Normal gastrointestinal temperature values measured through ingestible capsules technology: a systematic review

Climate change has amplified the importance of continuous and precise body core temperature (Tcore) monitoring in the everyday life. In this context, assessing Tcore through ingestible capsules technology, i.e., gastrointestinal temperature (Tgastrointestinal), emerges as a good alternative to prevent heat-related illness. Therefore, we conducted a systematic review to point out values of normal Tgastrointestinal measured through ingestible capsules in healthy humans. The study followed PRISMA guidelines and searched the PubMed and Scielo databases from 1971 to 2023. Our search strategy included the descriptors ("gastrointestinal temperature") AND ("measurement"), and eligible studies had to be written in English and measured Tgastrointestinal using ingestible capsules or sensors in healthy adults aged 18-59 at rest. Two pairs of researchers independently reviewed titles and abstracts and identified 35 relevant articles out of 1,088 in the initial search. An average value of 37.13 °C with a standard deviation of 0.24 °C was observed, independently of the gender. The values measured ranged from 36.70 °C to 37.69 °C. In conclusion, this systematic review pointed out the mean value of 37.13 ± 0.24 °C measured by ingestible capsules as reference for resting Tgastrointestinal in healthy adult individuals.

Heat exhaustion and heat stroke among active component members of the U.S. Armed Forces, 2019-2023

The most serious types of heat illnesses, heat exhaustion and heat stroke, are occupational hazards associated with many of the military's training and operational environments. These illnesses can typically be prevented by appropriate situational awareness, risk management strategies, along with effective countermeasures. In 2023, the crude incidence of heat stroke and heat exhaustion were 31.7 and 172.7 cases per 100,000 person-years, respectively. The rates of incident heat stroke declined during the 2019 to 2023 surveillance period, but rates of incident heat exhaustion increased over the same period. In 2023, higher rates of heat stroke were observed among male service members compared to their female counterparts, and female service members experienced higher rates of heat exhaustion compared to male personnel. Heat illness rates were also higher among those younger than age 20, Marine Corps and Army service members, non-Hispanic Black service members, and recruits. Leaders, training cadres, and supporting medical and safety personnel must inform their subordinate and supported service members of heat illness risks, preventive measures, early signs and symptoms of illness, and appropriate interventions.

Exertional rhabdomyolysis among active component members of the U.S. Armed Forces, 2019-2023

A largely preventable condition, exertional rhabdomyolysis persists as an occupational hazard of military training and operations, especially in high heat environments among individuals exerting themselves to their physical endurance limits. During the 5-year surveillance period of this study, unadjusted incidence rates of exertional rhabdomyolysis per 100,000 person-years among U.S. active component service members fluctuated, reaching a low of 38.0 cases in 2020 and peaking at 40.5 cases in 2023. The rate in 2020 constituted a decline of 3.8% from the rate in 2019 (39.5 cases). Beginning in 2020, incidence rates per 100,000 person-years gradually increased, by 1.8% in 2021 (38.7 cases), 5.3% in 2022 (40.0 cases), and 6.6% in 2023 (40.5 cases). Consistent with prior reports, subgroup-specific crude rates in 2023 were highest among men, those less than 20 years old, non-Hispanic Black service members, Marine Corps or Army members, and those in combat-specific and 'other' occupations. Recruits experienced the highest rates of exertional rhabdomyolysis during each year, with incidence rates 6 to 10 times greater than all other service members.

Exertional hyponatremia among active component members of the U.S. Armed Forces, 2008-2023

Exertional hyponatremia, or exercise-associated hyponatremia, occurs within 24 hours after physical activity due to a serum, plasma, or blood sodium concentration (Na+) below the normal reference range of 135 mEq/L. If not detected early and managed properly, hyponatremia can be fatal. From 2008 to 2023, 1,812 cases of exertional hyponatremia were diagnosed among U.S. active component service members (ACSMs), with an overall incidence rate of 8.3 cases per 100,000 person-years (p-yrs). In 2023 there were 153 cases of exertional hyponatremia diagnosed among ACSMs, resulting in a crude incidence rate of 11.7 per 100,000 p-yrs. Female service members, those older than 40, non-Hispanic Black service members, Marine Corps members, recruits, those in combat-specific occupations, and ACSMs stationed in the Northeast U.S. region had higher incidence rates of exertional hyponatremia diagnoses than their respective counterparts. During the surveillance period, annual rates of incident exertional hyponatremia diagnoses peaked in 2010 (12.8 per 100,000 p-yrs) and then decreased to a low of 5.3 cases per 100,000 p-yrs in 2013. Thereafter the incidence rate fluctuated but has increased from 6.2 per 100,000 p-yrs in 2017 to its second-highest level in 2023. Service members and their supervisors should be aware of the dangers of excessive fluid consumption and prescribed limits for consumption during prolonged physical activity including field training exercises, personal fitness training, or recreational activities, particularly in hot, humid weather.

Exertional heat stroke causes long-term skeletal muscle epigenetic reprogramming, altered gene expression, and impaired satellite cell function in mice

The effect of exertional heat stroke (EHS) exposure on skeletal muscles is incompletely understood. Muscle weakness is an early symptom of EHS but is not considered a major target of multiorgan injury. Previously, in a preclinical mouse model of EHS, we observed the vulnerability of limb muscles to a second EHS exposure, suggesting hidden processes contributing to declines in muscle resilience. Here, we evaluated the possible molecular origins of EHS-induced declines in muscle resilience. Female C57BL/6 mice [total n = 56; 28/condition, i.e., EHS and exercise control (EXC)] underwent forced wheel running at 37.5°C/40% relative humidity until symptom limitation (unconsciousness). EXC mice exercised identically at room temperature (22-23°C). After 1 mo of recovery, the following were assessed: 1) specific force and caffeine-induced contracture in soleus (SOL) and extensor digitorum longus (EDL) muscles; 2) transcriptome and DNA methylome responses in gastrocnemius (GAST); and 3) primary satellite cell function (proliferation and differentiation). There were no differences in specific force in either SOL or EDL from EXC. Only EHS solei exhibited lower caffeine sensitivity. EHS GAST exhibited higher RNA expression of genes encoding structural proteins of slow fibers, heat shock proteins, and myogenesis. A total of ∼2,500 differentially methylated regions of DNA that could potentially affect many cell functions were identified. Primary satellite cells exhibited suppressed proliferation rates but normal differentiation responses. Results demonstrate long-term changes in skeletal muscles 1 mo after EHS that could contribute to declines in muscle resilience. Skeletal muscle may join other, more recognized tissues considered vulnerable to long-term effects of EHS.NEW & NOTEWORTHY Exertional heat stroke (EHS) in mice induces long-term molecular and functional changes in limb muscle that could reflect a loss of "resilience" to further stress. The phenotype was characterized by altered caffeine sensitivity and suppressed satellite cell proliferative potential. This was accompanied by changes in gene expression and DNA methylation consistent with ongoing muscle remodeling and stress adaptation. We propose that EHS may induce a prolonged vulnerability of skeletal muscle to further stress or injury.

Does Prophylactic Stretching Reduce the Occurrence of Exercise-Associated Muscle Cramping? A Critically Appraised Topic

CLINICAL SCENARIO

Exercise-associated muscle cramps (EAMC) are sudden, painful, and involuntary contractions of skeletal muscles during or after physical activity. The best treatment for EAMC is gentle static stretching until abatement. Stretching is theorized to relieve EAMC by normalizing alpha motor neuron control, specifically by increasing Golgi tendon organ activity, and physically separating contractile proteins. However, it is unclear if stretching or flexibility training prevents EAMC via the same mechanisms. Despite this, many clinicians believe prophylactic stretching prevents EAMC occurrence.

CLINICAL QUESTION

Do athletes who experience EAMC during athletic activities perform less prophylactic stretching or flexibility training than athletes who do not develop EAMC during competitions?

SUMMARY OF KEY FINDINGS

In 3 cohort studies and 1 case-control study, greater preevent muscle flexibility, stretching, or flexibility training (ie, duration, frequency) was not predictive of who developed EAMC during competition. In one study, athletes who developed EAMC actually stretched more often and 9 times longer (9.8 [23.8] min/wk) than noncrampers (1.1 [2.5] min/wk).

CLINICAL BOTTOM LINE

There is minimal evidence that the frequency or duration of prophylactic stretching or flexibility training predicts which athletes developed EAMC during competition. To more effectively prevent EAMC, clinicians should identify athletes' unique intrinsic and extrinsic risk factors and target those risk factors with interventions.

STRENGTH OF RECOMMENDATION

Minimal evidence from 3 prospective cohort studies and 1 case-control study (mostly level 3 studies) that suggests prophylactic stretching or flexibility training can predict which athletes develop EAMC during athletic competitions.

