled trials or quasi-randomized controlled trials comparing fluid warming methods versus standard care or versus other warming methods used to maintain normothermia. Two review authors independently extracted data from eligible trials and settled disputes with a third review author. We contacted study authors to ask for additional details when needed. We collected data on adverse events only if they were reported in the trials. We included in this review 24 studies with a total of 1250 participants. The trials included various numbers and types of participants. Investigators used a range of methods to warm fluids to temperatures between 37°C and 41°C. We found that evidence was of moderate quality because descriptions of trial design were often unclear, resulting in high or unclear risk of bias due to inappropriate or unclear randomization and blinding procedures. These factors may have influenced results in some way. Our protocol specified the risk of hypothermia as the primary outcome; as no trials reported this, we decided to include data related to mean core temperature. The only secondary outcome reported in the trials that provided useable data was shivering. Evidence was unclear regarding the effects of fluid warming on bleeding. No data were reported on our other specified outcomes of cardiovascular complications, infection, pressure ulcers, bleeding, mortality, length of stay, unplanned intensive care admission and adverse events.Researchers found that warmed intravenous fluids kept the core temperature of study participants about half a degree warmer than that of participants given room temperature intravenous fluids at 30, 60, 90 and 120 minutes, and at the end of surgery. Warmed intravenous fluids also further reduced the risk of shivering compared with room temperature intravenous fluidsInvestigators reported no statistically significant differences in core body temperature or shivering between individuals given warmed and room temperature irrigation fluids. Warm intravenous fluids appear to keep patients warmer during surgery than room temperature fluids. It is unclear whether the actual differences in temperature are clinically meaningful, or if other benefits or harms are associated with the use of warmed fluids. It is also unclear if using fluid warming in addition to other warming methods confers any benefit, as a ceiling effect is likely when multiple methods of warming are used.

Protection Against Cold in Prehospital Care: Wet Clothing Removal or Addition of a Vapor Barrier

The purpose of this study was to evaluate the effect of wet clothing removal or the addition of a vapor barrier in shivering subjects exposed to a cold environment with only limited insulation available. Volunteer subjects (n = 8) wearing wet clothing were positioned on a spineboard in a climatic chamber (-18.5°C) and subjected to an initial 20 minutes of cooling followed by 30 minutes of 4 different insulation interventions in a crossover design: 1) 1 woolen blanket; 2) vapor barrier plus 1 woolen blanket; 3) wet clothing removal plus 1 woolen blanket; or 4) 2 woolen blankets. Metabolic rate, core body temperature, skin temperature, and heart rate were continuously monitored, and cold discomfort was evaluated at 5-minute intervals. Wet clothing removal or the addition of a vapor barrier significantly reduced metabolic rate (mean difference ± SE; 14 ± 4.7 W/m(2)) and increased skin temperature rewarming (1.0° ± 0.2°C). Increasing the insulation rendered a similar effect. There were, however, no significant differences in core body temperature or heart rate among any of the conditions. Cold discomfort (median; interquartile range) was significantly lower with the addition of a vapor barrier (4; 2-4.75) and with 2 woolen blankets (3.5; 1.5-4) compared with 1 woolen blanket alone (5; 3.25-6). In protracted rescue scenarios in cold environments with only limited insulation available, wet clothing removal or the use of a vapor barrier is advocated to limit the need for shivering thermogenesis and improve the patient's condition on admission to the emergency department.

The Effects of Multiple Doses of Glucocorticoids on the Inflammatory Response to Cardiopulmonary Bypass in Children

We previously demonstrated that a dose of glucocorticoids (GCs) administered prior to cardiopulmonary bypass (CPB) is effective at suppressing the inflammatory response to CPB and leads to an improved postoperative course. We evaluated whether an additional dose of GC administered eight hours prior to CPB would lead to further clinical benefit. We conducted a prospective study in which patients were randomized to receive placebo or GC eight hours prior to CPB, in addition to a dose of GC administered following induction of anesthesia. We measured serum inflammatory mediator levels and postoperative clinical parameters. Thirty-one patients were included in the study. Eighteen patients received two doses of GC and 13 patients received a single does of GC. Complement C3a levels were significantly lower at 24 hours following surgery in those patients who received two doses of GC (3136 ± 1650 vs 1779 ± 1616 ng/mL, P = .04). There was no significant difference in tumor necrosis factor (TNF)-α or interleukin (IL)-6 levels at any time between groups. There was no significant difference in core body temperature or renal function (based on serum creatinine levels) between groups. There was no significant difference between groups in duration of mechanical ventilation (2.4 ± 1.5 vs 3.6 ± 3.7 days, two vs one dose, respectively, P = .33) or length of stay in the intensive care unit ([ICU]; 3.4 ± 1.4 vs 4.9 ± 3.6 days, 2 vs 1 dose, respectively, P = .15). While those patients who received two doses of GC prior to surgery had significantly less complement activation postoperatively, clinical outcomes did not differ between groups. We conclude that the practice of administering an additional dose of GC prior to CPB is not supported. However, a large randomized study is needed to conclusively discount the potential benefit of this strategy.

