Changes In Core Body Temperature Research Articles

Effect of different delayed cooling time on organ injuries in rat models of exertional heat stroke

To investigate how the timing of cooling therapy affects organ injuries in rats with exertional heat stroke (EHS) and explore the possible mechanisms. A total of 60 adult male Wistar rat models of EHS were randomized into model group without active cooling after modeling, immediate cooling group with cold water bath immediately after modeling, delayed cooling groups with cold water bath at 5, 15 and 30 min after modeling, with another 12 mice without EHS as the normal control group. The changes in core body temperature of the mice were recorded and the cooling rate was calculated. After observation for 24 h, the mice were euthanized and blood samples were collected for detection of interleukin-1β (IL-1β), IL-2, IL-4, IL-6, IL-10, and interferon-γ, followed by pathological examination of the vital organs. The rats that died within 24 h were immediately dissected for examination. The number of deaths of the model rats within 24 h increased significantly with the time of delay of cooling treatment. The delay of cooling was positively correlated (r=0.996, P=0.004) while the cooling rate negatively correlated with the mortality rate (r=-0.961, P=0.009). The inflammatory cytokine levels presented with different patterns of variations among the cooling intervention groups. All the rat models of EHS had significant organ damages characterized mainly by epithelial shedding, edema, effusion, and inflammatory cell infiltration, and brain and renal injuries reached the peak level at 24 h after EHS. EHS causes significant nonspecific pathologies of varying severities in the vital organs of rats, and the injuries worsen progressively with the delay of cooling. There is a significant heterogeneity in changes of serum inflammatory cytokines in rats with different timing of cooling intervention following EHS.

MR-guided focused ultrasound in pediatric neurosurgery: current insights, technical challenges, and lessons learned from 45 treatments at Children's National Hospital.

MR-guided focused ultrasound (MRgFUS) is an evolving technology with numerous present and potential applications in pediatric neurosurgery. The aim of this study was to describe the use of MRgFUS, technical challenges, complications, and lessons learned at a single children's hospital. A retrospective analysis was performed of a prospectively collected database of all pediatric patients undergoing investigational use of MRgFUS for treatment of various neurosurgical pathologies at Children's National Hospital. Treatment details, clinical workflow, and standard operating procedures are described. Patient demographics, procedure duration, and complications were obtained through a chart review of anesthesia and operative reports. In total, 45 MRgFUS procedures were performed on 14 patients for treatment of diffuse intrinsic pontine glioma (n = 12), low-grade glioma (n = 1), or secondary dystonia (n = 1) between January 2022 and April 2024. The mean age at treatment was 9 (range 5-22) years, and 64% of the patients were male. With increased experience, the total anesthesia time, sonication time, and change in core body temperature during treatment all significantly decreased. Complications affected 4.4% of patients, including 1 case of scalp edema and 1 patient with a postprocedure epidural hematoma. Device malfunction requiring abortion of the procedure occurred in 1 case (2.2%). Technical challenges related to transducer malfunction and sonication errors occurred in 6.7% and 11.1% of cases, respectively, all overcome by subsequent user modifications. The authors describe the largest series on MRgFUS technical aspects in pediatric neurosurgery at a single institution, comprising 45 total treatments. This study emphasizes potential technical challenges and provides valuable insights into the nuances of its application in pediatric patients.

Dynamic Cooling – A concept of time-sensitive thermal regulation to cut cooling energy demand in office buildings