Tarp-Assisted Cooling for Exertional Heat Stroke Treatment in Wildland Firefighting

INTRODUCTION

Exertional heat stroke is a life-threatening emergency necessitating immediate treatment with rapid body cooling. A field-expedient alternative may be tarp-assisted cooling, requiring only water and a tarp. The objective of this study was to compare core temperature (Tc) cooling rates of tarp-assisted cooling using the limited resources available to a wildland firefighter and the current standard care provided in wilderness settings.

METHODS

This cross-over, randomized control trial of 17 healthy individuals consisted of exercise in a 42±1°C, 32±4% relative humidity environment while wearing wildland firefighter attire, followed by cooling. Body cooling consisted of either pouring 11 L of 25±1°C water over the torso while lying supine on a tarp configured to hold water close to the individual (Tarp) or dousing the water on the participant followed by lying supine with a light breeze, current standard care in the wilderness (Current Care). Cooling occurred until Tc reached 38°C.

RESULTS

Participants walked until a similar Tc was achieved in Tarp (39.59±0.04°C) and Current Care (39.55±0.22°C; P=0.36). Core temperature cooling rate was not different between Tarp (0.076±0.042°C·min-1) and Current Care (0.088±0.046°C·min-1; P=0.41).

CONCLUSIONS

In hyperthermic individuals, Tarp did not provide a faster cooling rate compared to the current exertional heat stroke care provided in the wilderness, and both provided a slower cooling rate than that provided by the traditional method of cold water immersion (>0.20°C·min-1) to treat exertional heat stroke patients.

How Does Environmental Temperature Affect Farmworkers' Work Rates in the California Heat Illness Prevention Study?

OBJECTIVE

Estimate the association between environmental temperature (wet bulb globe temperature [WBGT]) and work rate over the course of a workday.

METHODS

Repeated-measures regression was used to identify characteristics impacting work rate in a cross-sectional study of Latino farmworkers. Minute-by-minute work rate (measured by accelerometer) and WBGT were averaged over 15-minute intervals.

RESULTS

Work rate decreased by 4.34 (95% confidence interval [CI], -7.09 to -1.59) counts per minute per degree Celsius WBGT in the previous 15-minute interval. Cumulative quarter hours worked (2.13; 95% CI, 0.82 to 3.45), age (-3.64; 95% CI, -4.50 to -2.79), and dehydration at the end of workday (51.37; 95% CI, 19.24 to 83.50) were associated with counts per minute as were gender, pay type (piece rate vs hourly) and body mass index ≥25 kg/m 2 . The effects of pay type and body mass index were modified by gender.

CONCLUSION

Increased temperature was associated with a decrease in work rate.

Ovariectomy aggravates the pathophysiological response to exertional heat stroke in mice

Female mice have a greater capacity for exercising in the heat than male mice, reaching greater power output and longer times of heat exposure before succumbing to exertional heat stroke (EHS). Differences in body mass, size, or testosterone do not explain these distinct sex responses. Whether the ovaries could account for the superior exercise capacity in the heat in females remains unknown. Here, we determined the influence of ovariectomy (OVX) on exercise capacity in the heat, thermoregulation, intestinal damage, and heat shock response in a mouse EHS model. We performed bilateral OVX (n = 10) or sham (n = 8) surgeries in young adult (4 mo) female C57/BL6J mice. Upon recovery from surgeries, mice exercised on a forced wheel placed inside an environmental chamber set at 37.5 °C and 40% relative humidity until experiencing loss of consciousness (LOC). Terminal experiments were performed 3 h after LOC. OVX increased body mass by the time of EHS (sham = 3.8 ± 1.1, OVX = 8.3 ± 3.2 g, P < 0.05), resulted in shorter running distance (sham = 753 ± 189, OVX = 490 ± 87 m, P < 0.05), and shorter time to LOC (sham = 126.3 ± 21, OVX = 99.1 ± 19.8 min, P < 0.05). Histopathological assessment of the intestines revealed damage in the jejunum (sham = 0.2 ± 0.7, OVX = 2.1 ± 1.7 AU, P < 0.05) and ileum (sham = 0.3 ± 0.5, OVX = 1.8 ± 1.4 AU, P < 0.05). OVX increased mesenteric microvascular density (sham = 101 ± 25, OVX = 156 ± 66 10-2 mm/mm2, P < 0.05) and decreased concentration of circulatory heat shock protein 72 (HSP72) (sham = 26.7 ± 15.8, OVX = 10.3 ± 4.6 ng/mL, P < 0.05). No differences were observed in cytokines or chemokines between groups. Our findings indicate that OVX aggravates the pathophysiological response to EHS in mice.NEW & NOTEWORTHY Females outperform males in a mouse model of exertional heat stroke (EHS). Here, we show for the first time the impact of ovariectomy (OVX) on EHS pathophysiology. OVX resulted in a shorter exercise capacity in the heat, greater intestinal damage, and lower heat shock response following EHS.

The mental health of women and climate change: Direct neuropsychiatric impacts and associated psychological concerns

Climate change brings exposures to heat, air pollution, poorer quality food, and infectious disease that have significant direct effects on women and their mental health. These environmental impacts are multifaceted in their consequences and raise risks of depression, suicide, violent victimization, post-traumatic stress disorder, and various other neuropsychiatric symptoms. Women also suffer increased climate psychological risks from higher rates of stillbirth, preterm birth, and developmental problems in their children. Here we review what is known about the overlap of women's individual mental health and climate change, and highlight areas where more research is needed.

Estimation of the number of heat illness patients in eight metropolitan prefectures of Japan: Correlation with ambient temperature and computed thermophysiological responses

The number of patients with heat illness transported by ambulance has been gradually increasing due to global warming. In intense heat waves, it is crucial to accurately estimate the number of cases with heat illness for management of medical resources. Ambient temperature is an essential factor with respect to the number of patients with heat illness, although thermophysiological response is a more relevant factor with respect to causing symptoms. In this study, we computed daily maximum core temperature increase and daily total amount of sweating in a test subject using a large-scale, integrated computational method considering the time course of actual ambient conditions as input. The correlation between the number of transported people and their thermophysiological temperature is evaluated in addition to conventional ambient temperature. With the exception of one prefecture, which features a different Köppen climate classification, the number of transported people in the remaining prefectures, with a Köppen climate classification of Cfa, are well estimated using either ambient temperature or computed core temperature increase and daily amount of sweating. For estimation using ambient temperature, an additional two parameters were needed to obtain comparable accuracy. Even using ambient temperature, the number of transported people can be estimated if the parameters are carefully chosen. This finding is practically useful for the management of ambulance allocation on hot days as well as public enlightenment.

Body mass index, but not sex, influences exertional heat stroke risk in young healthy men and women

Exertional heat stroke (EHS) remains a persistent threat for individuals working or playing in the heat, including athletes and military and emergency service personnel. However, influence of biological sex and/or body mass index (BMI) on the risk of EHS remain poorly understood. The purpose of this study was to retrospectively assess the influence of sex and BMI on risk of EHS in the active-duty US Army. We analyzed data from 2016 to 2021, using a matched case-control approach, where each individual with a diagnosis of EHS was matched to five controls based on calendar time, unit ID, and job category, to capture control individuals who were matched to EHS events by location, time, and activity. We used a multivariate logistic regression model mutually adjusted for sex, BMI, and age to compare 745 (n = 61 F) individuals (26 ± 7 yr) with a diagnosed EHS to 4,290 (n = 384 F) case controls (25 ± 5 yr). Group average BMI were similar: 26.6 ± 3.1 (EHS) and 26.5 ± 3.6 kg/m² (CON). BMI was significantly (P < 0.0001) associated with higher risk of EHS with a 3% increase in risk of EHS for every unit increase in BMI. Notably, sex was not associated with any difference in risk for EHS (P = 0.54). These data suggest that young healthy people with higher BMI have significantly higher risk of EHS, but, contrary to what some have proposed, this risk was not higher in young women.

Heat Illness Requiring Emergency Care for People Experiencing Homelessness: A Case Study Series

Extreme heat and hot weather has a negative impact on human health and society. Global warming has resulted in an increase in the frequency and duration of heatwaves. Heat-related illnesses are a significant negative consequence of high temperatures and can be life-threatening medical emergencies. The severity of the symptoms can depend on the pre-existing medical conditions and vary from mild headaches to severe cases that can lead to coma and death. The risk of heat-related illness may be higher for people experiencing homelessness due to a lack of access to cool places and water, and the complex interactions between mental illness, medications and substance use disorder. This paper presents two cases of people experiencing homelessness who were admitted to the emergency department of a hospital in Sydney, Australia during a heatwave in November 2020. Both cases were adult males with known risk factors for heat-related illness including hypertension and schizophrenia (Case One) and hepatitis C, cirrhosis, and alcohol use disorder (Case Two). These cases show that severe weather can not only be detrimental to homeless people's health but can also cause a significant economic toll, evident by the $70,184 AUD expenditure on the care for these two cases. This case report highlights the requirement to determine the risk of heat-related illness to people experiencing homelessness and need to protect this vulnerable population from weather-related illness and death.

