Decrease In Core Body Temperature Research Articles

Alpha-2-adrenergic agonists reduce resting energy expenditure in humans during external cooling

ABSTRACT Intravenous alpha-2-adrenergic receptor agonists reduce energy expenditure and lower the temperature when shivering begins in humans, allowing a decrease in core body temperature. Because there are few data about similar effects from oral drugs, we tested whether single oral doses of the sedative dexmedetomidine (1 µg/kg sublingual or 4 µg/kg swallowed) or the muscle relaxant tizanidine (8 mg or 16 mg), combined with surface cooling, reduce energy expenditure and core body temperature in humans. A total of 26 healthy participants completed 41 one-day laboratory studies measuring core body temperature using an ingested telemetry capsule and measuring energy expenditure using indirect calorimetry for up to 6 hours after drug ingestion. Dexmedetomidine induced a median 13% – 19% peak reduction and tizanidine induced a median 15% – 22% peak reduction in energy expenditure relative to baseline. Core body temperature decreased a median of 0.5°C – 0.6°C and 0.5°C – 0.7°C respectively. Decreases in temperature occurred after peak reductions in energy expenditure. Energy expenditure increased with a decrease in core temperature in control participants but did not occur after 4 µg/kg dexmedetomidine or 16 mg tizanidine. Plasma levels of dexmedetomidine but not tizanidine were related to mean temperature change. Decreases in heart rate, blood pressure, respiratory rate, cardiac stroke volume index, and cardiac index were associated with the change in metabolic rate after higher drug doses. We conclude that both oral dexmedetomidine and oral tizanidine reduce energy expenditure and allow decrease in core temperature in humans.

Importance of Renal Graft Reperfusion Thermoregulation in Living Donor Kidney Transplant Patients: Gasometrical and Hemodynamical Study

INTRODUCTION: Hypothermia, defined as a decrease in core body temperature below 36°C, has a notable influence on hemodynamic variables during anesthesia, which is of great interest in perioperative medicine. Temperature regulation is crucial in anesthetic management because hypothermia can significantly impact the patient's cardiovascular functioning. Accidental (uncontrolled) hypothermia during anesthetic and surgical procedures carries considerable risks such as: Increases the incidence of surgical site infections, prolongs the effects of drugs administered during anesthesia, and disrupts normal coagulation, potentially increasing the risk of bleeding. For these reasons, body temperature regulation is a critical aspect to monitor and control during anesthesia. MATERIAL AND METHODS: A descriptive, observational, single-center, and retrospective study was carried out in patients undergoing a related living donor kidney transplant between June 2022-2023 at the Juarez Hospital in Mexico. All data were collected from the demographic sheets, laboratories and trans anesthetic sheets of the patient's file. The data was integrated into an Excel database and statistical processing was performed in SPSS or STATSm software. The statistical analysis was tested for normality according to Kolmogorov-Smirnov with Lilliefors correction, where it was found that the population has a normal or non-normal distribution. The Mann-Whitney U test was performed to compare the difference of the means between the two groups. A correlation was made with Kendall´s Tau coefficient; All statistical analyzes were performed with a value of p<0.05, considering these significantly. RESULTS: Of the 65 transplanted patients between Jun 2023 and June 2024 only 28 have appropriate inclusion criteria. Of the remaining 28, 16 were female (57.14%) and 12 were male (42.8%) with an average age of recipients of 30.2430.46 ±11.45 years with a weight of 58.23 ±10.47 kg, height 154.20 ±15.32 cm. Gasometrical and Hemodynamic Values upon Reperfusion with a Forced Air Turbine. The gasometrical variables before reperfusion were: Venous pH 7.41±0.05 (p=0.046); Arterial pH 7.40±0.04 (p=0.015); Venous Oxygen Saturation 68.2±9.74% (p = 0.039). Hemodynamic variables before reperfusion were: IC 3.67±1.77 lt/min/m2 (p=0.001); Stroke Volume 79.5±39.6 ml/beat (p=0.022), Oxygen Extraction 25.1±9.95% (p=0.001) and Myocardial Efficiency 0.28±0.06 (p=0.024); The gasometrical variables after reperfusion were: Venous pH 7.40±0.03; Arterial pH 7.380±0.04; Venous Oxygen Saturation 60.03±4.37%; The hemodynamic variables after reperfusion were: IC 2.88±0.48 liter/min/m2; Stroke Volume 65.4±16.01 ml/beat; Oxygen Extraction Rate 36.9±4.31% (p = 0.039) and Myocardial Efficiency 0.32±0.06 Gasometrical and Hemodynamic Values upon Reperfusion without Forced Air Turbine. The gasometrical variables before reperfusion were: Venous pH 7.32±0.04 (p=0.012); Arterial pH 7.30±0.04 (p=0.019); Venous Oxygen Saturation 64.7±8.27% (p = 0.026). Hemodynamic variables before reperfusion were Cardiac Index 3.28±1.66 lt/min/m2 (p=0.006); Stroke Volume 72.39±45.44 ml/beat (p=0.029); Oxygen Extraction 29.11±9.65% (p=0.001) and Myocardial Efficiency 0.268±0.08 (p=0.022). The gasometrical variables after reperfusion were: Venous pH 7.33±0.04; Arterial pH 7.320±0.05; Venous Oxygen Saturation 58.593±5.41%. The hemodynamic variables after reperfusion were: Cardiac Index 2.75±0.69 liter/min/m2, Stroke Volume 59.05±18.81 ml/beat, Oxygen Extraction Rate 38.47±6.17% and Myocardial Efficiency 0.31±0.05. CONCLUSIONS: Understanding the behavior of blood gas and hemodynamic variables upon reperfusion in transplant patients is essential for adequate kidney graft survival. In these patients, the use of a hot forced air turbine improves the conditions under which said reperfusion is performed, impacting not only at the blood gas level (venous pH, arterial pH and venous oxygen saturation) but also at the hemodynamic level (cardiac index, stroke volume, myocardial efficiency The limitations of the study are heterogeneity of the etiologies of CKD, sample size, and volume status prior to the procedure. To date the published works are consistent with the literature.

