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AANA Journal Aug 2023Temperature regulation during the perioperative period plays an essential role in keeping patients safe while optimizing their recovery. The World Health Organization...
Temperature regulation during the perioperative period plays an essential role in keeping patients safe while optimizing their recovery. The World Health Organization recommends preserving normothermia, identified as a core body temperature greater than 36°C, to minimize morbidity and mortality. The etiology of inadvertent perioperative hypothermia (IPH) varies in origin. Preoperative exposure, decreased ambient operating room (OR) temperature, skin exposure during preparation, unwarmed skin preparation and washout solutions, and lack of warming devices all contribute to IPH. Moreover, general and regional anesthesia blunt the physiologic response to hypothermia which originates in the hypothalamus. Postoperatively, patients with temperatures < 36°C are at greater risk for surgical site infection, increased mortality, longer length of hospital stay, higher 30-day readmission rates, among other complications. Identifying preoperative risk factors and OR practices that contribute to IPH, monitoring temperatures, and use of warming devices during the perioperative period can help to prevent IPH.
Topics: Humans; Hypothermia; Body Temperature; Surgical Wound Infection; Risk Factors; Anesthesia, Conduction; Intraoperative Complications
PubMed: 37527171
DOI: No ID Found -
Nature Sep 2023Maintaining body temperature is calorically expensive for endothermic animals. Mammals eat more in the cold to compensate for energy expenditure, but the neural...
Maintaining body temperature is calorically expensive for endothermic animals. Mammals eat more in the cold to compensate for energy expenditure, but the neural mechanism underlying this coupling is not well understood. Through behavioural and metabolic analyses, we found that mice dynamically switch between energy-conservation and food-seeking states in the cold, the latter of which are primarily driven by energy expenditure rather than the sensation of cold. To identify the neural mechanisms underlying cold-induced food seeking, we used whole-brain c-Fos mapping and found that the xiphoid (Xi), a small nucleus in the midline thalamus, was selectively activated by prolonged cold associated with elevated energy expenditure but not with acute cold exposure. In vivo calcium imaging showed that Xi activity correlates with food-seeking episodes under cold conditions. Using activity-dependent viral strategies, we found that optogenetic and chemogenetic stimulation of cold-activated Xi neurons selectively recapitulated food seeking under cold conditions whereas their inhibition suppressed it. Mechanistically, Xi encodes a context-dependent valence switch that promotes food-seeking behaviours under cold but not warm conditions. Furthermore, these behaviours are mediated by a Xi-to-nucleus accumbens projection. Our results establish Xi as a key region in the control of cold-induced feeding, which is an important mechanism in the maintenance of energy homeostasis in endothermic animals.
Topics: Animals; Mice; Body Temperature; Brain Mapping; Calcium; Feeding Behavior; Cold Temperature; Energy Metabolism; Thalamus; Optogenetics; Neurons; Nucleus Accumbens; Homeostasis; Thermogenesis
PubMed: 37587337
DOI: 10.1038/s41586-023-06430-9 -
Resuscitation Aug 2023Managing temperature is an important part of post-cardiac arrest care. Fever or hyperthermia during the first few days after cardiac arrest is associated with worse... (Review)
Review
Managing temperature is an important part of post-cardiac arrest care. Fever or hyperthermia during the first few days after cardiac arrest is associated with worse outcomes in many studies. Clinical data have not determined any target temperature or duration of temperature management that clearly improves patient outcomes. Current guidelines and recent reviews recommend controlling temperature to prevent hyperthermia. Higher temperatures can lead to secondary brain injury by increasing seizures, brain edema and metabolic demand. Some data suggest that targeting temperature below normal could benefit select patients where this pathology is common. Clinical temperature management should address the physiology of heat balance. Core temperature reflects the heat content of the head and torso, and changes in core temperature result from changes in the balance of heat production and heat loss. Clinical management of patients after cardiac arrest should include measurement of core temperature at accurate sites and monitoring signs of heat production including shivering. Multiple methods can increase or decrease heat loss, including external and internal devices. Heat loss can trigger compensatory reflexes that increase stress and metabolic demand. Therefore, any active temperature management should include specific pharmacotherapy or other interventions to control thermogenesis, especially shivering. More research is required to determine whether individualized temperature management can improve outcomes.