This paper focuses on how the existing sealed office typology can adapt to a warming world while minimizing the high energy demand for space cooling, through Dynamic Cooling, by adjusting the cooling temperature profile towards the average human circadian rhythm to mitigate heat stress during times of heightened thermal sensitivity. This concept is explored through a study in which we compared the effects of Dynamic Cooling, constant cooling, and no cooling on the core body temperature of 21 participants as well as a thermal dynamic simulation of 270 office space configurations under the same cooling profiles, comparing the total energy demand, peak loads, and overall hours of discomfort. The results of the study suggest the different conditioning profiles have no direct impact on the overall change in core body temperature throughout the day (difference < 0.04 K) but do influence the overall range throughout (from 0.37 K under constant cooling to 0.53 K under Dynamic Cooling). Additionally, there is no clear correlation between elevated indoor temperatures and CBT during the morning hours, questioning the necessity and effectiveness of pre-lunch cooling. This is underlined by the simulation findings, which reveal a non-linear relationship between savings in cooling demand and a decline in thermal comfort, with a 51.3 % reduction in ideal cooling energy demand and a 25.2 %–36 % increase of Over-Temperature-Kelvin-Hours, from a steady state cooling profile to a profile of Dynamic Cooling. The results of the study and simulation challenge traditional cooling standards and highlight the need for a balance between minimizing thermal discomfort and the necessary cooling energy demand.

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.

Physiological response of Katahdin ewes to the absence of shadows in tropical region of Mexico

This study evaluated the effect of environmental conditions on the physiological and body infrared temperature traits of Katahdin sheep. Ten recently reproductive-managed ewes were randomly segregated into two groups. The control group (CG) was under outdoor conditions with shadow access, and the experimental group (EG) was under outdoor conditions without shadow access. Traits were measured for 16 days, and the environmental traits confirmed significant differences between groups, with an average temperature-humidity index (THI) of 68.64±1.46 for the CG and 72.98±3.17 for the EG, with a breach of five units between groups. The THI was subsequently used to evaluate the heat load. Respiratory frequency was the physiological variable that responded the most to heat stress. The rectal temperature of the sheep was greater in the experimental group than in the control group, indicating an increase in heat stress. The EG also presented higher heat emissions from body regions, which was associated with changes in core body temperature and blood flow at the body surface. Differences in hematological parameters, such as the erythrocyte count, mean corpuscular volume, and total plasma protein concentration, were found between the groups. Infrared thermography was found to be efficient for estimating heat stress in sheep species, and head temperature was found to be a reliable indicator of physiological thermal stress.

Assessing the effects of oxytocin in changes of core body temperature during LPS-induced endotoxemia: A novel approach using Extended Poincaré Plot Analysis

Oxytocin has shown cardioprotective effects during inflammation and may modify the core body temperature changes in LPS-induced endotoxemia. Notably, the time series analysis of core body temperature fluctuations may indicate thermoregulation alterations. This study aims to assess the effects of oxytocin on changes in the core body temperature by analyzing the fluctuations of the temperature time series of endotoxemic rats.Twelve hours of continuous core body temperature fluctuations time series were obtained from adult male Dark Agouti rats implanted with a telemetric transmitter under the following treatment: lipopolysaccharide (LPS); oxytocin (O); lipopolysaccharide + oxytocin (LPS + O), and vehicle or control (C). The temperature fluctuations time series were analyzed using the Extended Poincaré Plot Analysis (EPPA), a novel approach for measuring nonlinear features, to compute the autocorrelation by Pearson's correlation coefficient r, the standard deviation perpendicular to the line of identity (SD1), and the standard deviation parallel to the line of identity (SD2).The autocorrelation of the temperature fluctuations assessed by Pearson's coefficient was significantly higher in the LPS group compared to control rats (C). Likewise, the co-administration of oxytocin during endotoxemia (LPS + O) significantly reduced the autocorrelation and increased the short-term variability (SD1) of temperature fluctuations compared to those recorded with a single dose of LPS. Thus, we concluded that oxytocin may introduce thermoregulatory changes under LPS-induced endotoxemia. The EPPA is a simple and powerful approach to assess physiological variability that can provide valuable insights into changes in thermoregulation.

The role of warmed-humidified carbon dioxide insufflation in colorectal surgery: A systematic review and meta-analysis.