Clinical Efficacy of 10 Min of Active Prewarming for Preserving Patient Body Temperature during Percutaneous Nephrolithotomy: A Prospective Randomized Controlled Trial.

Background: Percutaneous nephrolithotomy (PNL) poses a risk of hypothermia. Additionally, general anesthesia lowers the thresholds for shivering and vasoconstriction, which leads to dysfunction of central thermoregulation. Perioperative hypothermia is associated with adverse outcomes after surgery. In this study, we aimed to demonstrate that prewarming for 10 min can effectively prevent early hypothermia during PNL. Methods: A total of 68 patients scheduled for elective PNL were recruited to this study from January to June 2022, but two patients were excluded because of a change in the surgical plan. After randomization, patients in the prewarming group (n = 32) received warming using a forced-air warming device for 10 min in the preoperative area before being transferred to the operating room, while the controls (n = 34) did not. The incidence of hypothermia within the first hour after inducing general anesthesia was the primary outcome. Perioperative body temperatures and postoperative recovery findings were also evaluated. Results: Early intraoperative hypothermia decreased significantly more in the prewarming group than in the control group (9.4% vs. 41.2%, p = 0.003). Moreover, the net decrease in core body temperature during surgery was smaller in the prewarming group than in the control group (0.2 °C, vs. 0.5 °C, p = 0.003). In addition, the prewarmed patients had a lower incidence of postoperative shivering and a shorter post-anesthesia-care unit (PACU) stay (12.5% vs. 35.3%, p = 0.031; and 46 vs. 50 min, p = 0.038, respectively). Conclusions: Prewarming for 10 min decreased early hypothermia, preserved intraoperative body temperature, and improved postoperative recovery in the PACU.

Precooling via immersion in CO2-enriched water at 25°C decreased core body temperature but did not improve 10-km cycling time trial in the heat

ABSTRACT This study compared the effects of precooling via whole-body immersion in 25°C CO2-enriched water (CO2WI), 25°C unenriched water (WI) or no cooling (CON) on 10-km cycling time trial (TT) performance. After 30 min of precooling (CO2WI, CON, WI) in a randomized, crossover manner, 11 male cyclists/triathletes completed 30-min submaximal cycling (65%VO2peak), followed by 10-km TT in the heat (35°C, 65% relative humidity). Average power output and performance time during TT were similar between conditions (p = 0.387 to 0.833). Decreases in core temperature (Tcore) were greater in CO2WI (−0.54 ± 0.25°C) than in CON (−0.32 ± 0.09°C) and WI (−0.29 ± 0.20°C, p = 0.011 to 0.022). Lower Tcore in CO2WI versus CON was observed at 15th min of exercise (p = 0.050). Skin temperature was lower in CO2WI and WI than in CON during the exercise (p < 0.001 to 0.031). Only CO2WI (1029 ± 305 mL) decreased whole-body sweat loss compared with CON (1304 ± 246 mL, p = 0.029). Muscle oxygenation by near-infrared spectroscopy (NIRS), thermal sensation, and thermal comfort were lower in CO2WI and WI versus CON only during precooling (p < 0.001 to 0.041). NIRS-derived blood volume was significantly lower in CO2WI and WI versus CON during exercise (p < 0.001 to 0.022). Heart rate (p = 0.998) and rating of perceived exertion (p = 0.924) did not differ between conditions throughout the experiment. These results suggested that CO2WI maybe more effective than WI for enhanced core body cooling and minimized sweat losses.