Topics: Humans; Hypothermia; Temperature; Body Temperature Regulation; Body Temperature; Heart Arrest; Hypothermia, Induced
PubMed: 37355091
DOI: 10.1016/j.resuscitation.2023.109882 -
Journal of Clinical Anesthesia Aug 2023The effect of perioperative body temperature derangement on postoperative delirium remains unclear. This study aimed to evaluate the association between intraoperative... (Observational Study)
Observational Study
STUDY OBJECTIVE
The effect of perioperative body temperature derangement on postoperative delirium remains unclear. This study aimed to evaluate the association between intraoperative body temperature and postoperative delirium in patients having noncardiac surgery.
DESIGN
Single-center retrospective observational study.
SETTING
Tertiary university hospital.
PATIENT
Adult patients who had major noncardiac surgery under general anesthesia for at least two hours between 2019 and 2021.
INTERVENTIONS
Patients were classified into three groups according to their intraoperative time-weighted average body temperature: severe hypothermia (<35.0 °C), mild hypothermia (35.0 °C-36.0 °C), and normothermia (≥36.0 °C) groups.
MEASUREMENTS
The primary outcome was the risk of delirium occurring within seven days after surgery, which was compared using logistic regression analysis. A multivariable procedure was performed adjusting for potential confounders including demographics, history of hypertension, diabetes, atrial fibrillation or flutter, myocardial infarction, congestive heart failure, and stroke or transient ischemic attack, preoperative use of antidepressants and statins, preoperative sodium imbalance, high-risk surgery, emergency surgery, duration of surgery, and red blood cell transfusion. Cox regression analysis was also performed using the same covariates.
MAIN RESULTS
Among 27,674 patients analyzed, 5.5% experienced postoperative delirium. The incidence rates of delirium were 6.2% (63/388) in the severe hypothermia group, 6.4% (756/11779) in the mild hypothermia group, and 4.6% (712/15507) in the normothermia group. Compared with the normothermia group, the risk of delirium was significantly higher in the severe hypothermia (adjusted odds ratio, 1.43; 95% confidence interval, 1.04-1.97) and mild hypothermia (1.15; 1.02-1.28) groups. The mild hypothermia group also had a significantly increased risk of cumulative development of delirium than the normothermia group (adjusted hazard ratio 1.14; 95% confidence interval, 1.03-1.26).
CONCLUSIONS
Intraoperative hypothermia (even mild hypothermia) was significantly associated with an increased risk of postoperative delirium.
Topics: Adult; Humans; Body Temperature; Hypothermia; Emergence Delirium; Retrospective Studies; Regression Analysis; Postoperative Complications
PubMed: 36924749
DOI: 10.1016/j.jclinane.2023.111107 -
PloS One 2023Ectothermic animals can raise their body temperature under varying circumstances. Two such situations occur during sexual activity (as metabolic rate rises during...
Ectothermic animals can raise their body temperature under varying circumstances. Two such situations occur during sexual activity (as metabolic rate rises during copulatory movements) and during infection (to control pathogens more effectively). We have investigated these two situations using Tenebrio molitor males. We recorded the copulatory courtship behavior of sick (= infected with Metharizium robertsii fungus) vs healthy males and its link with body temperature. We predicted a positive relation between copulatory courtship (measured as antennal and leg contact behavior) and body temperature, especially in sick males. We found that the intensity of contacts correlated with increased body temperature in sick males. Previous studies in this species indicated that partner females laid fewer eggs after mating with sick males above a certain male body temperature threshold. Thus, our present findings suggest that females may detect male infection via intensity of antennal-mediated courtship, body temperature or their combination. If this is the case, females may assess male cues directly related to health status such as body temperature.
