Exertional Heat Stroke Cases Research Articles

Sex Differences in Biomarkers of End-Organ Damage following Exertional Heat Stroke in Humans

Women are participating in military and athletic activities in the heat in increasing numbers, but potential sex differences in sequelae from exertional heat illness remain poorly understood. We tested the hypothesis that women suffering from exertional heat stroke (EHS) would have similar severity of organ damage biomarkers compared to men, as measured in a hospital setting. We studied women and men presenting with EHS to the emergency department at Fort Moore, GA. We measured creatinine (CR), creatine kinase (CK), alanine-transaminase (ALT), aspartate aminotransferase (AST), and estimated glomerular filtration rate (eGFR). Core temperature was also assessed by medical personnel. Biomarker data were obtained for 62 EHS cases (11 women). Men were significantly taller, and heavier, had larger BMI and body surface area (p<0.05 for all). Highest recorded body core temperature was not different between groups (women: 41.11°C (40.06,41.67); men: 41.11°C (40.28,41.72), p=0.57). Women had significantly lower peak CR (women: 1.39 (1.2,1.48) mgꞏdL-1; men: 1.75 (1.53,2.16) mgꞏdL-1, p<0.01) and peak CK (women: 584 (268,2412) UꞏL-1; men: 2183 (724,5856) U•L-1, p=0.02). Peak ALT and AST were not different between groups; during recovery time points, ALT and AST were either similar or lower in women. Women spent approximately half as much time in the hospital following admittance compared to men. Our findings suggest that women may be less susceptible to organ injury resulting from EHS. Further research is necessary to understand the pathophysiology underlying these differences and how biomarkers of end-organ damage severity can differ between women and men following EHS.

Rebound Hyperthermia in Exertional Heat Stroke.

Exertional heat stroke (EHS) is a life-threatening condition requiring rapid reversal of hyperthermia to prevent poor health outcomes. Current treatment protocols aim for a cooling rate of 0.15 C/min using various modalities. This case report details a 22-year-old male who, despite initial successful cooling measures, experienced rebound hyperthermia, necessitating the use of endovascular cooling (EVC). The patient collapsed during a 19.3 km (12-mile) ruck march in Fort Moore, Georgia, with an initial core temperature of 41.6ºC. Conventional cooling methods, including ice sheets and chilled intravenous saline, adequately cooled the patient to target temperatures; however, discontinuation of cooling methods resulted in rebound hyperthermia. Endovascular cooling was eventually initiated, resulting in euthermia after 36 hours of continued use. During his hospital admission, the patient was evaluated thoroughly for underlying etiologies contributing to his rebound hyperthermia. This workup did not yield any concerning pathology, except for bilateral foot cellulitis noted on physical examination, which was subsequently managed with antibiotics. Despite initial complications, the patient recovered within 5 days and returned to duty after 2 months. Several case reports have been published regarding the use of EVC in the management of EHS. These reports, however, describe its use in initial management of EHS or in cases where hyperthermia was refractory to other conventional cooling methods. To our knowledge, this is the first report of its kind highlighting its successful implementation in rebound hyperthermia. Early recognition and initiation of cooling measures are critical in EHS cases. Future directions include developing EHS-specific EVC protocols for patients experiencing refractory or rebound hyperthermia.

Observation on the efficacy of continuous veno-venous hemodia-filtration combined with hemoperfusion HA380 in the treatment of 15 cases of heat stroke with multiple organ dysfunction syndrome

