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Giersch G, Garcia C, Stachenfeld N, Charkoudian N. Are there sex differences in risk for exertional heat stroke? A translational approach. Exp Physiol 2022; 107:1136-1143. [PMID: 35598159 DOI: 10.1113/ep090402] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 05/11/2022] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the topic of this review? This review discusses the current status of the literature in sex differences in exertional heat stroke. What advances does this review highlight? We utilize a translational model to explore possible physical and physiological differences with respect risk and treatment of exertional heat stroke. ABSTRACT Exertional heat stroke (EHS) is a potentially fatal condition brought about by a combination of physical activity and heat stress and resulting in central nervous system dysfunction and organ damage. EHS impacts several hundred individuals each year ranging from military personnel, athletes, to occupational workers. Understanding the pathophysiology and risk factors can aid in reducing EHS across the globe. While we know there are differences between sexes in mechanisms of thermoregulation, there is currently not a clear understanding if/how those differences impact EHS risk. The purpose of this review is to assess the current status of the literature surrounding EHS from risk factors to treatment using both animal and human models. We use a translational approach, considering both animal and human research to elucidate the possible influence of female sex hormones on temperature regulation and performance in the heat and highlight the specific areas with limited research. While more work is necessary to comprehensively understand these differences, the current research presented provides a good framework for future investigations. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Gabrielle Giersch
- Thermal and Mountain Medicine Division, U.S. Army Research Institute for Environmental Medicine, Natick, MA, USA.,Oak Ridge Institute for Science and Education, Belcamp, MD, USA
| | - Christian Garcia
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL, USA
| | - Nina Stachenfeld
- John B. Pierce Laboratory, Yale School of Medicine, New Haven, CT, USA
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, U.S. Army Research Institute for Environmental Medicine, Natick, MA, USA
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Bouchama A, Abuyassin B, Lehe C, Laitano O, Jay O, O'Connor FG, Leon LR. Classic and exertional heatstroke. Nat Rev Dis Primers 2022; 8:8. [PMID: 35115565 DOI: 10.1038/s41572-021-00334-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/20/2021] [Indexed: 12/28/2022]
Abstract
In the past two decades, record-breaking heatwaves have caused an increasing number of heat-related deaths, including heatstroke, globally. Heatstroke is a heat illness characterized by the rapid rise of core body temperature above 40 °C and central nervous system dysfunction. It is categorized as classic when it results from passive exposure to extreme environmental heat and as exertional when it develops during strenuous exercise. Classic heatstroke occurs in epidemic form and contributes to 9-37% of heat-related fatalities during heatwaves. Exertional heatstroke sporadically affects predominantly young and healthy individuals. Under intensive care, mortality reaches 26.5% and 63.2% in exertional and classic heatstroke, respectively. Pathological studies disclose endothelial cell injury, inflammation, widespread thrombosis and bleeding in most organs. Survivors of heatstroke may experience long-term neurological and cardiovascular complications with a persistent risk of death. No specific therapy other than rapid cooling is available. Physiological and morphological factors contribute to the susceptibility to heatstroke. Future research should identify genetic factors that further describe individual heat illness risk and form the basis of precision-based public health response. Prioritizing research towards fundamental mechanism and diagnostic biomarker discovery is crucial for the design of specific management approaches.
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Affiliation(s)
- Abderrezak Bouchama
- King Abdullah International Medical Research Center, Experimental Medicine Department, King Saud bin Abdulaziz University for Health Sciences, Ministry of National Guard - Health Affairs, Riyadh, Saudi Arabia.
| | - Bisher Abuyassin
- King Abdullah International Medical Research Center, Experimental Medicine Department, King Saud bin Abdulaziz University for Health Sciences, Ministry of National Guard - Health Affairs, Riyadh, Saudi Arabia
| | - Cynthia Lehe
- King Abdullah International Medical Research Center, Experimental Medicine Department, King Saud bin Abdulaziz University for Health Sciences, Ministry of National Guard - Health Affairs, Riyadh, Saudi Arabia
| | - Orlando Laitano
- Department of Nutrition & Integrative Physiology, College of Health and Human Sciences, Florida State University, Tallahassee, FL, USA
| | - Ollie Jay
- Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
| | - Francis G O'Connor
- Military and Emergency Medicine, Uniformed Services University, Bethesda, MD, USA
| | - Lisa R Leon
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
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Garcia CK, Renteria LI, Leite-Santos G, Leon LR, Laitano O. Exertional heat stroke: pathophysiology and risk factors. BMJ MEDICINE 2022; 1:e000239. [PMID: 36936589 PMCID: PMC9978764 DOI: 10.1136/bmjmed-2022-000239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 09/06/2022] [Indexed: 12/31/2022]
Abstract
Exertional heat stroke, the third leading cause of mortality in athletes during physical activity, is the most severe manifestation of exertional heat illnesses. Exertional heat stroke is characterised by central nervous system dysfunction in people with hyperthermia during physical activity and can be influenced by environmental factors such as heatwaves, which extend the incidence of exertional heat stroke beyond athletics only. Epidemiological data indicate mortality rates of about 27%, and survivors display long term negative health consequences ranging from neurological to cardiovascular dysfunction. The pathophysiology of exertional heat stroke involves thermoregulatory and cardiovascular overload, resulting in severe hyperthermia and subsequent multiorgan injury due to a systemic inflammatory response syndrome and coagulopathy. Research about risk factors for exertional heat stroke remains limited, but dehydration, sex differences, ageing, body composition, and previous illness are thought to increase risk. Immediate cooling remains the most effective treatment strategy. In this review, we provide an overview of the current literature emphasising the pathophysiology and risk factors of exertional heat stroke, highlighting gaps in knowledge with the objective to stimulate future research.