Maintenance of normothermia is a crucial part of enhanced recovery after colorectal surgery. Dry-cold carbon dioxide (CO2 ) traditionally used for insufflation in laparoscopic surgery and negative pressure operating theatres has been associated with intraoperative hypothermia. Studies suggest that use of warmed-humidified CO2 may promote normothermia. However, due to a scarcity of high-quality studies demonstrating a proven benefit on intraoperative core body temperature, its use in colorectal surgery remains limited. Therefore, the aim of this review was to evaluate the effects of warmed-humidified CO2 compared to traditional dry-cold CO2 , or ambient air in operating theatres, during colorectal surgery. A search of Medline, EMBASE, and CENTRAL was performed. Randomised controlled trials (RCTs) that compared patients receiving warmed-humidified CO2 with either dry-cold CO2 insufflation in laparoscopic procedures or no insufflation during open surgery were included. The primary outcome was change in intraoperative core body temperature. Secondary outcomes included length of stay, operating time, return of gastrointestinal function, wound infection, and postoperative pain. A pairwise meta-analysis was performed using inverse variance random effects. Among the six RCTs included, 208 patients received warmed-humidified CO2 (42.3% female, mean age: 65.8 years) and 210 patients received either dry-cold CO2 in laparoscopic procedures or no gas insufflation during open procedures (46.2% female, mean age: 66.1 years). No significant difference was found for change in intraoperative core body temperature (MD = 0.01, 95% CI: -0.1, 0.11, p = 0.90, very low certainty). Patients in the warmed-humidified CO2 group had significantly higher pain scores on postoperative day 1 (MD = 1.61, 95% CI: 0.91, 2.31, p < 0.05, very low certainty). No significant differences were found in any of the other secondary outcomes studied. Patients undergoing colorectal surgery receiving warmed-humidified CO2 do not experience any clinically meaningful difference in core body temperature change compared to their counterparts receiving dry-cold CO2 insufflation or no insufflation. However, patients may report greater pain scores on postoperative day 1 with warmed-humidified CO2 . There is likely no clinically important difference between warmed-humidified CO2 and dry-cold CO2 for patients undergoing colorectal surgery. Patient, clinician, and institution factors should be considered when deciding between these two insufflation modalities.

Sustained exercise load by young adult females while wearing surgical mask raises core body temperature measured with zero-heat-flux thermometer.

When a pandemic such as that caused by the novel coronavirus disease termed COVID-19 emerges, it is recommended to wear a mask when in public situations, with information regarding the impact on thermoregulation essential, especially during exercise or hard physical labor. The present study investigated changes in core body temperature (CBT) while wearing a surgical mask (SM) during exercise (TCBT) using a non-invasive zero-heat-flux (ZHF) thermometer. Nine young adult females performed ergometer exercise for 30min at 60 W with (mask group) and without (control) a SM under a non-hot condition, shown by wet bulb globe temperature (WBGT) findings. TCBT, mean skin temperature (TMST), heart rate (HR), and humidity in the perioral region of the face (%RH) were determined. Each of those markers showed increased values during exercise, with the increases in TCBT, HR, and %RH, but not TMST, during exercise found to be significantly greater in the mask group. HR reserve (%HRR), derived as load intensity during exercise, was also significantly higher in the mask group. Each subject completed all of the experimental protocols without noting pain or discomfort. These results suggest that wearing a SM while performing mild exercise contributes to increased TCBT associated with increased exercise intensity, expressed as %HRR in a non-heated condition. Furthermore, the ZHF thermometer was shown to be safe and is considered useful for conducting such studies. Additional examinations will be necessary to examine gender and age group differences, as well as the use of different exercise methods and intensity and ambient conditions.

Development of a geographic human heat balance equation to support public health analyses: An Arizona urban sun corridor application

Land surface temperature (LST) estimates often serve as urban heat islands maps and to infer human thermal comfort. Parallel to this, physiological heat balance calculations have been well documented to measure changes in body core temperature and measure risk of heat-related illness. However, there is a need for an improved spatially explicit method to assess human thermal comfort. Using spatial climate data measuring temperature, airflow, and humidity, we developed a geographic body heat storage (BHS) model based on heat exchange and evaporative heat loss from the human body. As proof of concept, we used heat-related illness emergency department visits in two Arizona metropolitan areas to demonstrate that BHS can improve LST's shortcomings, with its increased explanatory power of and linear fit to emergency records. The BHS model can support decision making for public health outcomes as heat risk increases with climate change and urban overheating to more closely approximate the human heat experience. BHS allows can be implemented in different climate regions and with investigations of additional physiological and community variables to better describe risk of heat-related illness.