To investigate the clinical efficacy of continuous veno-venous hemodia-filtration (CVVHDF) combined with hemoperfusion (HP) HA380 in the treatment of heat stroke patients with multiple organ dysfunction syndrome (MODS). A retrospective and observational study was conducted. A total of 15 patients with heat stroke combined with MODS who were admitted to the department of intensive care unit (ICU) of Suizhou Central Hospital/Hubei University of Medicine from July to September 2022 were selected as the study objects. All 15 patients were treated with CVVHDF combined with HA380 based on the comprehensive management strategy for severe illness. Organ function indicators [including total bilirubin (TBil), aspartate aminotransferase (AST), creatine kinase (CK), lactate dehydrogenase (LDH), creatinine (Cr), cardiac troponin T (cTnT), myoglobin (Myo), MB isoenzyme of creatine kinase (CK-MB), sequential organ failure assessment (SOFA)] and inflammatory indicators [including white blood cell count (WBC), neutrophil count (NEU), C-reactive protein (CRP), procalcitonin (PCT), and interleukin-6 (IL-6)] were collected. The improvements of the above indexes at admission, after the first HP, after the second HP, after the third HP, and on the 5th day of treatment were compared. Combined with the clinical outcome of patients, the comprehensive efficacy of CVVHDF combined with HA380 in the treatment of severe heat radiation disease was evaluated. There were 10 males and 5 females among the 15 patients. The average age was (64.5±11.5) years old. There were 6 cases of classical heat stroke and 9 cases of exertional heat stroke. Glasgow coma scale (GCS) was 3-8 at admission; SOFA score was 9-17 within 12 hours after admission; acute physiology and chronic health evaluation II (APACHE II) was 25-45 within 24 hours after admission. After treatment, the IL-6 level and SOFA score gradually decreased, and there were significant differences in the decrease after the second HP compared to admission [IL-6 (ng/L): 48.37 (15.36, 113.03) vs. 221.90 (85.87, 425.90), SOFA: 8.3±3.3 vs. 11.1±2.4, both P < 0.05]. The PCT level reached its peak after the first HP [12.51 (6.07, 41.65) μg/L], and then gradually decreased, and the difference was statistically significant after the third HP [1.26 (0.82, 5.40) μg/L, P < 0.05]. Compared those at admission, Cr level significantly improved after the first HP (μmol/L: 66.94±25.57 vs. 110.80±31.13, P < 0.01), Myo significantly decreased after the second HP [μg/L: 490.90 (164.98, 768.05) vs. 3 000.00 (293.00, 3 000.00), P < 0.05], After the third HP, the CK level also showed significant improvement [U/L: 476.0 (413.0, 922.0) vs. 2 107.0 (729.0, 2 449.0), P < 0.05]. After CVVHDF combined with 3 times HP treatment, the patient's inflammatory response was gradually controlled and organ function gradually recovered. On the 5th day of the disease course, WBC, PCT and IL-6 levels were significantly improved compared to admission, and AST, CK, LDH, Cr, Myo, CK-MB, and SOFA score were significantly corrected compared with those on admission. The 24-hour survival rate of 15 patients was 86.67%, and the 24-hour, 7-day and 28-day survival rates were both as high as 73.33%. The average mechanical ventilation time of 11 surviving patients was (101.8±22.0) hours, the average continuous renal replacement therapy (CRRT) time was (58.8±11.0) hours, the average length of ICU stay was (6.3±1.0) days, and the average total hospitalization was (14.6±5.2) days. CVVHDF combined with HP HA380 in the treatment of heat stroke patients with MODS can effectively improve organ function and alleviate the inflammatory storm, which is an effective means to improve the rescue rate and reduce the mortality of severe heat stroke patients.

The Role of Motivation to Excel in the Etiology of Exertional Heat Stroke.

Exertional heat stroke (EHS) is a medical emergency characterized by elevated body temperature and central nervous system dysfunction, and it can include dizziness, confusion and loss of consciousness, as well as long-term organ and tissue damage. EHS is distinct from classic, or passive, heat stroke and is most commonly observed during intense physical activity in warfighters, athletes, and laborers. EHS is an ongoing non-combat threat that represents a risk to both the health and readiness of military personnel. Potential risk factors and their mitigation have been the subject of investigation for decades. One risk factor that is often mentioned in the literature, but not well quantified, is that of individual motivation to excel, wherein highly trained military personnel and athletes exert themselves beyond their physiological limits because of a desire to complete tasks and goals. The motivation to excel in tasks with high standards of achievement, such as those within elite military schools, appears to create an environment in which a disproportionately high number of exertional heat illness casualties occur. Here, we review existing biomedical literature to provide information about EHS in the context of motivation as a risk factor and then discuss five cases of EHS treated at Martin Army Community Hospital at Fort Moore, GA, from 2020 to 2022. In our discussion of the cases, we explore the influence of motivation on each occurrence. The findings from this case series provide further evidence of motivation to excel as a risk factor for EHS and highlight the need for creative strategies to mitigate this risk.

