Keeping a Cool Head

Physiology ◽  
1986 ◽  
Vol 1 (2) ◽  
pp. 41-44 ◽  
Author(s):  
M Cabanac
Keyword(s):  
Heat Stress ◽  
Core Temperature ◽  
Heat Exchangers ◽  
The Body ◽  
Body Core Temperature ◽  
Mammalian Brain ◽  
Poor Tolerance ◽  
Selective Cooling ◽  
Body Core ◽  
The Brain

The mammalian brain has poor tolerance to increased temperature. However, when body core temperature rises during exercise or heat stress, the temperature of the brain can remain at a lower level, somewhat independent of the rest of the body. In several mammals the cooling of the brain is related to anatomically well-defined countercurrent heat exchangers. Humans lack these distinct anatomic structures, but significant cooling of the brain can nevertheless occur. Such selective cooling of the brain may have important medical implicantions.

Control of respiratory evaporative heat loss in exercising goats

1979 ◽  
Vol 46 (5) ◽  
pp. 978-983 ◽  
Author(s):  
J. B. Mercer ◽  
C. Jessen
Keyword(s):  
Heat Loss ◽  
Core Temperature ◽  
Heat Exchangers ◽  
The Body ◽  
Body Core Temperature ◽  
Evaporative Heat Loss ◽  
Hypothalamic Temperature ◽  
Body Core ◽  
Total Body ◽  
Rest And Exercise

Investigations were carried out to determine whether a nonthermal input is involved in the control of respiratory evaporative heat loss (REHL) in exercising goats. Two goats were implanted with hypothalamic perfusion thermodes and three goats were implanted with intravascular heat exchangers to clamp hypothalamic temperature and total body core temperature, respectively. At 30 degrees C air temperature REHL was measured while the animals were resting or walking on a treadmill (3 km.h-1, 5 degrees gradient). When the hypothalamic temperature was clamped between 33.0 and 43.0 degrees C the slopes of the responses relating increased REHL to hypothalamic temperature were similar during rest and exercise. However, the threshold hypothalamic temperatures for the increased REHL responses were lower during exercise than at rest, presumably due to higher extrahypothalamic temperatures. When the body core temperature was clamped between 37.0 and 40.4 degrees C the slopes of the responses relating increased REHL to total body core temperature during exercise showed only minor differences compared to those at rest, none of them conclusively indicating nonthermal influences.

scholarly journals Canine hyperthermia with cerebral protection

1976 ◽  
Vol 40 (4) ◽  
pp. 543-548 ◽  
Author(s):  
R. W. Carithers ◽  
R. C. Seagrave
Keyword(s):  
Core Temperature ◽  
Cold Water ◽  
Brain Temperature ◽  
Body Core Temperature ◽  
Whole Body ◽  
Similar Time ◽  
Data Points ◽  
Body Core ◽  
Heat Transfer System ◽  
The Brain

Extreme whole-body hyperthermia was achieved without lasting side effects in canines by elevating body core temperature to 42 degrees C, using a warm water bath. Cold water irrigation of the nasal alar fold permitted an additional core temperature elevation of 0.5–1.0 degrees C above brain temperature for periods up to 1.5 h. The brain-core temperature differential was maintained by a physiological arteriovenous heat exchanger located at the base of the brain. The maximum tolerable core temperature for the 21 nonirrigated dogs was 42 degrees C for 60–90 min, whereas that for the 28 irrigated dogs was 42.5–43 degrees C for similar time intervals. A mathematical model of the total heat transfer system described the observed dynamic temperature responses. It was the solution of a differential equation which fit the normalized experimental data points and predicted reasonable values for known and unknown experimental parameters.

Restoration of thermoregulation after exercise

2017 ◽  
Vol 122 (4) ◽  
pp. 933-944 ◽  
Author(s):  
Glen P. Kenny ◽  
Ryan McGinn
Keyword(s):  
Heat Loss ◽  
Core Temperature ◽  
Current Knowledge ◽  
Thermal Control ◽  
The Body ◽  
Body Core Temperature ◽  
Whole Body ◽  
Temperature Sensitive ◽  
Internal Core ◽  
Body Core