Exertional heat stroke in sport and the military: epidemiology and mitigation

NEW FINDINGS

What is the topic of this review? Exertional heat stroke epidemiology in sport and military settings, along with common risk factors and strategies and policies designed to mitigate its occurrence. What advances does it highlight? Individual susceptibility to exertional heat stroke risk is dependent on the interaction of intrinsic and extrinsic factors. Heat policies in sport should assess environmental conditions, as well as the characteristics of the athlete, clothing/equipment worn and activity level of the sport. Exertional heat stroke risk reduction in the military should account for factors specific to training and personnel.

ABSTRACT

Exertional heat illness occurs along a continuum, developing from the relatively mild condition of muscle cramps, to heat exhaustion, and in some cases to the life-threatening condition of heat stroke. The development of exertional heat stroke (EHS) is associated with an increase in core temperature stemming from inadequate heat dissipation to offset the rate of metabolically generated heat. Susceptibility to EHS is linked to the interaction of several factors including environmental conditions, individual characteristics, health conditions, medication and drug use, behavioural responses, and sport/organisational requirements. Two settings in which EHS is commonly observed are competitive sport and the military. In sport, the exact prevalence of EHS is unclear due to inconsistent exertional heat illness terminology, diagnostic criteria and data reporting. In contrast, exertional heat illness surveillance in the military is facilitated by standardised case definitions, a requirement to report all heat illness cases and a centralised medical record repository. To mitigate EHS risk, several strategies can be implemented by athletes and military personnel, including heat acclimation, ensuring adequate hydration, cold-water immersion and mandated work-to-rest ratios. Organisations may also consider developing sport or military task-specific heat stress policies that account for the evaporative heat loss requirement of participants, relative to the evaporative capacity of the environment. This review examines the epidemiology of EHS along with the strategies and policies designed to reduce its occurrence in sport and military settings. We highlight the nuances of identifying individuals at risk of EHS and summarise the benefits and shortcomings of various mitigation strategies.

A 3-D virtual human model for simulating heat and cold stress

In this study, we extended our previously developed anatomically detailed three-dimensional (3-D) thermoregulatory virtual human model for predicting heat stress to allow for predictions of heat and cold stress in one unified model. Starting with the modified Pennes bioheat transfer equation to estimate the spatiotemporal temperature distribution within the body as the underlying modeling structure, we developed a new formulation to characterize the spatial variation of blood temperature between body elements and within the limbs. We also implemented the means to represent heat generated from shivering and skin blood flow that apply to air exposure and water immersion. Then, we performed simulations and validated the model predictions with experimental data from nine studies, representing a wide range of heat- and cold-stress conditions in air and water and physical activities. We observed excellent agreement between model predictions and measured data, with average root mean squared errors of 0.2 °C for core temperature, 0.9 °C for mean skin temperature, and 27 W for heat from shivering. We found that a spatially varying blood temperature profile within the limbs was crucial to accurately predict core body temperature changes during very cold exposures. Our 3-D thermoregulatory virtual human model consistently predicted the body's thermal state accurately for each of the simulated hot and cold environmental conditions and exertional heat stress. As such, it serves as a reliable tool to assess whole-body, localized tissue, and, potentially, organ-specific injury risks, helping develop injury prevention and mitigation strategies in a systematic and expeditious manner.

Are there sex differences in risk for exertional heat stroke? A translational approach

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.

Sunburns and Sun Protection Behaviors among Male Hispanic Outdoor Day Laborers

Individuals who work outside are at increased risk for skin cancer due to excessive exposure to ultraviolet (UV) radiation. Little is known about UV exposures and sun safety practices of outdoor day laborers, who are disproportionately Hispanic. This study identified the correlates of sunburn and sun protection behaviors in a sample of male, Hispanic day laborers (n = 175). More than half of the participants (54.9%) experienced one or more sunburns when working during the past summer, and 62.9% reported having one or more symptoms of heat illness. The frequency of engaging in sun protection behaviors was suboptimal, including sunglasses use (M = 2.68, SD = 1.71), staying in the shade (M = 2.30, SD = 0.94), wearing sunscreen (M = 2.10, SD = 1.39), and wearing a wide-brimmed hat (M = 1.75, SD = 1.32), based on a 5-point scale (1 = never; 5 = always). Lower education level, higher levels of skin sensitivity to the sun, any symptom of heat illness, fewer barriers to wearing a wide-brimmed hat, and not wearing a wide-brimmed hat were associated with a greater number of sunburns. Factors associated with each sun protection behavior varied. Implications and directions for future research are discussed.

Status of US Emergency Medical Service Protocols Regarding Pre-Transfer Cooling for Exertional Heat Stroke

Objective: Exertional heat stroke (EHS) is a significant cause of morbidity and mortality in athletes and active individuals. In the field, initial management of exertional heat illness is based on rapid whole-body cooling. Cold-water immersion (CWI) is considered the superior cooling modality for EHS treatment. However, there often is a disconnect between the sports medicine community and the emergency medical service (EMS) community. Well-written emergency action plans may fail if EMS protocols do not allow for CWI in initial management. This is the first study to look at the current national EMS protocols regarding prehospital management of EHS. The purpose of our study was to assess the status of heat illness protocols regarding CWI for EHS in all 50 states plus Washington, DC. 

Methods: An internet search was performed to find EHS protocols. Statewide protocols were preferred. Several parameters were recorded for each protocol including whether: 1) CWI was the recommended cooling treatment for EHS and 2) CWI was explicitly permitted to be completed prior to transportation.

Results: We found nine of the 51 protocols, or 17.6%, explicitly recommended CWI and 11 of the 51, or 21.6%, specifically instructed EMS personnel to complete CWI or cooling methods prior to transport. However, six protocols, or 11.8%, provided the recommendation instructing some variation of the phrase “do not delay transport to cool the patient.”

Conclusion: Despite the medical literature endorsing CWI as the most effective treatment modality in a prehospital setting for exertional heat illness, EMS protocols largely fail to reflect this which leads to mismanagement and inadequate care of EHS patients. While CWI is not always available, all EMS protocols should include a systematic practical guideline for a heat illness patient when employing cooling treatment with an emphasis on CWI when available as the preferred treatment technique for EHS and the concept of “cool first, transport second.” 

Accuracy of Algorithm to Non-Invasively Predict Core Body Temperature Using the Kenzen Wearable Device

With climate change increasing global temperatures, more workers are exposed to hotter ambient temperatures that exacerbate risk for heat injury and illness. Continuously monitoring core body temperature (T_C) can help workers avoid reaching unsafe T_C. However, continuous T_C measurements are currently cost-prohibitive or invasive for daily use. Here, we show that Kenzen's wearable device can accurately predict T_C compared to gold standard T_C measurements (rectal probe or gastrointestinal pill). Data from four different studies (n = 52 trials; 27 unique subjects; >4000 min data) were used to develop and validate Kenzen's machine learning T_C algorithm, which uses subject's real-time physiological data combined with baseline anthropometric data. We show Kenzen's T_C algorithm meets pre-established accuracy criteria compared to gold standard T_C: mean absolute error = 0.25 °C, root mean squared error = 0.30 °C, Pearson r correlation = 0.94, standard error of the measurement = 0.18 °C, and mean bias = 0.07 °C. Overall, the Kenzen T_C algorithm is accurate for a wide range of T_C, environmental temperatures (13-43 °C), light to vigorous heart rate zones, and both biological sexes. To our knowledge, this is the first study demonstrating a wearable device can accurately predict T_C in real-time, thus offering workers protection from heat injuries and illnesses.

Deaths in bathtubs in Japan: Forensic and clinical implications

In Japan, deaths in bathtubs or bathtub deaths are frequently investigated as unnatural deaths. About 19,000 bathtub deaths occur annually in Japan. This pattern of death has become a social issue in forensic pathology and emergency medicine and public health. It is assumed that the death of an adult by drowning in a bathtub cannot be avoided due to disturbance of consciousness. The PubMed database was used for literature search using the retrieval words, "bathing "OR" bathtub "AND" submersion "OR" drowning "OR" death "OR" cardiopulmonary arrest". From the epidemiological characteristics and pathophysiological findings of bath mortality in Japan, three etiologies of impaired consciousness have been proposed: acute ischemic heart failure, heatstroke, and blood pressure fluctuation. Moreover, other causes such as epilepsy and alcohol or drug intake cannot be ignored as potential risks for death in a bathtub. It is also important to note the possibility of suicide and, although extremely rare, homicide in a bathtub. Despite research, the exact causal relationship between bathtub bathing and death remains unclear. Further, the cause of death by postmortem investigation is not always easily determined. Hence, it is desirable to carry out a field survey of causes of death, including bathing conditions, and, wherever possible, a complete autopsy survey. An exclusion of critical cases such as crime-related death, suicide, drug poisoning, and carbon monoxide poisoning is optimal. Of the many hypotheses about the causes of bathtub mortality, the most consistent hypothesis will be medically inferred from the death history, case findings, and test results.