Body Temperature Manipulation Increases Salivary Cortisol Independent of Exercise

The vast majority of circulating cortisol in the blood is bound and inactivated by binding proteins like corticosteroid-binding globulin (CBG) and albumin. The cortisol that is free of these binding proteins is secreted via saliva and other body fluids. Ex-vivo studies have shown that CBG binding to cortisol is temperature-dependent within the physiological range of human core body temperatures. Exercise is a standard experimental paradigm for inducing cortisol responses. However, these studies rarely consider that exercise-induced changes in core body temperature might increase free cortisol independent of psychological stress or physical exertion. We tested the effect of heat exposure without exertion or other stressors on saliva cortisol. 26 Participants (18 healthy and 8 with Major Depression MDD) sat motionless in a dry infrared sauna set to 65.5 degrees C (150 F). They had their tympanic membrane temperature and salivary cortisol measured as their body temperature increased. Exposure to exogenous heat significantly increased core body temperature from 36.93 C/98.48 F (95% CI 36.79-37.07 C, 98.23-98.73 F) to 38.42 C /101.16 F (95% CI 38.24-38.6 C, 100.83-101.48 F) after 45 minutes of heat exposure, F(15,42.33)=43.509, p<0.001. Concurrently saliva cortisol also increased significantly from 4.00 nmol/l (95%CI 1.89-6.11) to 9.87 nmol/l (95% CI 5.58-14.17), F(1,33.17)=6.64, p=0.015. Elevations in core body temperature can significantly increase free cortisol levels even in the absence of exercise or overt psychological stressors.

Core body temperature changes before sleep are associated with nocturnal heart rate variability.

Core body temperature (CBT) reductions occur before and during the sleep period, with the extent of presleep reductions corresponding to sleep onset and quality. Presleep reductions in CBT coincide with increased cardiac parasympathetic activity measured via heart rate variability (HRV), and while this appears to persist into the sleep period, individual differences in presleep CBT decline and nocturnal HRV remain unexplored. The purpose of the current study was to assess the relationship between individual differences in presleep CBT reductions and nocturnal heart rate (HR) and HRV in a population of 15 objectively poor sleeping adults [10 males, 5 females; age, 33 ± 4 yr; body mass index (BMI) 27 ± 1 kg/m2] with the hypothesis that blunted CBT rate of decline would be associated with elevated HR and reduced nocturnal HRV. Following an adaptation night, all participants underwent an overnight, in-laboratory sleep study with simultaneous recording of polysomnographic sleep including electrocardiography (ECG) and CBT recording. Correlations between CBT rate of change before sleep and nocturnal HRV were assessed. Blunted rate of CBT decline was significantly associated with increased heart rate (HR) in stage 2 (N2; R = 0.754, P = 0.001), stage 3 (N3; R = 0.748, P = 0.001), and rapid-eye movement (REM; R = 0.735, P = 0.002). Similarly, blunted rate of CBT decline before sleep was associated with reduced HRV across sleep stages. These findings indicate a relationship between individual differences in presleep thermoregulatory processes and nocturnal cardiac autonomic function in poor sleeping adults.NEW & NOTEWORTHY Core body temperature (CBT) reductions before sleep onset coincide with increases in heart rate variability (HRV) that persist throughout the sleep period. However, the relationship between individual differences in the efficiency of presleep core temperature regulation and nocturnal heart rate variability remains equivocal. The present study reports an association between the magnitude of presleep core body temperature changes and nocturnal parasympathetic activity, highlighting overlap between thermoregulatory processes before sleep and nocturnal cardiac autonomic function.