Early Prediction of Impending Exertional Heat Stroke With Wearable Multimodal Sensing and Anomaly Detection.

We employed wearable multimodal sensing (heart rate and triaxial accelerometry) with machine learning to enable early prediction of impending exertional heat stroke (EHS). US Army Rangers and Combat Engineers (N = 2,102) were instrumented while participating in rigorous 7-mile and 12-mile loaded rucksack timed marches. There were three EHS cases, and data from 478 Rangers were analyzed for model building and controls. The data-driven machine learning approach incorporated estimates of physiological strain (heart rate) and physical stress (estimated metabolic rate) trajectories, followed by reconstruction to obtain compressed representations which then fed into anomaly detection for EHS prediction. Impending EHS was predicted from 33 to 69 min before collapse. These findings demonstrate that low dimensional physiological stress to strain patterns with machine learning anomaly detection enables early prediction of impending EHS which will allow interventions that minimize or avoid pathophysiological sequelae. We describe how our approach can be expanded to other physical activities and enhanced with novel sensors.

Recommended water immersion duration for the field treatment of exertional heat stroke when rectal temperature is unavailable.

The recommended treatment for exertional heat stroke is immediate, whole-body immersion in < 10 °C water until rectal temperature (Tre) reaches ≤ 38.6°C. However, real-time Tre assessment is not always feasible or available in field settings or emergency situations. We defined and validated immersion durations for water temperatures of 2-26°C for treating exertional heat stroke. We compiled data for 54 men and 18 women from 7 previous laboratory studies and derived immersion durations for reaching 38.6°C Tre. The resulting immersion durations were validated against the durations of cold-water immersion used to treat 162 (98 men; 64 women) exertional heat stroke cases at the Falmouth Road Race between 1984 and 2011. Age, height, weight, body surface area, body fat, fat mass, lean body mass, and peak oxygen uptake were weakly associated with the cooling time to a safe Tre of 38.6°C during immersions to 2-26°C water (R2 range: 0.00-0.16). Using a specificity criterion of 0.9, receiver operating characteristics curve analysis showed that exertional heat stroke patients must be immersed for 11-12min when water temperature is ≤ 9°C, and for 18-19min when water temperature is 10-26°C (Cohen's Kappa: 0.32-0.75, p < 0.001; diagnostic odds ratio: 8.63-103.27). The reported immersion durations are effective for > 90% of exertional heat stroke patients with pre-immersion Tre of 39.5-42.8°C. When available, real-time Tre monitoring is the standard of care to accurately diagnose and treat exertional heat stroke, avoiding adverse health outcomes associated with under- or over-cooling, and for implementing cool-first transport second exertional heat stroke policies.

Heat stroke burden and validity of wearable-derived core temperature estimation during elite military training