Athletic Administrators' Reporting of Emergency Preparedness Regarding Policies and Procedures in Iowa Secondary Schools

CONTEXT

Secondary schools that offer school-sponsored athletic events should follow best-practice guidelines to provide policies that promote student health and safety.

OBJECTIVE

To assess emergency preparedness from the perspective of athletic administrators (AAs) in Iowa secondary schools.

DESIGN

Cross-sectional study.

SETTING

Online survey.

PATIENTS OR OTHER PARTICIPANTS

Ninety-eight AAs from Iowa completed the survey (age = 45.33 ± 10.22 years, years as an AA = 9.37 ± 8.14, years in current role = 7.72 ± 7.09).

MAIN OUTCOME MEASURES(S)

The 6-section survey contained with questions about access to athletic trainers (ATs), emergency action plans (EAPs), cardiopulmonary resuscitation (CPR), automated external defibrillators (AEDs), concussions, heat illness, and other general policies. Descriptive statistics (percentages and frequencies) were reported. Relative risk was calculated to compare schools with and those without access to ATs (P < .05).

RESULTS

Most respondents (76.5%, n = 75/98) reported their school had access to a licensed AT. The majority had a written EAP (83.3%, n = 70/84), but fewer than half (39.2%, n = 31/79) reviewed it annually and fewer than 10% (n = 6/85) reported practicing it each year. All respondents (100%, N = 78/78) stated they had an AED on campus. All respondents (N = 77/77) indicated that they were familiar with the Iowa High School Athletic Association's (IHSAA's) concussion policy and had a concussion guideline in place. Many respondents (95.9%, n = 71/74) described being familiar with the IHSAA's heat illness policy, but more than half (62.1%, n = 41/66) noted they did not have a heat illness policy in place at their school.

CONCLUSIONS

Most respondents indicated their school had access to ATs, followed the state-mandated concussion guidelines, and had an AED. Although participants reported having written EAPs in place, levels of annual EAP review and practice were low. These results suggest that schools would benefit from educational opportunities to improve safety policies.

Exercise hyperthermia induces greater changes in gastrointestinal permeability than equivalent passive hyperthermia

Hyperthermia and exertional heat illness increase gastrointestinal (GI) permeability, although whether the latter is only via hyperthermia is unclear. The aim of this pilot study was to determine whether different changes in GI permeability, characterized by an increased plasma lactulose:rhamnose concentration ratio ([L:R]), occurred in exercise hyperthermia in comparison to equivalent passive hyperthermia. Six healthy adult male participants (age 25 ± 5 years, mass 77.0 ± 6.7 kg, height 181 ± 6 cm, peak oxygen uptake [ V · O 2 peak ] 48 ± 8 ml.kg-1 .min-1 ) underwent exercise under hot conditions (Ex-Heat) and passive heating during hot water immersion (HWI). Heart rate (HR), rectal temperature (TCORE ), rating of perceived exertion (RPE), and whole-body sweat loss (WBSL) were recorded throughout the trials. The L:R ratio, peak HR, change in HR, and change in RPE were higher in Ex-Heat than HWI, despite no differences in trial duration, peak core temperature or WBSL. L:R was strongly correlated (p < 0.05) with HR peak (r = 0.626) and change in HR (r = 0.615) but no other variable. The greater L:R in Ex-Heat, despite equal TCORE responses to HWI, indicates that increased cardiovascular strain occurred during exercise, and exacerbates hyperthermia-induced GI permeability at the same absolute temperature.

Apparent temperature and heat-related illnesses during international athletic championships: A prospective cohort study

International outdoor athletics championships are typically hosted during the summer season, frequently in hot and humid climatic conditions. Therefore, we analyzed the association between apparent temperature and heat-related illnesses occurrence during international outdoor athletics championships and compared its incidence rates between athletics disciplines. Heat-related illnesses were selected from illness data prospectively collected at seven international outdoor athletics championships between 2009 and 2018 using a standardized methodology. The Universal Thermal Climate Index (UTCI) was calculated as a measure of the apparent temperature based on weather data for each day of the championships. Heat-related illness numbers and (daily) incidence rates were calculated and analyzed in relation to the daily maximum UTCI temperature and between disciplines. During 50 championships days with UTCI temperatures between 15℃ and 37℃, 132 heat-related illnesses were recorded. Average incidence rate of heat-related illnesses was 11.7 (95%CI 9.7 to 13.7) per 1000 registered athletes. The expected daily incidence rate of heat-related illnesses increased significantly with UTCI temperature (0.12 more illnesses per 1000 registered athletes/°C; 95%CI 0.08-0.16) and was found to double from 25 to 35°C UTCI. Race walkers (RR = 45.5, 95%CI 21.6-96.0) and marathon runners (RR = 47.7, 95%CI 23.0-98.8) had higher heat-related illness rates than athletes competing in short-duration disciplines. Higher UTCI temperatures were associated with more heat-related illnesses, with marathon and race walking athletes having higher risk than athletes competing in short-duration disciplines. Heat-related illness prevention strategies should predominantly focus on marathon and race walking events of outdoor athletics championships when high temperatures are forecast.

Characteristics of Prehospital Heat Illness Cases During the Annual Heat Wave Period in Telangana, India

OBJECTIVES

Global warming and more intense heat wave periods impact health. Heat illness during heat waves has not been studied in the prehospital setting of a low- and middle-income country (LMIC). Early intervention in the community and in the prehospital setting can improve outcomes. Hence, this paper aims to describe the characteristics of heat illness patients utilizing the ambulance service in Telangana state, India with the aim of optimizing public prevention and first aid strategies and prehospital response to this growing problem.

METHODS

This retrospective observational study reviewed patients presenting to Telangana's prehospital emergency care system with heat illness symptoms during the heat wave period from March through June in 2018 and 2019. Descriptive analysis was done on the prehospital, dispatch, and environmental data looking at the patients' characteristics and prehospital intervention.

RESULTS

There were 295 cases in 2018 and 230 cases in 2019 from March-June. The overall incidence of calls with heat illness symptoms was 1.5 cases per 100,000 people. The Scheduled Tribes (ST) had the highest incidence of 4.5 per 100,000 people. Over 96% were from the white income group (below poverty line) while two percent were from the pink income group (above poverty line). From geospatial mapping of the cases, the highest incidence of calls came from the rural, tribal areas. However, the time to response in rural areas was longer than that in an urban area. Males with an average age of 47 were more likely to be affected. The three most common symptoms recorded by the first responders were vomiting (44.4%), general weakness (28.7%), and diarrhea (15.9%). The three most common medical interventions on scene were oxygen therapy (35.1%), oral rehydration salt (ORS) solution administration (26.9%), and intravenous fluid administration (27.0%), with cold sponging infrequently mentioned.

CONCLUSION

This descriptive study provides a snapshot of the regions and groups of people most affected by heat illness during heat waves and the heterogeneous symptom presentation and challenges with management in the prehospital setting. These data may aid planning of prehospital resources and preparation of community first responders during heat wave periods.

Age- and Sex-Based Differences in Exertional Heat Stroke Incidence in a 7-Mile Road Race

CONTEXT

Sex, age, and wet-bulb globe temperature (WBGT) have been proposed risk factors for exertional heat stroke (EHS) despite conflicting laboratory and epidemiologic evidence.

OBJECTIVE

To examine differences in EHS incidence while accounting for sex, age, and environmental conditions.

DESIGN

Observational study.

SETTING

Falmouth Road Race, a warm-weather 7-mi (11.26-km) running road race.

PATIENTS OR OTHER PARTICIPANTS

We reviewed records from patients treated for EHS at medical tents.

MAIN OUTCOME MEASURE(S)

The relative risk (RR) of EHS between sexes and across ages was assessed with males as the reference population. Multivariate linear regression analyses were calculated to determine the relative contribution of sex, age, and WBGT to the incidence of EHS.

RESULTS

Among 343 EHS cases, the female risk of EHS was lower overall (RR = 0.71; 95% confidence interval [CI] = 0.58, 0.89; P = .002) and for age groups 40 to 49 years (RR = 0.43; 95% CI = 0.24, 0.77; P = .005) and 50 to 59 years (RR = 0.31; 95% CI = 0.13, 0.72; P = .005). The incidence of EHS did not differ between sexes in relation to WBGT (P > .05). When sex, age, and WBGT were considered in combination, only age groups <14 years (β = 2.41, P = .008), 15 to 18 years (β = 3.83, P < .001), and 19 to 39 years (β = 2.24, P = .014) significantly accounted for the variance in the incidence of EHS (R2 = .10, P = .006).