0295 Association between circadian rhythm of skin temperature and actigraphic sleep in free-living conditions: the HEIJO-KYO study

Abstract Introduction Skin temperature manipulation with little or no change in core body temperature affects sleep-wake states. However, the significance of 24-hour variation in skin temperature to sleep quality is unclear. We aimed to evaluate whether the circadian rhythm of distal skin temperature (DST) affects sleep quality in free-living conditions and to provide additional evidence about the relationship between thermal input to the skin and sleep-wake states. Methods In this cross-sectional study of 2,177 community-dwelling adults (Mean age 68.8 [SD 8.0] years), we measured DST using a temperature logger (Thermochron iButton, Maxim) at 3-minute intervals for seven consecutive days to calculate non-parametric indicators of circadian rhythm: intradaily variability (IV), interdaily stability (IS), and relative amplitude (RA). The participants underwent simultaneous 7-day wrist actigraphy (GT3X-BT, ActiGraph) to measure sleep objectively. The association between non-parametric indicators and 7-day means of sleep measures was evaluated using multivariable linear regression models. Results Lower quartiles of IV and higher quartiles of IS and RA were significantly associated with higher sleep efficiency, shorter wake after sleep onset, and longer total sleep time (all p &amp;lt;.001). After adjusting for potential confounders, including physical activity and outdoor temperature, the coefficients for the linear trend of sleep efficiency were −1.07 (95% confidence interval [CI]: −1.45, −0.69), 1.08 (95% CI: 0.75, 1.41), and 1.33 (95% CI: 0.83, 1.84) in IV, IS, and RA, respectively (all p &amp;lt;.001). Conclusion Circadian rhythms of DST with higher fluctuation, lower regularity across days, and blunted amplitude were associated with worse sleep quality. Our findings may be applied in thermoregulatory interventions to enhance sleep quality. Support (if any)

511 Eliminating System xc- Signaling Between Astrocytes and Neurons Selectively Impairs Complex Cognition

OBJECTIVES/GOALS: We aim to discover safer and more effective therapeutics for CNS disorders. Current therapeutic development is hindered by dosing out drugs for safe consumption. By identifying proteins with narrow functional roles in the brain (i.e., behavioral control), we can develop drugs targeting these proteins for improved treatment safety and efficacy. METHODS/STUDY POPULATION: We focused on an evolutionarily new, non-neuronal, non-synaptic glutamate signaling mechanism, system xc- (Sxc). Sxc activity was eliminated by mutating the gene Slc7a11 through pronuclear injection of zinc-finger nucleases into Sprague Dawley rat embryos to create a line of rats lacking Sxc (MSxc). To confirm Sxc mutation, we verified that tissue from MSxc rats had a complete lack of xCT, which is the regulatory subunit of Sxc that is encoded by Slc7a11. We also verified that astrocyte cultures generated from MSxc tissue lacked cystine-evoked glutamate release. Next, we measured development (body weight), CNS regulation of metabolism, and other indicators of generalized, non-specific brain function as well as behaviors that are reliant on behavioral control, such as impulse control and response inhibition. RESULTS/ANTICIPATED RESULTS: Eliminating Sxc was not lethal and did not impair development or produce widespread changes in brain function as is commonly observed when deleting other glutamate mechanisms. MSxc rats did not differ from wildtype in growth rate, central regulation of metabolism as reflected by absolute or diurnal changes in core body temperature, locomotor activity in a familiar or novel environment, or simple forms of cognition such as novel object recognition, or operant responding (food and cocaine-reinforced). In contrast, behaviors that rely on behavioral control were impaired. MSxc rats displayed deficits in impulse control and behavioral flexibility. We hypothesize that MSxc rats will also show deficits in response inhibition using the stop signal reaction time task, a common metric used in clinical populations. DISCUSSION/SIGNIFICANCE: Eliminating Sxc activity in rats produced deficits in behaviors reliant on impulse control, without impacting development or simple brain function. These results show the potential of targeting Sxc to restore behavioral control without generating therapeutically limiting adverse effects resulting from non-specific changes in brain function.

Association between circadian skin temperature rhythms and actigraphic sleep measures in real-life settings.

