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Advances in Physiology Education Sep 2015Thermoregulation is the maintenance of a relatively constant core body temperature. Humans normally maintain a body temperature at 37°C, and maintenance of this... (Review)
Review
Thermoregulation is the maintenance of a relatively constant core body temperature. Humans normally maintain a body temperature at 37°C, and maintenance of this relatively high temperature is critical to human survival. This concept is so important that control of thermoregulation is often the principal example cited when teaching physiological homeostasis. A basic understanding of the processes underpinning temperature regulation is necessary for all undergraduate students studying biology and biology-related disciplines, and a thorough understanding is necessary for those students in clinical training. Our aim in this review is to broadly present the thermoregulatory process taking into account current advances in this area. First, we summarize the basic concepts of thermoregulation and subsequently assess the physiological responses to heat and cold stress, including vasodilation and vasoconstriction, sweating, nonshivering thermogenesis, piloerection, shivering, and altered behavior. Current research is presented concerning the body's detection of thermal challenge, peripheral and central thermoregulatory control mechanisms, including brown adipose tissue in adult humans and temperature transduction by the relatively recently discovered transient receptor potential channels. Finally, we present an updated understanding of the neuroanatomic circuitry supporting thermoregulation.
Topics: Adaptation, Physiological; Adult; Body Temperature; Body Temperature Regulation; Female; Fever; Humans; Hypothermia; Male; Sensitivity and Specificity; Shivering; Skin Temperature; Sweating; Thermoreceptors; Thermosensing
PubMed: 26330029
DOI: 10.1152/advan.00126.2014 -
Neuroscience Letters Mar 2019Maintenance of mammalian core body temperature within a narrow range is a fundamental homeostatic process to optimize cellular and tissue function, and to improve... (Review)
Review
Maintenance of mammalian core body temperature within a narrow range is a fundamental homeostatic process to optimize cellular and tissue function, and to improve survival in adverse thermal environments. Body temperature is maintained during a broad range of environmental and physiological challenges by central nervous system circuits that process thermal afferent inputs from the skin and the body core to control the activity of thermoeffectors. These include thermoregulatory behaviors, cutaneous vasomotion (vasoconstriction and, in humans, active vasodilation), thermogenesis (shivering and brown adipose tissue), evaporative heat loss (salivary spreading in rodents, and human sweating). This review provides an overview of the central nervous system circuits for thermoregulatory reflex regulation of thermoeffectors.
Topics: Animals; Body Temperature; Body Temperature Regulation; Humans; Neural Pathways; Shivering; Skin Temperature; Thermogenesis
PubMed: 30586638
DOI: 10.1016/j.neulet.2018.11.027 -
Anesthesiology Aug 2008Most clinically available thermometers accurately report the temperature of whatever tissue is being measured. The difficulty is that no reliably... (Review)
Review
Most clinically available thermometers accurately report the temperature of whatever tissue is being measured. The difficulty is that no reliably core-temperature-measuring sites are completely noninvasive and easy to use-especially in patients not undergoing general anesthesia. Nonetheless, temperature can be reliably measured in most patients. Body temperature should be measured in patients undergoing general anesthesia exceeding 30 min in duration and in patients undergoing major operations during neuraxial anesthesia. Core body temperature is normally tightly regulated. All general anesthetics produce a profound dose-dependent reduction in the core temperature, triggering cold defenses, including arteriovenous shunt vasoconstriction and shivering. Anesthetic-induced impairment of normal thermoregulatory control, with the resulting core-to-peripheral redistribution of body heat, is the primary cause of hypothermia in most patients. Neuraxial anesthesia also impairs thermoregulatory control, although to a lesser extent than does general anesthesia. Prolonged epidural analgesia is associated with hyperthermia whose cause remains unknown.