CONCLUSIONS

In this unique investigation of EHS incidence in a road race, we found a 29% decreased EHS risk in females compared with males. However, when sex was considered with age and WBGT, only younger age accounted for an increased incidence of EHS. These results suggest that road race medical organizers should consider participant demographics when organizing the personnel and resources needed to treat patients with EHS. Specifically, organizers of events with greater numbers of young runners (aged 19 to 39 years) and males should prioritize ensuring that medical personnel are adequately prepared to handle patients with EHS.

Heat Acclimation Following Heat Acclimatization Elicits Additional Physiological Improvements in Male Endurance Athletes

The purpose of this study was to assess the effectiveness of heat acclimatization (HAz) followed by heat acclimation (HA) on physiological adaptations. 25 male endurance athletes (age 36 ± 12 y, height 178.8 ± 6.39 cm, body mass 73.03 ± 8.97 kg, and VO_2peak 57.5 ± 7.0 mL·kg^-1·min^-1) completed HAz and HA. HAz was 3 months of self-directed summer training. In the laboratory, a 5-day HA prescribed exercise to target a hyperthermic zone (HZHA) of T_rec between 38.50 and 39.75 °C for 60 min. Exercise trials were 60 min of running (59% ± 2% VO_2peak) in an environmental chamber (wet bulb globe temperature 29.53 ± 0.63 °C) and administered at: baseline, post-HAz, and post-HAz+HA. Measured variables included internal body temperature (T_rec), heart rate (HR), and sweat rate (SR). Repeated measure ANOVAs and post hoc comparisons were used to assess statistically significant (p < 0.05) differences. T_rec was lower post-HAz+HA (38.03 ± 0.39 °C) than post-HAz (38.25 ± 0.42 °C, p = 0.009) and baseline (38.29 ± 0.37 °C, p = 0.005). There were no differences between baseline and post-HAz (p = 0.479) in T_rec. HR was lower post-HAz (143 ± 12 bpm, p = 0.002) and post-HAz+HA (134 ± 11 bpm, p < 0.001) than baseline (138 ± 14 bpm). HR was lower post-HAz+HA than post-HAz (p = 0.013). SR was higher post-HAz+HA (1.93 ± 0.47 L·h^-1) than post-HAz (1.76 ± 0.43 L·h^-1, p = 0.027). Combination HAz and HA increased physiological outcomes above HAz. This method can be used to improve performance and safety in addition to HAz alone.

COVID-19 and Heat Illness in Tokyo, Japan: Implications for the Summer Olympic and Paralympic Games in 2021

The 2020 summer Olympic and Paralympic Games in Tokyo were postponed to July-September 2021 due to the coronavirus disease 2019 (COVID-19) pandemic. While COVID-19 has emerged as a monumental health threat for mass gathering events, heat illness must be acknowledged as a potentially large health threat for maintaining health services. We examined the number of COVID-19 admissions and the Tokyo rule for emergency medical care, in Tokyo, from March to September 2020, and investigated the weekly number of emergency transportations due to heat illness and weekly averages of the daily maximum Wet Bulb Globe Temperature (WBGT) in Tokyo in the summer (2016-2020). The peak of emergency transportations due to heat illness overlapped the resurgence of COVID-19 in 2020, and an increase of heat illness patients and WBGT has been observed. Respect for robust science is critical for the decision-making process of mass gathering events during the pandemic, and science-based countermeasures and implementations for COVID-19 will be warranted. Without urgent reconsiderations and sufficient countermeasures, the double burden of COVID-19 and heat-related illnesses in Tokyo will overwhelm the healthcare provision system, and maintaining essential health services will be challenging during the 2021 summer Olympic and Paralympic Games.

Using Twitter for Nursing Research: A Tweet Analysis on Heat Illness and Health

AIM

To provide an example of a tweet analysis for nurse researchers using Twitter in their research.

DESIGN

A content analysis using tweets about "heat illness + health."

METHODS

Tweets were pulled from Twitter's application programming interface with premium access using Postman and the key words "heat illness + health." All data cleaning and analysis was performed in R Version 3.5.2, and the tweet set was analyzed for term frequency, sentiment, and topic modeling. Principal R packages included LDAvis, tidytext, tm, and zyuzhet.

RESULTS

6,317 tweets were analyzed with a date range of April 6, 2009, to December 30, 2019. The most common terms in the tweets were heat (n = 4,532), illness (n = 4,085), and health (n = 2,257). Sentiment analysis showed that the majority of tweets (55%) had a negative sentiment. Topic modeling showed that there were three topics within the tweet set: increasing impact, prevention and safety, and symptoms.

CONCLUSIONS

Twitter can be a useful tool for nursing researchers, serving as a viable adjunct to current research methodologies. This practical example has facilitated a deeper understanding of the social media representation of heat illness and health that can be applied to other research.

CLINICAL RELEVANCE

Twitter serves as a tool for collecting health information for multiple groups, ranging from clinicians and researchers to patients. By utilizing the plethora of data that comes from the platform, we can work towards developing theories and interventions related to numerous health conditions and phenomena.

In pursuit of the unicorn

This short review was prompted by The Physiological Society's recent online symposium on variability. It does not deal with a specific methodology, but rather with the myth that certain environmentally-induced clinical conditions can be identified, quantified, simplified and monitored with a single methodology. Although this might be possible with some clinical conditions, others resist the prevailing reductionist approach of minimizing rather than exploring variation in pathogenesis and pathology, and will not be understood fully until the variation in cause and effect are embraced. This is likely to require comprehensive methodologies and collaboration.

Emergency Medical Service Directors' Protocols for Exertional Heat Stroke

Background and Objectives: Emergency Medical Service (EMS) protocols vary widely and may not implement best practices for exertional heat stroke (EHS). EHS is 100% survivable if best practices are implemented within 30 min. The purpose of this study is to compare EMS protocols to best practices for recognizing and treating EHS. Materials and Methods: Individuals (n = 1350) serving as EMS Medical or Physician Director were invited to complete a survey. The questions related to the EHS protocols for their EMS service. 145 individuals completed the survey (response rate = 10.74%). Chi-Squared Tests of Associations (χ²) with 95% confidence intervals (CI) were calculated. Prevalence ratios (PR) with 95% CI were calculated to determine the prevalence of implementing best practices based on location, working with an athletic trainer, number of EHS cases, and years of directing. All PRs whose 95% CIs excluded 1.00 were considered statistically significant; Chi-Squared values with p values < 0.05 were considered statistically significant. Results: A majority of the respondents reported not using rectal thermometry for the diagnosis of EHS (n = 102, 77.93%) and not using cold water immersion for the treatment of EHS (n = 102, 70.34%). If working with an athletic trainer, EMS is more likely to implement best-practice treatment (i.e., cold-water immersion and cool-first transport-second) (69.6% vs. 36.9%, χ² = 8.480, p < 0.004, PR = 3.15, 95% CI = 1.38, 7.18). Conclusions: These findings demonstrate a lack of implementation of best-practice standards for EHS by EMS. Working with an athletic trainer appears to increase the likelihood of following best practices. Efforts should be made to improve EMS providers’ implementation of best-practice standards for the diagnosis and management of EHS to optimize patient outcomes.

Individual risk factors associated with exertional heat illness: A systematic review

NEW FINDINGS

What is the topic of this review? Exertional heat illness (EHI) remains a persistent problem for athletes and individuals. This threat remains despite numerous athletic position statements and occupational guidance policies. This review explores primary evidence that demonstrates a direct association between 'known' risk factors and EHI. What advances does it highlight? Primary evidence to support 'known' risk factors associated with EHI is not comprehensive. Furthermore, it is not evident that single individual factors predispose individuals to greater risk. In fact, the evidence indicates that EHI can manifest in non-hostile compensable environments when a combination of risk factors is prevalent.

ABSTRACT

Despite the widespread knowledge of exertional heat illness (EHI) and clear guidance for its prevention, the incidence of EHI remains high. We carried out a systematic review of available literature evaluating the scientific evidence underpinning the risk factors associated with EHI. Medline, PsycINFO, SportDiscus and Embase were searched from inception to January 2019 with no date limitation, with supplementary searches also being performed. Search terms included permutations of risk and heat illness, with only studies in English included. Study selection, data extraction and quality assessment, using the QUALSYST tool, were performed by two independent reviewers. Of 8898 articles identified by the searches, 42 were included in the systematic review as primary evidence demonstrating a link between a risk factor and EHI. The quality scores ranged from 57.50 to 100%, and studies were generally considered to be of strong quality. The majority of risks attributable to EHI were categorized as those associated with lifestyle factors. The findings from the systematic review suggest complex manifestation of EHI through multiple risk factors rather than any one factor in isolation. Further research is needed to explore the accumulation of risk factors to help in development of effective preventative measures.

Do Alternative Cooling Methods Have Effective Cooling Rates for Hyperthermia Compared With Previously Established CWI Cooling Rates?