Skin temperature manipulation with little or no change in core body temperature affects sleep-wake states; however, the association of 24-hour skin temperature variation with sleep quality has not been investigated in a large-scale population. We examined the association between the circadian rhythm of distal skin temperature and sleep quality in real-life settings and aimed to provide additional evidence of the link between thermoregulation and sleep-wake states. In this cross-sectional study of 2,187 community-dwelling adults, we measured distal skin temperature at the ventral forearm at 3-minute intervals for 7 consecutive days to calculate nonparametric indicators of a circadian skin temperature rhythm, including intradaily variability, interdaily stability, and relative amplitude. Participants underwent simultaneous 7-day wrist actigraphy to objectively measure sleep quality. The association between nonparametric circadian skin temperature rhythm indicators and 7-day sleep measures was evaluated using multivariable linear regression models. Lower intradaily variability and higher interdaily stability and relative amplitude of distal skin temperature were significantly associated with higher sleep efficiency, shorter wake after sleep onset, and longer total sleep time (all P < .001). After adjusting for demographic, clinical, and environmental factors, the coefficients for the linear trend of sleep efficiency were -1.20 (95% confidence interval: -1.53, -0.87), 1.08 (95% confidence interval: 0.80-1.36), and 1.47 (95% confidence interval: 1.04-1.89) per quartile increase in intradaily variability, interdaily stability, and relative amplitude, respectively (all P < .001). Distal skin temperature with lower fluctuations and higher regularity and rhythm amplitudes was associated with better sleep quality. Our results could be applied in chronobiological interventions to improve sleep quality. Tai Y, Obayashi K, Yamagami Y, Saeki K. Association between circadian skin temperature rhythms and actigraphic sleep measures in real-life settings. J Clin Sleep Med. 2023;19(7):1281-1292.

TRPV1 inactivation alters core body temperature and serum corticosterone levels: Impacts on clock genes expression in the liver and adrenal glands

PurposeTRPV1 desensitization or blockade promotes hyperthermia in rodents. Daily changes in core body temperature (Tc), spontaneous locomotor activity (SLA), and glucocorticoids are temporal cues for peripheral clocks. Thus, this study aimed to evaluate the effects of both desensitization and blockade of TRPV1 on Tc, SLA, blood corticosterone, and the clock genes Per1 and Bmal1 in the liver and adrenal. Methods and ResultsResiniferatoxin (RTX, 20 μg kg−1) known to desensitize the intra-abdominal TRPV1 channels was i. p. administered in adult male rats. One day after, RTX rats displayed higher Tc than vehicle rats (control) in the light and dark phases. RTX rats showed higher corticosterone at zeitgeber time (ZT) 6 and ZT12 compared to ZT0. Control rats showed a rise in corticosterone at ZT12. RTX abolished the Per1 peak in both the liver and adrenal glands, whereas it enhanced the peak of Bmal1 expression in the liver and decreased it in adrenal glands. Circadian variation in Tc and SLA was unaffected despite higher Tc being found along the light phase up to 5 days after RTX injection. Acute blockade of TRPV1 with the antagonist AMG-517 injected at ZT0 increased Tc and reduced corticosterone without affecting SLA. In the liver, while AMG-517 did not affect Per1, it increased Bmal1 mRNA. In adrenal glands, AMG-517 increased Per1 and did not affect Bmal1 expression. Although rats exposed to a 60-min 34 °C environment showed similar hyperthermia to that observed in AMG-517 rats, neither corticosterone nor liver nor adrenal clock genes changed. ConclusionsInactivation of TRPV1 by abdominal desensitization or by antagonism alters the time-of-day changes of clock genes expression in the liver and adrenal, as well as corticosterone. TRPV1 may be necessary for signaling cyclical temporal cues for clock genes in the periphery but less critical for the circadian profile of Tc and SLA.

The efficacy of aggressive warming combined with tranexamic acid during total hip arthroplasty: a single-center retrospective study from southern China.