Topics: Anesthesia, General; Body Temperature; Body Temperature Regulation; Humans; Hypothermia; Monitoring, Intraoperative; Shivering; Skin Temperature; Sweating
PubMed: 18648241
DOI: 10.1097/ALN.0b013e31817f6d76 -
Postepy Higieny I Medycyny... Jan 2015This review focuses on the physiological responses and pathophysiological changes induced by hypothermia. Normal body function depends on its ability to maintain thermal... (Review)
Review
This review focuses on the physiological responses and pathophysiological changes induced by hypothermia. Normal body function depends on its ability to maintain thermal homeostasis. The human body can be divided arbitrarily into two thermal compartments: a core compartment (trunk and head), with precisely regulated temperature around 37°C, and a peripheral compartment (skin and extremities) with less strictly controlled temperature, and lower than the core temperature. Thermoregulatory processes occur in three phases: afferent thermal sensing, central regulation, mainly by the preoptic area of the anterior hypothalamus, and efferent response. Exposure to cold induces thermoregulatory responses including cutaneous vasoconstriction, shivering and non-shivering thermogenesis, and behavioral changes. Alterations of body temperature associated with impaired thermoregulation, decreased heat production or increased heat loss can lead to hypothermia. Hypothermia is defined as a core body temperature below 35ºC, and may be classified according to the origin as accidental (e.g. caused by exposure to a cold environment, drugs, or illness) or intentional (i.e. therapeutic), or by the degree of hypothermia as mild, moderate or severe. Classification by temperature is not universal. Lowering of body temperature disrupts the physiological processes at the molecular, cellular and system level, but hypothermia induced prior to cardiosurgical or neurosurgical procedures, by the decrease in tissue oxygen demand, can reduce the risk of cerebral or cardiac ischemic damage. Therapeutic hypothermia has been recommended as a clinical procedure in situations characterized by ischemia, such as cardiac arrest, stroke and brain injuries.
Topics: Cold Temperature; Humans; Hypothermia; Shivering
PubMed: 25614675
DOI: 10.5604/17322693.1136382 -
The Cochrane Database of Systematic... Apr 2015Inadvertent perioperative hypothermia (a drop in core temperature to below 36°C) occurs because of interference with normal temperature regulation by anaesthetic drugs,... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Inadvertent perioperative hypothermia (a drop in core temperature to below 36°C) occurs because of interference with normal temperature regulation by anaesthetic drugs, exposure of skin for prolonged periods and receipt of large volumes of intravenous and irrigation fluids. If the temperature of these fluids is below core body temperature, they can cause significant heat loss. Warming intravenous and irrigation fluids to core body temperature or above might prevent some of this heat loss and subsequent hypothermia.
OBJECTIVES
To estimate the effectiveness of preoperative or intraoperative warming, or both, of intravenous and irrigation fluids in preventing perioperative hypothermia and its complications during surgery in adults.
SEARCH METHODS
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 2), MEDLINE Ovid SP (1956 to 4 February 2014), EMBASE Ovid SP (1982 to 4 February 2014), the Institute for Scientific Information (ISI) Web of Science (1950 to 4 February 2014), Cumulative Index to Nursing and Allied Health Literature (CINAHL) EBSCOhost (1980 to 4 February 2014) and reference lists of identified articles. We also searched the Current Controlled Trials website and ClinicalTrials.gov.
SELECTION CRITERIA
We included randomized controlled trials or quasi-randomized controlled trials comparing fluid warming methods versus standard care or versus other warming methods used to maintain normothermia.
DATA COLLECTION AND ANALYSIS
Two review authors independently extracted data from eligible trials and settled disputes with a third review author. We contacted study authors to ask for additional details when needed. We collected data on adverse events only if they were reported in the trials.