ABSTRACT Objectives Exertional heat stroke (EHS) remains a significant health concern while training in hot environments, prompting the development of noninvasive wearable technology for monitoring estimated core temperature (ECT). The objective of this study was to review the effectiveness of an ECT device during elite military training by providing a case series of individuals who developed EHS. Methods This is a retrospective study of EHS cases during high-intensity training while wearing the ECT device, Zephyr BioharnessTM. Data was collected from January 2021 through September 2021 at the Air Force Special Warfare Training pipeline in San Antonio, TX. Rectal temperatures of EHS diagnoses, defined by central nervous system (CNS) dysfunction and rectal temperature approaching or >40°C (104°F), were compared to ECT reading via Zephyr BioharnessTM. Incidence rates and psychometric properties were calculated using R package. Results A total of 47,058 daily peak ECT measurements were collected among 1,364 trainees. A total of 499 trainees flagged as potential EHS by Zephyr BioharnessTM reading >39.7°C (103.5°F). The incidence of confirmed EHS was 0.8/1000 person-months. Of the 10 confirmed EHS cases (9 males, 1 female; age = 23.4 ± 2.7 yrs; BMI = 25 ± 2; body fat = 13 ± 5%), 8 trainees had a peak ECT reading below 39.7°C which resulted in a sensitivity of 20%, specificity of 98.9%, positive likelihood ratio (LR) of 18.93 (95% Confidence Interval [CI] 5.5–65.6), and a negative LR of 0.81 (95% CI 0.6–1.1). Conclusion ECT had substantial false positive and negative rates. Further studies are needed to validate this technology in other populations, and the algorithm used in this device needs to be refined to better capture the environmental and physical requirements in the special operations population.

Body Mass Index Influences on Exertional Heat Stroke Risk in Young Healthy Males and Females

Objective: To find the influence of body mass index on exertional heat stroke risk in young healthy males and females. Study Design: Retrospective case control study Place and Duration of Study: Department of Neurology, Sharif Medical &amp; Dental College, Lahore from 1st April 2022 to 30th September 2022. Methodology: Two hundred patients who came with exertional heat stroke and compared it with the normal healthy control’s information were enrolled. Exertional heat stroke (EHS) cases were placed in Group A while normal controls in group B. The information regarding heat illness, body size, gender, was documented in addition to their other demographic details was compared in the groups. Results: The mean age of the EHS cases in group A was 25.5±7.2 years while of controls in group B was 26.1±6.5 years. There was higher number of males within both groups. The BMI of group A was higher than group B having a mean value as 26.9±3.2 in group A. The odds ration showed that EHS cases with a higher BMI had an increased risk of heat stroke which has a significant association with age but not with the gender. Conclusion: There is a significant association between the higher body mass index and exertional heat stroke formation in young adults. Keywords: Body weight, Outcome, Military, Influence, Marker

Sequential organ failure assessment score as a predictor of the outcomes of patients hospitalized for classical or exertional heatstroke

Heatstroke is a life-threatening event that affects people worldwide. Currently, there are no established tools to predict the outcomes of heatstroke. Although the Sequential Organ Failure Assessment (SOFA) score is a promising tool for judging the severity of critically ill patients. Therefore, in this study, we investigated whether the SOFA score could predict the outcome of patients hospitalized with severe heatstroke, including the classical and exertional types, by using data from a Japanese nationwide multicenter observational registry. We performed retrospective subanalyses of the Japanese Association for Acute Medicine heatstroke registry, 2019. Adults with a SOFA score ≥ 1 hospitalized for heatstroke were analyzed. We analyzed data for 225 patients. Univariate and multivariable analyses showed a significant difference in the SOFA score between non-survivors and survivors in classical and exertional heatstroke cases. The area under the receiver operating characteristic curve were 0.863 (classical) and 0.979 (exertional). The sensitivity and specificity of SOFA scores were 50.0% and 97.5% (classical), 66.7% and 97.5% (exertional), respectively, at a cutoff of 12.5, and 35.0% and 98.8% (classical), 33.3% and 100.0% (exertional), respectively, at a cutoff of 13.5. This study revealed that the SOFA score may predict mortality in patients with heatstroke and might be useful for assessing prognosis.

Passive Heating after Heat‐ and Exercise‐Induced Collapse in Mice Induces a Severe Exertional Heat Stroke Phenotype that More Accurately Recapitulates Human Cases