The aim of the study was to evaluate the efficacy of aggressive warming combined with tranexamic acid (TXA) during total hip arthroplasty (THA). A total of 832 patients who underwent THA from October 2013 to June 2019 were divided into three groups according to the order of admission. There were 210 patients from October 2013 to March 2015 in group A, 302 patients from April 2015 to April 2017 in group B, and 320 patients from May 2017 to June 2019 in group C. Group A was the control group and was not given any measures. Group B was administered intravenously with 15 mg/kg TXA before skin incision and 3 h later without aggressive warming. Group C was administered intravenously with 15 mg/kg TXA before skin incision and 3 h later with aggressive warming. We evaluated the differences in the intraoperative blood loss, changes in core body temperature of patients at different stages during the operation, postoperative drainage, hidden blood loss, transfusion rate, drop of hemoglobin (Hb) on postoperative day 1 (POD1), prothrombin time (PT) of POD1, average hospitalization day, and complications. There were statistically significant differences among the three groups during the intraoperative blood loss, intraoperative changes in core body temperature, postoperative drainage, hidden blood loss, blood transfusion rate, drop of Hb on POD1 and average hospital stay (p<0.05). There was no statistical difference in PT on POD1 and the incidence of complications (p>0.05). Aggressive warming combined with TXA can significantly reduce the blood loss and transfusion rate of THA, and accelerate the recovery. We also observed that it does not increase the postoperative complications.

PS-C20-5: WARM IV INFUSION IN HYPERTENSIVE URGENCY

Background: Hypertensive Urgency is defined as marked elevation in systemic blood pressure without any evidence of end organ damage. At present, the condition is managed with intravenous (IV) antihypertensives, of which most common is Sodium Nitroprusside. Aim: In this abstract we explore the possibility of slow IV infusion of warm (37–38oC) Normal Saline along with IV antihypertensives for a better and faster management of Hypertensive Urgency. Content: The slow IV will gradually increase the core body temperature of the patient while preventing fluid overload. Homeostatic regulation of Systemic Blood Pressure is maintained by an intricate network of correlated mechanisms, most of which are temperature dependent. The raised body temperature will be useful to control the Blood Pressure through the following mechanisms - Cardiac Output: reduces as core body temperature increases. Baroreflex: decreased post-synaptic adrenergic vasoconstrictor responses. Chemoreceptors: vascular responsiveness to adrenergic receptor stimulation reduces at higher temperatures. RAAS: Kosunen et al recorded reduced Systolic and Diastolic Blood Pressures at raised body temperatures despite increased levels of Angiotensin II &amp; Aldosterone. Endothelin: Serum concentration of Endothelin-I reduces at higher temperatures. Sweat: Thermal stimulation of sweat gland will help excretion of both salt and water, thus maintaining the sodium balance. VEGF: VEGF-A, a potent vasodilator, is increased during elevated body temperature. However, apart from Blood Pressure, a change in core body temperature causes change in many other parameters as well, which must be considered during this discussion. Coagulation profile - Valeri et al noted no change in in-vivo coagulation states till 100oF Effect on other visceral organs - Internal visceral organs like Liver, Kidneys and Brain were not affected till 100oF Infection Control - Core body temperature close to 100oF has also been found to have a protective role against invasive fungal infections in the ICU Discussion: Though the effects of various antihypertensive drugs to raised body temperatures need to be tested, the above points prove that introducing a protocol of warm IV saline Infusion in patients of Hypertensive Urgency may be extremely beneficial, and also prevent clinical inertia.

A modelling framework for local thermal comfort assessment related to bicycle helmet use