MAIN RESULTS
We included in this review 24 studies with a total of 1250 participants. The trials included various numbers and types of participants. Investigators used a range of methods to warm fluids to temperatures between 37°C and 41°C. We found that evidence was of moderate quality because descriptions of trial design were often unclear, resulting in high or unclear risk of bias due to inappropriate or unclear randomization and blinding procedures. These factors may have influenced results in some way. Our protocol specified the risk of hypothermia as the primary outcome; as no trials reported this, we decided to include data related to mean core temperature. The only secondary outcome reported in the trials that provided useable data was shivering. Evidence was unclear regarding the effects of fluid warming on bleeding. No data were reported on our other specified outcomes of cardiovascular complications, infection, pressure ulcers, bleeding, mortality, length of stay, unplanned intensive care admission and adverse events.Researchers found that warmed intravenous fluids kept the core temperature of study participants about half a degree warmer than that of participants given room temperature intravenous fluids at 30, 60, 90 and 120 minutes, and at the end of surgery. Warmed intravenous fluids also further reduced the risk of shivering compared with room temperature intravenous fluidsInvestigators reported no statistically significant differences in core body temperature or shivering between individuals given warmed and room temperature irrigation fluids.
AUTHORS' CONCLUSIONS
Warm intravenous fluids appear to keep patients warmer during surgery than room temperature fluids. It is unclear whether the actual differences in temperature are clinically meaningful, or if other benefits or harms are associated with the use of warmed fluids. It is also unclear if using fluid warming in addition to other warming methods confers any benefit, as a ceiling effect is likely when multiple methods of warming are used.
Topics: Administration, Intravenous; Anesthesia; Body Temperature; Hot Temperature; Humans; Hypothermia; Infusions, Intravenous; Randomized Controlled Trials as Topic; Shivering; Therapeutic Irrigation
PubMed: 25866139
DOI: 10.1002/14651858.CD009891.pub2 -
Journal of Applied Physiology... May 2021The pathogenesis of metabolic diseases such as obesity and type 2 diabetes are characterized by a progressive dysregulation in energy partitioning, often leading to...
The pathogenesis of metabolic diseases such as obesity and type 2 diabetes are characterized by a progressive dysregulation in energy partitioning, often leading to end-organ complications. One emerging approach proposed to target this metabolic dysregulation is the application of mild cold exposure. In healthy individuals, cold exposure can increase energy expenditure and whole body glucose and fatty acid utilization. Repeated exposures can lower fasting glucose and insulin levels and improve dietary fatty acid handling, even in healthy individuals. Despite its apparent therapeutic potential, little is known regarding the effects of cold exposure in populations for which this stimulation could benefit the most. The few studies available have shown that both acute and repeated exposures to the cold can improve insulin sensitivity and reduce fasting glycemia in individuals with type 2 diabetes. However, critical gaps remain in understanding the prolonged effects of repeated cold exposures on glucose regulation and whole body insulin sensitivity in individuals with metabolic syndrome. Much of the metabolic benefits appear to be attributable to the recruitment of shivering skeletal muscles. However, further work is required to determine whether the broader recruitment of skeletal muscles observed during cold exposure can confer metabolic benefits that surpass what has been historically observed from endurance exercise. In addition, although cold exposure offers unique cardiovascular responses for a physiological stimulus that increases energy expenditure, further work is required to determine how acute and repeated cold exposure can impact cardiovascular responses and myocardial function across a broader scope of individuals.
Topics: Cold Temperature; Diabetes Mellitus, Type 2; Energy Metabolism; Humans; Insulin Resistance; Obesity; Shivering; Thermogenesis
PubMed: 33764169
DOI: 10.1152/japplphysiol.00934.2020 -
Journal of Internal Medicine Nov 1998Poikilothermia syndrome is a rare cause of intrinsic thermoregulatory failure. Patients with this syndrome regulate body temperature poorly, if at all. Recently, a... (Review)
Review
Poikilothermia syndrome is a rare cause of intrinsic thermoregulatory failure. Patients with this syndrome regulate body temperature poorly, if at all. Recently, a patient was referred to us who had clinical evidence of poikilothermia syndrome, as well as long-standing multiple sclerosis. Computerized tomography and magnetic resonance scanning failed to identify a hypothalamic lesion. The patient was gradually warmed to sweating, and then cooled to vasoconstriction and shivering. The core-temperature thresholds triggering each defence were calculated, after compensating for the changes in skin temperature. The calculated sweating threshold was 38.3 degrees C (normal: 37.0 +/- 0.3 degrees C). The vasoconstriction threshold was 34.4 degrees C (normal: 36.4 +/- 0.3 degrees C). The sweating-to-vasoconstriction interthreshold range was thus approximately 4 degrees C, which is between 10 and 20 times the normal value. The shivering threshold was 31.8 degrees C (normal: 35.6 +/- 0.3 degrees C). The vasoconstriction-to-shivering range was thus approximately 2.5 degrees C which is more than twice the normal value. The pattern of thermoregulatory failure in this patient resembled that resulting from general anaesthesia.