Performing exercise, especially in hot conditions, can heat the body, causing significant increases in internal body temperature. To offset this increase, powerful and highly developed autonomic thermoregulatory responses (i.e., skin blood flow and sweating) are activated to enhance whole body heat loss; a response mediated by temperature-sensitive receptors in both the skin and the internal core regions of the body. Independent of thermal control of heat loss, nonthermal factors can have profound consequences on the body’s ability to dissipate heat during exercise. These include the activation of the body’s sensory receptors (i.e., baroreceptors, metaboreceptors, mechanoreceptors, etc.) as well as phenotypic factors such as age, sex, acclimation, fitness, and chronic diseases (e.g., diabetes). The influence of these factors extends into recovery such that marked impairments in thermoregulatory function occur, leading to prolonged and sustained elevations in body core temperature. Irrespective of the level of hyperthermia, there is a time-dependent suppression of the body’s physiological ability to dissipate heat. This delay in the restoration of postexercise thermoregulation has been associated with disturbances in cardiovascular function which manifest most commonly as postexercise hypotension. This review examines the current knowledge regarding the restoration of thermoregulation postexercise. In addition, the factors that are thought to accelerate or delay the return of body core temperature to resting levels are highlighted with a particular emphasis on strategies to manage heat stress in athletic and/or occupational settings.

Thermal regulatory dysfunction of growth hormone in classical heat stroke?

1996 ◽  
Vol 134 (6) ◽  
pp. 727-730
Author(s):  
Abdulaziz Alzeer ◽  
Abdullah Al Arifi ◽  
Mohsen El-Hazmi ◽  
Arjumand S Warsy ◽  
Eric S Nylen
Keyword(s):  
Growth Hormone ◽  
Core Temperature ◽  
Heat Stroke ◽  
The Body ◽  
Body Core Temperature ◽  
Treatment Unit ◽  
Gh Secretion ◽  
Body Core ◽  
Time Of Admission ◽  
Regulatory Dysfunction

Alzeer A, Al Arifi A, El-Hazmi M, Warsy AS, Nylen ES. Thermal regulatory dysfunction of growth hormone in classical heat stroke? Eur J Endocrinol 1996;134:727–30. ISSN 0804–4643 Growth hormone (GH) secretion associated with classical (non-exertional) heat stroke (HS) was evaluated in 26 HS victims and 10 control (non heat-exhausted) subjects during the annual Hajj in Makkah, Saudi Arabia. On admission to the HS treatment unit, the GH level was 1.54 ± 0.14 ng/ml (approximately 3.5-fold higher in the HS victims compared to controls; p = 0.005). The GH levels subsequently declined by 78% by 24 h. The categorized GH response was significantly associated with survival for those subjects with a GH level of < 5.53 ng/ml by 6 h (chi-squared test; p = 0.06). In those patients who died (N = 6), there was a continued increase in GH levels from the time of admission, which peaked at 6 h. In those patients who survived, the GH levels peaked at the time of admission and declined rapidly thereafter. There was a direct correlation of age and GH level upon admission (p = 0.02), as well as to peak GH (p = 0.041). However, there was no relationship of GH level to either body core temperature or the cooling time. In summary, HS induced significant GH secretion. The degree of GH response was not related to the body core temperature and was more pronounced in older individuals and in those that died. Although patients with GH deficiency and HS are characterized by anhidrosis/hypohidrosis, there does not appear to be dysfunction of GH response to heat stress-associated HS. In contrast, a vigorous GH response at 6 h suggested a worse outcome. ES Nylen, Rm GE 246, VAMC, 50 Irving St, NW Washington, DC 20422, USA

scholarly journals Selective brain hypothermia: feasibility and safety study of a novel method in five patients

Perfusion ◽  
2019 ◽  
Vol 35 (2) ◽  
pp. 96-103 ◽  
Author(s):  
Seyed Mohammad Seyedsaadat ◽  
Silvana F Marasco ◽  
David J Daly ◽  
Robin McEgan ◽  
James Anderson ◽  
...  
Keyword(s):  
Cardiopulmonary Bypass ◽  
Brain Temperature ◽  
The Body ◽  
Body Core Temperature ◽  
Safety Study ◽  
Cardiopulmonary Function ◽  
Cooling Fluid ◽  
Body Core ◽  
Novel Method ◽  
The Brain