Thermal discomfort due to accumulated sweat increasing head skin wettedness may contribute to low wearing rates of bicycle helmets. Using curated data on human head sweating and helmet thermal properties, a modelling framework for the thermal comfort assessment of bicycle helmet use is proposed. Local sweat rates (LSR) at the head were predicted as the ratio to the gross sweat rate (GSR) of the whole body or by sudomotor sensitivity (SUD), the change in LSR per change in body core temperature (Δtre). Combining those local models with Δtre and GSR output from thermoregulation models, we simulated head sweating depending on the characteristics of the thermal environment, clothing, activity, and exposure duration. Local thermal comfort thresholds for head skin wettedness were derived in relation to thermal properties of bicycle helmets. The modelling framework was supplemented by regression equations predicting the wind-related reductions in thermal insulation and evaporative resistance of the headgear and boundary air layer, respectively. Comparing the predictions of local models coupled with different thermoregulation models to LSR measured at the frontal, lateral and medial head under bicycle helmet use revealed a large spread in LSR predictions predominantly determined by the local models and the considered head region. SUD tended to overestimate frontal LSR but performed better for lateral and medial head regions, whereas predictions by LSR/GSR ratios were lower and agreed better with measured frontal LSR. However, even for the best models root mean squared prediction errors exceeded experimental SD by 18–30%. From the high correlation (R > 0.9) of skin wettedness comfort thresholds with local sweating sensitivity reported for different body regions, we derived a threshold value of 0.37 for head skin wettedness. We illustrate the application of the modelling framework using a commuter-cycling scenario, and discuss its potential as well as the needs for further research.

Hydroxysafflor yellow A attenuates heat stroke-induced acute lung injury in mice by inhibiting necroptosis

To investigate the protective effect of hydroxysafflor yellow A (HSYA) against heat stroke (HS)-induced acute lung injury and its possible mechanism. The optimal dose of HSYA pretreatment via intraperitoneal injection prior to HS was determined in a mice by observing heat tolerance of the mice. C57BL/6J mice were pretreated with HSYA at the optimal dose or with Nec-1 (a RIP1 activation inhibitor) before HS, and the changes in core body temperature and survival of the mice were observed during the 72-h recovery period. At different stages of recovery, lung tissues, bronchoalveolar lavage fluid and blood samples were collected from the mice for assessing lung tissue pathology, wet-to-dry weight ratio and water content of the lungs; leukocyte and neutrophil counts, total protein levels and HMGB1 level in the bronchoalveolar lavage fluid (BLF) were also detected. Serum levels of TNF-α, IL-6 and HMGB1 were detected with ELISA, and the expression levels of RIP1, RIP3, MLKL-s358, MLKL and MLKL-s358 proteins in the lung tissues were detected using Western blotting. HSYA pretreatment at the moderate and high doses significantly improved heat tolerance of the mice with comparable effects. At the optimal dose of 2.25 mg/kg, HSYA pretreatment significantly increased heat tolerance of the mice (P<0.05), showing a similar effect with Nec-1 pretreatment. Pretreatment with HSYA and Nec-1 both significantly increased survival rate of the mice (P<0.05), lowered histopathological score and water content of the lungs, and reduced the levels of TNF-α, IL-6 and HMGB1 (P<0.05), leukocyte and neutrophil counts, and total protein and HMGB1 levels in the BLF (P<0.05). The mice during recovery from HS showed significantly increased RIP1 expression and MLKL-s358 phosphorylation level in the lung tissue (P<0.05), which were obviously lowered by HSYA pretreatment of the mice. Severe HS results in necroptosis in the lung tissue of mice, which can be alleviated by HSYA pretreatment.

Critical Care Nursing in Targeted Temperature Management (TTM) After Cardiac Arrest

Targeted temperature management (TTM) is a complex and sophisticated intensive-care procedure that is included in the American Heart Association guidelines for treating patients who remain unconscious after resuscitation from cardiac arrest. TTM has been demonstrated to reduce brain injury associated with reperfusion after resuscitation and to improve the neurological prognosis in patients with cardiac arrest. The TTM process may be divided into four phases: induction, maintenance, rewarming, and normothermia. The critical element in TTM is the quick lowering and slow raising of body temperature, which should be fine-tuned to maintain temperature stability and minimize variation. Caregivers should monitor the physiological changes caused by core body temperature change closely and manage possible complications such as shivering, hypo- and hyper-glycemia, electrolyte imbalance, skin injury, arrhythmia, and infection. Based on contemporary evidence and clinical experience, this article provides critical care nurses a summary and key points of each stage of TTM when used to take care of resuscitated patients after cardiac arrest. We hope this work may help improve patient safety and quality of care during the TTM procedure.