Topics: Body Temperature; Body Temperature Regulation; Humans; Male; Middle Aged; Multiple Sclerosis; Shivering; Sweating; Syndrome
PubMed: 9845860
DOI: 10.1046/j.1365-2796.1998.00384.x -
The Journal of Neuroscience Nursing :... Apr 2018Shivering is common during targeted temperature management, and control of shivering can be challenging if clinicians are not familiar with the available options and... (Review)
Review
BACKGROUND
Shivering is common during targeted temperature management, and control of shivering can be challenging if clinicians are not familiar with the available options and recommended approaches.
PURPOSE
The purpose of this review was to summarize the most relevant literature regarding various treatments available for control of shivering and suggest a recommended approach based on latest data.
METHODS
The electronic databases PubMed/MEDLINE and Google Scholar were used to identify studies for the literature review using the following keywords alone or in combination: "shivering treatment," "therapeutic hypothermia," "core temperature modulation devices," and "targeted temperature management."
RESULTS
Nonpharmacologic methods were found to have a very low adverse effect profile and ease of use but some limitations in complete control of shivering. Pharmacologic methods can effectively control shivering, but some have adverse effects, such that risks and benefits to the patient have to be balanced.
CONCLUSION
An approach is provided which suggests that treatment for shivering control in targeted temperature management should be initiated before the onset of therapeutic hypothermia or prior to any attempt at lowering patient core temperature, with medications including acetaminophen, buspirone, and magnesium sulfate, ideally with the addition of skin counterwarming. After that, shivering intervention should be determined with the help of a shivering scale, and stepwise escalation can be implemented that balances shivering treatment with sedation, aiming to provide the most shivering reduction with the least sedating medications and reserving paralytics for the last line of treatment.
Topics: Body Temperature; Buspirone; Humans; Hypothermia, Induced; Serotonin Receptor Agonists; Shivering
PubMed: 29278601
DOI: 10.1097/JNN.0000000000000340 -
Anaesthesia Mar 1992
Topics: Anesthesia, General; Animals; Hot Temperature; Humans; Hypothermia; Postoperative Complications; Shivering
PubMed: 1566983
DOI: 10.1111/j.1365-2044.1992.tb02114.x -
Therapeutic Hypothermia and Temperature... Dec 2015Meperidine is used for pain control and treatment of shivering. Concerns about neurotoxicity, particularly seizures, have led to efforts limiting meperidine use. We... (Review)
Review
Meperidine is used for pain control and treatment of shivering. Concerns about neurotoxicity, particularly seizures, have led to efforts limiting meperidine use. We reviewed the body of evidence linking meperidine to seizures. We searched PubMed for the terms meperidine, normeperidine, pethidine, and norpethidine; each was combined with the terms: seizure, epilepsy, epileptogenic, toxicity, overdose, seizure threshold, and convulsion. Articles were assessed for relevance. Semiologies were reviewed to ascertain seizure likelihood. Our search yielded 351 articles, of which 66 were relevant. Of these, 33 had primary clinical data on meperidine-associated seizures, comprising 50 patients. Twenty events were deemed likely to be seizures, 26 indeterminate, and 4 unlikely. Most studies were case reports. Confounding comorbidities were frequent. The evidence base for meperidine-associated seizures in man is scant. Seizure risk associated with meperidine appears to be overstated. The utility of meperidine should continue to be explored, especially for therapeutic hypothermia.
Topics: Analgesics, Opioid; Humans; Meperidine; Pain Threshold; Risk Assessment; Risk Factors; Seizures; Shivering
PubMed: 26087278
DOI: 10.1089/ther.2015.0013