Topics: Male; Animals; Female; Courtship; Tenebrio; Body Temperature; Cell Communication; Copulation
PubMed: 37682968
DOI: 10.1371/journal.pone.0291384 -
Australian Veterinary Journal Nov 2023Cattle control body temperature in a narrow range over varying climatic conditions. Endogenous body heat is generated by metabolism, digestion and activity. Radiation is... (Review)
Review
Cattle control body temperature in a narrow range over varying climatic conditions. Endogenous body heat is generated by metabolism, digestion and activity. Radiation is the primary external source of heat transfer into the body of cattle. Cattle homeothermy uses behavioural and physiological controls to manage radiation, convection, conduction, and evaporative exchange of heat between the body and the environment, noting that evaporative mechanisms almost exclusively transfer body heat to the environment. Cattle control radiation by shade seeking (hot) and shelter (cold) and by huddling or standing further apart, noting there are intrinsic breed and age differences in radiative transfer potential. The temperature gradient between the skin and the external environment and wind speed (convection) determines heat transfer by these means. Cattle control these mechanisms by managing blood flow to the periphery (physiology), by shelter-seeking and standing/lying activity in the short term (behaviourally) and by modifying their coats and adjusting their metabolic rates in the longer term (acclimatisation). Evaporative heat loss in cattle is primarily from sweating, with some respiratory contribution, and is the primary mechanism for dissipating excess heat when environmental temperatures exceed skin temperature (~36°C). Cattle tend to be better adapted to cooler rather than hotter external conditions, with Bos indicus breeds more adapted to hotter conditions than Bos taurus. Management can minimise the risk of thermal stress by ensuring appropriate breeds of suitably acclimatised cattle, at appropriate stocking densities, fed appropriate diets (and water), and with access to suitable shelter and ventilation are better suited to their expected farm environment.
Topics: Cattle; Animals; Body Temperature Regulation; Hot Temperature; Skin Temperature; Skin; Respiration
PubMed: 37620993
DOI: 10.1111/avj.13275 -
The Journal of Experimental Biology Sep 2023Ambient temperature (Ta) is a critical abiotic factor for insects that cannot maintain a constant body temperature (Tb). Interestingly, Ta varies during the day, between... (Review)
Review
Ambient temperature (Ta) is a critical abiotic factor for insects that cannot maintain a constant body temperature (Tb). Interestingly, Ta varies during the day, between seasons and habitats; insects must constantly cope with these variations to avoid reaching the deleterious effects of thermal stress. To minimize these risks, insects have evolved a set of physiological and behavioral thermoregulatory processes as well as molecular responses that allow them to survive and perform under various thermal conditions. These strategies range from actively seeking an adequate environment, to cooling down through the evaporation of body fluids and synthesizing heat shock proteins to prevent damage at the cellular level after heat exposure. In contrast, endothermy may allow an insect to fight parasitic infections, fly within a large range of Ta and facilitate nest defense. Since May (1979), Casey (1988) and Heinrich (1993) reviewed the literature on insect thermoregulation, hundreds of scientific articles have been published on the subject and new insights in several insect groups have emerged. In particular, technical advancements have provided a better understanding of the mechanisms underlying thermoregulatory processes. This present Review aims to provide an overview of these findings with a focus on various insect groups, including blood-feeding arthropods, as well as to explore the impact of thermoregulation and heat exposure on insect immunity and pathogen development. Finally, it provides insights into current knowledge gaps in the field and discusses insect thermoregulation in the context of climate change.
Topics: Animals; Body Temperature Regulation; Body Temperature; Insecta; Arthropods; Body Fluids
PubMed: 37699071
DOI: 10.1242/jeb.245751 -
Journal of Science and Medicine in Sport Nov 2023To assess how biomarkers indicating central nervous system insult (neurobiomarkers) vary in peripheral blood with exertional-heat stress from prolonged endurance... (Observational Study)
Observational Study
OBJECTIVES
To assess how biomarkers indicating central nervous system insult (neurobiomarkers) vary in peripheral blood with exertional-heat stress from prolonged endurance exercise.
DESIGN
Observational study of changes in neuron specific enolase (NSE), S100 calcium-binding protein B (S100β), Glial Fibrillary Acid Protein (GFAP) and Ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL1) at Brighton Marathon 2022.
METHODS
In 38 marathoners with in-race core temperature (Tc) monitoring, exposure (High, Intermediate or Low) was classified by cumulative hyperthermia - calculated as area under curve of Time × Tc > 38 °C - and also by running duration (finishing time). Blood was sampled for neurobiomarkers, cortisol and fluid-regulatory stress surrogates, including copeptin and creatinine (at rested baseline; within 30 min of finishing; and at 24 h).
