Combined stimuli of cold, hypoxia, and dehydration status on body temperature in rats: a pilot study with practical implications for humans

Abstract Objective As human thermoregulatory responses to maintain core body temperature (Tcore) under multiple stressors such as cold, hypoxia, and dehydration (e.g., exposure to high-altitude) are varied, the combined effects of cold, hypoxia, and dehydration status on Tcore in rats were investigated. The following environmental conditions were constructed: (1) thermoneutral (24 °C) or cold (10 °C), (2) normoxia (21% O2) or hypoxia (12% O2), and (3) euhydration or dehydration (48 h water deprivation), resulted in eight environmental conditions [2 ambient temperatures (Ta) × 2 oxygen levels × 2 hydration statuses)]. Each condition lasted for 24 h. Results Normoxic conditions irrespective of hypoxia or dehydration did not strongly decrease the area under the curve (AUC) in Tcore during the 24 period, whereas, hypoxic conditions caused greater decreases in the AUC in Tcore, which was accentuated with cold and dehydration (Ta × O2 × hydration, P = 0.040 by three-way ANOVA). In contrast, multiple stressors (Ta × O2 × hydration or Ta × O2 or O2 × hydration or Ta × hydration) did not affect locomotor activity counts (all P > 0.05), but a significant simple main effect for O2 and Ta was observed (P < 0.001). Heat loss index was not affected by all environmental conditions (all P > 0.05). In conclusion, decreases in Tcore were most affected by multiple environmental stressors such as cold, hypoxia, and dehydration.

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Physiological Responses of Medical Team Members to a Simulated Emergency in Tropical Field Conditions

Prehospital and Disaster Medicine ◽

10.1017/s1049023x12001847 ◽

2013 ◽

Vol 28 (2) ◽

pp. 139-144 ◽

Cited By ~ 20

Author(s):

Matt B. Brearley ◽

Michael F. Heaney ◽

Ian N. Norton

Keyword(s):

Body Temperature ◽

Environmental Conditions ◽

Core Body Temperature ◽

Physiological Responses ◽

Field Conditions ◽

Medical Team ◽

Team Members ◽

Medical Response ◽

Simulated Field ◽

Core Body

AbstractIntroductionResponses to physical activity while wearing personal protective equipment in hot laboratory conditions are well documented. However less is known of medical professionals responding to an emergency in hot field conditions in standard attire. Therefore, the purpose of this study was to assess the physiological responses of medical responders to a simulated field emergency in tropical conditions.MethodsTen subjects, all of whom were chronically heat-acclimatized health care workers, volunteered to participate in this investigation. Participants were the medical response team of a simulated field emergency conducted at the Northern Territory Emergency Services training grounds, Yarrawonga, NT, Australia. The exercise consisted of setting up a field hospital, transporting patients by stretcher to the hospital, triaging and treating the patients while dressed in standard medical response uniforms in field conditions (mean ambient temperature of 29.3°C and relative humidity of 50.3%, apparent temperature of 27.9°C) for a duration of 150 minutes. Gastrointestinal temperature was transmitted from an ingestible sensor and used as the index of core temperature. An integrated physiological monitoring device worn by each participant measured and logged heart rate, chest temperature and gastrointestinal temperature throughout the exercise. Hydration status was assessed by monitoring the change between pre- and post-exercise body mass and urine specific gravity (USG).ResultsMean core body temperature rose from 37.5°C at the commencement of the exercise to peak at 37.8°C after 75 minutes. The individual peak core body temperature was 38.5°C, with three subjects exceeding 38.0°C. Subjects sweated 0.54 L per hour and consumed 0.36 L of fluid per hour, resulting in overall dehydration of 0.7% of body mass at the cessation of exercise. Physiological strain index was indicative of little to low strain.ConclusionsThe combination of the unseasonably mild environmental conditions and moderate work rates resulted in minimal heat storage during the simulated exercise. As a result, low sweat rates manifested in minimal dehydration. When provided with access to fluids in mild environmental conditions, chronically heat-acclimatized medical responders can meet their hydration requirements through ad libitum fluid consumption. Whether such an observation is replicated under a harsher thermal load remains to be investigated.BrearleyMB, HeaneyMF, NortonIN. Physiological responses of medical team members to a simulated emergency in tropical field conditions. Prehosp Disaster Med. 2013;28(2):1-6.