Development of a mouse exertional heat stroke (EHS) model that more accurately recapitulates human EHS cases is essential in characterizing the pathophysiology of the condition and determining potential treatment options for heat stroke sequelae in humans. Previously developed murine heat illness models were either done passively [with or without anesthesia] or had an exertional component with little to no mortality and rapid recovery of mice following removal from the high‐temperature environment, effectively modeling a less severe heat illness, exertional heat injury (EHI). Accordingly, we examined whether leaving mice undisturbed in their environment following heat illness collapse results in an EHS model with a level of mortality that more accurately recapitulates the human condition. Trained mice were placed in a forced‐running wheel that gradually increased from low‐to‐moderate speed (3.0 to 8.5 m/min, increasing 0.5 m/min every 10 minutes). Ambient temperature was set at 25°C for Exercise Controls (ExC) and 37.5°C for EHI and EHS specimens while humidity was set at 30‐70% for all conditions. EHS and EHI mice ran in the wheels until losing consciousness; EHI mice were immediately returned to their home cage (25°C) while EHS mice and a conscious ExC counterpart were left undisturbed in their respective chambers for an additional 20 minutes before being returned to their home cages. Overall, higher mortality rates were observed in the EHS mice (14/63) compared to EHI (0/54) and ExC (0/52) mice. A subset of the mice were sacrificed at 48 hours following the exercise/heat bout (n=10‐12/group); in these mice, student’s T‐tests indicated that serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) was elevated in EHS vs. ExC while AST was elevated in EHS vs. EHI, suggesting EHS mice exhibited the most hepatic damage. We have developed a protocol to more accurately model human EHS in mice. Our working hypothesis is that heat 1) in the ambient environment and 2) produced by exertion lead to increased core body temperatures in mice that initiate tissue / organ damage. Inhibiting heat dissipation by leaving mice undisturbed in the warm environment exacerbates tissue / organ damage, resulting in a systemic inflammatory response and mortality in some cases.

Exertional heat illnesses in marching band artists: a case series.

Marching band (MB) artists frequently spend many hours engaged in outdoor physical activity. Anecdotal evidence and small studies have indicated that MB artists do experience heat-related health problems. Yet, unlike athletes, military personnel, or workers, there is very little research on heat-related hazards among this unique population. Here, we seek to understand the incidence and circumstances under which exertional heat illnesses (EHIs) occur among MB artists over a 31-year period (1990-2020) across the USA. Using an on-line news dataset, we identified 34 separate events and at least 393 total EHIs. Heat syncope (~ 55%) and heat exhaustion (~ 44%) comprised the majority of EHIs, although a small number of exertional heat stroke cases were also reported. EHIs were reported in all types of MB activities with ~ 32% during rehearsal, ~ 29% during parades, ~ 21% during competition, and ~ 15% during a performance. Also, the vast majority of events occurred with high school (~ 88%) marching bands. Finally, EHIs overwhelmingly occurred when the weather was unusually hot by local conditions. In light of these findings, we emphasize the need for MB specific heat polices that incorporate weather-based activity modification, acclimatization, education about EHIs, and access to on-site medical professionals.