Clinical Scenario: In the last few years, there have been several studies examining alternative cooling strategies in the treatment of exertional heat stroke (EHS). Morbidity and mortality with EHS are associated with how long the patient's core body temperature remains above the critical threshold of 40.5°C. Although cold-water immersion (CWI) is the gold standard of treatment when cooling a patient with EHS, more recent alternative cooling techniques have been examined for use in settings where CWI may not be feasible (ie, remote locations). Clinical Question: Do alternative cooling methods have effective core body temperature cooling rates for hyperthermia compared with previously established CWI cooling rates? Summary of Key Findings: The authors searched for studies using alternative cooling methods to cool hyperthermic individuals. To be included, the studies needed a PEDro score ≥6 and a level of evidence ≥2. They found 9 studies related to our focused clinical question; of these, 5 studies met the inclusion criteria. The cooling rates for hand cooling, cold-water shower, and ice-sheet cooling were 0.03°C/min, 0.08°C/min, and 0.06°C/min, respectively, whereas the tarp-assisted cooling with oscillation (TACO) method was the only method that had an acceptable cooling rate (range 0.14-0.17°C/min). Clinical Bottom Line: When treating EHS, if CWI is not available, the tarp-assisted cooling method may be a reasonable alternative. Clinicians should not use cold shower, hand cooling, or ice-sheet cooling if better cooling methods are available. Clinicians should always use CWI when available. Strength of Recommendation: Five level 2 studies with PEDro scores ≥6 suggest the TACO method is the only alternative cooling method that decreases core body temperature at a similar, though slower, rate of CWI. Hand cooling, cold showering, and ice-sheet cooling do not decrease core body temperature at an appropriate rate and should not be used in EHS situations if a modality with a better cooling rate is available.

Heat Adaptation in Military Personnel: Mitigating Risk, Maximizing Performance

The study of heat adaptation in military personnel offers generalizable insights into a variety of sporting, recreational and occupational populations. Conversely, certain characteristics of military employment have few parallels in civilian life, such as the imperative to achieve mission objectives during deployed operations, the opportunity to undergo training and selection for elite units or the requirement to fulfill essential duties under prolonged thermal stress. In such settings, achieving peak individual performance can be critical to organizational success. Short-notice deployment to a hot operational or training environment, exposure to high intensity exercise and undertaking ceremonial duties during extreme weather may challenge the ability to protect personnel from excessive thermal strain, especially where heat adaptation is incomplete. Graded and progressive acclimatization can reduce morbidity substantially and impact on mortality rates, yet individual variation in adaptation has the potential to undermine empirical approaches. Incapacity under heat stress can present the military with medical, occupational and logistic challenges requiring dynamic risk stratification during initial and subsequent heat stress. Using data from large studies of military personnel observing traditional and more contemporary acclimatization practices, this review article (1) characterizes the physical challenges that military training and deployed operations present (2) considers how heat adaptation has been used to augment military performance under thermal stress and (3) identifies potential solutions to optimize the risk-performance paradigm, including those with broader relevance to other populations exposed to heat stress.

Physical activity and work activities in Florida agricultural workers

BACKGROUND

Laboring in hot and humid conditions is a risk factor for heat-related illnesses. Little is known about the amount of physical activity performed in the field setting by agricultural workers, a population that is among those at highest risk for heat-related mortality in the United States.

METHODS

We measured accelerometer-based physical activity and work activities performed in 244 Florida agricultural workers, 18 to 54 years of age, employed in the fernery, nursery, and crop operations during the summer work seasons of 2015-2017. Environmental temperature data during the participant's workdays were collected from the Florida Automated Weather Network and used to calculate wet bulb globe temperature (WBGT). Generalized linear mixed model regression was used to examine the association between WBGT on physical activity, stratified by the agricultural sector.

RESULTS

Fernery workers had the highest overall volume of physical activity, spending nearly 4 hours in moderate to vigorous activity per workday. Activity over the course of the workday also differed by the agricultural sector. A reduction on average physical activity with increasing environmental temperature was observed only among crop workers.

CONCLUSIONS

The quantity and patterns of physical activity varied by the agricultural sector, sex, and age, indicating that interventions that aim to reduce heat-related morbidity and mortality should be tailored to specific subpopulations. Some workers did not reduce overall physical activity under dangerously hot environmental conditions, which has implications for policies protecting worker health. Future research is needed to determine how physical activity and climatic conditions impact the development of heat-related disorders in this population.

Appropriate Medical Care Standards for Organizations Sponsoring Athletic Activity for the Secondary School-Aged Athlete: A Summary Statement

OBJECTIVE

To present the appropriate medical care standards for organizations that sponsor athletic activities for secondary school-aged athletes.

DATA SOURCES

To develop the current standards and identify current best-practices evidence, the task force used a multistep process that included reviewing the existing 2004 Appropriate Medical Care for Secondary School-Aged Athletes consensus points and cross-referencing of National Athletic Trainers' Association (NATA) statements and official documents from the strategic alliance (the NATA, NATA Foundation, Board of Certification, and Commission on Accreditation of Athletic Training Education). Gaps in the recommendations from the 2004 Appropriate Medical Care for Secondary School-Aged Athletes document were identified by the task force, and the new appropriate medical care standards were developed and refined.

CONCLUSIONS AND RECOMMENDATIONS

Twelve standards, with supporting substandards, were developed that encompassed readiness to participate in activity; facilities; equipment; protective materials; environmental policies; nutrition, hydration, and dietary supplementation; wellness and long-term health; comprehensive emergency action plans; on-site immediate care; on-site therapeutic interventions; psychological concerns; and athletic health care administration. Collectively, these standards describe a comprehensive approach to providing appropriate health care to secondary school-aged athletes and should serve as a framework with which organizations can evaluate and improve the medical care supplied to adolescent athletes.

Successful Management of Severe Exertional Heat Stroke with Endovascular Cooling After Failure of Standard Cooling Measures

BACKGROUND

Exertional heat stroke (EHS) is a potentially life-threatening emergency requiring rapid reduction in core body temperature. Methods of cooling include cold water immersion, ice packs, cold water lavage, and chilled saline, among others. We report a case of EHS successfully cooled using an endovascular cooling device after traditional cooling methods failed to reduce core body temperature.

CASE REPORT

A 24-year old soldier collapsed during a 12-mile foot march while training in southern Georgia. His initial rectal temperature was 43.1°C (109.6°F). External cooling measures (ice sheet application) were initiated on site and Emergency Medical Services were called to transport to the hospital. Paramedics obtained a repeat rectal temperature of 42.4°C (108.4°F). Ice sheet application and chilled saline infusion were continued throughout transport to the Emergency Department (ED). Total prehospital treatment time was 50 min. Upon ED arrival, the patient's rectal temperature was 41.2°C (106.2°F). He was intubated due to a Glasgow Coma Scale score of 4, and endovascular cooling was initiated. Less than 45 minutes later his core body temperature was 37.55°C (99.6°F). He was admitted to the intensive care unit, where his mental status rapidly improved. He was found to have rising liver enzymes, and there was concern for his developing disseminated intravascular coagulation, prompting transfer to a tertiary care center. He was subsequently discharged from the hospital 14 days after his initial injury without any persistent sequelae. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The primary treatment for EHS is rapid reduction of core body temperature. When external cooling methods fail, endovascular cooling can be used to rapidly decrease core body temperature.

Use of the heat tolerance test to assess recovery from exertional heat stroke

Exercise or work in hot environments increases susceptibility to exertional heat illnesses such as exertional heat stroke (EHS). EHS occurs when body heat gain exceeds body heat dissipation, resulting in rapid body heat storage and potentially life-threatening consequences. EHS poses a dangerous threat for athletes, agriculture workers, and military personnel, as they are often exposed to hot environmental conditions that restrict body heat loss or contribute to body heat gain. Currently, there is limited guidance on return to activity (RTA) after an episode of EHS. While examining biomarkers in the blood is thought to be beneficial for determining RTA, they are not sensitive or specific enough to be a final determining factor as organ damage may persist despite blood biomarkers returning to baseline levels. As such, additional assessment tests to more accurately determine RTA are desired. One method used for determining RTA is the heat tolerance test (HTT, 120 minutes treadmill walking; 40°C, 40% relative humidity). Unfortunately, the HTT provides even less information about EHS recovery since it offers no test sensitivity or specificity even after years of implementation. We provide an overview of the HTT and the controversy of this test with respect to assessment criteria, applicability to tasks involving high metabolic workloads, and the lack of follow-up analyses to determine its accuracy for determining recovery in order to diminish the likelihood of a second EHS occurrence.

Climate Change: A Review of a Public Health Opportunity for the Northeast

[Full article available at http://rimed.org/rimedicaljournal-2019-02.asp].