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Affiliation(s)
- Christian K Garcia
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Liliana I Renteria
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL, USA
| | - Gabriel Leite-Santos
- Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, FL, USA
| | - Lisa R Leon
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
| | - Orlando Laitano
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, USA
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Emerson DM, Chen SCL, Torres-McGehee TM, Pfeifer CE, Emerson CC, Davis JM. An acute naproxen dose does not affect core temperature or Interleukin-6 during cycling in a hot environment. SPORTS MEDICINE AND HEALTH SCIENCE 2021; 3:243-251. [PMID: 35783372 PMCID: PMC9219352 DOI: 10.1016/j.smhs.2021.08.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 08/09/2021] [Accepted: 08/23/2021] [Indexed: 11/16/2022] Open
Abstract
Non-steroidal anti-inflammatory drugs’ anti-pyretic and anti-inflammatory effects has led some individuals to theorize these medications may blunt core body temperature (Tc) increases during exercise. We utilized a double-blind, randomized, and counterbalanced cross-over design to examine the effects of a 24-h naproxen dose (3–220 mg naproxen pills) and placebo (0 mg naproxen) on Tc and plasma interleukin-6 (IL-6) concentrations during cycling in a hot or ambient environment. Participants (n = 11; 6 male, 5 female; age = 27.8 ± 6.5 years, weight = 79.1 ± 17.9 kg, height = 177 ± 9.5 cm) completed 4 conditions: 1) placebo and ambient (Control); 2) placebo and heat (Heat); 3) naproxen and ambient (Npx); and 4) naproxen and heat (NpxHeat). Dependent measures were taken before, during, and immediately after 90 min of cycling and then 3 h after cycling. Overall, Tc significantly increased pre- (37.1 ± 0.4 °C) to post-cycling (38.2 ± 0.3 °C, F1.7,67.3 = 150.5, p < 0.001) and decreased during rest (37.0 ± 0.3 °C, F2.0,81.5 = 201.6, p < 0.001). Rate of change or maximum Tc were not significantly different between conditions. IL-6 increased pre- (0.54 ± 0.06 pg/ml) to post-exercise (2.46 ± 0.28 pg/ml, p < 0.001) and remained significantly higher than pre-at 3 h post- (1.17 ± 0.14 pg/ml, 95% CI = −1.01 to −0.23, p = 0.001). No significant IL-6 differences occurred between conditions. A 24-h, over-the-counter naproxen dose did not significantly affect Tc or IL-6 among males and females cycling in hot or ambient environments.
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Caldwell AR, Oki K, Ward SM, Ward JA, Mayer TA, Plamper ML, King MA, Leon LR. Impact of successive exertional heat injuries on thermoregulatory and systemic inflammatory responses in mice. J Appl Physiol (1985) 2021; 131:1469-1485. [PMID: 34528459 DOI: 10.1152/japplphysiol.00160.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The purpose of the study was to determine if repeated exertional heat injuries (EHIs) worsen the inflammatory response. We assessed the impact of a single EHI bout (EHI0) or two separate EHI episodes separated by 1 (EHI1), 3 (EHI3), and 7 (EHI7) days in male C57BL/6J mice (n = 236). To induce EHI, mice underwent a forced running protocol until loss of consciousness or core temperature reached ≥ 42.7°C. Blood and tissue samples were obtained 30 min, 3 h, 1 day, or 7 days after the EHI. We observed that mice undergoing repeated EHI (EHI1, EHI3, and EHI7) had longer running distances before collapse (∼528 m), tolerated higher core temperatures (∼0.18°C higher) before collapse, and had higher minimum core temperature (indicative of injury severity) during recovery relative to EHI0 group (∼2.18°C higher; all P < 0.05). Heat resilience was most pronounced when latency was shortest between EHI episodes (i.e., thermal load and running duration highest in EHI1), suggesting the response diminishes with longer recoveries between EHI events. Furthermore, mice experiencing a second EHI exhibited increased serum and liver HSP70, and lower corticosterone, FABP2, MIP-1β, MIP-2, and IP-10 relative to mice experiencing a single EHI typically at 30 min to 3 h after EHI. Our findings indicate that an EHI event may initiate some adaptive processes that provide acute heat resilience to subsequent EHI conditions. NEW & NOTEWORTHY Mice undergoing repeated exertional heat injuries, within 1 wk of an initial heat injury, appear to have some protective adaptations. During the second exertional heat injury, mice were able to run longer and sustain higher body temperatures before collapse. Despite this, the mice undergoing a second exertional heat injury were more resilient to the heat as evidenced by attenuated minimum body temperature, higher HPS70 (serum and liver), lower corticosterone, and lower FABP2.
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Affiliation(s)
- Aaron R Caldwell
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute of Science and Education, Oak Ridge, Tennessee
| | - Kentaro Oki
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Shauna M Ward
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Jermaine A Ward
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Thomas A Mayer
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute of Science and Education, Oak Ridge, Tennessee
| | - Mark L Plamper
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Michelle A King
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Lisa R Leon
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
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