Reply

Dear Editor:We appreciate the opportunity to respond to the letter about our investigation of age, sex, environmental conditions, and the incidence of exertional heat stroke (EHS) in a warm-weather road race.1 The letter author raises some points that allow us to further expand on our findings and, we hope, provide adequate context for his concerns.Overall, in examining the implications of this investigation, we appear to diverge from the author of the letter on a key point. He argues that EHS is preventable. Although every case of EHS is theoretically preventable, the large numbers of people with a variety of individual risk factors exercising in warm environments make total prevention nearly impossible. In addition to running road races, large-scale events involving exercise, such as military basic training,2 are subject to similar concerns regarding exertional heat illnesses despite comprehensive prevention efforts. However, we reiterate that data from this very race indicated that mortality from EHS did appear to be preventable with appropriate treatment.3The purpose of this investigation was to examine the factors that influenced the incidence of EHS on a population level. Furthermore, we sought to identify the factors that medical teams and race organizers might be able to consider before the road race to help determine the staff and supplies needed to appropriately treat patients with EHS. In our discussion, we fully acknowledged that EHS risk is multifactorial and consists of both intrinsic and extrinsic factors.4 However, the individual factors of the participants in running road races cited by the letter author (fitness, heat acclimatization, adiposity, and exertional intensity) are unknown and would likely require advanced laboratory techniques to ascertain. Even if these data were available for the cases presented, the utility of these analyses for onsite medical providers is limited. The mechanistic insights the author of the letter tried to glean from the presented data are beyond the scope of these data.Several times, the letter author referenced our findings, saying that males and youth were found to be at a higher risk of EHS. Throughout the paper, we referred to the results as applying to “younger runners,” not “youth,” and further clarified in the conclusion that these results primarily applied to runners aged 19 to 39 years. We made this distinction for many of the reasons the author of the letter stated, including the fact that the physiological and behavioral circumstances of individuals under the age of 18 participating in this race were unique.The letter author denoted several factors that may play a role in children having altered susceptibility to EHS. He correctly indicated that an altered body mass-to-surface area ratio did not solely explain the altered risk in youth individuals, and it is clear from his review that a description of the nuances of this risk extends beyond what is included in our manuscript. Runners under the age of 14 accounted for only 2.4% of race participants and 2.6% of patients with EHS. However, we would caution the author to avoid comparing EHS- and heat-related deaths (which include nonexertional cases); the mechanisms and causes of these conditions are clearly disparate.Finally, the author of this letter highlighted the claim that “only younger age accounted for an increased incidence of EHS,” yet we would like to stress that this statement was taken out of context: the other part of that sentence reads, “However, when sex was considered with age and WBGT [wet bulb globe temperature]. . .” We did not characterize age as the sole risk factor for EHS but rather our data supported that, of those variables we could study, age did statistically explain the greatest variance in EHS incidence.We conclude by emphasizing that our findings were epidemiologic in nature. Many factors influence an individual's susceptibility to EHS; by examining the patterns of EHS incidence in events such as the Falmouth Road Race, we can observe trends that either allow researchers to study these mechanisms in controlled environments or establish reference incidences for medical providers. We agree with the letter author's recommendations to increase community collaboration and minimize the risk globally for all runners using the precautions listed.

Exertional Heat Stroke at the Boston Marathon: Demographics and the Environment.

This study aimed to assess associations between exertional heat stroke (EHS) and sex, age, prior performance, and environmental conditions, and report on resources needed for EHS cases at the Boston Marathon. We analyzed participant characteristics, environmental data, and EHS medical encounters during the 2015-2019 Boston Marathon races. Among 136,161 starters, there was an incidence of 3.7 EHS cases per 10,000 starters (95% confidence interval, 2.8-4.9), representing 0.5% of all medical encounters. There were significant associations between sex and age (P < 0.0001), sex and start wave (P < 0.0001), and age group and start wave (P < 0.0001). Sex was not significantly associated with increased EHS incidence; however, age younger than 30 yr and assignment to the first two start waves were. All cases occurred at races with average wet bulb globe temperatures of 17°C-20°C. There was a linear correlation between EHS incidence and greater increases in wet bulb globe temperature from start to peak (R2 = 0.7688). A majority of cases (37; 72.5%) were race finishers; nonfinishers all presented after mile 18. Most were triaged 3-4 h after starting, and all were treated with ice water immersion. Treatment times were prolonged (mean (SD), 78.1 (47.5) min; range, 15-190 min); 29.4% (15 cases) developed posttreatment hypothermia, and 35.3% (18 cases) were given intravenous fluids. Most (31 cases; 64.6%) were discharged directly, although 16 cases (33.3%) required hospital transport. There were no fatalities. Younger and faster runners are at higher risk for EHS at the Boston Marathon. Greater increases in heat stress from start to peak during a marathon may exacerbate risk. EHS encounters comprise a small percentage of race-day medical encounters but require extensive resources and warrant risk mitigation efforts.