Background/objective: Reduction of brain temperature remains the most common method of neuroprotection against ischemic injury employed during cardiac surgery. However, cooling delivered via the cardiopulmonary bypass circuit is brief and cooling the body core along with the brain has been associated with a variety of unwanted effects. This study investigated the feasibility and safety of a novel selective brain cooling approach to induce rapid, brain-targeted hypothermia independent of the cardiopulmonary bypass circuit. Methods: This first-in-human feasibility study enrolled five adults undergoing aortic valve replacement with cardiopulmonary bypass support. During surgery, the NeuroSave system circulated chilled saline within the pharynx and upper esophagus. Brain and body core temperature were continuously monitored. Adverse effects, cardiopulmonary function, and device function were noted. Results: Patient 1 received cooling fluid for an insignificant period, and Patients 2-5 successfully underwent the cooling procedure using the NeuroSave system for 56-89 minutes. Cooling fluid was 12°C for Patients 1-3, 6°C for Patient 4, and 2°C for Patient 5. There were no NeuroSave-related adverse events and no alterations in cardiopulmonary function during NeuroSave use. Brain temperature decreased by 3°C within 15 minutes and remained at least 3.5°C colder than the body core. During a brief episode of hypotension in one patient, the brain cooled an additional 4°C in 2 minutes, briefly reaching 27.4°C. Conclusion: The NeuroSave system can induce rapid brain-targeted hypothermia and simultaneously maintain a favorable body–brain temperature gradient, even during hypotension. Further studies are required to evaluate the function of the system during longer periods of use.

Temporal Thermometry Fails to Track Body Core Temperature during Heat Stress

2007 ◽  
Vol 39 (7) ◽  
pp. 1029-1035 ◽  
Author(s):  
DAVID A. LOW ◽  
ALBERT VU ◽  
MARILEE BROWN ◽  
SCOTT L. DAVIS ◽  
DAVID M. KELLER ◽  
...  
Keyword(s):  
Heat Stress ◽  
Core Temperature ◽  
Body Core Temperature ◽  
Body Core

scholarly journals An intra ruminal heat exchanger for use in large concious animals

Rangifer ◽  
1985 ◽  
Vol 5 (1) ◽  
pp. 10 ◽  
Author(s):  
James B. Mercer ◽  
Helge K. Johnsen ◽  
Svein D. Mathiesen ◽  
Arnoldus Schytte Blix
Keyword(s):  
Heat Exchanger ◽  
Core Temperature ◽  
Heat Production ◽  
The Body ◽  
Body Core Temperature ◽  
Ruminant Species ◽  
Large Ruminant ◽  
Body Core ◽  
Total Body

<p>A method is described whereby it is possible to alter total body core temperature independently of environmetal temperature and/or exercise in conscious reindeer. The method employs the use of a simple heat exchanger introduced through a permanent rumen fistula. The heat exchanger consists of a 7 m long coil of flexible plastic tubing (OD, 10.0 mm, ID, 8.0 mm). By perfusing the tubing with thermostatically controlled water, heat can be added to or subtracted from the body core at rates equalling several times resting heat production. It is suggested that the method could be used in any large ruminant species.</p><p>En intra-rumenal varmeveksler til bruk i st&oslash;rre, uanesteserte dyr.</p><p>Abstract in Norwegian / Sammendrag: Vi har i denne unders&oslash;kelsen beskrevet en metode for hvordan kroppstemperatur hos uanesteserte reinsdyr kan endres uavhengig av omgivelsestemperatur og om dyret l&oslash;per eller ikke. Metoden inneb&aelig;rer bruk av en enkel varmeveksler som plasseres i dyrets vom gjennom en permanent vom-fistel. Varmeveksleren best&aring;r av en 7 m lang kveil av fleksibel plastslange (ytre diameter 10.0 mm, indre diameter 8.0 mm). Ved &aring; perfundere slangen med vann av en bestemt temperatur er det mulig &aring; fjerne eller tilf&oslash;re kroppen en varmemengde som tilsvarer flere ganger dyrets varmeproduksjon. Vi mener at denne metoden kan tilpasses alle store dr&oslash;vtyggere.</p><p>Potsiin asetettavan l&aring;mpotilan muuttajan k&aring;ytto suurilla nukkumattomilla el&aring;imill&aring;.</p><p>Abstract in Finnish / Yhteenveto: Tutkimuksessa olemme kuvanneet menetelman, jolla voidaan muuttaa nukuttamattoman poron ruumiinl&aring;mpotilaa riippumatta ulkolampotilasta tai siita juokseeko el&aring;in vai ei. Menetelmassa k&aring;ytaan yksinkertaista l&aring;mpotilan muuttajaa, joka asetetaan elaimeen pysyyan potsifistulan kautta. L&aring;mpotilan muuttaja kasitt&aring;a 7 m pitkan muoviletkurullan (letkun halkaisija 10.6 mm, reian halkaisija" 8.0 mmJTTaytt&aring;m&aring;lla letku tietyn lampoisell&aring; vedella on mahdollista joko laskea tai nostaa ruumiin lampom&aring;&aring;r&aring;a niin, etta se vastaa moninkertaisesti elaimen omaa l&aring;mmontuottoa. Oletamme, etta menetelm&aring;a voidaan kaytta&aring; kaikille suurille m&aring;rehtijoille.</p>

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