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Cooling Interventions Among Agricultural Workers: A Pilot Study

Workplace Health & Safety ◽

10.1177/2165079920976524 ◽

2020 ◽

pp. 216507992097652

Author(s):

Roxana Chicas ◽

Nezahualcoyotl Xiuhtecutli ◽

Lisa Elon ◽

Madeleine K. Scammell ◽

Kyle Steenland ◽

...

Keyword(s):

Body Temperature ◽

Core Body Temperature ◽

Heat Exposure ◽

The United States ◽

Agricultural Workers ◽

Control Group ◽

Temperature Threshold ◽

Convenience Sample ◽

Ambient Temperatures ◽

Core Body

Background Adverse health effects among agricultural workers due to chronic heat exposure have been characterized in the literature as not only due to high ambient temperatures but also due to intensive manual labor in hot and humid conditions. The aim of this study was to use biomonitoring equipment to examine the effectiveness of selected cooling devices at preventing agricultural workers from exceeding the core body temperature threshold of 38.0°C (Tc38) and attenuating heat-related illness symptoms. Methods A convenience sample of 84 agricultural workers in Florida was randomized to one of four groups: (a) no intervention, clothing as usual; (b) cooling bandana; (c) cooling vest; and (d) both the cooling bandana and cooling vest. Biomonitoring equipment worn by the participants included core body temperature monitor and an accelerometer to capture physical activity. Findings A total of 78 agricultural workers completed one intervention workday trial. Compared with the control group, the bandana group had lower odds of exceeding Tc38 (odds ratio [OR] = 0.7, 90% confidence interval [CI] = [0.2, 3.2]) and the vest group had higher odds of exceeding Tc38 (OR = 1.8, 90% CI = [0.4, 7.9]). The simultaneous use of cooling vest and bandana showed an effect little different from the control group (OR = 1.3, 90% CI = [0.3, 5.6]). Conclusion/Application to Practice This is the first field-based study to examine cooling intervention among agricultural workers in the United States using biomonitoring equipment. This study found that using a bandana while working in a hot agricultural environment has the potential to be protective against exceeding the recommended Tc38 threshold.

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Effects of 6-hydroxydopamine and pimozide on temperature maintenance by the chicken

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1980.239.3.r296 ◽

1980 ◽

Vol 239 (3) ◽

pp. R296-R302

Author(s):

D. L. Rowe-Murphy ◽

A. van Tienhoven ◽

N. R. Scott ◽

P. E. Hillman ◽

C. L. Wood ◽

...

Keyword(s):

Body Temperature ◽

Core Body Temperature ◽

Control Treatment ◽

Noradrenergic System ◽

Ambient Temperatures ◽

Drug Treatments ◽

Lower Maximum ◽

6 Hydroxydopamine ◽

Core Body

Intraventricular implants of pimozide in adult white leghorn hens were used to block dopamine (DA) receptors, and 6-hydroxydopamine (6-OHDA) was injected intraventricularly to destroy the noradrenergic system locally. The hens were exposed to ambient temperatures of 5 and 35 degrees C, and their core temperature was measured. One hundred micrograms of 6-OHDA significantly reduced the norepinephrine (NE) but not the DA content of the hypothalamus and reduced the uptake of [3H]NE but not of [3H]DA by synaptosomes in vitro. Neither of the drug treatments nor their combination affected average core body temperature (Tb) at either 5 or 35 degrees C. Pimozide treatment caused a lower maximum Tb at 35 degrees C and a higher maximum Tb at 5 degrees C than the control treatment. No evidence was obtained that 6-OHDA treatment affected body temperature regulation. It is concluded that neither the DA nor the NE system is essential for normal temperature maintenance in the hen exposed to either 5 or 35 degrees C.

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T6 Burn Survivors Can Perform Mild/moderate-intensity Exercise in Thermoneutral Conditions Without a Risk of Excessive Elevations in Core Body Temperature

Journal of Burn Care & Research ◽

10.1093/jbcr/irab032.005 ◽

2021 ◽

Vol 42 (Supplement_1) ◽

pp. S5-S6

Author(s):

Craig G Crandall ◽

Luke N Belval ◽

Matthew N Cramer ◽

Mu Huang ◽

Gilbert Moralez ◽

...