Incidence of Recurrent Exertional Heat Stroke in a Warm-Weather Road Race

Background and Objectives: Exertional heat stroke (EHS) survivors may be more susceptible to subsequent EHS; however, the occurrence of survivors with subsequent EHS episodes is limited. Therefore, the purpose of this study was to evaluate the incidence of participants with repeated EHS (EHS-2+) cases in a warm-weather road race across participation years compared to those who experienced 1 EHS (EHS-1). Materials and Methods: A retrospective observational case series design was utilized. Medical record data from 17-years at the Falmouth Road Race between 2003–2019 were examined for EHS cases. Incidence of EHS-2+ cases per race and average EHS cases per EHS-2+ participant were calculated (mean ± SD) and descriptive factors (rectal temperature (TRE), finish time (FT), Wet Bulb Globe Temperature (WBGT), age, race year) for each EHS was collected. Results: A total of 333 EHS patients from 174,853 finishers were identified. Sixteen EHS-2+ participants (11 males, 5 females, age = 39 ± 16 year) accounted for 11% of the total EHS cases (n = 37/333). EHS-2+ participants had an average of 2.3 EHS cases per person (range = 2–4) and had an incidence rate of 2.6 EHS per 10 races. EHS-2+ participants finished 93 races following initial EHS, with 72 of the races (77%) completed without EHS incident. Initial EHS TRE was not statistically different than subsequent EHS initial TRE (+0.3 ± 0.9 °C, p > 0.050). Initial EHS-2+ participant FT was not statistically different than subsequent EHS FT (−4.2 ± 7.0 min, p > 0.050). The years between first and second EHS was 3.6 ± 3.5 year (Mode: 1, Range: 1–12). Relative risk ratios revealed that EHS patients were at a significantly elevated risk for subsequent EHS episodes 2 years following their initial EHS (relative risk ratio = 3.32, p = 0.050); however, the risk from 3–5 years post initial EHS was not statistically elevated, though the relative risk ratio values remained above 1.26. Conclusions: These results demonstrate that 11% of all EHS cases at the Falmouth Road Race are EHS-2+ cases and that future risk for a second EHS episode at this race is most likely to occur within the first 2 years following the initial EHS incident. After this initial 2-year period, risk for another EHS episode is not significantly elevated. Future research should examine factors to explain individuals who are susceptible to multiple EHS cases, incidence at other races and corresponding prevention strategies both before and after initial EHS.

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

Sex, age, and wet-bulb globe temperature (WBGT) have been proposed risk factors for exertional heat stroke (EHS) despite conflicting laboratory and epidemiologic evidence. To examine differences in EHS incidence while accounting for sex, age, and environmental conditions. Observational study. Falmouth Road Race, a warm-weather 7-mi (11.26-km) running road race. We reviewed records from patients treated for EHS at medical tents. 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. 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). 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.

NEW GENES IN NEUROMUSCULAR DISEASES: O.03 Dominant mutations in the junctin gene are related to malignant hyperthermia and exertional heat stroke

Malignant hyperthermia (MH) and Exertional Heat Stroke (EHS) present hypermetabolic states leading to rhabdomyolysis and muscle rigidity with progressive hyperthermia; MH is triggered by volatile inhaled anesthetics, while EHS is triggered by exercise in hot/humid environment. Given the similarity of clinical features and the fact that a portion of EHS cases were diagnosed as MH susceptible by the in vitro contracture test, MH and EHS are believed to share common etiology. Mutations in RYR1 and CACNA1S have been found to be associated with MH; however the genetic cause remains to be identified in approximately 30% of MH cases.

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.

Exertional Heat-Stroke Management Practices and Intentions Among Secondary School Football Athletic Trainers.