Acute and Reversible Hypothalamic Symptoms in a Lateral Head Impact Mouse Model of Mild Traumatic Brain Injury.

Central autonomic and endocrine dysfunctions following traumatic brain injury (TBI) are believed to involve the hypothalamus; however, underlying mechanisms are unknown. Although chronic deficits might be caused by irreversible tissue damage, various neuroendocrine and autonomic symptoms are only observed transiently, suggesting they might result from a temporary alteration in the activity of hypothalamic neurons. We therefore examined if a mouse model of mild TBI could induce reversible autonomic phenotypes and cause acute changes in c-Fos expression within corresponding regions of the hypothalamus. Adult C57Bl/6 male mice were lightly anesthetized with isoflurane and subjected to TBI by lateral head impact using a Gothenburg impactor. Mice treated the same way, but without the head impact served as controls (shams). We monitored body weight and core body temperature by infrared thermography and performed immunohistochemistry against c-Fos in various regions of the hypothalamus. We determined that a projectile velocity of 9 m/s significantly delayed recovery from the anesthesia without inducing skull fractures and signs of discomfort disappeared within 3 h, as assessed by grimace scale. Compared with shams, TBI mice displayed a rapid decrease in core body temperature which resolved within 48 h. Daily body weight gain was also significantly lower in TBI mice on the day following injury but recovered thereafter. c-Fos analysis revealed a significantly higher density of c-Fos-positive cells in the paraventricular nucleus and a significantly lower density in the median preoptic nucleus and medial preoptic area. We conclude that mild TBI induced by a single lateral head impact in mice at 9 m/s produces acute and reversible symptoms associated with hypothalamic dysfunction accompanied by significant changes in c-Fos expression within relevant areas of the hypothalamus. These findings support the hypothesis that a temporary alteration of neuronal activity may underlie the expression of reversible central autonomic and neuroendocrine symptoms.

Influence of carbon side chain length on the in vivo pharmacokinetic and pharmacodynamic characteristics of illicitly manufactured fentanyls.

Since 2016, illicitly manufactured fentanyls and fentanyl analogs (referred to as IMFs) have contributed to an increase in drug overdoses. Although fentanyl has been characterized and evaluated extensively in animals and humans, many of the clandestinely synthesized analogs of fentanyl have not and users may unknowingly ingest these IMFs leading to overdose and potentially death. The pharmacodynamic (PD) and pharmacokinetic (PK) properties of four IMFs and fentanyl were evaluated in Sprague-Dawley rats. A 300-μg/kg subcutaneous dose of each compound (fentanyl, acetylfentanyl, cyclopropylfentanyl, butyrylfentanyl, and valerylfentanyl) was given. PD parameters were measured using a tail flick meter and core body temperature. Blood was drawn to evaluate PK parameters utilizing liquid chromatography tandem mass spectrometry (LC-MS/MS). Fentanyl displayed the greatest and longest lasting analgesia with a tail flick response of 10s (the maximum cutoff). Additionally, fentanyl produced an average -4.9°C in core body temperature resulting in the greatest decrease in core body temperature. Acetylfentanyl, with the shortest carbon side chain, displayed the shortest T½, and lowest AUC and Cmax and resulted in an increase in body temperature. There were no other PK differences among the IMFs assessed. As IMFs are commonly seen on the streets and can pose significant risks to users (although these risks do depend on other factors such as dose and route of administration), there is a benefit to having the pharmacological properties of these compounds characterized to better understand the potential harm to humans.

Cerebral Lactate Participates in Hypoxia-induced Anapyrexia Through its Receptor G Protein-coupled Receptor 81

Hypoxia-induced anapyrexia is thought to be a regulated decrease in body core temperature (Tcore), but the underlying mechanism remains unclear. Recent evidence suggests that lactate, a glycolysis product, could modulate neuronal excitability through the G protein-coupled receptor 81 (GPR81). The present study aims to elucidate the role of central lactate and GPR81 in a rat model of hypoxia-induced anapyrexia. The findings revealed that hypoxia (11.1% O2, 2 h) led to an increase in lactate in cerebrospinal fluid (CSF) and a decrease in Tcore. Injection of dichloroacetate (DCA, 5 mg/kg, 1 μL), a lactate production inhibitor, to the third ventricle (3 V), alleviated the increase in CSF lactate and the decrease in Tcore under hypoxia. Immunofluorescence staining showed GPR81 was expressed in the preoptic area of hypothalamus (PO/AH), the physiological thermoregulation integration center. Under normoxia, injection of GPR81 agonist 3-chloro-5-hydroxybenzoic acid (CHBA, 0.05 mg/kg, 1 μL) to the 3 V, reduced Tcore significantly. In addition, hypoxia led to a dramatic increase in tail skin temperature and a decrease in interscapular brown adipose tissue skin temperature. The number of c-Fos+ cells in the PO/AH increased after exposure to 11.1% O2 for 2 h, but administration of DCA to the 3 V blunted this response. Injection of CHBA to the 3 V also increased the number of c-Fos+ cells in the PO/AH under normoxia. In light of these, our research has uncovered the pivotal role of central lactate-GPR81 signaling in anapyrexia, thereby providing novel insights into the mechanism of hypoxia-induced anapyrexia.