Incidence and Characteristics of Bath-related Accidents

Objective Bath-related sudden cardiac arrests frequently occur in Japan. This study aimed to describe the actual incidence and characteristics of bath-related accidents, including non-fatal events, and to establish the etiology of bath-related sudden cardiac arrest. Methods This prospective cross-sectional observational study was conducted in Tokyo Metropolis and Saga and Yamagata Prefectures between October 2012 and March 2013. Emergency personnel enrolled events in this study when they recognized that activation of the emergency medical system was related to bathing. Surveillance cards were delivered and collected from the emergency personnel and attending physicians. Results In total, 4,593 events were enrolled (1,528 cardiac arrests, 935 survivors in need of help, 1,553 patients with acute illnesses, and 577 patients with injuries) in this study. In the group of survivors in need of help and with acute illness, consciousness disturbance and lethargy without any organic disease were recognized as the main symptoms. Acute coronary syndrome and stroke were infrequently diagnosed. Of the survivors, 30% had a body temperature above 38°C. Their consciousness level significantly correlated with their body temperature. Emergency personnel reported that 79% of sudden cardiac arrests were from victims whose faces were submerged in the tub water, while 18% of survivors had their faces submerged in the tub water. Conclusion This study revealed that accidents, including non-lethal events, frequently occur. The key symptoms were consciousness disturbance and lethargy characterized as a functional disorder and accompanied by an elevated body temperature. Those findings suggest that heat illness during hot water immersion causes drowning.

Emergency Preparedness of Secondary School Athletic Programs in Arizona

CONTEXT

Schools that sponsor athletic programs have an obligation to provide a safe environment with appropriate policies for addressing emergencies.

OBJECTIVE

To describe the emergency preparedness of secondary schools in Arizona specific to emergency action plans (EAPs), cardiac arrest, concussion, and heat illness.

DESIGN

Cross-sectional study.

SETTING

Online survey.

PATIENTS OR OTHER PARTICIPANTS

Athletic directors from 143 Arizona secondary schools (response rate = 54%).

INTERVENTION(S)

A 6-section survey that included questions related to athletic trainer (AT) access, EAPs, automated external defibrillators (AEDs), concussion, heat illness, and other policies.

MAIN OUTCOME MEASURE(S)

Descriptive statistics were reported. Comparisons of responses between schools with and without AT access were conducted with Mann-Whitney U tests.

RESULTS

Most respondents (81%, n = 116) indicated their school had access to an AT, and 95% (n = 125) of respondents reported their school had a written EAP. The AEDs were available at most (93%, n = 121) schools. All respondents were familiar with the interscholastic concussion policy, and 98% (n = 123) indicated they had a school-specific policy. Almost all respondents (99%, n = 121) reported being familiar with the state heat-illness policy. Environmental measures were taken before practices at 48% (n = 60) of schools. Schools with access to an AT were more likely to have an EAP, venue-specific EAPs, physician approval of EAPs, AEDs, heat-illness policies, and cold-water immersion tubs and to take environmental measures.

CONCLUSIONS

Whereas the majority of schools reported AT access, not all schools had adequate EAPs in place. Schools would benefit from educational opportunities regarding best practices and policy development to improve emergency preparedness.

Environmental Heat Exposure and Heat-Related Symptoms in United States Coast Guard Deepwater Horizon Disaster Responders

OBJECTIVES

The response to the 2010 Deepwater Horizon oil spill was impacted by heat. We evaluated the association between environmental heat exposure and self-reported heat-related symptoms in US Coast Guard Deepwater Horizon disaster responders.

METHODS

Utilizing climate data and postdeployment survey responses from 3648 responders, we assigned heat exposure categories based on both wet bulb globe temperature (WBGT) and heat index (HI) measurements (median, mean, maximum). We calculated prevalence ratios (PRs) and 95% confidence intervals (CIs) via adjusted Poisson regression models with robust error variance to estimate associations with reported heat-related symptoms. We also evaluated the association between use of personal protective equipment (PPE) and heat-related symptoms.

RESULTS

Those in the highest WBGT median-based heat exposure category had increased prevalence of heat-related symptoms compared to those in the lowest category (PR=2.22 [95% CI: 1.61, 3.06]), and there was a significant exposure-response trend (P&lt;.001). Results were similar for exposure categories based on WBGT and HI metrics. Analyses stratified by use of PPE found significantly stronger associations between environmental heat exposure and heat-related symptoms in those who did not use PPE (PR=2.23 [95% CI: 1.10, 4.51]) than in those who did (PR=1.64 [95% CI: 1.14, 2.36]).

CONCLUSIONS

US Coast Guard Deepwater Horizon disaster responders who experienced higher levels of environmental heat had higher prevalences of heat-related symptoms. These symptoms may impact health, safety, and mission effectiveness. As global climate change increases the frequency of disasters and weather extremes, actions must be taken to prevent heat-related health impacts among disaster responders. (Disaster Med Public Health Preparedness. 2019;13:561-569).

A method to reduce heat strain while clad in encapsulating outerwear

The use of personal protective equipment (PPE) increases the risk of heat related maladies. A means to enhance heat dissipation capacity of individuals clad in PPE would be of benefit. The glabrous skin regions of the hands, face, and feet are portals for direct heat transfer between the body core and the external environment. The effects of PPE outerwear and palmar glabrous skin cooling on heat storage were assessed. Subjects engaged in fixed load treadmill exercise in a thermoneutral environment (T_a = 20-24°C) or rested in a hot environment (45 ± 0.5°C). The use of PPE outerwear increased the rate of core temperature rise by five-fold during vigorous exercise. Palm cooling using a stationary water circulation system attenuated the rate of core temperature rise by 30-60% during rest and light, moderate, and vigorous exercise while wearing PPE outerwear. However, the subjects were tethered to the system. A wearable cooling system was devised that allowed free range of motion and unrestricted mobility. The wearable system provided thermal benefits equivalent to the use of the tethering cooling system. With optimization, this wearable cooling technique could neutralize the negative thermoregulatory effects of wearing PPE while engaged in light workload activities such as those encountered by healthcare professionals working in infectious disease treatment centers. For individuals working at higher workloads, such as firefighters, a wearable glabrous skin-based cooling system could extend work bout duration as well as enhance heat loss during episodic recovery periods.

Online pre-race education improves test scores for volunteers at a marathon

OBJECTIVES

This study examined whether an online course would lead to increased knowledge about the medical issues volunteers encounter during a marathon.

MATERIALS AND METHODS

Health care professionals who volunteered to provide medical coverage for an annual marathon were eligible for the study. Demographic information about medical volunteers including profession, specialty, education level and number of marathons they had volunteered for was collected. A 15-question test about the most commonly encountered medical issues was created by the authors and administered before and after the volunteers took the online educational course and compared to a pilot study the previous year.

RESULTS

Seventy-four subjects completed the pre-test. Those who participated in the pilot study last year (N = 15) had pre-test scores that were an average of 2.4 points higher than those who did not (mean ranks: pilot study = 51.6 vs. non-pilot = 33.9, p = 0.004). Of the 74 subjects who completed the pre-test, 54 also completed the post-test. The overall post-pre mean score difference was 3.8 ± 2.7 (t = 10.5 df = 53 p < 0.001). While subjects with all levels of volunteer experience demonstrated improvement, only change among first time marathon volunteers was significantly different from the others. Subjects reporting all degree/certification levels demonstrated improvement, but no difference in improvement was found between degree/certification levels.

CONCLUSION

In this follow-up to the previous year's pilot study, online education demonstrated a long-term (one-year) increase in test scores. Testing also continued to show short-term improvement in post-course test scores, compared to pre-course test scores. In general, marathon medical volunteers who had no volunteer experience demonstrated greater improvement than those who had prior volunteer experience.

Sports and environmental temperature: From warming-up to heating-up

Most professional and recreational athletes perform pre-conditioning exercises, often collectively termed a 'warm-up' to prepare for a competitive task. The main objective of warming-up is to induce both temperature and non-temperature related responses to optimize performance. These responses include increasing muscle temperature, initiating metabolic and circulatory adjustments, and preparing psychologically for the upcoming task. However, warming-up in hot and/or humid ambient conditions increases thermal and circulatory strain. As a result, this may precipitate neuromuscular and cardiovascular impairments limiting endurance capacity. Preparations for competing in the heat should include an acclimatization regimen. Athletes should also consider cooling interventions to curtail heat gain during the warm-up and minimize dehydration. Indeed, although it forms an important part of the pre-competition preparation in all environmental conditions, the rise in whole-body temperature should be limited in hot environments. This review provides recommendations on how to build an effective warm-up following a 3 stage RAMP model (Raise, Activate and Mobilize, Potentiate), including general and context specific exercises, along with dynamic flexibility work. In addition, this review provides suggestion to manipulate the warm-up to suit the demands of competition in hot environments, along with other strategies to avoid heating-up.

Cooling Effectiveness of a Modified Cold-Water Immersion Method After Exercise-Induced Hyperthermia

CONTEXT

 Recommended treatment for exertional heat stroke includes whole-body cold-water immersion (CWI). However, remote locations or monetary or spatial restrictions can challenge the feasibility of CWI. Thus, the development of a modified, portable CWI method would allow for optimal treatment of exertional heat stroke in the presence of these challenges.