Comparison of Rectal and Aural Core Body Temperature Thermometry in Hyperthermic, Exercising Individuals: A Meta-Analysis

To compare mean differences in core body temperature (T(core)) as assessed via rectal thermometry (T(re)) and aural thermometry (T(au)) in hyperthermic exercising individuals. PubMed, Ovid MEDLINE, SPORTDiscus, CINAHL, and Cochrane Library in English from the earliest entry points to August 2009 using the search terms aural, core body temperature, core temperature, exercise, rectal, temperature, thermistor, thermometer, thermometry, and tympanic. Study Selection: Original research articles that met these criteria were included: (1) concurrent measurement of T(re) and T(au) in participants during exercise, (2) minimum mean temperature that reached 38°C by at least 1 technique during or after exercise, and (3) report of means, standard deviations, and sample sizes. Nine articles were included, and 3 independent reviewers scored these articles using the Physiotherapy Evidence Database (PEDro) scale (mean = 5.1 ± 0.4). Data were divided into time periods pre-exercise, during exercise (30 to 180 minutes), and postexercise, as well as T(re) ranges <37.99°C, 38.00°C to 38.99°C, and >39.00°C. Means and standard deviations for both measurement techniques were provided at all time intervals reported. Meta-analysis was performed to determine pooled and weighted mean differences between T(re) and T(au). The T(re) was conclusively higher than the T(au) pre-exercise (mean difference [MD] = 0.27°C, 95% confidence interval [CI] = 0.15°C, 0.39°C), during exercise (MD = 0.96°C, 95% CI = 0.84°C, 1.08°C), and postexercise (MD = 0.71°C, 95% CI = 0.65°C, 0.78°C). As T(re) measures increased, the magnitude of difference between the techniques also increased with an MD of 0.59°C (95% CI = 0.53°C, 0.65°C) when T(re) was <38°C; 0.79°C (95% CI = 0.72°C, 0.86°C) when T(re) was between 38.0°C and 38.99°C; and 1.72°C (95% CI = 1.54°, 1.91°C) when T(re) was >39.0°C. The T(re) was consistently greater than T(au) when T(core) was measured in hyperthermic individuals before, during, and postexercise. As T(core) increased, T(au) appeared to underestimate T(core) as determined by T(re). Clinicians should be aware of this critical difference in temperature magnitude between these measurement techniques when assessing T(core) in hyperthermic individuals during or postexercise.

Influence of Midazolam and Glycopyrrolate on Intra-operative Body Temperature in Abdominal Surgical Patients

Purpose: influence of benzodiazepine (midazolam)or cholinergic inhibitor (atropine or glycopyrrlate) on intra-operative body temperature remains unclear and controversial. This study compares intra-operative body temperature in 50 abdominal surgical patients under general anesthesia between the administration of midazolam and glycopyrrolate in combination, or glycopyrrolate alone. Methods: Patients who underwent abdominal surgery were recruited from September 2008 through October 2009 at Gachon University Gil hospital in incheon. Core body temperature was measured in the right ear using a tympanic membrane thermometer at induction of general anesthesia and at 1 hr, 2 hr, and 3 hr after induction. Results: There were no differences in core body temperature at any measurement point between either patient group (F=1.08, <TEX>$p$</TEX>=.377). Core body temperature decreased throughout the 3 hr after induction in both groups (F=9.22, <TEX>$p$</TEX> <.001). Specially, core temperatures at induction of general anesthesia (p<.001), 1 hr (p<.001), 2 hr (<TEX>$p$</TEX> <.001), and 3 hr (<TEX>$p$</TEX> <.001) after induction were lower than before administration of midazolam and glycopyrrolate, or glycopyrrolate alone. Conclusion: We conclude that a cholinergic inhibitor (glycopyrrolate, 0.1 mg) therefore seems not to affect intra-operative body temperature of patients given a benzodiazepine (midazolam, 0.04 mg <TEX>$kg^{-1}$</TEX>), and not to increase body temperature in patients not given a benzodiazepine during the 3 hr after the induction of general anesthesia. Intra-operative warming therefore is needed to prevent hypothermia in surgical patients who receive pre-operative administration of midazolam and/or glycopyrrolate.