Comparison of Preemptive Post-Intubation 15 Mg/KgBW Paracetamol to 0.35 Mg/KgBW Meperidine in Incidence of Post-Anesthetic Shivering

Post anesthesia shivering (PAS) is a repetitive involuntary movement of one or more muscle groups as a result of a decrease in core body temperature. Pharmacological therapy in preventing PAS may include meperidine and paracetamol. This study compared the effectiveness of paracetamol to meperidine in reducing the incidence of post-anesthesia shivering. This study used an experimental randomized double-blind comparative analytic design on patients underwent exploratory laparotomy surgery under general anesthesia at Dr. Hasan Sadikin General Hospital Bandung, Indonesia, from September 2021 to August 2022. Patients with 50 ASA 1-2 physical status were included and divided into two groups. One group received 15 mg/kg group paracetamol and the other received 0.35 mg/kg meperidine. Data on tympanic membrane temperature and hemodynamics before and after induction and after extubating were collected. Furthermore, data on the results of the assessment of the incidence and grade of shivering in each treatment group were also collected. The results of this study showed that there was a decrease in the frequency of PAS in patients receiving intravenous 15 mg/kg paracetamol (p&lt;0.05), as well as less side effects in the form of nausea and vomiting (p &lt; 0.05). The incidence and degree of shivering after general anesthesia using intravenous 15 mg/kg paracetamol was lower compared to the use of 0.35 mg/kg meperidine. In the meperidine group, the decrease in body temperature was lower than in the paracetamol group, while the incidence of nausea and vomiting in the paracetamol group was lower than in the meperidine group. In conclusion, paracetamol reduces the incidence of post-anesthesia shivering better than meperidine.

Mini-HoLEP (MILEP) vs HoLEP: a propensity score-matched analysis.

Minimal invasiveness improves outcome in many surgical fields including urology. We aimed to assess intraoperative performance and clinical outcome of miniaturized holmium laser enucleation of prostate (MiLEP) (22FR). We ran a propensity score-matched analysis among all consecutive laser enucleations of prostate performed between 9/2022 and 2/2023. It resulted in two matched comparison groups: MiLEP 22 FR (n = 40) and holmium laser enucleation of prostate (HoLEP 26 Fr) (n = 40). Statistical analysis was performed. MiLEP was associated with significantly less intraoperative irrigation (20.5 L vs 15 L,p = 0.002E-3), less decrease in body core temperature (0.6°C vs 0.1°C,p = 0.003E-5), and less need for meatal dilation (25% vs 78%,p = 0.01E-3). These parameters were identified as being independent in the multivariate analysis. There was a trend toward less and a shorter period of postoperative stress incontinence (SI) for the MiLEP group compared to the HoLEP group: 15% and 42% (p = 0.01) at 1 month, 8% and 14% (p = 0.07) at 2 months, and 0 and 0.3% (p = 1) at 3 months, respectively. There were no differences in prostatic enucleation effectiveness, operative time, hospital stay, complications, and improvement in the international prostate symptom score and quality of life score. MiLEP is feasible and provides better maintenance of body core temperature, reduction in amount of fluid irrigation, and decrease in need for meatal dilation without affecting effectiveness in comparison with HoLEP. MiLEP may reduce early postoperative stress incontinence, thereby shortening the recovery period.