Keyword(s):

At Risk ◽

Body Temperature ◽

Environmental Conditions ◽

Core Body Temperature ◽

Burn Injuries ◽

Body Core Temperature ◽

Moderate Intensity ◽

Moderate Intensity Exercise ◽

Burn Survivors ◽

Core Body

Abstract Introduction Burned skin excision and subsequent grafting removes sweat glands, which impairs thermoregulation. Consequently, exercise prescribed for rehabilitation may expose individuals with burn injuries to a greater risk of hyperthermia, depending on exercise duration, intensity, and environmental temperature. Little is known regarding the risk of hyperthermia in adult burn survivors performing mild/moderate-intensity exercise under thermoneutral environmental conditions, i.e. conditions similar to the rehabilitation clinic and/or the gym. This project tested the hypothesis that burn survivors, across a wide range of percent total body surface area (%TBSA) burned, can participate in mild/moderate-intensity exercise in a thermoneutral environment without excessive elevations in core body temperature. Methods Twenty-eight well-healed burn survivors with low (23±5%TBSA; N=10), moderate (42±7%TBSA; N=9), and high (60±8%TBSA; N=9) sized burn injuries performed 60 minutes of cycle ergometry exercise (72±15 Watts, oxygen uptake rate of 1.25±0.21 L/min equivalent to 4.5±0.2 METs) in a 25°C and 23% relative humidity environment. Absolute gastrointestinal temperatures (Tcore) and changes in gastrointestinal temperatures (ΔTcore) were obtained at 15-minute increments throughout the exercise bout. A participant with an absolute Tcore of greater than 38.5°C, and/or a ΔTcore of >1.5°C, at any time point during the trial was categorized as being at risk for hyperthermia. Results Sixty minutes of exercise increased Tcore in all groups (Low: 0.72±0.21°C; Moderate: 0.42±0.22°C; High: 0.77±0.25°C, all P< 0.01 from pre-exercise baseline), resulting in similar absolute Tcore values of upon exercise termination (Low: 37.87±0.24°C; Moderate: 37.56±0.34°C; High: 37.76±0.47°C, P=0.19). Importantly, no participant was categorized as being at risk for hyperthermia, based upon the aforementioned criteria. Conclusions These data indicate that individuals with substantial %TBSA burned can exercise at a mild/moderate intensity for 60 minutes in thermoneutral environmental conditions without a risk of excessive elevations in body core temperature.

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Temperature gradients in trailers and changes in broiler rectal and core body temperature during winter transportation in Saskatchewan

Canadian Journal of Animal Science ◽

10.4141/cjas09083 ◽

2010 ◽

Vol 90 (3) ◽

pp. 321-330 ◽

Cited By ~ 25

Author(s):

T D Knezacek ◽

A A Olkowski ◽

P J Kettlewell ◽

M A Mitchell ◽

H L Classen

Keyword(s):

Body Temperature ◽

Core Body Temperature ◽

Cold Weather ◽

Heterogeneous Distribution ◽

Ambient Temperatures ◽

Temperature Recording ◽

Data Loggers ◽

Before And After ◽

Transportation Times ◽

Core Body

Temperature conditions inside commercial trailers transporting market-age broilers during four winter journeys were measured, and changes in the rectal and core body temperature of birds were quantified. Pre-selected modules were equipped with data loggers recording temperature every 72 s. Rectal temperatures were taken from eight birds in each of four modules immediately before and after each trip, and two or three birds, with temperature recording implants, were placed in each of two selected modules. Temperature heterogeneity was found among modules on all loads with average crate temperatures ranging from 10.9 to 30.7, 8.9 to 28.1, 2.5 to 26.1 and -0.7 to 16.5°C for transportation times of 191, 193, 178 and 18 min and ambient temperatures of -7.1, -27.1, -28.2 and -18.4°C, respectively. Wet birds, condensation and frost provided evidence for moisture accumulation during transportation. Body temperature recordings indicated the potential for the development of both hypothermia and hyperthermia, showing that cold stress can occur near air inlets and heat stress in poorly ventilated areas. Passive ventilation inside trailers resulted in crate temperatures 17.7 to 55.2°C above outside temperature. Mortality ranged from 0.7 to 1.4% but several deaths occurred during lairage, prior to processing. A heterogeneous distribution of airflow resulted in undesirable temperate and humidity conditions for some birds. Key words: Broiler, transportation, temperature gradient, mortality, cold weather

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