OBJECTIVE

 To determine the cooling rate of modified CWI (tarp-assisted cooling with oscillation [TACO]) after exertional hyperthermia.

DESIGN

 Randomized, crossover controlled trial.

SETTING

 Environmental chamber (temperature = 33.4°C ± 0.8°C, relative humidity = 55.7% ± 1.9%).

PATIENTS OR OTHER PARTICIPANTS

 Sixteen volunteers (9 men, 7 women; age = 26 ± 4.7 years, height = 1.76 ± 0.09 m, mass = 72.5 ± 9.0 kg, body fat = 20.7% ± 7.1%) with no history of compromised thermoregulation.

INTERVENTION(S)

 Participants completed volitional exercise (cycling or treadmill) until they demonstrated a rectal temperature (T_re) ≥39.0°C. After exercise, participants transitioned to a semirecumbent position on a tarp until either T_re reached 38.1°C or 15 minutes had elapsed during the control (no immersion [CON]) or TACO (immersion in 151 L of 2.1°C ± 0.8°C water) treatment.

MAIN OUTCOME MEASURE(S)

 The T_re, heart rate, and blood pressure (reported as mean arterial pressure) were assessed precooling and postcooling. Statistical analyses included repeated-measures analysis of variance with appropriate post hoc t tests and Bonferroni correction.

RESULTS

 Before cooling, the T_re was not different between conditions (CON: 39.27°C ± 0.26°C, TACO: 39.30°C ± 0.39°C; P = .62; effect size = -0.09; 95% confidence interval [CI] = -0.2, 0.1). At postcooling, the T_re was decreased in the TACO (38.10°C ± 0.16°C) compared with the CON condition (38.74°C ± 0.38°C; P < .001; effect size = 2.27; 95% CI = 0.4, 0.9). The rate of cooling was greater during the TACO (0.14 ± 0.06°C/min) than the CON treatment (0.04°C/min ± 0.02°C/min; t₁₅ = -8.84; P < .001; effect size = 2.21; 95% CI = -0.13, -0.08). These differences occurred despite an insignificant increase in fluid consumption during exercise preceding CON (0.26 ± 0.29 L) versus TACO (0.19 ± 0.26 L; t₁₂ = 1.73; P = .11; effect size = 0.48; 95% CI = -0.02, 0.14) treatment. Decreases in heart rate did not differ between the TACO and CON conditions (t₁₅ = -1.81; P = .09; effect size = 0.45; 95% CI = -22, 2). Mean arterial pressure was greater at postcooling with TACO (84.2 ± 6.6 mm Hg) than with CON (67.0 ± 9.0 mm Hg; P < .001; effect size = 2.25; 95% CI = 13, 21).

CONCLUSIONS

 The TACO treatment provided faster cooling than did the CON treatment. When location, monetary, or spatial restrictions are present, TACO represents an effective alternative to traditional CWI in the emergency treatment of patients with exertional hyperthermia.

Medical Evaluation for Exposure Extremes: Heat

Exertional heat illness can be a serious consequence of sports or exercise in hot environments. Participants can possess intrinsic or face extrinsic risk factors that may increase their risk for heat-related illness. Knowledge of the physiology and pathology of heat illness, identification of risk factors, and strategies to combat heat accumulation will aid both the practitioner and the participant in preparing for activities that occur in hot environments. Through preparation and mitigation of risk, safe and enjoyable wilderness adventure can be pursued.

Mandatory Rest Stops Improve Athlete Safety during Event Medical Coverage for Ultramarathons

INTRODUCTION

Provisions of medical direction and clinical services for ultramarathons require specific attention to heat illness. Heat stress can affect athlete performance negatively, and heat accumulation without acclimatization is associated with the development of exertional heat stroke (EHS). In order to potentially mitigate the risk of this safety concern, the Jungle Marathon (Para, Brazil) instituted mandatory rest periods during the first two days of this 7-day, staged, Brazilian ultramarathon.

METHODS

Race records were reviewed retrospectively to determine the number of runners that suffered an emergency medical complication related to heat stress and did not finish (DNF) the race. Review of records included three years before and three years after the institution of these mandatory rest periods.

RESULTS

A total of 326 runners competed in the Jungle Marathon during the 2008-2013 period of study. During the pre-intervention years, a total of 46 athletes (21%) DNF the full race with 25 (54.3%) cases attributed to heat-related factors. During the post-intervention years, a total of 26 athletes (24.3%) DNF the full race with four (15.4%) cases attributed to heat-related factors.

CONCLUSION

Mandatory rest stops during extreme running events in hot or tropical environments, like the Jungle Marathon, are likely to improve athlete safety and improve the heat acclimatization process.

Challenging Return to Play Decisions: Heat Stroke, Exertional Rhabdomyolysis, and Exertional Collapse Associated With Sickle Cell Trait

Context:

Sports medicine providers frequently return athletes to play after sports-related injuries and conditions. Many of these conditions have guidelines or medical evidence to guide the decision-making process. Occasionally, however, sports medicine providers are challenged with complex medical conditions for which there is little evidence-based guidance and physicians are instructed to individualize treatment; included in this group of conditions are exertional heat stroke (EHS), exertional rhabdomyolysis (ER), and exertional collapse associated with sickle cell trait (ECAST).

Evidence Acquisition:

The MEDLINE (2000-2015) database was searched using the following search terms: exertional heat stroke, exertional rhabdomyolysis, and exertional collapse associated with sickle cell trait. References from consensus statements, review articles, and book chapters were also utilized.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Results:

These entities are unique in that they may cause organ system damage capable of leading to short- or long-term detriments to physical activity and may not lend to complete recovery, potentially putting the athlete at risk with premature return to play.

Conclusion:

With a better understanding of the pathophysiology of EHS, ER, and ECAST and the factors associated with recovery, better decisions regarding return to play may be made.

Exertional Heat Stroke and Susceptibility to Malignant Hyperthermia in an Athlete: Evidence for a Link?

OBJECTIVE

To describe the possible association (pathophysiologic and clinical features) between exertional heat stroke (EHS) and malignant hyperthermia (MH).

BACKGROUND

Both EHS and MH are acute and life-threatening disorders. It has repeatedly been shown that EHS can occur in well-trained patients with known MH-associated mutation in the RYR1 gene in the absence of any extreme environmental conditions or extreme physical activity, thereby supporting a possible link between EHS and MH. In this case, a highly trained 30-year-old male athlete suddenly collapsed while running. He had initial hyperthermia (40.2°C) and progressive multiple organ failure requiring medical management in an intensive care unit. After he recovered completely, a maximal exercise test was performed and showed an obvious abnormality of oxidative metabolism in muscle; genetic analysis of the RYR1 gene identified a heterozygous missense variation p.K1393R. Consequently, the athlete was given appropriate information and allowed to progressively return to sport competition.

DIFFERENTIAL DIAGNOSIS

Doping, use of drugs and toxic agents, exercise-associated hyponatremia, exertional heat illness.

TREATMENT

Initial management started with the basic resuscitative guidelines of airway, breathing, and circulation (intubation). Cooling, administration of fresh frozen plasma, and intensive rehydration resulted in improvement.

UNIQUENESS

To our knowledge, ours is the first description of this MH mutation (p.K1393R) in the RYR1 gene that was associated with exertional rhabdomyolysis involving a dramatic impairment of oxidative metabolism in muscle.

CONCLUSIONS

Common features are shared by EHS and MH. Careful attention must therefore be paid to athletes who experience EHS, especially in temperate climates or when there are no other predisposing factors.

Predictive Factors for Hospitalization of Patients with Heat Illness in Yamaguchi, Japan

The objective of the study was to investigate the predictive factors for the hospitalization of patients who presented with mild to moderate heat illness at an emergency department. We conducted a retrospective survey of hospitals with an emergency department in Yamaguchi Prefecture, Japan. The survey questionnaire entries included patient age, sex, use of an ambulance, vital signs, blood examination conducted at the emergency department, the length of hospitalization, and outcome. We analyzed the predictive factors for hospitalization in patients with heat illness. A total of 127 patients were analyzed. Of these, 49 (37%) were admitted, with 59% discharged on the day following admission. In univariate analysis, the following inpatient characteristics were predictive for hospitalization: old age, low Glasgow Coma Scale score, elevated body temperature, increased serum C-reactive protein, and increased blood urea nitrogen. In logistic regression multivariate analysis, the following were predictive factors for hospitalization: age of ≥ 65 years (odds ratio (OR) 4.91; 95% confidence interval (CI) 1.42–17.00), body temperature (OR 1.97; 95% CI 1.14–3.41), Glasgow Coma Scale (OR 0.40; 95% CI 0.16–0.98), and creatinine (OR 2.92; 95% CI 1.23–6.94). The results suggest that the elderly with hyperthermia, disturbance of consciousness, and elevated serum creatinine have an increased risk for hospitalization with heat illness.