Sheehan’s Syndrome in a Fifty-Six-Year-Old Woman Presenting With a Retroperitoneal Mass: Perioperative Management During a Major Surgery

Patients with Sheehan’s syndrome (SS) can present with adrenal crisis, myxedema coma, hypoglycemia, and hyponatremia, which could be triggered by an infection or surgery. For the endocrinologist, a patient with SS who is scheduled for surgery presents a significant challenge as more likely to experience delayed emergence from anesthesia, hypotension that does not respond to the standard regimen, a decrease in core body temperature, and a decreased need for anesthetic drugs due to reduced metabolism. Here, to emphasize the significance of perioperative management to reduce the risk of morbidity and mortality from a potential adrenal crisis, we report the successful perioperative management of a 56-year-old woman with SS undergoing major surgery for the resection of a retroperitoneal tumor. The management plan for this patient comprised a perioperative intravenous hydrocortisone supplementation and thyroxine tablets on the morning of the procedure. In the operating room, the patient was started on norepinephrine, and she was given intravenous (IV) crystalloids and albumin. Healthcare providers should be aware of the perioperative risk of SS. No consensus, guidelines, or randomized trials for the safe perioperative management of patients with SS have been identified by a thorough review of the literature. Because of this, the perioperative care of these patients necessitates the utmost caution in addition to successful management based on close coordination between the endocrinologist, surgeon, and anesthetist. J Endocrinol Metab. 2023;13(1):39-42 doi: https://doi.org/10.14740/jem858

Changes in sleep profile on exposure to sodium chloride and artificially carbonated springs: a pilot study.

[Purpose] Herein, we aimed to investigate the effects of bathing in a sodium chloride spring and an artificially carbonated spring on core body temperature and electroencephalograms, to assess whether the springs facilitate sleep. [Participants and Methods] This randomized, controlled, crossover study evaluated the effects of a sodium chloride spring, an artificially carbonated spring, a plain hot bath, and no bath on sleep. The subjective evaluations and recording of temperature were performed before/after bathing at 40 °C for 15 min at 22:00 h, before nocturnal sleep (0:00-7:00 h), and after the participants (n=8) woke up in the morning. [Results] Bathing significantly increased the core body temperature, with significant subsequent declines observed until bedtime. Participants in the sodium chloride spring group had the highest average core body temperature, while participants in the no-bath group had the lowest average core body temperature before bedtime (23:00-0:00 h). During bedtime (1:00-2:00 h), the participants in the no bath group had the highest average core body temperature, while participants in the artificially carbonated spring group had the lowest average core body temperature. The amount of delta power/min in the first sleep cycle significantly increased in the bathing groups, with the highest value during bedtime being recorded in the artificially carbonated spring group, followed by the sodium chloride spring, plain hot bath, and no-bath groups. These sleep changes were associated with significant declines in the elevated core body temperature. Increased heat dissipation and decreased core body temperature were observed in the artificially carbonated spring and sodium chloride spring groups, which increased the delta power during the first sleep cycle compared with that observed in the plain hot bath group, followed by the no-bath group. [Conclusion] An artificially carbonated spring would be the most appropriate given each circumstance because it did not cause fatigue, as observed with the sodium chloride spring.

Effects of Seawater Immersion on Lethal Triad and Organ Function in Healthy and Hemorrhagic Shock Rats

IntroductionMarine casualties are increasing, and mortality from trauma associated with immersion in seawater is high. However, the associated pathophysiological characteristics remain unclear, limiting research into the early emergency treatment strategy. MethodsHealthy and 50% hemorrhagic shock rats were soaked in 15°C and 21°C seawater for 2 h, 4 h and 6 h, respectively, and the effects on vital signs, internal environment, tissue metabolism, lethal triad, vital organ functions and survival were observed. ResultsImmersion in seawater can cause death in healthy rats. Rats with hemorrhagic shock in 15°C seawater showed a lower survival rate than the corresponding groups in 21°C seawater. Moreover, compared with 21°C seawater, 15°C seawater played a more remarkable role in decreasing mean arterial pressure, heart rate, and respiration rate, increasing water content and decreasing Na+/K+-ATPase activity in the brain and lung; increase in plasma osmolality, Na+, K+, Cl−, and the occurrence of the lethal triad manifested by a decrease in core body temperature, pH, lactate, and an increase in coagulation parameters, as well as damage to cardiac, intestinal, hepatic, and renal functions in rats with hemorrhagic shock. ConclusionsImmersion in seawater at low temperatures could be lethal to healthy rats, causing the occurrence of a lethal triad and damage to vital organs. Furthermore, 15°C-seawater had a more significant effect than 21°C-seawater on aggravating the imbalance of internal environment and tissue metabolism, resulting in a higher incidence of the lethal triad and thus aggravating the dysfunctions of vital organs, which eventually resulted in higher mortality in rats with hemorrhagic shock.

Accidental hypothermia: pathophysiology, investigations and management.

Accidental hypothermia, defined as an unintentional decrease in core body temperature to below 35°C, adversely affects several body systems, including the cardiovascular, central nervous and renal systems. It is classified according to core body temperature from a maximum of 35°C in mild hypothermia to below 24°C in profound hypothermia. Patients with severe hypothermia (28°C-24°C) are at risk of cardiac arrythmias and cardiac arrest. In patients presenting with hypothermia, it is vital to prevent any further heat loss and quickly start rewarming them. Nurses working in the emergency department have a crucial role in supporting the optimal recovery of hypothermic patients. This article explains the pathophysiology of hypothermia, describes the investigations conducted in patients with accidental hypothermia and discusses management and nursing care.