Athletic trainers (ATs) are educated and trained in appropriate exertional heat-stroke (EHS) management strategies, yet disparities may exist between intended and actual uses in clinical practice. To examine the intended and actual uses of EHS management strategies among those who did and those who did not treat patients with suspected cases of EHS during the 2017 high school (HS) American football preseason. Cross-sectional study. Online questionnaire. A total of 1016 ATs who oversaw patient care during the 2017 HS American football preseason. Responding HS ATs recorded whether they had or had not managed patients with suspected EHS events during the 2017 HS American football preseason. Those who had managed patients with suspected cases of EHS reported the management strategies used; those who had not managed such patients described their intended management strategies. For each management strategy, z tests compared the proportions of actual use among ATs who managed patients with suspected EHS with the proportions of intended use among ATs who did not manage such patients. Overall, 124 (12.2%) ATs treated patients with suspected EHS cases during the 2017 HS American football preseason. Generally, the proportions of intended use of management strategies among ATs who did not treat patients with suspected EHS were higher than the actual use of those strategies among ATs who did. For example, ATs who did treat patients with suspected EHS were more likely than those who did not treat such patients to intend to take rectal temperature (19.6% versus 3.2%, P < .001) and immerse the athlete in ice water (90.1% versus 51.6%, P < .001). Inconsistencies occurred between intended and actual use of EHS management strategies. The standard of care for managing patients with suspected cases of EHS was not consistently used in clinical practice, although ATs who did not treat EHS stated they intended to use these management strategies more frequently. Future researchers should identify factors that preclude ATs from using the standard of care when treating patients with suspected cases of EHS.

Sex Differences In The Clinical Sequelae Of Exertional Heat Stroke In Military Servicemembers

Exertional heat stroke (EHS) represents a significant source of morbidity and mortality for the military and other occupational and athletic populations. EHS patients tend to present with elevated biomarkers of acute liver and kidney injury, rhabdomyolysis, and altered hematological parameters. However, little is know about how men and women may respond differently to EHS, in terms of clinical severity and/or biochemical responses. PURPOSE: The aim of this study was to characterize clinical and biochemical differences between male and female servicemembers immediately following an EHS episode. METHODS: We performed a retrospective analysis of EHS patient records in all US military personnel (41% between 20-24 years old) from 2008-2014 using the Military Health Systems Data Repository. We compared diagnoses of organ failure during the course of treatment and clinical laboratory markers of end organ damage. Sex differences in clinical outcomes are presented with odds ratios, and biomarker differences are presented as the median difference with 95% confidence intervals in brackets. RESULTS: A total of 2,529 EHS cases were recorded with 9.8% [8.7, 11.2] occuring in women. Per patient treatment cost was lower in women by $1110 [620, 1647]. Men were 2.35 [1.6, 3.58] times more likely to experience renal failure (p = < .001). Blood urea nitrogen, (difference = -121.05 mg/dL [41.9, 182.28]), myoglobin (difference = 3 ng/mL [2, 4]), aspartate transaminase (difference = 7 units/L [1, 14]), and alanine transaminase (difference = 13 units/L [8.5, 15.92]) were elevated in men (all p < .01). Platelet count was also lower in men compared to women (difference = -22.14*103 per uL [-39.25, -2.99], p = 0.03). CONCLUSION: Female servicemembers appear to have a slightly less severe response to EHS compared to their male counterparts. In particular, renal failure was more common, and numerous markers of end-organ damage (hepatic, renal, and cardiovascular) were more likely to be elevated immediately following EHS in men. Supported by USAMRDC; author views not official US Army or DoD policy.

Controversies in exertional heat stroke diagnosis, prevention, and treatment.

During the past several decades, the incidence of exertional heat stroke (EHS) has increased dramatically. Despite an improved understanding of this syndrome, numerous controversies still exist within the scientific and health professions regarding diagnosis, pathophysiology, risk factors, treatment, and return to physical activity. This review examines the following eight controversies: 1) reliance on core temperature for diagnosing and assessing severity of EHS; 2) hypothalamic damage induces heat stroke and this mediates "thermoregulatory failure" during the immediate recovery period; 3) EHS is a predictable condition primarily resulting from overwhelming heat stress; 4) heat-induced endotoxemia mediates systemic inflammatory response syndrome in all EHS cases; 5) nonsteroidal anti-inflammatory drugs for EHS prevention; 6) EHS shares similar mechanisms with malignant hyperthermia; 7) cooling to a specific body core temperature during treatment for EHS; and 8) return to physical activity based on physiological responses to a single-exercise heat tolerance test. In this review, we present and discuss the origins and the evidence for each controversy and propose next steps to resolve the misconception.