RESULTS
Finishing in 236 ± 40 min, runners showed stable GFAP and UCH-L1 across the marathon and next-day. Significant (P < 0.05) increases from baseline were shown post-marathon and at 24 h for S100β (8.52 [3.65, 22.95] vs 39.0 [26.48, 52.33] vs 80.3 [49.1, 99.7] ng·L) and post-marathon only for NSE (3.73 [3.30, 4.32] vs 4.85 [4.45, 5.80] μg·L, P < 0.0001). Whilst differential response to hyperthermia was observed for cortisol, copeptin and creatinine, neurobiomarker responses did not vary. Post-marathon, only NSE differed by exercise duration (High vs Low, 5.81 ± 1.77 vs. 4.69 ± 0.73 μg·L, adjusted P = 0.0358).
CONCLUSIONS
Successful marathon performance did not associate with evidence for substantial neuronal insult. To account for variation in neurobiomarkers with prolonged endurance exercise, factors additional to hyperthermia, such as exercise duration and intensity, should be further investigated.
Topics: Humans; Body Temperature; Marathon Running; Creatinine; Hydrocortisone; Running; Biomarkers
PubMed: 37777396
DOI: 10.1016/j.jsams.2023.09.011 -
European Journal of Medical Research Dec 2023This study was aimed to investigate the correlation between low body temperature and outcomes in critically ill patients with coronary heart disease (CHD).
BACKGROUND
This study was aimed to investigate the correlation between low body temperature and outcomes in critically ill patients with coronary heart disease (CHD).
METHODS
Participants from the Medical Information Mart for Intensive Care (MIMIC)-IV were divided into three groups (≤ 36.5 ℃, 36.6-37.4 ℃, ≥ 37.5 ℃) in accordance with body temperature measured orally in ICU. In-hospital, 28-day and 90-day mortality were the major outcomes. Multivariable Cox regression, decision curve analysis (DCA), restricted cubic splines (RCS), Kaplan-Meier curves (with or without propensity score matching), and subgroup analyses were used to investigate the association between body temperature and outcomes.
RESULTS
A total of 8577 patients (65% men) were included. The in-hospital, 28-day, 90-day, and 1-year overall mortality rate were 10.9%, 16.7%, 21.5%, and 30.4%, respectively. Multivariable Cox proportional hazards regression analyses indicated that patients with hypothermia compared to the patients with normothermia were at higher risk of in-hospital [adjusted hazard ratios (HR) 1.23, 95% confidence interval (CI) 1.01-1.49], 28-day (1.38, 1.19-1.61), and 90-day (1.36, 1.19-1.56) overall mortality. For every 1 ℃ decrease in body temperature, adjusted survival rates were likely to eliminate 14.6% during the 1-year follow-up. The DCA suggested the applicability of the model 3 in clinical practice and the RCS revealed a consistent higher mortality in hypothermia group.
CONCLUSIONS
Low body temperature was associated with increased mortality in critically ill patients with coronary heart disease.
Topics: Male; Humans; Female; Hypothermia; Body Temperature; Critical Illness; Retrospective Studies; Coronary Disease
PubMed: 38124189
DOI: 10.1186/s40001-023-01584-8 -
Trends in Neurosciences Jul 2023Ground squirrels exemplify one of the most extreme forms of mammalian hibernation and a convenient model for studying its mechanisms. Their thermoregulatory system... (Review)
Review
Ground squirrels exemplify one of the most extreme forms of mammalian hibernation and a convenient model for studying its mechanisms. Their thermoregulatory system demonstrates remarkable adaptive capabilities by maintaining optimal levels of body temperature both in active and hibernation states. Here, we review recent findings and unresolved issues regarding the neural mechanisms of body temperature control in ground squirrels.
Topics: Humans; Animals; Body Temperature Regulation; Body Temperature; Adaptation, Physiological; Hibernation; Sciuridae
PubMed: 37188617
DOI: 10.1016/j.tins.2023.04.008