Novel temperature-controlled sleep system to improve sleep: aproof-of-concept study.

The sleep-wake cycle is regulated by circadian Process C and homeostatic Process S. Selective thermal stimulation (STS) of the cervical spine region enhances glabrous skin blood flow (GSBF) and augments body heat dissipation to increase distal-to-proximal skin gradient (DPG) causing decrease of core body temperature (CBT), which can shorten sleep onset latency (SOL) and improve sleep quality. A total of 11 young healthy/normal sleeper males challenged to go to bed (lights-off) 2 h earlier than usual were subjected in a randomised order to non-consecutive treatment and control night-time sleep sessions. The treatment night entailed activation of a dual-temperature zone mattress with a cooler centre and warmer periphery plus STS pillow that applied mild heating to the cervical spinal skin for 30 min after lights-off for sleep. During the first 30 min after lights-off, GSBF (mean [standard error (SE)] Δ=49.77[19.13]perfusion units, p=0.013) and DPG (mean [SE] Δ=2.05[0.62]°C, p= 0.005) were significantly higher and CBT (mean [SE] Δ=-0.15[0.07]°C, p=0.029) was significantly lower in the treatment than control night, while there was no significant difference in these variables during the 45 min prior to lights-off (baseline). Moreover, SOL was significantly reduced (mean [SE] Δ=-48.6[23.4]min, p=0.032) and subjective sleep quality significantly better (p < 0.001) in the treatment than control night. In conclusion, the novel sleep facilitating system comprised of the STS pillow plus dual-temperature zone mattress induced earlier increase in GSBF and DPG and earlier decline in CBT. This resulted in statistically significant shortened SOL and improved overall sleep quality, thereby reducing sleep pressure of Process S, even under the challenging investigative protocol requiring participants to go to sleep 2 h earlier than customary.

Ketones Improve the Mitochondrial Coupling Efficiency of Brown Adipocytes

Brown adipose tissue (BAT) thermogenesis is an energy‐demanding response, and this capacity can be leveraged to dissipate excess energy in obesity and its associated metabolic complications. Therefore, understanding the regulatory mechanisms of BAT mitochondrial uncoupling and thermogenesis is crucial. Ketone bodies are endogenous metabolites mainly found during starvation and carbohydrate restriction; however, their regulatory role on BAT thermogenesis is elusive. In this study, we aim to investigate the potential metabolic reprogramming induced by ketones on BAT. We hypothesize that ketones are alternative fuels for BAT during energy/carbohydrate shortage and decrease mitochondrial uncoupling to counterbalance the systemic energy deficit. In mice, ketogenic diet reduces core body temperature by 0.4˚C. Using Seahorse respirometry in differentiated brown adipocytes, we found that ketones improve mitochondrial coupling efficiency (ATP‐linked respiration/ basal respiration) by 30%, implying an attempt to decrease thermogenesis. The gene Oxct1, encoding succinyl‐CoA:3‐ketoacid CoA transferase that is required for ketolysis, is abundantly expressed by brown adipocytes. BAT‐specific Oxct1 knockout renders mice more resistant to cold‐induced decrease in core body temperature during fasting or ketogenic diet, via mechanisms independent of UCP1. Together, our data suggest that ketones potentially communicate hunger to brown adipocytes, thus promoting mitochondrial coupling efficiency for energy conservation.

The effect of warm and humidified gas insufflation in gynecological laparoscopy on maintenance of body temperature: a prospective randomized controlled multi-arm trial

BackgroundHypothermia is defined as a decrease in body core temperature to below 36 °C. If intraoperative heat-preserving measures are omitted, a patient’s temperature will fall by 1 – 2 °C. Even mild forms of intraoperative hypothermia can lead to a marked increase in morbidity and mortality. Using warm and humidified gas insufflation in laparoscopy may help in the maintenance of intraoperative body temperature.MethodsIn this prospective randomized controlled study, we investigated effects of temperature and humidity of the insufflation gas on intra- and postoperative temperature management. 150 patients undergoing gynecologic laparoscopic surgery were randomly assigned to either insufflation with non-warmed, non-humidified CO2 with forced air warming blanket (AIR), humidified warm gas without forced air warming blanket (HUMI) or humidified warm gas combined with forced air warming blanket (HUMI+). We hypothesized that the use of warmed laparoscopic gas would have benefits in the maintenance of body temperature and reduce the occurrence of hypothermia.ResultsThe use of warm and humidified gas insufflation alone led to more hypothermia episodes with longer duration and longer recovery times as well as significantly lower core body temperature compared to the other two groups. In the comparison of the AIR group and HUMI + group, HUMI + patients had a significantly higher body temperature at arrival at the PACU (Post Anaesthesia Care Unit), had the least occurrence of hypothermia and suffered from less shivering.ConclusionThe use of warm and humidified gas insufflation alone does not sufficiently warm the patients. The optimal temperature management is achieved in the combination of external forced air warming and insufflation of warm and humidified laparoscopy gas.