Sex- and age-specific differences in core body temperature of C57Bl/6 mice

Gender-specific differences in longevity are reported across species and are mediated by mechanisms not entirely understood. In C57Bl/6 mice, commonly used in aging research, males typically outlive females. Since in these animals modest but prolonged reduction of core body (Tc) increased life span, we hypothesized that differential Tc may contribute to sex-specific longevity. Here, we compared the circadian profiles of Tc and locomotor activity (LMA) of male and female C57Bl/6 mice. Since Tc and LMA normally change with age, measurements were carried out in young (3 months) as well as in old (24 months) mice. In young females, Tc was influenced by estrous but was overall higher than in males. This difference was larger in old animals after age eliminated the variations associated with estrous. Although temperature homeostasis is regulated centrally by the sexually dimorphic hypothalamic preoptic area, these differences were uniquely dependent on the gonads. In fact, bilateral gonadectomy abolished the effects of estrous and increased resting Tc in males eliminating all sex-specific differences in Tc and LMA. These effects were only partially mimicked by hormonal replacement as Tc was affected by progesterone and to a lesser extent by estrogen but not by testosterone. Thus, gonadal-dependent modulation of Tc may be one of the physiological parameters contributing to gender-specific differences in longevity.

Effects of Stocking Density and Group Size on Thermoregulatory Responses of Laying Hens under Heat-Challenging Conditions

Sectors of the U.S. cage layer industry have begun adopting practices of reduced stocking density (i.e., increased cage floor space per hen) and varying group sizes. This study was conducted with 24 groups of 48 W-36 laying hens (39 to 46 weeks old) to assess the effects of cage floor space or stocking density (SD) (348, 387, 465, or 581 cm2 hen-1; 54, 60, 72, or 90 in.2 hen-1) and group size (GS) (8 or 16 hens per cage) on the ability of the hens to cope with heat challenge. Data were collected at thermoneutral (24°C or 76°F) and warm conditions (32°C or 90°F, followed by 35°C or 95°F). No differences in core body temperature (CBT) of the hens were observed among the treatment regimens at 24°C. In general, mean CBT increased with heat exposure duration (P < 0.0001) but leveled off after the 32°C phase. At 32°C, CBT was higher for GS of 16 vs. 8 (42.3°C vs. 42.1°C, P = 0.05) and higher for SD of 348 and 387 cm2 hen-1 than for 465 or 581 cm2 hen-1 (42.4°C and 42.2°C vs. 41.9°C and 42.1°C, respectively, P = 0.009). Bird body mass decreased as heat exposure duration increased (P < 0.0001), but no differences were observed among the treatments. No mortalities were observed during the thermoneutrality period, and the mortality rate increased with heat exposure duration. The results indicate that, while CBT was lower for lower SD, the increased space was not sufficient to offer a clear benefit for coping with heat challenge of 32°C followed by 35°C.

Effects of Training, Environment, and Host Factors on the Sweating Response to Exercise

Because metabolic heat production is proportional to the amount of work performed, the differences in core body temperature (Tcore) of humans exercising at similar absolute exercise intensities are due to differences in their efficiency of heat dissipation. The purpose of this paper is to delineate the effects of training status, heat acclimation, environmental conditions and host factors on the sweating response to exercise. These factors are reviewed in light of their effects on the biophysical enhancement or suppression of sweating, and modifications of the relationship between local sweat rate and Tcore (degrees C). Athletes are advised to optimize those factors that enhance, and eliminate those factors that diminish, the onset and responsiveness of sweating.

Effect of a single 3-hour exposure to bright light on core body temperature and sleep in humans

Seven human subjects were exposed to bright light (BL, approx, 2500 lux) and dim light (DL, approx, 6 lux) during 3 h prior to nocturnal sleep, in a cross-over design. At the end of the BL exposure period core body temperature was significantly higher than at the end of the DL exposure period. The difference in core body temperature persisted during the first 4 h of sleep. The latency to sleep onset was increased after BL exposure. Rapid-eye movement sleep (REMS) and slow-wave sleep (SWS; stage 3 + 4 of non-REMS) were not significantly changed. Eight subjects were exposed to BL from 20.30 to 23.30 h while their eyes were covered or uncovered. During BL exposure with uncovered eyes, core body temperature decreased significantly less than during exposure with covered eyes. We conclude that bright light immediately affects core body temperature and that this effect is mediated via the eyes.