Physiological Changes in Subjects Exposed to Accidental Hypothermia: An Update.

BackgroundAccidental hypothermia (AH) is an unintended decrease in body core temperature (BCT) to below 35°C. We present an update on physiological/pathophysiological changes associated with AH and rewarming from hypothermic cardiac arrest (HCA).Temperature Regulation and MetabolismTriggered by falling skin temperature, Thyrotropin-Releasing Hormone (TRH) from hypothalamus induces release of Thyroid-Stimulating Hormone (TSH) and Prolactin from pituitary gland anterior lobe that stimulate thyroid generation of triiodothyronine and thyroxine (T4). The latter act together with noradrenaline to induce heat production by binding to adrenergic β3-receptors in fat cells. Exposed to cold, noradrenaline prompts degradation of triglycerides from brown adipose tissue (BAT) into free fatty acids that uncouple metabolism to heat production, rather than generating adenosine triphosphate. If BAT is lacking, AH occurs more readily.Cardiac OutputAssuming a 7% drop in metabolism per °C, a BCT decrease of 10°C can reduce metabolism by 70% paralleled by a corresponding decline in CO. Consequently, it is possible to maintain adequate oxygen delivery provided correctly performed cardiopulmonary resuscitation (CPR), which might result in approximately 30% of CO generated at normal BCT.Liver and CoagulationAH promotes coagulation disturbances following trauma and acidosis by reducing coagulation and platelet functions. Mean prothrombin and partial thromboplastin times might increase by 40–60% in moderate hypothermia. Rewarming might release tissue factor from damaged tissues, that triggers disseminated intravascular coagulation. Hypothermia might inhibit platelet aggregation and coagulation.KidneysRenal blood flow decreases due to vasoconstriction of afferent arterioles, electrolyte and fluid disturbances and increasing blood viscosity. Severely deranged renal function occurs particularly in the presence of rhabdomyolysis induced by severe AH combined with trauma.ConclusionMetabolism drops 7% per °C fall in BCT, reducing CO correspondingly. Therefore, it is possible to maintain adequate oxygen delivery after 10°C drop in BCT provided correctly performed CPR. Hypothermia may facilitate rhabdomyolysis in traumatized patients. Victims suspected of HCA should be rewarmed before being pronounced dead. Rewarming avalanche victims of HCA with serum potassium > 12 mmol/L and a burial time >30 min with no air pocket, most probably be futile.

Попередження інтраопераційної ненавмисної гіпотермії у пацієнтів із політравмою

Актуальність. Ненавмисна гіпотермія розвивається спонтанно як наслідок травми, хірургічного втручання та наркозу в результаті порушення відповідності теплопродукції тепловтрат і пригнічення компенсаторної терморегуляційної відповіді. Мета: вивчити ефективність способу корекції інтраопераційної ненавмисної гіпотермії з використанням системи конвекційного обігріву в пацієнтів із політравмою. Матеріали та методи. Обстежено 20 пацієнтів із політравмою, яким проводились ургентні оперативні втручання. Пацієнти були розділені на 2 групи: I — основна група (n = 10), в якій інтраопераційно проводилося активне зігрівання системою конвекційного обігріву WarmAir 135 (CSZ) з використанням ковдр для зігрівання в умовах операційної; II — контрольна група (n = 10) без використання конвекційного зігрівання. Вивчалася температура ядра тіла (Тсо): початково, через 30, 60 хвилин і наприкінці операції. Розраховувалися наступні показники: мінімальна (Тмін.) і максимальна (Тмакс.) температура, середня температура (Тср.), температурний діапазон (Тдіап. = Tмакс. – Тмін.). Результати. У всіх пацієнтів із політравмою та проведенням ургентних хірургічних втручань відзначається розвиток клінічно значущої ненавмисної гіпотермії. На етапі 60 хвилин інтраопераційного періоду Тсо була вірогідно вище в I групі (35,38 ± 0,28 °С) порівняно з пацієнтами II групи (34,70 ± 0,39 °С) (p &lt; 0,05). Виявлено вірогідно вищий рівень середньої Тсо в I групі (35,53 ± 0,66 °С) порівняно з II групою (34,67 ± 1,74 °С) пацієнтів (p &lt; 0,05). Діапазон температур, який являє собою різницю максимальної та мінімальної Тсо, був вірогідно нижче в I групі пацієнтів (1,36 ± 0,74 °С) порівняно з II групою (4,55 ± 1,11 °С) (p &lt; 0,05). Висновки. Використання в комплексі інтенсивної терапії конвекційної системи зігрівання хоча й не дозволяє досягти вихідних значень Тсо, але попереджає прогресування поглиблення гіпотермії, ефективно забезпечуючи підтримку температурного гомеостазу у критичних пацієнтів із політравмою.

Energy-sparing by 2-methyl-2-thiazoline protects heart from ischaemia/reperfusion injury.

AimsCardiac ischaemia/reperfusion (I/R) injury remains a critical issue in the therapeutic management of ischaemic heart failure. Although mild hypothermia has a protective effect on cardiac I/R injury, more rapid and safe methods that can obtain similar results to hypothermia therapy are required. 2‐Methyl‐2‐thiazoline (2MT), an innate fear inducer, causes mild hypothermia resulting in resistance to critical hypoxia in cutaneous or cerebral I/R injury. The aim of this study is to demonstrate the protective effect of systemically administered 2MT on cardiac I/R injury and to elucidate the mechanism underlying this effect.Methods and resultsA single subcutaneous injection of 2MT (50 mg/kg) was given prior to reperfusion of the I/R injured 10 week‐old male mouse heart and its efficacy was evaluated 24 h after the ligation of the left anterior descending coronary artery. 2MT preserved left ventricular systolic function following I/R injury (ejection fraction, %: control 37.9 ± 6.7, 2MT 54.1 ± 6.4, P < 0.01). 2MT also decreased infarct size (infarct size/ischaemic area at risk, %: control 48.3 ± 12.1, 2MT 25.6 ± 4.2, P < 0.05) and serum cardiac troponin levels (ng/mL: control 8.9 ± 1.1, 2MT 1.9 ± 0.1, P < 0.01) after I/R. Moreover, 2MT reduced the oxidative stress‐exposed area within the heart (%: control 25.3 ± 4.7, 2MT 10.8 ± 1.4, P < 0.01). These results were supported by microarray analysis of the mouse hearts. 2MT induced a transient, mild decrease in core body temperature (°C: −2.4 ± 1.4), which gradually recovered over several hours. Metabolome analysis of the mouse hearts suggested that 2MT minimized energy metabolism towards suppressing oxidative stress. Furthermore, 18F‐fluorodeoxyglucose‐positron emission tomography/computed tomography imaging revealed that 2MT reduced the activity of brown adipose tissue (standardized uptake value: control 24.3 ± 6.4, 2MT 18.4 ± 5.8, P < 0.05). 2MT also inhibited mitochondrial respiration and glycolysis in rat cardiomyoblasts.ConclusionsWe identified the cardioprotective effect of systemically administered 2MT on cardiac I/R injury by sparing energy metabolism with reversible hypothermia. Our results highlight the potential of drug‐induced hypothermia therapy as an adjunct to coronary intervention in severe ischaemic heart disease.

Pharmacogenetic excitation of the median raphe region affects social and depressive-like behavior and core body temperature in male mice

AimsMedian raphe region (MRR) is an important bottom-up regulatory center for various behaviors as well as vegetative functions, but detailed descriptions and links between the two are still largely unexplored. MethodsPharmacogenetics was used to study the role of MRR in social (sociability, social interaction, resident intruder test) and emotional behavior (forced swim test) parallel with some vegetative changes (biotelemetry: core body temperature). Additionally, to validate pharmacogenetics, the effect of clozapine-N-oxide (CNO), the ligand of the artificial receptor, was studied by measuring (i) serum and brainstem concentrations of CNO and clozapine; (ii) MRR stimulation induced neurotransmitter release in hippocampus; (iii) CNO induced changes in body temperature and locomotor activity. Key findingsMRR stimulation decreased locomotion, increased friendly social behavior in the resident intruder test and enhanced depressive-like behavior. The latter was accompanied by diminished decrease in core body temperature. Thirty minutes after CNO injection clozapine was predominant in the brainstem. Nonetheless, peripheral CNO injection was able to induce glutamate release in the hippocampus. CNO had no immediate (<30 min) or chronic (repeated injections) effect on the body temperature or locomotion. SignificanceWe confirmed the role of MRR in locomotion, social and depressive-like behavior. Most interestingly, only depressive-like behavior was accompanied by changed body temperature regulation, which was also observed in human depressive disorders previously. This indicates clinical relevance of our findings. Despite low penetration, CNO acts centrally, but does not influence the examined basic parameters, being suitable for repeated behavioral testing.